X-Ray Board Reviewing Rules

Transcription

1 Volume 24, Issue 3 July-Sept 2018 Tennessee X-Ray X-Ray Board Reviewing Rules The Tennessee Board of Radiologic Imaging and Radiation Therapy had their first meeting on January 25, The minutes from that meeting are now available on the x-ray board site at At each meeting, the board is reviewing the current rules and making adjustments as they progress through the current rules. These proposed changes will have to go through a lengthy rulemaking process to become law. By reading these minutes, x-ray operators can see what changes might be coming to their license. The next x-ray board meeting will be held on July 24, Limited Scope Exam Renewing in 2019? Board Member Representation Term Expires Matthew Fakes Radiographer 9/30/19 Kae Fleming Educator 9/30/18 Karen Munyon Radiation Therapist 9/30/19 Pamela Ward MRI/CT Tech 9/30/18 Vacant Nuclear Med Tech 9/30/18 Gary Podgoski Radiologist 12/31/18 Chester Ramsey Medical Physicist 9/30/19 Vacant Physician 6/30/19 Vacant Public Member 9/30/18 Limited Scope Testing (LST) provides application processing services for eligible students wishing to sit for the American Registry of Radiologic Technologists (ARRT) Limited Scope of Practice in Radiology examination and the Bone Densitometry Equipment Operator examination for the state of Tennessee. Information is provided at If you renew your license next year in 2019, you need to complete your 20 CE credits by December 31, 2018 to be compliant with current state rules. Even though you must complete your CE credits within the 2 preceding calendar years, the due date for proof of that completion is not until your biennium renewal due date. INSIDE THIS ISSUE Puzzle Challenge 3 X-Ray Quiz 3 Amazing Facts 3 Online Access Instructions 4 Answer Sheet Instructions 4 DR-094 Article 5 DR-094 Post-Test 21 Link to XRN Order Form 23 Link to RES Enrollment 23 Link to CE Enrollment 23 Change of Address Form 24 Direct Reading DR-094 Image Production in DXA

2 1. You must obtain 20 continuing education credits every biennial period. The easiest way to accomplish this is to subscribe to X-Ray News on a yearly basis. X-Ray News will provide 10 CE credits each year if completed timely. 2. These credits must be completed in the 2 calendar years prior to your renewal date i.e. by the end of December the year before you renew. If you renew your license next year in 2019, then Important Facts to Remember About Your TN Medical X-Ray License you will need to complete your 20 CE credits by December 31, Your renewal period is every 2 years with the renewal date being the last day of your birth month. If you were born in an odd year then your renewal year will always fall in an odd year and vice versa. 4. Be sure to keep your address current with the state so you will receive your notice to renew. This is your responsibility. The state does not forward mail. You can update your address online at under TN X-Ray License on the top menu. Under the heading TN State X-Ray Links click on the link License Renewal & Address Update. A Continuing Education Publication for Limited Radiographers X-Ray News Office and Staff is published 3 to 4 times per year with each issue containing 2 or 4 credits. A yearly subscription provides 10 CE credits for TN medical or osteopathic limited x-ray licensees. Single issues will provide the necessary credits for TN podiatric x-ray licensees. These CE credits are approved by the Examining Boards of the Tennessee Health Related Boards. Copyright 2018 by X-Ray News, Inc. X-Ray News Office 420 E Iris Drive Nashville, TN Phone: ; Fax: Website: Call or us for: Subscription questions Submitting an article for publication Placing a classified radiology ad X-Ray News Staff Donna Smith, editor Ann Watson, technical editor James Becker, production assistant All Rights Reserved All articles, illustrations, and other materials carried herein are protected under U.S. copyright laws, and all rights thereto are reserved by the publisher, X-Ray News, Inc. Disclaimer X-Ray News (XRN) has performed diligent efforts to determine that all content is factual, and has obtained all rights to use any information or excerpts in all required instances. XRN denies all claims of liability regarding the content, or any action taken by the reader s erroneous interpretation of the content in any XRN Issue. Page 2 X-RAY NEWS VO LUME 24, ISSUE 3

3 1. C 2. C 3. B Puzzle Challenge The words used in this puzzle are taken from the article, DR-094: Image Production in DXA. Words may read normally, from right to left, bottom to top, top to bottom, or on any diagonal. Solution is below. Puzzle Words densitometry nuclear ultrasound calibration protocol inanimate phantom densitometer osteoporosis artifact femoral acquisition anatomy attenuation X-Ray Quiz 1. Currently, the most common cause for osteoporosis among women is: A. milk intolerance B. old age C. estrogen deficiency associated with menopause D. anticonvulsant therapy 2. What frequency does Medicare typically allow for follow-up scans? A. annually B. semiannually C. biennially D. Biannually 3. The typical number of vertebrae in a lumbar spine is: A. 4 B. 5 C. 7 D. 8 Amazing Facts The word osteoporosis comes from the Greek words osteon meaning bone, and poros, meaning a pore or a passage. Osteoporosis is not a condition exclusive to the elderly it can strike at any age. Men tend to develop osteoporosis years later than women do, because they are generally bulkier and have more bone mass to lose. Bones stop growing in length during puberty. Bone density and strength will change over the course of life, however. Hormone replacement therapy used to be prescribed long-term for postmenopausal women, but it is now thought to carry risks for heart health if taken in the long-term. Among those who fracture their hip, 12 to 20% die within one year after the fracture and more than 50% of the survivors are unable to return to independent living. I find that the harder I work, the more luck I seem to have. Thomas Jefferson X-RAY NEWS VO LUME 24, ISSUE 3 Page 3

4 ONLINE ACCESS INSTRUCTIONS For all X-Ray News subscribers who have chosen ALL ONLINE or POST-TEST ONLINE subscriptions: We automatically enroll you into X-Ray News Online, and then send you an containing access instructions to your account on X-Ray News Online. You are able to download the publication or read each issue online, and take the Post- Test for each Direct Reading. IMPORTANT: after successfully completing a Post- Test, be sure to save or print your Certificate of Documentation. If you already have an XRN Account with a prior subscription, each new issue will automatically open upon publication. If you have chosen a NO ONLINE subscription, then your Answer Sheet is mailed with the booklet. Please see the instructions below for using an Answer Sheet. ANSWER SHEET INSTRUCTIONS IMPORTANT: Use ONLY a #2 pencil on the answer sheet. Write your name on the NAME line. Write in the name of the Direct Reading Article on the SUBJECT line. Write the DR# on the PERIOD line. In the box headed I.D. Field, print the numbers of your XRN ID and then also fill in the ovals directly beside the numbers (see example). Your XRN ID is on your confirmation and address label. DO NOT put your license number in the ID field and DO NOT fill in the rest of the field with zeros, leave it empty. Do not fax your Answer Sheet. Before mailing your Answer Sheet, make a copy for your files in case it gets lost in the mail. You need to score 75% or better to receive the approved credit. Your CE report is mailed out by the 15th of each month if your answer sheet is received within the proceeding month. You are notified at that time if you did not receive a passing score. DO NOT send in your original documentation of credits when you renew your license. BUT be prepared to produce them if you receive an audit letter from the state s Audit Unit. Page 4 X-RAY NEWS VO LUME 24, ISSUE 3

5 Image Production in DXA Direct Reading DR-094 Approved for 4.0 CE Credits Jean M. Fisher, LPN, CBDT, MDXL and Donna H. Smith, BS The history of bone density measurement dates back to the 1940 s when radiologists could only make a diagnosis of bone mineral loss by analyzing radiographic images. Unfortunately, because the bone loss was not visible on plain x-ray film until approximately 30% to 50% of the trabecular bone was lost, it meant that a more sensitive quantitative method of determining bone mineral loss was needed. Bone densitometry had its origin in nuclear medicine in the early 1960 s when single-photon absorptiometry (SPA) was developed. A single energy photon beam is passed through bone and soft tissue to a detector where the amount of mineral in the path is then quantified. The introduction of an x-ray tube in place of a gamma ray source introduced single-energy x-ray absorptiometry (SXA). The beam was heavily filtered to produce the single beam. The 1970 s saw the development of dual photon absorptiometry (DPA). This technique used a photon beam that had 2 distinct energy peaks. One energy peak is absorbed more by the soft tissue and the other by bone. The soft-tissue component is subtracted to determine bone mineral density (BMD). It allowed for the first time spine and proximal femur BMD measurements. In the 1980 s, dual-energy x-ray absorptiometry (DXA) becomes the radiographic extension of DPA but uses an x-ray source instead of a radioactive isotope. This method is superior to DPA because the radiation source does not decay and the energy stays constant over time. About the same time quantitative computed tomography (QCT) was also developed using computed tomography (CT) but is costly and is no more accurate than DXA. The use of quantitative ultrasound (QUS) has been around since the 1960 s but has yet to achieve the degree of precision that is provided by DXA. There are several types of bone density machines available, however, this article focuses on the table or central DXA and it s clinical utilization in the diagnosis of bone loss. The table DXA has the tube or source of radiation under the table and the detector or image receptor is above the table, over the patient. When scanning, the transmitted radiation is received by the detector and the results are computed from the x-ray attenuation pattern striking the detector, not the scanned image. The images are then digitized and displayed with the results. The reports are printed out with images, X-RAY NEWS VO LUME 24, ISSUE 3 measurements, and graph comparisons to reference populations. The radiation levels in today s densitometers are lower than conventional x-ray machines and have generally been expressed as 5% to 10% of the exposure received in a chest x-ray. Many sources describe the scan exposure as very similar to the exposure received daily from natural background radiation. Fundamentals of X-Ray Production X-rays are produced when the electrons interact with matter and the kinetic energy of the electron s motion converts into an x-ray photon. Photons consist of many different energy wavelengths. The long wavelength photons do not contribute to the x-ray image and if not eliminated are absorbed by the patient. Filtering removes the long wavelength photons from the x-ray beam by absorption or attenuation. Another way to minimize the amount of radiation to the patient and reduce scatter radiation is by collimation which restricts the x-ray beam and produces a better radiographic image. In densitometry, the filters are built in and collimation is predetermined by the scan technology type. Properties of the X-Ray Beam Radiographic quantity and quality is controlled by primary exposure factors or the properties of the x-ray beam, which are exhibited in Table 1. Typically in radiography the x-ray beam properties are controlled by the operator and it utilizes single photon energy. The x-ray operator can change the current and Table 1 Primary Exposure Factors 1. milliamperes (ma) milli = Determines the quantity (amount) of radiation per time exposed Controls density and quantity Determines how long you produce 2. time (S) x-rays for a given exposure. The unit of time for x-ray production is 1 second 3. kilovolts (kv) kilo = 1000 Determines the energy (quality) of the beam of radiation (the exposure) Controls contrast and quality Page 5

6 voltage to manipulate the x-ray beam for different body parts. In DXA, the x-ray beam properties are selected automatically by the technology and not directly controlled by the operator. The exposure factors are determined by the patient s height, weight, scan type, and mode that is selected. DXA uses 2 different photon energies to distinguish the difference between bone and soft tissue. Dual Photon Energies Reduction in the number of photons in the x-ray beam is due to attenuation or absorption. Some of the x-ray beam is attenuated as it travels from the source to the image receptor (IR). The table attenuates some of the beam and the patient attenuates most of the beam. Attenuation depends on tissue density and thickness. The denser the tissue, the more radiation is attenuated. DXA allows us to record attenuation profiles at 2 levels: high energy and low energy. To measure BMD it is necessary to separate the x-ray attenuating properties of soft tissue and bone. This is accomplished by using 2 photon energies instead of single photon energy, which is used in conventional radiography. Dual energy produces high and low energy x-rays that are attenuated by bone and soft tissue then received by the detectors. Data is calculated at both energy levels and the mathematical subtraction of the soft tissue attenuation provides the bone image and BMD areal measurements in g/cm 2. DXA Components DXA is a relatively quick procedure that measures bone density at axial (central) sites such as the spine and femur; or appendicular (peripheral) sites that include the forearm, heel, or fingers. It is considered the gold standard because of reproducibility, availability, relative low cost and low patient dose. DXA reports provide BMD results and display images that verify proper positioning and accurate regions of interest (ROIs). The multi-detector DXA systems are equipped with a single and dual energy imaging mode. In single energy, a photon beam is passed through bone and soft tissue. The amount of mineral in the path of the beam is quantified, based on the difference between the beam intensity before and after passage through the region of interest (ROI). This mode may be used for vertebral fracture assessment (VFA) and displays an image of bone and soft tissue. In dual energy, a photon beam with 2 photon energies is passed through a region of the body containing both bone and soft tissue, attenuation of the beam occurs at both energy peaks. The image is digitized and utilizes a bone edge Fig. 1 Single energy Fig. 2 Dual energy detection algorithm which allows us to see an image of the bone without soft tissue. This is the standard mode used in DXA. In the United States, the major manufacturers of dual energy x-ray absorptiometers have chosen to use different methods to produce 2 x-ray energies. GE/Lunar and Norland/Swissray utilizes a rare earth filtered (k-edge filtration) x-ray source with a constant generator to produce an x-ray beam with a specific energy range with peaks near 40 and 70 kev, which is just above the k-absorption edge of the tissue in question. The photons are maximally attenuated at these energy levels to separate the bone from soft tissue in a quantifiable fashion to be measured by the pulse counting detectors. An external calibration must be done on a regular basis using a calibration block. Hologic utilizes an energy switching filter system that pulses between 100 and 140 kvp to produce the 2 photon energies that peak near 40 to 80 kev, which is necessary to distinguish bone from soft tissue. This energy switching system continuously calibrates the beam by passing it through a calibration drum with 3 segments representing bone, soft tissue, and air. Each of these segments distinguishes and measures the high and low energy x-rays. Densitometry manufacturers utilize detectors with either direct or indirect detector technology. Indirect technology uses a scintillator to convert x-rays to a visible light and phosphor to convert light to electrons, which are then transmitted electronically to the computer. Direct technology converts the photons directly to an electrical signal to be used by the software for measurement calculations in which the bone edge detection algorithms are applied. Pencil Beam and Fan Beam Technology Before the x-ray beam even reaches the patient it is collimated to either a pencil or fan beam. The first machines introduced specifically for detecting bone mass made use of pencil beam scanning technology and a single detector. The detector and highly collimated x-ray beam move in tandem in a rectilinear scan path. The pencil beam is accomplished by having a small circular pinhole in the collimator, Fig. 3 Pencil beam restricting the beam to what we might compare to the central ray in conventional equipment. A single detector receives the pencil beam. The arrival of the fan beam with a high density array of detectors eliminated the need for the rectilinear path Page 6 X-RAY NEWS VO LUME 24, ISSUE 3

7 because the data is acquired across an entire scan line simultaneously. The fanshaped x-ray beam releases more x-rays per unit of time than pencil beam technology and although it is faster with better image resolution, it increases the patient exposure and introduces geometric Fig. 4 Fan beam magnification. The fan beam is more comparable to the shape of a conventional x-ray beam and centering is very important. The array or fan beam is accomplished by using a slit shape in the collimator instead of a circular pinhole. The slit allows the beam to come out in a fan like pattern that is received by multi-detectors. One manufacturer utilizes a narrow angle fan beam which acquires the data using fan beam technology traveling in a rectilinear overlapping fashion. This combines the best of both pencil and fan beam technology. The dual energies are then attenuated by the patient producing a unique attenuation pattern at the detector. The information is transmitted electronically to the scanner where the software performs a mathematical computation that subtracts the soft tissue signals and produces a bone profile. Bone edge detection algorithms are applied and a two-dimensional area is calculated and reported as an estimated BMD. BMD is referred to as an areal technique because it is calculated by using the two-dimensions of height and width to measure an area versus a threedimensional volume measurement of height, width, and depth. Common physic issues encountered in densitometry include the following: Scintillating detector pile-up in K-edge filtration systems. High energy or low energy photons are only processed 1 at a time and an incoming photon may be missed if the previous photon has not been processed. Direct digital detectors do not have this problem. Crossover in k-edge filtration systems. Some high energy photons lose energy passing through the body and the detector counts it as low energy. Beam hardening in energy switching systems. With increasing body thickness, more low energy photons are absorbed by the body shifting the distribution toward high energy photons. Measuring BMD It is not possible to learn how strong or weak your bones are from a blood test or a risk factor questionnaire. The most accurate way to determine if you have osteoporosis is to measure your bone density. A BMD test can measure the density of bone in different parts of the skeleton and can predict the risk of future fractures. It can also assess the rate of bone density change with repeated or serial measurements and monitor the effectiveness of treatment. DXA is currently the gold standard for osteoporosis diagnosis and 3 statistical measurements provide the foundation for understanding. Additional knowledge of the standard scoring and densitometry Fig. 5 DXA scanner and workstation Image courtesy of GE Healthcare enhanced features is essential for the basic operation of today s densitometers. Basic Statistical Concepts Mean: commonly called the average, is the sum of the data values divided by the number of values. Standard Deviation (SD): a measurement of the variability that indicates the spread of the data around the mean, the smaller the spread, the smaller the SD. In DXA, a smaller SD is better. Percent coefficient of variation (%CV): the ratio of the SD divided by the mean of a normal distribution expressed as a percentage. This measurement allows for the comparison of the variability between different data sets and is frequently used to express precision. A smaller %CV means less variability which is preferred in densitometry. It is calculated as follows: %CV = (SD/Mean) x 100 Standard Scores Densitometry reports typically include non-diagnostic images, graphs and tables. The tables provide 3 bone density parameters reported as: bone mineral content (BMC) in grams, area in square centimeters, and BMD in grams per square centimeter. The BMC in the path of the x-ray beam is divided by the area of bone that results in an estimated BMD. The formula for calculating BMD is: BMD (g/cm 2 ) = BMC (g) Area (cm 2 ) Example: if the total lumbar spine BMC is 50g, and the area is 60cm 2, figure the BMD. BMC (50g) divided by ( ) the area (60cm 2 ) =.83, so the BMD is.83 g/cm 2. In order to express the BMD measurements in a clinically interpretative form, they are compared to normative databases. These results are reported as SD above or below the mean peak bone mass for a healthy young adult reference population, or SD above or below the mean for a healthy age-matched reference population. The SD appears on the report as a T and Z score. T-score: the number of SDs above or below the mean BMD of young, normal, sex-matched individuals with peak bone mass. It is the most clinically relevant value for diagnosis and is calculated as follows: T-score = measured BMD - young adult mean BMD young adult population SD X-RAY NEWS VO LUME 24, ISSUE 3 Page 7

8 Z-score: the number of SDs above or below the mean BMD for persons of the same age, sex, and ethnicity. It is not the standard for diagnosis but utilized to evaluate for secondary diagnosis in specific non-postmenopausal populations and is calculated as follows: Z-score = WHO Diagnostic Criteria In 1994, the World Health Organization (WHO) established the diagnostic categories based on T-score measurements by DXA devices at the spine, hip, or forearm. The following table lists the densitometric classifications: Advances in research demonstrated limitations and the realization that fracture risk could not be diagnosed by BMD alone. This lead to the fracture risk assessment (FRAX) project which was supported and endorsed by many skeletal health organizations including the International Society for Clinical Densitometry (ISCD). This is a nonprofit organization founded in June of 1993, which provides a central resource for a number of scientific disciplines with an interest in the assessment of skeletal health. They have official position conferences which establish standards or guidelines. Several ISCD positions regarding diagnosis are as follows: 1. Skeletal sites to measure: A. Measure BMD at both the PA spine and hip in all patients. B. Forearm BMD should be measured under the following circumstances: hip and/or spine cannot be measured or interpreted, measured BMD - age matched mean BMD age matched population SD Table 2 Osteoporosis Defined by BMD T-scores Normal Osteopenia (low bone mass) Osteoporosis Severe (established) Osteoporosis SD and above SD thru -2.4 SD SD and below SD and below with 1 or more fractures hyperparathyroidism, and obese patients that exceed the table weight limit. 2. In post-menopausal women, T-scores are the preferred score for diagnosis and the WHO densitometric classification is applicable. 3. Osteoporosis may be diagnosed in postmenopausal women and in men age 50 and older if the T-score of the lumbar spine, total hip or femoral neck is -2.5 or less. In certain circumstances the 33% radius (also called 1/3 radius) may be utilized. Diagnoses at any other ROI are not endorsed. 4. In pre-menopausal women and males under the age of 50 and pediatric populations, the Z-score not T-score, is preferred. 5. Osteoporosis cannot be diagnosed in men under the age of 50 on the basis of BMD alone. 6. For the purpose of Z-score calculation, the patient s self-reported ethnicity should be used. 7. The term osteopenia is retained, but low bone mass or low bone density is preferred. Review the following DXA scans to determine the WHO diagnosis based on any of the ISCD endorsed sites. These reports show inverted images, which are normally viewed as white but shown here as black. Figure 6 Focus on the numerical tables. The total T-score for the spine is -1.9, left total femur -0.6 and -0.7 for the right total femur. Based on this, the diagnosis according to WHO would be osteopenia or low bone mass. In this particular report, note that the left and right femur graphs display the femur neck values and not the total femur measurement. Frequently the femur neck BMD may be lower than the other femur ROIs, as noted in the right femur neck measurement. Graphic display of the lowest region is beneficial as an educational tool for patients. The graph is more easily understood than the scores. Fig. 6 GE Lunar Prodigy DXA report Figure 7 The total T-score for the spine is -0.1, left total femur 0.1 and -0.4 for the right total femur. They are all within the WHO normal limits. However, note that the patient is in Page 8 X-RAY NEWS VO LUME 24, ISSUE 3

9 the osteopenia range as shown in both femur graphs. If you look back at the numerical table, the left and right femoral neck is -1.4 and -1.5, respectively. Since the femur neck is an endorsed site for diagnosis, osteopenia is the appropriate diagnosis according to the WHO criteria. ISCD official positions state that the term osteopenia is retained, but low bone mass or low bone density is preferred. Fig. 8 GE Lunar Prodigy DXA report Fig. 7 GE Lunar Prodigy DXA report Figure 8 The total T-score for the spine is 0.3, right total femur 0.2 and -4.3 for the left total femur. Based on the total T-score of the left femur, the diagnosis of osteoporosis can be made. However, the interpreting physician consulted with a bone specialist and the diagnosis was concluded to be left femur localized osteoporosis, secondary to lower extremity hemiparesis. Note that there are more calculated regions on the numerical tables in this report than the previous reports. The reporting is customized and set up in accordance to the needs and preference of the department or interpreting physician. Although many values are shown here and can be overwhelming, remember to keep in mind the recommended reporting sites. Figure 9 Patient history: Height: 65 inches, Weight: 200 pounds; 5 years postmenopausal without replacement; minimal dietary calcium intake without supplementation of calcium or vitamin D; no routine exercise; no history of fracture, surgery or smoking; no high risk medications; no additional notable history. This follow-up report shows the comparison of 3 scans done on the same patient over a span of 5 years. For each measurement date, note the patient s age, the T-score and the percentage of change from the previous scan. There is also a column that indicates if there is a significant change, but some clinics prefer to calculate their own significant change based on a precision assessment. The focus of follow-up scans is the rate of change based on the BMD values, not the T-score. At this point, the T-score is only used as a reference for comparison to a normative database. Therefore, the computed percentage rate of change is derived from calculating the difference in the BMD units of measurements (g/cm2) from the previous scan. The T-score is utilized for the initial diagnosis but serial or follow-up scans are to monitor the Fig. 9 Portion of a follow-up report X-RAY NEWS VO LUME 24, ISSUE 3 Page 9

10 patient s bone changes over time. Note that the T-scores for all sites over the span of 5 years are within normal limits. Also note the percentage of change in the DualFemur total and neck mean from 2006 to Both sites had a drop of 7.1% and 6.8%, respectively. Although the BMD remains within the normal range, this significant bone loss is presumed to be related to the estrogen deficiency; with contributory factors including calcium and vitamin D insufficiency and sedentary lifestyle. The BMD increase of 5.9% in the spine density from 2009 until 2011 is most likely a false or invalid result at this stage of life. Increases in the spine are commonly associated with age-related pathology such as those seen with arthritic changes. An increase in the spine BMD with this patient s history would be questionable and not the expected outcome. Supplemental Assessments Today s densitometers have the capability to assess more than just the BMD. Some enhanced features include the ability to track bone loss, detect vertebral fractures, determine fracture probability, measure body composition, identify abdominal aortic calcification, and atypical femur fractures. Several descriptions of these assessments follow. Fracture Risk Assessment The WHO definition of osteoporosis is used for diagnosis and fracture risk assessment. The diagnosis serves as a guide for the intervention and treatment of patients. However, individuals with BMD values above the osteoporosis cutoff point have osteoporotic fractures. Therefore, the use of BMD values alone to determine true fracture risk presented some concerns that lead to the development of the FRAX. It was developed to calculate the 10-year probability of a hip fracture and the 10-year probability of a major osteoporotic fracture. FRAX is a computer based algorithm that was developed to help the healthcare provider identify and treat patients with a high risk for fractures based on these established clinical risk factors, as shown in Table 3. The FRAX tool identifies patients with clinical risk factors that are between the ages of 40 and 90. It is not indicated for use with premenopausal patients, those currently receiving treatment, or those that have no available femoral neck BMD value. It consists of a variety of questions in which the answers are entered into a calculation along with the femoral neck BMD value. A fracture prediction is obtained and a fracture probability of 3% for a hip fracture or 20% for major osteoporotic fracture is of concern, and should be evaluated for treatment. Originally the FRAX calculation tool required downloading, but it is now incorporated into the manufacturers software. A sample of the FRAX calculation tool follows on the next page. While FRAX is an effective tool, it has limitations that should be kept in mind. The clinical risk factors listed require a yes or no answer, and do not take account the amount or how many. For example, the dose of the medications is just as important as the type, and the risk of fractures increase with the number of prior fractures. Also, the FRAX tool uses only the BMD of the femoral neck and not the other measurement sites. Although falls are known to be a strong predictor of fracture risk, the fall related risk factors have not been included. Table 3 Risk Factors Age The model accepts ages between 40 and 90 years. If ages below or above are entered, the program will compute probabilities at 40 and 90 year, respectively. Sex Weight Height Previous fracture Parent fractured hip Current smoking Glucocorticoids Rheumatoid arthritis Secondary osteoporosis Male or female. Enter as appropriate. This should be entered in kg. This should be entered in cm. A previous fracture denotes more accurately a previous fracture in adult life occurring spontaneously, or a fracture arising from trauma which, in a healthy individual, would not have resulted in a fracture. Enter yes or no (see also notes on risk factors). This enquires for a history of hip fracture in the patient's mother or father. Enter yes or no. Enter yes or no depending on whether the patient currently smokes tobacco (see also notes on risk factors). Enter yes if the patient is currently exposed to oral glucocorticoids or has been exposed to oral glucocorticoids for more than 3 months at a dose of prednisolone of 5mg daily or more (or equivalent doses of other glucocorticoids) (see also notes on risk factors). Enter yes where the patient has a confirmed diagnosis of rheumatoid arthritis. Otherwise enter no (see also notes on risk factors). Enter yes if the patient has a disorder strongly associated with osteoporosis. These include type I (insulin dependent) diabetes, osteogenesis imperfecta in adults, untreated long-standing hyperthyroidism, hypogonadism or premature menopause (<45 years), chronic malnutrition, or malabsorption and chronic liver disease. Alcohol 3 or more units/day Enter yes if the patient takes 3 or more units of alcohol daily. A unit of alcohol varies slightly in different countries from 8-10g of alcohol. This is equivalent to a standard glass of beer (285ml), a single measure of spirits (30ml), a medium-sized glass of wine (120ml), or 1 measure of an aperitif (60ml) (see also notes on risk factors). Bone mineral density (BMD) (BMD) Please select the make of DXA scanning equipment used and then enter the actual femoral neck BMD (in g/cm2). Alternatively, enter the T-score based on the NHANES III female reference data. In patients without a BMD test, the field should be left blank (see also notes on risk factors) (provided by Oregon Osteoporosis Center). International Osteoporosis Foundation. Reprinted with permission from the IOF. All rights reserved. Page 10 X-RAY NEWS VO LUME 24, ISSUE 3

11 FRAX is a sophisticated risk assessment instrument, developed by the University of Sheffield in association with the World Health Organization. It uses risk factors in addition to DXA measurements for improved fracture risk estimation. It is a useful tool to aid clinical decision making about the use of pharmacologic therapies in patients with low bone mass. The International Osteoporosis Foundation supports the maintenance and development of FRAX. International Osteoporosis Foundation. Reprinted with permission from the IOF. All rights reserved. Fig. 10 FRAX calculation tool Fig. 11 GE FRAX report Vertebral Fracture Assessment Advances in densitometry have led to the availability of vertebral imaging for fracture evaluation with low radiation doses. The advanced quality of spine images using DXA have made it possible to recognize vertebral fractures utilizing low intensity single or dual energy x-rays on central scanners. GE Lunar labels this technology as lateral vertebral assessment (LVA) and Hologic uses instant vertebral assessment (IVA). Although the manufacturers of densitometry equipment label the lateral imaging differently, vertebral fracture assessment (VFA) is the commonly applied and recognized term. VFA can be a very useful tool to aid in identifying vertebral fractures. The presence of fractures is a strong predictor of patients future fracture risk. The detection of fractures involves the use of qualitative or quantitative morphometric methods. Morphometry is a technique that measures size and shape. Qualitative methods X-RAY NEWS VO LUME 24, ISSUE 3 Fig. 12 Lateral VFA primarily assess the shapes of the endplates and the anterior vertebrae for breaks. Quantitative methods are considered more reliable and detect the vertebral deformities based on the reduction in the heights of the vertebrae relative to the height of adjacent structures. The Genant method also called the semi-quantitative (SQ), reintroduced the qualitative feature of vertebral shape along with the approximate losses of vertebral height. It is the current clinical method of choice and less time consuming than the quantitative morphometry method. Thoracic and lumbar fractures are unique in that many are not detected and diagnosed clinically. VFA allows lateral viewing of these areas, from the T-4 to L5 spine levels, to evaluate for fractures. The ISCD indications for lateral spine imaging with standard radiography or densitometric VFA is indicated when the T-score is < -1.0 and 1 or more of the following is present: women age 70 years or men age 80 years, historical height loss > 4 cm (>1.5 inches), self-reported but undocumented prior vertebral fracture, or glucocorticoid therapy equivalent to 5 mg of prednisone or equivalent per day for 3 months. Although vertebral fractures are underdiagnosed, their presence is a substantial risk for subsequent fractures, independent of the BMD. The use of VFA technology offers the ability to detect these fractures with the advantages of reduced radiation exposure to the patient, cost effectiveness comparative to other modalities, and the convenience of being done at the same time as the DXA. Although the technology has decreased sensitivity in detecting mild fractures and lacks the ability to view the spine superior to T-7, there is significant evidence supporting the benefit of VFA use. It is important to emphasize that VFA is designed to detect vertebral fractures only and additional imaging may be necessary if any other abnormality is suspected. Fig. 13 Lateral VFA Image courtesy of GE Healthcare Pediatric Bone Densitometry Recent interest in bone growth and development of the pediatric patient has created the need to expand the currently available bone densitometry information. As discussed earlier, peak bone mass is gained by the time early adulthood is reached and then continues throughout life with periods of gradual or accelerated loss. With this in mind, you can understand the Page 11

12 importance of achieving the greatest peak mass as possible during the growing years. If optimal peak mass is not obtained, skeletal health begins with a deficit and increases the risk of fracture. Bone mass accumulation in pediatric and Fig. 14 Pediatric DXA scan Image courtesy of GE Healthcare adolescents can be influenced by many factors including: disease, nutritional issues, medications, environmental elements, and lack of weight bearing exercises. Measurements of bone density and body composition are of value in assessing the skeletal health of patients who are at risk. Developing children are sensitive to radiation and the principles of radiation safety must be applied. Image Gently is a collaborative initiative of radiology professional organizations (as well as other groups and individuals) that was launched in Its goal is to change radiology practice by increasing the awareness of opportunities for lowering radiation dose when imaging children. Methods to assess bone development in the pediatric patient include DXA, QCT, and QUS. Wide spread availability, reasonably low costs, and relatively low radiation exposure are some benefits of using DXA in pediatric patients as well as being the preferred method for assessing BMC and areal BMD (abmd) measurements. The posterior-anterior (PA) spine and total body less the head (TBLH) are the suggested sites in most pediatric subjects. Due to the variability of skeletal development in the hip of growing children it is not an endorsed site. It is essential for a DXA operator working with this patient population to have a good understanding of pediatric skeletal development and additional knowledge and training in pediatric densitometry. Software with pediatric upgraded algorithms is necessary to detect the bone edge and provide a BMD value for females and males under the age of 20. T-scores are not commonly utilized because they are related to peak bone mass and pediatric patients have not yet reached peak bone mass. For this reason the ISCD recommends the Z-score, not the T-score, for diagnosis and management of the pediatric patient. Current diagnosis of osteoporosis in pediatric populations as defined by ISCD includes the following: 1. The finding of 1 or more vertebral compression fractures is indicative of osteoporosis in the absence of local disease or high-energy trauma. 2. The diagnosis of osteoporosis in children and adolescents should not be made on the basis of densitometric criteria alone. 3. In the absence of vertebral compression fractures, the diagnosis of osteoporosis is indicated by the presence of both a clinically significant fracture history and BMD Z-score A clinically significant fracture history is 1 or more of the following: Two or more long bone fractures by age 10 years. Three or more long bone fractures at any age up to age 19 years. Additional established pediatric DXA interpretation parameters can be obtained from the ISCD website. Body Composition Body composition is not included in the ARRT content specifications; however, the increased utilization in research and the weight loss industry justifies basic coverage. DXA scanning was primarily designed for the diagnosis of osteoporosis and was initially applied to studies of the bone density at the lumbar spine, femoral neck, and forearm sites. DXA has been expanded to include the total skeleton and its regional parts, as well as soft-tissue composition measurement. The assessment which utilizes a 3 compartment method of (1) fat mass, (2) lean mass, and (3) bone mineral mass, can now be easily measured using a single whole body DXA scan with high precision and low scanning time. The DXA application of body composition for clinical indications include (1) monitoring obese patients undergoing bariatric surgery or other weight reduction programs, (2) prevention and management of cardiovascular and metabolic diseases, (3) management of different chronic diseases, (4) management of patients with behavioral eating disorders, and (5) monitoring patients with muscle weakness or poor physical functioning. Various regions of the body are defined as cuts on the image that are placed by the operator. These regional values and total body values are reported as grams of fat, lean, and bone mineral. The head is often excluded from the total regions due to the density of the skull. Defined specialized ROIs may include android and gynoid regions which are appropriate areas of interest when evaluating cardiovascular disease and the fat distribution effects. Fig. 15 GE Lunar Prodigy total body scan report Page 12 X-RAY NEWS VO LUME 24, ISSUE 3

13 Contraindication for DXA body composition includes pregnancy, exceeding the scanner weight limits, and recent administration of contrast material. Limitations in the use of clinical DXA for total body composition include body habitus and artifact. The manufacturer s algorithms are based on a normal body mass index (BMI) and extreme variances in the weight, whether underweight or overweight, has an effect on the report outcome. Knowledge and understanding of the role that body composition plays in the assessment and management of some diseases and the incidence of obesity in today s population have made body composition with DXA technology an appropriate application. Serial or Follow-up Scan Past experiences indicate that manufacturer training provided comprehensive instructions for scanning and analyzing but overlooked guidelines specific for serial scans. This is, in part, due to the fact that the DXA operators would not perform serial scans for several years. Once the patients started to return for serial scans, operators began to realize that there were some additional protocols that are unique to serial scans. Essentially that information had been self-taught until an increased awareness was initiated. The importance of serial scans had been underestimated until it became apparent that they are an integral part of patient care and management of bone loss. Serial scan guidelines are offered below: The patient s baseline biography must be retrieved and updated with an accurate height and weight, the operator s identification, and any other changes. Do not enter as a new patient. Use the same scanner that was used for the baseline scan, or a new scanner that has been cross calibrated with the old scanner. Duplicate the positioning of the baseline scan. It is crucial that the same positioning is utilized for an accurate comparison. This ensures that the change in the bone is factual or real and not related to technical issues. Use the same acquisition parameters as the baseline. The scanners usually alert that there is a change in the scan mode. Unavoidable circumstances such as extreme weight variation changes the scan mode and impact the values to some extent. Assure that the same ROIs as the baseline are used. Again, this is to confirm that the same areas are being compared since we are monitoring the actual change in bone. Use the compare or copy function following manufacturer recommendations. This reduces operator dependence and influences the BMD changes with optimal precision. This function allows the bone map from a previous scan to be copied onto the current scan image and provides a visual confirmation of positioning and ROI duplication. If the bone map does not fit precisely, and the positioning and ROIs appear correct, there may be a structural change. Limit the number of operators performing the DXAs and they should work equivalently. This is an ISCD recommendation to improve precision and limit the operator dependent inconsistencies. Ideally a patient Fig. 16 Hologic serial scan report Fig. 17 GE Lunar Prodigy serial scan report X-RAY NEWS VO LUME 24, ISSUE 3 Page 13

14 should have serial scans performed by the same operator who performed the baseline scan. Standards are compromised when there are more operators and this ultimately influences the accuracy and precision. Develop and adhere to protocols or the SOP to maintain high standards which improves the accuracy and precision. Document all deviations of the SOP or any information that needs to be considered in the final outcome. Calculate each operators precision error in order to determine the least significant change (LSC) value which is used in some clinics and endorsed by ISCD. Evaluate the BMD change, not the T-score change. Remember that the baseline DXAs are important for diagnostic purposes and serial scans compare the BMD change in subsequent scans to determine efficacy of treatment or monitor bone loss. The databases are periodically updated and may change but the patient s actual BMD measurement is an established value being compared over time. This comparison or change reflects a true BMD change in the patient, providing that all the scan protocol criteria was met. Acquisition and Analysis Producing a quality scan for diagnostic purpose requires a proper acquisition and correctly analyzed image. Although both are often thought of as one-step, think of it as a two-step process; first acquire a good scan and secondly, analyze it appropriately. Manufacturer specific acquisition and analysis guidelines must be followed thoroughly because the software applications were designed with this in mind. Since manufacturer procedures and requirements vary between the different manufacturers, model specific manufacturer training is highly recommended. Manufacturer training for the specific equipment that is being operated is also required by some states for licensure or certification. The following information is just an overview of scan acquisition and analysis. Future articles will provide a more in depth presentation on each of the sites that are typically scanned and the potential causes of problems related to acquisition and analysis of those sites. Scan Acquisition The acquisition of a good scan begins with basic knowledge of anatomy related to the routine scan sites. Relevant patient history, proper patient preparation, and accurate positioning are all contributory aspects that are completed prior to actually scanning the patient. It is thought that artifact in the image but outside the ROI has little or no impact. In actuality, the extent of the artifact influence is unknown. Operators should not assume that the attenuation properties of the artifact have no influence on the bone edge algorithms. Every operator should strive to acquire all scans with absolutely no external artifact. The internal artifact encountered requires documentation. After the scan is acquired the digital images should demonstrate and display all the appropriate anatomy for that scan type. A well acquired scan prior to the analysis is critical and it has to be rescanned if not correct. Scanners automatically analyze the scan once it is obtained, whether the acquisition is correct or not. When the auto analysis is inaccurate or a previously analyzed scan is discovered to be incorrect, it can be reanalyzed if the acquired scan image exhibits the appropriate anatomy with no motion or artifact. However, if the scan acquisition does not provide the correct criteria for the analysis, no amount of reanalyzing can resolve the problem. General Acquisition Criteria Regardless of the manufacturer, there are some general acquisition guidelines that apply to all: use appropriate scan speed or mode for the body habitus or build, correctly demonstrate anatomy for each scan type or site, eliminate motion, remove attenuating objects, document all artifacts, and utilize the manufacturer specific positioning aids or devices shown below. Fig. 18 Block Fig. 19 Norland femur Fig. 20 GE dual femur Fig. 21 Hologic femur Fig. 22 Hologic forearm Fig. 23 GE lunar forearm Fig. 24 VFA lateral positioner Page 14 X-RAY NEWS VO LUME 24, ISSUE 3

15 Scan Analysis Although manufacturers analysis procedures vary, they are structured to guide the operator through the process with minimal intervention. An automated analysis is generated once the acquisition is obtained and no manual operator analysis involvement is necessary unless the analysis is obviously inaccurate. Manual intervention or changes by the operator should only be done when necessary and the specific manufacturer procedures should be followed. The importance of manufacturer specific training cannot be emphasized enough and following the manufacturer guidelines is essential for analysis quality. Some examples of analyzed scans are shown in Fig. 25 thru Fig. 30. In each of the sites, the scan images on the left all have poorly defined ROIs. The scans on the right were re-analyzed with corrected placement of the ROIs in accordance with the manufacturer guidelines. In Fig. 25, the intervertebral (IV) lines are misplaced beginning with L2- L4, inaccurately defining the disc space. In Fig. 26, the IV line markers have been correctly placed to identify the appropriate disc space. In Fig. 27, the bottom edge of the global region should be further away from the lesser trochanter. This is analyzed per Hologic guidelines because the femoral Fig. 27 Hologic femur Fig. 28 Hologic femur neck box has 1 corner anchored at the greater trochanter and the other 3 in non-bone tissue. Fig. 28 displays the global region with wider margins below the lesser trochanter. This changed the other ROI placements slightly by the corrective action. In Fig. 29, the global region is placed too high and includes the wrist bones. The scanner measured them as the ultradistal ROI and misplaced all the other ROIs. In Fig. 30, the global box is Fig. 25 Hologic spine Fig. 26 Hologic spine Fig. 29 Hologic forearm Fig. 30 Hologic forearm moved down for correct placement at the tip of the ulnar styloid process. All of the ROIs are now appropriately identified. The GE femur scan in Fig. 31 has 1 corner of the femoral neck box that includes greater trochanteric bone. GE guidelines require the 4 corners of the femoral neck box in tissue, not in or attached to any bone. BMD Quality A good quality image for interpretation is not the intended goal but confirms correct ROIs and positioning. An accurate and precise quantitative measurement on stable equipment with operator scanning consistency is the desired outcome in densitometry. Two important performance measurements in densitometry are accuracy and precision. Although the 2 words accuracy and precision can be synonymous, they are differentiated in DXA. Accuracy reflects the true bone density or actual measurement of the site as compared to a known standard. This is important when making the initial diagnosis at baseline. Precision expresses reproducibility or consistency of repeat measurements. This is most important for determining or monitoring patients BMD changes over time. There are many factors that affect the accuracy and precision of Fig. 31 GE femur scan densitometry devices. Accuracy is usually affected by the technology whereas precision is mostly affected by the operator. The densitometry scan accuracy is influenced primarily by the scanner calibration and software updates. The scanner precision is determined by longitudinal quality control (QC) procedures set by the manufacturers. The operator affects the accuracy by appropriate selection of the scan type and mode. Operator precision is influence by the ability to duplicate the positioning, scan parameters, and ROI placement on all follow-up or serial scans. Patient variables such as abnormal anatomy, very low bone mass, and/or extremely thick or thin body habitus reflect the greatest precision errors. Factors that Impact Analysis In addition to properly labeling and defining the ROIs, the importance of anatomy knowledge needs to be reinforced when discussing analysis. Comprehension of basic anatomy must exist in order to recognize variant or abnormal anatomy that influences scan results. Other influential factors in addition to variant anatomy include artifacts or foreign objects. In radiology, the definition of artifact is an undesirable characteristic found on the image that, in most cases, could be avoided by the radiographer. A foreign object is anything in the radiograph that is not a natural part of the patient anatomy but is usually unavoidable by the X-RAY NEWS VO LUME 24, ISSUE 3 Page 15

16 radiographer. In densitometry, artifacts and foreign objects are typically referred to as artifacts. Artifacts contained in DXA scans can create a number of obstacles for the densitometry operator. Determining if an artifact is actually present can be difficult because the digital image and limited view does not always produce an optimal image. Standard practices, knowledge of variances, and experience, greatly improve the operator s ability that ultimately impacts the report, diagnosis, and disease management of the patient. Standard Practices The DXA images, especially in older scanners, diminish the ability of revealing many factors affecting the scan analysis. Establishing routine procedures or standard practices to follow when there is a questionable or difficult analysis, assist in the detection of influential factors, and should become a requirement in every densitometry department. Some standard procedures or practices are offered below. Fig. 32 Artifacts found in the spine, femur, and forearm Utilize image contrast or invert the image and look for obvious light or dark spots. This will not affect BMD results. Analyze the scan and look for sharp differences in the BMD, BMC, or area of adjacent vertebrae. Utilize the compare or copy function with serial scans and inspect for structural changes if the bone map doesn t align properly. Question the patient thoroughly about surgeries, fractures, congenital anomalies, artifacts or foreign objects such as surgical clips, staples, pins, screws, rods, or implants. This prevents unnecessary scanning of a non-diagnostic site and forewarns the operator. If an artifact is identified to be external, remove it and rescan. If an artifact is temporary such as barium or contrast dyes, reschedule scan. If internal artifact is present in the spine area, exclude involved vertebrae. Exclude the site for evaluation if there is only 1 evaluable vertebra. If artifact is visually apparent in the femur, scan the other femur. If it is determined that there are bilateral femur prosthesis or biomechanical devices, scan another site such as the forearm. If there is motion noted on the scan, the patient must be rescanned. Motion influences the ability and accuracy of the Fig. 34 Motion bone edge detection. Quality Control The original indications for bone mass measurements from National Osteoporosis Foundation (NOF) and guidelines for the clinical applications for bone densitometry from ISCD, called for strict QC procedures at clinical sites performing densitometry. Such procedures are crucial because alterations in the functioning of the machines occur despite the precision and accuracy of densitometers. In the past, the responsibility of detecting a shift or drift in the QC plotted graphs, prior to the need for service, typically fell on the operator. Today's automated densitometer QC procedures indicate a pass or fail condition before generating the report. Regular scanning on a anthropomorphic (human-like) phantom or calibration phantom allows monitoring of scanner stability by detecting shifts or drifts in the machine values before outright mechanical failure occurs. Shifts are abrupt changes and drifts are more subtle as shown in the plot graph illustration. These alterations require corrective action to ensure continued accuracy and precision. If the QC data point is outside the established limits it is flagged as a fail, which indicates that the scanner is out of control (OOC). Fig. 33 External spine artifact Fig. 35 Plot graph depicting a shift and a drift Procedures for Quality Control QC procedures verify that the scanner is functioning Page 16 X-RAY NEWS VO LUME 24, ISSUE 3

17 properly by performing various tests to detect mechanical or operational failures. Each manufacturer has individual quality control guidelines that must be performed at established intervals, requiring the use of a phantom of known BMD, BMC, and area values. Hologic systems have a continuous internal calibration during scanning and the QC procedure does not calibrate the system. If the QC procedure is not performed prior to scanning patients, an error message occurs and scanning is not allowed. The procedure involves completing an automatic analysis using an anthropomorphic phantom. Daily phantom scans are entered and plotted and compared to previous QC scans to tract the changes. The daily QC data point should fall within the upper and lower QC limits. These limits are based on Shewhart control charts and the 1.5% Rule (+/- 3 SD). If the data point falls outside the QC upper or lower limit, perform the procedure 2 more times. If both the second and third data points fall outside the QC limits, contact Hologic. If the second and third BMD data points fall within the limit and the CV value is < (less than or equal to) 0.60%, you may proceed with scanning patients. GE Lunar provides 2 phantoms for different purposes; 1 phantom known as the calibration block is used for daily quality assurance (QA) functions. The mechanical operation and calibration of the scanner are tested, confirming accurate, calibrated and stable equipment. If the QA scan procedure fails, repeat the procedure a second time and contact the manufacturer if not within the normal limits. The aluminum spine phantom is designed to mimic a region of the skeleton and it is used for QC. The QC is usually done by a service representative after maintenance or Fig. 36 Hologic QC anthropomorphic phantom Fig. 37 QC plot graph BMD report Fig. 38 GE calibration block Fig. 39 GE QC aluminum phantom service, to detect changes in the BMD values before QC failure. Every QC program at DXA facilities should adhere to manufacturer protocols for diagnostic quality, patient safety, and system maintenance. It is imperative that the procedures be followed per the manufacturer guidelines. If not recommended in the manufacturer protocol, ISCD advises the following procedures: perform daily QC scans prior to patient scanning, perform weekly phantom scans for any DXA system as an independent system calibration, plot and review data from calibration and phantom scans, verify the phantom mean BMD after any service is performed, establish and enforce corrective action thresholds that trigger a call for service, maintain service logs, and comply with government inspections, radiation surveys, and regulatory requirements. Precision Assessment Densitometry precision can be measured in vitro with an inanimate object, such as the phantoms used in daily QC. This is important to check for shifts or drifts and the scanner accuracy. Precision can also be done in vivo using living tissue to follow changes in BMD over time. This is important to determine that the change in BMD is a true value or an actual change rather than operator or scanner error. Precision assessment measures the ability of the scanner and the operator to reproduce technical factors of serial scans. It is done to calculate the precision error and the least significant change (LSC) for each measurement site. The LSC must be known to be confident that a BMD change is real and not due to technical error. Precision errors are either equipment or operator related. Assuming that the QC protocols have been met and the scanner is functioning properly, the major source of precision error in clinical densitometry is the operator. Proper positioning of the patient and correct scan analysis are the most important factors affecting measurement precision. The most common sources of serial spine scan variations is poor positioning, incomplete acquisition of L1-L4, inconsistent labeling of vertebrae, and misplaced intervertebral markers. Proximal femur variations are largely the result of poor rotation and positioning of the leg, inconsistent sizing of the ROIs and improper placement of the femoral neck box. Proper training in positioning and analysis consistency can minimized operator precision error and favorably impacts the densitometry departments BMD quality. ISCD precision assessment protocols and procedures are as follows: 1. Each DXA facility should determine its precision error and LSC. 2. The manufacturer precision error should not be used. 3. Every operator should perform an in vivo precision assessment using patients representative of the X-RAY NEWS VO LUME 24, ISSUE 3 Page 17

18 clinic s patient population. 4. Each operator should do 1 complete precision assessment after basic scanning skills have been learned and after having performed approximately 100 patient scans. 5. If a DXA facility has more than 1 operator, an average precision error combining data from all operators should be used to establish precision error and the LSC for the facility, provided the precision error for each operator is within an established range of acceptable performance. The minimum acceptable precision error for an individual operator is listed below and retraining is required if the values are worse. Lumbar Spine: 1.9% (LSC=5.3%) Total Hip: 1.8% (LSC=5.0%) Femoral Neck: 2.5% (LSC=6.9%) 6. A repeat precision assessment should be done if an operator's skill level has changed or if there is a change in the DXA system or operators. 7. Precision assessment should be standard clinical practice. Precision assessment is not research and may potentially benefit patients. It should not require approval of an institutional review board. The assessment procedure involves: measuring 15 patients 3 times or 30 patients 2 times, repositioning the patient after each scan type, completing scans within a certain time frame, participating consensual patients, and compliance with local radiologic safety regulations. Fig. 40 ISCD precision assessment tool Assistance with the precision assessment can be obtained from the densitometer manufacturers or ISCD. The ISCD Precision Assessment tool calculates the precision error and the LSC after the scan values of the patient scans are entered by the operator. This tool and additional resources are available at the ISCD website. Cross-Calibration of DXA Systems There are several factors that make it impossible to compare BMD or the LSC between facilities or machines without cross-calibration. This is mainly due to manufacturer technology variations such as (1) different dual energy production, (2) different detectors, (3) different calibration methods, (4) different bone edge detection algorithms, and (5) different ROIs. Due to these differences cross-calibration is required in order to compare the data of different scanners or between facilities. The following are ISCD cross-calibration requirements: When changing hardware, but not the entire system, or when replacing a system with the same technology (manufacturer and model), cross-calibration should be performed by having the same technologist do 10 phantom scans, with repositioning, before and after hardware change. If a greater than 1% difference in mean BMD is observed, contact the manufacturer for service and correction. When changing an entire system to the same manufacturer using a different technology, or when changing to a system made by a different manufacturer there are several approaches to crosscalibration. One approach is to scan 30 patients representative of the facility s patient population once on the initial system and then twice on the new system within 60 days. Measure those anatomic sites commonly measured in clinical practice, typically spine and proximal femur. Calculate the average BMD relationship and LSC between the initial and new machine using the ISCD DXA Machine Cross- Calibration Tool from the ISCD website. Use this LSC for comparison between the previous and new system. Inter-system quantitative comparisons can only be made if cross-calibration is performed on each skeletal site commonly measured. Once a new precision assessment has been performed on the new system, all future scans should be compared to scans performed on the new system using the newly established intra-system LSC. If a cross-calibration assessment is not performed, no quantitative comparison to the prior machine can be made. Consequently, a new baseline BMD and intra-system LSC should be established. Equipment Maintenance Acquiring a manufacturer preventative maintenance contract proves a worthwhile investment. It is imperative to scanner precision and the quality of patient care. The benefits outweigh the cost especially when you consider printer, computer, mechanical, hardware, and software replacement costs. The convenience of faster service and assistance with any issues that may arise is available to contract holders. Fig. 41 DXA accessory cart Maintaining the condition of the scanner and accessories takes little effort and the task consists of: (1) keeping the table pad clean and stain free, (2) maintaining dust free equipment, (3) organizing accessories for ease of access, and (4) preventing mechanical stress to the scanner arm in 2 ways: not storing items on it and not allowing patients Page 18 X-RAY NEWS VO LUME 24, ISSUE 3

19 to pull on it. In addition to proper equipment care, some equipment safety practices include: inspect pinch points on equipment & keep patients hands clear of those areas, examine electrical cords for any damage or placement which may be hazardous, follow proper power down and shut off of equipment, assure that the DXA table scanner has its own designated outlet, follow proper usage of emergency stop button, and post caution and safety signs. It s important to keep and maintain a service log for repairs. When relocating DXA scanners, recalibration is necessary to maintain QC. When equipment hardware is upgraded, it is necessary to recalibrate and reestablish baseline data for follow-up scans. Cross-calibration is required when new equipment is acquired, upgraded, or when there is a change in manufacturer. The manufacturer usually assists with the cross-calibration. File and Database Management Basic knowledge of the personal computer as it pertains to DXA instrumentation is essential for the DXA operator. The scanner is computer driven and the scan acquisition, analysis and archiving is computer controlled. Operators must understand the process and frequency of back up, archiving, locating, and restoring functions. The hardware is the physical components of the computer, such as the central processing unit (CPU), monitor, Fig. 42 DXA computer station keyboard and storage devices. The DXA software controls the scanning from the start to the finish, in addition to the calculations and report results. Software upgrades for densitometry comes from the manufacturer. Be sure to upgrade immediately and follow the instructions completely and do not install any software without manufacturer authorization. Digital networking allows a DXA scan to be done at 1 location and sent to another for interpretation or review. Picture Archiving and Communications System (PACS) convey images from all modalities to a digital archive and allows transmission of the images from the archive to a viewing station, workstation, or a remote station. Backup and Archiving The manufacturers specifications for data maintenance should be followed and general guidelines include a backup and archive of phantom scans, patient s scans, and all QC information. Storage of backup data off site is highly recommended. Some of the data storage and retrieval terms specific to densitometry are as follows: 1. Backup or the process of backing up refers to the copying of the original data, so that it may be used to restore the original after a data loss event. The original is not removed from the system. 2. Archive in densitometry means that the original data is being removed and stored. This allows the user to save disk space and eliminate accidental manipulation. 3. Locate means determining the storage location of archived scans. 4. Restore means installing an archived scan or data onto the computer hard drive. 5. Retrieve and update biographies; otherwise, you won t be able to utilize the compare and rate of change functions. Summary Bone densitometry is a means of measuring bone mineral density. DXA, considered the gold standard, is the most widely used bone density measurement technology and is used to diagnose, manage, and treat osteoporosis. The ultimate goal is to acquire accurate and precise quantitative measurement by the scanner, which requires careful, consistent positioning and scan acquisition from the operator. The operator performing the scan must be properly trained in equipment operations and scanner quality control, as well as scan acquisition and analysis. References 1. Fisher JM, Gregg PI. The Basics of Bone Densitometry. 13th ed. Radiology Education Seminars, Inc; Bonnick SL. Bone Densitometry in Clinical Practice. 3rd ed. Humana Press; Bonnick SL, Lewis LA. Bone Densitometry for Technologists. 3rd ed. Springer; Long BW, Frank ED, Ehrlich RA. Radiography Essentials for Limited Practice. 5th ed. St Louis, MO: Saunders; Frank ED, Long BW, Smith BJ. Merrill s Atlas of Radiographic Positioning & Procedures. Vol th ed. St Louis, MO: Mosby Inc: Glossary of Terms. American Bone Health Web site. Accessed March 13, Bone Density. Wikipedia Web site. Updated March 7, Accessed March 13, Bone Mass Measurements. Medicare Learning Network. dicare-preventive-services/mps-quickreferencechart- 1.html#BONE_MASS. Accessed March 13, International System of Units. Wikipedia Web site. New_SI.22. Updated March 13, Accessed March 13, Equivalent Dose. Wikipedia Web site. Updated March 5, Accessed March 13, Kanis JA. FRAX WHO Fracture Risk Assessment Tool.Shef.ac.uk Web site. Accessed March 13, McCloskey E. International Osteoporosis Foundation (IOF) Web site. FRAX - Identifying people at high risk of fracture. AX_report_16.pdf. Published Accessed March 13, X-RAY NEWS VO LUME 24, ISSUE 3 Page 19

20 13. Watts N.B., Lewiecki E.M., Miller P.D., Baim S. National Osteoporosis Foundation 2008 Clinician's Guide to Prevention and Treatment of Osteoporosis and the World Health Organization Fracture Risk Assessment Tool (FRAX): What They Mean to the Bone Densitometrist and Bone Technologist. J Clin Densitom. 2008; 11(4) Faulkner KG. Appropriate Use of Lateral Vertebral Assessment. GE Healthcare Web site. _use_of_lva.pdf. Published February Accessed March 25, Schousboe JT, Vokes T, Broy SB, Ferrar L, McKiernan F, Roux C, Binkley N. Vertebral Fracture Assessment: The 2007 ISCD Official Positions. J Clin Densitom. 2008; 11(1) Dual Energy X-ray Absorptiometry(DXA) Procedures Manual. Centers for Disease Control and Prevention Web site. pdf. Published January, Accessed March 15, Baim S, Wilson CR, Lewiecki EM, Luckey MM, Downs Jr RW, Lentle BC. Precision assessment and radiation safety for dualenergy X-ray absorptiometry: position paper of the International Society for Clinical Densitometry. J Clin Densitom. 2005; 8(4) Bone Densitometry Curriculum. American Society of Radiologic Technologists (ASRT). Published Accessed March 15, Body Composition Procedures Manual. Centers for Disease Control and Prevention Web site. sition_procedures_manual.pdf. Published Accessed March 15, Our DXA Technology. Hologic Web site. Published Accessed March 27, ISCD Official Positions. Accessed March 15, Radiation Units and Measurements. Radiation Emergency Medical Management Website. Accessed April 3, Jean M. Fisher, LPN, CBDT, MDXL has been in the field of bone densitometry for 22 years. She spearheaded the first NOF support group in Tennessee in 1996 and was active in a variety of community presentations including guest presentations for several pharmaceutical companies. She was on the technologist faculty for the International Society for Clinical Densitometry (ISCD), served as a board member, a member of the exam certification committee, and as a regional representative for techs in TN and the surrounding states. The past 17 years have been committed to the development and teaching of a bone densitometry course for Radiology Education Seminars, Inc. in Nashville, TN. She has authored several books on bone densitometry for publication and continues to be on the forefront of changes in her field. Donna H. Smith, BS is the editor of X-Ray News, Inc. and the assistant director of Radiology Education Seminars, Inc. where she is part of the developmental team for the bone densitometry course. She received her Bachelor of Science degree from the University of Arkansas at Little Rock in education. She has worked in various aspects of the healthcare field for the last 38 years, authored several medical works for publication, and incorporates natural healthcare into her daily living activities. TN REMINDER X-Ray News covers you for 10 CE credits per year as long as you successfully complete your post-tests timely. If you keep your subscription running, you should always have the required credits in any year for which you might be audited by the state s Audit Unit. Page 20 X-RAY NEWS VO LUME 24, ISSUE 3

21 Image Production in DXA Direct Reading DR-094 Post-Test Approved for 4.0 CE Credits Jean M. Fisher, LPN, CBDT, MDXL and Donna H. Smith, BS 1. Bone densitometry had its origin in which medical specialty? A. nuclear medicine B. radiology C. ultrasound D. neurology 2. DXA is an acronym for? A. double exposure x-ray absorption B. dead energy x-ray acquisition C. dual energy x-ray absorptiometry D. defined experimental x-ray access 3. How many photon energies are used to measure BMD? A. 1 B. 2 C. 3 D Which major manufacturer of DXA equipment utilizes an energy switching filter system? A. GE/Lunar B. Norland C. Swissray D. Hologic 5. Which of the following describes SD? A. average B. SD/Mean, expressed as a percent C. measurement of variability in a set of data around a central (standard) value D. refers to tests performed in/on a living body 6. Which of the following describes %CV? A. measurement of variability in a set of data around a central (standard) value B. average C. refers to tests performed in/on a living body D. SD/Mean, expressed as a percent 7. The formula for calculating BMD is: A. BMD = Area (cm2) BMC B. BMD = BMC (g) Area (cm2) C. BMD = Area (cm2) BMI D. BMD = BMC (g) BMI 8. Which BMD measurement score indicates the number of SDs from the average BMD of young, normal, sex-matched individuals with peak bone mass? A. T-score B. W-score C. V-score D. Z-score 9. Which BMD measurement score indicates the number of SDs from the average BMD for the patient s respective age and sex group? A. T-score B. W-score C. V-score D. Z-score 10. The WHO established diagnostic categories based on which measurements at the spine, hip, or forearm by DXA devices? A. T-score B. W-score C. V-score D. Z-score 11. In Fig. 6, what is the total T-score for the spine? A B C D In Fig. 7, what is the total T-score for the right total femur? A B C D Which assessment tool determines the 10 year probability of a hip fracture or other major osteoporotic fractures? A. FRAX B. DXA C. LVA D. VFA X-RAY NEWS VO LUME 24, ISSUE 3 Page 21

22 14. The FRAX tool uses only the BMD of which site? A. spine B. femoral neck C. forearm D. heel 15. Which advancement in densitometry technology aids in identifying vertebral fractures? A. FRAX B. serial scan C. VFA D. biomarkers 16. Which BMD value is used for the diagnosis and management of the pediatric patient? A. T-score B. Z-score C. SD score D. %CV score 17. What region is often excluded from the total regions in a body composition? A. android B. gynoid C. head D. trunk 18. Which is a FALSE statement regarding serial scans? A. the ROI's must be the same as the baseline scans B. the T-score is the value used for the comparison over time C. the number of DXA operators should be limited and work equivalently D. the acquisition parameters, such as scan mode, should be the same as the baseline 19. Accuracy in densitometry relates to the ability of the system to: A. measure the variability of the spread of data values around the mean B. reflect the actual measurement of the site C. reproduce the same results in repeat measurements of the same object D. reflect the bone measurement by the scanner software 20. Precision in densitometry is the ability to: A. measure the variability of the spread of data values around the mean B. measure the true value of an object C. express reproducibility or consistency of repeat measurements D. reflect the bone measurement by the scanner software 21. Which of the following would influence the accuracy of the scanner's bone edge detection? A. motion B. clothing C. artifact outside the ROI D. certain medications 22. Scanner quality control to detect shift or drift is accomplished by imaging what object? A. phantom B. filter C. grid D. patient 23. When should the densitometry QC be performed? A. daily prior to patient scanning B. daily between each patient C. weekly between every fifth patient D. daily after the last patient 24. What does a precision assessment calculate for each measurement site? A. the precision error and the least significant change (LSC) B. precision error and the true bone density C. the contrast between the bone and the soft tissue D. the true value of an object or tissue 25. Which term refers to the original data being removed and stored? A. backup B. archive C. restore D. locate CURRENT ? Each year, X-Ray News subscribers will receive an reminder to complete CE requirements by December if they renew in the following year. Page 22 X-RAY NEWS VO LUME 24, ISSUE 3

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