Mdiagnosing breast by using x-ray to both breasts. It

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1 Asian Journal of Medical and Clinical Sciences Estimation radiation risk during mammography in Sudan 1 1 1, Hifaa.Mohamed Khair, Hiba.Osman, Abdelmoneim Sulieman* 1 Al Neelain University, Faculty of Science and Technology, Department of Medical Physics,P.O.Box 170 Khartoum, Sudan Sudan University of Science and Technology. College of Medical Radiologic Science,P.O.Box 1908, Khartoum, Sudan Abstract Objective: The current study intends to determine the mean glandular dose (MGD) and the total dose per woman (for both breasts) for patients undergoing mammography and to evaluate the related factors affecting MGD. Methods: A total of 30patients were examined and the data were collected over three months at Radiation and isotope center Khartoum (RICK). The patient age was ranged from 39 to 65 year olds. Entrance surface doses (ESDs) and mean glandular dose (MGD) were calculated from patient exposure parameters using DosCal software. Results: The patient age was ranged from 39 to 65 year olds. The MGD for patient was in range mgy while calculated the MGD for patient was in range mGy. The mean MGD per woman was 1.5 mgy. Conclusions: The results are quite lower than the dose reference level determined by the American College of Radiologists (ACR, 3 mgy). Patient doses were within the international practice Key Words: Mammography, Breast, Radiation risk, Mean glandular dose, Measure entrance surface dose. Original Article Received : 15 May 01 Accepted : 10 Jul 01 Published: 10 Sep 01 INTRODUCTION ammography is the first choice method for Mdiagnosing breast by using x-ray to both breasts. It is a special type of x-ray imaging that uses low dose x-ray; high contrast, high-resolution film; and an x-ray system designed specifically for mammography to create detailed images of the breast. Routinely, mammographic images are taken one from the top (candiocaudal) and one from the side (mediolateral). It have two type digital and conventional mammography. Both types can be used for screening and for diagnosis. Screening Mammogram, this is performed in order to detect breast cancer before symptoms occur. The goal of screening mammography programs is to decrease mortality from breast cancer and Diagnostic Mammogram which is performed to help detect breast cancer if a woman has symptoms, such as a lump that can be felt in her breast [1]. The first attempts to use radiography for the diagnosis of breast abnormalities were made in the late190's, but mammography, as in current practice nowadays, using dedicated X-ray units, was developed in the 60s. The first period starts in 1913 with the observations of a German surgeon, laying the foundation for mammography. From 1940 to around 1970 followed the development of the technique by radiologists and th later by the industry, and the last quarter of the 0 century was dominated by the arrival of breast cancer screening, the use of ultrasound and magnetic resonance imaging and nowadays the [] transition to digital mammography systems. Breast cancer is a growing problem and the incidence of breast cancer increases with age. Mammography is the first Address for correspondence* Abdelmoneim Sulieman Al Neelain University, Faculty of Science and Technology, Department of Medical Physics, Sudan abdelmoneim_a@yahoo.com choice for diagnosing breast cancer problems. However, during the procedures and due to use of low energy in imaging, breast sensitive tissues will exposed to a significant radiation dose. Assessment of the breast dose is important because: When using ionizing radiation for such an organ containing sensitive glands like breast, it must be optimized to avoid increasing the chances of [3] inducing cancer in the patient. The breast has 0.1 tissue weighting factor for the effective dose examination. Therefore, it is necessary to evaluate the dose delivered to the breast to minimize the risk of radiation induced cancer. Optimization will increase the benefit versus risk ratio for the diagnostic procedure [4]. The benefit term from this ratio, presents the improvements on the diagnosis procedure, whereas the risk expresses the hazard from exposing the patient to an ionizing radiation, which always needs to be minimized. The aims of this study were to (i) estimate the radiation risk of mammography and to (ii) measure the dose during mammography. MATERIAL AND METHODS The data used in this study was collected from radiation and isotope center Khartoum (RICK) by data sheets; the data has been collected from February 01 to March 01. Patient data A total of 30 patients were examined in radiation and isotope center in Khartoum (RICK). The data were collected using a sheet for all patients in order to maintain consistency of the information. The following parameter were recorded age, weight, height, body mass index (BMI) derived from weight (kg)/(height (m) ) and exposure parameters were records.the dose was measured for two projection (candio-caudal (cc) medio-lateral( ML) for both breasts. The examination was collected according to the availability. X ray Machine The mammography images where made using (Giotto mammography image).study and it is conventional 56

2 Asian J Med Cli Sci May -Aug 01 Vol-1 Issue- mammography unit. The year of installation in 006.The contrast of the imaging system 6:1, the collimator formats is 18*4 and 4*30. Spot small focus was used for image contrast (Comet MCS 50mo/focus values ). The machine was equipped with exposure automatic control: 5-positionX-ray mobile sensor with manual shift. Solid state champers/1600mm. the tube voltage was automatic kvp selection with pre exposure by automatic technique. Fixed, solid state ionizing chamber with manual shift Post exposure display of kvp /mas values, and selected filtering, obtained with (0 point) and (1point) technique. The target of the X-ray tube is Molybdenum anode.3000 rpm. The inherent filtering: 0.5mm Be while the additional filtering: [5] 0.03 mm Molybdenum /0.5mm Rhodium (optional). Patient position The breast will be placed on a special platform and compressed with a paddle (often made of clear Plexiglas or other plastic). The technologist will gradually compress the breast and the patient may be asked to change positions between images. The routine views are a top-to-bottom view and an angled side view. The process will be repeated for the other breast. In positioning patients for routine screening mammogram, the following views are considered standard for the exam : Cranio-caudal (CC) =head to feet. Medio-lateral oblique (MLO) from the middle of the chest out to side of the body with x-ray tube at an angle. Proper breast positioning is based on an understanding of the normal breast anatomy and the [6] normal mobility of the breast. The mobile aspects of the breast are the lateral and inferior margins; the medial and superior margins are fixed. While it is desirable to have the nipple in profile on the routine views, the primary role in breast positioning is to show as match tissue as possible, if the nipple not shown in profile, an extra view for [7]. nipple profile can be done Image protocol In X- ray imaging, the exposure parameters used are selected according to breast thickness. The Standard (FFD) of cm was 65 cm used for all routine examination. Absorbed Dose calculations ESD measurements The Entrance Surface Dose (ESD) was measured using an ionization chamber attached to the X ray machine. The dose value was measured in terms of ESD in mgy. The dose per projection and total dose was measured. ESDs calculation method The entrance skin dose ESD is defined as the absorbed dose to air on X-ray beam axis at the point where X-ray beam enters the patient or a phantom, including the contribution of the backscatter. In this study the entrance skin doses ESDs calculated using the equation obtained by: ESD= OP (mgy/mas) mas BSF. Where radiation output of an x-ray tube at focus distance r. The tube output was obtained. The back scatter factor (BSF) used in this study was 1.07.To calculate the ESD, the Table 1 Characteristic of X ray machine. Model Operation frequency (khz) Power (kw) Tube voltage (kvp) Ripple Operation power (kw) E-40MGHF <1% 3.5 Table Generator characteristics, Film focus distance: Fixed 65cm film focusing distance X-ray tube generator Operation frequency Power Max absorbed power current (phase) (khz) (kw) Single-phase.30+/-10%50/60Hz 0A 40 5 Table 3: Patient demographic data, mean and sd, the range was presented in the parenthesis 57 Exam Mean Age (year) 47±6.9(39-65) Height (m) 1.57±0.1( ) Weight (kg) 71±0.1(43-100) BMI 8.8±4.8(19-39) Table 4: dose values of patient of mastectomy demographic data Exam MGDm Effective dose(m) ESDc MGDc Mean 6.3±1.8(.5-9.7) 1.5±0.4(0.6-.3) 0.07±0.0( ) 4.6±1.(-6) 1.1±0.3( ) Effective dose(c) 0.05±0.0( )

3 Asian J Med Cli Sci May -Aug 01 Vol-1 Issue- following X-ray tube exposure parameters were recorded for each patient take diagnostic examination: peak tube voltage (kvp), exposure current time product (mas) and focus-to-film distance (FFD). In addition to, the patient information i.e. patient [8] age and weight. RESULTS AND DISCUSSION Scientists agree that there is no safe dose of radiation. Cellular DNA in the breast is more easily damaged or induced Table 5: Show the previous studies results breast cancer in women by very small doses of radiation than thyroid tissue or bone marrow; in fact, breast cells are second only [9] to fetal tissues in sensitivity to radiation..this study intends to measure the dose during mammography and to analysis the factor that affects the patient exposure during the entire procedure and estimate risk to sensitive organ. Therefore this factor will be discussed in details including exposure factor, indication and organ of interest, patient's characteristics, machine specification imaging protocol and technologist skills. The main indication for these procedure were breast pain (36.3%) and Ca breast (18.1%).In this study operator are used mean tube voltage of 7 Author NO of Protocol Country Mean glandular patient dose mgy Martin et al ?000 CC-MLO Canada 3.7 mgy R. Edward Hedrick, 010 Chicago, Illinois 009 per 100?000 CC-MLO U.K 3.7 and 4.7 mgy 940 CC-MLO Netherlands Cumulative dose from0.3 to 4 mgy 705 CC-MLO Malaysia 48.9%+/-18.7% Noriah Jamal et al 009 JAMAL et al 001 a series of CC-MLO Malaysia 3.37 mgy patients F.O.Ogundare el al a series of CC-MLO Nigeria Less than.5mgy 009 patients Present study 30 CC-MLO Sudan 1.5mGy Figure 1: illusterated relationship between mas versus Figure : illustrated relationship between kvp versus Figure 3: illustrated relationship MGDc versus MGD Figure 4: illustrated relationship between mas versus versus ESDr 58

4 Asian J Med Cli Sci May -Aug 01 Vol-1 Issue- ESD Tube voltage versus versus ESDr y = 0.3x R = y = 0.106x -.19 R = Tube voltage (kvp) ESDr Linear (ESDr) Linear () Figure 5: illustrated relationship Tube voltage versus versus ESDr kvp has been used in all examination and 54.6 mas. In general, a linear relationship exists between tube current and radiation dose such that reducing the tube current by 50% and also decreases the dose by half. In addition, the relationship of peak kilo voltage and dose is linear. Basically, lowering the kvp will also lower the dose illustrated in (Figure 4,R²= 0.996) and (Figure5.R²=0.994) respectively. Descriptive statistics including minimum, maximum, mean and standard deviation values, were calculated for MGD per film and for each of the patient. The distributions of patient age, weight, body mass index, entrance surface dose, MGD per film, were also analyzed. The total number of patient were 30 women, the mean patient age (year) were 47 (39-65) mammography image done to women above 40 years old because in younger age breast tissue low contrast and high glandular density so cannot differentiating between normal and abnormal breast. No correlation was found between the patient radiation dose and patient's parameters (age, height, weight, BMI) were( R²=.013,0,045,.06 )respectively. In addition and due to biological variations, no correlation was detected between patient BMI and breast size and hence the breast. Most of the mean of patient height (m) were 1.57 ( ). The mean of patient weight (kg) were 71 (43-100). Height and weight to calculate BMI (weight (kg)/height (m ). The mean of BMI of patient (kg/m ) (9.19) ( ).The mean patient value of ESD (mgy) were 6.3mGy (.5-9.7) mgy. The relationship plotted between ESD with total kvp, total mas in figure 1 and figure.the mean effective dose (msv) were 0.07 ( ). The relationship between mean glandular dose and calculated mean glandular dose is linearity in figure3. The MGD of 1.5mGy is below the reference dose of 3mGy when using a grid. As expected, the surveyed units operated in the range mgy and only with out any compromise in existing image quality. The mean ESD per film for the MLO (1.8 mgy) was and CC view (1.5 mgy). This could be explained by the presence of pectoral muscle in the oblique view. While no image quality assessment was made, the associated films were judged to be clinically acceptable. No significant relationships were seen between MGD per woman with respect to BMI or age. In general X-ray tube voltage (50-150) kvp and high ability to penetrate depth organ, but in mammography the voltage should be between (-35) kvp and the tube current exposure time product(mas)should be at least(4-400),decrease photon energy increase radiation dose and increase breast thickness therefore use compression device to reduce thickness and dose. Also the dose affected by breast thickness and composition, image receptor and photon energy, because the breast is very sensitive to radiation and induced cancer. In this study MGD 1.5mGy lower from other study but in International practice according to different thickness, type of target filter combination and the technique was used conventional or digital mammography. There are some factors affecting image quality and patient dose in screen-film mammography. These include: beam quality, compression, imaging geometry, grids, receptor characteristics, processing of the film or digital image, and viewing conditions. If this is done correctly, a high-quality mammogram can be obtained at a reasonably low dose to the patient. The goal is not simply to use as low a dose as possible, because if this is done there is a large risk of degrading the performance of mammography in detecting or accurately characterizing small, node-negative cancers. The use of specially designed low-kilo voltage Bucky grid was reduced scattered radiation. And the introduction of smaller focal spots was used to improve imaging geometry. Magnification techniques, the automatic exposure controller still fails to provide appropriate and constant optical film density over a wide range of tissue thickness and absorption.. Exposure times of less than 1 second are recommended to avoid the unnecessary higher doses caused by longer exposure times and reciprocity law failure. The wide dynamic range in mammography can be reduced by a beam equalization filter, and thus be better adapted to the decreased latitude of modern high-contrast mammographic screen-film systems. The radiation dose was evaluated in this study using two methods: the dosimetric unit attached to the X ray system and a mathematical equation based on the output of the machine and exposure parameters. The measured values from the machine are always higher than calculated values. The range of variation was between 13% up to 60%. Although, mathematical equation in general has many drawbacks such as their dependence on the field size and patient parameters, it can be used for quick estimation where there is no other method to estimate the patient dose. CONCLUSION Mean Glandular dose (MGD) (with grid) for mammographic practice in Khartoum isotope and radiation center is 1.5 mgy. No regular dose measurement was available for all patients in order to estimate the radiation risks No significant relationships were seen between MGD per woman with respect to BMI or age. Patient doses were comparable with previous studies. Patient doses were within the international practice. Mathematical equation could be used in some situation where no dosimetric services available. Special concern should be paid to young patients A dedicated protocol will help to improve image quality and patient protection ACKNOWLEDGEMENTS The Authors would like to thank the staff of Medical Physics and Radiology Departments at RICK. REFERENCES 1. Jelena Bozek, Kresimir Delac, Mislav Grgic. Computer- 59

5 Asian J Med Cli Sci May -Aug 01 Vol-1 Issue- Aided Detection and Diagnosis of Breast Abnormalities indigital Mammography. 50th International Symposium ELMAR-008, 10-1 September 008, Zadar, Croatia.. Van Steen, R. Van Tiggelen. Short history of mammography: a belgian perspective. JBR BTR, 007, 90: Mohammad Zeidan. Assessment of Mean Glandular Dose in Mammography. Master of Science in Medical Physics. Department of Physics and Astronomy University of Canterbury. Christchurch, New Zealand European Commission. European protocol on dosimetry in mammography.report EUR 1663 (Bruxelles, Luxembourg: EC) Gitto 3D image manual. Avaialbe at www. gitto image operator s manual.accessed Magnetic ResonanceImaging(MRI):Breast.Availableat: adiologyinfo.org/en/news/newdetarget.cfm?id=14 s. accessed MammographyPositioning.pd 7. Horst Aichinger, Joachim Dierker,Sigrid Joite-Barfuß, Manfred Säb.Radiation Exposure and Image Quality in X- Ray Diagnostic Radiology. 8. Radiation Exposure From Annual Mammography Increases Breast Cancer Risk in Young High-Risk Women. Available at: accessed