Wetting Development Rinsing Fixation Washing Drying

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1 Dental Imaging Outline Image Prescription Photography Differential Diagnosis of Imaged Lesions IMAGING BASICS X-Rays are produced in an X-ray tube that consists of a Cathode (negative side) and an Anode (positive side). A high voltage current is generated in the Cathode causing the excitation of electrons. These electrons travel towards the anode and strike the focal spot to generate the X-rays. Electrical Energy - Kinetic Energy - X-rays Only 1 % of the energy produced by the electrons striking the Anode is converted into X-rays, the other 99% becomes heat. The size of the focal spot is important. The smaller the focal spot, the sharper the image produced. A smaller focal spot also results in the production of more heat. Traditional Radiographic Film: Processing Sequence Wetting Development Rinsing Fixation Washing Drying Traditional Radiographic Film: Developer Components: Reducing Agent Metol: converts exposed silver halide into black metallic silver Reducing Agent Hydroquinone: builds black tones and contrast in the image Activator Sodium Carbonate: softens the emulsion Restrainer Potassium Bromide: prevents development of unexposed silver halide Preservative Sodium Sulfite Solvent - Water Traditional Radiographic Film: Fixer Components: Fixing Agent Ammonium Thiosulfate: clears away the unexposed silver halide Acidifier Acetic or Sulfuric Acid: neutralizes the developer to stop developing process Hardener Aluminum Chloride or Sulfide: shrinks and hardens the emulsion Preservative Sodium Sulfite Solvent - Water

2 Rules for Accurate Image Formation X-rays should originate from as small a focal spot as possible. The distance between the focal spot and the film should be as long as possible. The film should be as close to the object as possible. The long axis of the object should be parallel to the film. The central ray should be parallel to the film. Source to Film (long) / Object to Film (short) Source to Film (long) / Object to Film (short) IMAGE INTERPRETATION Density and Contrast Density: the degree of blackness on a radiographic film Contrast: the difference in the densities on a film; the shades of gray on a film Density Is Affected by: Milliampere Seconds (mas) - the greater the mas, the greater the number of X-rays that strike the film, the denser the image Kilovoltage (KVP) - a higher KVP increases the penetrating power of the X-rays, more X-rays reach the film resulting in a denser image Density Is Affected by (continued): Source to Film Distance - the shorter the distance between the focal spot and the film, the more X-rays that strike the film, resulting in greater density on the image Inverse Square Law: doubling the distance results in a film with ¼ the density Inverse Square Law Contrast Is Affected by: Contrast is affected primarily by KVP Increasing KVP increases penetrating power of the X-rays More X-rays means more black on the image, which means less contrast Contrast and KVP have an inverse relationship Long Scale Contrast vs. Short Scale Contrast Long Scale Contrast (Periapical Images) Associated with higher KVP Greater tissue penetration resulting in smaller differences between densities Osseous changes in periodontal and periapical disease are better visualized with long scale contrast

3 Long Scale Contrast vs. Short Scale Contrast Short Scale Contrast (Bitewing Images) Associated with lower KVP Tissue penetration is less resulting greater differences in density between adjacent areas on a radiograph Dental caries is better visualized with short scale contrast - BWX The interproximal contacts should not be overlapped from the distal surface of the canine to the mesial surface of the third molar, to the extent that interpretation is possible. - BWX The crowns of the maxillary and mandibular teeth should be centered in the image from top to bottom. - BWX The crest of the alveolar bone should be visible with no superimposition of the crowns of adjacent teeth. - BWX The occlusal plane should be as horizontal as possible. - BWX The buccal and lingual cusps should not be excessively separated. In general, the cusp tips should be nearly superimposed (errors due to malpositioned teeth are acceptable) Buccal Object Rule: The image of the most buccal object moves, relative to the lingual object, in the same direction the beam is directed. SLOB Rule: same lingual opposite buccal The lingual object will move in the same direction that the tube head is moved. Buccal Object Rule Reasons For Dark Films Long exposure High KVp Short source to film distance High mas Reasons For Dark Films (cont.) Inaccurate timer Developing time too long Developer temperature too high Over-strengthed developer Reasons For Light Films Energy level too low (low mas) Film packet positioned backwards kvp too high Low contrast film

4 Reasons For Light Films (cont.) Developing time too short Developer temperature too low Contaminated developer (with fixer) Old or exhausted chemicals Reasons For Foggy Films Secondary exposure (cracked safelights, poor filters, exposure to light) Outdated film Improper film storage Faulty processing - PAN Problem: Anterior teeth in both arches are out of focus, they are blurred and narrow in appearance; spine is superimposed on ramus areas; premolars are severely overlapped Cause: Patient positioned too far forward in relation to the image layer - PAN Problem: Anterior teeth of both arches are out-of focus; they are blurred and wide in appearance; excessive ghosting of mandible and spine. Cause: Wide blurred anterior teeth are caused by the patient being positioned too far back in relation to the image layer. This also may increase ghosting of the mandible and spine. - PAN Problem: Apices of lower incisors are out-of focus and blurred; shadow of hyoid bone is superimposed on anterior mandible; condyles may be cut off at the top of radiograph; premolars are severely overlapped. Cause: Patient s head is tilted downward: chin is positioned back while forehead is positioned forward. - PAN Problem: Upper incisors are out-of-focus; hard palate is superimposed over apices of maxillary teeth; both condyles may be off the film. Cause: Patient s head is titled upward; chin may be too far forward, while forehead is tilted towards the back. - PAN Problem: One condyle is definitely larger than the opposing one; the neck also is longer on the larger side; image appears to be titled; one angle of the mandible is higher than the other. Cause: Patient s head is titled to one side; anatomical variations; film is crooked in cassette ( 5 inch film in a 6 inch cassette). - PAN Problem: Teeth on one side of midline appear wider and have severe overlapping of contacts, whereas teeth on the opposite side appear very narrow. Ramus on one side is much wider than the other. Condyles differ in size. Cause: Patient is twisted to one side (right or left) causing the mandible to fall outside the image layer. One side is in front of the image layer while the other side is behind the image layer; anatomic variation; asymmetry - PAN Problem: Dark shadow in the maxilla below the palate; maxillary apices are obscured. Cause: Patient s tongue was not fully on the roof of the mouth. - PAN Problem: Portion of image is blurred; lacks sharpness Cause: Blurred images on radiographs are the result of motion during exposure. Because only a small increment of panoramic film is being exposed at one time, patient movement results in only one portion of the image being blurred - PAN Problem: Pyramid-shaped opacity appears in the midline of the panoramic image. Cause: Patient was slumped; spinal column was not erect, causing a ghost image of the spine to be

5 superimposed in the center of the film IMAGE PRESCRIPTION Image Prescription If you think you need a radiograph, take it! Use sound clinical judgment! Review the list of conditions and situations listed in the guidelines radiography.asp#radiographs Image Prescription Bite Wing Images Recall Patient (adult - dentate) with clinical caries or at increased risk for caries Posterior Bitewing Exam at 6 to 18 month intervals Recall Patient (child primary, mixed dentition; adolescent permanent dentition) with clinical caries or at increased risk for caries Posterior Bitewing Exam at 6 to 12 month intervals if proximal surfaces cannot be examined visually or with a probe Image Prescription Bite Wing Images Recall Patient (adult- dentate) with no clinical caries and not at increased risk for caries Posterior Bitewing Exam at 24 to 36 month intervals Recall Patient with no clinical caries and not at increased risk for caries Child primary or mixed dentition: Posterior Bitewing Exam at month intervals Adolescent permanent dentition: Posterior Bitewing Exam at month intervals Panoramic Images Panoramic Images Advantages Increased coverage Relatively undistorted anatomical images Significant radiation dose reduction Simplicity and rapidity Panoramic Images Advantages Reduced superimposition Minimal infection control required Possibility to detect disease early Primary diagnosis of mandibular fractures Panoramic Images The following should be visible dentition nose and sinus mandibular body condyles and hyoid ramus and spine Cephalometric Radiography Uses of cephalometrics: Diagnosis of skeletal and dental malocclusions Planning orthodontic treatment Evaluation of orthodontic treatment results Prediction and evaluation of growth related changes Ceph Guidelines Distance between x-ray source and midsagittal plane of patient is kept constant at 5 feet

6 Distance between midsagittal plane and film is 15 cm Patient s head is positioned with Frankfort Horizontal plane parallel to the floor Other Extra-Oral Images Lateral Skull Projection Facial growth Retrognathia Prognathia Other Extra-Oral Images Posteroanterior Projection (PA) disease, trauma (midface fractures), developmental abnormalities Other Extra-Oral Images Water s Projection maxillary sinuses Other Extra-Oral Images Reverse Towne s Projection condylar fractures, medially displaced condyle Other Extra-Oral Images Sub-mental Vertex jug handle view zygomatic arches DIGITAL IMAGING Requirements X-ray Source Capture Medium Interface Viewing Medium Software Advantages No processing equipment required No chemicals or chemical waste Elimination of film Instant viewing (sort of) Advantages (continued) Less radiation dose to patient. Lower cost per image. Ability to adjust the image (lighten, darken, colorize, negative). Electronic consultation (submission) Advantages (continued)

7 Time Reduced time from image capture to viewing Reduced time to complete a full mouth series Reduced time between exposures when a re-take is necessary Time saving permits additional time for patient education and consultation Disadvantages High initial investment. Image quality less than traditional film. Bulky sensors (not PSP). Computer (computer network) required. Lack of hard copy (relative). Disadvantages (continued) Panoramic and Cephalometric units are more expensive. Legal issues. Third party acceptance varies. Integration of software into daily routine. Initial Cost $8,000 to $12,000 per work station (Michael Miles DDS) $11,700 to $15,500 per operatory (Gordon Christensen DDS, PhD) $20,000 to $22,000 for wireless Types of Direct Charged Couple Device (CCD) Complementary Metal Oxide Semiconductor (CMOS) Indirect Photo Stimuable Phosphors (PSP) DICOM and Communications in Medicine Ability to share images between different software Does not mean that capture media will work between manufacturers Direct Advantages Instant Viewing Disadvantages Sensor Thickness Must Contend with a Wire Higher Cost Charged Couple Device (CCD) Introduced in 1997 by Trophy Radiology. Requires a separate circuit board to convert an analogue signal to a digital signal. Early models were bulky. Newer models are much thinner (1mm vs. 14mm). Hard wired directly to computer so image viewing is almost instantaneous

8 Complementary Metal Oxide Semiconductor Direct connection with USB, no circuit board required. Less power requirement vs. CCD. Smaller pixel size. Lower manufacturing cost vs. CCD. Inferior image to CCDs until recently. CMOS/APS (active pixel sensor) latest technology In-Direct Advantages Smaller Plates No Cord Lower Cost Disadvantages Increased Time for Image Acquisition Still Need a Darkroom Photo Stimuable Phosphor Also called storage phosphor No sensor, uses an imaging plate Latent image is stored on the imaging plate Imaging plate is exposed to a laser beam that causes exposed storage phosphor to fluoresce Fluorescent signal is converted to a digital image Photo Stimuable Phosphor Photo Stimuable Phosphor What s New? Application of Cone Beam CT Implantology Pathology Impactions Orthognathic Surgery Airway Analysis TMJ Analysis Orthodontics 3D Dental Imaging New on the market Images areas new to dentists Who reads these images? What if I find something wrong, am I liable? 3D Dental Imaging 3-D volumetric images True anatomic measurements 14 BIT Gray Scale with Sub millimeter resolution Pan-sized footprint Fast Scan Time/Real time analysis

9 Low Radiation Higher resolution for all views 3D Dental Imaging Next Generation i-cat Shorter scan and reconstruction times Extended Field of View Manageable File Sizes Sleek Redesign 3D Dental Imaging 2D Dental Imaging RADIATION SAFETY Maximum Permissible Dose (MPD) The amount of radiation a person is allowed to receive from artificial sources Guidelines set by National Council on Radiation Protection and Measurement Maximum Permissible Dose (MPD) Two Categories for MPD Occupationally Exposed: those individuals expected to work around radiation as part of their job (Dentists, Hygienists, Assistants) MPD = 50 msv Non-Occupationally Exposed: those individuals who do not work directly with radiation (front desk staff, people in the waiting room, etc.) MPD = 5 msv Maximum Permissible Dose (MPD) Patients MPD does not apply to patients Pregnant Providers A pregnant provider (dentist, hygienist or assistant is permitted the MPD of non-occupationally exposed people) ALARA As Low As Reasonably Achievable does not specify a specific radiation dose for exposed persons take every measure possible to reduce radiation exposure to patients and providers radiation protection philosophy of choice Methods for Protecting Patients Highest Possible KVP Constant Potential X-Ray Machines Filtration Collimation Long beam indicating device

10 Methods for Protecting Patients Electronic Timers High Speed Film Intensifying Screens Film Holding Devices Lead Aprons and Collars Methods for Protecting Providers Position (90 to 135 degrees to beam) Distance (six feet) Shielding Radiation Dosimetry Monitoring Service Dead Man s Switches Time Shielding, Distance PHOTOGRAPHY Photographic Terminology Shutter The part of the camera that opens to allow light to strike the film or sensor. The amount of time the shutter remains open is referred to as shutter speed. Expressed as an inverse second (ex: a shutter speed of 500 is 1/500 of a second) Shutter Speed Photographic Terminology Aperture The size of the opening of the lens that regulates the amount of light that enters. Referred to as f-stop f is determined by dividing f (focal length of the lens) over D (diameter of the aperture) f = f/d Smaller aperture openings are represented by higher f-stop numbers. APERTURE APERTURE Photographic Terminology Depth of Field Range of distance from the lens within which objects will appear in focus. Distance between the nearest and farthest objects in focus. Directly affected by aperture. Smaller aperture results in greater depth of field. f 32 would have greater depth of field than f 3.5 Depth of Field Depth of Field is too narrow f 3.5 Need anterior and posterior teeth in focus Depth of Field Depth of Field is perfect f 32 Posterior and anterior teeth are in focus Photographic Terminology

11 Film Speed Represents the film s sensitivity to light. On digital cameras it represents the sensor s sensitivity to light. Expressed as an ASA or ISO. Higher speed means more light sensitivity. Higher speed better for lower lighting. Higher speed will have more grain or noise. Photographic Terminology Exposure The amount of light that reaches the film or sensor. Determined by the f-stop. Smaller f-stop means more light (higher number equals smaller opening) Also determined by position and intensity of the flash. Exposure Aperture Smaller opening (larger f stop)» less light Larger opening (smaller f stop)» more light Shutter speed Slower» permits smaller aperture opening Faster» need larger aperture opening Film speed Faster (larger ISO #)» needs less light Slower (smaller ISO #)» needs more light Exposure Tradeoffs Aperture Smaller opening» greater depth of field Larger opening» shallow depth of field Shutter speed Slower» camera movement causes blur Faster» shutter freezes action (no blur) Film speed Faster (larger ISO #)» coarser grain Slower (smaller ISO #)» finer grain Single Lens Reflex (SLR) Cameras SLR vs. Point and Shoot SLR What you see is what you get The image reflected of the mirror and through the prism is the image that will be captured on the film or sensor Point and Shoot What you see is kind of what you get View finder is just a window through the body of the camera Formats RAW TIF/TIFF (Tagged Image File Format) BMP (Bitmap) PNG (Portable Network Graphics) JPEG (Joint Photographic Experts Group) GIF (Graphics Interchange Format) Resolution Megapixel:

12 Derived from multiplying: number of horizontal pixels (dots) x number of vertical pixels (dots) Megapixel Pixels To help understand the relationship of the number of pixels (dpi) in an image to the size and sharpness of an image. Pixels Imagine that newsprint (which is made up of dots) had been printed on a balloon Pixels Photographing at a higher resolution and displaying it as a small image has the same effect as if you had reversed the process Resolution How much is enough? Depends on intended use Depends on output device Monitor Printer Depends on size of image Monitors Most monitor screens display either 72 or 96 ppi (pixels per inch) Camera resolution needed = monitor size x monitor output Monitor with 96 ppi 14 width x 96 ppi = 1344 pixels 11 height x 96 ppi = 1056 pixels 1344 x 1056 = 1,419,264 pixels Differential Diagnosis of Imaged Lesions Differential Diagnosis of Imaged Lesions Lucencies Opacities Mixed Density Lesions Unique Appearances Soft Tissue Radiopacities Radiolucencies Unilocular Radiolucencies: Pericoronal Unilocular Radiolucencies: Periapical Unilocular Radiolucencies: Other Locations Multilocular Radiolucencies Radiolucencies: Poorly Defined Borders

13 Radiolucencies: Multifocal or Generalized Radiolucencies Unilocular Radiolucencies: Pericoronal Dentigerous Cyst Odontogenic Keratocyst Ameloblastoma Ameloblastic Fibroma Adenomatoid Odontogenic Tumor Calcfying Odontogenic Tumor (Gorlin Cyst) Radiolucencies Unilocular Radiolucencies: Periapical Periapical Granuloma Periapical Cyst Periapical Cemento-Osseous Dysplasia (early) Periapical Scar Dentin Dysplasia Type I Radiolucencies Unilocular Radiolucencies: Other Locations Nasopalatine Duct Cyst Lateral Periodontal Cyst Residual Cyst Central Giant Cell Granuloma Stafne Bone Defect Ameloblastoma Odontogenic Keratocyst Radiolucencies Multilocular Radiolucencies Odontogenic Keratocyst Ameloblastoma Ameloblastic Fibroma Central Giant cell Granuloma Odontogenic Myxoma Aneurysmal Bone Cyst Cherubism Hyperparathyroidism (Brown Tumor) Radiolucencies Radiolucencies: Poorly Defined Borders Osteomyelitis Bisphosphonate Associated Necrosis Metatstatic Tumor Osteoradionecrosis Multiple Myeloma Focal Osteoporotic Marrow Defect

14 Radiolucencies Radiolucencies: Multifocal or Generalized Cemento-Osseous Dysplasia Nevoid Basal Cell Carcinoma Syndrome Multiple Myeloma Cherubism Hyperparathyroidism (multiple Browns Tumors) Langerhan s Cell Histiocytosis ( teeth floating in air ) Radiopacities Radiopacities: Well Defined Borders Radiopacities: Poorly Demarcated Borders Radiopacities: Multifocal or Generalized Radiopacities Radiopacities: Well Defined Borders Torus or Exostosis Retained Root Tip Condensing Osteitis Pseudocyst of the Maxillary Sinus Odontoma (Compound or Complex) Cemento-Osseous Dysplasia (late) Superimposed Image from Soft Tissue Radiopacities Radiopacities: Poorly Demarcated Borders Sclerosing Osteomyelitis Bisphosphonate Associated Osteonecrosis Fibrous Dysplasia Paget s Disease of Bone Osteosarcoma Chondrosarcoma Radiopacities Radiopacities: Multifocal or Generalized Florid Cemento-Osseous Dysplasia Idiopathic Osteosclerosis Bisphosphonate Associated Osteonecrosis Paget s Disease of Bone Gardner Syndrome Polyostotic Fibrous Dysplasia Osteopetrosis Mixed Radiolucencies/Radiopacities Mixed R/R: Well Demarcated Border Mixed R/R: Poorly Demarcated Border

15 Mixed R/R: Multifocal or Generalized Mixed Radiolucencies/Radiopacities Mixed R/R: Well Demarcated Border Cemento-Osseous Dysplasia (intermediate) Odontoma Central Ossifying Fibroma Adenomatoid Odontogenic Tumor Calcifying Epithelial Odontogenic Tumor (Pindborg Tumor Snow Driven Opacities) Calcifying Odontogenic Cyst (Gorlin Cyst) Cementoblastoma (intermediate) Mixed Radiolucencies/Radiopacities Mixed R/R: Poorly Demarcated Border Osteomyelitis Bisphosphonate Associated Osteonecrosis Metastatic Carcinoma Osteosarcoma Chondrosarcoma Mixed Radiolucencies/Radiopacities Mixed R/R: Multifocal or Generalized Florid Cemento-Osseous Dysplasia Bisphosphonate Associated Osteonecrosis Paget s Disease of Bone Unique Appearances Ground Glass Cotton Wool Sunburst Onion Skin Unique Appearances Ground Glass Fibrous Dysplasia Hyperparathyroidism Cotton Wool Cemento-Osseous Dysplasia Paget s Disease of Bone Gardner Syndrome Gigantiform Cementoma Unique Appearances Sunburst Osteosarcoma Intraosseous Hemangioma Onion Skin Ewings Sarcoma Langerhans Cell Histiocytosis

16 Proliferative Periostitis Soft Tissue Radiopacities Amalgam Tatoos Foreign Bodies Sialolith Calcified Lymph Node Phlebolith Osseous and Cartilaginous Choristomas Calcinosis Cutis Myostitis Ossificans References White, S. & Pharoah, M. Oral Radiology, Principles and Interpretation, 5 th ed., St Louis: Mosby Frommer, H. & Stabulas-Savage, J. Radiology for the Dental Professional, 8 th ed., St. Louis: Mosby, Langland O., et al. Principles of Dental Imaging, 2 nd ed., Baltimore: Lippincott, Williams & Wilkins, Neville, B., Damm, D., Allen, C. and Bouquot, J. Oral and Maxillofacial Pathology, 3 rd ed., St. Louis: Saunders, 2009.

RADIOGRAPHIC INTERPRETATION Differential Diagnosis

RADIOGRAPHIC INTERPRETATION Differential Diagnosis MODULE 1: The Introduction. Chief complaint Demographics Age Sex Race Historical findings Physical findings Clinical Radiographic Location Maxilla/mandible