2017 Course #4 Self-Study Course Contact Us: Phone 614-292-6737 Toll Free 1-888-476-7678 Fax 614-292-8752 E-mail smsosu@osu.edu Web dentistry.osu.edu/sms The Ohio State University College of Dentistry 305 W. 12th Avenue Columbus, OH 43210 Course Instructions: Read and review the course materials. Complete the quiz questions. Answer the 12 question test. A total of 9/12 questions must be answered correctly for credit. Submit your answers online at: http://dentistry.osu.edu/smscontinuing-education Check your email for your CE certification of completion (please check your junk/spam folder as well). About SMS CE courses: TWO CREDIT HOURS are issued for successful completion of this self-study course for the OSDB 2016-2017 biennium totals. CERTIFICATE of COMPLETION is used to document your CE credit and is emailed to each course participant. ALLOW 2 WEEKS for processing of your certificate. The Ohio State University College of Dentistry is a recognized provider for ADA CERP credit. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Concerns or complaints about a CE provider may be directed to the provider or to the Commission for Continuing Education Provider Recognition at www.ada.org/cerp. The Ohio State University College of Dentistry is approved by the Ohio State Dental Board as a permanent sponsor of continuing dental education. This continuing education activity has been planned and implemented in accordance with the standards of the ADA Continuing Education Recognition Program (ADA CERP) through joint efforts between The Ohio State University College of Dentistry Office of Continuing Dental Education and the Sterilization Monitoring Service (SMS). Frequently Asked Questions: Q: Who can earn FREE CE credits? A: EVERYONE - All dental professionals in your office may earn free CE credits. Each person must read the course materials and submit an online answer form independently. Q: Where can I find my SMS number? A: Your SMS number can be found in the upper right hand corner of your monthly reports, or, imprinted on the back of your test envelopes. The SMS number is the account number for your office only, and is the same for everyone in the office. Q: How often are these courses available? A: Four times per year (8 CE credits).
2017 Course #4 Digital Imaging Characteristics and Projection Geometry This is an OSDB Category B Supervised self-instruction course Written by: Constance Kuntupis, RDH, MA Edited by: Sydney Fisher, BS Nick Kotlar, BS Release Date: November 13, 2017 8:30am EST Last Day to Take Course Free of Charge: December 13, 2017 4:30pm EST Digital Radiography has been available for more than 25 years now, but it still has not replaced conventional film-based dental radiography completely. Conventional dental radiography relies on films to record radiographic images. Digital radiography is a filmless imaging system that is used to record radiographic images. When no film is used, no processing chemicals are required. Digital imaging uses an electronic sensor instead of film. The radiographic image is captured with an electronic sensor and appears instantly on a computer monitor. The electronic sensor breaks the x-ray image into electronic pieces of information composed of picture elements known as pixels. The digital image can now be presented and stored on a computer. Page 1
How are digital images formed? There are two ways of forming a digital image, direct digital imaging and indirect digital imaging. DIRECT DIGITAL IMAGING includes an x-ray machine and an intraoral sensor that is directly attached to the computer. The CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) sensors are the two types of digital image receptors available. The receptor or sensor is placed in the mouth of the patient and exposed to x-rays. The sensor captures the radiographic image and sends it to the computer monitor. This radiographic image appears on the computer monitor almost instantly after pushing the exposure button on the x-ray machine. DIRECT DIGITAL XRAY IMAGE WITH CORD INDIRECT DIGITAL XRAYS PSP SYSTEM INDIRECT DIGITAL IMAGING includes an x-ray machine, a photostimulable phosphor plate (PSP) system, a high speed scanner and computer. This type of digital imaging system is a wireless digital radiography system. A reusable photostimulable phosphor imaging plate fits into the patient s mouth similar to intraoral film. After the plate is exposed to radiation, it converts the x-ray energy into light. This indirect digital radiography system captures images in an analog format like film and then converts the digital data via the scanning process. After exposure to x-rays, the phosphor-coated plate is removed from the patient s mouth and placed in a laser scanning device where a laser scans the plate and produces an image that is transferred to a computer monitor. The radiographic images are then erased or removed from the photostimulable phosphor plates, which are wrapped in a protective barrier, and can be used again. A second method of indirect digital imaging is to scan traditional radiographs with a CCD camera. This method is similar to scanning your photographs and storing them on a computer. This method of indirect digital imaging is inferior to the two methods mentioned earlier because the resultant image is similar to a duplicate radiograph versus an original radiograph. Page 2
Does digital radiography reduce radiation exposure? This can be a challenging question to answer correctly because the answer could be both Yes and No. Less x-ray photons are required to form an image on the digital receptor. The CCD and CMOS sensors require about 50-80% less radiation exposure than conventional film. Some manufacturers claim as much as 90% less radiation exposure when comparing film to digital sensors. The reality, however, is that the reduction is somewhere between 0% and 50%, compared with the current standard of F-speed film. According to a Dutch study, 55% of clinicians using photostimulable phosphor plates and 65% of clinicians using solid-state systems report an increase in the number of radiographs taken as well as retakes due to the ease of remaking an image with a digital system. There is concern from the experts in the field of radiology about the dose reduction claims made by manufacturers. Dental radiographers must be aware of this concern and try very hard not to increase the number of radiographs taken when switching from conventional film-based dental radiography to digital radiography. Are digital images superior to conventional film images? At this time, there are differences regarding image quality and resolution. Resolution refers to the number of line pairs per millimeter (lp/mm). Digital manufacturers claim anywhere from 6 to as much as 22 lp/mm. Conventional F-speed film provides at least 20 lp/mm. The human eye is only capable of resolving 8 to 10 lp/mm, so does anthing above 10 lp/mm really matter? No. The truth is both conventional film and digital images are capable of producing diagnostic images. Digital images do, however, have some distinct advantages over film. Page 3
Advantages to Direct Digital Radiography Exposure Reduction - The charge-coupled device (CCD) requires less radiation to produce an image than traditional film. Digital Imaging reduces patient exposure by more than half. Also there is no need for retakes due to processing errors. Environmentally Friendly - There is no need for film mounts, film, lead foil or any of the hazardous chemicals associated with processing. Instant Image Available - The radiographer and the patient are able to see the digitized image on the computer monitor instantly. Image Enhancement - Images can be enhanced by viewing images in color or with digital subtraction (reversed gray-scale). Images can also be magnified, brightened and the contrast, sharpness and orientation can be altered. Patient Education - Patients are more accustomed to looking at computer screens than little pieces of film. The larger computer monitor and the ability to enhance the image for patient viewing makes it an effective teaching tool. Patients can view their radiograph instantly on the computer monitor and this facilitates communication with the radiographer. Image Storage - Digital images are placed in the patient s electronic chart and saved on your computer. This also makes them more easily transmittable and reproducible. Images can be electronically transmitted to other dentists and/or specialists without quality loss. Reduced Cost - No more need to purchase film, mounts, processors or processing solutions. Images can also be sent quickly to insurance companies leading to faster reimbursement from dental insurance companies. Disadvantages of Direct Digital Radiography Sensor Comfort - Patients may complain about the rigidity, thickness or bulkiness of the sensor. This could trigger a gag reflex for some patients. There is also a wire that is connected to the sensor that may be cumbersome for the patient and operator. Initially Expensive - The initial setup cost may be expensive. Infection Control - CCD sensors cannot be sterilized. Plastic sleeve barriers must be used to prevent cross contamination. The sensor and cable must be covered to keep them from coming into contact with saliva. Page 4
Advantages of Indirect Imaging/ Photo-Stimulable Phosphor (PSP) Patient Friendly - No bulky sensor. The receptor is the same size as film and is pretty flexible. Cordless - This system is cordless, which aides in the placement of the receptor. No change in technique is necessary. Inexpensive - The receptors or plates are inexpensive and reusable, however, they must be kept in an infection control barrier because the imaging plate cannot be sterilized. Environmentally Friendly - There is no need for film mounts, film, lead foil or any of the hazardous chemicals associated with processing. Disadvantages of Indirect Imaging/ Photo-Stimulable Phosphor (PSP) Less Resolution - PSP images have a limited amount of resolution, only 6 lp/mm. This image resolution is significantly less than what can be achieved with conventional film (approx. 20 lp/mm). However, 6 lp/mm is not much less than what the human eye can detect at 8 to 10 lp/mm. Time Consuming - The plastic plates are coated with a phosphor material which is sensitive to x-rays. The phosphor stores the x-ray energy just like the latent image is stored on film. The image is produced when the crystals in the phosphor plate release a blue fluorescent light during laser scanning. Therefore your image is not instantaneous like it is with direct digital imaging. The image is not visible on the computer until the receptor or plate has been scanned by a laser. Easily Damaged - Not all of the x-ray energy is released during scanning; therefore plates must be erased by exposing them to white light before they can be reused. The plate is somewhat delicate and can be scratched easily with dirt or by rough handling. Page 5
DENSITY: Radiographic density represents the degree of darkness of an image. White areas (e.g., metallic restorations) have no density and black areas (e.g., air spaces) have maximum density. The areas in between these two extremes (tooth structure, bone) are represented by various shades of gray. Image Characteristics Image density may be influenced by: Exposure factors Increasing milliamperage (ma), kilovoltage peak (kvp), and/or exposure time leads to an increase in density. Subject thickness A larger patient/subject head will result in reduced radiograph density. More x- rays are needed to produce a radiograph of ideal density. Object density Image density refers to the amount of darkness in an image. Object density is determined by type of material (metal, tooth structure, composite, etc.) and by amount of material. Metallic restorations have higher object density than teeth alone. Density decreases (image gets lighter) when object density increases, assuming no changes are made in the exposure factors. In the radiograph to the right, the post and core in each tooth has a high object density, resulting in low image density. Low Image Density Diagnostic High Image Density The overall density of the image affects the diagnostic value. Only the center image above has the proper density. The one on the left is too light (low density) and the image to the right is too dark (high density); Only the center image is diagnostic. Page 6
Image Characteristics (continued) RADIOLUCENT: Refers to dark areas of a radiograph (high film density); dark gray to black. Represents with little or no object density such as soft tissue, air, etc. RADIOPAQUE: Refers to light areas of a radiograph (low film density); light gray to white. Represents areas which have higher object density, such as gold crown, amalgam, etc. CHARACTERISTIC CURVE (H&D CURVE): Radiographs are commonly characterized by the relationship between the applied exposure and the resulting density. This relationship commonly varies over a range of densities, so the data is presented in the form of a curve, known as a characteristic curve or H&D curve (named for developers Hurter and Driffield). Page 7
Image Characteristics (continued) CONTRAST: Image contrast refers to the visual differences in shades ranging from black to white. This corresponds to a difference in densities existing between various regions of the digital image. High Contrast (Short Scale): A radiograph that shows few shades has high contrast, or short scale. (Image is mostly black and white; best for caries detection. Low Contrast (Long Scale): A radiograph with many shades of gray has low contrast, or a long scale. Best for identifying periodontal or periapical problems. Factors influencing contrast: a. Subject contrast - In order to see an image on the radiograph, the objects must have different object densities. If everything had the same object density, the radiograph would be blank. The teeth, restorations, bone, air spaces, etc., all have different object densities, allowing us to see them on the radiograph. b. kvp Kilovoltage peak (kvp) controls the energy (penetrating ability) of the x-rays. The higher the kvp, the more easily the x- rays pass through objects in their path, resulting in many shades of gray (lower contrast). At lower kvp settings, it is harder for x-rays to pass through objects with higher object densities, resulting in a higher contrast (short scale). c. Fog Fog can occur when film is exposed light, heat, or chemical fumes. This makes it harder to see the density differences (contrast), making the radiograph less diagnostic. d. Scatter radiation Scatter radiation is a secondary type of radiation that occurs when the useful beam intercepts any object, causing some x-rays to be scattered. Filtration and collimation reduces the amount of excess scatter radiation that is produced and provides better detailed images. 40 50 60 70 80 90 100 Increasing kvp, decreasing contrast
Image Characteristics (continued) FILTRATION: Low-energy x-rays do not contribute to the formation of an x-ray image; all they do is expose the body to radiation. Therefore, we need to get rid of them. The process of removing these low-energy x-rays from the x-ray beam is known as filtration. There are two components to x-ray filtration: inherent and added filtration. The combination of inherent and added filtration also work to reduce scatter radiation. Inherent Filtration: The materials present in the x-ray machine that the x-rays have to pass through are known as inherent filtration. These include the beryllium window of the x-ray tube, the oil in the tubehead, and the barrier material that keeps the oil from leaking out of the tubehead. Added Filtration: Added filtration typically refers to the addition of aluminum disks placed in the path of the x-ray beam. Disks of varying thicknesses, when combined with the inherent filtration, produce the total filtration for the x-ray machine. Federal regulations require that an x-ray machine capable of operating at 70 kvp or higher must have total filtration of 2.5mm aluminum equivalent. (The inherent filtration is equivalent to a certain thickness of aluminum). X-ray machines operating below 70 kvp need to have a total filtration of 1.5mm aluminum equivalent. Position Indication Device (PID) Added aluminum disc
Image Characteristics (continued) COLLIMATION: The collimator, located in the end of the position indication device (PID) where it attaches to the tubehead, is a lead disk with a hole in the middle (basically a lead washer). The collimator determines the size and shape of an x- ray beam. The picture at the right (top) shows the view from inside the PID, with a circular collimator in the middle. The collimator is then covered by an aluminum filter (light gray circle in the center). This will produce a round x-ray beam. The shape of the opening in the collimator determines the shape of the x-ray beam. The size of the opening determines the size of the beam at the end of the PID. PID s come in varying lengths; longer PID s have a smaller opening in the collimator. Collimator (circular) Collimator (circular) Collimation reduces scatter radiation. The x-ray beam continues to spread out as you get further from the x-ray source. More surface is exposed on the exit side of the patient than the entrance side. By collimating the beam, less overall surface is exposed and as a result, less scatter radiation is produced. Both of these things reduce patient exposure. 2.75 inches (7 cm) is the maximum diameter of a circular beam or the maximum length of the long side of a rectangular beam at the end of the PID. Rectangular Collimation is highly recommended for more detailed images and less radiation exposure to the patient. If you switch from a 7 cm round PID to a 6 cm round PID, the patient receives 25% less radiation because the area covered by the beam is reduced by 25%. Rectangular collimation (dotted line at left) results in the patient receiving 55% less radiation when compared to what they would receive with a 7 cm round PID.
Image Characteristics (continued) LATITUDE: A measurement of the range of exposures that will result in a diagnostic image. However, the wider the latitude, the lower the contrast. SPEED: Refers to the amount of radiation required to produce a radiograph of standard density. The higher the speed, the less radiation needed to properly expose the film. Higher speed films have larger silver halide crystals; the larger crystals cover more area and are more likely to interact with the x-rays. Ideal Digital Image Geometric Characteristics SHARPNESS: The capability of the x-ray receptor to reproduce the distinct, detailed outlines of an object. The sharper the image, the easier it is to make a diagnosis concerning subtle changes in the bone or tooth structure. The umbra in a radiograph refers to the sharp area of the image (the complete shadow), and it should reflect the actual anatomical area. The penumbra refers to the blurred edges of an anatomical structure (the partial shadow). The penumbra is the zone of a less sharp shadow along the edge of the image; the larger it is, the less sharp the image will be. The diagram below shows how the penumbra is formed. Sharpness is determined by: 1. Focal spot size The focal spot refers to the area of the anode surface which receives the beam of electrons from the cathode. With a larger focal spot, x- rays strike an object at more widely diverging angles because they begin farther apart at the anode. The sharp edge of the object blurs into a broader, fuzzier edge as the x-rays continue to spread out between the object and the image receptor. Therefore, a larger focal spot means less image detail and sharpness.
Sharpness is determined by: Ideal Digital Image Geometric Characteristics (continued) 2. Source-object distance The distance between the source of radiation and the object. Source-object distance can also refer to the distance between the focal spot and the object. The source refers to where the x-rays are produced, which is also called the x-ray tube. Moving the source farther away from the object (teeth) results in a sharper image that is less magnified, as shown in the left diagram below.. Source-object distance Object-receptor distance 3. Object-receptor distance The distance between the object to be imaged and the image receptor. If you decrease the object-receptor distance, sharpness will increase. The farther the receptor is from the tooth, the more the x-rays diverge, creating a wider penumbra. This decreases the sharpness of the image. When the receptor is moved closer to the tooth, the penumbra is smaller, creating a sharper image. 4. Patient motion Patient motion decreases sharpness. If the patient moves during the exposure of an x-ray image, the radiograph will be blurred, or unsharp, as seen to the right.
Ideal Digital Image Geometric Characteristics (continued) MAGNIFICATION: This results from the diverging path (spreading out) of the x-ray beam as it moves away from the target or source of the x-rays in the focal spot of the x-ray tube where the x-rays are produced. Magnification can be increased by: 1. Decreasing the source-object distance (though this will result in a larger penumbra and decreased image sharpness). 2. Increasing the object-receptor distance (this also results in a larger penumbra and decreased image sharpness). DISTORTION: A change in the shape of an object, or the relationship of that object with surrounding objects. CR refers to central ray in the images below. 1. Foreshortening is when the radiographic image measures shorter than the actual object. This happens when the x-ray source and image receptor are perpendicular, and the object being radiographed is angled. 2. Elongation is when the radiographic image appears longer than the actual object. This can happen when the x-ray is perpendicular to the object, but the image receptor is angled. Elongation can also happen when the object is parallel to the image receptor, but the x-ray tube is angled.
Avoiding Image Distortion The two most common techniques to avoid distortion are the Paralleling Technique and the Bisecting Angle Technique. 1. Paralleling Technique: The object (tooth) and image receptor are parallel to each other, and the x-ray beam is perpendicular. 2. Bisecting Angle Technique: The x-ray beam is perpendicular to the imaginary line that bisects the angle formed between the central axis of the object (tooth) and the image receptor. Paralleling Technique Bisecting Angle Technique Ideal Radiograph In the ideal radiograph, the image is the same size as the object, has the same shape and has a sharp outline with good density and contrast. Because the receptor must always be at some distance from the object, with bone and soft tissue in between, the object will always be magnified to some degree. Though magnified, the image of the object will usually have the same shape as the object when using the paralleling technique. The sharpness, density and contrast are maximized by using a longer distance between the x- ray source and the tooth and proper exposure factors. The mandibular molar periapical image above comes closest to satisfying the properties of an ideal radiograph (either paralleling or bisecting). The receptor is closer to the teeth in this location than in any other part of the mouth and the receptor is usually parallel with the teeth.
Helpful Link Learn Digital http://www.learndigital.net Articles Advances in Digital Radiography: Physical Principles and System Overview Körner et al. http://pubs.rsna.org/doi/full/10.1148/rg.273065075 Best Practices in Digital Radiography Herrmann, et al. https://www.asrt.org/docs/defaultsource/publications/whitepapers/asrt12_bstpracdigradwhp_final.pdf Better Imaging: The advantages of digital radiography Paul F. van der Stelt http://jada.ada.org/article/s0002-8177(14)63458-9/pdf Digital radiography: A comparison with modern conventional imaging G. J. Bansal https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2563775/ Worldwide Implementation of Digital Imaging in Radiology World Health Organization http://www-pub.iaea.org/mtcd/publications/pdf/pub1647web.pdf About the Author Constance Kuntupis, RDH, MA ASSISTANT PROFESSOR OF CLINICAL DENTISTRY IN THE DEPARTMENT OF RADIOLOGY, AT THE OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY. SHE RECEIVED HER BACHELOR OF ARTS DEGREE IN SECONDARY EDUCATION AND HER BACHELOR OF SCIENCE DEGREE IN DENTAL HYGIENE FROM WEST LIBERTY UNIVERSITY IN WEST VIRGINIA. AFTER SEVERAL YEARS OF CLINICAL EXPERIENCE AS A REGISTERED DENTAL HYGIENIST, MS. KUNTUPIS COMPLETED A MASTER OF ARTS DEGREE IN ADULT EDUCATION AND LIFELONG LEARNING AT THE OHIO STATE UNIVERSITY. AS A DENTAL HYGIENIST IN THE GENERAL PRACTICE RESIDENCY / ADVANCED GENERAL DENTISTRY CLINIC AT OSU FROM 1992 1998, MS. KUNTUPIS HAS SPECIALIZED IN PROVIDING CARE TO PATIENTS WITH SIGNIFICANT MEDICAL OR PHYSICAL DISABILITIES AND PATIENTS WITH SPECIAL NEEDS. MS. KUNTUPIS IS CURRENTLY AN ASSISTANT PROFESSOR OF CLINICAL DENTISTRY IN THE DEPARTMENT OF RADIOLOGY AT THE OHIO STATE COLLEGE OF DENTISTRY. SHE HAS COMPLETED NUMEROUS ORAL RADIOGRAPHY CONTINUING EDUCATION COURSES AND WORKSHOPS ACROSS THE COUNTRY AND HAS BEEN TEACHING ORAL RADIOGRAPHY TO DENTAL ALLIED HEALTH PROFESSIONALS FOR NEARLY 20 YEARS. MS. KUNTUPIS CAN BE REACHED AT KUNTUPIS.1@OSU.EDU Neither I nor my immediate family have any financial interests that would create a conflict of interest or restrict my judgement with regard to the content of this course
Post-Test Page 1 Answer each question ONLINE (link provided on SMS website) Answer 9 of 12 questions correctly to pass Answer post-course survey questions and click Finish Deadline is December 13, 2017 4:30pm 1. Radiographic density is defined as: a) A radiopaque radiograph b) A radiolucent radiograph c) The degree of blackness or darkness in a radiograph d) The difference in degrees of blackness between adjacent areas on a dental radiograph 2. The radiolucent area of a radiograph refers to the portion that is: a) Black b) White c) Gray d) Coated with an emulsion 3. Filtration and collimation reduce the amount of excess scatter radiation. a) True b) False 4. A beryllium window is an example of. a) Inherent filtration b) Added filtration 5. Which of the following changes will result in a radiograph with increased density? a) Increased milliamperage (ma) b) Increased kilovoltage peak (kvp) c) Increased exposure time d) All of the above 6. The Paralleling Technique and the Bisecting Angle Technique are used to avoid: a) Patient Motion b) Magnification c) Image distortion d) Low contrast Author Constance Kuntupis, RDH, MA kuntupis.1@osu.edu SMS Director John R. Kalmar, DMD, PhD Kalmar.7@osu.edu SMS Program Manager Sydney Fisher, BS Fisher.1057@osu.edu SMS Program Assistant Nick Kotlar, BS Kotlar.2@osu.edu
Post-Test Page 2 Answer each question ONLINE (link provided on SMS website) Answer 9 of 12 questions correctly to pass Answer post-course survey questions and click Finish Deadline is December 13, 2017 4:30pm 7. Which of the following describes the use of filtration in dental x- rays? a) A filter removes low-energy x-rays b) A filter creates more radiopacity in an image c) A filter creates fog on a radiographic image d) None of the above 8. A(n) restricts the size and shape of an x-ray beam at the end of a PID to a maximum of 2.75 inches. a) Filter b) Aluminum disc c) Oil barrier d) Collimator 9. Which of the following best minimizes patient exposure to radiation? a) Circular collimator b) Rectangular collimator 10. A smaller focal spot leads to: a) A smaller penumbra, and a sharper image b) A larger penumbra, and a fuzzier (less sharp) image 11. Fog on a radiograph occurs when film is exposed to light, heat or chemical fumes. a) True b) False 12. Which of the following would increase magnification of the radiographic image? a) Increasing source-object distance b) Increasing object-receptor distance Author Constance Kuntupis, RDH, MA kuntupis.1@osu.edu SMS Director John R. Kalmar, DMD, PhD Kalmar.7@osu.edu SMS Program Manager Sydney Fisher, BS Fisher.1057@osu.edu SMS Program Assistant Nick Kotlar, BS Kotlar.2@osu.edu End of Test