COMP Report: A survey of radiation safety regulations for medical imaging x-ray equipment in Canada.

X-ray regulations and room design methodology vary widely across Canada. The Canadian Organization of Medical Physicists (COMP) conducted a survey in 2016/2017 to provide a useful snapshot of existing variations in rules and methodologies for human patient medical imaging facilities. Some jurisdictions no longer have radiation safety regulatory requirements and COMP is concerned that lack of regulatory oversight might erode safe practices. Harmonized standards will facilitate oversight that will ensure continued attention is given to public safety and to control workplace exposure. COMP encourages all Canadian jurisdictions to adopt the dose limits and constraints outlined in Health Canada Safety Code 35 with the codicil that the design standards be updated to those outlined in NCRP 147 and BIR 2012.

Health Canada Safety Code 35: awareness of the impacts for diagnostic radiology in Canada.

Health Canada Safety Code 35 brings Canada's diagnostic imaging radiation output and protection standards to an international level. This Safety Code is comprehensive and will have broad implications for most health care facilities. This Safety Code outlines quality control procedures that will ultimately reduce patient dose while providing the best quality diagnostic images, all within a safe working environment. However, the Safety Code has some important omissions and errors of which radiologists should be aware, especially if they act as radiation safety officers. We hope that highlighting these issues will be the beginning of an ongoing dialogue between Health Canada, radiologists, medical physicists, and technologists that will not only bring awareness of Safety Code 35 but will provide a basis for updating, correcting, and improving future revisions of the Safety Code.

Assessment of patient doses in CR examinations throughout a large health region.

Optimization and standardization of radiographic procedures in a health region minimizes patient exposure while producing diagnostic images. This report highlights the dose variation in common computed radiography (CR) examinations throughout a large health region. The RadChex cassette was used to measure the radiation exposure at the table or wall bucky in 20 CR rooms, in seven hospitals, using CR technology from two vendors. Exposures were made to simulate patient exposure (21 cm polymethyl methacrylate) under standard conditions for each bucky: 81 kVp at 100 cm for anteroposterior abdomen table bucky exposures (180 cm for posteroanterior chest wall bucky exposures), using the left, the right, or the center automatic exposure control (AEC) cells. Protocol settings were recorded. An average of 37% variation was found between AEC chambers, with a range between 4% and 137%. A 60% difference in dose was discovered between manufacturers, which was the result of the manufacture's image processing algorithm and subsequently corrected via software updates. Finally, standardizing AEC cell selection during common chest examinations could reduce patient dose by up to 30%. In a large health region, variation in exam protocols can occur, leading to unnecessary patient dose from the same type of examination. Quality control programs must monitor exam protocols and AEC chamber calibration in CR to ensure consistent, minimal, patient dose, regardless of hospital or CR vendor. Furthermore, this report highlights the need for communication between radiologists, technologists, medical physicist, service engineers, and manufacturers required to optimize CR protocols.

Basic physics of ultrasound imaging.

The appearance of ultrasound images depends critically on the physical interactions of sound with the tissues in the body. The basic principles of ultrasound imaging and the physical reasons for many common artifacts are described.

Implementation of a new undergraduate radiology curriculum: experience at the University of British Columbia.

OBJECTIVES: The purpose of this study was to review and revise the undergraduate radiology curriculum at the University of British Columbia to improve radiology education to medical students and to meet the needs of a medical program with province-wide distribution. METHODS: We identified the radiology content of the curriculum from the Curriculum Management and Information Tool online database, from personal interviews with curriculum heads, and from published information. Undergraduates' and recent graduates' opinions were solicited by means of surveys. Information on radiology curricula at medical schools across Canada was gathered from email surveys and personal contacts with members of the Canadian Heads of Academic Radiology (CHAR). RESULTS: Review of our curriculum indicated that lack of a unified syllabus resulted in redundant content, gaps in knowledge, and lack of continuity in the curriculum. Results from the survey of programs across Canada indicated that most schools also lacked a formal radiology curriculum for medical students. By adapting the guidelines from the Association of Medical Student Education in Radiology, we revised our undergraduate radiology curriculum to emphasize integration and self-learning. The modified curriculum includes a combination of instructional technology, focused lectures in preclinical years, and in-context seminars in clerkship rotations. CONCLUSION: Most medical schools in Canada do not have a formal radiology curriculum for medical students. A structured curriculum is required to improve the quality of radiology teaching for medical students.

Radiation doses to patients receiving computed tomography examinations in British Columbia.

OBJECTIVE: To estimate the diagnostic reference levels and effective radiation dose to patients from routine computed tomography (CT) examinations in the province of British Columbia, Canada. METHODS: The patient weight, height and computed tomography dose index or dose linear product (DLP) were recorded on study sheets for 1070 patients who were referred for clinically indicated routine CT examinations at 18 radiology departments in British Columbia. Sixteen of the scanners were multidetector row scanners. RESULTS: The average patient dose varied from hospital to hospital. The largest range was found for CT of the abdomen, for which the dose varied from 3.6 to 26.5 (average 10.1) mSv. For head CT, the range was 1.7 to 4.9 (average 2.8) mSv; for chest CT, it was 3.8 to 26 (average 9.3) mSv; for pelvis CT, it was 3.5 to 15.5 (average 9.0) mSv; and for abdomen-pelvis CT, it was 7.3 to 31.5 (average 16.3) mSv. Reference dose values were calculated for each exam. These DLP values are as follows: head, 1300 mGy cm; chest, 600 mGy cm; abdomen, 920 mGy cm; pelvis, 650 mGy cm; and abdomen-pelvis, 1100 mGy cm. CONCLUSION: Among hospitals, there was considerable variation in the DLP and patient radiation dose for a specific exam. Reference doses and patient doses were higher than those found in similar recent surveys carried out in the United Kingdom and the European Union. Patient doses were similar to those found in a recent survey in Germany.

Radiation dose in abdominal computed tomography: the role of patient size and the selection of tube current.

OBJECTIVE: To develop an algorithm for selecting tube current for computed tomography (CT), based on patient weight, that produces abdominal CT images of consistent image quality. METHODS: We recorded body weight and radiation exposure parameters for 37 patients undergoing abdominal CT. Two radiologists blind to the CT technique independently graded 11 measures of image quality, using a 5-point (5 = excellent, 4 = good, 3 = acceptable, 2 = poor, and 1 = unacceptable) scale. These scores were averaged to generate an overall image quality score. Using linear regression, we found a target image noise level that corresponded to an overall image quality score of 4.5. We measured CT image noise in 9 uniformly attenuating regions of interest in the liver and abdominal aorta. We used linear regression to assess the relation between tube current and image noise. A prediction equation was developed to set the tube current in different-sized patients to produce images at the target noise level. Finally, we calculated the dose savings that would have resulted with this tube-current selection technique. RESULTS: Image noise was correlated with patient weight (r2 = 0.81). At an overall image quality score of 4.5, the noise was 16 HU. Using this target noise value, we determined the required tube current for each patient weight and found that the use of this technique would have reduced radiation exposure for all patients weighing less than 70 kg. The dose reduction for the smallest patient (35.4 kg) was 72%. CONCLUSION: To produce CT scans of similar quality, a simple prediction equation can be developed for any scanner to optimize radiation dose for patients of all body weights.

Dose reduction in CT while maintaining diagnostic confidence: diagnostic reference levels at routine head, chest, and abdominal CT--IAEA-coordinated research project.

PURPOSE: To measure radiation doses for computed tomography (CT) of the head, chest, and abdomen and compare them with the diagnostic reference levels, as part of the International Atomic Energy Agency Research coordination project. MATERIALS AND METHODS: The local ethics committees of all participating institutions approved the study protocol. Written informed consent was obtained from all patients. All scanners were helical single-section or multi-detector row CT systems. Six hundred thirty-three patients undergoing head (n = 97), chest (n = 243), or abdominal (n = 293) CT were included. Collected data included patient height, weight, sex, and age; tube voltage and tube current-time product settings; pitch; section thickness; number of sections; weighted or volumetric CT dose index; and dose-length product (DLP). The effective dose was also estimated and served as collective dose estimation data. RESULTS: Mean volumetric CT dose index and DLP values were below the European diagnostic reference levels: 39 mGy and 544 mGy . cm, respectively, at head CT; 9.3 mGy and 348 mGy . cm, respectively, at chest CT; and 10.4 mGy and 549 mGy . cm, respectively, at abdominal CT. Estimated effective doses were 1.2, 5.9, and 8.2 mSv, respectively. CONCLUSION: Comparison of CT results with diagnostic reference levels revealed the need for revisions, partly because the newer scanners have improved technology that facilitates lower patient doses.

Optimization of dose and image quality for computed radiography and digital radiography.

The surface doses to patients during chest, abdomen and pelvis radiography were measured over a period of 3 years, during which time computed radiography (CR) and digital radiography (DR) systems were introduced to replace film-screen systems. For film-screen and CR the surface doses were measured with thermoluminescent dosimeters. For DR the surface doses were calculated from the dose-area product (DAP) meter readings. Measurements were made for each type of examination and detector type on 10 average-size patients. Measurements were made immediately after the new systems were introduced, and subsequently as adjustments were made to optimize dose and image quality. Published diagnostic reference levels were used as target values in this optimization. Initially, CR doses were the same as or higher than for film-screen, and the doses were lower for DR compared to film-screen. Subsequent clinical experience with the systems led to changes in the technique used for chest examinations both for CR and for DR. For CR, it was possible to change the algorithm and decrease the dose to one quarter of the initial value with acceptable image quality. For DR, it was decided to reduce noise by increasing the dose by a factor of two. No changes were made to abdomen or pelvic imaging techniques for either CR or DR. The final patient surface doses using CR were similar to published diagnostic reference doses; for DR, all patient doses were less than published reference levels.

Assessment of PACS display systems.

This work describes our experience in reviewing the performance criteria for display systems and how we have implemented a practical approach to the assessment of the workstation environment in a large tertiary care hospital. The acceptance criteria contained in the draft report of Topic Group 18 of the American Association of Physicists in Medicine (AAPM) were used as a basis for assessment of primary and secondary displays. A telescopic photometer was used to measure the maximum luminance and the contrast ratio of the image for the displays used in our radiology department and in the operating and emergency rooms using the standard Society of Motion Picture and Television Engineers (SMPTE) pattern, in ambient light and with light decreased as much as possible. About half of the displays met the AAPM criteria for minimum luminance and contrast ratio in low light. None of the systems met the contrast ratio criteria in ambient light. The challenges in improving the performance and calibrating displays are discussed.

Change in patient doses from radiological examinations at the Vancouver General Hospital, 1991-2002.

OBJECTIVE: Much concern has been expressed over the radiation doses and potential harm from x-ray examinations. However, there have been few longitudinal studies in North America. A survey of doses from radiological examinations in Canada was last carried out in 1995. This study was undertaken to estimate the change in the number of patient examinations and patient dose since this last Canadian survey. METHODS: The number of radiological examinations and numbers of patients for the years 1991 to 2002 were obtained from workload statistics, which are reported to the Canadian government each year. Radiological examinations were of the following type: general, gastrointestinal or genitourinary, angiography, and computed tomography (CT). Average doses were calculated for each group of examinations. RESULTS: From 1991 to 2002 there was an increase of 28% in the total number of x-ray examinations performed. The proportion of most types of examination has stayed fairly constant, except for CT, which has increased fourfold in the last 8 years. The striking change is the increased contribution to patient effective dose from CT since 1996, these examinations now comprising nearly 60% of the total patient dose. The average annual effective dose per patient has nearly doubled-from 3.3 mSv in 1991 to 6.0 mSv in 2002. CONCLUSION: This paper provides a simple method for any Canadian hospital to estimate the radiation dose to its patients. At the Vancouver General Hospital (VGH), the number of patient examinations has increased by 28%, but the average annual patient effective dose has almost doubled. CT is now by far the largest contributor to patient dose in diagnostic radiology. Efforts need to be made to reduce patient dose by such methods as reduction in unnecessary exams, substitution of nonionizing techniques where possible, and optimization of dose.