Radiation Dose Survey for Common Computed Tomography Exams: 2013 British Columbia Results

Evaluation of Impact of Factors Affecting CT Radiation Dose for Optimizing Patient Dose Levels

The dose metrics and factors influencing radiation exposure for patients undergoing head, chest, and abdominal computed tomography (CT) scans were investigated for optimization of patient dose levels. The local diagnostic reference levels (DRLs) of adult CT scans performed in our hospital were established based on 28,147 consecutive examinations, including 5510 head scans, 9091 chest scans, and 13,526 abdominal scans. Among the six CT scanners used in our hospital, four of them are 64-slice multi-detector CT units (MDCT64), and the other two have detector slices higher than 64 (MDCTH). Multivariate analysis was conducted to evaluate the effects of body size, kVp, mAs, and pitch on volume CT dose index (CTDIvol). The local DRLs expressed in terms of the 75th percentile of CTDIvol for the head, chest, and abdominal scans performed on MDCT64 were 59.32, 9.24, and 10.64 mGy, respectively. The corresponding results for MDCTH were 57.90, 7.67, and 9.86 mGy. In regard to multivariate analysis, CTDIvol showed various dependence on the predictors investigated in this study. All regression relationships have coefficient of determination (R2) larger than 0.75, indicating a good fit to the data. Overall, the research results obtained through our workflow could facilitate the modification of CT imaging procedures once the local DRLs are unusually high compared to the national DRLs.

An Environmental Scan of the National and Provincial Diagnostic Reference Levels in Canada for Common Adult Computed Tomography Scans

Several regulatory bodies have agreed that low-dose radiation used in medical imaging is a weak carcinogen that follows a linear, non-threshold model of cancer risk. While avoiding radiation is the best course of action to mitigate risk, computed tomography (CT) scans are often critical for diagnosis. In addition to the as low as reasonably achievable principle, a more concrete method of dose reduction for common CT imaging exams is the use of a diagnostic reference level (DRL). This paper examines Canada's national DRL values from the recent CT survey and compares it to published provincial DRLs as well as the DRLs in the United Kingdom and the United States of America for the 3 most common CT exams: head, chest, and abdomen/pelvis. Canada compares well on the international scale, but it should consider using more electronic dose monitoring solutions to create a culture of dose optimization.

Periradicular infiltration of the lumbar spine: is iterative reconstruction software necessary to establish ultra-low-dose protocols? A quantitative and qualitative approach

PURPOSE

Computed tomography (CT)-guided periradicular infiltration therapy has emerged as an effective treatment option for patients with low back pain. Concern about radiation exposure requires approaches allowing significant dose reduction. The purpose of this study is to evaluate the need for iterative reconstruction software in CT-guided periradicular infiltration therapy with an ultra-low-dose protocol.

MATERIALS AND METHODS

One hundred patients underwent CT-guided periradicular infiltration therapy of the lumbar spine using an ultra-low-dose protocol with adaptive iterative dose reduction 3D (AIDR 3D) for image reconstruction. In addition, images were reconstructed with filtered back-projection (FBP). Four experienced raters evaluated both reconstruction types for conspicuity of anatomical and instrumental features important for ensuring safe patient treatment. Image noise was measured as a quantitative marker of image quality.

RESULTS

Interrater agreement was good for both AIDR 3D (Kendall's W = 0.83) and FBP (0.78) reconstructions. Readers assigned the same scores for all features and both reconstruction algorithms in 81.3% of cases. Image noise was significantly lower (average SD of 60.07 vs. 99.54, p < 0.05) for AIDR 3D-reconstructed images.

CONCLUSION

Although it significantly lowers image noise, iterative reconstruction software is not mandatory to achieve adequate image quality with an ultra-low-dose CT protocol for guiding periradicular infiltration therapy of the lumbar spine.

Diagnostic Reference Levels and Monitoring Practice Can Help Reduce Patient Dose From CT Examinations

OBJECTIVE

The purpose of this study is to establish provincial diagnostic reference levels (DRLs) and to determine whether this process may help reduce the patient radiation dose from the most frequently performed CT examinations.

MATERIALS AND METHODS

We investigated the following CT examinations: head, chest, low-dose chest, abdomen and pelvis, and chest, abdomen, and pelvis examinations. The sample for each protocol included 15 patients of average body weight (mean [± SD], 70 ± 20 kg). The differences in dose between scanners were evaluated using one-way ANOVA. Correlations between dose, scanner age, and the number of detector rows were assessed using the Pearson correlation coefficient. A sample of abdominal and chest examinations were randomized and blinded for review by experienced radiologists who graded diagnostic image quality. Provincial DRLs were calculated as the 75th percentile of patient dose distributions. For hospitals with doses exceeding the DRLs, dose reduction was recommended, followed by another survey.

RESULTS

The initial survey included data of 1185 patients, and an additional 180 patients were surveyed after protocol optimization. The differences between the mean values of the dose distributions from each scanner were statistically significant (p < 0.05) for all examinations. The variation was greatest for low-dose chest CT, with a greater than fivefold difference in the mean dose values noted between scanners. A very weak correlation was found between dose and scanner age or the number of detector rows. Analysis of image quality revealed no statistically significant differences in any scoring categories, with the exception of the noise category in abdominal imaging. Implementation of the DRLs allowed a reduction in patient dose of up to 41% as a result of a protocol change.

CONCLUSION

Establishing provincial DRLs allows an effective reduction in patient dose without resulting in degradation of image quality.

Knowing the Enemy: Health Care Provider Knowledge of Computed Tomography Radiation Dose and Associated Risks

BACKGROUND

There is ionizing radiation and associated risk from many medical imaging examinations, especially computed tomography (CT). Unfortunately, health care providers often have limited knowledge regarding radiation dose levels and potential risk.

RESEARCH OBJECTIVES

To assess knowledge of dose levels and risk among referring physicians, imaging technologists, and radiologists in Saskatoon, Saskatchewan, and to identify potential differences between and within those groups.

MATERIALS AND METHODS

A survey was designed and administered to health care professionals.

RESULTS

A total of 308 of 328 surveys were completed (91% response rate). Overall 73% of physicians, 97% of radiologists, and 76% of technologists correctly believed that there is a risk for cancer from an abdomen-pelvic CT scan. Although only 18% of physicians, 28% of radiologists, and 22% of technologists selected the most appropriate estimate of abdominal-pelvic CT dose in terms of chest x-ray equivalents, this is similar to other reported studies. Physicians and technologists who use CT were more likely to select the correct dose than those who do not. Most respondents (91% of physicians, 100% of radiologists, and 100% of technologists) felt that pregnant patients should always be informed about radiation dose as a risk. Although frequency of discussing risk decreased with increasing patient age, technologists were more likely to discuss risk at any age. A total of 93% of respondents expressed interest in receiving dose feedback from medical imaging procedures.

CONCLUSIONS

Radiologists and technologists generally showed better knowledge than referring physicians. Among physicians and technologists, knowledge was better in those who use CT than those who do not.