CT dose reduction: approaches, strategies and results from a province-wide program in Quebec

Establishing Diagnostic Reference Levels for CT Through a Provincial Medical Informatics Metadata Repository in Ontario

PURPOSE

To determine whether computed tomography radiation dose data could be captured electronically across hospitals to derive regional diagnostic reference levels for quality improvement.

METHODS

Data on consecutive computed tomography examinations from 8 hospitals were collected automatically in a central database (Repository) from April 2017 to September 2017. The most frequently performed examinations were used to determine the standard protocols for each hospital. Diagnostic reference levels across hospitals were derived using statistical distribution for 2 radiation dose metrics. These values were compared between hospitals, within and between hospitals by scanner and against national Health Canada achievable doses and diagnostic reference levels.

RESULTS

Three master protocol groups, Head, Abdomen-Pelvis, and Chest-Abdomen-Pelvis, accounted for 43% of all valid studies (N = 40 277). For the Repository, 11 of 12 mean values and 75th percentile diagnostic reference levels were below the Health Canada mean and 75th percentile values, and one was the same as the Health Canada value. Mean radiation dose by protocol varied by as much as 97% between hospitals. There was no consistent pattern in the difference between mean doses between large and small hospitals.

CONCLUSION

This electronic data acquisition process could be used to continually update achievable doses for frequently used computed tomography examinations in Ontario and eliminate the need for nationwide manual surveys. Results compared across institutions will allow hospitals to maintain achievable doses and lower patient exposure.

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.

Effects of dose reduction on bone strength prediction using finite element analysis

This study aimed to evaluate the effect of dose reduction, by means of tube exposure reduction, on bone strength prediction from finite-element (FE) analysis. Fresh thoracic mid-vertebrae specimens (n = 11) were imaged, using multi-detector computed tomography (MDCT), at different intensities of X-ray tube exposures (80, 150, 220 and 500 mAs). Bone mineral density (BMD) was estimated from the mid-slice of each specimen from MDCT images. Differences in image quality and geometry of each specimen were measured. FE analysis was performed on all specimens to predict fracture load. Paired t-tests were used to compare the results obtained, using the highest CT dose (500 mAs) as reference. Dose reduction had no significant impact on FE-predicted fracture loads, with significant correlations obtained with reference to 500 mAs, for 80 mAs (R²  = 0.997, p < 0.001), 150 mAs (R² = 0.998, p < 0.001) and 220 mAs (R² = 0.987, p < 0.001). There were no significant differences in volume quantification between the different doses examined. CT imaging radiation dose could be reduced substantially to 64% with no impact on strength estimates obtained from FE analysis. Reduced CT dose will enable early diagnosis and advanced monitoring of osteoporosis and associated fracture risk.