Local Diagnostic Reference Levels for Lung Cancer Screening In British Columbia
Abstract
Purpose
Optimize patient dose for Lung Cancer Screening (LCS) using local diagnostic reference levels (DRLs).
Methods
The provincial LCS program launched in May 2022 with accreditation requirements such that the standard sized patient CTDI < 3.0 mGy and that patient size and weight need to be recorded for every patient. Three assessments of DRLs were performed for all scanners participating in LCS in our Health Authority and protocol recommendations were made. 12-15 scanners were part of the study including models from GE, Siemens, and Canon. Some scanners were replaced or added to the fleet over the course of the study. Data were downloaded from the ACR-DIR for scanners capable and manually collected for the rest. Upper and Lower DRLs (75th and 25th percentiles, respectively) were determined and protocol recommendations were made. After an implementation period, data collection resumed. Three DRL iterations have been completed to date.
Results
Upper DRL decreased from 3.2 to 2.7 mGy and the Lower DRL decreased from 1.3 to 1.1 mGy. No intervention was needed based on the Lower DRL, while the GE scanners needed their doses reduced since the median values were near or above the Upper DRL. For Standard Sized patients, the Upper DRL decreased from 2.3 to 1.7 mGy while the lower DRL decreased from 1.0 to 0.9 mGy over the course of this study.
Conclusion
GE scanners had their Noise Indexes set too high initially and are slowly being reduced to ensure a sudden change in image quality does not occur for the Radiologists. Median CTDI values are well below accreditation standards and the DRL initiative is further reducing LCS population dose.