Analysis of Computed Tomography Radiation Doses Used for Lung Cancer Screening Scans

Abstract

ACR) has recognized the importance of minimizing radiation doses used for lung cancer screening (LCS) computed tomography (CT). However, without standard protocols, doses could still be unnecessarily high, reducing screening margin of benefit. OBJECTIVE To characterize LCS CT radiation doses and identify factors explaining variation. DESIGN, SETTING, AND PARTICIPANTSWe prospectively collected LCS examination dose metrics, from 2016 to 2017, at US institutions in the University of California, San Francisco International Dose Registry. Institution-level factors were collected through baseline survey.Mixed-effects linear and logistic regression models were estimated using forward variable selection. Results are presented as percentage excess dose and odds ratios (ORs) with 95% confidence intervals (CIs). The analysis was conducted between 2018 and 2019.MAIN OUTCOMES AND MEASURES Log-transformed measures of (1) mean volume CT dose index (CTDIvol, mGy), reflecting the average radiation dose per slice; (2) mean effective dose (ED, mSv), reflecting the total dose received and estimated future cancer risk; (3) proportion of CT scans using radiation doses above ACR benchmarks (CTDIvol >3 mGy, ED >1 mSv); and (4) proportion of CT scans using radiation doses above 75th percentile of registry doses (CTDIvol >2.7 mGy, ED >1.4 mSv).RESULTS Data were collected for 12 529 patients undergoing LCS CT scans performed at 72 institutions. Overall, 7232 participants (58%) were men, and the median age was 65 years (interquartile range [IQR], 60-70). Of 72 institutions, 15 (21%) had median CTDIvol and 47 (65%) had median ED above ACR guidelines. Institutions allowing any radiologists to establish protocols had 44% higher mean CTDIvol (mean dose difference [MDD], 44%; 95% CI, 19%-69%) and 27% higher mean ED (MDD, 27%; 95% CI, 5%-50%) vs those limiting who established protocols. Institutions allowing any radiologist to establish protocols had higher odds of examinations exceeding ACR CTDIvol guidelines (OR, 12.0; 95% CI, 2.0-71.4), and 75th percentile of registry CTDIvol (OR, 19.0; 95% CI, 1.9-186.7) or ED (OR, 8.5; 95% CI, 1.7-42.9). Having lead radiologists establish protocols resulted in lower odds of doses exceeding ACR ED guidelines (OR, 0.01; 95% CI, 0.001-0.1). Employing external vs internal medical physicists was associated with increased odds of exceeding ACR CTDIvol guidelines (OR, 6.1; 95% CI,. Having medical physicists establish protocols was associated with decreased odds of exceeding 75th percentile of registry CTDIvol (OR, 0.09; 95% CI, 0.01-0.59). Institutions reporting protocol updates as needed had 27% higher mean CTDIvol (MDD, 27%; 95% CI, 8%-45%).CONCLUSIONS AND RELEVANCE Facilities varied in LCS CT radiation dose distributions. Institutions limiting protocol creation to lead radiologists and having internal medical physicists had lower doses.

Latest CT technologies in lung cancer screening: protocols and radiation dose reduction

“…Current lung cancer screening protocols recommend repeated screening at either annual or biannual frequency for eligible individuals (10,11). On an individual level this may result in over 25 scans over a lifetime with in practice widely varying cumulative radiation dose (12,13). Consequently, the estimates for induced cancer risk by repeated screening for an entire population vary as well depending on the used CT protocol, CT generation and expertise of institutions to optimize CT protocols (12)(13)(14)(15).…”

“…On an individual level this may result in over 25 scans over a lifetime with in practice widely varying cumulative radiation dose (12,13). Consequently, the estimates for induced cancer risk by repeated screening for an entire population vary as well depending on the used CT protocol, CT generation and expertise of institutions to optimize CT protocols (12)(13)(14)(15). The aim of this review is to provide clinicians with an overview of the development of the CT protocol for lung cancer screening, the current protocol recommendations and radiation dose reduction possibilities in lung cancer CT screening.…”

The radiologist’s role in lung cancer screening

“…Of note, emphasis is placed on preferring conservative management of findings with relatively low clinical impact (e.g., control overdiagnosis) by thoracic radiologists and medical physicists. Despite guidelines from the American College of Radiology (ACR) on recommended CT radiation dose levels (13), a cohort study of 12,529 participants at 72 institutions in the US found a wide variation in the distribution of LCS CT doses across facilities (14). According to the authors, 21% of the institutions had median volume computed tomography dose index (CTDI vol ) above ACR benchmarks (>3 mGy).…”

Five-star rating system for acceptable quality and dose in CT

“…Studies with large multi-institution or national registry suggest that despite recommendations for reduced dose CT protocols for specific clinical indications and availability of dose monitoring data, adoption of dose-conscious CT protocols remain low [3,4]. Over 65% of participating CT facilities in the USA exceeded the recommended radiation dose level for lung cancer screening with low-dose CT [3].…”

“…Over 65% of participating CT facilities in the USA exceeded the recommended radiation dose level for lung cancer screening with low-dose CT [3]. Likewise, only 8% of US CT facilities used low-dose CT for kidney stones despite recommendations and evidence within the American College of Radiology Appropriateness Criteria [4]. This pattern hints at a widespread disregard for sufficient diagnostic quality at optimized or reduced radiation dose in favor of convenience, optimization, or medicolegal safety.…”