Full-Cohort Organ Dose Assessment from Low-Dose CT Lung Cancer Screening in the National Lung Screening Trial

Organ-specific dose estimates are needed to characterize radiation exposure from repeated low-dose computed tomography (CT) lung cancer screening in the National Lung Screening Trial (NLST). The objective was to estimate study-level doses and participant-level cumulative doses in the NLST CT screening cohort.

This retrospective dosimetry study included 25,051 NLST CT screening participants from the Lung Screening Study and American College of Radiology Imaging Network components after excluding participants with any examination lacking a valid manufacturer-appropriate tube current-time input. Image-series metadata were linked with age, sex, height, and weight, and then valid records were grouped into 69,601 study-level screening examinations. Organ absorbed doses and effective dose were calculated using the National Cancer Institute dosimetry system for Computed Tomography with sex- and body-size-specific adult phantoms. Scan-range-related dose uncertainty was assessed with 50 stochastic simulations.

Participants underwent a mean of 2.78 study-level screening examinations; the median study-level volume CT dose index was 3.30 mGy. Median (interquartile range) study-level lung, breast, heart wall, active marrow, and effective doses were 3.93 (3.13-4.96), 3.94 (3.14-5.04), 3.94 (3.14-5.01), and 1.26 (0.99-1.60) mGy, and 2.07 (1.65-2.59) mSv, respectively. Corresponding cumulative participant-level doses were 11.30 (8.89-14.50), 11.39 (9.01-14.75), 11.41 (8.93-14.66), and 3.63 (2.79-4.66) mGy, and 5.94 (4.69-7.64) mSv. Scan-range-related dose uncertainty was greatest for thyroid dose (mean coefficient of variation, 21.1%) and low for in-field organs.

Using NLST low-dose CT screening data, we estimated participant-level cumulative organ and effective doses and characterized variation across organs and body-size groups.