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CT Dose indices of all multi-detector row CT scanners used in the NLST

This study examines the CT dose indices of multi-detector row CT scanners used in the NLST, including statistically significant differences in CTDI by vendor, scanner models, and level of technology. The study aims to estimate radiation dose to the NLST population from both chest X-ray and CT exams.

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CT Dose indices of all multi-detector row CT scanners used in the NLST

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  1. CT Dose indices of all multi-detector row CT scanners used in the NLST Dianna Cody, Ph.D. Professor University of Texas M.D. Anderson Cancer Center Houston, TX

  2. Joint LSS-ACRIN Physics Team • LSS • Fred Larke • Randell Kruger • Mike Flynn • Xizeng Wu • ACRIN • Dianna Cody • Chris Cagnon • Mike McNitt-Gray • Tony Seibert • Phil Judy

  3. NLST Quality Control Program • Subject of Cagnon, et al paper (Acad Radiol 2006: 1431-1441.) • Certification for each CT scanner (entry) • Annual physics tests – DOSE measurement • Over course of trial, collected 221 dose measurements for 96 CT scanners

  4. Current Method • CT Dose Index • 10cm Pencil Ion Chamber • Electrometer • PMMA phantom • 16cm Diameter • 32cm Diameter

  5. Normalized CTDI • CTDI/mAs • Removes site-to-site variability (patient size) • Reflects MACHINE OUTPUT • All about the SCANNERS • Does NOT reflect patient dose • Does NOT reflect patient exposure • Does NOT reflect how sites operated scanners

  6. Statistically significant differences in CTDI by vendor? YES

  7. Statistically significant differences in CTDI by scanner models within a vendor? YES (3 out of 4)

  8. Statistically significant differences in CTDI among all models and all vendors? YES

  9. Statistically significant differences in CTDI by level of technology? YES

  10. Current physics plans • CT dose material presented at RSNA (2007) • Submitted manuscript to Radiology summarizing effective dose estimates from NLST chest CT exams (RSNA 2008) • Chest x-ray dose manuscript in preparation (RSNA 2010) • Hope to estimate radiation dose to NLST population from both CXR & CT exams

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