1. Dianna Cody, Ph.D. Professor University of Texas M.D. Anderson Cancer Center Houston, TX

2.  LSS  Fred Larke  Randell Kruger  Mike Flynn  Xizeng Wu  ACRIN  Dianna Cody  Chris Cagnon  Mike McNitt-Gray  Tony Seibert  Phil Judy

3.  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.  CT Dose Index  10cm Pencil Ion Chamber  Electrometer  PMMA phantom  16cm Diameter  32cm Diameter

5.  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

7. Statistically significant differences in CTDI by vendor? YES

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

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

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

11.  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