Frederick Joseph Larke MS, Presenter: Nothing to Disclose

Dianna Cody PhD, Abstract Co-Author: Speaker, Medical Technology Management Institute, Milwaukee, WI

Randell L. Kruger PhD, Abstract Co-Author: Nothing to Disclose

Christopher H. Cagnon PhD, Abstract Co-Author: Nothing to Disclose

Michael James Flynn PhD, Abstract Co-Author: Researcher, F. Hoffmann-La Roche Ltd Researcher, Shimadzu Corporation

Michael F. McNitt-Gray PhD, Abstract Co-Author: Member, Physics Committee, American College of Radiology Imaging Network (ACRIN) Consultant, ACRIN ACR Image Metrix Consultant, Rapiscan Systems UCLA Radiological Sciences has a research agreement with Siemens Medical Solutions Research grants from National Cancer Institute (NCI) and National Institute of Biomedical Imaging and Bioengineering (NIBIB).

Xizeng Wu PhD, Abstract Co-Author: Nothing to Disclose

Philip F. Judy PhD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

Integral to meeting the main objective of the NLST to determine whether lung cancer screening of a high risk cohort with "low dose" CT vs chest x-ray reduces lung cancer specific mortality, is an estimation of the radiation dose to participants receiving either of these two screening methods. This work reports on the estimated dose from CT scans. A companion work discusses dose from chest x-ray. Disclaimer: This work was funded by NIH-NCI ACRIN Grant#CA80098; and, for LSS (Lung Screening Study), by the Division of Cancer Prevention at NCI, NIH, and DHHS.

From 2003-2007, CT dose data were collected annually from 96 multi detector scanners at the NLST participating sites.The scan parameters employed in the measurements and calculations reflected the clinical parameters locally selected at each site and scanner for an average size patient, within the confines of the overall NLST CT specifications. From these data, CTDIvol values, representative of average tissue dose to a standard acrylic body phantom, were calculated. An estimate of effective (whole body) dose to a standard size patient was determined by utilizing the approach developed by the European Working Group for Guidelines on Quality Criteria in Computed Tomography. Utilizing our calculated CTDIvol values, the radio sensitivity “k” coefficient for chest (.017 mSv/mGy-cm), and a typical scan length of 35 cm resulted in a range of CT effective dose values for the trial that could be used to represent effective dose to a standard size patient.

 The mean CTDIvol equaled 3.4 mGy, with a standard deviation of 1.7 mGy. This equated to a mean effective dose for an average size patient of 2.0 mSv, with a standard deviation equal to 1.0 mSv (min/max = 0.5 - 7.0 mSv).

The CT exposure measurements and dose calculations performed during the NLST result in an estimated average effective dose to a standard size patient equal to 2.0 mSv, with SD = 1.0 mSv. This indicates a significant variation in dose among all sites and scanners, reflecting the dose range  that was felt necessary to achieve adequate image quality. For comparison, the dose for a typical standard chest CT is 8-9 mSv.

 Estimated "low dose" CT effective dose can be directly compared to estimated effective dose for CXR, in an effort to understand the relative radiation risk between these two screening procedures.

Larke, F, Cody, D, Kruger, R, Cagnon, C, Flynn, M, McNitt-Gray, M, Wu, X, Judy, P, et al, , Estimated Radiation Dose to Participants Receiving Low-Dose Multidetector CT Chest Scans in the National Lung Screening Trial (NLST: ACRIN#6654).  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6005733.html