Vincent Herlihy MD, Presenter: Nothing to Disclose

Cynthia H. McCollough PhD, Abstract Co-Author: Research grant, Siemens AG Research grant, General Electric Company

Theresa A Branham, Abstract Co-Author: Nothing to Disclose

Krista M Bush MA, Abstract Co-Author: Nothing to Disclose

Robert K. Zeman MD, Abstract Co-Author: Nothing to Disclose

To determine 1. The association of scan parameters that may indicate excessive patient dose with specific exam types and 2. Whether blinded clinical reviewers can use these parameters to meaningfully predict CTDIw for 3 basic exams.

The ACR CT Accreditation Program evaluated 829 sites from 2002-2004. Each site submitted adult and/or pediatric clinical exams chosen from a list of 19 choices. These were blindly assessed by clinical reviewers for image quality; dose-related comments that may indicate an excessively high dose such as appropriateness of mAs, kVp, pitch, and others were recorded. Sites also measured CTDIw for 3 basic exam types. Measured doses were compared to proposed reference value standards (adult CT head 60mGy, adult CT abdomen 35mGy, pediatric CT abdomen 25 mGy) and correlated with dose-related comments. Invalid CTDIw measurements were excluded from the dose analysis.

Dose-related comments were made for 583 of 2474 exams reviewed. The highest proportion of comments occurred for adult head exams (104 of 207 exams including excessive mAs-53 and incorrect gantry angle-40) and pediatric head exams (148 of 299 exams including excessive mAs-70 and incorrect gantry angle-58). There were 532 exams within the 3 basic exam categories for which CTDIw was recorded. Of 459 exams with no dose-related comments, 402 fell below the suggested reference value dose, 57 were above. Of 73 exams with dose-related comments, 57 fell below the reference value and 16 were above. Thus, while lack of dose-related comments failed to suggest exams exceeding the reference value in only 12.4% of exams, clinicians only correctly predicted dose in excess of the reference value in 21.9% (16/73).

Clinical reviewers performed marginally in using routinely displayed scan parameters such as mAs and kVp in predicting dose as assessed by CTDIw. While a reference value is not currently in place for pediatric head CT, this would be beneficial given the high proportion of dose-related comments about this exam in the ACR database.

Prospective and retrospective display of CT dose indices/indicators as part of routine patient exam data would assist radiologists in their dose reduction efforts.

Herlihy, V, McCollough, C, Branham, T, Bush, K, Zeman, R, Use of Clinical CT Scan Parameters to Predict Patient Dose versus Measured CT Dose Index (CTDIw): An Analysis of the American College of Radiology (ACR) CT Accreditation Database.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4439137.html