Donovan M. Bakalyar PhD, Presenter: Nothing to Disclose

John M. Boone PhD, Abstract Co-Author: Consultant, Varian Medical Systems, Inc Consultant, Artemis, Inc Research funded, Varian Medical Systems, Inc Research funded, FUJIFILM Holdings Corporation Research funded, Hologic, Inc Research funded, Creatv MicroTech, Inc Research funded, Siemens AG

Michael F. McNitt-Gray PhD, Abstract Co-Author: Institutional research agreement, Siemens AG Research Grant, Siemens AG Instructor, Medical Technology Management Institute

Robert L. Dixon PhD, Abstract Co-Author: Research Consultant, Koninklijke Philips Electronics NV

Heather Chen-Mayer PhD, Abstract Co-Author: Nothing to Disclose

Robert J. Pizzutiello MD, Abstract Co-Author: Consultant, Xoran Technologies, Inc Speakers Bureau, Xoran Technologies, Inc

Dianna D. Cody PhD, Abstract Co-Author: Nothing to Disclose

Iacovos Kyprianou PhD, Abstract Co-Author: Nothing to Disclose

Jeffrey H. Siewerdsen PhD, Abstract Co-Author: Advisory Board, Siemens AG Advisory Board, Carestream Health, Inc Research Grant, Siemens AG Research Grant, Carestream Health, Inc

Kirsten L. Boedeker MS, Abstract Co-Author: Employee, Toshiba Corporation

Kish Chakrabarti PhD, Abstract Co-Author: Nothing to Disclose

Keith J. Strauss MS, Abstract Co-Author: Nothing to Disclose

Shuai Leng PhD, Abstract Co-Author: Nothing to Disclose

Richard L. Morin PhD, Abstract Co-Author: Nothing to Disclose

Paul B. Sunde, Abstract Co-Author: Shareholder, Radcal Corp Employee, Radcal Corp

Sarah Eva McKenney BS, BA, Abstract Co-Author: Nothing to Disclose

Stephen Vastagh, Abstract Co-Author: Nothing to Disclose

J. Thomas Payne PhD, Abstract Co-Author: Nothing to Disclose

Thomas Toth, Abstract Co-Author: Employee, General Electric Company

Thomas W. Slowey, Abstract Co-Author: Nothing to Disclose

Wenzheng Feng, Abstract Co-Author: Nothing to Disclose

Zhitong Yang PhD, Abstract Co-Author: Nothing to Disclose

Lars Herrnsdorf, Abstract Co-Author: Co-owner, RTI Electronics AB

Marcus Soderberg PhD, Abstract Co-Author: Nothing to Disclose

Cynthia H. McCollough PhD, Abstract Co-Author: Research Grant, Siemens AG

Frederick Joseph Larke MS, Abstract Co-Author: Nothing to Disclose

Erin Angel PhD, Abstract Co-Author: Employee, Toshiba Corporation

CTDIvol and DLP are universally used members of the CTDI family of radiation dose indices. However, the phantoms and measurement techniques used for determining these values suffer from limitations that are especially evident for the growing number of cone beam and very wide fan beam CT machines. In accordance with the recommendations of AAPM Task Group 111, Task Group 200 has designed a phantom and has formulated testing procedures which are suitable over a broader range of machines and conditions than the current methodology.

Scanning was performed on a Philips Brilliance 64 CT scanner. The phantom is 30 cm in diameter, constructed of high density polyethylene, and is of sufficient length (60 cm) so that virtually no scatter from scanning the endpoints of the phantom will reach the central plane. The design allows placement of detectors at the center and at 0, 6.7 cm and at 13.4 cm from the central axis.  Typically a helical scan, long enough to encompass the entire phantom, is performed and the dose rate as a function of position is recorded. From this, the dose at the central plane can be calculated for any scan length up to and including Deq, the value that would be reached for an infinite scan. Scans at multiple radii foster determination of its average value, Deq,ave over the central plane, and the total energy that would be absorbed by an infinite phantom, Etot. (The total energy also requires the total number of rotations N.)

The approach to Deq can be described by a simple function h(L) which is highly robust, displays only a weak dependence on tube potential and z-axis collimation and can be determined from a single scan. Finite scans confirm the use of this function for determining the dose for any length L. Our measurements show that the central plane dose is substantially more uniform than that for the CTDI body phantom making the determination of Deq,ave and Etot relatively insensitive to the details of the dose profile. The phantom design is readily adaptable to the size specific dose estimate model of AAPM Task Group 204.

The AAPM-ICRU phantom and proposed measurement techniques are robust, simple and readily applied to the ever growing variety of CT design geometries.

The AAPM Task Group 200 has performed extensive measurements on a dose phantom which has been developed to meet the requirements of the broad range of current CT designs.

Bakalyar, D, Boone, J, McNitt-Gray, M, Dixon, R, Chen-Mayer, H, Pizzutiello, R, Cody, D, Kyprianou, I, Siewerdsen, J, Boedeker, K, Chakrabarti, K, Strauss, K, Leng, S, Morin, R, Sunde, P, McKenney, S, Vastagh, S, Payne, J, Toth, T, Slowey, T, Feng, W, Yang, Z, Herrnsdorf, L, Soderberg, M, McCollough, C, Larke, F, Angel, E, What We Have Learned From the AAPM—ICRU CT Dose Phantom.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033379.html