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

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

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

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

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

Richard L. Morin PhD, Abstract Co-Author: Advisory Board, American Imaging Management, Inc

Jeffrey H. Siewerdsen PhD, Abstract Co-Author: Research grant, Carestream Health, Inc Research grant, Siemens AG Medical Advisory Board, Carestream Health, Inc License agreement, Elekta AB

Stanley H.Y. Stern PhD, Abstract Co-Author: Nothing to Disclose

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

Thomas Louis Toth, Abstract Co-Author: Consultant, General Electric Company Former employee, General Electric Company Co-owner, Plexar Associates, Inc Employee, Plexar Associates, Inc

Stephen Vastagh, Abstract Co-Author: Nothing to Disclose

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

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

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

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

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

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

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

The AAPM-ICRU CT phantom has been designed to provide a streamlined and simplified CT dose index while accommodating a wider class of CT design geometries.

Over the past several years the universally utilized CT dose indices, CTDIvol and DLP, have come under close scrutiny, motivated in part by the advent of very wide fan beam (large multi-detector) CT scanners and cone beam 3-D systems.. AAPM Task Group 111 (TG111) was established to thoroughly examine the CTDI dosimetry paradigm and having done so, formulated a set of recommendations that were included in their report. AAPM Task Group 200 (TG200) has been created to implement these recommendations and in collaboration with the ICRU has designed, built and tested a phantom that will address some of the limitations of the current dose index system.

A limitation of CTDIvol is that its calculation is based on a specific scan length (10 cm) on a pair of cylinders of relatively short (15 cm along the z axis, 16 or 32 cm diameter). This technique results in an underestimation of dose in scans longer than 10 cm. The proposed phantom is a single polyethylene cylinder, 30 cm in diameter and 60 cm in length, which is sectioned into three 20 cm long pieces. It is long enough to capture the entire scatter tail. Thus, measurements at the cylinder’s central plane reach dose equilibrium value Deq. The dose is to be measured directly with a small radiation detector and a complete scan sequence rather than with a 10 cm long pencil chamber and a single gantry rotation in a fixed table position. The direct method leaves the measurements unconstrained by the fixed length of the pencil chamber.

The average value of Deq across the central plane of the cylinder is labeled Deq,ave, an analog of CTDIvol. Along with Deq,ave is the integral dose Etot. While serving some of the same purposes as DLP, it has been properly developed theoretically and consequently has a simple and physically meaningful interpretation. The use of a single phantom diameter requires that patient size specific information be taken into account to convert Deq into size specific dose estimates (SSDE), which is the topic of AAPM Task Group 204.  

Bakalyar, D, Boone, J, McNitt-Gray, M, McCollough, C, Dixon, R, Cody, D, Kyprianou, I, Morin, R, Siewerdsen, J, Stern, S, Strauss, K, Toth, T, Vastagh, S, Yang, Z, Chen-Mayer, H, Boedeker, K, Pizzutiello, R, Herrnsdorf, L, Payne, J, Chakrabarti, K, New CT Dose Phantom: Report on the AAPM ICRU Design.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11006237.html