Room: AAPM ePoster Library
Varian linacs are equipped with an RPM (Real-Time Position Management) system for respiratory gated treatment. However, some CT simulators are equipped with ANZAI belt for respiratory sorting. To eliminate the phase difference with the mix-match respiratory signal sorting, RPM as a 3rd-party input signal is usually used for gating treatments utilizing Varian linacs. This study is to establish and recommend a quality assurance program for 4-dimensional CT (4DCT) scan protocols on a Siemens DefinitionAS CT scanner input with multi-vendors respiratory signals.
Anzai AZ-733V respiratory phantom was used in this study with 15 rpm and 10 rpm repetition settings. Helical scan, AIP (average intensity projection) and MIP (maximum intensity projection) were generated from 4D-CT with phase-based sorting into 10 phases with Siemens software. In our study, 1 cm and 5 cm amplitude with 2 second, 4 second and 10 second breathing cycle scanned with 4D scan protocols (6 rpm, 9 rpm, and 12 rpm) were tested. The same scan was repeated with both Anzai (deep and standard) and RPM signals. Coherence of breathing signal detection, object volumes, lengths along the motion direction from AIPs and MIPs, motion movies and linearity of the signals were analyzed in this study.
Anzai absolute linearity can be reproduced with different gain and offset settings. RPM has good linearity. The volumes of the ball markers measured from MIP, AIP and helical scans were found to be consistent with different 4DCT acquisition conditions (scan setting for 6 or 12 respirations/minute, phantom oscillation speed at 10 or 15 cycles/minute), showing high reliability but slightly different baselines between the ANZAI and RPM monitoring system used for 4DCT.
A comprehensive quality assurance program for multi-vendors 4DCT scan protocols on a helical 4D-CT scanner is established and we recommend performing this test annually.