Long-term dosimetric stability of multiple TomoTherapy delivery systems.

Long-term dosimetric stability of multiple TomoTherapy delivery systems.
J Appl Clin Med Phys. 2017 May 02;:
Authors: Smilowitz JB, Dunkerley D, Hill PM, Yadav P, Geurts MW
Abstract
The dosimetric stability of six TomoTherapy units was analyzed to investigate changes in performance over time and with system upgrades. Energy and output were tracked using monitor chamber signal, onboard megavoltage computed tomography (MVCT) detector profile, and external ion chamber measurements. The systems (and monitoring periods) include three Hi-Art (67, 61, and 65 mos.), two TomoHDA (31 and 26 mos.), and one Radixact unit (11 mos.), representing approximately 10 years of clinical use. The four newest systems use the Dose Control Stability (DCS) system and Fixed Target Linear Accelerator (linac) (FTL). The output stability is reported as deviation from reference monitor chamber signal for all systems and/or from an external chamber signal. The energy stability was monitored using relative (center versus off-axis) MVCT detector signal (beam profile) and/or the ratio of chamber measurements at 2 depths. The clinical TomoHDA data were used to benchmark the Radixact stability, which has the same FTL but runs at a higher dose rate. The output based on monitor chamber data of all systems is very stable. The standard deviation of daily output on the non-DCS systems was 0.94-1.52%. As expected, the DCS systems had improved standard deviation: 0.004-0.06%....

Source: Journal of Applied Clinical Medical Physics - May 2, 2017 Category: Physics Authors: Smilowitz JB, Dunkerley D, Hill PM, Yadav P, Geurts MW Tags: J Appl Clin Med Phys Source Type: research