AAPM Task Group Report 306: Quality control and assurance for tomotherapy: An update to Task Group Report 148

Abstract

Since the publication of AAPM Task Group (TG) 148 on quality assurance (QA) for helical tomotherapy, there have been many new developments on the tomotherapy platform involving treatment delivery, on-board imaging options, motion management, and treatment planning systems (TPSs). In response to a need for guidance on quality control (QC) and QA for these technologies, the AAPM Therapy Physics Committee commissioned TG 306 to review these changes and make recommendations related to these technology updates. The specific objectives of this TG were (1) to update, as needed, recommendations on tolerance limits, frequencies and QC/QA testing methodology in TG 148, (2) address the commissioning and necessary QA checks,as a supplement to Medical Physics Practice Guidelines (MPPG) with respect to tomotherapy TPS and (3) to provide risk-based recommendations on the new technology

Investigation on the accuracy of field widths and the quantitative relationship with energy variations for dynamic jaws helical tomotherapy

“…Percentage of FWHM measurements exceeding the 1% tolerance level (symmetric) or the 0.5 mm tolerance level (asymmetric) in 10 mm FW were listed Table 2. According to AAPM TG‐306, 10 mm symmetric treatment slice width was the most unstable field width to comply with the 1% FWHM tolerance and the test was sensitive to the setup variation 4 . The failed measurements were repeated promptly after the setup verification such as the examination of the alignment between the surface of slab phantom and the gantry bore laser and couch speed uniformity.…”

“…The FWHM results between measured and reference profile were then compared. As recommended by AAPM Task Group 306, the difference between profile's FWHM for symmetric field should not be differed by more than 1% while using an absolute tolerance of 0.5 mm for asymmetric field widths 4 …”

“…3 For the standard governing the quality assurance of helical tomotherapy, AAPM task group 306 (TG-306) states the importance of measured FWHMs and recommends regular monitoring of the beam parameter to guarantee the agreement with the beam model. 4 A previous study by Katayama et al compared the performance between standard static mode and…”

“…Full width at half maximum (FWHM) of the beam profile is an important parameter directly related to the accuracy and reproducibility of the dose delivery during tomotherapy treatment 3 . For the standard governing the quality assurance of helical tomotherapy, AAPM task group 306 (TG‐306) states the importance of measured FWHMs and recommends regular monitoring of the beam parameter to guarantee the agreement with the beam model 4 …”

Impact of delivery time factor on treatment time and plan quality in tomotherapy

“…Tomotherapy (Accuray Inc., Sunnyvale, CA, USA) is an intensity-modulated radiotherapy (IMRT) technology that uses a 6 MV linear accelerator mounted on a slip-ring-gantry that moves in synchronization with a treatment couch [1]. Equipped megavolt computed tomography (CT) systems can be used for pretreatment patient setup veri cation, dose recalculation, and patient and machine quality assurance purposes [1][2][3]. The machine enables the delivery of a highly conformal dose to complex target volumes while minimizing the dose to critical normal tissues by slice-by-slice delivery with 64 binary multileaf collimators.…”