Implementation of TomoEDGE in the independent dose calculator CheckTomo

Abstract

PurposeCheckTomo is an independent dose calculation software for tomotherapy. Recently, Accuray (Accuray Inc., Sunnyvale, CA, USA) released an upgrade of its tomotherapy treatment device, called TomoEDGE Dynamic Jaws, which improves the quality of treatment plans by enhancing the dose delivery with the help of jaws motion. This study describes the upgrade of CheckTomo to that new feature.MethodsTo account for the varying width and off‐axis shift of dynamic jaws fields, the calculation engine of CheckTomo multiplies the treatment field profile by a penumbral filter and shifts the dose calculation grid. Penumbral filters were obtained by dividing the edge field profiles by that of the corresponding nominal field. They were sampled at widths 1.0, 1.8, and 2.5 cm at isocenter in the edges of the 2.5 and 5 cm treatment field.ResultsThe upgrade of CheckTomo was tested on 30 patient treatments planned with dynamic jaws. The gamma pass rate averaged over 10 abdomen plans was 95.9%, with tolerances of 3 mm/3%. For 10 head and neck plans, the mean pass rate was 95.9% for tolerances of 4 mm/4%. Finally, misplacement and overdosage errors were simulated. In each tested cases, the 2 mm/3% gamma pass rate fell below 95% when a 4 mm shift or 3% dose difference was applied.ConclusionsThese results are equivalent to what CheckTomo achieves in static jaws cases. So, in terms of dose calculation accuracy and errors detection, the upgraded version of CheckTomo is as reliable for dynamic jaws plans as the former release was for static cases.

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

“…63 Due to the uniqueness and complexity of tomotherapy delivery, most IDC software for conventional linacs are incompatible with tomotherapy. Even though not recommended by TG 148, some clinics have developed their own correction-based, [88][89][90][91] model-based, 92 or Monte Carlo-based 69,[93][94][95][96][97] algorithms for tomotherapy IDCs. While these algorithms demonstrated success in some clinics, most clinics still lack the means to incorporate tomotherapy IDC into their plan check process.…”

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

“…In TomoTherapy machines without TomoEDGE option, treatment was delivered by static jaws at fixed field width, either 10, 25, or 50 mm at isocenter during the entire treatment. Thus, the field penumbra along the longitudinal direction was approximately identical to the field size on both cranial‐caudal sides of the target volume 1 . Further to this beam characteristic, it is essential to limit the dose to organ at risk (OAR) by delivering the treatment with MLC collimated sub‐fields under the drawback of increasing treatment time.…”

“…Thus, the field penumbra along the longitudinal direction was approximately identical to the field size on both cranial‐caudal sides of the target volume. 1 Further to this beam characteristic, it is essential to limit the dose to organ at risk (OAR) by delivering the treatment with MLC collimated sub‐fields under the drawback of increasing treatment time.…”