Evaluation of Dosimetry Check software for IMRT patient‐specific quality assurance

Purpose Despite their availability and simplicity of use, Electronic Portal Imaging Devices (EPIDs) have not yet replaced detector arrays for patient specific QA in 3D. The purpose of this study is to perform a large scale dosimetric evaluation of transit and non‐transit EPID dosimetry against absolute dose measurements in 3D. Methods After evaluating basic dosimetric characteristics of the EPID and two detector arrays (Octavius 1500 and Octavius 1000SRS), 3D dose distributions for 68 VMAT arcs, and 10 IMRT plans were reconstructed within the same phantom geometry using transit EPID dosimetry, non‐transit EPID dosimetry, and the Octavius 4D system. The reconstructed 3D dose distributions were directly compared by γ‐analysis (2L2 = 2% local/2 mm and 3G2 = 3% global/2 mm, 50% isodose) and by the percentage difference in median dose to the high dose volume (%∆HDVD50). Results Regarding dose rate dependency, dose linearity, and field size dependence, the agreement between EPID dosimetry and the two detector arrays was found to be within 1.0%. In the 2L2 γ‐comparison with Octavius 4D dose distributions, the average γ‐pass rate value was 92.2 ± 5.2%(1SD) and 94.1 ± 4.3%(1SD) for transit and non‐transit EPID dosimetry, respectively. 3G2 γ‐pass rate values were higher than 95% in 150/156 cases. %∆HDVD50 values were within 2% in 134/156 cases and within 3% in 155/156 cases. With regard to the clinical classification of alerts, 97.5% of the treatments were equally classified by EPID dosimetry and Octavius 4D. Conclusion Transit and non‐transit EPID dosimetry are equivalent in dosimetric terms to conventional detector arrays for patient specific QA. Non‐transit 3D EPID dosimetry can be readily used for pre‐treatment patient specific QA of IMRT and VMAT, eliminating the need of phantom positioning.

supporting

confidence: 89%

“…Since patient specific IMRT and VMAT QA is performed by com- IMRT and VMAT QA. 8,11,13,14,[35][36][37] Figure 6a possibly due to the same spatial resolution issues as in the case circled in blue in Fig. 6.…”

Section: Transit Epid Non-transit Epidmentioning

confidence: 82%

Transit and non‐transit 3D EPID dosimetry versus detector arrays for patient specific QA

Olaciregui-Ruiz

Vivas-Maiques

Kaas

et al. 2019

“…The clinical availability of DC has been investigated by various research groups for DQA of linear accelerator (LINAC) and TomoTherapy ® ‐based IMRT plans . These studies reported that the DC‐calculated 3D volumetric gamma pass rates for the patient‐specific DQAs were greater than 90%.…”

Section: Discussionmentioning

confidence: 99%

“…It is possible to have discrepancies between the TomoTherapy ® TPS and DC‐calculated DVHs for target or normal structures even though the 3D volumetric gamma pass rates for the corresponding structures satisfy the gamma pass criteria. Especially when the tissue inhomogeneity is present in the target or surrounding normal structures, the dose distribution difference can be present due to the inherent difference of the dose calculation algorithm between the CCC algorithm in DC and convolution/superposition algorithm in TomoTherapy ® TPS . Users may need to determine the acceptable limit of the discrepancy about the DVH between the TomoTherapy ® TPS and DC.…”

Section: Discussionmentioning

confidence: 99%

Clinical implementation of Dosimetry Check™ for TomoTherapy^® delivery quality assurance

Chung

Kwon

Park

et al. 2018

PurposeThe delivery quality assurance (DQA) of intensity‐modulated radiotherapy (IMRT) plans is a prerequisite for ensuring patient treatments. This work investigated the clinical usefulness of a new DQA system, Dosimetry Check™(DC), on TomoTherapy®‐based helical IMRT plans.MethodsThe DQA was performed for 15 different TomoTherapy®‐based clinical treatment plans. In Tomotherapy® machines, the couch position was set to a height of 400 mm and the treatment plans were delivered using QA‐Treatment mode. For each treatment plan, the plan data and measured beam fluence were transferred to a DC‐installed computer. Then, DC reconstructed the three‐dimensional (3D) dose distribution to the CT images of the patient. The reconstructed dose distribution was compared with that of the original plan in terms of absolute dose, two‐dimensional (2D) planes and 3D volume. The DQA results were compared with those performed by a conventional method using the cheese phantom with ion chamber and radiochromic film.ResultsFor 14 out of the 15 treatment plans, the absolute dose difference between the measurement and calculation was less than 3% and the gamma pass rate with the 3%/3 mm gamma evaluation criteria was greater than 95% for both DQA methods. The P‐value calculated using Wilcoxon signed‐rank test was 0.256, which implies no statistically significance in determining the absolute dose difference between the two methods. For one treatment plan generated using the 5.0 cm field width, the absolute dose difference was greater than 3% and the gamma pass rate was less than 95% with DC, while the DQA result with the cheese phantom method passed our TomoTherapy® DQA tolerance.ConclusionWe have clinically implemented DC for the DQA of TomoTherapy®‐based helical IMRT treatment plans. DC carried out the accurate DQA results as performed with the conventional cheese phantom method. This new DQA system provided more information in verifying the dose delivery to patients, while simplifying the DQA process.

“…All plans had been recalculated in the Tomotherapy phantom (Cheese phantom) and delivered with the couch out of the bore. Dosimetry Check software v.5.5 (LifeLine Software Inc., Austin, TX, USA) was used to reconstruct the measured dose distribution from the acquired sinogram 17,18 . Three-dimensional global gamma analysis was performed with 3% of maximum dose/3 mm distance-to-agreement criteria and 10% dose threshold (TH) for head and neck and prostate, and 3%/2 mm 10% TH for stereotactic brain plans.…”

Section: A | Treatment Plans and Deliverability Evaluationmentioning

confidence: 99%

On the complexity of helical tomotherapy treatment plans

Santos

Ventura

Mateus

et al. 2020

Purpose Multiple metrics are proposed to characterize and compare the complexity of helical tomotherapy (HT) plans created for different treatment sites. Methods A cohort composed of 208 HT plans from head and neck (105), prostate (51) and brain (52) tumor sites was considered. For each plan, 14 complexity metrics were calculated. Those metrics evaluate the percentage of leaves with small opening times or approaching the projection duration, the percentage of closed leaves, the amount of tongue‐and‐groove effect, and the overall modulation of the planned sinogram. To enable data visualization, an approach based on principal component analysis was followed to reduce the dataset dimensionality. This allowed the calculation of a global plan complexity score. The correlation between plan complexity and pretreatment verification results using the Spearman’s rank correlation coefficients was investigated. Results According to the global score, the most complex plans were the head and neck tumor cases, followed by the prostate and brain lesions irradiated with stereotactic technique. For almost all individual metrics, head and neck plans confirmed to be the plans with the highest complexity. Nevertheless, prostate cases had the highest percentage of leaves with an opening time approaching the projection duration, whereas the stereotactic brain plans had the highest percentage of closed leaves per projection. Significant correlations between some of the metrics and the pretreatment verification results were identified for the stereotactic brain group. Conclusions The proposed metrics and the global score demonstrated to be useful to characterize and quantify the complexity of HT plans of different treatment sites. The reported differences inter‐ and intra‐group may be valuable to guide the planning process aiming at reducing uncertainties and harmonize planning strategies.