Dosimetric comparison of head and neck cancer patients planned with multivendor volumetric modulated arc therapy technology

Kathirvel, M; Subramani, V.; Subramanian, V.; Swamy, Shivakumar; Garg, Arun; Kala, S

doi:10.4103/0973-1482.203600

Cited by 5 publications

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“…Current treatment modalities introduced new radiotherapy techniques which improved the quality of treatment. IMRT is a widely used technique for head and neck cancers delivering a non-uniform dose from multiple angles to create a very conformal dose to targets with minimal complication to surrounding OARs [26,27]. In arc-based IMRT (VMAT), the intensity is modulated generating dose fluences throughout the gantry rotation with the aid of variable speed of gantry, MLC movements and dose rate with shorter delivery time than IMRT.…”

Section: Discussionmentioning

confidence: 99%

Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

et al. 2020

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Head and neck cancers form about 30% of the total malignancies registered in a year in India. More than 400,000 new cases are diagnosed per annum [1,2]. Radiotherapy plays a major role in the management of this diverse spectrum of malignancies in the definitive, adjuvant and palliative setting. The major proportion of patients in India present in the advanced stages of the disease which further cements the position of radiotherapy in the plan of management. In the radical scheme of treatment of head and cancers, Purpose: To evaluate the dosimetric variations in patients of head and neck cancer treated with definitive or adjuvant radiotherapy using optimized non-coplanar (ncVMAT) beams with coplanar (cVMAT) beams using volumetric arc therapy. Materials and Methods: Twenty-two patients of head and neck cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patients was planned using coplanar and non-coplanar orientations using an optimized couch angle and fluences. We analyzed the Conformity Index (CI RTOG), Dose Homogeneity Index (DHI), Heterogeneity Index (HI RTOG), low dose volume, target and organs-at-risk coverage in both the plans without changing planning optimization parameters. Results: The prescription dose ranged from 60 Gy to 70 Gy. Using ncVMAT, CI RTOG , DHI and HI RTOG , and tumor coverage (ID 95%) had improved, low dose spillage volume in the body V 5Gy was increased and V 10Gy was reduced. Integral dose and intensity-modulated radiation therapy factor had increased in ncVMAT. In the case of non-coplanar beam arrangements, maximum dose (D max) of right and left humeral head were reduced significantly whereas apex of the right and left lung mean dose were increased. Conclusion: The use of ncVMAT produced better target coverage and sparing of the shoulder and soft tissue of the neck as well as the critical organ compared with the cVMAT in patients of head and neck malignancy.

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Section: Discussionmentioning

confidence: 99%

Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

et al. 2020

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Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE^®

et al. 2020

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Previous work has shown that PRESAGE® can be used successfully to perform 3D dosimetric measurements of complex radiotherapy treatments. However, measurements near the sample edges are known to be difficult to achieve. This is an issue when the doses at air-material interfaces are of interest, for example when investigating the electron return effect (ERE) present in treatments delivered by magnetic resonance (MR)-linac systems. To study this effect, a set of 3.5 cm-diameter cylindrical PRESAGE® samples was uniformly irradiated with multiple dose fractions, using either a conventional linac or an MR-linac. The samples were imaged between fractions using an optical-CT, to read out the corresponding accumulated doses. A calibration between TPS-predicted dose and optical-CT pixel value was determined for individual dosimeters as a function of radial distance from the axis of rotation. This data was used to develop a correction that was applied to four additional samples of PRESAGE® of the same formulation, irradiated with 3D-CRT and IMRT treatment plans, to recover significantly improved 3D measurements of dose. An alternative strategy was also tested, in which the outer surface of the sample was physically removed prior to irradiation. Results show that for the formulation studied here, PRESAGE® samples have a central region that responds uniformly and an edge region of 6–7 mm where there is gradual increase in dosimeter response, rising to an over-response of 24%–36% at the outer boundary. This non-uniform dose response increases in both extent and magnitude over time. Both mitigation strategies investigated were successful. In our four exemplar studies, we show how discrepancies at edges are reduced from 13%–37% of the maximum dose to between 2 and 8%. Quantitative analysis shows that the 3D gamma passing rates rise from 90.4, 69.3, 63.7 and 43.6% to 97.3, 99.9, 96.7 and 98.9% respectively.

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Dosimetric Impact of Prescription Point Placement in Heterogeneous Medium for Conformal Radiotherapy Dose Calculation with Various Algorithms

Pandu,

Khanna,

Palanisamy

et al. 2024

Journal of Medical Physics

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Objective: The aim of the study is to compare the accuracy of dose calculation for different dose calculation algorithms with different prescription points (air, tissue, air–tissue interface in carcinoma lung patients and bone, tissue, and bone–tissue interface in carcinoma buccal Mucosa tumors). Materials and Methods: Forty-one patients with carcinoma lung and buccal mucosa were retrospectively selected for this study. A three-dimensional conformal radiotherapy reference plan was created using the prescription point in the tissue with Monte Carlo (MC) algorithms for both the groups of patients. The reference plan was modified by changing the prescription point and algorithms in the tissue, air, air–tissue interface for lung patients and tissue, bone, and bone–tissue interface for buccal mucosa patients. The dose received by the target volume and other organs at risk (OAR) structures was compared. To find out the statistical difference between different prescription points and algorithms, the statistical tests were performed with repeated measures ANOVA. Results: The target volume receiving 95% dose coverage in lung patients decreased to −3.08%, −5.75%, and −1.87% in the dose prescription point at the air–tissue interface with the dose calculation algorithms like MC, collapsed cone (CC), and pencil beam (PB), respectively, compared to that of the MC tissue. Spinal cord dose was increased in the CC and PB algorithms in all prescription points in patients with lung and buccal mucosa. OAR dose calculated by PB in all prescription points showed a significant deviation compared to MC tissue prescription point. Conclusion: This study will help demonstrate the accuracy of dose calculation for the different dose prescription points with the different treatment algorithms in radiotherapy treatment planning.

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Dosimetric comparison of head and neck cancer patients planned with multivendor volumetric modulated arc therapy technology

Abstract: VMAT plans by TPSP and TPSB offered clinically acceptable dose distributions. TPSB-based optimization showed enhanced sparing of serial organs whereas TPSP-based optimization showed superior sparing of parallel organs.

Cited by 5 publications

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Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE^®

Dosimetric Impact of Prescription Point Placement in Heterogeneous Medium for Conformal Radiotherapy Dose Calculation with Various Algorithms

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Dosimetric comparison of head and neck cancer patients planned with multivendor volumetric modulated arc therapy technology

Abstract: VMAT plans by TPSP and TPSB offered clinically acceptable dose distributions. TPSB-based optimization showed enhanced sparing of serial organs whereas TPSP-based optimization showed superior sparing of parallel organs.

Cited by 5 publications

References 0 publications

Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE®

Dosimetric Impact of Prescription Point Placement in Heterogeneous Medium for Conformal Radiotherapy Dose Calculation with Various Algorithms

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Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE^®