Junctioning longitudinally adjacent PTVs with Helical TomoTherapy

Garcia, Lourdes M.; Gerig, L; Raaphorst, Peter; Wilkins, David E.

doi:10.1120/jacmp.v11i2.3047

Cited by 3 publications

(4 citation statements)

References 25 publications

(30 reference statements)

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“…In order to use the TH&TD combination for the VGMT, it was necessary to verify whether the VGMT with the TH&TD delivery mode could create a dose gradient at the junction volume. Consequently, the TH&TD VGMT produced a linear dose-gradient and reduced dose variations due to setup errors at the matched junction [8,12,19], similar to that by the TH&TH VGMT.…”

Section: Discussionmentioning

confidence: 74%

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Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

Hong

Kim

et al. 2019

Radiat Oncol

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Background: Tomotherapy-based total body irradiation (TBI) is performed using the headfirst position (HFP) and feet-first position (FFP) due to treatment length exceeding the 135 cm limit. To reduce the dosimetric variation at the match lines, we propose and verify a volumetric gradient matching technique (VGMT) by combining TomoHelical (TH) and TomoDirect (TD) modes. Methods: Two planning CT image sets were acquired with HFP and FFP using 15 × 55 × 18 cm 3 of solid water phantom. Planning target volume (PTV) was divided into upper, lower, and gradient volumes. The junction comprised 2-cm thick five and seven gradient volumes (5-GVs and 7-GVs) to create a dose distribution with a gentle slope. TH-IMRT and TD-IMRT plans were generated with 5-GVs and 7-GVs. The setup error in the calculated dose was assessed by shifting dose distribution of the FFP plan by 5, 10, 15, and 20 mm in the longitudinal direction and comparing it with the original. Doses for 95% (D95) and 5% of the PTV (D5) were calculated for all simulated setup error plans. Absolute dose measurements were performed using an ionization chamber in the junction. Results: The TH&TD plan produced a linear gradient in junction volume, comparable to that of the TH&TH plan. D5 of the PTV was 110% of the prescribed dose when the FFP plan was shifted 0.7 cm and 1.2 cm in the superior direction for 5-GVs and 7-GVs. D95 of the PTV decreased to < 90% of the prescribed dose when the FF plan was shifted 1.1 cm and 1.3 cm in the inferior direction for 5-GVs and 7-GVs. The absolute measured dose showed a good correlation with the calculated dose in the gradient junction volume. The average percent difference (±SD) in all measured points was − 0.7 ± 1.6%, and the average dose variations between depths was − 0.18 ± 1.07%. Conclusion: VGMT can create a linear dose gradient across the junction area in both TH&TH and TH&TD and can minimize the dose sensitivity to longitudinal setup errors in tomotherapy-based TBI.

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Section: Discussionmentioning

confidence: 74%

“…Dose variations due to setup uncertainty at the junction can be reduced by the feathering technique in which the longitudinal location of the junction is varied across treatment fractions [8]. However, this technique is effort intensive in terms of treatment planning and patient setup for multiple junctions.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

Hong

Kim

et al. 2019

Radiat Oncol

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“…Initially, TBI was given with parallel opposed field or extended source skin distances (SSD) or other conventional methods which had their limitation like fabrication, a time-consuming process in addition to acute and late toxicities as sparing of OARs was difficult [6]. Also, setup errors of a few millimeters in the longitudinal direction at the junction volume can produce dose inhomogeneity [7]. The feathering technique can help to reduce dose inhomogeneity in which the longitudinal location of the junction is varied across treatment fractions [8].…”

Section: Comparison Of Different Dosimetric Indices For Volumetric Ar...mentioning

confidence: 99%

Comparison of Different Dosimetric Indices for Volumetric Arc Modulated Treatment Planning Using 2 Different Treatment Planning Systems: A Feasibility Study for Total Body Irradiation

Kumari,

Yadav,

Kumar

2023

Asian Pac J Cancer Care

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Objective: To compare two different treatment planning systems (TPSs) for plan quality and to check the feasibility of VMAT TBI on the Elekta linear accelerator ‘Versa HD’. Methods: Ten clinical VMAT TBI plans were replanned in Monaco TPS version 5 for retrospective dosimetric analysis and to check the feasibility of treatment delivery in Elekta Versa HD. A dose of 12 Gy in 6 fractions was prescribed to cover 95% PTV. The OARs were the lungs, kidneys, heart, liver, and brain. Dosimetric optimization and calculation were performed in Monaco TPS with a statistical uncertainty of 1%, 2 mm grid. The chosen criterion for plan evaluation and comparison was based on plan quality, dosimetric indices like conformity and homogeneity index, and OAR doses. The comparison of time for optimization, monitor units, and beam on time was also analyzed. Pre-treatment verification using Octavious phantom and gamma analysis using Low’s method with a dose difference of 3% and distance to agreement 3mm criteria was done. The dosimetry of 2 VMAT TBI plans were compared using Wilcoxon signed rank test. Result: The calculated average maximum and mean doses of the PTV were 14.3321Gy and 12.235Gy for eclipse; and 14.428Gy and 12.198Gy for the Monaco system, respectively. The planning time in Monaco was approx. 4.5–6hrs compared to 14–18hrs for Eclipse TPS. Statistically significant difference was observed between the results of 2 TPSs in terms of monitor units, mean doses to lungs, kidneys, heart, and liver and planning time (P < 0.05). However, calculated p values for HI, CI, and brain for both VMAT TBI plans were not statistically different. Conclusion: The study showed the feasibility of VMAT TBI for VERSA HD as it offers faster, better optimization in a single target compared to the Eclipse.

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“…Garcia et al applied the concept of stepped doses in sub‐PTVs to longitudinally adjacent PTVs treated with helical TomoTherapy …”

Section: Introductionmentioning

confidence: 99%

MLC‐based penumbra softener of EDW borders to reduce junction inhomogeneities

Szpala

Kohli

2017

J Applied Clin Med Phys

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Junctions of fields are known to be susceptible to developing cold or hot spots in the presence of even small geometrical misalignments. Reduction of these dose inhomogeneities can be accomplished through decreasing the dose gradients in the penumbra, but currently it cannot be done for enhanced dynamic wedges (EDW). An MLC‐based penumbra softener was developed in the developer mode of TrueBeam linacs to reduce dose gradients across the side border of EDWs. The movement of each leaf was individually synchronized with the movement of the dynamic Y jaw to soften the penumbra in the same manner along the entire field border, in spite of the presence of the dose gradient of the EDW. Junction homogeneity upon field misalignment for side‐matched EDWs was examined with the MV imager. The fluence inhomogeneities were reduced from about 30% per mm of shift of the field borders for the conventional EDW to about 2% per mm for the softened‐penumbra plan. The junction in a four‐field monoisocentric breast plan delivered to the Rando phantom was assessed with film. The dose inhomogeneities across the junction in the superior‐inferior direction were reduced from about 20% to 25% per mm for the conventional fields to about 5% per mm. The dose near the softened junction of the breast plan with no shifts did not deviate from the conventional plan by more than about 4%. The newly‐developed softened‐penumbra junction of EDW (and/or open) fields was shown to reduce sensitivity to misalignments without increasing complexity of the planning or delivery. This methodology needs to be adopted by the manufacturers for clinical use.

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Junctioning longitudinally adjacent PTVs with Helical TomoTherapy

Cited by 3 publications

References 25 publications

Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

Comparison of Different Dosimetric Indices for Volumetric Arc Modulated Treatment Planning Using 2 Different Treatment Planning Systems: A Feasibility Study for Total Body Irradiation

MLC‐based penumbra softener of EDW borders to reduce junction inhomogeneities

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