scholarly journals PO-0938 Spine SBRT plan comparison for Cyberknife and VMAT delivery incorporating intrafraction PTV margin

2019 ◽  
Vol 133 ◽  
pp. S505
Author(s):  
T. Oshea ◽  
C. Jones ◽  
C. Meehan
Keyword(s):  
Plan Comparison ◽  
Ptv Margin

scholarly journals Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Vanessa Da Silva Mendes ◽  
Lukas Nierer ◽  
Minglun Li ◽  
Stefanie Corradini ◽  
Michael Reiner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Coverage ◽  
Treatment Delivery ◽  
Ptv Margin ◽  
Delivery Times ◽  
Low Field ◽  
Treatment Plans

Abstract Background The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. Materials and methods 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. Results The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. Conclusions A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

scholarly journals Intra-fractional patient setup error during fractionated intracranial stereotactic irradiation treatment of patients wearing medical masks: comparison with and without bite block during COVID-19 pandemic

2020 ◽  
Vol 62 (1) ◽  
pp. 163-171
Author(s):  
Shingo Ohira ◽  
Naoyuki Kanayama ◽  
Riho Komiyama ◽  
Toshiki Ikawa ◽  
Masayasu Toratani ◽  
...  
Keyword(s):  
Target Volume ◽  
Setup Error ◽  
Dose Delivery ◽  
Stereotactic Irradiation ◽  
Bite Block ◽  
Ptv Margin ◽  
Computed Tomography Images ◽  
Irradiation Treatment ◽  
Before And After ◽  
Patient Setup

Abstract The immobilization of patients with a bite block (BB) carries the risk of interpersonal infection, particularly in the context of pandemics such as COVID-19. Here, we compared the intra-fractional patient setup error (intra-SE) with and without a BB during fractionated intracranial stereotactic irradiation (STI). Fifteen patients with brain metastases were immobilized using a BB without a medical mask, while 15 patients were immobilized without using a BB and with a medical mask. The intra-SEs in six directions (anterior–posterior (AP), superior–inferior (SI), left–right (LR), pitch, roll, and yaw) were calculated by using cone-beam computed tomography images acquired before and after the treatments. We analyzed a total of 53 and 67 treatment sessions for the with- and without-BB groups, respectively. A comparable absolute mean translational and rotational intra-SE was observed (P > 0.05) in the AP (0.19 vs 0.23 mm with- and without-BB, respectively), SI (0.30 vs 0.29 mm), LR (0.20 vs 0.29 mm), pitch (0.18 vs 0.27°), roll (0.23 vs 0.23°) and yaw (0.27 vs 22°) directions. The resultant planning target volume (PTV) margin to compensate for intra-SE was <1 mm. No statistically significant correlation was observed between the intra-SE and treatment times. A PTV margin of <1 mm was achieved even when patients were immobilized without a BB during STI dose delivery.

scholarly journals Direct plan comparison of RapidArc and CyberKnife for spine stereotactic body radiation therapy

2015 ◽  
Vol 67 (1) ◽  
pp. 116-122 ◽  
Author(s):  
Young Eun Choi ◽  
Jungwon Kwak ◽  
Si Yeol Song ◽  
Eun Kyung Choi ◽  
Seung Do Ahn ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Stereotactic Body Radiation Therapy ◽  
Plan Comparison ◽  
Stereotactic Body Radiation

PD-0554: CTV-to-PTV margin assessment for esophageal cancer radiotherapy based on accumulated dose analysis

2020 ◽  
Vol 152 ◽  
pp. S308
Author(s):  
M. Boekhoff ◽  
I. Defize ◽  
A. Kotte ◽  
N. Takahashi ◽  
J. Lagendijk ◽  
...  
Keyword(s):  
Esophageal Cancer ◽  
Margin Assessment ◽  
Cancer Radiotherapy ◽  
Ptv Margin ◽  
Accumulated Dose

scholarly journals Treatment planning for MLC based robotic radiosurgery for brain metastases: plan comparison with circular fields and suggestions for planning strategies

2017 ◽  
Vol 3 (2) ◽  
pp. 151-154
Author(s):  
Daniela Schmitt ◽  
Rami El Shafie ◽  
Sebastian Klüter ◽  
Nathalie Arians ◽  
Kai Schubert ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Low Dose ◽  
Treatment Time ◽  
Conformity Index ◽  
High Dose ◽  
Gradient Index ◽  
Plan Comparison ◽  
Robotic Radiosurgery ◽  
Target Volumes ◽  
Beam Transmission

AbstractTo evaluate the possible range of application of the new InCise2 MLC for the CyberKnife M6 system in brain radiosurgery, a plan comparison was made for 10 brain metastases sized between 1.5 and 9cm3 in 10 patients treated in a single fraction each. The target volumes consist of a PTV derived by expanding the GTV by 1mm and were chosen to have diversity in the cohort regarding regularity of shape, location and the structures needed to be blocked for beam transmission in the vicinity. For each case, two treatment plans were optimized: one using the MLC and one using the IRIS-collimator providing variable circular fields. Plan re-quirements were: dose prescription to the 70% isodose line (18 or 20Gy), 100% GTV coverage, ≥98% PTV coverage, undisturbed central high dose region (95% of maximum dose) and a conformity index as low as possible. Plan com-parison parameters were: conformity index (CI), high-dose gradient index (GIH), low-dose gradient index (GIL), total number of monitor units (MU) and expected treatment time (TT). For all cases, clinically acceptable plans could be gen-erated with the following results (mean±SD) for CI, GIH, GIL, MU and TT, respectively for the MLC plans: 1.09±0.03, 2.77±0.26, 2.61±0.08, 4514±830MU and 27±5min and for the IRIS plans: 1.05±0.01, 3.00±0.35, 2.46±0.08, 8557±1335MU and 42±7min. In summary, the MLC plans were on average less conformal and had a shallower dose gradient in the low dose region, but a steeper dose gradient in the high dose region. This is accompanied by a smaller vol-ume receiving 10Gy. A plan by plan comparison shows that usage of the MLC can spare about one half of the MUs and one third of treatment time. From these experiences and results suggestions for MLC planning strategy can be de-duced.

Effect of 3D Angular Displacement of Prostate CTV on PTV Margin

2009 ◽  
Vol 75 (3) ◽  
pp. S656-S657
Author(s):  
J. Suzuki ◽  
K. Tateoka ◽  
K. Shima ◽  
M. Hareyama ◽  
W. Saitou ◽  
...  
Keyword(s):  
Angular Displacement ◽  
Ptv Margin

PTV margin calculation for head and neck patients treated with VMAT: a systematic literature review

2021 ◽  
pp. 1-8
Author(s):  
Kristina Caruana ◽  
Nick Refalo ◽  
Denise Spiteri ◽  
José Guilherme Couto ◽  
Frank Zarb ◽  
...  
Keyword(s):  
Head And Neck ◽  
Target Volume ◽  
Target Volume Delineation ◽  
Ptv Margin ◽  
Volumetric Arc Therapy ◽  
Volume Delineation ◽  
Key Characteristics ◽  
Arc Therapy ◽  
Great Heterogeneity ◽  
Methodological Approaches

Abstract Aim: The intent of the review was to identify different methodological approaches used to calculate the planning target volume (PTV) margin for head and neck patients treated with volumetric arc therapy (VMAT), and whether the necessary factors to calculate the margin size with the selected formula were used. Materials and Methods: A comprehensive, systematic search of related studies was done using the Hydi search engine and different databases: MEDLINE, PubMed, CINAHL, ProQuest (Nursing and Allied Health), Scopus, ScienceDirect and tipsRO. The literature search included studies published between January 2007 and December 2020. Eligibility screening was performed by two reviewers. Results: A total of seven studies were found. All the reviewed studies used the Van Herk formula to measure the PTV margin. None of the studies incorporated the systematic errors of target volume delineation in the PTV equation. Inter-fraction translational errors were assessed in all the studies, whilst intra-fraction errors were only included in the margin equation for two studies. The studies showed great heterogeneity in the key characteristics, aims and methods. Findings: Since systemic errors from target volume delineation were not considered and not all studies assess intra-fraction errors, PTV margins may be underestimated. The recommendations are that studies need to determine the effect of target volume variance on PTV margins. It is also recommended to compare PTV margin results using various formulas.

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