scholarly journals Evaluation of Auto-Planning for Left-Side Breast Cancer After Breast-Conserving Surgery Based on Geometrical Relationship

2020 ◽  
Author(s):  
Yijiang Li ◽  
Han Bai ◽  
Danju Huang ◽  
Feihu Chen ◽  
Xuhong Liu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dose Distribution ◽  
Breast Conserving Surgery ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Ipsilateral Lung ◽  
Organ At Risk ◽  
Geometrical Relationship ◽  
Better Than

Abstract BackgroundThis study aimed to evaluate (1) the performance of Auto-Planning module embedded in Pinnnacle treatment planning system (TPS) with 30 left-side breast cancer plans; (2) the dose-distance relations based on overlap volume histogram (OVH) curve.Method30 patients with left-side breast cancer after breast-serving surgery were enrolled in this study. The clinical manual plan (MP) and the automatic plan (AP) were generated by Monaco and Auto-planning module respectively. The geometric relations between organ at risk (OAR) and planning target volume (PTV) of each patient were described by the overlap volume histogram (OVH). The patients were ranked according to the extension distance from PTV at a specific volume on the OVH curve. The MP and AP plans then were ranked to compare with the ranking of the OVH curves. Dosimetric difference between MP and AP plans were evaluated with statistical analysis.ResultThe comparative result shows a higher degree of correlation between AP and OVH curve. For different indicators, the dose distribution of , , in ipsilateral lung is more consistent with the distance-dose relation compared to the dose distribution of in heart. Dosimetric comparison shows a statistically significant improvement in ipsilateral lung and , and in heart of AP plans compared to MP plans. However, the result of ipsilateral lung of MP plans are better than that of AP plans.ConclusionThe overall results of AP plans are superior to MP plans. The dose distribution in AP plans are more consistent with the distance-dose relationship, which was described by OVH. After eliminating the interference of human factors, the AP is able to provide more stable and objective plans for radiotherapy patients.

Evaluation of Auto-Planning for Left-Side Breast Cancer After Breast-Conserving Surgery Based on Geometrical Relationship

2020 ◽  
Author(s):  
Yijiang Li ◽  
Han Bai ◽  
Danju Huang ◽  
Feihu Chen ◽  
Xuhong Liu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Correlation Coefficient ◽  
Dose Distribution ◽  
Breast Conserving Surgery ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Geometric Information ◽  
Ipsilateral Lung ◽  
Geometrical Relationship

Abstract Purpose: This study aimed to evaluate (1) the performance of the Auto-Planning module embedded in the Pinnacle treatment planning system (TPS) with 30 left-side breast cancer plans and (2) the dose-distance correlations between dose-based patients and overlap volume histogram-based (OVH) patients. Method: A total of 30 patients with left-side breast cancer after breast-conserving surgery were enrolled in this study. The clinical manual-planning (MP) and the Auto-Planning (AP) plans were generated by Monaco and by the Auto-Planning module in Pinnacle respectively. The geometric information between organ at risk (OAR) and planning target volume (PTV) of each patient was described by the OVH. The AP and MP plans were ranked to compare with the geometry-based patients from OVH. The Pearson product-moment correlation coefficient (R) was used to describe the correlations between dose-based patients (APs and MPs) and geometry-based patients (OVH). Dosimetric differences between MP and AP plans were evaluated with statistical analysis. Result: The correlation coefficient (mean R = 0.71) indicated that the AP plans have a high correlation with geometry-based patients from OVH, whereas the correlation coefficient (mean R = 0.48) shows a weak correlation between MP plans and geometry-based patients. For different indicators, the dose distribution of V5Gy in the ipsilateral lung (AP: mean R = 0.82; MP: mean R = 0.58) is more relevant to geometry-based patients compared to the dose distribution of in the heart (AP: mean R = 0.4; MP: mean R = 0.19). The dosimetric comparison revealed a statistically significant improvement in ipsilateral lung V5Gy and V10Gy and in the heart V5Gy of AP plans compared to MP plans. Conclusion: The overall results of AP plans were superior to MP plans. The dose distribution in AP plans was more consistent with the distance-dose relationship described by OVH. After eliminating the interference of human factors, the AP was able to provide more stable and objective plans for radiotherapy patients.

scholarly journals Evaluation of Auto-Planning for Left-Side Breast Cancer After Breast-Conserving Surgery Based on Geometrical Relationship

2021 ◽  
Vol 20 ◽  
pp. 153303382110330
Author(s):  
Yijiang Li ◽  
Han Bai ◽  
Danju Huang ◽  
Feihu Chen ◽  
Yaoxiong Xia
Keyword(s):  
Breast Cancer ◽  
Correlation Coefficient ◽  
Breast Conserving Surgery ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Weak Correlation ◽  
Geometric Information ◽  
Organ At Risk ◽  
Geometrical Relationship

Purpose: This study aimed to evaluate (1) the performance of the Auto-Planning module embedded in the Pinnacle treatment planning system (TPS) with 30 left-side breast cancer plans and (2) the dose-distance correlations between dose-based patients and overlap volume histogram-based (OVH) patients. Method: A total of 30 patients with left-side breast cancer after breast-conserving surgery were enrolled in this study. The clinical manual-planning (MP) and the Auto-Planning (AP) plans were generated by Monaco and by the Auto-Planning module in Pinnacle respectively. The geometric information between organ at risk (OAR) and planning target volume (PTV) of each patient was described by the OVH. The AP and MP plans were ranked to compare with the geometry-based patients from OVH. The Pearson product-moment correlation coefficient (R) was used to describe the correlations between dose-based patients (APs and MPs) and geometry-based patients (OVH). Dosimetric differences between MP and AP plans were evaluated with statistical analysis. Result: The correlation coefficient (mean R = 0.71) indicated that the AP plans have a high correlation with geometry-based patients from OVH, whereas the correlation coefficient (mean R = 0.48) shows a weak correlation between MP plans and geometry-based patients. The dosimetric comparison revealed a statistically significant improvement in the ipsilateral lung V5Gy and V10Gy, and in the heart V5Gy of AP plans compared to MP plans, while statistical reduction was seen in PTV V107% for MP plans compared to AP plans. Conclusion: The overall results of AP plans were superior to MP plans. The dose distribution in AP plans was more consistent with the distance-dose relationship described by OVH. After eliminating the interference of human factors, the AP was able to provide more stable and objective plans for radiotherapy patients.

scholarly journals Evaluating the Effect of the Silicone Prosthesis on the Photon Dose Distribution in Radiation Therapy of Breast Cancer

2021 ◽  
Author(s):  
Shaghayegh Olfat ◽  
Payam Samadi Miandoab ◽  
Nooshin Banaee
Keyword(s):  
Breast Cancer ◽  
Soft Tissue ◽  
Electron Density ◽  
Dose Distribution ◽  
Treatment Plan ◽  
Planning System ◽  
Treatment Planning System ◽  
Tissue Water ◽  
Air Cavity ◽  
Silicone Prosthesis

Purpose: Breast cancer is the most common malignancy among women which in some cases is followed by breast reconstructions. The objective of the experimental study is to investigate the effect of the silicone prosthesis implementation on the dose distribution of radiotherapy. Materials and Methods: Initially CT images of 7 mastectomy breast patients with silicone prosthesis were imported to the Monaco treatment planning system. A treatment plan consisting of two tangential photon fields with a prescription dose of 50Gy was arranged. To study the effect and water equivalency of silicone prosthesis, dose distribution of treatment plan was acquired in two conditions: 1) considering the real electron density of silicone prosthesis; 2) modifying (Relative electron density) RED of silicone prosthesis to 1 to virtually assume it as soft tissue (water). The results were then compared by VeriSoft software to evaluate the gamma index. Results: The obtained results indicated that the RED for the silicon prosthesis varies between 0.7 and 1.14 while the RED for soft tissue is approximately 1. Also, the Dose-volume histogram curves for both conditions indicated that the minimum and maximum differences ranged from 1% to 4%. The significant differences might be due to the presence of the air cavity or bubbles in the silicone prosthesis implementation or air voxels between prostheses and soft tissue. Conclusion: The obtained results showed that if there is no air cavity in silicone prosthesis and the surgery is performed in a way that no volume of air is left between the prosthesis and breast tissue, the effect and presence of silicone prosthesis will be similar to soft tissue (water).

Dosimetric feasibility of an anthropomorphic three-dimensional PRESAGE® dosimeter for verification of single entry hybrid catheter accelerated partial breast brachytherapy

2018 ◽  
Vol 17 (4) ◽  
pp. 403-410 ◽  
Author(s):  
Khalid Iqbal ◽  
Geoffrey S. Ibbott ◽  
Ryan G. Lafratta ◽  
Kent A. Gifford ◽  
Muhammad Akram ◽  
...  
Keyword(s):  
Dose Distribution ◽  
Three Dimensional ◽  
Target Volume ◽  
Normal Breast ◽  
Planning System ◽  
Treatment Planning System ◽  
Skin Dose ◽  
Line Profiles ◽  
Gamma Analysis ◽  
Ebt2 Film

AbstractPurposeTo determine the feasibility of an anthropomorphic breast polyurethane-based three-dimensional (3D) dosimeter with cavity to measure dose distributions and skin dose for a commercial strut-based applicator strut-adjusted volume implant (SAVI™) 6–1.Materials and methodsAn anthropomorphic breast 3D dosimeter was created with a cavity to accommodate the SAVI™ strut-based device. 2 Gy was prescribed to the breast dosimeter having D95 to planning target volume evaluation (PTV_EVAL) while limiting 125% of the prescribed dose to the skin. Independent dose distribution verification was performed with GAFCHROMIC® EBT2 film. The dose distribution from the 3D dosimeter was compared to the distributions from commercial brachytherapy treatment planning system (TPS) and film. Point skin doses, line profiles and dose–volume histogram (DVHs) for the skin and PTV_EVAL were compared.ResultsThe maximum difference in skin dose for TPS and the 3D dosimeter was 4% whereas 41% between the TPS and EBT2 film. The maximum dose difference for line profiles between TPS, 3D dosimeter, and film was 4·1%. DVHs of skin and PTV_EVAL for TPS and 3D dosimeter differed by a maximum of 4% at 5 mm depth and skin differed by a maximum 1·5% between TPS and 3D dosimeter. The criterion for gamma analysis comparison was 92·5% at ±5%±3 mm criterion. The TPS demonstrated at least ±5% comparability in predicting dose to the skin, PTV_EVAL and normal breast tissue.Conclusions3D anthropomorphic polyurethane dosimeter with cavity gives comparable results to the TPS dose predictions and GAFCHROMIC® EBT2 film results in the context of HDR brachytherapy.

scholarly journals TREATMENT PLANNING SYSTEM (TPS) KANKER PAYUDARA MENGGUNAKAN TEKNIK 3DCRT

2020 ◽  
Vol 6 (1) ◽  
pp. 150
Author(s):  
Wida Farhiyati ◽  
Rinarto Subroto ◽  
I Wayan Ari Makmur ◽  
Nurul Qomariyah ◽  
Rahadi Wirawan
Keyword(s):  
Breast Cancer ◽  
At Risk ◽  
Left Lung ◽  
Planning System ◽  
International Commission ◽  
Treatment Planning System ◽  
Anisotropic Analytical Algorithm ◽  
Analytical Algorithm ◽  
Organ At Risk ◽  
The Mean

ABSTRAKPenelitian ini bertujuan untuk mengevaluasi hasil  simulasi TPS teknik 3DCRT pada  kasus kanker payudara agar sesuai dengan standar yang diizinkan International Commission on Radiation Units and Measurements (ICRU). Proses TPS menggunakan program Eclipse dengan algoritma Anisotropic Analytical Algorithm. Kurva histogram dosis volume kumulatif 3DCRT dianalisis untuk mendapatkan dosis radiasi yang diterima organ at risk (OAR) paru-paru kiri, paru-paru kanan dan jantung. Hasil TPS  menunjukkan dosis yang diterima OAR berada di bawah batas ambang yang ditentukan yaitu paru-paru kiri dengan mean dose 54,7 cGy yang melingkupi volume 1238,5 cm3 dan pada paru-paru kanan dosis mean dose 2113,2 cGy melingkupi volume 1474,5 cm3 serta pada jantung mean dose 96,5 cGy melingkupi volume 175,5 cm3. Simulasi TPS yang dilakukan berhasil mendapatkan data perencanaan penyinaran  kasus kanker payudara yang memenuhi syarat dosis relatif yang melingkupi volume PTV yang diizinkan ICRU (volume terlingkupi 95%-107%) yaitu besarnya dosis relatif untuk target sebesar 95% yang melingkupi 95,5% volume target. Kata kunci: radioterapi, TPS, dosis, PTV, OAR. ABSTRACTThis study objective is to evaluate the simulation results of the 3DCRT technique TPS  in breast cancer cases to conform to the standards permitted by the International Commission on Radiation Units and Measurements (ICRU). The TPS process uses the Eclipse program with the Anisotropic Analytical Algorithm algorithm. The 3DCRT cumulative dose-volume histogram curve was analyzed to obtain the absorbed dose received by the organ at risk (OAR) of the left lung, right lung and heart. The TPS results show that the dose received by OAR was below the prescribed threshold of the left lung with a mean dose of 54.7 cGy covering a volume of 1238.5 cm3 and to the right lung the mean dose of 2113.2 cGy surrounding the volume of 1474, 5 cm3 and at the heart the mean dose of 96.5 cGy covers a volume of 175.5 cm 3. TPS simulation carried out successfully obtained data on the planning of radiation from breast cancer cases that met the relative dosage requirements that covered the volume of PTV permitted by ICRU (95% -107% enclosed volume), that is, the relative dose for the target of 95% which covered 95.5% of the target volume. Keywords: radiotherapy, TPS, dose, PTV, OAR.

scholarly journals Dosimetric evaluation of the gantry sag effect in clinical SRS plans

BJR|Open ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 20180026
Author(s):  
Egor Borzov ◽  
Alex Nevelsky ◽  
Rachel Bar-Deroma ◽  
Itzhak Orion
Keyword(s):  
Dose Distribution ◽  
Organs At Risk ◽  
Target Volume ◽  
Spatial Uncertainty ◽  
Planning System ◽  
Treatment Planning System ◽  
Maximum Point ◽  
Lower Quadrant ◽  
Volumetric Arc Therapy ◽  
Left And Right

Objectives: The gantry sag introduces a largely reproducible variation of the radiation field center around the radiation isocenter. The purpose of this work is to assess the change of the dose distribution caused by the gantry sag in clinical stereotactic plans. Methods: Brain stereotactic radio surgery treatment plans were evaluated and grouped according to radiation therapy planning technique. Group 1 was planned with volumetric arc therapy technique using coplanar arcs while Group 2—non-coplanar arcs. To simulate the gantry sag effect in the treatment planning system, the original plan segments were divided into four groups according to corresponding gantry angles: upper, lower, left and right quadrants. Then, isocenter of the upper quadrant was shifted towards “Gun”, isocenter of the lower quadrant was shifted towards “Target” and isocenter of the left and right quadrants was left at its original positions. The magnitude of the shift was 0.5, 1 and 1.5 mm in each direction, corresponding to 1, 2 and 3 mm of gantry isocenter diameter. To estimate the changes in dose distribution between the original and modified plans, the following dose–volume metrics were tracked: planning target volume (PTV) coverage (V99;PTV), hotspot dose in PTV (DPTV;0.015cc)), coldspot doses in PTV (DPTV;(V-0.015cc)), conformity and gradient indexes, maximum point doses in organs at risk (OAR, DOAR;0.015cc) and outside PTV (DoutsidePTV;0,015cc). For the second group of patients volume of brain receiving 12 Gy (V12Gy) was analyzed. Results: The mean relative change of all metrics was within −2%/+2.5% range for both techniques for isocenter diameter up to 2 mm. Isocenter diameter of 3 mm causes significant changes in V99;PTV, conformity and gradient indexes for coplanar, and additionally in DPTV;(V-0.015cc) for non-coplanar plans. The largest increase of maximum point dose in OAR was 1.1, 2.1 and 3.2% for ±0.5, ±1 and ±1.5 mm shift, respectively. Conclusion: The results demonstrate dosimetric effect of gantry sag depending on its value. By itself, the gantry sag effect does not produce clinically perceptible dose changes neither for PTV nor for OARs for shift ranges up to ±1 mm, both for coplanar and non-coplanar delivery techniques. For the larger gantry sag magnitude dosimetric changes can become significant, especially for non-coplanar plans. It indicates that 2 mm diameter tolerance of gantry isocenter postulated in TG-142 is reasonable, as variations in excess of this value start to affect the overall dosimetric and spatial uncertainty. Advances in knowledge: Dosimetric evaluation of the gantry sag effect in clinical stereotactic radio surgery plans is presented for the first time.

scholarly journals Noncoplanar Radiation using Tomotherapy: A Phantom Study

2020 ◽  
Vol 19 ◽  
pp. 153303382094577
Author(s):  
Masahiro Yuasa ◽  
Hiromasa Kurosaki
Keyword(s):  
Image Registration ◽  
Head And Neck ◽  
Treatment Planning ◽  
Planning Target Volume ◽  
Dose Distribution ◽  
Deformable Image Registration ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Computed Tomography Images

Background: There are very few studies on noncoplanar radiation in tomotherapy because deformable image registration is not implemented in the TomoTherapy Planning Station, a treatment planning device used in tomotherapy. This study examined whether noncoplanar radiation can be performed on the head using a tilt-type head and neck fixture and deformable image registration. Methods: Planning target volume spheres with diameters of 2, 3, and 4 cm were set on a head phantom, and computed tomography images were taken at 0° and 40° using a tilt-type head and neck fixture. Irradiation plans were created in the Tomotherapy Planning Station. Noncoplanar radiation was simulated, and the dose volume was evaluated by adding the 0° dose distribution and 40° dose distribution using the deformable image registration of the RayStation treatment planning system. Results: The ratio of the phantom volume to the irradiation dose for 20% to 30% of the planning target volume in noncoplanar radiation was smaller than that for 40% to 90% of the planning target volume in single-section irradiation at 0° or 40°. Conclusions: Noncoplanar radiation on the head region using tomotherapy was possible by using a tilt-type head and neck fixture, and the dose distribution could be evaluated using deformable image registration. This method helps reduce the dose of the organ-at-risk region located slightly away from the planning target volume.

HYBRID IMRT RADIATION TECHNIQUE COMPARISON WITH 3D-CRT FOR LEFT-SIDED WHOLE BREAST CANCER

2021 ◽  
Author(s):  
Nina Pavlović ◽  
◽  
Tatjana Miladinović ◽  
Darko Stojanović ◽  
Aleksandar Miladinović ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Radiation Therapy ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Conformity Index ◽  
Treatment Technique ◽  
Dose Ratio ◽  
Conformal Radiation Therapy ◽  
3D Crt

To identify the best treatment technique for patients with left-sided breast cancer, we compared plans obtained with a hybrid intensity-modulated radiation therapy (hIMRT) and conventional three- dimensional conformal radiation therapy (3D-CRT). Dosimetric indices for PTVs and OARs were calculated. Also, the dose coverage, homogeneity index, conformity index of the target, and the dose volumes of critical structures were analyzed. A sample of seven patients who were selected randomly treated in University Clinical Center Kragujevac between 2019 and 2020 was selected for the study. Therapy plans for both techniques were made with an ECLIPSE treatment planning system for each patient based on the same images and contours. The hybrid IMRT technique consists of two static opposed tangential fields and four optimized IMRT fields (dose ratio 70:30). For 3D-CRT planning, one isocenter with half-beam blocked tangential fields with wedges was used. All treatment plans were generated with 6 MV photon beam. Hybrid IMRT plans compared to the 3D-CRT resulted in better dose delivered to 95% (D95) of the planning target volume (PTV) and better heterogeneity HI and conformity CI. Protection for critical organs such as the heart, lungs, and contralateral breast is slightly worse than those obtained by 3D-CRT.

Dosimetric comparison of fractionated radiosurgery plans using frameless Gamma Knife ICON and CyberKnife systems with linear accelerator–based radiosurgery plans for multiple large brain metastases

2020 ◽  
Vol 132 (5) ◽  
pp. 1473-1479 ◽  
Author(s):  
Eun Young Han ◽  
He Wang ◽  
Dershan Luo ◽  
Jing Li ◽  
Xin Wang
Keyword(s):  
Brain Metastases ◽  
Gamma Knife ◽  
Linear Accelerator ◽  
Treatment Time ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Normal Brain ◽  
Large Brain ◽  
The Mean

OBJECTIVEFor patients with multiple large brain metastases with at least 1 target volume larger than 10 cm3, multifractionated stereotactic radiosurgery (MF-SRS) has commonly been delivered with a linear accelerator (LINAC). Recent advances of Gamma Knife (GK) units with kilovolt cone-beam CT and CyberKnife (CK) units with multileaf collimators also make them attractive choices. The purpose of this study was to compare the dosimetry of MF-SRS plans deliverable on GK, CK, and LINAC and to discuss related clinical issues.METHODSTen patients with 2 or more large brain metastases who had been treated with MF-SRS on LINAC were identified. The median planning target volume was 18.31 cm3 (mean 21.31 cm3, range 3.42–49.97 cm3), and the median prescribed dose was 27.0 Gy (mean 26.7 Gy, range 21–30 Gy), administered in 3 to 5 fractions. Clinical LINAC treatment plans were generated using inverse planning with intensity modulation on a Pinnacle treatment planning system (version 9.10) for the Varian TrueBeam STx system. GK and CK planning were retrospectively performed using Leksell GammaPlan version 10.1 and Accuray Precision version 1.1.0.0 for the CK M6 system. Tumor coverage, Paddick conformity index (CI), gradient index (GI), and normal brain tissue receiving 4, 12, and 20 Gy were used to compare plan quality. Net beam-on time and approximate planning time were also collected for all cases.RESULTSPlans from all 3 modalities satisfied clinical requirements in target coverage and normal tissue sparing. The mean CI was comparable (0.79, 0.78, and 0.76) for the GK, CK, and LINAC plans. The mean GI was 3.1 for both the GK and the CK plans, whereas the mean GI of the LINAC plans was 4.1. The lower GI of the GK and CK plans would have resulted in significantly lower normal brain volumes receiving a medium or high dose. On average, GK and CK plans spared the normal brain volume receiving at least 12 Gy and 20 Gy by approximately 20% in comparison with the LINAC plans. However, the mean beam-on time of GK (∼ 64 minutes assuming a dose rate of 2.5 Gy/minute) plans was significantly longer than that of CK (∼ 31 minutes) or LINAC (∼ 4 minutes) plans.CONCLUSIONSAll 3 modalities are capable of treating multiple large brain lesions with MF-SRS. GK has the most flexible workflow and excellent dosimetry, but could be limited by the treatment time. CK has dosimetry comparable to that of GK with a consistent treatment time of approximately 30 minutes. LINAC has a much shorter treatment time, but residual rotational error could be a concern.

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.

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