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 Differentiation of Using Flattening Filter Free Energy in Vmat Plans for Prostate Cancer

2018 ◽  
Vol 22 ◽  
pp. 01049 ◽  
Author(s):  
Yonca Yahşi Çelen ◽  
Atilla Evcin
Keyword(s):  
Prostate Cancer ◽  
Planning System ◽  
Treatment Planning System ◽  
Conformity Index ◽  
Dose Rates ◽  
Advantages And Disadvantages ◽  
Flattening Filter Free ◽  
Significant Difference ◽  
Treatment Plans ◽  
Flattening Filter

It is aimed to compare the values of conformity index (CI), homogeneity index (HI), monitor unit (MU) of volumetrically adjusted arthritis therapy (VMAT) plans using 10 prostate cancer patients with flattened filter (FF) and without flattening filter (FFF). In the study, treatment plans were prepared using 6 FF and 6 FFF in the Eclipse (ver.13.6) treatment planning system with Varian Trilogy Linear Accelerator. When planning was completed, CI averaged 0.87, HI averaged 0.44 and MU values were found to be 591 ± 26.8, 650 ± 33.06, respectively. When the PTV coverage, CI, HI and MU comparisons were made as a result of planning, there was no significant difference when comparing VMAT plans in FFF and FF energies. When we compare the MU values, the MU increase is seen when the straightening filter is removed. In both energy modes, good homogeneity in PTV was achieved with conventional francitation and close dose rates. No significant advantages and disadvantages of the unfiltered energy mode were observed in the assessment of plan quality in terms of CI, HI.

scholarly journals Initial Validation of Proton Dose Calculations on SPR Images from DECT in Treatment Planning System

2020 ◽  
Vol 7 (2) ◽  
pp. 51-61
Author(s):  
Sina Mossahebi ◽  
Pouya Sabouri ◽  
Haijian Chen ◽  
Michelle Mundis ◽  
Matthew O'Neil ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Treatment Planning ◽  
Effective Atomic Number ◽  
Dose Calculation ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Relative Electron ◽  
Treatment Plans ◽  
Proton Dose

Abstract Purpose To investigate and quantify the potential benefits associated with the use of stopping-power-ratio (SPR) images created from dual-energy computed tomography (DECT) images for proton dose calculation in a clinical proton treatment planning system (TPS). Materials and Methods The DECT and single-energy computed tomography (SECT) scans obtained for 26 plastic tissue surrogate plugs were placed individually in a tissue-equivalent plastic phantom. Relative-electron density (ρe) and effective atomic number (Zeff) images were reconstructed from the DECT scans and used to create an SPR image set for each plug. Next, the SPR for each plug was measured in a clinical proton beam for comparison of the calculated values in the SPR images. The SPR images and SECTs were then imported into a clinical TPS, and treatment plans were developed consisting of a single field delivering a 10 × 10 × 10-cm3 spread-out Bragg peak to a clinical target volume that contained the plugs. To verify the accuracy of the TPS dose calculated from the SPR images and SECTs, treatment plans were delivered to the phantom containing each plug, and comparisons of point-dose measurements and 2-dimensional γ-analysis were performed. Results For all 26 plugs considered in this study, SPR values for each plug from the SPR images were within 2% agreement with measurements. Additionally, treatment plans developed with the SPR images agreed with the measured point dose to within 2%, whereas a 3% agreement was observed for SECT-based plans. γ-Index pass rates were > 90% for all SECT plans and > 97% for all SPR image–based plans. Conclusion Treatment plans created in a TPS with SPR images obtained from DECT scans are accurate to within guidelines set for validation of clinical treatment plans at our center. The calculated doses from the SPR image–based treatment plans showed better agreement to measured doses than identical plans created with standard SECT scans.

scholarly journals Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Annika Mannerberg ◽  
Emilia Persson ◽  
Joakim Jonsson ◽  
Christian Jamtheim Gustafsson ◽  
Adalsteinn Gunnlaugsson ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Planning Target Volume ◽  
Dose Distribution ◽  
Time Frame ◽  
Target Volume ◽  
Anatomical Changes ◽  
Ptv Margin ◽  
Significant Difference ◽  
Adaptive Replanning ◽  
Treatment Plans

Abstract Background The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow. Methods Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1. Results The mean center of mass vector offset for the CTV was 1.92 mm [0.13 – 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between −10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01). Conclusions A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction.

scholarly journals The Treatment Planining of Rectum Tumors and The Use of The Wedge Filter for Ensuring The Correct Isodoses

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Idajet Selmani ◽  
Partizan Malkaj
Keyword(s):  
Planning Target Volume ◽  
Treatment Plan ◽  
Target Volume ◽  
The Body ◽  
Planning System ◽  
Treatment Planning System ◽  
Volume Of Interest ◽  
Dose Volume ◽  
Treatment Plans ◽  
Wedge Filter

One of the most important issues in the field of radiotherapy is the correct distribution of the dose around the volume of interest or planning target volume (PTV). For making this possible the exact isodose in a treatment plan has to cover the PTV, so it is used the wedge which is a part of the linear accelerator head. Wedge plays the role of a filter and usually it is called wedge filter. The wedge filter is in use almost in all treatment plans, for all the parts of the body. In this paper it is consider the use of the wedge filter for treatment of rectum tumors. The process starts with the scanning of the patient and the deliantion of the interest’s volums in the Monaco system. In the following the imagins have been sent in the treatment planning system for making the nesessary plans for treatment of the rectum. Two plans were done, one with the use of the wedge and the other without using it. The dose volume histogram helps for compering the results of the plans. The best conformity of the isodoses it was for the plan with the use of wedge through volume of interest, which is planning target volume (PTV).

scholarly journals Cone beam CT-based dose accumulation and analysis of delivered dose to the dominant intraprostatic lesion in primary radiotherapy of prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Jörg Tamihardja ◽  
Sinan Cirsi ◽  
Patrick Kessler ◽  
Gary Razinskas ◽  
Florian Exner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
At Risk ◽  
Organs At Risk ◽  
Peripheral Zone ◽  
Planning System ◽  
Treatment Planning System ◽  
Cone Beam ◽  
Target Coverage ◽  
Dose Accumulation ◽  
Delivered Dose

Abstract Background Evaluation of delivered dose to the dominant intraprostatic lesion (DIL) for moderately hypofractionated radiotherapy of prostate cancer by cone beam computed tomography (CBCT)-based dose accumulation and target coverage analysis. Methods Twenty-three patients with localized prostate cancer treated with moderately hypofractionated prostate radiotherapy with simultaneous integrated boost (SIB) between December 2016 and February 2020 were retrospectively analyzed. Included patients were required to have an identifiable DIL on bi-parametric planning magnetic resonance imaging (MRI). After import into the RayStation treatment planning system and application of a step-wise density override, the fractional doses were computed on each CBCT and were consecutively mapped onto the planning CT via a deformation vector field derived from deformable image registration. Fractional doses were accumulated for all CBCTs and interpolated for missing CBCTs, resulting in the delivered dose for PTVDIL, PTVBoost, PTV, and the organs at risk. The location of the index lesions was recorded according to the sector map of the Prostate Imaging Reporting and Data System (PIRADS) Version 2.1. Target coverage of the index lesions was evaluated and stratified for location. Results In total, 338 CBCTs were available for analysis. Dose accumulation target coverage of PTVDIL, PTVBoost, and PTV was excellent and no cases of underdosage in DMean, D95%, D02%, and D98% could be detected. Delivered rectum DMean did not significantly differ from the planned dose. Bladder mean DMean was higher than planned with 19.4 ± 7.4 Gy versus 18.8 ± 7.5 Gy, p < 0.001. The penile bulb showed a decreased delivered mean DMean with 29.1 ± 14.0 Gy versus 29.8 ± 14.4 Gy, p < 0.001. Dorsal DILs, defined as DILs in the posterior medial peripheral zone of the prostate, showed a significantly lower delivered dose with a mean DMean difference of 2.2 Gy (95% CI 1.3–3.1 Gy, p < 0.001) compared to ventral lesions. Conclusions CBCT-based dose accumulation showed an adequate delivered dose to the dominant intraprostatic lesion and organs at risk within planning limits. Cautious evaluation of the target coverage for index lesions adjacent to the rectum is warranted to avoid underdosage.

scholarly journals Multi-criteria optimization for planning volumetric-modulated arc therapy for prostate cancer

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257216
Author(s):  
Jongmoo Park ◽  
Jaehyeon Park ◽  
Sean Oh ◽  
Ji Woon Yea ◽  
Jeong Eun Lee ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Treatment Planning ◽  
Volumetric Modulated Arc Therapy ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Coverage ◽  
Arc Therapy ◽  
Femoral Heads ◽  
Treatment Volume ◽  
Dose Constraints

We aimed to compare the volumetric-modulated arc therapy (VMAT) plans with or without multi-criteria optimization (MCO) on commercial treatment-planning systems (Eclipse, Varian Medical System, Palo Alto, CA, USA) for patients with prostate cancer. We selected 25 plans of patients with prostate cancer who were previously treated on the basis of a VMAT plan. All plans were imported into the Eclipse Treatment Planning System version 15.6, and re-calculation and re-optimization were performed. The MCO plan was then generated. The dosimetric quality of the plans was evaluated using dosimetric parameters and dose indices that account for target coverage and sparing of the organs at risk (OARs). We defined the rectum, bladder, and bilateral femoral heads. The VMAT-MCO plan offers an improvement of gross treatment volume coverage with increased minimal dose and reduced maximal dose. In the planning treatment volume, the Dmean and better gradient, homogeneity, and conformity indexes improved despite the increasing hot and cold spots. When implemented through the MCO plan, a steeper fall off the adjacent OARs in the overlap area was achieved to obtain lower dose parameters. MCO generated better sparing of the rectum and bladder through a tradeoff of the increasing dose to the bilateral femoral heads within the tolerable dose constraints. Compared with re-optimization and re-calculation, respectively, significant dose reductions were observed in the bladder (241 cGy and 254 cGy; p<0.001) and rectum (474 cGy and 604 cGy, p<0.001) with the MCO. Planning evaluation and dosimetric measurements showed that the VMAT-MCO plan using visualized navigation can provide sparing of OAR doses without compromising the target coverage in the same OAR dose constraints.

scholarly journals Consistency Study of Multiparametric Magnetic Resonance and Computed Tomography Targeting in Targeted Radiotherapy for Prostate Cancer

2020 ◽  
Author(s):  
Zhen Xu ◽  
Xiao-Dong Li ◽  
Lu Fu ◽  
Yong-Hua Yu
Keyword(s):  
Prostate Cancer ◽  
Computed Tomography ◽  
Magnetic Resonance ◽  
Organs At Risk ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Area ◽  
Target Delineation ◽  
Significant Difference

Abstract Background: To compare the difference of location by computed tomography (CT) and multiparametric magnetic resonance imaging (mpMRI) on the target delineation and volume for organs at risk (OARs) among patients with prostate cancer. Methods: T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), and CT were performed among 11 patients who received radiotherapy for prostate cancer at our center between August 2018 and December 2019. The target areas were delineated using the Eclipse system, and the radiotherapy plans were made based on the treatment planning system (TPS) to compare target volume and dose-volume histogram (DVH) relative to rectum and bladder. Results: The clinical target volume (CTV) of T1WI and T2WI decreased by 18.8% (P=0.001) and 22.72% (P=0.003), respectively, compared with CT. The planning target volume (PTV) on T1WI and T2WI were 20.45% (P=0.015) and 22.31% (P= 0.008) smaller than that defined by CT. There was no significant difference in either CTV or PTV between the areas outlined on T1WI and T2WI. The DVH resulting from CT and MRI comparisons showed that the rectum and bladder dose levels were lower with MRI images compared with CT. It should be noted that at the lateral directions, the range of outlining on T2WI sequence were significantly smaller than others. Conclusion: Target planning based on mpMRI (T1WI, T2WI) is more precise than CT, which can significantly reduce the range of the target area and the volume of rectum and bladder exposed to high levels of radiation, improve the fitness and radiographic accuracy of the target area, especially on T2WI.

scholarly journals Voxel based evaluation of sequential radiotherapy treatment plans with different dose fractionation schemes

2020 ◽  
Vol 93 (1112) ◽  
pp. 20200197
Author(s):  
Gaganpreet Singh ◽  
Rose Kamal ◽  
Deepak Thaper ◽  
Arun Singh Oinam ◽  
Bhumika Handa ◽  
...  
Keyword(s):  
Target Volume ◽  
Planning System ◽  
Dose Fractionation ◽  
Treatment Planning System ◽  
Second Phase ◽  
Linear Quadratic ◽  
Data Set ◽  
Treatment Plans ◽  
Dose Scheme ◽  
Radiotherapy Treatment

Objective: This study presents a methodology for voxel-based evaluation of two phase sequential radiotherapy treatment plans having conventional dose scheme in the first phase and subsequent hypofractionation dose scheme in the second phase based upon different priority [planning target volume (PTV), clinical target volume (CTV) and organs at risk (OAR)] of display modes. Methods: A case of carcinoma prostate was selected for demonstration. Varian Eclipse treatment planning system (TPS) was used for contouring and planning. In the first phase, a dose of 52 Gy in 26 fractions to the PTV and in the second phase, a dose of 19.5 Gy in 3 fractions to the PTV Boost was planned on the same CT data set. Both the plans (Phase 1 and Phase 2) were exported and processed using “Voxel-based radiobiology display (VRb) tool”. Plan Sum for Biologically effective dose (BED)-Cube and equivalent dose of 2Gy (EQD2)-Cube was reconstructed using a combination of linear quadratic (LQ) and linear quadratic-linear (LQ-L) radiobiological models. Tumor control probability (TCP) and normal tissue complication probability (NTCP) for different target volumes and organs were also calculated using EQD2-volume histograms of the Plan Sum. Results: An in-house graphical user interface (GUI) is developed to present the qualitative and quantitative evaluation of the multiphase treatment plans with different display modes and dose regimens. The voxel based TCP obtained for the combined target volume was 90.56%. NTCP for the bladder and rectum was calculated from the Plan Sum histograms and found to be 0.33% and ~0.0% respectively. Conclusion: The proposed methodology using the VRb tool offers superior plan evaluation for multiphase sequential radiotherapy treatment plans over the existing methods. Advances in knowledge: PTV, CTV and OAR priority based display modes in VRb tool offers better understanding of radiobiological evaluation of sequential radiotherapy treatment plans.

scholarly journals A Comparison of in-house and Shared Rapidplan Models for Prostate Radiation Therapy Planning

2021 ◽  
Author(s):  
Elizabeth Ruth Claridge Mackonis ◽  
Jonathan Sykes ◽  
Nicholas Hardcastle ◽  
Anthony Espinoza ◽  
Alison Brown ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Treatment Technique ◽  
Local Planning ◽  
Lower Rectum ◽  
Study Results ◽  
Prostate Cancer Radiotherapy ◽  
Contouring Guidelines

Abstract PurposeKnowledge-based planning (KBP) can increase plan quality, consistency and efficiency. In this study, we assess the success of a using a publicly available KBP model compared with developing an in-house model for prostate cancer radiotherapy using a single, commercially available treatment planning system based on the ability of the model to achieve the centre’s planning goals. Methods and MaterialsTwo radiation oncology centres each created a prostate cancer KBP model using the Eclipse RapidPlan software. These two models and a third publicly-available, shared model were tested at three centres in a retrospective planning study. Results The publicly-available model achieved lower rectum doses than the other two models. However, the planning-target-volume (PTV) doses did not meet the local planning goals and the model could not be adjusted to correct this. As a result, the plans most likely to satisfy local planning goals and requirements were created using an in-house model. For centres without an existing in-house model, a model created by another centre with similar planning goals was found to be preferred. ConclusionsVariations in local planning practices including contouring, treatment technique and planning goals can influence the relative performance of KBP. The value of publicly available KBP models could be enhanced through standardisation of planning goals and contouring guidelines, providing information related to the planning goals used to create the model and increased flexibility to allow local adaptation of the KBP model.

scholarly journals Evaluation of dosimetric implications of Pareto and constrained mode of optimization for Monaco TPS generated VMAT plans in post operated carcinoma of the left breast

2021 ◽  
Vol 27 (1) ◽  
pp. 11-18
Author(s):  
Anoop Kumar Srivastava ◽  
Avinav Bharati ◽  
Madhup Rastogi ◽  
Surendra Prasad Mishra ◽  
Rohini Khurana ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Left Breast ◽  
Planning System ◽  
Radiotherapy Planning ◽  
Treatment Planning System ◽  
Breast Cancer Patients ◽  
Heart Volume ◽  
Treatment Plans ◽  
Dose Constraints

Abstract Intensity-modulated radiotherapy (IMRT) is being practiced for the last several years with a special approach for radiation therapy in post-mastectomy breast cancer patients. Meeting the cardiac dose constraints has always been a challenge during radiotherapy planning by both IMRT and VMAT (volumetric modulated arc therapy) of post-mastectomy left breast patients. With the advancement in IMRT planning techniques, it has been modified to VMAT with more degrees of freedom for modulation and is being utilised more frequently. This helps in obtaining a suitable plan for achieving both the dose homogeneity in target volume and dose constraints to Organ at Risk (OAR). 10 Patients with carcinoma of the left breast (post-mastectomy) were selected for this study. VMAT treatment plans for these patients were generated for 6 MV photons on the Monaco treatment planning system (TPS) using two types of optimization modes i.e. Pareto and Constrained mode available in Monaco TPS. For comparative dosimetric evaluation of the efficacy of these two types of optimization modes similar calculation algorithms, calculation grids, arcs, and beam sequencing parameters were used for generating treatment plans. The dosimetric quantities such as volume receiving more than 95% of the prescribed dose (V95), volume receiving more than 107% of the prescribed dose (V107) and Maximum dose (Dmax) for target volume, mean dose (Dmean) for heart, volume receiving more than 30 Gy (V30) volume receiving more than 20 Gy (V20) volume receiving more than 5 Gy (V5) for ipsilateral lung and total monitor units delivered were analysed for both optimization modes. A judicious mix of multiple planning parameters and variables using these two modes of optimization was applied and recorded. Both optimization modes yielded similar outcomes. However, Pareto mode has shown better coverage for planning target volume (PTV) with comparable doses to OARs.

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