Volumetric Modulated Arc Therapy Technique Research Articles

Volumetric modulated arc therapy total body irradiation improves toxicity outcomes compared to 2D total body irradiation.

Volumetric modulated arc therapy (VMAT) total body irradiation (TBI) allows for greater organ sparing with improved target coverage compared to 2D-TBI. However, there is limited evidence of whether improved organ sparing translates to decreases in toxicities and how its toxicities compare to those of the 2D technique. We aimed to compare differences in toxicities among patients treated with TBI utilizing VMAT and 2D techniques. A matched-pair single-institution retrospective analysis of 200 patients treated with TBI from 2014 to 2023 was performed. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method and compared using log-rank tests. Differences in characteristics and toxicities between the VMAT and 2D cohorts were compared using Fisher's exact test. Of the 200 patients analyzed, 100 underwent VMAT-TBI, and 100 underwent 2D-TBI. The median age for VMAT-TBI and 2D-TBI patients was 13.7 years and 16.2 years, respectively (p = 0.25). In each cohort, 53 patients were treated with myeloablative regimens (8-13.76 Gy), and 47 were treated with non-myeloablative regimens (2-4 Gy). For the entire VMAT-TBI cohort, lung Dmean, kidney Dmean, and lens Dmax were spared to 60.6% ± 5.0%, 71.0% ± 8.5%, and 90.1% ± 3.5% of prescription, respectively. For the non-myeloablative VMAT-TBI cohort, testis/ovary Dmax, brain, and thyroid Dmean were spared to 33.4% ± 7.3%, 75.4% ± 7.0%, and 76.1% ± 10.5%, respectively. For 2D-TBI, lungs were spared using partial-transmission lung blocks for myeloablative regimens. The VMAT-TBI cohort experienced significantly lower rates of any grade of pneumonitis (2% vs. 12%), nephrotoxicity (7% vs. 34%), nausea (68% vs. 81%), skin (16% vs. 35%), and graft versus host disease (GVHD) (42% vs. 62%) compared to 2D-TBI patients. For myeloablative regimen patients, rates of pneumonitis (0% vs. 17%) and nephrotoxicity (9% vs. 36%) were significantly lower with VMAT-TBI versus 2D-TBI (p < 0.01). Median follow-up was 14.3 months, and neither median OS nor PFS for the entire cohort was reached. In the VMAT versus 2D-TBI cohort, the 1-year OS was 86.0% versus 83.0% (p = 0.26), and the 1-year PFS was 86.6% and 80.0% (p = 0.36), respectively. Normal tissue sparing with VMAT-TBI compared to the 2D-TBI translated to significantly lower rates of pneumonitis, renal toxicity, nausea, skin toxicity, and GVHD in patients, while maintaining excellent disease control.

Investigation of the linear accelerator low dose rate mode for pulsed low-dose-rate radiotherapy delivery

Purpose. Pulsed volumetric modulated arc therapy (VMAT) was proposed as an advanced treatment that combines the biological benefits of pulsed low dose rate (PLDR) and the dosimetric benefits of the intensity-modulated beams. In our conventional pulsed VMAT technique, a daily fractional dose of 200 cGy is delivered in 10 arcs with 3 min intervals between the arcs. In this study, we are testing the feasibility of pulsed VMAT that omits the need to split into ten arcs and excludes any beam-off gaps. Methods. The study was conducted using computed tomographic images of 24 patients previously treated at our institution with the conventional PLDR technique. Our newly installed Elekta machine has a low dose rate option on the order of 25 MU min−1. PLDR requires an effective dose rate of 6.7 cGy min−1 with attention being paid to the maximum dose received within any point within the target not to exceed 13 cGy min−1. The quality of treatment plans was judged based on dose-volume histograms, isodose distribution, dose conformality to the target, and target dose homogeneity. The dose delivery accuracy was assessed by measurements using the MatriXX Evolution 2D array system. Results. All cases were normalized to cover 95% of the target volume with 100% of the prescription dose. The average conformity index was 1.03 ± 0.08 while the average homogeneity index was 1.05 ± 0.02. The maximum reported dose rate at any point within the target was 10.44 cGy min−1. The mean dose rate for all pulsed VMAT plans was 6.88 ± 0.1 cGy min−1. All cases passed our gamma analysis with an average passing rate of 99.00% ± 0.48%. Conclusion. The study showed the applicability of planning pulsed VMAT using Eclipse and its successful delivery on our Elekta linac. Pulsed VMAT using the machine’s low dose rate mode is more efficient than our previous pulsed VMAT delivery.

Effects of electron density force to 1.0 and fill to 1.0 on VMAT treatment plans for lung SBRT.

The aim of this study is to determine the effect of forcing and filling the electron density (ED) to 1.0 of the planning target volume (PTV) overdose distribution in lung SBRT treatment leading to shortening patient treatment time and increasing patient comfort by reducing MU/fraction due to ED manipulation effect. In this study, 36 lung SBRT plans of 12 suitable patients who prescribed a total dose of 50Gy in five fractions were generated with Monaco v.5.10 TPS using the Monte Carlo (MC) algorithm and volumetric modulated arc therapy (VMAT) technique by PTV ED values forcing as well as filling to 1.0 and comparatively assessed. The first group of plans was created by using the patient's original ED, second and third groups of plans were reoptimized by forcing and filling the ED of PTV to 1.0, respectively, therefore acquiring a new dose distribution which lead to comparatively assessment the effects of changes in ED on PTV and OAR doses. Assessment of treatment plans revealed that mean MU/fx numbers were decreased by 76% and 75.25% between Groups 1 and 2, Groups 1 and 3, respectively. The number of segments was also reduced in Group 1 by up to 15% compared with Groups 2 and 3. Maximum HI and CI differences for PTV between Groups 1 and 2 were less than 1% and Groups 1 and 3 were 1.5% which indicates all 3 group plans were comparable in terms of dose distribution within PTV. Forcing and filling the ED of PTV to 1.0 strategy has provided reduced a number of segments and MU/fx without a significant change in PTV mean and maximum doses, thereby decreasing treatment time and patient discomfort during treatment. This process should be considered in line of a potential number of patients as well as prescribed dose and MU/fx numbers.

COMPARATIVE RADIATION DOSIMETRY OF WHOLE BREAST RADIOTHERAPY USING IMRT AND VMAT TECHNIQUES IN LEFT SIDED BREAST CANCER PATIENTS AFTER BREAST CONSERVING SURGERY

Background:The radiotherapy of left sided breast cancers is mandatory and integral part of treatment and challenging because of surrounding critical structures posing increased risk of complications. The main objective of this study was to quantify doses toorgan at risk(OARs) including left lung, heart, contralateral breast, spinal cord, and planning target volume (PTV) using different radiation techniques like Intensity modulated radiation therapy (IMRT)&amp;volumetric modulated arc therapy (VMAT) and comparison of radiation dosimetry. Methods: A prospective study of 30 patients of left sided breast cancer who had undergone Breast Conservative Surgery (BCS) and chemotherapy was done for adjuvant radiation. For every patient radiation planning was done by two different techniques IMRT and VMAT. Then the comparison of radiation dosimetry parameters was done for all the techniques including the parameters like PTV coverage, doses to OAR like heart, left lung, contralateral breast and spinal cord and head of humerus. The Homogenity Index (HI) were calculated. Result: The Mean age of the patient was 46.7 years. When comparing the doses delivered in IMRT and VMAT Technique for left sided breast cancer post breast conservation surgery there was significant difference in PTV Breast and axilla V95 Gy. It was 96.2±1.9% (IMRT) vs 94.8±1.71% (VMAT), (p=0.004). However significant sparing of Organs at Risk was seen. With ipsilateral lung dose mean V5 Gy was 77.86± 9.68% (IMRT) v/s 83.04± 9.86 % (VMAT), (p=0.0446). Also mean V30 Gy was 14.6±4.82% with IMRT vs 16.54±5.86% with VMAT, (p=0.0169). Heart mean dose was 8.8±1.49 Gy with IMRT and 10.98±3.7 Gy with VMAT, (p=0.0227). Further V30 Gy for Heart was 4.61±3.8% with IMRT and 6.72±4.0% with VMAT, (p=0.0132).No significant difference was seen with IMRT and VMAT technique for contralateral lung, contralateral breast and spinal cord. Conclusion: In treatment of patients with radiation with left breast cancer patients post BCS using IMRT and VMAT technique it is seen significant dose reduction with IMRT Technique for ipsilateral lung and Heart as compared to VMAT technique. Significant V95 coverage for PTV Breast and axilla with IMRT as compared to VMAT. Hence in our Study IMRT technique was found to be superior for better sparing of Organ at risk and better PTV coverage.

Comparison of two different VMAT radiotherapy TPSs for pancreatic cancer using flattening filter free photon beam energy

BackgroundPancreatic cancer is a devastating disease with a poor prognosis, and radiation therapy plays a crucial role in its treatment and management. Conventional radiation therapy (RT) techniques have limitations in delivering adequate doses to the tumor while sparing surrounding normal tissues. However, modern RT techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT) have led to the development of novel approaches that can reduce toxicity. The incorporation of advanced imaging modalities, like four-dimensional computed tomography (4D-CT) and magnetic resonance imaging (MRI), enables enhancement of tumor control and improves conformality and treatment outcomes. Additionally, using flattening filter-free (FFF) beams can further enhance treatment efficiency and efficacy. PurposeThis study aims to compare two different VMAT techniques using two different treatment planning systems (TPSs), Monaco and Eclipse, in the treatment of pancreatic cancer II stage infiltrating duct carcinoma patients using an FFF photon beam. Materials and methods20 pancreatic cancer II stage infiltrating duct carcinoma patients were retrospectively analyzed, and each patient's plans were designed using the two TPSs. The dose distribution of the target using 6 MV FFF for TrueBeam-Varian and organs at risk (OARs) were compared. The monitor unit (MU), treatment time, conformity (CI), and homogeneity (HI) indices were also evaluated. ResultsFor pancreatic cancer patients, the mean dose of the planning target volume (PTV) in the Monaco plan was lower than the Eclipse plan. The plan evaluation parameters in Monaco and Eclipse were similar without significant differences (p-value = 0.152). The Monaco plan was better than the Eclipse plan regarding mean dose and V15Gy of the kidneys; the spinal cord was lowest in the Monaco plan, and the maximum dose and V45Gy of the spinal cord were 592.1 cGy and 1.37% lower than the Eclipse plan, respectively. ConclusionThe VMAT Monaco plan is a favorable TPS for pancreatic cancer patients, providing improved sparing of critical organs while maintaining adequate target coverage.

Evaluation of the conformity of intensity-modulated radiation therapy and volumetric modulated arc therapy using AAPM TG 119 protocol.

The aim of this work was to evaluate the conformity of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), and verify the accuracy of the planning and delivery system used in this work based on the AAPM TG-119 protocol. The Eclipse 13.6 treatment planning system (TPS) was used to plan the TG-119 test suite, which included four test cases: MultiTarget, Prostate, Head/Neck, and C-Shape for IMRT and VMAT techniques with 6 MV and 10 MV acceleration voltages. The results were assessed and discussed in terms of the TG-119 protocol and the results of previous studies. In addition, point dose and planar dose measurements were done using a semiflex ion chamber and an electronic portal imaging device (EPID), respectively. The planned doses of all test cases met the criteria of the TG-119 protocol, except those for the spinal cord of the C-Shape hard case. There were no significant differences between the treatment planning doses and the doses given in the TG-119 report, with p-values ranging from 0.974 to 1 (p > 0.05). Doses to the target volumes were similar in the IMRT and VMAT plans, but the organs at risk (OARs) doses were different depending on the test case. The planning results showed that IMRT is more conformal than VMAT in certain cases. For the point dose measurements, the confidence limit (CLpoint) of 0.030 and 0.021 were better than the corresponding values of 0.045 and 0.047 given in the TG-119 report for high-dose and low-dose areas, respectively. Regarding the planar dose measurements, the CLplanar value of 0.38 obtained in this work was lower than that given in the TG-119 report (12.4). It is concluded that the dosimetry measurements performed in this study showed better confidence limits than those provided in the TG 119 report. IMRT remains more conformal in certain circumstances than the more progressive VMAT. When selecting the method of delivering a dose to the patient, several factors must be considered, including the radiotherapy technique, energy, treatment site, and tumour geometry.

First clinical experience of total body irradiation using volumetric modulated arc therapy technique in Japan.

In recent years, advances in radiotherapy technology have led to the use of high-precision radiotherapy such as volumetric modulated arc therapy (VMAT). Total body irradiation using VMAT technique (VMAT-TBI) was performed for the first time in our hospital. A 56-year-old male patient diagnosed with B-cell acute lymphoblastic leukemia was performed TBI as pretreatment for haploidentical-related peripheral blood stem-cell transplantation. The prescribed dose was 4 Gy for planning target volume in two fractions. The treatment plan was divided into two plans: upper body and lower body with three and two isocenters, respectively. The overall treatment time with VMAT-TBI was approximately 55 min, and it was not significantly longer than that of moving couch techniques. VMAT-TBI is a less burdensome and more accurate treatment for patients, and it may be a useful treatment for TBI.

Dosimetric effect of collimator rotation on intensity modulated radiotherapy and volumetric modulated arc therapy for rectal cancer radiotherapy.

Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are the main radiotherapy techniques for treating and managing rectal cancer. Collimator rotation is one of the crucial parameters in radiotherapy planning, and its alteration can cause dosimetric variations. This study assessed the effect of collimator rotation on the dosimetric results of various IMRT and VMAT plans for rectal cancer. Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose-volume histograms [DVH]) as well as radiobiological findings were analyzed and compared. The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques. Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes.

Prediction of Radiation Therapy Dose Distribution Using Random Forest Algorithm in Volumetric Modulated Arc Therapy Technique for Brain Cancer

Optimization of radiation dose distribution in clinical planning using a Treatment Planning System (TPS) for radiotherapy patients is crucial to achieving a balance between therapeutic effectiveness and patient safety. However, this process is time-consuming and relies heavily on the expertise of medical physicists. In this study, dose prediction using machine learning was performed on the Planning Target Volume (PTV) and Organ at Risk (OAR) for brain cancer cases using the Volumetric Modulated Arc Therapy (VMAT) planning technique. The planning DICOM data were extracted for radiomic and dosiomic values, which were then used as input and output in this study using a random forest algorithm model. Model evaluation results indicated that the random forest model's performance in predicting dose had a Mean Square Error (MSE) value of 0.018. The Homogeneity Index (HI) and Conformity Index (CI) values for the clinical data were 0.136±0.134 and 0.939±0.131 respectively, while the predicted results were 0.136±0.039 and 0.949±0.006, with p-values for PTV and OAR features &gt; 0.05. Thus, it can be concluded that the random forest model is effective in predicting dose for PTV brain cancer and OAR and can function as a reference in the planning process.

Development and validation of an automated Tomotherapy planning method for cervical cancer

PurposeThis study aimed to develop an automated Tomotherapy (TOMO) planning method for cervical cancer treatment, and to validate its feasibility and effectiveness.Materials and methodsThe study enrolled 30 cervical cancer patients treated with TOMO at our center. Utilizing scripting and Python environment within the RayStation (RaySearch Labs, Sweden) treatment planning system (TPS), we developed automated planning methods for TOMO and volumetric modulated arc therapy (VMAT) techniques. The clinical manual TOMO (M-TOMO) plans for the 30 patients were re-optimized using automated planning scripts for both TOMO and VMAT, creating automated TOMO (A-TOMO) and automated VMAT (A-VMAT) plans. We compared A-TOMO with M-TOMO and A-VMAT plans. The primary evaluated relevant dosimetric parameters and treatment plan efficiency were assessed using the two-sided Wilcoxon signed-rank test for statistical analysis, with a P-value < 0.05 indicating statistical significance.ResultsA-TOMO plans maintained similar target dose uniformity compared to M-TOMO plans, with improvements in target conformity and faster dose drop-off outside the target, and demonstrated significant statistical differences (P+ < 0.01). A-TOMO plans also significantly outperformed M-TOMO plans in reducing V50Gy, V40Gy and Dmean for the bladder and rectum, as well as Dmean for the bowel bag, femoral heads, and kidneys (all P+ < 0.05). Additionally, A-TOMO plans demonstrated better consistency in plan quality. Furthermore, the quality of A-TOMO plans was comparable to or superior than A-VMAT plans. In terms of efficiency, A-TOMO significantly reduced the time required for treatment planning to approximately 20 min.ConclusionWe have successfully developed an A-TOMO planning method for cervical cancer. Compared to M-TOMO plans, A-TOMO plans improved target conformity and reduced radiation dose to OARs. Additionally, the quality of A-TOMO plans was on par with or surpasses that of A-VMAT plans. The A-TOMO planning method significantly improved the efficiency of treatment planning.

Evaluation of Normal Tissue Objective Function for Treatment Planning of Solitary Brain Metastasis Using Intensity-modulated Radiosurgery Techniques.

The purpose of this study was to systematically examine the normal tissue objective (NTO) function by comparing its variations for planning solitary brain metastasis with intensity-modulated and volumetric-modulated arc radiosurgery techniques. Twenty-two cases were retrospectively planned with two NTO parameter sets named A and B using intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. The Type A set used slope, k = 0.4 mm-1 plus end dose, De = 20%, whereas the Type B set used k = 1.0 mm-1 plus De = 10%. The resulting four plan types were assessed using mean dose to 5 mm exterior ring, normal brain receiving 12 Gy (V12), 5 Gy total brain dose volume (V5), gradient index (R50%), focal index (FI), Paddick conformity index (PCI), prescription isodose surface (PIDS), and MU/Gy. Brain doses were significantly lower for VMAT than for IMRT. R50% was more favorable for VMAT than for IMRT for each planning target volume (PTV). The mean FI was comparable between the corresponding IMRT and VMAT plan types. PCI was better for the IMRT_A plan type. PIDS was significantly lower for Type B plans than Type A for both techniques. For PTVs <3 cm3, IMRT plans showed poor dosimetry and required NTO settings stricter than Type B. The application of NTO variations demonstrated varied dosimetry for IMRT and VMAT techniques. The NTO parameter variations produced field size and/or beamlet size/shape variations. The strict NTO parameter set generated more conformal beam apertures to reduce the brain dose. VMAT plan types showed significantly lower brain doses and better dosimetry for all target sizes.

Minimizing normal tissue low dose bath for left breast Volumetric Modulated Arc Therapy (VMAT) using jaw offset.

With proper beam setup and optimization constraints in the treatment planning system, volumetric modulated arc therapy (VMAT) can improve target dose coverage and conformity while reducing doses to adjacent structures for whole breast radiation therapy. However, the low-dose bath effect on critical structures, especially the heart and the ipsilateral lung, remains a concern. In this study, we present a VMAT technique with the jaw offset VMAT (JO-VMAT) to reduce the leakage and scatter doses to critical structures for whole breast radiation therapy. The data of 10 left breast cancer patients were retrospectively used for this study. CT images were acquired on a CT scanner (GE, Discovery) with the deep-inspiration breath hold (DIBH) technique. The planning target volumes (PTVs) and the normal structures (the lungs, the heart, and the contralateral breast) were contoured on the DIBH scan. A 3D field-in-field plan (3D-FiF), a tangential VMAT (tVMAT) plan, and a JO-VMAT plan were created with the Eclipse treatment planning system. An arc treatment field with the x-jaw closed across the central axis creates a donut-shaped high-dose distribution and a cylinder-shaped low-dose volume along the central axis of gantry rotation. Applying this setup with proper multi-leaf collimator (MLC) modulation, the optimized plan potentially can provide sufficient target coverage and reduce unnecessary irradiation to critical structures. The JO-VMAT plans involve 5-6 tangential arcs (3 clockwise arcs and 2-3 counterclockwise arcs) with jaw offsets. The plans were optimized with objective functions specified to achieve PTV dose coverage and homogeneity; For organs at risk (OARs), objective functions were specified individually for each patient to accomplish the best achievable treatment plan. For tVMAT plans, optimization constraints were kept the same except that the jaw offset was removed from the initial beam setup. The dose volume histogram (DVH) parameters were generated for dosimetric evaluation of PTV and OARs. The D95% to the PTV was greater than the prescription dose of 42.56Gy for all the plans. With both VMAT techniques, the PTV conformity index (CI) was statistically improved from 0.62 (3D-FiF) to 0.83 for tVMAT and 0.84 for JO-VMAT plans. The difference in the homogeneity index (HI) was not significant. The Dmax to the heart was reduced from 12.15Gy for 3D-FiF to 8.26Gy for tVMAT and 7.20Gy for JO-VMAT plans. However, a low-dose bath effect was observed with tVMAT plans to all the critical structures including the lungs, the heart, and the contralateral breast. With JO-VMAT, the V5Gy and V2Gy of the heart were reduced by 32.7% and 15.4% compared to 3D-FiF plans. Significantly, the ipsilateral lung showed a reduction in mean dose (4.65-3.44Gy) and low dose parameters (23.4% reduction for V5Gy and 10.7% reduction for V2Gy) for JO-VMAT plans compared to the 3D-FiF plans. The V2Gy dose to the contralateral lung and breast was minimal with JO-VMAT techniques. A JO-VMAT technique was evaluated in this study and compared with 3D-FiF and tVMAT techniques. Our results showed that the JO-VMAT technique can achieve clinically comparable coverage and homogeneity and significantly improve dose conformity within PTV. Additionally, JO-VMAT eliminated the low-dose bath effect at all OARs evaluation metrics including the ipsilateral/contralateral lung, the heart, and the contralateral breast compared to 3D-FiF and tVMAT. This technique is feasible for the whole breast radiation therapy of left breast cancers.

A Prospective Study on the Use of Deep Inspiration Breath-Hold Technique in External Beam Radiotherapy for Breast Cancer

Background Breast cancer is the most common cancer and the leading cause of death in women. The deep inspiration breath-hold (DIBH) technique helps reduce the dose received by the heart and lungs in breast cancers during adjuvant radiotherapy (RT). We present the dosimetry of heart and lungs with DIBH technique, reproducibility, and ease of execution. Materials and Methods This is a prospective study among breast cancer patients planned for adjuvant RT following either breast conservation or mastectomy. Patients received adjuvant RT to a dose of 42.5 Gy/16 Fr to the chest wall/whole breast followed by a boost of 10 Gy/5 Fr for breast conservation surgery patients with either three-dimensional conformal RT or volumetric modulated arc therapy technique. The dosimetric parameters such as lung mean dose, heart mean dose, and V25 Gy were compared between DIBH and free-breathing (FB) scans. Data were analyzed using SPSS software, and p-value &lt;0.05 was considered statistically significant. Results The study was conducted from September 2018 to August 2020, and 32 patients were included. The compliance to the DIBH technique was good. The dose received by ipsilateral lung V20 (17 vs. 25%) and mean dose (9 vs. 12 Gy) were significantly lower in DIBH compared with FB (p &lt; 0.001). The V5 (31 vs. 15%), V25 (9 vs. 2%), and mean dose (7 vs. 3.3 Gy) to the heart were much higher in FB compared with DIBH (p &lt; 0.001). Conclusion DIBH-based RT treatment delivery for breast cancer patients requiring adjuvant RT showed good compliance and offers a significant reduction in radiation dose to the heart and lung.

Comprehensively evaluating the performance of Elekta high-definition dynamic radiosurgery for hypofractionated stereotactic radiotherapy of multiple brain metastases

PurposeTo evaluate the dosimetric and delivery performance of Elekta high-definition dynamic radiosurgery (HDRS) in hypofractionated stereotactic radiotherapy (HSRT) for multiple brain metastases (BMs) by comparison with a conventional single-isocenter noncoplanar volumetric modulated arc therapy (VMAT) technique using the RayStation treatment planning system (TPS). Materials and methodsFrom June 2022 to October 2023, thirty-two patients (a total of 140 BMs) treated with HSRT (30–48 Gy/3-6f) via HDRS-based single-isocenter noncoplanar VMAT (HDRS-VMAT) were retrospectively selected for this study. Each patient was replanned using RayStation TPS-based single-isocenter noncoplanar VMAT (RayStation-VMAT). HDRS-VMAT and RayStation-VMAT plans were compared in terms of the gradient index (GI), conformity index (CI), normal brain tissue (NBT) dose exposure, monitor units (MUs), homogeneity index (HI), delivery accuracy, and beam-on time (BOT). ResultsCompared with the RayStation-VMAT plan, the HDRS-VMAT plan achieved superior CI (1.14 ± 0.09 vs. 1.23 ± 0.12, P < 0.001) and GI (5.23 ± 1.18 vs. 7.83 ± 2.75, p < 0.001) but had greater HI values. Compared with the RyaStation-VMAT plan, the HDRS-VMAT plan also yielded significantly lower NBT dose exposures (V23Gy, V21Gy, V18Gy, V12Gy and Dmean) but at the cost of increased MUs (3659.16 ± 1225.28 vs. 2536.23 ± 785.80, p < 0.001). The difference in BOTs was minimal (<1 min), which was not considered clinically significant. Furthermore, the HDRS-VMAT exhibited a higher gamma passing rate across all criteria (P < 0.001), particularly under stricter criteria (2%/1 mm), achieving an approximately 3% increase. ConclusionCompared with RaySation-VMAT, HDRS-VMAT offers superior target conformity, better NBT sparing, and higher delivery accuracy while maintaining comparable delivery efficiency. This represents a promising approach for HSRT of multiple BMs.

Intensity Modulated Therapy for Patients With Breast Cancer. Practical Guidelines and Tips for an Effective Treatment Planning Strategy

PurposePractical guidelines and tips for effective and robust radiotherapy treatment planning for breast cancer patients are addressed for intensity-modulated fixed field or volumetric modulated arc therapy techniques. The concepts described here are general and valid on all the treatment planning systems. However, some details have been shown here applied to the Varian platforms used at the authors’ institutions. MethodsThe specific aspects of using C-arm or O-ring mounted linear accelerators are covered in the document, as well as tips for dealing with certain resource constraints, target cropping and skin flash aiming to reduce risks of skin toxicity and to manage (residual after breath control) respiration motion or oedema. ResultsA decision tree is presented, and practical solutions are discussed for cases where a target volume is contoured or not; where volumetric modulated arc therapy or fixed beams intensity modulation should be applied and details about the technical implementation (tangential IMRT, butterfly IMRT or VMAT, large partial VMAT arcs). Target cropping and skin flash implications are discussed in detail, and links to plan robustness are outlined. ConclusionsPractical guidelines for breast planning are presented and summarized with a decision tree and technical summaries.

Hybrid Treatment Planning for Chest Wall Irradiation Utilizing Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT): A Systematic Review.

Novel hybrid approaches for chest wall irradiation show promising outcomes regarding target coverage and sparing organs at risk (OARs). In this systematic review, we compared hybrid volumetric modulated arc therapy (H-VMAT) or hybrid intensity-modulated radiotherapy (H-IMRT) techniques with non-hybrid techniques, such as three-dimensional conformal radiation therapy (3DCRT), field-in-field (FIF), intensity-modulated arc therapy (IMRT), and volumetric modulated arc therapy (VMAT), for breast cancer patients with mastectomy. Our focus was the plan quality and dose distribution to the OARs. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, we performed a systematic review and quality appraisal of primary studies evaluating hybrid therapy to the chest wall and the OARs. An extensive online search of PubMed and Scopus databases was conducted using appropriate keywords. The dose to the OARs (lung, heart, and contralateral breast), planning target volume (PTV), homogeneity index (HI), and conformity index (CI) were extracted. The data were then tabulated and compared for the outcomes between modalities among the studies.Nine studies that met the search criteria were selected to evaluate the PTV coverage and dosimetric results of hybrid and non-hybrid techniques. In terms of 95% PTV coverage, among nine reviewed studies, the largest difference between the two techniques was between VMAT (47.6 Gy) and H-VMAT (48.4 Gy); for the conformity index, the largest difference was noted between 3DCRT (0.58) and H-VMAT (0.79). In both cases, differences were statistically significant (P < 0.005). Two studies showed dose homogeneity improvement within the treatment target in H-VMAT (0.15 and 0.07) compared with 3DCRT (0.41 and 0.12), with a P value of <0.001. Two studies did not report on the homogeneity index, and three others observed no statistical difference. Regarding OARs, in the comparison of H-VMAT and VMAT, the largest significant change was in the volume receiving 5 Gy (V5Gy) of the ipsilateral lung and the V10Gy of the contralateral lung. For the ipsilateral lung, V5Gy was 90.7% with VMAT versus 51.45% with H-VMAT. For the contralateral lung, V10Gy was 54.9% with VMAT versus 50.5% with H-VMAT. In six studies, the mean dose of the contralateral breast was lower in hybrid techniques than in single modalities: VMAT (4.2%, 6.0%, 1.9%, 7.1%, 4.57%) versus H-VMAT (1.4%, 3.4%, 1.8%, 3.5%, 2.34%)and IMRT (9.1%) versus H-IMRT (4.69%). Although most studies did not report on monitor units and treatment time, those that included them showed that hybrids had lower monitor units and shorter treatment times.Hybridtechniques in radiotherapy, such as combining two modalities, can indeed facilitate lower doses to OARsfor patients with a high risk of toxicities. Prospective clinical studies are needed to determine the outcomes of breast cancer treated with hybrid techniques.

Modeling of Gamma Index for Prediction of Pretreatment Quality Assurance in Stereotactic Body Radiation Therapy of the Liver.

The purpose of this study was to develop a predictive model to evaluate pretreatment patient-specific quality assurance (QA) based on treatment planning parameters for stereotactic body radiation therapy (SBRT) for liver carcinoma. We retrospectively selected 180 cases of liver SBRT treated using the volumetric modulated arc therapy technique. Numerous parameters defining the plan complexity were calculated from the DICOM-RP (Radiotherapy Plan) file using an in-house program developed in MATLAB. Patient-specific QA was performed with global gamma evaluation criteria of 2%/2 mm and 3%/3 mm in a relative mode using the Octavius two-dimensional detector array. Various statistical tests and multivariate predictive models were evaluated. The leaf speed (MILS) and planning target volume size showed the highest correlation with the gamma criteria of 2%/2 mm and 3%/3 mm (P < 0.05). Degree of modulation (DoM), MCSSPORT, leaf speed (MILS), and gantry speed (MIGS) were predictors of global gamma pass rate (GPR) for 2%/2 mm (G22), whereas DoM, MCSSPORT, leaf speed (MILS) and robust decision making were predictors of the global GPR criterion of 3%/3 mm (G33). The variance inflation factor values of all predictors were <2, indicating that the data were not associated with each other. For the G22 prediction, the sensitivity and specificity of the model were 75.0% and 75.0%, respectively, whereas, for G33 prediction, the sensitivity and specificity of the model were 74.9% and 85.7%%, respectively. The model was potentially beneficial as an easy alternative to pretreatment QA in predicting the uncertainty in plan deliverability at the planning stage and could help reduce resources in busy clinics.

DOSIMETRIC COMPARISON OF INTENSITY-MODULATED RADIATION THERAPY (IMRT) AND VOLUMETRIC-MODULATED ARC THERAPY (VMAT) IN RECTAL CANCER PATIENTS: A COMPREHENSIVE ANALYSIS

This study aimed to conduct a thorough dosimetric comparison between two advanced radiotherapy techniques, Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT), to ascertain the superior modality in terms of dose distribution and organ-at-risk sparing for rectal cancer patients. Thirty-three patients with ECOG performance status 1, aged between 18 to 60 years, diagnosed with Stage II to III rectal cancer, were included in this prospective study. Each patient underwent treatment planning with IMRT and VMAT techniques using Varian system simulation computed tomography scans. The dosimetric analysis encompassed the evaluation of target volume dose homogeneity, conformity, and doses to at-risk organs. The dosimetric comparison was conducted utilizing seven-field IMRT and dual arc VMAT plans. Statistical analysis was performed using paired t-tests and SPSS 20 software. Treatment plan constraints adhered to the RTOG 9406 guidelines, ensuring adequate planning target volume (PTV) coverage, homogeneity index, conformity index, and dose limits for organs at risk, including small bowel V20 (&lt;200cc), bladder V45 (&lt;21Gy), and femoral head V50 (≤30 Gy). Volumetric arc therapy plans demonstrated superior dose homogeneity to fixed-field intensity-modulated plans (p-value = 0.04), particularly in femoral head dose-limiting toxicity (p-value = 0.00). However, intensity-modulated therapy exhibited equivalent or superior performance in other evaluated parameters. Our findings suggest that while VMAT offers advantages in PTV coverage homogeneity and femoral head dose-limiting toxicity, IMRT remains competitive and potentially preferable in certain dosimetric aspects. The choice between IMRT and VMAT should be carefully considered based on individual patient characteristics and treatment goals. This comprehensive dosimetric comparison contributes valuable insights into optimizing radiotherapy planning for rectal cancer patients, potentially guiding clinical decision-making and improving treatment outcomes.

Measurement and Incorporation of Laryngeal Motion Using cine-MRI on an MR-Linear Accelerator to Generate Radiation Therapy Plans for Early-stage Squamous Cell Cancers of the Glottis

IntroductionSwallow-related motion of the larynx is most significant in the cranio-caudal directions and of short duration. Conventional target definition for radical radiotherapy includes coverage of the whole larynx. This study longitudinally examined respiration- and swallow-related laryngeal motions using cine-MRI. We further analysed the dosimetry to organs at risk by comparing 3D-conformal radiotherapy (3D-CRT), Volumetric-Modulated Arc Therapy (VMAT) and Intensity-Modulated Radiotherapy (IMRT) techniques. MethodsFifteen patients with T1-2 N0 glottic squamous cell carcinomas were prospectively recruited for up to three cine-MRI scans on the Elekta Unity MR-Linear accelerator, at the beginning, middle and end of a course of radical radiotherapy. Swallow frequency and motion of the hyoid bone, cricoid and thyroid cartilages and vocal cords were recorded during swallow and rest. Adapted treatment volumes consisted of GTV + 0.5-1 cm to a CTV with an additional ITV for personalised resting-motion. Swallow-related motion was deemed infrequent and was not accounted for in the ITV. We compared radiotherapy plans for 3D-CRT (whole larynx), VMAT (whole larynx), VMAT and IMRT (ITV for resting motion). ResultsResting- and swallow- motions were most prominent in the craniocaudal plane. There were no significant changes in the magnitudes of motions over the course of radiotherapy. There was a trend for a progressive reduction in the frequency of swallow. Treatment of partial-larynx volumes with intensity-modulated methods significantly reduced the dose to carotid arteries compared to whole-larynx. Robustness analysis demonstrated that when accounting for intra-fraction swallow, the total dose delivered to the ITV/PTV was maintained above 95%. ConclusionsSwallow-related motions are infrequent and accounting for resting motion in an ITV is sufficient. VMAT/IMRT techniques that treat more conformal targets can significantly spare critical organs at risk such as the carotid arteries and thyroid gland, potentially reducing the risk of carotid artery stenosis related and other complications long-term.

A phantom study investigating effective strategies for reducing fetal dose in pregnant patients with head and neck cancer

PurposeTo measure the out-of-field doses for various treatment planning techniques and assess the impact on fetal dose with and without the use of custom shielding. Materials and methodsA total of six treatment plans were generated with different treatment techniques such as 3-dimensional conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT), utilizing both 6 MV flattened beams and flattening filter-free (FFF) beams. The measurements were carried out both out-of-field at the surface and at depth to assess the dose reduction achieved by removing the flattening filter and incorporating shielding. ResultsThe custom-made frame shielding can effectively reduce the surface dose with a maximum reduction of 15.2% observed in VMAT plans and achieve a maximum reduction of 100% for cone beam computed tomography (CBCT) imaging. Out-of-field dose measurements conducted at depth, positioned 58 cm inferior to the target isocenter, reveal that the shielding effectiveness consistently remains the greatest for 3DCRT technique. A maximum reduction of 21% is observed when utilizing a flattening filter-free beam. ConclusionThe results of this study indicate that the 3DCRT technique exhibits the least amount of scatter radiation both near and far from the treatment isocenter, which is the most suitable approach for radiation therapy of pregnant patients. In cases where meeting dose constraints for critical organs becomes challenging, VMAT technique emerges as the most suitable treatment technique for reducing out-of-field doses. Additionally, a flattening filter-free beam significantly reduces out-of-field doses due to lower contributions from head scatter.