Homogeneity Index Values Research Articles

Dosimetry study comparing single-isocenter high-definition dynamic radiosurgery with multiple-isocenter cone-based stereotactic radiosurgery in treating multiple brain metastases

PurposeWe sought to compare two radiotherapeutic strategies for treating multiple brain metastases (MBM), assessing delivery efficiency, plan quality, and dosimetry of planning target volume (PTV) and normal tissue. MethodsOur study population included 21 patients treated for MBM, each reliant on high-definition dynamic radiosurgery (Monaco-HDRS) or cone-based stereotactic radiosurgery (SRS) treatment plans. Monaco-HDRS plans called for one isocenter for all targets. In cone-based plans, each target corresponded with one isocenter. To compare these modalities, we assessed: monitor units (MU); new conformity index (nCI); dose gradient index (GI); homogeneity index (HI); PTV minimum/maximum (Dmax/Dmin) and mean (Dmean) doses; maximum doses to lenses, optic nerves, and brainstem; and brain dose volumes at 3, 6, 10, 12, and 22 Gy (V3Gy-V22Gy). ResultsThe Monaco-HDRS treatment plan proved more efficient, displaying lower MU, HI, and nCI values and better dosimetry (Dmax/Dmin and Dmean) for PTV. The cone-based plan yielded a lower GI value and dose volumes at 3 Gy and 22 Gy (V3Gy, V22Gy) for brain. There were no significant differences among other parameters. ConclusionsThe Monaco-HDRS plan improved treatment efficiency, conformity, and homogeneity, although dose fall-off was worse. The cone-based plan reduced normal brain dose volumes at 3 Gy and 22 Gy.

Numerical investigation of in-cylinder gas motion dynamics in a heavy-duty direct injection hydrogen internal combustion engine

Mixture homogenization is one of the most important parameter for hydrogen internal combustion engines (H2ICE) to achieve near-zero NOx emissions and stable combustion, especially when premixed combustion strategy is used. On the other hand, inhomogeneities are inevitable due to the limited duration for mixing. This is more prominent in H2ICEs; those adopts low pressure direct injection (LPDI) system. Optimizing an engine to achieve higher level of homogeneity requires profound understanding of in-cylinder gas motion and mixing dynamics.To establish deeper comprehension of gas motion inside the cylinder, a 13-L LPDI H2ICE was modelled, and effect of different parameters were investigated by a holistic 1D-3D simulation methodology. While boundary conditions of operating point were obtained from the 1D simulations, different swirl numbers (SN), piston shapes and injector cap designs were simulated with 3D-CFD. Simulation results were analyzed based on uniquely defined parameters like homogeneity index (HI) and symmetricity of motion (SOM), as well as standard parameters like turbulence kinetic energy (TKE), and 3D visualizations of equivalence ratio iso-surfaces. Analysis showed that, there is a negative correlation between SN and HI under investigated conditions. Moreover, it was found that piston shapes which are promoting the tumble motion, improved average TKE by 31% and HI by 28% over base piston. This study aims to be a reference for the in-cylinder gas motion design of ultra-lean LPDI H2ICEs, where the target is retrofitting an existing diesel engine and attaining the best HI, SOM and TKE values at rated power conditions.

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.

An investigation of the advantages of the adjustable angle stitch template compared with CT-guided 125I seeds free-hand implantation in the treatment of non-small cell lung carcinoma

Objective: To investigate the advantages of adjustable angle needle path template compared with CT-guided 125I seeds free-hand implantation in the treatment of non-small cell lung carcinoma. Methods: This randomized controlled trial involved the retrospective analysis of the clinical data of 45 patients with non-small cell lung carcinoma who underwent 125I seeds implantation at the Shandong Cancer Hospital, Shaanxi Provincial Tumor Hospital and The Third Affiliated Hospital of Shandong First Medical University from May 2018 to January 2023. Patients were divided into the template (n=21) and free-hand (n=24) groups, according to the modality used. The template group comprised 16 males and 5 females, aged (66±12) years, while the free-hand group comprised 16 males and 8 females, aged (62±8) years. The dose distribution, implant quality, intraoperative computed tomography (CT) scan times, and 125I seed reseeding numbers after implantation were compared between the two groups to evaluate the potential advantages of adjustable angle needle path template-assisted implantation over free-hand 125I implantation. Results: Statistical comparison revealed no significant differences in age (t=1.16, P=0.253), tumor volume [(71±26) vs. (71±22) cm3, t=0.21, P=0.837), or any other baseline characteristics between the template and free-hand groups. Overall, 45 patients successfully completed the operation. In the template group, the mean values of the D90 (dose that was delivered to 90% of the target volume), V100 (the target volume receiving 100% of the prescription dose), coverage index (CI), relative dose homogeneity index (HI), and external volume index (EI) pre-and post-implantation were (131.0±2.1) vs. (131.1±5.5) Gy, 90.0%±0.4% vs. 91.0%±2.8%, 0.83±0.07 vs. 0.82±0.05, 41%±11% vs. 37%± 13%, and 4.3%(2.9%, 14.0%) vs.8.8%(5.2%,14.6%), respectively. None of these parameters showed any significant difference (all P>0.05). In the free-hand group, the mean value of D90 pre- and post-implantation was (131.4±2.9) vs.(128.6±8.6) Gy, showing no significant difference (P>0.05), the mean values of V100, CI, HI, and EI pre-and post-implantation were 90.0%±0.5% vs. 89.0%± 3.0%, 0.84±0.04 vs. 0.71±0.09, 41%±9% vs. 34%±10%, and 7.7% (4.9%,11.0%) vs.24.2% (14.3%, 35.3%), respectively, showing significant differences (all P<0.05). The number of reseeding seeds in the template group was lower than that in the free-hand group [2.0 (0,2.5) vs. 4.0 (2.0, 7.0), Z=-3.36, P=0.001], showing a statistically significant difference. Further, the number of CT scans in the template group was significantly less than that in the free-hand group (3.9±0.5 vs. 4.6±1.2, t=-2.54, P=0.016). The incidences of adverse reactions were 23.8% (5/21) and 33.3% (8/24) (χ2=12.86, P=0.002) in the template and free-hand groups, respectively, indicating a significant difference. Conclusion: Compared with free-hand implantation, use of the adjustable angle needle path template technique can shorten the operation time, reduce the number of scans, reduce the incidence of complications, and improve treatment efficacy to a certain extent.

Analysis of the treatment planning metrics and their correlation with morphology of intracranial lesions in Gamma Knife stereotactic radiosurgery.

Gamma Knife Radiosurgery (GKRS) has established a role in treating various benign brain pathologies. The radiosurgery planning necessitates a proper understanding of radiation dose distribution in relation to the target lesion and surrounding eloquent area. The quality of a radiosurgery plan is determined by various planning parameters. Here, we have reviewed various GKRS planning parameters and analyzed their correlation with the morphology of treated brain lesions. A total of 430 treatment plans (71 meningioma, 133 vestibular schwannoma/VS, 150 arteriovenous malformation/AVM, 76 pituitary adenoma/PA treated with GKRS between December 2013 and May 2023) were analyzed for target coverage (TC), conformity index (CI), homogeneity index (HI), and gradient index (GI). The values of CIPaddick and CILomax for PA were lower and differed significantly from meningioma, VS, and AVM. The value of HI for PA was higher and differed significantly when compared with meningioma, VS, and AVM. The values of HI for AVM were also significantly higher than VS and meningioma. The mean GI was 3.02, 2.92, 3.03, and 2.88 for meningioma, VS, AVM, and PA, respectively. The value of GI for meningioma and AVM was significantly higher when compared with the values for VS and PA. The mean TC was 0.94 for meningioma, 0.96 for VS, 0.95 for AVM, and 0.90 for PA. The value TC of PA was lower and differed significantly when compared with VS, AVM, and meningioma. Lesions with a volume of ≤1 cc had poor planning metrics as the spillage of radiation may be higher. The GKRS planning parameters depend on the size, shape, nature, and location of intracranial lesions. Therefore, each treatment plan needs to be evaluated thoroughly and a long-term follow-up is needed to establish their relation with clinical outcome.

Dosimetric Impact of Voluntary Deep Inspiration Breath Hold (DIBH) in Mediastinal Hodgkin Lymphomas: A Comparative Evaluation of Three Different Intensity Modulated Radiation Therapy (IMRT) Delivery Methods Using Voluntary DIBH and Free Breathing Techniques.

Hodgkin lymphomas are radiosensitive and curable tumors that often involve the mediastinum. However, the application of radiation therapy to the mediastinum is associated with late effects including cardiac and pulmonary toxicities and secondary cancers. The adoption of conformal IMRT and deep inspiration breath- hold (DIBH) can reduce the dose to healthy normal tissues (lungs, heart and breast). We compared the dosimetry of organs at risk (OARs) using different IMRT techniques for two breathing conditions, i.e., deep inspiration breath hold (DIBH) and free breathing. Twenty-three patients with early-stage mediastinal Hodgkin lymphomas were accrued in the prospective study. The patients were given treatment plans which utilized full arc volumetric modulated arc therapy (F-VMAT), Butterfly VMAT (B-VMAT), and fixed field IMRT (FF-IMRT) techniques for both DIBH and free breathing methods, respectively. All the plans were optimized to deliver 95% of the prescription dose which was 25.2 Gy to 95% of the PTV volume. The mean dose and standard error of the mean for each OAR, conformity index (CI), and homogeneity index (HI) for the target using the three planning techniques were calculated and compared using Student's t-test for parametric data and Wilcoxon signed-rank test for non-parametric data. The HI and CI of the target was not compromised using the DIBH technique for mediastinal lymphomas. The mean values of CI and HI for both DIBH and FB were comparable. The mean heart doses were reduced by 2.1 Gy, 2.54 Gy, and 2.38 Gy in DIBH compared to FB for the F-VMAT, B-VMAT, and IMRT techniques, respectively. There was a significant reduction in V5Gy, V10Gy, and V15Gy to the heart (p < 0.005) with DIBH. DIBH reduced the mean dose to the total lung by 1.19 Gy, 1.47 Gy, and 1.3 Gy, respectively. Among the 14 female patients, there was a reduction in the mean right breast dose with DIBH compared to FB (4.47 Gy vs. 3.63 Gy, p = 0.004). DIBH results in lower heart, lung, and breast doses than free breathing in mediastinal Hodgkin Lymphoma. Among the different IMRT techniques, FF-IMRT, B-VMAT, and F-VMAT showed similar PTV coverage, with similar conformity and homogeneity indices. However, the time taken for FF-IMRT was much longer than for the F-VMAT and B-VMAT techniques for both breathing methods. B-VMAT and F-VMAT emerged as the optimal planning techniques able to achieve the best target coverage and lower doses to the OARs, with less time required to deliver the prescribed dose.

Evaluation of intracranial stereotactic treatment plans: a comparison study of CyberKnife and TrueBeam systems

Abstract Background: Stereotactic radiotherapy (SRT) for patients with intracranial tumours are delivered using a dedicated platform or a conventional linear accelerator with a flattening filter-free beam. Materials and methods: This study compares treatment plans with intracranial tumours. A total of 29 patients were treated on CyberKnife and planned using the Accuray Precision. The same structure sets ws then exported to Varian Eclipse, and plans were made using a 6 MV FFF beam. Both plans were compared for parameters of target coverage, homogeneity index (HI), new conformity index (nCI), gradient index, selectivity index (SI), volumetric and OAR doses. Results: The treatment plans made for CyberKnife exhibit better results in terms of nCI (1·168 ± 0·08 versus 1·173 ± 0·077), SI (0·885 ± 0·05 versus 0·877 ± 0·05) and GI (3·64 ± 0·5 versus 4·45 ± 1·25), while HI values are better for TrueBeam. For OAR doses, in 65·5% and 72% of treatment plans, brainstem and optic pathways received lower doses on CyberKnife, respectively. In terms of dose spillage, Truebeam plans are better for very low doses (V5%), while for V10%, V20% and V50% CyberKnife plans are better. Conclusion: CyberKnife is a better modality for the delivery of SRS/SRT to intracranial tumours except for dose homogeneity where TrueBeam offered better results.

New method to optimize protection of the organs at risk allows to regain coverage and homogeneity in the Planning Target Volume

The construction of auxiliary structures within the Planning Target Volume (PTV) is proposed as a method to recover coverage and homogeneity, and to optimize the protection of the organs at risk (OARs) in radiotherapy treatment plans. To this purpose, it was performed the Volumetric Modulated Arc Therapy (VMAT) treatment planning of the “mock prostate” test. Three plans were optimized in the EclipseTM treatment planning system. In plan 1 (P1), it was defined an initial objective function only for the PTV. Then, the dose received by the OARs was restricted, guaranteeing the PTV level of coverage. Plan 2 (P2) used the same dose-volume objectives for the PTV as in P1, but more restrictive dose constraints were set for the OARs. From the dose distribution obtained in P2, it was built auxiliary subvolumes contained within the PTV to regain coverage and homogeneity in plan 3 (P3). To this end, it was compared the coverage (D95%), the Homogeneity Index (HI) and dose-volume histogram for the PTV, and OARs dose sparing for rectum and Bladder. P1 and P3 resulted in similar PTV coverage and HI values, however, the OARs received a lower dose in P3. Despite in P2 it was achieved a higher OARs protection, the PTV coverage and HI were considerably reduced. In this sense P3 allowed to reach the best balance between coverage, HI, and OARs protection. As a consequence of these results, it has been shown that the introduction of auxiliary structures as target subvolumes constitute a powerful and easy to implement tool in the treatment planning optimization process and can be employed in any pathology that requires VMAT.

Analisis Distribusi Dosis Berkas Foton pada Kanker Nasofaring dengan Teknik Intensity Modulated Radiation Therapy (IMRT) menggunakan Pesawat Linear Accelerator di Sub Instalasi Radioterapi RSUP Prof. Dr. I.G.N.G. Ngoerah

Analysis for the distribution of photon beam doses in nasopharyngeal cancer has been carried out with the Intensity Modulated Radiation Therapy (IMRT) technique at the Sub-Installation of RSUP Prof. Dr. I.G.N.G. Ngoerah. Calculations were carried out by analyzing the values of the Homogeneity Index (HI) and Conformity Index (CI) as well as radiation dose in Organs a t Risk (OAR). Data from 20 nasopharyngeal cancer patients were used, and a 6 MV energy photon beam with a total dose of 7000 cGy was used, using seven beams of irradiation direction. The data used are radiation doses of 2%, 50%, and 98%, target volume and 95%, and doses at OAR. These data are obtained from the Dose Volume Histogram (DVH) curve in the Treatment Planning System (TPS) process. The results obtained were the average dose distribution on cancer targets in the form of HI and CI values for 20 patients, namely the average HI value of 0.1231±0.0244, while the average CI value was 0.9856±0.022 which, when compared to ICRU report 83 of 2010 HI and CI values were still within the allowable standard limits. The average dose distribution in OAR for 20 patients was the mean spinal cord (4683.9±216.47) cGy, the average right eye (3909.7±605.45) cGy, the average left eye (3683.885±659.89) cGy, the average right optic nerve (4149.01±1099.68) cGy, the average left optic nerve (4174.355±1219.96) cGy, the average right lens (746.29±149.85) cGy, and the average left lens (753.03±144.32) cGy, all average values obtained by OAR are still within the allowable limits. Keywords: nasopharyngeal cancer, 6 MV, IMRT, homogeneity index, conformity index, organ at risk

Hyperarc Vmat and Vmat planning for stereotactic radiosurgery in multiple brain metastases

Automated treatment planning systems are available for linear accelerator (LINAC) based single and more isocenter multitarget stereotactic radiosurgery (SRS) of brain metastases. HyperArc Volumetric Modulated Arc Therapy (HA-VMAT) is a relatively new isocentric Volumetric Modulated Arc Therapy (VMAT) technique developed specifically for non-coplanar, multileaf collimator (MLC)-based stereotactic radiotherapy with automatic treatment optimization and dose delivery. The HA-VMAT planning approach was developed to accommodate dosing procedures for brain metastases stereotactic radiosurgery. In this study, it was aimed to compare the dosimetric parameters of treatment plans created with single and multi-isocenter retrospectively VMAT and HA-VMAT techniques in patients with lung cancer and multiple brain metastases (4–7) who received single and multi-fraction stereotactic radiosurgery (SRS). Using VMAT and HA-VMAT techniques, two separate treatment plans were created for each case, and tumor target coverage (homogeneity index (HI); conformity index (CI); gradient index (GI)) and organ at risk (OAR) were evaluated dosimetrically. Physical properties and Monitor unit (MU) values of both treatment approaches were compared. Treatment plans were created for study purposes and patients were not treated with these plans. In the study, HI (p = 0.000), CI (p = 0.000) and GI (p = 0.002) values calculated with the HA-VMAT technique are superior to the VMAT technique. Medium-low dose spreads (V4Gy-V16Gy) were significantly reduced in HA-VMAT plans compared to plans with VMAT. HA-VMAT plans result in lower MU than VMAT plans. HA-VMAT planning has significantly less radiation necrosis indicator (V8Gy-V16Gy) compared to VMAT plans. However, there are few studies investigating the ability of the HA-VMAT technique to create high-quality treatment plans for extracranial lesions. HA-VMAT may constitute one of the new options for SRS dose delivery for both single target and multiple targets.

Comparison of Hybrid Techniques with 3D-Conformal Radiotherapy in Patients with Lung Cancer

Purpose: It’s postulated that hybrid techniques (HT) with lower weighting of IMRT/VMAT component would improve lung dose-volume parameters despite some disadvantage in PTV homogeneity index (HI) and target coverage (TC). &#x0D; Material and Methods: Conformal plans were prepared using 6-10-15 MV-X photon energies while IMRT/VMAT plans of HTs were prepared using 6MV-X. Four HTs were developed having two different ratios (10% and 50%) of IMRT/VMAT component (h-IMRT1, h-IMRT2 and h-VMAT1, h-VMAT2, respectively). HTs were compared with 3D-CRT in terms of HI and TC for PTV, and total lung (TL) and contralateral lung (CL) V5Gy, V10Gy, V20Gy and mean lung dose (MLD). &#x0D; Results: All HTs were advantageous for HI and TC, while disadvantageous for TL and CL-V5Gy. H-IMRT2 provided better TC than h-IMRT1, and so did h-VMAT2 compared to h-VMAT1. Lower weighting of IMRT/VMAT decreased TL and CL-V5Gy in HTs. In addition, h-IMRT1 decreased TL and CL-MLD and CL-V20Gy compared to h-IMRT2, while h-VMAT2 decreased TL-V20Gy and CL-MLD compared to h-VMAT2. &#x0D; Conclusion: In the RT of lung tumors close to vertebra, it may be appropriate to suggest a ratio of IMRT/VMAT component about 10% in order to decrease the low and intermediate dose-wash lung volume, if HI and TC values are acceptable.

Relationship between the Patients’ Setup Errors with Dosimetric and Radiobiologic Parameters in Whole Breast Radiotherapy

Purpose: This study aimed to investigate the effect of the patients’ setup errors on dosimetric and radiobiologic parameters for left-sided Whole-Breast Irradiation (WBI) in three different radiotherapy techniques, including Intensity-Modulated Radiation Therapy (IMRT), Field-In-Field (FIF), and Conventional Wedge (CW).&#x0D; Materials and Methods: Computed Tomography (CT) images of 10 female patients with early-stage left-sided breast cancer were used to simulate different radiotherapy techniques (IMRT, FIF, and CW). The dosimetric parameters; Conformity Index (CI), Homogeneity Index (HI), the dose received by at least 95% (D95%) of Planning Tumor Volume (PTV), the volume of lung and heart that respectively received at least 20% (V20%) and 40% (V40%) of the prescribed dose, as well as, the radiobiologic parameters, including Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were assessed for setup errors in patients. The setup errors were assessed by shifting the isocenters and gantry angles of the treatment plans.&#x0D; Results: The D95% of the PTV for an isocenter misplacement plan in the posterior direction decreased by 66.99 (IMRT), 71.86 (CW), and 68.25% (FIF). The TCP of the PTV was reduced by 26.66, 39.16, and 36.97% for IMRT, CW, and FIF techniques, respectively. Increasing gantry angle by a ±10 degree caused a 43%, 41%, and 41% decrease in the D95% of IMRT, FIF, and CW techniques, respectively. The TCP values decreased about 18% in all three techniques with a ±10 degree gantry angle shift; however, the NTCP values of the heart and lungs increased for all three methods. The CI and HI values had significantly more changes with increasing setup errors in the IMRT than in the two techniques.&#x0D; Conclusion: The radiobiologic parameters in IMRT were less sensitive to setup errors compared to FIF and CW techniques. The radiobiological parameters can help estimate the setup errors along with physical parameters during breast radiotherapy.

The Impact of Grid Size and Statistical Uncertainty on the Accuracy of VMAT Plans Based on Dosimetric Parameters for Head and Neck Cancers

Aim Grid size and Statistical Uncertainty (SU) settings have an impact on the efficiency and accuracy of the treatment plans. Hence, it is very important, to find an optimum combination of the two-dose calculation parameters for efficient treatment planning. This study aims to study the impact of Grid Size and SU on Head and Neck cancer plans which were planned using the Volumetric-Modulated Arc Therapy (VMAT) technique. Materials and Methods 15 patients were selected for this retrospective study who had undergone radiation therapy at KMC, Manipal for various Head and Neck cancers. VMAT plans were generated for each case in Monaco 5.11 Treatment Planning System (TPS) using the Monte Carlo algorithm. For each patient, nine plans were generated in which the Grid size values were taken as 2 mm, 3 mm, and 5 mm and for each Grid size, SU settings were varied as 1%, 2%, and 5%. The plans were analysed and evaluated using outcome measures such as the Homogeneity Index (HI) and the Conformity Index (CI). Results The plans were evaluated as per the ICRU guidelines. In all the plans, PTV coverage achieved was above 95% with the maximum coverage (97.009) achieved with the 3 mm/1% combination. Overall, the effect of varying Grid Size and SU was insignificant in the plans generated, but there were few variations in the dose calculation parameters. For 2 mm/1%, 2 mm/2%, 2 mm/5%, 3 mm/1%, 3 mm/2%, 3 mm/5%, 5 mm/1%, 5 mm/2%, 5 mm/5%, the mean values of HI were 1.073, 1.078,1.078, 1.075, 1.0805, 1.0805, 1.068, 1.079, 1.089, and the mean values of CI were 0.968, 0.967, 0.967, 0.968, 0.958, 0.96, 0.954, 0.946, 0.948, respectively. Among all the combinations, the results for 5 mm/1% yielded more homogeneity, whereas 2 mm/1% and 3 mm/1% combinations resulted in better conformity. The 3 mm/1% combination gave maximum target coverage and quite fewer Monitor Units (MU) as well. Conclusion 3 mm Grid Size and 1% SU is suggested for the Head and Neck carcinomas planned using the VMAT technique.

Analysis of Radiation Dose Distribution and Organs at Risk in Breast Cancer Using Intensity Modulated Radiation Therapy Technique on A Linear Accelerator at RSUP Prof. Dr. I.G.N.G. Ngoerah

The aim of the study was to analyze the radiation dose distribution in breast cancer cases using IMRT techniques on a LINAC equipment, specifically examining the Conformity Index (CI), Homogeneity Index (HI), and radiation dose distribution to the OAR, including lungs and heart on a 6 MV photon beam energy LINAC equipment at the Radiotherapy Sub-Installation of Prof. Dr. I.G.N.G Ngoerah Hospital. Analysis of the Conformity Index (CI), Homogeneity Index (HI) and radiation dose distribution to the OAR, namely the lungs and heart in cases of right and left breast cancer using statistical data on the Dose Volume Histogram (DHV) graphic obtained from patient calculations using the Treatment Planning System (TPS) Monaco. The CI value for the right and left breast cancer cases is 0.9819 and 0.9942 respectively with a nonparametric statistical test result of 0.141 that greater than 0.05 which means it is not significant. Meanwhile, the HI values for the right and left breast cancer cases are 0.1211 and 0.1410 respectively with the multivariate statistical test result of 0.159 that greater than 0.05 which means it is not significant. For the dose distribution values in the lungs close and far from the cancer, the average values of 32.24% and 440.03 cGy for right breast cancer and 33.04% and 500.55 cGy for left breast cancer were obtained, respectively, with a multivariate statistical test value for both of them of 0.115 that greater than 0.05 in the lungs close to the cancer and 0.124≥0.05 in the lungs far from the cancer, which means insignificant. As for the heart, a value of 3.13% was obtained for right breast cancer and 8.02% for left breast cancer with a nonparametric statistical test result of 0.000 that less than 0.05 which means significant. This can be caused by the position of the heart in cases of left breast cancer closer to the target or cancer than cases of left breast cancer.

Dose Planning Evaluation of Intensity-Modulated Proton Therapy (IMPT) Technique Based on In-House Dynamic Thorax Phantom

One of the drawbacks of the Intensity Modulated Radiation Therapy (IMRT) technique is that the absorbed dose in healthy tissue is relatively high. Proton beam has characteristics that can compensate for these drawbacks. The Bragg peak characteristic of a proton beam allows the administration of high radiation doses to the target organ only. Non-Small Cell Lung Cancer (NSCLC) cases are located in the vicinity of many vital organs, so radiation doses that exceed a certain limit will have a significant impact on these organs. Proton is a heavy particle that exhibits interaction patterns with tissue heterogeneity that differ from that of photon. This study aims to determine the distribution of proton beam planning doses in the NSCLC cases with the Intensity Modulated Proton Therapy (IMPT) technique and compare its effectiveness with the IMRT technique. Treatment planning was done by using TPS Eclipse on the water phantom and on the in-house thorax dynamic phantom. The water phantom planning parameters used are one field at 0° and three fields at 45°, 135°, and 225°. In this study, a single, sum, and multiple field techniques on the in-house thorax dynamic phantom were used. The evaluation was performed by calculating Conformity Index (CI), Homogeneity Index (HI), and Gradient Index (GI) parameters for each treatment planning. As a result, a bit of difference in the CI the HI values are shown between IMPT and IMRT planning. The GI values of IMPT planning are in the range between 4.15-4.53, while the GI value of IMRT is 7.89. The histogram results of the planar dose distribution show that the IMPT treatment planning provides fewer off-target organ doses than the IMRT planning. Evaluation was also carried out on the IMPT treatment planning of target organs in five areas of interest and four OAR positions. The evaluation results were then compared with the IMRT measurement data. As a result, the value of the point doses at the target organ did not differ significantly. However, the absorbed dose with the IMPT technique at four OAR positions is nearly zero, which had a large difference compared to the IMRT technique.

Individualized estimates of intensity-modulated radiotherapy plans after breast conservation surgery for left-sided breast cancer

ObjectivesThe purpose of this study was to explore the influence of individual patient factors, such as volume of the planning target volume (PTV) (VPTV), cardiothoracic ratio (CTR), central lung distance (CLD), and maximal heart distance (MHD), on the design of treatment plans in terms of target dose coverage, integral dose, and dose to organs at risk (OAR) in early breast cancer.MethodsNinety-six patients were selected for this study. Radiation doses of 50 Gy and a simultaneous dose of 60 Gy in 25 fractions were administered to the whole breast and tumor bed, respectively. The intensity modulation plan (IMRT) of each patient uses both physical parameters and an equivalent uniform dose (EUD) to optimize the target function. Univariate and multivariate linear regression were used to analyze the relationship between predictive impact factors and OAR percent dose volume, conformity index (CI), and homogeneity index (HI).ResultsThe average CI and HI values of the left breast cancer plan were 0.595 ± 0.071 (0.3–0.72) and 1.095 ± 0.023 (1.06–1.18), respectively. The CTR (B = 0.21, P = 0.045), VPTV (B = 0.63, P = 0.000), volume of the lung (Vlung) (B = − 0.29, P = 0.005), and MHD (B = 0.22, P = 0.041) were identified as factors influencing the CI index of the left breast cancer intensity modulation plan. VPTV (B = 1.087, P = 0.022) was identified as the influencing factor of the HI index of the left breast cancer intensity modulation plan. volume of the heart (Vheart) (B = − 0.43, P = 0.001) and CLD (B = 0.28, P = 0.008) were influencing factors of the volume of lung (Vlung20) of the lung. The prediction formulas for left-sided breast cancer are noted as follows: CI = 0.459 + 0.19CTR-0.16CLD, Vlung10 = 35.5–0.02Vheart; and Vlung20 = 21.48 + 2.8CLD-0.018Vheart.ConclusionsCTR, CLD, and MHD can predict the rationality of the parameters of the left breast cancer IMRT. The calculation formula generated based on this information can help the physicist choose the optimal radiation field setting method and improve the quality of the treatment plan.

Multiple Brain Metastases Radiosurgery with CyberKnife Device: Dosimetric Comparison between Fixed/Iris and Multileaf Collimator Plans.

In our institution, stereotactic radiosurgery of multiple brain metastases is performed with the CyberKnife® (CK) device, using fixed/Iris collimators. In this study, nineteen fixed/Iris plans were recalculated with the multileaf collimator (MLC), to assess if it is possible to produce plans with comparable dosimetric overall quality. For consistent comparisons, MLC plans were re-optimized and re-normalized in order to achieve the same minimum dose for the total planning target volume (PTVtot). Conformation number (CN), homogeneity index (HI) and dose gradient index (DGI) metrics were evaluated. The dose to the brain was evaluated as the volume receiving 12 Gy (V12) and as the integral dose (ID). The normal tissue complication probability (NTCP) for brain radionecrosis was calculated as a function of V12. The reoptimized plans were reviewed by the radiation oncologist and were found clinically acceptable according to the The American Association of Physicists in Medicine (AAPM) Task Group-101 protocol. However, fixed/Iris plans provided significantly higher CN (+8.6%), HI (+2.2%), and DGI (+44.0%) values, and significantly lower ID values (-35.9%). For PTVtot less than the median value of 2.58cc, fixed/Iris plans provided significantly lower NTCP values. On the other side, MLC plans provided significantly lower treatment times (-18.4%), number of monitor units (-33.3%), beams (-46.0%) and nodes (-21.3%). CK-MLC plans for the stereotactic treatment of brain multi metastases could provide an important advantage in terms of treatment duration. However, to contain the increased risk for brain radionecrosis, it could be useful to calculate MLC plans only for patients with large PTVtot.

Stereotactic radiosurgery for limited brain metastasis using three different techniques: helical tomotherapy, volumetric modulated arc therapy, and cone-based LINAC radiosurgery.

Specific radiation delivered to tumors by stereotactic radiosurgery (SRS) has become widely used in the treatment of brain metastasis. This study aimed to compare radiation therapy planning and its parameters from SRS using three different modalities: helical tomotherapy (HT), volumetric modulated arc therapy (VMAT), and cone-based linac radiosurgery (Cone-based). Each contouring dataset of patents who experienced one to four brain metastasis received SRS in our center was re-planned to create radiation therapy planning in all three treatment systems (HT, VMAT, and Cone-based). The parameters of conformity index (CI), homogeneity index (HI), CI50, and gradient index (CGI) were analyzed to compare the effects of the three techniques. Decision score analysis was used to evaluate the performance on dosimetric and organs-at-risk parameters among the different techniques by applying the Cone-based technique as a benchmark. A total of 21 patients with 39 lesions were included in this study. The results from the decision score analysis demonstrated statistically identical CI, CI50, and CGI values between Cone-based and VMAT for single lesions. For multiple lesions, VMAT also provided better CI when compared to Cone-based technique while HT exhibited the poorest dosimetric parameters. Moreover, VMAT exhibited the lowest BrainV5Gy value and displayed the shortest beam-on time calculation. We have conducted a comprehensive comparison of SRS planning approaches. The Cone-based technique revealed the highest HI value, while VMAT provided the best estimated beam-on time value. HT displayed a feasible SRS modality for single lesions, but not for multiple lesions.

Radioterapi Linac Energi 6 MV Terhadap Kanker Serviks Pada Organ Rektum Menggunakan Teknik 3DCRT dan IMRT Di RSUP Sanglah Denpasar

Cervical cancer radiotherapy on the Linac aircraft uses a 6 MV energy photon beam with 3 Dimension Conformal Radiotherapy (3DCRT) and Intensity Modulation Radiation Therapy (IMRT) techniques. Radiotherapy planning on the 3DCRT and IMRT techniques is then compared by analyzing the dose distribution or planning target volume (PTV) coverage through the Conformity Index (CI) and Homogeneity Index (HI) and Organ At Risk (OAR) where the risk organ that is considered is the rectum. In this study, 30 data on cervical cancer patients were used at the Radiotherapy Installation at Sanglah Hospital Denpasar with a plan using a box system on the 3DCRT technique and the IMRT technique with rotation angles of 00, 900, 1800, and 2700 and a radiation dose of 5000 cGy. Comparison of these two techniques is done by analyzing the Dose Volume Histogram (DVH) curve on PTV coverage on the Treatment Planning System (TPS) computer. The results of this study indicate that the average CI value in the 3DCRT technique is 1.017542 while the IMRT technique is 1.019668, with the Mann Whitney test (Asymp.Sig = 0.492). Likewise, the HI value, where the 3DCRT technique averaged 0.089494 while the IMRT technique was 0.093126 with Mann Whitney test (Asymp.Sig = 0.487), both CI and HI values were not significant. While the percentage of the average dose of the rectum on both the 3DCRT and IMRT irradiation techniques are 96% and 87%, respectively. Cervical cancer radiotherapy using IMRT technique can minimize the absorbed dose in OAR (rectum).

Does CyberKnife improve dose distribution versus IMRT and VMAT on a linear accelerator in low-risk prostate cancer?

BackgroundHypofractionated stereotactic body radiation therapy (SBRT) for prostate cancer (PCa) can be delivered with the robot-assisted CyberKnife (CK) system or on a linear accelerator using dynamic intensity-modulated radiotherapy (IMRT) or volumetric arc radiotherapy (VMAT). This retrospective study was performed to determine whether CK offers better dose distribution than IMRT and/or VMAT.Materials and methodsTreatment plans for three techniques were prepared using the same treatment parameters (36.35 Gy, 7.25 Gy/fr). We evaluated target coverage, conformity index (CI), homogeneity index (HI), gamma index (GI), and organs at risk (OAR) constraints.ResultsThe mean planning target volume (PTV) dose for CK (39.58 Gy) was significantly greater than VMAT or IMRT (both 36.25 Gy). However, CK resulted in a wider dose range (31.48 to 45.89 Gy) vs. VMAT and IMRT (34.6–38.76 Gy). The mean dose to the rectum (V36Gy, mm3) was significantly lower (p < 0.001) in the CK plans (219.78 vs. 519.59 and 422.62, respectively). The mean bladder dose (V37Gy, mm3) was significantly greater for CK (3256 vs. 1090.75 for VMAT and 4.5 for IMRT (p < 0.001). CK yielded significantly better CI (1.07 vs. 1.17 and 1.25 for VMAT and IMRT, respectively; p < 0.01) and HI values (1.27 vs. 1.07 and 1.04; p < 0.01). GI values for the δd = 3mm, δ% = 3% criteria were 99.86 (VMAT), 99.07 (IMRT) and 99.99 (CK). For δd = 2mm, δ% = 2%, the corresponding values were 98.3, 93.35, and 97.12, respectively.ConclusionsFor most variables, CK was superior to both VMAT and IMRT. However, dynamic IMRT techniques, especially VMAT, do not differ significantly from CK plans and are therefore acceptable alternatives to CyberKnife.