Varian Eclipse Research Articles

Automatic couch position calculation using eclipse scripting for external beam radiotherapy.

PurposeThe treatment couch position of a patient in external beam radiation therapy (EBRT) is usually acquired during initial treatment setup. This procedure has shown potential failure modes leading to near misses and adverse events in radiation treatment. This study aims to develop a method to automatically determine the couch position before setting up a patient for initial treatment.MethodsThe Qfix couch‐tops (kVue and DoseMax) have embedded reference marks (BBs) indicating its index levels and couch centerline. With the ESAPI, a C# script was programmed to automatically find the couch‐top and embedded BBs in the planning CT and derive the treatment couch position according to treatment isocenter of a plan. Couch positions of EBRT plans with the kVue couch‐top and SBRT plans using the DoseMax were calculated using the script. The calculation was evaluated by comparing calculated positions with couch coordinates captured during the initial treatment setup after image guidance. The calculations were further compared with daily treatment couch positions post image‐guided adjustment for each treatment fraction.ResultsFor plans using the kVue couch‐top for various treatment sites, the median (5–95 percentiles) differences between calculated and captured couch positions were 0.1 (−0.2 – 0.9), 0.5 (−1.1–2.0), 0.10 (−1.3–1.3) cm in the vertical, longitudinal, and lateral direction respectively. For the DoseMax couch‐top, the median differences were 0.1 (−0.2–0.7), 0.2 (−0.3–1.1), and 0.2 (−0.7–0.9) cm in respective direction. The calculated positions were within 1 and 2 cm from the mean fraction positions for 95% patients on DoseMax and kVue couch‐top respectively.ConclusionsA method that automatically and accurately calculates treatment couch position from simulation CT was implemented in Varian Eclipse for Qfix couch‐tops. This technique increases the efficiency of patient setup and enhances patient safety by reducing the risks of positioning errors.

Outcomes of Squamous Cell Carcinoma Anal Canal treated with IMRT-VMAT-based Concurrent Chemoradiation: a Single Institutional Experience.

Chemoradiation is the standard of care in locally advanced carcinoma of the anal canal. However, the irregular surface and elective inguinal treatment poses a challenge for radiation planning and treatment with associated significant toxicity. In this retrospective study, we analysed the outcome of patients treated with intensity-modulated radiation therapy (IMRT) at our centre from 2012 to 2019. Records of patients treated with IMRT at our centre from 2012 to 2019 were reviewed. Patients with non-squamous histology and previous irradiation were excluded. Thus, 25 patients were found suitable for the study. Twenty-five patients with squamous cell carcinoma of the anal canal were treated at our centre from 2012 to 2019 using IMRT based chemoradiation. RTOG guidelines were followed for contouring and Varian Eclipse version 13(Palo Alto, California) was used for planning. Clinical response could be assessed in 20 patients and dosimetric data of all patients was available for review. The target volumes coverage goals as per ICRU 83 were achieved in all patients. The organ at risk constraints for bladder and femoral heads as per LATE-QUANTEC were achieved in most patients; however, the constraints for the rectum, testis and bowel bag were not achieved in the majority of the patients. The median duration of treatment break was 7days. Mitomycin C and 5-FU or capecitabine were given concurrently with radiation. Eighteen patients (72%) received 2cycles of chemotherapy, three (12%) received 1cycle of chemotherapy while 4(16%) patients did not receive any chemotherapy. Median follow-up was 7.5months. At median follow-up, 15(75%) patients were disease-free and asymptomatic, 2(10%) had residual disease and 3(15%) had progressive disease. Toxicity was assessed using CTCAE Version 5.0. Grade III skin toxicity was reported in 9(36%) of the patients and Grade III gastrointestinal toxicity was reported in 1 (4%) of the patients, no other grades III-IV toxicity was reported. Overall, the disease control was comparable to previous 3D-CRT studies but with much less toxicity. IMRT-based chemoradiation should be the standard of care in locally advanced carcinoma of the anal canal.

Comparison of gamma analysis with using different dosimetric systems for pre-treatment verification of intensity-modulated radiation therapy

The evaluation of the agreement between calculated and measured dose plays an essential role in the quality assurance procedures of intensity-modulated radiation therapy (IMRT). This study aimed to compare gamma analysis using portal dosimetry (PD), Epiqa, and 2D array detector for dose verification of radiotherapy treatment plans. Five field step-and-shoot IMRT plan was performed for 20 prostate IMRT patients using the dual-energy DHX linear accelerator (Varian Medical System, Palo Alto, Calif., USA). The treatment plans were created using Varian DHX Eclipse treatment planning system (TPS) version 15.1. All measurements were performed by aS500 EPID integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (1%/1 mm, 2%/2 mm, 3%/2 mm, and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann–Whitney U test and Kruskal–Wallis test, and p-value of p < 0.01 was considered to be significant. The average pass rate for 20 IMRT plans was above 95 for all devices with 2%/2 mm, 3%/2 mm, and 3%/3 mm. The mean and standard deviation pass rates (γ ≤ 1) were found to be 99.80 ± 0.19, 99.35 ± 0.34, and 97.53 ± 0.71 for PD, Epiqa, and 2D array, respectively. All IMRT plans passed 2%/2 mm, 3%/2 mm, and 3%/3 mm gamma by more than 95 of three dosimetric systems. They are all in good agreement with the literature. All three devices are acceptable for quality control of IMRT. Due to the simplicity and fast evaluation process, PD can be preferred for quality control.

Technical note: factors affecting dose distribution in the overlap region of two-segment total body irradiation by helical tomotherapy

ObjectiveTo assess the effects of various treatment planning parameters to identify the optimal gap distance for precise two-segment total body irradiation (TBI) using helical tomotherapy (HT) with fixed jaw mode.Methods and materialsData of a treatment plan for 8 acute leukemia patients (height range: 109–130 cm) were analyzed. All patients underwent total-body computed tomography (CT) with 5-mm slice thickness. A lead wire, placed at 10 cm above the patella, was used to mark the boundary between the two segments. Target volumes and organs at risk were delineated using a Varian Eclipse 10.0 physician’s workstation. Different distances between the lead wire and the boundary of the two targets were used. CT images were transferred to the HT workstation to design the treatment plans, by adjusting parameters, including the field width (FW; 2.5 cm, and 5 cm), pitch (0.287 and 0.430), modulation factor (1.8). The plans were superimposed to analyze the dose distributions in the overlap region when varying target gap distances, FWs, pitches to determine the optimal combinations.ResultsThe pitch did not affect the dose distribution in the overlap region. The dose distribution in the overlap region was mostly homogeneous when the target gap distance was equal to the FW. Increased FW diminished the effect of the target gap distance on the heterogeneous index of the overlap region.ConclusionsIn two-segment TBI treatments by HT with Helix mode, a gap distance equal to the FW may achieve optimal dose distribution in the overlap region.

Novel method of radiotherapy planning to improve the dose homogeneity at the junction region for breast cancer

AbstractObjectivesThis article introduces a new method to design the radiation therapy planning after radical surgery for breast cancer in order to provide a better homogeneity of the dose distribution in the junction region between the supra clavicular fossa and chest wall.MethodsA total of 15 women who received supra clavicular and chest wall irradiation therapy for breast cancer after radical surgery at Cancer Hospital Chinese Academy of Medical Sciences, Shenzhen Center, Shenzhen, China, between 1 October 2018 and 30 November 2019 were included. The prescription dose was 50 Gy/25 fractions. We designed a new plan on the basis of the original plan for each patient on an Varian Eclipse 13.6 planning system, which added two subfields to each tangential opposing field to change the dose distribution at the junction region. Statistical analysis of the target dose distribution – homogeneity index, conformal index, and irradiation doses to the ipsilateral lung, contralateral lung, heart, left‐side breast, and spinal cord – was carried out for the two groups and the differences were compared.ResultsWhen comparing the two plans, the planning target volume minimum dose (P = 0.04) and planning target volume of the junction region, which was defined as the target in the junction region minimum dose (P = 0.04), homogeneity index (P = 0.02), and conformal index (P = 0.01) for the new method plan were better than those for the original plan. However, there was no statistically significant difference in all dosimetric parameters of the organs at risk (P > 0.05) between the new and traditional method plans .ConclusionBoth plans by new and traditional methods for breast cancer after radical surgery can meet the clinical requirements. The prescription dose coverage, conformal index, and homogeneity index for the target in the new method plan were better than those in the traditional method plan. The new method plan provided a better homogeneity of the dose distribution in the junction region, but had no obvious effect on the dose distribution of the organs at risk. As a result, this new planning method can be used in clinical settings.

Monte Carlo calculations of radiotherapy dose in "homogeneous" anatomy.

Given the substantial literature on the use of Monte Carlo (MC) simulations to verify treatment planning system (TPS) calculations of radiotherapy dose in heterogeneous regions, such as head and neck and lung, this study investigated the potential value of running MC simulations of radiotherapy treatments of nominally homogeneous pelvic anatomy. A pre-existing in-house MC job submission and analysis system, built around BEAMnrc and DOSXYZnrc, was used to evaluate the dosimetric accuracy of a sample of 12 pelvic volumetric arc therapy (VMAT) treatments, planned using the Varian Eclipse TPS, where dose was calculated with both the Analytical Anisotropic Algorithm (AAA) and the Acuros (AXB) algorithm. In-house TADA (Treatment And Dose Assessor) software was used to evaluate treatment plan complexity, in terms of the small aperture score (SAS), modulation index (MI) and a novel exposed leaf score (ELS/ELA). Results showed that the TPS generally achieved closer agreement with the MC dose distribution when treatments were planned for smaller (single-organ) targets rather than larger targets that included nodes or metastases. Analysis of these MC results with reference to the complexity metrics indicated that while AXB was useful for reducing dosimetric uncertainties associated with density heterogeneity, the residual TPS dose calculation uncertainties resulted from treatment plan complexity and TPS model simplicity. The results of this study demonstrate the value of using MC methods to recalculate and check the dose calculations provided by commercial radiotherapy TPSs, even when the treated anatomy is assumed to be comparatively homogeneous, such as in the pelvic region.

Full automation of spinal stereotactic radiosurgery and stereotactic body radiation therapy treatment planning using Varian Eclipse scripting.

The purpose of this feasibility study is to develop a fully automated procedure capable of generating treatment plans with multiple fractionation schemes to improve speed, robustness, and standardization of plan quality. A fully automated script was implemented for spinal stereotactic radiosurgery/stereotactic body radiation therapy (SRS/SBRT) plan generation using Eclipse v15.6 API. The script interface allows multiple dose/fractionation plan requests, planning target volume (PTV) expansions, as well as information regarding distance/overlap between spinal cord and targets to drive decision‐making. For each requested plan, the script creates the course, plans, field arrangements, and automatically optimizes and calculates dose. The script was retrospectively applied to ten computed tomography (CT) scans of previous cervical, thoracic, and lumbar spine SBRT patients. Three plans were generated for each patient — simultaneous integrated boost (SIB) 1800/1600 cGy to gross tumor volume (GTV)/PTV in one fraction; SIB 2700/2100 cGy to GTV/PTV in three fractions; and 3000 cGy to PTV in five fractions. Plan complexity and deliverability patient‐specific quality assurance (QA) was performed using ArcCHECK with an Exradin A16 chamber inserted. Dose objectives were met for all organs at risk (OARs) for each treatment plan. Median target coverage was GTV V100% = 87.3%, clinical target volume (CTV) V100% = 95.7% and PTV V100% = 88.0% for single fraction plans; GTV V100% = 95.6, CTV V100% = 99.6% and PTV V100% = 97.2% for three fraction plans; and GTV V100% = 99.6%, CTV V100% = 99.1% and PTV V100% = 97.2% for five fraction plans. All plans (n = 30) passed patient‐specific QA (>90%) at 2%/2 mm global gamma. A16 chamber dose measured at isocenter agreed with planned dose within 3% for all cases. Automatic planning for spine SRS/SBRT through scripting increases efficiency, standardizes plan quality and approach, and provides a tool for target coverage comparison of different fractionation schemes without the need for additional resources.

Dose to Lungs and Kidneys during Total Body Irradiation: Are We Delivering the Expected Dose?

Total Body irradiation (TBI)-based conditioning is key component for hemopoietic stem cell transplantation. TBI dose calculation is traditionally based on point-dose calculations based on estimates of body separation at different levels with the umbilicus as a reference point, an approach followed as standard protocol at most institutions. This homogenous dose calculation technique does not take into account tissue heterogeneity. Limited data exists for TPS-based TBI planning systems especially in the setting of lung and kidney partial transmission blocks, which is a void in our understanding of TBI dose delivery and is explored in this study. Primary objective of the study was to assess differences between radiation treatment planning software (TPS) estimated doses with heterogeneity correction and point calculation estimated doses when delivering TBI. Secondary objective was to validate accurate treatment delivery through optically stimulated luminescent dosimetry (OSLD) measurements at umbilicus obtained at first TBI fraction. Our retrospective study involved virtual dosimetric simulation of total body CT scan datasets in patients treated with a prescribed dose of 12 Gy in six fractions delivered twice daily over three days. Patients received TBI using a translating couch AP/PA technique with lung and kidney shielding (transmission blocks to achieve < 7 Gy point dose). The Varian Eclipse TPS was used to calculate the 3D dose distribution to the lungs, kidneys, and heart. Paired t-test with a significance value of 0.05 was used to compare means. 24 patients (Male-11, female-13; Age range: 23-60 years; Diagnosis: AML-7, ALL-8, HL-1, NHL-6, MDS-2) with total body CT scan datasets available were included in the analysis. Contrary to expected dose with shielding (< 7 Gy), the TPS simulated mean dose to lungs was 11.08 Gy (SD: 0.61, p= 9.66E-22) and to kidneys was 8.98 Gy (SD: 0.62, p: 2.31E-14). TPS mean dose to the unshielded heart was 11.38 Gy. Compared to the point dose calculation of 2 Gy at the midpoint of the umbilicus, the mean OSLD dose measured during the first fraction of treatment was 2.08 Gy (SD: 0.058, p: 2.07E-9). Using TPS of total body CT scan data, we demonstrated much higher than expected dose to lungs and kidneys than expected from point-based calculations. This study has triggered a comprehensive outcomes analysis of institutional data for assessing toxicities in patients receiving TBI 12 Gy-based conditioning prior to SCT with the goal to revisit the 7-Gy dose limit to the lungs and kidneys. Institutions are encouraged to pursue similar analyses of their TBI systems to refine dose to critical organs. (Supported by the Radiation Oncology Summer Research Fellowship and the Office of Student Research at the University of Maryland School of Medicine).

Impact of computed tomography (CT) reconstruction kernels on radiotherapy dose calculation.

PurposeTo quantitatively evaluate the effect of computed tomography (CT) reconstruction kernels on various dose calculation algorithms with heterogeneity correction.MethodsThe gammex electron density (ED) Phantom was scanned with the Siemens PET/CT Biograph20 mCT and reconstructed with twelve different kernel options. Hounsfield unit (HU) vs electron density (ED) curves were generated to compare absolute differences. Scans were repeated under head and pelvis protocols and reconstructed per H40s (head) and B40s (pelvis) kernels. In addition, raw data from a full‐body patient scan were also reconstructed using the four B kernels. Per reconstruction, photon (3D and VMAT), electron (18 and 20 MeV) and proton (single field) treatment plans were generated using Varian Eclipse dose calculation algorithms. Photon and electron plans were also simulated to pass through cortical bone vs liver plugs of the phantom for kernel comparison. Treatment field monitor units (MU) and isodose volumes were compared across all scenarios.ResultsThe twelve kernels resulted in minor differences in HU, except at the extreme ends of the density curve with a maximum absolute difference of 55.2 HU. The head and pelvis scans of the phantom resulted in absolute HU differences of up to 49.1 HU for cortical bone and 45.1 HU for lung 300, which is a relative difference of 4.1% and 6.2%, respectively. MU comparisons across photon and proton calculation algorithms for the patient and phantom scans were within 1–2 MU, with a maximum difference of 5.4 MU found for the 20 MeV electron plan. The 20MeV electron plan also displayed maximum differences in isodose volumes of 20.4 cc for V90%.ConclusionClinically insignificant differences were found among the various kernel generated plans for photon and proton plans calculated on patient and phantom scan data. However, differences in isodose volumes found for higher energy electron plans amongst the kernels may have clinical implications for prescribing dose to an isodose level.

Haematotoxicity in IMRT/VMAT curatively treated anal cancer.

Curative chemoradiotherapy of squamous cell carcinoma achieves long-term complete remissions in most patients and minimizing treatment toxicity becomes crucial issue. The aim of the retrospective analysis was to determine an acceptable dose to the bone marrow for radiotherapy planning not leading to increased haematological toxicity. In the period 2013-2019, 40 patients with squamous cell carcinoma were curatively treated at the Department of Oncology of the University Hospital Motol using intensity modulated radiotherapy (IMRT) /volumetric modulated arc radiotherapy (VMAT) technique. Women make up 90% of the group, the average age at the time of dia-gnosis was 65 years (47-81). Chemotherapy mitomycin C and 5-fluorouracil was given to 68% of patients. The bone marrow was contoured in the Varian Eclipse planning system, version 15.6. Acute hematotoxicity (G3, 4, 5 according to Common Terminology Criteria for Adverse Events - CTCAE) was significantly associated with the concomitant chemoradiotherapy (P = 0.002) and the average dose to the bone marrow 27 Gy (P = 0.011). Late haematological toxicity was mild (maximum grade 1), asymptomatic, and no dependence of late haematotoxicity on any risk factor (age, gender, WHO performance status, bone marrow dose, CHT, BMI, smoking, stage) was proved. The overall survival at 5 years was 100% in stage I, 83% in stage II, 61% in stage III and 0% in stage IV. Local control at 5 years is 100% in stage I, 92% in stage II, 87% in stage III and 0% in stage IV. Local recurrence developed in 5% of radically treated patients. Distant metastases occurred in 8% of radically treated patients. Local recurrences or metastases occurred only during the first 2 years after the treatment. Radical chemoradiotherapy in the treatment of squamous cell anal carcinoma is highly effective. IMRT/VMAT enabled to apply a sufficiently effective dose to the tumor and elective areas and reduced not only acute skin, GI and GU toxicity, but also acute haematological toxicity in cases with the dose Dmean to bone marrow lower than 27 Gy. The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical, papers.

Assessment of Internal and External Surrogates for Lung Stereotactic Body Radiation Therapy

Purpose: To evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marker motion in correlation with lung tumor motion, to determine potential surrogate for respiratory gating radiation therapy (RGRT) depending on tumor localization, upper lobe (UL) vs lower lobe (LL).Methods: This study included 58 patients (34 male and 24 female) with small lung cancer (≤ 5cm), who underwent Stereotactic Body Radiation Therapy (SBRT). All patients were scanned and contoured in all ten phases (Varian Eclipse 13.7) after four-dimensional computed tomography simulation (4D-CT). The motion of internal markers and external markers were analyzed and correlated with tumor motion. The Pearson correlation coefficient (PCC) was used to evaluate the correlation between internal and external marker motion with tumor motion. Results: The median (range) values of tumor motion were 3.2 (0.6-11.0) vs 8.6 (4.0-24.0) mm in the UL vs LL. The median (range) values of organs motion and PCC comparing UL vs LL were: 2.0 (0.3-9.1) vs 6.0 (2.8-13.9) mm and 0.46 (0.30-0.95) vs 0.79 (0.50-0.94) to the lung; 11.9 (2.5-16.3) vs 12.5 (5.0-22.5) mm and 0.68 (0.11-0.93) vs 0.89 (0.30-0.99) to the diaphragm; and 3.9 (2.5-6.3) vs 7.6 (4.5-8.6) mm and 0.49 (0.20-0.70) vs 0.59 (0.36-0.83) to the heart. The external marker motion and correlation coefficient for UL and LL were 2.5 (0.9-7.4) vs 2.3 (1.0-5.9) mm and 0.54 (0.09-0.96) vs 0.73 (0.27-0.94).Conclusion: Lung and diaphragm motion correlate better with tumor motion than the external marker. Diaphragm motion can be an excellent indicator for treatment based on RGRT.

Automated Monte-Carlo re-calculation of proton therapy plans using Geant4/Gate: implementation and comparison to plan-specific quality assurance measurements.

Software re-calculation of proton pencil beam scanning plans provides a method of verifying treatment planning system (TPS) dose calculations prior to patient treatment. This study describes the implementation of AutoMC, a Geant4 v10.3.3/Gate v8.1 (Gate-RTion v1.0)-based Monte-Carlo (MC) system for automated plan re-calculation, and presents verification results for 153 patients (730 fields) planned within year one of the proton service at The Christie NHS Foundation Trust. A MC beam model for a Varian ProBeam delivery system with four range-shifter options (none, 2 cm, 3 cm, 5 cm) was derived from beam commissioning data and implemented in AutoMC. MC and TPS (Varian Eclipse v13.7) calculations of 730 fields in solid-water were compared to physical plan-specific quality assurance (PSQA) measurements acquired using a PTW Octavius 1500XDR array and PTW 31021 Semiflex 3D ion chamber. TPS and MC showed good agreement with array measurements, evaluated using γ analyses at 3%, 3 mm with a 10% lower dose threshold:>94% of fields calculated by the TPS and >99% of fields calculated by MC had γ ≤ 1 for>95% of measurement points within the plane. TPS and MC also showed good agreement with chamber measurements of absolute dose, with systematic differences of <1.5% for all range-shifter options. Reliable independent verification of the TPS dose calculation is a valuable complement to physical PSQA and may facilitate reduction of the physical PSQA workload alongside a thorough delivery system quality assurance programme. A Gate/Geant4-based MC system is thoroughly validated against an extensive physical PSQA dataset for 730 clinical fields, showing that clinical implementation of MC for PSQA is feasible.

Dosimetric verification of clinical radiotherapy treatment planning system

Background/Aim. In the past two decades, we have witnessed the emergence of new radiation therapy techniques, radiotherapy treatment planning system (TPS) with calculating algorithms for the dosage calculation in a patient, units for multislice computed tomography (CT) and image-guided treatment delivery. The aim of the study was investigating the significant difference in dosimetric calculation of radiotherapy TPS in relation to the values obtained by measuring on the linear accelerator (LINAC), and the accuracy of dosimetric calculation between calculating algorithms Analytical Anisotropic Algorithm (AAA) and Acuros XB in various tissues and photon beam energies. Methods. For End-to-End test we used the hetero-geneous phantom CIRS Thorax002LFC, which anatomically represents human torso with a set of inserts known as relative electron densities (RED) for obtaining a CT calibration curve, comparable to the ?reference? CIRS 062M phantom. For the AAA and Acuros XB algorithms and for 6 MV and 16 MV photon beams in the TPS Varian Eclipse 13.6, four 3D conformal (3DCRT), and one intensity modulated (IMRT) and volumetric modulated arc (VMAT) radiotherapy plans were made. Measurements of the absolute dose in Thorax phantom, by PTW-Semiflex ionization chamber, were carried out on three Varian-DHX LINACs. Results. The difference between ?reference? and measured CT conversion curves in the bone area was 3%. For 476 phantom measurements, the difference between measured and TPS calculated dose of 3?6%, was found in 30 (6.3%) cases. According to regression analysis, the standardized Beta coefficient for relative errors, 6 MV vs. 16 MV, was 0.337 (33.7%, p &lt; 0.001). Mean relative errors for AAA and Acuros XB, using Mann-Whitney test, for bones were 1.56% and 2.64%, respectively (p = 0.004). Conclusion. End-to-End test on Thorax002LFC phantom proved the accuracy of TPS dose calculation in relation to the one delivered to a patient by LINAC. There was a significant difference for photon energies relative errors (higher values are obtained for 16 MV vs. 6 MV). A statistically significant minor relative error in AAA vs. Acuros XB was found for the bone.

Effects of gas-filled temporary breast tissue expanders on radiation dose from modulated rotational photon beams

Gas-filled temporary tissue expanders (TTEs), implanted to assist in post mastectomy breast reconstructions, are expected to produce increased dosimetric uncertainty in breast radiotherapy treatments, due to their containing both a substantial metallic component and a comparatively large volume of gas. This study therefore builds on previous investigations of the dosimetric effects of gas-filled TTEs in static photon and electron beams, by examining the effects of these implants on dose distributions from common modulated rotational treatment techniques; volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT). Radiochromic film measurements were used to evaluate the accuracy of VMAT and HT dose calculations, for a humanoid phantom augmented with a sample Aeroform CO2-filled TTE (AirXpanders Inc, San Jose, USA) as well as purpose-designed and 3D printed “breast tissue.” Results showed that the TomoTherapy Hi-Art VoLO convolution-superposition algorithm (Accuray Inc, Sunnyvale, USA) produced comparatively accurate calculations of treatment dose within this complex phantom, including immediately anterior and posterior to the TTE. The Varian Eclipse Acuros (AXB) algorithm generally showed better agreement with the film measurement than the Varian Eclipse AAA algorithm (Varian Medical Systems, Palo Alto, USA), although the film measurements showed regions of 5% to 10% disagreement with both AAA and AXB in the dosimetrically-challenging region on the anterior side of the implant. Although the Aeroform CO2-filled TTE has substantial and obvious effects on the downstream dose from a static photon beam, the results of this study showed how inverse-planning of modulated rotational radiotherapy treatments can produce modulated fluence distributions that compensate for the dramatic density heterogeneities in the implant. Despite some disagreements with the planned dose, all film measurements showed that the use of inverse-planned modulated rotational photon beams resulted in comparatively homogeneous coverage of the radiotherapy target, in the complex patient-like phantom with a gas-filled TTE. Due to the importance of matching each planned fluence distribution to the density distribution within each TTE, careful use of available 3D imaging techniques is advisable, when modulated rotational radiotherapy treatments are delivered to patients with gas-filled TTEs.

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

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. 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. 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. The proposed methodology using the VRb tool offers superior plan evaluation for multiphase sequential radiotherapy treatment plans over the existing methods. PTV, CTV and OAR priority based display modes in VRb tool offers better understanding of radiobiological evaluation of sequential radiotherapy treatment plans.

Trajectory-based VMAT for cranial targets with delivery at shortened SAD.

Trajectory-based volumetric modulated arc therapy (tr-VMAT) treatment plans enable the option for noncoplanar delivery yielding steeper dose gradients and increased sparing of critical structures compared to conventional treatment plans. The addition of translational couch motion to shorten the effective source-to-axis distance (SAD) may result in improved delivery precision and an increased effective dose rate. In this work, tr-VMAT treatment plans using a noncoplanar "baseball stitch" trajectory were implemented, applied to patients presented with cranial targets, and compared to the clinical treatment plans. A treatment planning workflow was implemented: (a) beamlet doses were calculated for control points defined along a baseball stitch trajectory using a collapsed-cone convolution-superposition algorithm; (b) VMAT treatment plans were optimized using the column generation approach; (c) a final dose distribution was calculated in Varian Eclipse using the analytical anisotropic algorithm by importing the optimized treatment plan parameters. Tr-VMAT plans were optimized for ten patients presented with cranial targets at both standard and shortened SAD, and compared to the clinical treatment plans through isodose distributions, dose-volume histograms, and dosimetric indices. The control point specifications of the optimized tr-VMAT plans were used to estimate the delivery time. The optimized tr-VMAT plans with both shortened and standard SAD delivery yielded a comparable plan quality to the clinical treatment plans. A statistically significant benefit was observed for dose gradient index and monitor unit efficiency for shortened SAD tr-VMAT plans, while improved target volume conformity was observed for the clinical treatment plan (P≤0.05). A clear dosimetric benefit was not demonstrated between tr-VMAT delivery at shortened SAD compared to standard SAD, but shortened SAD delivery yielded a fraction size-dependent reduction in the estimated delivery time. The implementation of "baseball stitch" tr-VMAT treatment plans to patients presented with cranial targets demonstrated comparable plan quality to clinical treatment plans. The delivery at shortened SAD produced a fraction size-dependent decrease in estimated delivery time.

A fast robust optimizer for intensity modulated proton therapy using GPU.

Robust optimization has been shown to be effective for stabilizing treatment planning in intensity modulated proton therapy (IMPT), but existing algorithms for the optimization process is time‐consuming. This paper describes a fast robust optimization tool that takes advantage of the GPU parallel computing technologies. The new robust optimization model is based on nine boundary dose distributions — two for ±range uncertainties, six for ±set‐up uncertainties along anteroposterior (A‐P), lateral (R‐L) and superior‐inferior (S‐I) directions, and one for nominal situation. The nine boundary influence matrices were calculated using an in‐house finite size pencil beam dose engine, while the conjugate gradient method was applied to minimize the objective function. The proton dose calculation algorithm and the conjugate gradient method were tuned for heterogeneous platforms involving the CPU host and GPU device. Three clinical cases — one head and neck cancer case, one lung cancer case, and one prostate cancer case — were investigated to demonstrate the clinical feasibility of the proposed robust optimizer. Compared with results from Varian Eclipse (version 13.3), the proposed method is found to be conducive to robust treatment planning that is less sensitive to range and setup uncertainties. The three tested cases show that targets can achieve high dose uniformity while organs at risks (OARs) are in better protection against setup and range errors. Based on the CPU + GPU heterogeneous platform, the execution times of the head and neck cancer case and the prostate cancer case are much less than half of Eclipse, while the run time of the lung cancer case is similar to that of Eclipse. The fast robust optimizer developed in this study can improve the reliability of traditional proton treatment planning in a much faster speed, thus making it possible for clinical utility.

Standardized flattening filter free volumetric modulated arc therapy plans based on anteroposterior width for total body irradiation.

In this work, the feasibility of using flattening filter free (FFF) beams in volumetric modulated arc therapy (VMAT) total body irradiation (TBI) treatment planning to decrease protracted beam‐on times for these treatments was investigated. In addition, a methodology was developed to generate standardized VMAT TBI treatment plans based on patient physical dimensions to eliminate plan optimization time. A planning study cohort of 47 TBI patients previously treated with optimized VMAT ARC 6 MV beams was retrospectively examined. These patients were sorted into six categories depending on height and anteroposterior (AP) width at the umbilicus. Using Varian Eclipse, clinical 40 cm × 10 cm open field arcs were substituted with 6 MV FFF. Mid‐plane lateral dose profiles in conjunction with relative arc output factors (RAOF) yielded how far a given multileaf collimator (MLC) leaf must move in order to achieve a mid‐plane 100% isodose for a specific control point. Linear interpolation gave the dynamic MLC aperture for the entire arc for each patient AP width category, which was subsequently applied through Python scripting. All FFF VMAT TBI plans were then evaluated by two radiation oncologists and deemed clinically acceptable. The FFF and clinical VMAT TBI plans had similar Body–5 mm D98% distributions, but overall the FFF plans had statistically significantly increased or broader Body–5 mm D2% and mean lung dose distributions. These differences are not considered clinically significant. Median beam‐on times for the FFF and clinical VMAT TBI plans were 11.07 and 18.06 min, respectively, and planning time for the FFF VMAT TBI plans was reduced by 34.1 min. In conclusion, use of FFF beams in VMAT TBI treatment planning resulted in dose homogeneity similar to our current VMAT TBI technique. Clinical dosimetric criteria were achieved for a majority of patients while planning and calculated beam‐on times were reduced, offering the possibility of improved patient experience.

Optimization of autogenerated chest-wall radiation treatment plans developed for postmastectomy breast cancer patients in underserved clinics

Over the past decade, several strides have been made to improve the management of breast cancer in developing countries; however, there are still obstacles present. In the area of radiation therapy, these hurdles include limited access to radiotherapy treatment and scarcity of oncology specialists. In an effort to reduce inequities in cancer care while improving patient outcomes, our research is focused on developing automated postmastectomy radiation therapy (PMRT) plans for breast cancer patients in these underserved communities that can be further improved upon through treatment planning system (TPS) specific optimization guidelines. The automated planning tool utilized algorithms integrated with Varian's Eclipse TPS. The tool created PMRT plans that used monoisocentric tangents and supraclavicular (SCV) fields with a mix of high and low energy photon beams along with field-in-field (FIF) segments. The completed autogenerated PMRT plans were imported into Phillip's Pinnacle 9.10 and Varian's Eclipse 13.6 TPSs to be further improved through manual optimization; the time required to complete this step was measured and assessed. A senior dosimetrist, physicist, and physician evaluated the optimized plans for clinical acceptability. Guidelines were developed for the planning systems that can be implemented by personnel with either limited experience in radiation treatment planning or those with limited time to produce treatment plans. The autogenerated plans in conjunction with our guidelines have shown to significantly reduce the time required to produce a clinically acceptable PMRT plan from approximately 120 ± 60 minutes to just 13 ± 11 (Pinnacle) and 12 ± 7 (Eclipse) minutes, reducing the total uninterrupted treatment planning time by an average of 108 ± 51 minutes. The results from this research indicate that the autogenerated PMRT plans along with the optimization guidelines are a viable option to provide quality and clinically acceptable PMRT plans that are more efficient and consistent for postmastectomy breast cancer patients in severely underserved communities.

A Method to Correct Cone Beam CT (CBCT) Images Using Planning CT for Derivation of Plan of the Day in STEREOTACTIC Body Radiotherapy (SBRT)

A robust method for voxel by voxel enhancement of Cone-beam CT (CBCT) images using a priori knowledge from the planning Computed Tomography (pCT) scan has been developed and used to evaluate the dosimetric accuracy of pCT based CBCT correction method for SBRT dose verification in lung metastasis. This is a retrospective study under which SBRT is carried out in 10 patients presented with lung metastasis. pCT images of patients were acquired and treatment planning was carried out on Varian Eclipse (V11) for 30 Gy in 5 fractions. Daily imaging using CBCT has been done for each patient with an On-Board Imaging system. CBCT is corrected using Matlab function considering CT as fixed and CBCT as moving, the images are registered. Planning target volume (PTV), lung, heart and spine were recontoured on uncorrected CBCT and corrected CBCT separately and the calculated plan on CT is recalculated on both the CBCTs. The dose distribution between the pCT and both the CBCT images were compared. A paired sample test was performed to test the variations. The distribution of pixel intensity of corrected CBCT is closer to the pCT than the uncorrected CBCT. The maximum percentage difference between the corrected CBCT and pCT is 1% in PTV evaluation, which is 3.5% between uncorrected CBCT and pCT. The method increases the accuracy of CBCT density values and enabling the use of CBCT images for dose calculation in radiotherapy.