Irregular Surface Compensator Research Articles

Experience of the Hybrid technique for breast cancer planning in an oncology care center in Lima-Peru

ObjectiveTo investigate, describe and evaluate the dosimetric parameters of the hybrid technique as a combination of the 3D Irregular Surface Compensator (3D-ISC) technique and modulated volumetric arc therapy (VMAT) for breast cancer planning. MethodsThe study involved planning a patient with left breast cancer. Planning was carried out with 3D-ISC, VMAT and Hybrid techniques. The 3 techniques were compared with respect to the target volume (PTV), coverage, gradient and protection of organs at risk (OARs). The Eclipse version 13.6 planning system was used and the prescription of the dose obeyed the hypofractionated scheme of 40.05Gy in 15 sessions (267 cGy per fraction) followed by a 13.35Gy boost in 5 sessions. ResultsThe tangential field technique was the one with the lowest dose values delivered to healthy organs. However, with respect to the gradient, the VMAT technique was better. The Hybrid technique was the balance between the 3D-ISC and VMAT technique because after the evaluation of dosimetric parameters for both the OARs and the PTV coverage, values were found within the limits allowed according to the RTOG. ConclusionThe hybrid 3D-ISC and VMAT technique can be considered as a viable option for breast planning, achieving better control in OARs without losing priority over PTV coverage in addition to obtaining a good plan quality.

Dosimetric evaluation of irregular surface compensator and intensity-modulated radiotherapy in breast radiotherapy.

BackgroundThis dosimetric study aims to evaluate the dosimetric advantage of the irregular surface compensator (ISC) compared with the intensity-modulated radiotherapy (IMRT).Materials and methodsTen patients with whole breast irradiation were planned with the ISC and IMRT techniques. Six different beam directions were selected for IMRT and ISC plans. The treatment plans were evaluated with respect to planning target coverage, dose homogeneity index (DHI) and organs at risk (OARs) sparing. Monitor units (MUs) and the delivery time were analysed for treatment efficiency.ResultsThe ISC technique provides a better coverage of the PTV and statistically significantly better homogeneity of the dose distribution. For the ipsilateral lung and heart, ISC and IMRT techniques deliver almost the same dose in all plans. However, MU counts and delivery time were significantly lower with the IMRT technique (p < 0.05).ConclusionFor breast radiotherapy, when the ISC method was compared to the IMRT method, ISC provided better dose distribution for the target.

Abstract P4-12-10: Clinical implementation of the machine learning-based automated treatment planning tool for whole breast radiotherapy

Abstract Objectives: The machine learning (ML)-based automated treatment planning tool has been developed and evaluated for whole breast radiotherapy. This study implemented the tool in clinic and compared plan quality and planning efficiency with the manual treatment process for whole breast radiotherapy using irregular surface compensator technique. Methods: This study involved two phases. The 1st phase was to evaluate and the 2nd phase was to implement in the clinic. In the 1st phase, thirty whole breast or chest wall cases were planned by using the irregular surface compensator technique with fluence maps manually and iteratively edited to achieve uniform dose distribution to the target by planners. Patients were treated with these manual plans after physician’s approval. The evaluation phase thus compared our in-house ML-based automated treatment planning tool implemented in Eclipse Scripting Application Programming Interface (ESAPI) to these manual plans. The ML-based planning tool generated the fluence maps with the same beam parameters such as beam energy, gantry angle, collimator angle, and aperture shape as manual plans. Breast or chest wall clinical target volume (CTV) coverage based on the percentage CTV volume receiving 95% of the prescribed dose (V95%) and high-dose volume based on V105% were compared to evaluate the plan quality as well as the planning efficiency. Two-tailed Wilcoxon Signed-Rank test was performed to test the null hypothesis that the two planning schemes yield equivalent plan quality. In the 2nd phase, the planners used the automated planning tool for fourteen plans (twelve patients) followed by manual fluence modification as needed. Physicians reviewed and approved the plans, and patients were treated. Results: For the 1st phase, the mean planning time was 110.2 min with standard deviation (SD) of 62.8 min for the manual planning with the range from 25 to 270 min, and 6.4 min with SD of 2.1 min for the automated planning with the range from 4 to 12 min (p&amp;lt;0.01). CTV mean V95% was 96.7% (SD: 5.0%) for the manual planning and 96.7% (SD: 4.8%) for the automated planning (p=0.89). CTV mean V105% was 21.6% (SD: 29.8%) for the manual planning and 20.4% (SD: 30.5%) for the automated planning (p=0.22). Differences in doses to heart and lungs were negligible between the paired plans as the two planning schemes used the same beam parameters. For the 2nd phase, the mean planning time was 16.4 min (SD: 9.1 min) and the mean time for additional manual editing was 12.7 min (SD: 12.5 min). The mean total treatment planning time was 29.1 min (SD: 14.8 min).). CTV mean V95% was 97.2% (SD: 4.2%) and mean V105% was 8.2 % (SD: 3.6%). The manual post modifications were added by the planners with intention to improve the target coverage or to reduce high doses, yet, the difference between the plans without and without the manual post modification was negligible. Conclusion: The ML-based automated treatment planning tool through Varian ESAPI has been successfully implemented for clinical use going through two phases of study. Abiding to the same plan quality as manual process, the automated tool significantly reduced the planning time as the ML-based tool automate the iterative fluence editing process. Citation Format: Sua Yoo, Yang Sheng, Rachel Blitzblau, Suzanne Catalano, Jay Morrison, Leigh O'Neill, Fangfang Yin, Q. Jackie Wu. Clinical implementation of the machine learning-based automated treatment planning tool for whole breast radiotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-10.

Implementation of Machine Learning-Based Treatment Planning Tool for Whole Breast Radiotherapy Using Irregular Surface Compensator Technique

To implement the machine learning (ML)-based treatment planning tool and compare plan quality and planning efficiency with the manual treatment process for whole breast radiotherapy using irregular surface compensator technique. Thirty whole breast or chest wall cases were planned by using the irregular surface compensator technique with fluence maps manually and iteratively edited to achieve uniform dose distribution to the target. Patients were treated with these manual plans after physician’s approval. For each case, an in-house ML-based automated treatment planning tool was implemented in a programming interface and generated the fluence maps with the same beam parameters such as beam energy, gantry angle, collimator angle, and aperture shape as manual plans.An analytical algorithm software with 0.25cm grid size was used in dose calculation for all plans. Breast or chest wall clinical target volume (CTV) coverage based on the percentage CTV volume receiving 95% of the prescribed dose (V95%) and high-dose volume based on V105% were compared to evaluate the plan quality as well as the planning efficiency. Two-tailed Wilcoxon Signed-Rank test was performed to test the null hypothesis that the two planning schemes yield equivalent plan quality. The mean planning time was 110.2 min with standard deviation (SD) of 62.8 min for the manual planning with the range from 25 to 270 min, and 6.4 min with SD of 2.1 min for the ML-based planning with the range from 4 to 12 min (p<0.01). CTV mean V95% was 96.7% (SD: 5.0%) for the manual planning and 96.7% (SD: 4.8%) for the ML-based planning (p=0.89). CTV mean V105% was 21.6% (SD: 29.8%) for the manual planning and 20.4% (SD: 30.5%) for the ML-based planning (p=0.22). Differences in doses to heart and lungs were negligible between the paired plans as the two planning schemes used the same beam parameters. This study successfully implemented the ML-based automated treatment planning tool through scripting software. Abiding to the same plan quality as manual process, the automated tool significantly reduced the planning time as the ML-based tool automate the iterative fluence editing process. This technique demonstrated promising potential to significantly improve efficiency of the treatment planning for whole breast or chest wall radiotherapy.

Dosimetric Comparison of Irregular Surface Compensator and Field-in-Field for Whole Breast Radiotherapy.

Purpose:The purpose of the present study was to evaluate the dosimetric benefits of the irregular surface compensator (ISC) technique for whole breast radiotherapy compared with the field-in-field (FIF) technique.Materials and Methods:Radiotherapy was planned using both techniques in 50 breast cancer patients (25 left sided and 25 right sided). The Eclipse treatment planning system (Varian Medical Systems) was used for dose calculations. For the FIF technique, subfields were added to the main fields to reduce hot and cold regions; for the ISC technique, the fluence editor application was used to extend the optimal fluence. Planning target volume dose, dose homogeneity index (DHI), maximum dose, ipsilateral lung, and heart doses for the left breast irradiation and monitor unit (MU) counts required for treatment were compared between the two techniques.Results:Compared with the FIF technique, the ISC technique significantly decreased DHI values and volumes receiving >105% of the prescription dose, and increased volumes receiving >95% of the dose and MU count (P < 0.01 for all comparisons). For the heart and ipsilateral lung, the FIF technique significantly reduced volumes receiving >5 Gy compared with the ISC technique (P < 0.01); however, volumes receiving >10, 20, and 30 Gy and the values of a mean dose did not differ significantly between the techniques (P > 0.05).Conclusions:The ISC technique is preferred over the FIF technique.

Performance of the irregular surface compensator compared with four-field box and intensity modulated radiation therapy for gynecologic cancer

PurposeA retrospective planning study was undertaken to evaluate the dosimetric advantages of the irregular surface compensator (ISC) technique, a forward planning technique with electronic compensation algorithm available on Varian Eclipse treatment planning system. This was extensively compared to the conventional four-field box (4FB) and intensity modulated radiation therapy using 5 fields (IMRT5F) on gynecologic cancer patients. MethodsTwenty-two patients were enrolled. The prescribed dose was 50.4Gy in 28 fractions to the primary target including pelvic lymph nodes. 4FB treatment plans were generated, then fluence of anterior and posterior fields were modified to generate ISC plans. IMRT5F were inversely optimized with equally spaced five coplanar fields. Dose-volume parameters were evaluated for the comparison of three planning techniques. The MU and delivery time were also estimated. ResultsIn terms of target coverage, the conformity and homogeneity index of ISC (1.67 and 1.03, respectively) were superior to those of 4FB (2.43 and 1.06, respectively) but slightly inferior to those of IMRT5F (1.10 and 1.02, respectively). ISC also illustrated an overall improvement in normal organ saving. Compared to 4FB, the mean dose of the rectum was reduced by about 4.0–5.0Gy with ISC and IMRT5F. The volume receiving large doses was reduced for bladder with statistical significance with ISC and more with IMRT5F relative to 4FB. The mean number of MU per fraction were 200.86 (4FB), 446.09 (ISC) and 895.59 (IMRT5F). ConclusionThe ISC technique has the superior target coverage and healthy tissue sparing in comparison with conventional 4FB and comparable normal organ saving compared to IMRT5F. The ISC can be an available option for gynecologic radiotherapy.

Hodgkin lymphoma (HL) treatment using varian eclipse irregular surface compensator. A dosimetric analysis and clinical results

Introduction A recommended technique for a radiation therapy treatment for HL is a mantle field technique. This technique in most of the cases represents a challenge for the dose calculation not only for the irregularity and size of the field but for the anatomical area to cover; going from the neck to mediastinal region and in some cases up to the axillar regions, thus represents an important problem when the required dose distribution has to be uniform enough to achieve coverage suggested standards, especially for those anatomies with short neck and/or fat chests which leaded to an undesired hot spots on neck and chin mostly and their correspondent side effects. In order to avoid this and improved the treatment, since 2010, mantle techniques are treated with compensators observing improvements in the dose distribution obtained. Purpose To improved quality on mantle technique for HL diminishing side effects. Method Each of this treatment plans were calculated using the Varian Eclipse irregular surface compensator calculation technique and verified using gamma index criteria. Each plan were compared with the blocked field of the same size, shape and energy. Results and conclusions On the dosimetric comparisons we observed a hot spots from 5% to 12% lower than the observed with a conventional technique and an improved hot spot localization according to clinical criteria. Clinically, side effects expected according to experience with blocked fields were diminished on about 70% of the cases on a five years follow-up.

Improvement of dose homogeneity with irregular surface compensator in whole brain radiotherapy

AbstractPurposeThe aim of this study was to evaluate the dosimetric aspects of whole brain radiotherapy (WBRT) using an irregular surface compensator (ISC) in contrast to conventional radiotherapy techniques.MethodsTreatment plans were devised for 20 patients. The Eclipse treatment planning system (Varian Medical Systems) was used for dose calculation. For the ISC, a fluence editor application was used to extend the range of optimal fluence. The treatment plan with the ISC was compared with the conventional technique in terms of doses in the planning target volume (PTV), dose homogeneity index (DHI), three-dimensional (3D) maximum dose, eye and lens doses and monitor unit (MU) counts required for treatment.ResultsCompared with conventional WBRT, the ISC significantly reduced the DHI, 3D maximum dose and volumes receiving 105% of the prescription dose, in addition to reducing both eye and lens doses (p&lt;0·05 for all comparisons). In contrast, MU counts were higher for the ISC technique than for conventional WBRT (828 versus 328, p&lt;0·01).ConclusionThe ISC technique for WBRT considerably improved the dose homogeneity in the PTV. As patients who receive WBRT have improved survival, the long-term side effects of radiotherapy are highly important.

Poster - Thur Eve - 58: Dosimetric validation of electronic compensation for radiotherapy treatment planning

In this study we investigate the deliverability of dosimetric plans generated by the irregular surface compensator (ISCOMP) algorithm for 6 MV photon beams in Eclipse (Varian Medical System, CA). In contrast to physical tissue compensation, the electronic ISCOMP uses MLCs to dynamically modulate the fluence of a photon beam in order to deliver a uniform dose at a user defined plane in tissue. This method can be used to shield critical organs that are located within the treatment portal or improve dose uniformity by tissue compensation in inhomogeneous regions. Three site specific plans and a set of test fields were evaluated using the γ-metric of 3%/ 3 mm on Varian EPID, MapCHECK, and Gafchromic EBT3 film with a clinical tolerance of >95% passing rates. Point dose measurements with an NRCC calibrated ionization chamber were also performed to verify the absolute dose delivered. In all cases the MapCHECK measured plans met the gamma criteria. The mean passing rate for the six EBT3 film field measurements was 96.2%, with only two fields at 93.4 and 94.0% passing rates. The EPID plans passed for fields encompassing the central ∼10 × 10 cm2 region of the detector; however for larger fields and greater off-axis distances discrepancies were observed and attributed to the profile corrections and modeling of backscatter in the portal dose calculation. The magnitude of the average percentage difference for 21 ion chamber point dose measurements and 17 different fields was 1.4 ± 0.9%, and the maximum percentage difference was −3.3%. These measurements qualify the algorithm for routine clinical use subject to the same pre-treatment patient specific QA as IMRT.

EP-1231: Clinical implications of ISC technique for breast radiotherapy with comparison to SweBCG recommendations

Purpose/Objective: To determine the implications of using the Irregular Surface Compensator (ISC) technique in comparison to 3D conformational radiation therapy (3D-CRT) for breast cancer treatment. ISC is an electronic compensation algorithm that modulates the fluence across the radiation fields to compensate for irregularly shaped surfaces, aiming to deliver a homogeneous dose to a compensation plane.

Potential Benefit of Scanned Proton Beam versus Photons as Adjuvant Radiation Therapy in Breast Cancer

Abstract Purpose: To investigate the feasibility of using scanned proton beams as adjuvant radiation therapy for breast cancer. Long-term cardiopulmonary complications may worsen the quality of life and reduce the positive contribution of radiation therapy, which has been known to improve long-term control of locoregional disease as well as the long-term survival for these patients. Materials and Methods: Ten patients with stage I-III cancer (either after mastectomy or lumpectomy, left- or right-sided) were included in the study. The patients were identified from a larger group where dose heterogeneity in the target and/or hotspots in the normal tissues qualified them for irregular surface compensator planning with photons. The patients underwent planning with 2 scanned proton beam planning techniques, single-field uniform dose and intensity-modulated proton therapy, and the results were compared with those from irregular surface compensator. All volumes of interest were delineated and reviewed by experie...

Improvement of dose distribution with irregular surface compensator in whole brain radiotherapy

Improvement of dose distribution with irregular surface compensator in whole brain radiotherapy

Improvement of dose distribution with irregular surface compensator in whole breast radiotherapy.

Aim of this study was to compare the dosimetric aspects of whole breast radiotherapy (WBRT) between an irregular surface compensator (ISC) and a conventional tangential field technique using physical wedges. Treatment plans were produced for 20 patients. The Eclipse treatment planning system (Varian Medical Systems) was used for the dose calculation: For the physical wedge technique, the wedge angle was selected to provide the best dose homogeneity; for the ISC technique, the fluence editor application was used to extend the optimal fluence. These two treatment plans were compared in terms of doses in the planning target volume, the dose homogeneity index, the maximum dose, ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts required for treatment. Compared with the physical wedge technique, the ISC technique significantly reduced the dose homogeneity index, the maximum dose, the volumes received at 105% of the prescription dose, as well as reducing both the ipsilateral lung and heart doses (P < 0.01 for all comparisons). However, the monitor unit counts were not significantly different between the techniques (P > 0.05). Thus, the ISC technique for WBRT enables significantly better dose distribution in the planning target volume.

自作プログラムを用いた照射中のマルチリーフコリメータ動作の評価

Multi-leaf collimators (MLCs) are used to modulate intensity during intensity modulated radiation therapy (IMRT). Evaluation of MLC movement in IMRT is important, since the accuracy of MLC movements affects the dose distribution. This evaluation is conventionally performed using an attached Dynalog File Viewer (DFV). However, due to its being an overall evaluation, it is not possible to discover significant errors. In this study, we developed software that permits easy analysis of MLC movements that can be used to retrospectively evaluate MLC movement during irradiation. We also evaluated the usefulness of our in-house program and confirmed its potential for use in clinical scenarios. We created a program that can read MLC logfiles using Visual Basic 6.0 and visualize the temporal changes and movements of the MLC. To evaluate our in-house program's efficacy in analyzing dynamic MLC-QA (quality assurance), we compared the numerical results yielded by our in-house program and the DFV. The results showed that our in-house program was able to reveal errors below the error root mean square (RMS) values obtained using the DFV. Using irregular surface compensator (ISC) irradiation conditions in a clinical context, we compared our in-house program with the DFV and, using RMS analysis, identified cases that showed excessive error. Our in-house program can also be used to investigate whether unacceptable errors are present, as well as their cause, when using the MLC, as it allows easy real-time observation and evaluation of MLC movements. An additional benefit is that collecting the MLC logfile during actual treatment also allows it to be evaluated retrospectively after continuous MLC operation.

A New Method for Total Body Irradiation (TBI) Treatment Planning Using an “Irregular Surface Compensator”

A New Method for Total Body Irradiation (TBI) Treatment Planning Using an “Irregular Surface Compensator”

The dosimetric impact of respiratory breast movement and daily setup error on tangential whole breast irradiation using conventional wedge, field-in-field and irregular surface compensator techniques

To evaluate the dosimetric impact of respiratory breast motion and daily setup error on whole breast irradiation (WBI) using three irradiation techniques; conventional wedge (CW), field-in-field (FIF) and irregular surface compensator (ISC). WBI was planned for 16 breast cancer patients. The dose indices for evaluated clinical target volume (CTVevl), lung, and body were evaluated. For the anterior-posterior (AP) respiratory motion and setup error of a single fraction, the isocenter was moved according to a sine function, and the dose indices were averaged over one period. Furthermore, the dose indices were weighted according to setup error frequencies that have a normal distribution to model systematic and random setup error for the entire treatment course. In all irradiation techniques, AP movement has a significant impact on dose distribution. CTVevlD95 (the minimum relative dose that covers 95 % volume) and V95 (the relative volume receiving 95 % of the prescribed dose) were observed to significantly decrease from the original ISC plan when simulated for the entire treatment course. In contrast, the D95, V95 and dose homogeneity index did not significantly differ from those of the original plans for FIF and CW. With regard to lung dose, the effect of motion was very similar among all three techniques. The dosimetric impact of AP respiratory breast motion and setup error was largest for the ISC technique, and the second greatest effect was observed with the FIF technique. However, these variations are relatively small.

SU-E-T-436: Feasibility of Using the 'Irregular Surface Compensator' Planning Feature of the Eclipse TPS for Total Body Irradiation (TBI) Treatment Planning.

To investigate the feasibility of using the Irregular Surface Compensator (ISC) planning feature of the Eclipse treatment planning system (TPS) for Total Body Irradiation (TBI). TBI treatments require that the whole body receives within +-10% of the prescribed dose. Different body parts with different thicknesses compared to the umbilicus separation may receive higher or lower doses compared to the prescribed dose. Another challenge is to keep the lung dose below 10Gy to avoid complications. To mitigate this problem, physical compensators and blocks are used during the treatment for different body parts and lungs. This method presents a challenge during the treatment delivery and prolongs the treatment time due to patient setup, in-vivo on-line dosimetric monitoring and the adjustment of the compensators frequently during the treatment. We investigated the use of ISC planning feature of Eclipse TPS which is an electronic compensation method that calculates a fluence map based on the body contour from the CT image. The fluence map is delivered with dynamic MLCs . This TBI treatment technique was tested using a Rando phantom in Head First Supine position with lateral beams at SSD=250cm.The calculated fluence were edited so that the lung received <∼10Gy for 12Gy prescription. A single fraction of 2Gy was delivered and the in-vivo measurements were performed in the neck, lung and the umbilicus by using OSLDs. OSLD measurements and the Eclipse TPS predictionswere 200.4/195.0, 162.2/168.9, and 196.1/208.9 cGy for the neck, lung and the umbilicus respectively. The feasibility of using the 'Irregular Surface Compensator' feature of Eclipse TPS for TBI treatment planning was demonstrated. Good agreement (<6%) between the predicted and measured doses was obtained. The proposed planning and delivery simplifies the compensation and blocking to achieve uniform dose distributions and reduces the treatment time.

Cosmetic Results and Acute Toxicity using Breast Intensity Modulated Radiation Therapy with Simultaneous integrated Boost in Patients with Early-stage Breast Cancer

Materials/Methods: Sixty-two consecutive patients with TNM Staging (Tis, T2 and N0) were treated with the previously reported IMRT + SIB mono - isocenteric setup technique.* The planning target volumes were ipsilateral breast tissue and the boost (CT-defined resection cavity and surgical clips) with a 2-cm margin. A campsite inverse-planned IMRT plan for the boost with an irregular surface compensator planned IMRT for the breast with dynamic multileaf collimators was developed using Eclipse software (Varian Medical Systems). A total of 52.5 Gy in 30 fractions was prescribed to the breast and 60 Gy to the boost concomitantly. Toxicity scoring was based on the NCI CTC version 2.0. Early cosmetic results were evaluated in all patients using criteria established by the Harvard Group. Results: Thirty-eight patients treated had infiltrating breast cancer (IBC); stage I 45%, IIA 16%, while 24 had ductal carcinoma in situ (DCIS). The median breast volume was 855 cc and median cavity volume 198 cc. The average volume of the PTV-breast and PTV-boost receiving more than 95% of the prescribed dose was 97%. The volume of PTV-breast, excluding PTV- boost, receiving a dose higher than 95% of the boost dose was 58 cc (range, 35-109 cc). Median follow-up was 24 months. Acute Grade 2 dermatitis, edema, and hyperpigmentation were seen in 14% and two patients (3%) had Grade 3 dermatitis. Chronic Grade 2 breast edema was reduced by 75% in the patients who underwent IMRT compared to the conventional radiation therapy. Assessment of breast cosmesis at a minimum of twenty-four month follow-up was available in 70% of the cases of which 95% were judged good or excellent, while 5% had fair cosmesis. Conclusion: IMRT + SIB mono - isocenteric setup technique to the breast allows the radiobiologic advantage of higher dose per fraction to the tumor cavity - the site of highest risk of recurrence - while using conventional fractionation for the remaining breast tissue. This technique is extremely well tolerated and easily implemented with relatively low incidence of acute skin toxicity. *Coen et al., Int J Radiat Oncol Biol Phys 2006;66:923.