bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐T‐150: Comparing Normal Tissue Irradiated Volumes for Proton Vs. Photon Treatment Plans On Lung Patients
Authors: Liu A , Mohan R , Liao Z
Published: July 2016

Purpose:

The aim of this work is to compare the “irradiated volume” (IRV) of normal tissues receiving 5, 20, 50, 80 and 90% or higher of the prescription dose with passively scattered proton therapy (PSPT) vs. IMRT of lung cancer patients. The overall goal of this research is to understand the factors affecting outcomes of a randomized PSPT vs. IMRT lung trial.

Methods:

Thirteen lung cancer patients, selected randomly, were analyzed. Each patient had PSPT and IMRT 74 Gy (RBE) plans meeting the same normal tissue constraints generated. IRVs were created for pairs of IMRT and PSPT plans on each patient. The volume of iGTV, (respiratory motion‐incorporated GTV) was subtracted from each IRV to create normal tissue irradiated volume IRVNT. The average of IRVNT DVHs over all patients was also calculated for both modalities and inter‐compared as were the selected dose‐volume indices. Probability (p value) curves were calculated based on the Wilcoxon matched‐paired signed‐rank test to determine the dose regions where the statistically significant differences existed.

Results:

As expected, the average 5, 20 and 50% IRVNT's for PSPT was found to be significantly smaller than for IMRT (p < 0.001, 0.01, and 0.001 respectively). However, the average 90% IRVNT for PSPT was greater than for IMRT (p = 0.003) presumably due to larger penumbra of protons and the long range of protons in lower density media. The 80% IRVNT for PSPT was also larger but not statistically distinguishable (p = .224).

Conclusion:

PSPT modality has smaller irradiated volume at lower doses, but larger volume at high doses. A larger cohort of lung patients will be analyzed in the future and IRVNT of patients treated with PSPT and IMRT will be compared to determine if the irradiated volumes (the magnitude of “dose bath”) correlate with outcomes.
SU‐F‐T‐152: Experimental Validation and Calculation Benchmark for a Commercial Monte Carlo Pencil BeamScanning Proton Therapy Treatment Planning System in Heterogeneous Media
Authors: Lin L , Huang S , Kang M , Ainsley C , Simone C , McDonough J , Solberg T
Published: July 2016

Purpose:

Eclipse AcurosPT 13.7, the first commercial Monte Carlo pencil beam scanning (PBS) proton therapy treatment planning system (TPS), was experimentally validated for an IBA dedicated PBS nozzle in the CIRS 002LFC thoracic phantom.

Methods:

A two‐stage procedure involving the use of TOPAS 1.3 simulations was performed. First, Geant4‐based TOPAS simulations in this phantom were experimentally validated for single and multi‐spot profiles at several depths for 100, 115, 150, 180, 210 and 225 MeV proton beams, using the combination of a Lynx scintillation detector and a MatriXXPT ionization chamber array. Second, benchmark calculations were performed with both AcurosPT and TOPAS in a phantom identical to the CIRS 002LFC, with the exception that the CIRS bone/mediastinum/lung tissues were replaced with similar tissues that are predefined in AcurosPT (a limitation of this system which necessitates the two stage procedure).

Results:

Spot sigmas measured in tissue were in agreement within 0.2 mm of TOPAS simulation for all six energies, while AcurosPT was consistently found to have larger spot sigma (<0.7 mm) than TOPAS. Using absolute dose calibration by MatriXXPT, the agreements between profiles measurements and TOPAS simulation, and calculation benchmarks are over 97% except near the end of range using 2 mm/2% gamma criteria. Overdosing and underdosing were observed at the low and high density side of tissue interfaces, respectively, and these increased with increasing depth and decreasing energy. Near the mediastinum/lung interface, the magnitude can exceed 5 mm/10%. Furthermore, we observed >5% quenching effect in the conversion of Lynx measurements to dose.

Conclusion:

We recommend the use of an ionization chamber array in combination with the scintillation detector to measure absolute dose and relative PBS spot characteristics. We also recommend the use of an independent Monte Carlo calculation benchmark for the commissioning of a commercial TPS.

Partially supported by Varian Medical System under the master agreement between Varian and University of pennsylvania
SU‐F‐T‐169: A Periodic Quality Assurance Program for a Spot‐Scanning Proton Treatment Facility
Authors: Mundy D , Tryggestad E , Beltran C , Furutani K , Gilson G , Ito S , Johnson J , Kruse J , Remmes N , Tasson A , Whitaker T , Herman M
Published: July 2016

Purpose:

To develop daily and monthly quality assurance (QA) programs in support of a new spot‐scanning proton treatment facility using a combination of commercial and custom equipment and software. Emphasis was placed on efficiency and evaluation of key quality parameters.

Methods:

The daily QA program was developed to test output, spot size and position, proton beam energy, and image guidance using the Sun Nuclear Corporation rf‐DQA™3 device and Atlas QA software. The program utilizes standard Atlas linear accelerator tests repurposed for proton measurements and a custom jig for indexing the device to the treatment couch. The monthly QA program was designed to test mechanical performance, image quality, radiation quality, isocenter coincidence, and safety features. Many of these tests are similar to linear accelerator QA counterparts, but many require customized test design and equipment. Coincidence of imaging, laser marker, mechanical, and radiation isocenters, for instance, is verified using a custom film‐based device devised and manufactured at our facility. Proton spot size and position as a function of energy are verified using a custom spot pattern incident on film and analysis software developed in‐house. More details concerning the equipment and software developed for monthly QA are included in the supporting document. Thresholds for daily and monthly tests were established via perturbation analysis, early experience, and/or proton system specifications and associated acceptance test results.

Results:

The periodic QA program described here has been in effect for approximately 9 months and has proven efficient and sensitive to sub‐clinical variations in treatment delivery characteristics.

Conclusion:

Tools and professional guidelines for periodic proton system QA are not as well developed as their photon and electron counterparts. The program described here efficiently evaluates key quality parameters and, while specific to the needs of our facility, could be readily adapted to other proton centers.
SU‐F‐T‐171: Manufacturing Cost Effective Heterogeneous Phantoms for Use in Proton Therapy
Authors: Pruett J , Chen Y , Ahmad S , Johnson D
Published: July 2016

Purpose:

To study the feasibility of 3D printing cost effective heterogeneous phantoms for use in proton therapy treatment planning quality assurance.

Methods:

A desktop 3D printer was utilized to create a series of 2 cm × 2 cm × 4 cm PLA plastic blocks of varying fill materials and hexagonal fill pattern. The blocks were than tested when filled with air, polyurethane foam, paraffin, silicone, and caulk of calcium carbonate – acrylic polymer blend. The blocks were evaluated with a “GE Lightspeed” 16 slice CT scanner and average CT# of the materials’ centers evaluated. Blocks were then placed into a custom aperture fitted to a Mevion Proton system to determine the relative stopping power of each. Scans were performed in water tank with Marcus type parallel plate chamber under a beam with a range of 15 cm and modulation of 2 cm. Shifts in range occurring relative to the 80% distal edge of the open SOBP were evaluated.

Results:

The CT#s of the blocks were plotted against their measured relative stopping power. This curve was compared to that which is in clinical use. While the trend agrees generally, specific differences between the relative stopping powers were as great as 10%.

Conclusion:

We have demonstrated that it is possible to utilize different cost effective materials in the manufacturing of phantoms for use in proton therapy. While different materials may provide better agreement to established calibration curves, a custom curve specific to the materials used may be utilized to accurately predict proton treatment dose distributions.
SU‐F‐T‐174: Patient‐Specific Point Dose Measurement Using Fiber Optic Radiation Sensor Using Cerenkov Radiation for Proton Therapeutic Beam
Authors: Son J , Kim M , Yoon M , Shin D
Published: July 2016

Purpose:

A fiber‐optic radiation sensor using Cerenkov radiation (FOCR) has been widely studied for use as a dosimeter for proton therapeutic beam. We developed the FOCR, and it applied to patient‐specific point dose measurement in order to evaluate the effectiveness of the FOCR system for proton therapy QA.

Methods:

Calibration of FOCR was performed with an ionization chamber whose absolute doses were determined according to the IAEA TRS‐398 protocol. To determine the calibration curve, the FOCR was irradiated perpendicularly to the proton beam at the 13 dose levels steps. We selected five actual patient treatment plans performed at proton therapy center and compared the resulting FOCR measurements with the ionization chamber measurements.

Results:

The Cerenkov light yield of the FOCR increases linearly with as the dose measured using the ionization chamber increases from 0 cGy to 500 cGy. The results indicate that the fitting curve is linear, suggesting that dose measurement based on the light yield of the FOCR is possible. The results of proton radiation dose QA performed using the FOCR for 10 proton fields and five patients are good agreement with an ionization chamber.

Conclusion:

We carried out the patient QA using the FOCR for proton therapeutic beam and evaluated the effectiveness of the FOCR as a proton therapy QA tool. Our results indicate that the FOCR is suitable for use in patient QA of clinical proton beams.
SU‐F‐T‐175: Absorbed Dose Measurement Using Radiophotoluminescent Glass Dosimeter in Therapeutic Proton Beam
Authors: Chang W , Koba Y , Katayose T , Hariu M , Yasui K , Saitoh H
Published: July 2016

Purpose:

To measure the absorbed dose to water Dw in therapeutic proton beam with radiophotoluminescent glass dosimeter (RGD), a methodology was proposed. In this methodology, the correction factor for the LET dependence of radiophotoluminescent (RPL) efficiency and the variation of mass stopping power ratio of water to RGD (SPRw, RGD) were adopted. The feasibility of proposed method was evaluated in this report.

Methods:

The calibration coefficient in terms of Dw for RGDs (GD‐302M, Asahi Techno Glass) was obtained using 60Co beam. The SPRw, RGD was calculated by Monte Carlo simulation toolkit Geant4. The LET dependence of RPL efficiency was investigated experimentally by using a 70 MeV proton beam at National Institute of Radiological Sciences. For clinical usage, the residual range Rres was used as a quality index to determine the correction factor for RPL efficiency. The proposed method was evaluated by measuring Dw at difference depth in the 200 MeV proton beam.

Results:

For both modulated and non‐modulated proton beam, the SPRw, RGD increases more than 3 % where Rres are less than 1 cm. RPL efficiency decreases with increasing LET and it reaches 0.6 at LET of 10 keV µm−1. Dw measured by RGD (Dw, RGD) shows good agreement with that measured by ionization chamber (Dw, IC) and the relative difference between Dw, RGD and Dw, IC are within 3 % where Rres is larger than 1 cm.

Conclusion:

In this work, a methodology for using RGD in proton dosimetry was proposed and the SPRw, RGD and the LET dependence of RPL efficiency in therapeutic proton beam was investigated. The results revealed that the proposed method is useful for RGD in the dosimetry of proton beams.
SU‐F‐T‐178: Optimized Design of a Diamond Detector Specifically Dedicated to the Dose Distribution Measurements in Clinical Proton Pencil Beams
Authors: Moignier C , Tromson D , Marsolat F , De Marzi L , Pomorski M , Agelou M , Hernandez J Garcia , Lazaro D , Mazal A
Published: July 2016

Purpose:

In proton‐therapy, pencil beam scanning (PBS) dosimetry presents a real challenge due to the small size of the beam (about 3 to 8 mm in FWHM), the pulsed high dose rate (up to 100 Gy/s) and the proton energy variation (about 30 MeV to 250 MeV). In the framework of French INSERM DEDIPRO project, a specifically dedicated single crystal diamond dosimeter (SCDDo) was developed with the objective of obtaining accurate measurements of the dose distribution in PBS modality.

Methods:

Monte Carlo simulations with MCNPX were performed. A small proton beam of 5 mm in FWHM was simulated as well as diamond devices with various size, thickness and holder composition. The calculated doses‐to‐diamond were compared with the doses‐to‐water in order to reduce the perturbation effects. Monte‐Carlo simulations lead to an optimized SCDDo design for small proton beams dosimetry. Following the optimized design, SCDDos were mounted in water‐equivalent holders with electrical connection adapted to standard electrometer. First, SCDDos performances (stability, repeatability, signal‐to‐background ratio…) were evaluated with conventional photon beams. Then, characterizations (dose linearity, dose rate dependence…) with wide proton beams were performed at proton‐therapy center (IC‐CPO) from Curie Institute (France) with the passive proton delivery technique, in order to confirm dosimetric requirements. Finally, depth‐dose distributions were measured in a water tank, for native and modulated Bragg Peaks with the collimator of 12 cm, and compared to a commercial PPC05 parallel‐plate ionization chamber reference detector. Lateral‐dose profiles were also measured with the collimator of 5 mm, and compared to a commercial SFD diode.

Results:

The results show that SCDDo design does not disturb the dose distributions.

Conclusion:

The experimental dose distributions with the SCDDo are in good agreement with the commercial detectors and no energy dependence was observed with this device configuration.
SU‐F‐T‐179: Fast and Accurate Profile Acquisition for Proton Beam Using Multi‐Ion Chamber Arrays
Authors: Wang X , Mo X , Zou J , Chen T , Yue N , Zhang M
Published: July 2016

Purpose:

Proton beam profile measurement is more time‐consuming than photon beam. Due to the energy modulation during proton delivery, chambers have to move step‐by‐step instead of continuously. Multi‐ion chamber arrays are appealing to this task since multiple measurements can be performed at once. However, their utilization suffers from sparse spatial resolution and potential intrinsic volume‐averaging effect of the disk‐shaped ion chambers. We proposed an approach to measure proton beam profiles accurately and efficiently.

Methods:

Mevion S250 proton system and IBA Matrixx ion chamber arrays were used in this study. Matrixx has interchamber distance of 7.62 mm, and chamber diameter of 4.5 mm. We measured the same beam profile by moving the Matrixx seven times with 1 mm each time along y axis. All 7 measurements were superimposed to get a “finer” profile with 1 mm spatial resolution. Coarser resolution profiles of 2 mm and 3 mm were also generated by using subsets of measurements. Those profiles were compared to the TPS calculated beam profile. Gamma analysis was performed for 2D dose maps to evaluate the difference to TPS dose plane.

Results:

Preliminary results showed a large discrepancy between the TPS calculated profile and the single measurement profile with 7.6 mm resolution. A good match could be achieved when the resolution reduced to 3 mm by adding one extra measurement. Gamma analysis for 2D dose map of a 10×10 field showed a passing rate (γ ≤ 1) of 90.6% using a 3% and 3mm criterion for single measurement, which increased to 92.3% for 2‐measurement superimposition, and slightly further increased to 92.9% for 7‐measurement superimposition.

Conclusion:

The results indicated that 2 measurements shifted by 3mm using Matrixx generated a smooth proton beam profile with good matching to Eclipse beam profile. We suggest using this 2‐measurement approach in clinic for double scattering proton beam profile measurement.
SU‐F‐T‐195: Systematic Constraining of Contralateral Parotid Gland Led to Improved Dosimetric Outcomes for Multi‐Field Optimization with Scanning Beam Proton Therapy: Promising Results From a Pilot Study in Patients with Base of Tongue Carcinoma
Authors: Wu R , Crowford C , Georges R , Liu A , Amin M , Sio T , Gunn B , Poenisch F , Palmer M , Gillin M , Frank S , Zhu X
Published: July 2016

Purpose:

Treatment planning for Intensity Modulated Proton Therapy (IMPT) for head and neck cancer is time‐consuming due to the large number of organs‐at‐risk (OAR) to be considered. As there are many competing objectives and also wide range of acceptable OAR constraints, the final approved plan may not be most optimal for the given structures. We evaluated the dose reduction to the contralateral parotid by implementing standardized constraints during optimization for scanning beam proton therapy planning.

Methods:

Twenty‐four (24) consecutive patients previously treated for base of tongue carcinoma were retrospectively selected. The doses were 70Gy, 63Gy and 57Gy (SIB in 33 fractions) for high‐, intermediate‐, and standard‐risk clinical target volumes (CTV), respectively; the treatment included bilateral neck. Scanning beams using MFO with standardized bilateral anterior oblique and PA fields were applied. New plans where then developed and optimized by employing additional contralateral parotid constraints at multiple defined dose levels. Using a step‐wise iterative process, the volume‐based constraints at each level were then further reduced until known target coverages were compromised. The newly developed plans were then compared to the original clinically approved plans using paired student t‐testing.

Results:

All 24 newly optimized treatment plans maintained initial plan quality as compared to the approved plans, and the 98% prescription dose coverage to the CTV's were not compromised. Representative DVH comparison is shown in FIGURE 1. The contralateral parotid doses were reduced at all levels of interest when systematic constraints were applied to V10, V20, V30 and V40Gy (All P<0.0001; TABLE 1). Overall, the mean contralateral parotid doses were reduced by 2.26 Gy on average, a ∼13% relative improvement.

Conclusion:

Applying systematic and volume‐based contralateral parotid constraints for IMPT planning significantly reduced the dose at all dosimetric levels for patients with base of tongue cancer.
SU‐F‐T‐197: Investigating Optimal Oblique‐Beam Arrangement for Bilateral Metallic Prosthesis Prostate Cancer in Pencil Beam Scanning Proton Therapy
Authors: Rana S , Zheng Y , Cheng C , Singh H , Twyford T , Tesfamicael B , Park S
Published: July 2016

Purpose:

The main purpose of this study is to investigate the optimum oblique‐beam arrangement for bilateral metallic prosthesis prostate cancer treatment in pencil beam scanning (PBS) proton therapy.

Methods:

A computed tomography dataset of bilateral metallic prosthesis prostate cancer case was selected for this retrospective study. A total of four beams (rightanterior‐ oblique [RAO], left‐anterior‐oblique [LAO], left‐posterior‐oblique [LPO], and right‐posterior‐oblique [RPO]) were selected for treatment planning. PBS plans were generated using multi‐field‐optimization technique for a total dose of 79.2 Gy[RBE] to be delivered in 44 fractions. Specifically, five different PBS plans were generated based on 2.5% ± 2 mm range uncertainty using five different beam arrangements (i)LAO+RAO+LPO+RPO, (ii)LAO+RAO, (iii)LPO+RPO, (iv)RAO+LPO, and (v)LAO+RPO. Each PBS plan was optimized by applying identical dose‐volume constraints to the PTV, rectum, and bladder. Treatment plans were then compared based on the dose‐volume histograms results.

Results:

The PTV coverage was found to be greater than 99% in all five plans. The homogeneity index (HI) was found to be almost identical (range, 0.03–0.04). The PTV mean dose was found to be comparable (range, 81.0–81.1 Gy[RBE]). For the rectum, the lowest mean dose (8.0 Gy[RBE]) and highest mean dose (31.1 Gy[RBE]) were found in RAO+LAO plan and LPO+RPO plan, respectively. LAO+RAO plan produced the most favorable dosimetric results of the rectum in the medium‐dose region (V50) and high‐dose region (V70). For the bladder, the lowest (5.0 Gy[RBE]) and highest mean dose (10.3 Gy[RBE]) were found in LPO+RPO plan and RAO+LAO plan, respectively. Other dosimetric results (V50 and V70) of the bladder were slightly better in LPO+RPO plan than in other plans.

Conclusion:

Dosimetric findings from this study suggest that two anterior‐oblique proton beams arrangement (LAO+RAO) is a more favorable option with the possibility of reducing rectal dose significantly while maintaining comparable target coverage and acceptable bladder dose.
SU‐F‐T‐198: Dosimetric Comparison of Carbon and Proton Radiotherapy for Recurrent Nasopharynx Carcinoma
Authors: Sheng Y , Zhao J , Wang W , Lin L , Liu X , Shahnazi K
Published: July 2016

Purpose:

Various radiotherapy planning methods for locally recurrent nasopharynx carcinoma (R‐NPC) have been proposed. The purpose of this study was to compare carbon and proton therapy for the treatment of R‐NPC in terms of dose coverage for target volume and sparing for organs at risk (OARs).

Methods:

Six patients who were suffering from R‐NPC and treated using carbon therapy were selected for this study. Treatment plans with a total dose of 57.5Gy (RBE) in 23 fractions were made using SIEMENS Syngo V11. An intensity‐modulated radiotherapy optimization method was chosen for carbon plans (IMCT) while for proton plans both intensity‐modulated radiotherapy (IMPT) and single beam optimization (proton‐SBO) methods were chosen. Dose distributions, dose volume parameters, and selected dosimetric indices for target volumes and OARs were compared for all treatment plans.

Results:

All plans provided comparable PTV coverage. The volume covered by 95% of the prescribed dose was comparable for all three plans. The average values were 96.11%, 96.24% and 96.11% for IMCT, IMPT, and proton‐SBO respectively. A significant reduction of the 80% and 50% dose volumes were observed for the IMCT plans compared to the IMPT and proton‐SBO plans. Critical organs lateral to the target such as brain stem and spinal cord were better spared by IMPT than by proton‐SBO, while IMCT spared those organs best. For organs in the beam path, such as parotid glands, the mean dose results were similar for all three plans.

Conclusion:

Carbon plans yielded better dose conformity than proton plans. They provided similar or better target coverage while significantly lowering the dose for normal tissues. Dose sparing for critical organs in IMPT plans was better than proton‐SBO, however, IMPT is known to be more sensitive to range uncertainties. For proton plans it is essential to find a balance between the two optimization methods.
SU‐F‐T‐209: Multicriteria Optimization Algorithm for Intensity Modulated Radiation Therapy Using Pencil Proton Beam Scanning
Authors: Beltran C , Kamal H
Published: July 2016

Purpose:

To provide a multicriteria optimization algorithm for intensity modulated radiation therapy using pencil proton beam scanning.

Methods:

Intensity modulated radiation therapy using pencil proton beam scanning requires efficient optimization algorithms to overcome the uncertainties in the Bragg peaks locations. This work is focused on optimization algorithms that are based on Monte Carlo simulation of the treatment planning and use the weights and the dose volume histogram (DVH) control points to steer toward desired plans. The proton beam treatment planning process based on single objective optimization (representing a weighted sum of multiple objectives) usually leads to time‐consuming iterations involving treatment planning team members. We proved a time efficient multicriteria optimization algorithm that is developed to run on NVIDIA GPU (Graphical Processing Units) cluster. The multicriteria optimization algorithm running time benefits from up‐sampling of the CT voxel size of the calculations without loss of fidelity.

Results:

We will present preliminary results of Multicriteria optimization for intensity modulated proton therapy based on DVH control points. The results will show optimization results of a phantom case and a brain tumor case.

Conclusion:

The multicriteria optimization of the intensity modulated radiation therapy using pencil proton beam scanning provides a novel tool for treatment planning.

Work support by a grant from Varian Inc.
SU‐F‐T‐214: Re‐Thinking the Useful Clinical Beam Energy in Proton Therapy: An Opportunity for Cost Reduction
Authors: Bentefour El H , Lu H
Published: July 2016

Purpose:

We conducted a retrospective study of the useful clinical proton beam energy based on the beam range data of patients treated over the last 10 years at Massachusetts General Hospital Proton Therapy Center.

Methods:

Treatment field information were collected for all patients treated over the last 10 years (2005–2015) in the two gantry treatment rooms at MGH. The beam ranges for these fields were retrieved and categorized per treatment site. The 10 prostate patients that required the highest beam range (lateral fields) were selected. For these patients, anterior oblique beams (30–40 degrees) were simulated in a planning system to obtain the required beam ranges including the margins for potential range uncertainties.

Results:

There were a total of 4033 patients, treated with combined total of 23603 fields. All treatment indications were considered with the exception of ocular tumors generally treated in a fixed beam room. For all non‐prostate treatments (21811 fields), only 5 fields for 4 patients (1‐pancreas, 1‐lumbar chordoma, 2‐spine mets) required beam range greater than 25 cm. There were 446 prostate patients (1792 fields), with the required beam range from 22.3 to 29.0 cm; 386 of them had at least one of their lateral beam range greater than 25 cm. For the 10 prostate patients with highest lateral beam ranges (26 to 29 cm), their treatment with anterior oblique beams would drop the beam ranges below 25 cm (17.3 to 18.5 cm).

Conclusion:

if prostate patients are treated with anterior fields only, the useful maximum beam range is reduced to 25 cm. Thus a proton therapy system with maximum beam energy of 196 MeV is sufficient to treat all tumors sites with very rare exceptions (<0.1%). Designing such PT system would reduce the cost of proton therapy for hospitals and patients and increase the accessibility to the treatment.
SU‐F‐T‐231: Improving the Efficiency of a Radiotherapy Peer‐Review System for Quality Assurance
Authors: Hsu S , Basavatia A , Garg M , Kalnicki S , Tome W
Published: July 2016

Purpose:

To improve the efficiency of a radiotherapy peer‐review system using a commercially available software application for plan quality evaluation and documentation.

Methods:

A commercial application, FullAccess (Radialogica LLC, Version 1.4.4), was implemented in a Citrix platform for peer‐review process and patient documentation. This application can display images, isodose lines, and dose‐volume histograms and create plan reports for peer‐review process. Dose metrics in the report can also be benchmarked for plan quality evaluation. Site‐specific templates were generated based on departmental treatment planning policies and procedures for each disease site, which generally follow RTOG protocols as well as published prospective clinical trial data, including both conventional fractionation and hypo‐fractionation schema. Once a plan is ready for review, the planner exports the plan to FullAccess, applies the site‐specific template, and presents the report for plan review. The plan is still reviewed in the treatment planning system, as that is the legal record. Upon physician's approval of a plan, the plan is packaged for peer review with the plan report and dose metrics are saved to the database.

Results:

The reports show dose metrics of PTVs and critical organs for the plans and also indicate whether or not the metrics are within tolerance. Graphical results with green, yellow, and red lights are displayed of whether planning objectives have been met. In addition, benchmarking statistics are collected to see where the current plan falls compared to all historical plans on each metric. All physicians in peer review can easily verify constraints by these reports.

Conclusion:

We have demonstrated the improvement in a radiotherapy peer‐review system, which allows physicians to easily verify planning constraints for different disease sites and fractionation schema, allows for standardization in the clinic to ensure that departmental policies are maintained, and builds a comprehensive database for potential clinical outcome evaluation.
SU‐F‐T‐237: The Imaging and Radiation Oncology Core (IROC) Cooperatives Activities Supporting the NCI's National Clinical Trial Network
Authors: Followill D , Galvin J , Michalski J , Rosen M , FitzGerald T , Knopp M
Published: July 2016

Purpose:

The Imaging and Radiation Oncology Core (IROC) Cooperative has been active for the past two years supporting the National Clinical Trial Network and the details of that support are reported.

Methods:

There are six QA centers (Houston, Ohio, Philadelphia‐RT, Philadelphia‐DI, Rhode Island, St. Louis) providing an integrated RT and DI quality control program in support of the NCI's clinical trials. The QA Center's efforts are focused on assuring high quality data for clinical trials designed to improve the clinical outcomes for cancer patients worldwide. This program is administered through five core services: site qualification, trial design support, credentialing, data management, and case review.

Results:

IROC currently provides core support for 172 NCTN trials with RT, DI and RT/DI components. Many of these trials were legacy trial from the previous cooperative group program. IROC monitors nearly 1800 RT photon and 20 proton institutions. Over 28,000 beams outputs were monitored with 8% of the sites requiring repeat audits due to beam out of criteria. As part of credentialing, 950 QA phantoms have been irradiated, 515 imaging modalities evaluated and almost 4000 credentialing letters have been issued. In just year 2, 5290 RT and 4934 DI patient datasets were received (many using TRIAD) by IROC QA Centers to be prepared for review. During the past 2 years, a total of 6300 RT cases and 19,000 DI image sets were reviewed by IROC technical staff. To date, IROC has published 36 manuscripts.

Conclusion:

The QA services provided by IROC are numerous and are continually being evaluated for effectiveness, harmonized across all NCTN Groups and administered in an efficient and timely manner to enhance accurate and per protocol trial data submission. These efforts increase each NCTN Group's ability to derive meaningful outcomes from their clinical trials.

This work was supported by DHHS NIH grant 5U24CA180803
SU‐F‐T‐257: Comparison Study of the Biological and Physical Optimization for Cervical Carcinoma
Authors: Feng Z , Tao C , Zhu J , Yu G , Qin S , Yin Y , Li D
Published: July 2016

Purpose:

In this study, IMRT optimization based on biological related models were applied in the clinic for cervical carcinoma cases and the results were compared with the traditional physical optimization. Methods: Twenty patients of advanced stage cervical carcinoma were selected in this study. The treatment plan was generated on each patient using both biological and physical optimized model respectively. Additionally, the biological optimization was based on two basic models for bladder and rectum: Poisson (adjustable parameters: alpha/beta, gamma, D50) and Lyman‐Kutcher‐Burman (adjustable parameters: m, n, D50). And then each optimized biological plan was compared with the corresponding physical plan. During this comparison, all biological and physical parameters, such as NTCP,TCP, target coverage and homogeneous index(HI), were evaluated by paired T‐test to verify IMRT plans quality.

Results:

The NTCP values by biological optimization were lower than the values from corresponding physical optimization. For the bladder and rectum, the detail of NTCP values are 0.144 and 0.178 with p=0.028 for bladder, and 0.108 and 0.186 with p= 7.97E‐5 for rectum respectively. The mean dose and V40 of bladder and rectum were comparable, and there was no significant difference between these two optimizations. For PTV, both optimized models achieved similar target coverage and homogeneous index (For example, D98=53.4 Gy and 54.6 Gy from biological optimization and physical optimization respectively with p=2.94E‐9), and there were no significant differences in the tumor control probability(TCP) values.

Conclusion:

IMRT optimization based on biological model did not decrease the plan quality, and could spare bladder and rectum with lower NTCP value much more compared with traditional physical optimization for cervical carcinoma. Our initial experiment demonstrated that the biological optimization could be a potential alternative method to the traditional physical one.

We want to thank Dr. Lei Xing and Dr. Yong Yang in the Stanford University School of Medicine for this work. This work was jointly supported by NSFC (61471226), Natural Science Foundation for Distinguished Young Scholars of Shandong Province (JQ201516), and China Postdoctoral Science Foundation (2015T80739, 2014M551949).
SU‐F‐T‐261: Reconstruction of Initial Photon Fluence Based On EPID Images
Authors: Seliger T , Czarnecki D , Kussaether R , Maeder U , Engenhart‐Cabillic R , Poppe B , Zink K
Published: July 2016

Purpose:

Verifying an algorithm to reconstruct relative initial photon fluence for clinical use. Clinical EPID and CT images were acquired to reconstruct an external photon radiation treatment field. The reconstructed initial photon fluence could be used to verify the treatment or calculate the applied dose to the patient.

Methods:

The acquired EPID images were corrected for scatter caused by the patient and the EPID with an iterative reconstruction algorithm. The transmitted photon fluence behind the patient was calculated subsequently. Based on the transmitted fluence the initial photon fluence was calculated using a back‐projection algorithm which takes the patient geometry and its energy dependent linear attenuation into account. This attenuation was gained from the acquired cone‐beam CT or the planning CT by calculating a water‐equivalent radiological thickness for each irradiation direction. To verify the algorithm an inhomogeneous phantom consisting of three inhomogeneities was irradiated by a static 6 MV photon field and compared to a reference flood field image.

Results:

The mean deviation between the reconstructed relative photon fluence for the inhomogeneous phantom and the flood field EPID image was 3% rising up to 7% for off‐axis fluence. This was probably caused by the used clinical EPID calibration, which flattens the inhomogeneous fluence profile of the beam.

Conclusion:

In this clinical experiment the algorithm achieved good results in the center of the field while it showed high deviation of the lateral fluence. This could be reduced by optimizing the EPID calibration, considering the off‐axis differential energy response. In further progress this and other aspects of the EPID, eg. field size dependency, CT and dose calibration have to be studied to realize a clinical acceptable accuracy of 2%.
SU‐F‐T‐267: A Clarkson‐Based Independent Dose Verification for the Helical Tomotherapy
Authors: Nagata H , Hongo H , Kawai D , Takahashi R , Hashimoto H , Tachibana H
Published: July 2016

Purpose:

There have been few reports for independent dose verification for Tomotherapy. We evaluated the accuracy and the effectiveness of an independent dose verification system for the Tomotherapy.

Methods:

Simple MU Analysis (SMU, Triangle Product, Ishikawa, Japan) was used as the independent verification system and the system implemented a Clarkson‐based dose calculation algorithm using CT image dataset. For dose calculation in the SMU, the Tomotherapy machine‐specific dosimetric parameters (TMR, Scp, OAR and MLC transmission factor) were registered as the machine beam data. Dose calculation was performed after Tomotherapy sinogram from DICOM‐RT plan information was converted to the information for MU and MLC location at more segmented control points. The performance of the SMU was assessed by a point dose measurement in non‐IMRT and IMRT plans (simple target and mock prostate plans). Subsequently, 30 patients’ treatment plans for prostate were compared.

Results:

From the comparison, dose differences between the SMU and the measurement were within 3% for all cases in non‐IMRT plans. In the IMRT plan for the simple target, the differences (Average±1SD) were −0.70±1.10% (SMU vs. TPS), −0.40±0.10% (measurement vs. TPS) and −1.20±1.00% (measurement vs. SMU), respectively. For the mock prostate, the differences were −0.40±0.60% (SMU vs. TPS), −0.50±0.90% (measurement vs. TPS) and −0.90±0.60% (measurement vs. SMU), respectively. For patients’ plans, the difference was −0.50±2.10% (SMU vs. TPS).

Conclusion:

A Clarkson‐based independent dose verification for the Tomotherapy can be clinically available as a secondary check with the similar tolerance level of AAPM Task group 114.

This research is partially supported by Japan Agency for Medical Research and Development (AMED)
SU‐F‐T‐274: Modified Dose Calibration Methods for IMRT QA
Authors: Luo W , Westlund S
Published: July 2016

Purpose:

To investigate IMRT QA uncertainties caused by dose calibration and modify widely used dose calibration procedures to improve IMRT QA accuracy and passing rate.

Methods:

IMRT QA dose measurement is calibrated using a calibration factor (CF) that is the ratio between measured value and expected value corresponding to the reference fields delivered on a phantom. Two IMRT QA phantoms were used for this study: a 30×30×30 cm3 solid water cube phantom (Cube), and the PTW Octavius phantom. CF was obtained by delivering 100 MUs to the phantoms with different reference fields ranging from 3×3 cm2 to 20×20 cm2. For Cube, CFs were obtained using the following beam arrangements: 2‐AP Field ‐ chamber at dmax, 2‐AP Field ‐ chamber at isocenter, 4‐beam box ‐ chamber at isocenter, and 8 equally spaced fields and chamber at isocenter. The same plans were delivered on Octavius and CFs were derived for the dose at the isocenter using the above beam arrangements. The Octavius plans were evaluated with PTW‐VeriSoft (Gamma criteria of 3%/3mm).

Results:

Four head and neck IMRT plans were included in this study. For point dose measurement with Cube, the CFs with 4‐Field gave the best agreement between measurement and calculation within 4% for large field plans. All the measurement results agreed within 2% for a small field plan. Compared with calibration field sizes, 5×5 to 15×15 were more accurate than other field sizes. For Octavius, 4‐Field calibration increased passing rate by up to 10% compared to AP calibration. Passing rate also increased by up to 4% with the increase of field size from 3×3 to 20×20.

Conclusion:

IMRT QA results are correlated with calibration methods used. The dose calibration using 4‐beam box with field sizes from 5×5 to 20×20 can improve IMRT QA accuracy and passing rate.
SU‐F‐T‐275: A Correlation Study On 3D Fluence‐Based QA and 2D Dose Measurement‐Based QA
Authors: Liu S , Mazur T , Li H , Green O , Sun B , Mutic S , Yang D
Published: July 2016

Purpose:

The aim of this paper was to demonstrate the feasibility and creditability of computing and verifying 3D fluencies to assure IMRT and VMAT treatment deliveries, by correlating the passing rates of the 3D fluence‐based QA (P(ά)) to the passing rates of 2D dose measurementbased QA (P(Dm)).

Methods:

3D volumetric primary fluencies are calculated by forward‐projecting the beam apertures and modulated by beam MU values at all gantry angles. We first introduce simulated machine parameter errors (MU, MLC positions, jaw, gantry and collimator) to the plan. Using passing rates of voxel intensity differences (P(Ir)) and 3D gamma analysis (P(γ)), calculated 3D fluencies, calculated 3D delivered dose, and measured 2D planar dose in phantom from the original plan are then compared with those from corresponding plans with errors, respectively. The correlations of these three groups of resultant passing rates, i.e. 3D fluence‐based QA (P(ά,Ir) and P(ά,γ)), calculated 3D dose (P(Dc,Ir) and P(Dc,γ)), and 2D dose measurement‐based QA (P(Dm,Ir) and P(Dm,γ)), will be investigated.

Results:

20 treatment plans with 5 different types of errors were tested. Spearman's correlations were found between P(ά,Ir) and P(Dc,Ir), and also between P(ά,γ) and P(Dc,γ), with averaged p‐value 0.037, 0.065, and averaged correlation coefficient ρ‐value 0.942, 0.871 respectively. Using Matrixx QA for IMRT plans, Spearman's correlations were also obtained between P(ά,Ir) and P(Dm,Ir) and also between P(ά,γ) and P(Dm,γ), with p‐value being 0.048, 0.071 and ρ‐value being 0.897, 0.779 respectively.

Conclusion:

The demonstrated correlations improve the creditability of using 3D fluence‐based QA for assuring treatment deliveries for IMRT/VMAT plans. Together with advantages of high detection sensitivity and better visualization of machine parameter errors, this study further demonstrates the accuracy and feasibility of 3D fluence based‐QA in pre‐treatment QA and daily QA.

Research reported in this study is supported by the Agency for Healthcare Research and Quality (AHRQ) under award 1R01HS0222888. The senior author received research grants from ViewRay Inc. and Varian Medical System
SU‐F‐T‐281: Monte Carlo Investigation of Sources of Dosimetric Discrepancies with 2D Arrays
Authors: Afifi M , Deiab N , El‐Farrash A , Abd El‐Hafez A , Eldib A , Veltchev I , Ma C
Published: July 2016

Purpose:

Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA). Understanding the limitations and use of dosimeters to measure these dose distributions is critical to safe IMRT implementation. In this work, we used Monte Carlo simulations to investigate the possible sources of discrepancy between our measurement with 2D array system and our dose calculation using our treatment planning system (TPS).

Material and Methods:

MCBEAM and MCSIM Monte Carlo codes were used for treatment head simulation and phantom dose calculation. Accurate modeling of a 6MV beam from Varian trilogy machine was verified by comparing simulated and measured percentage depth doses and profiles. Dose distribution inside the 2D array was calculated using Monte Carlo simulations and our TPS. Then Cross profiles for different field sizes were compared with actual measurements for zero and 90° gantry angle setup. Through the analysis and comparison, we tried to determine the differences and quantify a possible angular calibration factor.

Results:

Minimum discrepancies was seen in the comparison between the simulated and the measured profiles for the zero gantry angles at all studied field sizes (4×4cm2, 10×10cm2, 15×15cm2, and 20×20cm2). Discrepancies between our measurements and calculations increased dramatically for the cross beam profiles at the 90° gantry angle. This could ascribe mainly to the different attenuation caused by the layer of electronics at the base behind the ion chambers in the 2D array. The degree of attenuation will vary depending on the angle of beam incidence. Correction factors were implemented to correct the errors.

Conclusion:

Monte Carlo modeling of the 2D arrays and the derivation of angular dependence correction factors will allow for improved accuracy of the device for IMRT QA.
SU‐F‐T‐288: Impact of Trajectory Log Files for Clarkson‐Based Independent Dose Verification of IMRT and VMAT
Authors: Takahashi R , Kamima T , Tachibana H
Published: July 2016

Purpose:

To investigate the effect of the trajectory files from linear accelerator for Clarkson‐based independent dose verification in IMRT and VMAT plans.

Methods:

A CT‐based independent dose verification software (Simple MU Analysis: SMU, Triangle Products, Japan) with a Clarksonbased algorithm was modified to calculate dose using the trajectory log files. Eclipse with the three techniques of step and shoot (SS), sliding window (SW) and Rapid Arc (RA) was used as treatment planning system (TPS). In this study, clinically approved IMRT and VMAT plans for prostate and head and neck (HN) at two institutions were retrospectively analyzed to assess the dose deviation between DICOM‐RT plan (PL) and trajectory log file (TJ). An additional analysis was performed to evaluate MLC error detection capability of SMU when the trajectory log files was modified by adding systematic errors (0.2, 0.5, 1.0 mm) and random errors (5, 10, 30 mm) to actual MLC position.

Results:

The dose deviations for prostate and HN in the two sites were 0.0% and 0.0% in SS, 0.1±0.0%, 0.1±0.1% in SW and 0.6±0.5%, 0.7±0.9% in RA, respectively. The MLC error detection capability shows the plans for HN IMRT were the most sensitive and 0.2 mm of systematic error affected 0.7% dose deviation on average. Effect of the MLC random error did not affect dose error.

Conclusion:

The use of trajectory log files including actual information of MLC location, gantry angle, etc should be more effective for an independent verification. The tolerance level for the secondary check using the trajectory file may be similar to that of the verification using DICOM‐RT plan file. From the view of the resolution of MLC positional error detection, the secondary check could detect the MLC position error corresponding to the treatment sites and techniques.

This research is partially supported by Japan Agency for Medical Research and Development (AMED)
SU‐F‐T‐289: MLC Fluence Sonogram Based Delivery Quality Assurance for Bilateral Breast Irradiation
Authors: Thiyagarajan Rajesh , Karrthick KP , Kataria Tejinder , Arunai N , Raj Nambi , Mahendran Ramu , Selvan Tamil , Duraikannu Palani
Published: July 2016

Purpose:

Performing DQA for Bilateral (B‐L) breast tomotherapy is a challenging task due to the limitation of any commercially available detector array or film. Aim of this study is to perform DQA for B‐L breast tomotherapy plan using MLC fluence sinogram.

Methods:

Treatment plan was generated on Tomotherapy system for B‐L breast tumour. B‐L breast targets were given 50.4 Gy prescribed over 28 fractions. Plan is generated with 6 MV photon beam & pitch was set to 0.3. As the width of the total target is 39 cm (left & right) length is 20 cm. DQA plan delivered without any phantom on the mega voltage computed tomography (MCVT) detector system. The pulses recorded by MVCT system were exported to the delivery analysis software (Tomotherapy Inc.) for reconstruction. The detector signals are reconstructed to a sonogram and converted to MLC fluence sonogram. The MLC fluence sinogram compared with the planned fluence sinogram. Also point dose measured with cheese phantom and ionization chamber to verify the absolute dose component

Results:

Planned fluence sinogram and reconstructed MLC fluence sinogram were compared using Gamma metric. MLC positional difference and intensity of the beamlet were used as parameters to evaluate gamma. 3 mm positional difference and 3% beamlet intensity difference were used set for gamma calculation. A total of 26784 non‐zero beamlets were included in the analysis out of which 161 beamlets had gamma more than 1. The gamma passing rate found to be 99.4%. Point dose measurements were within 1.3% of the calculated dose.

Conclusion:

MLC fluence sinogram based delivery quality assurance performed for bilateral breast irradiation. This would be a suitable alternate for large volume targets like bilateral breast, Total body irradiation etc. However conventional method of DQA should be used to validate this method periodically.