Treatment Planning Data Research Articles

Computed Tomography as a Source of Electron Density Information for Radiation Treatment Planning

To evaluate the performance of computed tomography (CT) systems of various designs as a source of electron density (rho(el)) data for treatment planning of radiation therapy. Dependence of CT numbers on relative electron density of tissue-equivalent materials (HU-rho(el) relationship) was measured for several general-purpose CT systems (single-slice, multislice, wide-bore multislice), for radiotherapy simulators with a single-slice CT and kV CBCT (cone-beam CT) options, as well as for linear accelerators with kV and MV CBCT systems. Electron density phantoms of four sizes were used. Measurement data were compared with the standard HU-rhoel relationships predefined in two commercial treatment-planning systems (TPS). The HU-rho(el) relationships obtained with all of the general-purpose CT scanners operating at voltages close to 120 kV were very similar to each other and close to those predefined in TPS. Some dependency of HU values on tube voltage was observed for bone- equivalent materials. For a given tube voltage, differences in results obtained for different phantoms were larger than those obtained for different CT scanners. For radiotherapy simulators and for kV CBCT systems, the information on rhoel was much less precise because of poor uniformity of images. For MV CBCT, the results were significantly different than for kV systems due to the differing energy spectrum of the beam. The HU-rho(el) relationships predefined in TPS can be used for general-purpose CT systems operating at voltages close to 120 kV. For nontypical imaging systems (e.g., CBCT), the relationship can be significantly different and, therefore, it should always be measured and carefully analyzed before using CT data for treatment planning.

Dosimetry evaluation of SAVI-based HDR brachytherapy for partial breast irradiation.

Accelerated partial breast irradiation (APBI) with high dose rate (HDR) brachytherapy offers an excellent compact course of radiation due to its limited number of fractions for early-stage carcinoma of breast. One of the recent devices is SAVI (strut-adjusted volume implant), which has 6, 8 or 10 peripheral source channels with one center channel. Each channel can be differentially loaded. This paper focuses on the treatment planning, dosimetry and quality assurance aspects of HDR brachytherapy implant with GammaMed Plus HDR afterloader unit. The accelerated PBI balloon devices normally inflate above 35 cc range, and hence these balloon type devices cannot be accommodated in small lumpectomy cavity sizes. CT images were obtained and 3-D dosimetric plans were done with Brachyvision planning system. The 3-D treatment planning and dosimetric data were evaluated with planning target volume (PTV)_eval V90, V95, V150, V200 skin dose and minimum distance to skin. With the use of the SAVI 6-1 mini device, we were able to accomplish an excellent coverage — V90, V95, V150 and V200 to 98%, 95%, 37 cc (<50 cc volume) and 16 cc (<20 cc volume), respectively. Maximum skin dose was between 73% and 90%, much below the prescribed dose of 34 Gy. The minimum skin distance achieved was 5 to 11 mm. The volume that received 50% of the prescribed radiation dose was found to be lower with SAVI. The multi-channel SAVI-based implants reduced the maximum skin dose to markedly lower levels as compared to other modalities, simultaneously achieving best dose coverage to target volume. Differential-source dwell-loading allows modulation of the radiation dose distribution in symmetric or asymmetric opening of the catheter shapes and is also advantageous in cavities close to chest wall.

SU-FF-T-239: Planning Dose Comparison of EBT Films and 2D Diode Array at Different Gantry Angles

Purpose: To evaluate the measured dose distributions using radiochromic EBT films and a 2D diode array as compared with treatment planning (TP) data at different gantry angles. Method and Materials: Radiochromic EBT films (ISP) were irradiated with 6MV photons on a Varian Cl‐iX linac at 10cm depth (100cm SAD, polystyrene phantom, 25×25×20cm3). The films were exposed, one at a time, at gantry of 0°,30°,60°,70°,80°,90° with a 10×10cm2 field and an IMRT field at collimator of 45°. The calibration films were irradiated at dmax (1.5cm) for doses up to 10Gy. All films were scanned using an Epson 10000XL flatbed scanner with 48‐bit color (RGB) and 75dpi. The pixel values were converted to doses using the established calibration curve. The 2D dose distributions were generated from the film data analysis. Similar experiments, with the same settings, were performed using a diode array (MapCheck™). An in‐house software was used to compare the measured doses from films and the diode array with the TP data at each gantry angle. Results: With the TP data as a reference (100%), the measured doses for 10×10 cm2 field at the isocenter were 100±2% from EBT film dosimetry for all the gantry angles studied. The diode array data showed a trend of angular dependence, decreasing from 100% at 0° down to 90% at 80° gantry angle. 1D dose profiles along the diagonal line in the cross‐plane and 2D dose distributions were compared. A gamma index analysis was also performed to evaluate comparisons of measurements and TP data. Conclusions: The quantification of 2D dose distributions for 10×10 cm2 and IMRT treatments at various gantry angles using EBT films was demonstrated. The results were compared with diode array data and TP. The EBT films could potentially be a useful dosimeter in patient‐specific QA, including IMRT, RapidArc, VMAT, and Tomotherapy.

SU-FF-T-234: A Simple Method for Quality Assurance of Proton Compensators

Purpose: Distal dose conformity to a target volume is achieved by choosing proper range of the proton beam and modifying it by custom designed compensator. The voxel of the compensator is milled precisely using a computerized machine. The, quality assurance of proton compensators that is used for patient treatment is a vital issue in proton therapy that is investigated. Methods and Materials: Forty one patient specific proton compensators were analyzed that were manufactured using Milltronics VM16 computerized machine. Comparisons were made between the treatment planning system output data file and the voxel depth of the compensator. Point depths were measured by Sheffield Discovery II and were input into OmniPro IMRT software. The spatial distributions and histograms of compensator depth differences were visualized and evaluated. The acceptable depth difference between the measured and specified depth 0.38mm was maintained. The acceptance criterion of the manufactured compensator was 95% data points. Results:. For 37 of the 41 compensators, all measured points passed the test. The average difference is ±0.04 mm with the max difference depth of 0.28mm. One compensator was rejected as 10.4% of the measured points failed the test. For 3 other compensators, about 2.7% of the measured points failed the test with the maximum difference of 9.8 mm. Spatial distribution of the poor quality points will be evaluated to decide if the compensators should be rejected. Conclusion: A method for proton compensator quality assurance based on an existing commercial software system is introduced. The QA approach is coupled with visualization and statistical evaluation. Spatial distributions of error points can be identified, which are valuable for further dose distribution analysis.

SU‐GG‐BRC‐08: Improving Buildup Region Measurement Accuracy Using a Surface Location Method

Purpose: To determine the depth of the inflection point in the buildup region of photon beam depth‐ionization curves for 11 cylindrical ionization chambers of differing designs and investigate dependencies of the inflection point on beam energy, electron contamination, and chamber design. Method and Materials: Each ionization chamber is carefully aligned to the water surface using a precision alignment telescope with a custom, high‐precision beam scanning system. Following alignment, depth‐ionization curves are obtained including scanning the chamber beyond the air‐water interface for 6, 10, and 25 MV photon beams. Measurements are made with and without a 1 mm lead foil in the beam for a 10×10 cm2 field. The inflection point in the measured depth‐ionization data is determined by finding the maximum in its second derivative. Results: The location of each chamber‐specific inflection point is invariant to changes in beam energy, electron contamination, and chamber orientation within the 0.5 mm measurement resolution. Eight chambers, whose outer diameters are within 0.7 mm of each other, exhibit inflection points that are within 0.5 mm of one another. The location of each chamber's inflection point is most strongly impacted by its outer radius and corresponds with the shallowest depth at which the chamber is fully submersed in the water, within 0.5 mm. Conclusion: The buildup region inflection point for a given cylindrical chamber is invariant to the beam variations studied and occurs at a depth equal to the chamber outer radius, within measurement resolution, for the 11 ionization chambers studied. Using this dependence, the inflection point can be used as a robust offline check to identify the water surface location and to identify inter‐setup/inter‐user setup variations. Higher quality surface localization can ease beam modeling and improve the quality of treatment planning data.

SU-FF-T-216: Comparison of a 2D and 3D Array of Diodes for IMRT QA

Purpose: To compare the IMRT QA pass/fail rates of a 2D diode array system MapCHECK™ and a cylindrical 3D diode array system Delta4™, and to investigate the benefit of DVH‐based IMRT QA. Methods and Materials: Eight treatment plans totaling 62 IMRT fields were measured using both MapCHECK and Delta4. The data were compared to the treatment planning data using Gamma analysis. Passing criteria was defined as 95% of measured points had to have a gamma value ⩽1.0 using a distance to agreement of 4mm, a 5% dose window, and a 10% dose threshold. Structures, including GTV and organs at risk (OAR), and dose volume histograms (DVHs) were exported from the treatment planning system to Delta4 for comparison to measured DVHs. Results: QA with Delta4 used an average of 466 detector points per field. Using gamma analysis, 60/62 (96.8%) IMRT fields passed with an average of 98.9% of detector points within a gamma value ⩽1.0 when measured on the Delta4. QA with MapCHECK used an average of 88 detector points per field. Application of the same gamma analysis resulted in 14/62 (22.6%) IMRT fields passing with an average of 91.3% of detector points with a gamma value ⩽1.0 as measured by MapCHECK. Further analysis of IMRT fields that failed using MapCHECK QA, indicated that the measured data was within 1–2% of the treatment plan. Planned GTV DVHs corresponded with the Delta4 measured GTV DVHs, however measured OAR DVHs differed from their planned DVHs. Conclusions: This study suggests that QA results acquired with Delta4 correspond more accurately to the actual treatment plan as compared to MapCHECK. Incorporating Delta4 into routine QA will decrease the overall QA analysis time. The increased pass rate with Delta4 may result from the increased amount of detectors per treatment field.

Radiation therapy plan checks in a paperless clinic

Traditional quality assurance checks of a patient's radiation therapy plan involve printing out treatment parameters from the treatment planning system and the “record and verify” (R&V) system and visually checking the information for one‐to‐one correspondence. In a paperless environment, one can automate this process through independent software that can read the treatment planning data directly and compare it against the parameters in the R&V system's database. In addition to verifying the data integrity, it is necessary to check the logical consistency of the data and the accuracy of various calculations. The results are then imported into the patient's electronic medical record. Appropriate workflows must be developed to ensure that no steps of the QA process are missed. This paper describes our electronic QA system (EQS), consisting of in‐house software and workflows. The EQS covers 3D conformal and intensity modulated radiation therapy, electrons, stereotactic radiosurgery, total body irradiation, and clinical set ups with and without virtual simulation. The planning systems handled by our EQS are ADAC Pinnacle and Varian FASTPLAN, while the R&V systems are LANTIS and VARIS. The improvement in our plan check process over the paperless system is described in terms of the types of detected errors. The potential problems with the implementation and use of the EQS, as well as workarounds for data that are not easily accessible through electronic means, are described.PACS numbers: 87.55.Qr, 87.55.tg, 87.55.tm

Impact of Manual and Automated Interpretation of Fused PET/CT Data on Esophageal Target Definitions in Radiation Planning

We compare CT-only based esophageal tumor definition with two PET/CT based methods: (1) manual contouring and (2) a semiautomated method based on specific thresholds. Patients with esophageal cancer treated at Brigham and Women's Hospital from 2003 to 2006 were identified. CT-based tumor volumes were compared with manual PET/CT-based volumes and semiautomated PET-based tumor volumes. Differences were scored as (1) minor if the superior or inferior extent of the primary tumor (or both) differed by 1-2 cm and (2) major if the difference was > 2 cm or if different noncontiguous nodal regions were identified as being grossly involved. Comparing CT-based gross tumor volumes (GTVs) to manually defined PET/CT-based GTVs, use of PET changed volumes for 21 of 25 (84%) patients: 12 patients (48%) exhibited minor differences, whereas for 9 patients (36%), the differences were major. For 4 (16%) patients, the major difference was due to discrepancy in celiac or distant mediastinal lymph node involvement. Use of automated PET volumes changed the manual PET length in 14 patients (56%): 8 minor and 6 major. The use of PET/CT in treatment planning for esophageal cancer can affect target definition. Two PET-based techniques can also produce significantly different tumor volumes in a large percentage of patients. Further investigations to clarify the optimal use of PET/CT data in treatment planning are warranted.

TH‐D‐350‐03: The Benefits of Integrating the Healthcare Enterprise (IHE) Efforts for the Radiation Oncology Physicist

Purpose: An issue for the practicing clinical physicist is the integration of computer systems in support of radiation therapy. Standards such as DICOM and HL7 exist, however, applications in the process apply these standards differently, resulting in unreliable exchanges of data at points in the imaging, planning, and delivery of treatment. Solving this problem requires the support of users, vendors, and professional societies to achieve a global solution and allow ‘best‐of‐breed’ selection of applications. Method and Materials: IHE (Integrating the Healthcare Enterprise) is an effort started by RSNA and HIMSS. Its goal is improving the integration of information systems in support of clinical care. IHE‐RO (IHE Radiation Oncology) is an effort supported by ASTRO, AAPM, other societies, and vendors aimed at identifying issues of computer integration and developing solutions. Meetings were held to identify bottlenecks in the treatment process. Use cases were written and an “Integration Profile” was developed for the exchange of CT, Region‐of‐interest, treatment plan, and 3D dose calculation data among different vendors. Vendors then tested their product implementations using test tools developed in support of the effort, 2 rounds of testing (informal and formal), and a public demonstration. Results: In the first two rounds of testing a number of incompatible interpretations of DICOM protocols were identified. At the formal Connectathon, manufacturers were able to prove compliance with the Integration Profile for applications that included RT‐Archive, CT‐Simulation, Treatment Planning, and Dose Display. Conclusion: IHE‐RO is an effort that is beneficial to the practicing medical physicist. It provides a venue for controlled and demonstrable testing of multi‐application compatibility. It reduces the effort required in selection and integration of new systems into clinical practice by providing a reference of proven integration. The improved robustness of application‐to‐application information transfer results in reduced quality assurance requirements of such interfaces.

A commissioning procedure for breast intracavitary electronic brachytherapy systems.

In this work, we report a comprehensive quality assurance (QA) process for the commissioning of an Electronic Brachytherapy (EB) system at one of the first U.S. sites to apply the device clinically. Thus far, EB systems have been released only for intracavitary breast treatments. As such, EB as an Accelerated Partial Breast Irradiation (APBI) treatment modality is relatively unstudied and is unfamiliar to many medical physicists. We present our documented experience as a guide for other institutions' EB commissioning process. Our tests included eight elements: A) well‐chamber constancy, B) beam stability, C) source positional accuracy, D) output stability, E) timer linearity, F) dummy marker/source position coincidence, G) controller functionality and safety interlocks, and H) treatment planning data verification following the AAPM TG‐43 recommendations. Together with TG‐43, our methodology provides a comprehensive EB system check for medical physicists commissioning such a device.PACS Numbers: 87.53.Jw, 87.53.Xd

SU-GG-T-391: Collection and Development of Relational Organization of Radiation Treatment Plan Data From a Commercial Radiation Treatment Planning System

Purpose: The goal of this work is to automatically collect and organize treatment planning statistics on a large number of patients for retrospective analysis.Method and Materials: A relational database was deigned to include all the metrics associated with treatment planning including: doses, volumes, beams, ROI shapes, prescriptions, IMRT constraints, and patient demographics. An interface was created to automatically populate the database from a commercial radiation treatment planning system (Pinnacle3, Philips Medical Systems, Milpitas CA). Outside of the internal scripting language of the treatment planning system, all essential components operate on open‐source software. Since this was implemented on an open‐standards client‐server database, multiple options are available for data mining. We have currently implemented a web interface to view the database contents and provide analysis tools. Results: A full treatment plan is evaluated and exported within just two minutes. Several major versions of the treatment planning system are supported by the export components of the system. Dozens of plans have been exported into the database, demonstrating full functionality and reliability. Conclusion: Previously, gaining access to certain plan statistics and data required the time‐consuming tasks of manually loading a plan, navigating its contents, and transcribing target information. These tasks can be eliminated by utilizing this database to store radiation treatment plan data. The overall concept and utility of the complete system has generated great interest, benefiting it with enhancements and refinements even prior to a large‐scale deployment. This work has been supported in part by a Sponsored Research Agreement with Philips Healthcare.

SU‐GG‐T‐447: Import of Gamma Knife Model C Treatment Plans Into CERR

Purpose: To import Gamma Knife treatment plans into an environment that allows for comparison and combination dose distributions with those from other treatment planning systems to include those for linear accelerators. Method and Materials: A set of software tools were developed that allow the binary files of GammaPlan, version 5.4, for Gamma Knife, Model C, to be converted and imported into CERR, version 3.0. The imported data files include CT scan sets, MR scan sets, anatomical contours, the location of the dose matrix relative to patient anatomy, the dose computed by GammaPlan. The functionality of CERR allows us to fuse image sets, contours and doses. Results: We were able to import GammaPlan treatment plan data into CERR for comparison and combination with a Varian Eclipse/Helios treatment plan for recurrent tumor in the same patient. The recurrent tumor extended into anatomical regions that precluded re‐treatment with the Gamma Knife, Model C. This allowed superposition of isodose distributions of the two treatment plans in one viewable format. Areas of dose overlap for the two plans were identified and the progression of disease relative to the initially treatment location was observed. Conclusion: The software tools extend the capabilities of CERR to view GammaPlan treatment plans and combine the doses from other treatment planning systems supported by CERR. Further work will incorporate full plan specifications, including shot locations, gamma angle, and time for each shot so that CERR can export in DICOM RT format. These tools provide the potential for multi‐institutional stereotactic radiosurgery trials that include participation of the Gamma Knife, Model C.

TH‐C‐352‐03: Introduction and Clinical Use of Electronic Brachytherapy

Electronic Brachytherapy (EBT) is internal radiation therapy that involves placing a miniature x‐ray source inside the patient close to or in the tumor. Recently, one EBT system (Axxent, Xoft Inc., Fremont, CA) has been released for clinical use. Because of its novelty, EBT has been relatively unstudied thus far in the clinical setting and is consequently unfamiliar to many medical physicists. The EBT modality offers several advantages over the Ir‐192 standard of care HDR brachytherapy source. Because of the relatively low energy of the EBT device (50 kV), treatments can be delivered in an unshielded room in contrast to the shielding required for HDR brachytherapy. The low external exposure rate also allows staff to remain near the treatment couch during dose delivery, offering the opportunity to provide comfort and encouragement in close proximity to the patient.As yet, recommendations for the commissioning of an EBT system have not been officially drafted. However, commissioning an EBT system should include tests of well‐chamber constancy, beam stability, source positional accuracy, output stability, timer linearity, dummy marker/source position coincidence, controller functionality and safety interlocks and treatment planning data verification following AAPM TG43 recommendations.Early EBT systems focused on treatment of the breast, using an intracavitary balloon catheter surgically implanted in a lumpectomy excision cavity. In comparison to Ir‐192, the EBT treatment results in a higher dose on the applicator surface, an equivalent distribution over the target region and a lower dose to normal structures around the implant area. Recent FDA clearances will allow the extension of EBT to additional sites, including endometrial applications.This lecture will provide an overview of EBT, a commissioning procedure, and examples of its clinical use.Educational Objectives:1. Gain basic knowledge of EBT as a potential HDR‐alternative treatment modality.2. Understand a proposed commissioning protocol for an EBT system.3. Learn about the current clinical uses for EBT.Conflict of Interest: Partial financial support was provided by Xoft, Inc.

Quality Assurance of Positron Emission Tomography/Computed Tomography for Radiation Therapy

Recent advances in radiation delivery techniques, such as intensity-modulated radiation therapy, provide unprecedented ability to exquisitely control three-dimensional dose distribution. Development of on-board imaging and other image-guidance methods significantly improved our ability to better target a radiation beam to the tumor volume. However, in reality, accurate definition of the location and boundary of the tumor target is still problematic. Biologic and physiologic imaging promises to solve the problem in a fundamental way and has a more and more important role in patient staging, treatment planning, and therapeutic assessment in radiation therapy clinics. The last decade witnessed a dramatic increase in the use of positron emission tomography and computed tomography in radiotherapy practice. To ensure safe and effective use of nuclide imaging, a rigorous quality assurance (QA) protocol of the imaging tools and integration of the imaging data must be in place. The application of nuclide imaging in radiation oncology occurs at different levels of sophistication. Quantitative use of the imaging data in treatment planning through image registration and standardized uptake value calculation is often involved. Thus, QA should not be limited to the performance of the scanner, but should also include the process of implementing image data in treatment planning, such as data transfer, image registration, and quantitation of data for delineation of tumors and sensitive structures. This presentation discusses various aspects of nuclide imaging as applied to radiotherapy and describes the QA procedures necessary for the success of biologic image-guided radiation therapy.

Quality Assurance Issues in Conducting Multi-Institutional Advanced Technology Clinical Trials

The National Cancer Institute-sponsored Advanced Technology Quality Assurance (QA) Consortium, which consisted of the Image-Guided Therapy QA Center, Radiation Therapy Oncology Group, Radiological Physics Center, Quality Assurance Review Center, and Resource Center for Emerging Technologies, has pioneered the development of an infrastructure and QA method for advanced technology clinical trials that requires volumetric digital data submission of a protocol patient's treatment plan and verification data. In particular, the Image-Guided Therapy QA Center has nearly 15 years experience in facilitating QA review for Radiation Therapy Oncology Group advanced technology clinical trials. This QA process includes (1) a data integrity review for completeness of protocol required elements, the format of data, and possible data corruption, and recalculation of dose-volume histograms; (2) a review of compliance with target volume and organ-at-risk contours by study chairs; and (3) a review of dose prescription and dose heterogeneity compliance by the Radiation Therapy Oncology Group Headquarters Dosimetry Group or the Radiological Physics Center dosimetrists (for brachytherapy protocols). This report reviews the lessons learned and the QA challenges presented by the use of advanced treatment modalities in clinical trials requiring volumetric digital data submission.

Proton versus photon radiotherapy for common pediatric brain tumors: Comparison of models of dose characteristics and their relationship to cognitive function

To determine whether proton radiotherapy has clinical advantages over photon radiotherapy, we modeled the dose characteristics of both to critical normal tissue volumes using data from patients with four types of childhood brain tumors. Three-dimensional imaging and treatment planning data, including targeted tumor and normal tissues contours, were acquired for 40 patients, 10 each with optic pathway glioma (OPG), craniopharyngioma (CR), infratentorial ependymoma (EP), or medulloblastoma (MB). Dose-volume data were collected for the entire brain, temporal lobes, cochlea, and hypothalamus from each patient. The data were averaged and compared based on treatment modality (protons vs. photons) using dose-cognitive effects models. Outcomes were estimated over 5 years. Relatively small critical normal tissue volumes such as the cochlea and hypothalamus may be spared from radiation exposure when not adjacent to the primary tumor volume. Larger normal tissue volumes such as the supratentorial brain or temporal lobes receive less of the low and intermediate doses. When applied to longitudinal models of radiation dose-cognitive effects, these differences resulted in clinically significant higher IQ scores for patients with MB and CR and academic reading scores in patients with OPG. Extreme differences between proton and photon dose distributions precluded meaningful comparison of protons and photons for patients with EP. Differences in the overall dose distributions, as indicated by modeling changes in cognitive function, showed that a reduction in the lower-dose volumes or mean dose would have long-term, clinical advantages for children with MB, CR, and OPG.

How does CT image noise affect 3D deformable image registration for image‐guided radiotherapy planning?

To measure the sensitivity of deformable image registration to image noise. Deformable image registration can be used to map organ contours and other treatment planning data from one CT to another. These CT studies can be acquired with either conventional fan-beam CT systems or more novel cone-beam CT techniques. However, cone-beam CT images can have higher noise levels than fan-beam CT, which might reduce registration accuracy. We have investigated the effect of image quality differences on the deformable registration of fan-beam CTs and CTs with simulated cone-beam noise. Our study used three CT studies for each of five prostate patients. Each CT was contoured by three experienced radiation oncologists. For each patient, one CT was designated the source image and the other two were target images. A deformable image registration process was used to register each source CT to each target CT and then transfer the manually drawn treatment planning contours from the source CT to the target CTs. The accuracy of the automatically transferred contours (and thus of the deformable registration process) was assessed by comparing them to the manual contours on the target CTs, with the differences evaluated with respect to interobserver variability in the manual contours. Then each of the target CTs was modified to include increased noise characteristic of cone-beam CT and the tests were repeated. Changes in registration accuracy due to increased noise were detected by monitoring changes in the automatically transferred contours. We found that the additional noise caused no significant loss of registration accuracy at magnitudes that exceeded what would normally be found in an actual cone-beam CT. We conclude that noise levels in cone-beam CTs that might reduce manual contouring accuracy do not reduce image registration and automatic contouring accuracy.

Detailed review and analysis of complex radiotherapy clinical trial planning data: Evaluation and initial experience with the SWAN software system

Contemporary radiotherapy clinical trials typically require complex three-dimensional (3D) treatment planning. This produces large amounts of data relating technique and dose delivery for correlation with patient outcomes. Assessment of the quality of this information is required to ensure protocol compliance, to quantify the variation in treatments given to patients and to enhance the power of studies to determine correlates of patient outcomes. A software system ('SWAN') was developed to facilitate the objective analysis, quality-assurance and review of digital treatment planning data from multi-centre radiotherapy trials. The utility of this system was assessed on the basis of its functionality and our experience of its use in the context of multi-centre clinical trials and trials-support activities. The SWAN system has been shown to have the functionality required for use in several multi-centre trials, including automated review and archive processes. Approximately 800 treatment plans from over 30 participating institutions have so far been assessed with the system for several treatment planning scenarios. To illustrate this we include a description of the use of the system for a large-recruitment prostate radiotherapy trial being undertaken in Australasia, including examples of how the review process has changed clinical practice. The successful implementation of SWAN has been demonstrated in a number of clinical trials. The software provides an opportunity for comprehensive review of treatment parameters that could impact on clinical outcomes and trial results. Such quality-assurance (QA) has previously been difficult or impossible to achieve, particularly for a clinical trial involving large numbers of patients. Such reviews have highlighted inconsistencies in clinical practice that have since been addressed through feedback from the review process. The process of data collection and review should be undertaken by dedicated, experienced and skilled staff in order to ensure efficiency.

A Survey of the ITC Volumetric Treatment Planning Data Archive Supporting RTOG Advanced Technology Clinical Trials

Purpose: Survey of volumetric treatment planning (TP) data, linked to outcomes, collected by the Image-guided Therapy QA Center (ITC) in 15 years of facilitating QA review for RTOG multi-institutional advanced technology (AT) clinical trials. Materials & Methods: The ITC as part of the Advanced Technology QA Consortium (ATC) collects volumetric TP data sets linked to outcomes for RTOG Advanced Technology clinical trials. CT images, target-volume/organ-at-risk contours, and 3D dose distributions exported from commercial TP systems are submitted to the ITC using either DICOM or RTOG Data Exchange format. ITC staff evaluates dataset integrity and completeness, and requests re-submission as needed. DoseVolume Histograms (DVHs) for required volumes are recalculated from submitted contours and dose distributions. RTOG dosimetrists and study chairs review contours and dose distributions for protocol compliance using ITC’s web-based Remote Review Tool (RRT). Clinical outcomes are reported to RTOG headquarters using protocol-specific forms. Results: The ITC has collected over 5000 complete TP data sets quantifying the relationship between image-based anatomy and planned doses. Disease sites treated in the 10 closed protocols (1800 cases) include prostate, lung, brain, head/neck, and breast. An additional 13 active protocols (>3500 cases) also include liver, cervix, and anus. A sample of data sets available for analysis is listed below. (Doses (Gy) and % volumes are the minimum/maximum/average values.) Prostate (3DCRT, N=984; PTV D98: 52.2/81.6/75.0, bladder Dmean: 4.9, 75.9, 37.7, rectum Dmean: 12.9, 72.5, 42.7, femoral heads Dmean: 1.8, 49.5, 32.4), HeadN PTV D98: 58.0/73.4/67.6, spinal cord D2: 32.8/44.8/39.6, parotid Dmean: 21.2/50.3/32.4, larynx Dmean: 3.9/57.7/32.9), Lung (3DCRT, N=158; PTV D98: 50.3/98.2/77.4, spinal cord D2: 0.1/60.1/26.0, esophagus Dmean: 0/63.8/15.9, heart Dmean: 0/45.3/10.5, liver Dmean: 0/19.3/1.2, brachial plexus Dmean: 0/57.7/4.6, lung V20: 5.3/46.6 /21.2 %,). The ITC has provided access to these TP protocol data sets for secondary analysis by: (1) export of entire TP data sets as RTOG data exchange files and (2) online data analysis using the RRT. External investigators have used these data for dose escalation trials in prostate (RTOG 9406) and lung cancer (RTOG 9311) and obtained two NIH R01 grants focused on the development of normal tissue complication probability (NTCP) models. Also, online access to RTOG 9406 TP data has been used to analyze erectile dysfunction following 3DCRT for prostate cancer. Using the contour editing feature in the RRT, penile bulb structures, not originally contoured for RTOG 9406, were delineated on these datasets. New DVHs were computed from the stored 3D dose distributions and compared with reported clinical outcomes (impotence). Such an analysis would have required an entirely new study if the volumetric TP data had not been archived in the ITC database. Conclusion: The ITC archive of volumetric images and dosimetry for RTOG Advanced Technology Clinical Trials is a rich resource for developing and testing models of tissue response to ionizing radiation. The value of this archive continues to grow with the incorporation of new data sets from new anatomical sites, and new imaging modalities. Supported by NIH U24 grant CA81647 and U10 grant CA21661

SU-FF-J-126: An Open-Source Radiotherapy Image Registration Toolkit Integrated with CERR

Purpose: We developed an image registration module for the open‐source system CERR (the computational environment for radiotherapy research) for the purpose of radiation therapyimage guidance quality assurance and image analysis. This new module provides functionality useful for registration algorithm optimization, visualization, analysis, and validation. Method and Materials: We implemented a series of automatic (rigid and deformable) and semi‐automatic image registration methods. We implemented 20+ original and variant deformable methods, including optical flow based methods with different constraints, level set motion based methods and demon based methods. We imported ITK rigid image registration methods into CERR, including affine transform, similarity transform, Euler3D transform, versor3D transform, etc. We also implemented a multi‐grid framework to improve the speed and accuracy of the automatic registration process. In addition, we implemented 3D control point matching methods. We use several similarity metrics, including MSE, cross correlation, MI etc., to quantitatively analyze and validate the registration results. For results visualization, we implemented functions such as difference, dynamic checkerboard, image mirror, deformation field vector and grid plotting, etc. We programmed the GUI in MATLAB and Java, deformable methods in MATLAB and ITK rigid registration methods in C++. Results: The new CERR module supports 3D rigid and deformable registration. By monitoring the registration process and measuring the results, we can optimize the registration methods by tuning the parameters. We tested the deformable methods with chest CT images and the results were satisfied. Conclusion: The goal of this work is to extend the functions of CERR, to provide an open source implementation of image registration algorithms for radiotherapy research. As an ongoing project, we plan to provide more registration methods and further improve the integration of the registration results with treatment planning data.