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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Measurements of isocenter path characteristics of the gantry rotation axis with a smartphone application

Purpose: For stereotactic radiosurgery, the AAPM Report No. 54 [AAPM Task Group 42 (AAPM, 1995)] requires the overall stability of the isocenter (couch, gantry, and collimator) to be within a 1 mm radius. In reality, a rotating system has no rigid axis and thus no isocenter point which is fixed in space. As a consequence, the isocenter concept is reviewed here. It is the aim to develop a measurement method following the revised definitions. Methods: The mechanical isocenter is defined here by the point which rotates on the shortest path in the room coordinate system. The path is labeled as “isocenter path.” Its center of gravity is assumed to be the mechanical isocenter. Following this definition, an image-based and radiation-free measurement method was developed. Multiple marker pairs in a plane perpendicular to the assumed gantry rotation axis of a linear accelerator are imaged with a smartphone application from several rotation angles. Each marker pair represents an independent measuring system. The room coordinates of the isocenter path and the mechanical isocenter are calculated based on the marker coordinates. The presented measurement method is by this means strictly focused on the mechanical isocenter. Results: The measurement result is available virtually immediately following completion of measurement. When 12 independent measurement systems are evaluated, the standard deviations of the isocenter path points and mechanical isocenter coordinates are 0.02 and 0.002 mm, respectively. Conclusions: The measurement is highly accurate, time efficient, and simple to adapt. It is therefore suitable for regular checks of the mechanical isocenter characteristics of the gantry and collimator rotation axis. When the isocenter path is reproducible and its extent is in the range of the needed geometrical accuracy, it should be taken into account in the planning process. This is especially true for stereotactic treatments and radiosurgery.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-76: A Software System to Monitor VMAT Plan Complexity in a Large Radiotherapy Centre

Purpose: To develop a system that analyses and reports the complexity of Volumetric Modulated Arc Therapy (VMAT) plans to aid in the decision making for streamlining patient specific dosimetric quality assurance (QA) tests. Methods: A software system, Delcheck, was developed in-house to calculate VMAT plan and delivery complexity using the treatment delivery file. Delcheck has the functionality to calculate multiple plan complexity metrics including the Li-Xing Modulation Index (LI-MI), multiplicative combination of Leaf Travel and Modulation Complexity Score (LTMCSv), Monitor Units per prescribed dose (MU/D) and the delivery complexity index (MIt) that incorporates the modulation of dose rate, leaf speed and gantry speed. Delcheck includes database functionality to store and compare plan metrics for a specified treatment site. The overall plan and delivery complexity is assessed based on the 95% conformance limit of the complexity metrics as Similar, More or Less complex. The functionality of the software was tested using 42 prostate conventional, 10 prostate SBRT and 15 prostate bed VMAT plans generated for an Elekta linear accelerator. Results: The mean(σ) of LI-MI for conventional, SBRT and prostate bed plans were 1690(486), 3215.4(1294) and 3258(982) respectively. The LTMCSv of the studied categories were 0.334(0.05), 0.325(0.07) and 0.3112(0.09). The MU/D of the studied categories were 2.4(0.4), 2.7(0.7) and 2.5(0.5). The MIt of the studied categories were 21.6(3.4), 18.2(3.0) and 35.9(6.6). The values of the complexity metrics show that LI-MI appeared to resolve the plan complexity better than LTMCSv and MU/D. The MIt value increased as the delivery complexity increased. Conclusion: The developed software was shown to be working as expected. In studied treatment categories Prostate bed plans are more complex in both plan and delivery and SBRT is more complex in plan and less complex in delivery as demonstrated by LI-MI and MIt. This project was funded through a Cancer Council NSW Project Grant (RG14-11)

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

ORNL Neutron Cross-Section Measurements in the Resolved Resonance Range for the NCSP

Nuclear criticality simulations test the quality and the consistency of the existing nuclear evaluated data libraries such as ENDF/B, JEFF, or JENDL. In some cases, the cross-section evaluations of those libraries are found insufficient to describe accurately criticality benchmarks. The US Nuclear Criticality Safety Program (NCSP) collaborates with the Joint Research Center (JRC) in Geel, Belgium, to perform high-resolution neutron-induced cross section measurements at the Geel Linear Accelerator (GELINA) to resolve deficiencies in nuclear data that have been emerging in criticality calculations. Problems with nuclear data include insufficient neutron energy range, missing covariances, and problems with previous experiments. For example, the use of the ENDF/B-VII.1 neutron cross section data for vanadium, cerium and zirconium in nuclear criticality safety calculations shows discrepancies between benchmark calculations measurements and demonstrates the need for reliable covariance data. For new covariances of existing data, a reevaluation of the old cross section data is needed. However, these data are in many cases no longer available. This deficit can be overcome only by obtaining new experimental data to serve as the basis of a new evaluation. Recent measurements were made of the neutron total and capture cross sections of natural vanadium and natural zirconium in the neutron energy range from 100 eV to several hundred keV. These measured data will be used to improve representation of the cross sections since most of the available evaluated data rely on old measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

SU-E-T-807: VMAT Vs. DIMRT Vs. SsIMRT Assessing the Dosimetric Parameters of Cervical Carcinoma Treatment with a 20-Patient Sample

Purpose: The purpose of this study is to assess the dosimetric parameters of cervical carcinoma treatment using 3 different radiation therapy delivery Methods: volumetric-modulated arc therapy (VMAT), the static-field dynamic multileaf collimator intensity-modulated radiation therapy (dIMRT) and the static-field step-and-shoot intensity-modulated radiotherapy (ssIMRT). Methods: Twenty patients with cervical carcinoma were selected to be planned with dual arc VMAT, dIMRT and ssIMRT using Monaco 3.3 TPS on the Axesse™ linear accelerator in this investigation. The total dose of the planning target volume (PTV) is 60Gy. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), delivery efficiency, dose of organs at risks (bladder, rectum, and femoral heads), were all measured. Results: Dose distribution in 3 different radiation therapy delivery methods satisfied clinical requirements. Mean HI of PTV with VMAT, dIMRT and ssIMRT is 1.08, 1.10, and 1.09 (p>0.05). Mean CI of PTV with VMAT, dIMRT and ssIMRT is 0.82, 0.8 and 0.8 (p>0.05). For the DVH of V10, V20 and V30 in bladder, there was a significant difference: VMAT>dIMRT=ssIMRT (p <0.05). For the DVH of V40 and V50, there was a significant difference: VMAT dIMRT >ssIMRT (p <0.05). Conclusion: The results show that VMAT has a great advantage in delivery efficiency than dIMRT and ssIMRT, without compromise to the PTV coverage, HI and CI. The delivery methods should be considered under the actual cervical carcinoma radiotherapy situation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-T-195: Gantry Angle Dependency of MLC Leaf Position Error

Purpose: The aim of this study was to investigate the gantry angle dependency of the multileaf collimator (MLC) leaf position error. Methods: An automatic MLC quality assurance system (AutoMLCQA) was developed to evaluate the gantry angle dependency of the MLC leaf position error using an electronic portal imaging device (EPID). To eliminate the EPID position error due to gantry rotation, we designed a reference maker (RM) that could be inserted into the wedge mount. After setting up the EPID, a reference image was taken of the RM using an open field. Next, an EPID-based picket-fence test (PFT) was performed without the RM. These procedures were repeated at every 45° intervals of the gantry angle. A total of eight reference images and PFT image sets were analyzed using in-house software. The average MLC leaf position error was calculated at five pickets (-10, -5, 0, 5, and 10 cm) in accordance with general PFT guidelines using in-house software. This test was carried out for four linear accelerators. Results: The average MLC leaf position errors were within the set criterion of <1 mm (actual errors ranged from -0.7 to 0.8 mm) for all gantry angles, but significant gantry angle dependency was observed in all machines. The error was smaller at a gantry angle of 0° but increased toward the positive direction with gantry angle increments in the clockwise direction. The error reached a maximum value at a gantry angle of 90° and then gradually decreased until 180°. In the counter-clockwise rotation of the gantry, the same pattern of error was observed but the error increased in the negative direction. Conclusion: The AutoMLCQA system was useful to evaluate the MLC leaf position error for various gantry angles without the EPID position error. The Gantry angle dependency should be considered during MLC leaf position error analysis.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Investigation of conformal and intensity-modulated radiation therapy techniques to determine the absorbed fetal dose in pregnant patients with breast cancer

The aim of this research was to investigate the fetal doses of pregnant patients undergoing conformal radiotherapy or intensity-modulated radiation therapy (IMRT) for breast cancers. An Alderson Rando phantom was chosen to simulate a pregnant patient with breast cancer who is receiving radiation therapy. This phantom was irradiated using the Varian Clinac DBX 600 system (Varian Medical System, Palo Alto, CA) linear accelerator, according to the standard treatment plans of both three-dimensional conformal radiation therapy (3-D CRT) and IMRT techniques. Thermoluminescent dosimeters were used to measure the irradiated phantom's virtually designated uterus area. Thermoluminescent dosimeter measurements (in the phantom) revealed that the mean cumulative fetal dose for 3-D CRT is 1.39 cGy and for IMRT it is 8.48 cGy, for a pregnant breast cancer woman who received radiation treatment of 50 Gy. The fetal dose was confirmed to increase by 70% for 3-D CRT and 40% for IMRT, if it is closer to the irradiated field by 5 cm. The mean fetal dose from 3-D CRT is 1.39 cGy and IMRT is 8.48 cGy, consistent with theoretic calculations. The IMRT technique causes the fetal dose to be 5 times more than that of 3-D CRT. Theoretic knowledge concerning the increase in the peripheral doses as the measurements approached the beam was also practically proven.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2014

WE-A-19A-01: SRT I: Comparison of SRT Techniques

Within the past several years, the field of radiosurgery has seen numerous technological enhancements, including new dedicated devices for stereotactic delivery, the use of re-locatable frames to facilitate fractionated delivery and the image guided frameless approaches. The goal of this symposium is to compare and contrast competing technologies for cranial SRS/SRT. The symposium will open with a review of the general concept of cranial SRS/SRT procedures as well as describe the key differences from conventional radiotherapy. The speakers will then review each of the delivery technique (Gamma Knife, CyberKnife and Conventional linear accelerator) in turn. The focus of each speaker will be to describe the general workflow of each SRS modality, indications and counterindications for treatment. To compare and contrast different technologies, 2–3 cases examples demonstrating interesting treatment situations and expected outcomes, a sample treatment plan (either live or pre-recorded with live commentary) demonstrating the treatment planning technique, and machine and patient-specific QA required for treatment (if applicable). Additionally, workflows and data describing the use of immobilization devices or tracking/monitoring during SRS/SRT delivery will also be discussed. The session will close with a roundtable discussion of methods to evaluate plan quality, and achievable technical and clinical goals for intracranial SRS. Learning Objectives: Understand the key differences between cranial SRS/SRT and conventional treatments. Review Gamma Knife, CyberKnife and Conventional Linac-based radiosurgery delivery techniques and quality assurance Compare and contrast treatment plans, treatment planning strategy and and quality assurance procedures for each technology. Be able to establish cranial SRS/SRT procedure with optimized quality assurance program for each technology.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-754: Three-Dimensional Patient Modeling Using Photogrammetry for Collision Avoidance

Purpose: To evaluate photogrammetry for creating a three-dimensional patient model. Methods: A mannequin was configured on the couch of a CT scanner to simulate a patient setup using an indexed positioning device. A CT fiducial was placed on the indexed CT table-overlay at the reference index position. Two dimensional photogrammetry targets were placed on the table in known positions. A digital SLR camera was used to obtain 27 images from different positions around the CT table. The images were imported into a commercial photogrammetry package and a 3D model constructed. Each photogrammetry target was identified on 2 to 5 images. The CT DICOM metadata and the position of the CT fiducial were used to calculate the coordinates of the photogrammetry targets in the CT image frame of reference. The coordinates were transferred to the photogrammetry software to orient the 3D model. The mannequin setup was transferred to the treatment couch of a linear accelerator and positioned at isocenter using in-room lasers. The treatment couch coordinates were noted and compared with prediction. The collision free regions were measured over the full range of gantry and table motion and were compared with predictions obtained using a general purpose polygon interference algorithm. Results: The reconstructed 3D model consisted of 180000 triangles. The difference between the predicted and measured couch positions were 5 mm, 1 mm, and 1 mm for longitudinal, lateral, and vertical, respectively. The collision prediction tested 64620 gantry table combinations in 11.1 seconds. The accuracy was 96.5%, with false positive and negative results occurring at the boundaries of the collision space. Conclusion: Photogrammetry can be used as a tool for collision avoidance during treatment planning. The results indicate that a buffer zone is necessary to avoid false negatives at the boundary of the collision-free zone. Testing with human patients is underway. Research partially supported by a grant from Varian Medical Systems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

The use of RapidArc volumetric-modulated arc therapy to deliver stereotactic radiosurgery and stereotactic body radiotherapy to intracranial and extracranial targets

Twenty-three targets in 16 patients treated with stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) were analyzed in terms of dosimetric homogeneity, target conformity, organ-at-risk (OAR) sparing, monitor unit (MU) usage, and beam-on time per fraction using RapidArc volumetric-modulated arc therapy (VMAT) vs. multifield sliding-window intensity-modulated radiation therapy (IMRT). Patients underwent computed tomography simulation with site-specific immobilization. Magnetic resonance imaging fusion and optical tracking were incorporated as clinically indicated. Treatment planning was performed using Eclipse v8.6 to generate sliding-window IMRT and 1-arc and 2-arc RapidArc plans. Dosimetric parameters used for target analysis were RTOG conformity index (CI{sub RTOG}), homogeneity index (HI{sub RTOG}), inverse Paddick Conformity Index (PCI), D{sub mean} and D5-D95. OAR sparing was analyzed in terms of D{sub max} and D{sub mean}. Treatment delivery was evaluated based on measured beam-on times delivered on a Varian Trilogy linear accelerator and recorded MU values. Dosimetric conformity, homogeneity, and OAR sparing were comparable between IMRT, 1-arc RapidArc and 2-arc RapidArc plans. Mean beam-on times {+-} SD for IMRT and 1-arc and 2-arc treatments were 10.5 {+-} 7.3, 2.6 {+-} 1.6, and 3.0 {+-} 1.1 minutes, respectively. Mean MUs were 3041, 1774, and 1676 for IMRT, 1-, and 2-arc plans, respectively. Although dosimetric conformity, homogeneity, and OAR sparing were similar between these techniques, SRS and SBRT fractions treated with RapidArc were delivered with substantially less beam-on time and fewer MUs than IMRT. The rapid delivery of SRS and SBRT with RapidArc improved workflow on the linac with these otherwise time-consuming treatments and limited the potential for intrafraction organ and patient motion, which can cause significant dosimetric errors. These clinically important advantages make image-guided RapidArc useful in the delivery of SRS and SBRT to intracranial and extracranial targets.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston

Purpose: To compare radiation machine measurement data collected by the Imaging and Radiation Oncology Core at Houston (IROC-H) with institutional treatment planning system (TPS) values, to identify parameters with large differences in agreement; the findings will help institutions focus their efforts to improve the accuracy of their TPS models. Methods and Materials: Between 2000 and 2014, IROC-H visited more than 250 institutions and conducted independent measurements of machine dosimetric data points, including percentage depth dose, output factors, off-axis factors, multileaf collimator small fields, and wedge data. We compared these data with the institutional TPS values for the same points by energy, class, and parameter to identify differences and similarities using criteria involving both the medians and standard deviations for Varian linear accelerators. Distributions of differences between machine measurements and institutional TPS values were generated for basic dosimetric parameters. Results: On average, intensity modulated radiation therapy–style and stereotactic body radiation therapy–style output factors and upper physical wedge output factors were the most problematic. Percentage depth dose, jaw output factors, and enhanced dynamic wedge output factors agreed best between the IROC-H measurements and the TPS values. Although small differences were shown between 2 common TPS systems, neither was superior to the other. Parameter agreement was constant over time from 2000 to 2014. Conclusions: Differences in basic dosimetric parameters between machine measurements and TPS values vary widely depending on the parameter, although agreement does not seem to vary by TPS and has not changed over time. Intensity modulated radiation therapy–style output factors, stereotactic body radiation therapy–style output factors, and upper physical wedge output factors had the largest disagreement and should be carefully modeled to ensure accuracy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Real-time soft tissue motion estimation for lung tumors during radiotherapy delivery

Purpose: To provide real-time lung tumor motion estimation during radiotherapy treatment delivery without the need for implanted fiducial markers or additional imaging dose to the patient.Methods: 2D radiographs from the therapy beam's-eye-view (BEV) perspective are captured at a frame rate of 12.8 Hz with a frame grabber allowing direct RAM access to the image buffer. An in-house developed real-time soft tissue localization algorithm is utilized to calculate soft tissue displacement from these images in real-time. The system is tested with a Varian TX linear accelerator and an AS-1000 amorphous silicon electronic portal imaging device operating at a resolution of 512 × 384 pixels. The accuracy of the motion estimation is verified with a dynamic motion phantom. Clinical accuracy was tested on lung SBRT images acquired at 2 fps.Results: Real-time lung tumor motion estimation from BEV images without fiducial markers is successfully demonstrated. For the phantom study, a mean tracking error <1.0 mm [root mean square (rms) error of 0.3 mm] was observed. The tracking rms accuracy on BEV images from a lung SBRT patient (≈20 mm tumor motion range) is 1.0 mm.Conclusions: The authors demonstrate for the first time real-time markerless lung tumor motion estimation from BEV images alone. The described system can operate at a frame rate of 12.8 Hz and does not require prior knowledge to establish traceable landmarks for tracking on the fly. The authors show that the geometric accuracy is similar to (or better than) previously published markerless algorithms not operating in real-time.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Measurement of ( n, γ ) cross section of 90 Zr [Abstract]

The isotopes of Zr with A = [90, 91, 92, 94] make up more than 97% of naturally occurring Zr and are important to many nuclear applications such as nuclear reactors. One of the attractive qualities of naturally occurring Zr isotopes is that they have a low σγ/σt ratio at most neutron energies, such that they improve the neutron economy in reactors by preferentially scattering neutrons rather than absorbing them. This same quality also presents a challenge to measuring the capture cross section, σγ, of Zr isotopes. The ENDF/B-VIII.0 library has a relative uncertainty of approximately 10-20% for incident neutron energies < 0.1 MeV, and uncertainty greater than 20% for energies > 0.1 MeV for the majority of natural Zr isotopes. This motivated the Nuclear Criticality Safety Program (NCSP) to embark on a campaign to accurately measure and evaluate these isotopes of Zr. Here we will show energy-dependent neutron capture cross section measurements for the first enriched sample to be measured: 90 Zr. The measurements of isotopically enriched samples are being carried out at the Geel Electron Linear Accelerator (GELINA) facility of the Joint Research Center - Geel (JRC-Geel) of the European Union. As isotopic enrichment is a costly process we are careful not to activate any of the samples, as this may hinder future radiation-sensitive measurements. The activation analysis is presented in a report by Brown et al.. Once we were satisfied that the Zr samples would not be activated by the measurements, the 90 Zr sample was fabricated at Oak Ridge National Laboratory (ORNL) and shipped to GELINA. The dimensions of the cylindrical sample are approximately 0.12 cm thick and a radius of 2.5 cm. Since 90 Zr is not chemically reactive to air, bare metallic samples were employed. The sample was measured at a flight path (FP) length of 60 m, using four C 6 D 6 detectors on FP14. The final paper will include experimental details and measured cross section data for 90 Zr compared to current evaluated nuclear data libraries.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

SU-E-T-199: Comparison Between Acuros XB and AAA in Homogeneous Phantoms for Volumetric Modulated Arc Therapy Plans

Purpose: To investigate the differences among Acuros XB (AXB) with dose-to-water report mode (AXBw), AXB with dose-to-medium report mode (AXBm) and Anisotropic Analytical Algorithm (AAA), in homogeneous phantoms and for volumetric modulated arc therapy (VMAT) plans. Methods: Nineteen clinically applied VMAT plans were transplanted to a Delta4 phantom and an I’mRT phantom to generate phantom plans, respectively. Each plan was calculated using AXBw, AXBm and AAA, respectively, utilizing the distributed calculation framework (DCF), and the calculation times were recorded. Each plan was delivered by the TrueBeam linear accelerator and measured using the Delta4 phantom and ionization chamber, respectively. The 3D gamma pass rates and point dose deviations were compared among AXBw, AXBm and AAA. Results: In terms of the gamma pass rates with both the criteria of 3 mm/3% (3 mm distance-to-agreement, 3% dose difference) and 2 mm/2%, AXBm demonstrated the significantly worst results, and no significant difference was found between AXBw and AAA. In terms of the point dose, AXBw was slightly closer to the measured dose compared with AAA, and AXBm demonstrated the maximum dose deviation from the measured dose. Moreover, AXB calculation consumed comparable time when the DCF was not busy, and consumed significantly less time when the DCF was busy. Conclusion: In the homogeneous phantoms and for the VMAT plans, AXBw has the best dose accuracy, and AAA is comparable to or slightly worse than AXBw, wheras AXBm has the worst dose accuracy. Furthermore, AXB has higher calculation efficiency than AAA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

WE-FG-202-06: The Use of Hybrid PET MRI for Identifying the Presence of Cardiac Inflammation Following External Beam Irradiation

Purpose: To monitor the evolution of radiation-induced cardiac inflammation in a canine model using hybrid positron emission tomography (PET/magnetic resonance imaging (MRI). Methods: Research ethics approval was obtained for a longitudinal imaging study of 5 canines after cardiac irradiation. Animals were imaged at baseline, 3 months, 6 months, and 12 months post cardiac irradiation using a hybrid PET-MRI system (Biograph mMR, Siemens Healthcare). The imaging protocol was designed to assess changes in cardiac inflammation using {sup 18}F-fluorodeoxyglucose ({sup 18}F-FDG) PET tracer. In order to image cardiac inflammation, the normal myocardial uptake of glucose was suppressed prior to the injection of {sup 18}F-FDG. The suppression of glycolysis was achieved through; fasting (16–21 hours prior to the start of imaging) and an intravenous injection of heparin immediately followed by a 20% lipid infusion 20 min prior to the injection of {sup 18}F-FDG. The standard uptake value (SUV) obtained from 17 myocardial regions were used to compare FDG scans. All animals received a simulation CT scan (GE Medical Systems) for radiation treatment planning. Radiation treatment plans were created using the Pinncale3 treatment planning system (Philips Radiation Oncology Systems) and designed to resemble the typical cardiac exposure during left-sided breast cancer radiotherapy. Cardiac irradiations were performed in a single fraction using a TrueBeam linear accelerator (Varian Medical Systems). Results: The delivered dose (mean ± standard error) to heart, left ventricle, and left anterior descending artery were 1.7±0.1 Gy, 2.7±0.1 Gy, and 5.5±0.3 Gy respectively. At these doses, a significant increase in {sup 18}F-FDG uptake within the entire heart relative to baseline (1.1±0.02 g/ml) uptake was observed. {sup 18}F-FDG uptake at 3 months, 6 months, and 12 months post irradiation were 1.8±0.03 g/ml, 2.4±0.06 g/ml, and 2.6±0.11 g/ml respectively. Conclusion: Low doses of limited cardiac irradiation show evidence of a persistent global inflammatory response that can be detected using {sup 18}F-FDG PET imaging. This work was supported through the Translational Breast Cancer Studentship award, funded in part by the Breast Cancer Society of Canada. Additional financial support is provided by the London Regional Cancer Program Catalyst Grant and the Thames Valley Veterinary Services.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Use of volumetric-modulated arc therapy for treatment of Hodgkin lymphoma

To evaluate volumetric-modulated arc therapy (VMAT) for treatment of Hodgkin lymphoma (HL) in patients where conventional radiotherapy was not deliverable. A planning computed tomography (CT) scan was acquired for a twelve-year-old boy with Stage IIIB nodular sclerosing HL postchemotherapy with positive positron emission tomography scan. VMAT was used for Phase 1 (19.8 Gy in 11 fractions) and Phase 2 (10.8 Gy in 6 fractions) treatment plans. Single anticlockwise arc plans were constructed using SmartArc (Philips Radiation Oncology Systems, Fitchburg, WI) with control points spaced at 4°. The inverse-planning objectives were to uniformly irradiate the planning target volume (PTV) with the prescription dose while keeping the volume of lung receiving greater than 20 Gy (V{sub 20} {sub Gy}) to less than 30% and minimize the dose to the other adjacent organs at risk (OAR). Pretreatment verification was conducted and the treatment delivery was on an MLCi Synergy linear accelerator (Elekta Ltd, Crawley, UK). The planning results were retrospectively confirmed in a further 4 patients using a single PTV with a prescribed dose of 19.8 Gy in 11 fractions. Acceptable dose coverage and homogeneity were achieved for both Phase 1 and 2 plans while keeping the lung V{sub 20} {sub Gy} at 22.5% for the composite plan. The beam-on times for Phase 1 and Phase 2 plans were 109 and 200 seconds, respectively, and the total monitor units were 337.2 MU and 292.5 MU, respectively. The percentage of measured dose points within 3% and 3 mm for Phase 1 and Phase 2 were 92% and 98%, respectively. Both plans were delivered successfully. The retrospective planning study showed that VMAT improved PTV dose uniformity and reduced the irradiated volume of heart and lung, although the volume of lung irradiated to low doses increased. Two-phased VMAT offers an attractive option for large volume sites, such as HL, giving a high level of target coverage and significant OAR sparing together with efficient delivery.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2014

TU-F-BRE-07: In Vivo Neutron Detection in Patients Undergoing Stereotactic Ablative Radiotherapy (SABR) for Primary Kidney Cancer Using 6Li and 7Li Enriched TLD Pairs

Purpose: Stereotactic ablative radiotherapy (SABR) for primary kidney cancer often involves the use of high-energy photons combined with a large number of monitor units. While important for risk assessment, the additional neutron dose to untargeted healthy tissue is not accounted for in treatment planning. This work aims to detect out-of-field neutrons in vivo for patients undergoing SABR with high-energy (>10 MV) photons and provides preliminary estimates of neutron effective dose. Methods: 3 variations of high-sensitivity LiF:Mg,Cu,P thermoluminescent dosimeter (TLD) material, each with varying {sup 6}Li / {sup 7}Li concentrations, were used in custom-made Perspex holders for in vivo measurements. The variation in cross section for thermal neutrons between Li isotopes was exploited to distinguish neutron from photon signal. Measurements were made out-of-field for 7 patients, each undergoing 3D-conformal SABR treatment for primary kidney cancer on a Varian 21iX linear accelerator. Results: In vivo measurements show increased signal for the {sup 6}Li enriched material for patients treated with 18 MV photons. Measurements on one SABR patient treated using only 6 MV showed no difference between the 3 TLD materials. The out-of-field photon signal decreased exponentially with distance from the treatment field. The neutron signal, taken as the difference between {sup 6}Li enriched and {sup 7}Li enriched TLD response, remains almost constant up to 50 cm from the beam central axis. Estimates of neutron effective dose from preliminary TLD calibration suggest between 10 and 30 mSv per 1000 MU delivered at 18 MV for the 7 patients. Conclusion: TLD was proven to be a useful tool for the purpose of in vivo neutron detection at out-of-field locations. Further work is required to understand the relationship between TL signal and neutron dose. Dose estimates based on preliminary TLD calibration in a neutron beam suggest the additional neutron dose was <30 mSv per 1000 MU at 18 MV.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

WE-AB-BRB-06: A Temperature Independent Plastic Scintillation Detector Capable of Simultaneous Dose and Temperature Measurement

Purpose: To evaluate a measurement method that renders plastic scintillation detectors temperature independent and capable of recovering dose and temperature information simultaneously. Methods: A novel approach was developed to account for the temperature dependence of plastic scintillation detectors (PSDs) without prior knowledge of the temperature. To enable this, the optical response of the scintillating element is separated into two sub-components, one being the response at a given temperature and the other accounting for the change in the optical emission spectrum with temperature. Using a previously demonstrated hyperspectral approach and following the proper calibration protocol, the contribution to scintillator emission and physical value of both dose and temperature can be obtained in real-time. To validate the method, dose and temperature were measured under cobalt irradiation in a temperature controlled water tank developed for this study. The temperature was varied from 22°C to 42°C. Depth-dose curves were also obtained during irradiations from a linear accelerator, first maintaining the water at room temperature and then warming it to 40°C and letting it cool down naturally over the course of the second measurement. Results: Dose measurements delivered with the Co-60 unit showed an average relative difference to the expected value of (1.0±0.8)%, with a maximum difference of 2.3% over the entire range of temperatures. The measured temperatures using the PSD were all within 1°C of the expected values. The difference between room temperature and warmer depth dose measurements differed by only (1.2±0.4)%. The dosimeter showed to be accurate for temporal resolution down to 0.1s. Conclusion: The proposed method was shown to reliably correct for the temperature dependence of a PSD. Additionally, it makes it possible to assess the temperature at the point of measurement. These are significant advances in PSD technology, particularly in relation to real-time in vivo dosimetry. Part of this research was supported by the Odyssey Program at The University of Texas MD Anderson Cancer Center.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-J-02: 4D Digital Tomosynthesis Based On Algebraic Image Reconstruction and Total-Variation Minimization for the Improvement of Image Quality

Purpose: In this paper, we implemented the four-dimensional (4D) digital tomosynthesis (DTS) imaging based on algebraic image reconstruction technique and total-variation minimization method in order to compensate the undersampled projection data and improve the image quality. Methods: The projection data were acquired as supposed the cone-beam computed tomography system in linear accelerator by the Monte Carlo simulation and the in-house 4D digital phantom generation program. We performed 4D DTS based upon simultaneous algebraic reconstruction technique (SART) among the iterative image reconstruction technique and total-variation minimization method (TVMM). To verify the effectiveness of this reconstruction algorithm, we performed systematic simulation studies to investigate the imaging performance. Results: The 4D DTS algorithm based upon the SART and TVMM seems to give better results than that based upon the existing method, or filtered-backprojection. Conclusion: The advanced image reconstruction algorithm for the 4D DTS would be useful to validate each intra-fraction motion during radiation therapy. In addition, it will be possible to give advantage to real-time imaging for the adaptive radiation therapy. This research was supported by Leading Foreign Research Institute Recruitment Program (Grant No.2009-00420) and Basic Atomic Energy Research Institute (BAERI); (Grant No. 2009-0078390) through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP)

62 RADIOLOGY AND NUCLEAR MEDICINE↗