bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐C‐BRA‐07: Virtual Bronchoscopy‐Guided IMRT Planning for Mapping and Avoiding Radiation Injury to the Airway Tree in Lung SAbR
Authors: Sawant A , Modiri A , Bland R , Yan Y , Ahn C , Timmerman R 
Published: June 2015

Purpose:Post‐treatment radiation injury to central and peripheral airways is a potentially important, yet under‐investigated determinant of toxicity in lung stereotactic ablative radiotherapy (SAbR). We integrate virtual bronchoscopy technology into the radiotherapy planning process to spatially map and quantify the radiosensitivity of bronchial segments, and propose novel IMRT planning that limits airway dose through non‐isotropic intermediate‐ and low‐dose spillage.Methods:Pre‐ and ∼8.5 months post‐SAbR diagnostic‐quality CT scans were retrospectively collected from six NSCLC patients (50–60Gy in 3–5 fractions). From each scan, ∼5 branching levels of the bronchial tree were segmented using LungPoint, a virtual bronchoscopic navigation system. The pre‐SAbR CT and the segmented bronchial tree were imported into the Eclipse treatment planning system and deformably registered to the planning CT. The five‐fraction equivalent dose from the clinically‐delivered plan was calculated for each segment using the Universal Survival Curve model. The pre‐ and post‐SAbR CTs were used to evaluate radiation‐induced segmental collapse. Two of six patients exhibited significant segmental collapse with associated atelectasis and fibrosis, and were re‐planned using IMRT.Results:Multivariate stepwise logistic regression over six patients (81 segments) showed that D0.01cc (minimum point dose within the 0.01cc receiving highest dose) was a significant independent factor associated with collapse (odds‐ratio=1.17, p=0.010). The D0.01cc threshold for collapse was 57Gy, above which, collapse rate was 45%. In the two patients exhibiting segmental collapse, 22 out of 32 segments showed D0.01cc >57Gy. IMRT re‐planning reduced D0.01cc below 57Gy in 15 of the 22 segments (68%) while simultaneously achieving the original clinical plan objectives for PTV coverage and OAR‐sparing.Conclusion:Our results indicate that the administration of lung SAbR can Result in significant injury to bronchial segments, potentially impairing post‐SAbR lung function. To our knowledge, this is the first investigation of functional avoidance based on mapping and minimizing dose to individual bronchial segments.The presenting author receives research funding from Varian Medical Systems, Elekta, and VisionRT.
SU‐C‐303‐01: Activation‐Induced Cytidine Deaminase Confers Cancer Resistance to Radiation Therapy
Authors: Yi S , La Count S , Liu J , Bai X , Lu L 
Published: June 2015

Purpose:To study the role of activation‐induced cytidine deaminase (AID) in malignant cell resistance to radiation therapy.Methods:We first developed several small devices that could be used to adopt radiation beams from clinical high dose rate brachy therapy (HDR) or linac‐based megavoltage machines to perform pre‐clinical cell and mouse experiments. Then we used these devices to deliver radiation to AID‐positive and AID‐silenced cancer cells or tumors formed by these cells in mice. Cells and mice bearing tumors received the same dose under the same experimental conditions. For cells, we observed the apoptosis and the cell survival rate over time. For mice bearing tumors, we measured and recorded the tumor sizes every other day for 4 weeks.Results:For cell experiments, we found that the AID‐positive cells underwent much less apoptosis compared with AID‐silenced cells upon radiation. And for mouse experiments, we found that AID‐positive tumors grew significantly faster than the AID‐silenced tumors despite of receiving the same doses of radiation.Conclusion:Our study suggests that AID may confer cancer resistance to radiation therapy, and AID may be a significant biomarker predicting cancer resistance to radiation therapy for certain cancer types
SU‐C‐303‐03: Dosimetric Model of the Beagle Needed for Pre‐Clinical Testing of Radiopharmaceuticals
Authors: Shang M , Sands M , Bolch W 
Published: June 2015

Purpose:Large animal models, most popularly beagles, have been crucial surrogates to humans in determining radiation safety levels of radiopharmaceuticals. This study aims to develop a detailed beagle phantom to accurately approximate organ absorbed doses for therapy nuclear medicine preclinical studies.Methods:A 3D NURBS model was created subordinate to a whole body CT of an adult beagle. Bones were harvested and CT imaged to offer macroscopic skeletal detail. Samples of trabecular spongiosa were cored and imaged to offer microscopic skeletal detail for bone trabeculae and marrow volume fractions.Results:Organ masses in the model are typical of an adult beagle. Trends in volume fractions for skeletal dosimetry are fundamentally similar to those found in existing models of other canine species.Conclusion:This work warrants its use in further investigations of radiation transport calculation for electron and photon dosimetry. This model accurately represents the anatomy of a beagle, and can be directly translated into a useable geometry for a voxel‐based Monte Carlo radiation transport program such as MCNP6.Work supported by a grant from the Hyundai Hope on Wheels Foundation for Pediatric Cancer Research.
SU‐C‐303‐04: Evaluation of On‐ and Off‐Line Bioluminescence Tomography System for Focal Irradiation Guidance
Authors: Zhang B , Wang K , Iordachita I , Reyes J , Tran P , Wong J 
Published: June 2015

Purpose:We have developed offline and on‐board bioluminescence tomography(BLT) systems for the small animal radiation research platform(SARRP) for radiation guidance of soft tissue targets. We investigated the effectiveness of offline BLT guidance.Methods:CBCT is equipped on both the offline BLT system and SARRP that are 10 ft. apart. To evaluate the setup error during animal transport between the two systems, we implanted a luminescence source in the abdomen of anesthetized mice. Five mice were studied. After CBCT was acquired on both systems, source centers and correlation coefficients were calculated. CBCT was also used to generate object mesh for BLT reconstruction. To assess target localization, we compared the localization of the luminescence source based on (1)on‐board SARRP BLT and CBCT, (2)offline BLT and CBCT, and (3)offline BLT and SARRP CBCT. The 3rd comparison examines if an offline BLT system can be used to guide radiation when there is minimal target contrast in CBCT.Results:Our CBCT results show the offset of the light source center can be maintained within 0.2 mm during animal transport. The center of mass(CoM) of the light source reconstructed by the offline BLT has an offset of 1.0 ± 0.4 mm from the ‘true’ CoM as derived from the SARRP CBCT. The results compare well with the offset of 1.0 ± 0.2 mm using on‐line BLT.Conclusion:With CBCT information provided by the SARRP and effective animal immobilization during transport, these findings support the use of offline BLT in close vicinity for accurate soft tissue target localization for irradiation. However, the disadvantage of the off‐line system is reduced efficiency as care is required to maintain stable animal transport. We envisage a dual use system where the on‐board arrangement allows convenient access to CBCT and avoids disturbance of animal setup. The off‐line capability would support standalone longitudinal imaging studies.The work is supported by NIH R01CA158100 and Xstrahl Ltd. Drs. John Wong and Iulian Iordachita receive royalty payment from a licensing agreement between Xstrahl Ltd and Johns Hopkins University. John Wong also has a consultant agreement with Xstrahl Ltd.
SU‐C‐204‐01: A Fast Analytical Approach for Prompt Gamma and PET Predictions in a TPS for Proton Range Verification
Authors: Kroniger K , Herzog M , Landry G , Traneus E , Dedes G , Parodi K 
Published: June 2015

Purpose:We describe and demonstrate a fast analytical tool for prompt‐gamma emission prediction based on filter functions applied on the depth dose profile. We present the implementation in a treatment planning system (TPS) of the same algorithm for positron emitter distributions.Methods:The prediction of the desired observable is based on the convolution of filter functions with the depth dose profile. For both prompt‐gammas and positron emitters, the results of Monte Carlo simulations (MC) are compared with those of the analytical tool. For prompt‐gamma emission from inelastic proton‐induced reactions, homogeneous and inhomogeneous phantoms alongside with patient data are used as irradiation targets of mono‐energetic proton pencil beams. The accuracy of the tool is assessed in terms of the shape of the analytically calculated depth profiles and their absolute yields, compared to MC. For the positron emitters, the method is implemented in a research RayStation TPS and compared to MC predictions. Digital phantoms and patient data are used and positron emitter spatial density distributions are analyzed.Results:Calculated prompt‐gamma profiles agree with MC within 3 % in terms of absolute yield and reproduce the correct shape. Based on an arbitrary reference material and by means of 6 filter functions (one per chemical element), profiles in any other material composed of those elements can be predicted. The TPS implemented algorithm is accurate enough to enable, via the analytically calculated positron emitters profiles, detection of range differences between the TPS and MC with errors of the order of 1–2 mm.Conclusion:The proposed analytical method predicts prompt‐gamma and positron emitter profiles which generally agree with the distributions obtained by a full MC. The implementation of the tool in a TPS shows that reliable profiles can be obtained directly from the dose calculated by the TPS, without the need of full MC simulation.
SU‐C‐204‐02: Improved Patient‐Specific Optimization of the Stopping Power Calibration for Proton Therapy Planning Using a Single Proton Radiography
Authors: Rinaldi I , Parodi K , Krah N 
Published: June 2015

Purpose:We present an improved method to calculate patient‐specific calibration curves to convert X‐ray computed tomography (CT) Hounsfield Unit (HU) to relative stopping powers (RSP) for proton therapy treatment planning.Methods:By optimizing the HU‐RSP calibration curve, the difference between a proton radiographic image and a digitally reconstructed X‐ray radiography (DRR) is minimized. The feasibility of this approach has previously been demonstrated. This scenario assumes that all discrepancies between proton radiography and DRR originate from uncertainties in the HU‐RSP curve. In reality, external factors cause imperfections in the proton radiography, such as misalignment compared to the DRR and unfaithful representation of geometric structures (“blurring”). We analyze these effects based on synthetic datasets of anthropomorphic phantoms and suggest an extended optimization scheme which explicitly accounts for these effects. Performance of the method is been tested for various simulated irradiation parameters. The ultimate purpose of the optimization is to minimize uncertainties in the HU‐RSP calibration curve. We therefore suggest and perform a thorough statistical treatment to quantify the accuracy of the optimized HU‐RSP curve.Results:We demonstrate that without extending the optimization scheme, spatial blurring (equivalent to FWHM=3mm convolution) in the proton radiographies can cause up to 10% deviation between the optimized and the ground truth HU‐RSP calibration curve. Instead, results obtained with our extended method reach 1% or better correspondence. We have further calculated gamma index maps for different acceptance levels. With DTA=0.5mm and RD=0.5%, a passing ratio of 100% is obtained with the extended method, while an optimization neglecting effects of spatial blurring only reach ∼90%.Conclusion:Our contribution underlines the potential of a single proton radiography to generate a patient‐specific calibration curve and to improve dose delivery by optimizing the HU‐RSP calibration curve as long as all sources of systematic incongruence are properly modeled.
SU‐C‐204‐03: In‐Vivo Range Verification and Tissue Response to Proton Radiotherapy Using Prompt Gamma Volume Histograms
Authors: Polf J , Lin M 
Published: June 2015

Purpose:To study if prompt gamma (PG) volume histograms created from PG images acquired during treatment delivery can be used to identify changes to beam range and tissue composition in response to proton radiotherapy.Methods:Monte Carlo simulations of a single field from a single treatment fraction (100 cGy) for prostate cancer were performed for the cases of: 1) an ideal patient setup, 1) a setup shift in the superior direction and 2) a reduction in oxygen concentration in the tumor. For each case, the 3 ‐Dimsional dose delivery and elemental PG emission in the patient for the treatment fraction were recorded and imported into a commercial treatment planning system. Changes in the dose volume histograms (DVH), as well as the PG volume histograms (PG‐VH) for the PG emission from oxygen and for the total PG emission (from all elements) were analyzed.Results:For the 1 cm superior shift, the prostate DVH and total PG‐VH both shifted toward lower doses with the shape of the curves remaining nearly unchanged, resulting in the DVH V95 dropping from 100 cGy to 90 cGy. For the total PG‐VH, the V95 fell from 50 to 38. For the reduced oxygen case, both the DVH and PG‐VH had a much different shape than for the ideal case, with a significant downward slope in the curves as a function of dose.Conclusions:The shift in the prostate PG‐VH for a superior shift in the patient setup correlated well with the DVH indicating it is possible to detect setup errors by analyzing the PG‐VH from prompt gamma images obtained during daily proton treatment delivery. Additionally, it may be possible to detect changes in the elemental concentrations of irradiated tissues by analyzing the shape of the PG‐VH.
SU‐C‐207‐01: Four‐Dimensional Inverse Geometry Computed Tomography: Concept and Its Validation
Authors: Kim K , Kim D , Kim T , Kang S , Cho M , Shin D , Suh T 
Published: June 2015

Purpose:In past few years, the inverse geometry computed tomography (IGCT) system has been developed to overcome shortcomings of a conventional computed tomography (CT) system such as scatter problem induced from large detector size and cone‐beam artifact. In this study, we intend to present a concept of a four‐dimensional (4D) IGCT system that has positive aspects above all with temporal resolution for dynamic studies and reduction of motion artifact.Methods:Contrary to conventional CT system, projection data at a certain angle in IGCT was a group of fractionated narrow cone‐beam projection data, projection group (PG), acquired from multi‐source array which have extremely short time gap of sequential operation between each of sources. At this, for 4D IGCT imaging, time‐related data acquisition parameters were determined by combining multi‐source scanning time for collecting one PG with conventional 4D CBCT data acquisition sequence. Over a gantry rotation, acquired PGs from multi‐source array were tagged time and angle for 4D image reconstruction. Acquired PGs were sorted into 10 phase and image reconstructions were independently performed at each phase. Image reconstruction algorithm based upon filtered‐backprojection was used in this study.Results:The 4D IGCT had uniform image without cone‐beam artifact on the contrary to 4D CBCT image. In addition, the 4D IGCT images of each phase had no significant artifact induced from motion compared with 3D CT.Conclusion:The 4D IGCT image seems to give relatively accurate dynamic information of patient anatomy based on the results were more endurable than 3D CT about motion artifact. From this, it will be useful for dynamic study and respiratory‐correlated radiation therapy.This work was supported by the Industrial R&D program of MOTIE/KEIT [10048997, Development of the core technology for integrated therapy devices based on real‐time MRI guided tumor tracking] and the Mid‐career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐C‐201‐01: Investigation of the Effects of Scintillator Surface Treatment On Light Output Measurements with SiPM Detectors
Authors: Valenciaga Y , Prout D , Chatziioannou A 
Published: June 2015

Purpose:To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM).Methods:Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light produced by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital‐SiPM sensor (DPC‐3200).Results:The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face.Conclusion:This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors.
SU‐D‐204‐07: Comparison of AAPM TG150 Draft Image Receptor Tests with Vendor Automated QC Tests for Five Mobile DR Units
Authors: Li G , Greene T , Nishino T , Willis C 
Published: June 2015

Purpose:To determine the consistency of digital detector (DR) tests recommended by AAPM TG150 and tests provided by commercially available DirectView Total Quality Tool (TQT).Methods:The DR tests recommended by the TG150 Detector Subgroup[1] were performed on 4 new Carestream DRX‐Revolution and one Carestream DRX1C retrofit of a GE AMX‐4 that had been in service for three years. After detector calibration, flat‐field images plus images of two bar patterns oriented parallel and perpendicular to the A‐C axis, were acquired at conditions recommended by TG150. Raw images were harvested and then analyzed using a MATLAB software previously validated[2,3,4]. Data were analyzed using ROIs of two different dimensions: 1) 128 × 128 ROIs matching the detector electronics; and 2) 256 × 256 ROIs, each including 4 adjacent smaller ROIs. TG150 metrics from 128 × 128 ROIs were compared to TQT metrics, which are also obtained from 128 × 128 ROIs[5].Results:The results show that both TG150 and TQT measurements were consistent among these detectors. Differences between TG150 and TQT values appear systematic. Compared with 128 × 128 ROIs, noise and SNR non‐uniformity were lower with 256 × 256 ROIs, although signal non‐uniformity was similar, indicating detectors were appropriately calibrated for gain and offset. MTF of the retrofit unit remained essentially the same between 2012 and 2015, but was inferior to the new units. The older generator focal spot is smaller (0.75mm vs. 1.2mm), and the SID for acquisition is 182cm as well, so focal spot dimensions cannot explain the difference. The difference in MTF may be secondary to differences in generator X‐ray spectrum or by unannounced changes in detector architecture. Further investigation is needed.Conclusion:The study shows that both TG150 and TQT tests are consistent. The numerical value of some metrics are dependent on ROI size.
SU‐D‐207‐01: Markerless Respiratory Motion Tracking with Contrast Enhanced Thoracic Cone Beam CT Projections
Authors: Chao M , Brousmiche S , Yuan Y , Rosenzweig K , Lo Y 
Published: June 2015

Purpose:To develop a novel technique to enhance the image contrast of clinical cone beam CT projections and extract respiratory signals based on anatomical motion using the modified Amsterdam Shroud (AS) method to benefit image guided radiation therapy.Methods:Thoracic cone beam CT projections acquired prior to treatment were preprocessed to increase their contrast for better respiratory signal extraction. Air intensity on raw images was firstly estimated and then applied to correct the projections to generate new attenuation images that were subsequently improved with deeper anatomy feature enhancement through taking logarithm operation, derivative along superior‐inferior direction, respectively. All pixels on individual post‐processed two dimensional images were horizontally summed to one column and all projections were combined side by side to create an AS image from which patient's respiratory signal was extracted. The impact of gantry rotation on the breathing signal rendering was also investigated. Ten projection image sets from five lung cancer patients acquired with the Varian Onboard Imager on 21iX Clinac (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique.Results:Application of the air correction on raw projections showed that more than an order of magnitude of contrast enhancement was achievable. The typical contrast on the raw projections is around 0.02 while that on attenuation images could greater than 0.5. Clear and stable breathing signal can be reliably extracted from the new images while the uncorrected projection sets failed to yield clear signals most of the time.Conclusion:Anatomy feature plays a key role in yielding breathing signal from the projection images using the AS technique. The air correction process facilitated the contrast enhancement significantly and attenuation images thus obtained provides a practical solution to obtaining markerless breathing motion tracking.