bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐C‐BRA‐06: Developing Clinical and Quantitative Guidelines for a 4DCT‐Ventilation Functional Avoidance Clinical Trial
Authors: Vinogradskiy Y , Waxweiler T , Diot Q , Castillo R , Guerrero T , Castillo E , Kavanagh B , Schubert L , Miften M 
Published: June 2015

Purpose:4DCT‐ventilation is an exciting new imaging modality that uses 4DCTs to calculate lung ventilation. Because 4DCTs are acquired as part of routine care, calculating 4DCT‐ventilation allows for lung function evaluation without additional cost or inconvenience to the patient. Development of a clinical trial is underway at our institution to use 4DCT‐ventilation for thoracic functional avoidance with the idea that preferential sparing of functional lung regions can decrease pulmonary toxicity. The purpose of our work was to develop the practical aspects of a 4DCT‐ventilation functional avoidance clinical trial including: 1.assessing patient eligibility 2.developing trial inclusion criteria and 3.developing treatment planning and dose‐function evaluation strategies.Methods:96 stage III lung cancer patients from 2 institutions were retrospectively reviewed. 4DCT‐ventilation maps were calculated using the patient's 4DCTs, deformable image registrations, and a density‐change‐based algorithm. To assess patient eligibility and develop trial inclusion criteria we used an observer‐based binary end point noting the presence or absence of a ventilation defect and developed an algorithm based on the percent ventilation in each lung third. Functional avoidance planning integrating 4DCT‐ventilation was performed using rapid‐arc and compared to the patient's clinically used plan.Results:Investigator‐determined clinical ventilation defects were present in 69% of patients. Our regional/lung‐thirds ventilation algorithm identified that 59% of patients have lung functional profiles suitable for functional avoidance. Compared to the clinical plan, functional avoidance planning was able to reduce the mean dose to functional lung by 2 Gy while delivering comparable target coverage and cord/heart doses.Conclusions:4DCT‐ventilation functional avoidance clinical trials have great potential to reduce toxicity, and our data suggest that 59% of lung cancer patients have lung function profiles suitable for functional avoidance. Our study used a retrospective evaluation of a large lung cancer patient database to develop the practical aspects of a 4DCT‐ventilation functional avoidance clinical trial.(R.C., E.C., T.G.), NIH Research Scientist Development Award K01‐CA181292 (R.C.), and State of Colorado Advanced Industries Accelerator Grant (Y.V.).
SU‐C‐303‐05: Photosensitizer Determination for PDT Using Interstitial and Surface Measurements of Fluorescence
Authors: Kim M , Finlay J , Zhu T 
Published: June 2015

Purpose:Photosensitizer concentration during photodynamic therapy (PDT) is an important parameter for accurate dosimetry. Fluorescence signal can be used as a measure of photosensitizer concentration. Two methods of data acquisition were compared to an ex vivo study both for in vivo and phantom models.Methods:Fluorescence signal of commonly used photosensitizer benzoporphyrin derivative monoacid ring A (BPD) was obtained in phantoms and mouse tumors using an excitation light of 405 nm. Interstitial fluorescence signal was obtained using a side‐cut fiber inserted into the tumor tissue of interest. Using a previously developed multi‐fiber probe, tumor surface fluorescence measurements were also collected. Signals were calibrated according to optical phantoms with known sensitizer fluorescence. Optical properties for each sample were determined and the influence of different absorption and scattering properties on the fluorescence signals was investigated. Using single value decomposition of the spectra, the sensitizer concentration was determined using the two different measurement geometries. An ex vivo analysis was also performed for tumor samples to determine the sensitizer concentration.Results:The two fluorescence signals obtained from the surface multi‐fiber probe and the interstitial measurements were compared and were corresponding for both phantoms and mouse models. The values obtained were comparable to the ex vivo measurements as well. Despite the difference in geometry, the surface probe measurements can still be used as a metric for determining the presence of sensitizer in small volume tumors.Conclusion:The multi‐fiber contact probe can be used as a tool to measure fluorescence at the surface of the treatment area for PDT and predict sensitizer concentration throughout the tumor. This is advantageous in that the measurement does not damage any tissue. Future work will include investigating the dependence of these results on intratumor sensitizer distribution.
SU‐C‐303‐06: Treatment Planning Study for Non‐Invasive Cardiac Arrhythmia Ablation with Scanned Carbon Ions in An Animal Model
Authors: Eichhorn A , Constantinescu A , Lehmann H I , Lugenbiel P , Takami M , Richter D , Prall M , Kaderka R , Thomas D , Bert C , Packer D L , Durante M , Graeff C 
Published: June 2015

Purpose:Scanned carbon ion beams might offer a non‐invasive alternative treatment for cardiac arrhythmia, which are a major health‐burden. We studied the feasibility of this procedure in an animal model. The underlying treatment planning and motion mitigation strategies will be presented.Methods:The study was carried out in 15 pigs, randomly distributed to 3 target groups: atrioventricular node (AVN, 8 animals with 25, 40, and 55 Gy target dose), left ventricular free‐wall (LV, 4 animals with 40 Gy) and superior pulmonary vein (SPV, 3 animals with 40 Gy). Breathing motion was suppressed by repeated enforced breathholds at end exhale. Cardiac motion was mitigated by an inhomogeneous rescanning scheme with up to 15 rescans. The treatment planning was performed using the GSI in‐house software TRiP4D on cardiac‐gated 4DCTs, applying a range‐considering ITV based on an extended CTV. For AVN and SPV isotropic 5 mm margins were applied to the CTV, while for the LV 2mm+2% range margins were used. The opposing fields for AVN and LV targets were optimized independently (SFUD), while SPV treatments were optimized as IMPT deliveries, including dose restrictions to the radiosensitive AVN.Results:Median value of D95 over all rescanning simulations was 99.1% (AVN), 98.0% (SPV) and 98.3% (LV) for the CTV and 94.7% (AVN) and 92.7% (SPV) for the PTV, respectively. The median D5‐D95 was improved with rescanning compared to unmitigated delivery from 13.3 to 6.5% (CTV) and from 23.4 to 11.6% (PTV). ICRP dose limits for aorta, trachea, esophagus and skin were respected. The maximal dose in the coronary arteries was limited to 30 Gy.Conclusion:We demonstrated the feasibility of a homogeneous dose delivery to different cardiac structures in a porcine model using a time‐optimized inhomogeneous rescanning scheme. The presented treatment planning strategies were applied in a pig study with the analysis ongoing.Funding: This work was supported in part by the Helmholtz Association, the American Heart Association Midwest Affiliate Postdoctoral Fellowship Grant, the Mayo Clinic Foundation, and the Goldsmith Foundation.
SU‐C‐204‐04: Patient Specific Proton Stopping Powers Estimation by Combining Proton Radiography and Prior‐Knowledge X‐Ray CT Information
Authors: Collins‐Fekete CA , Brousmiche S , Hansen D , Beaulieu L , Seco J 
Published: June 2015

Purpose:The material relative stopping power (RSP) uncertainty is the highest contributor to the range uncertainty in proton therapy. The purpose of this work is to develop a robust and systematic method that yields accurate, patient specific, RSP by combining 1) pre‐treatment x‐ray CT and 2) daily proton radiograph of the patient.Methods:The method is formulated as a linear least‐square optimization problem (min||Ax‐B||2). The parameter A represents the pathlength crossed by the proton in each material. The RSPs for the materials (water equivalent thickness (WET)/physical thickness) are denoted by x. B is the proton radiograph expressed as WET crossed. The problem is minimized using a convex‐conic optimization algorithm with xi<xi+1 constraint. The Gammex RMI‐465 phantom, with 13 material inserts, is used to investigate the optimal RSPs. The proton radiograph (B) is produced using Geant4 simulation. The matrix A is computed by calculating proton trajectories through the CT with the cubic‐spline approach. Geant4 RSPs are used as reference and the clinical HU‐RSP calibration curve is used as comparison. The convergence is investigated as a function of the number of angles and protons used. The radiographs angle which yield the most accurate RSPs are investigated.Results:Optimization with 9 angles and 104 protons/angle yields precise RSP (<0.75%) for all materials, except plastic lung (1.5%). Average deviation relative to Geant4 RSP is 0.5% and 3.5% using HU‐RSP. Using more than two angles or more than 4×103 proton does not further increase the RSP estimate accuracy. The insert distance to the beam initial plane is related to the RSP error for this insert material. Specific filters are applied on the proton angle and energy loss to remove nuclear interaction artefacts.Conclusion:The proposed formulation of the problem with prior knowledge x‐ray CT demonstrates serious potential to increase the accuracy of present RSP estimates.
SU‐C‐204‐07: The Production of Short‐Lived Positron Emitters in Proton Therapy
Authors: Buitenhuis H J T , Dendooven P , Diblen F , Biegun A K , van Goethem M‐J , van der Graaf E R , Brandenburg S 
Published: June 2015

Purpose:To investigate the production and effect of short‐lived positron emitters when using PET for in‐vivo range verification during a proton therapy irradiation.Methods:The integrated production of short‐lived positron emitters in the stopping of 55 MeV protons was measured in water, carbon, phosphorus and calcium targets. The experimental production rates are used to calculate the production on PMMA and a representative set of 4 tissue materials. The number of decays integrated over an irradiation in these materials is calculated as function of the duration of the irradiation, considering irradiations with the same total number of protons.Results:The most copiously produced short‐lived nuclides and their production rates relative to the relevant long‐lived nuclides are: 12‐N (T1/2 = 11 ms) on carbon (9.5% of the 11‐C production), 29‐P (T1/2 = 4.1 s) on phosphorus (20% of the 30‐P production) and 38m‐K (T1/2 = 0.92 s) on calcium (113% of the 38g‐K production). No short‐lived nuclides are produced on water. The most noticeable Result is that for an irradiation in (carbon‐rich) adipose tissue, 12‐N will dominate the PET image up to an irradiation duration of 70 s. On bone tissue, 15‐O dominates over 12‐N after 7–15 s (depending on the carbon‐to‐oxygen ratio).Conclusions:The presence of 12‐N needs to be considered in PET imaging during proton beam irradiations as, depending on tissue composition and PET scanning protocol, it may noticeably deteriorate image quality due to the large positron range blurring. The results presented warrant investigations into the energy‐dependent production of 12‐N, 29‐P and 38m‐K and their effect on PET imaging during proton irradiations.
SU‐C‐207‐04: Reconstruction Artifact Reduction in X‐Ray Cone Beam CT Using a Treatment Couch Model
Authors: Lasio G , Hu E , Zhou J , Lee M , Yi B 
Published: June 2015

Purpose:to mitigate artifacts induced by the presence of the RT treatment couch in on‐board CBCT and improve image qualityMethods:a model of a Varian IGRT couch is constructed using a CBCT scan of the couch in air. The model is used to generate a set of forward projections (FP) of the treatment couch at specified gantry angles. The model couch forward projections are then used to process CBCT scan projections which contain the couch in addition to the scan object (Catphan phantom), in order to remove the attenuation component of the couch at any given gantry angle. Prior to pre‐processing with the model FP, the Catphan projection data is normalized to an air scan with bowtie filter. The filtered Catphan projections are used to reconstruct the CBCT with an in‐house FDK algorithm. The artifact reduction in the processed CBCT scan is assessed visually, and the image quality improvement is measured with the CNR over a few selected ROIs of the Catphan modules.Results:Sufficient match between the forward projected data and the x‐ray projections is achieved to allow filtering in attenuation space. Visual improvement of the couch induced artifacts is achieved, with a moderate expense of CNR.Conclusion:Couch model‐based correction of CBCT projection data has a potential for qualitative improvement of clinical CBCT scans, without requiring position specific correction data. The technique could be used to produce models of other artifact inducing devices, such as immobilization boards, and reduce their impact on patient CBCT images.
SU‐C‐207‐05: A Comparative Study of Noise‐Reduction Algorithms for Low‐Dose Cone‐Beam Computed Tomography
Authors: Mukherjee S , Yao W 
Published: June 2015

Purpose:To study different noise‐reduction algorithms and to improve the image quality of low dose cone beam CT for patient positioning in radiation therapy.Methods:In low‐dose cone‐beam CT, the reconstructed image is contaminated with excessive quantum noise. In this study, three well‐developed noise reduction algorithms namely, a) penalized weighted least square (PWLS) method, b) split‐Bregman total variation (TV) method, and c) compressed sensing (CS) method were studied and applied to the images of a computer–simulated “Shepp‐Logan” phantom and a physical CATPHAN phantom. Up to 20% additive Gaussian noise was added to the Shepp‐Logan phantom. The CATPHAN phantom was scanned by a Varian OBI system with 100 kVp, 4 ms and 20 mA. For comparing the performance of these algorithms, peak signal‐to‐noise ratio (PSNR) of the denoised images was computed.Results:The algorithms were shown to have the potential in reducing the noise level for low‐dose CBCT images. For Shepp‐Logan phantom, an improvement of PSNR of 2 dB, 3.1 dB and 4 dB was observed using PWLS, TV and CS respectively, while for CATPHAN, the improvement was 1.2 dB, 1.8 dB and 2.1 dB, respectively.Conclusion:Penalized weighted least square, total variation and compressed sensing methods were studied and compared for reducing the noise on a simulated phantom and a physical phantom scanned by low‐dose CBCT. The techniques have shown promising results for noise reduction in terms of PSNR improvement. However, reducing the noise without compromising the smoothness and resolution of the image needs more extensive research.
SU‐C‐207‐07: Quantification of Coronary Artery Cross‐Sectional Area in CT Angiography Using Integrated Density: A Phantom Study
Authors: Johnson T , Ding H , Torabzadeh M , Molloi S 
Published: June 2015

Purpose:To investigate the feasibility of quantifying the cross‐sectional area (CSA) of coronary arteries using integrated density in a physics‐based model with a phantom study.Methods:In this technique the total integrated density of the object as compared with its local background is measured so it is possible to account for the partial volume effect. The proposed method was compared to manual segmentation using CT scans of a 10 cm diameter Lucite cylinder placed inside a chest phantom. Holes with cross‐sectional areas from 1.4 to 12.3 mm2 were drilled into the Lucite and filled with iodine solution, producing a contrast‐to‐noise ratio of approximately 26. Lucite rods 1.6 mm in diameter were used to simulate plaques. The phantom was imaged with and without the Lucite rods placed in the holes to simulate diseased and normal arteries, respectively. Linear regression analysis was used, and the root‐mean‐square deviations (RMSD) and errors (RMSE) were computed to assess the precision and accuracy of the measurements. In the case of manual segmentation, two readers independently delineated the lumen in order to quantify the inter‐reader variability.Results:The precision and accuracy for the normal vessels using the integrated density technique were 0.32 mm2 and 0.32 mm2, respectively. The corresponding results for the manual segmentation were 0.51 mm2 and 0.56 mm2. In the case of diseased vessels, the precision and accuracy of the integrated density technique were 0.46 mm2 and 0.55 mm2, respectively. The corresponding results for the manual segmentation were 0.75 mm2 and 0.98 mm2. The mean percent difference for the two readers was found to be 8.4%.Conclusion:The CSA based on integrated density had improved precision and accuracy as compared with manual segmentation in a Lucite phantom. The results indicate the potential for using integrated density to improve CSA measurements in CT angiography.
SU‐C‐201‐02: Quantitative Small‐Animal SPECT Without Scatter Correction Using High‐Purity Germanium Detectors
Authors: Gearhart A , Peterson T , Johnson L 
Published: June 2015

Purpose:To evaluate the impact of the exceptional energy resolution of germanium detectors for preclinical SPECT in comparison to conventional detectors.Methods:A cylindrical water phantom was created in GATE with a spherical Tc‐99m source in the center. Sixty‐four projections over 360 degrees using a pinhole collimator were simulated. The same phantom was simulated using air instead of water to establish the true reconstructed voxel intensity without attenuation. Attenuation correction based on the Chang method was performed on MLEM reconstructed images from the water phantom to determine a quantitative measure of the effectiveness of the attenuation correction. Similarly, a NEMA phantom was simulated, and the effectiveness of the attenuation correction was evaluated. Both simulations were carried out using both NaI detectors with an energy resolution of 10% FWHM and Ge detectors with an energy resolution of 1%.Results:Analysis shows that attenuation correction without scatter correction using germanium detectors can reconstruct a small spherical source to within 3.5%. Scatter analysis showed that for standard sized objects in a preclinical scanner, a NaI detector has a scatter‐to‐primary ratio between 7% and 12.5% compared to between 0.8% and 1.5% for a Ge detector. Preliminary results from line profiles through the NEMA phantom suggest that applying attenuation correction without scatter correction provides acceptable results for the Ge detectors but overestimates the phantom activity using NaI detectors. Due to the decreased scatter, we believe that the spillover ratio for the air and water cylinders in the NEMA phantom will be lower using germanium detectors compared to NaI detectors.Conclusion:This work indicates that the superior energy resolution of germanium detectors allows for less scattered photons to be included within the energy window compared to traditional SPECT detectors. This may allow for quantitative SPECT without implementing scatter correction, reducing uncertainties introduced by scatter correction algorithms.Funding provided by NIH/NIBIB grant R01EB013677; Todd Peterson, Ph.D., has had a research contract with PHDs Co., Knoxville, TN
SU‐D‐201‐03: Imaging Cellular Pharmacokinetics of 18F‐FDG in Inflammatory/Stem Cells
Authors: Zaman R , Tuerkcan S , Mahmoudi M , Toshinobu T , Kosuge H , Yang P , Chin F , McConnell M , Xing L 
Published: June 2015

Purpose:Atherosclerosis is a progressive inflammatory condition that underlies coronary artery disease (CAD)—the leading cause of death in the USA. Thus, understating the metabolism of inflammatory cells can be a valuable tool for investigating CAD. To the best of our knowledge, we are the first to successfully investigate the pharmacokinetics of [18F]fluoro‐deoxyglucose (18F‐FDG) uptake in a single macrophages and compared with induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs) with a novel imaging technique, radioluminescence microscopy, initially developed for cancer imaging.Methods:Live cells were cultured sparsely on Matrigel in a glass‐bottom dish and starved for 1 hour before incubation with 250 microCi of 18F‐FDG for 45 minutes. Excess radiotracer was removed using DMEM medium without glucose. Before imaging, DMEM (1 mL) was added to the cell culture and a 100 microm‐thin CdWO4 scintillator plate was placed on top of the cells. Light produced following beta decay was imaged with a highly sensitive inverted microscope (LV200, Olympus) fitted with a 40x/1.3 high‐NA oil objective, and an EM‐CCD camera. The images were collected over 18,000 frames with 4×4 binning (1200 MHz EM Gain, 300ms exposure). Custom‐written software was developed in MATLAB for image processing (Figure 1). For statistical analysis 10 different region‐of‐interests (ROIs) were selected for each cell type.Results:Figures 2A–2B show bright‐field/fusion images for all three different cell types. The relationship between cell‐to‐cell comparisons was found to be linear for macrophages unlike iPSCs and MSCs, which were best fitted with moving or rolling average (Figure 2C). The average observed decay of 18F‐FDG in a single cell of MSCs per second (0.067) was 20% and 36% higher compared to iPSCs (0.054) and macrophages (0.043), respectively (Figure 2D).Conclusion:MSCs was found to be 2–3x more sensitive to glucose molecule despite constant parameters for each cell type examined.
SU‐D‐201‐04: Study On the Impact of Tumor Shape and Size On Drug Delivery to Pancreatic Tumors
Authors: Soltani M , Bazmara H , Sefidgar M , Subramaniam R , Rahmim A 
Published: June 2015

Purpose:Drug delivery to solid tumors can be expressed physically using transport phenomena such as convection and diffusion for the drug of interest within extracellular matrices. We aimed to carefully model these phenomena, and to investigate the effect of tumor shape and size on drug delivery to solid tumors in the pancreas.Methods:In this study, multiple tumor geometries as obtained from clinical PET/CT images were considered. An advanced numerical method was used to simultaneously solve fluid flow and solute transport equations. Data from n=45 pancreatic cancer patients with non‐resectable locoregional disease were analyzed, and geometrical information from the tumors including size, shape, and aspect ratios were classified. To investigate effect of tumor shape, tumors with similar size but different shapes were selected and analyzed. Moreover, to investigate effect of tumor size, tumors with similar shapes but different sizes, ranging from 1 to 77 cm3, were selected and analyzed. A hypothetical tumor similar to one of the analyzed tumors, but scaled to reduce its size below 0.2 cm3, was also analyzed.Results:The results showed relatively similar average drug concentration profiles in tumors with different sizes. Generally, smaller tumors had higher absolute drug concentration. In the hypothetical tumor, with volume less than 0.2 cm3, the average drug concentration was 20% higher in comparison to its counterparts. For the various real tumor geometries, however, the maximum difference between average drug concentrations was 10% for the smallest and largest tumors. Moreover, the results demonstrated that for pancreatic tumors the shape is not significant. The negligible difference of drug concentration in different tumor shapes was due to the minimum effect of convection in pancreatic tumors.Conclusion:In tumors with different sizes, smaller tumors have higher drug delivery; however, the impact of tumor shape in the case of pancreatic tumors is not significant.