bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐C‐BRA‐02: Gradient Based Method of Target Delineation On PET/MR Image of Head and Neck Cancer Patients
Authors: Dance M , Chera B , Falchook A , Das S , Lian J 
Published: June 2015

Purpose:Validate the consistency of a gradient‐based segmentation tool to facilitate accurate delineation of PET/CT‐based GTVs in head and neck cancers by comparing against hybrid PET/MR‐derived GTV contours.Materials and Methods:A total of 18 head and neck target volumes (10 primary and 8 nodal) were retrospectively contoured using a gradient‐based segmentation tool by two observers. Each observer independently contoured each target five times. Inter‐observer variability was evaluated via absolute percent differences. Intra‐observer variability was examined by percentage uncertainty. All target volumes were also contoured using the SUV percent threshold method. The thresholds were explored case by case so its derived volume matched with the gradient‐based volume. Dice similarity coefficients (DSC) were calculated to determine overlap of PET/CT GTVs and PET/MR GTVs.Results:The Levene's test showed there was no statistically significant difference of the variances between the observer's gradient‐derived contours. However, the absolute difference between the observer's volumes was 10.83%, with a range from 0.39% up to 42.89%. PET‐avid regions with qualitatively non‐uniform shapes and intensity levels had a higher absolute percent difference near 25%, while regions with uniform shapes and intensity levels had an absolute percent difference of 2% between observers. The average percentage uncertainty between observers was 4.83% and 7%. As the volume of the gradient‐derived contours increased, the SUV threshold percent needed to match the volume decreased. Dice coefficients showed good agreement of the PET/CT and PET/MR GTVs with an average DSC value across all volumes at 0.69.Conclusion:Gradient‐based segmentation of PET volume showed good consistency in general but can vary considerably for non‐uniform target shapes and intensity levels. PET/CT‐derived GTV contours stemming from the gradient‐based tool show good agreement with the anatomically and metabolically more accurate PET/MR‐derived GTV contours, but tumor delineation accuracy can be further improved with the use PET/MR.
SU‐C‐BRA‐04: Use of Esophageal Wall Thickness in Evaluation of the Response to Chemoradiation Therapy for Esophageal Cancer
Authors: Wang J , Kang M , Kligerman S , Lu W 
Published: June 2015

Purpose:To quantitatively evaluate the esophageal cancer response to chemoradiation therapy (CRT) by measuring the esophageal wall thickness in CT.Method:Two datasets were used in this study. The first dataset is composed of CT scans of 15 esophageal cancer patients and 15 normal controls. The second dataset is composed of 20 esophageal cancer patients who underwent PET/CT scans before (Pre‐CRT) and after CRT (Post‐CRT). We first segmented the esophagus using a multi‐atlas‐based algorithm. The esophageal wall thickness was then computed, on each slice, as the equivalent circle radius of the segmented esophagus excluding the lumen. To evaluate the changes of wall thickness, we computed the standard deviation (SD), coefficient of variation (COV, SD/Mean), and flatness [(Max–Min)/Mean] of wall thickness along the entire esophagus.Results:For the first dataset, the mean wall thickness of cancer patients and normal controls were 6.35 mm and 6.03 mm, respectively. The mean SD, COV, and flatness of the wall thickness were 2.59, 0.21, and 1.27 for the cancer patients and 1.99, 0.16, and 1.13 for normal controls. Statistically significant differences (p < 0.05) were identified in SD and flatness. For the second dataset, the mean wall thickness of pre‐CRT and post‐CRT patients was 7.13 mm and 6.84 mm, respectively. The mean SD, COV, and flatness were 1.81, 0.26, and 1.06 for pre‐CRT and 1.69, 0.26, and 1.06 for post‐CRT. Statistically significant difference was not identified for these measurements. Current results are based on the entire esophagus. We believe significant differences between pre‐ and post‐CRT scans could be obtained, if we conduct the measurements at tumor sites.Conclusion:Results show thicker wall thickness in pre‐CRT scans and differences in wall thickness changes between normal and abnormal esophagus. This demonstrated the potential of esophageal wall thickness as a marker in the tumor CRT response evaluation.This work was supported in part by the National Cancer Institute Grant R01CA172638.
SU‐C‐303‐02: Correlating Metabolic Response to Radiation Therapy with HIF‐1alpha Expression
Authors: Campos D , Peeters W , Nickel K , Eliceiri K , Kimple R , Van Der Kogel A , Kissick M 
Published: June 2015

Purpose:To understand radiation induced alterations in cellular metabolism which could be used to assess treatment or normal tissue response to aid in patient‐specific adaptive radiotherapy. This work aims to compare the metabolic response of two head and neck cell lines, one malignant (UM‐SCC‐22B) and one benign (Normal Oral Keratinocyte), to ionizing radiation. Responses are compared to alterations in HIF‐1alpha expression. These dynamics can potentially serve as biomarkers in assessing treatment response allowing for patient‐specific adaptive radiotherapy.Methods:Measurements of metabolism and HIF‐1alpha expression were taken before and X minutes after a 10 Gy dose of radiation delivered via an orthovoltage x‐ray source. In vitro changes in metabolic activity were measured via fluorescence lifetime imaging (FLIM) to assess the mean lifetime of NADH autofluorescence following a dose of 10 Gy. HIF‐1alpha expression was measured via immunohistochemical staining of in vitro treated cells and expression was quantified using the FIJI software package.Results:FLIM demonstrated a decrease in the mean fluorescence lifetime of NADH by 100 ps following 10 Gy indicating a shift towards glycolytic pathways for malignant cells; whereas this benign cell line showed little change in metabolic signature. Immunohistochemical analysis showed significant changes in HIF‐1alpha expression in response to 10 Gy of radiation that correlate to metabolic profiles.Conclusion:Radiation induces significant changes in metabolic activity and HIF‐1alpha expression. These alterations occur on time scales approximating the duration of common radiation treatments (approximately tens of minutes). Further understanding these dynamics has important implications with regard to improvement of therapy and biomarkers of treatment response.
SU‐C‐303‐07: Influence of Image Registration Algorithms and Noise Levels On the Accuracy of Fractional Regional Ventilation
Authors: Liu Y , Badea C , Mistry N , D'souza W 
Published: June 2015

Purpose:The derivation of fractional regional lung‐ventilation (FRV) involves registering images corresponding to extreme phases of the respiratory cycle. The purpose of this work was to investigate the influence of registration algorithms and image noise on the accuracy of the mouse lung tidal volume (TV) by employing a density‐based mass‐conservation technique in the calculation of fractional regional lung ventilation (FRV).Methods:Three mice mechanically ventilated using a fixed volume (0.4 ml) ventilator. CT images were acquired at full‐inhale and end‐exhale breath hold. Deformable image registration between inhale and exhale images was performed using three image registration algorithms: B‐splines, Demons‐Diffusion and Demons‐Fluid model. The impact of noise was studied by adding Gaussian noise resulting in images with relative signal‐to‐noise ratio (SNR) of 1 (zero noise), 0.65 (relative to zero noise), 0.39 and 0.26. A density‐based technique for evaluation of FRV from CT images was used to calculate tidal volume. The global TV calculated from the FRV maps was benchmarked to the known ventilated mouse lung volume of 0.4 ml.Results:The TV obtained using the B‐splines, Demons‐Diffusion and Demons‐Fluid registration algorithms with zero noise (relative SNR=1) were 0.28±0.03 ml, 0.22±0.04 ml and 0.41±0.01 ml, respectively. We observed a decline in the calculated tidal volume as SNR decreased. The greatest decline (27%) was observed with the Demons‐Fluid algorithm. However, the absolute value of the calculated TV with a relative SNR=0.26 was 0.30±0.05 ml, still the most accurate TV of the three registration algorithms investigated. The B‐splines and Demons‐Diffusion algorithm were less sensitive to noise and resulted in TV declines of 18% with a relative SNR=0.26.Conclusion:The Demons‐Fluid image registration algorithm consistently provided the most accurate calculated absolute TV. Although it was the most sensitive to image noise, the calculated absolute TV was more accurate than the B‐splines and Demons Diffusion algorithms.
SU‐C‐204‐05: Simulations of a Portal Imaging System for Conformal and Intensity Modulated Fast Neutron Therapy
Authors: James S St. , Argento D , Stewart R 
Published: June 2015

Purpose:The University of Washington Medical Center offers neutron therapy for the palliative and definitive treatment of selected cancers. In vivo field verification has the potential to improve the safe and effective delivery of neutron therapy. We propose a portal imaging method that relies on the creation of positron emitting isotopes (11C and 15O) through (n, 2n) reactions with a PMMA plate placed below the patient. After field delivery, the plate is retrieved from the vault and imaged using a reader that detects annihilation photons. The spatial pattern of activity produced in the PMMA plate provides information to reconstruct the neutron fluence map needed to confirm treatment delivery.Methods:We used MCNP to simulate the accumulation of 11C activity in a slab of PMMA 2 mm thick, and GATE was used to simulate the sensitivity and spatial resolution of a prototype imaging system. BGO crystal thicknesses of 1 cm, 2 cm and 3 cm were simulated with detector separations of 2 cm. Crystal pitches of 2 mm and 4 mm were evaluated. Back‐projection of the events was used to create a planar image. The spatial resolution was taken to be the FWHM of the reconstructed point source image.Results:The system sensitivity for a point source in the center of the field of view was found to range from 58% for 1 cm thick BGO with 2 mm crystal pitch to 74% for the 3 cm thick BGO crystals with 4 mm crystal pitch. The spatial resolution at the center of the field of view was found to be 1.5 mm for the system with 2 mm crystal pitch and 2.8 mm for the system with the 4 mm crystal pitch.Conclusion:BGO crystals with 4 mm crystal pitch and 3 cm length would offer the best sensitivity reader.
SU‐C‐204‐06: Surface Imaging for the Set‐Up of Proton Post‐Mastectomy Chestwall Irradiation: Gated Images Vs Non Gated Images
Authors: Batin E , Depauw N , MacDonald S , Lu H 
Published: June 2015

Purpose:Historically, the set‐up for proton post‐mastectomy chestwall irradiation at our institution started with positioning the patient using tattoos and lasers. One or more rounds of orthogonal X‐rays at gantry 0° and beamline X‐ray at treatment gantry angle were then taken to finalize the set‐up position. As chestwall targets are shallow and superficial, surface imaging is a promising tool for set‐up and needs to be investigatedMethods:The orthogonal imaging was entirely replaced by AlignRT™ (ART) images. The beamline X‐Ray image is kept as a confirmation, based primarily on three opaque markers placed on skin surface instead of bony anatomy. In the first phase of the process, ART gated images were used to set‐up the patient and the same specific point of the breathing curve was used every day. The moves (translations and rotations) computed for each point of the breathing curve during the first five fractions were analyzed for ten patients. During a second phase of the study, ART gated images were replaced by ART non‐gated images combined with real‐time monitoring. In both cases, ART images were acquired just before treatment to access the patient position compare to the non‐gated CT.Results:The average difference between the maximum move and the minimum move depending on the chosen breathing curve point was less than 1.7 mm for all translations and less than 0.7° for all rotations. The average position discrepancy over the course of treatment obtained by ART non gated images combined to real‐time monitoring taken before treatment to the planning CT were smaller than the average position discrepancy obtained using ART gated images. The X‐Ray validation images show similar results with both ART imaging process.Conclusion:The use of ART non gated images combined with real time imaging allows positioning post‐mastectomy chestwall patients in less than 3 mm / 1°.
SU‐C‐207‐02: A Method to Estimate the Average Planar Dose From a C‐Arm CBCT Acquisition
Authors: Supanich MP 
Published: June 2015

Purpose:The planar average dose in a C‐arm Cone Beam CT (CBCT) acquisition had been estimated in the past by averaging the four peripheral dose measurements in a CTDI phantom and then using the standard 2/3rds peripheral and 1/3 central CTDIw method (hereafter referred to as Dw). The accuracy of this assumption has not been investigated and the purpose of this work is to test the presumed relationship.Methods:Dose measurements were made in the central plane of two consecutively placed 16cm CTDI phantoms using a 0.6cc ionization chamber at each of the 4 peripheral dose bores and in the central dose bore for a C‐arm CBCT protocol. The same setup was scanned with a circular cut‐out of radiosensitive gafchromic film positioned between the two phantoms to capture the planar dose distribution. Calibration curves for color pixel value after scanning were generated from film strips irradiated at different known dose levels. The planar average dose for red and green pixel values was calculated by summing the dose values in the irradiated circular film cut out. Dw was calculated using the ionization chamber measurements and film dose values at the location of each of the dose bores.Results:The planar average dose using both the red and green pixel color calibration curves were within 10% agreement of the planar average dose estimated using the Dw method of film dose values at the bore locations. Additionally, an average of the planar average doses calculated using the red and green calibration curves differed from the ionization chamber Dw estimate by only 5%.Conclusion:The method of calculating the planar average dose at the central plane of a C‐arm CBCT non‐360 rotation by calculating Dw from peripheral and central dose bore measurements is a reasonable approach to estimating the planar average dose.Research Grant, Siemens AG
SU‐C‐207‐03: Optimization of a Collimator‐Based Sparse Sampling Technique for Low‐Dose Cone‐Beam CT
Authors: Lee T , Kim I , Han B , Cho S 
Published: June 2015

Purpose:In computed tomography (CT) imaging, radiation dose delivered to the patient is one of the major concerns. Sparse‐view CT takes projections at sparser view angles and provides a viable option to reducing dose. However, a fast power switching of an X‐ray tube, which is needed for the sparse‐view sampling, can be challenging in many CT systems. We have earlier proposed a many‐view under‐sampling (MVUS) technique as an alternative to sparse‐view CT. In this study, we investigated the effects of collimator parameters on the image quality and aimed to optimize the collimator design.Methods:We used a bench‐top circular cone‐beam CT system together with a CatPhan600 phantom, and took 1440 projections from a single rotation. The multi‐slit collimator made of tungsten was mounted on the X‐ray source for beam blocking. For image reconstruction, we used a total‐variation minimization (TV) algorithm and modified the backprojection step so that only the measured data through the collimator slits are to be used in the computation. The number of slits and the reciprocation frequency have been varied and the effects of them on the image quality were investigated. We also analyzed the sampling efficiency: the sampling density and data incoherence in each case. We tested three sets of slits with their number of 6, 12 and 18, each at reciprocation frequencies of 10, 30, 50 and 70 Hz/ro.Results:Consistent results in the image quality have been produced with the sampling efficiency, and the optimum condition was found to be using 12 slits at 30 Hz/ro. As image quality indices, we used the CNR and the detectability.Conclusion:We conducted an experiment with a moving multi‐slit collimator to realize a sparse‐sampled cone‐beam CT. Effects of collimator parameters on the image quality have been systematically investigated, and the optimum condition has been reached.
SU‐C‐207‐06: In Vivo Quantification of Gold Nanoparticles Using K‐Edge Imaging Via Spectrum Shaping by Gold Filter
Authors: Chen H , Cormack R , Bhagwat M , Berbeco R 
Published: June 2015

Purpose:Gold nanoparticles (AuNP) are multifunctional platforms ideal for drug delivery, targeted imaging and radiosensitization. We have investigated quantitative imaging of AuNPs using on board imager (OBI) cone beam computed tomography (CBCT). To this end, we also present, for the first time, a novel method for k‐edge imaging of AuNP by filter‐based spectral shaping.Methods:We used a digital 25 cm diameter water phantom, embedded with 3 cm spheres filled with AuNPs of different concentrations (0 mg/ml – 16 mg/ml). A poly‐energetic X‐ray spectrum of 140 kVp from a conventional X‐ray tube is shaped by balanced K‐edge filters to create an excess of photons right above the K‐edge of gold at 80.7 keV. The filters consist of gold, tin, copper and aluminum foils. The phantom with appropriately assigned attenuation coefficients is forward projected onto a detector for each energy bin and then integrated. FKD reconstruction is performed on the integrated projections. Scatter, detector efficiency and noise are included.Results:We found that subtracting the results of two filter sets (Filter A:127 µm gold foil with 254 µm tin, 330 µm copper and 1 mm aluminum, and Filter B: 635 µm tin with 264 µm copper and 1 mm aluminum), provides substantial image contrast. The resulting filtered spectra match well below 80.7 keV, while maintaining sufficient X‐ray quanta just above that. Voxel intensities of AuNP containing spheres increase linearly with AuNP concentration. K‐edge imaging provides 18% more sensitivity than the tin filter alone, and 38% more sensitivity than the gold filter alone.Conclusion:We have shown that it is feasible to quantitatively detect AuNP distributions in a patient‐sized phantom using clinical CBCT and K‐edge spectral shaping.
SU‐D‐207‐02: Automated Respiratory Motion Tracking with Machine Vision
Authors: Armstrong H , Miften M 
Published: June 2015

Purpose:Current systems for obtaining respiratory information at time of treatment typically require the use of additional equipment and add to patient setup time. In this study, we develop a fully automated method to track respiratory motion by tracking the motion of the diaphragm surface, making use of only current imaging technology and without the need for additional mechanical, pneumatic, or optical devices.Methods:A statistical algorithm, RANdom SAmple Consensus (RANSAC), was used for direct tracking of the diaphragm surface through kV CBCT projection images. A third order polynomial was used to model the shape of the diaphragm. Model constraints based on the diaphragm shape as well as a small motion assumption (between adjacent projections) were incorporated to constrain the model. The changing position of the diaphragm along the Superior‐Inferior direction as the patient respires then gives the respiratory trace.Results:On the patients studied, the respiratory trace can be obtained with between 5,000 and 1,000,000 iterations of the RANSAC algorithm, per projection. Visual comparison with the projection images in a cine like mode shows the computed respiratory trace matches well with the true respiratory cycle. With a low number of iterations (<10,000 per projection), the diaphragm location computation time is similar to projection image acquisition and therefore the trace can be computed in real time.Conclusion:The RANSAC algorithm is a viable method for obtaining a respiratory trace with the patient on the treatment couch. Implementing the RANSAC algorithm on a GPU should allow for a significantly larger number of iterations while maintaining the ability to acquire the respiratory trace in real time. This method of obtaining a respiratory trace should reduce costs for technology such as 4DCBCT as well as reduce patient setup times and improve patient comfort.
SU‐D‐207‐06: Clinical Validations of Shading Correction for Cone‐Beam CT Using Planning CT as a Prior
Authors: Tsui T , Wei J , Zhu L 
Published: June 2015

Purpose:Current cone‐beam CT (CBCT) images contain severe shading artifacts mainly due to scatter, hindering their quantitative use in current radiation therapy. We have previously proposed an effective shading correction method for CBCT using planning CT (pCT) as prior knowledge. In this work, we investigate the method robustness via statistical analyses on studies of a large patient group and compare the performance with that of a state‐of‐the‐art method implemented on the current commercial radiation therapy machine ‐‐ the Varian Truebeam system.Methods:Since radiotherapy patients routinely undergo multiple‐detector CT (MDCT) scans in the planning procedure, we use the high‐quality pCT as “free” prior knowledge for CBCT image improvement. The CBCT image with no correction is first spatially registered with the pCT. Primary CBCT projections are estimated via forward projections of the registered image. The low frequency errors in the projections, which stem from mainly scatter, are estimated by filtering the difference between original line integral and the estimated scatter projections. The corrected CBCT image is then reconstructed from the scatter corrected projections. The proposed method is evaluated on 40 cancer patients.Results:On all patient images, we compare errors on CT number, spatial non‐uniformity (SNU) and image contrast, using pCT as the ground truth. T‐tests show that our algorithm improves over the Varian method on CBCT accuracies of CT number and SNU with 90% confident. The average CT number error is reduced from 54.8 HU on the Varian method to 40.9 HU, and the SNU error is reduced from 7.7% to 3.8%. There is no obvious improvement on image contrast.Conclusion:Large‐group patient studies show that the proposed pCT‐based algorithm outperforms the Varian method of the Truebeam system on CBCT shading correction, by providing CBCT images with higher CT number accuracy and greater image uniformity.