bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐BRF‐15: Interfractional Dose Variations in Parotid and Submandibular Glands in IG‐IMRT for Head and Neck Cancer
Authors: Chen X , Botros M , Ahunbay E , Wang D , Schultz C , Li X 
Published: July 2014

Purpose:To quantify interfractional anatomic changes and the dosimetric variations in the parotid and submandibular glands in image‐guided IMRT for head and neck cancer.Methods:Daily diagnostic‐quality CTs acquired during daily IGRT using an in‐room CT (CTVision, Siemens) for 16 head and neck cancer patients treated with IMRT were analyzed. The contours of parotid glands and submandibular glands on dialy CTs were generated using an auto‐segmentation tool (ABAS, Elekta) with manual editing by a single physician. The volumetric changes were measured and the center of mass (COM) of each gland was obtained. The positional changes of the glands were characterized by inter‐parotid and inter‐submandibular gland distances. The original plan was applied to each fraction CT with isocenter shifts based on the alignment of the tumor. The DVHs and commonly used dose volume parameters from daily plans were compared to the original plans.Results:From fraction 1 to fraction 31, the average volume reduction was roughly 25% for all glands. The changes of inter‐parotid and inter‐submandibular gland distances were significant, with these distances decreased by 1.7±4.3 mm and 1.4±2.7 mm in average from fraction 1 to fraction 31. The average distance changes between the glands to the isocenter were from 0.4 to 3.3 mm. The mean dose changes for the four glands were from 109 cGy to 265 cGy.Conclusion:Significant decreases in the volume, inter‐gland distance were found during IG‐IMRT for head and neck cancer. These changes result in significant variations in doses to these glands, indicating the need of adaptive replanning.
SU‐F‐18C‐03: Loss of Image Sharpness in CT Bone Imaging Due to Positioning Within the Scan Field of View – Possible Solutions
Authors: Ranallo F , Szczykutowicz T 
Published: July 2014

Purpose:To demonstrate how both the positioning of an object in the scan field of view (SFOV) and the size of the reconstructed field of view (RFOV) can both significantly affect and degrade the image sharpness.Methods:Clinical CT scans of the shoulders and elbows were inspected for image sharpness. GE scanners were used for the imaging with a “Bone Plus” reconstruction algorithm. In all scans the anatomy of interest was significantly displaced from the center of the SFOV (away from the scanner iso‐center). Radial and azimuthal image sharpness measurements using the Modulation Transfer Function (MTF) were made using the same RFOV at the center of the SFOV and at varying distances from the center. These MTF measurements were also made with varying values of the RFOV.Results:Clinical images with the bone anatomy of interest positioned farther from the center of the SFOV showed increasing image softness occasionally to the point of being non‐diagnostic. The MTF measurements showed that the resolution degraded significantly, by more than a factor of 2, moving from the center toward the periphery of the SFOV: from 12 cycles/cm to less than 6 cycles/cm at distances of 15 cm or more from the center of the SFOV. Increasing the RFOV beyond 20 cm also degraded the resolution, though less significantly.Conclusion:When preservation of bone detail is important one must not only use the proper bone reconstruction algorithm, but also must keep the body part as close to the center of the SFOV as possible. Though this may be difficult with some imaging tasks, such as imaging of the shoulder and elbow, every effort should be made to this end. For the best resolution, the RFOV should also be kept small, ideally to 20 cm or less.Partial research funding from GE HealthCare.
SU‐F‐18C‐05: Characterization of a Silicon Strip Photon‐Counting Detector in the Presence of Compton Scatter: A Simulation Study
Authors: Ziemer B , Ding H , Cho H 
Published: July 2014

Purpose:To investigate the effect of Compton scatter on detection efficiency and charge‐sharing for a Si strip photon‐counting detector as a function of pixel pitch, slice thickness and total pixel length.Methods:A CT imaging system employing a silicon photon‐counting detector was implemented using the GATE Monte Carlo package. A focal spot size of 300 µm, magnification of 1.33, and pixel pitches of 0.1 and 0.5mm were initially investigated. A 60 kVp spectrum with 3 mm Al filter was used and energy spectral degradation based on a prototype detector was simulated. To study charge‐sharing, a single pixel was illuminated, and the detector response in neighboring pixels was investigated. A longitudinally semiinfinite detector was simulated to optimize the quantum detection efficiency of the imaging system as a function of pixel pitch, slice thickness and depth of interaction. A 2.5 mm thick tungsten plate with a 0.01 mm by 1.5 mm slit was implemented to calculate the modulation transfer function (MTF) from projection‐based images. A threshold of 15 keV was implemented in the detector simulation. The preliminary charge sharing investigation results considered only scattering effects and the detector electronics related factors were neglected.Results:Using a 15 keV threshold, 1% of the pixel charge migrated into neighboring pixels with a pixel size of 0.1×0.1 mm2. The quantum detection efficiency was 77%, 84%, 87% and 89% for 15 mm, 22.5 mm, 30 mm, and 45 mm length silicon detector pixels, respectively. For a pixel pitch of 0.1 mm, the spatial frequency at 10% of the maximum MTF was found to be 5.2 lp/mm. This agreed with an experimental MTF measurement of 5.3 lp/mm with a similar detector configuration.Conclusion:Using optimized design parameters, Si strip photon‐counting detectors can offer high detection efficiency and spatial resolution even in the presence of Compton scatter.
SU‐F‐18C‐10: Clinical Implementation of Radiochromic Film Based CTDI Measurements
Authors: Quintero C , Tomic N , DeBlois F , Seuntjens J , Devic S 
Published: July 2014

Purpose:To evaluate accuracy and reproducibility of a radiochromic film‐based protocol to measure computer tomography dose index (CTDI) as a part of annual QA on CT scanners and kV CBCT systems attached to linear accelerators.Methods:Energy dependence of Gafchromic XR‐QA2(R) film model was tested over imaging beam qualities (50 – 140 kVp). Film pieces were irradiated in air to known values of air kerma in air (up to 10 cGy). Change in film reflectance was determined with an in‐house written code using images produced by a flatbed document scanner. Calibration curves for each beam quality were created, and film responses for same air‐kerma values were compared.Sets of film strips were placed into holes of a CTDI phantom and irradiated for several clinical scanning protocols on CT‐simulators and CBCT systems. Film reflectance change was converted into dose to water and used to calculate CTDIvol values. Measured CTDIvol values were compared to tabulated CTDIvol values.Results:Average variations of ±5.2% in the mean film reflectance change were observed in the energy range of 80 to 140 keV, and 11.1% between 50 and 140 keV. The averaged measured CTDI values presented a mean variation for the same machine and protocol of 2.6%. However, measured CTDI values were in average 10% lower than tabulated CTDI values for CT‐simulators, and 44% higher for CBCT systems.Conclusion:We found that in relatively broad range of beam qualities used in diagnostic radiology variation of film response is within ±5% resulting in ±15% systematic error in dose estimates if a single calibration curve is used. Relatively large discrepancy between measured and tabulated CTDI values for different protocols and imaging systems used within radiotherapy department strongly support the trend towards replacing CTDI value with equilibrium dose measurement in the center of cylindrical phantom as suggested by TG‐111.This work was supported by the Natural Sciences and Engineering Research Council of Canada, Contract No. 386009; Partial support by CREATE, Medical Physics Research Training Network grant of the Natural Science and Engineering Research Council, Contract No. 432290.
SU‐F‐18C‐14: Hessian‐Based Norm Penalty for Weighted Least‐Square CBCT Reconstruction
Authors: Sun T , Sun N , Wang J , Tan S 
Published: July 2014

Purpose:To develop a Hessian‐based norm penalty for cone‐beam CT (CBCT) reconstruction that has a similar ability in suppressing noise as the total variation (TV) penalty while avoiding the staircase effect and better preserving low‐contrast objects.Methods:We extended the TV penalty to a Hessian‐based norm penalty based on the Frobenius norm of the Hessian matrix of an image for CBCT reconstruction. The objective function was constructed using the penalized weighted least‐square (PWLS) principle. An effective algorithm was developed to minimize the objective function using a majorization‐minimization (MM) approach. We evaluated and compared the proposed penalty with the TV penalty on a CatPhan 600 phantom and an anthropomorphic head phantom, each acquired at a low‐dose protocol (10mA/10ms) and a high‐dose protocol (80mA/12ms). For both penalties, contrast‐to‐noise (CNR) in four low‐contrast regions‐of‐interest (ROIs) and the full‐width‐at‐half‐maximum (FWHM) of two point‐like objects in constructed images were calculated and compared.Results:In the experiment of CatPhan 600 phantom, the Hessian‐based norm penalty has slightly higher CNRs and approximately equivalent FWHM values compared with the TV penalty. In the experiment of the anthropomorphic head phantom at the low‐dose protocol, the TV penalty result has several artificial piece‐wise constant areas known as the staircase effect while in the Hessian‐based norm penalty the image appears smoother and more similar to that of the FDK result using the high‐dose protocol.Conclusion:The proposed Hessian‐based norm penalty has a similar performance in suppressing noise to the TV penalty, but has a potential advantage in suppressing the staircase effect and preserving low‐contrast objects.This work was supported in part by National Natural Science Foundation of China (NNSFC), under Grant Nos. 60971112 and 61375018, and Fundamental Research Funds for the Central Universities, under Grant No. 2012QN086.
MO‐A‐19A‐01: Interview Like Your Job Depended On It!
Authors: Miller R , Meineke M 
Published: July 2014

The purpose of our talk is to provide a relaxed and fun session for those seeking to improve their interviewing skills. You got your foot in the door, they liked your resume, and thought you looked interesting enough to bring out to meet face to face. How do you showcase your skills, while simultaneously showing them how well you would mesh with their current team? How do you respond to these newly popular questions that seem more interested in your feelings than in your technical skills? How do you pick up on the details that might clue you in that this potential employer isn' t right for you? Our session will give you concrete advice with examples to give you the tools you need to be successful in your next interview.Learning Objectives:

Review some basic interviewing skills in terms of behavioral questions, common etiquette and human interactions
Demonstrate a good interview
Review some basic negotiating tactics
MO‐A‐BRD‐03: Quantifying 19F‐Labeled Human Natural Killer Cell‐Trafficking with MRI
Authors: Ludwig KD , Bouchlaka MN , Gordon JW , Bednarz BP , Capitini CM , Fain SB 
Published: July 2014

Purpose:To determine 19F‐labeling efficiency in ex vivo MRI of cultured human Natural Killer (hNK) cells and to quantify 19F‐labeled NK cell trafficking in vivo in naive mice and in mice bearing pediatric cancers with MRI.Methods:One immunodeficient and one neuroblastoma tumorbearing mouse were anesthetized with ketamine and xylazine. The hNK and mouse NK cells isolated from healthy donor peripheral blood mononuclear cells or spleens were expanded and incubated for 24 hours in a commercially available perfluoropolyether (PFPE) tracer. NMR was performed on a 9.4T spectrometer to verify successful uptake of PFPE agent into NK cells. Imaging was performed on a 4.7T small animal MRI system using a 19F volume quadrature coil. 19F images were acquired using a spinecho sequence (1.1×1.1×2.0mm3 resolution, ∼42 minutes scan time). A 19F reference vial was placed contralateral to the tumor/injection site for in vivo quantification.Results:A dose‐dependent response of 19F signal was shown in mouse NK cells labeled with increasing concentrations of PFPE. NMR spectra of the separated cells and supernatant confirmed that 19F signal originated from within the hNK cells. In vitro signal from 19F‐labeled hNK cells was quantified as a function of cell concentration. About 1.6×106 hNK cells was determined to be the minimum cell concentration detectabilty for a 1.1×1.1×2.0mm3 voxel at the 42 minute scan time. 19F‐labeled hNK cells were injected into the flank or tumor directly. 19F signal stayed localized in flank or within the neuroblastoma tumor for at least 48 hours.Conclusion:19F‐labeling of NK cells has been confirmed in vitro, both with imaging and spectroscopic analysis. hNK injection into a neuroblastoma tumor‐bearing mouse showed that hNK cells can be successfully detected and tracked longitudinally in vivo. Improving sensitivity for quantification of trafficking patterns within the tumor is ongoing.
MO‐A‐BRD‐06: In Vivo Cherenkov Video Imaging to Verify Whole Breast Irradiation Treatment
Authors: Zhang R , Jarvis L , Gladstone D , Andreozzi J , Hitchcock W , Glaser A , Pogue B 
Published: July 2014

Purpose:To show in vivo video imaging of Cherenkov emission (Cherenkoscopy) can be acquired in the clinical treatment room without affecting the normal process of external beam radiation therapy (EBRT). Applications of Cherenkoscopy, such as patient positioning, movement tracking, treatment monitoring and superficial dose estimation, were examined.Methods:In a phase 1 clinical trial, including 12 patients undergoing post‐lumpectomy whole breast irradiation, Cherenkov emission was imaged with a time‐gated ICCD camera synchronized to the radiation pulses, during 10 fractions of the treatment. Images from different treatment days were compared by calculating the 2‐D correlations corresponding to the averaged image. An edge detection algorithm was utilized to highlight biological features, such as the blood vessels. Superficial dose deposited at the sampling depth were derived from the Eclipse treatment planning system (TPS) and compared with the Cherenkov images. Skin reactions were graded weekly according to the Common Toxicity Criteria and digital photographs were obtained for comparison.Results:Real time (fps = 4.8) imaging of Cherenkov emission was feasible and feasibility tests indicated that it could be improved to video rate (fps = 30) with system improvements. Dynamic field changes due to fast MLC motion were imaged in real time. The average 2‐D correlation was about 0.99, suggesting the stability of this imaging technique and repeatability of patient positioning was outstanding. Edge enhanced images of blood vessels were observed, and could serve as unique biological markers for patient positioning and movement tracking (breathing). Small discrepancies exists between the Cherenkov images and the superficial dose predicted from the TPS but the former agreed better with actual skin reactions than did the latter.Conclusion:Real time Cherenkoscopy imaging during EBRT is a novel imaging tool that could be utilized for patient positioning, movement tracking, treatment monitoring, superficial dose and skin reaction estimation and prediction.
MO‐A‐BRD‐08: Radiosurgery Beyond Cancer: Real‐Time Target Localization and Treatment Planning for Cardiac Radiosurgery Under MRI Guidance
Authors: Ipsen S , Blanck O , Oborn B , Bode F , Liney G , Keall P 
Published: July 2014

Purpose:Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting >2.5M Americans and >4.5M Europeans. AF is usually treated with minimally‐invasive, time consuming catheter ablation techniques. Radiosurgery of the pulmonary veins (PV) has been proposed for AF treatment, however is challenging due to the complex respiratory and cardiac motion patterns. We hypothesize that an MRI‐linac could solve the difficult real‐time targeting and adaptation problem. In this study we quantified target motion ranges on cardiac MRI and analyzed the dosimetric benefits of margin reduction assuming real‐time MRI tracking was applied.Methods:For the motion study, four human subjects underwent real‐time cardiac MRI under free breathing. The target motion on coronal and axial cine planes was analyzed using a template matching algorithm. For the planning study, an ablation line at each PV antrum was defined as target on an AF patient scheduled for catheter ablation. Various safety margins ranging from 0mm (perfect tracking) to 8mm (untracked motion) were added to the target defining the PTV. 30Gy single fraction IMRT plans were then generated. Finally, the influence of a 1T magnetic field on treatment beam delivery was calculated using the Geant4 Monte Carlo algorithm to simulate the dosimetric impact of MRI guidance.Results:The motion study showed the mean respiratory motion of the target area on MRI was 8.4mm (SI), 1.7mm (AP) and 0.3mm (LR). Cardiac motion was small (<2mm). The planning study showed that with increasing safety margins to encompass untracked motion, dose tolerances for OARs such as the esophagus and airways were exceeded by >100%. The magnetic field had little impact on the dose distribution.Conclusion:Our results indicate that real‐time MRI tracking of the PVs seems feasible. Accurate image guidance for high‐dose AF radiosurgery is essential since safety margins covering untracked target motion will result in unacceptable treatment plans.
MO‐A‐BRD‐09: A Data‐Mining Algorithm for Large Scale Analysis of Dose‐Outcome Relationships in a Database of Irradiated Head‐And‐Neck (HN) Cancer Patients
Authors: Robertson SP , Quon H , Kiess AP , Moore JA , Yang W , Cheng Z , Sharabi A , McNutt TR 
Published: July 2014

Purpose:To develop a framework for automatic extraction of clinically meaningful dosimetric‐outcome relationships from an in‐house, analytic oncology database.Methods:Dose‐volume histograms (DVH) and clinical outcome‐related structured data elements have been routinely stored to our database for 513 HN cancer patients treated from 2007 to 2014. SQL queries were developed to extract outcomes that had been assessed for at least 100 patients, as well as DVH curves for organs‐at‐risk (OAR) that were contoured for at least 100 patients. DVH curves for paired OAR (e.g., left and right parotids) were automatically combined and included as additional structures for analysis. For each OAR‐outcome combination, DVH dose points, D(Vt), at a series of normalized volume thresholds, Vt=[0.01,0.99], were stratified into two groups based on outcomes after treatment completion. The probability, P[D(Vt)], of an outcome was modeled at each Vt by logistic regression. Notable combinations, defined as having P[D(Vt)] increase by at least 5% per Gy (p<0.05), were further evaluated for clinical relevance using a custom graphical interface.Results:A total of 57 individual and combined structures and 115 outcomes were queried, resulting in over 6,500 combinations for analysis. Of these, 528 combinations met the 5%/Gy requirement, with further manual inspection revealing a number of reasonable models based on either reported literature or proximity between neighboring OAR. The data mining algorithm confirmed the following well‐known toxicity/outcome relationships: dysphagia/larynx, voice changes/larynx, esophagitis/esophagus, xerostomia/combined parotids, and mucositis/oral mucosa. Other notable relationships included dysphagia/pharyngeal constrictors, nausea/brainstem, nausea/spinal cord, weight‐loss/mandible, and weight‐loss/combined parotids.Conclusion:Our database platform has enabled large‐scale analysis of dose‐outcome relationships. The current data‐mining framework revealed both known and novel dosimetric and clinical relationships, underscoring the potential utility of this analytic approach. Multivariate models may be necessary to further evaluate the complex relationship between neighboring OARs and observed outcomes.This research was supported through collaborations with Elekta, Philips, and Toshiba.
MO‐A‐BRD‐10: A Fast and Accurate GPU‐Based Proton Transport Monte Carlo Simulation for Validating Proton Therapy Treatment Plans
Authors: Wan Chan Tseung H , Ma J , Beltran C 
Published: July 2014

Purpose:To build a GPU‐based Monte Carlo (MC) simulation of proton transport with detailed modeling of elastic and non‐elastic (NE) protonnucleus interactions, for use in a very fast and cost‐effective proton therapy treatment plan verification system.Methods:Using the CUDA framework, we implemented kernels for the following tasks: (1) Simulation of beam spots from our possible scanning nozzle configurations, (2) Proton propagation through CT geometry, taking into account nuclear elastic and multiple scattering, as well as energy straggling, (3) Bertini‐style modeling of the intranuclear cascade stage of NE interactions, and (4) Simulation of nuclear evaporation. To validate our MC, we performed: (1) Secondary particle yield calculations in NE collisions with therapeutically‐relevant nuclei, (2) Pencil‐beam dose calculations in homogeneous phantoms, (3) A large number of treatment plan dose recalculations, and compared with Geant4.9.6p2/TOPAS. A workflow was devised for calculating plans from a commercially available treatment planning system, with scripts for reading DICOM files and generating inputs for our MC.Results:Yields, energy and angular distributions of secondaries from NE collisions on various nuclei are in good agreement with the Geant4.9.6p2 Bertini and Binary cascade models. The 3D‐gamma pass rate at 2%–2mm for 70–230 MeV pencil‐beam dose distributions in water, soft tissue, bone and Ti phantoms is 100%. The pass rate at 2%–2mm for treatment plan calculations is typically above 98%. The net computational time on a NVIDIA GTX680 card, including all CPU‐GPU data transfers, is around 20s for 1×107 proton histories.Conclusion:Our GPU‐based proton transport MC is the first of its kind to include a detailed nuclear model to handle NE interactions on any nucleus. Dosimetric calculations demonstrate very good agreement with Geant4.9.6p2/TOPAS. Our MC is being integrated into a framework to perform fast routine clinical QA of pencil‐beam treatment plans. Hardware for such a system will cost under $5000.This work was funded in part by a grant from Varian Medical Systems, Inc.