bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐I‐56: High‐Precision Gamma‐Ray Analysis of Medical Isotopes
Authors: Chopra N , Chillery T , McCutchan E , Chowdhury P , Smith C , Lister C 
Published: July 2016

Purpose:Advanced, time‐resolved, Compton‐suppressed gamma‐ray spectroscopy with germanium detectors is implemented for assaying medical isotopes to study the radioactive decay process leading to a more accurate appraisal of the received dose and treatment planning. Lowell's Array for Radiological Assay (LARA), a detector array that is comprised of six Compton‐suppressed high‐purity germanium detectors, is currently under development at UMass‐Lowell which combines Compton‐suppression and time‐and‐angle correlations to allow for highly efficient and highly sensitive measurements.Methods:Two isotopes produced Brookhaven Linac Isotope Producer (BLIP) were investigated. 82Sr which is the parent isotope for producing 82Rb is often used in cardiac PET. 82Sr gamma‐ray spectrum is dominated by the 511keV photons from positron annihilation which prevent precise measurement of co‐produced contaminant isotopes. A second project was to investigate the production of platinum isotopes. Natural platinum was bombarded with protons from 53MeV to 200MeV. The resulting spectrum was complicated due to the large number of stable platinum isotopes in the target, the variety of open reaction channels (p,xn), (p,pxn), (p,axn).Results:By using face‐to‐face NaI(Tl) counters 90‐degrees to the Compton‐suppressed germaniums to detect the 511keV photons, a much cleaner and more sensitive measurement of 85Sr and other contaminants was obtained. For the platinum target, we identified the production of 188–189–191–195Pt, 191–192–193–194–195–196Au and 186–188–189–190–192–194–189–190–192–194Ir. For example, at the lower energies (53 and 65MeV), we measured 191Pt production cross‐sections of 144mb and 157mb. Considerable care was needed in following the process of dissolving and diluting the samples to get consistent results. The new LARA array will help us better ascertain the absolute efficiency of the counting system and more reliable production cross‐sections.Conclusion:Modern HPGe spectroscopic techniques provide enhanced sensitivity, promising precise quantification of the quality of radioisotopes used in medical physics. Using new decay information may have non‐trivial impact on treatment planning and dose‐assessment.
SU‐F‐I‐64: Comparison of Lipid Contents Using STEAM and PRESS with in Vivo High‐Resolution Spectra at 9.4 T
Authors: Song K‐H , Lim S‐I , Yoo C‐H , Choe B‐Y 
Published: July 2016

Purpose:The objective of this study is to compare lipid contents using localized point‐resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) sequences to assess lipid resonances in the liver, using in vivo high‐resolution spectra at 9.4 T.Methods:The examinations were performed on a Bruker 9.4T scanner using 4‐channel animal coil for higher resolution. We used PRESS (repetition time [TR]/ TE = 3500/20 ms; number of signal averages [NSA] = 128; acquisition data points = 2048) and STEAM (TR/TM/TE = 3500/10/20 ms; NSA = 128; acquisition data points = 2048). Lipid relaxations in HF diet mice were estimated at a fixed TR of 5000 ms, and TEs of 20–70 ms. All spectra acquired were processed using the Advanced Method for Accurate, Robust, and Efficient Spectral (AMARES) fitting algorithm including in the Java‐based Magnetic Resonance User Interface (jMRUI) software package. Preprocessing was performed using an automatic frequency shift and the Hankel‐Lanczos Singular Value Decomposition (HLSVD) filter with subtraction of water peak (4.70 ppm).Results:To accurately quantify lipid content, a sequence was selected. The total lipid and total saturated fatty acid were differently changed in HF diet mice that underwent PRESS compared with those that underwent STEAM (total lipid, p < 0.05; total saturated fatty acid, p < 0.001). Compared with PRESS, STEAM showed different total unsaturated fatty acid value (p < 0.001). Compared with PRESS, STEAM showed different total unsaturated and poly unsaturated bonds (total unsaturated bond, p<0.001; poly unsaturated bond, p < 0.001).Conclusion:Due to stronger J‐coupling effects on the PRESS sequence, the accurate estimation could not be obtained. STEAM is less sensitive to J‐coupling and gives a theoretically more accurate estimate at 9.4T.
SU‐F‐J‐04: Automated Detection of Diabetic Retinopathy Using Deep Convolutional Neural Networks
Authors: XU Kele , ZHU Li , WANG Ruixing , LIU Chang , ZHAO Yi 
Published: July 2016

Purpose:In this work, we explore to use very deep convolutional neural network (CNN) for the automatic classification of diabetic retinopathy using color fundus image.Methods:We apply translation, stretching, rotation and flipping to the labeled dataset. The original number of labeled‐frames is 3000, while after augmentations, 6000 frames with labels are used for the CNN training task. Several different CNN architectures have been proposed and tested. The architecture of our network contains 18 layers with parameters, consists of 12 convolutional layers, some of which followed by max‐pooling layers, and two fully connected layers. For a given input, the networks output two probabilities sum to 1, one for each class (as our problem is a two class classification problem).Results:To make a comparison, the performance of CNN‐based are compared to previous automatic classification attempts using the hand‐crafted features, such as: hard exudates, red lesions, micro‐aneurysms and blood vessel detection. We obtained an accuracy of 94.54% on our dataset using CNN, which rank as the highest with the comparison with previous handcrafted features‐based classifiers.Conclusion:With limited number of medical staff, an automated system can significantly decrease the tedious manual labor involved in diagnosing large quantities of retinal images. In this work, we explore the potential usage of CNN in retinal image classification. The results are encouraging and a clinical evaluation will be undertaken in order to be able to integrate the presented algorithm in a tool to diagnosis of diabetic retinopathy.
SU‐F‐J‐17: Patient Localization Using MRI‐Guided Soft Tissue for Head‐And‐Neck Radiotherapy: Indication for Margin Reduction and Its Feasibility
Authors: Qi X , Yang Y , Jack N , Santhanam A , Yang L , Chen A , Low D 
Published: July 2016

Purpose:On‐board MRI provides superior soft‐tissue contrast, allowing patient alignment using tumor or nearby critical structures. This study aims to study H&N MRI‐guided IGRT to analyze inter‐fraction patient setup variations using soft‐tissue targets and design appropriate CTV‐to‐PTV margin and clinical implication.Methods:282 MR images for 10 H&N IMRT patients treated on a ViewRay system were retrospectively analyzed. Patients were immobilized using a thermoplastic mask on a customized headrest fitted in a radiofrequency coil and positioned to soft‐tissue targets. The inter‐fraction patient displacements were recorded to compute the PTV margins using the recipe: 2.5∑+0.7σ. New IMRT plans optimized on the revised PTVs were generated to evaluate the delivered dose distributions. An in‐house dose deformation registration tool was used to assess the resulting dosimetric consequences when margin adaption is performed based on weekly MR images. The cumulative doses were compared to the reduced margin plans for targets and critical structures.Results:The inter‐fraction displacements (and standard deviations), ∑ and σ were tabulated for MRI and compared to kVCBCT. The computed CTV‐to‐PTV margin was 3.5mm for soft‐tissue based registration. There were minimal differences between the planned and delivered doses when comparing clinical and the PTV reduced margin plans: the paired t‐tests yielded p=0.38 and 0.66 between the planned and delivered doses for the adapted margin plans for the maximum cord and mean parotid dose, respectively. Target V95 received comparable doses as planned for the reduced margin plans.Conclusion:The 0.35T MRI offers acceptable soft‐tissue contrast and good spatial resolution for patient alignment and target visualization. Better tumor conspicuity from MRI allows soft‐tissue based alignments with potentially improved accuracy, suggesting a benefit of margin reduction for H&N radiotherapy. The reduced margin plans (i.e., 2 mm) resulted in improved normal structure sparing and accurate dose delivery to achieve intended treatment goal under MR guidance.
SU‐F‐J‐18: Feasibility of Open Mask Immobilization with Optical Imaging Guidance (OIG) for H&N Radiotherapy
Authors: Zhao B , Maquilan G , Anders M , Jiang S , Schwartz D 
Published: July 2016

Purpose:Full face and neck thermoplastic masks provide standard‐of‐care immobilization for patients receiving H&N IMRT. However, these masks are uncomfortable and increase skin dose. The purpose of this pilot study was to investigate the feasibility and setup accuracy of open face and neck mask immobilization with OIG.Methods:Ten patients were consented and enrolled to this IRB‐approved protocol. Patients were immobilized with open masks securing only forehead and chin. Standard IMRT to 60–70 Gy in 30 fractions were delivered in all cases. Patient simulation information, including isocenter location and CT skin contours, were imported to a commercial OIG system. On the first day of treatment, patients were initially set up to surface markings and then OIG referenced to face and neck skin regions of interest (ROI) localized on simulation CT images, followed by in‐room CBCT. CBCTs were acquired at least weekly while planar OBI was acquired on the days without CBCT. Following 6D robotic couch correction with kV imaging, a new optical real‐time surface image was acquired to track intrafraction motion and to serve as a reference surface for setup at the next treatment fraction. Therapists manually recorded total treatment time as well as couch shifts based on kV imaging. Intrafractional ROI motion tracking was automatically recorded.Results:Setup accuracy of OIG was compared with CBCT results. The setup error based on OIG was represented as a 6D shift (vertical/longitudinal/lateral/rotation/pitch/roll). Mean error values were −0.70±3.04mm, −0.69±2.77mm, 0.33±2.67 mm, −0.14±0.94 o, −0.15±1.10o and 0.12±0.82o, respectively for the cohort. Average treatment time was 24.1±9.2 minutes, comparable to standard immobilization. The amplitude of intrafractional ROI motion was 0.69±0.36 mm, driven primarily by respiratory neck motion.Conclusion:OGI can potentially provide accurate setup and treatment tracking for open face and neck immobilization. Study accrual and patient/provider satisfaction survey collection remain ongoing.This study is supported by VisionRT, Ltd
SU‐F‐J‐36: Comparison of Ball Bearing and Iso‐Cube Phantoms for KV‐MV Iso‐Center Coincidence Check
Authors: Markovich A , Yang C 
Published: July 2016

Purpose:To compare two different quality assurance tools for kV‐MV isocenter coincidence check.Methods:Ball‐Bearing device (BBD) (Elekta) provided along with a CBCT equipped LINAC and isocenter cube phantom (CP) (a commercial product of Modus Medical Devices) are utilized to check the coincidence between the MV and kV beam isocenters. The microstepping meter of the BBD allows precision adjustment to better than 0.01mm in three directions. The BBD is aligned to the MV‐isocenter with the lasers and followed by taking MV‐images of at two collimator angles at each cardinal gantry, then its position adjusted. This process takes in iterative steps until 0.25mm tolerance is achieved. Four planar kV‐images are taken at cardinal angles and deviations of BBD position from kVisocenter are evaluated. CP is positioned on the couch with the lasers at known offset from the isocenter. CBCT is utilized to set the cube to its kV isocenter with the precision of linac's couch (1mm). MV‐images are taken at various gantry, collimator, and couch angles and evaluated with the CP manufacturer provided QA software to determine coincidence of the 6mm steel ball at cube center with MV‐isocenter. Three sets of measurements, one after another, were performed on the same day for each phantom on the same linac.Results:Assuming little variation between kV and MV isocenters in a short time, BBD measurements are more reproducible than CP. With comparable conditions both methods agree within 0.5 mm in each direction, while for BBD average standard deviation was 0.07mm and for iso‐cube 0.3mm.Conclusion:Since BBD is more reliable and its results are more reproducible, it should be used during the monthly QA. Since CP is a more efficient device, it should be used for daily QA. A comparison study between the two devices should be periodically performed.
SU‐F‐J‐48: Effect of Scan Length On Magnitude of Imaging Dose in KV CBCT
Authors: Deshpande S , Dhote D , Naidu S , Sutar A , Kannan V 
Published: July 2016

Purpose:To study effect of scan length on magnitude of imaging dose deposition in Varian kV CBCT for head & neck and pelvis CBCT.Methods:To study effect of scan length we measured imaging dose at depth of 8 cm for head and neck Cone Beam Computed Tomography (CBCT) acquisition (X ray beam energy is used 100kV and 200 degree of gantry rotation) and at 16 cm depth for pelvis CBCT acquisition (X ray beam energy used is 125 kV and 360 degree of gantry rotation) in specially designed phantom. We used farmer chamber which was calibrated in kV X ray range for measurements .Dose was measured with default field size, and reducing field size along y direction to 10 cm and 5 cm.Results:As the energy of the beam decreases the scattered radiation increases and this contributes significantly to the dose deposited in the patient. By reducing the scan length to 10 Cm from default 20.6 cm we found a dose reduction of 14% for head and neck CBCT protocol and a reduction of 26% for pelvis CBCT protocol. Similarly for a scan length of 5cm compared to default the dose reduction in head and neck CBCT protocol is 36% while in the pelvis CBCT protocol the dose reduction is 50%.Conclusion:By limiting the scan length we can control the scatter radiation generated and hence the dose to the patient. However the variation in dose reduction for same length used in two protocols is because of the scan geometry. The pelvis CBCT protocol uses a full rotation and head and neck CBCT protocol uses partial rotation.
SU‐F‐J‐50: Study On the Magnetic Field Effect On the Exradin W1 Plastic Scintillation Detector
Authors: Wen Z , Therriault‐Proulx F , Owens C , Ibbott G , Beddar S 
Published: July 2016

Purpose:To study the response of the Exradin W1 plastic scintillator detector to a 6 MV photon field in the presence of a strong magnetic field (B).Methods:An Exradin W1 scintillator detector coupled to a SuperMax two‐channel electrometer, both manufactured by Standard Imaging, Inc., was first calibrated in a Co‐60 beam. The Cerenkov Light Ratio (CLR) was obtained following the procedure recommended by the manufacturer. Subtracting signal in channel 2 multiplied by CLR from the signal in channel 1 should lead to a Cerenkov‐free signal. The W1 scintillator was placed in a plastic phantom inside a dipole electromagnet (GMW Associates) that could produce a strong B field, and irradiated using a 6 MV beam from an Elekta Versa HD LINAC. Signals from both channels of the W1 scintillator were acquired as a function of B (0 ‐ 1.5 T).Results:The signals from both channels increased as a function of the B field strength. At 1.5 T, channel 1 increased by 11% compared to the baseline (B=0 T), while channel 2 increased by 22%. Applying the recommended Cerenkov correction led to a 2% difference between dose measurement with and without a magnetic field. The values between B=0.3 T and B=1.5 T remained constant.Conclusion:Signals from the Exradin W1 plastic scintillation detector increased as the B field increased. This increase mainly comes from a change in the amount of Cerenkov light coupled within the optical fiber. Removing the Cerenkov component following the procedure recommended by the manufacturer showed to be an effective way to measure dose accurately in strong magnetic fields. The cause for the residual 2% difference is currently under investigation.We acknowledge research support from Elekta AB.
SU‐F‐J‐52: A Novel Approach to X‐Ray Tube Quality Assurance for CBCT Systems in Order to Better Assess the Patient Imaging Dose in a Large, Multi‐Unit Treatment Facility
Authors: Buckley L , Webb R , Lambert C , Nyiri B , Gerig L 
Published: July 2016

Purpose:To standardize the tube calibration for Elekta XVI cone beam CT (CBCT) systems in order to provide a meaningful estimate of the daily imaging dose and reduce the variation between units in a large centre with multiple treatment units.Methods:Initial measurements of the output from the CBCT systems were made using a Farmer chamber and standard CTDI phantom. The correlation between the measured CTDI and the tube current was confirmed using an Unfors Xi detector which was then used to perform a tube current calibration on each unit.Results:Initial measurements showed measured tube current variations of up to 25% between units for scans with the same image settings. In order to reasonably estimate the imaging dose, a systematic approach to x‐ray generator calibration was adopted to ensure that the imaging dose was consistent across all units at the centre and was adopted as part of the routine quality assurance program. Subsequent measurements show that the variation in measured dose across nine units is on the order of 5%.Conclusion:Increasingly, patients receiving radiation therapy have extended life expectancies and therefore the cumulative dose from daily imaging should not be ignored. In theory, an estimate of imaging dose can be made from the imaging parameters. However, measurements have shown that there are large differences in the x‐ray generator calibration as installed at the clinic. Current protocols recommend routine checks of dose to ensure constancy. The present study suggests that in addition to constancy checks on a single machine, a tube current calibration should be performed on every unit to ensure agreement across multiple machines. This is crucial at a large centre with multiple units in order to provide physicians with a meaningful estimate of the daily imaging dose.
SU‐F‐J‐73: Simple Approach for Quantification of Metal Artifact Reduction Capabalities of Dual‐Energy CT
Authors: Lamichhane N , Padgett K , Li X , Mihaylov I 
Published: July 2016

Purpose:To present a simple method for quantification of dual‐energy CT metal artifact reduction capabilitiesMethods:A phantom was constructed from solid water and a steel cylinder. Solid water is commonly used for radiotherapy QA, while steel cylinders are readily available in hardware stores. The phantom was scanned on Siemens Somatom 64‐slice dual‐energy CT system. Three CTs were acquired at energies of 80kV (low), 120kV (nominal), and 140kV (high). The low and high energy acquisitions were used to generate dual‐energy (DE) monoenergetic image sets, which also utilized metal artifact reduction algorithm (Maris). Several monoenergetic DE image sets, ranging from 70keV to 190keV were generated. The size of the metal artifact was measured by two different approaches. The first approach measured the distance from the center of the steel cylinder to a location with nominal (undisturbed by metal) HU value for the 120kV, DE 70keV, and DE 190keV image sets. In the second approach, the distance from the center of the cylinder to the edge of the air pocket for the above mentioned three image sets was measured.Results:The DE 190keV synthetic image set demonstrated the largest reduction of the metal artifacts. The size of the artifact was more than three times the actual size of the milled hole in the solid water in the DE 190keV, as compared to more than 7.5 times larger as estimated from the 120kV uncorrected imageConclusion:A simple phantom for quantification of dual‐energy CT metal artifact reduction capabilities was presented. This inexpensive phantom can be easily built from components available in every radiation oncology department. It allows quick assessment and quantification of the properties of different metal artifact reduction algorithms, available on modern dual‐energy CT scanners.
SU‐F‐J‐90: Effects of Optimization Cost Function On Ventilation in SBRT of NSCLC
Authors: Mihaylov I , Latifi K , De Ornelas‐Couto M , Moros E , Zhang G 
Published: July 2016

Purpose:To explore the effects of dose‐volume (Dvh) and dose‐mass (Dmh) inverse optimization approaches on the lung ventilation for SBRT in NSCLC.Methods:Six cases were studied. For each case ventilation was computed on voxel‐by‐voxel basis, derived from the time‐resolved (4D) CT scans. Ventilation is defined as voxel volume change between full inspiration and full expiration, divided by voxel volume. The ventilation volume was mapped to full expiration phase. For each patient case two IMRT plans were created ‐ one with Dvh and one with Dmh quadratic objective function, applied to the OARs. The OARs used as dose limiting structures were lung, spinal cord, esophagus, and heart. After obtaining the IMRT solutions average doses as well as 2000 cGy isovolumes and isomases were extracted for ventilation volumes of 0.5, 0.9, 1.1, 1.2, and 1.5. Ventilation volume of 0.5 incorporates all CT voxels having a voxel volume change (exhale‐to‐inhale) 50% and more. Similarly, ventilation volume of 1.5 encompasses all CT voxels with volume change of 150% and more. Thereby, ventilation volume of 0.5 encompasses almost the entire lung, while ventilation volume of 1.5 represents ∼1% of ventilation 0.5 volume. The doses, the isovolumes, and the isomasses derived from the Dvh optimization were used as references.Results:The results indicate that with decreasing ventilation (from 1.5 to 0.5) the differences between Dvh and Dmh derived tallied quantities decrease. For some cases the differences between the average doses for the different ventilation volumes are up to 20%. The changes in the isovolumes and the isomasses for the different ventilations are much more dramatic and can differ by a factor of 3.5.Conclusion:This is the first investigation on the effects of different optimization schemes on lung ventilation. The presented results indicate that the larger the ventilation the more dramatic the effects.Supported in part by NIH R01 CA163360