bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐29: A Prior Information Based Total‐Variation Digital Tomosynthesis Reconstruction Algorithm
Authors: Jian Y , Cai J , Yin F 
Published: November 2011

Purpose: To develop a total‐variation (TV) based compressive sensing image reconstruction algorithm using a set of limited‐angle projections by applying a prior image information to enhance the image quality and anatomic information of current Four&#8208;dimensiona Digital Tomosynthesis (4D‐DTS). In the iterative algorithm, both TV regularization and Bspline deformation field are included to accurately reconstruct 4D‐DTS images in order to reduce imaging dose. Methods: For 4D Cone Beam Computed Tomography (4D‐CBCT), images of different phases share similar anatomical struture, and their difference can be used as sparseness prior in the 4D‐DTS reconstruction. The Bspline tensor transforms the reference image to fit the target image, and is regulated by TV penalty terms in the cost function of the unconstrained optimization problem. Nonlinear conjugate gradient method is applied to solve the unconstrained problem. Results: Several phase pairs of 4D‐CBCT are used examples. With voxel per region sets 50, the algorithm can have the most similarity with the target image with the fastest convergence. By decreasing Bspline resolution, the deformation will be become more flexible while losing some accuracy of registration. The similarity between target image and resulted image can be tuned by regularization factor, which will enable us to determine how much additional information is needed to build the new image volume. The integrated built CPU and GPU platform provides the acceleration tools of forward/backward projection and Bspline coefficients calculation for large‐scale 4D‐CBCT data in the iteration process, which is 100 times faster than using only software method. Conclusions: The performance of the algorithm is determined by two built‐in parameters in the algorithm: Bspline Resolution and Regulization Factor, whose tuning can favor different edge and resolution performances or fidelity and similarity to the target measurements, and also determine the flexibility and accuracy during the registration.Research sponsored by Varian Medical System.
SU‐E‐I‐47: Characterization of Beryllium Oxide Optically Stimulated Luminescence Detectors for Use in Diagnostic Radiology
Authors: Eller S , Rodriguez M , Ruan C , Yukihara E 
Published: November 2011

Purpose: To determine the response of beryllium oxide (BeO) optically stimulated luminescence (OSL) detectors in diagnostic radiology and to develop a protocol for proper handling and readout. Methods: The BeO OSL detectors used in this study are ∼4.7 mm × ∼4.7 mm × 0.5 mm chips and weigh ∼32 mg each (Thermalox 995, Brush Ceramic Products, Brush Wellman, Inc.). Detectors were annealed at 700 °C for 15 minutes prior to irradiation and protected from light. The dose response, minimum detectable dose, and reproducibility were determined using 90Sr/90Y beta sources. Clinical irradiations were performed at OUHSC with a radiographic unit (Proteus XR/a, GE Healthcare). An 6 cm3 ionization chamber (model 10X5‐6, Radcal Corporation), A12O3:C OSLDs (Luxel™, Landuaer, Inc.), and LiF:Mg,Ti (TLD‐100, Thermo Fisher Scientific, Inc.) were also used for comparison. The relative response of each type of detector was determined by varying the preset tube voltage of the radiographic unit from 50–130 kVp. The OSL and TL signals were read using a Riso/ TL/OSL‐DA‐15 automated reader (Riso/ National Laboratory), which uses continuous blue stimulation for the OSL measurements. Results: BeO was found to be very sensitive, with a minimum detectable dose of ∼20 μGy using the Riso/ OSL reader. The dose response is linear up to ∼5 Gy, and the reproducibility using a proper methodology is less than 1.2 %. BeO under‐responds to low energy photons by a factor less than 20% relative to 130 kVp, whereas Luxel™ over‐responds to low energy photons by a factor less than 40% relative to 130 kVp. Conclusions: This study demonstrates the dosimetric properties of BeO for applications in diagnostic radiology and indicates that BeO may require energy correction factors to be applied.Stephen Eller was supported by ProCure Treatment Centers, Inc.
SU‐E‐I‐54: A Database for Estimating Scanner‐Specific CT Organ Dose
Authors: Rupcich F , Schmidt T 
Published: November 2011

Purpose: To develop a database for estimating scanner‐specific organ dose in a voxelized patient model for any spectral shape and angular tube current modulation setting. The database enables the estimation of organ dose for both existing and novel acquisition techniques without requiring Monte Carlo simulations. Methods: The transport of monoenergetic photons through three phantoms was simulated with the PENELOPE Monte Carlo radiation transport routines at 5 – 150 keV in 1 keV increments at 1000 projections in 0.36 degree increments. The source‐to‐detector distance for each simulation was 100 cm, with a source‐to‐isocenter distance of 50 cm. The lateral and axial extents of the detector were 100 cm and 16 cm respectively, while the detector pixel resolution was 0.25 mm. The first phantom was a 0.5 mm resolution anthropomorphic voxelized female phantom, while the other two phantoms were standard head and chest CTDI cylinders modeled using mathematical quadrics. Results: The simulations resulted in a normalized dose deposition table for numerous organs quantifying the typical dose deposited in the organ per emitted photon for each energy level and projection angle. The values in this table can be multiplied by an incident spectrum and number of photons at each projection angle and summed across all energies and angles to estimate the total organ dose. Similarly, the CTDIvol for a particular acquisition can be estimated from the dose deposition tables for the CTDI phantoms. The estimated CTDIvol can be used along with a physical CTDIvol measurement to convert the organ dose calculated from the database to a scanner specific estimate. Conclusions: The proposed database and procedure enable the estimation of scanner‐specific organ dose for CT scans utilizing any spectral shape and angular tube current modulation scheme without requiring Monte Carlo simulations.This project is funded in part by the US Food and Drug Administration, Office of Womenˈs Health (OWH), and by the Oak Ridge Institute of Science and Engineering (ORISE). Performance of Monte Carlo simulations were made possible by NSF grant OCI‐0923037.
SU‐E‐I‐98: Neurovascular Device Localization Accuracy Dependence on Exposure, Temporal Filtering, and Motion Blur for Real Time Imaging with the Microangiographic Fluoroscope
Authors: Panse A , Jain A , Bednarek D , Rudin S 
Published: November 2011

Purpose: To study the accuracy of localization during fluoroscopy for static and moving objects and its dependence on quantum noise determined by exposure and temporal filtering and on motion blur determined by speed of object movement. Methods: A stainless steel stent (90 micron struts) used as object of interest was mounted on a stepper motor controlled linear stage with effective step size of 1.7 micron. The new high resolution 35‐ micron‐ pixel Microangiographic Fluoroscope (MAF) was used for imaging the stent as it was moved forward 7500 steps and brought back to the original position for different speeds. Fluoroscopy was performed at 4 different exposures. The object detection algorithm available in LabVIEW IMAQ Vision software was used to localize the stent using different temporal filtering weights. Results: (a) For fixed exposure, stationary object localization accuracy is improved by a factor of 5 for higher temporal filtering compared to no temporal filtering; however, for moving objects the error in localization increased 50 percent due to motion blurring when the filter weight was increased from 4 to 8. (b) For fixed temporal filtering, localization accuracy improved with higher exposure. Doubling the exposure improved accuracy 3 times for stationary and 1.5 times for the moving object. (c) Localization accuracy for stationary objects at a given dose and temporal filtering is similar to that at twice the dose and half the temporal filtering weight, whereas that for moving objects was found to be slightly better for the latter case. (d) Localization accuracy was observed to decrease proportionally with increased object speed due to increased motion blur. Conclusions: Localization accuracy in high quantum noise situations can be improved by increasing the temporal filtering. There is a need to implement variable weight temporal filtering depending on the amount of motion detected.Support: NIH Grants R01‐EB008425, R01‐EB002873
SU‐E‐I‐117: Quantifying Search and Classification Performance in Lesion Localization Tasks
Authors: Chakraborty D 
Published: November 2011

Purpose: Search involves identifying the locations of potential lesions. Classification involves determining if an identified region is a lesion. The area (AUC) under the ROC curve is affected by both search and classification performance. The purpose of this work is to suggest a method for quantifying the two distinct contributions. Methods: The search model for free‐response data involves sampling from noise and signal site unit variance normal distributions. It predicts ROC curves that extend from (0,0) to (x,y), where (x,y) is to the lower left of (1,1). The quantity (y‐x) is proposed as a measure of search performance. It equals the perpendicular distance from (x,y) to the chance diagonal multiplied by the square root of 2. The probability that a sample from the signal distribution is greater than a sample from the noise distribution is proposed as a measure of classification performance. AUC performance is the probability that the highest sample from an abnormal image is greater than the highest sample from a normal image. Search, classification and AUC performance were calculated for mammographer data from a FROC study in which 5 radiologists interpreted 96 normal and 89 disease‐present cases in breast tomosynthesis (BT) and digital mammography (DM) modalities. Results: Search performance ranged from zero to 0.65, classification performance ranged from 0.64 to 0.98 and AUC performance ranged from 0.68 to 0.88. AUC correlated positively with search performance while classification performance was inversely correlated with search performance. All three measures were greater for the BT modality. Conclusions: The method, which is applicable to FROC or ROC data, allows separation of physically distinct contributions to AUC, and consequent identification of the weak link. The preliminary results suggest that search is generally the weak link but that radiologists may learn to compensate for poor search performance with better classification performance.This work was supported by grants from the Department of Health and Human Services, National Institutes of Health, R01‐EB005243 and R01‐ EB008688.
SU‐E‐J‐48: Measurement of Radiation Induced Pulmonary Function Change from 4DCT
Authors: Ding K , Du K , Cao K , Reinhardt J , Christensen G , Benedict S , Buatti J , Bayouth J 
Published: November 2011

Purpose: 4DCT can be used to measure pulmonary function change following radiation therapy for adaptive treatment planning. The purpose of this study is to analyze the effects of the measurement variation and compare the planned radiation dose and pulmonary function change due to radiation not measurement variation. Methods: Two 4DCT data sets before RT scanned with thirty minutes break and one 4DCT data set acquired 5 months after RT from one patient were used in this study. Tissue volume and vesselness preserving image registration algorithm was applied to register the maximum inhalation image to the maximum exhalation image for the calculation of local lung expansion as a measurement of regional pulmonary function (PF). The pulmonary function changes (PFC) before RT and after RT were calculated via the PF ratio between two 4DCT scans. The radiation induced pulmonary function change (RI‐PFC) is calculated from PFC after RT by filtering measurement variation calculated in PFC before RT. We compared the RI‐PFC with planned radiation dose at the contralteral/ipsilateral lung, and the upper/lower lobes of the ipsilateral lung. Results: Significant measurement difference is found between lobes in the same ipsilateral lung. For the contralateral lung in the RI‐PFC region, the average radiation dose is 2.5 Gy and the average PFC value is 1.10. For the ipsilateral lung in the RI‐PFC region, left upper lobe shows the average ration dose as 59.1 Gy with average PFC value 0.9, and the left lower lobe shows the average ration dose as with 2.5 Gy the average PFC value 1.14. Conclusions: We described a technique that uses 4DCT, image registration and biomechanical analysis to measure regional pulmonary function change. We compared the radiation induced pulmonary function change to the planned radiation dose distribution and examined the differences in different lungs, and at the lobar level.This work was supported in part by NIH grant HL079406 and EB004126.
SU‐E‐J‐51: Automatic Detection of Markers Based on Threshold Clustering in 3D CT Images for Image‐Guided Radiation Therapy
Authors: Jia J , Huang S , Li J , Pei X , Cao R 
Published: November 2011

Purpose: Marker‐based registration, needed especially when there is no sufficient bony anatomy for adequate match, plays an important role in the image guided radiation therapy (IGRT) systems, of which the accuracy of registration greatly depends on that of the location of the markers embed. Since the manual marker detection has many limits for its time consuming and labor intensive, it is essential to enable an automatic detection of makers to help to cut down the human error in registration as well as to get a speedup of the registration process, making IGRT systems more efficient. Methods: In this study, we present a simple and efficient clustering method based on the k‐means clustering algorithm, which we call threshold‐based clustering. This method is established in three procedures. First, we got a set of segmented 3D CT images using binary thresholding method since the value of the markers is far different from that of the CT images. Second, the calculation was done by comparing the spacial distance between every two possible marker candidates to make marker points with similar intensity clustered. Finally, the centers of markers can be obtained after a given number of iteration time which can be changed according to the prior estimated number of markers. Results: This method has been tested on 46 CT slices with a size of 512*512. Markers were successfully identified in at least 99.00%. It took less than a second to detect three markers with the average location accuracy of 0.56mm compared to 1.50mm for the conventional manual technique. Conclusions: It has been testified that the method proposed can accurately detect the location of the markers within 3D CT images. Our results demonstrate the subvoxel accuracy can be achieved completely automatically which makes the method well suited for clinical applications.Supported by the National Natural Science Foundation under grant No.30900386 and the Anhui Provincial Natural Science Foundation under grant No. 090413095 and 11040606Q55
SU‐E‐J‐67: Dual Resolution CT‐Based Phantoms for Monte Carlo Simulation Against Small‐Field Irradiations in Tiny/heterogeneous Tissues
Authors: Chao T , Hsieh Y , Lee C , Tu S , Cheng H , Tung C 
Published: November 2011

Purpose: Dose over/underestimation is a common problem for highly irregular fields or around tiny and heterogeneous tissues such as the mucosa/epidermis near teeth/false teeth, skin, bone marrow, vestibulocochlear nerve, and pituitary glands, leading to unexpected normal tissue complications or tumour recurrence. Owing to the limitation of computer efficiency and RAM capacity, it is impossible at present to construct a very high‐resolution phantom for calculating tumour/organ dose together with realistic and accurate dose estimation for tiny and heterogeneous tissues in one simulation. This study aimed to develop dull resolution CT‐based phantoms for Monte Carlo simulation against small‐field irradiation in tiny/heterogeneous tissues. Methods: A homemade VC++ 6.0 code was developed to translate DICOM CT images to dual resolution CT‐based phantoms in the format of an egs‐phantom used in DOSXYZnrc. This code uses regular spatial resolution to define the tumour/organ, but enhances the resolution around the region of interest. This dual resolution phantom can be used for patient treatment evaluation and dose distribution around tiny and heterogeneous tissues in one simulation. Results: A dual resolution pure water phantom will not impact the outcome of MC simulation under large uniform field irradiation. However, the results of this pure water phantom under small field irradiation showed dose underestimation of more than 30% owing to the partial volume effect of not using enhanced resolution. Another dual resolution heterogeneous phantom was used to investigate the interface dose distribution near the boundary of different materials. Finally, a dual‐resolution CT‐based phantom, BigMouse, was created to study the dose distribution around teeth. Isodose curves and PDD/profile comparisons showed that enhanced resolution doses were higher when irradiation fields or phantoms were not uniform. Conclusions: Dose underestimation due to over‐sized voxels can cause severe damage to mucosa in the oral cavity.This work was supported by NSC99‐2314‐B‐182‐040‐MY2 from the National Science Council, Taiwan and CMRPD180162 from the Chang Gung Memorial Hospital
SU‐E‐J‐117: 4D‐CT: Low Pitch Helical. How Low Should You Go?
Authors: Klahr P , Dhanantwari A 
Published: November 2011

Purpose: A basic tenet of 4D‐CT in helical mode is that each voxel at each position must be illuminated for the entire breathing cycle. This gives rise to the oft quoted equation pitch factor (PF) < BPM/RPM (breaths per minute divided by revolutions per minute). For cine axial mode, the equivalent requirement is the cine time (TC) > breathing period. The objective of this study is to demonstrate that these formulae are incorrect for helical scans and will require overlapped scans in cine axial mode. The PF adjustment and overlap percent are dependent on scanner geometry and reconstructed field of view (FOV). Methods: With wide detector scanners, it cannot be assumed that the x‐ray beam is parallel. Therefore, in calculating the total illumination time of any voxel, beam divergence must be addressed. It can be shown analytically that the FOV and source to isocenter distance will have significant impact on the time each voxel remains in the view of the multi‐detector rings. Results: Based on these calculations, PF is inversely dependent on FOV with a larger FOV requiring a lower pitch. In cine axial mode, the overlap percent increases with FOV. This overlap percent means that each couch increment will be less than the full detector collimation Conclusions: The commonly used approach for estimating PF or TC based on BPM is incorrect because it ignores the effects of beam divergence. For a geometrically accurate 4D‐CT scan, a new formula was developed and it is dependent on FOV and source to CT isocenter distance. A method to account for beam divergence in axial scans was also described.Authors are employees of Philips Healthcare
SU‐E‐J‐166: An Assessment of Single‐Fiducial versus Multiple‐Fiducial Prostate Positioning Accuracy
Authors: de Kruijf W , Verstraete J , van den Bergh L , Hol S , Davits R , Wijsman B , Neustadter D , Corn B , Poortmans P , Haustermans K 
Published: November 2011

Purpose: Implanted fiducial markers are commonly used for high accuracy positioning of the prostate in radiation therapy. One source of error in fiducial‐based patient positioning is the rotation and deformation of the prostate. The sensitivity of fiducial‐based positioning to rotation and deformation depends upon the location of the center of mass (COM) of the fiducials relative to the COM of the prostate and on the stability of this geometric relationship throughout the treatment. This work assesses the geometric stability within the prostate of a single implanted trackable fiducial marker (Tracer, Navotek Medical Ltd.) relative to the COM of 4 gold seeds. Methods: In a multi‐site ethics committee approved clinical trial, 20 prostate radiation therapy patients were implanted with 4 gold seeds and one Tracer. CBCT imaging was performed during 5 treatment sessions to measure the locations of the implants. The locations of the Tracer and the COM of the gold seeds were compared in each treatment session, and the stability of the Tracer relative to the COM of the gold seeds from treatment to treatment was assessed. Results: The mean change in position of the Tracer relative to the COM of the gold seeds was 2mm +/− 1mm (mean +/− std) and increased with the distance between the Tracer and the COM of the gold seeds and with the amount of rotation of the prostate as estimated based on the positions of the gold seeds, as expected. Conclusions: The stability of the Tracer relative to the COM of the gold seeds was found to be similar in magnitude to the differences in positioning between any two highly accurate positioning methods. These results support the assertion that a single fiducial, placed near the COM of the prostate, can provide positioning accuracy comparable to multiple fiducials distributed around the prostate.This research was funded by Navotek Medical Ltd.
SU‐E‐T‐32: An Integrated IGART Planning Environment
Authors: Zhang B , Fatyga M , Sleeman W , Dogan N 
Published: November 2011

Purpose: Open Radiological Archiving and Communication System(ORACS) relational research database, which stores images, projections, plans, trials and doses etc, is the backbone for Image Guided Adaptive Radiation Therapy (IGART) Research Project at VCU. Philips Pinnacle3 is being used by this project for IGART adaptive planning of Virtual Clinical Trials (VCT). Therefore, in order to establish a user‐friendly interactive environment and facilitate collaboration between different sub‐projects, seamless integration of these two systems will be a must. Methods: It is well‐known that Pinnacle3 lacks the capacity to interact with a database server. However, we take advantage of Pinnacleˈs configurability and scripting power to enhance Pinnacle with new GUI controls, which invoke a middleware layer to access ORACS database. Users can import images from ORACS database through remote web services or locally, and save contours and plans and doses and other derived Pinnacle data back to ORACS database by simply clicking these new GUI controls. Moreover, a Pinnacle database can be re‐created easily and entirely from ORACS database through these new GUI controls and the middleware layer. The same technique can be used to create connection between Pinnacle3 and other database servers. Also because ORACS database uses web services for data access, if a specific middleware is created, any Treatment Planning System can access ORACS database interactively. Results: We presented a software infrastructure for seamless integration of ORACS research database and Philips Pinnacle3, which created an integrated virtual clinical trial environment for IGART researchers at our institution. Conclusions: Contemporary IGART research imposes new demands on the IT infrastructure of Radiation Oncology departments. We created a data management system which takes first steps towards managing new and complex tasks of automated analysis of large data sets.NIH Grant P01 CA11602