bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐D‐220‐05: Optoacoustic Thermometry for Noninvasively Monitoring Thermal‐ Ablation Therapy in Real‐Time
Authors: Chitnis P , Mamou J , Gross D 
Published: November 2011

Purpose: to demonstrate the feasibility of optoacoustic imaging (OAI) and a signal processing scheme based on singular‐value decomposition (SVD) for noninvasively monitoring localized temperature changes during thermal‐ ablation therapy. Methods and Materials: A bolus of Indocyanine Green (ICG), which strongly absorbs 800‐nm light, was injected in excised chicken and bovine samples using a 26‐gauge needle in order to mimic optical absorption in a blood‐rich tumor. A wire thermocouple was inserted at the injection site to provide “ground truth” measurement of local temperature. A custom‐designed, 1.5‐MHz high‐intensity focused transducer (HIFU) transducer delivered therapeutic energy in two modes: continuous wave (CW) mode and pulsed mode (80% duty cycle, thermometry performed intermittently during the off periods); and two focal intenstities: 1 kW/cm2 (cavitation absent) or 4 kW/cm2 (cavitation present). The HIFU transducer had a central opening to accommodate a linear, diagnostic imaging probe. The light from a pulsed, 800‐nm laser was delivered at the injection site using a bifurcated fiber bundle oriented normal to the imaging plane. The optoacoustic signals emanating from the target site were simultaneously acquired and digitized across the 64 central elements of the imaging array using a fully‐programmable research ultrasound engine at a pulse‐repetition rate of 10 Hz. SVD analysis of the time‐varying OA signals was performed to extract the contributions of temperature change. Results: The OA amplitude exhibited a direct correlation with change in temperature during heating induced by HIFU and subsequent cooling; this provided adequate means of monitoring temperature changes during pulsed HIFU exposures. Despite the presence of broadband noise associated with inertial cavitation for CW HIFU exposures at high intensity, the SVD analysis was able to extract the local temperature‐time profile accurately with root‐mean‐squared error less than 5&#61616;C. Conclusion: OAI provides a viable, noninvasive method for monitoring local temperature changes in tissue during thermal‐ablation therapies.This research was support by the Bioengineering Research Fund provided by Riverside Research
MO‐D‐220‐08: Quantitative Embryonic Central Nervous System Imaging Using High‐ Frequency Annular Arrays
Authors: Ketterling JA , Aristizabal O , Mamou J , Filoux E 
Published: November 2011

Purpose: The central nervous system (CNS) is the first organ to develop during mammalian embryogenesis and the CNS dynamically evolves well into the postnatal stages. Abnormal CNS phenotypes are normally visualized in vivo or with fixed samples using magnetic resonance imaging (MRI). Current MRI coil technology does not permit early‐stage in vivo imaging of the mouse embryo CNS. Here, a custom‐made, high‐frequency‐ultrasound annular‐array system operating at 38 MHz was utilized to perform in vivo imaging of early‐stage mouse embryo CNS. Methods: A custom‐made ultrasound scanning system using a piezopolymer‐based annular array was utilized for the imaging studies. The array had five equal‐area elements, a 6 mm total aperture, and a 12 mm geometric focus. The scanning system was designed to perform five scans across an object in order to acquire all transmit‐to‐receive data (25 data sets). This data was then synthetically focused to achieve enhanced depth of field and lateral resolution. In addition, the system utilized a coded‐excitation scheme to enhance SNR and penetration depth, and a respiratory gate to reduce motion artifacts. A full 3D volumetric data set could be acquired in approximately 2 minutes. Results: In vivo, in utero volumetric data were acquired from 78 mouse embryos spanning embryonic days 10 to 13. The data sets were processed with a semi‐automated image segmentation algorithm and brain volumes were calculated. The results indicated that during these mid‐gestational stages, there was an increase in CNS volume of 38% while volumetric renderings revealed the complex remodeling of the neuroarchitecture showing more cell proliferation than increase in brain mass. Conclusions: High‐frequency annular arrays with coded excitation offer an effective means of acquiring in vivo, in utero ultrasound data of the embryonic mouse and can be used to rapidly analyze the normal or abnormal development of the CNS during longitudinal studies.This research was supported by the National Institutes of Health (EB008606).
MO‐F‐BRC‐05: Minimization of the Total Inter‐Segment Time for the Real‐Time Tumor Tracking with Step & Shoot IMRT
Authors: Han‐Oh S , Yang X , Lerma F , Miller R , Yi B 
Published: November 2011

Purpose: We developed an algorithm to minimize total inter‐segment time (TIST) for the MLC‐based real‐time tumor tracking with step‐and‐shoot IMRT. This algorithm optimizes a starting phase of tumor motion for each segment to minimize TIST. Methods: The optimizing algorithm consists of four steps: (1) implementation of feathering motion for the closed leaves that will be opened at the next segment, (2) calculation of inter‐segment time for all segments, (3) reordering segments to minimize TIST, and (4) optimization of the starting phase of tumor motion for each segment to minimize TIST. Thirty step‐and‐shoot IMRT fields from five patients with lung and abdominal cancer were used to test the algorithm. Tumor motion was varied with a period (2.0 to 4.0 s) and a peak‐to‐peak distance (0.5 to 4.0 cm). TIST and duty cycle for each field were compared to those from the strategy of starting each segment at end‐of‐exhale. Results: The TIST was reduced by 54.0% on average (from 30.2 ± 16.9 to 13.9 ± 10.6 s) and, the effective duty cycle was increased from 32 ± 10% to 52 ± 15% for a tumor motion with 4 s and 1.0 cm peak‐to‐peak. More reduction in the TIST was observed from 45.1 to 72.1% with an increase of the period from 2 to 8 s; effect of reduction was degraded by 54.5 to 46.2% when the peak‐to‐peak increased from 0.5 to 4.0 cm. The TIST increased when a field size formed by x‐jaws increased (correlation coefficient: 0.7). Conclusions: : Total treatment time was reduced noticeably with the algorithm presented in this study so that real‐time tumor tracking can be delivered with step‐and‐shoot IMRT with an increased duty cycle.This research was supported in part by a NIH grant 1R01CA133539‐01A2 and in part by the Intramural Research Program of the NIH, NCI.
MO‐F‐214‐05: The Impact of 6MV Non‐Reference Photon Energy Spectra on OSLD Response
Authors: Scarboro S , Followill D , Kerns J , Kry S 
Published: November 2011

Purpose: Optically stimulated luminescent dosimeters (OSLD) are becoming more popular for dose measurement in a clinical setting. The OSLD response is dependent on photon energy and that energy response is typically determined only for the photon spectrum at the reference dose calibration point (dmax on CAX for a 10cm×10cm field). Previous work has shown that variations exist in photon energy spectra as a result of measurement conditions and treatment parameters; however the effects of these energy variations on OSLD response have not been characterized. Method and Materials:Theoretical energy correction factors were calculated for a range of clinical conditions, including 6MV static and modulated (IMRT) fields, in‐field and out‐of‐field measurement positions, and in the presence of heterogeneous materials. These factors were calculated using previously determined photon energy spectra and Burlin cavity theory. Measured energy correction factors using OSLD nanoDots™ from Landauer, Inc. have also been determined under matching conditions, and the measured and calculated responses were compared. Results: When OSLD are used to measure dose for in‐field locations, the dosimeter response was as much as 5% different from the reference location due to perturbations in the spectra. The presence of heterogeneities at in‐field measurement locations did not significantly impact the OSLD response; however a substantial energy response occurred for the soft spectra that exist outside of the treatment field. At these measurement locations, OSLD may over‐respond by 20% or more, relative to the response at the dose calibration location. Conclusion: OSLD exhibit a non‐trivial energy response due to the increased effective atomic number. Variations in the photon energy spectra may impact the response of OSLD by as much as 20% and additional non‐reference energy correction factors may be necessary when measuring dose away from the dose calibration position.Work supported by PHS grant CA 10953 awarded by NCI, DHHS
MO‐F‐214‐08: A New Method for Linear Accelerator Characterization for VMAT Using Cine‐EPID
Authors: Rowshanfarzad P , Sabet M , McCowan P , McCurdy B , OˈˈConnor D , Greer PB 
Published: November 2011

Purpose: A cine‐EPID based method to separately measure the mechanical motion characteristics of gantry, jaws and multi‐leaf collimator as a function of gantry angle during VMAT has been developed. Methods: Irradiations were performed using 6 MV beams of a Varian Trilogy linear accelerator with an aS1000 EPID. Images were acquired using 360 MU irradiations at 600 MU/min in cine acquisition mode at 2 Hz frame‐rate. To establish the gantry isocentre, a Winston‐Lutz technique was used with a circular collimator rigidly attached to the gantry head. The displacement of the centre of a fixed tungsten ball at isocentre from the field centre was determined on each image with a sub‐pixel thresholding technique. EPID coordinates were transformed to room coordinates. Jaw and MLC sag relative to the gantry head were determined from the displacement of a gantry‐mounted tungsten ball relative to static jaw and MLC positions. MLC speed constancy was determined by segmenting MLC positions on each image for a constant leaf‐speed test pattern. Gantry speed constancy was assessed with an independent liquid‐based inclinometer and the linac gantry angle potentiometer. Results: The gantry isocentre was ∼ 1 mm amplitude with changes in isocentre occuring over time suggesting frequent measurement is required. Jaw sag was found to be very small ∼ 0.2 mm amplitude, with MLC sag ∼ 0.6 mm. Average leaf speed was found to be consistent for the MLC leaves however the variation in speed varied systematically across the leaf bank which requires further investigation. Gantry speed was consistent although the inclinometer was found to lag ∼ 2 degrees in reading from the potentiometer. Conclusions: The cine‐EPID based method quantifies the mechanical motion characteristics of the linac as a function of gantry angle during arc‐therapy with improved precision and efficiency of quality assurance over previous methods.This work supported by NHMRC Grant 569211
MO‐F‐214‐09: Ion Radiography: Measuring High Soft Tissue Contrast and WEPL with An Amorphous Silicon Detector
Authors: Telsemeyer J , Huber L , Jäkel O , Martišíková M 
Published: November 2011

Purpose: Ion beam therapy is a highly precise form of radiotherapy, which offers the potential for higher dose to the tumor, while better sparing of healthy tissue as compared to photons. Currently, dose calculations, patient positioning verification and diagnostics are based on X‐ray radiography or computed tomography. However, there are several predicted advantages for ion radiography in comparison to X‐ray imaging. Ideally, the stopping power of the particles traversing through the patient can be measured directly, which would improve the treatment planning accuracy (Med. Phys. 32(1), 2005). Furthermore, ion radiographies may be used for on‐board patient positioning verification with very low dose to the patient (Med. Phys. 22(4), 1995) and for cancer diagnostics due to the high soft tissue contrast (Investigative Radiology 13(2), 1978). To exploit these possibilities, we are currently investigating an amorphous silicon flat‐panel detector (RID256L by Perkin Elmer, Inc. Wiesbaden, Germany) for radiographic imaging with ions. Methods: In this contribution we investigate detailed studies on soft tissue contrast and direct measurement of water‐equivalent path length (WEPL). 10 mm thick soft tissue‐equivalent rods (Gammex 467‐ Phantom), embedded in PMMA, have been irradiated with protons and carbon ions at the Heidelberger Ion‐Beam Therapy Center (HIT), Germany. Additional slabs of PMMA were placed between the phantom and the detector to measure the contrast in different depths. Results: The high tissue contrast reached in the ion radiographies enables to differentiate between all six soft tissue equivalent inserts, ranging from adipose to liver, even in high penetration depths. By comparing the measured signal with reference measurements in depth of PMMA, the water‐equivalent thickness of the inserts could be determined with an accuracy better than 0.5% of the known thickness. Conclusions: Our measurements show that the investigated flat‐panel is promising for patient diagnostic ion imaging and direct WEPL measurements.This work is funded by the Virtual Institute “Heavy Ion Therapy” of the HGF under the contract no. 15185.
MO‐F‐211‐05: GPU Computation for Voxelwise Kinetic Modeling of Hepatic Perfusion
Authors: Wang H , Cao Y 
Published: November 2011

Purpose: To accelerate computation speed of time‐consuming voxelwise hepatic perfusion estimation from dynamic contrast enhanced (DCE) imaging using graphics processing unit (GPU) hardware, thus facilitating high resolution DCE analysis of large tissue regions for perfusion assessment. Methods: Voxelwise perfusion estimation for large tissue regions are assigned to a GPU for parallel computation with a CUDA block for one voxel computation. The Nelder‐Mead simplex algorithm for the nonlinear least squares fitting of a hepatic kinetic model is executed in each block. To compute the convolution in the cost function in frequency domain, the general Cooley‐Tukey algorithm with the radix‐2 inverse FFT is implemented in a block. The algorithms are programmed using CUDA 3.2 on the GPU of NVIDAˈs Tesla C2050. Simulated dynamic curves are used to evaluate the GPU implementation. The computation time of the GPU perfusion estimation per voxel is compare with that from a CPU. By varying the number of time points in the dynamic curves, we also examine the performance improvement with respect to the share memory usage. Results: The perfusion estimation with single precision float GPU computation has accuracy of greater than 99% of the truth. The GPU implementation is approximately 30 times faster than the CPU computation for the number of voxels greater than 100. The result also shows less share memory usage produces higher performance. Conclusions: We implement the voxelwise hepatic perfusion estimation from DCE imaging on GPU, which significantly accelerates the computation speed. Further optimization of the GPU codes, such as share memory usage, will improve the performance. The GPU programs are valuable for a study of liver perfusion after irradiation as well as useful for other DCE imaging modeling for high performanceThe work is supported in part by PO1CA59827 and RO1CA132834.
MO‐F‐220‐01: The Future of Ultrasound Systems and Imaging
Authors: Metz S 
Published: November 2011

A brief look at the history of Ultrasound systems and imaging and a look into the future driven by miniaturization and advances in system electronics and imaging systems.The promise of ubiquitous Ultrasound is fast approaching. Advanced in analog and digital hardware as well as the miniaturization of computer and embedded systems is allowing manufacturers to produce compact Ultrasound systems with solid imaging performance.This talk will look at the history of ultrasound and what advances in systems and software are driving the use of ultrasound in new environments and what issues are related to workflow and simplification of the ultrasound exam.Learning Objectives:1. Understanding of the history of Ultrasound in the current age.2. Understanding how miniaturization and new advances are making Ultrasound available in new clinical area.3. Understand issues related to operator independence and workflow issues to simplify the Ultrasound exam.
MO‐F‐220‐04: Quantitative Ultrasound Imaging
Authors: Rognin N 
Published: November 2011

The objective measurement of tissue pathological state by medical imaging plays an increasing role in clinical practice. The ultrasound imaging modality offers dedicated solutions based on image‐derived quantitative measurements for evaluating a variety of diseases in cardiology, radiology and oncology. Our presentation will show three solutions developed by Toshiba for quantifying myocardial contractility, liver fibrosis and tumor perfusion, respectively.The first part of the presentation will demonstrate a solution for quantification of left ventricular contractility, which is an important clinical indicator of the cardiac function. To quantity regional motion abnormalities, a 3D wall motion tracking technique was implemented in an analysis software application. The technique tracks the speckle pattern, frame‐by‐ frame, over a cardiac cycle to calculate a field of motion vectors in 3D. This field is then processed to measure clinical parameters, such as strain values in different directions (longitudinal, circumferential and radial) and volumetric values (left ventricle ejection fraction).The second part of the presentation will demonstrate a solution for evaluating liver fibrosis. Tissue characterization consists in differentiating subtle changes in ultrasound speckle patterns, indicative of the tissue microstructures, which remain non perceptible to human visual inspection. The solution, named Acoustic Structure Quantification (ASQ), was developed to quantify the homogeneity of the speckle pattern using the probability function (PDF) of the echo amplitude in a region of interest. The PDF is estimated using a modified chi‐square distribution. The peak value of that distribution was found to be a promising quantitative parameter to distinguish fibrotic tissue from normal tissue in liver.The last part of the presentation will describe a solution for quantifying perfusion using dynamic contrast enhanced ultrasound (D‐CEUS). The technique utilizes an intravenous injection of microbubble contrast agent, which supports ultrasound imaging of macro‐vascularization. The D‐CEUS technique is a promising application for monitoring tumor response to cancer therapies. Our approach uses a mathematical function to model the contrast uptake (or time‐intensity‐curve) in a region of interest outlining a tumor. From that function, quantitative parameters are derived that are indicative of blood flow dynamics, which vary during the course of the therapy.
MO‐G‐BRA‐01: Evaluation of Prostate Post‐Implant Dosimetry by Tracking Edema Resolution with Deformable Image Registration
Authors: Zhai Y , Jiang Y , Papademetris X , Roberts K , Nath R , Chen Z 
Published: November 2011

Purpose: To evaluate post‐implant dosimetry of prostate implants by tracking edema‐induced movements of implanted sources and tissue sub‐volumes using deformable image registration on post‐implant serial CT images. Methods: Post‐implant serial CT imaging was used to characterize the variations of prostate volume and movements of implanted sources during edema resolution. Seven post‐implant time points, up to 42 days, were selected. Deformable image registrations performed between each consecutive pair of CT images were used to track the spatial movements and tissue deformation using the Yale BioImage Suite non‐rigid image registration algorithm. The history of tissue movement was used in a 4D dose calculation approach to determine the dose actually received by each tissue sub‐volume in presence of prostate edema. Results: Tracking of tissue sub‐volume was validated using simulated datasets with known tissue deformations. Post‐implant dose rate distributions calculated at different post‐implant times were accumulated to corresponding tissue sub‐volumes. The dose distributions determined with full considerations of source migration and tissue deformation were compared to conventional approach using one static post‐implant image set. We observed that the hot and cold spot positions were moving around with edema evolution. Overdose at the peripheral of prostate would cause problems to the adjacent organs. The edema‐induced tissue and source movements caused overdose and deficit dose magnitudes were up to 1.12E04 cGy and −1.23E+04 cGy respectively, and overdose and deficit dose volumes were up to 10.37% and 10.26% respectively, and the percentage of hot or cold volume dynamically varied from 1.4% to 20.63% with post‐implant timing. Conclusions: Post‐implant dosimetry based on actual source position and tissue deformation during edema resolution was obtained using serial post‐implant CT imaging and deformable image registration. It provides a more realistic documentation of the actual dose delivered and could be used to compensate edema‐induced dose deficits and assess the risk of overdose.This research project is currently funded by the NIH grant R01CA134627‐ 01 “Prostate Edema in Permanent Interstitial Brachytherapy”.
MO‐G‐BRB‐05: Quantitative Evaluation of Non‐Uniform Dose Patterns for Preclinical Radiobiology Studies
Authors: Stewart J , Lindsay P , Jaffray D 
Published: November 2011

Purpose: Prompted by a desire to increase the complexity and precision with which radiation can be distributed at the small scale demanded by preclinical studies, several institutions have developed dedicated platforms for small animal irradiation research. Such systems have the potential to probe the physiological response of spatially inhomogeneous dose distributions in the controlled preclinical environment. The performance of such a system (Xrad225Cx, Precision X‐Ray, Inc., North Branford, CT) in terms of its ability to spatially modulate dose was assessed for a dose pattern broadly characterized as ‘grid’ therapy. Methods: By programming the animal positioning stage to move between a series of irradiations, complex dose patterns can be delivered. A spatially modulated grid irradiation pattern consisting of a 5×11 array of irradiations delivered with a fixed 1 mm diameter circular collimator and a 2 mm distance between the isocenter of each irradiation was delivered. Individual irradiations were performed for 30 seconds at an energy of 225 kVp and current of 13 mA. Gafchromic EBT2 radiochromic film placed between two 4.9 mm thick water equivalent slab phantoms was used for quantitative dosimetric analysis. After irradiation, the films were scanned at a resolution of 400 DPI (∼0.06 mm/pixel). Results: The 55 separate irradiations forming the ‘grid’ pattern were delivered with 93% of the irradiations within 0.15 mm of the desired 2.0 mm spacing. Dose falloff from each individual irradiation was rapid with a typical falloff of 1.24 Gy / mm (57% / mm). The dose‐depth curve was roughly exponential with a decay constant of 0.040 / mm. Conclusions: The preliminary characterization of the delivered dose demonstrates the ability of the small animal irradiation platform to deliver precisely modulated dose distributions comparable to that employed in ‘grid’ therapy. This dosimetric capability holds promise for in vivo radiobiological studies of complex radiation delivery schemes.Some of the co‐authors are inventors of the small animal irradiation system described herein, and may financially benefit through its successful commercialization by Precision X‐Ray, Inc.