bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐G‐17A‐03: MR‐Based Cortical Bone Segmentation for PET Attenuation Correction with a Non‐UTE 3D Fast GRE Sequence
Authors: Ai H , Hwang K , Pan T 
Published: July 2014

Purpose:To determine the feasibility of identifying cortical bone on MR images with a short‐TE 3D fast‐GRE sequence for attenuation correction of PET data in PET/MR.Methods:A water‐fat‐bone phantom was constructed with two pieces of beef shank. MR scans were performed on a 3T MR scanner (GE Discovery™ MR750). A 3D GRE sequence was first employed to measure the level of residual signal in cortical bone (TE1/TE2/TE3=2.2/4.4/6.6ms, TR=20ms, flip angle=25°). For cortical bone segmentation, a 3D fast‐GRE sequence (TE/TR=0.7/1.9ms, acquisition voxel size=2.5×2.5×3mm3) was implemented along with a 3D Dixon sequence (TE1/TE2/TR=1.2/2.3/4.0ms, acquisition voxel size=1.25×1.25×3mm3) for water/fat imaging. Flip angle (10°), acquisition bandwidth (250kHz), FOV (480×480×144mm3) and reconstructed voxel size (0.94×0.94×1.5mm3) were kept the same for both sequences. Soft tissue and fat tissue were first segmented on the reconstructed water/fat image. A tissue mask was created by combining the segmented water/fat masks, which was then applied on the fast‐GRE image (MRFGRE). A second mask was created to remove the Gibbs artifacts present in regions in close vicinity to the phantom. MRFGRE data was smoothed with a 3D anisotropic diffusion filter for noise reduction, after which cortical bone and air was separated using a threshold determined from the histogram.Results:There is signal in the cortical bone region in the 3D GRE images, indicating the possibility of separating cortical bone and air based on signal intensity from short‐TE MR image. The acquisition time for the 3D fast‐GRE sequence was 17s, which can be reduced to less than 10s with parallel imaging. The attenuation image created from water‐fat‐bone segmentation is visually similar compared to reference CT.Conclusion:Cortical bone and air can be separated based on intensity in MR image with a short‐TE 3D fast‐GRE sequence. Further research is required to optimize the strategy to reduce Gibbs artifacts.
MO‐G‐18C‐03: Evaluation of Deformable Image Registration for Lung Motion Estimation Using Hyperpolarized Gas Tagging MRI
Authors: Huang Q , Zhang Y , Liu Y , Hu L , Miller W , Yin F , Cai J 
Published: July 2014

Purpose:Hyperpolarized gas (HP) tagging MRI is a novel imaging technique for direct measurement of lung motion during breathing. This study aims to quantitatively evaluate the accuracy of deformable image registration (DIR) in lung motion estimation using HP tagging MRI as references.Methods:Three healthy subjects were imaged using the HP MR tagging, as well as a high‐resolution 3D proton MR sequence (TrueFISP) at the end‐of‐inhalation (EOI) and the end‐of‐exhalation (EOE). Ground truth of lung motion and corresponding displacement vector field (tDVF) was derived from HP tagging MRI by manually tracking the displacement of tagging grids between EOI and EOE. Seven different DIR methods were applied to the high‐resolution TrueFISP MR images (EOI and EOE) to generate the DIR‐based DVFs (dDVF). The DIR methods include Velocity (VEL), MIM, Mirada, multi‐grid B‐spline from Elastix (MGB) and 3 other algorithms from DIRART toolbox (Double Force Demons (DFD), Improved Lucas‐Kanade (ILK), and Iterative Optical Flow (IOF)). All registrations were performed by independent experts. Target registration error (TRE) was calculated as tDVF – dDVF. Analysis was performed for the entire lungs, and separately for the upper and lower lungs.Results:Significant differences between tDVF and dDVF were observed. Besides the DFD and IOF algorithms, all other dDVFs showed similarity in deformation magnitude distribution but away from the ground truth. The average TRE for entire lung ranged 2.5−23.7mm (mean=8.8mm), depending on the DIR method and subject's breathing amplitude. Larger TRE (13.3–23.7mm) was found in subject with larger breathing amplitude of 45.6mm. TRE was greater in lower lung (2.5−33.9 mm, mean=12.4mm) than that in upper lung (2.5−11.9 mm, mean=5.8mm).Conclusion:Significant differences were observed in lung motion estimation between the HP gas tagging MRI method and the DIR methods, especially when lung motion is large. Large variation among different DIR methods was also observed.
MO‐G‐18C‐07: Improving T2 Determination and Quantification of Lipid Methylene Protons in Proton Magnetic Resonance Spectroscopy at 3 T
Authors: Breitkreutz D. , B. G. Fallone , Yahya A. 
Published: July 2014

Purpose:To improve proton magnetic resonance spectroscopy (MRS) transverse relaxation (T2) determination and quantification of lipid methylene chain (1.3 ppm) protons by rewinding their J‐coupling evolution.Methods:MRS experiments were performed on four lipid phantoms, namely, almond, corn, sunflower and oleic acid, using a 3 T Philips MRI scanner with a transmit/receive birdcage head coil. Two PRESS (Point RESolved Spectroscopy) pulse sequences were used. The first PRESS sequence employed standard bandwidth (BW) (∼550 Hz) RF (radiofrequency) refocussing pulses, while the second used refocussing pulses of narrow BW (∼50 Hz) designed to rewind J‐coupling evolution of the methylene protons in the voxel of interest. Signal was acquired with each sequence from a 5×5×5 mm3 voxel, with a repetition time (TR) of 3000 ms, and with echo times (TE) of 100 to 200 ms in steps of 20 ms. 2048 sample points were measured with a 2000 Hz sampling bandwidth. Additionally, 30 mm outer volume suppression slabs were used to suppress signal outside the voxel of interest. The frequency of the RF pulses was set to that of the methylene resonance. Methylene peak areas were calculated and fitted in MATLAB to a monexponentially decaying function of the form M0exp(‐TE/T2), where M0 is the extrapolated area when TE = 0 ms and yields a measure of concentration.Results:The determined values of M0 and T2 increased for all fatty acids when using the PRESS sequence with narrow BW refocussing pulses. M0 and T2 values increased by an average amount (over all the phantoms) of 31% and 14%, respectively.Conclusion:This investigation has demonstrated that J‐coupling interactions of lipid methylene protons causes non‐negligible signal losses which, if not accounted for, Result in underestimations of their levels and T2 values when performing MRS measurements.Funded by the Natural Sciences and Engineering Research Council of Canada and the Canadian Breast Cancer Foundation – Prairies.NWT
MO‐G‐18C‐09: Thermal Characterization and Initial Imaging Results From the Diffusive Quantitative Imaging Phantom (DQIP)
Authors: Yanasak N , Li X , Buzzelli M , Randazzo A 
Published: July 2014

Purpose:The goals of this project were a) to characterize thermal relaxation of the phantom and b) to demonstrate correlations between temperature, signal‐to‐noise ratio (SNR) and diffusion tensor imaging (DTI) metrics. A site‐based clinical DTI protocol was used in this study. The hypothesis is that thermal stability of the phantom will be adequate such that temperature monitoring during a scan may be neglected.Methods:The Diffusive Quantitative Imaging Phantom (DQIP) is a prototype phantom consisting of fifteen cylindrical compartments containing capillary arrays, encased in a larger compartment. Thermal stability of the phantom was established using a cork container and a Peltier incubator. After the phantom was cooled or heated, thermal relaxation was measured as the phantom was allowed to return to room temperature, with and without cork. A clinical‐grade DTI protocol was used to collect scan and temperaturedependent data from the phantom over ten days. SNR and thermal dependences of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were characterized by scanning a heated or cooled phantom over several hours.Results:The phantom temperature was stable within ±0.08°C/hour per degree difference from the scan room using the cork enclosure, compared to ±0.3°C/hour per degree difference without the cork enclosure. During scanning, temperature variation was ∼ 0.1°C/hour. The dependences of (FA, ADC) on (SNR, temperature) were characterized for the heating and cooling experiments. However, for the range of temperature (1.2°C) and SNR (max: ±77%) variations in a particular compartment over all daily measurements, no significant improvement in total variation was achieved after regressing out temperature and SNR, although one compartment showed significant decline after regression.Conclusion:Thermal stability of the DQIP phantom and incubator system is sufficient for neglecting temperature variations during scanning. For a standard clinical protocol, SNR dependence of FA and ADC are not sufficient to warrant correction.Schott Glass North America and The Phantom Laboratory have donated materials and personnel time to this project.
TU‐A‐BRF‐01: MR Guided Radiation Therapy
Authors: Stanescu T , Balter J , Nyholm T , Lagendijk J 
Published: July 2014

In recent years, there has been an increasing interest in the development of new technologies focused on the deeper integration of MR in radiotherapy. The innovations span from image data acquisition and post‐processing to clinical implementation of MR‐guided RT systems and workflow development. The session is intended to provide a review of the key and most recent advancements. Targeted discussions will cover topics which currently define the concept of MR‐guided radiotherapy including a) system commissioning, quality control and safety, b) MR data manipulation for dose computations and treatment simulation, c) quantification/management of organ motion and treatment delivery guidance.Learning Objectives:

Understand the concept and specifics of MR‐guided radiotherapy;
Understand the requirements for system integration in clinical workflow;
Become familiar with the proposed strategies for system commissioning, RT planning and delivery guidance.
TU‐A‐17A‐02: In Memoriam of Ben Galkin: Virtual Tools for Validation of X‐Ray Breast Imaging Systems
Authors: Myers K , Bakic P , Abbey C , Kupinski M , Mertelmeier T 
Published: July 2014

This symposium will explore simulation methods for the preclinical evaluation of novel 3D and 4D x‐ray breast imaging systems – the subject of AAPM taskgroup TG234. Given the complex design of modern imaging systems, simulations offer significant advantages over long and costly clinical studies in terms of reproducibility, reduced radiation exposures, a known reference standard, and the capability for studying patient and disease subpopulations through appropriate choice of simulation parameters. Our focus will be on testing the realism of software anthropomorphic phantoms and virtual clinical trials tools developed for the optimization and validation of breast imaging systems. The symposium will review the stateof‐ the‐science, as well as the advantages and limitations of various approaches to testing realism of phantoms and simulated breast images. Approaches based upon the visual assessment of synthetic breast images by expert observers will be contrasted with approaches based upon comparing statistical properties between synthetic and clinical images. The role of observer models in the assessment of realism will be considered. Finally, an industry perspective will be presented, summarizing the role and importance of virtual tools and simulation methods in product development. The challenges and conditions that must be satisfied in order for computational modeling and simulation to play a significantly increased role in the design and evaluation of novel breast imaging systems will be addressed.Learning Objectives:

Review the state‐of‐the science in testing realism of software anthropomorphic phantoms and virtual clinical trials tools;
Compare approaches based upon the visual assessment by expert observers vs. the analysis of statistical properties of synthetic images;
Discuss the role of observer models in the assessment of realism;
Summarize the industry perspective to virtual methods for breast imaging.
TU‐A‐9A‐02: Analysis of Variations in Clinical Doppler Ultrasound Peak Velocity Measurements
Authors: Zhang Y , Stekel S , Tradup D , Hangiandreou N 
Published: July 2014

Purpose:Doppler ultrasound (US) peak velocity (Vmax) measurements show considerable variations due to intrinsic spectral broadening with different scanning techniques, machines and manufacturers. We developed a semi‐automated Vmax estimation method and used this method to investigate the performance of a US system for clinical Doppler Vmax measurement.Methods:Semi‐automated Vmax is defined as the velocity at which the computed mean spectral profile falls to within 1 background standard deviation of the background mean. GE LOGIQ E9 system with 9L and ML6‐15 probes were studied with steady flow (5.3 – 12.5 ml/s) in a Gammex OPTIMIZER 1425A phantom. All Doppler spectra were acquired by 1 operator at the distal end of 5 mm angular tube using a modified clinical carotid artery protocol. Repeatability and variation of Vmax to scanning parameters and probes were analyzed and reported as percentage, i.e. (max‐min)/mean.Results:Vmax estimation had good repeatability (3.1% over 6 days for 9L, and 3.6% for ML6‐15). For 9L probe, varying gain, compression, scale, SV depth and length, and frequency had minimal impact on Vmax (all variations less than 4.0%). Beam steering had slightly higher influence (largest variations across flow rates were 4.9% for 9L and 6.9% for ML6‐15). For both probes, Doppler angle had the greatest effect on Vmax. Percentage increase of Vmax was largely independent of actual flow rates. For Doppler angle varied from 30 to 60°, Vmax increased 24% for 9L, and 20% for ML6‐15. Vmax measured by ML6‐15 were lower than that by 9L at each Doppler angle with differences less than 5%.Conclusion:The proposed Vmax estimation method is shown to be a useful tool to evaluate clinical Doppler US system performance. For the tested system and probes, Doppler angle had largest impact in measured Vmax.
TU‐A‐9A‐06: Semi‐Automatic Segmentation of Skin Cancer in High‐Frequency Ultrasound Images: Initial Comparison with Histology
Authors: Gao Y , Li X , Fishman K , Yang X , Liu T 
Published: July 2014

Purpose:In skin‐cancer radiotherapy, the assessment of skin lesion is challenging, particularly with important features such as the depth and width hard to determine. The aim of this study is to develop interative segmentation method to delineate tumor boundary using high‐frequency ultrasound images and to correlate the segmentation results with the histopathological tumor dimensions.Methods:We analyzed 6 patients who comprised a total of 10 skin lesions involving the face, scalp, and hand. The patient’s various skin lesions were scanned using a high‐frequency ultrasound system (Episcan, LONGPORT, INC., PA, U.S.A), with a 30‐MHz single‐element transducer. The lateral resolution was 14.6 micron and the axial resolution was 3.85 micron for the ultrasound image. Semiautomatic image segmentation was performed to extract the cancer region, using a robust statistics driven active contour algorithm. The corresponding histology images were also obtained after tumor resection and served as the reference standards in this study.Results:Eight out of the 10 lesions are successfully segmented. The ultrasound tumor delineation correlates well with the histology assessment, in all the measurements such as depth, size, and shape. The depths measured by the ultrasound have an average of 9.3% difference comparing with that in the histology images. The remaining 2 cases suffered from the situation of mismatching between pathology and ultrasound images.Conclusion:High‐frequency ultrasound is a noninvasive, accurate and easy‐accessible modality to image skin cancer. Our segmentation method, combined with high‐frequency ultrasound technology, provides a promising tool to estimate the extent of the tumor to guide the radiotherapy procedure and monitor treatment response.
TU‐A‐9A‐07: X‐Ray Acoustic Computed Tomography (XACT): 100% Sensitivity to X‐Ray Absorption
Authors: Xiang L , Ahmad M , Nikoozadeh A , Pratx G , Khuri‐Yakub B , Xing L 
Published: July 2014

Purpose:To assess whether X‐ray acoustic computed tomography (XACT) is more sensitive to X‐ray absorption than that of the conventional X‐ray imaging.Methods:First, a theoretical model was built to analyze the X‐ray absorption sensitivity of XACT imaging and conventional X‐ray imaging. Second, an XACT imaging system was developed to evaluate the X‐ray induced acoustic signal generation as well as the sensitivity improvement over transmission x‐ray imaging. Ultra‐short x‐ray pulses (60‐nanosecond) were generated from an X‐ray source operated at the energy of 150 kVp with a 10‐Hz repetition rate. The X‐ray pulse was synchronized with the acoustic detection via a x‐ray scintillation triggering to acquire the X‐ray induced acoustic signal.Results:Theoretical analysis shows that X‐ray induced acoustic signal is sensitive only to the X‐ray absorption, while completely insensitive to out the X‐ray scattering and fluorescence. XACT has reduced background and increased contrast‐to‐noise ratio, and therefore has increased sensitivity compared to transmission x‐ray imaging. For a 50‐μm size, gadolinium insertion in tissue exposed to 40 keV X‐rays; the sensitivity of XACT imaging is about 28.9 times higher than that of conventional X‐ray imaging.Conclusion:X‐ray acoustic computer tomography (XACT) as a new imaging modality combines X‐ray absorption contrast and high ultrasonic resolution in a single modality. It is feasible to improve the imaging sensitivity with XACT imaging compared with conventional X‐ray imaging. Taking advantage of the high ultrasonic resolution, it is possible to perform 3‐D imaging with a single x‐ray pulse with arrays of transducers without any mechanical motion of the imaging system. This single‐shot capability offers the potential of reducing radiation dose by a factor of 1000, and imaging 100 times faster when compared to the conventional X‐ray CT, and thus revolutionizing x‐ray imaging applications in medicine and biology.The authors gratefully acknowledge the Department of Defense Prostate Cancer Research Programs W81XWH‐13‐1‐0481 (LX), the National Institutes of Health 1R01 CA133474 and 1R21 A153587, and SRFDP (20124407120012) for funding.
TU‐A‐9A‐08: Alternative Magnetic Particle Imaging Methods
Authors: Weaver J 
Published: July 2014

Purpose:Magnetic particle imaging (MPI) is being actively developed for applications where truly quantitative maps of the magnetic nanoparticle distribution are required. The applications include thermal therapies and cell tracking applications. Our Objectives: is to demonstrate the preliminary feasibility of alternative methods of imaging magnetic nanoparticles.Methods:Current MPI methods use an alternating magnetic field (AMF) to induce a magnetization and a static field gradient to localize their position. The magnetization is in the same direction as the AMF so only the harmonics of the magnetization can be isolated from the AMF by recording the signal at the harmonic frequencies. We recently introduced a method of using a small static field to induce a component of the magnetization in the direction perpendicular to the AMF for spectroscopic sensing applications. The perpendicular magnetization is geometrically as well as spectrally isolated from the AMF. Here we used equilibrium, Langevin function simulations to show that the perpendicular magnetization can be used to image nanoparticles using two gradient geometries. Simulations used 100nm iron oxide nanoparticles and a 75mT gradient over the field of view.Results:The perpendicular magnetization is entirely in the even harmonics as opposed to the current MPI methods where the magnetization is entirely in the odd harmonics. Localization can be achieved with static gradient fields in either the direction perpendicular to the AMF or in the same direction as the AMF. Using a stepped field in combination with a 2mT sinusoidal field and perpendicular gradients, a condition number of 8 can be achieved. Using an 80mT sinusoidal field and in‐line gradients, a condition number of 5 can be achieved with faster imaging.Conclusion:The perpendicular magnetization at the even harmonics can be used to produce low noise images with reasonably conditioned reconstructions.
TU‐A‐12A‐05: Evaluating the Consistency of Lesion Volumetry in Chest CT After Substantial Dose Reduction
Authors: Young S , McNitt‐Gray M 
Published: July 2014

Purpose:To quantify how the choice of dose affects semi‐automated lung lesion volume measurements on chest CT.Methods:We created a framework consisting of three parts: (1) software to simulate reduced‐dose sinograms from real clinical CT scans, (2) semi‐automated contouring tools for measuring lesion volumes, and (3) figures of merit to quantify reader performance. Three readers measured 35 lung lesions on images acquired with our routine chest protocol (Siemens Definition Flash, 120 kV, 250 reference mAs, B45f kernel) and four simulated fractions of the clinical protocol (25%, 10%, 3%, and 1%). To quantify reader performance, we compared the percent differences between clinical and reduced‐dose volumes against 15% and 30% thresholds, inspired by a QIBA claim about the reliability of tumor volume change measurements. We analyzed the distribution of percent differences at each dose, as well as outliers in those distributions.Results:The 35 clinical lesions produced volumes ranging from 150 mm^3 to 22500 mm^3, corresponding to effective spherical diameters of 7 to 35 mm. The distributions of percent differences appeared consistent across the dose levels we considered, with the majority of absolute percent differences less than 15%. Some exceptions to this rule were smaller lesions that did not comply with QIBA’s definition of a clinically‐relevant lesion.Conclusion:Our framework shows promise for quantifying the effects of dose on various clinical tasks. Based on the relatively small patient cohort in this study, the task of measuring clinicallyrelevant lesion volumes seemed to be independent of dose down to the 1% level (corresponding to a phantom CTDIvol value of 0.21 mGy), with the exception of a few outliers that did not comply with the QIBA definition of measurable, clinically‐relevant lesions. For QIBA‐compliant lesions, the dose level does not appear to affect reader performance.