bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐DE‐206‐04: MRI Pulse Sequences ‐ Spin Echo, Gradient Echo, EPI, Non‐Cartesia
Authors: Pooley R. 
Published: July 2016

Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation.This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner, and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner.

Learning Objectives:
Understand the origin of the MR signal and contrast from the spin physics level.
Understand the main hardware components of a MRI scanner and their purposes
Understand steps for MR image formation including spatial encoding and image reconstruction
Understand the main kinds of MR pulse sequences and their characteristics.
WE‐DE‐209‐03: Spirometric Motion Management System
Authors: Hadley S. 
Published: July 2016

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance.

Learning Objectives:
Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes.
Provide an overview of the technical aspects.
Describe work flow for patient simulation and treatment.
Give an overview of commissioning and routine.
Provide practical tips for clinical implementation.
WE‐DE‐207B‐01: Optimization for Contrast‐Enhanced Spectral Mammography Based On Photon‐Counting Detectors
Authors: Ding H , Molloi S 
Published: July 2016

Purpose:To investigate the feasibility of optimizing the imaging parameters for contrast‐enhanced spectral mammography based on Si strip photon‐counting detectors.Methods:A computer simulation model using polyenergetic spectra from a tungsten anode x‐ray tube and a Si‐based photon‐counting detector was evaluated for contrast‐enhanced spectral mammography. The simulation traces the emission of photons from the x‐ray source, attenuation through the breast and subsequent absorption in the detector. The breast was modeled as a mixture of adipose and mammary gland tissues with a breast density of 30%. A 4 mm iodine signal with a concentration of 4 mg/ml was used to simulate the enhancement of a lesion. Quantum efficiency of the detector was calculated based on the effective attenuation length in the Si strips. The figure‐of‐merit (FOM), which was defined as the decomposed iodine signal‐to‐noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre‐filtrations for breast of various thicknesses and densities.Results:The optimal imaging parameters, which lead to the highest FOM, were found at a beam energy of 45 kVp with a splitting energy at 34 keV for an averaged breast thickness of 4 cm with a standard 0.75 mm Al pre‐filtration. The optimal tube voltage varied slightly from 46 to 44 kVp as the breast thickness increases from 2 to 8 cm. The optimal tube voltage decreased to 42 kVp when the Al pre‐filtration was increased to 3 mm.Conclusion:This simulation study predicted the optimal imaging parameters for application of photon‐counting spectral mammography to contrast‐enhanced imaging. The simulation results laid the ground work for future phantom and clinical studies.Grant funding from Philips Medical Systems.
WE‐DE‐207B‐03: Influence of Local Anatomical Variations On Detection of Multifocal and Multicentric Breast Cancer
Authors: Wen G , Markey M , Park S 
Published: July 2016

Purpose:We employed a novel model observer to assess the impact of local anatomic variations on the detection of multiple breast tumors depicted on mammograms. We expect the study to be valuable for future task‐based assessments and optimizations of x‐ray based breast imaging techniques (e.g., digital breast tomosynthesis for diagnosis of multifocal multicentric breast cancer (MMBC)).Methods:Regions of interest (ROIs) from four different sets of clustered lumpy background simulations were extracted as the image background. A random number of circular Gaussians were inserted to simulate cases with multicentric lesions. The task of the model observer was to perform a multiple‐lesion detection task, making both image‐level and location‐specific detection decisions based on the overall information from individual ROIs and their interactions. The detectability at each of the possible signal location was measured using channelized Hotelling observers with a novel implementation of partial least squares channels. The power law exponent β of local anatomical noise power spectrum, and spatial covariances K within the ROIs were computed to represent local background variations. The relationships between β, K and the detectability were evaluated.Results:β and/or K were different across the ROIs. Location‐specific signal‐to‐noise ratio (SNR) results showed statistically significant correlations between β, K and the detectability. Specifically, a ROI with a higher value of β, and/or K with larger and more variable off‐diagonal elements was associated with a lower SNR at that ROI. These results also demonstrate the potential of the model observer to adapt to the variations in anatomical backgrounds.Conclusion:We conducted a model observer study to explore the influence of local anatomical backgrounds on detecting MMBC. The study suggests that the optimal imaging settings may need to be adjusted when the clinical task of interest changes (e.g., find only the largest tumor versus find every tumor).This work is supported by National Science Foundation (NSF) Award CBET‐1445713.
WE‐DE‐207B‐08: Towards Standardization of X‐Ray Filters in Digital Mammography‐Enabled Breast Tomosynthesis Systems
Authors: Shrestha S , Vedantham S , Karellas A 
Published: July 2016

Purpose:In digital breast tomosynthesis (DBT) systems capable of digital mammography (DM), Al filters are used during DBT and K‐edge filters during DM. The potential for standardizing the x‐ray filters with Al, instead of K‐edge filters, was investigated with intent to reduce exposure duration and to promote a simpler system design.Methods:Analytical computations of the half‐value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for K‐edge filters (50µm Rh; 50µm Ag) were compared with Al filters of varying thickness. Two strategies for matching the HVT from K‐edge and Al filtered spectra were investigated: varying the kVp for fixed Al thickness, or varying the Al thickness at matched kVp. For both strategies, Al filters were an order of magnitude thicker than K‐edge filters. Hence, Monte Carlo simulations were conducted with the GEANT4 toolkit to determine if the scatter‐to‐primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Al and K‐edge filters.Results:Results show the potential for replacing currently used Kedge filters with Al. For fixed Al thickness (700µm), ±1 kVp and +(1–3) kVp change, matched HVT of Rh and Ag filtered spectra. At matched kVp, Al thickness range (650,750)µm and (750,860)µm matched the HVT from Rh and Ag filtered spectra. Photon fluence/mAs with Al filters were 1.5–2.5 times higher, depending on kVp and Al thickness, compared to K‐edge filters. Although Al thickness was an order higher than K‐edge filters, neither the SPR nor the scatter PSF differed from K‐edge filters.Conclusion:The use of Al filters for digital mammography is potentially feasible. The increased fluence/mAs with Al could decrease exposure duration for the combined DBT+DM exam and simplify system design. Effect of x‐ray spectrum change due to Al filtration on radiation dose, signal, noise, contrast and related metrics are being investigated.Funding support: Supported in part by NIH R21CA176470 and R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
WE‐DE‐207B‐10: Library‐Based X‐Ray Scatter Correction for Dedicated Cone‐Beam Breast CT: Clinical Validation
Authors: Shi L , Vedantham S , Karellas A , Zhu L 
Published: July 2016

Purpose:Scatter contamination is detrimental to image quality in dedicated cone‐beam breast CT (CBBCT), resulting in cupping artifacts and loss of contrast in reconstructed images. Such effects impede visualization of breast lesions and the quantitative accuracy. Previously, we proposed a library‐based software approach to suppress scatter on CBBCT images. In this work, we quantify the efficacy and stability of this approach using datasets from 15 human subjects.Methods:A pre‐computed scatter library is generated using Monte Carlo simulations for semi‐ellipsoid breast models and homogeneous fibroglandular/adipose tissue mixture encompassing the range reported in literature. Projection datasets from 15 human subjects that cover 95 percentile of breast dimensions and fibroglandular volume fraction were included in the analysis. Our investigations indicate that it is sufficient to consider the breast dimensions alone and variation in fibroglandular fraction does not significantly affect the scatter‐to‐primary ratio. The breast diameter is measured from a first‐pass reconstruction; the appropriate scatter distribution is selected from the library; and, deformed by considering the discrepancy in total projection intensity between the clinical dataset and the simulated semi‐ellipsoidal breast. The deformed scatter‐distribution is subtracted from the measured projections for scatter correction. Spatial non‐uniformity (SNU) and contrast‐to‐noise ratio (CNR) were used as quantitative metrics to evaluate the results.Results:On the 15 patient cases, our method reduced the overall image spatial non‐uniformity (SNU) from 7.14%±2.94% (mean ± standard deviation) to 2.47%±0.68% in coronal view and from 10.14%±4.1% to 3.02% ±1.26% in sagittal view. The average contrast to noise ratio (CNR) improved by a factor of 1.49±0.40 in coronal view and by 2.12±1.54 in sagittal view.Conclusion:We demonstrate the robustness and effectiveness of a library‐based scatter correction method using patient datasets with large variability in breast dimensions and composition. The high computational efficiency and simplicity in implementation make this attractive for clinical implementation.Supported partly by NIH R21EB019597, R21CA134128 and R01CA195512.The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
WE‐DE‐207B‐12: Scatter Correction for Dedicated Cone Beam Breast CT Based On a Forward Projection Model
Authors: Shi L , Vedantham S , Karellas A , Zhu L 
Published: July 2016

Purpose:The image quality of dedicated cone‐beam breast CT (CBBCT) is fundamentally limited by substantial x‐ray scatter contamination, resulting in cupping artifacts and contrast‐loss in reconstructed images. Such effects obscure the visibility of soft‐tissue lesions and calcifications, which hinders breast cancer detection and diagnosis. In this work, we propose to suppress x‐ray scatter in CBBCT images using a deterministic forward projection model.Method:We first use the 1st‐pass FDK‐reconstructed CBBCT images to segment fibroglandular and adipose tissue. Attenuation coefficients are assigned to the two tissues based on the x‐ray spectrum used for imaging acquisition, and is forward projected to simulate scatter‐free primary projections. We estimate the scatter by subtracting the simulated primary projection from the measured projection, and then the resultant scatter map is further refined by a Fourier‐domain fitting algorithm after discarding untrusted scatter information. The final scatter estimate is subtracted from the measured projection for effective scatter correction. In our implementation, the proposed scatter correction takes 0.5 seconds for each projection. The method was evaluated using the overall image spatial non‐uniformity (SNU) metric and the contrast‐to‐noise ratio (CNR) with 5 clinical datasets of BI‐RADS 4/5 subjects.Results:For the 5 clinical datasets, our method reduced the SNU from 7.79% to 1.68% in coronal view and from 6.71% to 3.20% in sagittal view. The average CNR is improved by a factor of 1.38 in coronal view and 1.26 in sagittal view.Conclusion:The proposed scatter correction approach requires no additional scans or prior images and uses a deterministic model for efficient calculation. Evaluation with clinical datasets demonstrates the feasibility and stability of the method. These features are attractive for clinical CBBCT and make our method distinct from other approaches.Supported partly by NIH R21EB019597, R21CA134128 and R01CA195512.The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
WE‐C‐TOUR‐T‐01: Microdosimeters for Therapy
Authors: Das I. 
Published: July 2016

Tour Leader: Indra Das, NYU Langone Medical Center, New York, NYTour Guides:Hsui Ai, Indiana University School of Medicine, Indianapolis, INPaulina Galvis, NYU Langone Medical Center, New York, NYOlga Volotoskova, NYU Langone Medical Center, New York, NYParticipating Vendors:IBAPTW – New YorkRTI Electronics, Inc.Standard Imaging, Inc.Sun Nuclear CorporationSmall fields are increasing used in specialized radiation treatments such as Gammaknife, Cyberknife, Tomotherapy, IMRT, VMAT, SRS and SBRT. Due to small field size electron transport creates lateral electronic disequilibrium and thus dosimetry could be very difficult. Microdetectors are used for small field dosimetry which will be discussed in preface of this tour as below:
Understanding small field e.g. meaning and definition of small field
IAEA definition and approach
Characteristics of microdetectors in terms of perturbation, recombination, correction
Suitability of microdetectors in small field dosimetry
WE‐F‐204‐01: Some Lessons from a Career in Research
Authors: Mohan R. 
Published: July 2016

In recent years heavy focus has been placed on clinical careers in medical physics, and the pathways to such careers are well‐known and well‐described. For the future advancement of the field of medical physics, it is necessary the focus also include research‐oriented careers. It is important for the younger generation of medical physicists to know that there are many career opportunities in research, and that it is quite possible to build a successful career in which research is a major component. We will hear from those who have already blazed a trail of success in academic and industry research careers in order to understand some of the most important decisions to make and skills to develop in order to be successful. Topics such as how to build a research program, how to develop your own lab, and how to initiate good collaborations are not generally taught explicitly but are integral to succeeding in a research career. Skills such as these are often best learned from the experiences of others. The challenges encountered in transitioning from graduate student to faculty member, securing the first grant, and moving into an industry research position will be highlighted and discussed.

Learning Objectives:
Identify career paths built on interest in research
Understand basic steps to starting and maintaining a research career
Identify differences between research careers in academia and industryM. Giger, support by NIH and COI will be listed. J. Dempsey, ViewRay, Inc. has provided financial support for my research. R. Mohan, support from NIH.
WE‐FG‐206‐09: Association of Prostate Volumes with Restricted Diffusion and Prostate Cancer Aggressiveness
Authors: Tschudi Y 
Published: July 2016

Purpose:To create an automatic workflow for evaluation of thresholds of restricted diffusion, based on Apparent Diffusion Coefficient (ADC) values in multiparametric (mp)MRI of the prostate. To investigate the association of these volumes with biopsy Gleason Score (GS).Methods:Patients with prostate cancer, imaged on 3T Discovery MR750 (GE, Waukesha, WI) magnet were selected from departmental database based on the presence of mpMRI exam. All subsequent analyses were performed using Java plugins in MIM (MIM, Cleveland, Ohio). Prostate, peripheral zone (PZ) and urethra were contoured manually for each patient. The procedure defines three volumes on ADC in PZ, related to high (<T1 µm2/s), medium (<T2 µm2/s), and low risk (<T3 µm2/s), where T1<T2<T3. The thresholds for each patient were set 200 µm2/s apart, i.e. T2=T1+200 µm2/s and T3=T1+400 µm2/s. The thresholds were offset by 100 µm2/s for the transition zone (TZ). Pixels with ADC<400 µm2/s and within the urethra are excluded from the analysis. The correlations between (i) ADC volume sizes; and (ii) the fractions of the volumes from the prostate volume (ADC/Prostate) and GS were investigated with Spearman correlation.Results:mpMRIs from 139 the analysis. The correlations between (i) ADC volume sizes; and (ii) the fractions of the volumes from the prostate volume (ADC/Prostate) and GS were investigated with Spearman correlation.Results:mpMRIs from 139 selected patients with mpMRI acquired between May, 2012 and February, 2016, were analyzed. Six values for T1 were investigated starting from 750 to 950 µm2/s with step of 50 µm2/s. All correlations between ADC volumes and ADC/Prostate volumes and GS were significant. The following thresholds for PZ/TZ: 950/700, 1100/900 and 1200/1100 performed the best for high, mid and low risk. The correlation coefficients of of ADC high and ADC high/Prostate were 0.45 and 0.469 with p‐values <<0.00001.Conclusion:To the best of our knowledge, this is the first report which associates volumes of low diffusion and GS.
WE‐FG‐206‐11: Measuring Mechanical Biomarkers of Liver Tumors Using Tagged MRI
Authors: Xia X , Zhu M , Sun L , Sacks M , Genin G , Hu C , Guo L , Feng Y 
Published: July 2016

Purpose:Early detection of liver cancer improves patient prognosis dramatically. We propose a novel approach in which liver deformation is tracked during the cardiac cycle using tagged MRI. Strain concentrations that arise from material mismatches between the tumor and non‐tumor regions were compared in patients with liver tumors.Methods:Tagged MR images were acquired from four liver cancer patients in the coronal plane in a 3.0T scanner. In each cardiac cycle, a total of 25 time frames were acquired with a FOV of 289×359 mm2 and a resolution of 180×224. Lagrangian strain fields were calculated from displacement fields estimated from the tag lines using the HARP algorithm. Tumor and non‐tumor regions of interest (ROIs) were delineated manually by a trained physician. The non‐tumor ROI was defined as a region surrounding the tumor but away from the left lobe adjacent to the heart. A one‐tail paired T‐test was used to compare the strain distributions from the tumor and non‐tumor ROIs.Results:The strain fields reflected heterogeneity of liver mechanical properties and the nature of the loading. The left lobe had the highest strain magnitude because of its proximity to the heart. However, the maximum principal strain (E1) of the tumor ROI was significantly lower than that of the non‐tumor ROI.Conclusion:Cardiac contraction produced measureable strains in the liver, with statistically significant differences between tumor and non‐tumor ROIs. Lower strains in the tumor ROIs, observed for all patients, reflected the higher stiffness of the tumor, and showed the potential of using biomechanical properties as a biomarker for tumor diagnosis. Future work will focus on the question of whether tumors that are not visible to a trained physician can be identified using these strain fields.Funding supports are provided by grant BK20140356 (YF) from Jiangsu Province, grant 61503267 (YF) from National Natural Science Foundation, and by grant K511701515 (YF) from Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.
WE‐F‐209‐01: Radiation Safety Surveys in Diagnostic Imaging
Authors: Dillon C. 
Published: July 2016

Over the past few years, numerous Accreditation Bodies, Regulatory Agencies, and State Regulations have implemented requirements for Radiation Safety Surveys following installation or modification to x‐ray rooms. The objective of this session is to review best practices in performing radiation safety surveys for both Therapy and Diagnostic installations, as well as a review of appropriate survey instruments.This session will be appropriate for both therapy and imaging physicists who are looking to increase their working knowledge of radiation safety surveys.

Learning Objectives:
Identify Appropriate Survey Meters for Radiation Safety Surveys
Develop best practices for Radiation Safety Surveys for Therapy units that include common areas of concern.
Develop best practices for Radiation Safety Surveys of Diagnostic and Nuclear Medicine rooms.
Identify acceptable dose levels and the factors that affect the calculations associated with performing Radiation Safety Surveys.
WE‐F‐209‐02: Radiation Safety Surveys of Linear Accelerators
Authors: Martin M. 
Published: July 2016

Over the past few years, numerous Accreditation Bodies, Regulatory Agencies, and State Regulations have implemented requirements for Radiation Safety Surveys following installation or modification to x‐ray rooms. The objective of this session is to review best practices in performing radiation safety surveys for both Therapy and Diagnostic installations, as well as a review of appropriate survey instruments.This session will be appropriate for both therapy and imaging physicists who are looking to increase their working knowledge of radiation safety surveys.

Learning Objectives:
Identify Appropriate Survey Meters for Radiation Safety Surveys
Develop best practices for Radiation Safety Surveys for Therapy units that include common areas of concern.
Develop best practices for Radiation Safety Surveys of Diagnostic and Nuclear Medicine rooms.
Identify acceptable dose levels and the factors that affect the calculations associated with performing Radiation Safety Surveys.