bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐P‐11: Gurukkul – A Cloud Based Resident Management System
Authors: Palaniswaamy G , Morrow A , Oddiraju S , Gutti V , Rangaraj D
Published: July 2014

Aim:

To evaluate Gurukkul, a commercially available software tool that can help residency programs maintain documentation and compliance with accreditation standards. It helps both the resident and residency program to effectively manage responsibilities. Materials: Gurukkul has different modules to track resident progress and help manage the program effectively.Administration: ‐Three levels of access: admin, mentor and resident; each with different rights to appropriately upload documents, edit and review information enabling the program compliance with accreditation standards. Management: ‐Configure, view and edit several modules to track and review resident progress such as: Rotation description, Rotation schedule, Course and Seminar management. ‐Checklists to evaluate resident competency in each rotation. ‐Alerts, reminders and notifications of upcoming deadlines, pending tasks and approvals.Performance: ‐View reports tracking individual and group performance throughout the program. ‐Enable accountability by tracking time of completion and approval of tasks. ‐Dashboard to view current activities and alerts Evaluation: ‐360° evaluations for residents, faculty and program tailored to institutional performance metrics. Self‐assessment: ‐Configure, schedule and administer testing materials linked to rotation topics. ‐Guide education through question‐based approach.

Results:

Advantages: Organized platform for managing residency program. Performance monitor and dashboard ensure timeliness of tasks. Self‐assessment modules better prepare residents for rotation exams. Reading and competency checklists help complete assigned tasks. Timelines were met after using this system unlike before where we used to miss reports and resident presentations. Administration and documentation time reduced significantly as they were better organized and readily available. Reduces administration/documentation time. Helpful during accreditation site visits. Disadvantages: Time‐consuming initial setup.

Conclusion:

This tool is multi‐functional as: residency program management, resident management, resident learning resource, resident and program evaluation. It relieves documentation and management time from faculty and residents that can be used towards actual learning. Dashboards keep everyone up‐to‐date. Specifically, it can help immensely during accreditation site visits.

Dr. Rangaraj is the founder of Crux Quality Solutions LLC which markets Gurukkul.
SU‐C‐17A‐06: Motion Compensation in Dynamic Contrast Enhanced MRI
Authors: Liu W , Sung K , Ruan D
Published: July 2014

Purpose:

To apply a newly developed shape‐based registration scheme for motion compensation in MR urography and verify its efficacy in facilitating quantitative functional analysis.

Methods:

We have recently developed a shape‐based registration scheme that is robust w.r.t. intensity inconsistency. In this study, we utilized this robust registration tool to estimate kidney motion during the MRU scans and compensate for such motion to facilitate the quantitative functional analysis. To validate the efficacy of this scheme, MRU analysis was performed on dataset acquired from sedated subjects to obtain ground‐truth (motion‐free) functional estimates. Physiologically sound motion was then simulated to synthesize image sequences influenced by respiratory motion. Quantitative assessment and comparison were performed amongst ground‐truth, calculations without and with motion compensation for the following set of functional parameters: the contrast dynamic of the left and right cortex, medulla and aorta, the Patlak number and the globular filtration rate (GFR) based on the Patalk‐Rutland model, and the Patlak differential renal function (pDRF).

Results:

Without motion compensation, the generated relative enhancement curves contained large fluctuations and the estimated GFR values were underestimated by 26% (75.4 ml/min) and 30% (95.3 ml/min) compared with the ground truth of 101.9ml/min and 134.3ml/min for the left and right kidney respectively. Such large errors could result in misleading diagnosis if a typical threshold of 90ml/min were used to determine renal function abnormality. Upon proposed motion compensation, the relative enhancement curves were much smoother and the GFR estimation errors for the left and right kidneys reduced to 0.4% and 1.6% respectively, demonstrating the advantage of the introduced motion compensation method.

Conclusion:

The developed motion compensation method has demonstrated its ability to facilitate quantitative MRU functional analysis, with improved accuracy of pharmacokinetic modeling and quantitative parameter estimations. Future work will consider incorporating more complex and realistic pharmacokinetic models into the MRU analysis.
SU‐C‐18A‐05: Registration Accuracy of MR‐Based Images to On‐Board Megavoltage Cone‐Beam CT for Brain Patient Setup
Authors: Pinnaduwage D S , Chen J , Descovich M , Hwang Ken‐Ping , Pouliot J
Published: July 2014

Purpose:

To quantify the difference in isocenter shifts when co‐registering MR and MR‐based pseudo CTs (pCT) with on‐board megavoltage conebeam CT (CBCT) images.

Methods:

Fast Spoiled Gradient Echo MRs were used to generate pCTs (research version of Advantage Sim MD™, GE Healthcare) for ten patients who had prior brain radiotherapy. The planning CT (rCT) for each was co‐registered with the MR, and the plan isocenter and two other reference points were transferred to the MR and pCT. CBCT images (with the machine isocenter) from a single treatment day were coregistered with the 3 test images (MR, pCT and rCT), by two observers and by an automated registration algorithm. The reference points were used to calculate patient shifts and rotations from the registrations. The shifts calculated from the test image registrations were compared to each other and to the shifts performed by the therapists who treated the patients on that day.

Results:

The average difference in absolute value between the isocenter shifts from the MR‐, pCT‐ and rCT‐CBCT registrations, and the therapist shifts, were 2.02, 3.01 and 0.89 mm (craniocaudal), 1.14, 1.34 and 0.46 mm (lateral), and 1.37, 3.43 and 1.43 mm (vertical), respectively. The MR‐ and pCT‐CBCT registrations differed by 1.99, and 2.53 mm (craniocaudal), 1.36, and 1.37 mm (lateral), and 0.74 and 2.34 mm (vertical), respectively, from the average rCT‐CBCT shifts. On average, differences of 2.39 (craniocaudal), 1.28 (lateral) and 2.84 mm (vertical) were seen between the MR and pCT shifts. Rotations relative to the CBCT coordinate system were on average <2° for the MR and rCT, and <6° for the pCT.

Conclusion:

In this study, FSPGR MR‐CBCT registrations were more precise compared to the pCT‐CBCT registrations. For improved accuracy, MR sequences that are optimal for bony anatomy visualization are necessary.

GE healthcare has provided a research version of Advantage Sim MD to UCSF. No financial support was provided.
SU‐C‐18A‐06: Tracking Fuzzy Border Using Geodesic Curve and Its Application to Liver Segmentation On Planning CT
Authors: Yuan Y , Chao M , Sheu R , Rosenzweig K , Lo Y
Published: July 2014

Purpose:

To investigate the feasibility of using geodesic curves to track fuzzy borders between liver and chest wall and to evaluate how it could improve the performance of automatic liver segmentation on treatment planning CT images.

Methods:

The performance of automatic liver segmentation usually suffers from the fuzzy borders between liver and the adjacent chest wall due to similar HU values on non‐contrast‐enhanced planning CT images. To address this issue, geodesic curves were used to track these fuzzy borders. We first constructed a horizontal gradient map on the coronal‐view images. After automatically identifying one starting and one ending point, a minimal distance map (MDM) was constructed by evolving a front starting from an infinitesimal circle around the ending point to every pixel on the image. The value of each point in MDM represents the minimal distance from the point to the ending point, which combines both arc length and gradient magnitude along the path. The front evolution was numerically solved by fast‐marching method. We coupled this method with our automatic liver segmentation method, in which an initial contour was firstly estimated by adaptive thresholding and then a distance‐regularized geodesic active contour model was used to further refine the contour. Besides visual assessment, dice similarity coefficient (DSC) was calculated to quantitatively compare the computer‐generated contours with manual outlines.

Results:

This study included five patients with 597 CT slices who received SBRT liver treatment. We observed clear separation between liver and chest wall after delineation. The results of automatic segmentation were in excellent agreement with manual outlines, yielding all DSCs higher than 0.9 with mean of 0.93.

Conclusion:

The preliminary results demonstrate that geodesic curve can be used to track fuzzy borders between liver and chest wall, and thus to improve the performance of automatic liver segmentation on planning CT images.
SU‐C‐18C‐05: Evaluation of Endovascular Procedures Using Precise Patient Specific Phantoms Created Using Additive Manufacturing
Authors: Russ M , Iacobucci G , Wood R , O' Hara R , Rudin S , Ionita C
Published: July 2014

Purpose:

The development of patient specific models for endovascular procedures using additive manufacturing.

Methods:

The work to be presented is composed of two parts: manufacturing and testing of patientspecific phantoms. Phantom manufacturing began with acquisition of 3D patient data and segmentation for the generation of a printable STL file. The models were printed using a Polyjet printer, Objet Eden260V. Once printed, the phantoms were cleaned of support material, and tested for geometric accuracy as compared to the original patient specific data. Imaging validation using x‐ray angiography and qualitative evaluation of mechanical properties were also performed during an endovascular image‐guided intervention. Several iterations of phantoms have been printed and tested, and optimal design parameters have been determined for a favorable manufactured output.

Results:

The most challenging aspect of phantom manufacturing, as experienced in both simple and complex phantoms, is the removal of support material. Cleaning support material from inside of vessels can be mechanically difficult due to tortuous designs, and must be performed delicately to prevent wall rupture. Phantoms required NaOH baths and high‐pressure washing to eliminate all support materials. Phantom accuracy testing showed size variations of 120μm, a very good agreement with the original design. Interventionists experienced similar back pressure from phantoms when testing mechanical behavior in simulated clinical procedures.

Conclusion:

This process can serve as a viable tool for procedures and devices, and present unique learning opportunities for the endovascular field as a whole.

Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐D‐18A‐06: Variation of Controlled Breath Hold From CT Simulation to Treatment and Its Dosimetric Impact for Left‐Sided Breast Radiotherapy with a Real‐Time Optical Tracking System
Authors: Mittauer K , Deraniyagala R , Li J , Lu B , Liu C , Lightsey J , Yan G
Published: July 2014

Purpose:

Different breath‐hold (BH) maneuvers (abdominal breathing vs. chest breathing) during CT simulation and treatment can lead to chest wall positional variation. The purpose of this study is to quantify the variation of active breathing control (ABC)‐assisted BH and estimate its dosimetric impact for left‐sided whole‐breast radiotherapy with a real‐time optical tracking system (OTS).

Methods:

Seven breast cancer patients were included. An in‐house OTS tracked an infrared (IR) marker affixed over the xiphoid process of the patient at CT simulation and throughout the treatment course to measure BH variations. Correlation between the IR marker and the breast was studied for dosimetric purposes. The positional variations of 860 BHs were retrospectively incorporated into treatment plans to assess their dosimetric impact on breast and cardiac organs (heart and left anterior descending artery [LAD]).

Results:

The mean intrafraction variations were 2.8 mm, 2.7 mm, and 1.6 mm in the anteroposterior (AP), craniocaudal (CC), and mediolateral (ML) directions, respectively. Mean stability in any direction was within 1.5 mm. A general trend of BH undershoot at treatment relative to CT simulation was observed with an average of 4.4 mm, 3.6 mm, and 0.1 mm in the AP, CC, and ML directions, respectively. Undershoot up to 12.6 mm was observed for individual patients. The difference between the planned and delivered dose to breast targets was negligible. The average planned/delivered mean heart doses, mean LAD doses, and max LAD doses were 1.4/2.1, 7.4/15.7, and 18.6/31.0 Gy, respectively.

Conclusion:

Systematic undershoot was observed in ABC‐assisted BHs from CT simulation to treatment. Its dosimetric impact on breast coverage was minimized with image guidance, but the benefits of cardiac organ sparing were degraded. A real‐time tracking system can be used in junction with the ABC device to improve BH reproducibility.
SU‐D‐18C‐02: Feasibility of Using a Short ASL Scan for Calibrating Cerebral Blood Flow Obtained From DSC‐MRI
Authors: Wang P , Chang T , Huang K , Yeh C , Chien C , Wai Y , Lee T , Liu H
Published: July 2014

Purpose:

This study aimed to evaluate the feasibility of using a short arterial spin labeling (ASL) scan for calibrating the dynamic susceptibility contrast‐ (DSC‐) MRI in a group of patients with internal carotid artery stenosis.

Methods:

Six patients with unilateral ICA stenosis enrolled in the study on a 3T clinical MRI scanner. The ASL‐cerebral blood flow (‐CBF) maps were calculated by averaging different number of dynamic points (N=1‐45) acquired by using a Q2TIPS sequence. For DSC perfusion analysis, arterial input function was selected to derive the relative cerebral blood flow (rCBF) map and the delay (Tmax) map. Patient‐specific CF was calculated from the mean ASL‐ and DSC‐CBF obtained from three different masks: (1)Tmax< 3s, (2)combined gray matter mask with mask 1, (3)mask 2 with large vessels removed. One CF value was created for each number of averages by using each of the three masks for calibrating the DSC‐CBF map. The CF value of the largest number of averages (NL=45) was used to determine the acceptable range(< 10%, <15%, and <20%) of CF values corresponding to the minimally acceptable number of average (NS) for each patient.

Results:

Comparing DSC CBF maps corrected by CF values of NL (CBFL) in ACA, MCA and PCA territories, all masks resulted in smaller CBF on the ipsilateral side than the contralateral side of the MCA territory(p<.05). The values obtained from mask 1 were significantly different than the mask 3(p<.05). Using mask 3, the medium values of Ns were 4(<10%), 2(<15%) and 2(<20%), with the worst case scenario (maximum Ns) of 25, 4, and 4, respectively.

Conclusion:

This study found that reliable calibration of DSC‐CBF can be achieved from a short pulsed ASL scan. We suggested use a mask based on the Tmax threshold, the inclusion of gray matter only and the exclusion of large vessels for performing the calibration.
SU‐D‐18C‐03: In Vivo MR Imaging Using a Combined Single‐Point Dixon and Phase‐Sensitive Inversion Recovery Technique
Authors: Son J , Hazle J , Ma J
Published: July 2014

Purpose:

To demonstrate combined single‐point Dixon water/fat separation and phase sensitive inversion recovery imaging in in vivo brain images acquired in a single scan.

Methods:

A single inversion recovery image is acquired with an inversion‐time (TI) selected to maximize the dynamic range of the longitudinal magnetization of the water signals and at an echo time (TE) to introduce an orthogonal phase‐difference (i.e. 90°) between the fat and water signals. In the image reconstruction, spatially smooth background phase errors due to static magnetic field inhomogeneity are estimated by applying a region growing based phase correction algorithm: the algorithm first determines spatial phase jumps of 180° and then the second spatial phase jumps of 90°. After the background phase‐errors are removed from the acquired image, phase sensitive inversion recovery (PSIR) water‐only image and a separate fat‐only image can be generated as the real and imaginary parts of the phase‐corrected image, respectively.

Results:

The pulse sequence was implemented on a 3T whole‐body clinical scanner and a single brain image of a healthy volunteer was acquired. The acquired image was confirmed to contain an orthogonal phase difference between water and fat boundaries and 180o phase difference between the boundaries of long and short T1‐water tissues. The background phase errors were successfully determined and removed by the proposed phase correction algorithm and uniformly separated fat‐only and PSIR water‐only images were reconstructed without artefacts.

Conclusion:

We demonstrated combined single‐point Dixon water/fat separation and PSIR imaging in in vivo brain images acquired in a single scan. Such images can be useful when fat suppression and enhanced T1‐contrast are desired. Potential areas of application may include imaging of the brain or myocardium.
SU‐D‐18C‐06: Initial Experience with Implementing MRI Safety Guidelines for Patients with Pacemakers – Medical Physicist Perspective
Authors: James J , Place V , Edmonson H , Felmlee J , Pooley R , Panda A
Published: July 2014

Purpose:

Several institutions have developed MRI guidelines for patients with MR‐unsafe or MR‐conditional pacemakers. Here we highlight the role of a medical physicist in implementing these guidelines for non‐pacemaker dependent patients. Guidelines: Implementing these guidelines requires involvement from several medical specialties and a strong collaboration with the site MRI supervisor to develop a structured workflow. A medical physicist is required to be present during the scan to supervise the MR scanning and to maintain a safety checklist that ensures: 1) uninterrupted patient communication with the technologist, 2) continuous patient physiologic monitoring (e.g. blood pressure and electrocardiography) by a trained nurse, 3) redundant patient vitals monitoring (e.g. pulse oximetry) due to the possibility of in vivo electrocardiography reading fluctuations during image acquisition. A radiologist is strongly recommended to be available to review the images before patients are discharged from the scanner. Pacemaker MRI should be restricted to 1.5T field strength. The MRI sequences should be optimized by the physicist with regards to: a) SAR: limited to <1.5 W/Kg for MR‐unsafe pacemakers in normal operating mode, b) RF exposure time: <30 min, c) Coils: use T/R coils but not restricted to such, d) Artifacts: further optimization of sequences whenever image quality is compromised due to the pacemaker. In particular, cardiac, breast and left‐shoulder MRIs are most susceptible to these artifacts. Possible strategies to lower the SAR include: a) BW reduction, 2) echo‐train‐length reduction, 3) increase TR, 4) decrease number of averages, 5) decrease flip angle, 6) reduce slices and/or a combination of all the options.

Conclusion:

A medical physicist in collaboration with the MR supervisor plays an important role in the supervision/implementation of safe MR scanning of pacemaker patients. Developing and establishing a workflow has enabled our institution to scan over 30 patients with pacemakers without complications, including 3 cardiac MR exams.
SU‐D‐12A‐03: Improve Scatter Correction in CBCT Reconstruction to Improve the Image Quality for Large Patients
Authors: Tan Jun , Li Hua , Li Hui , Anastasio Mark , Yang Deshan
Published: July 2014

Purpose:

CBCT images by pelvis scan of larger patients often have lower soft tissue perceptibility, larger amount of artifacts, and lower image intensity uniformity than images of smaller patients. We hypothesize that the poor image quality is related to inaccurate or non‐optimal scattering correction during image reconstruction. To test the hypothesis, we implemented a new scattering correction algorithm and optimized its coefficients in order to understand if pelvis CBCT image qualities can be improved with better scattering correction methods and more optimal coefficients.

Methods:

A scatter correction algorithm using a fast scatter kernel superimposition with multiple kernel groups was implemented. The kernel parameters are the same as Varian TrueBeam machine, including 3 thickness groups, detector point‐scatter function parameters. Detector scatter correction and bowtie filter correction were also implemented. A 48 cm wide phantom and another 43 cm wide phantom were simulated by enclosing a 38 cm pelvis phantom with 5 cm thick plastic flaps. A comparison was made between the phantom CBCT images reconstructed by the TrueBeam machine and the ones reconstructed by our in‐house reconstruction program with the new scattering correction method.

Results:

CBCT images reconstructed using our in‐house program with the new scattering correction method showed much less streaking artifacts, better intensity uniformity and comparative soft tissue contrast. The standard deviation of a soft tissue region is 17.1 HU for the 48 cm phantom and 16.8 for the 43 cm phantom using our program, compared to 36.9 HU for the 48 cm phantom and 25.9 for the 43 cm phantom using the TrueBeam machine.

Conclusion:

Our results suggested that a better scattering algorithm could improve the pelvis CBCT scan image quality considerably for larger patients.
SU‐D‐12A‐05: Iterative Reconstruction Techniques to Enable Intrinsic Respiratory Gated CT in Mice
Authors: Sun T , Liu Y , Sun N , Mistry N , Tan S
Published: July 2014

Purpose:

Longitudinal studies of lung function in mice need the ability to image different phases of ventilation in free‐breathing mice using retrospective gating. However, retrospective gating often produces under‐sampled and uneven angular samples, resulting in severe reconstruction artifacts when using traditional FDK based reconstruction algorithms. We wanted to demonstrate the utility of iterative reconstruction method to enable intrinsic respiratory gating in small‐animal CT.

Methods:

Free‐breathing mice were imaged using a Siemens Inveon PET/micro‐CT system. Evenly distributed projection images were acquired at 360 angles. Retrospective respiratory gating was performed using an intrinsic marker based on the average intensity in a region covering the diaphragm. Projections were classified into 4 and 6 phases (finer temporal resolution) resulting in 138 and 67 projections respectively. Reconstruction was carried out using 3 Methods: conventional FDK, iterative penalized least‐square (PWLS) with total variation (TV), and PWLS with edge‐preserving penalty. The performance of the methods was compared using contrast‐to‐noise (CNR) in a region of interest (ROI). Line profile through a specific region was plotted to evaluate the preserving of edges.

Results:

In both the cases with 4 and 6 phases, inadequate and non‐uniform angular sampling results in artifacts using conventional FDK. However, such artifacts are minimized using both the iterative methods. Using both 4 and 6 phases, the iterative techniques outperformed FDK in terms of CNR and maintaining sharp edges. This is further evidenced especially with increased artifacts using FDK for 6 phases.

Conclusion:

This work indicates fewer artifacts and better image details can be achieved with iterative reconstruction methods in non‐uniform under‐sampled reconstruction. Using iterative methods can enable free‐breathing intrinsic respiratory gating in small‐animal CT. Further studies are needed to compare the computational complexity for large datasets.
SU‐E‐P‐01: An Informative Review On the Role of Diagnostic Medical Physicist in the Academic and Private Medical Centers
Authors: Weir V , Zhang J
Published: July 2014

Purpose:

The role of physicist in the academic and private hospital environment continues to evolve and expand. This becomes more obvious with the newly revised requirements of the Joint Commission (JC) on imaging modalities and the continued updated requirements of ACR accreditation for medical physics (i.e., starting in June 2014, a physicists test will be needed before US accreditation). We provide an informative review on the role of diagnostic medical physicist and hope that our experience will expedite junior physicists in understanding their role in medical centers, and be ready to more opportunities.

Methods:

Based on our experience, diagnostic medical physicists in both academic and private medical centers perform several clinical functions. These include providing clinical service and physics support, ensuring that all ionizing radiation devices are tested and operated in compliance with the State and Federal laws, regulations and guidelines. We also discuss the training and education required to ensure that the radiation exposure to patients and staff is as low as reasonably achievable. We review the overlapping roles of medical and health physicist in some institutions.

Results:

A detailed scheme on the new requirements (effective 7/1/2014) of the JC is provided. In 2015, new standards for fluoroscopy, cone beam CT and the qualifications of staff will be phased in. A summary of new ACR requirements for different modalities is presented. Medical physicist have other duties such as sitting on CT and fluoroscopy committees for protocols design, training of non‐radiologists to meet the new fluoroscopy rules, as well as helping with special therapies such as Yittrium 90 cases.

Conclusion:

Medical physicists in both academic and private hospitals are positioned to be more involved and prominent. Diagnostic physicists need to be more proactive to involve themselves in the day to day activities of the radiology department.
SU‐E‐P‐04: Transport Theory Learning Module in the Maple Environment
Authors: Both J
Published: July 2014

Purpose:

The medical physics graduate program at the University of Miami is developing a computerized instructional module which provides an interactive mechanism for students to learn transport theory. While not essential in the medical physics curriculum, transport theory should be taught because the conceptual level of transport theory is fundamental, a substantial literature exists and ought to be accessible, and students should understand commercial software which solves the Boltzmann equation.But conventional teaching and learning of transport theory is challenging. Students may be under prepared to appreciate its methods, results, and relevance, and it is not substantially addressed in textbooks for the medical physicists. Other resources an instructor might reasonably use, while excellent, may be too briskly paced for beginning students. The purpose of this work is to render teaching of transport theory more tractable by making learning highly interactive.

Methods:

The module is being developed in the Maple mathematics environment by instructors and graduate students. It will refresh the students' knowledge of vector calculus and differential equations, and will develop users' intuition for phase space concepts. Scattering concepts will be developed with animated simulations using tunable parameters characterizing interactions, so that students may develop a “feel” for cross section. Transport equations for one and multiple types of radiation will be illustrated with phase space animations. Numerical methods of solution will be illustrated.

Results:

Attempts to teach rudiments of transport theory in radiation physics and dosimetry courses using conventional classroom techniques at the University of Miami have had small success, because classroom time is limited and the material has been hard for our students to appreciate intuitively.

Conclusion:

A joint effort of instructor and students to teach and learn transport theory by building an interactive description of it will lead to deeper appreciation of the transport theoretical underpinnings of dosimetry.
SU‐E‐P‐10: Imaging in the Cardiac Catheterization Lab – Technologies and Clinical Applications
Authors: Fetterly K
Published: July 2014

Purpose:

Diagnosis and treatment of cardiovascular disease in the cardiac catheterization laboratory is often aided by a multitude of imaging technologies. The purpose of this work is to highlight the contributions to patient care offered by the various imaging systems used during cardiovascular interventional procedures.

Methods:

Imaging technologies used in the cardiac catheterization lab were characterized by their fundamental technology and by the clinical applications for which they are used. Whether the modality is external to the patient, intravascular, or intracavity was specified. Specific clinical procedures for which multiple modalities are routinely used will be highlighted.

Results:

X‐ray imaging modalities include fluoroscopy/angiography and angiography CT. Ultrasound imaging is performed with external, trans‐esophageal echocardiography (TEE), and intravascular (IVUS) transducers. Intravascular infrared optical coherence tomography (IVOCT) is used to assess vessel endothelium. Relatively large (>0.5 mm) anatomical structures are imaged with x‐ray and ultrasound. IVUS and IVOCT provide high resolution images of vessel walls. Cardiac CT and MRI images are used to plan complex cardiovascular interventions. Advanced applications are used to spatially and temporally merge images from different technologies. Diagnosis and treatment of coronary artery disease frequently utilizes angiography and intra‐vascular imaging, and treatment of complex structural heart conditions routinely includes use of multiple imaging modalities.

Conclusion:

There are several imaging modalities which are routinely used in the cardiac catheterization laboratory to diagnose and treat both coronary artery and structural heart disease. Multiple modalities are frequently used to enhance the quality and safety of procedures. The cardiac catheterization laboratory includes many opportunities for medical physicists to contribute substantially toward advancing patient care.
SU‐E‐I‐01: A Fast, Analytical Pencil Beam Based Method for First Order X‐Ray Scatter Estimation of Kilovoltage Cone Beam X‐Rays
Authors: Liu J , Bourland J
Published: July 2014

Purpose:

To analytically estimate first‐order x‐ray scatter for kV cone beam x‐ray imaging with high computational efficiency.

Methods:

In calculating first‐order scatter using the Klein‐Nishina formula, we found that by integrating the point‐to‐point scatter along an interaction line, a “pencil‐beam” scatter kernel (BSK) can be approximated to a quartic expression when the imaging field is small. This BSK model for monoenergetic, 100keV x‐rays has been verified on homogeneous cube and cylinder water phantoms by comparing with the exact implementation of KN formula. For heterogeneous medium, the water‐equivalent length of a BSK was acquired with an improved Siddon's ray‐tracing algorithm, which was also used in calculating pre‐ and post‐ scattering attenuation. To include the electron binding effect for scattering of low‐kV photons, the mean corresponding scattering angle is determined from the effective point of scattered photons of a BSK. The behavior of polyenergetic x‐rays was also investigated for 120kV x‐rays incident to a sandwiched infinite heterogeneous slab phantom, with the electron binding effect incorporated. Exact computation and Monte Carlo simulations were performed for comparisons, using the EGSnrc code package.

Results:

By reducing the 3D volumetric target (o(n3)) to 2D pencil‐beams (o(n2)), the computation expense can be generally lowered by n times, which our experience verifies. The scatter distribution on a flat detector shows high agreement between the analytic BSK model and exact calculations. The pixel‐to‐pixel differences are within (‐2%, 2%) for the homogeneous cube and cylinder phantoms and within (0, 6%) for the heterogeneous slab phantom. However, the Monte Carlo simulation shows increased deviation of the BSK model toward detector periphery.

Conclusion:

The proposed BSK model, accommodating polyenergetic x‐rays and electron binding effect at low kV, shows great potential in efficiently estimating the first‐order scatter from small imaging fields. We are investigating more thoroughly to improve performance and explore applications.
SU‐E‐I‐10: Automatic Monitoring of Accumulated Dose Indices From DICOM RDSR to Improve Radiation Safety in X‐Ray Angiography
Authors: Omar A , Bujila R , Nowik P , Karambatsakidou A
Published: July 2014

Purpose:

To investigate the potential benefits of automatic monitoring of accumulated patient and staff dose indicators, i.e., CAK and KAP, from DICOM Radiation Dose Structured Reports (RDSR) in x‐ray angiography (XA).

Methods:

Recently RDSR has enabled the convenient aggregation of dose indices and technique parameters for XA procedures. The information contained in RDSR objects for three XA systems, dedicated to different types of clinical procedures, has been collected and aggregated in a database for over one year using a system developed with open‐source software at the Karolinska University Hospital. Patient weight was complemented to the RDSR data via an interface with the Hospital Information System (HIS).

Results:

The linearly approximated trend in KAP over a time period of a year for cerebrovascular, pelvic/peripheral vascular, and cardiovascular procedures showed a decrease of 12%, 20%, and 14%, respectively. The decrease was mainly due to hardware/software upgrades and new low‐dose imaging protocols, and partially due to ongoing systematic radiation safety education of the clinical staff. The CAK was in excess of 3 Gy for 15 procedures, and exceeded 5 Gy for 3 procedures. The dose indices have also shown a significant dependence on patient weight for cardiovascular and pelvic/peripheral vascular procedures; a 10 kg shift in mean patient weight can result in a dose index increase of 25%.

Conclusion:

Automatic monitoring of accumulated dose indices can be utilized to notify the clinical staff and medical physicists when the dose index has exceeded a predetermined action level. This allows for convenient and systematic follow‐up of patients in risk of developing deterministic skin injuries. Furthermore, trend analyses of dose indices over time is a valuable resource for the identification of potential positive or negative effects (dose increase/decrease) from changes in hardware, software, and clinical work habits.
SU‐E‐I‐11: Cascaded Linear System Model for Columnar CsI Flat Panel Imagers with Depth Dependent Gain and Blur
Authors: Peng B , Lubinsky A , Teymurazyan A , Zheng H , Zhao W
Published: July 2014

Purpose:

To implement a depth dependent gain and blur cascaded linear system model (CLSM) for optimizing columnar structured CsI indirect conversion flat panel imager (FPI) for advanced imaging applications.

Methods:

For experimental validation, depth dependent escape efficiency, e(z), was extracted from PHS measurement of different CsI scintillators (thickness, substrate and light output). The inherent MTF and DQE of CsI was measured using high resolution CMOS sensor. For CLSM, e(z) and the depth dependent MTF(f,z), were estimated using Monte Carlo simulation (Geant4) of optical photon transport through columnar CsI. Previous work showed that Monte Carlo simulation for CsI was hindered by the non‐ideality of its columnar structure. In the present work we allowed variation in columnar width with depth, and assumed diffusive reflective backing and columns. Monte Carlo simulation was performed using an optical point source placed at different depth of the CsI layer, from which MTF(z,f) and e(z) were computed. The resulting e(z) with excellent matching with experimental measurements were then applied to the CLSM, Monte Carlo simulation was repeated until the modeled MTF, DQE(f) also match experimental measurement.

Results:

For a 150 micron FOS HL type CsI, e(z) varies between 0.56 to 0.45, and the MTF at 14 cycles/mm varies between 62.1% to 3.9%, from the front to the back of the scintillator. The overall MTF and DQE(f) at all frequencies are in excellent agreement with experimental measurements at all frequencies.

Conclusion:

We have developed a CLSM for columnar CsI scintillators with depth dependent gain and MTF, which were estimated from Monte Carlo simulation with novel optical simulation settings. Preliminary results showed excellent agreement between simulation results and experimental measurements. Future work is aimed at extending this approach to optimize CsI screen optic design and sensor structure for achieving higher DQE(f) in cone‐beam CT, which uses high kVp.
SU‐E‐I‐14: Comparison of Iodine‐Labeled and Indium‐Labeled Antibody Biodistributions
Authors: Williams L
Published: July 2014

Purpose:

It is often assumed that animal biodistributions of novel proteins are not dependent upon the radiolabel used in their determination. In units of percent injected dose per gram of tissue (%ID/g), organ uptake results (u) may be obtained using either iodine or metal as radioactive labels. Iodination is preferred as it is a one‐step process whereas metal labeling requires two chemical procedures and therefore more protein material. It is important to test whether the radioactive tag leads to variation in the uptake value.

Methods:

Uptakes of 3antibodies to Carcinoembryonic Antigen (CEA) were evaluated in a nude mouse model bearing 150 to 300 mg LS174T human colon cancer xenografts. Antibodies included diabody (56 kDa), minibody (80kDa) and intact M5A (150 kDa) anti‐CEA cognates. Both radioiodine and indium‐111 labels were used with uptakes evaluated at 7 time(t) points out to 96 h. Ratios (R) of u(iodine‐label)/u(indium‐label) were determined for liver, spleen, kidneys, lung and tumor.

Results:

Hepatic loss was rapid for diabody and minibody; by 24 h their R values were only 2%; i.e., uptake of iodine was 2% of that of indium for these 2 antibodies. By contrast, R for the intact cognate was 50% at that time point. Splenic results were similar. Tumor uptake ratios did not depend upon the antibody type and were 50% at 24 h.

Conclusions:

Relatively rapid loss of iodine relative to indium in liver and spleen was observed in lower mass antibodies. Tumor ratios were larger and independent of antibody type. Aside from tumor, the R ratio of uptakes depended on the antibody type. R values decreased monotonically with time in all tissues and for all cognates. Using this ratio, one can possibly correct iodine‐based u (t) results so that they resemble radiometal‐derived biodistributions.
SU‐E‐I‐17: Comparison of Two Novel Algorithms for the Modulation Transfer Function of CT Using a Simple Cylindrical Phantom
Authors: Kam S , Jeon H , Youn H , Kim H , Park D
Published: July 2014

Purpose:

To compare and analyze two novel algorithms for the assessment of modulation transfer functions (MTFs) of computed tomography (CT) systems using a simple acrylic cylindrical phantom

Method and Materials:

Images of the acrylic cylindrical phantom were acquired by a GE LightSpeed 16 RT (GE Healthcare, Milwaukee, WI) using 120 kVp, 330 mA, 2.5 mm slice thickness, 10 cm field‐of view (FOV), four reconstruction kernels (e.g. standard, soft, detail, bone, and lung). Two different algorithms were used to analyze images for MTF assessment. First, Richard et al. suggested a task‐based MTF assessment method through an edge spread function (ESF) which described pixel intensities as a function of distance from the center. The MTF was obtained as the absolute value of Fourier transform of the differentiated ESF. Second, Ohkubo et al. devised an effective method to determine the point spread function (PSF) of CT system accompanied with verification. The line spread function (LSF), which was the one‐dimensional integration of the PSF, was used to obtain the MTF. We validated the reliability of two above‐mentioned methods through the comparison with a conventional method using a thin tungsten wire phantom.

Results:

The measured MTFs by two methods were mostly similar each other for standard, soft, and detail kernels. In 0.6 lp/mm, the MTF difference between two methods were 0.012(standard), 0.004(soft), and 0.037(detail). They also coincided with the MTF by the conventional method well. However, there were considerable distinctions for bone and lung kernels containing edge enhancement that might cause undershoots near the peak of the LSF.

Conclusions:

We compared two novel methods to assess task‐based MTFs for clinical CT systems especially using a simple acrylic cylindrical phantom with high‐convenience and low‐cost, and validated them against a conventional method. This work can provide a practical solution to users for the quality assurance of CT.
SU‐E‐I‐19: CTDI Values for All Protocols: Using the Ratio of the DLP Measured in CTDI Phantoms to the Measured Air Exposure
Authors: Raterman G , Gauntt D
Published: July 2014

Purpose:

To propose a method other than CTDI phantom measurements for routine CT dosimetry QA. This consists of taking a series of air exposure measurements and calculating a factor for converting from this exposure measurement to the protocol's associated head or body CTDI value using DLP. The data presented are the ratios of phantom DLP to air exposure ratios for different scanners, as well as error in the displayed CTDI.

Methods:

For each scanner, the CTDI is measured at all available tube voltages using both the head and body phantoms. Then, the exposure is measured using a pencil chamber in air at isocenter. A ratio of phantom DLP to exposure in air for a given protocol may be calculated and used for converting a simple air dose measurement to a head or body CTDI value. For our routine QA, the exposure in air for different collimations, mAs, and kVp is measured, and displayed CTDI is recorded. Therefore, the ratio calculated may convert these exposures to CTDI values that may then be compared to the displayed CTDI for a large range of acquisition parameter combinations.

Results:

It was found that all scanners tend to have a ratio factor that slightly increases with kVp. Also, Philips scanners appear to have less of a dependence on kVp; whereas, GE scanners have a lower ratio at lower kVp. The use of air exposure times the DLP conversion yielded CTDI values that were less than 10% different from the displayed CTDI on several scanners.

Conclusion:

This method may be used as a primary method for CT dosimetry QA. As a result of the ease of measurement, a dosimetry metric specific to that scanner may be calculated for a wide variety of CT protocols, which could also be used to monitor display CTDI value accuracy.
SU‐E‐I‐22: Dependence On Calibration Phantom and Field Area of the Conversion Factor Used to Calculate Skin Dose During Neuro‐Interventional Fluoroscopic Procedures
Authors: Rana V K , Vijayan S , Rudin S R , Bednarek D R
Published: July 2014

Purpose:

To determine the appropriate calibration factor to use when calculating skin dose with our real‐time dose‐tracking system (DTS) during neuro‐interventional fluoroscopic procedures by evaluating the difference in backscatter from different phantoms and as a function of entrance‐skin field area.

Methods:

We developed a dose‐tracking system to calculate and graphically display the cumulative skin‐dose distribution in real time. To calibrate the DTS for neuro‐interventional procedures, a phantom is needed that closely approximates the scattering properties of the head. We compared the x‐ray backscatter from eight phantoms: 20‐cm‐thick solid water, 16‐cm diameter water‐filled container, 16‐cm CTDI phantom, modified‐ANSI head phantom, 20‐cm‐thick PMMA, Kyoto‐Kagaku PBU‐ 50 head, Phantom‐Labs SK‐150 head, and RSD RS‐240T head. The phantoms were placed on the patient table with the entrance surface at 15 cm tube‐side from the isocenter of a Toshiba Infinix C‐arm, and the entrance‐skin exposure was measured with a calibrated 6‐cc PTW ionization chamber. The measurement included primary radiation, backscatter from the phantom and forward scatter from the table and pad. The variation in entrance‐skin exposure was also measured as a function of the skin‐entrance area for a 30×30 cm by 20‐cm‐thick PMMA phantom and the SK‐150 head phantom using four different added beam filters.

Results:

The entranceskin exposure values measured for eight different phantoms differed by up to 12%, while the ratio of entrance exposure of all phantoms relative to solid water showed less than 3% variation with kVp. The change in entrance‐skin exposure with entrance‐skin area was found to differ for the SK‐150 head compared to the 20‐cm PMMA phantom and the variation with field area was dependent on the added beam filtration.

Conclusion:

To accurately calculate skin dose for neuro‐interventional procedures with the DTS, the phantom for calibration should be carefully chosen since different phantoms can contribute different backscatter for identical exposure parameters.

Research supported in part by Toshiba Medical Systems and NIH Grants R43FD0158401, R44FD0158402 and R01EB002873
SU‐E‐I‐23: Design and Clinical Application of External Marking Body in Multi‐ Mode Medical Images Registration and Fusion
Authors: Chen Z , Gong G
Published: July 2014

Purpose:

To design an external marking body (EMB) that could be visible on computed tomography (CT), magnetic resonance (MR), positron emission tomography (PET) and single‐photon emission computed tomography (SPECT) images and to investigate the use of the EMB for multiple medical images registration and fusion in the clinic.

Methods:

We generated a solution containing paramagnetic metal ions and iodide ions (CT' MR dual‐visible solution) that could be viewed on CT and MR images and multi‐mode image visible solution (MIVS) that could be obtained by mixing radioactive nuclear material. A globular plastic theca (diameter: 3–6 mm) that mothball the MIVS and the EMB was brought by filling MIVS. The EMBs were fixed on the patient surface and CT, MR, PET and SPECT scans were obtained. The feasibility of clinical application and the display and registration error of EMB among different image modalities were investigated.

Results:

The dual‐visible solution was highly dense on CT images (HU>700). A high signal was also found in all MR scanning (T1, T2, STIR and FLAIR) images, and the signal was higher than subcutaneous fat. EMB with radioactive nuclear material caused a radionuclide concentration area on PET and SPECT images, and the signal of EMB was similar to or higher than tumor signals. The theca with MIVS was clearly visible on all the images without artifact, and the shape was round or oval with a sharp edge. The maximum diameter display error was 0.3 ± 0.2mm on CT and MRI images, and 1.0 ± 0.3mm on PET and SPECT images. In addition, the registration accuracy of the theca center among multi‐mode images was less than 1mm.

Conclusion:

The application of EMB with MIVS improves the registration and fusion accuracy of multi‐mode medical images. Furthermore, it has the potential to ameliorate disease diagnosis and treatment outcome.