Toshiba Medical Systems Corporation Research Articles

Using Acoustic Structure Quantification During B‐Mode Sonography for Evaluation of Hashimoto Thyroiditis

This study aimed to evaluate the usefulness of Acoustic Structure Quantification (ASQ; Toshiba Medical Systems Corporation, Nasushiobara, Japan) values in the diagnosis of Hashimoto thyroiditis using B-mode sonography and to identify a cutoff ASQ level that differentiates Hashimoto thyroiditis from normal thyroid tissue. A total of 186 thyroid lobes with Hashimoto thyroiditis and normal thyroid glands underwent sonography with ASQ imaging. The quantitative results were reported in an echo amplitude analysis (Cm(2)) histogram with average, mode, ratio, standard deviation, blue mode, and blue average values. Receiver operating characteristic curve analysis was performed to assess the diagnostic ability of the ASQ values in differentiating Hashimoto thyroiditis from normal thyroid tissue. Intraclass correlation coefficients of the ASQ values were obtained between 2 observers. Of the 186 thyroid lobes, 103 (55%) had Hashimoto thyroiditis, and 83 (45%) were normal. There was a significant difference between the ASQ values of Hashimoto thyroiditis glands and those of normal glands (P < .001). The ASQ values in patients with Hashimoto thyroiditis were significantly greater than those in patients with normal thyroid glands. The areas under the receiver operating characteristic curves for the ratio, blue average, average, blue mode, mode, and standard deviation were: 0.936, 0.902, 0.893, 0.855, 0.846, and 0.842, respectively. The ratio cutoff value of 0.27 offered the best diagnostic performance, with sensitivity of 87.38% and specificity of 95.18%. The intraclass correlation coefficients ranged from 0.86 to 0.94, which indicated substantial agreement between the observers. Acoustic Structure Quantification is a useful and promising sonographic method for diagnosing Hashimoto thyroiditis. Not only could it be a helpful tool for quantifying thyroid echogenicity, but it also would be useful for diagnosis of Hashimoto thyroiditis.

TU-F-CAMPUS-I-05: Investigation of An EMCCD Detector with Variable Gain in a Micro-CT System

Purpose: To investigate the performance of a newly built Electron Multiplying Charged Coupled Device (EMCCD) based Micro-CT system, with variable detector gain, using a phantom containing contrast agent of different concentrations. Methods: We built a micro- CT system with an EMCCD having 8 microns pixels and on-chip variable gain. We tested the system using a phantom containing five tubes filled with different iodine contrast solutions (30% to 70%). First, we scanned the phantom using various x-ray exposures values at 40 kVp and constant detector gain. Next, for the same tube currents, the detector gain was increased to maintain the air value of the projection image constant. A standard FDK algorithm was used to reconstruct the data. Performance was analyzed by comparing the signal-to-noise ratio (SNR) measurements for increased gain with those for the low constant gain at each exposure. Results: The high detector gain reconstructed data SNR was always greater than the low gain data SNR for all x-ray settings and for all iodine features. The largest increases were observed for low contrast features, 30% iodine concentration, where the SNR improvement approached 2. Conclusion: One of the first implementations of an EMCCD based micro- CT system was presented and used to image a phantom with various iodine solution concentrations. The analysis of the reconstructed volumes showed a significant improvement of the SNR especially for low contrast features. The unique on-chip gain feature is a substantial benefit allowing the use of the system at very low x-ray exposures per frame.Partial support: NIH grant R01EB002873 and Toshiba Medical Systems Corp. Partial support: NIH grant R01EB002873 and Toshiba Medical Systems Corp.

MO‐F‐CAMPUS‐I‐01: A System for Automatically Calculating Organ and Effective Dose for Fluoroscopically‐Guided Procedures

Purpose:A system was developed that automatically calculates the organ and effective dose for individual fluoroscopically‐guided procedures using a log of the clinical exposure parameters.Methods:We have previously developed a dose tracking system (DTS) to provide a real‐time color‐coded 3D‐ mapping of skin dose. This software produces a log file of all geometry and exposure parameters for every x‐ray pulse during a procedure. The data in the log files is input into PCXMC, a Monte Carlo program that calculates organ and effective dose for projections and exposure parameters set by the user. We developed a MATLAB program to read data from the log files produced by the DTS and to automatically generate the definition files in the format used by PCXMC. The processing is done at the end of a procedure after all exposures are completed. Since there are thousands of exposure pulses with various parameters for fluoroscopy, DA and DSA and at various projections, the data for exposures with similar parameters is grouped prior to entry into PCXMC to reduce the number of Monte Carlo calculations that need to be performed.Results:The software developed automatically transfers data from the DTS log file to PCXMC and runs the program for each grouping of exposure pulses. When the dose from all exposure events are calculated, the doses for each organ and all effective doses are summed to obtain procedure totals. For a complicated interventional procedure, the calculations can be completed on a PC without manual intervention in less than 30 minutes depending on the level of data grouping.Conclusion:This system allows organ dose to be calculated for individual procedures for every patient without tedious calculations or data entry so that estimates of stochastic risk can be obtained in addition to the deterministic risk estimate provided by the DTS.Partial support from NIH grant R01EB002873 and Toshiba Medical Systems Corp.

WE‐G‐204‐06: Grid‐Line Artifact Minimization for High Resolution Detectors Using Iterative Residual Scatter Correction

Purpose:Anti‐scatter grid‐line artifacts are more prominent for high‐resolution x‐ray detectors since the fraction of a pixel blocked by the grid septa is large. Direct logarithmic subtraction of the artifact pattern is limited by residual scattered radiation and we investigate an iterative method for scatter correction.Methods:A stationary Smit‐Rοntgen anti‐scatter grid was used with a high resolution Dexela 1207 CMOS X‐ray detector (75 µm pixel size) to image an artery block (Nuclear Associates, Model 76‐705) placed within a uniform head equivalent phantom as the scattering source. The image of the phantom was divided by a flat‐field image obtained without scatter but with the grid to eliminate grid‐line artifacts. Constant scatter values were subtracted from the phantom image before dividing by the averaged flat‐field‐with‐grid image. The standard deviation of pixel values for a fixed region of the resultant images with different subtracted scatter values provided a measure of the remaining grid‐line artifacts.Results:A plot of the standard deviation of image pixel values versus the subtracted scatter value shows that the image structure noise reaches a minimum before going up again as the scatter value is increased. This minimum corresponds to a minimization of the grid‐line artifacts as demonstrated in line profile plots obtained through each of the images perpendicular to the grid lines. Artifact‐free images of the artery block were obtained with the optimal scatter value obtained by this iterative approach.Conclusion:Residual scatter subtraction can provide improved grid‐line artifact elimination when using the flat‐field with grid “subtraction” technique. The standard deviation of image pixel values can be used to determine the optimal scatter value to subtract to obtain a minimization of grid line artifacts with high resolution x‐ray imaging detectors.This study was supported by NIH Grant R01EB002873 and an equipment grant from Toshiba Medical Systems Corp.

MO‐F‐CAMPUS‐I‐02: Stability Investigation of a Gamma Fitting Algorithm for Angiographic Parametric Imaging at Low X‐Ray Exposures Using a Patient Specific Neurovascular Phantom

Purpose:To analyze the stability of a Gamma fitting algorithm based on digital subtraction angiography sequences, at different exposure, hence noise levels.Methods:Starting with a patient CT volume, we built a 3D printed neurovascular phantom which contained a complete Circle of Willis with major arteries and five aneurysms. We placed the phantom in a 15 cm water bath and connected it to a flow loop containing a peristaltic pump which simulated physiological relevant flow conditions. We injected 10 ml contrast boluses using an automatic contrast injector at a rate of 10 ml/sec. Digital Subtraction Angiography images were acquired at 30 frames/sec and processed with a gamma fitting based algorithm, to yield parametric maps of: Mean transit time (MTT), Time‐to‐Peak (TTP), Bolus Arrival Time (BAT). Starting with the optimal exposure parameters selected by the x‐ray system automatic exposure control, while keeping the same kV, we lowered the mA and exposure per frame in four steps until we reached the minimum value allowed by the system. We analyzed the variation of the MTT, TTP and BAT for various artery signal to noise ratios using four ROIs.Results:The peak (maximum opacification) SNRs for full dose and minimum dose were: 35 and 13 for 4 mm arteries and 18 and 7 for 2 mm arteries. The parameters standard deviation expressed as a percent fraction of the value measured at the full dose value, were: MTT=2.4%, BAT=0.5% and TTP=1.9% for 4 mm vessels and MTT=3.7%, BAT=5.4% and TTP=6.3% for 2 mm vessels.Conclusion:Despite a significant decrease of the peak SNR the algorithm performed very well displaying variations less than 6.3% of the ideal conditions. Partial Support: NIH grant R01EB002873 and Toshiba Medical Systems Corp.Partial Support: NIH grant R01EB002873 and Toshiba Medical Systems Corp.

TH-AB-201-01: A Real-Time Skin-Dose Mapping System for Region-Of-Interest (ROI) Fluoroscopy

Purpose: The real-time dose-tracking system (DTS) which we developed for fluoroscopically–guided procedures has been upgraded so that it can track the patient skin dose when using a region-of-interest (ROI) beam attenuator. Methods: ROI fluoroscopy is a method for greatly reducing patient dose by inserting an attenuator with an aperture into the x-ray beam. The aperture defines an ROI with normal dose and image quality, while under the attenuator the dose and quality are reduced. A moveable copper ROI attenuator has been installed in the collimator assembly of a Toshiba Infinix system. The DTS provides a 3D-dose mapping on a patient graphic and, to track dose for ROI fluoroscopy, the software now models the attenuator shape and position. A calibration file provides values for the transmission of the attenuator as a function of kVp and beam filtration and dose corrections are performed if a ray to a given point on the patient graphic is determined to intersect the attenuator. Backscatter is included in the skin-dose determination and is dependent on the ROI beam size projected onto the patient. In the current version, a spatially invariant factor corrects for backscatter within the ROI and from the ROI region into the attenuated region. The agreement of the dose distribution calculated by the DTS with the actual distribution was verified by measurement with calibrated radiochromic film and a 20-cm PMMA phantom. Results: The DTS is able to accurately model the size and position of the ROI attenuator as projected onto the patient graphic. Measurements with radiochromic film show the skin-dose estimation agreement to be within +/−12%, with most error arising from the spatial variation of backscatter. Conclusion: The dose distribution on the patient can now be tracked in real-time with acceptable accuracy when the new dose-saving feature of ROI fluoroscopy is used. This research was supported in part by Toshiba Medical Systems Corporation and NIH Grant R01EB002873.

Evaluation of MRI-US Fusion Technology in Sports-Related Musculoskeletal Injuries

A combination of magnetic resonance imaging (MRI) with real-time high-resolution ultrasound (US) known as fusion imaging may improve visualization of musculoskeletal (MSK) sports medicine injuries. The aim of this study was to evaluate the applicability of MRI-US fusion technology in MSK sports medicine. This study was conducted by the medical services of the FC Barcelona. The participants included volunteers and referred athletes with symptomatic and asymptomatic MSK injuries. All cases underwent MRI which was loaded into the US system for manual registration on the live US image and fusion imaging examination. After every test, an evaluation form was completed in terms of advantages, disadvantages, and anatomic fusion landmarks. From November 2014 to March 2015, we evaluated 20 subjects who underwent fusion imaging, 5 non-injured volunteers and 15 injured athletes, 11 symptomatic and 4 asymptomatic, age range 16-50years, mean 22. We describe some of the anatomic landmarks used to guide fusion in different regions. This technology allowed us to examine muscle and tendon injuries simultaneously in US and MRI, and the correlation of both techniques, especially low-grade muscular injuries. This has also helped compensate for the limited field of view with US. It improves spatial orientation of cartilage, labrum and meniscal injuries. However, a high-quality MRI image is essential in achieving an adequate fusion image, and 3D sequences need to be added in MRI protocols to improve navigation. The combination of real-time MRI and US image fusion and navigation is relatively easy to perform and is helping to improve understanding of MSK injuries. However, it requires specific skills in MSK imaging and still needs further research in sports-related injuries. Toshiba Medical Systems Corporation.

WE‐G‐204‐05: Relative Object Detectability Evaluation of a New High Resolution A‐Se Direct Detection System Compared to Indirect Micro‐Angiographic Fluoroscopic (MAF) Detectors

Purpose:To evaluate the task specific imaging performance of a new 25µm pixel pitch, 1000µm thick amorphous selenium direct detection system with CMOS readout for typical angiographic exposure parameters using the relative object detectability (ROD) metric.Methods:The ROD metric uses a simulated object function weighted at each spatial frequency by the detectors’ detective quantum efficiency (DQE), which is an intrinsic performance metric. For this study, the simulated objects were aluminum spheres of varying diameter (0.05–0.6mm). The weighted object function is then integrated over the full range of detectable frequencies inherent to each detector, and a ratio is taken of the resulting value for two detectors. The DQE for the 25µm detector was obtained from a simulation of a proposed a‐Se detector using an exposure of 200µR for a 50keV x‐ray beam. This a‐Se detector was compared to two microangiographic fluoroscope (MAF) detectors [the MAF‐CCD with pixel size of 35µm and Nyquist frequency of 14.2 cycles/mm and the MAF‐CMOS with pixel size of 75µm and Nyquist frequency of 6.6 cycles/mm] and a standard flat‐panel detector (FPD with pixel size of 194µm and Nyquist frequency of 2.5cycles/mm).Results:ROD calculations indicated vastly superior performance by the a‐Se detector in imaging small aluminum spheres. For the 50µm diameter sphere, the ROD values for the a‐Se detector compared to the MAF‐CCD, the MAF‐CMOS, and the FPD were 7.3, 9.3 and 58, respectively. Detector performance in the low frequency regime was dictated by each detector's DQE(0) value.Conclusion:The a‐Se with CMOS readout is unique and appears to have distinctive advantages of incomparable high resolution, low noise, no readout lag, and expandable design. The a‐Se direct detection system will be a powerful imaging tool in angiography, with potential break‐through applications in diagnosis and treatment of neuro‐vascular disease.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU-D-204-05: Quantitative Comparison of a High Resolution Micro-Angiographic Fluoroscopic (MAF) Detector with a Standard Flat Panel Detector (FPD) Using the New Metric of Generalized Measured Relative Object Detectability (GM-ROD)

Purpose: In endovascular image-guided neuro-interventions, visualization of fine detail is paramount. For example, the ability of the interventionist to visualize the stent struts depends heavily on the x-ray imaging detector performance. Methods: A study to examine the relative performance of the high resolution MAF-CMOS (pixel size 75µm, Nyquist frequency 6.6 cycles/mm) and a standard Flat Panel Detector (pixel size 194µm, Nyquist frequency 2.5 cycles/mm) detectors in imaging a neuro stent was done using the Generalized Measured Relative Object Detectability (GM-ROD) metric. Low quantum noise images of a deployed stent were obtained by averaging 95 frames obtained by both detectors without changing other exposure or geometric parameters. The square of the Fourier transform of each image is taken and divided by the generalized normalized noise power spectrum to give an effective measured task-specific signal-to-noise ratio. This expression is then integrated from 0 to each of the detector’s Nyquist frequencies, and the GM-ROD value is determined by taking a ratio of the integrals for the MAF-CMOS to that of the FPD. The lower bound of integration can be varied to emphasize high frequencies in the detector comparisons. Results: The MAF-CMOS detector exhibits vastly superior performance over the FPD when integrating over allmore » frequencies, yielding a GM-ROD value of 63.1. The lower bound of integration was stepped up in increments of 0.5 cycles/mm for higher frequency comparisons. As the lower bound increased, the GM-ROD value was augmented, reflecting the superior performance of the MAF-CMOS in the high frequency regime. Conclusion: GM-ROD is a versatile metric that can provide quantitative detector and task dependent comparisons that can be used as a basis for detector selection. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

SU-E-I-53: Comparison of Kerma-Area-Product Between the Micro-Angiographic Fluoroscope (MAF) and a Flat Panel Detector (FPD) as Used in Neuro-Endovascular Procedures

Purpose: To determine the reduction of integral dose to the patient when using the micro-angiographic fluoroscope (MAF) compared to when using the standard flat-panel detector (FPD) for the techniques used during neurointerventional procedures. Methods: The MAF is a small field-of-view, high resolution x-ray detector which captures 1024 × 1024 pixels with an effective pixel size of 35μm and is capable of real-time imaging up to 30 frames per second. The MAF was used in neuro-interventions during those parts of the procedure when high resolution was needed and the FPD was used otherwise. The technique parameters were recorded when each detector was used and the kerma-area-product (KAP) per image frame was determined. KAP values were calculated for seven neuro interventions using premeasured calibration files of output as a function of kVp and beam filtration and included the attenuation of the patient table for the frontal projections to be more representative of integral patient dose. The air kerma at the patient entrance was multiplied by the beam area at that point to obtain the KAP values. The ranges of KAP values per frame were determined for the range of technique parameters used during the clinical procedures. To appreciate the benefit of the higher MAF resolution in the region of interventional activity, DA technique parameters were generally used with the MAF. Results: The lowest and highest values of KAP per frame for the MAF in DA mode were 4 and 50 times lower, respectively, compared to those of the FPD in pulsed fluoroscopy mode. Conclusion: The MAF was used in those parts of the clinical procedures when high resolution and image quality was essential. The integral patient dose as represented by the KAP value was substantially lower when using the MAF than when using the FPD due to the much smaller volume of tissue irradiated. This research was supported in part by Toshiba Medical Systems Corporation and NIH Grant R01EB002873.

SU-E-I-55: The Contribution to Skin Dose Due to Scatter From the Patient Table and the Head Holder During Fluoroscopy

Purpose: To determine contributions to skin dose due to scatter from the table and head holder used during fluoroscopy, and also to explore alternative design material to reduce the scatter dose. Methods: Measurements were made of the primary and scatter components of the xray beam exiting the patient table and a cylindrical head holder used on a Toshiba Infinix c-arm unit as a function of kVp for the various beam filters on the machine and for various field sizes. The primary component of the beam was measured in air with the object placed close to the x-ray tube with an air gap between it and a 6 cc parallel-plate ionization chamber and with the beam collimated to a size just larger than the chamber. The primary plus scatter radiation components were measured with the object moved to a position in the beam next to the chamber for larger field sizes. Both sets of measurements were preformed while keeping the source-to-chamber distance fixed. The scatter fraction was estimated by taking the ratio of the difference between the two measurements and the reading that included both primary and scatter. Similar measurements were also made for a 2.3 cm thick Styrofoam block which could substitute for the patient support. Results: The measured scatter fractions indicate that the patient table as well as the head holder contributes an additional 10–16% to the patient entrance dose depending on field size. Forward scatter was reduced with the Styrofoam block so that the scatter fraction was about 4–5%. Conclusion: The results of this investigation demonstrated that scatter from the table and head holder used in clinical fluoroscopy contribute substantially to the skin dose. The lower contribution of scatter from Styrofoam suggests that there is an opportunity to redesign patient support accessories to reduce the skin dose. Partial support from NIH grant R01EB002873 and Toshiba Medical Systems Corporation Equipment Grant

Strain wave elastography for evaluation of renal parenchyma in chronic kidney disease.

Chronic kidney disease (CKD) is an important and costly health problem in developed countries and has a tendency to progress to end-stage renal disease regardless of the aetiology. This progress ends in interstitial fibrosis, which decreases the elasticity of tissue. Elastography is a developing technique to assess tissue elasticity. The aim of this study was to determine the difference of strain index (SI) value of renal parenchyma between patients with CKD and healthy individuals. In addition, SI differences of inter-stages were studied. Toshiba (Toshiba Medical Systems Corporation, Otawara, Japan) Aplio™ 500 ultrasound device and 3.5- to 5.0-MHz convex probe were used for the elastography examinations. A total of 58 patients with CKD from nephrology and endocrinology clinics (30 males and 28 females; mean age, 56.14 ± 11.60 years) and 40 normal healthy individuals (19 males and 21 females; mean age, 51.70 ± 11.71 years) were included in this prospective study. The mean SI of normal healthy individuals and patients with CKD (regardless of stages) was 0.42 ± 0.30 and 1.81 ± 0.88, respectively (p < 0.001). SI values were not statistically significant among the CKD stages (except CKD Stages 1 and 3). The area under the receiver operating characteristic curve was 0.956 for SI. The optimal cut-off value for the prediction of CKD was 0.935 (sensitivity, 88% and specificity, 95%). SI value of sonoelastography can be used to differentiate patients with CKD and healthy individuals. Sonoelastography is an acceptable technique to approach patients with CKD, but we have not shown that it can reliably differentiate different stages. Determining a cut-off SI value between normal and diseased renal parenchyma can help in the diagnosis of CKD.

Abstract 16584: Abnormal Right Ventricular Strain by Cardiac Magnetic Resonance in Preclinical Arrhythmogenic Right Ventricular Cardiomyopathy

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy characterized by regional wall motion abnormalities of the right ventricle (RV) that have not previously been quantified, resulting in challenges / errors in diagnosis of the disease. RV strain is poorly assessed with tagged cardiac magnetic resonance (CMR) due to the thin RV wall. We applied novel feature tracking analysis to assess RV strain in patients with ARVC. Methods: 106 subjects (30 controls, 37 preclinical ARVC [mutation+], and 39 overt ARVC [mutation+, Task Force+] patients) underwent 4 chamber and axial cine imaging using SSFP sequences. The RV was divided into subtricuspid (ST), anterior wall (AW), and apical (Ap) regions. Each region was analyzed to determine peak longitudinal strain and strain-rate using Multimodality Tissue Tracking (MTT) software (MTT Version 6.0.4725, Toshiba Medical Systems Corporation, Tokyo, Japan). Results: Average age was 33.6 ± 16.1 years (48.2% women); there were no differences between groups. In the 4 chamber view, mean global and segmental strain and strain rates decreased in magnitude from control (-37.7% ± 11.2) to preclinical (-32.2% ± 11.5) to overt ARVC (mean -22.2% ± 11.9). Differences between groups most pronounced in the subtricuspid segment, and reached statistical significance between overt ARVC and both control and preclinical ARVC (p &lt; 0.01). A similar trend was observed in longitudinal strain measured in the axial view, but these trends were inconsistent; statistical significance was met globally, but most individual segments did not reach statistical significance. Conclusions: Longitudinal RV strain as measured by CMR feature tracking in ARVC appears able to quantify wall motion abnormalities in overt ARVC, as well as define subtle abnormalities in patients with preclinical ARVC.

WE-E-18A-12: Sampling Correction of Parametric Imaging Maps Derived From Digital Subtraction Angiography in Vascular Phantoms

Purpose: To implement corrections for system sampling distortions in parametric imaging maps derived from digital subtraction angiography and test this approach in a controlled flow experiment using a neurovascular phantom. Methods: Depending on the exposure time and frame rate, imaging system sampling can cause distortion of the time density curves (TDC) used in parametric imaging. To solve this problem we implemented a distortion correction algorithm. A flow circuit set to physiologic conditions was created using an internal carotid artery phantom. Parametric imaging maps (PIM) were derived by measuring TDC's at each pixel location in the map. Each TDC was corrected by adding its numerical derivative multiplied by the sampling interval. PIM's were derived for two different contrast bolus injection volumes (5 and 10 ml), and four injection rates (5, 10, 15 and 20 ml/s). We derived PIM's for mean-transit-time (MTT), time-to-peak (TTP) and bolus-arrival-time (BAT). Colored maps were derived for each parameter; values were recorded at precise locations and compared between corrected and uncorrected cases for all injections techniques. Results: For corrected MTT's maps, the correlation with the injection techniques was still strong but the correction resulted in 10 to 30% smaller MTT's. At the inlet location, the corrected MTT's were between 2-0.25 seconds. For corrected BAT and TTP maps, the inlet values changed 20%. Conclusion: The experiment showed that the distorted PIM's for MTT are strongly correlated with the injection conditions and they agree with the expected theoretical values. Sampling correction reduces the BAT and TTP dependence on the injection technique which is expected since these particular parameters should be mostly related to the flow conditions rather than the injection technique. Supported by NIH Grant: 2R01EB002873 and equipment grant from Toshiba Medical Systems Corporation

SU‐E‐QI‐06: Design and Initial Validation of a Precise Capillary Phantom to Test Perfusion Systems

Purpose:To design a precise perfusion phantom mimicking capillaries of the brain vasculature which could be used to test various perfusion protocols and algorithms which generate perfusion maps.Methods:A perfusion phantom was designed in Solidworks and built using additive manufacturing. The phantom was an overall cylindrical shape of diameter and height 20mm and containing capillaries of 200μm or 300μm which were parallel and in contact making up the inside volume where flow was allowed. We created a flow loop using a peristaltic pump and contrast agent was injected manually. Digital Subtraction Angiographic images and low contrast images with cone beam CT were acquired after the contrast was injected. These images were analyzed by our own code in LabVIEW software and Time‐Density Curve, MTT and TTP was calculated.Results:Perfused area was visible in the cone beam CT images; however, individual capillaries were not distinguishable. The Time‐Density Curve acquired was accurate, sensitive and repeatable. The parameters MTT, and TTP offered by the phantom were very sensitive to slight changes in the TDC shape.Conclusion:We have created a robust calibrating model for evaluation of existing perfusion data analysis systems. This approach is extremely sensitive to changes in the flow due to the high temporal resolution and could be used as a golden standard to assist developers in calibrating and testing of imaging perfusion systems and software algorithms.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU‐E‐I‐29: Generalized Relative Object Detectability (G‐ROD): A Metric for Comparing X‐Ray Imaging Detector Systems

Purpose:To determine the relative task‐specific performance of two x‐ray imaging detectors including the effect of other components of the imaging chain.Methods:The relative object detectability (ROD) was defined as the ratio of the integral of the detective‐quantum efficiency (DQE) of a detector weighted by the square of the Fourier Transform (or frequency spectrum) of the object to the same integral for a second detector. The generalized ROD (G‐ROD) is calculated by replacing DQE by the generalized DQE (GDQE) which includes geometric unsharpness and scatter to evaluate the total imaging chain. The G‐ROD was calculated for the micro‐angiographic fluoroscope (MAF) relative to a flat‐panel detector (FPD) for low (1.05) and high (1.2) magnifications with two focal‐spot sizes, small (0.3 mm) and medium (0.5 mm), and for the same value of scatter fraction. Solid spheres from 50 to 600 microns were simulated as the objects for this evaluation. The G‐ROD results were compared with those of the ROD which considers the detectors alone.Results:For 50‐micron spheres, the ROD is 7.93 and, for the small [medium] focus, the G‐ROD is 6.74 [5.22] at low magnification and 3.03 [1.66] at high magnification, indicating superior performance of the MAF particularly at low magnification. Both ROD and G‐ROD decrease monotonically with size and remain around one above 400‐microns. The G‐ROD decreases more dramatically with low compared to high magnification for both focal spots.Conclusion:In all cases, the MAF performs better than the FPD and the decreasing trend of the G‐ROD indicates that the performance of both detectors becomes similar as the object size increases and becomes nearly equal above 400‐micron diameter sphere size. Finally, increased magnification and focal‐spot size decrease the G‐ROD, indicting that they degrade the performance of the MAF more than that of the FPD for a small‐object viewing task.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU‐E‐I‐83: Parallel Programming Upgrades for the Control Acquisition, Processing and Image Display System (CAPIDS) of the Micro Angiographic Fluoroscope (MAF)

Purpose:CAPIDS is a unique software platform designed to control and acquire images from the high‐resolution MAF detector, process them and display them in a clinical environment. The images are then stored for optional playback at a later stage. CAPIDS also acquires and records the exposure parameters from the x‐ray unit. We present new parallel programming modifications using the host computer system's Graphics Processing Unit (GPU) and Central Processing unit (CPU) to improve the system performance for the various MAF imaging tasks.Methods:Multicore CPU's allow for concurrent tasks to be executed at the same time in parallel. During runtime, CAPIDS has three concurrent tasks: image acquisition and processing, image saving, and exposure parameter acquisition. Parallel programming constructs from LabVIEW allow each tasks to be executed on a separate core.GPU's allow for the same task to be performed on independent data sets in parallel. During runtime, all the image processing including flat‐field correction, digital image subtraction, image averaging, and temporal recursive filtering are performed on the GPU.Results:The new version of CAPIDS with all the parallel programming updates was successfully used for the first time to control the MAF, acquire the images, process the images and display the images during an actual clinical intervention. The images were acquired under fluoroscopy, digital subtraction angiography, and roadmap modes.Conclusion:Distributing concurrent tasks to different cores of a multicore CPU results in an efficient utilization of resources, efficient power management and increases operation speed. Use of GPU's for image processing further enhances the speed of operation.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU‐E‐CAMPUS‐I‐04: Automatic Skin‐Dose Mapping for An Angiographic System with a Region‐Of‐Interest, High‐Resolution Detector

Purpose:Our real‐time skin dose tracking system (DTS) has been upgraded to monitor dose for the micro‐angiographic fluoroscope (MAF), a high‐resolution, small field‐of‐view x‐ray detector.Methods:The MAF has been mounted on a changer on a clinical C‐Arm gantry so it can be used interchangeably with the standard flat‐panel detector (FPD) during neuro‐interventional procedures when high resolution is needed in a region‐of‐interest. To monitor patient skin dose when using the MAF, our DTS has been modified to automatically account for the change in scatter for the very small MAF FOV and to provide separated dose distributions for each detector. The DTS is able to provide a color‐coded mapping of the cumulative skin dose on a 3D graphic model of the patient. To determine the correct entrance skin exposure to be applied by the DTS, a correction factor was determined by measuring the exposure at the entrance surface of a skull phantom with an ionization chamber as a function of entrance beam size for various beam filters and kVps. Entrance exposure measurements included primary radiation, patient backscatter and table forward scatter. To allow separation of the dose from each detector, a parameter log is kept that allows a replay of the procedure exposure events and recalculation of the dose components. The graphic display can then be constructed showing the dose distribution from the MAF and FPD separately or together.Results:The DTS is able to provide separate displays of dose for the MAF and FPD with field‐size specific scatter corrections. These measured corrections change from about 49% down to 10% when changing from the FPD to the MAF.Conclusion:The upgraded DTS allows identification of the patient skin dose delivered when using each detector in order to achieve improved dose management as well as to facilitate peak skin‐dose reduction through dose spreading.Research supported in part by Toshiba Medical Systems Corporation and NIH Grants R43FD0158401, R44FD0158402 and R01EB002873

SU‐C‐18C‐05: Evaluation of Endovascular Procedures Using Precise Patient Specific Phantoms Created Using Additive Manufacturing

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‐E‐I‐40: New Method for Measurement of Task‐Specific, High‐Resolution Detector System Performance

Purpose:Although generalized linear system analytic metrics such as GMTF and GDQE can evaluate performance of the whole imaging system including detector, scatter and focal‐spot, a simplified task‐specific measured metric may help to better compare detector systems.Methods:Low quantum‐noise images of a neuro‐vascular stent with a modified ANSI head phantom were obtained from the average of many exposures taken with the high‐resolution Micro‐Angiographic Fluoroscope (MAF) and with a Flat Panel Detector (FPD). The square of the Fourier Transform of each averaged image, equivalent to the measured product of the system GMTF and the object function in spatial‐frequency space, was then divided by the normalized noise power spectra (NNPS) for each respective system to obtain a task‐specific generalized signal‐to‐noise ratio. A generalized measured relative object detectability (GM‐ROD) was obtained by taking the ratio of the integral of the resulting expressions for each detector system to give an overall metric that enables a realistic systems comparison for the given detection task.Results:The GM‐ROD provides comparison of relative performance of detector systems from actual measurements of the object function as imaged by those detector systems. This metric includes noise correlations and spatial frequencies relevant to the specific object. Additionally, the integration bounds for the GM‐ROD can be selected to emphasis the higher frequency band of each detector if high‐resolution image details are to be evaluated. Examples of this new metric are discussed with a comparison of the MAF to the FPD for neuro‐vascular interventional imaging.Conclusion:The GM‐ROD is a new direct‐measured task‐specific metric that can provide clinically relevant comparison of the relative performance of imaging systems.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation