bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐06: A Robust and Improved Method of Analysis for Dose Calibrator Linearity Data Based On First Principles
Authors: Gress DA , Kappadath SC 
Published: July 2014

Purpose:Identify shortcomings in the common mathematical methods of dose calibrator linearity analysis, then propose an improved and more robust method.Methods:Precision of activity measurements using attenuator sleeves was measured using inter‐user (several users) & intra‐user (single user) measurements. We performed retrospective follow‐up investigation of several reported dose calibrator linearity failures at our institution. Common methods of linearity analysis generate best‐fits without using the known decay constant, no‐weighting of data points, and/or compare scaled values to the “zero” measurement (inherently assumed to be error‐free).Fixing the known slope (‐λ) of our data on a semilog plot, we then use least‐squares methodology to find y‐intercept of data's best fit line, against which linearity is assessed.Results:Two‐sigma precision ranges of attenuator sleeve measurements were ±0.4–1.2% for inter‐user measurements, and ±0.4–2.1% for intra‐user measurements. Retrospective analysis of all reported dose calibrator linearity failures from previous four years showed that robust least squares method of analysis would have prevented all repeat testing. Trending data using different methods shows more consistent data ranges (max. deviation 4.9–6.7% versus 3.2–4.2% for select datasets) i.e. more consistent device performance (as anecdotally expected) is demonstrated when analyzed with least squares method. Lower absolute maximum variation values are also calculated across nearly all linearity data sets when using least squares method of analysis.Conclusion:Precision of attenuator sleeve measurements confirm signal averaging must be used in analysis. Dose calibrator performance specification for accuracy is 1%. Linearity tolerance for heightened scrutiny, and arguably a best practice action limit, is 5%. Thus a considerable fraction of the allowed tolerance for the test can be occupied by measurement error. Proposed method of analysis is improvement over other common methods based on first principles, and is demonstrated to be robust.
SU‐E‐I‐12: Characterization of Edge Effects in a Commercial Low‐Dose Image Processing System
Authors: Marsh R , Silosky M 
Published: July 2014

Purpose:Minimizing radiation dose while preserving image quality is critical in fluoroscopic imaging. One recent development is a noise reduction system (Allura Clarity) offered by Philips. Others have reported approximately 50% reduction in air kerma when using Clarity. These studies, however, provide only a cursory look at how the Clarity system affects image quality. The purpose of this work was to evaluate the effect of Clarity on the appearance of high‐frequency image information.Methods:A lead attenuator with a smooth edge was imaged on two Philips Allura FD20 detectors: one with Clarity and one without. The edge was positioned in the center of the field of view and images were obtained under the following conditions: 40cm and 11cm fields of view, single shot and continuous fluoroscopy modes, and using abdomen and cardiac protocols, for a total of sixteen imaging conditions. Profiles were drawn perpendicular to the edge across 80% of its length, averaged to reduce noise, normalized to the maximum pixel value, and plotted as a function of distance.Results:For all single‐shot acquisitions and most fluoroscopic images, overshoot of the edge was observed. This effect was more substantial for single‐shot acquisitions (∼20%) than for fluoroscopic images (∼50%). For fluoroscopic acquisition, the overshoot decayed more quickly with the Clarity system. However, the system with Clarity introduced a ringing effect for both single‐shot and fluoroscopic images that is not present on the non‐Clarity system.Conclusion:Previous reports have demonstrated a substantial dose reduction when using Clarity but the impact this has on image appearance has not been characterized. One demonstrated difference is the change in appearance of high‐frequency image information. It remains to be determined whether this effect may impact clinical images adversely.
SU‐E‐I‐13: Comparison of CCD and CMOS Micro‐Angiographic Fluoroscope (MAF) Detector Systems Using Contrast Measurements for Specific Imaging Tasks Related to Neuro‐Endovascular Image‐Guided Interventional (EIGI) Procedures
Authors: Rana R , Jain A , Setlur Nagesh S , Bednarek D , Rudin S 
Published: July 2014

Purpose:To compare the performance of two high‐resolution detector systems for use during neuro‐EIGI procedures.Methods:The task‐specific performance of custom high‐resolution CCD and CMOS micro‐angiographic fluoroscopes (MAF) was compared. To simulate the attenuation of x‐rays by a patient in neuro‐EIGIs, a modified ANSI head phantom was used. A bar phantom with 0.05‐mm thick lead was used to simulate the contrast and size of EIGI devices used in neuro EIGIs. The bar phantom, placed at an angle of 6.5 degrees relative to the pixel rows of both detectors, was imaged for 88kVp using the small 0.3mm focal spot in order to decrease the geometric unsharpness and preserve the high‐resolution capabilities of both detectors. The resultant images have a geometric object magnification of 1.25, similar to that of a clinical neuro‐EIGI, and a fixed field size was used to keep the scatter the same for both detectors. For images obtained using each detector, we calculated and compared the contrast of the averaged line profiles for the 5.0, 5.6 and 6.3 lp/mm bar pattern groups, which have lead‐line widths of 100, 89, and 79 microns, respectively.Results:For the MAF‐CCD, the measured contrasts were 0.020, 0.019 and 0.013 for the 5.0, 5.6 and 6.3 line pair groups, respectively, and for the MAF‐CMOS the contrasts were 0.025, 0.019 and 0.014 for the 5.0, 5.6 and 6.3 line pair groups, respectively.Conclusion:For the very small lines of the bar pattern, the MAF‐CMOS appears to provide almost the same contrast as compared to the MAF‐CCD, within the measurement error; however, noise and dynamic range characteristics remain to be studied before concluding that the MAF‐CMOS can replace the MAF‐CCD during task‐specific neuro‐EIGI procedures where high spatial resolution is required.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.
SU‐E‐I‐18: CT Scanner QA Using Normalized CTDI Ratio
Authors: Randazzo M , Tambasco M , Russell B 
Published: July 2014

Purpose:To create a ratio of weighted computed tomography dose index (CTDIw) data normalized to in‐air measurements (CTDIair) as a function of beam quality to create a look‐up table for frequent, rapid quality assurance (QA) checks of CTDI.Methods:The CTDIw values were measured according to TG‐63 protocol using a pencil ionization chamber (Unfors Xi CT detector) and head and body Polymethyl methacrylate (PMMA) phantoms (16 and 32 cm diameter, respectively). Single scan dose profiles were measured at each clinically available energy (80,100,120,140 kVp) on three different CT scanners (two Siemens SOMATOM Definition Flash and one GE Optima), using a tube current of 400 mA, a one second rotation time, and the widest available beam width (32 × 0.6 mm and 16 × 1.25 mm, respectively). These values were normalized to CTDIair measurements using the same conditions as CTDIw. The ratios (expressed in cGy/R) were assessed for each scanner as a function of each energy's half value layer (HVL) paired with the phantom's appropriate bow tie filter measured in mmAl.Results:Normalized CTDI values vary linearly with HVL for both the head and body phantoms. The ratios for the two Siemens machines are very similar at each energy. Compared to the GE scanner, these values vary between 10–20% for each kVp setting. Differences in CTDIair contribute most to the deviation of the ratios across machines. Ratios are independent of both mAs and collimation.Conclusion:Look‐up tables constructed of normalized CTDI values as a function of HVL can be used to derive CTDIw data from only three in‐air measurements (one for CTDIair and two with added filtration for HVL) to allow for simple, frequent QA checks without CT phantom setup. Future investigations will involve comparing results with Monte Carlo simulations for validation.
SU‐E‐I‐20: Dead Time Count Loss Compensation in SPECT/CT: Projection Versus Global Correction
Authors: Siman W , Kappadath S 
Published: July 2014

Purpose:To compare projection‐based versus global correction that compensate for deadtime count loss in SPECT/CT images.Methods:SPECT/CT images of an IEC phantom (2.3GBq 99mTc) with ∼10% deadtime loss containing the 37mm (uptake 3), 28 and 22mm (uptake 6) spheres were acquired using a 2 detector SPECT/CT system with 64 projections/detector and 15 s/projection. The deadtime, Ti and the true count rate, Ni at each projection, i was calculated using the monitor‐source method. Deadtime corrected SPECT were reconstructed twice: (1) with projections that were individually‐corrected for deadtime‐losses; and (2) with original projections with losses and then correcting the reconstructed SPECT images using a scaling factor equal to the inverse of the average fractional loss for 5 projections/detector. For both cases, the SPECT images were reconstructed using OSEM with attenuation and scatter corrections. The two SPECT datasets were assessed by comparing line profiles in xyplane and z‐axis, evaluating the count recoveries, and comparing ROI statistics. Higher deadtime losses (up to 50%) were also simulated to the individually corrected projections by multiplying each projection i by exp(‐a*Ni*Ti), where a is a scalar. Additionally, deadtime corrections in phantoms with different geometries and deadtime losses were also explored. The same two correction methods were carried for all these data sets.Results:Averaging the deadtime losses in 5 projections/detector suffices to recover >99% of the loss counts in most clinical cases. The line profiles (xyplane and z‐axis) and the statistics in the ROIs drawn in the SPECT images corrected using both methods showed agreement within the statistical noise. The count‐loss recoveries in the two methods also agree within >99%.Conclusion:The projection‐based and the global correction yield visually indistinguishable SPECT images. The global correction based on sparse sampling of projections losses allows for accurate SPECT deadtime loss correction while keeping the study duration reasonable.
SU‐E‐I‐21: Deformation Mapping and Shape Prediction with 3D Tumor Volume Morphing
Authors: Mao S , Wu H , Fang S , Lu M 
Published: July 2014

Purpose:To compare projection‐based versus global correction that compensate for deadtime count loss in SPECT/CT images.Methods:SPECT/CT images of an IEC phantom (2.3GBq 99mTc) with ∼10% deadtime loss containing the 37mm (uptake 3), 28 and 22mm (uptake 6) spheres were acquired using a 2 detector SPECT/CT system with 64 projections/detector and 15 s/projection. The deadtime, Ti and the true count rate, Ni at each projection, i was calculated using the monitor‐source method. Deadtime corrected SPECT were reconstructed twice: (1) with projections that were individually‐corrected for deadtime‐losses; and (2) with original projections with losses and then correcting the reconstructed SPECT images using a scaling factor equal to the inverse of the average fractional loss for 5 projections/detector. For both cases, the SPECT images were reconstructed using OSEM with attenuation and scatter corrections. The two SPECT datasets were assessed by comparing line profiles in xyplane and z‐axis, evaluating the count recoveries, and comparing ROI statistics. Higher deadtime losses (up to 50%) were also simulated to the individually corrected projections by multiplying each projection i by exp(‐a*Ni*Ti), where a is a scalar. Additionally, deadtime corrections in phantoms with different geometries and deadtime losses were also explored. The same two correction methods were carried for all these data sets.Results:Averaging the deadtime losses in 5 projections/detector suffices to recover >99% of the loss counts in most clinical cases. The line profiles (xyplane and z‐axis) and the statistics in the ROIs drawn in the SPECT images corrected using both methods showed agreement within the statistical noise. The count‐loss recoveries in the two methods also agree within >99%.Conclusion:The projection‐based and the global correction yield visually indistinguishable SPECT images. The global correction based on sparse sampling of projections losses allows for accurate SPECT deadtime loss correction while keeping the study duration reasonable.
SU‐E‐I‐25: Determining Tube Current, Tube Voltage and Pitch Suitable for Low‐ Dose Lung Screening CT
Authors: Williams K , Matthews K 
Published: July 2014

Purpose:The quality of a computed tomography (CT) image and the dose delivered during its acquisition depend upon the acquisition parameters used. Tube current, tube voltage, and pitch are acquisition parameters that potentially affect image quality and dose. This study investigated physicians' abilities to characterize small, solid nodules in low‐dose CT images for combinations of current, voltage and pitch, for three CT scanner models.Methods:Lung CT images was acquired of a Data Spectrum anthropomorphic torso phantom with various combinations of pitch, tube current, and tube voltage; this phantom was used because acrylic beads of various sizes could be placed within the lung compartments to simulate nodules. The phantom was imaged on two 16‐slice scanners and a 64‐slice scanner. The acquisition parameters spanned a range of estimated CTDI levels; the CTDI estimates from the acquisition software were verified by measurement. Several experienced radiologists viewed the phantom lung CT images and noted nodule location, size and shape, as well as the acceptability of overall image quality.Results:Image quality for assessment of nodules was deemed unsatisfactory for all scanners at 80 kV (any tube current) and at 35 mA (any tube voltage). Tube current of 50 mA or more at 120 kV resulted in similar assessments from all three scanners. Physician‐measured sphere diameters were closer to actual diameters for larger spheres, higher tube current, and higher kV. Pitch influenced size measurements less for larger spheres than for smaller spheres. CTDI was typically overestimated by the scanner software compared to measurement.Conclusion:Based on this survey of acquisition parameters, a low‐dose CT protocol of 120 kV, 50 mA, and pitch of 1.4 is recommended to balance patient dose and acceptable image quality. For three models of scanners, this protocol resulted in estimated CTDIs from 2.9–3.6 mGy.
SU‐E‐I‐29: Generalized Relative Object Detectability (G‐ROD): A Metric for Comparing X‐Ray Imaging Detector Systems
Authors: Singh V , Jain A , Bednarek D , Rudin S 
Published: July 2014

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‐35: Investigation of Commercially Available Image Uniformity Filters in MRI Imaging
Authors: Zhou Y 
Published: July 2014

Purpose:To investigate and compare the performance of two types of imaging filters that are used in commercial MRI scanners to improve the image uniformity for phased array coil imaging.Methods:ACR QC phantom and manufacturer supplied sphere phantom were used and the axial images were acquired using the ACR standard T1 protocol and a standard clinical axial T1 protocol. The scanner platform used in the measurement is an open‐bore 3T system (GE MRI 750w). An 8 Channel HD phased array head coil was used. The image acquisition was done with no imaging filter, a calibration based filter (PURE), and an image based filter (SCIC). The Percentage Image Uniformity (PIU) was calculated according to the ACR guideline. Profile plot of the images were obtained to assess detailed performance of the filters. The ROI at the center of the sphere phantom across different slices were also recorded.Results:The PIU values are 74.5% (no filter), 81.6% (PURE), and 92.1 (SCIC). Only the result from the SCIC filter would pass the ACR accreditation criteria. The profile plot also shows that the PURE leaves a valley like shape towards the center of the phantom. However, due to the factor that PURE filter utilizes the information from a volumetric calibration; it yields more uniform intensity across slices.Conclusion:This work indicates that the SCIC filter yields the highest in‐plane uniformity value, but the PURE filter yields better cross slice uniformity. The choice of filter for clinical imaging may depend on specific applications. The result needs to be verified for consistency on multiple systems using both phantoms and patients to fully understand the impact on image quality.
SU‐E‐I‐38: Meeting the ACR QC Requirements for Mechanically Scanned Transducers
Authors: Blatnica A , Errico A 
Published: July 2014

Purpose:To investigate methods and phantoms, both commercially available and fabricated, that will comply with the Geometric Accuracy Quality Control test for mechanically scanned transducers.Methods:A Gammex UTED was modified to enable caliper dimension measurements by insertion of polyester thread “pins” using needles and a locating jig that allowed placement of the thread at 14mm intervals. The modified phantom was evaluated on a Philips iU22 US system with a VL13‐5 broadband linear array transducer with single sweep 3D volume acquisition. 2D (axial and lateral) caliper measurements were made on inserted pins. The transducer was rotated 90 degrees and a 3D sweep was acquired, with measurements taken on the reconstructed slices in the scanning direction. A CIRS model 054GS US phantom was then imaged using the same techniques and methods, with measurements being taken on the lateral resolution pins (3mm and 7mm spacing) at 3cm depth and the results were compared.Results:3D measurements in the lateral direction for the CIRS phantom showed an average difference (over multiple scanning techniques) of 9.7% at 4mm spacing and 7.9% at 7mm spacing. The modified UTED produced an average difference of 6.7% at 14mm spacing. Corresponding 2D caliper measurements resulted in a 3.0% difference for the CIRS and −3.7% for the UTED. Lateral resolution decreased from 2D to 3D scanning by 207% for the CIRS (0.53mm to 1.625mm) and 82% for the UTED (1.080mm to 1.970mm).Conclusion:The modified UTED phantom compares favorably with the CIRS phantom. Issues with lateral resolution blurring in the 3D sweeps can cause inconsistencies in caliper measurements, therefore yearly consistency should be the standard, not an absolute measurement. It is possible for a facility to modify a less expensive phantom that will allow them to meet the QC requirements for Geometric Accuracy set forth by the ACR.
SU‐E‐I‐42: Normalized Embryo/fetus Doses for Fluoroscopically Guided Pacemaker Implantation Procedures Calculated Using a Monte Carlo Technique
Authors: Damilakis J , Stratakis J , Solomou G 
Published: July 2014

Purpose:It is well known that pacemaker implantation is sometimes needed in pregnant patients with symptomatic bradycardia. To our knowledge, there is no reported experience regarding radiation doses to the unborn child resulting from fluoroscopy during pacemaker implantation. The purpose of the current study was to develop a method for estimating embryo/fetus dose from fluoroscopically guided pacemaker implantation procedures performed on pregnant patients during all trimesters of gestation.Methods:The Monte Carlo N‐Particle (MCNP) radiation transport code was employed in this study. Three mathematical anthropomorphic phantoms representing the average pregnant patient at the first, second and third trimesters of gestation were generated using Bodybuilder software (White Rock science, White Rock, NM). The normalized embryo/fetus dose from the posteroanterior (PA), the 30° left‐anterior oblique (LAO) and the 30° right‐anterior oblique (RAO) projections were calculated for a wide range of kVp (50–120 kVp) and total filtration values (2.5–9.0 mm Al).Results:The results consist of radiation doses normalized to a) entrance skin dose (ESD) and b) dose area product (DAP) so that the dose to the unborn child from any fluoroscopic technique and x‐ray device used can be calculated. ESD normalized doses ranged from 0.008 (PA, first trimester) to 2.519 μGy/mGy (RAO, third trimester). DAP normalized doses ranged from 0.051 (PA, first trimester) to 12.852 μGy/Gycm2 (RAO, third trimester).Conclusion:Embryo/fetus doses from fluoroscopically guided pacemaker implantation procedures performed on pregnant patients during all stages of gestation can be estimated using the method developed in this study.This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ‘Education and Lifelong Learning’, ARISTIA (Research project: CONCERT)