bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐I‐06: Fractal Dimension: A Tool to Quantify CT Images
Authors: Jauhari R , Munshi P
Published: November 2011

Purpose: Medical imaging techniques produce images containing a lot of information about the anatomical structures being investigated. This information is valuable for making correct diagnosis, choosing the most adequate therapy, and so on. The analysis of medical images has been performed visually by physicians. Recently a strong impulse has been given to develop automated or semi‐automated systems capable of assisting physicians in this task. However, presence of noise and masking of structures, the variability of biological shapes and tissues, imaging system anisotropy etc. make the automated analysis of medical images a very hard task. With this objective, fractal based quantification of CT images of brain have been explored. Methods: The most important properties of fractals are self‐similarity, chaos and non‐integer fractal dimension (FD). Self‐similar means that structures are repeated at different scales of size. The fractal dimension gives a quantitative measure of self‐similarity and scaling. Two trans‐axial CT sections (one normal brain and one diseased brain) of different patients are included in this study. Both the images were in the digital form and of size 512 × 512 pixels. Each image was subjected to computation of fractal dimension (FD) by a fractal algorithm coded in C programming language. Results: The results show that FD of normal brain and diseased brain images were 2.78 and 2.62 respectively. The difference in the FD values is an indicator that the texture of images is different from one another. Higher value of FD of normal image also indicates that it is relatively ˈsmoothˈ than the diseased brain image which is intuitively correct in the clinical situation. Conclusions: The methodology adopted in this study will be useful as an automated and standardized tool in the hands of physicians for interpretation of CT images in different clinical environments. However, its relative effectiveness will depend on more data and clinical correlation.
SU‐E‐I‐18: Cone‐Beam‐CT Dose Simulation of Dental Cone‐Beam‐CT Using GMctdospp
Authors: Voigt J , Wulff J , Güldner C , Fiebich M
Published: November 2011

Purpose: Flat‐panel based digital volume tomography (DVT) gained more and more popularity over the last years, especially in otorhinolaryngology. These systems offer excellent image quality, especially high resolution, in relation to the purchasing price. It is discussed controversially, how DVT compares to multi‐slice computed tomography with respect to radiation dose and image quality. To determine the organ dose for DVT and CT systems is still complex. Thus, we present a Monte‐Carlo simulation via GMctdospp to simulate DVT and CT examinations and determine the related organ dose. Methods: GMctdospp is a frontend of the EGSnrc user code ctdospp, which was developed in house for simulations of CT examinations. GMctdospp was extended by a DVT‐mode for simulating cone‐beam CT examinations too. The software was calibrated to simulate a DVT system and using a 300 mm long pencil chamber for free air measurement of the dose length product along the z‐axis. To prove that the simulation is correct, the DLP was also measured in the central chassis of a 16 cm CTDI‐phantom for validation. In addition we compared the results of the simulations, using anthromorphic voxel phantoms, with the results of measurements, which were performed earlier using an anatomic head phantom. This was done to prove that the simulation delivers repeatable results. Results: The results of the validation and the comparison to the measurements fit excellent. In addition the simulated values of the eye lense dose fit very well to measurements previously performed. The eye lense dose simulation delivered equal results for all used voxel phantoms. Conclusions: It was shown that Monte Carlo simulations are able to substitute extensive dose measurements in radiologic diagnostics without loss in accuracy. We were able to prove that MC simulations with GMctdospp offer a time saving and easy to use methodology for dose optimization.
SU‐E‐I‐20: Megavoltage and Kilovoltage Cone‐Beam Computed Tomography Image Guidance for Lung Radiotherapy
Authors: Vlad R M , Sixel K , Kosowan S , Hart M , Iqbal F , El‐Mallah M , Vandermeer A
Published: November 2011

PURPOSE: To evaluate the geometric accuracy of patient set‐up in lung cancer radiotherapy using daily megavoltage cone‐beam computed tomography (MV‐CBCT) image guidance, and compare this with kilovoltage (kV)‐CBCT image guidance performed under a similar protocol. Methods: Set‐up accuracy using MV‐CBCT was analyzed in eleven lung cancer patients (246 fractions). The MV‐CBCT and CT planning data sets were matched on‐line by a radiation oncologist and/or radiation therapist using manual registration of any two independent structures (spinal canal, carina and gross tumour volume) to determine the couch shift required for the correct treatment set‐up. For each patient, the couch was adjusted when positional discrepancies exceeded ±2mm in any direction. To estimate the intra‐fraction motion, a repeat MV‐CBCT was taken after treatment, for the first four treatment fractions. Lung cancer patients to be treated under kV‐CBCT image guidance will be recruited in the coming months. Results: The average systematic error was 4.0mm and 37% of all delivered fractions exceeded significant 3D‐positioning errors of 5mm on the initial MV‐CBCT. The MV‐CBCT demonstrated that initial set‐up errors larger than 2mm in any direction occurred in 72% of all fractions. After couch shift to correct the set‐up, the average intra‐fraction systematic error, including the residual error, was reduced to 2.5mm, and never exceeded 5mm. Errors larger than 2mm, in any direction, were measured for 43% of all delivered fractions on the repeat MV‐CBCT. A margin of 5 mm between CTV and PTV was estimated to account for set‐up errors including the intra‐fraction motion for lung cancer radiotherapy using MV‐CBCT image guidance. Conclusion: The analysis indicated that using daily MV‐CBCT image guidance in lung cancer patients treated with radiotherapy results in reducing the set‐up errors, therefore allowing for reduced PTV margins. This is similar with data reported in literature for lung patients treated under kV‐CBCT image guidance.
SU‐E‐I‐23: A Novel Denoising Method for Dual Energy CT Based on Prior Image Constrained Compressed Sensing (PICCS)
Authors: Szczykutowicz TP , Chen G.‐H
Published: November 2011

Purpose: To demonstrate the enhancement of contrast to noise ratio (CNR) and dose reduction in dual energy CT when the Prior Image Constrained Compressed Sensing (PICCS) Algorithm is used to reconstruct images. Methods: CT projection data was acquired over a range of mAs (10–500 mAs) at 80 and 140 kVp. A material density plug phantom and a live canine were scanned to allow for quantitative and qualitative evaluation. Standard filtered back projection (FBP) and PICCS images were reconstructed from the data at a range of mAs levels. The 80–140 kVp images were then decomposed into material density (MD) images. CNR and noise variance measurements were then compared between the FBP and PICCS images. CNR and MD measurements were taken on the density plug phantom for a variety of different plug materials. Noise variance was measured inside the cranium of the canine MD images. Results: (1) In phantom studies, the difference between FBP and PICCS MD images were within 4.3% (average difference 1.8%) for all ROIs at 500 mAs. However, at this dose level, the average (over all plug materials) CNR improvement factor of PICCS MD images over FBP was 44. (2) In in vivo animal studies, when compared with the FBP images, the noise standard deviation in PICCS images was 32.7 times lower at 30 mAs and 17.7 times lower at 200 mAs. (3) Due to the CNR enhancement in PICCS images, features like blood vessels and epidermis/adipose boundaries were visible on PICCS MD images that were unidentifiable on even the highest mAs FBP MD images. Conclusions: At a fixed radiation dose level, CNR can be significantly improved when the PICCS algorithm is used to reconstruct dual energy CT images. At a fixed CNR level, PICCS reconstruction enables significantly lower radiation dose in dual energy CT imaging.
SU‐E‐I‐38: Constrained ‐ Total ‐ Variation ‐ Minimization ‐ Based Image Reconstruction in Breast CT
Authors: Bian J , Yang K , Han X , Sidky E , Boone J , Pan X
Published: November 2011

Purpose: Current breast‐CT prototypes acquire data at a large number of views because analytical algorithms such as FDK are used. Constrained‐ total‐variation‐minimization‐based algorithms, however, have the potential to reconstruct images from data collected at a substantially lower number of views, thus further reducing imaging dose to patients. In this study, we investigate and compare reconstructions from data collected in breast‐CT patient studies with both FDK and constrained‐TV‐minimization‐based algorithms. Methods: In breast CT, a small imaging dose has to been distributed among a large number of views required by analytic algorithms, which results in a low signal‐to‐noise ratio (SNR) level of the data. Reconstruction from low‐SNR data is challenging for analytic and, in particular, iterative algorithms such as constrained‐TV‐minimization‐based algorithms, which often leads to artifacts such as blocky appearance or salt‐ and‐pepper artifact. We have developed a constrained‐TV‐minimization algorithm (ASD‐POCS) and carefully implemented for reconstruction from low‐SNR breast‐CT data. In this work, we investigate image reconstruction using ASD‐POCS algorithm from breast‐CT patient data acquired in a clinical trial carried out at UC‐Davis. For each study, data were acquired at 500 views over 360 degrees with a circular‐cone‐beam configuration. We also created data sets that are subsets of the 500‐view data. Images were reconstructed from the 500‐view and created data sets, using both FDK and ASD‐POCS algorithms. Results: The results of our study suggest that the ASD‐POCS algorithm may yield improved images, depending on data quantitative and evaluation metrics, over the FDK algorithm. For example, the contrast‐to‐noise ratios in ASD‐POCS images are generally higher than that in FDK images. For images with calcifications, this means possibly higher calcifications contrast. Conclusions: Our preliminary results suggest that the proposed technique can potentially improve image quality of breast CT. The proposed algorithm can further reduce total imaging dose in breast CT by reducing the number of views.
SU‐E‐I‐48: Cloud Computing for Interventional Fluoroscopy Dose Assessment
Authors: Johnson P.B. , Borrego D. , Bolch W.E.
Published: November 2011

Purpose: To explore the application of cloud computing for quantifying and documenting patient radiation dose in interventional fluoroscopy. Methods: In this study, a framework has been developed for providing personalized Monte Carlo based dose reports for patients undergoing interventional fluoroscopic procedures. The framework is built around the DICOM Radiation Dose Structured Report (RDSR) and the ability to automatically translate the imbedded information into an input file for the MCNPX radiation transport code. A three‐step program was written to perform this task. The first step imports the RDSR and fills each row of a 2D array with the geometric and dose parameters connected to each irradiation event. The second step culls the array and summarizes the information into a limited number of irradiation events where geometric parameters for similar events are averaged and dose information summed. In the final step, each row of the summarized array is translated into an MCNPX input file by completing sections of a template file. An anthropometrically‐matched hybrid phantom selected from the UF patient‐dependent series is used to represent each patient. Initial testing was performed using twenty RDSRs received from Shands Jacksonville Medical Center. Monte Carlo simulation was executed on the ALRADS dosimetry cluster at the University of Florida, Gainesville. Results: The program successfully received twenty RDSRs via the internet and processed over 50 MCNPX input files. Detailed patient dose reports were returned on demand within 24 hours. Conclusions: While individual radiation transport is impractical within the clinic, a major technological shift has been towards internet‐based “cloud computing” where programs are run on off‐site servers accessed via the internet. In this environment and with the tools developed in this research, RDSRs can be uploaded from the clinic to the web and returned within a matter of hours as detailed radiation dose reports.
SU‐E‐I‐51: Estimating Effective Dose from Phantom Dose Measurements in Atrial Fibrillation Ablation Procedures
Authors: Anderson‐Evans C , Wallace T , Toncheva G , Hranitzky E , Hurwitz L , Yoshizumi T
Published: November 2011

Purpose: The purpose of this study was three‐fold: (a) to estimate organ doses and effective dose (ED) for atrial fibrillation (AF) ablation from clinical fluoro times, (b) to estimate carcinogenic risks for organ doses, and (c) to derive the dose conversion coefficient (DCC) for estimating the ED from the DAP. Method and Materials: A biplane fluoroscopic system was used for the AF ablation procedures (RAO 30°, LAO 45°). ED was measured for low dose and normal dose modes. For acquisition of organ dose measurements, 20 diagnostic MOSFET detectors were placed at selected organs in a male anthropomorphic phantom. The DAP was recorded from the system console and validated independently. Biplane fluoroscopy was performed for 10 minutes to measure the dose rate for each organ. Organ doses were computed by multiplying organ dose rate and the average fluoro time. The ED was computed by summing the product of each organ dose and the corresponding tissue weighting factor (ICRP 103). Age and gender specific carcinogenic risks (life‐time attributable risks and relative risks) for stomach, colon, liver, lung, breast, and bone marrow were computed by BEIR VII report (2006). Results: The ED was computed for an average AF ablation fluoroscopic time of 88 minutes. ED were 28 mSv and 46 mSv for low and normal modes respectively. The corresponding DAP were 49 Gy cm2 and 89 Gy cm2 and derived DCC were 0.57 and 0.58 mSv Gy‐1 cm‐2 for low and normal mode respectively. Relative risk (RR) for leukemia were 1.086 and 1.091 for male and female at age 30. RR for lung cancer incidence were 1.022 and 1.073 for male and female at age 30. Conclusions: The ED for AF ablation procedure can easily be estimated by multiplying the derived DCC by the console‐displayed DAP.  
SU‐E‐I‐53: On the Characterization and the Characteristics of the GafChromic XRQA2 Radiochromic Films
Authors: Giaddui T , Cui Y , Galvin J , Chen W , Yu Y , Xiao Y , Jefferson Thomas
Published: November 2011

Purpose: To investigate the impacts of scanning parameters on the characterization of the GafChromic XRQA2 films and eventually on the accuracy of the measured kV doses when both reflection and transmission scanning modes are used. To study some characteristics of this film model. Methods: GafChromic XR‐QA2 (International Specialty Products, Wayne, NJ) films were irradiated in air by the X‐ray Volume Imager (XVI) mounted on the Elekta linear accelerator (Elekta, Crawley, UK). They were then scanned using the Epson Expression 10000 XL flat‐bed document scanner (Seiko Epson Corporation, Nagano, Japan) and analyzed using ImageJ software (National Institute of Health, Bethesda, MD). The effect of the scanning parameters: scanning reproducibility; scanner non uniformity; scanner resolution (dpi); scanner configuration; region of interest of the analysis; and scanning orientation on the characterization process was investigated. Film characteristics such as post irradiation growth of pixel value were also studied. Results: The characterization process is sensitive to the scanning parameters. Each parameter could lead to a variation in the mean pixel value (PV), which would eventually affect the uncertainty of the measured doses. The magnitudes of these variations were found to differ from one parameter to another and ranged from 1 % to 5% and even more. The scanner nonuniformity in particular led to a variation from 5% to 15% in the mean PV. Scanner resolution and configuration were also identified as important parameters. Post irradiation growth of PV was observed over the first 24 h (increased by 5%) and leveled off thereafter (< 0.5% change). Conclusions: The magnitudes of the effect of the different scanning parameters on the PV have been quantified, some of them found to be significantly affecting the PV. Hence, the scanning procedure must be carried out with a great care in order to minimize the uncertainty of the measured doses.
SU‐E‐I‐58: Evaluation of Radiation Dose and Image Quality for TheVarian Cone Beam Computed Tomography System
Authors: Cheng H , Wu V , Liu E , Kwong D
Published: November 2011

Purpose: To evaluate the radiation dose and image quality on the Varian cone beam computed tomography (CBCT) system of software Version 1.4.13. This study investigated organ absorbed dose, total effective dose, and image quality of the CBCT system for the 200 degrees head‐and‐neck and 360 degrees pelvic scanning protocols.Methods: A calibrated Farmer chamber and two standard cylindrical Perspex CT dosimetry phantoms with diameter of 16 cm head and 32 cm body phantoms were used to measure the weighted CBCT dose index (CBCTDIw) of the Varian CBCT system. The absorbed dose of different organs was measured in a female anthropomorphic phantom with thermoluminescent dosimeters (TLD) and the total effective dose was estimated according to International Commission on Radiological Protection (ICRP) Publication 103. The dose measurement and image quality were studied for head‐and‐neck and pelvic regions.Results: The CBCTDIw of the head‐and‐neck and pelvic protocols were 36.6 and 29.4 mGy, respectively. The absorbed dose to lens for the head‐and‐neck protocol was 3.8 mGy. The total effective doses from the head‐and‐neck and pelvic protocols were 1.7 and 8.2 mSv, respectively. The additional secondary cancer risks of the head‐and‐neck cancer with 33 fractions and pelvic cancer with 35 fractions of daily CBCT might be up to 0.28% and 1.44%, respectively. For low‐contrast resolution, 7 mm in diameter at 1% target contrast level was observed for both the head‐and‐ neck and pelvic protocols; whereas for the high‐contrast spatial resolutions, 7 and 4 lp/cm were demonstrated for the head‐and‐neck and pelvic protocols, respectively Conclusions: The Varian CBCT of software Version 1.4.13 provided volumetric information for image guidance with acceptable image quality and lower radiation dose. This imaging tool gave a better standard for patient daily setup verification.
SU‐E‐I‐67: Monte Carlo Evaluation of CT‐Scanner Scatter Dose to Operator and Comparison with Measurements
Authors: Jans HS , Long B , Robinson D
Published: November 2011

Purpose: To investigate the scatter dose received by a CT‐scanner operator from walls and ceiling as a function of the height of the shielding barrier between the operator and the scanner. To compare Monte Carlo (MC) simulated data with measurement. Methods: MC simulations were performed, using the Penelope algorithm. The CT scanner and a typical, lead‐shielded control console were modeled in cylindrical coordinates. An x‐ray photon spectrum of 120 kVp impinging on a water‐phantom was modeled and the resulting scatter dose profile obtained in CT suite and operator room. This simulation was repeated with varying heights of the lead shield: between 6 ft. and 15ft (height of the concrete ceiling). Finally measurements were obtained of a cross section of the scatter dose profile in the operator room, using a 64 slice CT scanner (Toshiba Aquilion), a water‐equivalent phantom and an NaI‐based survey meter; the measured dose profiles are compared with the simulated ones. Dose reduction at the operator console resulting from increased wall height was measured and compared to simulation. Results: Simulating the extension of the lead shield from a height of 6 ft. all the way to the ceiling resulted in dose reduction at the operator console of two orders of magnitude. Measured dose profiles show good qualitative agreement with the simulated profiles. Measured dose reduction for increased barrier height was larger than simulated, likely owing to the simplified geometry used in simulating the CT scanner and room geometry. Conclusions: Additional contribution of dose scattered at the ceiling and back wall of an operator console can be significant; its varying contribution is given as a function of barrier height. MC simulation provides good qualitative agreement with the measurement. Improved modeling of the CT‐suite is likely needed to enhance quantitative agreement.
SU‐E‐I‐68: Fast and Accurate Estimation of Organ Doses in Medical Imaging Using a GPU‐Accelerated Monte Carlo Simulation Code
Authors: Badal A , Badano A
Published: November 2011

Purpose: To present a Monte Carlo (MC) x‐ray transport simulation code that uses a massively parallel graphics processing units (GPU) to generate medical images of voxelized patient models and estimate organ doses. Methods: We updated MC‐GPU, a CUDA‐based open‐source code for the simulation of radiographic projections and CT, to include the capability to tally 3D dose distributions. Since electrons are not transported, deposited doses are assumed to be equivalent to photon KERMA. The validity of this assumption was investigated by comparing it with the general‐purpose MC code PENELOPE in the simulation of a posterior‐anterior chest examination with 1010, 60‐keV x rays and a realistic female phantom with 1‐mm voxels. The stability of the simulation in a 480‐core GPU was also benchmarked using a sequential execution in a single CPU core. A utility to post‐process the voxel doses and report average and peak organ doses and effective dose for the procedure (and their uncertainty) has been developed. Results: The accuracy of the dose values generated by MC‐GPU was successfully validated. Average relative differences in the doses from PENELOPE and MC‐GPU executed in CPU and GPU were below 2%, in the expected range for statistical fluctuations. The simulation speeds were 46554 x rays/s with PENELOPE (electron transport disabled), 158216 x rays/s with MC‐GPU in a CPU, and 5124867 x rays/s in a GPU (simulation time in the GPU: 32.5 minutes, 32‐fold speedup compared to the CPU). The average and peak doses in breast and skin were estimated as 1.1 and 3.4 eV/g, and 1.7 and 15.6 eV/g per history respectively. Conclusion: The presented code can estimate organ doses 110 times faster than a general‐purpose MC code with comparable accuracy. A multi‐GPU execution of MC‐GPU has the potential to provide accurate organ doses in a CT scan in near real‐time.
SU‐E‐I‐73: The “Routine” Enhanced Chest CT: Does It Exist?
Authors: Cook T , Gefter W , Kim W , Boonn W
Published: November 2011

Purpose: The phrase “routine” is often used to describe CT exams, for example, a “routine enhanced chest CT”. To assess the consistency of a routine exam, we compare the scan parameters and corresponding dose‐length product (DLP)‐based dose estimates for an enhanced, single‐phase chest CT acquired on six different CT scanners. Methods: Scan parameters and dose estimates for 3,184 enhanced chest CT exams performed in 2010 are extracted from image‐based dose sheets using RADIANCE. RADIANCE is an open‐source automated pipeline for extracting CT‐related dose parameters. X‐ray tube voltage kV, tube current mA, reference mA used for tube current modulation and DLP‐based estimated effective dose (ED) were compared for the following scanners: 16‐slice (2), 40‐slice (1), 64‐slice dual source (2) and 64‐slice single source (1). Results: Nearly all studies were performed at 120 kV, and when a reference mA was prescribed, it was predominantly either 180 or 200 mA. However, the actual mA ranged from less than 100 mA to more than 600 mA. ED estimates for the two dual source 64‐slice scanners were similar, approximately 8 +/− 2 mSv. However, the ED estimates on the two 16‐slice scanners, 6.96 +/− 1.78 mSv and 7.91 +/− 3.04 mSv, did not coincide. Furthermore, no correlation was observed between detector size and estimated ED. However, for all six scanners, the ED estimate increased linearly with increasing mA. Since the kV was nearly constant at 120, this likely represents the effect of the variable mA. Conclusions: Despite being a “routine” exam, an enhanced chest CT varies significantly in terms of scan parameters and dose estimates across six scanners within the same department. This necessitates not only the standardization and optimization of protocols at a departmental level, but also a means for regular review and optimization of departmental protocols.
SU‐E‐I‐74: Modality SR: Using the DICOM Radiation Dose Structured Report
Authors: Paden R , Pavlicek W , Peter M , Boltz T
Published: November 2011

Purpose: To describe a testing workflow for generation, transfer, and use of DICOM Radiation Dose Structured Reports (RDSRs). Methods: Equipment supporting RDSR was acceptance tested to validate the creation of report, and to validate reported parameters. A Computed Tomography (CT) scanner and three x‐ray angiographic (XA) suites were tested. Testing of the RDSR includes; validating creation and viewing of reports on acquisition device, transfer of reports from device to viewing workstations, storage of objects in PACS archive and in a quality assurance tool (DICOM parsing database), reviewing report data in comparison to in‐room displayed values or image DICOM field values. Results: At installation, each acquisition device needed to be configured to create DICOM RDSR, and none allowed viewing. Our PACS archive would not display report, but was able to receive and store the RDSR. Retrieval of RDSRs to a workstation with a viewer was allowed. A DICOM receiver was configured to accept the reports, parse the parameters, and store information in a database. Selected parameters from CT RDSRs include CTDIvol, DLP, and body part for irradiation events. RDSRs from angiographic suites include air kerma, kerma area product, as well as patient and C‐arm geometry for each footswitch event. Conclusions: Although the Radiation Dose Structured Report is not fully integrated between acquisition devices, viewing workstations, and image archives, a workflow can be developed to view and validate the RDSR. The RDSR is a valuable tool providing information needed for patient dosimetry.
SU‐E‐I‐78: CT Usage in Adult Patients at An Academic Medical Center: A Snapshot
Authors: Naveed M , Huda W , Tipnis S , Mah E , Frey G
Published: November 2011

Purpose: To document the use of CT imaging in adult patients for a typical day in the Radiology department at the Medical University of South Carolina, and estimate the corresponding patient effective doses and use of iodinated contrast. Method: We reviewed the dose summary sheets of all adult patients who underwent CT examinations on six scanners installed at MUSC on one day (13 September 2010). We obtained the total Dose Length Product (DLP), and computed the corresponding DLP weighted average CTDIvol. Dosimetry data for head and neck CT scans pertain to a 16 cm dosimetry phantom and for body scans pertain to a 32 cm dosimetry phantom. Estimates of the effective doses (E) based on ICRP 103 weighting factors were obtained using nominal E/DLP conversion factors (∼ 3 μSv/mGy‐cm in head/neck; ∼ 18 μSv/mGy‐cm in body). Also recorded was whether iodinated contrast was used each patient examination. Results: A total of 120 adult patients underwent CT examinations with a mean age of 51± 17 years. Overall, 30% of the patient examinations involved the head and neck, with a mean CTDIvol of 62 ± 33 mGy and a mean DLP of 1490 ± 1000 mGy‐cm. The remaining 70% were body examinations with a mean CTDIvol 19 ± 11 mGy and a mean DLP of 990 ± 710 mGy‐cm. A total of 46% of patients were scanned with no iodinated contrast, 33% had contrast, and the remaining 21% had scans performed both with and without contrast. Conclusions: Adult patients undergoing CT examinations have effective doses of the order of 4 mSv for head and neck CT examinations, and of the order of 15 mSv for body examinations, and with slightly more than half receiving iodinated contrast.
SU‐E‐I‐80: Dose Metrics, the Relationship, and Reduction Strategies for Interventional Procedures
Authors: Zhang J , Qin L , Garry O
Published: November 2011

Purpose: Interventional Radiological (IR) procedures result in the highest individual doses in most radiology practices. Recently FDA unveiled initiative to reduce unnecessary radiation exposure from medical imaging. To achieve this goal, the understanding of dose metrics and their relationships from IR procedures is a must. This study aims to summarize dose metrics, investigate the relationship and develop strategies for IR dose reduction and overdose alert. Methods: A Rando phantom was used to investigate entrance skin dose (ESD) in two Siemens flat panel fluoroscopy systems (Artis and Atris Biplane) using typical protocols for neuro, chest and abdominal interventional procedures. Fluoroscopy time, dose‐area product (DAP), and reference dose were recorded from consoles. Exposure rate and cumulative dose at different surface (skin) locations of the imaged areas were measured with a RadCal dosimeter and a Unfors Patient Skin Dosimeter (PSD, with 4 sensors). The relationships among dose metrics were then analyzed for different clinical settings and dose reduction/overdose alert strategies were discussed. Results: Linear relationships among different dose metrics are observed for fixed clinical setting (SID, image area, fluoroscopy mode, etc). With changes in clinical settings, the linear relationship changes accordingly, which causes difficulty in directly predicting ESD by any single dose metric. However, combining different settings may give a reasonable estimation of patient skin dose during IR procedure. Conclusions: Considering different clinical settings, ESD can be estimated from dose metrics in the current fluoroscopy systems and used as indicator of patient dose during IR procedures. This information and related strategies may potentially reduce the risk of patient overdose.
SU‐E‐I‐82: CT Protocol Translation in a Multi‐Vendor, Multi‐Hospital Environment
Authors: Arbique G , Blackburn T , Gallet J , Guild J , Anderson J
Published: November 2011

Purpose: To review issues involved with designing CT protocols for achieving consistent standards in a multi‐vendor and multi‐institutional enterprise.Methods: Achieving consistent CT protocols is complicated by a variety of factors. Even in a given institution, CTˈs from different vendors complicate standardizing protocols. An approach based on uniform CTDI values for exam types may meet with resistance due to individual radiologist image preference. The situation is further complicated in multi‐institutional settings where patient demographics, radiologist, and clinician cultures can vary widely. At UT Southwestern, there are three major institutions using CT equipment from different vendors and servicing distinct patient population groups. A childrenˈs hospital, a teaching county hospital, and a university hospital are serviced by a common radiology group. Recent media attention to CT dose, and recommendations by the Conference of Radiation Control Program Directors (CRCPD) have spurred State regulatory bodies to draft requirements for dose management. Examples are given outlining methods to achieve consistent protocols across our facilities, based on experience at UT Southwestern.Results: The approach at UT Southwestern was based on CRCPD recommendations. Further guidance was found in ACR, the Image Gently, and Image Wisely campaigns. A specific result, is given of translating a set of pediatric protocols from the childrenˈs hospital to adult facilities employing CTˈs from different vendors Conclusions: CT protocols can be standardized in multi‐vendor and multi‐ institutional environments. A critical aspect of the process is buy‐in from the radiology staff and further support from management.
SU‐E‐I‐83: Filling the Gap: Using Detailed Machine Parameters to Refine Skin Dose Calculations for Fluoroscopic Sentinel Events
Authors: Guild J , Arbique G , Gallet J , Blackburn T , Anderson J
Published: November 2011

Purpose: To examine the role that detailed machine logs, supplementary procedural documentation and vendor‐generated technique and dosimetry information can play in refining calculation of peak skin dose for sentinel event investigations.Methods: Vendor‐specific machine logs, skin‐dose estimations, and procedural observations can supplement the fluoroscopic times and air kerma values that all fluoroscopic machines are required to report since 2006. Information available from vendors varies considerably, and in some cases specific application products must be purchased to access this information. Information embodied may include table position, c‐arm geometry, collimation, individual run and fluoro acquisition dosimetry, technique factors (mA, kVp, pulse configuration), mode of operation and other data. Peak skin dose estimates based on HIS/RIS data and DICOM image headers were compared to calculations supplemented by the detailed machine logs and vendor dosimetry estimates. Skin dose maps were generated from air kerma readings and from the DICOM information associated with each run. Assumptions are necessary in this approach to apportion the fluoroscopic contribution, which can be 80% of the air kerma. Corresponding skin dose maps were generated with inclusion of more detailed machine log data and the resulting peak skin dose location and magnitudes were compared.Results: Significant deviations were observed between peak skin dose calculations based on DICOM information alone with attendant assumptions versus those obtained with more detailed machine log data. Detailed logs provide complementary information that replaces assumptions on fluoroscopic dose contributions with more reliable values. Conclusions: Additional information from vendorˈs logs and dose‐ estimates and from other sources can increase the confidence in skin‐dose calculations, but the specific assumptions made by both the physicist and the vendor in making such estimates must be carefully examined. The comparison enables the stand‐alone assumptions to be validated and also allows evaluation of vendor dosimetry estimates.
SU‐E‐I‐84: Development of Average Glandular Dose Estimation Program by EUREF Protocol
Authors: Otsuka T , Suzuki S , Tanaka K , Hibi R , Matsunaga Y , Ogura M
Published: November 2011

Purpose: Average glandular dose (AGD) evaluation has EUREF protocol other than ACR protocol. There exists the report about the dose estimate program by ACR protocol, but there is not report regarding the dose estimate program of the EUREF protocol.　Moreover, there is PCXMC in the patient dose estimation software of a general radiography, fluoroscopy, and angiography. However, the patient dose cannot be estimated with PCXMC with mammography. The program by the EUREF protocol was constructed by using the measurement data. Method and Materials: The basic data used 80(6 manufacturers and 22 models) mammography of the Chubu Region in Japan. The data of the half value layer to calculate the AGD used non‐ invasive X‐ray analyzer. The output was measured by the EUREF protocol. Dosimetry was used with an ionization chamber dosimeter (model 9015) and an ionization chamber (parallel plate type 6.0 cc) both made by Radcal. Software used Visual Basic Ver6.0 of Microsoft. The dose estimation program made “mode that inputs irradiance condition and age” and “mode that inputs measurements”. The dose of 10 various machines not included in the basic data was calculated by using the dose estimation program made to confirm the error margin, and it compared it with measurements. Conclusions: The program that handily calculated the AGD and the entrance surface dose by inputting the irradiance condition and the age was developed. The estimated error was about 20 %.
SU‐E‐I‐90: A Simple Method to Estimate Magnetic Field Homogeneity at Distant Point Locations
Authors: Yee S , Li W , Ogden K
Published: November 2011

Purpose: Although the measurement of magnetic field homogeneity is a key task for physicists, the methods, including those suggested by ACR guideline that are based on the spectral analysis and gradient echo phase images, are sometimes not available, or often require a specially designed phantom. Here, a new method of measuring field homogeneity is introduced as simpler yet generally applicable to any phantom scans. Methods: A general purpose phantom composed of commonly available materials (grapes and fish oil capsules fixed in agaros solution) and a fiducial frame (used for GammKnife treatment and readily available around us) were scanned using a series of conventional spin echo sequence at Philips 1.5 T Intera system (TR=500 ms, TE=20 ms, Nex=1, FOV =250 cm, matrix 256 × 256, thickness=3 mm). The phantom was scanned 6 times while changing the pixel bandwidth gradually in the range between 81.4 and 415.6 Hz, which respectively corresponds to the fat chemical shift (3.4 ppm) of 2.670 to 0.523 pixels. The field inhomogeneity between two spatially distant points (12 cm apart) referenced by the fiducial frames (Fig. 1) was estimated by the linear fitting of the equations (see supporting material). Results: The frequency offset value at a point can be attributed to both spatially dependent and spatially independent offsets (e.g. chemical shift of the material). However, the subtraction of two offset values, obtained from the same material but at different locations, would cancel the spatially independent offsets. Therefore, when the offset values for points 1 and 2 (2.5054 vs. 2.0503 ppm, Fig. 2) are subtracted, the difference (0.46 ppm) would be the spatial magnetic field inhomogeneity over the two 12 cm apart points. Conclusions: The introduced method could be a useful alternative way of measuring magnetic field homogeneity and can be incorporated into any phantom setting.
SU‐E‐I‐97: A Protocol for Attenuation Characterization of Neurovascular Devices under Fluoroscopic Conditions
Authors: Vedantham S , Gounis M , Wakhloo A , Karellas A
Published: November 2011

Purpose: Current approaches for ensuring adequate visualization of neuroendovascular devices that are implanted under fluoroscopic guidance, such as stents and flow diverters, are based on ad hoc methods and measures. Lack of specific standards makes it difficult to determine the adequacy of device contrast under clinical conditions. Inadequate device contrast due to low attenuation may result in increased radiation dose to the patient either due to prolonged fluoroscopy or due to the use of high dose‐ rate imaging sequence. Alternatively, this may lead to inaccurate positioning of these devices within cerebrovascular structures with potential impact on clinical outcome. We developed a protocol and applied it for evaluating such devices. Methods: The protocol comprises three parts: quantitative measurement of equivalent attenuation (in mm of Al) under conditions used for characterizing imaging system performance (RQA5 of IEC standards), visual assessment of device contrast in homogenous background (water phantom) of anatomically relevant thickness, and visual assessment of the device contrast with anatomic background. Ten devices (2 Ni‐Ti stents, 7 Co‐Cr and 1 Ni‐Ti flow diverters) were assessed using this protocol. Results: Quantitative assessment of the stents showed substantial equivalent attenuation of the device end/tip marker (Pt) bands but poor attenuation characteristics of the device body. The flow diverters demonstrated improved attenuation along the device body than the stents. The newer generation of flow diverters with Pt wires interwoven with the Co‐Cr wires demonstrated improved attenuation characteristics compared to previous generation which did not include Pt wires. Visual assessment under homogenous (16 cm water phantom) and anatomic background (skull phantom immersed in 16 cm water) provided qualitative confirmation. Conclusions: The proposed protocol with further refinements can serve as the basis for evaluating the adequacy of x‐ray contrast of neuroendovascular devices that are implanted under fluoroscopic guidance.

Devices provided by Surpass Medical LTD. (Tel Aviv, Israel). Research supported in part by NIH/NCI R01CA128906 and NIH/NIBIB R21EB007767. The contents are sole responsibility of the authors and do not reflect the official views of the NIH, NCI or NIBIB.

MG: Has been a consultant per hour for Micrus Endovascular and Codman Neurovascular; receives research support from Stryker Neurovascular, Micrus Endovascular, Codman Neurovascular, Neurointerventional Technologies, Neuravi, Thrombolysis Scientific Inc, and Concentric Medical.

AW: Has been a consultant per hour for Codman Neurovascular, Stryker Neurovascular, Boston Medical Associates, Surpass Medical Ltd; holds ownership interest in Surpass Medical Ltd; receives research support from Philips Healthcare.
SU‐E‐I‐110: Do Reconstruction Parameters Affect CT‐Based Kidney Stone Volume Quantification?
Authors: Chen L , Wang J , Duan X , Yu L , Leng S , McCollough C
Published: November 2011

Purpose: To investigate the effects of reconstruction field‐of‐view (FOV), slice increment and kernel on the quantification of kidney stone volume. Methods: Three concentrations (200, 400 and 800 mg/cc) and two sizes (21.87 and 99.9 mm3) of hydroxyapatite (HA: Ca5(PO4)OH) cylinders were used to simulate kidney stones of 3 and 5 mm diameter, respectively). These were submerged in a 30 cm wide water phantom and scanned on a dual‐ source CT scanner operating in dual‐energy mode. Reconstruction was performed with a) FOVs from 50 to 300 mm at 50 mm interval; b) image reconstruction increments of 0.1, 0.3 and 0.6 mm; c) 6 recon kernels, from very smooth to medium sharp, all using a 0.6 mm image thickness. CT data were segmented and volumes calculated using volume‐rendered 3D images of each stone, commercial software (Analyze, version10.0) and fixed CT number thresholds (130, 250 and 550 HU for HA200, HA400 and HA800, respectively). Differences in volume between measured and reference values, normalized to the reference values were calculated. The range (maximum — minimum) in normalized volume differences were used to assess the overall influence of various reconstruction parameters. Results: Although normalized volume differences varied with cylinder concentration and size, the differences among FOVs were not substantial (<10.61%). The normalized volume differences among image increments were very small (< 2.45%), except for the lowest concentration/smallest size (differences up to 8.14%), where the smallest image increment was most accurate (differences < 3.02%). Very smooth kernels decreased volume accuracy by as much as 16.19%. Conclusions: Reducing reconstruction FOV did not increase accuracy of volume measurements. Overlap between reconstructed images was beneficial for volume measurement of low concentrations of HA (200 mg/cc) and small size (3 mm diameter) objects. Very smooth kernels were not suitable for volume measurement due to too much edge blurring.
SU‐E‐I‐118: Differential Analysis (DA) ‐ A New Approach for Evaluating the Clinical Utility of Image Processing Algorithms
Authors: Huda W , Tipnis S , Vincent D , Spampinato M , Rumboldt Z
Published: November 2011

Purpose: To describe a new method, called Differential Analysis (DA), of evaluating image processing algorithms in radiological imaging. Methods: Thirty head CT images which showed abnormal findings were selected. Each abnormal image was paired with a normal head CT image at the same anatomical location. All images were processed using standard filtered back projection (FBP) and a new algorithm called iterative reconstruction in image space (IRIS). Three experienced neuroradiologists evaluated the image pairs and assigned a score from 1 to 10, based on how easy / difficult it was to differentiate between normal and abnormal findings. A score of 1 would indicate a barely visible lesion, implying that the processing allows poor differentiation between abnormal and normal pathology, whereas a score of 10 indicated a readily visible lesion, implying excellent differentiation. All evaluations were performed independently and in a random order. The results permitted a differential score “delta” (i.e., IRIS score minus FBP score) to be obtained, with positive values showing IRIS to be superior to FBP, and vice versa. Results: Two observers had positive to negative delta ratios of 3 to 2, and one observer had a positive to negative delta ratio of 1. The ratio of positive to negative delta values for all observers was 2.5. Pooled delta scores showed 18 values less than −1, 38 values between −1 and +1, and 34 values greater than +1. Overall, twice as many images processed using IRIS showed improvements in the differential score as compared with filtered back projection. Conclusions: We describe here a new method to evaluate image processing algorithms in radiological imaging which we propose to call Differential Analysis. Application of this method to a new Iterative Reconstruction algorithm (IRIS) showed improved visibility of brain lesions on CT.
SU‐E‐I‐124: Diffusion Tensor Imaging of the Sciatic Nerve at 3T
Authors: Jambawalikar S , Friedman M , Gould E , Li H , Button T
Published: November 2011

Purpose: To use diffusion tensor imaging (DTI) to visualize and evaluate normal fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the sciatic nerve in four volunteers at 3T.Methods: Initially, T1‐ weighted axial anatomic reference images were performed for anatomic reference (TR/TE, 641/10; flip angle 90 degrees; field of view, 128 mm; number of signal averages(NSA) of 2. Next, single‐shot spin‐echo echo‐ planar DTI sequences were performed with parameters: TR/TE, 5300/69; flip angle 90 degrees; field of view 16 cm; matrix size 128 × 128; 2 NSA; slice thickness 4 mm; number of slices, 40. Diffusion weighting with a b value of 1,000 s/mm2 was applied in 32 different directions. Total required imaging time was approximately 15 minutes. Image data was transferred to a workstation and fiber tracking was performed with Philips advanced tractography software available on the scanner and workstation. Color coded maps demonstrating the sciatic nerve were used to place circular regions‐of interest were then drawn over the nerve location demonstrated on the color coded maps to determine FA and ADCResults: In four volunteers (all males, average age = 40) the sciatic nerve was well visualized and had an average +/− SD FA of 0.52+/−0.20and ADC of ACD of 0.78+/−0.38 Conclusions: Normal FA and ADC values of the sciatic nerve could be measured using DTI and fiber tracking. Further studies are needed but these results suggest that FA and ADC can potentially be used to evaluate peripheral neuropathy and be used in patient follow‐up.