bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐09: Application of LiF:Mg,Cu (TLD‐100H) Dosimeters for in Diagnostic Radiology
Authors: Sina S , Zeinali B , Karimipourfard M , Lotfalizadeh F , Sadeghi M , Faghihi R 
Published: July 2014

Purpose:Accurate dosimetery is very essential in diagnostic radiology. The goal of this study is to verify the application of LiF:Mg,Cu,P (TLD100H) in obtaining the Entrance skin dose (ESD) of patients undergoing diagnostic radiology. The results of dosimetry performed by TLD‐100H, were compared with those obtained by TLD100, which is a common dosimeter in diagnostic radiology.Methods:In this study the ESD values were measured using two types of Thermoluminescence dosimeters (TLD‐100, and TLD‐100H) for 16 patients undergoing diagnostic radiology (lumbar spine imaging). The ESD values were also obtained by putting the two types of TLDs at the surface of Rando phantom for different imaging techniques and different views (AP, and lateral). The TLD chips were annealed with a standard procedure, and the ECC values for each TLD was obtained by exposing the chips to equal amount of radiation. Each time three TLD chips were covered by thin dark plastic covers, and were put at the surface of the phantom or the patient. The average reading of the three chips was used for obtaining the dose.Results:The results show a close agreement between the dose measuered by the two dosimeters.According to the results of this study, the TLD‐100H dosimeters have higher sensitivities (i.e.signal(nc)/dose) than TLD‐100. The ESD values varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD‐100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for measurements.Conclusion:The TLD‐100H dosimeters are suggested as effective dosimeters for dosimetry in low dose fields because of their higher sensitivities.
SU‐E‐I‐27: Establishing Target Exposure Index Values for Computed Radiography
Authors: Murphy N , Tchou P , Belcher K , Scott A 
Published: July 2014

Purpose:To develop a standard set of target exposure index (TEI) values to be applied to Agfa Computed Radiography (CR) readers in accordance with International Electrotechnical Committee 62494‐1 (ed. 1.0).Methods:A large data cohort was collected from six USAF Medical Treatment Facilities that exclusively use Agfa CR Readers. Dose monitoring statistics were collected from each reader. The data was analyzed based on anatomic region, view, and processing speed class. The Agfa specific exposure metric, logarithmic mean (LGM), was converted to exposure index (EI) for each data set. The optimum TEI value was determined by minimizing the number of studies that fell outside the acceptable deviation index (DI) range of +/− 2 for phototimed techniques or a range of +/−3 for fixed techniques. An anthropomorphic radiographic phantom was used to corroborate the TEI recommendations. Images were acquired of several anatomic regions and views using standard techniques. The images were then evaluated by two radiologists as either acceptable or unacceptable. The acceptable image with the lowest exposure and EI value was compared to the recommended TEI values using a passing DI range.Results:Target EI values were determined for a comprehensive list of anatomic regions and views.Conclusion:Target EI values must be established on each CR unit in order to provide a positive feedback system for the technologist. This system will serve as a mechanism to prevent under or overexposures of patients. The TEI recommendations are a first attempt at a large scale process improvement with the goal of setting reasonable and standardized TEI values. The implementation and effectiveness of the recommended TEI values should be monitored and adjustments made as necessary.
SU‐E‐I‐30: Image Analysis in Ultrasonography for Diagnosis of Sjoegren's Syndrome Using Dual‐Tree Complex Wavelet Transform
Authors: Matsui T , Ohki M , Nakamura T , Takagi Y 
Published: July 2014

Purpose:Sjoegren's syndrome (SS) is an autoimmune disease invading mainly salivary and lacrimal glands. Ultrasonography is used for an initial and non‐invasive examination of this disease. However, the ultrasonography diagnosis tends to lack in objectivity and depends on the operator's skills. The purpose of this study is to propose a computer‐aided diagnosis (CAD) system for SS based on a dual‐tree complex wavelet transform (DT‐CWT) and machine learning.Methods:The subjects of this study were 174 patients suspected of having SS at Nagasaki University Hospital and examined with ultrasonography of the parotid glands. Out of these patients, 77 patients were diagnosed with SS by sialography. A region of interest (ROI) of 128 × 128 pixels was set within the parotid gland that was indicated by a dental radiologist. The DT‐CWT was applied to the images in the ROI and every image was decomposed into 72 sub‐images of the real and imaginary components in six different resolution levels and six orientations. The statistical features of the sub‐image were calculated and used as data input for the support vector machine (SVM) classifier for the detection of SS. A ten‐fold cross‐validation was employed to verify theResultof SVM. The accuracy of diagnosis was compared by a CAD system with a human observer performance. Results:The sensitivity, specificity, and accuracy in the detection of SS were 95%, 86%, and 91% through our CAD system respectively, while those by a human observer were 84%, 81%, and 83% respectively.Conclusion:The proposed computer‐aided diagnosis system for Sjoegren's syndrome in ultrasonography based on dual‐tree complex wavelet transform had a better performance than a human observer.
SU‐E‐I‐33: Initial Evaluation of Model‐Based Iterative CT Reconstruction Using Standard Image Quality Phantoms
Authors: Gingold E , Dave J 
Published: July 2014

Purpose:The purpose of this study was to compare a new model‐based iterative reconstruction with existing reconstruction methods (filtered backprojection and basic iterative reconstruction) using quantitative analysis of standard image quality phantom images.Methods:An ACR accreditation phantom (Gammex 464) and a CATPHAN600 phantom were scanned using 3 routine clinical acquisition protocols (adult axial brain, adult abdomen, and pediatric abdomen) on a Philips iCT system. Each scan was acquired using default conditions and 75%, 50% and 25% dose levels. Images were reconstructed using standard filtered backprojection (FBP), conventional iterative reconstruction (iDose4) and a prototype model‐based iterative reconstruction (IMR). Phantom measurements included CT number accuracy, contrast to noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD), and noise power spectrum (NPS).Results:The choice of reconstruction method had no effect on CT number accuracy, or MTF (p<0.01). The CNR of a 6 HU contrast target was improved by 1–67% with iDose4 relative to FBP, while IMR improved CNR by 145–367% across all protocols and dose levels. Within each scan protocol, the CNR improvement from IMR vs FBP showed a general trend of greater improvement at lower dose levels. NPS magnitude was greatest for FBP and lowest for IMR. The NPS of the IMR reconstruction showed a pronounced decrease with increasing spatial frequency, consistent with the unusual noise texture seen in IMR images.Conclusion:Iterative Model Reconstruction reduces noise and improves contrast‐to‐noise ratio without sacrificing spatial resolution in CT phantom images. This offers the possibility of radiation dose reduction and improved low contrast detectability compared with filtered backprojection or conventional iterative reconstruction.
SU‐E‐I‐40: New Method for Measurement of Task‐Specific, High‐Resolution Detector System Performance
Authors: Loughran B , Singh V , Jain A , Bednarek D , Rudin S 
Published: July 2014

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
SU‐E‐I‐48: The Behavior of AEC in Scan Regions Outside the Localizer Radiograph FOV: An In Phantom Study of CT Systems From Four Vendors
Authors: Supanich M , Bevins N 
Published: July 2014

Purpose:This review of scanners from 4 major manufacturers examines the clinical impact of performing CT scans that extend into areas of the body that were not acquired in the CT localizer radiograph.Methods:Anthropomorphic chest and abdomen phantoms were positioned together on the tables of CT scanners from 4 different vendors. All of the scanners offered an Automatic Exposure Control (AEC) option with both lateral and axial tube current modulation. A localizer radiograph was taken covering the entire extent of both phantoms and then the scanner's Chest‐Abdomen‐Pelvis (CAP) study was performed with the clinical AEC settings employed and the scan and reconstruction range extending from the superior portion of the chest phantom through the inferior portion of the abdomen phantom. A new study was then initiated with a localizer radiograph extending the length of the chest phantom (not covering the abdomen phantom). The same CAP protocol and AEC settings were then used to scan and reconstruct the entire length of both phantoms. Scan parameters at specific locations in the abdomen phantom from both studies were investigated using the information contained in the DICOM metadata of the reconstructed images.Results:The AEC systems on all scanners utilized different tube current settings in the abdomen phantom for the scan completed without the full localizer radiograph. The AEC system behavior was also scanner dependent with the default manual tube current, the maximum tube current and the tube current at the last known position observed as outcomes.Conclusion:The behavior of the AEC systems of CT scanners in regions not covered by the localizer radiograph is vendor dependent. To ensure optimal image quality and radiation exposure it is important to include the entire planned scan region in the localizer radiograph.
SU‐E‐I‐55: White Matter Fiber Tract Abnormalities by Voxel Wise Correlation Analysis in Neurodegenerative Disease
Authors: Juh R , Suh T 
Published: July 2014

Purpose:We evaluated the relationship between white matter (WM) tract disintegration and gray matter (GM) atrophy in patients with Alzheimer's disease (AD), mild cognitive impairment (MCI) and controls, using diffusion tensor imaging (DTI) and an optimized voxel‐based analysisMethods:Voxel‐based WM tract statistics was used to obtain whole‐brain maps of WM bundles for FA. Voxel‐based morphometry (VBM) was conducted to detect regions of gray matter (GM) atrophy in the AD, MCI group relative to the control group. FA maps were processed to make voxel‐wise comparison of tract based analysis in whole brain between each the two groups. The relationship between locations of abnormalities in the WM and GM were examined.Results:Patients with AD showed significant GM atrophy in posterior cingulate gyrus (BA31, 32) to the precuneus, the middle temporal lobe (BA19), the superior frontal (BA9) to the anterior cingulate (BA 32), the medial frontal lobe (BA 11, BA25), the hippocampus, the parahippocampal gyrus (BA30/34) and the insula, and WM tract disintegrity of the uncinate fasciculus, posterior cingulate fasciculus and fornix compared with the control and MCI groups. These abnormalities in the AD group were caused by either structural changes in GM atrophy or neural dysfunction due to functional disconnections in the WM tract.Conclusion:The GM atrophy resulting from WM tract disintegration or GM atrophy itself may be the first step in the AD process, resulting in anatomically congruent correlations between WM disintegration and regional GM atrophy. Using tract based spatial statistics and voxel based analysis, both of which are useful in investigating GM and WM changes in individuals with neurodegenerative disorders.
SU‐E‐I‐59: Image Quality and Dose Measurement for Partial Cone‐Beam CT
Authors: Abouei E , Ford N 
Published: July 2014

Purpose:To characterize performance of cone beam CT (CBCT) used in dentistry investigating quantitatively the image quality and radiation dose during dental CBCT over different settings for partial rotation of the x‐ray tube.Methods:Image quality and dose measurements were done on a variable field of view (FOV) dental CBCT (Carestream 9300). X‐ray parameters for clinical settings were adjustable for 2–10 mA, 60–90 kVp, and two optional voxel size values, but time was fixed for each FOV. Image quality was assessed by scanning cylindrical poly‐methyl methacrylate (PMMA) image quality phantom (SEDENTEXCT IQ), and then the images were analyzed using ImageJ to calculate image quality parameters such as noise, uniformity, and contrast to noise ratio (CNR). A protocol proposed by SEDENTEXCT, dose index 1 (DI1), was applied to dose measurements obtained using a thimble ionization chamber and cylindrical PMMA dose index phantom (SEDENTEXCT DI). Dose distributions were obtained using Gafchromic film. The phantoms were positioned in the FOV to imitate a clinical positioning.Results:The image noise was 6–12.5% which, when normalized to the difference of mean voxel value of PMMA and air, was comparable between different FOVs. Uniformity was 93.5ߝ99.7% across the images. CNR was 1.7–4.2 and 6.3–14.3 for LDPE and Aluminum, respectively. Dose distributions were symmetric about the rotation angle's bisector. For large and medium FOVs at 4 mA and 80–90 kVp, DI1 values were in the range of 1.26–3.23 mGy. DI1 values were between 1.01–1.93 mGy for small FOV (5×5 cm2) at 4–5 mA and 75–84 kVp.Conclusion:Noise decreased by increasing kVp, and the CNR increased for each FOV. When FOV size increased, image noise increased and CNR decreased. DI1 values were increased by increasing tube current (mA), tube voltage (kVp), and/or FOV.Funding for this project from NSERC Discovery grant, UBC Faculty of Dentistry Research Equipment Grant and UBC Faculty of Dentistry S. Wah Leung Endowment Fund.
SU‐E‐I‐65: The Joint Commission's Requirements for Annual Diagnostic Physics Testing of Nuclear Medicine Equipment, and a Clinically Relevant Methodology for Testing Low‐Contrast Resolution
Authors: West W. Geoffrey , Gray David Clinton 
Published: July 2014

Purpose:To introduce the Joint Commission's requirements for annual diagnostic physics testing of all nuclear medicine equipment, effective 7/1/2014, and to highlight an acceptable methodology for testing lowcontrast resolution of the nuclear medicine imaging system.Methods:The Joint Commission's required diagnostic physics evaluations are to be conducted for all of the image types produced clinically by each scanner. Other accrediting bodies, such as the ACR and the IAC, have similar imaging metrics, but do not emphasize testing low‐contrast resolution as it relates clinically. The proposed method for testing low contrast resolution introduces quantitative metrics that are clinically relevant. The acquisition protocol and calculation of contrast levels will utilize a modified version of the protocol defined in AAPM Report #52.Results:Using the Rose criterion for lesion detection with a SNRpixel = 4.335 and a CNRlesion = 4, the minimum contrast levels for 25.4 mm and 31.8 mm cold spheres were calculated to be 0.317 and 0.283, respectively. These contrast levels are the minimum threshold that must be attained to guard against false positive lesion detection.Conclusion:Low contrast resolution, or detectability, can be properly tested in a manner that is clinically relevant by measuring the contrast level of cold spheres within a Jaszczak phantom using pixel values within ROI's placed in the background and cold sphere regions. The measured contrast levels are then compared to a minimum threshold calculated using the Rose criterion and a CNRlesion = 4. The measured contrast levels must either meet or exceed this minimum threshold to prove acceptable lesion detectability.This research and development activity was performed by the authors while employed at West Physics Consulting, LLC. It is presented with the consent of West Physics, which has authorized the dissemination of the information and/or techniques described in the work.
SU‐E‐I‐69: How to Appropriately Calculate Effective Dose for CT Using Either SSDE Or DLP
Authors: Brady S , Mirro A , Moore B , Kaufman R 
Published: July 2014

Purpose:To demonstrate how to calculate effective dose (E) using specific dose estimates (SSDE), and to correct the current method using CT dose length product (DLP).Methods:The institutional review board waived the need to obtain informed consent for this analysis. Data were analyzed from 352 chest and 241 abdominopelvic CT images (mean age 6.2 years ± 5.1; range 5–55 kg). To calculate E using SSDE, SSDE was first calculated for chest and abdominopelvic regions. 23 individual organ dose values were estimated using the patient's weight and effective diameter to look up a conversion factor that was multiplied by patient SSDE. Organ doses were averaged within patient weight‐based populations, and used to calculate E by the method of weighted summation of organ dose with ICRP 103 tissue weighting factors (E_ICRP). E was calculated using population averaged CT examination DLP for the chest and abdominopelvic region using k‐coefficients published in AAPM Report 96 (E_DLP).Results:E_DLP was different by an average of 21% (1.4/1.1) in the chest and 42% (2.4/3.4) in the abdominopelvic region as compared to calculating E_ICRP. K‐coefficients published in AAPM Report 96 did not account for pitch factor other than unity, were derived using a 32 cm diameter CTDI phantom only, and used ICRP 60 tissue weighting factors. Once corrected for pitch factor, the appropriate size of CTDI phantom, and ICRP 103 tissue weighting factors, E_DLP improved in agreement with E_ICRP to better than 7% (1.4/1.3) and 4% (2.4/2.5) for the chest and abdominopelvic regions, respectively.Conclusion:Current use of DLP to calculate E was shown to be deficient when compared to the method using ICRP tissue weighting factors due to the outdated means by which the k‐coefficients were derived. This study demonstrates a means to calculate E_ICRP using patient SSDE and how to appropriately correct E_DLP.
SU‐E‐I‐77: A Noise Reduction Technique for Energy‐Resolved Photon‐Counting Detectors
Authors: Lam Ng A , Ding H , Cho H , Molloi S 
Published: July 2014

Purpose:Finding the optimal energy threshold setting for an energy‐resolved photon‐counting detector has an important impact on the maximization of contrast‐to‐noise‐ratio (CNR). We introduce a noise reduction method to enhance CNR by reducing the noise in each energy bin without altering the average gray levels in the projection and image domains.Methods:We simulated a four bin energy‐resolved photon‐counting detector based on Si with a 10 mm depth of interaction. TASMIP algorithm was used to simulate a spectrum of 65 kVp with 2.7 mm Al filter. A 13 mm PMMA phantom with hydroxyapatite and iodine at different concentrations (100, 200 and 300 mg/ml for HA, and 2, 4, and 8 mg/ml for Iodine) was used. Projection‐based and Image‐based energy weighting methods were used to generate weighted images. A reference low noise image was used for noise reduction purposes. A Gaussian‐like weighting function which computes the similarity between pixels of interest was calculated from the reference image and implemented on a pixel by pixel basis for the noisy images.Results:CNR improvement compared to different methods (Charge‐Integrated, Photon‐Counting and Energy‐Weighting) and after noise reduction was highly task‐dependent. The CNR improvement with respect to the Charge‐Integrated CNR for hydroxyapatite and iodine were 1.8 and 1.5, respectively. In each of the energy bins, the noise was reduced by approximately factor of two without altering their respective average gray levels.Conclusion:The proposed noise reduction technique for energy‐resolved photon‐counting detectors can significantly reduce image noise. This technique can be used as a compliment to the current energy‐weighting methods in CNR optimization.
SU‐E‐I‐82: Improving CT Image Quality for Radiation Therapy Using Iterative Reconstruction Algorithms and Slightly Increasing Imaging Doses
Authors: Noid G , Chen G , Tai A , Li X 
Published: July 2014

Purpose:Iterative reconstruction (IR) algorithms are developed to improve CT image quality (IQ) by reducing noise without diminishing spatial resolution or contrast. For CT in radiation therapy (RT), slightly increasing imaging dose to improve IQ may be justified if it can substantially enhance structure delineation. The purpose of this study is to investigate and to quantify the IQ enhancement as a result of increasing imaging doses and using IR algorithms.Methods:CT images were acquired for phantoms, built to evaluate IQ metrics including spatial resolution, contrast and noise, with a variety of imaging protocols using a CT scanner (Definition AS Open, Siemens) installed inside a Linac room. Representative patients were scanned once the protocols were optimized. Both phantom and patient scans were reconstructed using the Sinogram Affirmed Iterative Reconstruction (SAFIRE) and the Filtered Back Projection (FBP) methods. IQ metrics of the obtained CTs were compared.Results:IR techniques are demonstrated to preserve spatial resolution as measured by the point spread function and reduce noise in comparison to traditional FBP. Driven by the reduction in noise, the contrast to noise ratio is doubled by adopting the highest SAFIRE strength. As expected, increasing imaging dose reduces noise for both SAFIRE and FBP reconstructions. The contrast to noise increases from 3 to 5 by increasing the dose by a factor of 4. Similar IQ improvement was observed on the CTs for selected patients with pancreas and prostrate cancers.Conclusion:The IR techniques produce a measurable enhancement to CT IQ by reducing the noise. Increasing imaging dose further reduces noise independent of the IR techniques. The improved CT enables more accurate delineation of tumors and/or organs at risk during RT planning and delivery guidance.