bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐C‐105‐06: Development of a High Resolution EPID Solution for Small Field Dosimetry
Authors: Han B , Luxton G , Yu S , Lu M , Wang L , Mok E , Xing L
Published: July 2013

Purpose: The increasing use of small beams in VMAT and SBRT presents significant challenges and calls for new tools for dosimetry measurements. The purpose of this study is to investigate a high spatial‐resolution (0.2mm) amorphous silicon flat‐panel electronic portal imaging device (EPID) for small field dosimetry. Methods: A previously‐developed EPID dosimetry system was used to measure the dose distribution of small fields from raw EPID‐measured images. The response of the EPID specific to the linac was obtained by using a Monte Carlo simulation and a comprehensive calibration of the detector. The dosimetry system was validated against measurements of field sizes greater than 3×3cm2. In the present study, the EPID‐based dosimetry measurement technique was used to obtain the relative output factor for small fields from 0.5cm to 3cm respectively created by both the jaws and the MLCs. 6MV, 10MV, and 15MV photon beams from a Varian TrueBeam were tested. The results were compared with measurements using EBT3 film, EDGE diode detector, and PinPoint ion chamber. Results: The diode measurement was considered as a reference in this study based on the expectation that its small size(0.8mm) avoids the field size‐dependent artifacts of larger detectors. For jaw‐defined fields between 2 and 3cm, measurements with all detectors agreed with diode measurements to within 2.7%. For jaw field sizes <2cm, the relative output factors measured using the EPID, film and PinPointTM were lower than the diode by averages of 3.5%, 15.1% and 23.1%, respectively. For MLC fields, output factors measured with EPID, film and PinPoint were found to differ from the diode measurements by averages of +1.7%, −2.2% and −8.1%, respectively. Conclusion: The high spatial resolution EPID dosimetry system proved to be an accurate and efficient dosimetric tool for small field measurements. Accurate output factors can be measured for independent dosimetry calibration and verification.
SU‐C‐WAB‐03: Assessing the Correlation Between Quantitative Measures of Contour Variability and Physician's Qualitative Measure for Clinical Usefulness of Auto‐Segmentation in Prostate Cancer Radiotherapy
Authors: Gautam A , Weiss E , Williamson J , Ford J , Sleeman W , Jan N , Saraiya S , Orton M , Zhang L , Murphy M
Published: July 2013

Purpose: To assess the correlation between quantitative measures of contour variability and physician's qualitative measure for clinical usefulness of auto‐segmentation in prostate cancer radiotherapy Methods: Our study was based on three serial CT images (one planning and two under‐treatment image sets) for each of five prostate cancer patients. On each CT image, bladder, prostate and rectum were manually contoured by three experienced physicians. Deformable image registration (ITK Demons) was used to register each of the under‐treatment CT images to the planning CT image. The resultant displacement vector fields were used to automatically segment planning CT organs by deformably mapping manual contours on the treatment CT's to the planning CT. For qualitative assessment of automatic and manual contours, trial was conducted with four radiation oncology residents. Each resident was shown sets of randomly chosen manual or automatic bladder, prostate and rectum contours overlaid on the planning CT image in Pinnacle (Philips TPS) using a total of hundred‐thirty‐five contours. Residents were asked to accept/reject contour based on its clinical usability. Quantitatively, surface distances and DICE coefficient were computed between inter‐observer manual contours (manual/manual) and between each automatic and its corresponding manual contour (auto/manual). Results: No statistically significant differences were found in mean surface distances between manual/manual and auto/manual contours for bladder and rectum while manual/manual contour distances were significantly smaller for prostate. The distribution of DICE values between manual/manual and auto/manual contours were also similar. Qualitatively, acceptance rates for manual contours were significantly higher than that for automatic contours. Conclusion: No correspondence was found between qualitative and quantitative measure for manual and automatic contours for rectum and bladder while the two measures appear to be related for prostate. This study suggests that using quantitative measures for evaluating auto‐segmentation without a qualitative calibration might not always be predictive of its clinical usefulness.(Supported by NIH P01CA166602) This work was supported by NIH Grant P01 CA 166602 E. Weiss and J. Williamson have grants from Varian medical systems and Philips Radiation Oncology Systems.
SU‐C‐116‐01: Patient Specific Average Glandular Dose in Mammography
Authors: Patel V , Highnam R , Tromans C , Pizzutiello RJ , Destounis S
Published: July 2013

Purpose: It is essential to keep the dose to the breast as low as possible during routine mammography screening while achieving high diagnostic quality images. Currently, mammography systems report average glandular dose (AGD) assuming a 4.5 cm compressed thickness, 50% glandular and 50% adipose tissue equivalent phantom and typical x‐ray beam characteristics. In this paper, we estimate the AGD for specific breasts on specific mammography systems. Methods: For 16 digital mammograms, the technique parameters such as kVp, mAs and compressed thickness were collected from the DICOM header. An automated software system (Volpara (R), Wellington, New Zealand) estimated breast glandularity by analyzing each digital mammogram. For the specific mammography systems used, entrance air kerma and half‐value layer (HVL) was measured for various kVp and target/filter combinations at various compressed breast thicknesses. The patient‐specific AGD was calculated from dose models developed by Dance et. al. These AGD estimates were compared with those generated by the mammography system. Results: For the 16 mammograms that were analyzed, the calculated patient‐specific AGD ranged from 1.99 ± 0.20 mGy to 3.73 ± 0.37 mGy for breasts with range of calculated glandularity (approximately 3% to 27%) and compression thickness (45 mm to 68 mm). Our preliminary results show that our estimated patient‐specific AGDs differed from the AGD reported on the mammography system for each mammogram by an average of approximately 32%. The maximum difference between our estimated patient‐specific AGD and the displayed AGD was approximately 46%. Conclusion: Dose estimations implemented by manufacturers may underestimate the actual patient AGD significantly as they do not account for the specific breast tissue composition, compressed breast thickness or x‐ray beam parameters of the specific mammography system used. Patient‐specific dose estimates may give a better indication of the actual dose delivered, and therefore the risk to the patient.
SU‐C‐116‐05: Using Maximum Intensity Projection in the Evaluation of Digital Breast Tomosynthesis: A Phantom Observer Study From the American College of Radiology Imaging Network PA 4006 Trial
Authors: Thomas M , Matsutani Y , Conant E , Maidment A
Published: July 2013

Purpose: Characterize the effect of slice level and maximal intensity projection (MIP) slab thickness on image quality in digital breast tomosynthesis (DBT). Methods: Eight ACRIN 4006 PA DBT acquisitions of the ACR Mammography Accreditation Phantom were selected from the Hospital of the University of Pennsylvania (n=4) and Einstein Medical Center, Philadelphia, PA (n=4). An experienced medical physicist scored each phantom by first recording scores at single slice levels in increments of increasing depth to confirm the score for each level. Scoring was next repeated with a 40‐mm MIP by identical method. MIP thickness was then decreased in 10‐mm increments and scored again. If a difference in score occurred between 10‐mm MIP slab thickness differences, objects were rescored at the intermediate 5‐mm MIP slab thickness, and so forth. Results: Fiber, speck and mass scores are all sensitive to slice level (single slice) or central slice level (MIP). Specks are the most sensitive. Scores can change substantially if slice level is shifted by one slice when viewing single slices or MIP slabs which are less than 10 mm thick. Scores of fibers and masses decrease with increasing MIP slab thickness, while speck scores do not change substantially. Even when all objects are ostensibly in the MIP volume, their location in the volume affects the score. Scores are degraded when the objects are nearer the top or bottom slice of the MIP slab. Conclusion: In single slice review, slice level substantially affects phantom score, thus care in slice selection is necessary. Increasing MIP slab thickness does not appear to substantially degrade image quality of specks, supporting the clinical practice of using MIP in the review of calcifications. MIP review of phantoms may add value in visualizing artifacts outside the plane of review.
SU‐E‐I‐16: A Data Compression Device for 4D CBCT
Authors: Ren W , Dai J
Published: July 2013

Purpose: 4D Cone beam computed tomography (CBCT) produce hundreds of images daily which are useless for diagnosis. A key problem is to effectively compress these similar imaging data daily and easily invoke them when necessary. The aim of this study is to develop a data compression device for CBCT with appropriate compressing ratio and reserving the image quality. Methods: Kilovoltage (kV) CBCT image from one patient was acquired for each treatment fraction to correct patient setup. The transverse CBCT images were reconstructed from the raw data using a XVI system. The compression device was written in C++ using dicomtk library, allowing a selectable tradeoff between storage size and image quality, then Qt software which is a cross‐platform application and UI framework was used to package this compression algorithm. In this study, JPEG (Joint Photographic Experts Group) algorithm was employed since it is the most commonly method for imaging processing. Results: After compression, the original 1.53GB file was compressed to 461.1MB for lossless while 264.3MB for lossy compression. To evaluate the impact of the lossy compression on image quality, the compressed image and the original image were compared by using PSNR (Peak signal noise ratio), there were no obvious distortions between them. Conclusion: A new effective data compression device for CBCT is developed without apparent influence on the image quality, and this could improve the efficiency of daily 4D CBCT and fascinate other advanced treatment techniques like adaptive tumor detection and tracking.
SU‐E‐I‐23: X‐Ray Attenuation Comparison for Four Head Phantoms at the Circle of Willis
Authors: Harten T , Rosenbaum S , Ionita C , Bednarek D , Rudin S
Published: July 2013

Purpose: To compare the x‐ray attenuation of three commercial anthropomorphic head phantoms with a uniform head‐equivalent phantom and a cadaver for both lateral and frontal views. Methods: We compared the attenuation of various phantoms used for evaluating angiographic equipment used in neurovascular interventions. These include three commercial anthropomorphic phantoms, (RS‐240T, SK150, and PBU‐50), with uniform solid phantoms, and a cadaver head using the same fluoroscopy technique parameters at 80 kVp for four different fields of view (FOV) centering on the Circle of Willis: 8, 7, 6, and 5 inches. The uniform phantom for the frontal plane was 13 mm of aluminum and 15 cm of acrylic and the AAPM head equivalent was for the lateral plane. A 5‐cm diameter ionization chamber placed at the source of x‐rays and a 20‐cm diameter placed at the flat‐panel‐detector were used for exposure measurements enabling average attenuation determination. Results: The percent differences of exposure rates were calculated relative to those of the uniform phantoms. The results for the lateral plane show that the PBU‐50 is similar to the AAPM phantom. For the smallest FOV, the attenuation percent differences are 64.5% (RS‐240T), 47.6% (SK150), 22.8% (PBU‐50), and 59.3% (cadaver), with the average being 48.5%±16.1. For the frontal plane, the SK150 is closest to the uniform head‐equivalent phantom. For the smallest FOV, the attenuation percent differences were 36.9% (RS‐240T), 12.3% (SK150), 39.1% (PBU‐50), and 41.0% (cadaver), with the average as 32.3%±11.7. Results for the other FOVs were similar. Conclusion: This study identifies a general similarity between commercial anthropomorphic phantom and cadaver heads with some differences for one phantom in each view as well as a substantial difference between commercial anthropomorphic phantoms and standardized uniform phantoms. This study indicates that caution is required when selecting the appropriate phantom for evaluating angiographic imaging equipment. (Support: NIH Grant 2R01EB002873) Support: NIH Grant 2R01EB002873
SU‐E‐I‐28: Assessment of Maximum Patient Skin Dose for Interventional Radiology Procedures: Method and Uncertainty Analysis
Authors: Farah J , Trianni A , Carinou E , Dabin J , Deangelis C , Domienik J , Knezevic Z , Kopec R , Malchair F , Negri A , Novak L , Siiskonen T , Vanhavere F , Clairand I
Published: July 2013

Purpose: To develop a method for the assessment of patient's maximum skin dose in interventional radiology procedures. Methods: In the framework of EURADOS WG12, a European measurement protocol was developed to determine fluoroscopy patient skin dose for interventional procedures. The method investigates the use of XR‐RV3 gafchromic films, punctual TLDs and TLD sheets to intercept the X‐ray beam and measure the maximum skin dose. Beside investigating the optimal detector positioning, the method also looks for the most appropriate reading equipments and process (post‐exposure time analysis, projection vs. transmission scanning, etc.), calibration conditions (backscattering conditions, beam qualities etc.) and fitting procedure (inversely proportional to dose vs. traditionally‐used polynomials) based on a careful uncertainty investigation, Finally, the different dosemters are compared to establish the most practical and efficient method for clinical practice. Results: XR‐RV3 films, being large area dosemeters, proved to reproduce with good accuracy the dose distribution over the patient skin. Nonetheless, significant dependence with beam energy and quality, reading and fitting process was observed, which introduces important uncertainties in maximum skin dose measurement. Meanwhile, TLDs enabled precise dose estimates with lower uncertainty values but point TLD detectors may implicate missing the maximum dose location on the patient skin. Thus, TLD sheets could represent the most adapted tool for the assessment of fluoroscopy‐induced skin doses. However, nowadays, these are used only in few laboratories and remain inaccessible in clinical practice. The given recommendation on calibration, reading, fitting and data analysis will help Medical Physicists to conduct accurate dose assessments and optimize the radiation protection of the patient. Conclusion: The developed protocol standardizes practices of patient skin dose estimates in interventional radiology. Based on these results, the assessment, at European level, of alerts for interventional procedures using real‐time Kerma‐Area Product and Cumulative Air Kerma as skin dose indicators will be carried out. Research funded in the framework of EURADOS WG12. No disclosures, no conflict of interest.
SU‐E‐I‐29: Dosimetric Characterization of a Tableside Fluoroscopy with Dynamic Flat Panel Detector
Authors: Zhang J , Fain A , DiSantis D
Published: July 2013

Purpose: A tableside fluoroscopy system with dynamic flat panel detector (FPD) has been recently introduced. Compared to conventional fluoroscopy system with image intensifier II, the FPD fluoroscopy system has potential in dose reduction while improving image quality. As the first of its kind, radiation dose of the FPD system has yet to be investigated. This study is to investigate patient dose from a tableside FPD fluoroscopy and compare to those from a conventional II system. Methods: A whole body anthropomorphic phantom was used for dose measurements with three common GI fluoroscopic procedures: Barium Swallow, Barium upper GI, and Cystogram. Radiation doses were obtained in the chest, the upper abdomen, and the pelvis, respectively. Different pulse fluoroscopy rates (15 and 7.5 frames/sec) were used for the FPD system, while continuous mode was used in II system. Entrance skin exposure, exposure rate, and fluoroscopy time were measured using an Unfors dosimeter (Unfors RaySafe, Inc., Hopkinton, MA) and with a radiography/fluoroscopy detector. Dose‐area‐product (DAP) was recorded from both systems. Image quality was evaluated by an attending radiologist and radiology resident. Results: Radiation dose of the FPD system strongly depends on initial exposure setting for the pulse. With default protocols, the FPD system delivers more radiation than II system for chest imaging (700.4 mR/min vs. 549.2 mR/min). With pelvic imaging, both the 15 and 7.5 fps setting delivered less radiation dose compared to the II system (806.4 mR/min, 1195 mR/min vs. 1330 mR/min). The dose rate for abdominal imaging varied with pulse rate. Image quality was substantially improved on the FPD fluoroscopy system. Conclusion: Compared to the II system, clinical protocols and dose reduction program of the tableside fluoroscopy system with dynamic FPD can be optimized, potentially reducing patient radiation dose with no loss or even improved image quality.
SU‐E‐I‐36: Investigation of Renal CT Dose Reduction by Using Model Based Iterative Reconstruction
Authors: Page L , Kundra V , Rong J
Published: July 2013

Purpose: To evaluate the feasibility of dose reduction from using ModelBased Iterative Reconstruction (MBIR) in renal and vasculature CT studies. Methods: A tissue equivalent abdominal CT dose phantom (CIRS 007TE) was scanned using a GE HD750 scanner. To simulate a ureter and vasculature in CT images, tubes of varying diameters (12mm, 5mm, 2mm, and 1mm) were inserted into the center hole of the phantom. To achieve the appropriate Hounsfield Units (HU) simulating the anatomy of interest, the tubes were filled with a contrast agent (Omnipaque 350) diluted by water at concentrations of 1:8, 1:30, and 1:50. Each of these combinations were scanned using an existing renal protocol at 140 kVp(Display CTDIvol 24mGy) and repeated using reduced scan techniques to achieve lower radiation doses of 13.2, 3.6, 1.6, and 0.8mGy. These were also repeated at 120 kVp. The images were then reconstructed using MBIR. To assess image quality, the contrast‐to‐noise ratio (CNR) was measured for each contrast object. The average CNR was then calculated over five consecutive image slices. Based on CNR achieved at various dose levels, dose reduction factors were estimated for each combination of object sizes and contrast concentrations. Results: Image noises were reduced substantially over the entire dose range by using MBIR. For the large objects at lower doses, there was more noise reduction. At 0.8mGy, the noise was reduced by a factor of four. The 1mm objects at lower concentrations and low dose were not visible. For the 12mm object size group, average CNR increased by a factor of 3 over three concentrations. The dose reduction was estimated to be a factor of 15–30. Conclusion: It is feasible to achieve very low dose (sub‐mGy) renal CT and vasculature phantoms by using MBIR. The results of this study provide guidance in our effort for clinical protocol optimization.
SU‐E‐I‐40: Survey of Radiation Beam Width in CT According to ACR 2012 CT QC Manual
Authors: Lin Y , Hwang Y , Liu H , Wang Y , Tsai C
Published: July 2013

Purpose: To survey CT radiation beam width using in clinical protocols according to America College of Radiology (ACR) 2012 CT Quality Control Manual. We assessed the relationship between nominal collimated and radiation beam width. Methods: Radiation beam width was measured using a self‐developed film (GAFCHROMIC XR CT2) for 346 CT scanners. The film was placed at the isocenter of CT scanner. Nominal collimated beam widths (N×T) using for clinical examinations of routine adult head, adult abdomen, and 5‐years pediatric abdomen were measured. Results: The performance criteria set by ACR 2012 CT Quality Control Manual are that the measured radiation beam width should be accurate to within 3 mm or 30% of the nominal collimated beam width (NxT), whichever is less. According to our survey, the fail rates were 18.8% for adult head examinations, 15.0% for adult abdomen examinations 20.1% for 5‐years pediatric abdomen examinations. If the criteria were set to within 3 mm or 30% whichever is greater, the fail rates dropped to 8.2%, 0.6%, and 2.0%, respectively. Toshiba CT scanners have to pay more attention to meet ACR criteria because the fail rate was from 39% to 75%. Conclusion: This survey gave a view of relationship of nominal and radiation beam width in different protocols and manufacturers. About twenty percent of CT scanners cannot pass the ACR criteria of radiation beam width.
SU‐E‐I‐53: Radiation Dose‐Dependent Characteristics of CT Images Reconstructed with Statistical Iterative Algorithms
Authors: Genovese L , Price R , Pickens D
Published: July 2013

Purpose: To characterize the dependence of image noise, contrast‐to‐noise and noise structure in CT images on algorithm weighting‐factors (AWF) and radiation dose for three different commercially available iterative reconstruction algorithms. Methods: Images were acquired using the 20 cm ACR CT accreditation phantom on scanners manufactured by three different vendors at four different CTDI levels from approximately 10 mGy‐70 mGy. Images were reconstructed using conventional filtered backprojection (FBP) image reconstruction and with each vendor's proprietary statistical iterative reconstruction (SIR) algorithms: ASiR™, SAFIRE™ and iDOSE™. At each CTDI level, images were reconstructed with multiple AWF. Image noise (standard deviation of background near contrast objects), contrast‐to‐noise (CNR) and Noise Power Spectrum (NPS) were plotted as a function of both weighting factor and CTDI. Results: All SIR algorithms demonstrated significant improvement in both noise reduction and CNR, typically 30%– 60% depending upon the AWF. NPS was found to be a function of both reconstruction kernel and SIR weighting factor. All SIR reconstructed images showed the same general shift in noise power to lower spatial frequencies with increased AWF regardless of vendor. With dose reduction as high as 80%, heavily weighted SIR reconstructed images can produce CNR values comparable to images produced with 100% dose levels. Conclusion: All three SIR algorithms provide significant noise reduction and CNR improvement with minimal reduction of spatial resolution. The noise‐reduction performance with different algorithm weighting was approximately linear for all SIR algorithms. For all CTDI levels measured, each algorithm was capable of providing increased CNR by at least a factor of 90%. However, the weighting factors are vendor specific, thus a direct comparison is not appropriate. The use of greater SIR weighting factors also resulted in a shift in the NPS to lower spatial frequencies, producing a background texture that could potentially affect image interpretation.
SU‐E‐I‐56: An Overview of a CT Protocol Optimization Process at a Major University Hospital Medical Center; Including Details On Physics Support, IT Support, and a Radiologist Based Quality Assurance Program
Authors: Ranallo F , Szczykutowicz T , Pozniak M , Bruce R
Published: July 2013

Purpose: Modern CT departments with multiple scanner architectures can easily have hundreds of different protocols for different size patients and clinical requirements. Unless a systematic approach is taken to the optimization and quality assurance of these protocols, care to the patient in the form of image quality, dose, and clinical usability of the CT exams can be compromised. The purpose of this study is to present the model that has been put into a operational form after being organically developed by the medical physicists, radiologists, IT staff, and CT technologists at our over the last several years. Methods: The process of CT protocol formation will be covered including: assessment of the CT scanner technology by the medical physicist, clinical protocol requirements determined by clinicians, optimization of protocols parameters by the medical physicist, final review of the protocols by the entire protocol optimization team, and the subsequent clinical application of the protocols. After implementation, a clinical quality assurance program enables radiologists to score CT exams while reading them on a standard PACS workstation and concurrently the medical physics team monitors the radiation dose (patient size specific) and reviews image quality concerns made by radiologists. The IT infrastructure for this QA assurance process will also be presented. Results: We have successfully gone through several iterations of the CT protocol optimization procedure presented in this study at our institution. The incorporation of new technologies was reviewed and fit into our protocol optimization process as well. The operational procedures defined in this study have greatly increased the efficiency with which we manage and optimize protocols at our institution. Conclusion: CT protocol optimization is an ongoing process; constant monitoring of patient dose and image quality, incorporation of new scanner technologies, and changing clinical requirements all necessitate an organized approach to CT protocols optimization. Equipment grant from GE healthcare.
SU‐E‐I‐60: Use of Monte Carlo‐PENELOPE Method to Determine Radiation Dose to Organs and Tissues From Mammography
Authors: Leidens M , Goes E , Nicolluci P
Published: July 2013

Purpose: The principal motivation to the radiographic examination of the breast is the early detection of breast cancer. However, the absorbed dose in other organs and tissues resulting from these examinations has not been well established. A study was performed in order to obtain an estimate of the dose absorbed in the lung, heart and red bone marrow resulting from a standard mammogram using Monte Carlo and a phantom. Methods: Monte Carlo‐PENELOPE toolkit, that included an mathematical anthropomorphic phantom, was used to simulate the conditions present in mammography by using screen‐film system. The breast was simulated under compression considering the presence of adipose tissue and cranio‐caudal view. The simulation was carried out using x‐rays of 25 keV. Relative organ dose was calculated considering the ratio of dose to each organ per unit dose to breast. Results: According to the methodology used here, the heart received relative dose of 0.033%. The lung was the organ that received the highest relative dose, 0.14%, while the red bone marrow received the lowest relative dose, 0.0013%. Conclusion: The radiation dose to the organs considered in this study, except the breast, is extremely low. However, our findings may be important in epidemiological studies concerning the use of ionizing radiation.
SU‐E‐I‐68: Preliminary Evaluation of Potential MRI Contrast Materials for the Purpose of MR‐Ultrasound Fusion Application in the Abdomen
Authors: Favazza C , Gorny K , Felmlee J , Washburn M , Trester P , Fowler C , Hangiandreou N
Published: July 2013

Purpose: To evaluate a variety of materials that might serve as fiducial markers for abdominal MRI‐ultrasound fusion applications. Methods: Two experiments were performed: (1) in a phantom, a broad set of candidate materials were evaluated based on visibility in spin echo T1 and T2, and gradient echo T1 and T2* MRI pulse sequences; (2) the leading candidates were evaluated using standard clinical abdominal pulse sequences, both in a phantom and volunteer. Experiment 1 evaluated: two commercial fiducial MRI markers (IZI Medical Products and Beekley Medical); vitamin E and fish oil capsules; water; and copper sulfate solution. Experiment 2 evaluated fish oil capsules and copper sulfate solution. In experiment 2, ultrasound coupling gel was also evaluated. Liquids were poured in wells drilled in a plexiglass base. All scanning was performed with a clinical 1.5T GE Signa Excite scanner. For each pulse sequence, maximum intensity projection images (MIPs) were formed, after removing the phantom signals. Visibility was evaluated by rank ordering signal magnitude in the MIPs. Results: In experiment 1, copper sulfate solution and fish oil were superior to the other materials. In experiment 2, ultrasound gel and copper sulfate solution were clearly superior to the other materials, and were easily seen in the all of the phantom and volunteer images. Conclusion: Based on these preliminary experiments, ultrasound gel and copper sulfate solution appear to be the most promising fiducial marker materials for MRI‐ultrasound fusion applications in the abdomen.
SU‐E‐I‐70: Use of Blade Sequences to Eliminate Motion and Pulsation Artifacts in Knee MR Imaging
Authors: Lavdas E , Mavroidis P , Hatzigeorgiou V , Roka V , Arikidis N , Oikonomou G , Andrianopoulos K , Notaras I
Published: July 2013

Purpose: The purpose of this study is to evaluate the ability of Proton Density (PD)‐BLADE sequences in reducing or even eliminating motion and pulsatile flow artifacts in knee MRI examinations. Methods: Eighty consecutive patients, who had been routinely scanned for knee examination, participated in the study. The following pairs of sequences with and without BLADE were compared: a) PD Turbo Spin Echo (TSE) Sagittal (SAG) Fat Saturation (FS) in thirty five patients, b) PD TSE Coronal (COR) FS in nineteen patients, c) T2 TSE AXIAL in thirteen patients and d) PD TSE SAG in thirteen patients. Both qualitative and quantitative analyses were performed based on the signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and relative contrast (ReCon) measures of normal anatomic structures. The qualitative analysis was performed by experienced radiologists. Also, the presence of image motion and pulsation artifacts was evaluated. Results: Based on the results of the SNR, CRN and ReCon for the different sequences and anatomical structures, the BLADE sequences were significantly superior in nineteen cases, whereas the corresponding conventional sequences were significantly superior in six only cases. The BLADE sequences eliminated motion artifacts in all the cases. However, motion artifacts were shown in: a) six PD TSE SAG FS, b) three PD TSE COR FS, c) three PD TSE SAG, and d) two T2 TSE AXIAL conventional sequences. In our results, it was found that in PD FS sequences (Sagittal and Coronal) the differences between the BLADE and conventional sequences regarding the elimination of motion and pulsatile flow artifacts were statistically significant. In all the comparisons, the PD FS BLADE sequences (coronal and sagittal) were significantly superior to the corresponding conventional sequences regarding the classification of their image quality. Conclusion: This technique appears to be capable to potentially eliminate motion and pulsatile flow artifacts in knee MR images.
SU‐E‐I‐71: Detection of Articular Knee Cartilage Defects Using PD BLADE with Fat Saturation (FS), PD FS and T2 3D DESS with Water Excitation (WE)
Authors: Mavroidis P , Lavdas E , Topalzikis T , Kyriakis I , Roka V , Kostopoulos S , Glotsos D , Zilidis K , Stathakis S , Tsagkalis A , Papanikolaou N , Vassiou K , Batsikas G
Published: July 2013

Purpose: The purpose of this study, is to compare the sequences: 1) proton density (PD) BLADE with fat saturation (FS) coronal (COR), 2) PD FS COR, 3) multi‐planar reconstruction (MPR) with 3mm slice thickness and 4) multi‐planar reconstruction (MPR) with 1.5mm slice thickness, both derived from the T2 3D‐double‐echo steady state (DESS) with water excitation (WE) sagittal (SAG) sequence, regarding their abilities to identify changes in the femorotibial condyle cartilage in knee MRI examinations. Methods: Thirty three consecutive patients with osteoarthritis (18 females, 15 males; mean age 56 years, range 37‐71 years), who had been routinely scanned for knee examination using the previously mentioned image acquisition techniques, participated in the study. A quantitative analysis was performed based on the relative contrast (ReCON) measurements, which were taken both on normal tissues as well as on pathologies. Additionally, a qualitative analysis was performed by two radiologists. Motion and pulsatile flow artifacts were evaluated. Results: The PD BLADE FS COR sequence produced images of higher contrast between Menisci and Cartilage, Fluid and Cartilage, Pathologies and Cartilage as well as of the Conspicuousness Superficial Cartilage and it was found to be superior to the other sequences (p<0.001). The sequences T2 3D DESS 1.5mm and T2 3D DESS 3mm were significantly superior to the PD BLADE FS COR and the PD FS COR sequences in the visualization of Bone, Cartilage and the Conspicuousness Deep Surface Cartilage. This pattern of results is also confirmed by the quantitative analysis. Also, in the PD BLADE FS COR sequence, the results of the Truncation Artifact, Pulsation Artifact, Edge Sharpness and Blurring Artifacts, were superior to the other sequences (p<0.001). Conclusion: PD FS BLADE sequences are ideal for the depiction of the cartilage pathologies compared to the conventional PD FS and T2 3D DESS sequences.
SU‐E‐I‐72: Image Quality Verification for Off‐Center Variation Using ACR Phantom in Open MRI
Authors: Hong CP , Lee DH , Han B
Published: July 2013

Purpose: Image quality assurance of the MR image is rigorously required for MRI‐based treatment planning, simulation in radiation oncology. In this work, we investigated image quality for off‐center variation using ACR phantom laterally shifting in open MRI. Methods: MR data acquisitions were performed using an open 0.32T MRI (Magfinder II, SciMedix Co., Ltd., Korea) with a permanent magnet. The MR configuration has a patient aperture of 1370 mm and an effective field of view (FOV) of 400 mm. The patient table can be laterally moved up to 120 mm relative to the magnets center. The 2D T1 weighted axial images of the ACR standard phantom were acquired with the following imaging parameters: TR = 400 ms, TE = 15 ms, matrix = 256 256, FOV = 320 mm, slice thickness = 5 mm, bandwidth = 52.6 kHz. The conventional axial image was acquired with the phantom placed at the isocenter, the phantom shifted images were positioned 30 mm, 60 mm, 90mm and 120 mm off‐center to the left, and the phantom shifted images were positioned 30 mm, 60 mm, 90mm and 120 mm off‐center to the right. Results: For uniformity of image intensity from isocenter to off‐center, integral uniformity in the right off‐center direction was 93%, 92%, 91%, 80%, and 47%, respectively. Non‐uniformity and geometrical distortion were severely generated by off‐center area compared to the isocentric region in open MRI. Conclusion: Because open MRI can be easily adapted to move laterally, wide‐range mapping can be easily achieved to shift the patient table. We developed image quality verification for off‐center variation through a phantom moving laterally to cover the entire FOV without specially designed heavy phantom.
SU‐E‐I‐73: Using Radial Basis Functions with Compact Support and Total Variations Regularization for Deformable Registration of Fetal MR Images
Authors: En Q , Xie Y , Zhou W
Published: July 2013

Purpose: The human brain is extraordinarily complex, and yet its origin is a simple tubular structure. Characterizing its anatomy at different stages of human fetal brain development not only aids in understanding this highly ordered process but also provides clues to detecting abnormalities caused by genetic or environmental factors. magnetic resonance images (MRI) has been used for quantitative studies of brain development in utero. However, non‐rigid registration of a sequence of MRI volumes remains to be a challenging problem. The authors present our recent results on the development of a computationally inexpensive radial basis functions (RBF) and total‐variation (TV) regularization algorithm for elastic alignment of MRI images. Methods: Our algorithm based on the landmarks and radial basis function with compact support,to registration of MR images which have an improved locality,allow to constrain elastic deformations to image parts where required .Then total‐variation regularization to account for the motion discontinuity close to the contact surface between fetal and uterus wall. The algorithm has been compared to the symmetric forces Demons methods. Results: Using a series of validation experiments on fetal cases. The authors demonstrate that using RBF with compact to find the region of interest (ROI) then using total variation registration techniques can all recover volume deformations in MRI image series with reasonable accuracy;Moreover,The proposed total variation registration technique has substantial computational advantage over the other approaches. Conclusion: The proposed RBF and TV registration technique has the potential for implementation on a computationally inexpensive platform and has the capability of recovering non‐rigid deformations in tissue with reasonable accuracy. This work is supported in part by grants from National Natural Science Foundation of China (NSFC: 81171402), NSFC Joint Research Fund for Overseas Research Chinese, Hong Kong and Macao Young Scholars (30928030), National Basic Research Program 973 (2010CB732606) from Ministry of Science and Technology of China, Guangdong Innovative Research Team Program (No. 2011S013) of China, Science and Technological Program for Dongguan's Higher Education, Science and Research, and Health Care Institutions(Grant No.2011108101001), and grant Comprehensive Strategic Cooperation Project of Guangdong province and Chinese academy of sciences (Grant No.2011B090300079).
SU‐E‐I‐74: Extracting Information From a Series of MR Images by MultiParameter Imaging
Authors: Yu S , Xie Y , An M , Li R , Wu S , Yang Y
Published: July 2013

Purpose: To develop a framework to integrate valuable information from a series of MR images by multi‐parameter imaging, and generate images for medical diagnosis and analysis. Methods: The proposed framework consists of three steps. Firstly, a technique, multi‐parameter imaging, is defined. It scans the same section of a subject with same situation except one variable imaging parameter. Then these images are interpolated by iterative curvature‐based interpolation (ICBI). Finally, we develop a new data fusion method by optimizing mean square error (MSE) to fuse information from these interpolated images. Results: The proposed framework is tested on 50 series of clinical MR images from 5 patients, and the results are validated from visual assessment and SNR. Conclusion: This paper contributes: 1) a technique, multi‐parameter imaging, is defined. 2) For the image series by multi‐parameter imaging, a data fusion method by optimizing MSE is developed. 3) A framework incorporating multi‐parameter imaging, interpolation and data fusion is presented. The framework generates two images with high visual quality. One provides tissue details for diagnosis, and the other enhances anatomical edges and variations of signals are valuable for medical analysis. This work is supported in part by grants from National Natural Science Foundation of China (NSFC: 81171402), NSFC Joint Research Fund for Overseas Research Chinese, Hong Kong and Macao Young Scholars (30928030), National Basic Research Program 973 (2010CB732606) from Ministry of Science and Technology of China, and Guangdong Innovative Research Team Program (No. 2011S013) of China.
SU‐E‐I‐75: An Inexpensive Scanner‐Independent Luminescent Motion Monitor for MRI
Authors: Wahi‐Anwar M , Gearhart A , Little D , Rotella J , Lemieux S
Published: July 2013

Purpose: To develop and test an inexpensive single‐channel motion monitor to track and feedback information about patient movement in realtime. Methods: The motion monitor utilizes an optical motion sensor to track patient movement. The components are a 2000 lumens light source, a light detector and an analog‐to‐digital converter that connects via USB to a computer. The InstaCal software directs the signal into the Matlab Data Acquisition Toolbox for processing. Fiber optic cables were used to transmit the light from the source and detector during an MRI scan. A movable cylindrical gel phantom, 11.4cm outer diameter and 15.2 cm length, was designed and constructed for testing, including inserts for geometric distortion and spatial resolution. Movement magnitude (2mm, 4mm, 6mm), and direction (roll, pitch, yaw) were varied. Dynamic echo‐planar imaging (EPI), TR=2s, spatial resolution = 3mm × 3mm × 3mm, was performed on the gel phantom and human subjects to compare motion monitor results to results from motion correction software. Anatomical images were acquired, scantime 4 minutes, spatial resolution = 1mm × 1mm × 1mm, using magnetization‐prepared rapid acquisition with gradient echo, MP‐RAGE, to compare the effects of motion at 30 seconds versus motion at 2 minutes.Results: Motion was viewable in real‐time during monitor tests on the phantom that demonstrated sensitivity as small as 2mm. MPRAGE images with motion occurring closer to the center of k‐space, at 2 minutes, showed more image distortion than those with motion near the edge of k‐space, at 30 seconds. This was evident in both phantom trials and human trials.Conclusion: The motion monitor developed was sensitive to movements larger than 2mm in both the test phantom and the human subjects. Adding sensors, positioned at different angles on the head, would boost the sensitivity of the motion monitor to a wider range of motions.
SU‐E‐I‐77: A Phantom to Assess EIT/CT Imaging System
Authors: Krishnan K , Liu J , Thomas S , Kohli K
Published: July 2013

Purpose: Fusion of Electrical Impedance Tomography (EIT) and Computed Tomography (CT) can potentially provide functional EIT information along with high resolution anatomical information from CT. In this study, we have developed a phantom for evaluating an EIT/CT imaging system. Methods: An electrically conductive phantom was prepared by pouring a molten mixture of gelatin solution and glycerol into a cylindrical container. The mixture was then allowed to solidify. A cylindrical cavity was then created at the center of the medium. Sixteen electrodes were attached equi‐distantly around the phantom. A fixed current was injected through a pair of electrodes, and the induced boundary voltages across all pairs of neighboring electrodes were measured sequentially. The entire voltage measurement process was repeated for all combinations of electrodes through which the current was injected. EIT images were obtained from the boundary voltage data using EIDORS software. The CT data was acquired using a Phillips CT Scanner. EIT and CT data were also collected when the central cavity of the medium was filled with de‐ionized water and 0.9% saline separately. The two images were combined using the boundary and statistical information, extracted using the morphological image processing modules of Matlab. Image quality was evaluated by measuring the entropy of the CT, EIT and the fused images. Results: Phantom regions of saline and distilled water show distinct contrast as compared to CT which fails to differentiate the regions. The location of the contrast objects was found to match their expected locations with respect to CT. Conclusion: We have developed a phantom to assess EIT/CT image quality. The phantom can be extended to include measures such as signal to noise, contrast to noise, relative information content and geometric accuracy of an EIT/CT imaging system.
SU‐E‐I‐79: The Relationship Between Uncinate Fasciculus, Posterior Cingulate Fasciculus Abnormalities and Gray Matter Atrophy by Voxel Wise Correlation Analysis in Patients with Alzheimer's Disease
Authors: Juh R , Suh T
Published: July 2013

Purpose: We evaluated the relationship between white matter (WM) tract disintegration and gray matter (GM) atrophy in patients with Alzheimers disease (AD), mild cognitive impairment (MCI) and controls, using diffusion tensor imaging (DTI) and an optimized voxel‐based analysis. Methods: Two hundred thirty one individuals (61 controls, 116 MCI and 54 AD) were included. 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‐83: Evaluation of Penalizing Functions in Compressed Sensing to Recover Undersampled Data in PET Imaging
Authors: Valiollahzadeh S , Clark J , Mawlawi O
Published: July 2013

Purpose: Previously we proposed the use of compressed sensing (CS) techniques to recover partially sampled data in PET imaging (Valiollahzadeh et al IEEE MIC 2012). Here we compare the effect of various penalizing functions on the accuracy of the recovered activity concentration (AC) in PET imagesMethods: The recovery of partially sampled data using CS techniques requires minimizing a cost function describing a sparse model while being subject to the constraint of a partially observed data set. In this work we define the cost function as the summation of two terms: a Poisson log likelihood function to model the noise, and a penalty term to represent the sparse model. Four sparse models were evaluated: a TV model which assumes the image has a sparse representation in the finite difference domain; a linear combination of a wavelet and TV (WT) model; a recursive dyadic partitions (RDP) model which which estimates the structure of an image; and a variant of RDP that utilizes a cyclespun translation invariant version known as RDPTI. These 4 algorithms were tested using an IEC phantom containing 6 spheres (10:1 ratio). The phantom was imaged on a D‐RX PET/CT scanner twice; once with all detectors operational (baseline) and once with 4 detector blocks at each of 0, 90, 180 and 270° turned off to create a partially sampled (PS) image. The PS image was corrected using the 4 different algorithms and the resultant images were compared to baseline by evaluating the mean AC in the spheres and background. Results: The average percent error in AC for the spheres (background) for the TV, WT, RDP and RDPI algorithms were 12.6(5.3), 4.3(5.1), 8.9(7.6), and 10.7(13)% respectively. Conclusion: WT gave the most accurate AC and the least spurious artifacts suggesting its superior performance over the other algorithms.