bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐E‐04: Building and Strengthening the First Master's Program in Medical Physics in The Gulf Region
Authors: Maalej N , Al‐Karmi A , Al‐Sadah J , Abdel‐Rahman W
Published: June 2012

Purpose: The first medical physics Master's program in the Arabian Gulf region was started in 2002 at King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia. Methods: After consulting with national and international representatives from the AAPM, IOMP, the University of Wisconsin‐Madison and King Faisal Specialist Hospital and Research Center (KFSHRC) we constructed a versatile and rigorous curriculum. The program requires the completion of 7 core courses, 7 required labs, a minimum of 3 elective courses, a research project, a four‐month clinical rotation and passing and a comprehensive examination. The success of the program required very close collaboration with national hospitals such as King Fahad Specialist Hospital in Dammam (KFSH‐D), KFSHRC, and Riyadh Military Hospital. We cemented the collaboration with a formal agreement between KFUPM and KFSH‐D, whereby the clinical medical physicists are actively involved in teaching lectures and labs, evaluating students' performance and co‐supervising their clinical rotation and research projects. In order to prepare our graduates for their medical physics careers, we emphasize innovative learning methods such as students centered learning, execution of course projects, experiential learning and acquiring research skills and tools such as Monte Carlo simulations. Results: Our graduates have succeeded in securing clinical positions in some of the best hospitals in the region and achieved high employer satisfaction. Some students have gone to pursue their PhD's in North America and Europe. Many of our students succeeded in publishing their projects in international journals and international conferences. One of our students was instrumental in obtaining a US patent (US Patent # 785298) for an innovative x‐ray tube design. Conclusions: We have achieved national recognition through the excellence of our graduates. In order to maintain high education quality standards and achieve international recognition, we are presently working to acquire IAEA approval and CAMPEP accreditation.
SU‐E‐I‐08: KV XVI Cone Beam‐CT Dose Measurement Using Gafchromic XRQA2 Film
Authors: Giaddui T , Cui Y , Yegingil Z , Xie J , Chen W , Galvin J , Yu Y , Xiao Y
Published: June 2012

Purpose: To study the effect of different filters on the dose response curves of the Gafchromic XRQA2 film. To measure the kV XVI cone‐beam CT (CBCT) surface dose received during 3D and 4D imaging protocols in three body regions (head and neck, chest and pelvis). Methods: GafChromic XR‐ QA2 film (International Specialty Products, Wayne, NJ) dose response curves were generated for three irradiation settings: 100 kVp S20/F0; 120 kVp S20/F0 and 120 kVp S20/F1(F1 is a Bowtie filter). Film pieces were irradiated in air by the X‐ray Volume Imager (XVI) mounted on the Elekta Synergy linear accelerator (Elekta, Crawley, UK) and their responses were correlated to air kerma measurements. To measure the CBCT surface dose, film pieces were taped on the surface of a male Alderson Rando Phantom (Alderson Research Laboratories, Inc., Long Island City, New York) at four different places (Anterior, Posterior, Right Lateral, Left Lateral). Results: The dose response curves of XRQA2 film generated with F1 and F0 filters were found to differ by 5 to 7% when the air kerma changed between 2 and 5 cGy. This was less than the observed difference (more than 15%, especially at low air kerma) in the dose response curves when different energies (100 and 120 kVp) and same filter were used. Surface dose ranged between 0.02 cGy and 4.99 cGy. The lowest average surface dose (0.05 cGy) was observed when the fast head and neck protocol was used, whilst the highest average surface dose (3.06 cGy) was noticed when the chest m20 protocol was used. Conclusions: Filters seem to have less effect on the dose response of the film compared with energy. Gafchromic XRQA2 film was used successfully to measure the XVI CBCT surface dose. The dose was found to vary from one imaging protocol to another, with 4D protocols not necessarily delivering more doses.
SU‐E‐I‐17: Characterization of Rotating Source MicroCT for Evaluating in Vivo Murine Trabecular Bone
Authors: Arentsen L , Azimi R , Alaei P , Fairchild G , Kidder L , Hui S
Published: June 2012

Purpose: The objective of this study is to determine the optimal physical parameters of the Inveon Multi‐modality microCT to assess the trabecular bone of mice. Methods: The x‐ray Source‐to‐Axis Distance is increased from 100mm to 183mm to 263mm. Similarly, combining local pixels, or binning, is examined from no binning to 2 to 4. Energy is varied from 40kVp to 80kVp in 10kVp increments and filter thickness is changed from no filtration to 1.5mmAl in 0.5mmAl increments. A lucite phantom with six different density‐equivalent rods is used to measure changes in Hounsfield Units (HU) and calibrate Bone Mineral Density estimation. Mice are scanned at four different magnification and binning combinations to evaluate dose and microstructure changes of high to low resolution images. Results: An increase in magnification and decrease in binning results in an effective pixel size ranging from 95μm to 9μm. This decreases the signal to noise ratio from 19.2 to 1.7HU and density estimation from 1585 to 1383mg/cc for 1250mg/cc equivalent material. Increasing the average energy of the radiation beam also decreases HU estimation from 1466HU to 1132HU. Higher resolution scans extend the scan time and absorbed dose from 5.1 to 13.4min and 3.9 to 125cGy respectively. An 18 micron pixel provides distinguishable trabecular bone surface from cortices with a 4.2HU signal to noise ratio. Conclusions: A high magnification, binning of 2, 80kVp beam with a 0.5mmAl filter are the optimal parameters to evaluate the trabecular bone of mice for the Inveon MM microCT unit. This work was supported by the National Institute of Health grants (1R01CA154491‐ 01, 1R03AR055333‐01A1 and 1K12‐HD055887‐01). This work was also supported by PHS Cancer Center Support Grant P30 CA77398. This work was also supported by PHS Cancer Center Support Grant P30 CA77398. Susanta K Hui is a scholar of the BIRCWH (Building Interdisciplinary Careers in Women's Health) program. Luke Arentsen is supported by the Grant in Aid funding from the Universit
SU‐E‐I‐20: The Application of Traditional Snake Model and Balloon‐Snake Model in Automatic Organ Contouring
Authors: Bai T , Yin Y
Published: June 2012

Purpose: To compare the traditional Snake model and Balloon‐Snake model on automatic organ contouring. Methods: For tumors in brain, chest and abdomen, two patients were enrolled for each part. Grey matter, lung and liver for each patient were contoured automatically by Snake model and Balloon‐Snake model, and were also contoured manually by radiologist respectively. Characteristics and dynamic capabilities were compared between the two models. Results: The traditional Snake model will bring good contouring Result only if the primary contour is close enough to the target edge. But, if the force field area is relatively small, the automatic contouring will not bring good Result on boundary deep concave. The Balloon‐Snake model can overcome those shortcomings and improve the traditional Snake model. However, the primary model of Balloon‐Snake can not cross border, doesn't work well on boundary cracks reconstruction, has small force field. Conclusions: The Balloon‐Snake model improved the traditional Snake model and has better dynamic capabilities. It has also more practical value on automatic organ contouring.
SU‐E‐I‐33: Advances in Dose Metrics and Dose Reduction Strategies for Interventional Fluoroscopy
Authors: Weir V , Zhang J , Bruner A
Published: June 2012

Purpose: To explore recent advances in available dose metrics and dose reduction features and their impacts during various fluoroscopy procedures. Methods: Besides traditional dose metrics (cumulative dose, DAP, etc), recent methods such as real time dose mapping and dose calculation from DICOM information and their relevance to entrance skin exposure (ESE) are demonstrated. Dose reduction features and their potential effects on ESE are explored for different interventional procedures, including dose setting options, frame rate settings, wedges, software options and how these help reduce patient dose, etc. Real time dose monitoring techniques such as DoseAware are investigated. Dose alert such as flagging higher doses at about half of the Joint Commission sentinel event limit, Dose Index Registry and their impacts are discussed. Habit related practices, such as a physician leaning over patients, are highlighted, also taking foot off the fluoroscopy pedal when not needed, and best places to stand are illustrated. A practice improvement procedure involving measurement, analysis and improvement actions is instituted. We also discuss the impact of physician follow up letters to patients who might not have reached the JC Sentinel Event limits but may still have skin issues. Results: In our institutes, these efforts have led to reduction of both patient dose and personnel exposure for interventional procedures. The recording of technical parameters and fluoroscopy dose by the staff has led to a better understanding of appropriate dose levels and technique settings for each procedure. Conclusions: This article can serve as a refresher for radiological staff on how to protect patients and themselves from high doses, while providing the best care possible. It can also serve as criteria for health care providers to institute changes and make quality improvement in interventional practices.
SU‐E‐I‐34: Air Kerma to Estimated Entrance Skin Dose Look‐Up Tables: A Tool to Improve Dose Awareness in the Angiography Suite
Authors: Dickinson R , Kanal K , Zamora D , Stewart B
Published: June 2012

Purpose: Although air kerma (AK) is displayed during a case, often it does not represent the entrance skin dose (ESD), which can be estimated. The purpose of this work is to develop and provide system‐customized AK‐to‐ ESD look‐up tables (LUTs) for immediate reference so that physicians can better evaluate the likelihood of deterministic skin reactions to weigh the risk‐versus‐benefit of continuing high‐dose procedures. Methods: Four correction factors are applied to estimate ESD from AK: inverse square correction from the interventional reference point to the average entrance table position, backscatter factor, mean energy absorption coefficient ratio, and measured table attenuation. Correction factors are room and service specific; therefore, room‐specific AK‐to‐ESD LUTs are posted for easy reference. LUTs also list corresponding tissue reactions and their approximate time‐of‐onset. Protocols can be established for nurse or technology staff to provide verbal AK dose notifications during the case at crucial skin reaction dose thresholds (e.g. 2Gy indicating possible skin erythema and 5Gy indicating potentially prolonged recovery or permanent skin damage). Patient follow‐up protocols can be established if the estimated ESD exceeds a set trigger level (e.g. 5Gy). Staff and physicians surveys evaluate usefulness and impact of dose awareness by system users. Results: Two surveys report feedback on LUTs from physicians and technologists with 14 years median experience (range: 3–24 years). Over three‐quarters of all angiography system users identify the LUTs and verbal dose notifications as positively affecting the institution's ‘Patient First’ initiative and roughly one‐half of the imaging system users indicate that the LUTs and site‐specific dose trigger level improves the dose awareness of care providers. Conclusions: Our efforts have focused on educating care providers about the differences between displayed AK and the estimated ESD. LUTs provide physicians and staff an immediate reference for estimated ESD and the associated deterministic skin effects at specific dose levels.
SU‐E‐I‐43: Reducing Scanogram Dose Without Affecting the Planned Tube Current Modulation of a Diagnostic Abdomen/pelvis CT Scan
Authors: Zhang D , Angel E
Published: June 2012

Purpose: In tube current modulated CT scans, scanograms (localizer radiographs) are needed prior to the diagnostic scan to obtain the attenuation properties of each patient which is then used to plan the mA modulation of the diagnostic scan. The purpose of this study was to investigate whether lowering the dual‐scanogram dose affects the mA modulation scheme. Although scanograms use relatively low dose, the goal of this study is to reduce radiation dose from scanograms even further in keeping with the ALARA principle. Methods: Abdomen‐pelvis CT exams were performed on an anthropomorphic phantom (Pixy RS102 phantom, Radiology Support Devices) using a Toshiba Aquilion CT scanner with SUREExposure tube current modulation. Various combinations of kVp and mAs were used to acquire dual‐scanograms (AP and lateral); parameters for the diagnostic scan following the scanograms were fixed. For each kVp, the mA was reduced in intervals from a baseline 100% mA level, including 80%, 60%, 40%, 20% of the baseline, and a minimum level of 10mA. For each exam the resulting CTDIvol and total mAs were compared. Results: When scanogram kVp was reduced from 120kVp (default) to 100kVp and 80kVp, both CTDIvol and total mAs of the diagnostic scan increased slightly (up to 4.3%). When scanogram mA was decreased in intervals representing 80%, 60%, 40%, and 20% of baseline, there was little to no effect (less than 3%) on CTDIvol and total mAs for the diagnostic scan. For the minimum mA scanograms, CTDIvol was affected by up to 5.5% and total mAs was affected by up to 6.1% (at 80kVp). It should be noted that for 120kVp, the decrease of both CTDIvol and total mAs was within 1% at all reduced scanogram dose levels. Conclusions: It was suggested to use the default 120kVp scanogram to minimize the dose from the diagnostic scan. However, the mA of dual‐scanograms may be significantly reduced without affecting planned mA of the exam.
SU‐E‐I‐55: Cumulative Radiation Exposure and Cancer Risk Estimates in Pediatric Hydrocephalus Patients Undergoing Repeat Or Multiple CT
Authors: Wang X , Han Q , Cornett J , Escort E , Zhang J
Published: June 2012

Purpose: Children with a shunt for hydrocephalus often undergo multiple follow‐up head CT scans, increasing the risk for long‐term effects of ionizing radiation. The study is to define a conservative estimate of frequent CT head scans for pediatric patients with a shunt for hydrocephalus and to quantify their cumulative CT radiation doses and lifetime attributable risk of developing cancer. Methods: All children at age of less than 17 years with a shunt for hydrocephalus who underwent non‐enhanced head CT at a tertiary hospital between 2007 and 2011 were identified and categorized by total number of scans per study period as non‐frequently (<3), or frequently (>=3) scanned. We retrospectively identified the number of CT head scans, dose length product (DLP) and the applied scan parameters according to age, gender and study time. Effective doses were estimated using age‐ specific DLP to effective dose conversion coefficients. Lifetime attributable cancer risk was then estimated based on the BEIR VII. Results: During the 5‐year study period, a total of 264 children (mean age, 5.5 years; range less than one month to 17 years; 146 boys and 118 girls) underwent 747 CT head scans, of whom 100 patients (41.7%) were frequently scanned. The median and mean of frequently scans are 4 and 5.33, with the most frequently scanned patient underwent 34 CT head scans from birth to 4 years and 1 month age. The average effective dose was 15.71 mSv, ranging from 3.65 mSv to 64.70 mSv. The estimated lifetime attributable cancer risk is one in 637, ranging from one in 2739 to one in 155, based on the standardized BEIR VII conversion of 0.0001/mSv. Conclusions: The children with shunts have a substantially increased risk of developing cancer from cumulative CT radiation exposure.
SU‐E‐I‐56: Threshold Effect of ASIR Before Which Image Improve and After Which Image Degrades
Authors: Abdulkhaliq F , Mail N , Saoudi A
Published: June 2012

Purpose: This study showed to what extent ASIR improves CT‐image and to what extent it degrades it. Methods: In our study we used GE HD750 CT‐scanner, Siemens Sensation CT‐scanner, Catphan, PTW‐pin‐ion‐ chamber, CTDI‐phantom. We measured the CT‐dose using the PTW‐pinion‐chamber and CTDI‐phantom. Image‐quality and noise were evaluated using catphan and GE water phantom. Results: Image noise reduce as higher levels of ASIR are applied. A phantom scan showed that 50%ASIR with 50% lower‐dose (10.8mGy) achieved the same image noise of standard FBP image with full dose 21.7mGy (noise∼5). To confirm that the two same‐noise images retain same image‐quality, two scans were compared; one with full dose 260mAs(21.7mGy) and the other one with 50% lower dose 130mAs(10.8mGy). The results showed that ASIR failed to retain the same quality. For high contrast resolution, 50%ASIR reduced the resolution of patterns = 71p/cm, however it improved the detectability of patterns = 61p/cm. ASIR has degraded the CNR of the low‐contrast‐objects of = 5HU (CNR of 1.4 at 260mAs STND to CNR of 1.08 at 130mAs ASIR), however it improved the CNR of the low‐contrast‐objects of = 10HU (CNR of 2.35 at 260mAs STND to CNR of 2.63 at 130mAs ASIR). ASIR degraded the edges and killed some of the small objects. This shows that ASIR has a critical point of improve/degrade. Also, ASIR can improve images for the same dose, but with high levels of ASIR (e.g. 100%ASIR), cause disapear of small low contrast objects (e.g. 2mm). Conclusions: People think that ASIR only improves image and reduces patient dose. Our study showed that ASIR has some drawbacks. There is a threshold before wich ASIR is positive and after which ASIR is negative. Recently only GE provide ASIR in the market but our study showed that other CTs such as Siemens can do similar performance like ASIR
SU‐E‐I‐61: Phantom Design for Phase Contrast Breast Imaging
Authors: Vedantham S , Karellas A
Published: June 2012

Purpose: Phase contrast breast imaging has the potential to improve visualization of anatomic structures. While the physics is well‐understood, there are several choices for implementation. In order to evaluate these choices, it is essential to design a phantom for phase contrast imaging with appropriate breast‐equivalent materials. Methods: Phantoms for mammography use materials that mimic the x‐ray attenuation properties of breast tissue. Hence, the refractive index decrement (delta) was determined for breast tissues of varying glandular fraction [Hammerstein, Radiology 130(2):485–91, 1979] for the energy range (5–100 KeV) relevant to mammography and breast CT using XOP software (Version 2.3, ESRF, France) and compared to that of commonly used phantom materials. Delta for 50% and 70% glandular breast‐equivalent material (CIRS Inc., Norfolk, VA), solid water, BR‐12, polymethyl methacrylate (PMMA), beeswax (C46H92O2, density: 0.97 g/cm3) and paraffin wax (C25H52, density: 0.95 g/cm3) were determined. Microcalcifications in vivo are either of oxalate or phosphate composition. Delta of calcium oxalate monohydrate (COM) and calcium hydroxyapatite (CH) were determined and compared with that of calcium carbonate, gold and aluminum. Results: In terms of delta, paraffin wax (4% higher) and beeswax (4% higher) best simulated 50% and 100% glandular breast, respectively. Delta of other commonly used phantom materials such as 50% and 70% glandular breast‐equivalent material, solid water, and BR‐12 were two orders of magnitude higher, and that of PMMA was 28% higher, than 50% glandular breast tissue. For microcalcifications, delta of gold was 4.6 to 6.5 times higher than that of COM and CH, respectively. Delta of aluminum and calcium carbonate were found to straddle that of COM and CH. Conclusions: For phase contrast imaging, a phantom comprising paraffin wax to simulate 50% glandular background tissue, beeswax to simulate a mass equivalent to 100% glandular tissue, and calcium carbonate or aluminum to simulate microcalcifications is appropriate. Supported in part by the National Institutes of Health (NIH) grants R01 CA128906 and R21 CA134129. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or NCI.
SU‐E‐I‐63: Performance Study of An Electron‐Tracking Compton Camera for Medical Imaging
Authors: Kabuki S , Kimura H , Kubo H , Ogawa K , Kunieda E , Tanimori T
Published: June 2012

Purpose: Conventional gamma‐ray detector, PET and SPECT, have the limitation of energy and field of view. These limitations are major problems of studying for a new medical imaging. Therefore, we have developed the new imaging detector which is an electron‐tracking Compton camera (ETCC). Methods: A reconstruction method of Compton camera (CC) is using the physics principle. Because of using physics principle, CC can have a wide energy dynamic range and wide field of view. Conventional CC, however, cannot catch Compton recoil electron tracks, and this is one of the reasons of low imaging power. We have developed a time projection chamber (TPC) using micro pixel chamber (μPIC) as the new detector for ETCC. The μPIC is 2‐dimensional gaseous detector and this position resolution is less than 400 μm. Using this detector, ETCC can get electron tracks which are generated from Compton scattering. In this paper, we show the prototype ETCC performance and imaging results. Results: ETCC achieved a wide energy dynamic range (200–1300keV) and wide field of view (3 steradian). Also we succeeded in imaging new imaging reagents using mice as follows; (1) F‐18‐FDG (511 keV) and I‐131‐MIBG (364 keV) simultaneous imaging for double clinical tracer imaging, (2) Zn‐65‐ porphyrin (1116 keV) imaging for high energy gamma‐ray imaging and, (3) imaging of some minerals (Mn‐54, Zn‐65) in mice and so on. And we succeeded in 3‐D imaging which has imaged only one direction using one head camera. Conclusions: We have developed the ETCC for new medical imaging device and succeeded in imaging the some imaging reagents. We started to develop the new ETCC which can image the mouse within 30 min. Thus, this detector has the possibility of new medical imaging.
SU‐E‐I‐64: 1H‐MRS Quality Assurance in Short and Long Term Using a Phantom Object
Authors: Barreto F Rodrigues , Salmon C Garrido
Published: June 2012

Purpose: To evaluate intrinsic variability of 1H‐MRS single voxel technique for short and long periods of time using a metabolic phantom in a clinical protocol (hippocampi). Methods: A solution with several metabolites (NAA, Cre, Cho, Lac, M‐Ins, Glu, Gln) was placed in a spherical round glass with 300 mL. MRS data were acquired in a 3 T MRI scanner, with a PRESS sequence of TE/TR=35/1500 ms, 2048 data points, 1725 Hz of bandwidth, 6 cm3 VOI centered in the phantom and NSA of 128. A total of 130 spectra were obtained from 27 acquisition dates (5 spectra/date without removing the phantom) over 15 months. Spectra were processed with LCModel software to reduce the human variability during spectra processing. SNR and FWHM outputs from LCModel are mean calculated values from identified resonances. Results: Spectra from each acquisition date showed no mean deviations superior to 4% for all metabolites except for Lac (14 %). During 15 months all metabolites showed inferior deviations to 12%, once again except for Lac (20.5%). The worst estimated concentration was from Gln, which represent 60% of the expected value. The mean SNR was 16.3±2.1. There was no correlation between SNR and mean FWHM from resonances, thus wrong water suppression must be the main factor for variable SNR. Conclusions: NAA was the most stable metabolite in the whole analysis period with a variation of 6.8%, and Gln was the less stable with a 25.4% variation. FWHM was more variable than SNR, possible due to shimming variability, although it showed no influence in SNR. It was observed two types of artifacts in some spectra generated by unbalanced gradients, B0 inhomogeneity and also insufficient amplitude from crusher gradients. Temporal analysis demonstrated the feasibility of compare results obtained on measurements of the same date and for long periods due to low deviations provided by the technique.
SU‐E‐I‐66: Is T2 Individual Correction in MRS for Fat Quantification Tool Necessary?
Authors: Salmon C Garrido , Trad H , Domenici F , Arruda E , Elias J
Published: June 2012

Purpose: In nonalcoholic steatohepatitis (NASH) the fat quantification is necessary. One of the most used in vivo quantification method is the magnetic resonance spectroscopy (MRS). It is well known the importance of T2 correction to improve the accuracy and precision of this method; however the T2 measurements require time consumption. In this work we estimated the T2 values for water and fat in NASH patient with different fat contents in order to verify if a generic T2 correction is adequate for fat quantification in the clinical routine. Methods: 19 NASH patients (48±10 years, 9 female) underwent MR procedure several times. Imaging was performed on a 3.0T clinical MRI scanner using a 3P‐Dixon method. MRS data was acquired using single voxel (3×3×3 cm) PRESS acquisition (TR=1500ms, 1024points, 2 KHz bandwidth). The PRESS acquisition was performed in a single TE (60 ms, 32 averages) and multiple TE (32,45,80 and 135 ms; 16 averages). The software jMRUI was used for peak quantification. The MRS results were T2 corrected using generic values (T2fat=55ms and T2water=25 ms) for single TE data and individual values estimated from multi‐TE data before fat fraction calculation. A linear correlation was estimated between the fat fraction obtained using 3P‐Dixon and the spectroscopy methods. Results: The T2 values estimated were 69±14 and 27±3 ms for fat and water, respectively. The correlation coefficients between 3P‐Dixon and the spectroscopy methods were: 0.75 for MRS‐individual and 0.82 for MRS‐general. Conclusions: The procedure using a generic T2 value was more correlated to Dixon than one using individual values, suggesting that is more important a good signal‐to‐noise ratio than a very precise T2 value for correction. The reduced range of T2water values doesn't reflect any considerable iron deposition in NASH patients. In diseases with low iron deposition it's not necessary the individual T2 correction for fat quantification from MRS data.
SU‐E‐I‐70: Semi‐Automatic, User‐Driven Breast, Chest Wall and FGT Segmentations Based on Hough Transform, Morphology Tools and Histogram Technology
Authors: Wang Y , Deasy J
Published: June 2012

Purpose: Preliminary analysis shows that breast fibroglandular tissue (FGT) ratio and background parenchymal enhancement (BPE) of magnetic resonance (MR) imaging are predictive of future breast cancer risk. Adequate methods for automatic/semi‐automatic breast and chest wall segmentation, and FGT histogram extraction and analysis were not available. Methods: This method is tested on the retrospective HIPAA‐compliant study, which includes 1275 women who underwent breast MR imaging between December 2002 and February 2008. The method works in user‐directed stages for each image slice: 1. A straight‐line and ellipse Hough transform are applied to detect chest wall boundaries and separate out the chest region if it is present. 2. Edge detection and morphology tools are deployed to segment out the breast region. Human input is required to justify and adjust the segmentation result. 3. Typical breast MRI histograms have double peaks, of fat regions and FGT content inside the segmented breast. Human input is needed here to justify and select a proper segmentation threshold value for whole breast FGT segmentation. Interactive GUIs were developed in Matlab for all the human input sections. Results: Various chest wall boundary lines are detected by Hough transform. Breast region is segmented out either automatically by the morphology tools or redefined by researchers if there is no proper boundaries available in the MR images. Breast region is analyzed by histogram technology to separate FGT from fat. Conclusions: We have developed a semi‐automatic human‐guided breast segmentation method for MRI based on Hough transform, morphology tools and histogram technology. This approach enables novel breast segmentation and analysis.
SU‐E‐I‐74: White Matter Tract Disintegrate of Frontal and Limbic Regions in Mild Cognitive Impairment with Depression
Authors: Juh R , Suh T , Kim S
Published: June 2012

Purpose: Mild cognitive impairment with depression (MCID) is common and associated with disability and cognitive impairment, with high probability of relapse. Hypothesize that 1) a sign of WM disintegration would be observed in MCID than MCI nondepression (MCIND), especially in frontal and limbic regions and patients with depression would show reduced GM density in the hippocampus, amygdala, anterior gyrus cingulate, and dorsolateral prefrontal cortex (DLPFC) and dorsomedial prefrontal cortex (DMPFC) 2) the abnormalities of long association fiber tracts integrity are correlated with geriatric depression. Methods: Forty‐two subjects (20 nondepressed, 22 depressed) underwent DTI and cognitive assessment. Depression was initially assessed by means of the Korean version of the 30‐item Geriatric Depression Scale (K‐GDS). All patients scoring 19 or higher on the K‐GDS were screened as depressed. An automated tract‐based statistical analysis method was used to derive estimates of fractional anisotropy (FA) for each subject. Group effects and correlations with clinical features on DTI parameters were examined. Results: We found cross‐sectional differences in WM tract disintegration on posterior cingulum, splenium of corpus callosum, uncinate fasciculus, genu, thalamus, internal and external capsule of limbic in MCID. These results support changes in the structural integrity of neuronal cells in these specific important brain regions constituting a fronto‐limbic‐cerebellar network during depressive and in particular during the course of depression. The different parts of the frontal lobes have afferent and efferent connections with other neocortical, limbic, and subcortical regions and participate in the limbic‐cortico‐striatal‐pallidal‐thalamic circuits. Conclusions: Findings are suggestive of loss of integrity in WM fiber within frontal, temporal and limbic regions, increasing the evidence that implicates disruptions to the limbic‐orbitofrontal networks in the pathogenesis of MCID. These neuroanatomical circuits play an important role in the regulation and modulation of affect and emotion, and contribute to the pathogenesis of late‐life depression.
SU‐E‐I‐75: A New Method for Prostate Cancer Localization Using Multispectral MRI
Authors: Guo Y , Ni H , Long M , Zhang Y , Ming X , Feng Y
Published: June 2012

Purpose: To develop a new method for automatic localization of prostate cancer using multispectral MRI data. Methods: Multispectral MRI including MR spectroscopic imaging (MRSI), T2 weighted MRI, diffusion weighted imaging (DWI) and dynamic contrast‐enhanced (DCE) MRI, has been used for cancer target localization. The combination of multiple MRI imaging technologies provides more useful information than one single technology alone about prostate cancer and has advantages for target definition in radotherapy treatment and quantitative evaluation of tumor response. However, manual cancer localization using multispectral MRI dataset is a tedious task and prone to inter‐/intra‐observer variability. Automatic localization methods using multispectral MRI data is highly desired. In this paper, a fuzzy fusion framework for automatically localizing prostate cancer with multispectral MRI data is presented. Firstly, for each kind of MRI images, a membership function is created to calculate the membership‐degrees of image elements belonging to cancer region. Secondly, a fuzzy fusion operator is used to fuse different membership‐ degrees corresponding to the same regions. Lastly, the Result of fusion is further adjusted with fuzzy region growing process, leading to the final membership‐degree map. And cancer volume is finally defined by setting up a threshold on the map. Results: The new method was tested with one multispectral MRI patient dataset and results from our experimental study are compared with the one obtained form a manual method performed by an experienced pathologist. Quantitative analysis shows that the specificity is 98.89%, sensitivity is 62.85% and accuracy is 95.42%, respectively. It illustrates the feasibility of utilizing this framework in the clinical application. Conclusions: The feasibility study shows the new method reported in this paper achieves automatic localization for prostate cancer and can be easily implemented in clinical applications. We are currently conducting a clinical study for testing the effectiveness and reliability, and further developing this method. *supported by NSFC‐81171342 support by National Science Foundation of China (NSFC‐81171342)
SU‐E‐I‐76: Optimizing Imaging Parameters for a Novel Radiographic Imaging System for the Detection of Corrosion in Aluminum Aircraft Structures
Authors: Hammonds J , Price R , Donnelly E , Pickens D
Published: June 2012

Purpose: A laboratory‐based phase‐contrast radiography/tomosynthesis imaging system previously (Med. Phys. Vol. 38, 2353 May 2011) for improved detection of low‐contrast soft‐tissue masses was used to evaluate the sensitivity for detecting the presence of thin layers of corrosion on aluminum aircraft structures. Methods: The evaluation utilized a test object of aluminum (2.5 inch × 2.5 inch × 1/8 inch) on which different geometric patterns of 0.0038 inch thick anodized aluminum oxide was deposited. A circular area of radius 1 inch centered on the phantom's midpoint was milled to an approximate thickness of 0.022 inches. The x‐ray source used for this investigation was a dual focal spot, tungsten anode x‐ray tube. The focal used during the investigation has a nominal size of 0.010 mm. The active area of the imager is 17.1 cm × 23.9 cm (2016 × 2816 pixels) with a pixel pitch of 0.085 mm. X‐ray tube voltages ranged from 20–40 kVp and source‐ to‐object and object‐to‐image distances were varied from 20–100 cm. Performance of the phase‐contrast mode was compared to conventional absorption‐based radiography using contrast ratio and contrast‐to‐noise ratios (C/N). Phase‐contrast performance was based on edge‐enhancement index (EEI) and the edge‐enhancement‐to‐noise (EE/N) ratio. Results: for absorption‐based radiography, the best C/N ratio was observed at the lowest kVp value (20 kVp). The optimum sampling angle for tomosynthesis was +/− 8 degrees. Conclusions: Comparing C/N to EE/N demonstrated the phase‐contrast techniques improve the conspicuity of the oxide layer edges. This work provides the optimal parameters that a radiographic imaging system would need to differentiate the two different compounds of aluminum. Subcontractee from Positron Systems Inc. (Boise, Idaho) through United States Air Force grant (AF083‐225).
SU‐E‐I‐84: A Novel Approach for the Attenuation Correction of PET Data in PET/MR Systems
Authors: Chang T , Clark J , Mawlawi O
Published: June 2012

Purpose: To evaluate the use of non‐attenuated PET images (PET‐NAC) as a means for the attenuation correction (AC) of PET images in PET/MR systems. Methods: A 3 step iterative segmentation process is proposed. The first step is used to segment the body contour from the NAC PET images using an active contour algorithm (Kass et al., Int J Comput Vision, 321–331 (1988)). The second step was to segment the lung region from the resultant image using an optimal thresholding approach (Xu et al., IEEE T Nucl Sci, 43, 331–336 (1996)). The purpose of the third step was to delineate parts of the heart and liver from the lung contour using a region growing approach since these parts were unavoidably included in the lung contour of the second step. Finally the attenuation coefficients of the bed were included based on CT images to eliminate the impact of the couch on the accuracy of AC. The final attenuation map was then used to AC the raw PET data and Result in a final PET image (PET‐IAC). To assess the proposed segmentation approach, a phantom and six patients were scanned on a GE Discovery‐RX PET/CT scanner. PET‐IAC was then generated from PET‐ NAC using the proposed approach and compared to those of CT‐AC PET (PET‐CTAC). Visual inspection and SUV measurements between PET‐IAC and the PET‐CTAC for phantom and patient studies were performed to assess the accuracy of image quantification. Results: Visual inspection showed a small difference between the PET‐IAC and PET‐CTAC. PET‐IAC tumor SUVs were on average equal to 103±9% compared to the SUVs from the PET‐CTAC in the phantom study, and 110±7% in the patient studies. Conclusions: Preliminary results suggest that PET‐NAC for the AC of PET images is feasible in the clinic. Such an approach can potentially be an alternative method of MR‐based AC in PET/MR imaging.
SU‐E‐I‐85: Evaluation of a Solid‐State Dosimeter Module for Measuring Nuclear Medicine Radionuclides
Authors: Wendt R
Published: June 2012

Purpose: A recently introduced solid‐state dosimeter module (UDOS001, Teledyne Microelectronic Technologies, Los Angeles, CA) requires only external power (e.g., from two nine‐volt batteries in series) and a battery‐ powered data recorder to assemble a compact, portable dosimeter. This device was developed for radiation detection and monitoring of a wide range of radiation types. It has a nominal minimum energy of 100 keV. The present study sought to determine its suitability for measuring the dose from radionuclides used in nuclear medicine. Methods: Three radionuclides (initially 4.77 mCi of F‐18, 3.86 mCi of I‐131, and 12.4 mCi of Tc‐99m) were measured at a distance of one meter and at several different angles of incidence. The most sensitive analog output of the dosimeter was digitized by a battery‐powered data logging device (Track‐It 5VDC, Monarch Instrument, Amherst NH). These data were transferred from the data logger into a Windows 7 personal computer, formatted as an Excel 2010 spreadsheet and converted from voltage to dose using the manufacturer's nominal calibration factor of 14 urad/19.5 mV step. The dose rate was determined from the slope of a linear fit to the cumulated dose as a function of time. Results: The nominal calibration of the dosimeter gives dose rate measurements that are close to published gamma ray dose rate constants for these radionuclides (0.65 vs. 0.70, 0.25 vs. 0.28, and 0.071 vs. 0.078 mrad/mCi‐hr respectively). The angular dependence of the response is greater at 140 keV than at 511 keV, but an acceptance angle of at least 90 degrees has uniform response with all three radionuclides. Conclusions: A better calibration factor would be 0.154 urad/19.5 mV step at these gamma ray energies. This dosimeter can be used to measure the dose from common radionuclides used in nuclear medicine.
SU‐E‐I‐86: Image Fusion Verification Using a Vendor‐Independent Phantom
Authors: Dyer S , Goodenough D , Levy J
Published: June 2012

Purpose: To evaluate the image fusion accuracy of a hybrid PET/CT or SPECT/CT system using a recently developed vendor‐independent phantom. Methods: The basic design of the fusion verification phantom is a 10 cm urethane cube with three 1 mm diameter channels each fitted with standard Luer connection designed to be filled with a radioactive solution. The channels also have a 0.4 mm diameter steel wire inserted in each channel. There are two versions of this cube phantom with different orientations of the wire/liquid filled channels. There is the perpendicular cube with three channels each parallel to the x, y and z axes. The second cube orientation has two opposing angled channels and one that is perpendicular to the cube base. When imaged with either a PET/CT or SPECT/CT device the wire yields a high contrast image against a high signal target of the radioisotope filled channel. Both phantoms are scanned on various vendor and model hybrid systems. Results: Three plane reconstructed data of the perpendicular fusion phantom generates images with point source like targets of the emission and transmission data for quick visual evaluation of registration accuracy for x, y and z shifts. A series of axial reconstructed images can be used to evaluate alignment when using the opposing ramp fusion phantom. The unique utility of the opposing ramps allows for verification of a z‐axis offset from the single axial image data. Alignment data are presented from a number of PET/CT and SPECT/CT systems. Conclusions: The use of either the perpendicular or opposing ramp fusion phantom provides a convenient QC vendor independent tool for evaluation of image alignment accuracy of hybrid imaging systems. The design supports a simple 3D processing with a straightforward visual interpretation of alignment.
SU‐E‐I‐93: External Beam Radiation Cherenkov Emission in Tissue Used for Tissue Oxygen Sensing
Authors: Zhang R , Kanick S , Vinogradov S , Esipova T , Pogue B
Published: June 2012

Purpose: To show that Cherenkov emission is generated by external radiotherapy beam in tissue, and could serve as optical source to excite an oxygen sensitive phosphor, Oxyphor G4, within tissue. The intensity and lifetime of the phosphorescence was measured with a time‐gated system and reveals the oxygenation levels in the tissue phantom. Methods: A tissue phantom made with PBS, 1% v/v Intralipid‐20% (Sigma Aldrich), 1% v/v whole blood and Oxyphor G4 in 1 μM concentration is irradiated by 18MeV external radiotherapy electron beam at a dose rate of 4 Gy/min generated by a medical linear accelerator (Varian LINAC 2100C, Varian Medical Systems). On one side of the phantom, a fiber bundle is used to conduct optical signal to a spectrometer connected to a fast gating ICCD (PI‐MAX3, Princeton Instruments). For each oxygenation level, a series of spectrum of phosphorescence at different time points is measured by the time domain gating technique. Lifetime of phosphorescence is analyzed by exponential fitting and is validated by comparison to an independent analysis by frequency domain phosphorimetry. Monte Carlo simulations using GEANT4, of the fiber optic collection of Cerenkov light were performed to decide the sensitivity of the optical system for a range of specified geometries and beam types. Simulation results identify the effective depth within the phantom that is sampled by the optical collection of the Cerenkov signal. Results: Simulations show that we can detect the Cherenkov signals comes from an approximately 5 mm depth from within the tissue phantom. Lifetime of the phosphorescence and pO2 of the phantom could be measured and calculated correctly by the time domain gating system. Conclusions: This work indicates time domain gating techniques combined with an oxygen sensitive phosphor are capable of accurately monitoring tissue oxygenation from a reasonable sampling depth in tissue in vivo during external beam radiotherapy. NIH grant R01CA109558
SU‐E‐I‐95: Multiscale Normalized Metal Artifact Reduction (MS‐NMAR) in Computed Tomography
Authors: Tang S , Tang X
Published: June 2012

Purpose: Medical x‐ray CT devices produce images of high quality; however, the metal artifacts may arise from the adverse effect of metal materials present in the imaged objects. Conventional methods for metal artifact reduction (MAR) substitute the contaminated projection data corresponding to metal traces by specific interpolations in the projection space. Nevertheless, these methods usually introduce new artifacts, because the prior information of the imaged object (i.e., the prior image) was not involved. Therefore, a normalized MAR (NMAR) has further been invented, in which the projection space interpolation was carried out with respect to the ratio (i.e., normalization) of projection raw data to re‐projection of the prior image. This feature renders NMAR a very high accuracy. However, the normalization in NMAR is more reasonable for the larger scale contents rather than for the smaller scale details. Methods: The proposed MS‐NMAR method is a generalization of NMAR with a dedicated multiscale framework. Both projection raw data and re‐projection of the prior image ill be decomposed into each scale. The normalization followed by the linear interpolation is performed in each scale, in which the larger the scale is the wider the interval the linear interpolation is operated with. Composite projection data are acquired by summing the projection components in all scales. MS‐NMAR corrected image is reconstructed from the composite projection data. Results: Real CT data are used to verify the efficiency of the proposed method, and to compare with conventional MAR and NMAR. The quality of reconstructed image after MAR is evaluated by inspecting the region around the metal material. Conclusions: Both NMAR and MS‐NMAR have a better performance as compared with the conventional MAR. Meanwhile, MS‐NMAR outperforms NMAR, considering it hinders the productions of new artifacts while reducing the original metal artifacts. This work is partially supported by the US National Institute of Health through grants P50‐AG025688 and 2P50AG025688.
SU‐E‐I‐103: Detecting Anomalous Pixels and Correlated Artifacts in Digital Detectors from Flat‐Field Images
Authors: Dave J , Gingold E , Yorkston J , Bercha I , Goldman L , Walz‐Flannigan A , Willis C
Published: June 2012

Purpose: Anomalous pixels may be defined as those pixels whose exposure response relationship is deviant from the typical, expected or calibrated response. A group of anomalous pixels may Result in visible correlated artifacts. Here we demonstrate an approach to identify anomalous pixels and correlated artifacts using flat‐field images. Methods: Using manufacturer specific calibration geometry, sets of four flat‐field images per detector were obtained with varying input air kerma values (0.5 to 160 μGy) from 9 digital detectors at 6 institutions. Images obtained before and after calibration, with both proper and improper gain maps and structured artifacts were additionally acquired with some detectors. Image analysis methodology under consideration by AAPM Task Group 150 was used.After eliminating 10mm borders, images were divided into square regions (100mm2). Anomalous pixels were identified as pixels within each region with valuesabove or below ±3 standard deviations (SD) relative to the mean value of the region. If these pixels were identified in all four images comprising a set, then they were reported as anomalous. Line artifacts were identified as rows and columns with cumulative profile values that were above or below ±3 SD with respect to the mean value of neighboring profiles in the set of four flat‐field mages. Results were verified with visual inspection of the images. Results: For four sets of images, the algorithm did not identify any anomalous pixels, and none were spotted on visible inspection as well, while for five sets of images the identified anomalous pixels matched visual inspection results. Anomalous pixel detection failed in regions with an unusually large number of defects and structured noise, since those regions exhibited relatively large SD. Line artifacts consistent with visual analysis were identified correctly when present. Conclusions: A practical approach to identify anomalous pixels and correlated artifacts from flat‐field images is demonstrated.