bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐18: Quantifying the Geometric Accuracy of the On Board Imager Over a One‐Year Period
Authors: Lovelock D , LoSasso T , Ali I , Amols H , Ling C , Yamada Y , Pham H , Munro P
Published: July 2006

Purpose: To quantify the geometric accuracy of the On Board Imager in both the kV radiographic and cone beam imaging modes. Method and Materials: The Winston‐Lutz test was performed to localize a 5mm tungsten sphere placed within +/− 0.25 mm of the radiation isocenter. The sphere was imaged with half fan cone beam scans, and kV radiographs at the 4 principal gantry angles. The displacement of the sphere from the ‘imaging isocenter’ (the actual position of a point object that the imaging system would find to be at isocenter) was determined for each imaging mode. This test has been repeated 18 times over a period of one year. Results: The average displacement of the sphere from the imaging isocenter using a half fan technique was found to be 0.9 mm Right, 0.9 mm Anterior, and 1.1 mm Inferior, assuming a head first supine orientation. These offsets are incorporated in image‐guided patient setup procedures. Small systematic errors as a function of gantry angle were also measured for the radiographs. A point at the radiation isocenter will appear about 1mm higher in a right lateral image than in a left lateral image. A similar left / right discrepancy exits for anterior and posterior images. Conclusion: The systematic geometric errors of the kV imaging equipment and associated techniques need to be measured and incorporated into the procedure of on‐line image‐guided patient treatment. For the On Board Imager, a geometric accuracy of better than 1mm can be achieved.
SU‐FF‐I‐23: Comparision of Amplitude‐Based and Phased‐Based Binning Techniques for Respiratory Correlated CT
Authors: Klahr P , Starkschall G , Hanley J , Covitch Adam
Published: July 2006

Purpose: To evaluate amplitude‐based and phase‐based approaches for generating respiratory correlated CT (RCCT) images in terms of spatial coherence and residual motion artifacts. Method and Materials: A programmable robot arm (Kawasaki, FS‐2, KRI, Wixom, MI) with an attached phantom consisting of 3 – 6 cm. diameter spheres was used to simulate various breathing patterns. Both the Varian RPM system and a bellows device were used as surrogates for monitoring. The robot arm was commanded to perform asymmetric “exhale/inhale” sequences with a variable cycle time, and it allowed for multi‐axis trajectories, hysteresis and pseudo‐random motion. The effectiveness of amplitude‐based and phase‐based binning algorithms on the resultant images of a spherical phantom was quantified by calculating the average deviation from a spherical surface. Both binning methods were applied to patient data sets and qualitatively evaluated. Results: Amplitude‐based binning produces fewer artifacts, especially when the breathing frequency was varied during the acquisition. When using phase‐based techniques the measured radii of spherical objects had twice the variance as compared to amplitude‐based algorithms. Conclusion: Amplitude‐based binning has merit in generating RCCT image volumes. Preliminary results suggest that they generate fewer artifacts and are more accurately correlated to the internal organ motion, especially when the breathing frequency varied during the acquisition. More investigation is warranted to evaluate the impact of this new methodology on treatment planning and delivery. Conflict of Interest: The author is an employee of Philips Medical Systems.
SU‐FF‐I‐27: CT Urography Radiation Dose Using Automatic Exposure Control
Authors: Nawfel R , Judy P , Klokeid K , Silverman S
Published: July 2006

Purpose: To measure and compare patient radiation doses during CT urography with automatic exposure control (both angular and z‐axis tube current modulation) to patient radiation doses without automatic exposure control (tube current modulation alone), and to correlate these doses with corresponding image noise measurements. Method and Materials: Skin doses were measured by exposing thermoluminescent dosimeters placed on the abdomen (AP) and side (lateral position) of 18 patients examined with CT urography consisting of automatic exposure control (CARE Dose 4D group), and 20 different patients examined with angular tube current modulation only (CARE Dose group). Mean and standard deviation of patient skin doses were calculated. The CT urography protocol included three volumetric acquisitions of the abdomen and pelvis. Effective doses were calculated and used to compare radiation risk between the two patient groups. The variation in effective dose with patient size was also evaluated. Image noise was evaluated by calculating the standard deviation of pixel values from a region of interest in patient liver images. Results: The mean skin dose for CARE Dose 4D patients (63.4 ± 16.4 mGy) was 14.2% higher than that of CARE Dose patients (54.4 ± 7.39 mGy). The mean effective dose for CARE Dose 4D patients (10.6 ± 2.3 mSv) was 17.1% higher than that of CARE Dose patients (8.8 ± 1.8 mSv). Image noise increased with increasing patient size, however the increase was less for patients exposed with automatic exposure control. Conclusion: Patient effective dose, and thus radiation risk was 17.1% higher for CT urography patients examined with automatic exposure control compared to those examined with tube current modulation alone. Using automatic exposure control techniques in CT may be useful in reducing dose in small patients, however, for large patients the dose may actually increase to compensate for the increase in image noise.
SU‐FF‐I‐29: Investigation of the Perspecta Display for 4D Visualization
Authors: Rivard MJ , Melhus CS , Napoli J , Gong X , Chu JCH
Published: July 2006

Purpose: Recent advancements in radiologic imaging (IGRT) have acquired 4D anatomic data permitting characterization of organ motion towards improving radiotherapy delivery. For radiation oncology patients, images illustrating temporal migration or tumor motion as a result of innate biological function can provide significant benefit towards improving target accuracy and minimizing healthy tissue dose. This study examines the utility of the Perspecta Spatial 3D system (Actuality Systems Inc) to display dynamic 3D data in comparison to flat panel 2D displays. Method and Materials: The AqSim (Philips Medical Systems) CT scanner was used to obtain scans of a patient with lung cancer, and entered into the Pinnacle3 treatment planning system (Philips Medical Systems). A clearly delineated lung tumor was contoured in each pertinent CT slice. Ten scans (64 slices each) were obtained during the breathing cycle. Data were viewed side‐by‐side on a flat panel display and the Perspecta 3D system for comparison. Results: The Perspecta display permitted simultaneous visualization of ten CT scans at ∼ 1 Hz per dataset which was similar to the natural breathing rate during image acquisition. Optimal static beam orientation for dynamic target coverage and OAR avoidance was more easily accomplished on the Perspecta than on the 2D display. Conclusion: The 3D Perspecta display successfully depicted anatomic motion, clearly indicating tumor and OAR motion. In comparison to the 2D flat panel display, the Perspecta display permitted the radiation oncology team to readily visualize the temporal nature of lung tumor location for consideration during treatment planning. This application could play an important role in defining and displaying 4D patient data, which was previously relegated to predominantly 2D RTP systems. Furthermore, breath‐hold and coached breathing techniques may be quantitatively evaluated using this method. Conflict of Interest Statement: Actuality Systems Inc. provided the 3D display used in this study.
SU‐FF‐I‐37: A Comparison of Full‐Field Digital and Screen‐Film Mammography Dose
Authors: Schueler B
Published: July 2006

Purpose: To determine whether mammograms acquired with a full‐field digital mammography (FFDM) unit using automatic exposure control (AEC) reduce patient radiation dose and exposure time as compared to screen‐film mammograms. Method and Materials: Exposure techniques and mean glandular dose (MGD) for FFDM and screen‐film mammography was compared for breast tissue equivalent attenuation slabs of varying thickness (2–8 cm) and glandular content (0–100%). FFDM images were acquired with a Lorad Selenia unit with AEC set to the manufacturer's recommended levels. Screen‐film mammograms were acquired with a Lorad M‐IV unit and Kodak Min‐R 2000 screen‐film system with AEC adjusted for an ACR accreditation phantom optical density of 1.8 OD. In addition, a patient survey including 150 mammograms compared the FFDM exposure techniques and MGD with the patient's corresponding screen‐film mammogram acquired 1 year prior. A 50% glandular tissue content was assumed. Results: For breast tissue equivalent attenuation slabs 4 cm thick or more, FFDM AEC was found to call for higher x‐ray beam energy exposures than screen‐film, resulting in lower MGD (mean 40%) and exposure time (mean 50%). Below 4 cm, FFDM kVp was lower than screen‐film, causing higher MGD (mean 15%) and exposure time (mean 20%). For the patient survey, FFDM resulted in a significantly lower MGD (mean 35%) and exposure time (mean 52%) than the corresponding screen‐film mammogram. Similar to the attenuation slabs, the FFDM dose and exposure time were generally higher than screen‐film for 2–4 cm compressed breast thickness and lower than screen‐film for 4 cm and above. Conclusion: FFDM using manufacturer's recommended dose settings results in significant dose reduction as compared to screen‐film mammography, particularly for 4 cm compressed breast thickness and above.
SU‐FF‐I‐40: Evaluation of Different Ways to Describe An X‐Ray Spectrum and the Implications in the Absorbed Energy in a Head Voxel Model
Authors: Cassola V , Hoff G
Published: July 2006

Purpose: To evaluate the behavior in absorbed energy due by approximation in irradiation energy spectra description to Monte Carlo simulation. Method and Materials: A head voxel model was coupled to GEANT4.7 program to obtain the absorbed energy distribution in anatomical structures of the model. Three simulations were realized, using an x‐ray beam parallel to the left side of the model, with an isotropic beam distribution. First the energy beam was defined according to “Catalogue of Diagnostic X‐ray Spectra and Other Data”, using 70.0 kVp of tube tension, with 17° target angle, W as target material, without ripple and with 1.0 mm Al of add filtration. After that the beam was defined as monoenergetic at 30.5 keV, representing the mean energy of the cataloged spectrum. Other monoenergetic beam of 29.5 keV was used, representing the first HVL energy according the catalogued spectrum. Results: The simulation using the catalogued spectrum was defined as reference. The simulation, using the 30.5 keV monoenergetic beam, shows twenty structures (71%) with differences larger than 10%, when compared to the reference data, including five structures (18%) that presented differences upper than 20%. In the simulation using monoenergetic beam corresponding to the first HVL energy, fourteen structures (50%) presented differences larger that 10%, compared to the reference data, including four structures (14%) showing differences upper than 20%. To both simulations total absorbed energy showed difference down to 7%, compared to the reference. Conclusion: The absorbed energy is dependent on the x‐ray spectra description; it means that the configurations of the spectra (photon flux, mean energy and HVL energy) significantly interfere in absorbed energy distribution. This kind of approximation must be avoided, when we try to describe the absorbed energy accurately, especially in simulations used in radiological protection applied to radiological area.
SU‐FF‐I‐42: The Influence of Bowtie Filter Selection, Patient Size and Patient Centering On CT Dose and Image Noise
Authors: Toth T , Ge Z , Daly M
Published: July 2006

Purpose: Bowtie filters have been used on CT scanners for many years to reduce patient dose. In this study we rigorously characterized bowtie filter dose and noise performance and discovered some significant clinical implications for the CT scanner technologist. Methods and Materials: Various size and shape phantoms were scanned on a GE LightSpeed VCT scanner using each available bowtie filter with phantoms positioned at 0 mm, 30 mm and 60 mm below isocenter. Surface and CTDI doses were measured along with image noise. Relationships for dose and noise were determined using regression methods and compared to computer simulated results. An algorithm was developed to determine the centering error from scout scans and subsequently used to evaluate the clinical implications for 273 adult body patients. Results: The measured noise and dose performance agreed with simulations and indicated an optimum bowtie filter can be selected as a function of phantom size. The 32cm CTDI phantom scanned on the large, medium and small bowtie filters produced a dose savings of 29%, 24%, and 17% respectively compared to the flat filter for similar image noise. However, the surface dose increased by 18% and 41% for the miscentered cases while image noise increased by 2% and 13% with the optimum CTDI phantom bowtie. The noise increased even more (5% and 20%) for a miscentered nominal body shaped phantom. The clinical scout scan analysis indicated that 54% of patients were miscentered by 20 mm to 60 mm. With this miscentering, the surface dose penalty for the 32 cm CTDI phantom would range from 22 % to 71% assuming mAs is also increased to compensate for noise,. Conclusions: Clinical image quality and dose efficiency can be significantly improved on scanners with bowtie filters if technologists can nominally center the patient region to be scanned.
SU‐FF‐I‐44: Management of Patient Radiation Dose in Interventional Fluoroscopy
Authors: Balter S , Egan M , Gonzalez I , Hawkey M , Moses J
Published: July 2006

Purpose: Some complex interventional procedures require significant amounts of radiation for their completion. In 2006 JCAHO added a 15Gy single field fluoroscopic skin dose to the list of sentinel events. An active radiation management program contributes to optimization of the patient's benefit/risk ratio. Method and Materials: Periodic equipment quality testing and calibration. Patient radiation history to determine the quantity and location of previous significant radiation events Appropriate patient consent Operator and staff dose management during the procedure Documentation and clinical follow‐up when significant doses of radiation are used Continuing clinical follow‐up when deterministic injuries are suspected or observed Results: Our program was implemented in June 2005. Significant issues include acquisition of the patient's radiation history, active management of dose rate by operators during procedures, and complete documentation at the end of each procedure. Post procedural patient discussions and integrating radiation follow‐up into our standard 30 day post‐intervention telephone call were easy. The initial trigger level for immediate justification of significant radiation usage and patent follow up was 3 Gy cumulative dose at the IEC interventional reference point. In January 2006 and after consultation with the institutional radiation safety committee, the trigger was raised to 5 Gy (corresponding to a peak skin dose in the range 2 –3 Gy for most procedures). Special rules apply to patients with unusual or multiple procedures. Conclusion: The world‐wide occurrence of a major deterministic injury is estimated to be one or two orders of magnitude less frequent than death from an interventional procedure. Simple technical improvements such as better dose displays, low‐dose‐rate defaults, and automated data collection would be helpful. With these, operators and monitoring nurses can more easily maintain a level of dose awareness during a procedure appropriate to an ongoing benefit/risk analysis.
SU‐FF‐I‐45: Labview Graphical User Interface for Micro Angio‐Fluoroscopic High Resolution Detector
Authors: Keleshis C , Ionita C , Rudin S
Published: July 2006

Purpose: A graphical user interface based on LabView software was developed to control a Micro Angio‐Fluoroscopic detector (MAF) for real‐time acquisition, display and rapid frame transfer of high resolution images of a region‐of‐interest. Method and Materials: A MAF detector was built by our group using a CsI(Tl) phosphor, fiber‐optic taper and Light Amplifier optically coupled to a progressive scan charged coupled device (CCD) camera which provides real‐time 12 bit, 1k × 1k images. During image acquisition, the MAF detector is inserted in the x‐ray beam of an angiographic unit, between the x‐ray image intensifier and the patient. Images can be captured in continuous or triggered mode and the camera can be programmed by a computer using the serial communication. A graphical user interface was developed to control the camera modes such as gain and pixel binning as well as to acquire, store, display, and process the images. Results: The program, written in LabView, has the following capabilities: camera initialization, synchronized image acquisition with the x‐ray pulses, flat field correction, window and level adjustment, brightness and contrast control, and looped play‐back of the acquired images. Acquisition starts when the first triggering pulse is read by the interface. The acquired sequence of images is automatically displayed in a loop after completion of acquisition and the images can be stored or deleted at the user's discretion. Frame rates can be up to 30fps in 2×2 binning mode and 25fps unbinned. Conclusion: The user friendly implementation of the interface along with the high frame rate acquisition and display for this unique high resolution detector may provide angiographers a new capability for visualizing details of small endovascular devices such as stents and hence enable more accurate image guided localization. (Support: NIH Grants R01NS43924, R01EB002873).
SU‐FF‐I‐47: A Method of the Pixelized Detectors Coordinate Resolution and MTF Estimation
Authors: Grabski V , Brandan M‐E , Villaseñor Y , Belmont E
Published: July 2006

Purpose: We propose a simple method to estimate MTF and coordinate resolution of pixelized detectors used in digital imaging systems. Method and Materials: The traditional determination of coordinate resolution for pixelized detectors is mainly based on the use of line spread function measurements. The proposed method is based on the determination of the statistical correlation between neighbour elements in the detector. The correlation is evaluated by means of statistical noise measurement of the isolated elements and the linear combination of neighbour elements. To suppress the possible contribution of the beam spatial variation, the difference between values of neighbour elements is used. The distribution of differences between the detector neighbour pixels is constructed for the pixels sharing an edge (either in X or Y directions), or having one common vertex (U or V). For the validation of the method, we have studied the GE Senographe 2000D mammography unit digital detector. The detector has been irradiated by X‐rays across its entire surface. The dependence of the resolution on the photon intensity value and the pixel coordinate has been studied. The resolution function has been considered as a result of convolution of Gaussian and uniform distributions. Results: The coordinate resolution of the studied detector, having pixel size of 100 μ, is of the order of 50 –55 μ, that is, almost twice the value conditioned by pixel geometrical size. A small asymmetry between the X and Y directions has been detected. The reconstructed modulation transfer function agrees with MTF measurements of the studied detector, within a few percent. Conclusion: The proposed method can be useful for the estimation of coordinate resolution, line spread function and modulation transfer function of the detectors used in the systems of medical digital imaging.
SU‐FF‐I‐53: Mega‐Voltage CT Image: An Attempt to Enhance Image Quality
Authors: Overbeck C , Hui S
Published: July 2006

Purpose: TomoTherapy uses Megavoltage CT (MVCT) to verify patient position and alignment prior to treatment and it is usually good enough to verify the patient's position and anatomy prior to treatment. However, a greater resolution and contrast in patient images obtained by the MVCT scan would be beneficial in verifying patient anatomy and set‐up. The effects that changing the MVCT dose and consequently the signal to noise ratio (SNR) had on MVCT image quality and resolution were studied. Method and Materials: A “cheese” phantom with a resolution plug (different size holes) was scanned. The machine pulse amplitude control (PAC) value was varied in intervals from 2.22 to 3.34 to adjust delivered dose and the resulting images were analyzed. The dose was measured with an A1SL ion chamber at the clinically used PAC value of 2.78 to be 2 cGy, 0.4 cGy at a Pac value of 2.22 and 3.8 cGy at a PAC value of 3.34. Results: Increasing the PAC value leads to an increase in both dose and energy. In observing the images that were taken, it can be see that the resolution and quality of the image improves as the PAC value is increased. When comparing the MVCT image taken at the normal PAC value of 2.78 and an increased PAC value of 3.34, the smaller diameter density plug holes can be seen more clearly, the contrast between the holes and the cheese phantom are more sharply defined, and the holes appear more concentric for the image taken at PAC 3.34. Conclusion: Slightly higher dose during an MVCT scan can improve the image quality and resolution for the TomoTherapy system. These observations will be used in future investigation of more complex imaging tasks to improve MVCT imaging. Conflict of Interest: Main author is an employee of TomoTherapy, Inc.
SU‐FF‐I‐54: A Monte Carlo Model of the Discovery ST PET Scanner
Authors: Schmidtlein C , Turner A , Nehmeh S , Mawlawi O , Erdi Y , Humm J , Amols H , Kirov A
Published: July 2006

Purpose: To evaluate the accuracy of a GATE (Geant4 Application for Tomographic Emission) Monte Carlo model of a commercial PET scanner for purposes of simulating the generation, propagation, and detection of annihilation photons in PET scanners, and for evaluating image scatter fractions, resolution, sensitivity, and other scanning parameters. Methods: We compare GATE results to experimental data from a GE Discovery ST PET scanner. Our 3D PET simulation model of the GE Discovery ST scanner consists of 10,080 detectors grouped in modules and blocks following the vendor's specifications. NEMA'01 PET commissioning phantoms are also accurately modeled. More than 2 billion positron histories were followed to simulate measured PET scans of the NEMA phantom. Results: The simulated GE Discovery ST's radial sensitivity ratios for the NEMA'01 phantoms agree to within 0.6% of measured values ( versus , sensitivities R are in cps/kBq). The scatter fraction agreement is within 1.6% (the measured and simulated scatter fractions are 45.1% and 45.8% respectively). The model also accurately simulates the behavior of the time curves (measured peak true counts 338 kcps at 32.9 kBq/cc and simulated peak true counts 340 kcps at 32 kBq/cc). In addition, the spatial resolution of the scanner is simulated. Conclusions: The validated model accurately predicts scanner response and performance parameters, can be used to evaluate and improve PET resolution, image quality, and quantitative accuracy, and will aid in the determination of optimum scan parameters. In conjunction with CT images, the model can also be used to assess the accuracy of tumor segmentation for radiation therapy treatment planning. This work is sponsored in part by National Cancer Institute Grant PO1‐CA059017, by the summer fellowship program of the American Association of Physicists in Medicine, and by an internal seed grant.
SU‐FF‐I‐55: Data Mining and Knowledge Discovery Methodology Development Using Predicting Transmembrane Proteins by Synergy of Computational and Molecule Biophysics Approaches as An Example
Authors: Yang J , Yang M Q
Published: July 2006

Motivation: We consider developing data mining and knowledge discovery methodology in medical physics is important. We use predicting membrane proteins as an example, because such proteins account for roughly one third of proteins encoded in Human Genome and comparative genomes, and play crucial roles ranging from signal transduction to energy metabolism, but their structures can not be determined well by experimental methods. Since Human Genome had been completely sequenced, function and structure of proteins coded for by Human Genome are not known well. In our attempts to construct methods for automated large‐scale structural and functional annotation of genes and proteins in Human Genome and comparative genomes, the identification of transmembrane proteins is thus an important, but also very difficult task. We used a broad array of techniques that combined computational and biomedical physics approaches for the above task. Results: We developed a hybrid unsupervised‐supervised classifier using new variants of the Self‐ Organizing Feature Map algorithms, in combination with novel Feature Generation, Feature Selection and Ensemble Methods such as Boosting with bagging and boosting with confidence Information. Our combined computational and biomedical physics approaches proved beneficial by showing larger areas in our predictor's ROC curves. We will discuss the effectiveness our synergic approaches, and also provide comparisons to more traditional classifiers such as neural networks, decision trees and support vector machines. The framework that we developed can be broadly applied to other medical physics problems and marks a beginning of methodology development, not only in molecular biophysics and genomics, but also in medical physics.
SU‐FF‐I‐58: Demonstration of the Use of A Capillary Phantom to Monitor DTI Image Processing: Dyadic Sorting of Tensor Eigenvalues
Authors: Yanasak N , Allison J
Published: July 2006

Purpose: To verify the existence of noise‐dependent systematic bias in diffusion tensor imaging (DTI) data using a phantom composed of arrays of glass capillary fibers; and to use the phantom to monitor the corrective effect of using dyadic sorting for alleviating this bias when calculating average quantities in a region of interest (ROI). Method and Materials: A phantom containing glass capillary arrays and undoped water was constructed. Seventeen DTI series of images from a 3.0T GE scanner were acquired, where TR was adjusted between series to vary the signal intensity via T1 contrast. Five different values of TR were chosen. Averaging of some of these series together allowed for observations at eight unique values of SNR. Eigenvalues and eigenvectors of the diffusion tensor were calculated as well as fractional anisotropy. After calculation of the average eigenvalues and eigenvectors in ROIs containing the arrays and free water, these average values were used to sort eigenvector‐eigenvalue dyadic pairs to maximize overlap between the average values and individual voxel values. Final averages were calculated after sorting. Results: Noise‐dependent bias was observed using arrays of fibers, resulting in a separation of the two lowest eigenvalues which should be equivalent. Dyadic sorting assists with correcting this bias, although usefulness is confined to regions of lower FA and with higher SNR. Iterative sorting does not greatly improve the performance. Conclusion: This work suggests that glass capillary arrays can be used for monitoring systematic bias at a variety of SNR values, and for quantifying the amount of correction that one will observe using a particular scheme, in principle. Future investigation will examine the efficacy of other correction schemes.
SU‐FF‐I‐64: Modification of Multidirectional Distortion for DTI and Tractography
Authors: Yoon SI , Jahng GH , Khang HS , Kim YJ , Choe BY
Published: July 2006

Purpose: To modify the assigned optimization of acquisition parameters for precise measurement of diffusion in anisotropic systems. Materials and Methods: Diffusion weighted MR data were acquired from healthy volunteer, using 1.5T Siemens Avanto (Siemens, Erlangen, Germany) with actively shielded magnetic field gradients (maximum amplitude, 40mT/m). The parameters for optimal schemes were derived for each measurement based on the estimated mean diffusivity and T2 measurements. Data were analyzed on an independent workstation (Pentium IV, 3.2 GHz CPU). The diffusion weighted images were corrected for gradient tables and ECC using DTI Studio software (Radiology, Johns Hopkins University, SOM). Results and Conclusion: Each individual measurement of Dxx, Dyy, and Dzz can be optimized in the way as with optimal diffusion weighting the x, y, z, and other index. The more precise assessment of Tr(D) is needed, the more measurements should be made. In our study, consider the variances of each of the unique elements of the diffusion tensor. Acknowledgment: This study was supported by a grant of the Seoul R&BD Program, the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea. (02‐PJ3‐PG6‐EV07‐0002) and a grant of the 2005 Nuclear R&D Plan Program, Ministry of Science & Technology, Korea.
SU‐FF‐I‐65: Assessment of Advanced Algorithm in Non‐Linear Curve Fitting for DSC in Human Brain
Authors: Yoon SI , Jahng GH , Khang HS , Kim YJ , Choe BY
Published: July 2006

Purpose: To develop an advanced non‐linear curve fitting (NLCF) algorithm for dynamic susceptibility contrast (DSC) study of the brain. Methods and Materials: Twenty healthy volunteers participated for the acquisition of T1‐weighted and T2*‐ weighted dynamic contrast enhanced (DCE) MR imaging. Sequential images were continuously recorded during the first passage of contrast agent with the signal intensity for ROI. The generalized kinetic model with NLF was modified with the consideration of coefficient factor. Results: The blood perfusion and volume estimation were accurately evaluated in the T2*‐weighted dynamic contrast enhanced (DCE)‐MR images. From each of the recalculated parameters, a perfusion weighted image was outlined by using the modified non‐linear curve fitting algorithm. The present study demonstrated an improvement of an estimation of the kinetic parameters from the dynamic contrast‐enhanced (DCE) T2*‐weighted magnetic resonance imaging data with using contrast agents. Conclusion: In conclusion, we developed non‐linear curve fitting algorithm for DSC study. And the data point from the gamma‐variation curve fitting with Levenberg‐Marquardt could be useful to achieve the physiological information in the clinical cases. Acknowledgement: This study was supported by a grant of the Seoul R&BD Program, the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea. (02‐PJ3‐PG6‐EV07‐0002) and a grant of the 2005 Nuclear R&D Plan Program, Ministry of Science & Technology, Korea.
SU‐FF‐I‐67: Magnetization Transfer After Bee Venom Acupuncture Treatment to Osteoarthritis
Authors: Yoon M , Choe B , Chang H
Published: July 2006

Purpose: Magnetization Transfer (MT) is based on well‐defined biophysical and biochemical properties. Bee Venom Acupuncture(BVA) demonstrated anti‐inflammatory and analgesic actions oriental clinical trials. The purpose of the present study was to evaluate the data from experimental and clinical studies and to show further ways to better comprehend the effectiveness of BVA and MT. Materials and Methods: In order to achieve our objective it was necessary to optimize a suitable interleaved Magnetization transfer contrast (MTC)/ GRE. Using a 1.5T GE system, set in Ja‐Sang Korean Oriental Hospital, was imaged with MTC parameters suggested by Barker GJ et al. Results: MTC assessed compositional and structural changes and thickness measurements to assess loss of cartilage substance. In principal, all these techniques are applicable in vivo. Compositional and structural properties are considered to reflect earlier stages of disease and may thus improve the chances to depict potentially reversible alterations. Discussions: Cartilage volumetric properties and cartilage loss may be involved later in the course of the disease but are easier to be described. MRI quantification of cartilage volume is based on the acquisition of a high resolution 2D data providing good contrast between the cartilage and the surrounding tissues in the joint as well as a homogeneity of the signal within the cartilage in order to facilitate semi automated segmentation. Conclusions: Articular Cartilage(AC) is a tissue capable of transferring and distributing impressive forces across a joint. Venom injected by BVA have created hope that cartilage breakdown can be modulated. These ways creates a need for a non invasive diagnostic tool that can provide quantitative parameters and contribute to evaluate the efficacy of these therapeutic efforts.
SU‐FF‐I‐68: False Positive Analysis of Functional MRI During Simulated Deep Brain Stimulation
Authors: Liu HL , Huang CM , Lim SN , Kuan WC , Chen HM , Wu T , Hsu YY
Published: July 2006

Purpose: Recent studies showed that MRI can be safely performed on patients with deep brain stimulation (DBS) device in place when the stimulator is turned off. By interleaving the DBS and echo‐planar imaging (EPI) acquisition, functional MRI (fMRI) may be a useful tool for understanding the mechanism of DBS as well as helping the localization of electrodes. This study aimed to investigate the possible false positive activations due to the limited time interval between the end of DBS and the start of EPI acquisition. Method and Materials: The study was performed using a 1.5‐T Philips MRI scanner with a DBS electrode (Medtronic, Minneapolis MN) positioned in the center of a gel‐filled phantom. The experimental run consisted of alternative 5 stimulation‐off and 4 stimulation‐on blocks (the stimulator was turned on for 2 seconds immediately after each readout). The control run consisted of total stimulation‐off blocks. A single‐shot GE EPI (TR/TE = 6000ms/60ms, FOV = 192mm, matrix = 64×64, SW = 3mm) was used, with 10/30 slices per measurement in for long/short inter‐scan waiting times (ISWT). Data were analyzed using SPM2. False activation and deactivation volumes were computed at different statistical thresholds. Results: For both activation and deactivation, no false positive voxels were detected for all conditions at corrected p<0.05 or uncorrected p<0.001. For uncorrected p>0.001, number of false activated/deactivated voxels increased with p‐value increased. No increased trend was observed with the experimental conditions as compared to the control conditions. Similar trends were observed when comparing activation vs. deactivation and long vs. short ISWT. Conclusion: An ISWT of 2230 ms (TR= 6s, 30‐slice acquisition) was found to be sufficient for placing a 2‐s DBS without increased false positive detections of activation/deactivation. A statistical threshold of p<0.001 or tighter is recommended for fMRI involving the similar amount of total voxels as this study.
SU‐FF‐I‐70: Asymmetric Spin Echo in FMRI at 3T: A Quantitative Evaluation of BOLD Response and Signal Drop Off
Authors: Hou P , Steinberg J , Chen D , moeller F , Narayana P
Published: July 2006

Purpose: To quantitatively evaluate the fMRI BOLD response of the asymmetric spin echo (ASE) EPI acqusition and signal drop offs at 3T. Applications in the frontal cortical and orbital frontal cortical (OFC) areas from finger tapping and olfactory stimulation were investigated. Method and Materials: ASE EPI was developed and tested on a 3.0T scanner. Phantom was used for quantitative distortion measurement by the GRE‐, SE‐, and ASE‐EPI sequences. For olfactory testing, subjects were presented with 12s of olfactory stimuli interspersed by 28s of air with a total scan time of 7 minutes. Subjects were trained to inhale and exhale following a prompts on the screen. Eight subjects were studied for finger tapping and six subjects for olfactory. The BOLD intensity and correlation were measured in the frontal cortical area for finger tapping, and in the orbital frontal area for olfactory stimulation studies. Results: The signal drop off is relatively small when the echo shift is 5 msec and 10 msec compare to SE‐EPI, but is significantly better compared to GRE‐EPI. The optimal BOLD response from olfactory test was detected by ASE with 35 msec TE, and 10 msec echo shift. Almost no BOLD effect detected from SE at TE of 35 ms and with ASE at TE of 35 ms and 5 ms echo shift. Echo shift of 15 msec had strong artifacts. GRE‐EPI was not useable for the olfactory study because almost all the signal dropped off in the OFC area. Conclusions: ASE‐EPI offers reasonable BOLD response without significant reduction in the slice coverage like SE‐EPI. It can detect BOLD response where the signal is small and susceptibility is strong. GRE‐EPI is preferred when the BOLD response is located in the less susceptible areas. ASE‐EPI with 10 msec echo shift appears to be optimal for olfactory study at 3T.
SU‐FF‐I‐71: Diffusion Tensor Imaging Analysis Using Mapping Analysis in Temporal Lobe Epilepsy
Authors: Juh R , Su M , Lee C , Suh T , Nalcioglu O
Published: July 2006

Purpose: Diffusion tensor imaging (DTI) can provide information regarding early pathological changes, such as neuronal cellular changes in gray matter or demyelination in white matter tracts. Voxel‐based statistical analysis can be performed to compare changes in a group of patients and control. In this study we investigated whether the seizure focus in patients with temporal lobe epilepsy (TLE) can be identified compared to controls. Method and Materials: Ten normal control (36±7y) with no history of neurological disease, and 10 TLE patients (30±10y) diagnosed with temporal lobe epilepsy were included in this study. The ADC and FA maps acquired from each patient was compared to the normal group data, and also the whole patient group was compared to the control group on a voxel‐by‐voxel basis using SPM. Results: In this study we investigated whether the patients with temporal lobe epilepsy showed abnormality in DTI compared to normal controls. The three of ten patients, a well localized region in the temporal lobe gray matter was found to show significantly increased ADC, which might be associated with the seizure focus As the long‐term seizure may damage the tissues, the involved areas may show changes in DTI. Every patient showed a different pattern, some with a well‐localized focus with increased ADC which might be associated with seizure focus. The FA maps were also analyzed, however no significant changes were found localized in the white matter, rather in the same gray matter area, suggesting that the effect was mediated from ADC changes. Conclusions: The SPM analysis of ADC maps acquired from each individual patient compared to a normal group might provide a means of accurately identifying focal abnormalities prior to more invasive diagnostic procedures and possible epilepsy surgery. The occult epileptogenic regions may be identified using voxel‐based statistical analysis of ADC.
SU‐FF‐I‐72: Evaluation of Dual‐Energy Subtraction of Digital Mammography Images Under Conditions Found in a Commercial Unit
Authors: Brandan M‐E , Ramírez V
Published: July 2006

Purpose: Radiological contrast‐to‐noise ratio (CNR) has been calculated for subtracted images of calcifications after dual‐kVp subtraction combining beams available in a Senographe 2000D. Method: 2002 Lemacks' et al. formalism has been used in the CNR calculations. Assumed spectra were from 1997 Boone et al. parameterization and the study was limited to a lowest 25 kV Mo/Mo and a highest 40 kV Rh/Rh beams, and 1R total exposure. Results: For a standard case combining 25 kVp Mo/Mo and 40 kVp Rh/Rh beams (total mean glandular dose about 2.5 cGy) predicted maximum CNR for 300 m calcification in 5 cm thick, 50% glandular, breast is about 1.2, below Rose's criterium for visualization for standard case. The effect that input factors might have on predictions has been evaluated. Choice between alternative spectra can affect CNR by 50%, assumed calcification composition leads to differences of 67% in calculated CNR, and assumed breast tissue composition can alter CNR by 45%; these results are weakly dependent on calcification or breast thickness, or on the assumed fraction of glandular tissue. CNR values are related to detected spectra effective energy. Calculations predict that above 37 kVp Mo/Mo beams are more energetic than Rh/Rh at same kVp, due to beam hardening. Conclusions: This work has found differences of the order of 40–70% in calculated CNR depending on the choice of any of the following model parameters: initial spectra, calcification composition, and breast tissue composition. The evaluation gives modest results for the CNR (values smaller than the Rose's criterium) in the subtracted microcalcification images using the equipment beams, but improvements could be attained by hardening the high‐energy exposure beam.
SU‐FF‐I‐75: Geometric Magnification in Digital Mammography
Authors: Tipnis S , Schueler B , Fetterly K
Published: July 2006

Purpose: The goal of this study was to investigate the effect of varying geometric magnifications on the edge definition as well as conspicuity of calcifications in images obtained using a full field digital mammography system. Method and Materials: Images of the wax insert of an ACR mammography phantom, sandwiched between two clear acrylic slabs simulating scattering in breast tissue were obtained on flat panel FFDM system at five different geometric magnifications between 1.4 and 2.2 plus a contact image. The x‐ray technique was the same for all images. All images were viewed on a soft copy work station. Observers were asked to judge the quality of the images in terms of edge definition (largest speck group) and conspicuity (two smallest speck groups) and assign a score on a scale of 1 to 4 for each speck in the group. Additionally, the system MTF was measured using the edge method at each of the magnifications in order to correlate the system response with the observer scores. The MTF was measured in the anode‐cathode (AC) direction as well as perpendicular (LR) to it. Results: The trends in the scores indicated that the conspicuity of the smallest speck group increased with magnification. The edge definition of the largest speck group was found to increase and then decrease depending on the magnification, reaching a maximum at a magnification of 1.6. This correlates well with the measured MTF in the LR direction. Conclusion: Geometric magnification improves image quality in digital mammography. Conspicuity of the smallest calcifications improves with magnification. However, this is accompanied by a decrease in the edge definition of the larger calcifications after a magnification of 1.6. The optimum magnification depends on the specific task (edge definition or conspicuity).
SU‐FF‐I‐78: Estimate Standard Uptake Value (SUV) in F18 FDG PET Tumor Imaging
Authors: Luo J
Published: July 2006

Objective: This study was to evaluate factors that may affect SUV in F18 FDG PET tumor imaging. Method: Twenty patients with single pulmonary nodules and five with multiple nodules were evaluated. Whole body scan was performed one hour post injection of 15 mCi of F18 FDG on a dedicated PET scanner (Siemens‐CTI Exact). OS‐EM reconstruction was employed. Reconstructed images were then transferred to a Siemens eSoft workstation for image display and analysis. Volume of lesion was adjusted around the hot nodule in the pulmonary area. The ROI was automatically defined by iso‐contour (10%, 25%, 35%, and 50% respectively) and used to calculate activity in Bq/ml, lesion volume and average SUV within the region. 3‐D image fusion started with manual registration based on axial, sagittal and coronal display of the PET and the CT data. The SUVs were calculated using RoI defined by 50% or 25% iso‐contour. The same RoIs were applied to dedicated PET data and to transformed image from PET‐CT fusion. Result: Average lesion size was 3.9 cm3 at 50% iso‐contour and increased to 5.9 cm3 when the iso‐contour was 10%. PET SUV measured 4.77 compared with 4.47 from PET CT fusion image with 50% isocontour and 3.36 compared with 3.79 respectively with 25% isocontour for a large lesion in right lung. Lesion volume decreased about 30%. Conclusion: Manually adjusting the iso‐contour to fit the lesion based on visual inspection on PET images demonstrated significant difference between a pre‐set threshold and image guided iso‐contour on the lesion size, activity uptake and the average SUV. Measured SUV and lesion volume (50% isocontour) decreased when the PET CT fusion image was used in comparison with dedicated PET scan.
SU‐FF‐I‐80: Monte Carlo Simulations of GSF Family Voxel Phantoms for Quantification of Renal Planar Scintigraphy
Authors: Brambilla C , Burkhardt G , Borges J , Marques da Silva A
Published: July 2006

Purpose: To analyze quantitatively the influence of different renal uptakes of ‐DMSA on the absolute index of renal function (IRF), using Monte Carlo simulated images of voxel phantoms family. Method and Materials: Four anthropomorphic phantoms of GSF family (Baby, Helga, Donna and Children) were simulated with SimSET code. The phantoms have different dimensions in the region of interest (e.g. renal depth, distance between kidneys, renal volume, body volume). Planar acquisitions were modeled using a parallel LEHR collimator. The phantoms were positioned 10 cm from the collimator. A 20% energy window was used to acquire projection onto 128 × 128 matrices. The energy resolution was modeled with a 10% Gaussian function. For each phantom, five normal and abnormal uptakes were assigned, from 50%–50% (normal) to 10%–90% (severe). The IRF was calculated using the software DMSAQuant, based on the Raynaud method. The results were compared with true activity in each kidney, known by Monte Carlo simulations. Results: The results of the IRF have shown differences between the calculated indexes and the true index. The higher deviations (75%) are associated with lower relative uptakes (10%). For relative uptakes higher than 40%, the difference between the calculated indexes and the true index remains constant between 5% and 10%. Conclusion: Our results showed that Raynaud method do not provide accurate values of the absolute IRF when lower relative uptakes are present due to renal diseases. The results have shown that the values of the absolute index of the diseased kidney are influenced by the contralateral kidney. This could be justified because the method only corrects renal depth and age. We suggest that more studies will need to be done to clarify the factors influencing the renal quantification and to model a new correction factor.

This work was supported by CNPq, Radiopharmacus and FAPERGS.