bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐03: Computer‐Aided Diagnostic Scheme for Detection of Hepatocellular Carcinoma in Contrast‐Enhanced Hepatic CT: Preliminary Results
Authors: Grelewicz Z , Suzuki K , Kohlbrenner R , Obajuluwa A , Ng E , Tompkins R , Epstein M , Hori M , Baron R
Published: April 2010

Purpose: Hepatocellular carcinoma (HCC) is one of the most common primary malignant tumors of the liver. We developed a computer‐aided diagnostic (CAD) scheme for detection of HCC in arterial‐phase hepatic CT in order to assist radiologists in their HCC detection. Materials and Methods: Our database consists of isotropic arterial‐phase CT scans of 14 patients acquired with a multi‐detector‐row CT system with a 64 channel detector scanner, which includes 16 radiologist‐determined HCCs that were confirmed pathologically. Lesion sizes ranged 6–50 mm, with a mean of 22.6 mm. We developed a CAD scheme consisting of 1) liver segmentation, using fast‐marching rough‐segmentation followed by geodesic‐active‐contour fine‐segmentation coupled with a level‐set algorithm, 2) detection of HCC candidates from the segmented liver, based on a watershed segmentation algorithm, 3) calculation of both 2D and 3D morphologic‐, intensity‐ and texture‐based features of the detected candidates, and 4) classification of HCC candidates by means of linear discriminant analysis (LDA) of the calculated features, with a stepwise feature selection method based on the Wilks. lambda and the F value. The performance of the CAD scheme was evaluated by free‐response receiver‐operating‐characteristic analysis. Results: With the candidate selection segment of the detection scheme, we achieved 100% sensitivity with 15.1 false positives per patient. Of the 254 calculated features, the stepwise LDA selected 45 “useful” features for candidate characterization. Using these 45 features, we decreased the false positive rate to 6.1 false positives per patient, with no loss in sensitivity. Conclusion: In contrast‐enhanced arterial‐phase hepatic CT, our CAD scheme achieved a 100% sensitivity in detection of HCCs with 6.1 false positives per patient. This detection scheme could assist radiologists in detecting HCCs; thus, it would potentially improve radiologists' detection sensitivity for HCCs.
SU‐FF‐I‐05: Hybrid Computer‐Aided Diagnosis System for Lung Nodules in CT‐Chest Exams
Authors: Amjadi A , Richter A , Fiebich M
Published: April 2010

Purpose: A computer‐aided diagnosis system for the selection of lung nodules in computer tomography (CT) chest studies was improved. The previous CAD scheme is based on a region‐based detection and analysis scheme. The results of this system were promising with a sensitivity of about 40 % for nodules larger 4 mm diameter and an average false positive rate of 6, tested in 88 CT studies. Material and methods: To improve sensitivity, an additional detection scheme was implemented. This method is based on a multi‐scale detection method. The image data were smoothed with a 3D Gaussian filter and computed the Hessian matrix and eigenvectors and eigenvalues for all pixels detected by the first algorithm. By analyzing the eigenvalues spherical structure can be located. For further segmentation a region growing method was implemented and further analysis of the detected structures was performed. The results of both method were combined. Results: To test the detection algorithms we used 19 CT studies. Our CAD system detected 58% of the nodules with a false‐positive rate of 16 per study. Mean computation time was 4.5 minutes on a standard PC. Conclusion: Combination of two CAD schemes improved the performance of the system significantly. More effort should be made in combining different computer‐aided diagnosis schemes for lung nodule detection in CT of the chest.
SU‐FF‐I‐06: COPDGene Study Quality Assurance Phantom
Authors: Judy P , Estepar R San Jose , Hoffman E , Lynch D ,   for the COPDGene investigators
Published: April 2010

Purpose: Image characteristics of a quality assurance phantom designed for the COPDGene Study were evaluated. The COPDGene Study is a multi‐center genome wide association study of COPD and COPD related CT phenotypes. Methods and Materials: COPDGene Phantoms were imaged using all the vendor CT scanners involved in the Study to determine the scanners. uniformity. The inspiration protocol was used: a tube potential of 120 kVp and an effective mAs of 200. The phantom consists of a elliptical foam region (250 mm by 150 mm) to simulate lung surrounded by a soft tissue ring (350 mm by 250 mm). A 30mm acrylic rod, 30mm air hole, and hole for a water bottle were present in the foam. Polycarbonate rods to simulate airways with walls were embedded in the foam. The scan data was reconstructed using several reconstruction kernels. The means and standard deviations of the 6 uniform regions were measured using regions‐of‐interest of various sizes. The 6 regions were: water, acrylic rod, air in hole, lung simulating material, soft tissue ring, and air out side phantom. The wall thickness and the lumen radius of the 6 tubes in the phantom were measured using the FWHM method. These measurements were averaged over sections that spanned about 30 mm.Results: Standard error of the CT number measurements was less than 1 HU. The CT number of the lung simulating material was −855 HU. A systematic difference between scanners was observed. The range of CT numbers was largest for acrylic, 14 HU, and smallest for water, 5 HU. No systematic variation between CT scanners for the size measurements could be demonstrated. The range of the size measurements was 0.1 mm.Conclusion: The COPDGene phantom will be useful for QA evaluations during the COPDGene Study.
SU‐FF‐I‐20: Visibility of Simulated Microcalcifications with An ASi/aSe Flat Panel Detector Based Cone Beam CT System
Authors: Shen Y , Ge S , Chen L , Yi Y , You Z , Han T , Zhong Y , Liu X , Lai C , Wang T , Shaw C
Published: April 2010

Purpose: To investigate the visibility of microcalcifications (MCs) with an aSi/aSe flat panel detector (FPD14, Anrad Corporation) based cone beam CT (CBCT) system. Method and materials: A bench top experimental CBCT system was configured for breast imaging and used to image a breast phantom with embedded simulated MCs of various sizes. A paraffin cylinder with a diameter of 135 mm and a height of 40 mm was used to simulate a 100% adipose breast. Calcium carbonate grains, ranging from 125 to 425 μm in size, were used to simulate the microcalcifications. 25 MCs from same size group were arranged into a 5 × 5 cluster and embedded at the center of a 15 mm diameter paraffin rod to make an MC insert, which may be inserted into a hole at the center of the breast phantom for imaging. The breast phantom with MCs was scanned at various exposure levels. 300 projection images were acquired over 360° and reconstructed with Feldkamp's backprojection algorithm using a ramp filter. The images were reviewed by 6 readers. The ratios of visible MCs, averaged over all readers, were plotted as the function of the square root of measured dose level and image signal‐to‐noise ratio (SNR). Results: It was found that 90% visibility was achieved for 224 – 250 μm calcifications at an SNR of 16.8 or an isocenter dose of 5.2 mGys. 70% visibility was achieved for 224 – 250, 212 – 224, 200 – 212, 180 – 200, 160 – 180, 150 – 160 and 124 – 140 μm calcifications at an SNR of 16.8, 16.8, 25.1, 25.1, 44.5, 44.5 and 52.6, respectively. Conclusions: Percentage of visible MCs increased with the image SNR and isocenter dose. Higher SNRs and isocenter dose are required for imaging smaller MCs.
SU‐FF‐I‐25: Quantitative Analysis of the Influence of KV Beam Characteristics and Image Acquisition Parameters On Image Quality in Cone‐Beam CT
Authors: Samant S , Gopal A
Published: April 2010

Purpose: Image quality in cone‐beam CT (CBCT) imaging is influenced by a variety of factors associated with the selection of image acquisition parameters like kVp, tube current, field size, beam filter, number of projections, and reconstruction filter. An improper selection of scan protocols may lead to unoptimized image quality and unnecessary dose to the patient. Therefore, a rigorous study of CBCT image quality and its dependence on beam characteristics is vital. In this work, the relative influences of pertinent image acquisition parameters are evaluated for a clinical Elekta XVI CBCT system. Method and Materials: Image quality measurements were conducted using a conventional CatPhan phantom, wherein the line‐pair bar inserts and uniform slices were used to characterize spatial resolution and noise via modulation transfer function (MTF) and noise power spectrum (NPS) respectively for several combinations of kVp/current, field size, beam filters, and gantry rotation arcs. CTDI dose estimates were also acquired for each scan protocol. Overall image quality was evaluated in terms of the detective quantum efficiency (DQE), obtained from MTF and NPS spectra and normalized using the CTDI doses and a fluence — CTDI dose conversion factor obtained from Monte Carlo simulations. Results: The MTF, NPS and DQE measurements indicated that overall image quality was severely affected by the increased scatter from larger field sizes, and from the use of incomplete projection arcs. The use of beam filters led to some reduction in scatter and improved image quality, while also reducing patient dose. Conclusions: The image quality measurements indicated that the appropriate choice of scan parameters can lead to improved image quality and sparing of patient dose. However, more detailed investigations may be necessary to optimize CBCT image quality, including a better choice of beam compensators and possible use of anti‐scatter grids.
SU‐FF‐I‐40: Proton Computed Tomography Reconstruction Using Compressed Sensing and Prior Image Constrained Compressed Sensing
Authors: Wang DX , Mackie TR , Tome WA
Published: April 2010

Purpose: To study the feasibility of proton computed tomography (CT) reconstruction using compressed sensing (CS) and prior image constrained compressed sensing (PICCS). Proton CT images can be used for pre‐therapy planning, image guidance and registration verification. Method and Materials: Projections of 200 MeV proton beams onto an ellipsoid phantom was simulated using Geant4 Monte Carlo simulation toolkit. The position and energy of the entrance and exit protons were recorded. Straight‐line path (SLP) estimation was used to represent proton paths, and simultaneous algebraic reconstruction technique (SART) with CS was used to reconstruct a proton stopping power image for a 2‐mm thick slice of the phantom. PICCS was used to reconstruct the image from highly undersampled data with an accurate and well‐registered prior image. A Gradient transform was used to yield a sparse data set for CS and PICCS. Results: SART with CS reconstructed a 320×320 proton stopping power image of the central slice of the phantom after 10 iterations. A proton/pixel ratio of 0.2 is sufficient to reconstruct an image of correct geometry. The average proton stopping power of the reconstructed materials cortical bone, water, and air were found to agree with the expected values from ICRU Report 49 within 8.3%, 0.6%, and 3.8% respectively. Employing a prior image and PICCS in the reconstruction, a proton/pixel ratio as low as 0.05 was found to be sufficient, and the reconstruction time of less than 2 minutes was achieved using a serial algorithm. Reconstruction artifacts in the images were minimal. Conclusion: With CS, or with PICCS plus a prior image, SART can reconstruct a proton CT image of good quality within minutes. This paves the road to a clinically feasible approach toward low‐dose pre‐proton therapy treatment planning and image guidance using a fast‐reconstructed proton CT image with a well‐registered kV‐CT prior image.
SU‐FF‐I‐42: Improving Noise Uniformity in Volumetric CT Via ROI‐Based Weighting Scheme in Cone Beam Image Reconstruction
Authors: Tang X
Published: April 2010

Purpose: To present an ROI‐based weighting scheme for cone beam image reconstruction to improve noise uniformity. Method and Materials: In CT imaging, the noise in near‐iso area is significantly larger than outer area. The root cause of this phenomenon is that the system transfer function of backprojection is reversely proportional to the iso‐distance of pixels to be reconstructed. Though this phenomenon is intrinsic and has been observing since the advent of CT imaging, we address this undesired noise non‐uniformity by extending the 3D weighted cone beam filtered backprojection (CB‐FBP) algorithm that has been previously published by us. As demonstrated previously, the noise level of images reconstructed by the 3D weighted CB‐FBP algorithm monotonically increases with the strength of 3D weighting. In addition to its dependence on view angle, orthogonal iso‐distance and cone angle, the extended 3D weighting scheme integrates a dependence on the iso‐distance of pixels to be reconstructed, i.e., the larger the iso‐distance, the stronger the weighting. Consequently, the noise at near‐iso area is reduced while that at outer area is increased. Results: The helical body phantom (HBP) simulated by computer is employed to evaluate the performance of the extended 3D weighting scheme to improve noise uniformity, in which 128 detector rows corresponding to 8.46 degree cone angle is assumed. The results shows that, with the integration of dependence on the iso‐distance of pixels to be reconstructed, the extended weighting scheme can improve noise uniformity by more than 30%, while its efficacy in suppressing artifacts caused by longitudinal truncation can be retained. Conclusion: The intrinsic noise non‐uniformity in CT images can be improved significantly using the ROI‐based 3D weighting scheme proposed in this study. It is believed that, the extended 3D weighting scheme can find its applications in the pursuit of clinical excellence using volumetric CT as the modality.
SU‐FF‐I‐48: Optimization of Image Acquisition Parameters for Patient Setup Using Megavoltage Cone‐Beam Digital Tomosynthesis
Authors: Descovich M , Kanner M , Morin O , Faddegon B , Cheung J , Sawkey D , Aubin M , Maltz J , Bani‐Hashemi A , Pouliot J
Published: April 2010

Purpose/Objective(s): Digital Tomosynthesis (DT) is an imaging technique for reconstructing multiple tomograms from 2D projections acquired over a limited gantry arc (20°–40°). This study evaluates the use of megavoltage cone‐beam (MVCB) DT images acquired with a high contrast imaging beam line for patient setup. The objective is to determine the optimal parameters (gantry arc, imaging dose) resulting in the least dose to normal tissue while maximizing the positioning accuracy, as compared with MVCBCT. Method and Materials: Coronal and sagittal DT tomograms of prostate (3), head and neck (2), spine (2) and lung (2) patients were reconstructed from a limited subset of projection data, and registered to the planning‐CT. The translational shifts required for patient alignment were calculated and compared with those provided by MVCBCT‐CT registration. The registration was guided by gold markers for prostate patients, bony landmark for head and neck and spine patients, bones and air cavities for lung patients. Online DT images were acquired on an anthropomorphic female thorax phantom to evaluate the applicability of DT imaging to breast patient setup. The imaging dose was measured with thermoluminescent dosimeters on the ipsilateral and contralateral breast. The measurements were compared with dose calculations. Results: DT provides positioning accuracy comparable to CBCT, with positioning difference of ⩽0.1 cm for prostate patients and ⩽0.3 cm for the other sites. Forty degrees arc DT provides the best alignment precision. Phantom studies show that DT images acquired with doses as low as 0.3 cGy are suitable for patient alignment, and the dose to the contralateral breast is negligible. Conclusion: DT is a viable alternative to CBCT for patient setup. Due to the low imaging dose and the sparing of the contralateral breast, DT has potential in breast patient setup.

Conflict of Interest: Research sponsored by Siemens OCS.
SU‐FF‐I‐52: Comprehensive CT Dosimetry Database for Pediatric and Adult Reference Males and Females: A Monte Carlo Study
Authors: Lee C , Kim K , Bolch W
Published: April 2010

Purpose: To establish an organ dose database for pediatric and adult male and female reference individuals undergoing computed tomography (CT) examinations and to develop software providing the dose information within a graphical user interface (GUI). Methods and Material: A series of hybrid computational human phantoms was developed at the University of Florida by using realistic patient CT images and flexible Non‐Uniform Rational B‐Spline (NURBS) surfaces. The phantoms include newborn, 1, 5, 10, 15, and adult male and female matched to the four reference data: reference organ mass from ICRP Publication 89, anthropometric data from CDC, tissue composition from ICRU Report 46, and intestine models of ICRP Publication 100. The 12 reference phantoms were ported into MCNPX2.5 code where helical fan beams from SOMATOM Sensation 16 helical multi‐slice CT scanner were modeled. Organ absorbed doses were calculated for Head, Chest, Abdomen, Pelvis, CAP examinations. Software was developed to provide the dosimetry database with GUI. The scanner matching algorithm was employed from the commercial software CT‐EXPO to take different scanner parameters from different scanner models into account. Results: Normalized values of organ absorbed dose (mGy/100 mAs) were calculated for 25 organs in the 12 phantoms undergoing CT examinations were calculated. The comprehensive CT dose database was incorporated into GUI‐supported software to provide realistic and consistent dosimetry information to end‐user. The dose results were compared with those from CT‐EXPO and significant differences were shown in major organ absorbed doses which were mainly caused by the anatomical difference between UF hybrid phantoms and limited stylized and old voxel phantoms in CT‐EXPO. Conclusion: The software developed in this study significantly improved accuracy and consistency of organ dose assessments in CT examinations which have not been implemented in a couple of previous CT dose evaluation software.

This work is funded by the NCI Radiation Epidemiology Branch
SU‐FF‐I‐73: Automated Analysis of Contrast Detail Phantom Images for Quality Control
Authors: Jingu R , Ohki M , Arimura H , Morishita J , Toyofuku F , Higashida Y
Published: April 2010

Purpose: A contrast detail (CD) phantom is used for quality control of X‐ray imaging systems. However, the observation of CD phantom images is time‐consuming, and there are intra‐ and inter‐observer variations in quality assessment. Therefore, we attempted to develop an automated approach for analysis of contrast detail phantom images for quality control of X‐ray imaging systems. Method and Materials: A CD phantom (Kyoto‐Kagaku Co.) with similar signals to the CDRAD phantom (Artinis Medical Systems) was used in this study. The CD phantom images were obtained by a computed radiography (CR) system under the condition of chest radiography (120kV, 6.4mAs). Five CR images with various image qualities were prepared by changing the thickness of plexiglass plates with the CD phantom, and evaluated by five observers on a liquid crystal display for medical use. The automated analysis program provided the CD curve and the image quality figure (IQF). The size of circular region of interest (ROI) was adjusted to each signal in CD phantom image for increasing the signal detection. Results: In all images, the computerized analysis showed higher signal detection than human observers. In the case that the plexiglass plate with 8 cm thickness was used, the IQF obtained by a computer was 5.5, which was superior to the averaged IQF, 4.0±0.3 by human observers. There was no variation in evaluation by the computer, whereas there were remarkable variations among human observers. A strong correlation (R = 0.91) between computed analysis and human observers was shown in the IQF. Conclusion: The automated analysis program provides a fast and objective evaluation of CD phantom images for quality control.
SU‐FF‐I‐75: Verification of Reported DLP for Philips Brilliance CT Scanners
Authors: Scott A , Merrill R , Wu X
Published: April 2010

Purpose: Recent concerns about accumulated radiation dose and collective risk prompted a check of the software reported CT dose index (CTDIVol) and dose‐length‐product (DLP) of the Philips Brilliance CT scanners. The CTDIVol and the DLP were measured for comparison with the reported values using the high‐resolution chest protocol (commonly used for COPD). Method and Materials: A Philips Brilliance 40‐slice CT scanner was used with the high‐resolution chest protocol, which has a technique of 120 kVp and 200 mAs/slice, a detector collimation of 2×0.625 mm, a reconstructed scan thickness of 1.25 mm, and a table increment of 10 mm. Measurements were made using a cylindrical Lucite phantom 32 cm in diameter and 15 cm in length, with axial holes drilled in the center and near the surface at 90 degree intervals. The radiation dose was measured using a Keithley electrometer and a 10 cm pencil chamber. Dose measurements were made along the phantom's center axis and along its surface. Results: While the dose measurements are consistent with the reported CTDIVol, a serious error was discovered in the reported DLP. The reported value appears to be calculated as the product of the CTDIVol multiplied by the number of shots (16) and the collimation width (1.25 mm) while the correct formulation of DLP is the CTDIVol multiplied by the scan length (151 mm). This results in an underestimate of dose by a factor of 8. Conclusion: Accurate estimates of radiation risk require correct reporting of the effective dose, which is related to DLP. We have verified that the Philips 64‐slice also has the same error and it is possible that other Philips protocols with a large table increment relative to the slice width will too. A physicist should verify that the DLP reported is consistent with actual measurements.
SU‐FF‐I‐79: Development of The Practical Guidelines of PET‐CT Quality Control
Authors: Kwang K , Lee B , Choe J
Published: April 2010

Introduction: Positron emission tomography combined with computed tomography (PET‐CT) provides both functional and anatomical images of high quality noninvasively. Recently, increase in the use of PET‐CT for diagnosis of the cancer and the planning of radiation therapy accrues the demands for accurate evaluation of system performance and well designed programs of quality assurance. We analyzed the quality assurance practice in the PET‐CT laboratories and developed the practical guidelines of PET‐CT quality assurance. Methods: The survey questionnaire were send to 60 PET‐CT laboratories and the data of quality assurance practice were collected. We reviewed the surveyed data and the quality assurance systems of foreign counties and made the practical guidelines of PET‐CT quality assurance. Results: The developed practical guidelines of PET‐CT quality assurance consists of practical items of performance evaluation and protocols for quality assurance. For 30 PET‐CT laboratories, we are investigating the usefulness of the new guidelines. Conclusions: We developed the new practical guidelines of PET‐CT quality assurance. These guidelines could be used to guarantee the confidence of PET‐CT imaging as a quality assurance keeper.
SU‐FF‐I‐91: A Fast and Robust Dynamic Tracking Method of the Moving Deformable Targets in the Fluoroscopy Image Sequence for Image Guided Radiotherapy
Authors: Yang L , Jabbour S , Zhou J , Haffty B , Foran D , Yue N
Published: April 2010

Purpose: To develop a robust dynamic tracking technology on the continuously acquired fluoroscopy for precise positioning of a moving deformable target volume in the 3D conformal radiotherapy (3DCRT). Method and Materials: A novel one‐step forward prediction based collaborative trackers are utilized to achieve both temporal consistency and failure recovery in dynamic tracking of the fluoroscopy image sequence. The robustness to complex background and weak edges is obtained from the learned discriminative detector and boundary classifiers. The temporal consistency is preserved by the template tracker. Instead of building specific models for different organs or different imaging modalities, all the major steps in this algorithm are based on learning. Results: This technology was tested and evaluated on clinically acquired fluoroscopy of patients who were under radiation therapy treatments. The tested data sets consisted of three complete sequences of the fluoroscopy lung image on which the target volumes not only moved but also changed in shape and size. As demonstrated in the supporting materials, the method can successfully track both the tumors located in the thorax and upper abdomen, even though they exhibited significant respiratory induced motions and deformation. Moreover, the tracking speed is comparable to the refreshing rate of fluoroscopy with non‐ observable lagging time. Conclusion: The one‐step forward prediction based collaborative tracking technology has been successfully applied on the continuously acquired fluoroscopic images to track the movement and shape change of the deformable target. With the current computer technologies, this process can be automated with minimum to none human intervention. This technology has significant potentials in the gated radiotherapy and can be used to control the beam‐on timing and gating window. This study is supported by Varian medical system.
SU‐FF‐I‐94: Study of Image Registration Methods Based On the Pelvic Bone and Its Contour for Prostate Cancer Treatment
Authors: Qi P
Published: April 2010

Purpose: Because of different imaging contrasts in the MVCBCT and the planning CT, image registration between the two modalities may introduce additional uncertainties in image guided radiotherapy (IGRT). For a group of ten prostate patients concurrently treated with the pelvic lymph nodes, we compared two alignment methods: one directly aligns the pelvic bone from the MVCBCT to that of the planning CT; the other aligns the pelvic bone from the MVCBCT to the contour of the pelvic bone from the planning CT. Method and Materials: On the first day of treatment, the treatment positions for all patients were verified with an extended field of view (FOV) MVCBCT to include the entire pelvic bone. Subsequently, the reduced FOV‐MVCBCT was used daily to localize the prostate with implanted markers. Only the FOV‐MVCBCT was used to identify uncertainties in patient positioning. For each patient, the MVCBCT was manually registered with the two alignment methods. Each alignment method was repeated three times by a single observer in three separate times. Results: For each patient, the difference of mean shift along the left‐right (X), anterior‐posterior (Y), and inferior‐posterior (Z) directions was small between two alignment methods. The mean standard deviation of 10 patient measurements for the contour based and bone based registration were 0.6 mm vs. 0.7 mm, 1.2 mm vs. 1.2 mm, and 0.6 mm vs. 1.6 mm along the X, Y, and Z directions, respectively. Particularly, more large deviations (> 2mm), 4 out of 10 patients, were observed in the Z direction with the bone based registration method. Conclusion: The contour based image registration method achieved more consistent measurement than the bone based registration in verification of the treatment position for prostate patients concurrently treated with pelvic lymph nodes.

Research is supported by Siemens Corporation.
SU‐FF‐I‐95: Sensitivity of Biological Correlations to Different Registration Parameters
Authors: Yip S , Jeraj R
Published: April 2010

Purpose: Determining spatial correlation between biological phenotypes is important for understanding tumor biology necessary for biologically‐based radiotherapy or treatment assessment. Inaccurate image registration is one of the major uncertainties in determining such correlation. This study aims to investigate the sensitivity of correlation between different biological phenotypes to different registration techniques and parameters. Method and Materials: Seven HNSCC patients underwent PET/CT imaging with [18F]FDG, [18F]FLT, and [61Cu]CuATSM imaging to assess multiple biological phenotypes— metabolism, proliferation, and hypoxia respectively. Rigid and deformable registrations with various set of parameters (included similarity measures, optimizers, and resampling schemes) were performed on both CT and PET images sets for tumor co‐registration. Correlation was measured by the correlation coefficient (CC), which was calculated based on registered tumor regions. Differences among CCs and joint histograms with respect to different registration techniques and parameters were used to quantify the sensitivity of image correlations. Results: Correlations were rather sensitive to similarity measures. Normalized Mutual Information exceeded Euclidean and Correlation measures with CCs of 0.25 and 0.19 respectively. Varying resampling schemes had no significant effect on the correlation as changes in CC were <0.03. More moderate changes were observed when different optimizers were varied (differences in CC were <0.15). In addition to the optimization parameters, the choice of the manually segmented registration region had a significant effect on the overall level of correlation. Deformable registration of CT occasionally introduced unnecessary tumor size variation thus leading to lower CC than rigid registration by as much as 0.16. Conclusion: Correlations between different phenotypes of tumors are most sensitive to similarity measures and registration techniques (includes rigid and deformable registration). Uncertainty in the correlations is mainly due to misregistration of different biological representations of tumor. Uncertainty can be reduced with more precise segmentation of the registration region, which contains only tumor.
SU‐FF‐I‐99: Multi‐Level Regularization Approaches of Non‐Parametric Deformable Registrations
Authors: Kuo H , Mah D , Wu A , Chuang K , Hong L , Yaparpalvi R
Published: April 2010

Purpose: Most deformation algorithms using a single value smoother during optimization. We investigate multi‐level regularizations (smoothers) during the multi‐resolution iteration of two non‐parametric deformable registrations (symmetry demon (SD) and diffeomorphic (DM) algorithms) and compare to a conventional single value smoother. Method and materials: Smoothers were applied at 5 different levels of multi‐resolution image registration process. Results were compared in terms of convergence rate, similarity measures (mean square error MSE and normal correlation NC), and Jacobian determinant of the vector displacement field (VDF), which measures how a voxel volume changes after registration. Six patients (mean 400×300×70 pixels) with large internal organ movement (five from 4DCT, one patient who was scanned with full and empty bladder) were evaluated in this study. The liver and lung displacement and bowel movements were approximately 1.5cm. The bladder volume changed by > 250cm3. Results: As smoothers increase their convergence rate decreases, however, smaller smoothers also have large negative value of the Jacobian determinant suggesting that the one‐to‐one mapping has been lost; i.e. image morphology is not preserved. In the SD method, the multi‐level smoother calculates faster than the large single value smoother and is equivalent to the smallest single value smoother. For the DM algorithm, since our multi‐level smoothers were implemented at the smoothing matrix (S) and the update field (U), calculation times are longer. The similarity measured by MSE, NC, and visual comparisons show that the multi‐level implementation has better results than large single value smoothers, and better or equivalent for smallest single value smoother. Conclusion: Multi‐level regularization combined with multi‐resolution has the advantage of preserving the morphology of the images and the registration results.
SU‐FF‐I‐102: Investigation of CT/MRI Fusion Error for Prostate IMRT
Authors: Li J , Chen L , Shan G , Ma C
Published: April 2010

Purpose: Both CT and MR images are used for target delineation in many institutions for prostate IMRT treatment. The uncertainty of prostate registration between these two sets of images caused by the image fusion process will affect the accuracy of the target delineation. The magnitude of image fusion error and its effects on target delineation were investigated. Materials and Method: For this study, both CT and MR T2 images were taken for prostate patients treated with low dose rate brachytherapy for dosimetry evaluation three weeks after the seed implant. MR images were usually taken within 30 minutes following the CT scan. CT and MR images were fused based on bony structures and some soft tissue land marks that were visible on both images. Image fusion errors were examined by checking the positions of the implanted seeds (two seeds at the prostate base and two at the apex) on both CT and MR images for 30 patients. The differences of seed positions between CT and MR images were analyzed and the mean and the standard deviation were calculated. Results: The differences of seed positions were clearly visible after the CT and MR images were carefully fused based on bony structures and visible soft tissue land marks. The mean of the difference is 1.6mm and the 1σ standard deviation is 1.4mm for these 30 patients. The median value is 1.5mm and the maximum difference is up to 8.1mm. This error will be transferred to the target delineation if only MR images were used for contouring and the CT images were used for IMRT planning. Conclusions: Image fusion errors can contribute significantly to the target delineation error that can not be ignored when designing the treatment margin for advanced prostate treatment especially for target localization based on implanted fiducials.
SU‐FF‐I‐106: Volume Viewer: A Segmentation and Surface Reconstruction Toolset for Non‐Transverse Image Planes
Authors: Abraham C , Low D , Sowell R , Gokhroo G , Grimm C , Ju T , Liu L
Published: April 2010

Purpose: To develop novel segmentation software that allows users to segment regions of interest and reconstruct three‐dimensional surfaces using non‐transverse image planes. Method and Materials: To date the manual segmentation process in radiation oncology has been performed on consecutive transverse computed tomography (CT) image planes. This method of contouring provides little information about the ends of a structure and is poorly suited for structures whose longitudinal axis lies oblique to the transverse plane. Due to these limitations it has been illustrated that the segmentation of structures using only transverse planes is prone to error and time consuming in nature. We hypothesize that the intelligent selection and use of non‐transverse image planes will reduce observer error and the time burden of the segmentation process. At present few treatment planning systems offer segmentation in non‐transverse planes. The development of this software has four phases: 1) Navigation and segmentation toolsets. 2) Segmentation validation. 3) Curve and vertex processing. 4) Three‐dimensional surface reconstruction. Results: The first and fourth phases are complete. Phases two and three are currently underway with data from a user study illustrating process improvements to be addressed by our software. Our initial results are promising and indicate that it is possible to generate accurate surfaces with a significant reduction in the segmentation burden. Conclusions: The current method of manual structure segmentation is not ideal and represents a significant bottleneck in the treatment planning process. This software promises to improve the accuracy and efficiency of the segmentation process through the use of non‐transverse image planes. While this software was specifically developed to improve the segmentation process, we feel the use of non‐transverse image planes is directly applicable to segmentation and dose distribution review.
SU‐FF‐I‐115: Physical Characteristics of a New Flat‐Panel Digital X‐Ray Detector
Authors: Cho H , Kim H , Park H , Lee C , Yu A , Kim D , Lee Y
Published: April 2010

Purpose: We have characterized a new flat‐panel digital x‐ray detector. Physical characteristics of new flat‐panel detector has been measured and evaluated by using previous flat‐panel detector as the reference method. Method and Materials: The new flat‐panel detector has a pixel size of 0.168mm and detecting area of 17″ × 17″. The previous flat‐panel detector has a pixel size of 0.139mm and detecting area of 14″ × 17″. The modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the two systems were measured. For these two detectors use RQA5 radiographic condition. The MTF of the detectors were evaluated using slit method. The NPS were measured by two‐dimensional Fourier analysis of center portion of the averaged image. The DQE were assessed from the MTF, the NPS, given exposure and photons per mm2‐mR. Results: For the new flat‐panel detector, the MTF at 3cycles/mm which is Nyquist frequency of new detector was measured as 55%. The maximum DQE value at spatial frequencies between 0 and 1cycles/mm was 55% for the new flat‐panel detector. For the previous flat‐panel detector, the MTF at 3cycles/mm was measured as 59%. The maximum DQE value at spatial frequencies between 0 and 1cycles/mm was 50% for previous flat‐panel detector. The MTF of a new flat‐panel detector was slightly lower than that of a previous flat‐panel detector. The NPS curves of the two detectors were generally similar at the wide range of the spatial frequencies. For the DQE of the new flat‐panel detector was also similar with previous flat‐panel detector at frequency above 1cycles/mm. However, in the frequencies below 1cycles/mm, new flat‐panel detector was higher than previous flat‐panel detector. Conclusion: The new flat‐panel detector is able to provide good imaging performance in the detection of low contrast objects.
SU‐FF‐I‐124: Automatic Identification of Water and Fat Images From a Symmetrically‐Sampled Dual‐Echo Dixon Technique
Authors: Ahmad M , Liu Y , Slavens Z , Low R , Merkle E , Hwang K , Vu A , Ma J
Published: April 2010

Purpose: Dixon techniques can produce useful separate water‐only and fat‐only images. Correct automatic identification of water and fat images after they are separated is a necessary requirement for proper image annotation and archival. Previously, the difference between the signal intensity histograms of water‐only and fat‐only images has been exploited for image identification. Here we demonstrate a more robust method that is based on the intrinsic asymmetry between the water and fat chemical shift spectra. Method and Materials: A total of 131 patient datasets (each containing approximately 100 separated water‐only and fat‐only image pairs) were randomly selected from different scanners. The proposed method is based on the observation that while water spectrum is a single peak, the fat spectrum is approximately bi‐modal and contains a secondary peak near water resonance. Further, the method exploits the fact that most in vivo tissues are either water‐dominant or fat‐dominant. As a result, pixels with only fat will in general have non‐zero signal intensity in the water‐only image. In contrast, pixels with only water will have zero intensity in the fat‐only image. A simple statistical parameter was calculated from the pair of the water‐only and fat‐only images and used to decide which of the two images is water and which is fat. Visual identification was used as the gold standard. Results: The spectrum based image identification method was correct in 98% of the 13496 total image pairs. In comparison, a pure histogram based algorithm had a success rate of only 41.5%. When applied to only the central 90% of the slices for all image datasets, the new method easily achieved a 100% success rate. Conclusion: In comparison to a pure histogram based method, the new method is shown to be much less susceptible to variations in scanning protocols, patients, and the injection of contrast agents.
SU‐FF‐I‐125: Assessment of Inter and Intra‐Scanner Variation in Diffusion Tensor Imaging Using the ACR Phantom
Authors: Pasciak A , Wang J
Published: April 2010

Purpose: Diffusion Tensor Imaging (DTI) has become a widely used MRI sequence to assess patient response to many forms of therapy. In order to track small changes in patient DTI parameters in a clinical setting, knowledge of inter‐scanner and intra‐scanner variations is necessary to insure that a perceived patient therapy response is statistically significant. Ideally, inter and intra‐scanner variations should be determined from a large sample of healthy patients so that scanner specific effects can be quantified. However, this type of analysis is not practical in most institutions. Because of the lack and availability of DTI phantoms which closely model typical pathology, we will assess the usefulness of the MRI ACR phantom for this application. Method and Materials: Clinical DTI acquisitions were performed using the ACR phantom on 8 GE scanners (two 3T and six 1.5T) using an 8‐channel head coil at M.D. Anderson Cancer Center to assess inter‐scanner variations. Repeated acquisitions were also performed at each scanner to assess intra‐scanner variations. DTI image sets were analyzed using several ROIs in homogeneous regions of the phantom. Axial profiles were obtained for each ROI in each scan for several DTI parameters. Results: We have compared several DTI parameters obtained from our scans of the ACR phantom to published patient measurements as well as patient data gathered from our own institution and found that the ACR phantom is quite viable for quantification of inter and intra‐scanner variations in DTI measurement. Conclusion: This work suggests that the widely available ACR phantom may be useful for assessing DTI variability between scanners. With this information, it may be possible for institutions to schedule consecutive DTI acquisitions for a single patient on scanners which behave similarly, limiting the effects of inter‐scanner variations on physicians' ability to assess therapy response.
SU‐FF‐I‐127: Properties Evaluation of a New MRI Contrast Agent Based On Gd —Loaded Nano Particles Coated with Two Different Nano Materials
Authors: Riyahi‐Alam N , Behrouzkia Z , Jahromi S Haghgoo
Published: April 2010

Objective: The aim of this study was performing the properties evaluation of two novel emulsions composed of a) silicon‐based nanocomposite polymer(NCP) and b) Diethylene glycol (DEG) based coating material both loaded with gadolinium(III) oxide nanoparticles. The contrast enhancement evaluation of Gd loaded nanoparticles in comparison with Magnevist(Gd‐DTPA), indicated that gadolinium‐nanocomposite polymer emulsions(Gd‐NCPE&Gd‐DEG) could produce a good MR signal and therefore could be useful potential contrast mediums for cell tracking in magnetic resonance molecular imaging(MRMI). Materials and Methods: This study was involved with nanoparticles composed gadolinium (III) oxide (Gd2O3), a) emulsified with a silicon‐based nanocomposite polymer, POSS‐PCU (Polyhedral oligomeric silsesquioxane‐poly(carbonate‐urea)urethane) and b) capped with Diethylene glycol (DEG) by polyol method starting from of Gd2O3 large particles, leading to Gd2O3 nano size capping with polymers. The size and morphological structure of these nanoparticles determined by particle size analyzer(zeta sizer) and Transmission Electronic Microscope(TEM). Proton relaxation times were measured with a 1.5‐T MRI siemense scanner. The measurements were performed in aqueous solution. Results: The results showed a significantly higher incremental relaxivity for nanoparticles compared to Gd‐DTPA in concentrations ⩽1.5mM. In such concentrations, the slope of r1 relaxivity(1/T1) vs. concentration curve of Gd‐DTPA and were 4.33, 7.98 s−1 mM−1. The slope of r2 relaxivity(1/T2) vs. concentration curve of Gd‐DTPA and were 5.06, 13.75 s−1 mM−1. Conclusion: The study indicates the possibility of obtaining high relaxivity compared to Gd‐DTPA using Gd2O3 as contrast agent. Keywords: Gd2O3 Nanoparticle, nanocomposite polymer, MRI Contrast Agents, Relaxivity.
SU‐FF‐I‐131: High Spatial Resolution 1H Magnetic Resonance Spectroscopic Imaging Of Human Breast Cancer At 3T
Authors: Feng W , Wu W , Hua J , Jiang Q , Xuan Y , Hanson R , Hu J
Published: April 2010

Purpose: To demonstrate the feasibility of high spatial resolution 1H magnetic resonance spectroscopic imaging (MRSI) of human breast cancer in a clinical setting at 3T. Method and Materials: The pulse sequence consists: outer volume pre‐saturation (OVP), independent CHESS pulses for water and lipid suppression, and standard PRESS pulse sequence with an elliptical weighted k‐space sampling scheme. Ten patient studies were performed in a 3.0 Tesla whole‐body clinical imager (Siemens Trio). A four‐channel breast coil (two for each breast) was used for both MRI and MRS. Patients lay prone with their breasts in the coil wells; when possible, gentle breast compression was applied to minimize motion. After global shimming, clinical DCE‐MRI was performed which defined the volume of interest for MRSI. Data processing consisted of line broadening, standard fast Fourier transformations, and phasing. Results: All ten studies were technically successful. The spectra were acquired with FOV = 120×120mm2; TR of 1500ms, TE of 80ms, slice thickness of 14mm, and 24×24 elliptical weighted k‐space sampling with 2 averages for total acquisition of 11.9minutes. All spectra are good in spectral quality, and Cho signals are clearly visible in the MRI‐lesion area, consistent with malignancy, while there was no detectable Cho in the control area. Interestingly, the distribution of Cho signal was nonuniform across the MRI lesion. Conclusion: To our knowledge, this is the first 2D/3D MRSI study of human breast cancer with short TE (less than 135ms) at 3T and highest spatial resolution (up to 0.25cm3) to date. In summary, we have presented a robust technique for high spatial resolution in vivo 1H MRSI of human breast cancer that uses the combined advantages of high field, short TE, multi‐voxel, and high spatial resolution itself to overcome shimming and lipid suppression difficulty, and demonstrated its potential for routine clinical examination.
SU‐FF‐I‐133: Assessing the Magnetic Resonance Imaging Performance of Gadolinium‐Hyaluronic Acid Polymer Contrast Agents in Phosphate Buffered Saline
Authors: Kasraie Nima , Clarke G , Oviatt H
Published: April 2010

The aim was to investigate HA as a potential contrast agent for first‐pass myocardial perfusion imaging*, and to assess the imaging performance of gadolinium‐hyaluronic acid (HA) polymer complexes from HA‐ligand constructs by determining the proton longitudinal relaxivities and accurate relaxation rates in saline solutions at 10.72 MHz. Imaging of same solutions in well defined dialysis tubing at 3T using a constructed phantom was then used to measure the rate of diffusion to determine if the Gd‐complex polymer conjugate would have a sufficiently large hydrodynamic size to prevent immediate perfusion through vascular wall‐like conditions to account for leaks from the intravascular to interstitial space.

Samples denoted as HW02‐18 Sample A and HW02‐18 Sample B were successfully prepared by coupling an amine functionalized DTPA with HA via EDC/NHS coupling methods. These produced the highest relaxation rates and relaxivities at 10.72 MHz compared to the other preparation methods. Twenty four hours post‐injection, Gadodiamide showed a signal to noise ratio of unity, while HW‐147 continued to retain some degree of contrast relative to the background. The slope of the logarithmic fit corresponding to HW01‐147 was estimated at −0.006 compared to −0.01 of Gadodiamide, a much steeper drop indicating smaller molecular size and faster perfusion rate across the dialysis membranes. This is demonstrative of the Gd ion's relative freedom to influence the R1 of extracellular water molecules, while the molecular size of the Gd‐polymer complex has a molecular radius that is sufficiently large to prevent vascular‐like perfusion. This is a necessary prerequisite for HA bound Gd as a contrast agent for first‐pass myocardial perfusion imaging.