bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐36: Cone‐Beam Artifact Reduction in Wide Collimation Pediatric Head Imaging
Authors: Dhanantwari AC , Patel R , Shechter G 
Published: November 2011

Purpose: Cone‐beam artifacts can be a significant contributor in the degradation of brain image quality. The purpose of this study is to evaluate the frequency split cone‐beam reduction reconstruction algorithm as a means of improving IQ in brain imaging. The design of the frequency split filters and their effect on image quality and noise are evaluated. Also the potential of increasing the x‐ray beam collimation and reducing total scan time for head imaging is investigated. Method and Materials:Head scans from Philips iCT 256 slice and Brilliance 64 scanners, and simulations based on the Philips iCT 256 slice scanner were used in this study. The scans were reconstructed using conventional reconstruction techniques and frequency split reconstruction. The level of cone‐beam artifacts introduced when using larger beam collimations and the effectiveness of frequency split reconstruction for reducing cone‐beam artifacts were investigated. Also, the effect of the filters parameters in frequency split reconstruction on image quality and on noise texture were evaluated. The pediatric head IQ from the clinical data sets, and especially the delineation of the bone‐brain boundary and contrast detail in the posterior fossa, were evaluated. Results: Review of images reconstructed with frequency split reconstruction show significant reduction in the level of cone‐beam artifacts. Clinical images show significant improvements in uniformity and contrast in the posterior fossa. Improvement in image uniformity of up to1 5 HU has been realized by frequency split reconstruction. With proper design of frequency split filters, the change in image noise and NPS and can be minimized while achieving significant reduction of cone‐beam artifacts. Conclusions: Cone‐beam artifacts can be a significant contributor to image artifacts. The optimized frequency split reconstruction algorithm realizes significant IQ improvements in heads imaging. The frequency split cone‐beam reduction algorithm could also result in shorter scan times by allowing wider collimations during scan.Authors are employed by Philips Healthcare
SU‐E‐I‐45: The Human Imaging Research Office (HIRO): Advancing the Role of Imaging in Clinical Research
Authors: Armato S , Gruszauskas N , MacMahon H , Torno M , Li F , Engelmann R , Starkey A , Pudela C , Marino J , Chang P , Giger M 
Published: November 2011

Purpose: The clinical imaging infrastructure has been designed for the consistent execution of standard‐of‐care imaging examinations. Many imaging protocols for clinical research, however, have unique requirements that may burden the established infrastructure. Our purpose was to develop a solution to the many imaging demands and challenges presented by clinical research.Methods: We have created the Human Imaging Research Office (HIRO) at our institution. The HIRO is responsible for coordinating the acquisition, collection, analysis, and maintenance of images and related data associated with clinical research studies involving human subjects. The purpose of the HIRO is to coordinate, harmonize, and streamline the imaging aspects of clinical research, so that these non‐standard examinations can be performed as required by the study protocol. In effect, the HIRO is becoming the institutional resource for a broad spectrum of research imaging needs. The activities and services of the HIRO include site validation and image quality verification, development of standardized research‐specific requisition and reporting forms, scheduling, implementation of research billing codes, study‐specific image‐based measurements, collection of customized image databases, and distribution of anonymized images to researchers and study sponsors.Results: The HIRO has helped facilitate the acquisition of images for clinical research for 117 active, pending, or recently closed clinical research studies. These clinical research studies are being conducted by 60 unique principal investigators across 14 different sections and departments within the Medical Center. The HIRO has filled over 650 requests for de‐identified images, accounting for over 42.3 million images Conclusions: Imaging for clinical research often has requirements that differ substantially from those of clinical imaging. The complex infrastructure for standard‐of‐care imaging typically is stressed by the unique technical and administrative needs of a research protocol. The HIRO is able to respond effectively to the dynamic imaging needs of clinical research.SGA, HM, and MLG receive royalties and licensing fees through the University of Chicago related to computer‐aided diagnosis. HM is a consultant for Riverain Medical.
SU‐E‐I‐46: Methods to Determine Peak Skin Dose and Organ Doses for Computed Tomography Examinations
Authors: de las Heras H , Minniti R , Wilson S , Benevides L , Skopec M , Chakrabarti K 
Published: November 2011

Purpose: This work describes methodologies for determining peak skin dose (PSD) and organ doses in computer tomography (CT) examinations. These methods are demonstrated for the routine adult head protocol. This work allows directly relating the widely used CT dose index parameter, CTDIvol, to actual PSD and organ dose values.Methods: Values of the CT dose index, CTDIvol, available in all commercially available CT units tested in this work, were derived independently from ionization chamber measurements. Simultaneously, either, PSDs (first method) or organ doses (second method) were measured as well. In the first method, PSDs were measured using radiochromic film placed on the outer surface of the phantom. Optical densities were measured with a transmission densitometer. In the second method doses to the brain, eye lens and face skin were measured using an anthropomorphic head phantom configured with optical stimulated luminescence (OSL) dosimeters. The ionization chamber, films and OSLs used in these measurements were calibrated at NIST in x‐ray beams that spectrally approximated those typically produced by CT scanners in clinical use.Results: The suggested PSD method is reliable, cheap and fast. PSD values of up to 160 mGy were observed in a single scan in some CT scanners. Variations in the PSD values up to a factor of 2 are observed for a fixed value of CTDIvol, which supports characterizing independently each scanner using the proposed methods. Results show a quite homogenous distribution of organ doses inside the head. Conclusions: Clinical facilities may apply these methods to relate the values of CTDIvol shown on their CT units to actual PSDs and organ doses delivered. Furthermore, this provides a direct method for obtaining PSD and organ dose, as opposed to the more common practice approach of estimating effective dose derived from CT machine parameter values (CTDIvol and scan length).The first author was funded by an ORISE grant at FDA. He is working for Quart GmbH since March 1, 2011. We are very thankful to Chad Mitchell for his initial encouragement on this project, to Dave Spelic for his advice on the manuscript, and to the group of CT technicians at NIH and NNMC.
SU‐E‐I‐63: Multi‐Channel Film Dosimetry with Non‐Uniformity Correction
Authors: Micke A , Lewis D , Yu X 
Published: November 2011

Purpose: A new method to evaluate radiochromic film dosimetry data scanned in multiple color channels is presented. The multi‐channel method allows for the separation and removal of the non‐dose‐dependent portions of a film image and performs superior to the traditional single channel method. Methods: Exposed radiochromic films were scanned in RGB format on a flatbed color scanner and measured to build calibration. Images were converted to dose maps using both single color channel and multi‐channel method. The multi‐channel method allows for the separation of the scanned signal into one dose‐dependent part and another dose‐independent part and enables the correction of a variety of disturbances including non‐ uniformities of the film as well as scanner related artifacts. The fundamental mathematics of the two methods is described and the dose maps calculated with both methods are compared and analyzed. Results: The multi‐channel dosimetry method was shown to remove effectively non‐dose dependent abnormalities from radiochromic dosimetry film images and improve the integrity of the dose information and also reduces random noise in the dose images and mitigates scannerrelated artifacts such as lateral position dependence. In providing an ability to calculate dose maps from data in all the color channels the multi‐channel method provides the ability to examine the agreement between the color channels. The method permit compensation for nonuniformities in the film, increases the signal to noise level, mitigates scanners effect of the calculated dose map and extends the evaluable dose range to 10 cGy – 100. Conclusions: Multi‐channel dosimetry is shown to have significant advantages over single channel method in ensuring the best data integrity and dosimetric accuracy.All authors are employees of International Specialty Products, Manufacturer of Gafchromic Films
SU‐E‐I‐102: Enhancement of Registration Accuracy Using Landmark Information
Authors: Shusharina N , Wang Y , Sharp G 
Published: November 2011

Purpose: To use point landmarks for rapid, interactive correction of local registration failures caused by significant anatomy changes. Methods: Our landmark‐based method utilizes a semi‐automatic procedure. First, we define mismatched areas on reference and test images using contours, which are converted into corresponding sets of landmarks. Second, a program calculates a landmark displacement field, which is used to update an existing displacement field. We use Gaussian radial basis functions (RBF) to create a vector field which exactly interpolates landmark correspondences in the reference and test images. The calculated field is regularized by penalizing large second derivatives. The solution for regularization is stated analytically and yields an efficient computational scheme. Results: The method was applied to register two pairs of prostate images acquired from patients at different points during treatment. These registrations are challenging due to a significant enlargement of the rectum in one case, and change of bladder filling in the other case. To improve the accuracy of automatic registration, we used an expert‐defined contours of the rectum, bladder and prostate as guidance for landmark placement and applied our matching method. As a result, the organs of interest were accurately matched and the regularization assured a diffeomorphic deformation. Conclusion: We have developed a practical method for correcting or enhancing inadequate automatic registration results for medical images containing large anatomical changes. The method integrates landmark matching and regularization.Gaussian basis functions are used because they allow an analytical solution, leading to a very efficient computational scheme.
SU‐E‐I‐112: New Algorithm for Identification of Differences between Noisy Medical Images
Authors: Mitev K , Gerganov G , Kawrakow I 
Published: November 2011

Purpose: To present a method for image comparisons and detection of statistically significant differences (SSDs) between medical images that contain a significant amount of noise, where standard similarity measures like mutual information do not work very well. Methods: The basic idea is that if there are two noisy images which contain SSDs, these differences will appear as outliers in the distribution of pixel intensities in the difference image. Therefore, the method applies a statistical test and identifies the outliers found as SSDs. The tests for outliers are applied on the entire difference image (global approach), on a part of the image around a tested pixel (local approach), or both (mixed approach). The mixed approach first uses a global approach to exclude a set of outliers before invoking the local approach. For performance assessment, the algorithm is applied to synthetic image pairs with known noise levels and SSDs. It is also tested on PET images reconstructed with different algorithms from the STIR package using sinograms obtained from MC PET simulations using egs_pet, on electron beam dose distributions computed with the VMC++ code, on CT and SPECT images. Results: Best performance is achieved with a mixed approach. For the synthetic images the mixed approach identifies SSDs that are larger than four standard deviations of the noise. Visible differences between pairs of PET, CT, SPECT and dose distribution images are also successfully identified. Conclusions: A new method for automatic detection of significant differences between noisy medical images is presented. The method has potential for application in situations where a quantitative comparison and identification of regions of differences is difficult or not possible due to the presence of significant amount of noise. The algorithm is applicable to PET, SPECT and CT imaging as well as to problems related to comparisons of dose distributions.Supported by Bulgarian NSF grant DDVU 02/42. We are grateful to A. Kirov and C.R. Schmidtlein for the useful discussions.
SU‐E‐I‐130: Improved Quantification of Cerebral Metabolites in Hepatic Encephalopathy Using 2D L‐COSY and ProFit
Authors: Huda A , Sarma M , Nagarajan R , Hinkin C , Wilson N , Gupta R , Sayre J , Guze B , Han S , Thomas M 
Published: November 2011

Purpose: To detect, separate, and quantify more cerebral metabolites than is currently possible with one‐dimensional magnetic resonance spectroscopy (1D MRS) by using 2D localized correlated spectroscopy (2D L‐COSY) with prior‐knowledge fitting algorithm (ProFit). Methods: 14 patients with minimal hepatic encephalopathy (MHE) (mean age ± standard deviation (SD) = 53.3± 10.6 years) and 18 control subjects (52.7±12.6 years) were studied with 1.5T GE MR Scanner. A body coil for transmission and a 3‐ inch surface coil for reception were used. A localizer followed by high‐ resolution T1‐weighted axial images (TR/TE = 800/8 ms, 35 slices, 4 mm thickness with no gap) were collected. We used a CHESS sequence for water suppression. 2D L‐COSY spectra were recorded using the following parameters: TE = 30 ms; TR = 2000 ms; total number of scans = 768 (96 &#916;t1 increments and 8 averages per &#916;t1); and spectral width, F1 = 625 Hz and F2 = 2500 Hz. A 27ml voxel was placed on the anterior cingulate gyrus. A battery of neuropsychological tests (NP) was done to correlate the MRS results with the NP data. Results: : The 2D L‐COSY data processed with the ProFit was able to separate and quantify fourteen cerebral metabolites in both healthy controls and patients as opposed to five with 1DMRS. The ratios of myoinositol (mI), glutamate (Glu), total choline, scyllo‐inositol (sI), phosphoethanolamine (PE), and total NAA with respect to creatine (Cr) showed a statistically significant decline in patients compared to healthy controls whereas the ratio of glutamine to Cr (Gln/Cr) was significantly increased. Conclusions: Our technique allows for separation and quantitation of Glu from Gln, strengthening the astrocyte‐ ammonia detoxification hypothesis in HE. In addition, clear separation of glycerol‐phosphocholine (GPC) from total choline in conjunction with the decline in PE, points to a decrease in phospholipid metabolism in HE.This research was supported by National Institute of Mental Health (NIMH) grant #1R01MH06569501A1
SU‐E‐I‐132: Whole‐Brain DCE Quantitative Perfusion Imaging
Authors: Gauderon P , Salluzzi M , Lauzon M , McCreary C , Smith M , Frayne R 
Published: November 2011

Purpose: To develop a whole‐brain acquisition protocol based on dynamic contrast enhanced (DCE) MR imaging that is able to provide absolute brain tissue perfusion estimates and to assess, evaluate and minimize the uncertainty in the estimates of contrast agent concentration. Methods: Preliminary in vivo data was collected using a 3D spoiled‐gradient recalled echo (SPGR) sequence with TR/TE/flip angle (FA) = 2.5 ms/1.15 ms/15°. The spatial resolution was 1.7×1.7×4.0 mm3. A variable rate k‐space sampling scheme and view sharing resulted in a temporal resolution of 2.4 s. The perfusion estimates were calculated using indicator‐dilution theory. Based on preliminary data, simulations estimating the uncertainty and sensitivity to misestimated parameters in the concentration measures were performed. Tissue parameters and contrast agent relaxivities were obtained from literature. The SNR before contrast injection was extracted from the preliminary data. Results: Absolute perfusion maps were successfully generated for the whole brain in all three subjects. As predicted, the low signal enhancement in cerebral tissue, especially in white matter, resulted in noisy perfusion maps. The range of the cerebral blood flow (CBF) and cerebral blood volume (CBV) maps corresponded to the range of the values reported in literature. The mean transit times (MTT) however were overestimated. The simulations showed that a FA of 9° minimizes the concentration coefficient of variation in white matter. However, the sensitivity to misestimated parameters was reduced with increasing FA: a FA > 20° was beneficial. For realistic SNR levels, averaging 5 acquisitions of the signal before contrast agent arrival were sufficient. More baseline measurements did not significantly decrease the signal variance. Conclusion: It is possible to acquire qualitatively acceptable whole‐brain bolus tracking data using a DCE sequence. In addition, the FA influences the uncertainty and sensitivity in concentration estimates when using a SPGR sequence.Grant support from the Canadian Institutes for Health Research, Canada Research Chairs Program and Hopewell Professorship in Brain Imaging.
SU‐E‐I‐135: Image Reconstruction by Derivatives in Frequency Domain
Authors: Shen J 
Published: November 2011

Purpose: To demonstrate a novel theorem relating the spatial frequency domain partial derivatives; to show that using autocalibrating signals images can be unwrapped using k space partial derivatives and noise amplification in SENSE reconstruction can be reduced without making any assumptions on the characteristics of images to be reconstructed. Methods: Phantom and human brain images were acquired using a standard GE 3.0 Tesla Excite scanner (General Electric, Waukesha, WI) equipped with eight receive channels. Standard eight‐channel receive‐only head coils and a transmit body coil were used for image data acquisition. Results: As a proof of concept, a gradient echo phantom image was reconstructed in k space using 20 ACS lines for R=2. Partial derivatives for No. 63, 64, 65, 66, and 67 ky lines were measured by fitting the five tightly spaced ky points at each (x,ky) coordinate to a third order polynomial. Two sets of aliased images were obtained: a conventional one described by a sum of products between spin density and coil sensitivity and a new one described by a sum of products among spin density, coil sensitivity and y ordinate of the aliased pixel. There are no visible reconstruction artifacts in the unwrapped individual coil images. In image domain, the new contraints derived from k space partial derivatives were used to improve the conditioning of SENSE encoding matrices. The derivative constraints are different from regularization, the latter leads to loss in spatial resolution. For an MPRAGE brain image with R=6 the first order derivatives alone was found to reduce the largest SENSE g factor by 61% (from 23.1 to 8.9). Conclusions: Derivatives in k space can be used for parallel imaging reconstruction in both k space and image domains.Funded by NIMH, NIH
SU‐E‐I‐144: Radiation Dose Reduction in Monochromatic Phase Contrast X‐Ray Mammography Using Equally Sloped Tomography
Authors: Zhao Y , Brun E , Fahimian B , Bravin A , Sztrókay A , Coan P , Miao J 
Published: November 2011

Purpose: In mammography, while maintaining the image quality, it is necessary to keep the delivered dose as low as possible since breast is a highly radiosensitive organ. Monochromatic phase contrast X‐ray mammography has shown its potential at higher sensitivity and lower impact in terms of dose delivery compared to absorption based diagnostic X‐ray mammography. An exact Fourier‐based iterative technique termed Equally Sloped Tomography(EST) has been newly developed and implemented on it. Using this technique, we conducted a series of comparative experiments to explore the further more radiation dose reduction in phase contrast mammography through reduction of projection numbers. Methods: Experiment took place at the biomedical beamline at ESRF(ID17). Full Human breasts samples were fixed in 4% formalin solution. Planar imaging and Computed Tomography(CT) modalities were combined to PCI techniques at 60KeV and using a 2kx2k taper optics CCD detector(45 micron pixel). The number of projections scanned was 2000 and digitally removed to 512 for reconstructions. Comparison reconstructions were produced by Filtered‐Back Projection(FBP) with a standard uncropped‐ramp filter. To optimize the result, Non‐local‐means regularization was applied for post‐processing in both cases. Results: Compared to the FBP reconstruction using 2000 projections, EST using 512 projections has comparable SNRs and CNRs, no obvious contrast degradation is observed between tumor and normal glandular tissue. In addition, the collagen exhibit similar visibility. Conclusions: Our results indicate that in the phase contrast mammography, EST technique can reduce the dose up to 50%∼75% by reducing number of projections, while images have comparable quality as the full dose FBP reconstruction. Furthermore, it makes the acquisition time 2∼4 times faster, which is important in in‐vivo imaging. The main reason for this is that EST is an exact Fourier‐based iterative algorithm that can incorporate different physical and mathematical constraints. It is always guided towards a lowest‐possible noisy state while keeping strictly consistent with measurements.Research sponsored by UC Discovery / TomoSoft Technologies Grant #ITL07‐10166.