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High resolution X-ray imaging of bone-implant interface by large area flat-panel detector

JOURNAL OF INSTRUMENTATION 2011年第1期6卷 C01038-C01038页

作者： Kytyr, D. Jirousek, O. Dammer, J. Acad Sci Czech Republic Inst Theoret & Appl Mech Prague 19000 9 Czech Republic Czech Tech Univ Inst Expt & Appl Phys Prague 12800 2 Czech Republic

The aim of the research was to investigate the cemented bone-implant interface behavior (cement layer degradation and bone-cement interface debonding) with emphasis on imaging techniques suitable to detect the early defects in the cement layer. To simulate in vivo conditions a human pelvic bone was implanted with polyurethane acetabular cup using commercial acrylic bone cement. The implanted cup was then loaded in a custom hip simulator to initiate fatigue crack propagation in the bone cement. The pelvic bone was then repetitively scanned in a micro-tomography device. Reconstructed tomography images showed failure processes that occurred in the cement layer during the first 250, 000 cycles. A failure in cemented acetabular implant - debonding, crumbling and smeared cracks has been found to be at the bone-cement interface. Use of micro-focus source and high resolution flat panel detector of large physical dimensions allowed to reconstruct the micro-structural models suitable for investigation of migration, micro-motions and consecutive loosening of the implant. The large area flat panel detector with physical dimensions 120 x 120mm with 50 mu m pixel size provided a superior image quality compared to clinical CT systems with 300 - 150 mu m pixel size.

关键词： computerized Tomography (CT) and Computed Radiography (CR) medical-image reconstruction methods and algorithms, computer-aided so

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Variance-reduction normalization technique for a compton camera system

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JOURNAL OF INSTRUMENTATION 2011年第1期6卷 C01040-C01040页

作者： Kim, S. M. Lee, J. S. Kim, J. H. Seo, H. Kim, C. H. Lee, C. S. Lee, S. J. Lee, M. C. Lee, D. S. Seoul Natl Univ Med Res Ctr Dept Nucl Med Seoul 110744 South Korea Seoul Natl Univ Med Res Ctr Inst Radiat Med Seoul 110744 South Korea Seoul Natl Univ Coll Med Interdisciplinary Programs Radiat Appl Life Sci M Seoul 110744 South Korea Seoul Natl Univ Dept Biomed Sci Seoul 151742 South Korea Seoul Natl Univ WCU Dept Brain & Cognit Sci Seoul 151742 South Korea Hanyang Univ Dept Nucl Engn Seoul 133791 South Korea Chung Ang Univ Dept Phys Seoul 156756 South Korea Paichai Univ Dept Elect Engn Taejon 302735 South Korea Seoul Natl Univ WCU Dept Mol Med & Biopharmaceut Sci Seoul 151742 South Korea

For an artifact-free dataset, pre-processing (known as normalization) is needed to correct inherent non-uniformity of detection property in the Compton camera which consists of scattering and absorbing detectors. The detection efficiency depends on the non-uniform detection efficiency of the scattering and absorbing detectors, different incidence angles onto the detector surfaces, and the geometry of the two detectors. The correction factor for each detected position pair which is referred to as the normalization coefficient, is expressed as a product of factors representing the various variations. The variance-reduction technique (VRT) for a Compton camera (a normalization method) was studied. For the VRT, the Compton list-mode data of a planar uniform source of 140 keV was generated from a GATE simulation tool. The projection data of a cylindrical software phantom were normalized with normalization coefficients determined from the non-uniformity map, and then reconstructed by an ordered subset expectation maximization algorithm. The coefficient of variations and percent errors of the 3-D reconstructed images showed that the VRT applied to the Compton camera provides an enhanced image quality and the increased recovery rate of uniformity in the reconstructed image.

关键词： Compton imaging medical-image reconstruction methods and algorithms, computer-aided so

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Calibration of pinhole MicroSPECT using a single point source

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JOURNAL OF INSTRUMENTATION 2009年第5期4卷 P05008-P05008页

作者： Zhou, R. Ma, T. Liu, Y. Wu, Z. Wang, S. Jing, Y. Cheng, J. Tsinghua Univ Dept Engn Phys Beijing 100084 Peoples R China

To calibrate pinhole MicroSPECT system, two improved methods using only a single point source were proposed. The uniqueness of calibration result by the proposed methods was proved theoretically. And simulation calibration of a dual-head system was carried out to validate the performance of the proposed methods. The simulation results show that reasonable calibration error is given by both proposed methods.

关键词： Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA) computerized Tomography (CT) and Computed Radiography (CR) medical-image reconstruction methods and algorithms, computer-aided so

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Quantitative proton magnetic resonance spectroscopy without water suppression

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JOURNAL OF INSTRUMENTATION 2009年第06期4卷 P06014-P06014页

作者： Ozdemir, M. S. De Deene, Y. Fieremans, E. Lemahieu, I. Univ Ghent IBBT IBiTech MEDISIP Dept Elect & Informat Syst B-9000 Ghent Belgium Ghent Univ Hosp Dept Radiotherapy B-9000 Ghent Belgium

The suppression of the abundant water signal has been traditionally employed to decrease the dynamic range of the NMR signal in proton MRS ((1)H MRS) in vivo. When using this approach, if the intent is to utilize the water signal as an internal reference for the absolute quantification of metabolites, additional measurements are required for the acquisition of the water signal. This can be prohibitively time-consuming and is not desired clinically. Additionally, traditional water suppression can lead to metabolite alterations. This can be overcome by performing quantitative 1H MRS without water suppression. However, the non-water-suppressed spectra suffer from gradient-induced frequency modulations, resulting in sidebands in the spectrum. Sidebands may overlap with the metabolites, which renders the spectral analysis and quantification problematic. In this paper, we performed absolute quantification of metabolites without water suppression. Sidebands were removed by utilizing the phase of an external reference signal of single resonance to observe the time-varying the static field fluctuations induced by gradient-vibration and deconvolving this phase contamination from the desired NMR signal. The quantification of metabolites was determined after sideband correction by calibrating the metabolite signal intensities against the recorded water signal. The method was evaluated by phantom and in vivo measurements in human brain. The maximum systematic error for the quantified metabolite concentrations was found to be 10.8%, showing the feasibility of the quantification after sideband correction.

关键词： Data processing methods Simulation methods and programs MRI (whole body, cardiovascular, breast, others), MR-angiography (MRA) medical-image reconstruction methods and algorithms, computer-aided so

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The influence of software filtering in digital mammography image quality

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JOURNAL OF INSTRUMENTATION 2009年第5期4卷 P05018-P05018页

作者： Michail, C. Spyropoulou, V. Kalyvas, N. Valais, I. Dimitropoulos, N. Fountos, G. Kandarakis, I. Panayiotakis, G. Technol Educ Inst Athens Dept Med Instruments Technol Athens 12210 Greece Univ Patras Sch Med Dept Med Phys Patras 26500 Greece

Breast cancer is one of the most frequently diagnosed cancers among women. Several techniques have been developed to help in the early detection of breast cancer such as conventional and digital x-ray mammography, positron and single-photon emission mammography, etc. A key advantage in digital mammography is that images can be manipulated as simple computer image files. Thus non-dedicated commercially available image manipulation software can be employed to process and store the images. The image processing tools of the Photoshop (CS 2) software usually incorporate digital filters which may be used to reduce image noise, enhance contrast and increase spatial resolution. However, improving an image quality parameter may result in degradation of another. The aim of this work was to investigate the influence of three sharpening filters, named hereafter sharpen, sharpen more and sharpen edges on image resolution and noise. image resolution was assessed by means of the Modulation Transfer Function (MTF). In conclusion it was found that the correct use of commercial non-dedicated software on digital mammograms may improve some aspects of image quality.

关键词： image filtering X-ray detectors X-ray mammography and scinto- and MRI-mammography medical-image reconstruction methods and algorithms, computer-aided so

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Focused microwave radiometry from a possible functional imaging perspective: theoretical optimization of the properties of a microwave radiometry system

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JOURNAL OF INSTRUMENTATION 2009年第5期4卷 P05011-P05011页

作者： Giamalaki, M. I. Karanasiou, I. S. Uzunoglu, N. K. Natl Tech Univ Athens Microwave & Fiber Opt Lab Sch Elect & Comp Engn GR-15773 Athens Greece

A non-invasive imaging system, consisting of an ellipsoidal conductive cavity and radiometric receivers, designed and constructed in our laboratory the past few years is restudied. In order to enhance the system's focusing properties thus its performance, the head is covered by a dielectric matching layer while the receiving antenna is more realistically modelled and also covered by two layers of dielectric properties similar to those of the head. The electric field distribution inside the head is calculated for two frequencies and for matching layers of different dielectric properties and thicknesses, through a theoretical electromagnetic analysis using a Green's function technique. Sensitivity of the system focusing properties is observed when the head or the source center is moved away from the system's geometrical focal areas.

关键词： Radiation monitoring medical-image reconstruction methods and algorithms, computer-aided so

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An automated computerized methodology for the segmentation of in vivo acquired DSA images: application in the New Zealand hindlimb ischemia model

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JOURNAL OF INSTRUMENTATION 2009年第05期4卷 P05014-P05014页

作者： Kagadis, G. C. Diamantopoulos, A. Samaras, N. Daskalakis, A. Spyridonos, P. Katsanos, K. Karnabatidis, D. sourgiadaki, E. Cavouras, D. Siablis, D. Nikiforidis, G. C. Univ Patras Sch Med Dept Med Phys GR-26504 Patras Greece Univ Patras Sch Med Dept Radiol GR-26504 Patras Greece Univ Patras Sch Med Dept Anesthesiol GR-26504 Patras Greece Technol Educ Inst Athens Dept Med Instrumentat Technol GR-12210 Athens Greece

In-vivo dynamic visualization and accurate quantification of vascular networks is a prerequisite of crucial importance in both therapeutic angiogenesis and tumor anti-angiogenesis studies. A user independent computerized tool was developed, for the automated segmentation and quantitative assessment of in-vivo acquired DSA images. Automatic vessel assessment was performed employing the concept of image structural tensor. Initially, vasculature was estimated according to the largest eigenvalue of the structural tensor. The resulted eigenvalue matrix was treated as gray-matrix from which the vessels were gradually segmented and then categorized in three main sub-groups;large, medium and small-size vessels. The histogram percentiles, corresponding to 85%, 65% and 47% of prime eigenvalue gray-matrix were optimally found to give the thresholds T1, T2 and T3 respectively, for extracting vessels of different size. The proposed methodology was tested on a series of DSA images in both normal rabbits (group A) and in rabbits with experimental induced chronic hindlimb ischemia (group B). As a result an automated computerized tool was developed to process images without any user intervention in either experimental or clinical studies. Specifically, a higher total vascular area and length were calculated in group B compared to group A (p=0.0242 and p=0.0322 respectively), which is in accordance to the fact that significantly more collateral arteries are developed during the physiological response to the stimuli of ischemia.

关键词： X-ray radiography and digital radiography (DR) medical-image reconstruction methods and algorithms, computer-aided so image reconstruction in medical imaging

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Integrating multiscale polar active contours and region growing for microcalcifications segmentation in mammography

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JOURNAL OF INSTRUMENTATION 2009年第07期4卷 P07009-P07009页

作者： Arikidis, N. S. Karahaliou, A. Skiadopoulos, S. Likaki, E. Panagiotakis, G. Costaridou, L. Univ Patras Dept Med Phys Fac Med Patras 26500 Greece Univ Patras Dept Radiol Fac Med Patras 26500 Greece

Morphology of individual microcalcifications is an important clinical factor in microcalcification clusters diagnosis. Accurate segmentation remains a difficult task due to microcalcifications small size, low contrast, fuzzy nature and low distinguishability from surrounding tissue. A novel application of active rays ( polar transformed active contours) on B-spline wavelet representation is employed, to provide initial estimates of microcalcification boundary. Then, a region growing method is used with pixel aggregation constrained by the microcalcification boundary estimates, to obtain the final microcalcification boundary. The method was tested on dataset of 49 microcalcification clusters ( 30 benign, 19 malignant), originating from the DDSM database. An observer study was conducted to evaluate segmentation accuracy of the proposed method, on a 5-point rating scale ( from 5: excellent to 1: very poor). The average accuracy rating was 3.98 +/- 0.81 when multiscale active rays were combined to region growing and 2.93 +/- 0.92 when combined to linear polynomial fitting, while the difference in rating of segmentation accuracy was statistically significant (p < 0.05).

关键词： medical-image reconstruction methods and algorithms, computer-aided so X-ray mammography and scinto- and MRI-mammography

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Evaluation of brain perfusion in specific Brodmann areas in Frontotemporal dementia and Alzheimer disease using automated 3-D voxel based analysis

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JOURNAL OF INSTRUMENTATION 2009年第5期4卷 P05020-P05020页

作者： Valotassiou, V. Papatriantafyllou, J. Sifakis, N. Karageorgiou, C. Tsougos, I. Tzavara, C. Zerva, C. Georgoulias, P. Univ Hosp Larissa Nucl Med Dpt Larisa Greece Gen Hosp G Gennimatas Neurol Dpt Athens Greece Alexandra Univ Hosp Nucl Med Dpt Athens Greece

Introduction. Brain perfusion studies with single-photon emission computed tomography (SPECT) have been applied in demented patients to provide better discrimination between frontotemporal dementia (FTD) and Alzheimer's disease (AD). Aim. To assess the perfusion of specific Brodmann (Br) areas of the brain cortex in FTD and AD patients, using NeuroGam processing program to provide 3D voxel-by-voxel cerebral SPECT analysis. Material and methods. We studied 34 consecutive patients. We used the established criteria for the diagnosis of dementia and the specific established criteria for the diagnosis of FTD and AD. All the patients had a neuropsychological evaluation with a battery of tests including the mini-mental state examination (MMSE). Twenty-six patients (16 males, 10 females, mean age 68.76 +/- 6.51 years, education 11.81 +/- 4.25 years, MMSE 16.69 +/- 9.89) received the diagnosis of FTD and 8 patients (all females, mean age 71.25 +/- 10.48 years, education 10 +/- 4.6 years, MMSE 12.5 +/-3.89) the diagnosis of AD. All the patients underwent a brain SPECT. We applied the NeuroGam software for the evaluation of brain perfusion in specific Br areas in the left (L) and right (R) hemispheres. Results. Statistically significant hypoperfusion in FTD compared to AD patients, was found in the following Br areas: 11L (p < 0.0001), 11R, 20L, 20R, 32L, 38L, 38R, 44L (p < 0.001), 32R, 36L, 36R, 45L, 45R, 47R (p < 0.01), 9L, 21L, 39R, 44R, 46R, 47L (p < 0.05). On the contrary, AD patients presented significant (p < 0.05) hypoperfusion in 7R and 39R Br areas. Conclusion. NeuroGam processing program of brain perfusion SPECT could result in enhanced accuracy for the differential diagnosis between AD and FTD patients.

关键词： Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA) medical-image reconstruction methods and algorithms, computer-aided so

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Design an adaptive quality control phantom to optimize uniformity, collimator hole angulation and center of rotation of SPECT

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JOURNAL OF INSTRUMENTATION 2008年第02期3卷 P02009-P02009页

作者： Zeinali, H. Zamani Ghiassi-Nejad, M. Mirzai, A. Amir Kabir Univ Technol Dept Phys Tehran Iran Tarbiat Modares Univ Dept Biophys Tehran Iran

The main objective of this research is to introduce a newly developed device called "Adaptive Quality Control Phantom" (AQCP) designed to perform the QC tests. AQCP is the computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce any spatial distribution of gamma rays to simulate QC phantoms. To establish and prove the proper functionality and the accurate performance of AQCP, different tests that include systematic uniformity, collimator hole angulation and center of rotation were conducted by this device and the results, findings and differences of these tests as compared with the QC classic method tests are discussed and analyzed in detail in this paper. According to the different tests carried out by AQCP, the authors achieved the following: the performance of systematic uniformity test shows a considerable reduction in the technologist dose compared to the IAEA-TECDOC-602 method. The collimator hole angulation for LEHR, LEUHR and LEHS collimators were measured by using a point source and computer-controlled cylindrical positioning, the results of which show that the measurement accuracy for absolute angulation errors is better than 0.018 degrees. A method for center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. Based on the discussion made in this paper regarding AQCP, the authors believe that this device is able to simulate QC phantoms.

关键词： gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA) medical-image reconstruction methods and algorithms, computer-aided so

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