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Nuclear Science, IEEE Transactions on

Issue 3  Part 2 • Date June 1999

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Displaying Results 1 - 25 of 49
  • Conference author index

    Publication Year: 1999 , Page(s): 754 - 755
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    Freely Available from IEEE
  • X-ray imaging using a 320×240 hybrid GaAs pixel detector

    Publication Year: 1999 , Page(s): 507 - 512
    Cited by:  Papers (13)
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    We present room temperature measurements on 200 μm thick GaAs pixel detectors, which were hybridized to silicon readout circuits. The whole detector array contains 320×240 square shaped pixel with a pitch of 38 μm and is based on semi-insulating liquid-encapsulated Czochralski (LEC) GaAs material. After fabricating and dicing, the detector chips were indium bump flip chip bonded to CMOS readout circuits based on charge integration and finally evaluated. This readout chip was originally designed for the readout of flip chip bonded infrared detectors, but appears to be suitable for X-ray applications as well. A bias voltage between 50 V and 100 V was sufficient to operate the detector at room temperature. The detector array did respond to X-ray radiation by an increase in current due to production of electron hole pairs by the ionization processes. Images of various objects and slit patterns were acquired by using a standard X-ray source for dental imaging. The new X-ray hybrid detector was analyzed with respect to its imaging properties. Due to the high absorption coefficient for X-rays in GaAs and the small pixel size, the sensor shows a high modulation transfer function up to the Nyquist frequency View full abstract»

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  • Multi-PSPMT scintillation camera

    Publication Year: 1999 , Page(s): 702 - 708
    Cited by:  Papers (27)  |  Patents (5)
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    Gamma ray imaging is usually accomplished by the use of a relatively large scintillating crystal coupled to either a number of photomultipliers (PMTs) (Anger Camera) or to a single large Position Sensitive PMT (PSPMT). Recently the development of new diagnostic techniques, such as scintimammography and radio-guided surgery, have highlighted a number of significant limitations of the Anger camera in such imaging procedures. In this paper a dedicated gamma camera is proposed for clinical applications with the aim of improving image quality by utilizing detectors with an appropriate size and shape for the part of the body under examination. This novel scintillation camera is based upon an array of PSPMTs (Hamamatsu R5900-C8). The basic concept of this camera is identical to the Anger Camera with the exception of the substitution of PSPMTs for the PMTs. In this configuration it is possible to use the high resolution of the PSPMTs and still correctly position events lying between PSPMTs. In this work the test configuration is a 2 by 2 array of PSPMTs. Some advantages of this camera are: spatial resolution less than 2 mm FWHM, good linearity, thickness less than 3 cm, light weight, lower cost than equivalent area PSPMT, large detection area when coupled to scintillating arrays, small dead boundary zone (<3 mm) and flexibility in the shape of the camera View full abstract»

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  • Design and experimental validation of a quantitative myocardial 201Tl SPECT system

    Publication Year: 1999 , Page(s): 720 - 726
    Cited by:  Papers (7)
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    We have developed a quantitative SPECT system, and evaluated its potential for quantitative assessment of biophysiological functions, in the myocardium particularly, with 201Tl. Our approach included the development of a transmission system that provides accurate attenuation μ maps, and the implementation of ordered-subset EM reconstruction with transmission data-based attenuation correction in addition to scatter correction using the transmission-dependent convolution subtraction (TDCS) technique. The transmission system was designed using Monte Carlo simulation to minimize the scatter in the transmission projection data while keeping sensitivity loss to a minimum, and was attached to an opposing two-head gamma camera fitted with parallel beam collimators. Observed μ values agreed with the theoretical expected values in both phantoms and a human thorax. Phantom experiments with 201Tl also demonstrated that, with corrections for both attenuation and scatter, the observed images were directly proportional to the actual radioactivity distribution for various phantom geometries. Attenuation correction without scatter correction improved images in deep structure, but resulted in significant artifacts in the chest phantom in addition to dependency of observed radioactivity concentrations on the diameter of cylindrical phantoms. Absolute quantitation of biophysiological functions, which is well established in PET, is shown to be feasible using SPECT, if both quantitative attenuation and scatter corrections are employed View full abstract»

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  • Investigation of depth-of-interaction by pulse shape discrimination in multicrystal detectors read out by avalanche photodiodes

    Publication Year: 1999 , Page(s): 462 - 467
    Cited by:  Papers (18)  |  Patents (4)
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    The measurement of depth of interaction (DOI) within detectors is necessary to improve resolution uniformity across the FOV of small diameter PET scanners. DOI encoding by pulse shape discrimination (PSD) has definite advantages as it requires only one readout per pixel and it allows DOI measurement of photoelectric and Compton events. The PSD time characteristics of various scintillators were studied with avalanche photodiodes (APD) and the identification capability was tested in multi-crystal assemblies with up to four scintillators. In the PSD time spectrum of an APD-GSO/LSO/BGO/CsI(Tl) assembly, four distinct time peaks at 45, 26, 88 and 150 ns relative to a fast test pulse, having resolution of 10.6, 5.2, 20 and 27 ns, can be easily separated. Whereas the number and position of scintillators in the multi-crystal assemblies affect detector performance, the ability to identify crystals is not compromised. Compton events have a significant effect on PSD accuracy, suggesting that photopeak energy gating should be used for better crystal identification. However, more sophisticated PSD techniques using parametric time-energy histograms can also improve crystal identification in cases where PSD time or energy discrimination alone is inadequate. These results confirm the feasibility of PSD DOI encoding with APD-based detectors for PET View full abstract»

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  • Multi-frequency reference function to reduce noise in functional MRI

    Publication Year: 1999 , Page(s): 513 - 519
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    Functional MRI requires acquisition of a time-series of images, making it prone to detecting noise due to gross motion, internal physiological fluctuations, and any magnetic field changes. All of these effects lead to spurious activation, reducing the reliability of functional images. We have designed a unique protocol to present stimuli in fMRI where the presentation sequence contains a combination of frequencies that minimizes the overlap of true activity with noise and any physiological fluctuations, reducing the detection of spurious activation. The results of our studies suggest that the multi-frequency stimuli presentation approach is effective in reducing noise and artifacts View full abstract»

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  • A 3-D Monte Carlo simulation of a small animal positron emission tomograph with millimeter spatial resolution

    Publication Year: 1999 , Page(s): 697 - 701
    Cited by:  Papers (6)
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    We have used the EGS4 Monte Carlo code of W.R. Nelson et al. (1985) to simulate the performance of a positron emission tomograph (PET) for small animals. The PET scanner is a four-head detector, made of matrices of 400 YAP:Ce (yttrium aluminium perovskite doped with cerium) finger-like crystals (2×2×30 mm3 each), coupled to Hamamatsu R2486-06 position-sensitive photomultipliers. 3D reconstruction algorithms have been applied to the 3D simulated data. The reconstructed volume was 2×2×2 cm3, the same as that of the reference mouse brain. The Monte Carlo results show that a spatial resolution below 2 mm (FWHM) can be obtained over the 2×2×2 cm3 volume with a sensitivity of about 600 counts/(μCis) for a gantry diameter of 15 cm and a threshold of 50 keV View full abstract»

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  • Self-normalization of emission data in 3D PET

    Publication Year: 1999 , Page(s): 709 - 712
    Cited by:  Papers (10)
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    Demonstrates that dead-time mismatch between the normalization and emission acquisitions in 3D positron emission tomography (PET) can introduce high-frequency circular image artifacts. We describe a simple correction scheme for this problem, where appropriate correction factors are calculated from the emission data itself, thus avoiding the necessity of acquiring normalization data at a range of different count-rates. In this scheme, “pseudo-detector efficiencies” are calculated from the emission data by the application of a conventional normalization algorithm. The mean systematic variation in these pseudo-efficiencies with position within the block detector is then calculated, and appropriate correction factors are applied to the original emission data. We show that this “self-normalization” scheme can remove normalization artifacts in both uniform and non-uniform phantom studies, and that it is also effective in vivo View full abstract»

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  • Singles transmission scanning for rotating positron cameras with large-area detectors

    Publication Year: 1999 , Page(s): 737 - 742
    Cited by:  Papers (2)
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    Describes the novel geometry and initial results of a singles transmission system for PETRRA, a whole-body PET camera with rotating planar detectors. Special frames mounted on to the front face of each detector support a collimated 137Cs source in various positions. Cone-beam transmission data are acquired during 360° gantry rotation and images are reconstructed using the Feldkamp (1984) algorithm. The radial transaxial field of view (FOV) can be increased by using two source positions displaced either side of the central position. The truncated data acquired from each source position are combined to form a complete dataset. The axial FOV depends on the amount of collimation in the axial direction and could be increased by horizontal couch motion. Preliminary singles transmission images of both real and simulated thorax phantoms have been obtained. The effects of varying the linear sampling interval, the number of projections and the axial FOV have been studied. The singles transmission scanning system developed for PETRRA could be applied to other PET cameras with large planar detectors View full abstract»

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  • Quantitative evaluation of information loss for Compton cameras

    Publication Year: 1999 , Page(s): 587 - 593
    Cited by:  Papers (11)  |  Patents (1)
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    Compton cameras decouple the inverse relationship between spatial resolution and detection sensitivity which compromises the performance of conventional collimated cameras. However, this improvement is usually achieved at the expense of the amount of information conveyed by each detected photon. In this paper, we propose a simple approach to calculate the information loss for a ring Compton camera. We describe this information loss as “decoding penalty”, defined as the ratio of the variance of reconstructed intensity for a pixel of interest for a ring Compton camera to that for a mechanically collimated camera normalized on a per-detected-photon basis. The uniform Crame´r-Rao bound, our mathematical tool, provides a lower bound on the variance that is dependent on the system and data statistics alone, rather than the estimator. The results suggest that ring Compton cameras perform comparably to conventional collimated cameras at an incident photon energy of 140 keV and substantially outperform their counterparts at 364 keV View full abstract»

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  • Prospects for time-of-flight PET using LSO scintillator

    Publication Year: 1999 , Page(s): 474 - 478
    Cited by:  Papers (85)  |  Patents (15)
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    We present measurements of the timing properties of lutetium orthosilicate (LSO) scintillator crystals coupled to a photomultiplier tube (PMT) and excited by 511 keV photons. These crystals have dimensions suitable for use in PET cameras (3×3×30 mm3 ). Coincidence timing resolution of 475 ps fwhm is measured between detectors utilizing two such crystals, significantly worse than the 300 ps fwhm predicted based on first principles for small crystals and measured in 3 mm cubes. This degradation is found to be caused by the scintillation light undergoing multiple reflections at quasi-random angles within the scintillator crystal, which has two effects. First, it slows down the effective information propagation speed within the crystal (to an effective nˆ=3.9-5.3). Since the incident annihilation photon travels with n=1, information from interactions at different depths arrives at the PMT with different time delays. Second, the random nature of the reflection angles (and path lengths) introduce dispersion and so a 10%-90% rise time of 1 ns to the optical signal View full abstract»

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  • Depth identification accuracy of a three layer phoswich PET detector module

    Publication Year: 1999 , Page(s): 485 - 490
    Cited by:  Papers (89)  |  Patents (6)
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    We describe a PET detector module that provides three levels of depth-of-interaction (DOI) information. The detector is a 9×9 array of 2 mm×2 mm×12 mm deep phoswich crystal elements, each consisting of 4 mm long LSO (entrance layer), GSO (middle layer) and BGO (exit layer) crystals joined optically together end-to-end. The BGO exit layer is directly coupled to a miniature position-sensitive photomultiplier tube (PSPMT). Delayed charge integration, a method that exploits differences in the light decay times of these scintillators, is used to determine the layer-of-interaction. DOI accuracy, measured by scanning a slit source of 511 keV radiation along the length of the module was 86% for the LSO layer, 80% for the GSO layer and 84% for the BGO layer. Energy resolution at 511 keV was 19% for LSO, 21% for GSO and 40% for BGO. Apparent gain differed between layers in the ratios 2.7:1.9:1.0 (LSO:GSO:BGO). Crystal separation was good between crystals in the LSO layer, acceptable between crystals in the GSO layer and poor between crystals in the BGO layer due, primarily, to the pronounced spatial nonlinearity of the PSPMT. The delayed charge integration method, however, does appear suitable for obtaining multi-level depth information when DOI effects are particularly significant, e.g. in very small ring diameter PET scanners for small animal imaging View full abstract»

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  • Development of a small gamma camera using wavelength-shifting fibres coupled to inorganic scintillation crystals for imaging 140 keV gamma rays

    Publication Year: 1999 , Page(s): 576 - 582
    Cited by:  Papers (4)
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    We are developing a small gamma camera for scintimammography with Tc99m (140 keV). The camera is based on coupling wavelength-shifting fibres (WSF) to the surface of an inorganic scintillation crystal-CsI(Na)-in order to obtain information about the position of interaction of the gamma rays. We have performed experimental measurements on the light output of 1 mm round multi-clad WSFs coupled to two CsI(Na) slabs, 3 and 5 mm thick. The results show a mean of 3.8 photoelectrons per gamma ray interaction of Co57 122 keV, with a mean of 1 photoelectron at the fibre located nearest the collimated beam of gamma rays, for the 3 mm thick crystal. Simulations based on the single electron response of photomultiplier tubes show that a 1.7 mm FWHM spatial resolution can be achieved with this camera design. The camera can be shaped to suit any application, it is compact and has low cost, which, together with its predicted performance in terms of spatial resolution, makes this concept very promising as a small gamma camera for 140 keV View full abstract»

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  • Image characteristics and effective dose estimation of a cone beam CT using a video-fluoroscopic system

    Publication Year: 1999 , Page(s): 686 - 690
    Cited by:  Papers (6)
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    We developed a cone-beam CT system to acquire volume data of high-contrast objects, such as bone, lung and blood vessels (enhanced by contrast agents), that were amenable to 3D image processing. An X-ray tube and a large-area detector were mounted on a frame and rotated around an object in 12 seconds. The large-area detector consisted of a fluorescent plate and a CCD (charge-coupled device) video camera. While the X-ray tube was rotated around the object, X-ray pulses were generated, and 360 projected images were collected in a 12-second scan. A 256×256×256 matrix image was reconstructed using a parallel processor with a reconstruction time of 6 minutes. Image characteristics, such as spatial resolution, image noise and distortion, were evaluated by phantoms and compared with those of helical CT. Organ or tissue doses by the scan were determined by an in-phantom measurement. The effective dose recommended by the International Commission on Radiological Protection's Publication 60 (ICRP60) was evaluated using the organ or tissue doses. The results showed an isotropic resolving power of less than 1.6 mm and no distortion of the images, though they showed larger image noise and effective dose than that of helical CT View full abstract»

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  • Causes and corrections for 3D image artifact in HCT

    Publication Year: 1999 , Page(s): 748 - 753
    Cited by:  Papers (4)
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    In recent years, helical computed tomography (HCT) has gained significant popularity in clinical applications. The advantages of HCT include the capability of scanning a complete anatomical volume in a single breath-hold and the capability of generating images at arbitrary locations. Because of the inherent inconsistency in the helical data set, however, recent studies have unveiled various HCT-related image artifacts. In this paper, we have performed a detailed analysis on one of the artifacts in the 3D shaded surface display (SSD): the “grooving” artifact. We have developed an analytical model to show that the artifact is caused by the angular-dependent edge response of the HCT reconstruction algorithm. The accuracy of the model is confirmed by both computer simulations and phantom experiments. Based on the model, we have presented several correction algorithms to combat the grooving artifacts. Computer simulations and phantom experiments are used to demonstrate the effectiveness and robustness of the corrections View full abstract»

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  • An MCP-based system for beta autoradiography

    Publication Year: 1999 , Page(s): 636 - 638
    Cited by:  Papers (12)
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    Describes a pre-commercial prototype autoradiography system which can be used to image a variety of radio-labelled biological samples, ranging from lymphocyte proliferation assays to semi-thin whole-body tissue slices. These samples can be imaged with high spatial resolution (~70 microns) and high sensitivity (e.g. 3H-minimum detectable activity 0.001 Bq in 20 hours) over a wide (5-6 orders of magnitude) dynamic range. Specimens are automatically presented, through a vacuum load-lock, to an imaging microchannel plate (MCP) detector operating in high (~10-6 mbar) vacuum. We present images obtained from tritium-labelled samples and discuss the importance of the new system for a variety of biological techniques View full abstract»

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  • Conceptual design of a high-sensitivity small animal PET camera with 4π coverage

    Publication Year: 1999 , Page(s): 498 - 502
    Cited by:  Papers (17)  |  Patents (1)
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    We present a conceptual design of a high-sensitivity PET camera that completely encloses a small animal in a rectangular volume formed by 6 planar banks of detector modules. The 4π geometry and 3 attenuation-length fast scintillators provide significantly higher sensitivity than contemporary animal PET cameras, while the depth of interaction (DOI) measurement and small crystal width achieve isotropic, high spatial resolution. The absolute sensitivity is 24 kcps/μCi, ~120 times higher than contemporary systems; the true event count rate is increased by covering 10 times the solid angle using 80% efficient detectors. For a 29 g “mouse”, the total scatter event rate is 11% of the total true event rate. A short (2 nsec) coincidence window and the absence of out of field activity implicit with whole animal coverage yield a small random fraction. Assuming a maximum system count rate of 10 Mcps (achievable with electronics under development), the noise equivalent count rate as a function of activity concentration has a maximum of 6.6 Mcps at 25 μCi/cc. 2D reconstruction algorithms indicate a spatial resolution of 2.3 mm fwhm through most of the field of view View full abstract»

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  • A differential attenuation method for simultaneous estimation of SPECT activity and attenuation distributions

    Publication Year: 1999 , Page(s): 535 - 541
    Cited by:  Papers (16)
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    A penalized weighted least squares (PWLS) reconstruction algorithm is described that simultaneously estimates activity and attenuation distributions from emission sinogram data alone. This estimation technique is based on differential attenuation information and is applicable to any SPECT imaging isotope with emissions at two or more distinct energies, after compensating for Compton scatter. A rotation-based forward projector is used to efficiently model photon attenuation at multiple emission energies, as well as distance-dependent spatial resolution. The algorithm was tested using simulated scatter-free 201Tl projection data from a single-slice numerical cardiac phantom with a large cold myocardial defect. Poisson noise was added to the projection data to mimic clinically realistic count densities. The activity estimates resulting from the proposed method had fewer artifacts and were substantially more accurate than images reconstructed with filtered backprojection without compensation for attenuation. Several techniques were employed to reduce the time required for the iterative routine to converge and to improve the stability of the solution, including: (1) a pre-conditioning image variable transformation; (2) a coarse-to-fine grid initialization schedule; and (3) a convex hull image mask determined directly from the projection data. The combined effect of these techniques was a reduction in computation time by a factor of ~200 View full abstract»

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  • A practical 3D tomographic method for correcting patient head motion in clinical SPECT

    Publication Year: 1999 , Page(s): 667 - 672
    Cited by:  Papers (33)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB)  

    Patient motion during brain SPECT studies can degrade resolution and introduce distortion. We have developed a correction method which incorporates a motion tracking system to monitor the position and orientation of the patient's head during acquisition. Correction is achieved by spatially repositioning projections according to the measured head movements and reconstructing these projections with a fully 3D algorithm. The method has been evaluated in SPECT studies of the Hoffman 3D brain phantom performed on a triple head camera with fan beam collimation. Movements were applied to the phantom and recorded by a head tracker during SPECT acquisition. Fully 3D reconstruction was performed using the motion data provided by the tracker. The correction accuracy was assessed by comparing the corrected and uncorrected studies with a motion-free study, both visually and by calculating the mean squared error (MSE). In all studies, motion correction reduced the distortion and improved the MSE by a factor of two or more. We conclude that this method can compensate for head motion under clinical SPECT imaging conditions View full abstract»

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  • Image oscillation reduction and convergence acceleration for OS-EM reconstruction [PET imaging]

    Publication Year: 1999 , Page(s): 603 - 607
    Cited by:  Papers (2)
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    Investigates the use of two approaches to reduce the image oscillation of OS-EM (ordered subset expectation maximization) reconstruction that is due to the inconsistencies among different partial subsets of the projection measurements (the sinogram) when considering as a group. One approach pre-processes the sinogram to make it satisfy a sinogram consistency condition. The second approach takes the average of the intermediary images (i.e. it smoothes image values over sub-iterations). Both approaches were found to be capable of reducing the image oscillation, and a combination of both was most effective. With these approaches, the convergence of OS-EM reconstruction is further improved. For computer-simulated data and real PET data, a single iteration of this new OS-EM reconstruction was shown to yield images comparable to those with 80 EM iterations View full abstract»

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  • Imaging of an artery from skin surface using beta camera

    Publication Year: 1999 , Page(s): 583 - 586
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Dynamic images of positron distribution in artery was measured from the skin surface of human subject using beta camera for noninvasive measurement of the input function. After estimating the possibility of the method by some phantom studies, the beta camera was attached from the skin surface on the artery of wrist during the PET measurement using the O-15 water injection method. After injection of O-15 water, dynamic images of the artery were measured. Regions of interest (ROIs) were set on the artery and on the adjacent area of the artery. From the ROIs analysis, a time activity curve similar to that measured by the invasive technique was noninvasively obtained View full abstract»

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  • Initial results from a PET/planar small animal imaging system

    Publication Year: 1999 , Page(s): 571 - 575
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A pair of stationary, opposed scintillation detectors in time coincidence is being used to create planar projection or tomographic images of small animals injected with positron-emitting radiotracers. The detectors are comprised of arrays of individual crystals of Bi12GeO20 coupled to position-sensitive photomultiplier tubes. The system uses FERA (LeCroy Research Systems) charge-sensitive ADCs and a low-cost digital I/O board as a FERA bus-to-host bridge. In projection mode, the animal is placed within the 55 mm×45 mm useful field of view of the detectors, and images are formed from coincidence lines that fall close to the normals of both detectors. In tomographic mode, the animal is placed on a rotation stage between the detectors and rotated around a vertical axis to acquire all possible lines of response. Tomographic images are then reconstructed from those lines falling within a user-specified angle of each detector normal. In mice, the system is capable of high-speed, whole-body dynamic projection imaging, and whole-body tomographic imaging of slowly varying tracer distributions. An ECG gating capability is also available for evaluating cardiac function. This system is currently being used to study tracer transport in normal and genetically engineered mice View full abstract»

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  • Absolute quantitation of myocardial activity in phantoms

    Publication Year: 1999 , Page(s): 659 - 666
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    We have developed a new technique for compensating myocardial SPECT images for partial volume errors using co-registered X-ray CT images. The CT-derived myocardial mass defines a template that can be assigned a unit activity and mathematically projected with a realistic physical model of the radionuclide imaging process, including non-ideal collimation and incorporating an object-specific attenuation map from CT. The template projections then are reconstructed using a SPECT reconstruction algorithm to obtain a pixel-by-pixel partial-volume correction for the myocardial SPECT image. Experiments in phantoms demonstrate that this technique substantially improves the absolute quantitation of myocardial radionuclide concentration, reducing the accuracy error from approximately 50% to less than 8%. This method also can by used for correcting background effects such as “spill-in” of background counts from uptake in the liver View full abstract»

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  • A 3D HIDAC-PET camera with sub-millimetre resolution for imaging small animals

    Publication Year: 1999 , Page(s): 468 - 473
    Cited by:  Papers (94)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    A HIDAC-PET camera consisting essentially of 5 million 0.5 mm gas avalanching detectors has been constructed for small-animal imaging. The particular HIDAC advantage-a high 3D spatial resolution-has been improved to 0.95 mm fwhm and to 0.7 mm fwhm when reconstructing with 3D-OSEM methods incorporating resolution recovery. A depth-of-interaction resolution of 2.5 mm is implicit, due to the laminar construction. Scatter-corrected sensitivity, at 8.9 cps/kBq (i.e. 0.9%) from a central point source, or 7.2cps/kBq (543cps/kBq/cm 3) from a distributed (40 mm diameter, 60 mm long) source is now much higher than previous, and other, work. A field-of-view of 100 mm (adjustable to 200 mm) diameter by 210 mm axially permits whole-body imaging of small animals, containing typically 4 MBqs of activity, at 40 kcps of which 16% are random coincidences, with a typical scatter fraction of 44%. Throughout the field-of-view there are no positional distortions and relative quantitation is uniform to ±3.5%, but some variation of spatial resolution is found. The performance demonstrates that HIDAC technology is quite appropriate for small-animal PET cameras View full abstract»

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  • The watershed algorithm: a method to segment noisy PET transmission images

    Publication Year: 1999 , Page(s): 713 - 719
    Cited by:  Papers (18)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    Attenuation correction is essential to PET imaging but often requires impractical acquisition times. Segmentation of short, noisier transmission scans has been proposed as a solution. We report that a 3D morphological tool-the watershed algorithm-is well adapted for segmenting even two-minute PET transmission images. The technique is non-iterative, fast and fully 3D. It inherently ensures class continuity and eliminates outliers. Pre-filtering the data induced smoother class edges, showing that a multi-resolution approach could be used to deal with the partial volume effect and excessive noise in the data. The algorithm was tested on two-minute scans of a torso phantom and on a human study View full abstract»

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