A radiological imaging apparatus of the present invention comprises an image pickup device and a medical examinee holding device that is provided with a bed. The image pickup device includes a large number of radiation detectors and radiation detector support plates. A large number of radiation detectors are mounted around the circumference of a through-hole and arranged in the axial direction of the through-hole. The radiation detectors are arranged in three layers formed radially with respect to the center of the through-hole and mounted on the lateral surfaces of the radiation detector support plates. Since the radiation detectors are not only arranged in the axial direction and circumferential direction of the through-hole but also arrayed in the radial direction, it is possible to obtain accurate information about a γ-ray arrival position in the radial direction of the through-hole (the positional information about a radiation detector from which a γ-ray image pickup signal is output). The use of accurate information about γ-ray arrival increases the tomogram accuracy. As a result, the present invention enhances the tomogram accuracy, that is, the PET examination accuracy.

Radiological imaging apparatus

UNLABELLED With the introduction of 99mTc-teboroxime, a previously undocumented artifact has shown up in cardiac SPECT imaging. In the images, the uptake values near the inferior wall are lower than expected. The artifact has been reported in the literature, but an adequate explanation has not yet been provided. The high uptake of 99mTc-teboroxime in the liver has been demonstrated to be the cause of this artifact. METHODS With simulations we show that an artifact can be reproduced by applying filtered backprojection (without corrections for attenuation) of attenuated and blurred projections. The conclusions from the simulations are validated with SPECT and PET phantom measurements. Maximum likelihood expectation maximization (ML-EM) reconstruction is applied to evaluate the effect of accurate attenuation correction. The influence of the high liver uptake on the convergence of ML-EM was also evaluated. RESULTS The artifact results mainly when the photon attenuation during reconstruction is ignored. This results in a distorted reconstruction of the liver. These distortions affect the neighboring inferior wall of the myocardium. While the use of opposite projections reduces the effect, accurate attenuation correction nearly eliminates it. A small additional deformation is caused by the position dependence of the spatial resolution of the gamma camera. It was also noted that the presence of the liver slows down the convergence of ML-EM in the heart region. CONCLUSION The liver-heart artifact is an attenuation effect and is eliminated by attenuation correction. The local convergence of ML-EM is affected by the total image content.

http://jnm.snmjournals.org/content/36/1/133.full.pdf

A study of the liver-heart artifact in emission tomography

Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2-[]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small and mainly affect parameters related to early and late time points on the impulse response function ( and, to a lesser extent, VD). The optimal number of EM iterations was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands.

/pdf/parametric-image-reconstruction-using-spectral-analysis-of-3sgypoanfa.pdf

Parametric image reconstruction using spectral analysis of PET projection data.

Dynamic computed tomography (CT) imaging aims at reconstructing image sequences where the dynamic nature of the living human body is of primary interest. The main applications concerned are image-guided interventional procedures, functional studies and cardiac imaging. The introduction of ultra-fast rotating gantries along with multi-row detectors and in near future area detectors allows huge progress toward the imaging of moving organs with low-contrast resolution. This paper gives an overview of the different concepts used in dynamic CT. A new reconstruction algorithm based on a voxel-specific dynamic evolution compensation is also presented. It provides four-dimensional image sequences with accurate spatio-temporal information, where each frame is reconstructed using a long-scan acquisition mode on several half-turns. In the same time, this technique permits to reduce the dose delivered per rotation while keeping the same signal to noise ratio for every frame using an adaptive motion-compensated temporal averaging. Results are illustrated on simulated data.

Dynamic X-ray computed tomography

Quantitative assessment of regional myocardial blood flow with thallium-201 and SPECT☆

Data acquisition in SPECT assumes that there is no change in radionuclide distribution during data collection However, this assumption is not valid in radiopharmaceuticals with rapid temporal changes in radioactivity Artifacts and quantitative errors are studied using phantom studies, mathematical models, and clinical myocardial data Projection data of each model were sequentially multiplied by weighting coefficients that varied mono-exponentially with time, and the SPECT images were reconstructed A long data acquisition time in comparison to the clearance of the tracer can be a significant cause of artifact When the myocardial septum-to-lateral count ratio is used as an index of distortion, a shorter acquisition time than the effective half-life of the tracer is required to reduce the error of the septum-to-lateral count ratio to within 10% Since 180 degrees rotation acquisition causes artifacts depending on the direction of rotation, 360 degrees acquisition is preferable Continuous repetitive rotation acquisition is a suitable method for dynamic SPECT to reduce quantitative errors and artifacts

http://jnm.snmjournals.org/content/33/6/1200.full.pdf

A simulation of dynamic SPECT using radiopharmaceuticals with rapid clearance.

PROBLEM TO BE SOLVED: To improve scatter correction accuracy of a nuclear medicine diagnosis device that can perform coincidence counting of multiple nuclide.SOLUTION: The nuclear medicine diagnosis device includes: a gamma-ray detection portion which detects gamma-rays; a counting distribution data generating portion which generates, based on an output from the gamma-ray detection portion, a first counting distribution data of gamma-ray having an energy in a first energy window corresponding to a first nuclide and a second counting distribution data of gamma-ray having an energy in a second energy window corresponding to a second nuclide; a storage portion which stores an attenuation coefficient distribution of radiation related to a subject; a reconstruction portion which reconstructs a first image data on which an attenuation correction is performed based on the attenuation coefficient distribution and the first counting distribution data; a scattered radiation counting distribution generation portion which generates, based on the first image data and the attenuation coefficient distribution, a counting distribution of a first scattered radiation derived from the first nuclide having the energy in the second energy window; a scattering correction section which performs a scattering correction on the second counting distribution data based on the counting distribution of the first scattered radiation.

Nuclear medicine diagnosis device, medical image processor and medical image diagnosis device

PROBLEM TO BE SOLVED: To provide a nuclear medicine diagnostic equipment which can enhance the image quality of an image, irrespective of whether a collimator being synchronized with a semiconductor sensing element. SOLUTION: The nuclear medicine diagnostic equipment, which is related to the sensitivity direction of the semiconductor sensing element prescribed by the arrangement relationship between the element and the opening part of the collimator and which corrects deviational angle from its normal direction. Its 'correction' in this case refers to a mapping processing operation, where positional information constituting a signal from the element obtained on the assumption that the deviation angle exists is realigned to positional information according to the normal direction or a processing operation, where when the image is a tomogram, a signal which is acquired at each rotation angle of the sensing element is allocated to a projection angle at which the signal is regarded as projection data, regarding a projection angle at which the deviation angle is subtracted with reference to the rotation angle. COPYRIGHT: (C)2001,JPO

Nuclear medicine diagnostic equipment and data processing method in the equipment, and recording medium for recording program related to the method

PURPOSE: To collect an emission data and a transmission data while ensuring the effective view sufficiently at the time of collecting the transmission data by enhancing the picture quality (e.g. resolution) of an SPECT image. CONSTITUTION: The TCT-SPECT simultaneous collection system collects a transmission data based on the radiation detected through a detector 5b simultaneously, or substantially simultaneously, with an emission data based on the radiation detected through a detector 5a. A radiation source 7B is disposed oppositely to an incident face for providing a desired effective view with respect to the incident face of the detector 5b receiving a radiation from the radiation source 7B. The radiation source 7B is provided with an arm 7A for supporting the detector 5b.

Tct-spect simultaneous collection system

PROBLEM TO BE SOLVED: To overcome the drawbacks of conventionally used amorphous Se and polycrystalline semiconductor and to use a thin film transistor (hereinafter referred to as "TFT") widely used at present. Provided is a radiation detector including a photoelectric conversion member that can be matched with a signal readout circuit using the same. SOLUTION: The photoelectric conversion member 11 in the radiation detector according to the present invention has a function of generating charges by the incidence of radiation, and a plurality of charges collected and arranged on one surface thereof in a two-dimensional matrix. It has an electrode 12 and a bias electrode 11a on the other surface. The member 11 Is composed of a single crystal semiconductor. A plurality of the photoelectric conversion members 11 are arranged in a two-dimensional matrix of pixels each having a set of a TFT, a pixel electrode, and a capacitor. 00 are arranged two-dimensionally. This arrangement is such that the charge collecting electrodes 12 and the pixel electrodes 100 have a one-to-one correspondence.

Nobuatsu Motomura

Papers

A simulation of dynamic SPECT using radiopharmaceuticals with rapid clearance.

Nuclear medicine diagnosis device, medical image processor and medical image diagnosis device

Nuclear medicine diagnostic equipment and data processing method in the equipment, and recording medium for recording program related to the method

Tct-spect simultaneous collection system

Radiation detector assembly and medical image diagnosis device