Improvement of brain single photon emission tomography (SPET) using transmission data acquisition in a four-head SPET scanner

Abstract

Attenuation coefficient maps (mu-maps) are a useful way to compensate for non-uniform attenuation when performing single photon emission tomography (SPET). A new method was developed to record single photon transmission data and a mu-map for the brain was produced using a four-head SPET scanner. Transmission data were acquired by a gamma camera opposite to a flood radioactive source attached to one of four gamma cameras in the four-head SPET scanner. Attenuation correction was performed using the iterative expectation maximization algorithm and the mu-map. Phantom studies demonstrated that this method could reconstruct the distribution of radioactivity more accurately than conventional methods, even for a severely non-uniform mu-map, and could improve the quality of SPET images. Clinical application to technetium-99m hexamethyl-propylene amine oxime (HMPAO) brain SPET also demonstrated the usefulness of this method. Thus, this method appears to be promising for improvement in the image quality and quantitative accuracy of brain SPET.

Effect of Signal Filtering on Image Quality of Projection-Based Magnetic Particle Imaging

“…It is known, however, that the image quality of a reconstructed image using the ML-EM algorithm depends on the iteration number [15]. Thus, it will also be necessary to study the dependency of the image quality and quantitativity of the MPI image on the iteration number.…”

“…In order to acquire projection data for image reconstruction, a sample (phantom) placed in the receiving coil was rotated over 180˚ at a sampling angle of 5˚ and translated from −16 to 16 mm in the x-direction at 1 mm intervals using an XYZ-axes rotary stage (HPS80-50X-M5, Sigma Koki Co., Tokyo, Japan), which was controlled using LabVIEW (National Instruments Co., TX, USA). Each set of projection data was transformed into 64 bins by linear interpolation and image reconstruction was performed using the filtered back-projection (FBP) method with a ramp filter [11] as a reconstruction filter or the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15. The details of the FBP method and the ML-EM algorithm are described in our previous paper [3].…”

Improvement of image resolution of brain SPECT by use of the wide-angle offset acquisition method

“…In the present study, a new method of offset acquisition was devised. Data were acquired using a dualdetector SPECT system with shifting of the sampling angle by one half, and the maximum likelihood-expectation maximization (MLEM) method was used for reconstruction [2,3] . In this study, projection data with a sampling angle of 6°were acquired and used for image reconstruction, simulating a larger sampling angle than employed with the usual method.…”

Truncation correction of fan beam transmission data for attenuation correction using parallel beam emission data on a 3-detector SPECT system

“…Recently, attenuation correction has been performed using attenuation coefficient maps obtained by transmission computed tomography (TCT) in each patient [1,2]. However, the TCT method using a cardiac fan beam collimator with high sensitivity and resolution in deep areas [3] is not as common as the TCT for cerebral blood flow single photon emission computed tomography (SPECT), because there are problems such as the artifacts caused by the truncation of projection data outside the effective field of view (FOV) [4,5].…”