Simulation study on a stationary data acquisition SPECT system with multi-pinhole collimators attached to a triple-head
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ORIGINAL ARTICLE
Simulation study on a stationary data acquisition SPECT system with multi-pinhole collimators attached to a triple-head gamma camera system Koichi Ogawa • Yuta Ichimura
Received: 12 February 2014 / Accepted: 21 May 2014 Ó The Japanese Society of Nuclear Medicine 2014
Abstract Objectives The aim of the study was to develop a new SPECT system that makes it possible to acquire projection data stationary using a triple-head gamma camera system. Methods We evaluated several data acquisition geometry with multi-pinhole collimators attached to a triple-head gamma camera system. The number of pinholes for each camera was three to twelve, and we located these holes on collimator plates adequately. These collimator holes were tilted by predefined angles to efficiently cover the field of view of the data acquisition system. Acquired data were reconstructed with the OS-EM method. In the simulations, we used a three-dimensional point source phantom, brain phantom, and myocardial phantom. Attenuation correction was conducted with the x-ray CT image of the corresponding slice. Results Reconstructed images of the point source phantom showed that the spatial resolution could be improved with the small number of pinholes. On the other hand, reconstructed images of the brain phantom showed that the large number of pinholes yielded images with less artifact. The results of the simulations with the myocardial phantom showed that more than eight pinholes could yield an accurate distribution of activity when the source was distributed only in the myocardium. Conclusions The results of the simulations confirmed that more than eight pinholes for each detector were required to reconstruct an artifact free image in the triple-head SPECT system for imaging of brain and myocardium.
K. Ogawa (&) Y. Ichimura Department of Applied Informatics, Faculty of Science and Engineering, Hosei University, 3-7-2 Kajinocho, Koganei, Tokyo 184-8584, Japan e-mail: [email protected]
Keywords Multi-detector SPECT Multi-pinhole collimator Stationary data acquisition
Introduction Single photon emission CT (SPECT) and positron emission tomography (PET) are tomographic imaging techniques designed to examine the function of organs by detecting gamma rays emitted from radiopharmaceuticals in a patient’s body. Generally, the quality of SPECT images is worse than that of PET images in terms of the spatial resolution. However, SPECT study uses inexpensive radiopharmaceuticals with a relatively long half-life, and so most hospitals use SPECT systems for the diagnosis of myocardial and brain diseases. The disadvantages of the SPECT system are mainly caused by the collimator used to determine the direction of the gamma rays that enter the scintillation detector [1]. Generally, a parallel-hole collimator or fan-beam collimator is used for the SPECT system. The geometrical efficiency of a collimator depends on the diameter and length of a hole [2], while due to its low efficiency the data acquisition time becomes long. This increases the burden
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