Design and performance evaluation of a 20-aperture multipinhole collimator for myocardial perfusion imaging applications
ABSTRACT Single photon emission computed tomography (SPECT) myocardial perfusion imaging remains a critical tool in the diagnosis of coronary artery disease. However, after more than three decades of use, photon detection efficiency remains poor and unchanged. This is due to the continued reliance on parallel-hole collimators first introduced in 1964. These collimators possess poor geometric efficiency. Here we present the performance evaluation results of a newly designed multipinhole collimator with 20 pinhole apertures (PH20) for commercial SPECT systems. Computer simulations and numerical observer studies were used to assess the noise, bias and diagnostic imaging performance of a PH20 collimator in comparison with those of a low energy high resolution (LEHR) parallel-hole collimator. Ray-driven projector/backprojector pairs were used to model SPECT imaging acquisitions, including simulation of noiseless projection data and performing MLEM/OSEM image reconstructions. Poisson noise was added to noiseless projections for realistic projection data. Noise and bias performance were investigated for five mathematical cardiac and torso (MCAT) phantom anatomies imaged at two gantry orbit positions (19.5 and 25.0 cm). PH20 and LEHR images were reconstructed with 300 MLEM iterations and 30 OSEM iterations (ten subsets), respectively. Diagnostic imaging performance was assessed by a receiver operating characteristic (ROC) analysis performed on a single MCAT phantom; however, in this case PH20 images were reconstructed with 75 pixel-based OSEM iterations (four subsets). Four PH20 projection views from two positions of a dual-head camera acquisition and 60 LEHR projections were simulated for all studies. At uniformly-imposed resolution of 12.5 mm, significant improvements in SNR and diagnostic sensitivity (represented by the area under the ROC curve, or AUC) were realized when PH20 collimators are substituted for LEHR parallel-hole collimators. SNR improves by factors of 1.94-2.34 for the five patient anatomies and two orbital positions studied. For the ROC analysis the PH20 AUC is larger than the LEHR AUC with a p-value of 0.0067. Bias performance, however, decreases with the use of PH20 collimators. Systematic analyses showed PH20 collimators present improved diagnostic imaging performance over LEHR collimators, requiring only collimator exchange on existing SPECT cameras for their use.
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ABSTRACT: 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. 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. 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. 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.Annals of Nuclear Medicine 06/2014; 28(8). DOI:10.1007/s12149-014-0865-2 · 1.51 Impact Factor
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ABSTRACT: Several new technologies for single photon emission computed tomography (SPECT) instrumentation with parallel-hole collimation have been proposed to improve detector sensitivity and signal collection efficiency. Benefits from improved signal efficiency include shorter acquisition times and lower dose requirements. In this paper, the authors show a possibility of over an order of magnitude enhancement in photon detection efficiency (from 7.6 × 10(-5) to 1.6 × 10(-3)) for dopamine transporter (DaT) imaging of the striatum over the conventional SPECT parallel-hole collimators by use of custom-designed 20 multipinhole (20-MPH) collimators with apertures of 0.75 cm diameter.Medical Physics 11/2014; 41(11):112501. DOI:10.1118/1.4897567 · 3.01 Impact Factor