Abstract
Purpose of the Study: Scattered gamma photons in single photon emission computed tomography (SPECT) is one of the main issues that degrade the image quality. There are several types of scatter correction methods. However, none of the technique is applied in routine clinical Tc-99m SPECT imaging. Therefore, Zinc (Zn) material filter was constructed for pre-filtration of scattered gamma photons in Tc-99m single photon emission computed tomography (SPECT).Materials and Methods: Tc-99m radioactivity was administered into the Carlson’s phantom. Planar and tomographic data were acquired with and without hot regions insert, respectively, with and without material filter. Scatter to non-scatter ratio was measured from the photopeak region of Tc-99m spectra. Tomographic images were generated using filtered back projection method. Contours on images were drawn with ImageJ software. Images obtained with and without material filter were analysed in terms of detectability of hot regions.Results: Remarkable decrease (≈ 21%) in the ratio of scattered to non-scattered gamma photons with material filter was achieved. Detectability of smaller hot regions with material filter was enhanced. In terms of sizes of all hot regions, material filter results appear closer to the original sizes.Conclusion: Material filter technique could be applied in Tc-99m clinical SPECT, while organ phantom studies are needed.
Highlights
Introduction and the scintillation detectora significant fraction of the scattered gamma photons would be pre-filtered from the imageSingle photon emission imaging; planar and tomography have played a significant role in the diagnosis of diseases
Due to poor energy resolution of imaging equipment, up to 40% of scattered gamma photons are detected in the standard energy window (20% centered at 140 keV) data which degrades the quality of reconstructed image [1,2]
Earlier studies show the effect of Zn 0.2 mm thick material filter on spatial resolution, system uniformity and system volume sensitivity, [8] contrast, signal-to-noise ratio (SNR), detectability of Tc-99m single photon emission computed tomography (SPECT) hot and cold regions [9]
Summary
Introduction and the scintillation detectora significant fraction of the scattered gamma photons would be pre-filtered from the imageSingle photon emission imaging; planar and tomography have played a significant role in the diagnosis of diseases. The aim of this study is to construct a material filter from a flat sheet of another material; Zinc (Zn) to preferentially absorb some fraction of scattered gamma photons before reaching the scintillation detector – NaI (Tl) – of the gamma camera. This filter has been constructed for Tc-99m (140 keV) considering the most common use as a radionuclide in single photon emission computed tomography. It is expected that; the use of zinc material filter can play a vital role in enhancing the quality of Tc-99m SPECT images
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