Deprez, Karel

Van Audenhaege, Karen

Van Holen, Roel

Vandenberghe, Stefaan

English

Ghent University Academic Bibliography

 Development of a compact MicroSPECT System for sequential SPECT-MRI   Primary Authors: Prof. VAN HOLEN, Roel (Ghent University) <roel.vanholen@ugent.be>  Co-authors: Ms. VAN AUDENHAEGE, Karen (Ghent University) <karen.vanaudenhaege@ugent.be> Mr. DEPREZ, Karel (Ghent University) <k.deprez@ugent.be> Prof. VANDENBERGHE, Stefaan (Ghent University) <stefaan.vandenberghe@ugent.be>   Abstract content INTRODUCTION The main limitations for operating a microSPECT scanner in the vicinity of an microMRI scanner are the system size and the compatibility of the collimators and detectors with the MR. We are currently developing a benchtop-sized microSPECT system that can be placed on the table in front of the magnet. Therefore, multi-lofthole collimators are used that form many (100 in total) minified object projections onto the detector. Previously, our simulation results have demonstrated a reconstructed spatial resolution around 900 micron in combination with a 0.4% sensitivity. These results are based on our previous generation NaI(Tl) scintillation detectors (5mm) with a 1 mm intrinsic resolution. OBJECTIVE The purpose of this study is twofold. First, we investigate a thin scintillator (2mm NaI(Tl)) to obtain even higher spatial resolution to further increase the spatial resolution of our system, while giving up about 60% of the sensitivity due to the smaller crystal thickness. Furthermore, we test our collimators inside the MR bore to investigate the influence of the collimator on MR T1 T2 and T2* images. Our collimator is a pure tungsten multi-lofthole collimator developed using additive manufacturing. METHODS A 2mm NaI(Tl) detector was coupled to an MA-PMT (H8500, Hamamatsu) using a 2mm quartz glass light guide. A robot-controlled beam source (Tc99m) scanned the surface of our detector in 1 mm steps. From this calibration measurement, the mean detector response functions (MDRFs) were derived. These MDRFs serve as input for a Maximum Likelihood positioning algorithm. Spatial resolution was measured at different detector locations and the FWHM was calculated as a measure for intrinsic resolution. Our pure tungsten multi-lofthole collimator was placed inside the MR bore of a Bruker Pharmascan 70/16, next to a homogeneous water phantom. T1, T2 and T2* images were recorded with and without the collimator next to the phantom. We re-shimmed the magnetic field with the collimator in place. The percent difference of the images without collimator present are calculated. RESULTS With our 2mm thick crystal coupled to the MA-PMT we were able to obtain an average spatial resolution of 750 micron over the detector surface. From the MR measurements, we obtained 1.06% difference for the T1 images with and without collimator present. We observed 0.084% difference for the T2 images and a 2.5% difference for the T2* weighted images. CONCLUSION The first steps towards the development of our bench top microSPECT system have been completed. The detector shows very good spatial resolution performance while our collimator does not disturb the T1, T2 and T2* images of a homogeneous water phantom. T2* showed the largest diference, which is expected because of the higher sensitivity to magnetic field inhomogeneities. In a next phase, our detector/collimator setup will be tested in proximity of the magnet.!

Development of a compact MicroSPECT system for sequential SPECT- MRI

https://biblio.ugent.be/publication/3119695/file/3119712

Development of a compact MicroSPECT system for sequential SPECT- MRI

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Ghent University Academic Bibliography