Performance evaluation of side-by-side optically coupled monolithic LYSO crystals.
Med Phys
; 49(8): 5616-5626, 2022 Aug.
Article
en En
| MEDLINE
| ID: mdl-35689501
ABSTRACT
BACKGROUND:
Significant interest has been recently shown for using monolithic scintillation crystals in molecular imaging systems, such as positron emission tomography (PET) scanners. Monolithic-based PET scanners result in a lower cost and higher sensitivity, in contrast to systems based on the more conventional pixellated configuration. The monolithic design allows one to retrieve depth-of-interaction information of the impinging 511 keV photons without the need for additional hardware materials or complex positioning algorithms. However, the so-called edge-effect inherent to monolithic-based approaches worsens the detector performance toward the crystal borders due to the truncation of the light distribution, thus decreasing positioning accuracy.PURPOSE:
The main goal of this work is to experimentally demonstrate the detector performance improvement when machine-learning artificial neural-network (NN) techniques are applied for positioning estimation in multiple monolithic scintillators optically coupled side-by-side.METHODS:
In this work, we show the performance evaluation of two LYSO crystals of 33 × 25.4 × 10 mm3 optically coupled by means of a high refractive index adhesive compound (Meltmount, refractive index n = 1.70). A 12 × 12 silicon photomultiplier array has been used as photosensor. For comparison, the same detector configuration was tested for two additional coupling cases (1) optical grease (n = 1.46) in between crystals, and (2) isolated crystals using black paint with an air gap at the interface (named standard configuration). Regarding 2D photon positioning (XY plane), we have tested two differentmethods:
(1) a machine-learning artificial NN algorithm and (2) a squared-charge (SC) centroid technique.RESULTS:
At the interface region of the detector, the SC method achieved spatial resolutions of 1.7 ± 0.3, 2.4 ± 0.3, and 2.6 ± 0.4 mm full-width at half-maximum (FWHM) for the Meltmount, grease, and standard configurations, respectively. These values improve to 1.0 ± 0.2, 1.2 ± 0.2, and 1.2 ± 0.3 mm FWHM when the NN algorithm was employed. Regarding energy performance, resolutions of 18 ± 2%, 20 ± 2%, and 23 ± 3% were obtained at the interface region of the detector for Meltmount, grease, and standard configurations, respectively.CONCLUSIONS:
The results suggest that optically coupling together scintillators with a high refractive index adhesive, in combination with an NN algorithm, reduces edge-effects and makes it possible to build scanners with almost no gaps in between detectors.Palabras clave
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Bases de datos:
MEDLINE
Asunto principal:
Fotones
/
Tomografía de Emisión de Positrones
Idioma:
En
Revista:
Med Phys
Año:
2022
Tipo del documento:
Article
País de afiliación:
España