Reducing Calibration Time in PET Systems Based on Monolithic Crystals

In the past years, the gamma-ray detector designs based on the monolithic crystals have demonstrated to be excellent candidates for the design of high-performance PET systems. The monolithic crystals allow to achieve the intrinsic detector resolutions well below state-of-the-art; to increase packing...

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Autores principales:	Marta Freire, Gabriel Cañizares, Sara Echegoyen, Andrea Gonzalez-Montoro, Antonio J. Gonzalez
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	positron emission tomography monolithic crystals calibration total-body PET whole-body PET Medicine (General) R5-920
Acceso en línea:	https://doaj.org/article/d448a1ed2e624d31b135155feba5335d
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spelling	oai:doaj.org-article:d448a1ed2e624d31b135155feba5335d2021-11-10T05:57:40ZReducing Calibration Time in PET Systems Based on Monolithic Crystals2296-858X10.3389/fmed.2021.734476https://doaj.org/article/d448a1ed2e624d31b135155feba5335d2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fmed.2021.734476/fullhttps://doaj.org/toc/2296-858XIn the past years, the gamma-ray detector designs based on the monolithic crystals have demonstrated to be excellent candidates for the design of high-performance PET systems. The monolithic crystals allow to achieve the intrinsic detector resolutions well below state-of-the-art; to increase packing fraction thus, increasing the system sensitivity; and to improve lesion detectability at the edges of the scanner field of view (FOV) because of their intrinsic depth of interaction (DOI) capabilities. The bottleneck to translate to the clinical PET systems based on a large number of monolithic detectors is eventually the requirement of mechanically complex and time-consuming calibration processes. To mitigate this drawback, several methods have been already proposed, such as using non-physically collimated radioactive sources or implementing the neuronal networks (NN) algorithms trained with simulated data. In this work, we aimed to simplify and fasten a calibration process of the monolithic based systems. The Normal procedure consists of individually acquiring a 11 × 11 22Na source array for all the detectors composing the PET system and obtaining the calibration map for each module using a method based on the Voronoi diagrams. Two reducing time methodologies are presented: (i) TEST1, where the calibration map of one detector is estimated and shared among all others, and (ii) TEST2, where the calibration map is slightly modified for each module as a function of their detector uniformity map. The experimental data from a dedicated prostate PET system was used to compare the standard calibration procedure with both the proposed methods. A greater similarity was exhibited between the TEST2 methodology and the Normal procedure; obtaining spatial resolution variances within 0.1 mm error bars and count rate deviations as small as 0.2%. Moreover, the negligible reconstructed image differences (13% deviation at most in the contrast-to-noise ratio) and almost identical contrast values were reported. Therefore, this proposed method allows us to calibrate the PET systems based on the monolithic crystals reducing the calibration time by approximately 80% compared with the Normal procedure.Marta FreireGabriel CañizaresSara EchegoyenAndrea Gonzalez-MontoroAntonio J. GonzalezFrontiers Media S.A.articlepositron emission tomographymonolithic crystalscalibrationtotal-body PETwhole-body PETMedicine (General)R5-920ENFrontiers in Medicine, Vol 8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	positron emission tomography monolithic crystals calibration total-body PET whole-body PET Medicine (General) R5-920
spellingShingle	positron emission tomography monolithic crystals calibration total-body PET whole-body PET Medicine (General) R5-920 Marta Freire Gabriel Cañizares Sara Echegoyen Andrea Gonzalez-Montoro Antonio J. Gonzalez Reducing Calibration Time in PET Systems Based on Monolithic Crystals
description	In the past years, the gamma-ray detector designs based on the monolithic crystals have demonstrated to be excellent candidates for the design of high-performance PET systems. The monolithic crystals allow to achieve the intrinsic detector resolutions well below state-of-the-art; to increase packing fraction thus, increasing the system sensitivity; and to improve lesion detectability at the edges of the scanner field of view (FOV) because of their intrinsic depth of interaction (DOI) capabilities. The bottleneck to translate to the clinical PET systems based on a large number of monolithic detectors is eventually the requirement of mechanically complex and time-consuming calibration processes. To mitigate this drawback, several methods have been already proposed, such as using non-physically collimated radioactive sources or implementing the neuronal networks (NN) algorithms trained with simulated data. In this work, we aimed to simplify and fasten a calibration process of the monolithic based systems. The Normal procedure consists of individually acquiring a 11 × 11 22Na source array for all the detectors composing the PET system and obtaining the calibration map for each module using a method based on the Voronoi diagrams. Two reducing time methodologies are presented: (i) TEST1, where the calibration map of one detector is estimated and shared among all others, and (ii) TEST2, where the calibration map is slightly modified for each module as a function of their detector uniformity map. The experimental data from a dedicated prostate PET system was used to compare the standard calibration procedure with both the proposed methods. A greater similarity was exhibited between the TEST2 methodology and the Normal procedure; obtaining spatial resolution variances within 0.1 mm error bars and count rate deviations as small as 0.2%. Moreover, the negligible reconstructed image differences (13% deviation at most in the contrast-to-noise ratio) and almost identical contrast values were reported. Therefore, this proposed method allows us to calibrate the PET systems based on the monolithic crystals reducing the calibration time by approximately 80% compared with the Normal procedure.
format	article
author	Marta Freire Gabriel Cañizares Sara Echegoyen Andrea Gonzalez-Montoro Antonio J. Gonzalez
author_facet	Marta Freire Gabriel Cañizares Sara Echegoyen Andrea Gonzalez-Montoro Antonio J. Gonzalez
author_sort	Marta Freire
title	Reducing Calibration Time in PET Systems Based on Monolithic Crystals
title_short	Reducing Calibration Time in PET Systems Based on Monolithic Crystals
title_full	Reducing Calibration Time in PET Systems Based on Monolithic Crystals
title_fullStr	Reducing Calibration Time in PET Systems Based on Monolithic Crystals
title_full_unstemmed	Reducing Calibration Time in PET Systems Based on Monolithic Crystals
title_sort	reducing calibration time in pet systems based on monolithic crystals
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/d448a1ed2e624d31b135155feba5335d
work_keys_str_mv	AT martafreire reducingcalibrationtimeinpetsystemsbasedonmonolithiccrystals AT gabrielcanizares reducingcalibrationtimeinpetsystemsbasedonmonolithiccrystals AT saraechegoyen reducingcalibrationtimeinpetsystemsbasedonmonolithiccrystals AT andreagonzalezmontoro reducingcalibrationtimeinpetsystemsbasedonmonolithiccrystals AT antoniojgonzalez reducingcalibrationtimeinpetsystemsbasedonmonolithiccrystals
_version_	1718440514335801344

Reducing Calibration Time in PET Systems Based on Monolithic Crystals

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