Position algorithm for monolithic scintillation crystals based on charge projection readout

Pani, R.; Bettiol, M.; Preziosi, Enrico; Cinti, M.N.; Borrazzo, Cristian; Pellegrini, R.; Castro, Elisabetta Di; Fabbri, Andrea

doi:10.1088/1748-0221/11/01/c01061

Cited by 26 publications

(18 citation statements)

References 15 publications

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“…In order to improve the determination of the 3D position of interaction of gamma-photons in the crystal, a simplified algorithm customized for rows and columns readout, and able to take into account the DOI information, has been implemented. This DOI-dependent [20] algorithm, named RTP [25], corrects the error in position estimation for gamma rays that interact close to the crystal edges, for which a cut-off of the scintillation light distribution occurs.…”

Section: Methodsmentioning

confidence: 99%

The MINDVIEW project: First results

et al. 2018

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We present the first results of the MINDVIEW project. An innovative imaging system for the human brain examination, allowing simultaneous acquisition of PET/MRI images, has been designed and constructed. It consists of a high sensitivity and high resolution PET scanner integrated in a novel, head-dedicated, radio frequency coil for a 3T MRI scanner. Preliminary measurements from the PET scanner show sensitivity 3 times higher than state-of-the-art PET systems that will allow safe repeated studies on the same patient. The achieved spatial resolution, close to 1 mm, will enable differentiation of relevant brain structures for schizophrenia. A cost-effective and simple method of radiopharmaceutical production from C-carbon monoxide and a mini-clean room has been demonstrated. It has been shown thatC-raclopride has higher binding potential in a new VAAT null mutant mouse model of schizophrenia compared to wild type control animals. A significant reduction in TSPO binding has been found in gray matter in a small sample of drug-naïve, first episode psychosis patients, suggesting a reduced number or an altered function of immune cells in brain at early stage schizophrenia.

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Section: Methodsmentioning

confidence: 99%

The MINDVIEW project: First results

et al. 2018

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“…However, the edge effect is still present in the peripheral region of the detector when statistical and analytical methods are used, especially when some type of reflection treatment is applied to the crystal faces. Modifications of the CoG, such as the so-called raise-to-power (RTP) algorithm [28], allows one to partially mitigate that effect, but the need of calibration procedures is still required.…”

Section: Introductionmentioning

confidence: 99%

Calibration of Gamma Ray Impacts in Monolithic-Based Detectors Using Voronoi Diagrams

Freire

González-Montoro

Sánchez

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

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Molecular imaging systems, such as positron emission tomography (PET), use detectors providing energy and a 3-D interaction position of a gamma ray within a scintillation block. Monolithic crystals are becoming an alternative to crystal arrays in PET. However, calibration processes are required to correct for nonuniformities, mainly produced by the truncation of the scintillation light distribution at the edges. We propose a calibration method based on the Voronoi diagrams. We have used 50 × 50 × 15 mm 3 LYSO blocks coupled to a 12 × 12 SiPMs array. We have first studied two different interpolation algorithms: 1) weighted average method (WAM) and 2) natural neighbor (NN). We have compared them with an existing calibration based on 1-D monomials. Here, the crystal was laterally black painted and a retroreflector (RR) layer added to the entrance face. The NN exhibited the best results in terms of XY impact position, depth of Interaction, and energy, allowing us to calibrate the whole scintillation volume. Later, the NN interpolation has been tested against different crystal surface treatments, allowing always to correct edge effects. Best energy resolutions were observed when using the reflective layers (12%-14%). However, better linearity was observed with the treatments using black paint. In particular, we obtained the best overall performance when lateral black paint is combined with the RR.

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“…The planar impact coordinates ( x, y ) were calculated using the rows and column SiPM signals by applying a modified version of the center of gravity algorithm (COG) in which the row and column values are risen to the power of 2 to improve the system linearity ( 19 ). The DOI value was estimated as E/I max where E is the energy calculated as the sum of the rows or columns, and I max is the maximum value of the row or column, respectively ( 12 ).…”

Section: Methodsmentioning

confidence: 99%

Reducing Calibration Time in PET Systems Based on Monolithic Crystals

et al. 2021

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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.

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Position algorithm for monolithic scintillation crystals based on charge projection readout

Cited by 26 publications

References 15 publications

The MINDVIEW project: First results

The MINDVIEW project: First results

Calibration of Gamma Ray Impacts in Monolithic-Based Detectors Using Voronoi Diagrams

Reducing Calibration Time in PET Systems Based on Monolithic Crystals

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