Innovative Photodetector Module for advanced Hybrid “Magnetic Resonance Imaging/Positron Emission Tomography” Scanners for Nuclear Medicine

Project Information

INNMEDSCAN

Grant agreement ID: 101086178

DOI

10.3030/101086178

EC signature date 9 November 2022

Start date 1 March 2023

End date 28 February 2027

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 1 458 200,00

Coordinated by

COFAC COOPERATIVA DE FORMACAO E ANIMACAO CULTURAL CRL
Portugal

Periodic Reporting for period 1 - INNMEDSCAN (Innovative Photodetector Module for advanced Hybrid “Magnetic Resonance Imaging/Positron Emission Tomography” Scanners for Nuclear Medicine)

Reporting period: 2023-03-01 to 2025-02-28

Summary of the context and overall objectives of the project

The primary objective of INNMEDSCAN is the design, development, and validation of a highly sensitive semiconductor-based photodetector module that will significantly improve PET-MRI scanner performance. The project sets out to create a prototype detector module at Technology Readiness Level (TRL) 4, meaning that it will be rigorously tested and validated in a laboratory environment before further clinical development.
To achieve its objectives, the project is structured into six Work Packages (WPs):
• WP1: Design and Pilot-Scale Production of Innovative Detectors
Objective: To develop and engineer high-tech silicon photodetectors, producing pilot-scale prototypes for further integration into hybrid PET-MRI scanner detector modules.
Outcome: Fabrication of functional silicon photodiodes, featuring an n-type silicon substrate with two p-type epitaxial layers and n-type pixels arranged between them.
• WP2: Assessment of Photodetector Performance
Objective: To conduct experimental research to evaluate the operating characteristics of the developed photodetectors.
Outcome: Comprehensive performance protocols, including measurements of radiation resistance and operational changes post-irradiation. Certification of newly developed photodetectors.
• WP3: Development and Testing of Electronic Components and Software
Objective: To design and develop electronic modules and software required for the INNMEDSCAN detector module.
Outcome: Creation of electronic circuits and components, including their design, modeling, and calibration, along with the development of specialized software for data acquisition and processing.
• WP4: Assembly of the Prototype Detector Module for PET-MRI Scanners
Objective: To integrate the photodetectors, electronic components, and software into a functional prototype detector module.
Outcome: A fully assembled and operational detector module optimized for next-generation PET-MRI scanners.
• WP5: Testing and Validation of the Prototype Detector Module
Objective: To analyze, optimize, and validate the performance of the developed detector module, ensuring it meets medical imaging standards.
Outcome: Comprehensive technical documentation with design recommendations for further improvements and adaptation for medical use.
• WP6: Project Management and Dissemination
Objective: To oversee project coordination, knowledge dissemination, and industry engagement, ensuring efficient implementation and long-term impact

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The comparison of results with experimental data indicates that the developed model within Work Package 1 provides an accurate representation of both single-element avalanche photodiodes (APDs) and multi-pixel avalanche photodiodes (SiPMs) operating in overvoltage mode. Upon completion of the avalanche process, the pixel potential of the SiPM decreases below the breakdown voltage by a value equal to the applied overvoltage.
The parasitic capacitance, which bypasses the quenching resistor, leads to sharpening of the output signal edge and enhances the gain factor of the avalanche process. This phenomenon suggests a novel approach for increasing the gain coefficient of SiPMs with high pixel density. The proposed new SiPM design, featuring increased parasitic capacitance, is expected to offer significant advantages over existing counterparts in terms of response speed and gain performance.
The bulk charge resistance within SiPMs imposes a limitation on the device's gain factor. To mitigate this undesirable effect, the ratio of the bulk charge thickness to the characteristic pixel size must be reduced by more than a factor of 100.
A method for achieving maximum SiPM response speed has been proposed, which involves the implementation of additional individual parasitic capacitances (Cq) that bypass the corresponding quenching microresistors. It has been established that a Cq value of only 10% of the pixel's intrinsic capacitance (Cp) is sufficient to attain the theoretical limit of response speed, reaching approximately 17 GHz.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The INNMEDSCAN project has made significant advancements in photodetector technology for hybrid PET-MRI scanners, surpassing existing solutions in terms of detection efficiency, speed, and signal processing capabilities.
• High-Performance Multi-Pixel Avalanche Photodiodes (SiPMs) with Enhanced Gain and Speed
The project has developed next-generation silicon photomultipliers (SiPMs) with an optimized pixel structure that significantly improves photon detection efficiency (PDE > 40%), compared to conventional SiPMs, which typically achieve PDE values of 25–30%.
A new avalanche photodiode design was introduced, incorporating increased parasitic capacitance to sharpen the signal response and enhance gain performance. This novel approach boosts the gain factor of SiPMs with high pixel density, addressing limitations observed in existing photodetector architectures.
• Breakthrough in SiPM Design for Improved Time-of-Flight (TOF) Imaging
The bulk charge resistance, which traditionally limits the gain factor of SiPMs, was successfully mitigated by reducing the bulk charge thickness-to-pixel size ratio by over 100 times, leading to superior linearity and signal stability.
• Advanced Readout Electronics and Data Acquisition System
The integration of analog-to-digital conversion (ADC) with high-speed processing enabled real-time data acquisition, improving dynamic range and image contrast in PET-MRI scans.

74th International Astronautical Congress, Baku, Azerbaijan

Scientific seminar. Mingechevir State University, Mingechevir, Azerbaijan

Discussion of Results. Institute of Radiation Problems, Baku, Azerbaijan

ODAE conference. Funchal, Portugal

Scientific seminar in the Institute of Radiation Problems, Baku, Azerbaijan.

Round table. National Nuclear Research Center, Absheron region, Azerbaijan

Kick of meeting_ March 2023_Lisbon_Portugal