MRI Coil Development Strategies for Hybrid MR-PET Systems: A Review

Simultaneously operating MR-PET systems have the potential to provide synergetic multi-parametric information, and, as such, interest surrounding their use and development is increasing. However, despite the potential advantages offered by fully combined MR-PET systems, implementing this hybrid integration is technically laborious, and any factors degrading the quality of either modality must be circumvented to ensure optimal performance. In order to attain the best possible quality from both systems, most full MR-PET integrations tend to place the shielded PET system inside the MRI system, close to the target volume of the subject. The radiofrequency (RF) coil used in MRI systems is a key factor in determining the quality of the MR images, and, in simultaneous acquisition, it is generally positioned inside the PET system and PET imaging region, potentially resulting in attenuation and artefacts in the PET images. Therefore, when designing hybrid MR-PET systems, it is imperative that consideration be given to the RF coils inside the PET system. In this review, we present current state-of-the-art RF coil designs used for hybrid MR-PET experiments and discuss various design strategies for constructing PET transparent RF coils.

Miniaturized USB-powered multi-channel module for gamma spectroscopy and imaging

LAILA is a miniaturized eight-channel electronic readout system for compact γ-ray detectors, combining high-resolution spectroscopy capability with position sensitivity. Compactness is achieved by the combination of a novel CMOS front-end ASIC (Application-Specific Integrated Circuit) for analog processing of a large signal current from Silicon PhotoMultiplier (SiPM) solid-state photodetectors, with a microcontroller-based data acquisition system. The adoption of automatic gain regulation in the gated-integrator stage of the ASIC offers an 84 dB dynamic range, combining single-photon sensitivity with an extended input photon energy range (20 keV-4 MeV, using 30 μm-cell SiPMs). Using this module with properly merged 144 SiPM pixels coupled to a 3 in.-thick lanthanum bromide scintillation crystal, a 3% energy resolution at 662 keV and 1 cm spatial resolution in the estimation of the interaction coordinates are experimentally demonstrated in this work.

Challenges for Microelectronics in Non-Invasive Medical Diagnostics

Microelectronics is emerging, sometimes with changing fortunes, as a key enabling technology in diagnostics. This paper reviews some recent results and technical challenges which still need to be addressed in terms of the design of CMOS analog application specific integrated circuits (ASICs) and their integration in the surrounding systems, in order to consolidate this technological paradigm. Open issues are discussed from two, apparently distant but complementary, points of view: micro-analytical devices, combining microfluidics with affinity bio-sensing, and gamma cameras for simultaneous multi-modal imaging, namely scintigraphy and magnetic resonance imaging (MRI). The role of integrated circuits is central in both application domains. In portable analytical platforms, ASICs offer miniaturization and tackle the noise/power dissipation trade-off. The integration of CMOS chips with microfluidics poses multiple open technological issues. In multi-modal imaging, now that the compatibility of the acquisition chains (thousands of Silicon Photo-Multipliers channels) of gamma detectors with Tesla-level magnetic fields has been demonstrated, other development directions, enabled by microelectronics, can be envisioned in particular for single-photon emission tomography (SPECT): a faster and simplified operation, for instance, to allow transportable applications (bed-side) and hardware pre-processing that reduces the number of output signals and the image reconstruction time.