Large-volume applications of high-brightness LEDs are well established for signaling and signage. They are expected to replace conventional lamps in automotive applications in the near future and incandescent, halogen and fluorescent lamps at least in some general illumination applications within a few years. Innovative driver circuits optimized with respect to functionality, efficiency, cost, size and reliability are an enabler for the successful introduction of new LED based lighting products. This paper consists of two parts. In the first part, the influence of the LED current waveform, which depends on the driver topology and control, on the luminous flux and hence, the luminous efficiency is investigated experimentally for different LEDs, i.e. a red, a green and a blue 1 W LED. In the second part, an LED driver with PCB integrated capacitive layers and a transformer made of ferrite polymer compound having an extreme high power density is presented. This driver uses highly integrated passive components. This new concept is named emPIC (embedded passives integrated circuit). All passive components will be integrated in the printed circuit board (PCB) using structured layers of different materials. Experimental results taken from the driver demonstrate that the LED current ripple stays within the margins defined in the first part of this paper.

Novel electronic readout schemes of analog SiPMs have shown impressive timing performance of γ-detectors in positron emission tomography (PET). However, transfering these novel concepts to system level is key to exploit the improved coincidence time resolution (CTR) in (pre-)clinical imaging. In this study, the commercially available TOFPET2 ASIC from PETsys Electronics S.A. is tested in terms of the best achievable CTR. The measurable CTR limits will be obtained by state-of-the-art high-frequency (HF) readout, minimizing the impact of the electronic front-end on the time resolution. We achieved (73 ± 1) ps with the HF readout and (134 ± 10) ps with the TOFPET2 ASIC for a Ce-, and Cadoped lutetium-oxyorthosilcate (LYSO) crystal of 2×2×3 mm 3 size. We show that SiPM signal amplification and an effectively reduced TOFPET2 input stage impedance boost the CTR of a 20-mm high LYSO:Ce crystal to (187 ± 8) ps. Our studies also lead to the observation of side peaks in the coincidence time difference spectrum. This peaks are studied in depth and a conclusion on the ASIC for 100-ps PET applications is drawn.

No abstract

In state-of-the-art positron emission (PET) tomography systems, application-specific integrated circuits (ASICs) are commonly used to precisely digitize the signals of analog silicon photo-multipliers (SiPMs). However, when operating PET electronics in a magnetic resonance (MR) system, one faces the challenge of mutual interference of these imaging techniques. To prevent signal deterioration along long analog signal lines, PET electronics with a low power consumption digitizing the signals close to the SiPMs are preferred. In this study, we evaluate the power consumption of the TOFPET2 ASIC. Its power consumption ranges from 3.6 mW/channel to 7.2 mW/channel as a function of the input stage impedance and discriminator noise settings. We present an analytical model allowing to compute the power consumption of a given ASIC configuration. The configured input stage impedance and discriminator noise have an impact on the coincidence resolution time, energy resolution, and dark count rate. Since TOFPET2 ASICs delivers state-ofthe art performance with a power consumption similar or even lower than other ASICs typically used for PET applications, it is a favorable candidate to digitize the signals of SiPMs in future simultaneous PET/MR systems.

No abstract

No abstract

Background and purpose The restricted bore diameter of current simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) systems can be an impediment to achieving similar patient positioning during PET/MRI planning and radiotherapy. Our goal was to evaluate the B 1 transmit (B 1 + ) uniformity, B 1 + efficiency, and specific absorption rate (SAR) of a novel radiofrequency (RF) body coil design, in which RF shielded PET detectors were integrated with the specific aim of enabling a wide-bore PET/MRI system. Materials and methods We designed and constructed a wide-bore PET/MRI RF body coil to be integrated with a clinical MRI system. To increase its inner bore diameter, the PET detectors were positioned between the conductors and the RF shield of the RF body coil. Simulations and experiments with phantoms and human volunteers were performed to compare the B 1 + uniformity, B 1 + efficiency, and SAR between our design and the clinical body coil. Results In the simulations, our design achieved nearly the same B 1 + field uniformity as the clinical body coil and an almost identical SAR distribution. The uniformity findings were confirmed by the physical experiments. The B 1 + efficiency was 38% lower compared to the clinical body coil. Conclusions To achieve wide-bore PET/MRI, it is possible to integrate shielding for PET detectors between the body coil conductors and the RF shield without compromising MRI performance. Reduced B 1 + efficiency may be compensated by adding a second RF amplifier. This finding may facilitate the application of simultaneous whole-body PET/MRI in radiotherapy planning.

No abstract