The renewal of interest in Time of Flight Positron Emission Tomography (TOF-PET), as well as the necessity to precisely tag events in high energy physics (HEP) experiments at future colliders are ...pushing for an optimization of all factors affecting the time resolution of the whole acquisition chain comprising the crystal, the photo detector, and the electronics. The time resolution of a scintillator-based detection system is determined by the rate of photoelectrons at the detection threshold, which depends on the time distribution of photons being converted in the photo detector. The possibility to achieve time resolution of about 100ps FWHM requires an optimization of the light production in the scintillator, the light transport and its transfer from the scintillator to the photo detector. In order to maximize the light yield, and in particular the density of photons in the first nanosecond, while minimizing the rise time and decay time, particular attention must be paid to the energy transfer mechanisms to the activator as well as to the energy transition type at the activator ion. Alternatively other light emission mechanisms can be considered. We will show that particularly Cerenkov emission can be used for this purpose. Special emphasis was put on the light transport within the crystal and at its interface with the photo detector. Since light is produced isotropically in the scintillator the detector geometry must be optimized to decrease the optical path-length to the photo detector. Moreover light bouncing within the scintillator, affecting about 70% of the photons generated in currently used crystals, must be reduced as much as possible. We also investigate photonics crystals that are specifically designed to favor specific light propagation modes at the limit of total reflection inside and outside of the crystal, and how they might increase the light transfer efficiency to the photo detector and hence improve time resolution. Examples for the production and deposition of photonics crystals as layers on LYSO and LuYAP crystals are shown here, as well as first results on an improved light extraction due to this method.
The MAPS foil Beolé, S; Carnesecchi, F; Contin, G ...
arXiv.org,
10/2022
Paper, Journal Article
Open access
We present a method of embedding a Monolithic Active Pixel Sensor (MAPS) into a flexible printed circuit board (FPC) and its interconnection by means of through-hole copper plating. The resulting ...assembly, baptised "MAPS foil", is a flexible, light, protected, and fully integrated detector module. By using widely available printed circuit board manufacturing techniques, the production of these devices can be scaled easily in size and volume, making it a compelling candidate for future large-scale applications. A first series of prototypes that embed the ALPIDE chip has been produced, functionally tested, and shown to be working.
In pregnancy a glomerular or mixed glomerular/tubular proteinuria in excess of 0.5 g/day was found in EPH-gestosis or preceding glomerular disease. A pure tubular proteinuria was not found in ...EPH-gestosis. The severity of the clinical picture was positively correlated with the daily protein loss.
In the framework of the European FP6's BioCare project, we develop a novel, time-based, photo-detector readout technique to increase sensitivity and timing precision for molecular imaging in PET and ...CT. The project aims to employ Avalanche Photo Diode (APD) arrays with state of the art, high speed, front end amplifiers and discrimination circuits developed for the Large Hadron Collider (LHC) physics program at CERN, suitable to detect and process photons in a combined one-unit PET/CT detection head. In the so-called time-based approach our efforts focus on the system's timing performance with sub-nanosecond time-jitter and -walk, and yet also provide information on photon energy without resorting to analog to digital conversion. The bandwidth of the electronic circuitry is compatible with the scintillator's intrinsic light response (e.g. les40ns in LSO) and hence allows high rate CT operation in single-photon counting mode. Based on commercial LSO crystals and Hamamatsu S8550 APD arrays, we show the system performance in terms of timing- and energy resolution as well as its rate behavior (SPICE, simulating a high intensity X-ray beam). If proven viable, this technique may lead to the construction of a compact, radiation tolerant, and cost effective PET/CT detection head in one unit.
Human papillomavirus (HPV) standardization and DNA cytophotometry were carried out in 29 cases of cervical intraepithelial neoplasia (CIN) grades I-III. A prognostically unfavorable DNA distribution ...pattern with an aneuploid stemline was found in 14 of the 16 dysplasias with HPV types 16 and 18, while in 11 of 13 dysplasias with HPV types 6 and 11 there was a favorable DNA distribution with a euploid-polyploid stemline. Among 178 colposcopically, cytologically and histologically confirmed cervical lesions, there was a statistically significant incidence of HPV 16/18 infections in severe dysplasias and carcinomas, while HPV 6/11 was found predominantly in mild cervical lesions. It seems that CIN can be divided into high- and low-risk lesions not only by the degree of severity and the DNA distribution pattern but also by HPV typing.
This paper contains a compilation of parameters influencing the charge collection process extracted from a comprehensive study of partially depleted Monolithic Active Pixel Sensors with small (<25 ...um\(^2\)) collection electrodes fabricated in the TowerJazz 180 nm CMOS process. These results gave guidance for the optimisation of the diode implemented in ALPIDE, the chip used in the second generation Inner Tracking System of ALICE, and serve as reference for future simulation studies of similar devices. The studied parameters include: reverse substrate bias, epitaxial layer thickness, charge collection electrode size and the spacing of the electrode to surrounding in-pixel electronics. The results from pixels of 28 um pitch confirm that even in partially depleted circuits, charge collection can be fast (<10 ns), and quantify the influence of the parameters onto the signal sharing and amplitudes, highlighting the importance of a correct spacing between wells and of the impact of the reverse substrate bias.
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