Elia Conti

The RD53 Collaboration's SystemVerilog-UVM Simulation Framework and its General Applicability to Design of Advanced Pixel Readout Chips

The foreseen Phase 2 pixel upgrades at the LHC have very challenging requirements for the design of hybrid pixel readout chips. A versatile pixel simulation platform is as an essential development tool for the design, verification and optimization of both the system architecture and the pixel chip building blocks (Intellectual Properties, IPs). This work is focused on the implemented simulation and verification environment named VEPIX53, built using the SystemVerilog language and the Universal Verification Methodology (UVM) class library in the framework of the RD53 Collaboration. The environment supports pixel chips at different levels of description: its reusable components feature the generation of different classes of parameterized input hits to the pixel matrix, monitoring of pixel chip inputs and outputs, conformity checks between predicted and actual outputs and collection of statistics on system performance. The environment has been tested performing a study of shared architectures of the trigger latency buffering section of pixel chips. A fully shared architecture and a distributed one have been described at behavioral level and simulated; the resulting memory occupancy statistics and hit loss rates have subsequently been compared.

Use of a CMOS Image Sensor for an Active Personal Dosimeter in Interventional Radiology

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. Due to skin tissues and peripheral blood irradiation, these exposures can result in deterministic effects (radiodermatitis, aged skin, and hand depilation) or stochastic ones (skin and non-solid cancer incidence). The authors present a novel approach to perform online monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor. The performance of the sensor as an X-ray radiation detector has been evaluated with a proper experimental setup: the number of photons and the generated charge have been assessed as dosimetric observables from the frames acquired by the sensor using a two-threshold clustering algorithm, the efficiency of which has been evaluated as well. The correlation of these observables with passive dosimeter dose measurements has been analyzed: a good linearity has been demonstrated, and the response difference between pulsed and continuous operational modes is reduced to less than 10%, marking a distinct improvement with respect to commercial Active Personal Dosimeters.

Performance of CMOS imager as sensing element for a Real-time Active Pixel Dosimeter for Interventional Radiology procedures

Staff members applying Interventional Radiology procedures are exposed to ionizing radiation, which can induce detrimental effects to the human body, and requires an improvement of radiation protection. This paper is focused on the study of the sensor element for a wireless real-time dosimeter to be worn by the medical staff during the interventional radiology procedures, in the framework of the Real-Time Active PIxel Dosimetry (RAPID) INFN project. We characterize a CMOS imager to be used as detection element for the photons scattered by the patient body. The CMOS imager has been first characterized in laboratory using fluorescence X-ray sources, then a PMMA phantom has been used to diffuse the X-ray photons from an angiography system. Different operating conditions have been used to test the detector response in realistic situations, by varying the X-ray tube parameters (continuous/pulsed mode, tube voltage and current, pulse parameters), the sensor parameters (gain, integration time) and the relative distance between sensor and phantom. The sensor response has been compared with measurements performed using passive dosimeters (TLD) and also with a certified beam, in an accredited calibration centre, in order to obtain an absolute calibration. The results are very encouraging, with dose and dose rate measurement uncertainties below the 10% level even for the most demanding Interventional Radiology protocols.

Pixel chip architecture optimization based on a simplified statistical and analytical model

The technical challenges related to increased collision rates of the LHC will significantly affect detector electronics design. Efficient hit processing is achieved in pixel detectors by grouping pixels in regions, which share buffering logic. We present an approach to determine an optimized sharing strategy between pixels, depending on the shape of clustered hits in the detector. Simple statistical models of such shapes have been developed with respect to the position in the detector. The buffering performance of different pixel region configurations has been compared, showing significant improvement from architectures that do not feature pixel grouping.

Study of dosimetric observables to be used in Active Pixel Sensor based devices for Interventional Radiology applications

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted low doses of ionizing radiation. The authors present a novel approach to perform on line monitoring of the staff during interventional procedures by using a device based on a CMOS Active Pixel Sensor (APS). The sensor performance as an X-ray radiation detector has been evaluated with a dedicated experimental set-up and dosimetric observables have been assessed from the frames acquired by the sensor using a purposely designed algorithm. A data reduction strategy has also been implemented without significant loss of the performances. Finally a linear correlation with dosimetric measurements made using TLDs has been verified.

A portable dosimetric system based on a CMOS image sensor for radiation protection in Interventional Radiology

Systems based on Wireless Sensor Networks (WSN) provide monitoring for a wide range of applications in healthcare. Network nodes take care of data acquisition, processing and transmission and are therefore required to be wireless and low-power. The authors present the first version of the prototype of a portable wireless dosimetric system based on a commercial CMOS image sensor to be used during Interventional Radiology (IRad) procedures. A proprietary data processing and reduction algorithm has been implemented in the prototype. Current consumption of the transmitting unit of the prototype has been measured for battery sizing. Both system response and algorithm performance have been investigated and consistency with results obtained using the same model of CMOS sensor with its own acquisition system provided by the manufacturer has been demonstrated.

An active pixel sensor based system for real time dosimeter in interventional radiology

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. Due to of skin tissues and peripheral blood irradiation, these exposures can result in deterministic effects (radiodermatitis, aged skin, hands depilation) or stochastic ones (skin and non-solid cancers incidence). The authors present a novel approach to perform on line monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor. A good linearity with passive dosimeters (TLD) dose measurements has been demonstrated and the response difference between pulsed and continuous operational modes is reduced to less than 10%, marking a distinct improvement with respect to commercial active pixel dosimeters (APDs).

An active pixel sensor to detect diffused X-ray during Interventional Radiology procedure

Interventional radiologists and staff members are frequently exposed to protracted and fractionated low doses of ionizing radiation due to diffused X-ray radiation. The authors propose a novel approach to monitor on line staff during their interventions by using a device based on an Active Pixel Sensor developed for tracking applications. Two different photodiode configurations have been tested in standard Interventional Radiology working conditions. Both options have demonstrated the capability to measure the photon flux and the energy flux to a sufficient degree of uncertainty.

179: Characterization of wireless personal dosimeter prototype for Interventional Radiology medical operators

VI. CONCLUSIONS • Main features of the commercially available active personal dosimeters: − semiconductor technology − real-time evaluation of dose and/or dose rate − alarm at a pre-set dose and/or dose rate < level (opt.). Performance is not satisfactory for X-ray fields used in IR procedures (low energies and pulsed fields) [Villani, 2013]. With pulsed X-ray beams the response decreases: − as the dose equivalent rate increases − from 10 to 40% when pulse rate increases from 1 to 20 pps.

A Dosimetric Device Based on CMOS Image Sensor for Interventional Radiology

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. The authors present a novel approach to perform on line monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor (APS). The performance of the sensor as an X-ray radiation detector has been evaluated with a proper experimental set-up: the number of photons and the generated charge have been assessed as dosimetric observables. The correlation of these observables with the dose measured by the passive dosimeters has been analyzed: a good linearity has been demonstrated and the response difference between pulsed and continuous operational modes is reduced to less than 10 %, marking a distinct improvement with respect to commercial Active Personal Dosimeters.