A frontend ASIC for Microdosimetry

TL;DR

This paper presents a specialized ASIC designed for microdosimetry sensors to improve LET measurement in carbon ion radiotherapy, enabling more accurate treatment planning.

Contribution

The work introduces a low-noise, multi-channel ASIC tailored for microdosimetry sensors with specific input capacitance and saturation charge ranges.

Findings

ASIC achieves below 15 electrons ENC at 75 fC range.

Designed for input capacitances up to 3 pF with four readout channels.

Enables new microdosimetric measurements in radiotherapy.

Abstract

Recent clinical evidence shows a correlation between linear energy transfer (LET) and tumor control in carbon ion radiotherapy. This prompts the direct inclusion of LET into the treatment planning. Currently, LET is mainly extracted from simulations. Good clinical practice requires adopting measurement routines that correlate with LET, such as microdosimetry. In this work, we describe an application-specific integrated circuit (ASIC) for reading out microdosimeteric sensors. The ASIC is designed for input capacitances up to 3 pF. It contains four readout channels, each with a different saturation charge ranging from 75 fC to 3.2 pC. In the 75 fC range, at 1 pF input capacitance and a shaping time of 1 microseconds, the ASIC has an equivalent noise contribution (ENC) below 15 electrons at ambient temperature. This low noise level is expected to enable new measurement possibilities, including the assessment of microdosimetric proton spectra in the low-LET region of the entrance channel, as well as studying the contribution of delta electrons.