Low-Dose High-Resolution TOF-PET Using Ionization-activated Multi-State Low-Z Detector Media

TL;DR

This paper introduces a novel low-dose, high-resolution PET scanner concept using ionization-activated multi-state low-Z detector media, enabling precise event localization and energy measurement through persistent molecular state changes.

Contribution

It proposes a new PET detection method utilizing ionization-induced state changes in low-Z media, with simulations demonstrating potential dose reduction and high spatial-temporal resolution.

Findings

High-resolution line-of-response measurement achieved

Significant dose reduction indicated by simulations

Effective localization using time-of-flight MCP-PMT detectors

Abstract

We propose PET scanners using low atomic number media that undergo a persistent local change of state along the paths of the Compton recoil electrons. Measurement of the individual scattering locations and angles, deposited energies, and recoil electron directions allows using the kinematical constraints of the 2-body Compton scattering process to perform a statistical time-ordering of the scatterings, with a high probability of precisely identifying where the gamma first interacted in the detector. In these cases the Line-of-Response is measured with high resolution, determined by the underlying physics processes and not the detector segmentation. There are multiple such media that act through different mechanisms. As an example in which the change of state is quantum-mechanical through a change in molecular configuration, rather than thermodynamic, as in a bubble chamber, we present simulations of a two-state photoswitchable organic dye, a `Switchillator', that is activated to a fluorescent-capable state by the ionization of the recoil electrons. The activated state is persistent, and can be optically excited multiple times to image individual activated molecules. Energy resolution is provided by counting the activated molecules. Location along the LOR is implemented by large-area time-of-flight MCP-PMT photodetectors with single photon time resolution in the tens of ps and sub-mm spatial resolution. Simulations indicate a large reduction of dose.