Metascintillators for Ultrafast Gamma Detectors: A Review of Current State and Future Perspectives

Abstract

Scintillation detector development is an active field of research, especially for its application to the medical imaging field and in particular to the positron emission tomography (PET). Effective sensitivity and signal-to-noise ratio in PET are greatly enhanced when improving detector timing capabilities: the availability to provide time-of-flight (TOF) information. However, physical barriers related to the characteristics of available organic and inorganic scintillators create a tradeoff between photon kinetics and gamma detection efficiency. We introduce the novel concept of metascintillators, composite topologies comprising of multiple scintillating and light-guiding materials functioning in synergy, that break this compromise. We provide an overview of published, ongoing and upcoming developments within this framework. Unconventional topologies, such as the multiple slabs approach comprising of a high-Z host and a fast emitter; materials such as CdSe/CdS nanoplatelets; and treatments related to nanostructured metamaterials and photonic interactions, are reviewed and complemented with new, unpublished advances in simulations and analysis. Future perspectives are further presented, encompassing developments in signal analysis and system integration. Within this concept, an improved generation of detectors and PET scanners with unprecedented time resolution is researched, paving the way toward the 10-ps TOF PET challenge for the advancement of PET and improvement of public health.

Design rules for time of flight Positron Emission Tomography (ToF-PET) heterostructure radiation detectors

“… [4] , [5] ), and 2) develop a family of radiation sensing heterostructures - in which multiple materials work in synergy to achieve the production of ultra-fast photons and short attenuation length (e.g. [6] , [7] for example of single crystal functionalization and heterostructure concept and [8] , [9] , [10] , [11] for its application to radiation detector development). This article further presents the concept of heterostructure radiation detector materials and the implications associated with the use of multiple materials in term of inherent scintillation mechanism, and achievable performance.…”

Image Reconstruction Analysis for Positron Emission Tomography with Heterostructured Scintillators

“…Denser than plastic materials could be considered in future heterostructured detector designs that can also have different geometry than stacking layers, like fiberbased designs [26]. An alternative to plastic scintillators can be the nanocrystals [19], [41], [42].…”

“…For heterostructured scintillators, the basic idea is that the gamma ray is stopped by the dense inorganic scintillator, while the recoil electron deposits some of its energy in the fast organic material, resulting in better overall timing resolution. In lit-erature, the term metascintillator has been used to describe heterostructured scintillators [19], picking up the concept of metamaterials in material science. These heterostructured scintillators take a step forward in the improvement of time resolution as sought by the 10 ps challenge [20].…”

Time of Flight in Perspective: Instrumental and Computational Aspects of Time Resolution in Positron Emission Tomography

“…For example, detectors using the hybrid Cherenkov/scintillation approach may have a non-Gaussian TOF-kernel [219]. The same may be the case for detectors based on metamaterials [43,220], where different events can have a very different timing resolution. For those PET systems, the reconstruction model will have to account either for the average non-Gaussian uncertainty or for the timing uncertainty associated with each event, if such information is available [218,219].…”

“…A variety of researchers, among others from the high-energy physics community, are currently advocating the so-called “10 ps challenge.” A plethora of novel approaches are under investigation, based on, for example, prompt emissions, such as Cherenkov and hot-intraband luminescence, or enhanced luminesce resulting from quantum-confinement in nano- and metamaterials [ 43 ], [ 218 ]. Also under investigation are systems in which lasers are used to actively probe transient phenomena caused by the absorption of annihilation photons [ 221 ], [ 222 ].…”