Abstract
We present the most recent advances in photo-detector design employed in time of flight positron emission tomography (ToF-PET). PET is a molecular imaging modality that collects pairs of coincident (temporally correlated) annihilation photons emitted from the patient body. The annihilation photon detector typically comprises a scintillation crystal coupled to a fast photo-detector. ToF information provides better localization of the annihilation event along the line formed by each detector pair, resulting in an overall improvement in signal to noise ratio (SNR) of the reconstructed image. Apart from the demand for high luminosity and fast decay time of the scintillation crystal, proper design and selection of the photo-detector and methods for arrival time pick-off are a prerequisite for achieving excellent time resolution required for ToF-PET. We review the two types of photo-detectors used in ToF-PET: photomultiplier tubes (PMTs) and silicon photo-multipliers (SiPMs) with a special focus on SiPMs.
Highlights
Recent advances in the field of medical imaging have greatly facilitated the transition from technologies used to accurately image structures inside the human body to technologies sensitive enough to provide functional and biological information at the cellular and the molecular level
Sensors 2010, 10 tomography (PET) is considered to be one of the most sensitive in-vivo molecular imaging modalities despite its significantly inferior spatial resolution compared to imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI)
The improvement of Positron emission tomography (PET) detector technology is an active field of research and efforts are focused on addressing the limits in spatial resolution and sensitivity achieved in PET
Summary
Recent advances in the field of medical imaging have greatly facilitated the transition from technologies used to accurately image structures inside the human body to technologies sensitive enough to provide functional and biological information at the cellular and the molecular level. A PET acquisition will eventually result in a number of identified detector pairs that have simultaneously detected the two annihilation photons, or otherwise stated, the positron annihilation event. These pairs will be subsequently assigned a virtual line connecting the two detection points (line of response, LoR). To date the detectors typically used in PET have a finite time resolution of a few nanoseconds (ns) allowing for detection of photon events within a predefined time window. Time of flight PET (ToF-PET) is an advance over traditional PET that exploits the time difference ∆t in detection of the two photon events and correlates it to the position ∆x of the annihilation point with respect to the center of the field of view (FoV) according to the formula (Figure 2) [2]:.
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