Hybrid Imaging: Instrumentation and Data Processing

Abstract

State-of-the-art patient management frequently requires the use of non-invasive imaging methods to assess the anatomy, function or molecular-biological conditions of patients or study subjects. Such imaging methods can be singular, providing either anatomical or molecular information, or they can be combined, thus, providing "anato-metabolic" information. Hybrid imaging denotes image acquisitions on systems that physically combine complementary imaging modalities for an improved diagnostic accuracy and confidence as well as for increased patient comfort. The physical combination of formerly independent imaging modalities was driven by leading innovators in the field of clinical research and benefited from technological advances that permitted the operation of PET and MR in close physical proximity, for example. This review covers milestones of the development of various hybrid imaging systems for use in clinical practice and small-animal research. Special attention is given to technological advances that helped the adoption of hybrid imaging, as well as to introducing methodological concepts that benefit from the availability of complementary anatomical and biological information, such as new types of image reconstruction and data correction schemes. The ultimate goal of hybrid imaging is to provide useful, complementary and quantitative information during patient work-up. Hybrid imaging also opens the door to multi-parametric assessment of diseases, which will help us better understand the causes of various diseases that currently contribute to a large fraction of healthcare costs.

Low-Dose Imaging in a New Preclinical Total-Body PET/CT Scanner

“…The sensitivity of the total body PET detector design matches or exceeds that of other current preclinical scanners. Cal-Gonzalez et al (27) report on a number of existing systems with around 9% sensitivity. The row and column readout approach reduces the amount of SiPM signals that need acquiring from 12 × 12 signals to 12+12.…”

What scans we will read: imaging instrumentation trends in clinical oncology

“…Image resolution, which drives lesion detection, is determined by the size of the imaging detector elements, which is on the order of 3 mm in clinical PET systems [14]. The resulting imaging resolution is somewhat lower due to detrimental effects from positron range effects, which vary depending on the energy of the positron emitted, detector penetration and depth-of-interaction (DOI).…”

“…The standard PET detector is composed of the scintillation material that stops/detects the annihilation photons and an electronic devicea photomultiplier tube (PMT)coupled to the end of the detector material, that, in turn, transforms the detected scintillation photon into an electrical signal, which typically involves signal amplification and processing. The ideal PET scintillator material has a high stopping powersufficient to attenuate the 511 keV annihilation photons, high scintillation light outputto facilitate accurate detection of the annihilation photons, fast decay time -to minimize deadtime, high energy resolution -to better discriminate against scattered photons, and low cost (Suppl Table 1) [14].…”

“…This knowledge is subsequently used during image reconstruction to more precisely inform on where the annihilation event occurred within the PET field-of-view (FOV) as compared to conventional PET imaging. The knowledge about the arrival time has been shown to improve the resultant signal-to-noise ratio (SNR) of reconstructed PET images [14]. For example, a 300 ps timing resolution improves the SNR of ToF images by about 30% when compared to non-ToF images.…”

NEMA NU‐4 2008 performance evaluation of Xtrim‐PET: A prototype SiPM‐based preclinical scanner

“…PET scanners featuring SiPM‐based detectors exhibit a multitude of advantages over photomultiplier tubes (PMTs)‐based designs. This includes lower operation voltage, higher quantum efficiency, miniature size, robustness and immunity to magnetic field, which facilitates integration with other imaging modalities, such as magnetic resonance imaging (MRI) . The compact, portable and cost‐effective SiPM‐based preclinical scanner evaluated in this work (Xtrim‐PET) was recently developed by our group .…”