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

Abstract

Ionizing radiation constitutes a health risk to imaging scientists and study animals. Both PET and CT produce ionizing radiation. CT doses in pre-clinical in vivo imaging typically range from 50 to 1,000 mGy and biological effects in mice at this dose range have been previously described. [ 18 F]FDG body doses in mice have been estimated to be in the range of 100 mGy for [ 18 F]FDG. Yearly, the average whole body doses due to handling of activity by PET technologists are reported to be 3–8 mSv. A preclinical PET/CT system is presented with design features which make it suitable for small animal low-dose imaging. The CT subsystem uses a X-source power that is optimized for small animal imaging. The system design incorporates a spatial beam shaper coupled with a highly sensitive flat-panel detector and very fast acquisition (<10 s) which allows for whole body scans with doses as low as 3 mGy. The mouse total-body PET subsystem uses a detector architecture based on continuous crystals, coupled to SiPM arrays and a readout based in rows and columns. The PET field of view is 150 mm axial and 80 mm transaxial. The high solid-angle coverage of the sample and the use of continuous crystals achieve a sensitivity of 9% (NEMA) that can be leveraged for use of low tracer doses and/or performing rapid scans. The low-dose imaging capabilities of the total-body PET subsystem were tested with NEMA phantoms, in tumor models, a mouse bone metabolism scan and a rat heart dynamic scan. The CT imaging capabilities were tested in mice and in a low contrast phantom. The PET low-dose phantom and animal experiments provide evidence that image quality suitable for preclinical PET studies is achieved. Furthermore, CT image contrast using low dose scan settings was suitable as a reference for PET scans. Total-body mouse PET/CT studies could be completed with total doses of <10 mGy.

A Multi-Scale and Multi-Technique Approach for the Characterization of the Effects of Spatially Fractionated X-ray Radiation Therapies in a Preclinical Model

“…The doses currently delivered when imaging post mortem soft tissues are strongly dependent on the chosen voxel size, among the different experimental parameters. As an example, for a single CT performed at ESRF-ID17 with a monochromatic beam of 35 keV, the dose delivered to an excised soft-tissue sample (e.g., a rat brain) is about 150 Gy with a voxel size of 3.25 3 µm 3 , while for voxel sizes of 6 3 -8 3 µm 3 the dose ranges from hundreds of mGy to few Gy, which is in line with the delivered doses in conventional micro-CT full-animal scans [74,75]. The dose can be further lowered if, e.g., iterative or machine learning methods are used for CT reconstruction [76,77].…”

Supplemental minimal‐activity PET/CT to validate ambiguous findings with less than 1 mSv: Proof of concept

“…Elaborate efforts are being made to reduce radiation exposure from PET/CT in clinical and preclinical settings 3,4 . Typically, PET/CT is a whole‐body examination aiming at a comprehensive diagnostic statement.…”

Biodistribution of andrographolide to assess the interior‐exterior relationship between the lung and intestine using microPET

“…3 For example, inflammation in the lung can cause abnormal bowel function and constipation, and problems in the physiological processes of the lung can lead to diarrhea. The outbreak of the new coronavirus pneumonia (COVID- 19) in Wuhan, Hubei Province, China in December 2019 has attracted great attention at home and abroad, posing a major challenge to clinical treatment. 4,5 Pneumonia induced by COVID-19 infection is mainly characterized by fever, weakness and dry cough, and a small number of patients also experience nasal congestion, runny nose, diarrhea and other symptoms.…”

“…15 With research advancements, Micro-PET has been used in clinical analysis to observe the occurrence and development of cancer, 16 epilepsy 17 and neurological diseases 18 and to guide other new developments. 19 One promising application is that MicroPET can be used to study the mechanism of action of drugs and evaluate the effect of drugs through the establishment of different animal models. 20 It can also promote the results of animal experiments to clinical practice, providing an important experimental basis for the further use of clinical pharmacokinetics and clinical pharmacodynamics.…”

“…Initially, it was used for human research, especially blood flow and glucose metabolism in the heart and brain 15 . With research advancements, MicroPET has been used in clinical analysis to observe the occurrence and development of cancer, 16 epilepsy 17 and neurological diseases 18 and to guide other new developments 19 . One promising application is that MicroPET can be used to study the mechanism of action of drugs and evaluate the effect of drugs through the establishment of different animal models 20 .…”