Feb 29, 2024
Micro-PET CT procedures for brain imaging of rats
- 1KU Leuven. Nuclear Medicine & Molecular Imaging. Molecular Small Animal Imaging Center. ‘MoSAIC’;
- 2KU Leuven. Neurobiology and Gene therapy lab
Protocol Citation: christopher.cawthorne, María Sanchiz Calvo, Eduard Bentea 2024. Micro-PET CT procedures for brain imaging of rats. protocols.io https://dx.doi.org/10.17504/protocols.io.e6nvwdw2zlmk/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: February 29, 2024
Last Modified: May 31, 2024
Protocol Integer ID: 95962
Keywords: ASAPCRN, PET, PET-CT, imaging, rats
Abstract
Micro-PET CT procedures for brain imaging of rats
Materials
Clinical grade 18F-FE-PE2I was obtained from the hospital radiopharmacy at UZ Leuven
A range of PET radiotracers and radioligands (“radiopharmaceuticals”) can be used to
image biochemical flux and receptor density in rodents. PET
radiopharmaceuticals are administered in very low ‘tracer’ doses to avoid
pharmacological effects, the specific activity of the tracer must be carefully
evaluated to ensure this assumption is met.
Typically rats are anaesthetised throughout the scanning process. Commonly this is with
isoflurane (as described here), but other regimes may be necessary depending on
the biological system to be studied. Whether animals are anaesthetised
throughout the entire period of tracer uptake depends on both the relation of
the tracer with the biological system being studied and the quantitation method
used
For studies of the rat brain, full length dynamic scanning allows a range of
quantitative approaches to be compared. Typically rats are anesthetized in a
warmed chamber before transfer to a warm mat for tail vein cannulation.
Catheters are best constructed in-house using pharma-grade tubing of low
diameter, to allow optimum length to be determined to allow injection when the
animal is in the imaging cell in the PET scanner. Catheter needles are
typically 23G or larger. Catheters should be checked for integrity immediately
before scanning using sterile saline solution. Heparin may be added, though if
the time between cannulation and injection is minimised this is optional
The tail is cleaned with an ethanol wipe and warmed before a lateral vein is
cannulated (this should be visible). In rats, the potency of the line can be
confirmed by withdrawing a small amount of blood before reinjection. Cannulated
animals must be placed in the specialised imaging cell before transfer to the
scanner. Imaging cells differ between manufacturer, however temperature and
respiration are usually monitored and this must be confirmed before scanning is
implemented
Syringe activities before injection should be measured in a dose calibrator, and
residues after injection measured in the same way – importantly the exact time
of measurement should be recorded. All equipment should be set to the same
time.
Typically the scan will be started before radiotracer is injected. Injection should be
done over 20-30 seconds and the beginning and end of injection recorded, though
if backpressure is felt this indicates the cannula is no longer potent and the
injection should be abandoned. For this reason, syringe pump use requires
additional validation. At the end of injection, the catheter should be removed
if possible to allow measurement of residue. For quantitative scans, the
catheters are not flushed.
Dynamic PET images should be acquired for long enough to allow kinetic modelling. This
depends on the radiotracer but times of 90-120 min are not uncommon. The brain should
be at, or close to, the center of the field of view.
After PET scanning, a CT image should be acquired for attenuation correction. The CT
field of view must be equal or larger to the PET field of view.