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Anesthetics change tissue proton NMR relaxation
S J Karlik1, J Fuller, A W Gelb
1Department of Diagnostic Radiology, University Hospital, University of Western Ontario, London, Ontario, Canada.
Acta Radiologica. Supplementum
|January 1, 1986
Summary
Intravenous anesthesia is preferred over inhalational anesthesia for magnetic resonance imaging (MRI) due to fewer changes in tissue proton NMR relaxation times. Injectable anesthetics like Innovar and ketamine caused minor alterations, unlike inhalational agents.
Area of Science:
- Biomedical imaging
- Anesthesiology
- Biophysics
Background:
- Pharmaceuticals can alter tissue proton NMR relaxation times.
- Anesthesia is crucial for animal studies and medical imaging.
Purpose of the Study:
- To compare the effects of injectable and inhalational anesthetics on tissue proton NMR relaxation times.
- To determine the optimal anesthetic for MRI studies.
Main Methods:
- Proton NMR T1 and T2 relaxation times were measured in excised rat tissues.
- Six rats were used for each anesthetic treatment group.
- Injectable anesthetics (Innovar, pentobarbital, ketamine, alpha-chloralose) and inhalational anesthetics (halothane, enflurane, isoflurane) were tested.
Main Results:
- Sodium pentobarbital and alpha-chloralose showed no significant changes in relaxation times.
- Innovar increased brain and kidney relaxation times; ketamine increased heart relaxation times.
- Inhalational anesthesia caused widespread changes in liver, muscle, fat, heart, spleen, and lung relaxation times.
- No changes in tissue water content were observed.
Conclusions:
- Intravenous anesthesia is preferable to inhalational anesthesia for MRI due to minimal changes in tissue relaxation properties.
- The lack of brain relaxation time changes suggests anesthesia mechanisms do not primarily involve brain water alterations.