China
Africa
Explore chapters and articles related to this topic
Radionuclide Production
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Oxygen-15 is produced by deuteron bombardment of natural nitrogen through the 14N(d,n)15O nuclear reaction. An alternative is the reaction 15N(p,n)15O if a deuterium beam is not available. In this case, the target needs to be enriched. In the nitrogen target, molecular oxygen (15O2) is produced directly. Direct production of carbon dioxide (C15O2) is possible by mixing the target gas with 5 per cent of natural carbon dioxide as a carrier. Water (H215O) is preferable made by processing molecular oxygen-15.
Principles of Positron Emission Tomography
Published in W. R. Wayne Martin, Functional Imaging in Movement Disorders, 2019
Two methods have been developed to measure the regional cerebral metabolic rate for oxygen (rCMRO2) with PET. One uses continuous inhalation of 15O-labeled oxygen (15O2) and was developed in conjunction with the steady-state technique for measuring rCBF.12,78 The other, which uses a brief inhalation of 15O2, is a companion method to the PETautoradiographic method.65 The principles underlying these methods are the same. A fraction of the oxygen (approximately 0.40) that is delivered to the brain is extracted and used in the oxidative metabolism of glucose. Both methods measure this regional oxygen extraction fraction (rOEF). The rate of oxygen utilization is determined from the product of rOEF and the rate of oxygen delivery which equals rCBF multipled by arterial oxygen content.
11C, 13N, and 15O Tracers
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Roy S. Tilbury, Alan S. Gelbard
The 15O in labeled carbon dioxide labeled with 15O exchanges rapidly with 16O in water, due to its equilibrium with bicarbonate ion. For this reason C0150 has been used for the measurement of regional pulmonary oedema in humans140, 141 and for the detection and quantitation of left-to-right shunts.142, 144 These methods are attractive because they are noninvasive, requiring only a breath of radioactive gas, easily repeat-able, and give only a small radiation exposure to the patient. Radioactive oxygen - 150 administered to humans continuously by inhalation has been used to measure oxygen utilization rate in the brain, and carbon dioxide -150 has been used to measure regional cerebral blood flow.144 Harper146 has devised a method for the continuous i.v. administration of H2150 to humans for the measurement of regional blood flow.
Hepatic blood volume is decreased in patients with cirrhosis and does not decrease further after a meal like in healthy persons
Published in Scandinavian Journal of Gastroenterology, 2021
Oxygen-15 labeled carbon monoxide (15O-CO) binds specifically to erythrocytes and is thus confined to the vascular volume. Inhalation of 15O-CO can therefore be used to determine the fractional hepatic blood volume (HBV; mL blood/mL liver tissue), calculated as the ratio between the concentration of 15O-CO (kBq/mL liver tissue) in liver tissue measured by a positron emission tomography (PET) and that measured in peripheral blood samples (kBq/mL blood). Using this method, Taniguchi et al. found a mean HBV of 20.5 mL blood/100 mL liver tissue in healthy human subjects, 18.2 mL blood/100 mL liver tissue in patients with chronic hepatitis, and 16.1 mL blood/100 mL liver tissue in patients with cirrhosis. In a recent 15O-CO PET study, Honka et al. found a minor decrease in mean HBV in both obese patients and healthy subjects after a meal [7], but the physiological effects of a meal on HBV have not been determined in patients with cirrhosis. After a meal, there is a substantial increase in splanchnic and thus hepatic blood flow [7–10].
Cognitive and neural effects of exercise following traumatic brain injury: A systematic review of randomized and controlled clinical trials
Published in Brain Injury, 2020
Bhanu Sharma, David Allison, Patricia Tucker, Donald Mabbott, Brian W. Timmons
It has been purported (albeit in the healthy state) that angiogenesis or changes in cerebral blood volume secondary to exercise may be responsible for the suite of exercise-induced neural changes (49). Studies have demonstrated that in mTBI, patients with persistent symptoms and no structural brain abnormalities have regional hypoperfusion (relative to healthy controls) in several brain areas, including the frontal, prefrontal, and temporal cortices, as well as sub-cortical structures (57). (See Len et al. (58) for a review on the persisting nature of cerebral blood flow (CBF) reductions following brain injury, as well as how trauma can impact cerebral autoregulation, reactivity, and oxygenation.) Moreover, longitudinal studies have shown that normalization of CBF in athletes with concussion is associated with recovery (59), while other prospective studies have related gray matter cerebrovascular reactivity with symptom burden in adults with mTBI (60). Given the association between CBF and TBI-related impairments, and that exercise (as per a recent and methodologically rigorous study using oxygen-15-labeled H20 and positron emission tomography (28)) increases regional CBF in the early and late stages of exercise in healthy male adolescents, future studies should examine the effects of exercise interventions in TBI on CBF. Further, assessing the association between CBF with other markers of TBI recovery (such as heart rate variability, which has previously and preliminarily been correlated with regional CBF (61)) can offer evidence that changes in readily measured heart rate variability serve as proxy for neural recovery via CBF normalization.