Acta radiologica
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Age- and sex-related changes of metabolites in healthy adult brains have been examined with different (1)H magnetic resonance spectroscopy (MRS) methods in varying populations, and with differing results. A long repetition time and short echo time technique reduces quantification errors due to T(1) and T(2) relaxation effects and makes it possible to measure metabolites with short T(2) relaxation times. ⋯ The concentrations of several metabolites in cerebral supraventricular white matter are age dependent on (1)H MRS, even in young and middle-aged people, and age dependency can be nonlinear. Each (1)H MRS study of the brain should therefore take age into account, whereas sex does not appear to be so important. The use of macromolecule and lipid evaluations is compromised by less successful quantification and large variations in healthy people.
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The concentration of N-acetylaspartate (NAA) in hippocampus, as measured with magnetic resonance spectroscopy (MRS), and the ratio of NAA/(choline (Cho) + creatine (Cr)) are valuable tools in the lateralization of temporal lobe epilepsy (TLE). MRS of hippocampus is also increasingly used to study certain psychiatric and degenerative diseases. However, the reliability of such measurements of hippocampus has been questioned. ⋯ Metabolite concentrations in the mesial temporal lobe obtained with MRS imaging represent the mean value of hippocampus and a considerable amount of adjacent tissue. To assess the hippocampus alone, an actual voxel well below 1 cm(3) and a sub-centimeter slice thickness are required.
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Arterial input functions may differ between brain regions due to delay and dispersion effects in the vascular supply network. Unless corrected for, these differences may degrade quantitative estimations of cerebral blood flow in dynamic susceptibility contrast magnetic resonance perfusion imaging (DSC-MRI). ⋯ Given knowledge of neurovascular anatomy, the current blind approach seemingly produced reasonable estimates of voxel-specific arterial input functions. In addition to potentially reducing quantification errors in DSC-MRI, these user-independent voxel-specific arterial input functions could be useful for visualizing abnormal blood supply patterns in patients.
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Pulmonary embolism (PE) is the third most common cause of cardiovascular death. When PE is fatal, right ventricular failure usually occurs within the first few hours, so right ventricular dysfunction (RVD) should be diagnosed rapidly to identify patients who could benefit from fibrinolytic therapy. ⋯ PA obstructive index of more than 50% and RV/LV ratio >1.5 are useful diagnostic criteria for severe PE and poor patient outcome.
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Concern has been raised regarding the mounting collective radiation doses from computed tomography (CT), increasing the risk of radiation-induced cancers in exposed populations. ⋯ By reducing X-ray tube potential from 120 to 100 kVp, while keeping all other scanning parameters unchanged, the radiation dose to the patient may be almost halved without deterioration of diagnostic quality, which may be of particular benefit in young individuals.