Summary: Regional CBF (rCBF) was measured quanti tatively using the inert-gas washout technique with xenon-133 and single-photon emission computed tomog raphy. Tomographic data were reconstructed by filtered back projection, and flow was calculated according to the double-integral method, Ninety-seven subjects ranging in age from 20 to 59 years received a single examination; eight of these received a second examination within 1 h of the first; seven others received a second examination separated from the first by 1-10 days. Transverse-section images were obtained at 2, 6, and 10 cm above and par allel to the canthomeatal line (CML). Cortical gray matter flows were obtained from 12 brain regions in the slice 6The measurement of regional CBF (rCBF) in hu mans began with the pioneering work of Kety and Schmidt (1945) in which they employed the nitrous oxide method to measure mean hemispheric blood flow. A decade later, Lassen and lngvar (196 1) adapted this technique to the external detection of radioactive inert-gas tracers, namely 85Kr. By using multiple detectors, multiple brain regions could be examined for abnormalities in rCBF. Advances in tracer technology led to the widespread use of 1 33 Xe in place of 8 5Kr, while advances in detectors, col limation, and data analysis led to ever increasing number of probes (up to 254) and thus regions of brain subjected to rCBF analysis (Veall and Mallett, 1966; Obrist et aI., 1975; Risberg et aI., 1975; lngvar, 1976; Sveinsdottir et aI., 1977; Lassen et aI. , 1978). where there was no difference. Flow was higher in women than in men and declined mildly with age for both sexes (slope = -0.33 mllmin/lOO g/year; p < 0.05).
A new k-space trajectory measurement technique is proposed and demonstrated. This technique measures the k-space trajectory, in seconds, using only a few readout lines, using phase values of acquired MR signals. As a result of the technique's efficiency, k-space trajectory measurement using patient data becomes possible. The utility of this techniques is demonstrated in phantom and human studies at 4.1 T.
A new method of visualizing acute myocardial infarction in humans following intravenous injection of 15 mCi-5 mg of 99mTc stannous pyrophosphate in 23 patients is reported. Fifteen patients had histories suggestive of acute myocardial infarction and subsequently developed electrocardiogram and enzyme changes that confirmed the clinical diagnosis. Eleven of the 15 patients were scanned 3-5 days postinfarction, and all had positive scintigrams. The four remaining patients were scanned 7-10 days after their myocardial infarction; two had positive scintigrams. In those 8 patients with chest pain but without ECG and enzyme changes suggestive of myocardial infarction, scintigrams were negative. Positive scintigrams in the patients with myocardial infarction are thought to be due to incorporation of pyrophosphate into the crystalline structure of the hydroxyapatite found within the mitochondria of irreversibly damaged myocardial cells. The location of the acute myocardial infarction by scintigram correlated well with ECG localization in the 13 patients with positive scintigrams. This imaging method shows promise in 1) identifying the presence of acute myocardial infarction in patients with chest pain, 2) determining the location of acute myocardial infarction with a high degree of accuracy, 3) detecting the extension of the infarction, and 4) the possibility of determining the size of acute myocardial infarctions.From the
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