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PubMed1981

[Continuous measurement of regional cerebral blood flow using krypton-81 m (author's transl)].

In order to obtain sequential change of cerebral blood flow using the intracarotid 81mKr infusion method, we devised a new method by using the radiation from cervical internal carotid artery as the concentration of radioisotope in the blood perfused to the brain. Under continuous intracarotid injection of 81mKr, the radio activity obtained from the surface of the skull is proportional to the cerebral blood flow. However, since the method depends upon the infusion of a given volume of radioisotope per unit of time into the internal carotid artery, changes in the blood flow through the internal carotid artery result in changes in the concentration of radioisotope perfused to the brain. Under such conditions, the radioactivity obtained from the surface of the skull does not indicate the changes in blood flow. In such a case, the value obtained from the radioactivity (count rate) in the ROI of the brain divided by concentration of radioisotope in the blood perfused to the brain indicates the changes in cerebral blood flow. Our attention was drawn to the fact that the radioactivity measured from a constant area of the cervical internal carotid artery per unit of time is an indicator of the blood concentration of radioisotope following in the internal carotid artery, provided that, there are no changes in the size of lumen of internal carotid artery. According to this method devised by us, it had been possible to follow extremely short period changes in cerebral blood flow following CO2 inhalation, change of blood pressure (autoregulation) and administration of various drugs.

Adult↗
PubMed1978

Krypton-81m.

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Computers↗
PubMed1993

[Right ventricular function in patients with dilated cardiomyopathy: assessment using krypton-81 m blood pool scintigraphy].

The characteristics and pathogenesis of right ventricular dysfunction in 14 patients with dilated cardiomyopathy (DCM) were investigated by equilibrium right ventricular blood pool scintigraphy using ultrashort-lifetime 81mKr. Thirteen patients with severe left ventricular dysfunction due to old anterior myocardial infarction (OMI) and nine normal subjects were used as controls. The right ventricular end-diastolic pressure and volume index, mean pulmonary arterial pressure, and total pulmonary vascular resistance index were almost the same in the DCM and OMI patients. The right ventricular ejection fraction was 44.2 +/- 6.0% (mean +/- SD) in DCM patients and 47.1 +/- 7.9% in OMI patients, both significantly lower than those in the normal subjects (54.5 +/- 5.3%), but with no difference between the two case groups. The right ventricular peak filling rate was significantly reduced in both case groups as compared with the normal subjects (2.46 +/- 0.81 EDV/sec). The reduction was significantly greater (p < 0.05) in the DCM group (0.97 +/- 0.47 EDV/sec) than in the OMI group (1.61 +/- 0.46 EDV/sec). Cineangiography showed that the wall motion abnormality of the interventricular septum was remarkable in OMI patients, but was relatively mild in DCM patients. Lesions of the interventricular septum may be of major importance in right ventricular dysfunction in OMI, while extensive severe damage to the right ventricular free wall may be important in DCM. 81mKr blood pool scintigraphy is useful in the study of the right ventricular systolic and diastolic function. The diastolic parameters are more sensitive indicators for evaluation of right ventricular function in DCM than the systolic parameters.

Cardiomyopathy, Dilated↗
PubMed1993

Controlled delivery of krypton-81m boli in normal subjects: results and implications.

Interregional sequential filling potentially affects lung ventilation imaging, depending on the distribution of the tracer within the inspired volume. We investigated its importance quantitatively under near tidal breathing conditions in the upright lung using a short-lived radioactive tracer. Ten normal volunteers performed two runs of 900-ml breaths (from functional residual capacity) in which 100 ml of 81mKr boli were delivered "early" or "late" in inspiration, i.e., 50 ml or 450 ml volumetric depth. Apex-to-base gradients in the vertical profile were -106 +/- 22 (s.e.) counts/cm (early) and -187 +/- 24 (s.e.) counts/cm (late). Ratios of upper-to-lower regional ventilation (U/L) were 0.88 +/- 0.01 (s.e.) (early) and 0.81 +/- 0.01 (s.e.) (late). Simulations with a compartment model show that a simple pattern of sequential filling can by itself account for the experimental results observed. Control over 81mKr delivery can be important to physiologically accurate assessment of ventilation-perfusion matching. Controlled delivery techniques could also modify effectiveness and targeting of other inhaled agents including therapeutic aerosols.

Administration, Inhalation↗
PubMed1977

Assessment of regional cerebral blood flow by continuous carotid infusion of krypton-81m.

In order to obtain functional images of brain perfusion, we exploited a new concept, which is to take advantage of the short half-life of a radioactive tracer. Under continuous intracarotid infusion of a solution of Kr-81m (T1/2 = 13 sec; produced from its parent, 4.6-hr Rb-81), this tracer will never reach equilibrium within the brain because of the rapid radioactive decay. Its distribution will therefore reflect regional arrival of the nuclide, indicating regional cerebral blood flow rather than volume. During continuous infusion of Kr-81m, perfusion images can be obtained by simply collecting counts with a gamma camera and recording on Polaroid film. The procedure is readily repeatable in order to get images in multiple veiws or to follow minute-by-minute changes of cerebral perfusion.

Aged↗
PubMed2004

Even-tempered Slater-type orbitals revisited: from hydrogen to krypton.

Even-tempered Slater-type orbital basis sets were developed in 1973, based on total atomic energy optimization. Here, we revisit ET STOs and propose new sets based on past experience and recent computational studies. From preliminary atomic and molecular tests, these sets are shown to be very well balanced and to perform, at lower cost, almost as well as a very large (close to complete) basis set.

Journal Article↗