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At least 397 records · Page 22Linked to original sources
PubMed1989

Evaluation method for krypton-81m reservoir administration systems.

Large variations have been reported in counting rates during lung ventilation studies using different 81mKr administration systems and among different patients. A method was set up to determine the activity utilization efficiency (AUE) using various administration systems. For that purpose a simple lung simulator was developed for combination with reservoir administration systems to be tested. It was found that under normal breathing conditions the AUE is 50% using a reservoir system and only 18% in the absence of a reservoir in the administration system. The measured results were confirmed by a mathematic model. The suggested simulator is suitable for use in hospitals and also enables an indirect check on the 81Rb/81mKr generator performance.

Equipment Design↗
PubMed1985

The uniformity of liver perfusion as measured by krypton-85 clearance.

The uniformity of regional liver perfusion was studied in eight anaesthetised dogs by measuring the clearance of 85Kr with three beta detectors, and the results were compared with independent measurements of mean perfusion by electromagnetic flowmetry. The intra-hepatic flow distribution was found to be heterogeneous, with a coefficient of variation between locations which averaged 17%. The pattern of flow varied from liver to liver, and there was no consistent tendency for any one of a limited number of locations to be better or less well perfused than any other. Discrepancies between 85Kr clearance and flowmeter measurements were of a similar magnitude to inter-regional variations in flow, and there was no evidence of a systematic difference between the two measurement techniques. Individual 85Kr clearance measurements can misrepresent the perfusion of the liver as a whole, and averaging several measurements performed in different locations is likely to yield a better estimate of mean flow.

Animals↗
PubMed1986

Significance of single ventilation/perfusion mismatches in krypton-81m/technetium-99m lung scintigraphy.

The significance of a single area of ventilation/perfusion (V/P) mismatch in lung scans performed on patients suspected of pulmonary embolism (PE) was evaluated. Ten of 20 patients with this scan finding were found to have PE. An intermediate probability of PE was found with segmental (71%) or subsegmental (45%) single V/P mismatches. Seven of 16 patients with a single V/P mismatch and without a matching radiographic opacity had PE. Three of the four patients who had a V/P mismatch and a matching radiographic opacity were found to have PE. Multiview ventilation imaging with 81mKr was found to have advantages for the evaluation of single V/P mismatches. Based on the data available at this time, a single V/P mismatch suggests an intermediate probability of PE.

Adult↗
PubMed1986

Evaluation of the accuracy of steady-state krypton-81m method for calculating right ventricular ejection fraction.

The accuracy of a steady-state 81mKr method for calculating the right ventricular ejection fraction (RVEF) has been examined in this study. Causes of errors using this method and their effects on the calculated RVEF were evaluated. The results suggested that mixing in the right ventricle during continuous infusion of 81mKr was homogenous, allowing for the calculation of ejection fraction using the count rate ratio. Lung activity was quite important and could not be neglected in computing RVEF, but the use of [99mTc]MAA lung perfusion scanning seemed to allow a correct subtraction of this background activity. The delineation of right ventricular regions of interest (ROIs) was complicated by the translation movements of the right ventricle during heart contraction. These ROIs should be drawn carefully on the count density distribution images and data shown by parametric images; such as first and second harmonic phase, amplitude images, and composite stroke volume image should be considered. Furthermore, this study demonstrates the superiority of the 81mKr technique compared with 99mTc methods for computing RVEF. In conclusion, even if the true accuracy of the 81mKr method for calculating RVEF cannot be proven due to the lack of reference methods, strong, suggestive evidence that the technique should be accurate is shown here.

Adult↗