Evaluation of regional cerebral circulation based on absolute mean transit times in radionuclide cerebral angiography

Abstract

In radionuclide cerebral angiography (RCA) the analysis of the activity-time curves recorded over the hemispheres following an intravenous bolus injection of a radioactive indicator permits the evaluation of absolute cerebral mean transit times (MTTcb). The inverse of MTTcb is an index of cerebral blood flow. The bolus parts of the cerebral activity curves were fitted with gamma-variate functions. The duration of the injection bolus and its subsequent dispersion through the cardiopulmonary circulation were corrected for using the activity curve over the aortic arch. In a control material of 52 subjects MTTcb was uncorrelated with age and equal to 3.2 +/- 0.67 s (means +/- 1 SEE) for the 37 subjects younger than 60. For the fifteen subjects older than 60, mean MTTcb showed a steep increase with age. The results were in close agreement with those obtained by other researchers using either correction of cerebral curves based on a physical flow model or direct injections into the internal carotid artery. Comparison of RCA with x-ray carotid angiography in 12 subjects was satisfactory. Repeated RCA examinations in nine subjects a few days apart yielded a reproducibility of 0.7 s for MTTcb. The RCA is non-invasive, rapid, easy to perform and without risk for the patient. The RCA is recommended for quantitative evaluation of major alterations in cerebral perfusion.

Prognostic Evaluation Based on Cortical Vein Score Difference in Stroke

“…On the basis of transit times reported in the literature, 30–33 the approximate arch to retinal circulation time for contrast was 0.77 seconds. From the above the approximate cerebral transit time for the contrast before the scanner reaches the skull base was 6.58 seconds (4.23–11.23).…”

Early Changes in Liver Perfusion Caused by Occult Metastases in Rats: Detection with Quantitative CT

“…Time-attenuation curves.-The time-attenuation curves for the regions of interest ( Fig 2) were analyzed by means of a mathematical deconvolution method (Appendix) (15,(23)(24)(25) that takes advantage of the linear relationship between the iodine concentration and the CT attenuation numbers. The deconvolution method allows the tissue response to be standardized for any contrast material injection and, hence, calculation of the perfusion parameters.…”

Measurement of regional cerebral blood flow using ultrafast computed tomography. Theoretical aspects.

“…Methods for determining the AUC and (t) based on the fitting of a gamma-variate function to time-concentration data have been described in detail, 17 and it is generally possible to obtain suitable data for ROIs of various sizes. However, in cross-sectional imaging methods such as CT, the use of a small ROI, such as that for a peripheral artery, can introduce errors that can have a major impact in the calculation of rCBF.…”

“…If blood flow through an ROI is modeled as flowing through a single well-mixed compartment, the washout of blood from the region is exponential in form. 17 For such a model, the mean transit (or washout) time is equivalent to the standard deviation of transit times, and thus k would be 1. Attempts to describe blood flow with more sophisticated models such as multiple parallel compartments have resulted in values that are clearly at odds with experimental results, 19 suggesting that the value of k must be determined empirically.…”