Focal cerebral ischemia measured by the intra-arterial 133xenon method. Limitations of 2-dimensional blood flow measurements.

Abstract

SUMMARY The limitations of 2-dlmendooal isotope techniques in the study of focal cerebral ischemia were investigated using the intra-carotid '"xenon injection method and a 254 multidetector scintillation camera. To make sure that the detectors "look" directly on infarcted areas, only patients with infarcts involving cortical surface structures were included in the study. Eleven such patients were found among 43 consecutive patients with completed stroke, all investigated with CT-scan. The blood supply to the infarcted areas was evaluated using 3 different approaches: 1) The first minute washout of '"xenon (rCBF), 2) the initial distribution of isotope during the first 5 sec and 3) the cumulated counts recorded during 15 mm. Compton scatter and the "look through phenomenon" were responsible for the majority of counts recorded from the infarcted areas and the blood flow recorded was found to be grossly overestimated and much more influenced by the blood flow in the surroundings than in the iscbemlc area itself. However, using the 3 approaches, infarcted areas were always disclosed by our equipment.It is concluded that 2-dlmensional isotope technique is not reliable for quantifying focal ischemic lesions. The method should be limited to the qualitative demonstration of the ischemic lesions for which it is fully reliable.

A dynamic concept of middle cerebral artery occlusion and cerebral infarction in the acute state based on interpreting severe hyperemia as a sign of embolic migration.

“…Abundant evidence of such a development is accumulated in the literature 8 32 -42~52 and the following other possible explanations can be ruled out: 1) The severely hyperemic areas cannot be collaterally perfused areas: The early filling veins draining the hyperemic areas were not localised distal to the occlusion as would be expected if these areas were collaterally perfused-they were localised proximal to the occlusion. The angiograms as well as the isotopeangiograms 29 obtained in connection with the flow study clearly showed that the areas were filled anterogradely and as expected very rapidly. Collaterally perfused areas in patients with MCA occlusion moreover appears to be low flow areas rather than hyperemic areas in the acute state.…”

Blood Flow and Vascular Reactivity During Attacks of Classic Migraine'Limitations of the Xe‐133 Intraarterial Technique

“…As reported from our laboratory at least 40% of the counts originate from isotope deposited (and washed out) in surrounding areas with a higher flow. 15 This accords quite well with the estimates of Bolmsjo 19 showing that, for a 3.3 cm 2 area "seen" with a narrow collimator ("fine hole") as used in the present study, 28% to 41% of ipsilateral cortical counts were scattered from extraregional sources. Thus, the washout curve obtained from a low flow area is the sum of the washout of isotope actually deposited in the low flow area (this represents true flow) and the washout of Compton-scattered radiation from the surroundings (with a higher flow).…”

“…A major disadvantage of this method is that CBF in low flow areas is heavily overestimated because of scattered radiation (Compton scatter). 12,15 Moreover, true changes of CBF in the low flow area are in many cases difficult or impossible to detect because of Compton scatter.…”

Migraine With and Without Aura: The Same Disease Due to Cerebral Vasospasm of Different Intensity. A hypothesis based on CBF studies during migraine.

“…17,18 With the Xenon-133 intraarterial injection method CBF must decrease by 15% or more in order to be considered significantly reduced. 19 Because of Compton scatter, focal CBF reductions, however, become underestimated with the Xenon-133 techniques. When measuring a focal CBF reduction of 15% it should be remembered that the true CBF reduction in the area is about 20%.…”