Tissue pertechnetate and iodinated contrast material in ischemic stroke

Radiologic study of injection drug use complications

The complications of injection drug use (IDU) can lead to a wide variety of clinical problems that range from complications localized to the injection site to more disseminated disease. The radiologic workup of these problems uses multiple modalities, depending on the location and type of problem to be investigated. This article discusses and illustrates some of the local and disseminated complications that can occur after IDU.

Leucocyte scanning--a valuable tool in diagnosing cerebral abscess--a survey

Intracerebral abscess is a diagnosis which occasionally can be difficult to establish by using CT scan only. This survey describes the usefulness of a supplementary indium-111 autologous granulocyte scan which may increase the diagnostic specificity in the differential diagnosis between neoplasm and intracranial abscess. Judging from the literature and our own investigations the application of the granulocyte scan is discussed with special reference to the possible pitfalls which can give both false negative and false positive results.

Uptake of radiolabeled ions in normal and ischemia-damaged brain

The regional concentrations of nine radiochemicals were measured in rat brain after induction of cerebral ischemia to identify tracers concentrated by brain undergoing selective neuronal necrosis. Transient (30 minute) forebrain ischemia was produced in the rat; 24 hours after cerebral recirculation the radiochemicals were injected intravenously and allowed to circulate for 5 hours. The brain concentrations of the radiochemicals in dissected regions were determined by scintillation counting. Forebrain ischemia of this nature will produce extensive injury to striatal neurons but will spare the great majority of neocortical neurons at 24 hours. The regional concentrations of these radiochemicals varied considerably in both control and ischemic animals. In postischemic animals, 4 radionuclides (63Ni, 99TcO4, 22Na, and [3H]tetracycline) were concentrated in the irreversibly damaged striatum in amounts ranging from 1.4 to 2.4 times greater than in normal tissue. The concentrations of 65Zn, 59Fe, 32PO4, and 147Pm in postischemic brain were similar to or less than those in normal brain. The concentration of [14C]EDTA was increased in injured and uninjured brain of postischemic rats. Autoradiographic analysis of the distribution patterns of some of these ions in normal animals showed that 99TcO4, 22Na, 65Zn, and 59Fe were distributed more uniformly throughout the brain than were 32PO4, 63Ni, and 147Pm. At 24 or 48 hours after ischemia, 63Ni, 99TcO4, and 22Na were preferentially concentrated in the damaged striatum and hippocampus, whereas 65Zn, 59Fe, 32PO4, and 147Pm did not accumulate in irreversibly injured tissue. Of the radiochemicals tested to date, Ni, TcO4, and tetracycline may be useful for diagnosing ischemic brain injury in humans, using positron emission tomography.

Regional cerebral blood flow after occlusion of the middle cerebral artery

Occlusions of the middle cerebral artery (MCA) are mostly of embolic origin (appr. 80%) and give rise to about one third of all ischemic strokes, most of these being major strokes. MCA occlusions lasting for less than 1/2 h are tolerated without occurrence of permanent tissue damage. Occlusions lasting between 1/2 h to 4-8 h lead to permanent tissue damage and neurological deficits that are proportional to the duration of occlusion. Maximal tissue damage is obtained after 4-8 h occlusion. A cerebral blood flow of 8-23 ml/100 gr/min is sufficient for cellular viability but insufficient for normal tissue function ("ischemic penumbra"). Cellular function is completely abolished in the interval 8-16 ml/100 gr/min and flow at that level is tolerated only for 1-3 h before neuronal death ensues. In the interval 18-23 ml/100 gr/min there is some functional activity although it is reduced. Experimental and clinical evidence suggests that flow in this interval may be tolerated for several days, months or even longer ("chronic ischemic penumbra"). After MCA occlusion the blood flow falls below 8 ml/100 gr/min in most cases and permanent MCA occlusion always leads to relatively large areas of frank infarction. The ischemic infarcts may be surrounded by collaterally perfused areas where the blood flow is pressure-dependent (impaired autoregulation) and quite commonly insufficient for normal neuronal function (below 23 ml/100 gr/min). Such collaterally perfused areas may include a "chronic ischemic penumbra". Emboli causing MCA occlusions commonly disintegrate and/or migrate more peripherally within the first few weeks post stroke. This leads to reperfusion and changes of ischemic infarcts into hyperemic infarcts where flow is severely increased. The vascular reactivity is completely abolished in hyperemic infarcts and the hyperemic state lasts for about two weeks. Probably, anemic infarcts are equivalent to ischemic infarcts while the hemorrhagic variety is equivalent to hyperemic infarcts. The "partial infarct" with selective neuronal necrosis occurs in experimental animals after MCA occlusions of less than four h but not after permanent MCA occlusion. The significance of partial infarction in human stroke is not clarified. The extent of irreversible tissue damage can be reduced only if therapy sets in within 4-8 h after the occlusion. If a "chronic penumbra" exists the extension of reversible tissue damage can be reduced if therapy aimed at increasing the blood flow in the penumbra sets in within weeks or even months after the stroke.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain scintigraphy with Tc99-pertechnetate in the evaluation of patients with cerebrovascular lesions. The diagnostic value related to age of the lesion and to the size, type and localisation revealed by CT-scan

Brain scintigraphy with Tc99-pertechnetate (Tc99-scan) was performed 4 times in 95 consecutive stroke patients: on average 5 days, 18 days, 103 days and 194 days after the stroke. The type (infarct, hematoma), size and localisation of the lesion was evaluated by CT-scan performed 3 times in all: on average 3 days, 18 days and 207 days after the stroke. The detection rate of Tc99-scan was 31% on day 5, 47% on day 18, 18% on day 103 and 9% on day 194. The detection rate was however highly dependent upon: (i) the localisation of the lesion, i.e. superficially localised lesions were nearly always identified (90%) while infarcts localised deep in the hemisphere were identified in only 20% of the patients; (ii) the size of the lesion, i.e. large deep infarcts were seen with a much higher frequency than small deep infarcts. The detection rate of the CT-scan was practically not dependent upon the time of investigation: 63% on day 3, 70% on day 18, 69% on day 207. The detection rate of the Tc99-scan and CT-scan was nearly identical for large superficially localised lesions 2-3 weeks after the stroke. In this period, however, CT-scan identified 30 deep infarcts. Only 12 of these were identified by Tc99-scan.