Detection of Altered Cerebral Arterial Blood Flow Using Technetium-99m Pertechnetate and the Gamma-Ray Scintillation Camera

In a previous communication (2) outlining some of the possible applications of the gamma camera (Pho/Gamma, Nuclear-Chicago), it was shown that an occlusion of the middle cerebral artery could be detected. Further experience has since been obtained in applying this technic to patients with cerebral vascular accidents and brain tumors, and the results are given in detail below. Technic The gamma camera detector is placed against the head in the fronto-vertex or vertex position. Ten to fifteen milli-curies technetium-99m pertechnetate is rapidly injected into an antecubital vein, and after an initial 0–15-second exposure scintiphoto, serial 5-second exposure scintiphotos are obtained. A small vein of the hand may also be used if a blood pressure cuff is employed as a tourniquet and inflated above systolic pressure. The test agent is injected through a short 25-gauge needle and the cuff rapidly released while still inflated. Results and Discussion Figure 1 represents a cerebral Tc99m flow study obtained in a normal patient. The 15–19-second exposure scintiphoto shows an equal right and left middle cerebral artery “blush“ and activity along the path of the anterior cerebral arteries (Fig. 1, A). In the 20–24-second interval (Fig. 1, B) only a diffuse distribution of activity is observed in the brain substance, with a high concentration in the region of the tor-cular Herophili. A conventional 100,000 count scintiphoto taken ten minutes after injection of Tc99m and without moving the patient is illustrated in Figure 1, C. Cerebral Vascular Accidents Case I (Fig. 2). In a patient with a sudden onset of left hemiparesis of three days duration, an absent right middle cerebral blush is observed in the Tc99m flow (Fig. 2, D). The frontal, left, and right lateral brain scintiphotos obtained approximately fifteen minutes after the injection are normal. Case II (Fig. 3). A cerebral vascular accident occurred two days before the brain study on June 21, 1966. Although an absent left middle cerebral artery blush is noted in the 15–19-second scintiphoto (Fig. 3, A), the conventional scintiphoto is negative (Fig. 3, B). The patient was recalled for a repeat study thirteen days later (July 4, 1966), and this time the brain scan was clearly positive in both the left lateral (Fig. 3, C) and the fronto-vertex (Fig. 3, D) projections. Comment: The two cases point out the principal merit of the Tc99m flow study: that is, it can detect an altered blood flow immediately after the insult and before the conventional brain scan becomes positive. There were also patients in whom the Tc99m flow was abnormal, and positive brain scans were not obtained until as long as four weeks after the cerebrovascular accident. It has been reported that in about 50 per cent of all these cases the brain scans are never positive (2). The next two cases demonstrate some interesting features of the Tc99m flow in patients with cerebrovascular accidents.