Evolution of temporal lobe hypoperfusion in transient global amnesia: a serial single photon emission computed tomography study.

Previous functional neuroimaging studies performed during transient global amnesia (TGA) have not answered the central question regarding the etiology of TGA, namely: whether the observed hypoperfusion in the mesial temporal lobe structures reflects a primarily ischemic process or whether it represents a secondary phenomenon resulting from locally decreased metabolism. The authors performed Tc 99-m-bicisate brain single photon-emission computed tomography (SPECT) scanning in a 66-year-old man during an episode of TGA, 24 hours after the episode and 3 months after the episode. To the authors' knowledge, this is the only reported study in which a follow-up SPECT scan was performed within 24 hours. The initial study showed bilateral mesial temporal lobe hypoperfusion that partially resolved after 24 hours and returned to normal at 3 months. Resolution of the SPECT scan abnormalities correlated well with resolution of the memory loss. These findings agree with previously reported SPECT, positron-emission tomography (PET), and diffusion magnetic resonance imaging (MRI) studies that indicate the mesial temporal lobe structures as the major site of pathology in TGA. The authors suggest that a process causing decreased local metabolism, such as cortical spreading depression, constitutes the primary pathophysiologic mechanism in this case.

The role of 99m-Tc HMPAO SPECT in the diagnosis of Creutzfeldt-Jacob disease.

A patient with acute dementia underwent imaging of the brain with technetium-99m hexamethylpropyleneamine oxime single-photon emission computed tomography. Regional perfusion abnormalities were identified in multiple locations, particularly in the left frontal lobe. This information was used to direct an open brain biopsy, which led to a diagnosis of Creutzfeldt-Jacob disease.

Gastrointestinal bleeding: improved localization with cine scintigraphy.

Studies of gastrointestinal bleeding, done with technetium-99m-labeled red blood cells were performed in 52 consecutive patients to determine whether cinematic acquisition and display localized sites of bleeding more accurately than did conventional static imaging. Computerized images were obtained for 15 seconds per image in 15-minute sets. Interpretations based on a cinematic display were compared with those based on standard 1-minute images obtained every 5 minutes. Pathologic confirmation of a site of bleeding was obtained in 21 patients. The cinematic display demonstrated bleeding not seen on static images and yielded either more accurate localization or increased sensitivity in eight of 21 patients (38%). Linear regression showed that the cinematic correlation (r = .98) to the actual site of bleeding was better than either of two readers' interpretations of the static display (r = .93, P less than .02; and r = .88, P less than .0004). The mean error for cinematic localization of bleeding (0.4 anatomic segments +/- 0.6 [standard deviation]) was less than that for the static interpretations (1.1 anatomic segments +/- 1.4) (P less than .01). It is concluded that computerized cinematic acquisition and display of scintigrams improves localization and detection of gastrointestinal bleeding.

Comparison of left anterior oblique and geometric mean gastric emptying.

A left anterior oblique image (LAO) and the geometric mean of anterior and posterior counts have both been proposed as methods for acquiring gastric emptying data. Both approaches are used to correct for the changes in attenuation that occur as the depth of radiolabeled solids changes during gastric emptying. These two methods were compared by using a power exponential curve fit to calculate a lag phase, an equilibrium emptying rate, and a half-time for gastric emptying in 20 patients. There were no significant differences (mean +/- 1 s.e.m.) in the measured half-emptying time (115 +/- 10 versus 104 +/- 7 min) (p = 0.08) or rate of gastric emptying (0.015 +/- 0.002 versus 0.015 +/- 0.002 min-1) (p = 0.56) for LAO imaging versus the geometric mean. However, the LAO measurements of the lag phase were significantly higher (69 +/- 7 min) than the geometric mean (53 +/- 6 min) measurements (p = 0.004). This resulted in 4/20 (20%) of patients with normal geometric mean lag phase measurements who would have been reclassified as abnormal using the LAO method.

Thallium-201 SPECT increases detectability of thyroid cancer metastases.

Thallium-201- (201Tl) chloride is known to accumulate in metastatic foci of differentiated thyroid carcinoma, but small and deep-seated lesions are generally not detectable by planar imaging. We have evaluated the use of 201Tl-chloride single-photon emission computed tomography (SPECT) in 41 post-thyroidectomy patients with differentiated thyroid carcinoma and one with medullary carcinoma; planar imaging alone was done in eight additional patients (total 50). Of 20 patients with known metastatic disease, planar 201Tl images were positive in 12 (60%) but SPECT revealed an additional 5 (25%) who had metastases (total 85%). SPECT revealed foci as small as 1.0 cm in the neck and 1.5 cm in the lungs, and was particularly useful in detection of disseminated micronodular pulmonary metastases, especially in patients whose scans were negative with diagnostic doses of 131I. Some pitfalls in interpretation of the tomographic reconstructions were found. Thallium-201 SPECT is a marked improvement over planar imaging in the detection of metastases of differentiated thyroid cancer.

Quantitative distribution of radiolabeled 5-aminosalicylic acid enemas in patients with left-sided ulcerative colitis.

Rectally administered suspensions of 5-aminosalicylic acid (5-ASA) are topically effective in treating left-sided ulcerative colitis. The extent to which the contents of these enemas are distributed to inflamed mucosal linings has not previously been determined. This study was undertaken to validate a technique for labeling 5-ASA with 99mTc and to quantitate the distribution of [99mTc]5-ASA in eight patients with left-sided ulcerative colitis. Eight patients underwent three colonic scintigraphic exams within five days, receiving a 60-ml radiolabeled 5-ASA enema into the unprepared rectum for each study, with sequential anterior abdominal images obtained for 4 hr. Activity within the rectum, sigmoid, descending, transverse, and ascending colon was quantitated. Over 50% of the labeled enema had advanced beyond the rectum in five of eight patients and in six of eight patients by 30 min and 60 min, respectively. The distribution of [99mTc]5-ASA was quantitatively reproducible when repeated in the same patient on different days, despite apparent visual differences. By 2 hr, the amount of the enema present within the rectum decreased significantly (P less than 0.05) compared to the initial distribution. The amount of enema present within the descending colon was increased significantly at 0.5 hr (P less than 0.05) and at 2 hr (P less than 0.01). There were no significant changes in the distribution from initial values for the sigmoid, transverse, or ascending colon at any time. In each of these cases the spread of the enema to or beyond the extent of disease was documented. In patients with left-sided ulcerative colitis, small volume [99mTc]5-ASA enemas reliably reach the area of inflammation.

Single photon emission computed tomography and renal pseudotumor.

Single photon emission computed tomography (SPECT), recently introduced into clinical nuclear medicine, potentially offers improved spatial resolution compared to planar imaging by eliminating activity from surrounding structures, and permitting three-dimensional reconstructions. Its clinical applications to date have been limited. A case where SPECT with Tc-99m dimercaptosuccinic acid (DMSA) better demonstrated a renal pseudotumor (a benign column of Bertin) compared to planar imaging is reported.