Park Ch

Prognostic significance of ST-segment depression during adenosine perfusion imaging

To determine the significance of ST-segment depression during adenosine perfusion imaging for predicting future cardiac events, 188 patients with interpretable electrocardiograms were assessed 1 to 3 years (mean 21.5 +/- 6.6 months) after adenosine testing. At least 1 mm of ST-segment depression was observed in 32 (17%) patients, with > or = 2 mm of ST-segment depression in 10 (5.3%). Thirty-seven cardiac events occurred during the study period: 2 cardiac deaths, 5 nonfatal myocardial infarctions, 6 admissions for unstable angina, and 24 revascularizations. Univariate predictors of events were a history of congestive heart failure, previous non-Q-wave myocardial infarction, previous coronary angioplasty, use of antianginal medication, ST-segment depression during adenosine infusion (particularly > or = 2 mm), any reversible perfusion defect, transient left ventricular cavity dilation, and the severity of perfusion defects. Multivariate analysis identified > or = 2 mm ST-segment depression as the most significant predictor of cardiac events (relative risk [RR] = 6.5; p = 0.0001). Other independent predictors of events were left ventricular dilation (RR = 3.8; p = 0.002), previous coronary angioplasty (RR = 3.3; p = 0.001), a history of non-Q-wave myocardial infarction (RR = 2.3; p = 0.01), and the presence of any reversible defect (RR = 2.0; p = 0.05). We conclude that ST-segment depression occurs uncommonly during adenosine infusion, but the presence of > or = 2 mm of ST-segment depression is an independent predictor of future cardiac events and provides information in addition to that obtained from clinical variables and the results of adenosine perfusion imaging.

The attenuation effect in brain SPECT.

False perfusion defects simulating Alzheimers disease can be attributed to skull thickness and head holders of a SPECT scan table. Brain phantom SPECT was performed using a different type of head holder in order to evaluate the effect of attenuation due to head holders and skull thickness on brain SPECT. Skull thickness was measured in 10 normal or non-Alzheimers patients and 10 patients with suspected Alzheimers disease. Visual and quantitative analysis of regional perfusion showed a 19% count loss due to attenuation by commercially available head holders and average skull thickness, less than 18% count difference between frontal-temporal and parietal-occipital skull in non-Alzheimers disease patients, and more than 22% count difference observed in suspected Alzheimers patients.

Brain SPECT in a patient with post-stroke hallucination

A patient developed visual hallucinations following a left-sided cerebrovascular accident (CVA). Brain SPECT using Tc-99m HMPAO demonstrated increased perfusion at the biparieto-occipital lobes. Following antiepileptic medication, repeat brain SPECT showed interval decrease in perfusion in the same areas with the symptomatic relief of hallucinatory episode. While it is possible that the interval decrease is due to natural resolution, the authors believe that it is likely due to drug treatment.

Scintigraphic evaluation of regional migratory osteoporosis

Three patients with regional migratory osteoporosis (RMO) of the lower extremity were observed over a period of time with clinical and scintigraphic follow-up. The diagnosis of RMO is clinically and radiographically difficult, but a three-phase bone image is very helpful in diagnosing patients with RMO.

Co-existent parathyroid adenoma and thyroid carcinoma. Nonspecificity of dual tracer parathyroid imaging for parathyroid lesions

Dual tracer parathyroid imaging (DTPI) using Tc-99m and TI-201 has a reported sensitivity of 92% for the detection of parathyroid adenomas. A patient with biopsyproven parathyroid adenoma as well as papillary thyroid carcinoma is presented. To date, this is the first such case ever to be reported and implies that DTPI, although a sensitive diagnostic modality for parathyroid adenoma detection, is not specific. The diagnosis of primary hyperparathyroidism has recently been established more frequently than in the past due to detection of elevated serum calcium levels on routine blood samples, relatively sensitive parathormone (PTH) assays, and noninvasive imaging modalities such as nuclear medicine, CT scanning, and ultrasonography. At our institution, we have successfully detected the location of parathyroid adenomas in many cases, using the dual tracer method with TI-201 and Tc-99m, confirmed at surgery. We present a case of primary hyperparathyroidism in which two distinct lesions were detected by nuclear imaging: one lesion was proven at surgery to be a parathyroid adenoma, while the other represented thyroid carcinoma.

Small parathyroid adenoma associated with hyperactive bone demonstrated by Tc-99m MIBI scintiscan

A 58-year-old man patient with a history of hyperparathyroidism with recurrent renal stones was evaluated by ultrasonography of the neck and Tc-99m methoxy isobutyl isonitrile (MIBI) scintigraphy. Both imaging modalities correctly visualized a parathyroid adenoma. Increased Tc-99m MIBI uptake was noted in the sternum, clavicle, and shoulders. These findings are the result of hyperactive bone turnover rate occurring secondary to the hyperparathyroidism

The "count loss" artifact in Tc-99m HMPAO leukocyte SPECT of the abdomen.

During SPECT studies of the abdomen with Tc-99m labeled autologous leukocytes, the authors had observed false defects involving the vertebral bodies of the lower thoracic spine in two patients. To investigate this “count loss” artifact, a phantom simulating liver, spleen, and spine was constructed. Four clinical situations were simulated by positioning cylinders in the different locations: normal spine-spleen model, normal liver-spine-spleen model, spine-enlarged spleen model, and enlarged liver-spine-enlarged spleen model. SPECT studies were performed at different concentration ratios between the spleen and the spine on the disparate models with varying distance from the spleen to the spine. The results showed that the count loss artifact is not only related to the concentration ratio between the structures but also is related to the size, position, and distance between the structures. The correction steps for this artifact include: 1) identifying average count value of the spine and spleen from ECT sinogram count data, and 2) replacing the original high-count value in the spleen by the count value close to the average value at the region of the spine in the 120 raw projection data. Using these new modified ECT data, the reconstructed orthogonal images are almost free of the count loss artifact.

Scintigraphic recognition of papillary muscles and papillary muscle ischemia.

During stress thallium imaging, papillary muscles (anterolateral and posteromedial) appear scintigraphically as focal regions of enhanced activity in sites corresponding to their anatomic position. In the normal case, enhancement after exercise is greater than or equal to enhancement at rest. With papillary muscle ischemia, the involved papillary muscle demonstrates more enhanced activity at rest than at postexercise. This pattern change with papillary muscle ischemia was observed in four patients. Three cases demonstrated complete reversal of those ischemic changes after angioplasty and the remaining case failed to show any significant improvement after angioplasty.

Lymphedema of the lower extremities: Evaluation by microcolloidal imaging

Contrast lymphangiography has been the traditional radiographic method for imaging the lymphatic system of the lower extremities. Because of the difficulty in performing the procedure and its potential side effects, radionuclide lymphanglography is a safe and reliable alternative. Technetium-99m labeled to antimony trisulfide colloid was used in nine patients presenting with lymphedema of the lower extremities. The procedure was relatively simple to perform, and no adverse effects were noted.

Giant parathyroid adenoma demonstrated by dual tracer parathyroid imaging

Noninvasive diagnostic imaging modalities have played an increasingly important role in preoperative localization of parathyroid lesions. The radionuclide method using Tl-201 and Tc-99m subtraction imaging is quite successful in detecting such lesions, with a reported sensitivity of 92%. A case of surgically proven primary hyperparathyroidism, caused by an unusually large parathyroid adenoma and detected by the dual tracer method, is presented.