Comparison of supine versus prone tomographic myocardial imaging. Effect on false-positive rate.

As in most other nuclear medicine facilities, tomographic myocardial imaging was started here with the patients in the supine position. However, previous planar imaging experience indicated a high number of false-positive results using the supine position for left lateral views of the myocardium. Evaluating the accuracy of supine position SPECT imaging was considered necessary. In 1991, 228 myocardial imaging procedures were performed during a period of 3 months. Coronary arteriography followed within 3 months in 67 of these patients, permitting evaluation of the accuracy of the imaging procedure interpretations. These correlations revealed the accuracy of myocardial imaging to be only 73%. This was caused mainly by a rather large number of false-positive results (24%) occurring mostly in the inferior-posterior wall. A similar comparison was performed in 1992 after a change to prone position for routine tomographic myocardial imaging with 63 of 295 patients undergoing coronary arteriography. These data revealed an increase in the overall accuracy to 81% and a decrease in the false-positive results to 16%. The improvements were almost entirely in the inferior-posterior regions with no significant change in the false-positive results in the anterior wall. These findings provide convincing evidence that the prone position should be selected for tomographic myocardial imaging.

A tumor of the lung featuring increased pulmonary arterial perfusion.

An area of relatively increased tracer activity on a perfusion lung scan was found in the same location as a radiodense lung mass. The lesion responsible for this unusual combination of findings was identified after lobectomy and tissue examination to be poorly differentiated adenosquamous carcinoma.

Intrahepatic gallbladder.

Intrahepatic gallbladder must be distinguished from other lesions which also produce an area of decreased tracer concentration on liver scan. Identification is imperative because it determines therapy. A scan performed with rose bengal labeled with iodine 131 was used in this case.

Radionuclide cerebral angiography and the timing of aneurysm surgery.

Forty-five patients with subarachnoid hemorrhage due to verified intracranial aneurysms were studied prospectively to determine whether delaying operations in those patients with abnormal cerebral perfusion, assessed by radionuclide dynamic scanning, would lower case management mortality. Twenty-nine patients had intracranial operations when their radionuclide dynamic scans demonstrated normal perfusion. The one death in this group occurred in a patient who suffered a massive hemorrhage during operation as the bone flap was elevated. There were no instances of delayed spasm after operation. Of the 16 remaining patients who were treated without operation, 5 died. Only 1 of these deaths resulted from recurrent hemorrhage. This patient had normal cerebral perfusion but was not operated upon because of severe associated medical problems. Cerebral infarction occurred in 10 of the 16 unoperated patients, all of whom had persistently decreased cerebral perfusion. Four of these patients died of their infarctions or related causes. Although a trend related vessel caliber as seen on arteriograms and perfusion delay seen on dynamic scanning, individual exceptions were numerous. This study shows that radionuclide scanning, a safe procedure, is useful for identifying two types of patients: those with normal perfusion prone to rebleeding in whom an early operation is safe and those in whom perfusion is decreased. The latter group is prone to cerebral infarction, but rebleeding from the aneurysm is unlikely. Operation should be delayed in these patients until cerebral perfusion returns to normal or for several weeks if cerebral perfusion remains diminished.

Cerebral perfusion, vascular spasm, and outcome in patients with ruptured intracranial aneurysms.

In a retrospective study of 44 patients with verified ruptured intracranial aneurysms, the results of radionuclide cerebral perfusion scintigraphy (dynamic brain scanning) and the presence or absence of arteriographic spasm were correlated with the clinical outcome. The data indicated that patients with normal dynamic scans had a better outcome as a group and following intracranial surgery than those in whom perfusion was reduced. Patients with normal perfusion had a higher incidence of preoperative rebleeding from their aneurysms, while patients with reduced perfusion had a higher incidence of infarction, especially after intracranial surgery. There was no correlation between the presence or absence of arteriographic spasm and the results of the dynamic scans, and nor correlation between the presence of absence of spasm and the outcome of the group as a whole. However, in some individual cases with severe spasm, reduced perfusion on the dynamic scan and a poor outcome were noted. It was concluded that the results of the dynamic scan correlated better with eventual patient outcome than the presence or absence of arteriographic spasm. It is therefore suggested that patients in Grades I and II with normal dynamic scans be operated on promptly to prevent rebleeding, and that surgery in patients in Grades I and II with abnormal dynamic scans be delayed until the dynamic scan returns to normal.

A test for evaluation of peritoneo-venous shunt function: concise communication.

A simple imaging procedure has been devised for patients with peritoneovenous shunts when ascites reaccumulates and a decision must be made on whether or not to revise the shunt. A dose of 99mTc-sulfur colloid is injected into the peritoneal cavity and imaging of the abdomen and chest is performed 30 and 60 min later. After checking for tracer distribution throughout the peritoneal cavity, one looks for radioactivity in the liver and spleen and in the anterior chest tube. With a properly functioning shunt and effective breathing exercises, these are easily identifiable. If the shunt is obstructed, tracer activity will remain in the peritoneal cavity and thus cannot be identified in the liver or spleen.

Evaluation of radioactive potassium and its analogues for imaging myocardial infarcts.

An extensive clinical evaluation was undertaken to assess the value of myocardial infarct imaging with radioactive potassium and analogues. Of 130 patients so examined, 80 were diagnosed as having suffered infarcts in the recent or distant past on the basis of all information other than the scan. The radionuclide imaging results were abnormal in 87.5% overall, 97% in acute transmural infarcts, and 83% in lesions over 3 weeks old. In 50 patients not considered to have had myocardial infarcts or contusions, apparently false abnormal results were obtained in 15%. These were all patients in whom additional diagnostic help was desired after the ordinary laboratory tests and electrocardiograms. Excellent agreement of infarct location was discovered on comparing radionuclide scans with radiographic contrast ventriculography. On comparing electrocardiograms with scans for infarct location, 85% complete or partial correlation was revealed. Agreement between scan abnormalities and significant-appearing coronary arteriographic lesions was rather poor, causing one to realize that 43K scan abnormalities indicate regions of poor blood extraction by old or recent infarcts, rather than just poor regional arterial perfusion. While costly, radionuclide scans often provide worthwhile information about presence or absence of infarcts as well as about their location and size. Electrocardiograms and blood enzyme levels each cost less, but are almost always performed in serial fashion. This makes them actually more expensive than a single scan. Furthermore, a normal scan in a patient being considered for acute coronary care may be used as potent argument against the presence of an infarct, thereby saving costly intensive care and monitoring.