Brandy S. Walker

Interdisciplinary evaluation of cerebral hemodynamics in the treatment of arteriovenous fistulae associated with giant varices

The techniques for the treatment of intracranial arteriovenous fistulae include angiographic balloon occlusion of the fistula as well as direct surgical attack. Regardless of the method, the occurrence of severe hyperemia caused by a lack of autoregulation after obliteration of the fistula remains a significant concern. We report the use of single photon emission computed tomography and transcranial Doppler studies to assess the occurrence of hyperemia during trial balloon occlusion of such fistulae in two patients. Single photon emission computed tomography and transcranial Doppler studies confirmed the lack of hyperemia during the test occlusion, allowing consideration of treatment plans involving acute fistula occlusion without the difficulty imposed by gradual occlusion and permitting a more accurate evaluation of risk. The purpose of this report is to illustrate how clinical evaluation of intracranial hemodynamics can contribute significantly to treatment decisions.

Reverse redistribution of thallium-201 detected by SPECT imaging after dipyridamole in angina pectoris

Reverse redistribution refers to a thallium-201 perfusion defect that develops or becomes more evident on delayed imaging compared with the initial image immediately after stress. To determine the diagnostic importance of reverse redistribution after intravenous dipyridamole, thallium-201 single photon emission computed tomography and quantitative coronary arteriography were performed in 90 men with angina pectoris. Of the 250 myocardial segments analyzed, reverse redistribution was present in 17 (7%). Minimal coronary cross-sectional area in proximal vessel segments was less than or equal to 2.0 mm2 more often in regions with transient perfusion abnormalities than in regions with reverse redistribution (66 vs 29%, p less than 0.05). Compared with regions exhibiting transient perfusion abnormalities, regions with reverse redistribution had larger proximal arterial diameters (1.9 +/- 1.1 vs 1.3 +/- 1.1 mm, p less than 0.001) and cross-sectional areas (3.9 +/- 3.1 vs 2.2 +/- 2.6 mm2, p less than 0.001). Coronary artery dimensions and relative stenosis severity did not differ between those regions with normal perfusion and those with reverse redistribution. Reverse redistribution detected by thallium-201 single photon emission computed tomographic imaging after dipyridamole is uncommon, appears to occur as frequently in normal subjects as in patients undergoing coronary arteriography and does not indicate the presence of severe coronary artery disease.

Detection and Staging of Small Cell Lung Carcinoma with a Technetium-labeled Monoclonal Antibody A Comparison with Standard Staging Methods

Tumor-associated radiolabeled monoclonal antibodies (MoAb) can detect neoplasms in a variety of settings. The authors conducted a study comparing the ability to detect and stage small cell lung carcinoma by using a Tc-99m labeled monoclonal antibody (NR-LU-10 Fab) (NeoRx Corp, Seattle, WA) with standard staging methods. Standard staging included a physical examination, chest x-ray, a battery of radionuclide scans and/or computerized tomographic studies (head, abdomen, and bone), and bone marrow examination. A total of 22 comparisons were performed in 17 patients (five patients had revaluations after therapy). Fifty-four (74%) of the 73 lesions defined by standard staging were detected by the radiolabeled MoAb. Seven of eight patients (88%) classified by standard staging as having “limited stage” disease on presentation were concordantly “limited stage” by radio-immunoimaging. One patient deemed “limited stage” by standard staging was correctly upstaged (bone marrow involvement) as a result of the radiolabeled MoAb. Two patients found to have extensive disease at diagnosis were characterized as “limited stage” by the MoAb, for an overall staging accuracy of 0.88. Thirteen of 19 missed lesions were smaller than 2 cm (10 were smaller than 1 cm; 3 measured 1 to 2 cm). This comparative study shows that radioimmunoimaging by Tc-99m labeled NR-LU-10 Fab antibody is capable of complementing standard staging methods used in the evaluation of small cell lung carcinoma.

Comparison of dipyridamole-Doppler echocardiography to thallium-201 imaging and quantitative coronary arteriography in the assessment of coronary artery disease

This study was undertaken to determine whether Doppler measurements of systolic aortic and diastolic mitral blood flow velocities could reliably detect the presence of reversible myocardial perfusion defects during intravenous dipyridamole-thallium-201 imaging. In addition, the ability of dipyridamole-Doppler echocardiography to predict the presence of significant coronary artery disease (CAD) was evaluated. Baseline and post-dipyridamole Doppler studies were performed in 10 normal control subjects and 23 patients with CAD. Aortic peak velocity and acceleration increased from baseline to post-dipyridamole in normal subjects by 0.07 +/- 0.07 m/s (p = 0.016) and 2.1 +/- 2.0 m/s2 (p = 0.009), respectively. The ratio of early to late peak transmitral velocities decreased slightly in normal subjects, by 0.18 +/- 0.72 (difference not significant), whereas the ratio of early to late transmitral velocity-time integrals increased by 0.07 +/- 0.93 (difference not significant). The response of aortic velocity and acceleration to intravenous dipyridamole was not significantly different between normal subjects, patients without reversible thallium-201 perfusion defects and patients with reversible thallium-201 perfusion defects. Furthermore, only 3 of 14 subjects with reversible thallium-201 perfusion defects had abnormal (greater than 2 standard deviations from the mean) responses of aortic velocity or acceleration to intravenous dipyridamole. No patient had an abnormal response of the early to late mitral peak velocity ratio. In addition, the response of Doppler aortic and mitral indexes to intravenous dipyridamole was not able to identify the presence of significant CAD as assessed by quantitative coronary arteriography.(ABSTRACT TRUNCATED AT 250 WORDS)

Radionuclide imaging of bone marrow metastases with a Tc-99m labeled monoclonal antibody to small cell lung carcinoma

The detection of metastatic disease confined to the bone marrow compartment has in the past been technically limited. We have identified excellent imaging of bone marrow metastases during the evaluation of a Tc-99m labeled monoclonal antibody (NR-LU-10 Fab) (NeoRx Corp., Seattle, WA). This occurred during a study to assess the monoclonal antibodys ability to detect sites of small cell cancer (primary and metastatic). The study by design compares areas seen by the monoclonal antibody scan with those found by standard staging methods in patients with small cell lung cancer. Standard staging included chest x-rays, bone scans, CT studies of the abdomen, and histologic examination of the bone marrow. Fifteen patients have been evaluated, four on two occasions, for a total of 19 monoclonal imaging studies. Metastasis to the marrow compartment was identified by the monoclonal imaging in all patients whose bone marrow biopsies were positive for small cell carcinoma, and it was primarily responsible for the eventual detection of extensive disease (marrow involvement) in one patient. Thus it appears that compartmental bone marrow imaging for metastatic disease is possible with immunoscintigraphy.

Detection of cerebral hypoperfusion during trial carotid occlusion with reversal following extracranial-intracranial bypass prior to permanent occlusion

The authors describe a patient with a large intracavernous aneurysm of the right internal carotid artery and a marked decrease in focal brain blood flow induced by temporary carotid balloon occlusion. The patient subsequently underwent a superficial temporal to middle cerebral artery bypass followed by successful carotid occlusion using detachable balloons placed proximal to the aneurysm. Postoperative rCBF demonstrated normal perfusion in the region of the right internal carotid artery distribution as well as normalization of perfusion to a previous area of baseline perfusion abnormality. Cerebral brain blood flow imaging was useful in the initial evaluation as well as the management of this patient.

Analysis of thallium-201 single-photon emission computed tomography after intravenous dipyridamole using different quantitative measures of coronary stenosis severity and receiver operator characteristic curves

The presence of significant coronary artery disease in individual vessels was assessed using thallium-201 single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Coronary angiograms were analyzed using quantitative computer-assisted techniques in 81 men patients. Eleven men with a less than 3% probability of coronary artery disease were used as a control population. Three definitions of a hemodynamically significant coronary stenosis were studied independently: (1) a greater than 50% luminal diameter narrowing; (2) an absolute cross-sectional area less than or equal to 2.0 mm2; or (3) a greater than or equal to 70% cross-sectional area obstruction. Myocardial perfusion after dipyridamole was analyzed using the quantitative (polar map) method in 213 regions from the group with known coronary anatomy and using 33 regions from the group with a low likelihood of disease. Receiver operating characteristic curves were used to define the best cut-off point for the discrimination between normal and abnormal perfusion. When related to each of the three quantitative angiographic criteria, the optimum balance between sensitivity and specificity occurred at a defect size of greater than or equal to 8% for the left anterior descending artery, greater than or equal to 4% for the circumflex artery, and greater than 0% for the right coronary artery. Using a luminal diameter narrowing of greater than 50% to define the presence of significant coronary artery disease, these corresponded to respective sensitivities and specificities of 0.82 and 0.76 for the left anterior descending artery, 0.71 and 0.71 for the circumflex artery, and 0.76 and 0.82 for the right coronary artery. Thus analysis of receiver operator characteristic curves provides a means to define abnormalities for the SPECT polar map program after dipyridamole stress. Different definitions of coronary stenosis significance as determined by quantitative angiography did not substantially alter the results of the thallium imaging data and thus suggest that these definitions are functionally similar.