Tumor and infection localization in AIDS patients: Ga-67 and Tl-201 findings.

Examples of Ga-67 and Tl-201 scans in AIDS patients performed at St. Vincent's Hospital and Medical Center of New York are presented. Use of these methods is the adopted approach at this institution in AIDS patients for localizing sites of tumor or infection involvement. A Ga-67 scan is the most common nuclear medicine examination performed on AIDS patients. Sequential Tl-201 and Ga-67 scans have a role in differentiating Kaposi's sarcoma from malignant lymphoma and opportunistic infections. For intracranial lesions, Tc-99m MIBI or Tl-201-201-201-201 chloride can differentiate malignant from benign inflammatory lesions.

Comparison between 201Tl-chloride and 99Tc(m)-sestamibi SPET brain imaging for differentiating intracranial lymphoma from non-malignant lesions in AIDS patients.

The aim of this study was to compare 201Tl-chloride and 99Tc(m)-sestamibi (MIBI) SPET brain imaging for differentiating brain lymphoma from other intracranial lesions in AIDS patients. Both studies were performed on the same day in 17 AIDS patients with intracranial enhancing lesions on either CT or MRI. Eleven patients underwent brain biopsy and six patients were followed clinically. We calculated the radiopharmaceutical uptake ratio of the lesion to that on the contralateral side with the guidance of CT or MRI findings. Ratios of 1.5 or more were considered to represent malignant lesions and ratios < 1.5 were considered to represent benign lesions. Biopsy revealed four cases of lymphoma, four cases of toxoplasmosis and two cases of progressive multi-focal leukoencephalopathy; one biopsy yielded necrosis. Both the MIBI and 201Tl studies yielded no false-negative cases of lymphoma (sensitivity 100%). Of the 13 non-lymphoma cases, the 201Tl studies showed seven true-negative cases (specificity 54%) and the MIBI studies showed nine true-negative cases (specificity 69%). The biopsies of the false-positive cases (toxoplasmosis) showed a pattern of healing after medical treatment. We conclude that MIBI is more helpful than 201Tl because of higher specificity and equal sensitivity. The medical treatment of toxoplasmosis is a cause of false-positive 201Tl and MIBI studies.

Sites of tuberculous involvement in patients with AIDS. Autopsy findings and evaluation of gallium imaging.

The purpose of this study was to review autopsy and gallium scan findings in two different acquired immune deficiency syndrome (AIDS) patient populations who had a confirmed diagnosis of tuberculosis (TB) to identify organs involved and accuracy of clinical diagnosis. The first group was comprised of 29 autopsies between January 1982 and December 1994, including only 18 patients who were diagnosed before death. Organs most commonly involved were the lymph nodes (59%), lungs (56%), spleen (53%), liver (45%), and kidneys (37%). Other opportunistic infections were present in 18 (59%) of autopsies, with more than one opportunistic infection present in 11 (37%) of the autopsies. Lungs were involved in 79% of all autopsies. The second population group included 94 patients with AIDS with a proven diagnosis of TB, only 24 of whom had gallium scans in the period between January 1992 and December 1994. Chest x-ray results were negative in 4 patients (17%); gallium scan results were positive in 16 patients (66%). The reasons for false-negative gallium scan results were due to anti-tuberculous treatment for periods varying from 2-21 months in 7 patients or the presence of extra pulmonary tuberculosis. The sites of TB involvement in the chest were: lung parenchyma in 5 patients (19%, 4 in mid and lower lung, and 1 in upper fields). There was lymph node involvement in all 16 patients (24 locations with mediastinal involvement in 23%, supraclavicular 23%, axillary 11%, retroperitoneal 11%, and inguinal region in 4%. We conclude that (1) tuberculosis in patients with AIDS behaves similar to primary tuberculosis; (2) the combination of chest x-ray and gallium imaging is sensitive for the diagnosis of pulmonary tuberculosis in patients with AIDS; (3) the involvement of mediastinal lymph nodes in gallium scans in the presence or absence of chest x-ray abnormalities should raise the possibility of TB involvement in patients with human immunodeficiency virus; (4) anti-TB treatment decreases the sensitivity of gallium scan.

Lung-heart ratio in stress thallium myocardial perfusion imaging in patients with a history of a previous pneumonectomy.

Increased TI-201 lung-heart ratio after treadmill exercise or pharmacologic stress is an indicator of left ventricular dysfunction. After pneumonectomy, it is not reliable because of increased pulmonary circulation in the remaining lung. The authors present an example of normal stress TI-201 myocardial perfusion imaging with an increased lung-heart ratio of TI-201 uptake.