Evaluation of sequential thallium and gallium scans of the chest in AIDS patients.

UNLABELLED: With decreasing incidence of pneumocystis carinii pneumonia (PCP) in AIDS as a result of prophylactic regimens, there is a higher incidence of tuberculosis (TB), mycobacterium avii complex (MAC), kaposi sarcoma and malignant lymphoma. There is a need for differentiating these various pathological entities. The purpose of this study was for a retrospective evaluation of sequential thallium and gallium scans in AIDS patients for differentiating intrathoracic kaposi sarcoma from malignant lymphoma and opportunistic infections. METHODS: A total of 181 patients had both studies completed between March 1992 and May 1994. The final diagnosis was verified only in 83 patients. Results were correlated with the CD4 counts, bronchoscopic and chest radiograph findings. RESULTS: In patients with pulmonary kaposi sarcoma and no opportunistic infections (19 patients), a thallium-positive, gallium-negative pattern was detected in 17 patients with a sensitivity of 89%. In the presence of kaposi sarcoma plus opportunistic infections, this pattern was only detected in 7 of 19 patients (sensitivity dropped to 37%). In 45 patients with opportunistic infections and no kaposi sarcoma, only two false-positive findings were found in patients with cytomegalic virus pneumonia for a specificity of 96%. For the whole group of 83 patients, sensitivity was 63%; specificity 95%; positive predictive value 92%; accuracy 81%; and negative predictive value 75%. CONCLUSION: A thallium-positive, gallium-negative pattern in AIDS patients has a high specificity for the diagnosis of kaposi sarcoma, however, the sensitivity dropped from 89% to 37% in the presence of opportunistic infections.

Diffuse bilateral lung uptake of TI-201 chloride in CMV pneumonitis. Case presentation with histopathologic correlation.

Diffuse intense lung uptake of TI-201 chloride without abnormal Ga-67 citrate in a case of cytomegalovirus pneumonitis in a patient with AIDS is presented. An autopsy performed within 4 days of imaging revealed no pulmonary pathology other than diffuse cytomegalovirus infection with abundant histiocytes and inclusion bodies and pulmonary congestive heart failure. Among the various mechanisms of TI-201 accumulation, active transport through Na-K ATPase appears to be predominant in this case, as suggested by innumerable histiocytes. It is the authors' experience that positive TI-201 uptake without abnormal Ga-67 accumulation is highly specific for pulmonary Kaposi sarcoma. The presence of such discrepancy between TI-201 and Ga-67 uptake in AIDS patients decreases the specificity of a TI-201 positive/Ga-67 negative lesion for pulmonary Kaposi sarcoma, especially with the rising incidence of both cytomegalovirus and Kaposi sarcoma in AIDS patients.

Diffuse Tl-201 uptake in the lungs. Etiologic classification and pattern recognition.

Diffuse Tl-201 uptake in the lungs could be because of cardiac, neoplastic, inflammatory, or interstitial lung disease. Examples from the different categories, differential diagnosis, and different patterns are presented. The authors discuss the different mechanisms of increased Tl-201 uptake in the lungs which vary according to the underlying pathology.