Thallium-201-chloride and technetium-99m-MIBI SPECT of primary and metastatic lung carcinoma

We compared technetium-99m-MIBI (Tc-99m MIBI) with thallium-201-chloride (Tl-201) SPECT imaging in patients with lung carcinoma. In addition, we compared the imaging characteristics of Tl-201 and Tc-99m MIBI after radiation therapy. Thirty-seven patients with primary lung carcinoma were evaluated with SPECT imaging for metastasis to the mediastinal lymph nodes and brain. Patients were imaged with Tl-201 chloride images 10 and 180 min after injection. Patients were also imaged 10 min after injection of Tc-99m MIBI. The sensitivity of Tl-201 SPECT for the primary lesion and brain metastasis was 97.1% and 70.0% respectively at 10 min and 97.1% and 60.0% at 180 min. The sensitivity of Tc-99m MIBI SPECT was 97.1% (for the identification of the primary lesion) and 50.0% (for the detection of brain metastasis) at 10 min. The uptake ratios (count in tumor/count in normal lung or brain) at 10 min on the Tl-201 SPECT and on the Tc-99m MIBI SPECT were not significantly different for the primary tumor or for brain metastasis. The uptake ratios were better for Tc-99m MIBI than for Tl-201 [2.82 vs. 1.99 (p<0.05)] for mediastinal lymph nodes. Decreasing uptake ratios and retention index with both agents after radiation therapy are concordant to the follow-up clinical course. Tc-99m MIBI SPECT is more sensitive in the detection of metastasis to mediastinal lymph nodes than Tl-201 SPECT.