Evalution of Tl-201 SPECT in Differential Diagnosis of Benign and Malignant Lesion of the Chest

Tl-201 SPECT was examined in 22 being and 15 malignant lesions, with a size equal to or more than 10 mm on chest CT, and we evaluated the usefulness of this modality in differential diagnosis of benign and malignant lesions. The Tl-201 SPECT image was obtained 15min. (early scan) and 2-3hr. (delayed scan) following the intravenous injection of a dose of 240MBq Tl-201 Chrolide. The ^<201>TlCl uptake in the benign lesions was not corelated to the size of the lesions, while the ^<201>TlCl uptake in the malignant lesions was obtained in only lesions with a size equal to or more than 25×20 mm. We calculated the lesion/normal contralateral lung ratio of ^<201>TlCl activity in early & delayed scans, and the retention index using the method of Tonami et al. Retention index in malignant lesions (21.5±8.9%) showed significantly higher than that in the benign lesions (-4.6±11.4%) (p<0.01). Therefore, when the border-line value of the retention index was set at 10%, and the lesions with higher values were diagnosed as malignancy, the value of the sensitivity, accuracy and specificity showed 92%, 93%, and 92% respectively. These results indicate that the Tl-201 SPECT is a potentially useful method for differential diagnosis of benign and malignant lesions in the chest.

Thallium201

SRECT

Lung Cancer

benign lesions