Technetium-99m(V)-DMSA and thallium-201 in brain tumor imaging: correlation with histology and malignant grade

This study was performed to compare imaging ability between pentavalent 99mTc-DMSA and 201TlCl in primary and metastatic brain tumors and to evaluate the relationship between retention and histologic malignancy.

Patients with a brain tumor were selected by MRI and/or CT. Dynamic, early and delayed static SPECT images of the brain were obtained immediately, 30 min and 3 hr after intravenous administration of approximately 555 MBq 99mTc(V)-DMSA and 111 MBq 201Tl-Cl, respectively. Both studies were performed on separate days within a week. Uptake ratios, retention ratio and retention index were calculated and compared with tumor histology and malignancy grade.

One-hundred six studies were performed on 100 patients and 118 lesions were demonstrated: 16 glioblastomas, 13 anaplastic astrocytomas (Grade III), 19 astrocytomas (Grade II), 29 meningiomas, 11 schwannomas and 14 metastases. Approximately 93% and 88%, respectively, of primary and metastatic brain tumors were demonstrated by 99mTc(V)-DMSA and 201TlCl. The early uptake ratios were closely related to the tumor vascularity, but had no statistically significant difference in the tumor histology or histologic malignancy on either radiopharmaceuticals. The delayed uptake ratio, retention ratio and retention index were higher in malignant tumors than benign ones on 99mTc(V)-DMSA, however, there was no statistically significant difference between benign and malignant tumors on 201TlCl.

Technetium-99m(V)-DMSA washout from the tumor was highly dependent upon its histology and histologic malignancy. The delayed uptake ratio, retention ratio and retention index significantly reflected tumor histology and clearly distinguished between benign and malignant tumors with a statistically significant difference. There was no statistically significant difference in 201TlCl uptake or washout among the brain tumors. Technetium-99m-DMSA is superior to 201TlCl in imaging quality, sensitivity to brain tumors and specificity for differentiating benign tumors from malignant ones. These results could suggest the clinical utility of 99mTc(V)-DMSA in imaging primary and metastatic brain tumors and differentiating their histological malignancy grade noninvasively.