Abstract
Background:
We evaluated the value of single-photon emission computed tomography/computed tomography (SPECT/CT) with a hybrid camera for 99mTc-tetrofosmin (TF) imaging of brain tumors and metastases after radiotherapy.
Methods:
Forty (40) patients (27 with primary brain tumors and 13 with intracranial metastases) were examined 6 months after radiation therapy. SPECT images were first evaluated alone and then reinterpreted by adding the anatomic (CT) data. Tumor-to-background ratio values were calculated in the nonattenuation-corrected (T1/B1) and in the CT-attenuation-corrected (T2/B2) images. Scintigraphic results were compared with clinical follow-up.
Results:
SPECT was true positive for viable tumor tissue in 21 patients and negative in 19. SPECT/CT contributed in 10 of 40 patients (25%): It improved the visualization of lesions in the deep temporal lobe, in the orbital region, and in the posterior fossa. SPECT/CT was useful in 4 of 8 patients with suspicion of radionecrosis. The hybrid camera did not significantly contribute both in patients with a negative scan or with large frontotemporal tumors. When all the lesions were considered, no significant difference was found between T1/B1 and T2/B2. In small lesions (<2 cm), T2/B2 was significantly higher (p = 0.04) than T1/B1. When the clinical outcome was considered, patients with a significant SPECT/CT contribution had a longer average survival than patients with a positive scan, in which the hybrid camera did not provide any substantial information (13.3 vs. 8.2 months; p = 0.0007).
Conclusions:
Hybrid SPECT/CT can be useful to better characterize small lesions that are deeply located and in areas of high physiologic background. Further studies and larger series are needed to more accurately define the potential clinical impact of hybrid imaging in patients' management.