Differentiating recurrent brain tumors from radiation necrosis with the use of thallium brain imaging

Objectives Differentiation of a recurrent brain tumor vs. radiation necrosis in a patient post radiation therapy can be challenging. While magnetic resonance imaging (MRI) and computed tomography (CT) provide sensitive anatomical detection of cerebral lesions, these methods are not specific in determining whether a lesion contains viable tumor cells. The purpose of this study is to assess the significance of thallium-201 brain imaging in differentiating recurrent brain tumor from radiation necrosis.

Methods Several patients from Beth Israel Deaconess Medical Center who had been treated with radiation therapy for cerebral lesions were reviewed. These patients had equivocal MRI or CT findings showing a mass lesion post therapy and were then referred for a thallium-201 brain scan for further clarification.

Results Of the cases reviewed, a substantial number of patients were provided results that deciphered whether the patient suffered from radiation necrosis or recurrent brain tumor on the basis of the thallium-201 brain scan performed.

Conclusions The use of thallium-201 brain imaging is helpful when differentiating recurrent brain tumors from radiation necrosis in patients post radiation therapy. This is due to the ability of thallium-201 to accurately mark viable living tumor cells indicative of recurrent tumor vs. an absence of activity representing nonviable tumor cells or necrotic tissue, in conjunction with the anatomical landmarks from the CT or MRI portion.