Use of SPECT to distinguish recurrent brain tumor from persistent activity at a craniotomy site

A 50-year-old male underwent extensive left frontal lobe resection for a Grade II astrocytoma. Resection margins were free of tumor, and the patient suffered no significant postoperative neurologic deficits. One month later the patient was referred to radiation therapy for further evaluation and possible treatment. Unenhanced and enhanced transmission computed tomograms (CT) were interpreted as suspicious for recurrent tumor. However, using CT, which is essentially an anatomic technique, may not allow one to distinguish between surgical changes and the morbid anatomic findings of recurrent tumor. Because Tc-99m DTPA will cross the blood-brain barrier at sites of active intercranial disease, brain scintigraphy frequently is of value in distinguishing between recurrent tumor with an unstable blood-brain barrier and healed surgical changes with a stabilized blood-brain barrier. Therefore, clinicians requested that a Tc-99m DTPA brain scintigram be performed so as to distinguish between active disease and healed surgical changes.