99Tcm-ECD brain imaging in epilepsy - a case study

Full text: A 33-year-old male presented with a 20 year history of epilepsy, consisting of three to four seizures per day, and was enrolled in the St Vincents Epilepsy study for surgical evaluation. 99Tcm-ECD (99Tcm-ethyl cysteinate diethylester), or Bicisate, is a new radiopharmaceutical used for the assessment of cerebral perfusion. It has a very important application in ictal imaging in epilepsy patients, as it is chemically stable for eight hours following reconstitution. This enables patients to be injected immediately at the time of their seizures, and results in a higher incidence of true ictal studies. The patient was admitted to the 99Tcm-ECD study for EEG monitoring, MRI imaging, and SPECT scanning. He was injected with 99Tcm-ECD during a 30 second seizure and underwent an ictal SPECT scan, followed by an inter ictal SPECT scan two days later. The MRI and EEG findings were inconclusive, yet suggested a right sided lesion. The ictal and inter ictal SPECT studies were compared and analysed using the SISCOM technique which allows a subtraction of the inter ictal from the ictal SPECT, and co-registration with MRI. This demonstrated that the epileptogenic focus was situated in the right frontal lobe, and the patient subsequently underwent successful surgical removal of this area. At his six month follow up, the patient is seizure free. This case study emphasises the suitability of 99Tcm-ECD in epilepsy brain scanning, particularly in patients with seizures of very short duration, helping to evaluate them for localisation of their epileptogenic focus prior to definitive surgical resection. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc