Comparative study of 99mTc-ECD and 99mTc-HMPAO for peri-ictal SPECT: qualitative and quantitative analysis

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Abstract
OBJECTIVES Most studies that clinically validated peri-ictal SPECT in intractable partial epilepsy had used technetium-99m-hexamethylpropylene amine oxime (99mTc-HMPAO or 99mTc-exametazime) as the radiopharmaceutical. Because of some theoretical advantages, technetium-99m-ethyl cysteinate diethylester (99mTc-ECD or99mTc-bicisate) is increasingly being used instead. This study compares unstabilised 99mTc-HMPAO and99mTc-ECD in the performance of peri-ictal SPECT in partial epilepsy. METHODS The injection timing and localisation rates in 49 consecutive patients with partial epilepsy who had peri-ictal injections with unstabilised99mTc-HMPAO were compared with 49 consecutive patients who had peri-ictal injections with 99mTc-ECD. Quantitative cortical/subcortical and cortical/extracerebral uptake ratios were also compared. Subtraction SPECT coregistered to MRI (SISCOM) was performed in patients whose interictal SPECTS were available. RESULTS In the99mTc-ECD patients, the latency from seizure commencement to injection was shorter (median 34 v 80 seconds, pv 57.1%, p99mTc-ECD images (median 5.0v 3.6, and 2.5 v2.2 respectively; both p0.05). Blinded review of the SISCOM images were localising in a higher proportion of the99mTc-ECD patients (40/45 (88.9%)v 25/37 (67.6%), pCONCLUSION 99mTc-ECD compares favourably with unstabilised 99mTc-HMPAO as a radiopharmaceutical for peri-ictal SPECT studies. Its use results in earlier injections and less frequent postictal injections than unstabilised 99mTc-HMPAO, thereby enhancing the sensitivity and the specificity of peri-ictal SPECT for the localisation of intractable partial epilepsy.

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