Comparative study of 99mTc-ECD and99mTc-HMPAO for peri-ictal SPECT: qualitative and quantitative analysis
- Terence J O’Briena,
- Benjamin H Brinkmannb,
- Brian P Mullanc,
- Elson L Soa,
- Mary F Hauserc,
- Michael K O’Connorc,
- Joseph Hungc,
- Clifford R Jackc
- aDepartment of Neurology, bDepartment of Biomedical Imaging, cDepartment of Diagnostic Imaging, Mayo Clinic, Rochester, MN, USA
- Dr E L So, Department of Neurology, Section of Electroencephalography, Mayo Clinic, 200 First Street, Rochester, MN 55905, USA. Telephone 001 507 284 8307; fax 001 507 284 8686.
- Received 15 April 1998
- Revised 24 September 1998
- Accepted 16 October 1998
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, p<0.0001) and there was a lower rate of postictal injections (16.3% v 57.1%, p<0.0001). The cortical/extracerebral and cortical/subcortical uptake ratios were greater in the 99mTc-ECD images (median 5.0v 3.6, and 2.5 v2.2 respectively; both p<0.005), but the relative peri-ictal increase in uptake in the cortical focus did not differ significantly (median 37.0% v 37.0%; p>0.05). 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%), p<0.05), and had a better concordance with EEG, MRI, and with the discharge diagnosis.
CONCLUSION 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.
