Different uptake of 99mTc-ECD and 99mTc-HMPAO in the same brains:: analysis by statistical parametric mapping

The purpose of this study was to investigate the differences between technetium-99m ethyl cysteinate dimer (Tc-99m-ECD) and technetium-99m hexamethylpropylene amine oxime (Tc-99m-HMPAO) uptake in the same brains by means of statistical parametric mapping (SPM) analysis. We examined 20 patients (9 male, 11 female, mean age 62+/-12 years) using Tc-99m-ECD and Tc-99m-HMPAO single-photon emission tomography (SPET) and magnetic resonance imaging (MRI) of the brain less than 7 days after onset of stroke. MRI showed no corti cal infarctions. Infarctions in the pens (6 patients) and medulla (1), ischaemic periventricular white matter lesions (13) and lacunar infarction (7) were found on MRI. Split-dose and sequential SPET techniques were used for Tc-99m-ECD and Tc-99m-HMPAO brain SPET, without repositioning of the patient. All of the SPET images were spatially transformed to standard space, smoothed and globally normalized, The differences between the Tc-99m-ECD and Tc-99m-HMPAO SPET images were statistically analysed using statistical parametric mapping (SPM) 96 software. The difference between two groups was considered significant at a threshold of uncorrected P values less than 0.01, Visual analysis showed no hypoperfused areas on either 99mTc-ECD or Tc-99m-HMPAO SPET images. SPM analysis revealed significantly different uptake of Tc-99m-ECD and Tc-99m-HMPAO in the same brains. On the Tc-99m-ECD SPET images, relatively higher uptake was observed in the frontal, parietal and occipital lobes, in the left superior temporal lobe and in the superior region of the cerebellum. On the Tc-99m-HMPAO SPET images, relatively higher uptake was observed in the medial temporal lobes, thalami, periventricular white matter and brain stem. These differences in uptake of the two tracers in the same brains on SPM analysis suggest that interpretation of cerebral perfusion is possible using SPET with Tc-99m-ECD and Tc-99m-HMPAO.