[Cerebral perfusion sonography in comparison with perfusion MRT: a study with healthy volunteers]

Perfusion harmonic imaging (PHI) has been used for several years now in neurological as well as other patients. The aim of the study was to compare PHI with perfusion-weighted MR tomography (pMRT) for the evaluation of cerebral parenchymal perfusion. Furthermore, the influence of different trigger intervals on the contrast kinetics in PHI was analysed.

Fifteen healthy individuals were evaluated with two transtemporal PHI investigations and one pMRT. In PHI, 62 time-triggered images at two different trigger intervals (1 and 0.4 Hz) were recorded after an intravenous bolus of 2 ml of SonoVue(R). pMRT was carried out according to a standard technique using 0.2 mmol/kg Gadolinium-DTPA (Magnevist) and T2*-weighted EPI-sequences. Time-intensity curves of PHI and pMRT-determined data including peak intensity (PI), time-to-peak-intensity (TTP [s]), and area-under-the-curve (AUC) were calculated off-line from 4 regions of interest: ipsi- and contralateral thalamus (i-TH, k-TH), lentiform nucleus (NUC), and white matter (ML). These parameters were compared between the data sets of the two different trigger intervals. Additionally, ratios of the above parameters were calculated to compare the two methods (TH/NUC and TH/ML).

Comparison of the two trigger intervals showed significantly lower AUC-values at the higher trigger interval, while the trigger interval had no significant impact on PI- and TTP- values. A good correlation was seen between the trigger intervals for AUC-values and, to a lesser extent, for PI-values. TTP-values did not correlate. TTP was the only depth-independent parameter. There was no significant difference between PHI and pMRT in 10 of 12 parameter ratios analysed. Merely the PI-ratio of i-TH/ML was significantly different at both trigger intervals.

Regarding the development of adequate set-ups for transcranial PHI, further parameters with impact on contrast agent kinetics (MI, dose of contrast agent) have to be taken into account in addition to the trigger interval. Our findings suggest that, within certain limits, PHI is an imaging technique representing a valuable alternative to MR perfusion imaging, with the TTP representing the most reliable parameter. The AUC is useful for semi-quantitative evaluation of brain perfusion.