Ultrasonic assessment of physiological echo-contrast agent distribution inbrain parenchyma with transient response second harmonic imaging

Objectives. The present study was designed to provide normal data of transi ent response second harmonic imaging (TRSHI) examinations of cerebral echo contrast enhancement using different modes of electrocardiogram (ECG) gatin g and echo-contrast agent doses. Materials and Methods. Fifty-five patients were examined in an axial diencephalic plane of section using the transtem poral acoustic bone:window., TRSHI examinations (ECG gating: systolic, fram e-rate once every 2 cardiac cycles = "basical instrument setting") could be performed in 50 individuals with adequate insonation conditions after appl ication of 4 g of a galactose-based microbubbles suspension in a concentrat ion of 400 mg/ml. For comparison, diastolic ECG gating (20 patients). cardi ac-cycle triggering frequency of once every 2 seconds (15 patients), or an echo contrast agent dose of 2 g Levovist (R) (15 patients) were used. Analy sis of peak intensities (Pls) and areas under the curve (AUCs) was done in posterior (region of interest [ROI]a) and anterior (ROIb) parts of the thal amus, in the lentiform nucleus (ROIc), and the white matter (ROId). Results . In 41 patients with basical instrument setting, characteristic time inten sity curve (TIC) could be detected in all ROIs. in ROIa(90%) and ROIb (82%) , focal contrast enhancement was most difficult to visualize, and in ROIc a nd ROId, characteristic TICs were observable in more than 90% of the examin ations. Background subtracted Pls and AUCs were significantly higher in ROI c (mean Pi: 12.2 +/- 8 acoustic units [AUs]; mean AUG: 598.8 +/- ,451.1 AU x Cardiac cycles), and ROId (11.8 +/- 6.9;559.2 +/-: 404) as compared to RO Ia (8.3 +/- 5.2; 368.9 +/- 242.7) and ROIb (7.1 +/- 4.7; 2982 +/- 199.1) (P < .0001). Values for corresponding examinations with a diastolic ECG gatin g and a cardiac cycle triggering frequency of once every 2 seconds were not different as compared to the basical instrument setting. A4 g Levovist dos e increased the portion of typical TIC in ail ROIs. PI of 4 g examinations were significantly higher in ROId and ROIb as compared to the 2 g examinati on. Conclusion, Our findings indicate that TRSHI allows noninvasive assessm ent of focal cerebral contrast enhancement in the majority of patients with adequate insonation conditions. This study provides data about normal quan titative and qualitative TRSHI values in patients without cerebrovascular d iseases. A dose of 4 g Levovist is recommended in those individuals with in accurate echo contrast enhancement using the 2 g dose.