Comparison of consecutive bolus tracking and flash replenishment measurements for the assessment of tissue hemodynamics using contrast-enhanced ultrasound (CEUS) in an experimental human squamous cell carcinoma model

摘要

Purpose: To evaluate "bolus-tracking" (BT) and "flash-replenishment" (FR) for the assessment of tissue hemodynamics by contrast-enhanced ultrasound (CEUS) in an experimental small-animal-squamous- cell-carcinoma-model. Since the underlying tissue is the same, strong correlations between parameter outcomes of both techniques are expected. Methods and materials: Human hypopharynx-carcinoma-cells were subcutaneously injected into the left flank of 18 female athymic-nude-rats. After 10 days of subcutaneous tumour growth, bolus tracking and flash-replenishment measurements were performed consecutively in the same imaging plane in each rat after bolus-injection of SonoVue via the lateral tail vein using a high-end ultrasound system with a 15 MHz probe. Video-sequences were analysed with dedicated software (VueBox ?, Bracco-Suisse ?). From BT measurements, the parameters peak enhancement (PE BT), wash-in area-under-the-curve (Wi-AUC BT), mean transit time (MTT BT), wash-in-rate (WiR BT) and perfusion-index (Wi-PI BT) were derived; FR yielded estimates of relative-blood-volume (rBV FR), mean transit time MTT FR, relative blood flow rBF FR and wash-in rate Wi-R FR. Results: In all rats, BT and FR measurements could be completed successfully. Highly significant correlations were observed between rBV FR and PE BT, rBV FR and Wi-AUC BT, rBV FR and MTT BT, rBV FR and WiPI BT, MTT FR and MTT BT, rBF FR and PE BT, rBF FR and Wi-AUC BT, rBF FR and WiR BT, rBF FR and WiPI BT, WiR FR and PE BT, WiR FR and Wi-AUC BT, WiR FR and WiR BT and WiR FR and WiPI BT. Conclusion: Whereas bolus tracking can be used in a wide range of modalities including CEUS, CT and MR, FR as a technique for the assessment of tissue hemodynamics is unique to CEUS. Although BT and FR yield different parameters, the underlying tissue hemodynamics are equal. In this work, we were able to demonstrate strong correlations between different parameters of both modalities in a small-animal-tumor-model, indicating that flash-replenishment is a valid alternative to the more established bolus-tracking technique. Although the lack of absolute, quantitative parameters hinders a direct comparison of both modalities, FR and BT should both be suitable for a relative comparison, e.g. between baseline and follow-up examinations.