Stomach emptying evaluation by ultrasound and susceptometric measurements with a hybrid transducer

Gastric emptying reflects a diversity of important physiological functions. Alternating Current Biosusceptometry (ACB) is an inexpensive, radiation-free, and noninvasive method to evaluate gastric emptying, but its response depends on the spatial distribution of the magnetized material and does not have anatomical information. The hybrid transducer - which combines ACB and ultrasound probe - improved susceptometric measurements potential, namely the spatial localization of the magnetized source. This study monitored relative stomach emptying in rats with the aid of the hybrid transducer. Yogurt mixed with ferrite particles was injected into the rats´ stomach. The hybrid transducer was placed on the rat´s abdominal during experiments. Susceptometric signal and power Doppler (PWD) data were saved and post-processed. In a second experiment, a volumetric image from axial sequences was obtained by means of a transducer displacement system. The relative stomach emptying was evaluated on the bases of PWD images and the susceptometric signal with the hybrid transducer. PWD maps highlighted the movement of magnetic particles (due magnetic force from ACB excitation coils) and showed the rats´ stomach location with anatomic information (B-mode). After the acquisition period, the mean relative ACB signal decayed by 4.6 ± 0.1%, and the mean relative PWD area decreased by 4.5 ± 0.2% as a result of stomach emptying. However, these values diminished (~0.5%) when stomach shape was larger and the meal was more widely spread. The distribution spatial was more sensitive to PWD than ACB. The PWD volumetric image provided details of the stomach wall, which may enable minimally invasive detestation of abnormalities. Ultrasound image increased ACB spatial resolution and furnished additional anatomical information.