A computer-controlled ultrasound pulser-receiver system for transskull fluid detection using a shear wave transmission technique

Abstract

The purpose of this study was to evaluate the performance of a computer-controlled ultrasound pulser-receiver system incorporating a shear mode technique for transskull fluid detection. The presence of fluid in the sinuses of an ex vivo human skull was examined using a pulse-echo method by transmitting an ultrasound beam through the maxilla bone toward the back wall on the other side of the sinus cavity. The pulser was programmed to generate bipolar pulse trains with 5 cycles at a frequency of 1 MHz, repetition frequency of about 20 Hz, and amplitude of 100 V to drive a 1-MHz piezoelectric transducer. Shear and longitudinal waves in the maxilla bone were produced by adjusting the bone surface incident angle to 45 degrees and 0 degrees, respectively. Computer tomography (CT) scans of the skull were performed to verify the ultrasound experiment. Using the shear mode technique, the echo waveform clearly distinguishes the presence of fluid, and the estimated distance of the ultrasound traveled in the sinus is consistent with the measurement from the CT images. Contrarily, using the longitudinal mode, no detectable back wall echo was observed under the same conditions. As a conclusion, this study demonstrated that the proposed pulser-receiver system with the shear mode technique is promising for transskull fluid detecting, such as mucus in a sinus.

Fig. 1

A block diagram of the computer-controlled ultrasonic pulser-receiver system

Fig. 2

Circuit schematic of the high-voltage power supply.

Fig. 3

Equivalent feedback resistor divider network for the high-voltage power supply.

Fig. 4

Circuit schematic of the pulse generator.

Fig. 5

Circuit schematic of the solid-state switch, S₁.

Fig. 6

Circuit schematic of the echo amplifier.

Fig. 7

Circuit schematic of the analog-to-digital converter and memory.

Fig. 8

Experimental setup for detecting the presence of fluid in the maxillary sinuses.

Fig. 9

Orientations of the transducer for the echo measurements with (a) shear and (b) longitudinal propagations. Sagittal view of the maxilla bone is shown and the skull was upside down.

Fig. 10

Software front panel for the pulser-receiver system.

Fig. 11

Software front panel showing the axial, sagittal and coronal views of the human skull used in the fluid detection experiment.

Fig. 12

Measured transducer voltage for shear propagation in bone: (a) left sinus filled with water, (b) right sinus filled with water, (c) left sinus filled with air, and (d) right sinus filled with air

Fig. 13

Measured transducer voltage for longitudinal propagation in bone: (a) left sinus filled with water, (b) right sinus filled with water, (c) left sinus filled with air, and (d) right sinus filled with air

Fig. 14

Sagittal CT images of the skull (upside down), with indication of the transducer position for shear propagation, showing the (a) left and (b) right maxillary sinuses of the ex vivo human skull used in the sinus fluid detection experiment.