Development and Testing of an Angled, High Frequency Ultrasound Probe for Minimally Invasive Spine Surgeries

As spine surgeries for decompression of the spinal cord and nerve roots trend towards minimally invasive approaches, conventional visualization methods for surgical guidance, such as ultrasound, are often ineffective. This is because conventional imaging probes are too large to fit down the limited access routes used in these approaches. We have developed a miniature high-resolution ultrasound phased array specifically for this application. The probe has a cross section of 4 mm by 4 mm, length of 16 cm from the handle, and an angled tip that enables imaging at a 40-degree angle from forward looking. The image window was steered between +/-32 degrees with an imaging depth of 15 mm. The array was micromachined using a picosecond laser, had 64 sub-diced elements, and an operating frequency of 30 MHz. The axial and lateral resolution were measured to be 33 μm and 116 μm, respectively, and the secondary lobes were suppressed to -60 dB. During preliminary clinical studies, patients were imaged during minimally invasive spine surgery, where the spinal cord anatomy and compression points could clearly be visualized.