Kazunari Ishida

Magnetic Resonance Imaging (MRI) Compatible Ultrasound Therapeutic System

Since an ultrasound (US) imaging system can image in real-time and interactively, it can be used as an image guidance assisting magnetic resonance imaging (MRI) for minimally invasive therapy. The effects of MRI-compatible US probes on MRI monitoring were evaluated, and it was found that the MRI-compatible US probes, whose backing material contained 100 ppm ferrite, did not disturb MR monitoring except at a few mm radius from the US probes position. MRI temperature monitoring of a swine liver irradiated with a high-intensity focused US beam from an MRI-compatible therapeutic transducer with US image guidance was then performed, and the potential usefulness of such a therapeutic system in minimally invasive therapy was demonstrated.

Approaches to overcome current limitations of HIFU treatment

Noninvasive therapy with HIFU has been successfully applied to transrectal treatment of prostate cancer as well as benign prostate hyperplasia. However, there are two major technical reasons why its clinical application to other organs is currently limited: (1) low throughput of treatment and (2) lack of penetration to deep tissues. To multiply the throughput, a split‐focus technique, in which the focal spot is enlarged primarily in the lateral direction, was developed. An electronically variable focus array transducer was also developed to enhance the throughput. An approach to treat a large volume of uterus myoma by coagulating its feeding arteries has been studied. The tissue volume to be coagulated can be thereby reduced by orders of magnitude. The penetration and throughput can potentially be improved at the same time by delivering a microbubble agent to the target tissue. It was theoretically predicted that a microbubble agent could multiply the ultrasonic tissue absorption. The effectiveness of thi...

Compact High-Pressure Light Scattering Cell with Low Stray Light

We have designed and constructed a compact high pressure light scattering cell which can hold a cube sample as large as 10×10×10 mm3. The cell dimension is about 10×8×10 cm3, and the body material is beryllium-copper alloy. The large sample ensures a low stray light level and the new design for the light collection window permits a large light collection angle (18°). The simple sealing method enables even inexperienced personnel to use this optical cell. We have tested the cell up to a pressure of 0.8 GPa by recording the low-lying Raman spectra of a ferroelectric crystal KH2PO4.