Hiroyuki Itagaki

Higher-Order Brain Function Analysis by Trans-Cranial Dynamic Near-Infrared Spectroscopy Imaging

Near-infrared spectroscopy is discussed from the viewpoint of human higher-order brain function analysis. Pioneering work in this field is reviewed; then we describe our concept of noninvasive trans-cranial dynamic optical topography and its instrumentation. Also, the validity of its functional images is assessed from both physical and physiological viewpoints. After confirming the validity of this method, we have applied it to a wide variety of fields such as clinical medicine, cognitive science, and linguistics in collaboration with researchers at several other institutes. Further application possibilities and the future of trans-cranial dynamic optical topography are also discussed.

Transient brain activity used in magnetic resonance imaging to detect functional areas.

FUNCTIONAL areas were detected with short stimuli eliciting transient brain activity using the method of ‘transient’ regions of interest (ROIs) and functional magnetic resonance imaging (fMRI). This method was validated by comparing the results with sustainedly activated areas identified conventionally. Eighty-eight and 89% of the total areas of transient ROIs derived from 0.2 and 2 s stimulation, respectively, were identified at 5–7 s and 5–9 s, respectively, after stimulus onset. Eighty-eight and 76%, respectively, of these areas overlapped ‘conventional’ ROIs derived from 20 s stimulation. These results suggest that the delineation of transient ROIs, by targeting a period ∼7 s after transient neural activity, can be useful for fMRI studies of cognitive functions.

Intra-operative guidance with real-time information of open MRI and manipulators using coordinate-integration module

Assuming the surgery under open magnetic resonance imaging (MRI) equipment with manipulators, we developed the coordinate-integration module and the real-time functions that could display the manipulators position on the volume data of MRI and could obtain the cross-section images of MRI at the manipulators position. The small field of view from an endoscope is the problem in most of the minimally invasive surgeries with manipulators. Therefore, we propose an endoscopic surgery with manipulators under open MRI equipment. The coordinate-conversion parameters were calculated in the coordinate-integration module by calibration with an optical tracking system and markers. The delay of the manipulator-position display on the volume data was approximately within 0.5 second though it depended on the amount of the volume data. We could also obtain the cross-section images of MRI at the manipulators position using the information from the coordinate-integration module. With these functions, we can cope with the change of the organ shape during surgery with the guidance based on the individual information. Furthermore, we can use the manipulator as an MRI probe to define cross-section position like an ultrasonic probe.

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.

MRI-compatible ultrasonic probe for minimally invasive therapy

The effects of magnetic resonance imaging (MRI)-compatible ultrasound (US) probes on MRI monitoring were evaluated. It was found that MRI-compatible US probes with backing material containing 100 ppm ferrite, did not disturb MR monitoring except within a few mm radius from the US probes position. MRI temperature monitoring of an excised 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.