Kyojiro Nambu

New possibilities for stereotaxis. Information-guided stereotaxis.

Information-guided stereotaxis, assisted by visualization of medical information, will become the next generation of neurosurgical systems. We performed 76 open MRI surgeries at Tokyo Women’s Medical University between March 3, 2000 and April 12, 2001. Of them, comparisons of pre- and post-operative MR images for malignant gliomas in 21 cases revealed an average resection rate of 90.3% (the maximum 100%, the minimum 55%). In this article we describe real time updated navigation, augmented reality navigation, three-dimensional navigation, chemical navigation, information-guided navigation system (High definition visual Computer Aided Surgery System: HivisCAS), and open MRI-guided surgery that we are developing.

Surgical workflow monitoring based on trajectory data mining

This research aims at investigating intermediate-scale workflows using the surgical staffs movement pattern. In this study, we have introduced an ultrasonic location aware system to monitor intraoperative movement trajectories on surgical staffs for the workflow analysis. And we developed trajectory data mining for surgical workflow segmentation, and analyzed trajectory data with multiple cases. As a result, in 77.18% of total time, a kind of current operation stage could be correctly estimated. With high accuracy 85.96%, the estimation using trajectory data was able to distinguish whether a current 5 minutes was transition time from one stage to another stage or not.. Based on these results, we are implementing the surgery safe support system that promotes safe & efficient surgical operations.

Intraoperative multichannel audio-visual information recording and automatic surgical phase and incident detection

Identification, analysis, and treatment of potential risk in surgical workflow are the key to decrease medical errors in operating room. For the automatic analysis of recorded surgical information, this study reports multichannel audio visual recording system, and its review and analysis system. Motion in operating room is quantified using video file size without motion tracking. Conversation among surgical staff is quantified using fast Fourier transformation and frequency filter without speech recognition. The results suggested the progression phase of surgical procedure.

A Noise Reduction Method Based on a Statistical Test of High Dimensional Pixel Vectors for Dynamic and Volumetric Images

A noise reduction method applicable for dynamic and three-dimensional imaging modalities was evaluated. We applied our method to images obtained by CT, MRI, SPECT, angiography, and numerical phantom data, and measured the reduction of image noise. The standard deviation of the noise was reduced to 12–13% in a numerical dynamic phantom, 35–46% in dynamic CT, 19%-23% in a dynamic scintigram, 6–8% in dynamic SPECT, 13–15% in volumetric MRI of PVA resolution phantom, 12–17% in volumetric MRI of a PVA head phantom, and 50–53% in angiography of a moving phantom. The method reduced noise effectively, while spatial and temporal resolution remained satisfactory.

Method for reducing noise in X-ray images by averaging pixels based on the normalized difference with the relevant pixel.

A real-time digital filter for noise reduction in X-ray images is proposed. The filter is based on averaging of only similar pixels (pixels that differ only little) rather than neighboring pixels, which are averaged in conventional linear low-pass filters. The effectiveness of the filter was evaluated by computer simulation, where original images that were acquired by X-ray exposure were processed in accordance with the filter algorithm. The resulting images were evaluated in terms of the pre-sampled modulation transfer function (MTF), the noise power spectrum (NPS), and the lag. Comparison of the filtered and original images revealed that the NPS was reduced for the full range of spatial frequencies in the filtered image, resulting in a reduction of total noise power to about 1/9 the level in the original image with no degradation in the MTF or lag. The usefulness of the filter was demonstrated in fluoroscopic, digital subtraction angiography (DSA) and mammographic phantom studies. The filter was found to have the potential to reduce the patient dose by reducing the noise in dynamic as well as static X-ray images.

Correlation between Surgical Manipulations and the Variation of Surgeon's Heart Rate in Brain Surgery: Technical Note

For improvement of surgical performance and safety, we record surgeries by video cameras. However, analysis of the video records is time consuming. To help this task, we are developing methods to automatically mark up significant time points in the surgery. As a possible mean for the marking, we focused on the surgeons heart rate. During a craniotomy of an intracranial glioma, we recorded the surgeons electrocardiogram using a telemeter and measured the R-to-R interval (RRI). We detected the stable state of heart rate as a peak-to-peak RRI of less than 5% of the mean of RRI data from 15 consecutive heartbeats. We also quantified the frequency of brain touches by the surgeon under the surgical microscope. We examined the association between the stability of surgeons heart rate and the brain touches using a chi-square test. As the result, the stable state of surgeons heart rate was associated with the brain touches (p < 0.05, odds ratio 5.1). We edited a one-minute digest video of the surgery based on only the heart rate data, and it was sufficient to understand how the surgery was preceded.

Open MRI compatible HivisCAS video microscope system for neurosurgery

We are developing a video microscope system “HivisCAS (High Definition Visual Computer Aided Surgery system)”, which guides the surgeon by enhancing the live microscope image with superimposed computer graphics of the surgical plan map in 0.5 mm accuracy[1]. On the other hand, we have introduced an intraoperative MRI (AIRIS II 0.3T; Hitachi, Tokyo). To update the surgical plan map by intraoperative images, we modified the video microscope to be compatible with the open MRI, and evaluated its problems and performance.