Effects of occlusal disharmony on working memory performance and prefrontal cortex activity induced by working memory tasks measured by NIRS.

The effects of artificial occlusal disharmony (AOD) on working memory function and prefrontal cortex (PFC) activity in the elderly were examined. We evaluated working memory function using the modified Sternberg test (ST). We measured activity in the bilateral PFC during ST using near-infrared spectroscopy (NIRS) before and after AOD: the mandibular position was displaced by a splint for 10 min. AOD caused a gradual increase of oxyhemoglobin (oxy-Hb) in the bilateral PFC. The response time of ST (six digits) after AOD was longer than that before AOD. The oxy-Hb increase during ST after AOD was smaller than that before AOD. These results indicate that short-term physical stress caused by AOD decreased working memory function in elderly subjects, associated with a decrease of the evoked PFC activity during working memory function.

[Progress in NIRS monitoring of cerebral blood flow].

Various studies have demonstrated the usefulness of near infrared spectroscopy (NIRS) for detecting cerebral ischemia during a carotid endarterectomy; however, it is difficult to apply NIRS to the diagnosis of ischemic stroke, since commercially available NIRS, which uses continuous-wave light, does not provide quantitative values of baseline hemoglobin (Hb) concentrations. In contrast, time-resolved near-infrared spectroscopy (TRS) permits quantitative measurement of Hb concentrations. We applied TRS to detection of cerebra vasospasm after subarachnoid hemorrhage (SAH). We investigated 11 age-matched controls and 14 aneurysmal SAH patients that comprised 10 patients with World Federation of Neurological Societies (WFNS) grade V and 4 patients with WFNS grade II. Employing TR-NIRS, we measured the cortical oxygen saturation (CoSO2) and baseline Hb concentrations in the middle cerebral artery territory. The CoSO2 and Hb concentrations remained stable after SAH in 6 patients; digital subtraction angiography (DSA) did not reveal vasospasm in these patients. In 8 patients, however, CoSO2 and total Hb decreased abruptly between 5 and 9 days after SAH. DSA revealed diffuse vasospasms in 6 of 8 patients. The reduction of CoSO2 predicted occurrence of vasospasm at a cutoff value of 3.9%-6.4% with 100% sensitivity and 85.7% specificity. Trans cranial Doppler (TCD) failed to detect vasospasm in 4 cases, whereas TR-NIRS could. Finally, TRS performed on day 1 after SAH revealed significantly higher CoSO2 than that of the controls (p = 0.048), but there was no significant difference in total Hb. TRS detected vasospasm by evaluating the CBO in the cortex and may be more sensitive than TCD, which assesses the blood flow velocity in the M1 portion. TRS may be useful for the diagnosis of ischemic events in stroke patients.

Mapping of optical pathlength of human adult head at multi-wavelengths in near infrared spectroscopy.

Measurement of multichannel continuous-wave near-infrared spectroscopy (CW-NIRS) is dependent on the modified Beer-Lambert law, which includes optical pathlength (PL) as an essential parameter. PLs are known to differ across different head regions and different individuals, but the distribution of PLs for the whole head has not been evaluated so far. Thus, using time-resolved near-infrared spectroscopy (TR-NIRS), we measured the optical characteristics including PL, scattering coefficients (mu'(s)), and absorption coefficients (mu(a)) at three wavelengths (760, 800, 830 nm). Then, we constructed maps of these parameters on the subjects' head surface. While the PLs in nearby channels are similar, they differ depending on the regions of the head. The PLs in the region above the Sylvian fissure tended to be shorter than those in the other regions at all of the wavelengths. The difference in the distribution of PLs may be attributed to differences in tissue absorption and scattering properties. The current study suggests the importance of considering PL differences in interpreting functional data obtained by CW-NIRS.

Compact forceps manipulator using friction wheel mechanism and gimbals mechanism for laparoscopic surgery.

This paper reports evaluation of compact forceps manipulator designed for assisting laparoscopic surgery. The manipulator consists of two miniaturized parts; friction wheel mechanism which rotates and translates forceps (62 x 52 x 150[mm3], 0.6 [kg]), and gimbals mechanism which provides pivoting motion of forceps around incision hole on the abdomen (135 x 165 x 300 [mm3], 1.1 [kg]). The four-DOF motion of forceps around the incision hole on the abdomen in laparoscopic surgery is realized. By integration with robotized forceps or a needle insertion robot, it will work as a compact robotic arm in a master-slave system. It can also work under numerical control based on the computerized surgical planning. This table-mounted miniaturized manipulator contributes to the coexistence of clinical staffs and manipulators in the today's crowded operating room. As the results of mechanical performance evaluation with load of 4 [N], positioning accuracy was less than 1.2 [deg] in pivoting motion, less than 4 [deg] in rotation of forceps, less than 1.2 [mm] in longitudinal translation of forceps. As future works, we will modify mechanism for sterilization and safety improvement, and also integrate this manipulator with robotized forceps to build a surgery assisting robotic system.