Biomedical subjects
Publications and source records attributed to Tetsuo Kojima.
We have demonstrated high-peak-power generation at 1 kW average power by applying an acousto-optic Q switch to a quasi-cw diode-pumped Nd:YAG master oscillator power amplifier. We achieved a maximum peak power of 2.3 MW by driving the Q switch in burst mode. The average repetition rate was 6 kHz. The corresponding beam quality was M2 = 9.
A novel configuration for a multirod solid-state laser system is proposed. We stabilize the thermal-lens-dependent variation in the output-beam parameters by extracting the laser beam from the collimating point of periodic beam propagation. The performance is confirmed with a 100-W class diode-pumped Nd:YAG laser-amplifier system to demonstrate tenfold stabilization of the output-beam diameter.
We demonstrate a novel method of equalizing a laser diode (LD) beam into a circular beam. This method uses the twist effect of graded index (GI) fiber optics. An asymmetric LD beam with beam qualities of M2 = 500 in the slow axis and M2 = 4 in the fast axis is converted successfully into a symmetric circular beam with a beam quality of M2 = 175. The circular-output beam with 92% coupling efficiency from the fiber input to the fiber output is obtained with a 5-m-long GI1200 (1200 means a core diameter of 1200 microm) fiber for a 2-W LD array. We extend the experiments to a higher-power source with higher asymmetric beam qualities of M2 = 3000 and M2 = 4. By slightly bending the GI10000 (10000 means a core diameter of 10,000 microm) fiber, we have succeeded in generating a symmetric beam with a improved beam quality of M2 = 2000. The average beam quality is preserved when the asymmetric ratio is not high, and the beam quality degradation ratio is investigated up to asymmetric ratios of 750.
In vitro and in vivo experimental studies have shown that a new two-strand technique increases the tensile strength of flexor tendon repair and eliminates gap formation at the healing repair site. The purpose of the current study was to clinically evaluate the new technique, followed by an aggressive active mobilization program. Seven digits with zone II flexor tendon lacerations were treated using the technique, employing a heavy (2-0) braided polyester suture. The patients were encouraged to perform active mobilization of the injured digits by themselves with almost a full range of flexion and extension after they were instructed by the surgeon for few days from the first postoperative day. All patients were followed up for at least 6 months, except for one, with whom contact was lost in 14 weeks postoperatively. Six of the seven digits were evaluated as excellent in 6 months by the original Strickland criteria, thus showing that the combination of the new repair technique and aggressive active mobilization is effective for zone II flexor tendon repair.