The laser computed tomographic images of human premolar teeth were studied in the visible and near-IR regions by the coherent detection imaging (CDI) method that is based on the optical heterodyne detection technique. Using cw single frequency lasers at 514.5, 632.8 and 770nm, laser CT images of human teeth were reconstructed with sub-millimeter resolution. The image contrast is shown to be wavelength dependent.
The diluted fat emulsion Intralipid-10%and red blood cells extract from human blood were introduced circulating into the pulp cavity of the tooth through an inserted thin silicon tube to simulate in vivo conditions. The image contrast was found to be enhanced on the introduction of red blood cells at 514.5nm. Diluted Intralipid-10%solutions exhibited attenuation of the detected intensity of light due to its highly scattering character at longer wavelengths.
Use of visible short wavelength as well as red and near-IR wavelength regions should make optical CT very attractive for variety of practical applications in dentistry.

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A high power diode laser system is recently developing for a laser surgery use. Clinical evaliation was carried out to confirm the efficiency and safety with a total 63 patients using a diode laser surgery system which has the maximum output power 20 watts.
In particular laser cutting and coagulated treatments of lung were performed with 27 patients and satisfactory results (sharp cutting and no bleeding) were observed. Since there was on negative side effect reported, this laser system was confirmed to be efficient and safe treatment device.

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We conducted several experimental studies of YAG Laser for transurethral balloon laser therapy (TUBAL) using phantoms and canine models and clinical results of TUBAL for Benign Prostatic Hypertrophy and nonbacterial prostatitis. The following results were obtained.
1. It was shown that pulse YAG-laser induced heat penetration in the phantom was deeper than that induced by conventional continuous wave laser.
2. TUBAL-T without urethral cooling and TUBAL-H were examined in a canine model were shown. Immediately after TUBAL-T, coagulative necrosis was observed around the urethra and the tissue started to slough off within 1week. Cavity formation and reepithelialization were completed after 4weeks. Eight weeks after TUBAL-H, urethral compliance increased significantly. Histologically, atrophic changes were observed in epithelial cells after 8weeks.
3. To enhance the effect of TUBAL, we performed the following three experiments. We devised a shield balloon laser probe which can irradiate in lateral directions mainly and found that it caused deep heat penetration on both side. An ultrafine carbon solution was injected into the prostate to enhance heat induction during TUBAL-T, and found that a high temperature spot formed in the same area. We also devised a double switching balloon probe that can irradiate two areas (bladder neck and midprostaitc portion) at the same time, and found that by changing the switch, the interstitial temperature at the top of the balloon became higher than that midprostate.
4. In Benign Prostatic Hypertrophy patients, subjective symptoms were improved more effectively by TUBAL-T than objective findings. TUBAL-H was also effective for chronic prostatitis.

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Transurethral balloon laser thermotherapy (TUBAL-T) is a new technique using Nd: YAG laser for benign prostatic hyperplasia (BPH), which can be performed under local anesthesia on an outpatient basis. In this method, laser irradiation is performed through 360° with a laser balloon catheter that is placed transurethrally in the prostatic urethra. Theoretically, the prostatic tissue is sufficiently coagulated and necrotised, while the urethral mucosa is preserved cooling with the circulating water in the laser balloon catheter.
From December 1993, we treated 20 cases with symptomatic BPH by TUBAL-T using PROSTALASE^TM (SLT Japan Co. Tokyo). We employed 50 to 60 watts laser output powers for 60 minutes. The clinical efficacy of the treatment was evaluated subjectively by AUA symptom score, objectively by urodynamics and imaging studies. At 3 months after the treatment, AUA symptom score, prostatic volume and post-voiding residual significantly decreased in all 15 evaluable cases, although uroflowmetric parameters showed no change. One the other hand, 3-year-followup study demonstrated that only 6 patients had satisfaction on urination without any supplementary treatment; 3 patients received transurethral resection of the prostate, 5 were treated with α₁-blocker and 1 dropped out.
In 4 cases, a clear prostatic cavity, which was connected to the urethra beside the vermontanum, was detected by imaging and ednoscopic studies. Concerning adverse events, massive haematuria, incontinence, stricture, retrograde ejaculation, impotence or rectal injury was not observed in any patients.
We conclude that TUBAL-T is applicable to high risk patiets without anesthesia, but needs some reform to improve the outcomes.

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Transurethral prostatectomy is performed using Ho: YAG laser in this study. Prostatic tissue is cut by underwater shockwave induced by Ho: YAG laser irradiation. The advantage of this method compared with transurethral prostatectomy using high frequency electrical current is that bleeding is little and there is no possibility of having hyponatremia. Another advantage of this method compared with transurethral prostatectomy using Nd: YAG laser is that the force of urinary stream greatly improves just after the operation.

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Two methods of holmium laser surgery were perfomed for the patients with benign prostatic hyperplasia. One method was a combination procedure using the Nd: YAG laser for standard circumferential coagulation followed by holmium laser ablation. The other one was holmium laser resection of the prostate. In the patients who had the combination procedure, although there was no bleeding during surgery and postopertive parameters were good, recatheterization rate was high. The early results of the holmium laser resection of the prostate showed an advantage over the combination technique with regard to formation of a cavity identical to transurethral resection of the prostate in the prostatic urethra, catheterization time and early improvement of subjective and objective symptoms. Although long term follow-up is necessary, holmium laser resection of the prostate is considered to be a effective alternative for benign prostatic hyperplasia.

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Nd: YAG laser with a wave length of 1064 um has many favorable characteristics, and has been widely applied to soft tissue procedures, One of the advantages of Nd: YAG laser is the high tissue penetration rate, and the conact method makes good use of this advantage. Using free beam contact irradiation, laser energy can be delivered to the tissue efficiently and can vaporize tissue and coagulate surrounding tissue.
Prostatic surgery using contact irradiation technique with Nd: YAG laser was performed in 81 patients with symptomatic BPH at Nihon University Hospital. We evaluated the efficacy and safety of Nd: YAG laser using contact irradiation technique as compared with standard TURP. Prostatic surgery using contact irradiation method with Nd: YAG laser was equal or slightly inferior to standard TURP in efficacy but less invasive than standard TURP.

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Transurethral ballon laser thermotherapy (TUBAL-T) is one of the new methods which can be selected for treatment of prostaic hypertrophy. It is a safe method with minimum surgical invasion. In this method, a special laser balloon catheter is insert ed transurethrally and fixed in the prostatic urathra, and the prostate is irradiated in a 360-degree direction with Nd: YAG laser by means of a laser probe attached inside the balloon. The temperature of the prostatic tissue is raised to at least 45°C by this method, resulting in degenerative necrosis of the tissue. Consequently, the volume of the prostate is reduced, degeneration and decrease in alpha-adrenergic receptor in the prostate occur, and dysuria is improved. In the present study, the basic and clinical results concerning TUBAL-T published to date were reviewed, and the clinical usefulness of this method was confirmed, The trial of new therapeutic techniques including improvement of the laser balloon and the use of the laser absorption materials were discussed.

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