Development and clinical evaluation of medical robot assisted photodynamic therapy of port wine stains.

BACKGROUND: Port wine stains (PWS) are a kind of skin disease for which photodynamic therapy (PDT) has already achieved good results. With manual operation of clinical PDT, the laser density is uneven and laser irradiation of the lesion is arbitrary and non-uniform. In addition, lengthy manual operation tires doctors; thus a robot system has been developed to assist them. METHODS: First, a novel medical manipulator consisting of five passive joints (robot arm) and two active joints (robot wrist) was developed to automatically improve the uniformity of laser irradiation. Second, image processing of the lesion was introduced. Third, kinematics and path planning of the robot were analysed, and safety precautions were introduced. Then, accuracy tests of the robot wrist and robot system were conducted separately before clinical application. Finally, a total of 50 PWS cases were treated using the robot system. The clinical outcomes and comparison of non-parametric values were employed to evaluate the robot system. RESULTS: The accuracies of the robot wrist and robot system were shown to meet the requirements of clinical PDT treatment. The robot system performed successfully in 50 PWS cases. Doctors can devote more energy to clinical judgments during treatment with the assistance of the robot system. All the PWS have shown different degrees of improvement. The results show that the robot system is useful in assisting doctors for the PDT treatment of PWS. CONCLUSIONS: The experiments show the feasibility and usefulness of the robot system in assisting doctors giving PDT treatment for PWS. The robot system can lighten the load on doctors and improve the therapeutic effect.

[Imaging port wine stain by optical coherence tomography].

Optical coherence tomography is an appropriate imaging method for biomedical science, due to its advantages of noninvasive nature, high resolution and fast imaging speed. Because most biological tissues have the characteristic of high scattering coefficient, OCT system can just obtain the structural images several millimeters below the surface of the tissues. The superficial depth of OCT's penetration limits application in dermatology field. As a common disease, the port wine stain (PWS) is a indication of OCT, because of its superficial lesion and significant expansion of blood vessels. To get deeper penetration in the skin, the authors employed 1 310 nm superluminescent diode as light source, optimized the light intensity ratio of reference delay arm and sample arm and control polarization, and the research of PWS imaging in vivo was accomplished. Besides, OCT is able to gather clear image and key characteristic parameters, such as the depth of epidermis layer, the diameter of blood vessel, etc. OCT will play an important role in the diagnosis and therapy of PWS.

[The simultaneous measurements of time-dependent laser-induced fluorescence intensity of hematoporphyrin monomethyl ether in animal tissues with rheumatoid arthritis].

Since the selectivity of photodynamic therapy (PDT) depends on the distribution of a photosensitizer in a tissue during the treatment, an investigation of drug distribution is a key step for performing PDT effectively. The distribution of photosensitizer absorbed in tissues is adjusted by the animal body system, so an apparatus that can measure the fluorescence intensity of photosensitizer in different tissues of the same body simultaneously is in demand. To achieve precise estimate of tissue selectivity of the photosensitizer, a spatially separated three-channel laser-induced fluorescence (LIF) detection system was set up and employed in the present study to measure the fluorescence intensity of Hematoporphyrin Monomethyl Ether (HMME) in different tissues of the same body simultaneously. The time-dependent variations in the concentrations of HMME within the skin,cartilage, normal synovium and inflammatory synovium of rabbit were monitored in vivo. The results obtained showed that the synovium has higher absorptivity of HMME thanthe skin and cartilage. The difference is distinct from the very beginning of injection. Although the quantity of HMME absorbed in the inflammatory synovium is not very high in the first 20 min, it is still 6 times higher than that in the skin and cartilage. In addition, the absorptivity of HMME is much stronger for the inflammatory synovium than that for the normal synovium. If thelaser beam irradiates outside the joint for the rheumatoid arthritis, tissues around the inflammatory synovium have less HMME, thereby causing weak PDT effect. This would help reduce the side effect of PDT. Thus we suggest that for PDT treated rheumatoid arthritis, taking the first 20 min after the injection for outside-the-joint excitation employing HMME maybe a good choice.