Within surgery and medicine the traditional application of the laser is as an incisional and ablative tool. The surgical laser systems of 20 years ago had the same basic tissue effect as today, near instantaneous vaporization of a target tissue by a highly focussed and pin-point accurate beam of light.

Although the utility of medical diagnostics based on stable isotope breath tests is well established, the instrumentation available to implement these procedures has been a barrier to their introduction. A tunable diode laser spectrometer for the measurement of isotopic ratios in a clinical setting will be described. The diode laser-based system allows direct measurement without any sample preparation at a cost significantly lower than current techniques. The system design and performance will be presented along with the considerations necessary to allow the instrument to be viable in the clinical environment.

More than 10 million units of human blood components are processed annually in the United States. Although donor screening and testing have greatly lowered the risk of transmission of viral and protozoan infectious agents, additional sterilization procedures which also preserve blood component function would be of significant value. Use of UV-A and visible-light-range photosensitizers for sterilization of blood platelets and red blood cells, respectively, is currently being aggressively investigated in laboratory-scale optical-mechanical systems. With successful demonstration of the efficacy and safety of these sterilization techniques, implementation in the blood bank setting will require scale-up to optical-mechanical systems capable of handling approximately 25,000 units daily in 500 - 1,000 blood banks in the United States.

The failure rate of cancer treatment remains unacceptably high, still being a leading cause of mortality in adults and children despite major advances over the past 50 years in the fields of surgery, radiation therapy and, more recently, chemo and immunotherapy. Surgical access to some deep tumors of the head and neck and other areas often require extensive dissections with residual functional and cosmetic deformities. Repeated treatment is not possible after maximum dose radiotherapy and chemotherapy is still limited by its systemic toxicity. An attractive solution to these problems would be the development of a new adjunctive method combining the best features of interstitial laser therapy for selective tumor destruction via minimally invasive techniques for access and 3-D magnetic resonance imaging (MRI) as a monitoring system for laser-tissue interactions. Interstitial laser therapy (ILT) via fiberoptics allow laser energy to be delivered directly into deeper tissues. However, this concept will become clinically useful only when noninvasive, accurate, and reproducible monitoring methods are developed to measure energy delivery to tissues. MRI has numerous advantages in evaluating the irreversible effects of laser treatment in tissues, since laser energy includes changes not only in the thermal motions of hydrogen protons within the tissue, but also in the distribution and mobility of water and lipids. These techniques should greatly improve the use of ILT in combination with MRI to allow treatment of deeper, more difficult to reach tumors of head and neck and other anatomical areas with a single needle stick.

The embryonic area of interventional MRI, i.e. interstitial therapy under MR guidance, includes deep tissue laser ablation of lesions. Laser fibers can be located inside lesions by first inserting an MR-compatible cannula into the lesion and then inserting the laser fiber through the cannula into the lesion. Two factors are critical in selecting alloys for cannulae: the material should exhibit so little magnetic susceptibility that it will neither distort the MR image nor torque even at high field strengths, yet it should exhibit enough susceptibility defect that the cannula can be visualized by MR during positioning. Wires of metals and alloys were tested in a magnetometer to measure their magnetic moment, and imaged with spin echo and gradient echo MRI. Direct measurement of magnetic moment was a good indicator of MR- compatibility. Artifacts visualized with spin echo pulse sequences were smaller than those produced with gradient echo sequences.

An intelligent surgical laser system, which can help the ophthalmologist to achieve higher precision and control during their procedures, has been developed by ISL as model CLS 4001. In addition to the laser and laser delivery system, the system is also equipped with a vision system (IPU), robotics motion control (MCU), and a tracking closed loop system (ETS) that tracks the eye in three dimensions (X, Y and Z). The initial patient setup is computer controlled with guidance from the vision system. The tracking system is automatically engaged when the target is in position. A multi-level tracking system is developed by integrating our vision and tracking systems which have been able to maintain our laser beam precisely on target. The capabilities of the automatic eye setup and the tracking in three dimensions provides for improved accuracy and measurement repeatability. The system is operated through the Surgical Control Unit (SCU). The SCU communicates with the IPU and the MCU through both ethernet and RS232. Various scanning pattern (i.e., line, curve, circle, spiral, etc.) can be selected with given parameters. When a warning is activated, a voice message is played that will normally require a panel touch acknowledgement. The reliability of the system is ensured in three levels: (1) hardware, (2) software real time monitoring, and (3) user. The system is currently under clinical validation.

Medical procedures such as arthroscopy have placed increasing demands on the output performance of the CTH:YAG laser at 2.1 micrometers . Intensive research has been conducted to improve the average power, pulse energies, and rep rates while reducing any failure mechanisms. The results of this work is reported along with a discussion of the important engineering parameters concerning the design of a high power medical CTH:YAG laser.

The interaction of pulsed ultraviolet radiation with the zona pellucida of human oocytes which had failed to fertilize in standard IVF cycles, was investigated. Two lasers were studied: a 100 ps pulsed Nd:YAG with a nonlinear crystal emitting light at 266 nm, and a 15 ns XeCl excimer laser with 308 nm radiation. Incisions in the zona were made by aiming the beam tangentially to the oocyte. The results indicate superior, high precision performance by the excimer laser creating trenches as narrow as 1 micrometers and as shallow as 1 micrometers . The incision size was found to be sensitive to the laser's energy and to the position of the microscope's objective focal plane, but relatively insensitive to the laser pulse repetition rate. Once the minimum spot size was defined by the system parameters, the laser beam was used to curve out any desired zona shape. This laser microsurgery technique as applied to partial zone dissection or zona drilling could prove very useful as a high-precision, non-contact method for treatments of low fertilization rate and for enhancing embryo implantation rates in patients undergoing IVF treatments.

The endoscope is finding an almost exponential growth in many surgical specialties. This appears to be an area in which applications will stimulate the development of new technology. We would like to present the essentials of a new system that will significantly improve the capabilities of the surgeon and offer him new alternatives in the management of many conditions.

We present the results of an experiment to demonstrate high average power uv radiation at 266 and 213 nm obtained from the fourth and fifth harmonics of a Nd:YAG laser. The second harmonic of the infrared laser was generated in an LBO (lithium triborate) crystal, the fourth harmonic by doubling the output of the LBO in a BBO (beta barium borate) crystal, and the fifth harmonic was obtained by sum frequency mixing of the fourth harmonic and the fundamental beam in another BBO crystal. In this paper we report high average power uv radiation at 266 nm (1.3 W) and at 213 nm (0.54 W). To our knowledge, these are the highest powers ever achieved at these wavelengths in an AO Q-switched, Gaussian single-mode Nd:YAG system.

Clinical data shows that short pulse duration lasers used in laser induced shock wave lithotripsy severely damage optical fibers on both the proximal and distal ends which is unsuitable for clinical use. An Alexandrite laser system has been developed that uses dynamic pulse stretching of the Q-switched laser pulse and improved optical fiber coupling to eliminate the fiber damage. The method of pulse stretching presented controls the laser output pulse energy from 50 to 150 millijoules and temporal shape from 0.5 to 1.5 microseconds. This yields effective fragmentation of calculi without damage to the optical fiber.

Nearly all laser systems currently used in different medical disciplines of laser treatment are-- except for the tunable dye and alexandrite laser--one-wavelength systems with a very specific applicability to a single monotherapeutic procedure. According to the wavelength used, they can only either heat, coagulate, vaporize, or ablate due to the characteristic physical absorption behavior of hard and soft tissue material. Modular and multiwavelength laser systems--especially solid-state lasers, due to their excellent reliability--are therefore gaining interest, because they can easily provide tunable wavelengths in the UV, VIS and near-IR spectral region with exchangeable optical modules. This makes them ideal candidates for multipurpose and multidiscipline clinical use. A laser concept of a modular and multiwavelength solid-state laser system based on a pulsed alexandrite laser oscillator with additional optical modules to provide therapeutic radiation for laser-lithotripsy, laser- angioplasty, neurosurgery, general surgery, and dentistry is discussed.

Immunophototherapy (IPT) is an experimental method of medical treatment that seeks to provide for the selective destruction of diseased cells and microbes such as human immunodeficiency virus (HIV)-T4 cells and the rapid elimination of their toxic by-products from the human body. Photosensitive monoclonal or polyclonal antibody fragments, which are specific to the diseased cell or microbe, will be used to treat acquired immunodeficiency syndrome (AIDS) and related infections. These antibody fragments are tagged with photosensitive compounds and metal colloids and then intravenously injected into the patient. The tagged antibodies quickly and selectively bind to the diseased cells or microbes in the blood stream and affected organs. These cells or microbes are then selectively destroyed by irradiation of these complexes with light of the proper wavelength. This light activates the photosensitive material which then creates singlet oxygen that destroys the microbe or cell. Toxic products of lysis are quickly discharged from the body by activation of the reticuloendothelial system. IPT has been demonstrated by Biotronics to be very effective in the in vitro selective destruction of specified cell types. In a proposed AIDS-treatment research program, IPT will be first demonstrated in vitro for a set of infected blood samples using commercially-available antibodies labeled with appropriate photosensitizers. Efficacy will be determined by a p24 antigen immunodiagnostic test that will indicate the % inhibition in comparison to controls and samples treated with the drug AZT. Subcontracted animal efficacy studies will use a SCID-hu mouse model and PCR/DNA-RNA for endpoint analysis. Toxicity studies of animal (rat) models will be based on post-treatment investigations of lymph nodes, spleen, liver and other organs.

Simultaneous exposure of Merocyanine 540 dye containing cultured tumor cells to 514-nm laser light (93.6 J/cm²) results in virtually complete cell destruction. Under identical conditions, 40% of the normal progenitor (CFU-GM) cells survive the treatment. Laser- photoradiation treated, cultured breast cancer cells also were killed, and living tumor cells could not be detected by clonogenic assays or by anti-cytokeratin monoclonal antibody method. Thus, laser photoradiation therapy could be useful for purging of contaminating tumor cells from autologous bone marrow.

Transmission of viral diseases through blood products remains a problem in transfusion medicine. A number of methods have been developed to inactivate viral pathogens in plasma and plasma fractions, including: dry heating, wet heating, solvent-detergent treatment, and immunoaffinity purification. While some of these methods successfully inactivate pathogenic viruses, inactivation may be incomplete or result in damage to labile plasma proteins and cells. We have developed a photochemical decontamination system (PCD) for platelet concentrates (PC) utilizing treatment with long wavelength ultraviolet radiation (UVA, 320 - 400 nm) and 8-methoxypsoralen (8-MOP). This system is capable of inactivating 25 - 30 logs/hr of bacteria E. coli or S. aureus, 6 logs/hr of bacteriophage fd, 0.9 log/hr of bacteriophage R17 and 1.1 logs/hr of feline leukemia virus (FeLV) in PC. Immediately following 6 hrs of PCD treatment, platelet integrity and function of PCD treated and control PC were equivalent. After overnight storage PCD treated and control PC platelet properties were equal, but there was a slight reduction in TXB-2 production of PCD treated PC compared to controls. Following PCD treatment, PC were stored for 48 to 96 hrs. Platelet counts, morphology scores, extracellular LDH levels, aggregation response, dense body (db) content, and alpha granule ((alpha) g) content of PCD treated and control PC were comparable. We assessed the ability of the PCD technique to inactivate intracellular and extracellular virus, quantified the degree of DNA adduct formation in contaminating lymphocytes, and measured the inhibition of polymerase chain reaction (PCR) mediated amplification of intracellular DNA. High titers of cell-free murine cytomegalovirus added to human platelet concentrates (final concentration 10⁶) were inactivated by PCD within 30 min. Cat renal fibroblasts infected at high levels with feline rhinotracheitis virus (FeRTV) were seeded into PC followed by PCD treatment with inactivation of 4.8 logs of FeRTV within 10 minutes. Purified human lymphocytes were seeded into PC and treated with PCD in the presence of ³H 8-MOP. Six hours of PCD treatment resulted in the formation of 9.3 to 12.8 8-MOP adducts per 1000 base pairs (bp) of DNA. PCR amplification of a 242 bp segment at the HLA-DQ(alpha) locus was examined. Inhibition of PCR DNA amplification was dependent on the numbers of 8-MOP adducts formed, and no amplification was present when greater than 12 adducts per 1000 bp were formed. These studies indicate that PCD can effectively inactivate high titers of cell-associated and cell-free virus seeded into standard human PC. The efficiency of DNA adduct formation can be quantitated, and the level of 8-MOP adduct formation in lymphocytes contaminating PC is comparable to the level of adduct formation in cellular DNA reported in the absence of platelets.

More than 10 million units of human blood components are transfused annually in the United States. Although donor screening and testing have greatly lowered the risk of transmission of viral and protozoan infectious agents, additional sterilization procedures which also preserve blood component function would be of significant value. Use of visible-light-range photosensitizers for sterilization of red blood cells is currently being aggressively investigated in laboratory-scale optical-mechanical systems. Both the photochemical sterilization process and the optical-mechanical system must operate without introducing significant alteration in the properties of the red cells. With successful demonstration of the efficacy and safety of these sterilization techniques, implementation in the blood bank setting will require scale-up to optical-mechanical systems capable of handling approximately 50,000 units daily in 500 - 1,000 blood banks in the United States.

Lasers are instruments that may enhance the surgeons ability to perform surgery. Many medical lasers sit unused. Lack of use is associated with 'user unfriendliness'. Nurses and surgeons often cite factors such as complexity, location, and types of controls, and content of displays. Other factors such as culture-ethnology and its relationship to command words and symbols, affect understandability of controls, displays and user friendliness. Laser designers and engineers must analyze the interaction between laser users and products. They must fully understand the training limitations and unique working environments (surgical specialty) of operators. Laser design and operation must coincide with specific needs and expectations of the nurses and physicians. Poor design and engineering compromises results in non use of expensive instrumentation, products which are ineffective for clinical use, and could potentially increase the risk of possible injury to patients and staff. This paper discusses the design and operation of medical laser systems. The advantages and disadvantages of several laser systems will be presented. User interfaces for controls - color, function, touch activation, labels and size, sound cues, laser activation, type and amount of feedback information during operation; design of storage for accessories, and need for features such as pulsing, and milliwatts will be discussed. We will present what we consider to be an ideal laser system.

Development of fiber optic laser interactive systems that not only deliver the specific frequency wavelength, but have sensing and detection qualities, would complement and expand diagnostic and therapeutic modalities. This capability could allow for measurement of irradiation parameters and consequences quantitatively. The challenge is to find the fertile ground of new concepts to be developed by dedicated pursuit and insistence.

As hospitals acquire a greater variety of laser systems and related instrumentation, many institutions are realizing the benefits of having an in-house biomedical laser specialist. The responsibilities of this specialized position may include: assisting laser procedures and research projects, operating and maintaining laser instrumentation, acting as medical laser safety officer, developing training and education programs, and directing hospital laser programs. This paper will describe the training and education profile of a biomedical laser/electro-optic specialist. The benefit of their expertise to a hospital laser program will be discussed as it relates to: increased laser utilization, greater laser safety awareness, lower maintenance costs, and research and educational projects.

Approximately a dozen states have regulatory or statutory authority in the area of nonionizing radiation. With only half that number having established laser regulations. Examples are Texas, Florida, Arizona, Mass. many more are considering establishing such rules, such as N.J., Il., Neb. On the federal level, the Food and Drug Administration has been the most active entity. OSHA has just recently established laser safety guidelines for its inspection staff. In March of 1990 the State of Arizona enacted rules for the control of Nonionizing radiation. This fell under Article 14 of Tittle 12 of the Arizona Administrative Code, which is under the authority of the Arizona Radiation Regulatory Agency. The rules cover a wide range of nonionizing sources, but the major emphasis is in the area of laser devices. While all class lasers fall under Article 14, only Class IIIb and Class IV laser use facilities are required to be registered and inspected by the agency. The rules apply to all Class IIIb and Class IV laser users, meaning medical, industrial, entertainment, and also research facilities.

Ninety interstitial lesions were produced in ex-vivo sheep liver using various power outputs (5, 10, and 20 Watts) and exposure times for delivery of 200 Joules of the Nd:YAG laser energy. For the purpose of determining lesion reproducibility, two different methods of laser energy delivery to tissue, namely, the bare fiber optic and the sapphire diffuser tip techniques, were utilized. Cross-sectional magnetic resonance imaging (MRI) or laser treated specimens were performed on a 1.5 Tesla superconducting magnet. Images were examined for shape and extent of damage, as well as uniformity. Lateral and longitudinal extent of thermal injury was measured from the image of each lesion. Results showed that the diffuser tip method is better able to reproduce lesions than the bare fiber method, particularly when high levels of laser power are employed. This study indicates the need for development of MRI-compatible diffuser tip technology for use in MRI-guided interstitial laser therapy.

Prototype of a commercial laser system, capable of performing various surgical operations, was developed and produced. The laser unit can emit, separately or simultaneously, radiation with wavelengths 1.06 and 2.1 (mu) at an average power up to 30 and 6.5 W correspondingly. The construction of an optical scheme and power supply gives wide flexibility of the laser output parameters. Possible medical applications of the 1 - 2 micron laser system are considered.