Geert H. M. Gijsbers

Assessment of clinical outcome after flashlamp pumped pulsed dye laser treatment of portwine stains : A comprehensive questionnaire

&NA; A generally accepted method to assess the clinical outcome of laser treatment of portwine stains is not available. This paper describes the development and evaluation of a comprehensive questionnaire for the assessment of the following portwine stain characteristics: color (hue and lightness), sharpness of boundary, pigmentation, size, shape, skin surface‐structure, and hypertrophy of underlying tissue. The questionnaire was applied to photographs of 70 patients with previously untreated portwine stains in the head/neck area. Photographs were taken before treatment and after five treatments of the entire portwine stain with a flashlamp pumped pulsed dye laser. Each photograph was evaluated separately by a panel of five professionals: the treating physician, two plastic surgeons, a dermatologist, and a clinical photographer. Treatment results were assessed by comparing ratings before and after treatment. Agreement among raters was acceptable for all portwine stain characteristics, as was shown by weighted kappa analysis. The reliability of the answers was further improved by taking the average rating of the five panel members. The scores thus obtained were very reliable, with Cronbach alpha coefficients of 0.8 on average. After five treatments of the entire portwine stain, the most considerable changes were measured in the ratings for color (lightening of the stain by 33 percent), boundary (sharpness reduced by 38 percent), and size (13‐percent decrease). Using the questionnaire can be helpful in the design of comparative clinical trials on portwine stain treatment and may facilitate comparison of treatment results between different treatment centers and/or different lasers. (Plast. Reconstr. Surg. 102: 42, 1998.)

Tissue ablation and gas formation of two excimer laser systems : an in vitro evaluation on porcine aorta

The relationship between tissue ablation volume and the formation of insoluble gas of the currently available excimer laser systems is unknown. This aspect was evaluated in two excimer laser systems.

Excimer laser coronary angioplasty: Initial experience in Amsterdam

This paper reports on the initial clinical experience with 308 nm XeCl-excimer laser coronary angioplasty (ELCA) in the Academic Medical Center in Amsterdam and on calculations of light fluence rate distributions resulting from laser beams incident on tissue.Monte Carlo numerical computations were used to compute the light fluence rate distributions of a finite 308 nm excimer laser beam with various diameters incident on a liquid-tissue interface. It was found that light scattering is an important component in the resulting light distribution in aortic tissue. The calculations predict that there will be hardly any broadening of the beam outside the laser beam area. Therefore, the distributions from different fibres in multifibre catheters will not overlap unless the fibres are closely packed together. As a consequence of scattering the fluence rate at the surface of the tissue was larger than the incident power density and showed a considerable decrease from the centre to the edge of the beam. However, the physics of tissue ablation by fibres in contact with tissue are different and at present not well understood.The clinical results of the first 18 patients treated with the Dymer 200+ excimer laser (Advanced Interventional Systems, Irvine, CA, USA) are given. Six patients had abrupt closure solved by balloon angioplasty, but complicated by a small myocardial infarction. One patient had emergency by-pass surgery for abrupt closure after laser followed by balloon angioplasty (probably a dissection and thrombus). In one patient we perforated in a bend of a RCA with a 2.0 catheter following a second pass. We had two in hospital deaths (4 and 14 days after treatment). At 6 months follow-up, eight patients had restenosis or occlusion at the lased segment.However, the results of the first 1000 patients enrolled in the American ELCA-Registry are more promising. In the light of these results it can be concluded that a randomized trial balloon angioplasty versus excimer laser angioplasty appears to be indicated.

Temperature increase during in vitro 308 nm excimer laser ablation of porcine aortic tissue

The temperature increase of porcine aortic tissue irradiated with 220 ns XeCl 308 nm excimer laser pulses above ablation threshold have been measured by means of an IR camera. The decay of the temperature increase after a laser pulse is characterized by a fast decay during the first few milliseconds followed by a slow decay over a prolonged period, suggesting temperature accumulation at repetition rates used in laser angioplasty. The decay is adequately described by the theoretical prediction of the diffusion of heat after adiabatic heating of the tissue by a short laser pulse. From the temporal behavior of the decrease of temperature after a laser pulse, attenuation coefficients at 308 nm could be estimated. Attenuation coefficients after a single pulse are smaller than attenuation coefficient after multiple pulses. The temperature increases found in the experiments might explain thermal damage in myocardial tissue in earlier experiments. In an experimental set up simulating the situation during clinical excimer laser angioplasty, temperature increases of 43 degree(s)C average were found.

Efficient debulking with minimal vascular damage in excimer laser coronary angioplasty

Present day XeCI excimer laser coronary angioplasty (ELCA) with multifiber catheters is a safe and efficacious therapeutic modality. However, ELCA related complications, such as perforation, acute closure and arterial wall dissection, have been reported. These complications are at least partly attributed to vascular wall damage inflicted by fast expanding water vapor bubbles and insoluble gas induced by excimer laser pulses. It has been shown that the single pulse fluence threshold for the formation of a fast expanding bubble is about 20 mJ/mm2. Also, it has been observed that the gas yield increases sharply above 30 mJ/mm2. Therefore, it is conceivable that the vascular damage in ELCA caused by fast expanding bubbles and the accumulation of insoluble gas may be reduced by reducing the size and strength of the fast expanding bubbles and the gas yield by using fluences below 20 mJ/mm2.

Gas production in tissue phantoms and tissue by XeCl excimer laser: effect of beam delivery system geometry

In excimer laser coronary angioplasty (ELCA) an XeCl excimer laser at 308 nm is used to ablate atherosclerotic plaque in a stenosed coronary artery. In previous experiments we have seen that during ablation of cardiovascular tissues under saline, there is always a release of a stream of insoluble gas bubbles. We believe that this gas plays a crucial role in the understanding of the recanalization process in ELCA where a laser beam delivery catheter is brought in contact with the plaque in a tight space. It is well conceivable that the gas may help to recanalize an artery as a kind of dottering effect but especially in a tight stenosis the gas accumulation may enhance the damage to the vessel wall. The aim of the study was to investigate the dependency of the gas production by a XeCl excimer laser on the energy density and the diameter of the beam delivery system, to establish whether the effects of gas could be minimized or would be independent on the beam delivery system.

Temperature response of biological tissues to nonablative pulsed CO2 laser irradiation

The surface temperature behavior as a function of time of water and tissue phantoms irradiated with non-ablative CO2 laser pulses (2 ms) is measured. The temperature decay is very slow and the temperature increase due to the pulse is still non-zero at 70 ms after the pulse is terminated. The slow decay results in accumulation of temperature after multiple pulses at 10 Hz. The thermal behavior suggests that to avoid temperature accumulation when applying (super) pulsed CO2 irradiation, repetition rates must be smaller than 10 Hz.

In Vivo Wavklength Dependent Characteristics Of Hematoporphyrine-Derivative (HpD)

Fluorescence excitation spectra are recorded from HpD in living RUC-2 tumors implanted in rats. The experiments show that, compared with the excitation spectrum of HpD in solution, the Soret excitation band at 400 nm decreases with respect to the minor excitation bands at longer wavelengths. The excitation efficiencies at 503 nm and 625 nm are comparable with the efficiency at 400 nm. The differences in the in vivo and in vitro excitation spectra are caused by the wavelength dependent penetration depth of the excitation light due to absorption of blood and tissue.