DOUBLE WAVELENGTH (980 NM AND 808 NM) DIODE LASER
IN THE ENDOSCOPIC TREATMENT OF ANGIO-DYSPLASIAS
OF THE DIGESTIVE TRACT
EVIMEDICA Bergamo (Italy)
Endoscopy Centre General hospital of Bologna (Italy)

SUMMARY

The present report evaluates the utilisation in digestive endoscopy of double wavelength (980 nm and 808 nm) DIODE laser.
The two different wavelengths are emitted in rapid succession by the same device.
980 nm laser is the one most frequently used in hemostasis and in the recanalization of stenoses.
808 nm diode laser has a penetration of 2 mm (compared to 4 mm for 980 nm diode laser), and results in less dispersion of heat, as well as a more even diffusion in adjacent tissues. In conditions in which the gut wall is thin, it makes it possible to operate with a higher degree of safety and a reduced risk of perforation.
This study presents some preliminary data comparing the results of successive utilisation, on the one hand with 980 nm diode laser (28 referrals), and, on the other hand, with double wavelength laser (16 referrals), to treat angio-dysplasias.

INTRODUCTION
The treatment of angio-dysplasias in the digestive tract as a whole, and in particular in the cecum constitutes one of the non-palliative therapeutic applications of DIODE laser in digestive endoscopy.
However, the DIODE laser generally utilised in digestive endoscopy (with emission of a 980 nm laser beam) gives rise to a problem in the treatment of angio-dysplasias: in the absence of conditions of reflection, at a distance of 1 cm from the tissue, its tissue penetration is 4 mm per cm2, per second. Consequently, in the case of a lesion in a particularly thin bowel wall, the thermal effect may reach the deep layers of the bowel and expose it to a risk of perforation. This risk is high in the case of treatment of angio-dysplasias of the cecum.
DIODE laser can oscillate at two different wavelengths, 980 nm and 808 nm. It is normally used at 980 nm because it has an energy effectiveness approximately four times greater than that which can be obtained at 808 nm. This is why 980 nm DIODE has generally been commercialised and used until now. However, a 808 nm wavelength, although four times less powerful than 980 nm, offers certain advantages:

a) a depth of tissue penetration (per cm2, per second, and at a distance of 1 cm) of 0.5 mm;
b) lower heat dispersion by the blood and a more even diffusion of laser light in the tissues.

These characteristics of 808 nm DIODE laser mean that it is particularly appropriate in the treatment of angio-dysplasias.

MATERIALS AND METHODS
Instruments
In order to obtain equipment with multiple functions, in recent years combinations have been made of CO2 and DIODE laser. The result however has been a bulky piece of equipment which could not be used endoscopically, since CO2 laser could not be transmitted by optical fibres.
Two laser manufacturers have recently produced a DIODE laser which makes various functions possible by means of the emission of two wavelengths (980 nm and 808 nm) transmitted by the same optical fiber. In the present trial a DIODE laser was used which makes it possible to transmit consecutively through the same optical fiber, from the same piece of equipment, a 980 nm laser beam, and within a few milliseconds, a 808 nm laser beam.
Therefore the endoscopist has two wavelengths available, in the same optical fiber, with an external diameter of 1 mm, both in the same piece of laser equipment, the classic 980 nm, and the 808 nm, which makes it possible to operate where 980 nm is reflected or only slightly absorbed, namely in whitish and high water-content tissues, and in cases in which 980 nm would present a risk of perforation. As well as these characteristics, DIODE laser presents certain significant advantages: air cooling, 220 v power supply, light weight and portability.
The endoscopes used were Fuji operating video-endoscopes, which it was not necessary to modify since they were already equipped with shields against DIODE laser radiation, with a 3.8 nm channel and a system of supplementary lavage.
The laser room is equipped with safety devices against laser radiation, combustion fumes and electrical risks, in compliance with official CEI standards.

Material
Between January 1993 and March 1998, 486 patients were treated endoscopically with DIODE laser for curative or palliative purpose. In this survey of cases, the angiodysplastic lesions treated with two different means are divided into two distinct therapeutic periods, A and B (Table 1):

In period A, 28 cases were referred to us with a view to endoscopic treatment with 980 nm DIODE laser. The mean size, measured as the axis, or the sum of the longest axes of the largest lesion, was 13 mm (range 5-20). Of the 28 cases, 20 were treated (71%), while the others were excluded because of the notable size of the lesions and the potential risk of hemorrhage and/or perforation. The mean number of sessions required for complete eradication of the lesions was 1.5 (range 1-3). Total energy emitted was 1 900 Joules (range 800-3 200), in brief impulses, and with an increased power of 25 W, in order to avoid producing thermal effects on the lower layers of the wall and to reduce the risk of perforation. Complete eradication  due to the first session of laser treatment was achieved in 13 cases (65%). No complications were observed.

In period B, 16 cases were referred to us with a view to endoscopic treatment with DIODE laser, though only the 808 wavelength was used. The mean size of the lesions was 15 mm (range 6-30).
All the cases referred were treated, with a mean number of 1.5 sessions (range 1-3). Total energy emitted for the complete cycle of treatment was 330 J (range 120-750 J.). Complete eradication was achieved in 14 cases (87,5%). No complications were observed.

DISCUSSION
The number of cases treated is clearly not sufficiently high to draw statistically valid conclusions. Moreover, the difference in the number of cases, and in the size of the lesions, in periods A and B, makes it difficult to make a direct comparison between them. However, it must be remembered that these are comparatively rare pathologies, for which the choice of indications and methods is a function of the risks incurred. This preliminary study is one of the first applications of 808 nm DIODE laser in digestive endoscopy. Nevertheless, these preliminary results make it possible to compare certain data from periods A and B: the number of cases treated, the total energy emitted, the number of complete eradications in the first cycle of treatment.
In period B, the number of cases treated was higher, and none were excluded, since there were no counter-indications in the case of larger angio-dysplasias and those located in positions with a high risk of perforation or hemorrhage.
Moreover, in period B the percentage of complete eradications was higher than in period A, since it was possible to treat larger lesions more safely and effectively with 808 nm DIODE laser. Finally, these more complete eradications were achieved with a total quantity of energy emitted which was lower than that of period A.
No significant complications were observed during either of the two periods, but in the period B it was possible to accept cases presenting higher risks than in period A.

CONCLUSIONS
In conclusion, 980 nm DIODE laser poses certain problems for the endoscopist in the treatment of angio-dysplasias, because of the deep penetration of the thermal effect. However, 808 nm appears to palliate these problems because of its more superficial penetration. The trials carried out in the course of the past year with double wavelength (980 nm - 808 nm) DIODE, with particular reference to the laser treatment of high risk lesions (angio-dysplasias), indicate the utility of further studies using this application.
The preliminary data in the present study could serve as the basis of a randomised study, in a number of centers, of this rather infrequent pathology which, because of the location and the dimension of the lesions, exposes the patient to a certain risk of complications after treatment with 980 nm DIODE laser.