Biomedical Engineering Reference
In-Depth Information
The stained inner side of the patches were positioned on the exterior surface
of the recipient capsule, so as to maintain the original orientation and curva-
ture. This procedure facilitated adhesion between the tissues to be welded. The
patch was then irradiated along its external perimeter by means of contiguous
laser spots emitted by a 200-
m-core fiber, whose tip was gently pressed onto
the patch surface (contact welding technique). Exposure times were found to
be critical to avoid heat damage. Continuous wave irradiation, which is typi-
cally employed in other laser welding applications, was unsuitable, while pulses
around 100 ms (with energies of 30-50 mJ) provided the best results. Once
welded, the capsular patch showed good adhesion to the recipient anterior
capsular surface. Preliminary biomechanical tests performed on laser-welded
anterior capsule flaps showed that the load resistance of welded specimens was
comparable to that of healthy tissues. Standard histology analysis indicated
good adhesion between the apposed samples and thermal damage localized in
the treated area.
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15.3 Applications in Microvascular Surgery
Microvascular anastomosis is a surgical technique for the connection of two
small-calibre blood vessels (both arteries and veins) with typical diameters
of a few hundreds of micrometers. It is commonly used in various surgical
fields, such as plastic and reconstructive surgery to restore traumatized or
thrombotic vessels, as well as in neurosurgery in the treatment of cerebral
ischemia, vascular malformations, or skull base tumors [71,72]. In this regard,
conventional suturing methods are associated with various degrees of vascular
wall damage, which can ultimately predispose to thrombosis and occlusion at
the anastomotic site [73]. To minimize vascular wall damage and improve long-
term patency, various alternative nonsuture methods have been investigated
experimentally and, in some cases, in the clinical practice [74-76].
Laser welding of arteries was reported in 1979 by Jain and Gorisch [77] to
perform vascular anastomosis by the use of a Nd:YAG laser. Then, other lasers
(e.g., argon [78] and CO
2
[79]) were used experimentally with questionable re-
sults. Further improvements came with the introduction of low-energy diode
lasers in association with exogenous chromophores and solders [80, 81]. More
recently, in vitro and in vivo acute studies have better defined some technical
aspects of end-to-end arterial laser welding [82, 83]. Despite the large number
of experimental studies reported in the literature, very few have reached the
clinical phase, mainly due to the lack of clear evidence of the advantages of-
fered by laser-assisted suturing (when compared with conventional methods),
and of reproducibility of results.
Experimental studies on diode laser-assisted end-to-end microvascular
anastomosis (LAMA) in association with ICG topical application in femoral
arteries and veins of rats were reported by some of us since 1993 [80, 81]. In
the design and development phases of these studies [80], the number of suture
