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ABSTRACT: Thermal diffusion during laser-induced interstitial thermotherapy (LITT) has not yet been fully investigated in heterogeneous tissue architecture such as liver. LITT was performed on rabbit liver tumours to analyse the role of biliary structures in thermal diffusion.
Twenty-four VX2 tumours were grafted onto 12 rabbit livers. The animals were randomly separated into two groups when tumour size reached 8 mm. Thermotherapy was performed by delivering the 830-nm output of a diode laser to the centre of the tumour with a 300-,microm fibre. Irradiation conditions were 1.5 W over 900 sec. On day 7 or 14, the tumours were removed and stained with haematoxylin-eosin and picrosirius red F3BA (PR). Thermal damage was evaluated by PR and electron microscopic examinations.
Among the treated tumours, recurrences were found both at the periphery (one on day 7, seven on day 14) and within the treated area (two on day 7, two on day 14). All recurrences were located in the vicinity of the biliary structures, which are frequently spared from thermal injury.
Biliary ducts lead to a heat sink, thereby facilitating tumour recurrences.
Lasers in Surgery and Medicine 02/1999; 24(4):269-75. · 2.75 Impact Factor
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ABSTRACT: Hepatic and biliary structures present during embryonic Carnegie stage 23 were analyzed and compared in OFA-IOPS rat and human embryos. The group of embryos was composed of 3 rat specimens-crown rump length (CRL) 16 mm, age 16 days 5 hours post coltus- and of 1 human embryo- CRL 31 mm, age 57 days PC-. The specimens were submitted to serial histological sections with graphic reconstruction. In both species, the basic architecture of liver parenchyma was established including parenchymal cords or plates alternating with hepatic sinusoids. Veinous channels were clearly defined. The intrahepatic biliary system, referred as ductal plates (DP) developed into the periportal connective tissue while the portal spaces were not yet existing. DP was recognized either as a single layered cuboidal structure or as a double layered one dilated to form mature tubular ducts. The latter layout was more frequent in the rat. Except for gallbladder which is never present in the rat, similarity and presence of the same hepatic structure in both species at the end of the embryonic period (stage 23) suggest that the rat is a good experimental model for liver development and will be useful to understand the mechanism of congenital anomalies and specially the involvement of ductal plates in the congenital diseases of intrahepatic bile ducts.
Morphologie 10/1998; 82(258):11-4.
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ABSTRACT: The actual mechanism by which laser irradiation welds tissue is presently unknown; however, collagen is a major constituent of tissue welded by laser irradiation.
Collagen was extracted from the abdominal aorta of Wistar rats by acetic acid extraction and repeated pepsin digestion after tissue welding (254 W/cm2) by using an 830-nm diode laser. The collagen levels were determined by using the Sircol Collagen Assay (Biocolor, Northern Ireland).
Compared with untreated aorta, the collagen content of the treated vessel was obvious decreased (P < 0.001) immediately after laser irradiation. Levels then increased by day 3, with a peak at day 10 (P < 0.002). The collagen content returned to normal levels on day 30 and remained at this level throughout the rest of the experimental period.
These results suggest that a proportion of the collagen molecules in the vessel are denatured by the heat of the laser. Collagen synthesis is stimulated during the healing process after laser welding with the parameters used in the present study.
Lasers in Surgery and Medicine 02/1998; 22(4):207-11. · 2.75 Impact Factor
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ABSTRACT: Hepatic structures appearing during embryonic Carnegie stages 11-23 were analyzed and compared in OFA-IOPS rat and human embryos. The group of rats--crown-rump length (CRL) 2-16 mm, 10-16 days postcoitus--was composed of 127 specimens (52 of stages 11-12, 55 of stages 13-19, and 20 of stages 20-23), the human group of 9 embryos at stages 14-23--CRL 5-31 mm, age 32-57 days--and human stages 11-13 were described according to former literature. The specimens were subjected to serial histological sections with graphic reconstructions. In both series, stage 11 was characterized by hepatic diverticulum development, stage 12 and thereafter by cellular differentiation (septum transversum giving the liver stroma and hepatic diverticulum the hepatic trabeculae), and stage 13 by epithelial cord proliferation enmeshing stromal capillaries. From stage 14, the hepatic gland and its vascular channels presented considerable enlargement while hematopoietic function appeared. From this stage, the development of cystic primordium, never present in rat, was constant in man. At stage 18, after a period of obturation due to epithelial proliferation, the bile ducts became reorganized and ensured the continuity between liver cells and gut. From stages 18 to 23, biliary ductules developed in periportal connective tissue producing ductal plates that received biliary capillaries. Except for gallbladder, similarity and presence of the same hepatic structures in man and rat during the embryonic period stages 11-23 permit us to consider the rat as a good experimental model for liver development, for example, in studies on teratology and congenital anomalies.
Microscopy Research and Technique 12/1997; 39(4):314-27. · 1.79 Impact Factor
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ABSTRACT: A series of 240 diode laser assisted end-to-end microvascular anastomoses (LAMA) and conventional manual anastomoses (CMA) were performed in the left and right common carotid of Wistar rats, respectively. In comparison with the two anastomotic methods, optic and scanning electron microscopic examinations were achieved from Day 0 to Day 210, in order to clarify the mechanism of media repair after diode laser welding, especially the long-term results. In the LAMA group, the cut vessel edges were welded without obvious thermal necrosis after laser treatment. On Day 10, media repair was underlined by circular bulges corresponding to the folds of cut vessel endings brought together. Inflammatory cells were regularly scattered in the adventitia in the vicinity of the anastomotic site, and were gaining ground intensively in the media by Day 20. At this time, the parallel organization of elastic laminae disappeared while the collagen network developed. On Day 120, irregular elastic fibres aggregated in the anastomotic site. On Day 210, reconstituted elastic lamina was present. In the CMA group, on Day 20, fibrotic repair appeared between cut vessel edges, and the injury incorporated by sutures was important. The elastic laminae were not reconstituted by Day 210 in any case. This microscopic study proves that the long-term repair of diode LAMA facilitates media repair and prevents fibrotic scarring of the media.
Lasers in Medical Science 12/1997; 12(4):300-6. · 2.00 Impact Factor
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ABSTRACT: The process of aneurysm formation after laser welding is described.
The mechanism of aneurysm formation after laser-assisted microarterial anastomosis is presently unclear.
A series of 830-nm diode-laser-assisted longitudinal aortorrhophy with a condition of 400 to 500 J/mm2 for 1 cm length of anastomosis versus conventional manual anastomoses were performed in 90 Wistar rats. To compare this technique with normal media process, a histologic examination of aneurysm formation was conducted.
The results show that there are two important factors that cause aneurysm formation after laser-assisted anastomosis: 1) the vessel wall is damaged by laser heating; 2) proliferation of collagen fiber at the adventitia is absent during media reconstruction.
Journal of Clinical Laser Medicine & Surgery 02/1997; 15(4):175-9.
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ABSTRACT: The mechanism of laser tissue welding is elusive, but collagen transitions are somehow involved. Collagen fiber modifications observed after 830 nm diode laser welding are presented in this study.
A 830 nm diode laser assisted longitudinal aortorrhaphy was performed on 37 Wistar rats, with shots of 0.5 W in power, 8 sec in duration and 250 W/cm2 in irradiance. Energy utilized ranged from 400-550 J/ mm2 for 1 cm-length of anastomosis. After laser welding, histological modifications in collagen fibers were observed through optic, scanning electron, and electron microscopic examination.
After laser welding, collagen fibers lost a proportion of birefringence. Under electron microscope, the different changes in collagen fibers were visualized being either fused, "roped," swollen, or dissolved, surrounded by normal ones situated in the same zone.
These data suggest that diode laser heating denatured part of the collagenic fibers, and that these morphologic changes play an important role in laser welding.
Lasers in Surgery and Medicine 02/1997; 21(5):438-43. · 2.75 Impact Factor
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ABSTRACT: Hepatic and biliary structures appearing during embryonic Carnegie stages 15-23 were analyzed in OFA rat embryos. The group of rats with crown rump length 7.5-16 mm and 12.8-16 days after coitus yielded 55 specimens (23 of stages 15-16, 20 of stages 17-18, 9 of stages 19-22 and 3 of stage 23). The embryos were submitted to serial histological sections with graphic reconstructions. From stage 15 to the end of the embryonic period, the hepatic gland and its vascular channels (transverse portal sinus and hepatocardiac veins) presented considerable enlargement while hematopoietic function appeared. At stage 17, occlusion due to epithelial proliferation was evident in the hepatic duct. At stage 18, the duct became recanalized and assured the continuity between liver cells and gut. From stage 18 to 23, biliary ductules developed in periportal connective tissue forming ductal plates which received biliary caniculi. Except for the gall-bladder which is never present in the rat, similarity and presence of the same hepatic structures in man and in the rat during the embryonic period stages 15-23 suggest that the rat is a good experimental model for liver development and will be useful in the understanding of congenital anomalies.
Acta Anatomica 02/1997; 160(3):172-8.
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ABSTRACT: Interstitial Laser Hyperthermia (ILH) has been investigated since the early 80s in the treatment of deep seated tumors. The purpose of this study was to evaluate the efficiency of diode ILH (830 nm) in a subcutaneous tumor model. STUDY DESIGN/MATERIALS AND METHOD: The antitumoral effect of diode ILH was assessed in a randomized study performed on 80 Swiss nu/nu mice. The tumor model was a subcutaneously implanted HT29 colonic carcinoma. The animals were assigned to four groups of 20 mice: Groups 1 and 3 were treated by ILH, groups 2 and 4 were not treated (control groups). Tumors were removed on day 3 in groups 1 and 2, and on day 30 in groups 3 and 4. The treatment was performed on tumors of 8 mm in diameter and a volume of 140 mm3. A laser irradiation of 360 J (power: 0.2 W; irradiation time: 1800 s) was delivered through a 300 microns optical fiber implanted in the tumor. The laser parameters insured temperatures of 46 degrees C in the central part of the tumor and 42 degrees C at the periphery. Tumor features were evaluated on day 3 and day 30.
Untreated tumors grew rapidly up to a mean volume of 241 mm3 on day 3 (group 2) and 2,000 mm3 on day 30 (group 4). Treated tumors regressed to a mean volume of 32 mm3 on day 3 (group 1). On day 30, 40% of the tumors had totally disappeared and 60% showed partial response with small and peripheral residual tumor of 172 mm3 on an average, as to say 11.2 times smaller than in group 4.
ILH with a low power 830 nm diode laser is an efficient treatment of subcutaneous tumor model. Partial responses are attributed to an insufficient heating at the tumor periphery. More precise control of the peripheral tumor temperature will improve the ILH results.
Lasers in Surgery and Medicine 02/1996; 19(4):445-50. · 2.75 Impact Factor
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ABSTRACT: A diode-laser (830 nm)-assisted carotid artery end-to-end microanastomosis (LAMA) and a contralateral manual suture anastomosis (CMA) were performed in 70 Wistar rats. The vessel sealing was performed on the left carotid by laser pulses (average 3) of 500 mW power and 4.5 sec exposure time, the beam being focused on a spot of 300 microns diameter (700 W/cm2). The CMA was achieved on the right carotid by six 10-0 stitches. From day 0 to day 210, 40 specimens underwent scanning electron microscopy. The laser impact produced a wall injury of 100 microns in width, with an immediate sealing effect due to protein denaturation and collagen fusion of media and adventitia. The anastomosis became re-endothelialized by day 3, while the longitudinal arrangement of the endothelial cells was restored from day 10 on. In the long term, a thick collagenous meshwork of collagen and elastic fibers maintained the strength of the media, while normal endothelium covered the anastomosis. Inversely, after CMA vessel repair was delayed, and the anastomotic line was more irregular and underlined by medial fibrotic scar. In both anastomoses, the patency rate was 93 percent, with nonlethal complications. The advantages of LAMA vs. CMA were: shorter operating time (13 min/22 min), reduced intraoperative trauma, better healing of endothelium, and a miniaturization of the laser source well adapted to microsurgery.
Journal of Reconstructive Microsurgery 02/1995; 11(1):37-41; discussion 42. · 1.43 Impact Factor
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ABSTRACT: A series of direct carotid end-to-end laser anastomosis vs. direct manual suture was carried out on a series of 70 Wistar rats (mean weight 260 g). Both common carotids (0.8-1.2 mm) were sectioned and repaired. The left side (n = 70) was submitted to laser-assisted microvascular anastomosis (LAMA) performed by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave) without chromophore. The right side (n = 70) underwent a control manual suture (CMA). The diode laser energy was delivered into a micromanipulator coupled to a Zeiss operating microscope with a focused spot of 300 microns in diameter. After placement of three 10.0 stitches for edge coaptation, the LAMA was achieved using laser shots (average 3) of 500 mW power, 4.5 s duration, and 700 W/cm2 irradiance each. The CMA was performed by means of six 10.0 stitches. The good vascular flow was confirmed by Doppler spectral analysis (n = 466) carried out from day 0 to day 90. Light and scanning electron microscopy (n = 82) showed that re-endothelialization after LAMA was gaining ground on day 3, whereas collagenous network developed in the media scar by day 10. In contrast, after CMA the arterial repair was delayed on day 20, inducing a media fibrotic scar. The patency rate was 93% in both anastomoses. The shorter operating time (13 min for LAMA vs. 22 min for CMA) and the noncontact laser technique are the main intraoperative advantages. The technical benefits of the diode laser are pointed out.
Lasers in Surgery and Medicine 02/1994; 14(3):229-37. · 2.75 Impact Factor
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ABSTRACT: A crossed carotid end-to-end anastomosis was performed in 20 Wistar rats by means of a diode laser device (wavelength 830
nm and power output 3 W in continuous wave). The diode laser energy was delivered into a micromanipulator coupled to an OPMI
1 Zeiss operating microscope with a focused spot of 300 μm diameter. The vessel sealing was effected on common carotids (0.8–1.2
mm) using laser shots (average 9) of 680 mW power and 4.5 s duration and 962 W cm−2 irradiance each. The good vascular flow was confirmed by Doppler spectral analysis and angiography performed on days 0, 10
and 30. Light and scanning electron microscopy showed that reendothelialization was complete on day 10 whilst collagenous
fusion of media and adventitia was obvious. The patency rate was 90% impaired by a lethal thrombosis. The efficiency of the
diode laser was compared to that of other types of LAVA and to manual microanastomosis.
Lasers in Medical Science 04/1993; 8(1):33-38. · 2.00 Impact Factor
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ABSTRACT: The coagulation effect, penetration depth and healing process of the 510.6 nm (green) and 578.2 nm (yellow) wavelengths of
copper vapour laser (CVL) were compared in vivo in rabbit liver (n=15). A pulsed CVL, the Cu 15 from Oxford Laser—pulse repetition 10 kHz, peak-power 70 kW, pulse width 25 ns, and average
maximal power 16W—was used connected to a dichroic system. The beam was transmitted through a 1000 μm quartz fibre and focused
with a handpiece providing a 2 mm diameter spot size. By means of this delivery system 270 focused lesions are achieved at
a power output of 2.65 W (power density 80 W cm−2) with irradiation times of 3, 5 and 10 s. The operative and microscopic verifications were achieved at 0 hour, and on days
3, 10, 20 and 30. Immediately after laser application, the lesions were triangular, well demarcated, and characterized by
a central vaporization surrounded by four peripheral zones: carbonization; coagulation; oedema; and transition. The penetration
depth was noticeably bigger in the yellow wavelength than with green wavelength, evidenced on day 10 by superior size of yellow
wavelength photocoagulations and coagulation necrosis. Fibrosis appeared by day 3 and was gaining ground quickly and intensively
after yellow wavelength while the fibrotic reaction was delayed on day 10 after green wavelength. The more penetrating effect
of yellow wavelength advocates for its use in liver tumour destruction and photoradiation therapy while the green wavelength,
inducing less aggressive effect on the surrounding tissue, seems more suitable for liver resection.
Lasers in Medical Science 02/1993; 8(1):27-32. · 2.00 Impact Factor
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ABSTRACT: The hepatic structures appearing during Carnegie stages 11-14 were analyzed in a series of 61 OFA rat embryos. The group of embryos (crown-rump length 2-7 mm, 10th-12th days after coitus) was composed of 52 specimens of the somite period (stages 11 and 12) and of 9 specimens of the postsomite period (stages 13 and 14). The embryos were submitted to serial histological sectioning with graphic reconstruction. Stage 11 was characterized by the development of the hepatic diverticulum induced by differential growth of the endodermal plate and fixed contact between the entoderm and endothelium lining the heart. Stage 12 presented obvious signs of cellular differentiation, the septum transversum giving the liver stroma and the hepatic diverticulum the epithelial trabecula. At stage 13 the epithelial cords enmeshed the stromal capillaries, while hepatocardiac veins drained the hepatic flow into the sinus venosus. Stage 14 was recognized by the presence and development of the hepatic lobes and the enlargement of vascular channels. The cystic bud was never observed. The identification of these features permits to precise the hepatic developmental staging in rats and to obtain accurate criteria for the characterization of the end of the somite period and the beginning of the postsomite period.
Acta Anatomica 02/1992; 144(1):45-50.
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ABSTRACT: Thirty six hepatic lesions (12-18 mm) of localized hyperthermia are induced in eleven pigs by means of a Nd-YAG laser. Laser shots of 80 W/10 sec. are transmitted through a stereotaxic handpiece coupled to a water cooling circulation protecting the optic fibre. The handpiece placement is performed through an ultrasound-guided trocar. The efficiency of the irradiation is visualized by immediate temperature increasing, by ultrasonographic imaging and by anatomical verifications from operating time to four months. The center of lesion initially occupied by coagulative necrosis is rapidly marginated by a gaining ground fibrosis. At long term a fibrotic network invades the scar and confirms healing free of complications. This ultrasonographically assisted technique is proposed for deep vaporisation of disseminated hepatic metastases.
Journal de Chirurgie 04/1988; 125(3):178-82. · 0.50 Impact Factor
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ABSTRACT: Thirty six deep focal hepatic lesions were induced in eleven piglets by means of an Nd-YAG laser. Laser shots of 80 W power and 10 s duration were used, the beam being transmitted through an echoguided stereotaxic handpiece. From day 0 to day 120, the animals underwent ultrasonographic and morphological controls. At lasering time an hyperechoic image--12-18 mm in diameter--appeared due to boiling of tissue water. During the twenty postoperative days the lesion core was an echo-free area due to tissue vaporization, surrounded by an hyperechoic ring of increasing fibrosis, containing neovascularization and biliary ductules, while the hypoechoic outer area represented the peripheral halo of edema. In the long term, hyperechoic structures--swollen fibrotic septa of homogeneous fibrotic network--invaded the lesion site confirming good healing.
Ultrasound in Medicine & Biology 02/1988; 14(4):287-91. · 2.29 Impact Factor
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ABSTRACT: Thirty-six deep hepatic lesions of localized photocoagulation were induced in 11 pigs by means of a neodymium-YAG laser. Laser applications of 80 W/10 sec (10.190 W/cm2) were transmitted through a handpiece coupled to a water-cooling circulation system to protect the quartz fiber and positioned through an echo-guided trocar. During irradiation, temperature was sufficient for vaporization up to 5 mm from the laser source and high enough for tumor cell kill at a 10-mm distance (54 degrees C/60 sec). Intraoperative ultrasound visualized increasing photocoagulation (12-18 mm), and further controls demonstrated an echo-free core of vaporization progressively covered by increasing fibrosis, well demarcated from normal parenchyma. Microscopy revealed central coagulative necrosis marginated from the third day by a growing fibrosis. By day 20 immunoblasts and mast cells were in profusion in the lesion border, and by day 120 a fibrotic network had invaded the scar and confirmed healing free of complication. This technique is proposed for deep vaporization of disseminated hepatic metastases.
Lasers in Surgery and Medicine 02/1988; 8(5):501-9. · 2.75 Impact Factor
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ABSTRACT: A new device, composed of a hand-piece (250 mm in length, and 5 mm in diameter) connected to a cooling circulation, has been
developed for the purpose of inducing focal coagulation deep in the liver, using a high-power Nd-YAG laser. The device, guiding
and protecting the optical fibre, withstands a power-setting of 100 W and allows means transmission of 80% during intrahepatic
application with an average power density of 10 200 W/cm2. Thirty-six lesions of 12–18 mm in diameter were made in 11 pigs under ultrasound control with laser shorts of 80 W mean
power output for 10s duration. Intrahepatic thermocouples showed a high rise in temperature in the core of the lesion, inducing
vaporization, while moderate hyperthermia (54.4%C/60s on average), high enough for tumour cell kill, was observed 1 cm from
the laser source. Immediately after irradiation ultrasound revealed a central echo-free lesion, well defined on day 3 by a
hyperechoic border and invaded from day 20 by internal hyperechoic enhancement. Anatomical examination demonstrated, on day
0, an excavated site of vaporization which was surround, from day 3 on wards, by an increasing ring of connective tissue,
and which was covered, from day 30 onwards, by a fibrotic network gaining ground towards the centre of the lesion. Good healing
free of complications, was observed after four months' follow-up. The technique is proposed for photocoagulation of deep metastases.
Lasers in Medical Science 01/1988; 3(1):111-117. · 2.00 Impact Factor
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ABSTRACT: A carotid end-to-end anastomosis was performed in 50 Wistar rats by means of a Coherent 900 argon laser. The vessel sealing was obtained with laser shots (average 19) of 300 mW power and 5-second duration, the beam being focused in a spot of 150 micron diameter (1,700 W/cm2). From day 0 to day 120, 25 specimens underwent semithin and electron microscopic examinations. The results showed the immediate sealing effect of the argon laser owing to protein denaturation and collagen fusion of the media and adventitia 100 micron in width. Re-endothelialization of the anastomotic line began by day 3, while myofibroblast proliferation was observed in the media by day 10. By day 20 media scar was still occupied by numerous myofibroblasts and surrounded by abundant collagen and elastic fibres. At long term the endothelial repair was complete and the anastomotic strength was assured by medial collagenous network.
Lasers in Surgery and Medicine 02/1987; 7(3):258-62. · 2.75 Impact Factor
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World Journal of Surgery 11/1986; 10(5):829-33. · 2.36 Impact Factor
