Comparative investigations of the effects of the neodymium:YAG laser at 1.06 microns and 1.32 microns on tissue

Analysis of laparoscopic laser liver resection in standardized porcine model

BACKGROUND

Hepatocellular carcinoma is a highly prevalent and lethal primary neoplasia of the liver and metastases of other malignancies affect most frequently the liver. Minimally invasive surgical approach for liver resections is advancing. Dissection of liver parenchyma by laparoscopic technique remains challenging and new technologies are in need. Therefore, we asked whether it is feasible to dissect liver tissue comparably in terms of speed and hemostasis with a non-contact 1.9-µm cw-laser device and whether there are differences in the postoperative healing process compared to a gold standard device (ultrasound aspirator) in an experimental model.

METHODS

Laparoscopic laser and ultrasound aspirator standardized partial liver resections were performed in seven pigs. Resection time, hemostasis time, and blood loss were evaluated. After at least 10 days, representative specimen of the resection areas was collected via re-laparoscopy and biopsy and side effects like hematoma, abscess, or bilioma were noted. Histologically, coagulation necrosis margin, granulation tissue zone, tissue fibrosis, and giant cell count were analyzed.

RESULTS

Laparoscopic laser liver resection was three times faster compared to the laparoscopic ultrasound aspirator. Blood loss was equal in both groups. No side effects like hematoma or bilioma occurred. Histologically, specimen showed the same expansion of coagulation necrosis zone and granulation tissue. Fibrotic scar could be determined in three cases in both groups, respectively. However, giant cell count was significant higher in the laser resection group.

CONCLUSIONS

The 1.9-µm cw-laser device enables a safe and fast liver resection in an experimental pig model compared to a gold standard (ultrasound aspirator) laparoscopic liver resection method. Wound healing is not interfered by laser liver resection.

The Nd:YAG LIMAX® 120 high-output laser: local effects and resection capacity on liver parenchyma

Various technical options are available for the resection of liver metastases, including CUSA, Ultracision, water-jet, and stapler devices. It has been shown that new generation high-output lasers are suitable for the resection of lung metastases. The goal of the present study was to evaluate the local effects of laser application on liver parenchyma. Livers of freshly slaughtered pigs (N = 6) were analyzed. The handheld laser was vertically held in the clamp of a hydraulic machine and sharply focused on the liver surface. The diode pumped Nd:YAG laser LIMAX® 120 (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) moved evenly over the liver surface at speeds of 5, 10, and 20 mm/s. Laser outputs of 60 and 120 W were applied at every speed. Histological sections (hematoxylin and eosin (HE) staining) of the extension area of vaporization and coagulation were analyzed by the use of the ImageJ software. In addition, the area of the liver parenchyma cut by the laser within 1 min was measured. The vaporized zone appeared wedge-shaped after histological section, whereas the area of coagulation appeared radiated outward. At 10 mm/s and 60 W, the mean vaporization of the measured zone was 356.6 ± 3.9 μm in length. Superficial coagulation was observed at 20 mm/s laser speed, without effective resection. At 120 W and 5 mm/s working speed, the mean vaporization zone and the average width of coagulation were largest with 664.6 ± 5.9 and 375.6 ± 2.3 μm, respectively. The laser output power of 120 W allowed resection of an area of 6 ± 0.4 cm(2) of liver parenchyma within 1 min. The Nd:YAG Laser LIMAX® 120 might be an effective tool for liver parenchyma dissection when it is applied at maximum output (120 W) and at a constant working speed of 5 mm/s.

Lobe-sparing resection of multiple pulmonary metastases with a new 1318-nm Nd:YAG laser--first 100 patients

BACKGROUND

A new 1318-nm Nd:YAG laser has been developed to utilize the second wavelength (1318 nm; 40 watt) to more precisely cut, coagulate, and seal lung tissue adjacent to pulmonary nodules. This laser allows a precise intraparenchymal nodulectomy with a 5-mm rim of tissue destruction and subsequent lung parenchymal reapproximation to avoid lobar distortion. Resection of multiple, bilateral, and recurrent tumors in the lung is facilitated by this laser technique.

METHODS

In 100 consecutive patients (53 men, mean age 60 years; 47 women, mean age 61 years) with various primaries (most commonly renal and colorectal), 155 laser resections were performed via anterolateral thoracotomy (staged 3 to 4 weeks, if bilateral) using a new 1318-nm Nd:YAG laser. All palpable and visible masses were removed with 2 to 3-mm visible tumor margins (plus a 5-mm rim of residual lung necrosis secondary to laser energy dispersal) if the tumor or residual lung ratio was judged favorable. No stapling devices or bioadhesives were used.

RESULTS

Six hundred thirty-two metastases (6.3 per patient, range 1 to 124) were resected. Despite 41% centrally located metastases, tumor resections were possible in 95% of patients with only a 5% lobectomy rate. Of the 100 patients, 67 were considered "curative" with complete metastasectomy by inspection and palpation, and 23 were judged incomplete from too extensive tumor or residual lung, miliary lung spread, or pleural studding. There were no associated mortalities and two complications, including bleeding (1) and a prolonged airleak (1), both treated conservatively. Follow-up was complete in all patients for a median of 26.5 months with clinic visits and chest computed tomographic scan every 3 to 6 months. Nine recurrences were detected and underwent reoperation. Overall survival in the completely resected "curative" group was 85% at 1 year, 71% at 2 years, 69% at 3 years, 57% at 4 years, and 32% at 5 years; in the completely resected "palliative" group, they were 70% at 1 year, 36% at 2 years, 12% at 3 years, and 0 at 4 years; in the incomplete group, they were 56% at 1 year, 30% at 2 years, and 0 at 3 years.

CONCLUSIONS

The new 1318-nm Nd:YAG laser is parenchyma-sparing, improves complete resection rates, and potentially improves survival with fewer required lobectomies.

Effects of Nd: and Ho:yttrium-aluminium-garnet lasers on human dentine fluid flow and dental pulp-chamber temperature in vitro

Dentine specimens were prepared from freshly extracted third molars and initial permeability measured. Each specimen was subjected to Nd:yttrium-aluminium-garnet (YAG) (1.06 or 1.32 microns wavelength) or Ho:YAG (2.10 microns wavelength) laser energy while temperatures in the pulp chambers were recorded. Permeability was again measured and the surfaces examined by scanning electron microscopy. Six crown segments were used for each laser variable and eight permeability measurements were taken before and eight after laser exposure, while temperature was recorded during treatment. All wavelengths reduced permeability but temperature rises were high enough to have caused pulpal damage, indicating that shorter treatment times and lower power settings may be necessary if used in vivo.

Myocardial temperatures during in vivo endocardial Nd:YAG laser irradiation

To determine safety and efficacy of neodymium:YAG laser irradiation of the endocardium, temperatures at both the epicardium and the endocardium were recorded for thermal damage evaluation. A total of 48 coagulation lesions were created at power settings of 20 and 30 W in 20 open chest dogs by transcatheter endocardial laser irradiation. Tissue temperatures were monitored by epicardial thermography (Tepi), and by endocardial thermocouples at the catheter tip (Tprox) and 4 mm below the endocardial surface (Tdist). In group I the optical fiber extended 1 mm from the catheter and irradiation times ranged from 3 to 60 sec. Tepi reached > or = 57 degrees after a weighted average of 5 sec of laser irradiation (n = 44). In group II the fiber was retracted 1 mm from the catheter tip, and irradiation times were 100 to 150 sec. Tepi reached > or = 57 degrees C after a weighted average of 30 sec (n = 4). Blood vessels were recognized as heat sinks until coagulation occurred. Lesion volume showed a proportional increase with total delivered energy. From the observed timeframes in epicardial temperature rise it is suggested that total direct light absorption at the epicardium was the main contribution to Tepi, and the Nd:YAG laser can efficiently create transmural lesions. The epicardial temperatures remained below 80 degrees C in combination with the constant movement of the epicardial wall suggested safety from thermal damage to the ambient organs.

Endoscopic palliation of tracheobronchial malignancies

The prognosis for tracheobronchial tumours remains poor. Most patients can be offered only palliation. When the main symptom is breathlessness or refractory haemoptysis from a large airway tumour endoscopic treatment may be very effective. Over the last decade most attention has focused on the neodymium YAG laser. This often produces dramatic effects but has some important limitations. In the last few years better techniques for stenting and intrabronchial radiotherapy (brachytherapy) have also been developed. This article discusses the range of techniques now available and aims to help clinicians decide which patients may benefit from referral to centres providing these techniques.

Application of pulsed and continuous wave 1.32 and 1.06 microns wavelengths of the Nd:YAG laser in the canine tracheobronchial tree: a comparative study

Previous investigations have shown good clinical potential for the use of the 1.32 microns wavelength Nd:YAG laser because its soft tissue absorption is better than that of the 1.06 microns wavelength Nd:YAG laser. The 1.32 microns wavelength Nd:YAG laser has an absorption coefficient in water that is 10 times higher than the 1.06 microns wavelength Nd:YAG laser. A comparative in vivo study of laser soft tissue effects was performed by using the 1.32 microns wavelength and the 1.06 microns wavelength Nd:YAG lasers in a pulsed wave (PW) mode and continuous wave (CW) mode using a non-contact endoscopic delivery system. A standard 5 mm mucosal lesion was made in the canine tracheobronchial tree down to the level of the perichondrium. Soft tissue and cartilage effects were examined by light and scanning electron microscopy, acutely, 1 week and 2 weeks after operation, and a comparison was made between the different laser modalities. To create similar lesions, higher energy was required when using the 1.06 microns wavelength Nd:YAG laser. Soft tissue injury was greater with the 1.06 microns wavelength in CW mode, and no cartilage damage occurred in the PW mode. Soft tissue and cartilage repair after 1 and 2 weeks was better with the 1.32 microns wavelength laser. In comparison, the CO2 laser and the contact Nd:YAG laser proved to be more precise cutting tools than the 1.32 microns wavelength or the 1.06 microns wavelength Nd:YAG lasers. Both Nd:YAG laser wavelengths were useful for coagulation and vaporization of tissues and blood vessels. More studies are needed to determine the effect of the new 1.32 microns wavelengths on endotracheal tumors.

Vasovasostomy in the murine vas deferens: comparison of the Nd:YAG laser at 1.06 microns and 1.318 microns to the CO2 laser

A comparison is made of laser anastomoses of the murine vas deferens at different energies with the neodymium (Nd):YAG laser at 1.06 micron and 1.318 micron and with the CO2 laser. A total of 28 welds were performed with a free-hand technique employing a 600-micron silicon fiber with the Nd:YAG and a hand piece with a 500-micron spot size for the CO2. After 6 weeks, all animals were sacrificed and the vasa evaluated for patency. Fifteen out of 28 controls repaired with microsurgical techniques were found to be patent; 4/10 vasa were patent with use of the Nd:YAG at 1.318 micron at laser energies of 300 mW and 500 mW. At 1.06 micron, only 1/4 anastomoses was patent at a power setting of 1 W. None of the anastomoses performed with the CO2 laser was patent. Histologic study revealed intense fibrosis in all the lasered vasa, with sperm granuloma formation associated with most anastomoses. Although this is a preliminary study, it appears that the Nd:YAG laser at 1.318 micron and a power setting of 300-500 mW provides patency rates superior to the Nd:YAG at 1.06 micron and to the CO2 lasers and is equivalent to standard micro-surgical techniques in the murine vas deferens.

Laser-induced alteration of collagen substructure allows microsurgical tissue welding

Tissue welding is a potentially important biomedical application of laser technology. The structural alterations basic to this phenomenon were studied in experimental repair of lesions of the rat carotid artery and sciatic nerve. A modified neodymiumdoped yttrium-aluminum-garnet laser operating at a wavelength of 1.319 micrometers was used in conjunction with conventional suture techniques. Histological and fine-structural analysis revealed a homogenizing change in collagen with interdigitation of altered individual fibrils that appeared to be the structural basis of the welding effect.