The use of the Nd-YAG and the CO2 laser in neurosurgery

Summary Over the last 3 years 120 patients have been operated on using laser techniques. This technique was chosen where technical difficulties were anticipated due to the size, the vascular supply or the localization of the process. Although the use of laser technique requires experimental work, before it can be applied clinically some distinct advantages could be demonstrated when compared with the use of the bipolar cautery.Due to its shrinking effect the laser beam is target oriented and makes the surgical procedure safe without the use of additional instruments. The Nd-YAG laser was preferred in tumors with a rich vascular supply. Thus there was a definitely decreased need for blood transfusions in patients operated on with the laser. Even those parts of the tumors that can not easily be reached, using conventional techniques can now be eliminated by laser irradiation.The variable distance between the handpiece of the laser instrument and the target organ allows a pin point as well as a more diffuse irradiation. Since it is not necessary to touch the tissue, laser techniques are particularly useful in critical areas, e. g. close to the brainstem or the spinal cord, because they make it unnecessary to touch the tissue.The question as to whether the use of laser technique will reduce the rate of recurrent tumor growth needs further studies based on longer follow-up periods. Further technical improvements are needed to make the laser device a true microinstrument. Finally a combination of both laser types — that is the Nd-YAG laser for coagulation and the CO₂ laser for cutting -might be a definite advantage.Dedicated to Prof. Dr. Dr. h. c. K. J. Zülch on occasion of his 70th birthday.     

The use of the Nd-YAG laser in neurosurgery

Whereas the focused CO2 laser may be used as a cutting instrument in less vascularized tissue with limited trauma to the surrounding tissue, use of the defocused Nd-YAG laser results in homogeneous coagulation with an energy-dependent depth effect. Thus, residual tumor tissue may be cauterized selectively with a depth effect which can be predicted with satisfactory precision. Tumor shrinkage and demarcation based on different absorption properties facilitates dissection and, moreover, allows the preservation of healthy tissue. The excellent coagulating properties of the Nd-YAG laser render it especially effective in cases of highly vascularized meningeal tumors.     

连续Nd:YAG激光治疗皮肤血管瘤的疗效观察

目的观察连续Nd:YAG激光(1064nm)治疗皮肤血管瘤的疗效。方法根据不同血管瘤的类型,选用适当的照射功率、照射时间和照射方式。蜘蛛痣、化脓性肉芽肿和较浅的草莓状血管瘤选用扫描式照射,输出功率为15~30W,直到病灶变为灰白色或轻微凹陷;较深的海绵状血管瘤和混合型血管瘤将光纤插入瘤体内并作扇形推进照射,输出功率为30~50W,每个方向照射2~3s,直到瘤体凹陷变平。结果139例患者经过1~5次治疗后,病灶消失,无明显的瘢痕形成。其中草莓状血管瘤59例,治愈39例,有效19例,无效1例;海绵状血管瘤28例,治愈8例,有效19例,无效1例;蜘蛛痣25例,全部治愈;化脓性肉芽肿17例,全部治愈;混合型血管瘤10例,治愈1例,有效6例,无效3例。随访2年,无复发。结论连续Nd:YAG激光是治疗除鲜红斑痣外各种血管瘤的一种有效方法。     

The role of pulse length in limiting distant damage to vascular tissue caused by the Nd-YAG laser

The total damage caused by equivalent doses of energy given to human cadaver vascular tissue over the same time scale from three Nd-YAG lasers of different pulse lengths is quantified. The continuous wave (c.w.) laser produces vacuolation and coagulation around a vaporized crater; the 100 μs pulsed laser produces less surrounding damage and the 10 ns pulsed laser none at all. The areas of damage in five craters made with 10 J energy were measured from histology slides using a digitising platten, and it was found that in each case the total amount of damage was the same, even though the depth of the craters made varied. The dose response for vaporization of the 10 ns pulsed laser was the greatest at 35 μm/J and that of the c.w. laser was least at 8 μm/J. A pulse length of 100 μs may not be the optimum for limiting surrounding tissue damage during laser angioplasty but it produces much less damage than a c.w. laser and unlike the 10 ns pulses is easily transmissible down an optical fibre.     

Nd-YAG laser ablation of arteriosclerotic obstructions: Clinical long-term results in femoropopliteal artery occlusions

Laser recanalization of peripheral artery occlusions was performed in 338 patients. A continuous wave Nd-YAG laser was used in combination with sapphire-probe laser catheters. The initial recanalization rate was 85%. Complications such as dissections, perforations, emboli and spasm were observed in 14%. The cumulative patency rate after 3 years was 48%.     

Effects of super-pulsed Nd-YAG laser on arterial tissue: comparison with continuous wave

The effects of a super-pulsed Nd-YAG laser at 1.32 μm wavelength on normal or atherosclerotic human arterial tissue were evaluated and compared with those obtained with continuous wave. One joule per pulse was delivered through a 0.2 mm optical fibre with a pulse width of 10 ms at 10 Hz (super-pulse), or 10 W (10 J) were delivered at continuous wave in saline or blood. Ten joules were delivered with super-pulse or continuous wave for each tissue specimen. The aortic specimens were lased either by continuous wave or super-pulse. At super-pulse mode, ablation efficiency (mm³ J⁻¹) was 0.0149±0.0044 for normal tissue in saline, 0.0148±0.0043 for atheroma in saline, 0.0138±0.0062 for normal tissue in blood, and 0.0146±0.0049 for atheroma in blood. There was no significant difference between the groups. At continuous wave mode, ablation efficiency was 0.0507±0.0299 for atheroma in blood (p<0.001 vs super-pulse). However, extensive charring was observed with continuous wave lasing (41% with continuous against 14% with pulsed mode,p<0.001). Heavily calcified plaques were also ablated at 1.5 J per pulse and 15 W (continuous wave), resulting in extensive charring with continuous wave (77% vs 18% with super-pulse,p<0.01). In conclusion, at super-pulse mode, 1.32 μm Nd-YAG laser has neither the selectivity for atheroma nor influence of blood, thermal injury induced by super-pulse is less than that induced by continuous wave (cw), calcified plaques can be ablated by super-pulse, and super-pulsed Nd-YAG laser angioplasty is safer to use than continuous wave.     

Percutaneous peripheral laser angioplasty with a pulsed Nd-YAG laser and sapphire tips

Percutaneous transluminal laser angioplasty with a pulsed Nd-YAG laser (1064 nm wavelength, 100s pulse duration, up to 0.4 J per pulse, 10 Hz repetition rate) coupled to optical fibres with sapphire tips of 1.8 and 2.2 mm diameter was performed under experimental conditions and then in 30 chronic occlusions of femoral and popliteal arteries in 22 patients.The experimental study in 11 human cadaverous arteries revealed that this laser system was effective in the recanalization of seven femoropopliteal occlusions, but the relative rigidity of the sapphire-tipped contact probe prevented its access to two infrapopliteal vessels. Two perforations occurred after the recanalization of 18 and 15 cm, respectively.Clinically the procedure was successful in 17 out of 25 sessions (68%). The probe formed a primary channel of at least 2.0 mm width which was further dilated by conventional balloon catheter. Ankle/brachial systolic pressure index (ABPI) increased from 0.43±0.13 to 0.79±0.21 after the procedure. In eight cases complications occurred. Two reocclusions were treated by Streptokinase infusion, two procedures were repeated 2 months later, one patient was referred to elective bypass surgery, and three patients were treated conservatively. Six patients were followed-up for more than 6 months. In one patient claudication of 400 m reappeared. ABPI showed a moderate decrease from 0.84±0.20 to 0.69±0.19.These first results are encouraging and it is likely that this method could become an important adjunct to balloon angioplasty.     

Fibrescopic Nd-YAG laser treatment of superficial bladder tumours in outpatients

The neodymium-YAG (Nd-YAG) laser has been used via a flexible cystoscope to treat 48 superficial bladder tumours in 39 patients. The procedure can usually be performed with minimal discomfort under topical urethral anaesthesia alone or supplemented by a small dose of benzodiazepine. It is therefore suitable for use in ambulant outpatients. Local tumour clearance can be expected when this method is used. The savings in hospital admission costs and general anaesthesia may justify the comparatively high capital cost of the laser.     

Nd-YAG laser for general surgery

We report here our clinical experiences with Nd-YAG laser on general surgery, and evaluate the results of this procedure. From December 1979 to December 1981, we applied Nd-YAG laser to various operations as a hemostatic and cutting tool. For hemostasis, we used conventional quartz fiber which was covered with sterile tube, and hemostatic efficacy was examined especially in the subcutaneous bleeding and the bleeding from solid organs. For cutting, we used special devices, ie, Medilas YAG surgical probe (noncontact-type probe), and a laser blade (contact-type probe), and performed four liver resections. It is concluded that the hemostatic efficacy of Nd-YAG laser to various bleeders was proved in general surgical procedures, and furthermore this laser can cut tissue if we utilize these devices. When comparing these two devices, we would prefer the contact-type probe.     

Hysteroscopic treatment of uterine bleeding with the Nd-YAG laser

This preliminary study involves 45 patients, referred to us for hysterectomy, who complained of uterine bleeding that was resistant to conventional treatment. Prior to surgery, these patients had a diagnostic hysteroscopy which showed that the bleeding was due to submucosal fibroids, to intrauterine or cervical polyps, either alone or in association with adenomyosis, or to adenomyosis alone. These patients were treated as outpatients with the Nd-YAG laser, by using paracervical anaesthesia. In 80%, the menstrual cycle has returned to normal after a short follow-up (four cycles). Three patients required hysterectomy because hysteroscopy was impossible owing to multiple fibroids. Two patients have been lost to follow-up observations. In addition, there was a beneficial result on secondary dysmenorrhoea. Wherever necessary, uterine septa and synechiae were divided. Between six and 10 weeks after treatment, a follow-up hysteroscopy was performed. This confirmed that there was no recurrence of the underlying lesion, that the treated areas were scarred and that the endometrium in these areas was functional. Longer follow-up is necessary to assess the precise proportion of hysterectomies that can be avoided by using this technique.     

Endoscopic Nd-YAG laser therapy of gastric polyposis

Thirteen patients with gastric polyposis (113 polyps) were treated by endoscopic Nd-YAG laser irradiation. Among them there were five cases with adenomas, six with hyperplastic polyps and two with inflammatory polyps. Ninety-six polyps were <1 cm, 13 polyps were 1 cm, and four polyps were 2 cm. In the patient who had the largest number of lesions, 22 polyps were found at endoscopic examination. All but two patients were regularly followed up endoscopically for 2–5 years after treatment and showed no sign of recurrence. Mild bleeding occurred in three cases. No perforation or any other serious complications occurred. The results were encouraging. It is concluded that endoscopic Nd-YAG laser ablation of gastric polyposis is effective, simple to perform, safe and deserves recommendation.     

The bactericidal activity of pulsed Nd-YAG laser radiation in vitro

Pulsed Nd-YAG laser irradiation of bacteria has been suggested as a possible means of treating contaminated intra-oral sites although relatively few studies have been conducted. In this investigation, the antimicrobial activity of a pulsed Nd-YAG laser was assessed in vitro for a range of oral bacteria using several pulse energies and exposure durations. Pure cultures of each organism were lased in saline suspensions followed by standard colony counting techniques for test and control samples. Microbial inhibition was found to be organism-dependent and varied with energy dose and pulse energy. For all nine test species 120-mJ laser pulses proved more efficient than 80-mJ pulses, with 99.9% kills compared with around 90% kills after exposure to 1800 pulses. These killing activity levels compare favourably with those achieved with other lasers in vitro.     

Lesser curve photoseromyolysis with the Nd-YAG laser

We confirmed in animal experiments that the Nd-YAG laser can be used to replace conventional surgical techniques for duodenal ulcer disease—lesser curve seromyotomy, as proposed by Taylor. The experiments suggest that the operative time may be halved using the laser. We confirmed that the ideal laser parameters for this technique were: wavelength 1319nm and power output 15 W, using a contact sapphire tip, with repeated pulses of 0.25 s. Histological studies were performed to show the effect of the laser on the stomach wall and on the vagus nerve. It was shown that the pH was elevated from 1.3 to 6.9 or even higher.The first successful operation on man with this technique was performed in May 1989.     

Laser coagulation zones induced with the Nd-YAG laser in the liver

Laser-induced interstitial thermotherapy (LITT) has become a method to treat different types of tumours. To increase the effectiveness of LITT in liver tissue, a new thermo-controlled application system was developed. In in vivo experiments in five pigs, ellipsoidal coagulation regions (3 and 5 cm diameter) were found in the liver within 10 min, which corresponds to a volume of about 20 cm3. In real time, the increasing coagulation zone, which appeared as a hyperechogenic halo, could be observed via ultrasound. The power of the laser source during laser treatment was controlled dynamically via thermosensors. Macroscopically and microscopically, the coagulation zones showed well-demarcated borders of the coagulation lesions, and the surrounding tissue appeared vital. The reparative reaction after irradiation was early fibrosis. For 4 weeks, the surrounding scar capsule, containing fibrocytes, biliary ductules and collagen fibres, enlarged. As a result, the coagulation necrosis became more and more fragmented between collagen fibres, and was largely resorbed. The absence of complications in these pig experiments suggests that this technique of dynamic laser light application is safe and useful for therapy of metastases which are not resectable.     

Extent of thermal penetration of Nd-YAG laser — histological considerations

Summary The extent of thermal penetration of Nd-YAG laser was studied histologically. The material was obtained from seven cases of various types of intracranial and extracranial tumours and normal temporal muscle obtained at operation. After irradiation of the tumour surface with the laser, the tumours were removed and depth and width of pathological changes caused by heat were studied. Histologically, materials consisted of a vaporized surface, carbonized, vesicular, necrotic, oedematous layers and surrounding intact brain tumour tissue. There was a direct relationship between the thermal effect and the irradiated thermal energy (watt × exposure time × pulse number). The results showed that the thermal effect was limited to a depth of 6 to 10 mm from the irradiated surface when irradiated 4 times at the power of 90 watts for 2 seconds.     

Histological studies of myocardium zones irradiated with Nd-YAG laser

Histological investigation of the dog's myocardium performed 7 and 25 days after irradiation with different doses of Nd-YAG laser show that the damage zone has the shape of a hollow sphere with minor changes in cardiomyocytes in the central part of the sphere. The small blood vessels in the irradiated zone remained undamaged as well. A tentative explanation of the physical process that leads to this type of coagulation zone is given.     

Present status of laser neurosurgery

A three-fold approach to the status of laser neurosurgery was taken: 1) Questionnaire to Program Directors for neurosurgery training in the United States and Canada; 2) an analysis of titles in the preliminary neurosurgery program of the Fifth International Congress of Neurosurgery; 3) A literature survey covering the last 3 years of publication. The results showed increasing interest in the use of lasers in neurosurgery, especially for neoplasms in brain and spinal canal. The CO2 laser still dominates the field but Neodymium YAG is also finding wide use. The author comments on directions that laser neurosurgery may take in the future. Special emphasis is made on new applications combining advanced technologies, including CAT scanning, ultrasonography, stereotaxic techniques, and computer control.     

Buschke-Lowenstein tumour of the penis. Treatment with Nd-YAG laser

A case of Buschke-Lowenstein tumour of the penis successfully treated with Nd-YAG laser is described. A 25-year-old male patient developed a fast growing, warty and vegetating tumour. Eight months before admission, Podophyllin and electrosurgery were unsuccessful. After laser treatment, the clinical, histological and functional results were completely satisfactory.     

Contact Nd-YAG laser in mastectomy and axillary evacuation: a prospective randomized study

Thirty patients underwent modified mastectomy for breast cancer. They were allocated into three operation groups. Group A (n=10) underwent conventional operation, group B (n=10) contact Nd-YAG laser operation, and group C (n=10) conventional mastectomy with laser evacuation of the axillary lymph nodes. The operation with contact Nd-YAG laser was slower (p<0.05) than the conventional operation. Laser significantly reduced pre-operative bleeding (p<0.01), but there were post-operative wound seromas in 50% of the cases. No other complications occurred. It is concluded that contact Nd-YAG laser is safe and reduces bleeding by sealing small vessels. However, there seems to be a risk for post-operative wound seromas particularly after radical axillary lymph node dissection.     

Low power interstitial Nd-YAG laser photocoagulation in normal rabbit brain

The safe, effective, clinical application of interstitial laser irradiation to destroy brain tumour tissue requires a knowledge of the relation of the extent of laser-induced (thermal) necrosis to the delivered laser power and total energy, and to time post-irradiation. We have conducted experiments to determine these relationships in normal rabbit brain. Irradiation by a Nd-YAG laser (1064 nm), at powers of 0.5–3.0 W and exposures of 200–1333 s produced well-defined necrotic lesions whose size increased with both the power and the total energy delivered. Lesions of 6 mm diameter made by 0.75 W for 1000s were well tolerated by animals allowed to recover from anaesthesia following irradiation. The diameter of the lesion was greatest at 48 h after irradiation. Following evolution of a characteristic healing response to necrosis in brain, the residual damage at 4 weeks was no greater in volume than that of the acute lesion. The results suggest that low power interstitial Nd-YAG laser photocoagulation in brain can be reliably and safely effected.