Laser Surgery
Laser surgery is a medical procedure in which a focused laser beam is utilized as a precision tool for cutting, excising, or otherwise manipulating tissues. Depending on the intended purpose of the surgery, the specific wavelength and type of laser is used.
Advantages of laser surgery
- Precision and Accuracy: Laser surgery is unmatched in its precision. A laser beam can be focused in a spot diameter of less than one micron, and remove tissue just a fraction of a micron in depth per each pulse. It also can target specific tissues without causing damage to surrounding areas. This precision is particularly valuable in delicate or intricate surgeries.
- Minimally Invasive Procedures: Quite often, laser surgery can be used as a minimally invasive alternative to traditional surgical techniques. This can result in smaller incisions, reduced bleeding, and shorter recovery times for patients compared to traditional surgical methods. In some cases, laser surgery is the only option, such as to remove tumors or diseased brain tissue that is too deep inside the brain to safely access it using other neurosurgical methods.
- Coagulation and Hemostasis: Lasers generally provide a bloodless surgical field due to their effective coagulating blood vessels. The cause of hemostasis depends on the wavelengths of the laser used in the surgery. If the main chromophore is hemoglobin, which is the case of red and green lasers the coagulation of blood is responsible for clogging the disrupted blood vessels. On the other hand, if the laser wavelength is absorbed by water (CO2-laser, Nd:YAG, diode lasers operating at 980nm, 1470nm, and 1950nm) the contraction of the vascular wall collagen results in constriction of the vessel and hemostasis. Laser-induced hemostasis helps to control bleeding and reduce the need for sutures or staples.
- Selectivity: A unique property of a laser scalpel is its potential for selectively targeting a particular lesion without affecting the surrounding tissue. For example, an inflamed sebaceous gland that causes acne can be destroyed by laser light with a wavelength that is strongly absorbed by fat, without any collateral damage to the skin.
- Faster healing: due to less extensive collateral damage and the potential benefits of photobiomodulation.
What types of surgeries use lasers?
Ophthalmology
Ophtalmology has been the vanguard of using lasers for surgery. The most prominent applications, with millions of surgeries performed annually, are cataract surgery, and refractive eye surgery. The preferred today technology for cataract surgery utilizes infrared femtosecond lasers. Refractive eye surgery, of which LASIK is the best known and most commonly performed technology for correcting vision problems utilizes excimer lasers. Both lasers have the ability to remove a tiny amount of tissue per pulse (a fraction of a micron), thus providing an outstanding degree of accuracy without collateral damage to the surrounding tissue. Computer-controlled laser scanning along with eye movement control systems that provide feedback to the laser scan allow for complex and extremely precise ablation patterns to be performed with excellent safety, efficacy, and predictability of clinical outcomes of the surgery.
Urology.
Lasers have become an integral part of the modern urologic armamentarium, which is constantly evolving. It is more efficient than conventional treatments, and often safer interventions in patients with comorbidities. The main areas of applications include lithotripsy, benign prostatic hyperplasia (BPH), and bladder cancer.
Laser lithotripsy yields effective stone ablation for various stone densities, locations, and compositions, providing better outcomes than pneumatic lithotripsy with a significant reduction in surgery time and higher stone-free rates. Ho:YAG laser has become the instrument of choice for this procedure. The recent addition of Moses technology to Ho:YAG devices has substantially increased the efficacy of lithotripsy.
However, it appears that Thulium YAG, and particularly Thulium Fiber Laser are poised to replace Ho:YAG in laser lithotripsy. They provide fine and fast fragmenting and dusting capabilities that disintegrate all types of stones into particles of less than 100 µm in size. They also provide significantly reduced retropulsion during fragmentation.
Benign prostatic hyperplasia (BPH) has been a battlefield for laser technologies since the early 1980s. Multiple devices and technologies have been proposed including ablation, vaporization, resection, and endoscopic enucleation (EEP). However, the current consensus is that EEP is a preferred treatment for BPH of any size. Many lasers have shown their efficacy in benign prostatic hyperplasia (BPH) surgery, but unlike lithotripsy, there is no one “Gold standard” for this procedure. However, recently developed thulium-fiber lasers (TFL), promise not only to establish themselves as a device of choice for BPH surgery but also to become multipurpose tools, capable of laparoscopy and lithotripsy. The main feature of TFL distinguishing it from Ho:YAG is that it emits light with the wavelength of 1.94 mm, which corresponds to the peak of water absorption resulting in a penetration depth of only 0.15 mm. However, the dramatic improvement in penetration depth with TFL is not the only advantage of this device. Unlike Ho:YAG laser which operates only in a pulsed mode, TFL can work in two modes, superpulse mode for lithotripsy and quasicontinuous mode (QCW) able to effectively coagulate for soft tissues.
Despite the evident success of laser technologies in treating benign prostatic hyperplasia, this triumph has not translated into a success story for prostate cancer (PC).
Common treatments for PC, such as radical prostatectomy and external radiation therapy, indeed offer excellent long-term efficacy. However, within 5 years of treatment, patients often experience treatment-related complications and side effects, including urinary incontinence, erectile dysfunction, and bowel urgency. These issues significantly impact the quality of life.
In light of these challenges, there is a pressing need for alternative technologies that can enhance clinical outcomes. The primary challenge of laser ablation appears in the obscuration of the laparoscopy operating field due to smoke formation during laser surgery. However, a promising solution has emerged in the form of MRI imaging-guided focal laser ablation for the treatment of clinically localized prostate cancer. This cutting-edge technology offers a precise and targeted approach, allowing for the removal of cancerous tissue while minimizing damage to surrounding healthy structures. Consequently, this approach holds the potential to reduce treatment-related morbidity significantly. Clinical studies have utilized a 30W diode laser operating at 980nm with MRI guidance, showcasing encouraging results. However, it is worth noting that the Tm fiber laser is emerging as a viable alternative.
Laser transurethral resection of Bladder Tumor using Ho:YAG or thulium Tm:YAG, seems efficient, and safe. Numerous studies claim that laser en bloc resection is superior to conventional technology in terms of complications, quicker catheter removal, decreased hospital stay, and recurrence rate. Moreover, it was demonstrated that laser ablation of bladder tumors can be performed under local anesthesia, reducing the treatment cost stemming from general anesthesia and hospital stays. The introduction of TFL promises further improvements, as its QCW operation does not produce steam bubbles that damage tissue and obscure the operation field. However, the most interesting device technology development is in diode lasers. Diode lasers operating at 980nm, 1470nm and 1940nm efficiently vaporize tissue and provide effective hemostasis on par with the TFL. And their cost is significantly lower, making them affordable to many clinics.
Table 1. Laser used in Urology.
Laser | Wavelength | Mode of action | Absorption coef in water 1/cm | Absorption coef in blood 1/cm | Penetration depth, μm | Technology |
Nd:YAG | 1.06 | CW | 0.12 | 5 | 10 | Ablation/vaporization, coagulation, lithotripsy |
Ho:YAG | 2.1 | Pulsed | 26 | 0.4 | Ablation/vaporization, resection, enucleation, lithotripsy | |
Tm:YAG | 2.01 | CW | 52 | 0.2 | Ablation/vaporization, resection, enucleation | |
Green KTP:YAG LBO:YAG | 0.53 | CW | 266 | 0.8 | Ablation/vaporization, enucleation | |
0.98 | CW and pulses | 0.43 | 2 | 0.5-5 | Ablation/vaporization | |
1.47 | CW and pulses | 7.2 | 2.5 | 0.5-5 | Ablation/vaporization | |
DL 1940 | 1.94 | CW and pulses | 114 | 0.15 | resection, enucleation | |
Tm fiber | 1.94 | Pulsed and QCW | 114 | 0.15 | resection, enucleation, lithotripsy | |
DL blue | 0.45 | CW and pulses | 340 | 0.7-0.9 | Ablation/vaporization |
Oncology.
Lasers have been routinely used in oncology for at least 50 years. While initially they were applied in excisional procedures, they are hardly better in these applications than an old cold scalpel. The advantages of lasers in oncology come from their ability to produce the effects that cannot be achieved otherwise: photo-chemical effects (PDT), hyperthermia, and ablation. Another area of laser application in oncology is palliative surgery, which may not treat the cancer but makes the patient feel or function better.
Photodynamic therapy is a method of tumor destruction in which a compound with preferential affinity to cancerous cells is administered to a patient systemically – usually intravenously. Then laser light is used to “activate” this compound. When the compound absorbs light of a particular wavelength it releases toxic oxygen radicals, which in turn destroys malignant cells without detrimental effect on the healthy cells. Argon lasers were initially used in PDT, but currently, they are being universally replaced by diode lasers. Similar ideas are behind the use of nanoparticles in the photothermal ablation of cancer. Gold-based nanoparticles strongly absorb light in the therapeutic window of tissue absorption between 600nm and 900nm. If the nanoparticles are selectively accumulated in the tumor, the light will be selectively absorbed by the tumor causing a local increase in the temperature and death of malignant cells. Unlike PDT, which requires a particular laser wavelength for activating the photosensitive compound, any near-infrared laser can be employed for heating gold nanoparticles. Still, diode lasers are the best for this purpose.
Laser interstitial thermal therapy (LITT) is a minimally invasive procedure that uses laser light to induce hyperthermia of tumor cells. LITT is performed by implanting an optical fiber into the tumor and elevating its temperature above the protein denaturation threshold (42C). In general, LITT is particularly well suited for treating deep-seated or otherwise difficult-to-access lesions, wherever an optical fiber can be introduced percutaneously into a tumor. This technology has been applied for treating primary and metastatic tumors in the liver, pancreas, breast thyroid nodules, uterus, and brain. Almost exclusively diode and Nd:YAG lasers were used for these purposes.
The biggest disadvantage of laser-induced hyperthermia is the lack of visual control during the procedure, and the inability to control tissue temperature in-situ, making the extent of thermal damage uncertain. However, the recent resurgence of interest in this technology is sparked by advances in intraoperative magnetic resonance imaging (MRI) techniques that now enable real-time thermometry using T1-weighted 2D images obtained during the procedure. Currently, there are two laser systems approved by the FDA for LITT. One uses a 12-Watt 1064 nm Nd:YAG laser and the other uses a 15-Watt 980 nm diode laser. As laser diode technology is superior and cheaper in this application, diode laser-based systems will likely dominate the field.
Laser ablation is an alternative to the traditional resectional surgery. Among the new minimally invasive methods proposed in recent years, laser ablation is shown to possess several advantages, in particular, the ability to define a precisely controlled, homogeneous, and reproducible pattern of ablation. Moreover, laser ablation can be performed in deep-lying organs by delivering laser energy via a small and flexible optical fiber. Unlike LITT, laser ablation is performed using high-power lasers operating in pulsed mode. High energy laser pulse is absorbed in a small volume of tissue raising cell water temperature above boiling point, thus instantly vaporizing it. As the volume of water vapors is significantly larger than the water, the vapor pressure ruptures the cell membrane and ejects vapors and cellular structure debris (See figure below).
Despite claims by some laser surgical equipment manufacturers that laser surgery does not induce any collateral damage, inevitably the margins will be affected by the laser energy. There will be heat transfer from the ablated volume inside the remaining tissue, which will experience elevated temperatures. The layer of coagulation will line up the incision. This layer is responsible for the hemostatic effect of laser surgery. Outside the coagulation layer, there is also a layer of tissue that has been subjected to hyperthermia. The thickness of these layers depends on the wavelength, power, pulse duration, and spot size. It is usually in the range of several tens of microns to 100s of microns. Another collateral effect of laser surgery is carbonization. Cell structures consist of organic molecules with a lot of carbon atoms. The ejected material consists of water vapors and debris of these organic molecules. There is not enough oxygen in the affected volume to convert all carbon into volatile carbon dioxide, therefore some of the carbon is ejected as smoke, and a carbon-rich deposit forms on the incision boundary (carbonization). Formation of this carbon crust can help to seal blood vessels, but it is detrimental to wound healing.
Any powerful enough laser that emits light at a wavelength strongly absorbed by water can be used for surgery. Currently, CO2-laser, Diode-lasers operating at 980nm, 1470nm, and 1940nm, Ho:YAG, Tm:YAG, and TFL are successfully employed in surgery for ablation of soft tissues, but it is more than likely that in the future only diode lasers and Thulium fiber lasers will remain.
While the ablation mechanism described previously utilizes the absorption of light by water, this is not the only chromophore (a molecule that absorbs light) that can be targeted by laser light and cause tissue ablation. Melanin and proteins were utilized by visible light lasers (excimer laser, argon laser, and recently blue diode-lasers) for this purpose.
Oral and maxillofacial.
Laser technology has become the standard of care for many oral and maxillofacial surgical (OMS) procedures. Lasers are not only superior to conventional cutting tools used in OMS but also provide multiple opportunities for the development of novel procedures. Vast clinical experience supports their safety, reliability, and efficacy in surgical applications. Lasers have been used in surgical procedures involving both the hard and soft tissues of the oral cavity.
Soft Tissue Clinical Applications. For many intraoral soft tissue surgical procedures, the laser is a viable alternative to the scalpel. The main advantages of laser are:
- Ability to provide hemostasis, thus reducing hemorrhaging (resulting in a clear operative field), no need for sutures, and reduced swelling;
- Better spatial control of desired tissue changes, which enhances the precision of surgery. The result is smaller wounds compared to a scalpel allowing for faster tissue healing and decreased scarring.
The mentioned advantages are presumed to decrease postoperative pain. The most popular and effective lasers nowadays for soft tissue procedures are CO2 and Diode lasers. Lasers are ubiquitous in soft tissue procedures such as gingivectomy, frenectomy, incisional and excisional biopsies, removal of diseased tissue around the implants, removal of granulation tissue, etc.
Snoring and Apnea. For nearly three decades, uvulopalatoplasty has served as a treatment option for snoring and obstructive sleep apnea. This procedure involves progressively widening the oropharynx through “successive vaporizations of the vibrating soft palate, wide posterior tonsil pillars, and redundant posterior pharyngeal mucosa” to prevent obstructions during sleep.
Laser-assisted uvulopalatoplasty presents several advantages over traditional uvulopalatoplasty, such as avoiding the need for hospitalization and general anesthesia. The use of the carbon dioxide CO2-laser has shown promising short-term results, with a clinical success rate ranging from 70% to 95%. However, long-term follow-up studies have yielded conflicting results regarding the durability of these outcomes, suggesting a decline over time and the occurrence of delayed complications.
A recent advancement involves a non-ablative procedure utilizing the Er: YAG laser, emitting light at a wavelength of 2,940 nm with minimal depth of penetration. This method proves to be an effective means of soft palate tightening without the postoperative complications associated with other types of ablative lasers.
Dermatology
There is probably no laser that was not tried for some cosmetic procedures – we want to look good. Laser surgery is frequently used in dermatology for cosmetic procedures, such as laser skin resurfacing to address wrinkles, scars, and pigmentation issues. It is also used for the removal of skin lesions, tattoos, and birthmarks. Recently, lasers were also applied to body contouring and acne treatment.
Skin rejuvenation. Laser resurfacing is a cosmetic procedure employing a laser to enhance the skin’s appearance or address minor facial imperfections. During the process, the laser eliminates the thin outer layer of skin known as the epidermis and raises the temperature of the underlying skin, the dermis, thereby prompting the production of collagen—a protein that enhances skin firmness and texture. As the epidermis heals and regenerates, the treated area manifests a smoother and tighter appearance.
While carbon dioxide (CO2) lasers are commonly used for skin resurfacing, the Er:YAG laser is favored for its reduced side effects and quicker recovery. Recently, Tm-fiber lasers and long-wavelength 1940nm diode lasers have also been employed.
The extended post-operative recovery period, lasting at least a week, prompted the exploration of an alternative approach known as non-ablative resurfacing. In this technique, lasers are employed to induce uniform thermal damage to the dermis while safeguarding the epidermis through cooling. This method stimulates collagen growth, presenting a less aggressive alternative to ablative lasers and resulting in a shorter recovery time. While the outcomes are not as pronounced as those achieved with ablative procedures, non-ablative resurfacing is particularly effective for addressing mild-to-moderate photodamage and early signs of skin aging. It works to enhance skin pigmentation and texture without causing physical injury to the skin surface.
Advancements in skin resurfacing include the use of fractionated lasers, which deliver energy through fractional photothermolysis. In this process, an array of small laser beams generates numerous microscopic areas of thermal injury, ranging from 100-400 um in width and 300-700 um in depth. These areas, termed microscopic treatment zones, consist of columns of thermal damage surrounded by sections of normal skin, serving as reservoirs of healthy tissue and stem cells for effective remodeling and rejuvenation. This method ensures safe and swift healing.
Vascular lesions contain oxygenated hemoglobin, which strongly absorbs visible light at 418, 542 and 577 nm. This allows the use of lasers that operate at close wavelengths aiming to destroy the target cells and not to harm the surrounding tissue. Many different lasers have been used to treat these conditions including argon, APTD, KTP, krypton, copper vapor, copper bromide, pulsed dye lasers, diode-lasers, and Nd:YAG. However, the pulsed dye laser at a wavelength of 585nm has become the laser of choice for most vascular lesions because of its superior clinical efficacy. It is successfully used for treating a variety of vascular lesions including superficial vascular malformations (port-wine stains), telangiectases, haemangiomas, and pyogenic granulomas. The 577nm wavelength that appears to produce the best clinical outcomes was for a long time quite challenging to obtain in laser physics. The pulsed dye lasers that output light at a close wavelength of 585nm tend to be complex and have several shortcomings such as the use of toxic solvents and the relatively short lifetime of the dyes. Recent developments of optically pumped diode lasers, as well as frequency-doubled fiber lasers, promise to replace dye lasers in clinical use.
Hair removal recently become a popular cosmetic procedure, as it is less painful and much quicker than electrolysis. It is more efficient in the removal of dark hair, and it may take several months before regrowth is evident. Several treatment cycles are often required with the spacing between treatments depending on the body area being treated.
Long-pulsed ruby, Nd:YAG, and alexandrite lasers are successfully used for this procedure. However, they are quickly been displaced by 810nm diode lasers.
Laser-assisted lipolysis became a widely accepted modality for the removal of unwanted fatty tissue, which is in many cases, superior to liposuction. Laser lipolysis liquefies fatty tissue, coagulates small blood vessels, and more significantly promotes tissue tightening. One of the advantages of laser lipolysis is fast patient recovery. Most patients can return to normal daily activities already next day. Laser lipolysis may diminish postoperative pain, ecchymoses, and edema because of the coagulation of blood and lymphatic vessels. Additionally, due to the liquefaction of adipose tissue, a small cannula size (~1mm) can be used to remove fat upon subsequent suction aspiration, inflicting less trauma. Moreover, in many cases aspiration is not required at all in smaller areas, such as submental, inner thighs, and knees, further limiting direct tissue trauma.
The most common lasers for this application are Nd:YAG laser operating at 1319 nm, and 980nm diode laser. It is worth noting that neither wavelength is specific for the fat absorption. Therefore, it is reasonable to assume that diode lasers operating at the 1208nm and 1720nm peaks of fat absorption will produce superior clinical outcomes.
Cardiovascular surgery
Transmyocardial laser revascularization (TMR) is a treatment for patients with coronary artery disease who have not responded to or are not eligible for procedures such as angioplasty and stenting, and coronary artery bypass surgery. During surgical procedures laser is used to create multiple microscopic channels through the heart muscle into the left ventricle, thus providing the flow of oxygen-rich blood to the heart muscle and reducing the chest pain (angina). The mechanism of angina alleviation is debatable, some studies suggest that it may work by stimulating angiogenesis (the growth of new blood vessels) in the heart muscle, but the alternative explanation attributes it to destroying nerve fibers. Currently only CO2-lasers and Ho:YAG are FDA approved for TMR. The reason is mostly historical – at the time of the approval, they were clearly better than other laser types. Recently developed Thulium fiber lasers undoubtedly possess superior specifications for applications in TMR, and we should see them soon in clinical practice.
Laser coronary angioplasty is a technology for managing balloon-untreatable coronary artery lesions, which uses laser light to “vaporize” the blockage in the artery. Initial application of argon and Nd: YAG lasers for this procedure produced disappointing results, and was plagued by complications caused by collateral thermal injuries to the blood vessels. However, the development of excimer lasers that output light at shorter wavelengths (usually 308nm), which has a very small penetration depth allowed for a precision ablation of plaque tissue with insignificant thermal injury to the vessel.
Gastroenterology.
Hemorrhoidal disease is a morbid condition that affects more than 80% of the world’s population at least once in a lifetime. While non-surgical treatments are considered to be the primary option for grades one to three (grade I-III), when they fail a hemorrhoidoplasty is necessary. Laser surgery proved to be superior to other surgical technologies, as it can be performed under local anesthesia, does not require sutures, and results in faster recovery and less postoperative pain. Nd:YAG lasers were initially used for this procedure as early as in the 60s. However, CO2 lasers have replaced them and currently are the most common laser equipment used for hemorrhoidoplasty today. Recently developed Thulium fiber lasers, as well as diode lasers operating at 980nm, 1470nm, and 1940nm are poised to disrupt the CO2-laser dominance. The preliminary data indicate that they all provide better clinical outcomes. Furthermore, diode lasers are more compact, robust, and cheaper.
Instead of Epilogue.
Nd:YAG and CO2-lasers have been grandfathered in many modern clinical applications of lasers, but they will be eventually displaced by Thulium fiber lasers and diode lasers in the majority of surgical applications.
A noticeable exception is ophthalmology where the battle between excimer lasers and femtosecond lasers continues without a clear winner in site. If I had to predict the outcome of this competition, I would bet on femtosecond laser technology – these lasers have better beam parameters and more precise control of the ablation process.
The Er-lasers will continue to dominate in hard tissue ablation. However, we expect the femtosecond lasers to challenge them in this area.