The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology

Abstract

Background: Tremendous advances have been made in the medical application of the laser in the past few decades. Many diseases in the dermatological field are now indications for laser treatment that qualify for reimbursement by many national health insurance systems. Among laser types, the carbon dioxide (CO2) laser remains an important system for the dermatologist.

Rationale: The lasers used in photosurgery have wavelengths that differ according to their intended use and are of various types, but the CO2 laser is one of the most widely used lasers in the dermatology field. With its wavelength in the mid-infrared at 10,600 nm, CO2 laser energy is wellabsorbed in water. As skin contains a very high water percentage, this makes the CO2 laser ideal for precise, safe ablation with good hemostasis. In addition to its efficacy in ablating benign raised lesions, the CO2 laser has been reported to be effective in the field of esthetic dermatology in the revision of acne scars as well as in photorejuvenation. With the addition of fractionation of the beam of energy into myriad microbeams, the fractional CO2 laser has offered a bridge between the frankly full ablative indications and the nonablative skin rejuvenation systems of the 2000s in the rejuvenation of photoaged skin on and off the face.

Conclusions: The CO2 laser remains an efficient, precise and safe system for the dermatologist. Technological advances in CO2 laser construction have meant smaller spot sizes and greater precision for laser surgery, and more flexibility in tip sizes and protocols for fractional CO2 laser treatment. The range of dermatological applications of the CO2 laser is expected to continue to increase in the future.

Keywords: CO2 laser; fractional laser; laser ablation; nevus; photorejuvenation; verruca.

Figures

Fig. 1:

Wavelength is sown on the x-axis (200–400 nm, UV; 400 - 7 - nm, visible light; 700 – 2000 nm, nearinfrared; > 2000 nm, mid-infrared) with an arithmetic scale from 200 – 1000 nm (1.0 µm) and a logarithmic scale from 1.0 µm and longer. The y-axis denotes the coefficient of molar extinction in logarithmic units. This can be thought of as denoting the degree of penetration into tissue: the lower the value on the y-axis, the better the penetration of light at the given wavelength. The absorption spectra are for the laser tissue chromophores comprising the major biological pigments (oxy- and deoxyhemoglobin and melanin) and water. Note the high absorption in water at 10,600 nm, the wavelength of the CO2 laser.

Fig. 2:

Manipulation of the biological effect of the laser beam through moving the handpiece towards or away from the focal point of the beam, shown in 2a. (2b): Linear motion of the handpiece can give laser incision. Note the zone of RTD adjacent to the ablated tissue. The focused beam can also be used to excise tissue en bloc, with traction being applied to the lesion as indicated. Note the use of a wet cotton bud as a backstop to prevent damage to the normal tissue behind the lesion. (2c): By slightly defocusing the beam, and reducing the irradiance, bulk vaporization of tissue is achieved, again leaving a zone of RTD around the ablated tissue. (2d): By moving the handpiece further away from the tissue, a dramatic drop in irradiance is achieved which will result in nonablative coagulation of tissue. This is useful for swift hemostasis of small bleeding or oozing vessels.

Fig. 3:

Temperature-dependent bioreaction zones from a surgical CO2 laser impact illustrated schematically with a typical histological pattern shown alongside the schematic. Please see the text for details.

Fig. 4:

Temporal mode of a laser beam illustrated schematically. (4a): Continuous wave (CW). (4b): Switched, chopped or gated CW beam, producing a series of square waveforms. These are not, strictly speaking, “pulses”, because a pulsed beam has a pulsewidth of 1 ms or less. (4c): A train of laser pulses with pulsewidths of from ms tons, with a long interpulse interval, is seen by the tissue the average power of the peak power and zero watts during the long interpulse interval. This known as quasi-CW. (4d): Quasi-CW can also be delivered as so-called “superpulsed” or “ultrapulsed” modes as illustrated. The ultrapulse dmode is also known as the char-free mode because it produces less charring due to the very short pulsewidths, much less than the thermal relaxation time of the target tissue.

Fig. 5:

A case of nevus cell nevus on the left posterior cheek of a 23-year old female treated with CO2 laser vaporization. (5a): Baseline findings. The lesion was determined to be benign. (5b): The findings immediately after treatment with the slightly defocused CO2 laser in quasi-CW, output power of 2.4 W, frequency 50 Hz. (5c): The area of interest 10 weeks after treatment with removal of the lesion and good cosmesis. (SmartXide laser, DEKA, Italy)

Fig. 6:

Multiple planar warts in a 28-year-old male treated with CO2 laser ablation. (6a): Immediately after irradiation the warts have been vaporized down into normal tissue architecture using the slightly defocused beam of the CO2 laser in quasi-CW, 10 W output power, frequency of 100 Hz. (6b): The result 3 weeks after the treatment. Some small touch-up treatments were required (circles) but otherwise with no sign of recurrence. The patient is wart-free some 6 months post-treatment. (SmartXide laser, DEKA, Italy)

Fig. 7:

Histological specimens (hematoxylin and essoin stain) showing the differences between the nonablative fractional effect in tissue (left panel) and the ablative effect (right panel). The zones of normal tissue between the MNZs and MACS is clearly seen in both specimens. Histology courtesy of Prof. WS Kim, Department of Dermatology, Sungkyunkwan University, Seoul, South Korea, scale bars as shown. (eCO2 system, Lutronic. Goyang, South Korea)

Fig. 8:

Despite the high absorption in tissue water, the CO2 microbeams are capable of a MAC deeper than 2 mm in human tissue in vivo (hematoxylin and eosin staining). With all other parameters remaining the same, changing the pulse energy alters the penetration depth achieved. from the left, the pulse energies were 4 mJ, 22 mJ. 60 mJ and 160 mJ with MAC depths ranging from 100 µm to 2.4 mm. The zone of RTD, however, does not change as dramatically as the depth, maintaining the advantages of fractionation of the beam while still inducing active wound repair and tissue remodeling. The 160 mJ specimen is interesting, because it actually shows two MACs in 3-dimensions, one behind and to the right of the main MAC in this 2-dimensional specimen. Only the very top of the ablative zone is seen, but the RTD is clearly visible extending down into the dermis. Another MAC-associated RTD zone appears to the left of the main MAC, oval marking. Histology courtesy of Prof. WS Kim, Department of Dermatology, Sungkyunkwan University, Seoul, South Korea, scale bars as shown. Note that the right hand image has been reduced in size to fit the illustration, as can be seen from the size of the 100 µm scale bar. (eCO2 system, Lutronic. Goyang, South Korea)

Fig. 9:

(9a): Baseline appearance of acne scars on the right cheek of a 32-year-old female patient. (9b): Result 3 weeks after 3 treatments separated by 4 weeks with a fractional CO2 laser, output power of 20 W, microbeam spacing of 600 µm. The re areas are typical of the post-acne redness seen especially in Asian skin types III/IV following treatment of acne scars, and are part of the wound-healing process where active revascularization is more clearly seen under an immature epidermis. (SmartXide laser, DEKA, Italy)

Fig. 10:

Fractional CO2 laser applied off the face in the rejuvenation of the arms of this 72-year-old lady. (10a): Baseline appearance of the right forearm and back of the hand. (10b): 4 weeks after 1 session of fractional CO2. (eCO2 system, Lutronic, Goyang, South Korea: Photography courtesy of Mark Rubin MD, Los Angeles, CA, USA)