Clinical and histologic effects of facial skin rejuvenation with pulsed- and continuous-wave...

A E S T H E T I C S U R G E R Y J O U R N A L ~ S E P T E M B E R / O C T O B E R 2 0 0 1 399

Clinical and Histologic Effects of FacialSkin Rejuvenation with Pulsed- andContinuous-wave Flash-scanned CO2 Lasers

Mario A. Trelles, MD, PhD; Lourdes Pardo, MD; Oswaldo Trelles, Dr Eng, PhD;Mariano Velez, MD; Luisa García-Solana, MD; Josepa Rigau, MD, PhD; and T. Juan José Chamorro, MD, PhD

Learning Objectives:

The reader is presumed to have some understanding of the use of lasers in skin resurfac-ing. After studying the article, the participant should be able to:

1. Deduce the circumstances in which laser resurfacing provides effective treatment oftissue and understand the overall mechanisms involved in tissue rejuvenation.

2. Evaluate the significance of erythema in tissue that has undergone therapeutic laserresurfacing.

3. Explain why greater residual thermal damage to tissue leads to better long-term resultswhen laser resurfacing is done under well-controlled circumstances.

Physicians may earn 1 hour of Category 1 CME credit by successfully completing theexamination based on material covered in this article. The examination begins on page409.

Background: The selection of the ideal laser for facial resurfacing is debatable.Objective: The purpose of the study was to determine whether any clinical and histologicdifferences existed in short- and long-term results after treatment with the CoherentUltraPulse 5000G laser (a pulsed laser; PL) and the Sharplan Silk Touch laser (a contin-uous-wave laser [CWL] with a flash scanner).Methods: Eight patients underwent facial resurfacing treatment on different areas. Ineach case, one side was treated with the PL and the other with the CWL. The conditionof the patients and the treated tissue were monitored periodically after treatment.Histologic assessment of punch biopsies was performed 3 months and 1 year after treat-ment with hematoxylin-eosin, Masson trichromic, and Verhoeff’s stains.Results: The areas treated with the PL achieved earlier epithelialization with a good

Dr. Mario A. Trelles, Dr. García-Solana, Dr. Velez, and Dr. Rigauare from the Instituto MédicoVilafortuny, Antoni de GibernatFoundation, Cambrils, Spain; Dr.Pardo is from the Department ofPlastic Surgery, The Hospital ofthe 9th of October, Valencia,Spain; Dr. Oswaldo Trelles is fromthe Department of Architectureand Computer Technology,University of Malaga, Malaga,Spain; and Dr. Chamorro is fromthe Department of Plastic andReconstructive Surgery,University Hospital-La-Fe,Valencia, Spain.

Accepted for publication July 17,2001.

The authors have no financialinterests to disclose in the prod-ucts discussed in this article.

Reprint requests: Mario A. Trelles,MD, PhD, Instituto MédicoVilafortuny, Antoni de GimbernatFoundation, Av. Vilafortuny 31, E-43850 Cambrils, Tarragona,Spain.

Copyright © 2001 by TheAmerican Society for AestheticPlastic Surgery, Inc.

1084-0761/2001/$35.00 + 0

70/1/119150

doi:10.1067/maj.2001.119150

Continuing Medical Education Article—Facial Aesthetic Surgery

S c i e n t i f i c F o r u m

appearance. Longer-lasting erythema was observed on theside treated with the CWL. On a histologic level,although the PL–treated tissue epithelialized more quick-ly, at 3 months and 1 year the collagen was better com-pacted and better aligned in the CWL–treated tissue, andthe macroscopic appearance of the CWL–treated areaswas more enhanced.Conclusions: The more active vascularization seen in theCWL–treated tissue, associated with the longer-lastingerythema and possibly greater collateral thermal injury, ispossibly the reason for the better collagenization andremodeling of collagen and elastin fibers as comparedwith the results with the PL–treated tissue. This mayexplain the longer effect associated with CWL treatment.The clinician would do well to bear in mind the histolog-ic findings as well as the macroscopic clinical resultswhen assessing the long-term effects of laser skin resur-facing. (Aesthetic Surg J 2001;21:399-411.)

Only a small number of studies have examinedthe long-term results of skin resurfacing withdifferent types of lasers, including those of

Alster and Garg,1,2 Alster,2 Waldorf et al,3 Fitzpatricket al,4 Lowe et al,5 and Lask et al.6 Trelles7 and Trelleset al8 have investigated the histologic changes in tissueresulting from laser treatment.

The clinical application of laser technology hasallowed the selective vaporization of a thin layer of tis-sue with varying thermal damage to the adjacentareas. A variety of CO2 laser systems are available,including pulsed lasers (PL) such as the Coherent5000C UltraPulse with the Computer PatternGenerator (CPG) (Coherent Inc., Santa Clara, CA) andcontinuous-wave lasers (CWL) such as the SharplanSilk Touch laser system (ESC/Sharplan, Yokneam,Israel), which uses flash-scanning technology.

The Coherent PL operates with high-power energy pulsesof up to 500 mJ per pulse. Each pulse is less than 1 ms induration and is delivered in a collimated beam with a rel-atively large diameter of 3 mm. The hand piece can beheld at relatively large distances (approximately 10 cm)from the target tissue because the beam is collimated. Thefluence achieved with this laser is in the order of 7 J/cm2.

The Sharplan CWL with Silk Touch technology emits acontinuous beam with a focal point of 200 µm at the tis-sue, delivered by means of a flash-scanner system thatsweeps the light over the tissue. The spiral movement of

4 0 0 A e s t h e t i c S u r g e r y J o u r n a l ~ S e p t e m b e r / O c t o b e r 2 0 0 1 Volume 21, Number 5


the laser achieves very high fluences (around 5 to 15J/cm2 or greater) on any of the points over which itmoves with the Silk Touch system: the sweeping is per-formed in less than 1 ms on each of the points on whichthe laser light falls.

In an earlier histologic study, we showed that the CWL’spenetration into the skin with 2 passes was comparableto that achieved with 3 passes with the PL.8 The presentstudy was designed to determine whether any differencesexist in short- and long-term clinical and histologicresults between the two lasers.

Methods

Eight patients aged between 54 and 72 years gave theirconsent to participate in the study. Patients received nopreoperative topical treatment with retinoids.

Treatment

All treatment areas were divided into 2 equal parts; 1part was treated with the Sharplan system (CWL) and theother with the Coherent system (PL). The parameterschosen for treatment protocols were those that our previ-ous experience had indicated were the most appropriatefor each type of laser.9 Parameters for the CWL treatmentprotocol were as follows: power, 18 W; scanning pat-terns, 9 and 3 mm; 2 passes, with 450 ms per scanningpass and 400 ms between scans. For the PL, parameterswere as follows: energy, 300 mJ; power, 60 W; CPG den-sity, 6; 3 passes. The incident power and the exposuretime are important reference points that are alwaysexpressed in relation to the unit area to calculate theenergy density (ED). In the following equation, where Pis the power in watts, t is the time in seconds, and A isthe treated area per spot in square centimeters:

After laser resurfacing of each area with either the CWLor the PL, flupametasone-gentamicine (FG) ointment wasapplied to the entire treated area. No dressing wasapplied, and the exudate was carefully pat-dried withgauze before applying the ointment. The FG ointmentwas applied hourly by massaging it into the area whereresurfacing had been done until exudation ceased 3 or 4days later. Oral prednisolone (3 mg 3 times a day for 5days) was also prescribed. Acyclovir was applied topical-ly to the lip vermilion in the patients who received full-

PD= J/cm2P × tA

� �

face and perioral resurfacing. A broad-spectrum antibiot-ic, to be taken 4 times a day for 5 days, was prescribedfor patients who underwent full-face resurfacing.

On the third or fourth postoperative day, when exuda-tion had begun to decrease, FG was reduced to just 1application per day, and a nutritive calendula-basedcream, Tt1 Cosmética Activa,10 was applied hourly. Assoon as re-epithelization was achieved, Tt2 CosméticaActiva was prescribed to prevent hyperpigmentation. Tt5,which contains avocado, mosquette rose oils, and a sun-screen, was prescribed to nourish the skin and protect itfrom the sun. Patients were also advised to avoid expo-sure to sunlight.

Postoperative check-ups were scheduled at 2, 10, 20, 30,40, 50, and 60 days after resurfacing and then at 3, 8,and 12 months, although patients were attended to atany time they desired.

Evaluation

The parameters evaluated were the degree of erythema,the limitations posed by makeup in covering erythema,and skin texture. Statistical analyses of the above-men-tioned criteria were carried out with an analysis of vari-ance. Evaluation of erythema was done at 15 days and 1,2, 3, and 4 months after treatment. Data on makeup lim-itations for covering erythema were assessed at 2, 4, 6,and 8 weeks.

Photographs were taken under identical lighting condi-tions with the patient in the same position with Kodak100 ASA film (Rochester, NY) before and immediatelyafter treatment and whenever judged important for thedata files. At all check-ups at 8 months and 1 year, theaesthetic results were evaluated by both the patient andby the clinician who performed the treatment.

To evaluate erythema after treatment, photographs ofthe 8 patients of each group were evaluated for thedegree of redness by using the Kodak Color chart scaleof reds as proposed by Ginsbach.11 Once the erythemawas judged to be acceptable by the doctor examiningthe photographs, it was categorized as grade 1 (very lit-tle). Grades 2 through 4 were assigned according to theintensity of the redness in the photographs.

Two weeks after laser treatment, skin recovery was suf-ficient to permit the use of makeup to cover erythema.The makeup was a mixture of Tt1 Cosmetica Activa

(Calendula cream) and Tt3 Cosmetica Activa (facialcolor makeup) that achieved a color similar to the skinadjacent to the treated area. A series of grades for eval-uating the limitations of makeup in covering erythemawas established in which normal covering capacity, asdefined by the patient’s opinion, was assigned grade 3(covers satisfactorily). When assigning grades, thequantity of Tt3, that is to say the amount of colormakeup necessary to achieve maximal erythema cover,was considered. In 2 patients chosen at random, make-up with sufficient color was used to cover erythema asmuch as possible on both treatment areas.

Skin texture, as determined by aspect and touch, wasassessed for the first time 10 days after treatmentwhen re-epithelialization was confirmed. The skin’saspect was assessed with use of an image magnifier.Touch was evaluated by gently running the fingerover the skin’s surface, and the results were evaluatedby Fitzpatrick’s criteria for assessment of the areastreated, homogeneity, roughness, and fineness.3

Subsequent assessments were determined at 20 daysand at 3, 8, and 12 months after surgery. Punch biop-sies (1 mm) were taken before resurfacing and at 3months and 1 year postoperatively for examinationwith hematoxylin-eosin and Masson’s trichromicstaining as well as with Verhoeff’s technique specificallyfor evaluation of elastin fiber. A blinded histologistevaluated histologic samples chosen at random and wasasked to compare the selected preparations.

Results

Immediately after resurfacing, the PL–treated facial areasshowed better homogeneity than those treated with theCWL system. Significant edema developed on both sidesof the face, caused by the thermal effect of the treatment.The skin surface on each side was fine and equally shinyafter treatment.

Re-epithelialization occurred more quickly on the side ofthe face treated with the PL system. The fine, crusty filmformed by proteic secretion began to fall off on postoper-ative day 7 on the areas treated with the PL system,whereas the crust on the side treated with the CWL sys-tem, which was slightly thicker, usually fell off at 10 to12 days postoperatively (Figure 1). In 4 of the 8 patientstreated with the CWL, it was possible to discern circularmarks caused by the spiral scanning pattern of the CWLflash-scanning system.

A E S T H E T I C S U R G E R Y J O U R N A L ~ S E P T E M B E R / O C T O B E R 2 0 0 1 4 0 1Clinical and Histologic Effects of Facial Skin Rejuvenationwith Pulsed- and Continuous-wave Flash-scanned CO2 Lasers


Photographic evaluationAt 15 days after treatment, extreme erythema was evi-dent in the areas treated with both systems. The differ-ences at this time between the treated sides were notsignificant. One month after treatment, erythema wasgraded “significant” in the CWL–treated areas and“mild” in the PL–treated areas (Figure 2). Two monthslater, erythema on the PL–treated side was qualified as“very little,” whereas erythema on the areas treated withthe CWL system was assessed as “mild” in 5 patients and“significant” in the other 3 patients.

At 3 and 4 months after treatment, the photographs onthe PL–treated side showed “very little” erythema; pho-tographs of the CWL–treated side achieved this grading

only 4 months after treatment. Statistical evaluation ofthe data showed significantly less erythema (P < .05) onthe PL–treated areas at 1, 2, and 3 months after treat-ment (Figure 3).

In the patients selected for the erythema cover-up test,both sides of the face required similar quantities ofmakeup 2 weeks after treatment. However, 4 weekspostoperatively, the quantity of color makeup used toachieve balanced skin color bilaterally was greater onthe PL side because of the more intense erythemacaused by the CWL treatment. In the makeup tests at 6and 8 weeks after treatment, the differences were notsignificant (Figure 4).



Figure 1. Post-treatment view of a patient 10 days after laser resurfacingtreatment of the upper lip. The PL was applied on the right side of thepatient’s face and the CWL on the left. The fine crust resulting from laserapplication seems to detach itself earlier on the side treated with the PL.

Figure 2. A, Close-up photograph of the cheek of a patient 1 month afterresurfacing treatment with the CWL. Round images caused by the SilkTouch system are evident. B, Close-up photograph of the cheek treated byPL 1 month after treatment. The erythema is more homogeneous.

A

B

Figure 3. Assessment of erythema in 8 patients who underwent full-face laser resurfacing.

In all 8 patients, at 10 days, 20 days, and 3 monthsafter treatment, skin texture was assessed as significant-ly better on areas treated with the PL laser. However,these differences became insignificant at 8 months, andat 12 months, skin texture was rated better in the areastreated with the CWL system (Figure 5), though thequality of results was judged excellent for both types oflaser (Figures 6 and 7).

Histologic evaluation

Histologically, the skin preoperatively showed a thin epi-dermis with an enlarged stratum corneum and a fine stra-tum spinosum (Figure 8, A). The dermis was elastotic,and collagen fibers were randomly arranged.

At 3 months after treatment, the configuration of theepithelium observed in both samples was mature, withnormal structure. The PL samples and the CWL samples

showed increases in the basal pigmentation of approxi-mately equal proportions. The dermoepidermal junctionhad a flat appearance, with cells aligned in palisade(Figure 8, B and C). An increase in collagen, which washorizontally disposed in the CWL samples, was the mostnotable change. The interfibrillary spaces were broader inthe PL samples.

One year after laser resurfacing, hematoxylin-eosin staining of the PL samples demonstrated mature ker-atin with signs of flaking. The epidermis formed a nar-rower band in comparison with the CWL samples. Inthe CWL samples, keratin appeared in sheets, which ischaracteristic of young tissue. The dermis was thickerand had a greater number of cells, demonstrating thecharacteristic alignment of the basal cells at the der-moepidermal junction. This alignment was less welldefined in the PL samples.



Figure 4. Limitations of makeup to cover erythema in 8 patients who underwent full-face laser resurfacing.

Figure 5. Assessment of skin texture in 8 patients who underwent full-face laser resurfacing.



Figure 6. A, Pre-treatment view of a patient before resurfacing. Rhytids, skin flaccidity, and some cutaneous pigmentations caused by aged skin areevident. B, Post-treatment view 3 months after resurfacing with both CWL and PL.

A B

Figure 7. A, Pre-treatment view of a patient with Fitzpatrick type I skin. Significant rhytids and aged skin, mostly caused by exposure to sunlight, areevident. B, Post-treatment view 2 months after laser resurfacing. No significant differences are seen between the side treated with the CWL and thattreated with the PL.

AB

In the PL samples, the dermis had clear signs of elas-tosis, showing a band of separation immediatelybelow the basal layer. The CWL samples showedfibers aligned horizontally to the basal layer and werewell compacted with abundant fibers and evidentthickness. In both samples, inflammatory infiltratewas relatively abundant. In the samples examinedwith Masson’s trichromic staining, collagen showedexcellent compacting with horizontally aligned fibersin the CWL specimens. The PL samples presented

abundant wide interfibrillary spaces, with characteris-tic signs of elastosis.

Verhoeff’s technique demonstrated that in the CWLsamples, elastin fibers were aligned in a way particularto young tissue. The alignment followed that of the col-lagen fibers, and both fibers appeared to be linked. In thePL specimens, elastin fibers appeared to be disorganizedand granular, with evident signs of aging and abundantwide interfibrillary spaces (Figures 9 through 11).



Figure 8. A, Random pretreatment skin sample from a patient shows fine epidermis and heavy keratin sheets. The dermis exhibits signs of elastosisand wide interfibrillary spaces (hematoxylin-eosin stain, original magnification ×400). B, Post-treatment skin sample taken from the side treated withthe PL 3 months after laser resurfacing. Note the wide epidermis, which exhibits great cellularity and signs of activity. The basal layer of the epidermisis well defined with no separation from the dermis, which is shown by well-compacted collagen. Abundant vessels with inflammatory signs are present.C, Post-treatment skin sample taken from the side treated with the CWL 3 months after laser resurfacing. Fine keratin with signs of rich cellular activi-ty can be seen. The basal layer still does not show the characteristic palisade disposition of the epidermal basal cells. The dermis demonstrates horizon-tally disposed collagen with fiber activity and rich inflammatory infiltrate. The collagen band in the dermis is wide and clearly defined(hematoxylin-eosin stain, original magnification ×400).

A

B

C

Discussion

The choice of the ideal laser for resurfacing is still amatter of debate. Histologic examination, provides anobjective method for the comparison of the effects ofthe different systems proposed that may be correlatedwith postoperative clinical assessments.12-14 Changes inthe appearance of the skin can be observed 7 to 15days after treatment when re-epithelialization is

achieved. Maturation of the dermis with respect to col-lagen characteristics and elastin fibers is achieved at 2to 3 months after treatment.15



Figure 9. A, Skin samples from the same patient illustrated in Figure 8taken 1 year after resurfacing. Note the matured keratin and a flat epi-dermis visible on the side treated with the PL. A separation layer belowthe basal of the epidermis is evident. The dermis demonstrates signs ofelastosis. Irregular disposition of the collagen and slight lymphocyticinfiltrate are also seen. B, Note the wide epidermis and keratin sheet onthe side treated with the CWL. The basal layer is well defined, with thecells aligned in palisade. Signs of elastosis are present in the deep dermis,including collagen in horizontal disposition in all the junctional der-moepidermal planes and light lymphocytic infiltrate (hematoxylin-eosin,original magnification ×400).

A

B

Figure 10. Skin samples taken from a patient 1 year after laser resur-facing. A, Excellent compacting of the collagen and horizontally dis-posed fibers are evident on the side treated with the CWL. Few signs oflymphocytic infiltration or signs of active circulation are visible. B,Signs of elastosis, including wide interfibrillary spaces and an irregularcollagen disposition, are evident on the side treated with the PL(Masson’s trichromic, original magnification ×200).

A

B



The differences in tissue damage caused by CWL versusPL resurfacing explain the differences in clinical and his-tologic results seen in the early stages of wound healing.The energy produced by the laser at the skin surfacevaporizes tissue, but this energy is also responsible for theshrinkage of the dermis through dehydration. This ther-mal injury produces a dermal stimulation with a resultantinflammatory reaction, the consequence of which isactive angiogenesis and tissue remodeling. This activeangiogenesis is reflected in the skin erythema. Higher lev-els of stimulation result in a more prolonged inflammato-ry reaction, greater effects on collagen remodeling,formation of new fibers, and a longer recovery time.16

Compared with the PL system, the 10% to 20% overlapdelivered by the CWL flash-scanned system producesgreater heat at high-energy densities with a relativelylonger irradiation time, and thus a higher level of vascu-larization, though at the cost of less precision. The moreintense erythema associated with the CWL treatmentreflects a stronger inflammatory reaction with moreactive angiogenesis.17 For this reason, in histologic speci-mens, the lesions in samples from CWL–treated tissueappear deeper than those from PL–treated tissue and arethe cause of the longer recovery time required forCWL–treated epithelium. Skin texture was significantlybetter in the surfaces treated with the PL system becauseof the more prolonged inflammatory reaction on theCWL–treated surfaces, which required more time for col-lagen remodeling. At the same time, the samples fromCWL–treated tissue demonstrate production of morecompact collagen with more abundant elastin fibers,which provide the longer treatment effect associated withthis laser compared with that of PL resurfacing.

Conclusion

In conclusion, the more intense thermal energy deliveredby the CWL system resulted in a longer recovery time butalso in more profound results. Surgeons must bear inmind that the mode of energy delivery has a significantbearing on the final outcome.�

References

1. Alster TA, Garg HA. Treatment of facial rhytids with the Ultrapulsatehigh energy Carbon Dioxide Laser. Plast Reconstr Surg 1996;98:791-194.

2. Alster TS. Comparison of two high-energy Pulser Carbon DioxideLaceres in the treatment of periorbital rhytides. Dermatol Surg1996;22:541-545.

3. Waldorf HA, Kauvar ANB, Geronemus RG. Skin resurfacing of fine todeep rhytides using a Char-free Carbon Dioxide Laser, in 47 patients. JDermatol Surg 1995;21:940-946.

4. Fitzpatrick RF, Goldman MP, Saturn M, Tope WD. Pulsed CO2 resurfac-ing of photodamaged facial skin. Arch Dermatol 1996;132:395-402.

5. Lowe NJ, Lask G, Griffin ME, Maxwell A, Lowe P, Quilada F. Skin resur-facing with the Ultra Pulse Carbon Dioxide Laser. Dermatol Surg1995;21:1025-1029.

6. Lask G, Keller G, Lowe N, Gormley D. Laser skin resurfacing with theSilk Touch Flashscanner for facial rhytides. Dermatol Surg1995;21:1021-1024.

7. Trelles MA. Histopathology of laser resurfacing [abstract]. Sixth Inter.Symposium on Cosmetic Laser Surg. San Francisco, March 1997; 20-22.

8. Trelles MA, Coates J, Trelles OR, Trelles K, Curto M, Clarke A.Histological correlation in laser skin resurfacing. Laceres Med Sci1995;10:279-282.

Figure 11. Skin samples taken from a patient 1 year after laser resur-facing. A, The elastin fibers are aligned and interlaced with the collagenfibers on the side treated with the CWL. A wide collagen band is visibleimmediately below the basal layer of the epidermis. B, Disorderedelastin fibers and detached interfibrillary spaces characteristic of elasto-sis are evident on the side treated with the PL (Verhoeff’s stain, originalmagnification ×200).

A

B

9. Trelles MA, Rigau J, García L, Mellor K. Coherent versus Sharplan dansle resurfacing cutané: modifications du collagène et de l’elastine”. JMéd Esth et Chir Derm 1998;25:15-20.

10. Tt Cosmetica Activa© Laser Skin Resurfacing and Chemical Peeling.(Brochure: General Information for the Medical Professional.)Laboratory Profarplan (Av. Diagonal 436, 08037 Barcelona, Spain)Spain; 1999.

11. Ginsbach GA. Tool for the evaluation of colour in Port wine stains.Laceres Med Sci 1991;6:49-52.

12. Apfelberg DB, Smoller B. Ultrapulse Carbon Dioxide Laser with CPGScanner for deepithelialization: clinical and histological study. PlastReconstr Surg 1997;99:2089-2094.

13. Cotton J, Hood AF, Gonin R, et al. Histologic evaluation of preauricular

and postauricular human skin after high-energy short pulsed carbon

dioxide laser. Arch Dermatol 1996;132:425-428.

14. Stuzin JM, Baker TM, Kligman AM. Histologic effects of the highenergy

pulsed CO2 laser on photoaged facial skin. Plast Reconstr Surg

1997;99:2036-2050.

15. Trelles MA, David L, Rigau J. Penetration depth of Ultrapulse carbon

dioxide laser in human skin. Dermatol Surg 1996;22:863-866.

16. Trelles MA, Mordon S, Svasand LO, Mellor TK, Rigau J, García L. The

origin and role of erythema after CO2 laser resurfacing: a clinical and

histological study. Dermatol Surg 1998;24:25-29.

17. Riches DWH. The multiple role of macrophages in wound healing. In:

Clark RAF, Henson PM, eds. The Molecular and Cellular Biology of

Wound Repair. New York: Plenum Press; 1988; 213-233.



Continuing Medical Education Examination—Facial Aesthetic Surgery:Clinical and Histologic Effects of Facial Skin RejuvenationInstructions for Category 1 CME Credit

ASAPS CME Program No. ASJ-CME-FAS-13. The American Society for Aesthetic Plastic Surgery is accredited by theAccreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The American Society for Aesthetic Plastic Surgery designates this educational activity for a maximum of 1 hour inCategory 1 credit toward the American Medical Association Physician’s Recognition Award for correctly answering 14questions to earn a minimum score of 70%. Each physician should claim only those hours of credit that he/she actuallyspent in the educational activity.

Please return the examination (photocopy or tear out) with your full name and address, your ASAPS or ASPS identifica-tion number, and a self-addressed, stamped return envelope to the following address:

ASJ CMEc/o ASAPS Central Office11081 Winners Circle, Suite 200Los Alamitos, CA 90720-2813

If you are not a member of either ASAPS or ASPS, please note this on your examination. The deadline for receipt ofexaminations for Category 1 CME credit based on this activity is April 15, 2002.



Multiple Choice

1. A linear increase in the spot diameter produces:A. A linear increase in power densityB. A linear decrease in power densityC. A quadratic increase in power densityD. A quadratic decrease in power densityE. An exponential increase in power density

2. One year after laser resurfacing, histologic samples ofboth skin treated by continuous-wave laser (CWL)and skin treated by pulsed laser (PL) demonstrate:A. Clear signs of elastosisB. Abundant inflammatory infiltrateC. Wide interfibrillary spacesD. Compacted collagen

3. Which of the following is the apparent cause of thegreater erythema caused by CWL resurfacing?

A. Greater inflammationB. Greater vascular neoformationC. Slower recovery of the epidermisD. None of theseE. All of these

4. Why does tissue recover more rapidly after PL resur-facing than after CWL resurfacing?A. Shorter time acting on tissueB. Better vaporization controlC. Less residual thermal damageD. All of theseE. None of these

5. The tissue’s inflammatory reaction to CO2 laserresurfacing is a result of: A. Laser absorption B. Laser absorption and thermal conductionC. Thermal conduction and residual thermal damageD. Laser absorption and residual thermal damageE. A and C

6. Which of the following skin reactions does not occurimmediately after CO2 laser resurfacing?A. VaporizationB. Skin dehydrationC. BleedingD. Debris on the skin’s surfaceE. Collagen shrinking

7. The following histologic characteristics are typical ofaged skin:A. Increased interfibrillary spacesB. Random collagen disposition C. ElastosisD. A and CE. A, B, and C

8. Long-term results of laser skin resurfacing are related to:A. Greater inflammationB. Greater residual thermal damageC. Increased vascularizationD. Slower tissue restructuringE. All of the above

9. The laser energy absorbed in resurfacing isresponsible for:A. Capillary ruptureB. Tissue vaporization and dehydrationC. Collagen shrinkageD. A and BE. B and C

10. The power density of CWL flash-scanned systemsproduces greater heat on tissue compared withthat of PL systems because of:A. Higher energy densityB. Longer irradiation timeC. Bulkier scanner hand devicesD. A and BE. A, B, and C

True or False

11. Overlapping of scanning devices in resurfacingproduces additional heat in the overlapped irradi-ated tissue. T F

12. Overlapping in resurfacing produces greatervaporization but with less precision.T F

13. The differences in tissue damage produced by theCWL and PL systems are the reason for differ-ences in histologic results.T F

14. Long-term treatment efficacy is correlated withgreater residual thermal damage to tissue.T F

15. Camouflage of erythema is not an important post-treatment issue after laser resurfacing.T F

16. Histologic examination of skin samples is helpfulin assessing the long-term effects of laser skinresurfacing.T F

17. Preoperative topical treatment with retinoids isalways required before laser skin rejuvenation.T F

18. Possible complications of CO2 laser resurfacinginclude persistent erythema, milia, hyperpigmen-tation, and hypopigmentation.T F

19. Significant edema is evident immediately afterCWL skin resurfacing but not immediately afterPL skin resurfacing.T F

20. CO2 laser energy is well absorbed in the skinbecause of its rich water content and thereforedoes not leave residual thermal damage.T F



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