© 2002 by the American Society for Dermatologic Surgery, Inc. • Published by Blackwell Publishing, Inc.ISSN: 1076-0512/02/$15.00/0 • Dermatol Surg 2002;28:199–204

YOUNG INVESTIGATOR’S AWARD WINNER

This study nicely quantitates the clinical effects of non-ablative laser treatments, i.e. increased skin smoothness re-ported by patients. However, readers should not interpret these results as validating significant visual improve-ment in either scars or wrinkles. Also noteworthy is that skin hydration from application of EMLA cream pro-vided significantly more improvement in fine facial lines than following five non-ablative laser treatments.

William P. Coleman, III, MD

3D In-Vivo Optical Skin Imaging for Topographical Quantitative Assessment of Non-AblativeLaser Technology

Paul M. Friedman, MD,*

†

Greg R. Skover, PhD,

‡

Greg Payonk, PhD,

‡

Arielle N. B. Kauvar, MD,* and Roy G. Geronemus, MD*

*

Laser and Skin Surgery Center of New York, New York, NY,

†

DermSurgery Associates, Houston, TX, and

‡

Skin Research Center, Johnson and Johnson Consumer Companies, Skillman, NJ

background.

A new method for treating facial rhytides andacne scars with nonablative laser and light source techniqueshas recently been introduced. Given the inherent limitations ofphotographic and clinical evaluation to assess subtle changesin rhytides and surface topography, a new noninvasive objec-tive assessment is required to accurately assess the outcomesof these procedures.

objective.

The purpose of this study was to measure and ob-

jectively quantify facial skin using a novel, noninvasive,

In-vivo

method for assessing three-dimensional topography. Thisdevice was used to quantify the efficacy of five treatment ses-sions with the 1064 nm QS Nd:YAG laser for rhytides andacne scarring, for up to six months following laser treatment.

methods.

Two subjects undergoing facial rejuvenation pro-cedures were analyzed before and after therapy using a 30-mm,three-dimensional microtopography imaging system (PRIMOS,GFM, Teltow, Germany). The imaging system projects lighton to a specific surface of the skin using a Digital Micromirror

Device (DMD

Texas Instruments, Irving, TX) and recordsthe image with a CCD camera. Skin Surface microtopographyis reconstructed using temporal phase shift algorithms to gen-erate three-dimensional images. Measurements were taken atbaseline, at various times during the treatment protocol, andthen at three and six-month follow-up visits. Silicone skin rep-licas (FLEXICO, Herts, England) were also made before and

after the laser treatment protocol for comparison to

In-vivo

acquisition.

results.

Skin roughness decreased by 11% from baseline af-ter three treatment sessions in the wrinkles subject, while a26% improvement of skin roughness was recorded by 3D

In-vivo

assessment six months following the fifth treatment ses-sion. The subject with acne scarring demonstrated a 33% de-crease in roughness analysis after three treatment sessions by3D

In-vivo

assessment. A 61% improvement in surface topog-raphy was recorded 3-months following the fifth treatmentsession, which was maintained at the 6-month follow-up.

conclusion.

Three-dimensional

In-vivo

optical skin imagingprovided a rapid and quantitative assessment of surface to-pography and facial fine lines following multiple treatmentsessions with a 1064-nm QS Nd:YAG laser, correlating withclinical and subjective responses. This imaging technique pro-vided objective verification and technical understanding ofnonablative laser technology. Wrinkle depth and skin rough-ness decreased at the three and six-month follow-up evalua-tions by 3D

In-vivo

assessment, indicating ongoing dermalcollagen remodeling after the laser treatment protocol. Futureapplications may include comparison of nonablative lasertechnology, optimization of treatment regimens, and objectiveevaluation of other aesthetic procedures performed by derma-tologists.

Background

A VARIETY OF methods have been used to treat fa-

cial rhytides associated with photoaging including derma-

brasion, chemical peels, and ablative laser resurfacing.

1–7

Nonablative laser and light source techniques have re-cently been introduced as a treatment that selectivelyheats the upper dermis, inducing a wound healing re-

sponse in the papillary and upper reticular dermis with-

out epidermal ablation.

8–12

Histologic studies have shownthat new collagen production and deposition results fromsuch procedures, and that removal of the epidermis and

Address correspondence and reprint requests to: Paul M. Friedman, MD,Director of Laser Surgery, DermSurgery Associates, 7515 Main, Suite240, Houston, TX 77030, or email: pmfriedman@dermsurgery.org

200

friedman et al.: 3-d-in-vivo skin imaging

Dermatol Surg 28:3:March 2002

portions of the dermis are not required for neocollagene-sis and collagen remodeling.

8,10

Improved skin textureand turgor have been reported by patients and physi-cians, but has been difficult to quantify given the inher-ent limitation of photographic and clinical evaluation.

Optical profilometry has been shown to measurewrinkle depth by quantifying contours of silicone rub-ber replicas, capturing surface topography,

13,14

andmay also serve as a valid and reliable method for de-termining an improvement in acne scarring.

4

How-ever, it is highly operator-dependent and may producea variety of artifacts. The type of replica material usedmay accentuate or diminish the actual skin surface to-pography. Mixing of the replica material may enhanceor delay the speed of curing altering the impression atthe various time points. Polymerization of the materialmay alter the skin’s microtopography. Material curingmay change altering the recovery of precise skin repli-cas. Furthermore, positioning of the patient in a su-pine position is required to provide a horizontal sur-face permitting the curing of the material from a liquidto a solid state producing a gravitational artifact.

Direct three-dimensional

In-vivo

skin imaging canminimize these and other inherent artifacts associatedwith optical profilometry. To acquire an exact 3D im-pression of skin microtopography the technique usedmust achieve high lateral resolution with minimal ver-tical interference, or noise, enabling accurate reconstruc-tion of images. Images must be acquired rapidly withoutaltering the surface. The system must be able to 1. Adaptto highly contoured surfaces without losing resolution, 2.Calibrate with ease and ensure accurate measurement ofreconstructed images and 3. Identify suitable landmarkspermitting comparative image assessment.

The PRIMOS optical three-dimensional

In-vivo

skinmeasurement device (PRIMOS, GFM, Tetlow, Ger-many) used in this study deploys a parallel stripe patternimaging technique that is projected onto the skin surfaceand depicted on the CCD chip of a high resolution cam-era. Light patterns are created by a digital micromirrorprojector (Texas Instruments, Irving TX). The use of mi-cromirror-based digital light projectors is advantageouswhen applied to optical 3D

In-vivo

skin measurementbecause the light intensity is high, exposure time is shortand the light can be controlled point and/or pixelwise.

15

The 3D effect is achieved by means of minute elevationdifferences on the skin surface deflecting the parallelprojection stripes to produce a qualitative and quantita-tive measurement of the skin’s profile. Images are digi-tized and transferred for computer assisted quantitativeevaluation and measurement. Mathematical algorithmsembedded in the analytical software reconstruct thedata into a highly precise 3D profile of the skin surface.

The vertical and lateral resolution of a stripe pro-jection measurement device such as the PRIMOS opti-

cal system are essentially determined by the field ofview (FOV) used, the number of pixels of the record-ing camera and the accuracy of the determination ofthe smallest stripe deflections that can be processed. Ahighly precise area recovery was developed for thePRIMOS device that makes it possible to realize themeasurement position on the skin surface with a preci-sion of 1/10 pixel. Therefore, for the measurementfield of 30

�

24 mm, using a 640

�

480 pixel CCD,positioning precision of 3

�

m can be attained.

Methods

The study protocol conformed to the ethical guidelines ofthe 1975 Declaration of Helsinki and approved as a pro-spective clinical trial by the Essex Institutional ReviewBoard, Inc., Lebanon, NJ.

Two subjects were evaluated by three-dimensional mi-crotopography to demonstrate how quantitatively measur-able changes in the skin following nonablative laser technol-ogy could be assessed with the PRIMOS device. Subject 1had class III rhytides and skin phototype II, and was evalu-ated from October 2000 through August 2001. Images wereacquired prior to therapy, before and after application oftopical anesthetic under occlusion, immediately after one la-ser treatment session, and at specified follow-up visits. Fur-thermore, at the completion of the trial the subject was im-aged in the same location one month following BOTOX(Allergan Inc., Irvine, CA) injections.

Subject 2 had mild atrophic acne scarring and skin pho-totype II. 3D

In-vivo

microtopography and silicone rubberimpressions were taken before treatment, at various timesduring treatment, and three and six months following thecompletion of the laser treatment protocol.

Laser Treatment

The subjects were treated five times at 2–3 week intervals. Atopical anesthetic (EMLA cream, Astra USA, Westborough,MA) was applied under occlusion for one hour prior to eachtreatment. Immediately before treatment, the EMLA waswashed off the treatment area and followed by gentle cleansingwith alcohol. The Q-Switched Nd:YAG laser (Medlite IV,Continuum, Santa Clara, CA) (

�

�

1064 nm) was used witha spot size 6 mm, fluence 3–3.5 J/cm

2

. Multiple passes withthe laser were performed to the periorbital and perioral re-gions until a clinical end point of erythema was obtained.The subject with acne scarring received multiple laser passesto both cheeks, extending from the nasolabial fold to thepreauricular area and jawline until a clinical end point of er-ythema was obtained. The subjects applied a sunscreen ofSPF30 or higher daily to the treatment areas.

Clinical Photography

Photographs were taken before and after the procedure with aNikon N6006 camera Nikkor 60 mm F2.8 lens and CSI Twin

Dermatol Surg 28:3:March 2002

friedman et al.: 3-d-in-vivo skin imaging

201

Flash (Canfield Scientific, Fairfield, NJ) using KODAK Ko-dachrome film. Replicate photographs were taken from 0

�

,45

�

(right) and 45

�

(left) using a standardized reproduction ra-tio of 1 : 6 (f/16) for full facial photographs and 1 : 3 (f/22) forclose-up photographs. The subject was positioned in a CSIhead restraint enabling comparative photographs to be takenthroughout the study (Canfield Scientific, Fairfield, NJ). Preand post treatment photographs were assessed by two physi-cians and graded on a four point scale where (0% changefrom baseline was graded as no improvement, 1–25% changegraded as mild improvement, 26–75% change graded as amoderate improvement, 75–100% a marked improvement).

Skin Surface Topography

Patients were positioned in front of the light projector andthe head position fixed and recorded using a head restraint.Three-dimensional microtopography was performed withthe PRIMOS 30 mm imaging system (PRIMOS Imaging Sys-tem, G.F.M. Teltow, Germany). A digital micro mirror de-vice (Texas Instruments, Irving TX) creates a parallel stripepattern imaging technique that is projected onto the skinsurface and depicted on the CCD chip of a high-resolutioncamera. Images are digitized and transferred for computerassisted quantitative evaluation and measurement. Mathe-matical algorithms embedded in the analytical software re-construct the data into a highly precise 3D profile of theskin surface.

Algorithms contained in the evaluation software permitStar Roughness to be calculated from the acquired surfaceprofile. The average of 16 profile lines arranged in a radialarray were used to assess the surface. Two different rough-ness equations were used to analyze the data. Roughness(

R

a

) is the arithmetic average of the absolute values of allpoints of the profile. In other words,

R

a

is the height of therectangle with the same length and surface as the profile en-closes in the specified sector. The value yields an impressionof surface smoothness therefore was used to analyze surfaceimages taken from subjects with acne scarring. On the otherhand, Roughness (

R

z

) is the mean peak to valley height andis the arithmetic average of the maximum peak to valleyheight of the roughness values Y1 to Y5 of 5 consecutivesampling sections over the filtered profile. Alternatively, thisvalue yields an impression of the prominence of wrinkles thatare the greatest contributors effecting the surface deflectionin the crow’s feet area of patients with photodamage.

16

Silicone Impressions

Silicone skin replicas (FLEXICO, Herts, England) were madebefore and after the laser treatment protocol to measure sur-face texture and topography. Impressions were taken fromrepresentative areas on the cheek from patient 2 with acnescarring. Analysis was performed with the PRIMOS 30 mmimaging system. The light projector was rotated 90 degreesperpendicular to mounting stand stage. The replica was posi-tioned underneath the light source and the image acquired ina similar manner to the in-vivo acquisition.

17

Results

A reduction in the Rz value occurred following appli-cation of the topical anesthetic under occlusion for 1hr, likely from moisture retention in the skin (Figure1). An increase in Rz was observed immediately fol-lowing the laser treatment consistent with mild abra-sion. Rz decreased by 11% from baseline after threetreatment sessions, while a 26% improvement of sur-face topography was recorded six months followingthe fifth treatment session. BOTOX injections in theperiorbital and glabela areas were performed aftercompletion of the study protocol, and

In-vivo

imaginga month later demonstrated a further 15% decrease inskin roughness (Figure 1).

The subject with acne scarring demonstrated a de-crease in Ra at each follow-up visit by

In-vivo

assess-ment (Figure 2). Ra decreased by 33% after threetreatment sessions. A 61% improvement was recorded3-months following the fifth treatment session whichwas maintained at the 6-months follow-up. Compari-

Figure 1. Roughness Analysis (Rz) of photodamaged skin follow-ing nonablative laser resurfacing. Images from the periorbitalarea were captured with the PRIMOS 30 mm imaging system (PRI-MOS Imaging System, G.F.M. Teltow, Germany). Images were digi-tized and saved for computer assisted quantitative evaluation andmeasurement. Algorithms contained in the evaluation softwarepermit Roughness to be calculated from the acquired surface pro-file. Sixteen profile lines arranged in a radial display were used tocompute the average surface roughness. Roughness (Rz) is themean peak to valley height and is the arithmetic average of themaximum peak to valley height of the roughness values Y1 to Y5of 5 consecutive sampling sections over the filtered profile mea-sured in micrometers. Time points: Baseline: pretreatment, PostEMLA: measurement after one hour of topical anesthetic underocclusion before laser treatment, Post Laser: immediately follow-ing laser procedure, Mid Tx: measurement before the fourth lasertreatment, 6 month FU: six months after five laser treatments, 1month Botox: 1 month after BOTOX injections.

202

friedman et al.: 3-d-in-vivo skin imaging

Dermatol Surg 28:3:March 2002

son of

In-vivo

vs. replica impression Ra acquisitionwas performed utilizing the PRIMOS imaging device.The

In-vivo

surface changes correlated with the clini-cal assessment and subjective responses of a 25–50%improvement after three treatment sessions, and a greaterthan 50% improvement at the 3- and 6-months follow-

up. In contrast, replica analysis demonstrated an 8–18%improvement of surface topography at the follow-upvisits (Figure 2).

Evaluation of clinical photography did not clearlydemonstrate these changes in skin topography (Figure3,4). The high-resolution camera images obtained withthe PRIMOS camera before and after treatment (Fig-ure 5,6) clearly demonstrates the improvement of sur-

Figure 3. Photograph of subject with acne scarring before treatment.

Figure 2. Roughness Analysis (RA) of acne scarred skin followingnonablative laser resurfacing. Images from the cheek were cap-tured with the PRIMOS 30 mm imaging system (PRIMOS ImagingSystem, G.F.M. Teltow, Germany). Silicone replicas were taken fromthe same area. Both the In-vivo and replica images were digitizedand saved for quantitative measurement. Algorithms contained inthe evaluation software permit Roughness to be calculated fromthe acquired surface profile. Sixteen profile lines arranged in a ra-dial display were used to compute the average surface roughness.Roughness (Ra) is the arithmetic average of the absolute values ofall points of the profile. In other words, Ra is the height of the rect-angle with the same length and surface as the profile encloses inthe specified sector. Time points: Baseline: pretreatment, Mid Tx:measurement before the fourth laser treatment, 3 and 6 month FU:three and six months after five laser treatments.

Figure 4. Photograph of subject with acne scarring three monthsafter the end of five treatments.

Figure 5. High resolution camera image of subject with acne scar-ring before treatment.

Dermatol Surg 28:3:March 2002

friedman et al.: 3-d-in-vivo skin imaging

203

face topography in this patient. Color coded heightdisplay of surface topography show smoother skintexture 3-months after the five treatment sessions bythe evenness in color distribution with greater amount of color closer to the 0 height after the laser treat-

ments (Figures 7 and 8).

Discussion

The study of nonablative laser technology for facialfine lines and acne scarring is a new area of clinical re-search for which appropriate evaluation criteria arebeing determined. Conventional methods of evaluationhave included photographic and clinical assessment,which have inherent limitations. Computerized imageanalysis of silicone replicas has been shown to be a re-producible, objective technique for measuring skin to-pography.

18

Three-dimensional

In-vivo

imaging pro-vides a real time, objective analysis of patient specificcharacteristics potentially enabling clinicians to predictthe limitations and efficacy of various aesthetic proce-dures. Consequently, we sought to complement the sub-jective reporting with an objective technique that couldreproducibly measure changes in surface topography.

After 3–5 treatment sessions with a QS Nd:YAG la-ser, we quantified improvement of surface topographyusing 3D

In-vivo

skin imaging in subjects with acnescarring and facial fine lines. Surface topography andfacial fine lines were effectively captured by the PRI-MOS imaging system initially, during the treatmentsequence and months after therapy. Evaluation of suc-

Figure 6. High resolution camera image of subject with acne scar-ring three months after the end of five treatments.

Figure 7. Color coded surface topography image of subject withacne scarring before treatment (Ra � 90.4 �m).

Figure 8. Color coded surface topography image of subject withacne scarring three months after the end of five treatments (Ra �37.0 �m).

204

friedman et al.: 3-d-in-vivo skin imaging

Dermatol Surg 28:3:March 2002

cessive images suggests that the method provides rapidand reliable data that can document outcomes through-out the rejuvenation process. Subjects were assessedover 11 months, with photography, skin replicas and3D

In-vivo

imaging. The subjects showed successiveimprovement at the end of the treatment sequencecontinuing through the subsequent evaluation timepoints, suggesting ongoing dermal collagen remodel-ing. The greatest percentage improvement was ob-served with

In-vivo

imaging at three months followingthe treatment protocol. The improvement plateauedand held constant at the final six-month evaluation.

3D

In-vivo

optical imaging provided higher resolu-tion of skin topography than analysis by clinical pho-tography or skin replicas changes, and were in agree-ment with clinical assessment and patient subjectiveresponses. This data corroborate results presented byBoyes et al. demonstrating a substantial correlationbetween subjective clinical assessment and objective3D

In-vivo

imaging following nonablative laser proce-dures.

19

These results suggest that 3D

In-vivo

skin im-aging provides a rapid and accurate method to quan-tify measurable changes in subjects with acne scarringand photodamage. This imaging technique also pro-vided an objective verification and technical under-standing of this evolving technique. The value of thisimaging technique is currently being evaluated furtherin a larger trial being performed at our center.

Future application of PRIMOS imaging of the mi-crotopography of human skin

20

may provide an objec-tive measure for comparison of nonablative laser tech-nology and post-treatment topical regimens. This devicemay also allow for the objective evaluation of otheraesthetic procedures performed by dermatologists, in-cluding soft tissue augmentation, BOTOX, and topi-cal antiaging medications. Furthermore, accurate as-sessment of facial topography may enable clinicians toachieve desirable affects while minimizing complica-tions. This technique may also provide an objectivemodality for the cosmetic and pharmaceutical indus-try to evaluate the efficacy of rationings, alpha hy-droxy acids, beta hydroxy acids, and antioxidants fortheir effects on facial wrinkling.

Acknowledgments

The authors would like to express oursincere appreciation to Marisol Edward, Judy Dulberg, Al-exis Moreno, and Michelle Turnbull of the Laser & SkinSurgery Center of New York Research Department for theirclinical assistance. Furthermore, to Dick Jackson, D-Jackson

Software Consulting Calgary, Canada, for his invaluable ex-pertise in developing the software for the 3D image process-ing and analysis.

References

1. Waldorf HA, Kauvar AN, Geronemus RG. Skin resurfacing of fineto deep rhytides using a char-free carbon dioxide laser in 47 pa-tients. Dermatol Surg 1995;21:940–6.

2. Fitzpatrick RE, Goldman MP, Satur NM, et al. Pulsed carbon diox-ide laser resurfacing of photoaged skin. Arch Dermatol 1996;132:395–402.

3. Hruza GJ. Skin resurfacing with lasers. Fitzpatricks J Clin Derma-tol 1995;3:38–41.

4. Jordan R, Cummins C, Burls A. Laser resurfacing of the skin forthe improvement of facial acne scarring: a systematic review of theevidence. Br J Dermatol 2000;142:413–23.

5. Alster TS, West TB. Resurfacing of atrophic facial acne scars with ahigh-energy, pulsed carbon dioxide laser. Dermatol Surg 1996;22:151–5.

6. Laufman R, Hibst R. Pulsed erbium. YAG laser ablation in cutane-ous surgery. Lasers Surg Med 1996;19:324–30.

7. Kye YC. Resurfacing of pitted facial scars with a pulsed Er: YAGlaser. Dermatol Surg 1997;23:880–3.

8. Kelly KM, Nelson JS, Lask G, Geronemus RG, Bernstein LJ. Cryo-gen spray cooling in combination with nonablative laser treatmentof facial rhytids. Arch Dermatol 1999;135:691–4.

9. Zelickson BD, Kilmer SL, Bernstein E, et al. Pulsed dye laser ther-apy for sun damaged skin. Lasers Surg Med 1999;25:229–36.

10. Menaker GM, Wrone DA, Williams RM, Moy RL. Treatment offacial rhytids with a nonablative laser: a clinical and histologicstudy. Dermatol Surg 1999;25:440–4.

11. Goldberg DJ, Metzler C. Skin resurfacing utilizing a low fluenceNd: YAG laser. J Cutan Laser Ther 1999;1:23–7.

12. Goldberg DJ, Whitworth J. Laser skin resurfacing with theQ-Switched Nd: YAG laser. Dermatol Surg 1997;23:903–7.

13. Marks R. Methods for the assessment of the effects of topical reti-noic acid in photoaging and actinic keratoses. J Intern Med Res1990;18 (Suppl. 3:29) C–34.

14. Grove GL, Grove MJ, Leyden JJ. Optical profilometry. an objectivemethod for quantification of facial wrinkles. J Am Acad Dermatol1989;21:631–7.

15. Jaspers S, Hopermann H, Sauermann G, Hoppe U, Lunderstädt R,Ennnen J. Rapid in vivo measurement of the topography of humanskin by active image triangulation using a digital micromirror de-vice. Skin Res Technol 1999;5:195–207.

16. Schreiner V, Sauermann G, et al. Characterization of the Skin Sur-face by ISO Parameters for Microtopography. In: Wilhelm, K-P, El-sner, P, Berardesca, E, Maibach, HI, eds. Bioengineering of theSkin: Skin Surface Imaging and Analysis. CRC Press, Inc, Boca Ra-ton, FL., 1997.

17. Payonk GS, Kollias N, Poster Exhibit AAD 59th Annual Meeting,Washington, D.C., March, 2001.

18. Grove GL, et al. Skin replica analysis of photodamaged skin aftertherapy with tretinoin emollient cream. J Am Acad Dermatol 1991;25:231–7.

19. Boyes LE, Goldman MP, Payonk GS, Skover GR. American Societyfor Laser Medicine and Surgery Twenty-First Annual Meeting,New Orleans, LA, April, 2001.

20. Hof C, Hopermann H. Comparison of Replica- and In Vivo-Mea-surement of the Microtopography of Human Skin, Report der Uni-versität der Bundeswahr Hamburg, Institut für Automatsierung-stechnik, 2000.