Lasers in Surgery and Medicine 12:675-678 (1992)

Laser Reflections From Surgical Instruments Rodney L. Wood, Jr., David H. Sliney, and Robert A. Basye Laser Microwave Division, U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland 21010 (R.L.W., D.H.S.); Simpson/Basye, Inc., 430 Ayre Street, Wilmington, Delaware 19804 (R.A.B.)

The potential hazards to the eye and skin from accidental exposures caused by reflected laser beams from surgical instruments has long been of concern to operating room staff members. Reflectance values for argon neodymium:YAG and C 0 2 laser wavelengths were measured from 29 reference surfaces used on surgical instruments. From these measurements, nominal hazard zones could be determined for typical reflection hazards. 0 1992 Wiley-Liss, Inc.

Key words: hazards, safety, reflections

struments [4,5]. However, it has been difficult to analyze the results from different instruments beThere has been an ongoing controversy as to cause of the effect of a wide variety of surface the value of blackening and/or roughening the curvatures (Fig. 2), and the lack of a standard surfaces of surgical instruments to reduce the risk curved surface. Therefore, a series of 29 flat stainfrom potentially hazardous laser reflections [l- less-steel plates were treated with different sur61. Users have complained that some ebonized face finishes to provide a means for determining coatings do not survive many sterilizations and the reflective effectiveness of different finishes. there have been a number of questions as to Measurements were then made of C0,-laser specwhich type of surface treatment provides superior ular (mirror-like) reflections from the differently reduction in the potential hazard from laser beam treated surfaces. reflections from surgical instruments in the operating field. Any metal surface may serve as a mirror- MATERIALS AND METHODS like (i.e., specular) reflector at far-infrared waveA 100-W carbon-dioxide laboratory laser lengths such as the carbon-dioxide laser wave- having an unfocused beam was directed at a selength of 10.6 p,m [2]. Even a metal surface that ries of 29 flat metal surfaces having different surappears very dull in visible light may actually face finishes. In addition, the beam was also behave like a polished mirror at 10.6 pm. This directed at a ceramic tile, characteristic of operoccurs because the property of specularity (mir- ating room theaters. The COz laser was adjusted ror-like behavior) is dependent upon wavelength. t o maintain a 20-W CW output power as moniA surface with microscopic roughness features of tored by a Scientec Model 360-206, 2 in disk calothe order of 2 p,m appears dull at 0.5 pm (green light), but may behave as a mirror at 10.6 pm. If the average surface discontinuity has dimensions Accepted for publication August 12, 1992. much greater than the incident wavelength, then Address reprint requests to David H. Sliney, Laser Microreflections will be diffuse (Fig. 1); but if the dis- wave Division, US.Army Environmental Hygiene Agency, continuity is much smaller than the wavelength, Aberdeen Proving Ground, MD 21010. reflections will be specular [ll. The opinions or assertions herein are those of the authors and There have been previous studies aimed at should not be construed as reflecting oficial positions of the measuring the reflection properties of surgical in- U S. Department of the Army or Department of Defense. INTRODUCTION

0 1992 Wiley-Liss, Inc.

Wood et al.

676

Keithley Voltmeter

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Detector

I

I CO, Laser

Fig. 1. Surface roughness and specularity. If the dimensions of microscopic irregularities are greater than the wavelength of incident optical radiation, the reflection will be diffuse [after Sliney and Wolbarsht, 19801.

/

Sample

Fig. 3. Experimental arrangement. A calibrated 7-mm aperture was placed at a reference distance from the target sample in order to measure a relative irradiance for comparison against the worst-case, flat, stainless-steel plate.

then placed behind a 7-mm limiting aperture placed at one of three distances from the target surface and along an axis of the reflected specular FOCUS€D B€AM COLIMAT€D BEAM beam (if it existed) as shown in Figure 3. Although, initially a 1-mm aperture was chosen to sample the reflected beam pattern, it was determined that a 7-mm aperture was required to adequately collect sufficient reflected / / laser energy for reliable measurements. The 7FLAT mm aperture was sufficient to sample “hot spots” SPECULAR SURFACE at the measurement distance employed, since all surfaces tested were smooth and without line patterns such as “brushed” aluminum. Although a pyroelectric detector could have been used to pro/vide greater sensitivity, this type of detector could be easily damaged by the specularly reflected I/ beam. CURVED The worst-case, most-reflective target was a SPECULAR SURFACE flat, polished plate of stainless steel used as a reference. The angle of incidence on this and all other target surfaces was approximately 20” and the detector was positioned to be centered in a specularly reflected beam by achieving a maximal reading on the calorimeter. The 29 other target surfaces were placed in the same target position and the amount of power ROUGHENED SURFACE: entering the 7-mm aperture was measured at one DIFUSE REFLECTION or several of 3 different distances: 52 cm, 37 cm, and 22 cm. Although some measurements were Fig. 2. The curvature of the specular surface and the degree made at 52 cm from the treated surfaces, the reof beam focussing will greatly influence the beam irradiance at a distance from the reflecting surface [after Sliney, 19891. flected radiant power was not always sufficient t o be detected at that distance, and all meaurements were repeated at a distance of 11 cm from the rimeter. The beam was directed at a target sur- target. The calorimeter was carefully adjusted face at an angle of approximately 20” from the prior to each exposure and was allowed to come to normal to the surface. The disc calorimeter was thermal equilibrium for each reading. The 7-mm

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Laser Reflection Hazards

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TABLE 1.Laser Reflected Power From Surgical Grade Stainless Steel Samples Reflected irradiance in W/cm2 at 15 cm Der watt incident Sample Ceramic tile 408A #408B SB-DAT SB-AC SB-BCC SB-CT (180 grit), No coating Silver finish #lo1 (bead blast), grey #lo1 (bead blast), gold #lo2 (bead blast), grey #lo2 (bead blast), gold #lo3 (fine grit), grey #lo3 (fine grit), gold #lo4 (80 grit), grey #lo4 (80 grit), gold #lo6 (20grit), grey #lo6 (20grit), gold #lo7 (starblast), grey #lo7 (starblast), gold 232-SB(180 grit) 230-C(180 grit) #418 (180 grit), new black Black speculum Gold speculum Silver speculum 101A.grey 101A; i o l d Cr SS mount

Nd:YAG (1,064nm)

7.28x 10-3 1.40x 10-4 8.68x 2.03x 10-4 2.44x 10-~ 1.82x 10-4 2.91x 10-~ 1.01 x 10-3 4.57x 10-2 -

-

-

-

-

-

aperture plate could heat up and reradiate farinfrared radiation. To be certain that we measured only the directly reflected laser radiation, the long-term value was distinguished from the near-term value by recording the calorimeter reading after 10-15 sec of exposure t o the refleeted laser light.

1o3

6,o2 I

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5

lo'

m U 2

=U RESULTS AND DISCUSSION

COP 2.18X lo-' 2.36x 10-4 2.83x lo-' 1.10x 10-4 4.59x 10-5 3.48x 10-5 6.83x 10-5 1.27x lo-' 4.75x 10-1 7.55x 10-3 2.02x 10-2 1.43x lo-' 1.80x lo-' 7.50x 10-4 9.50x 10-4 6.50x 10-4 9.0x 10-4 6.5x 10-4 1.15x 10-3 9.5x 10-4 1 . 1 5 10-3 ~ 2.0x 10-4 6.5x 10-4 1.5x 10-4 1.5x 1 0 - ~ 1.9x 10-3 2.7x 10-3 7.0x lo-' 1.56x 10-1 8.07x lo-'

100

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Table 1presents the measured data for these C? 10-l treated surfaces. Actual measured values have been normalized to reflected irradiance per inci10-2 ' ' ' ' ' ' , , , ' ' ' ' ' ' ' ' ,' x' dent watt for ready intercomparison. The rough1 10 100 loo0 ened, black surface finish with a fluoropolymer Distance (cm) material was shown to be over 400 times better than the referenced stainless steel and 9 Fig. 4.Calculated reflected irradiance values as a function of distance from four of the samples based upon the measuretimes better than grit-b1asted surfaces' The ments reported in Table 1.These are worst-case reflected levfluoropolymer coating Over a roughened surface els, since the reference surface was flat. was shown t o be 46 times better than the roughened surface alone. To make easy use of the results, we have calculated the reflected irradiance tion of distance for an incident power of 40 W at for four representative surfaces (Fig. 4)as a func- the C 0 2 wavelength. A power of 40 W was chosen '

'

Wood et al. to represent the upper range of COz laser power REFERENCES 678

be worstused in surgery‘ These case reflected levels since the reference surface was flat. Therefore, one could state that the nominal hazard zone (NHZ) from any surgical instrumerit reflections would be no greater than the values plotted in Figure 4 for 40 W power. If the the NHZ laser power were limited to would be reduced to one-half those plotted in Figure 4.

w,

CONCLUSIONS

The black fluoropolymer surface was shown t o be clearly superior to any of the other surface treatmentsfor minimizing reflections. Nominal surfaces fiehazard distances for quently extend only to the immediate area of the surgical field.

1. Sliney DH, Wolbarsht ML. “Safety with Lasers and Other Optical Radiation Sources.= New Yo&: Plenum publishing, 1980. 2. Sliney DH. Laser safety for plastic surgery and dermatology. In: Altschuler BM, ed. “Lasers in Plastic Surgery and Dermatology.” New York: Thieme Medical Publishers, 1992, 3. Sliney DH, Trokel SL. “Medical Lasers: Their Safe Use.” New York Springer-Verlag, 1992. 4. Driver I, Taylor C. The effect of surface finish on the reflection of CO, laser beams from specula. Phys Med Biol 1987; 32(2):227-235. 5. Friedman NR, Saleeby ER, Rubin MG, Sandu T, Krull EA. Safety parameters for avoiding acute ocular damages from the reflected CO, (10.6 microns) laser beam. J Am Acad Dermatol 1987; 17(5 Pt 1):815-818. 6. American National Standards Institute (ANSI). “Safe Use of Lasers in Health Care Facilities. American National Standard 2-136.3-1988,”Florida: Laser Institute of America, 1988.

Laser reflections from surgical instruments.

The potential hazards to the eye and skin from accidental exposures caused by reflected laser beams from surgical instruments has long been of concern...
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