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Recent Progress Recent Progress inin
Medical Laser TechnologiesMedical Laser Technologies________________________________________________________
光子光子 (Photon) vs. (Photon) vs. 光波光波 (Wave) (Wave) ----------------------------------------------- ----------------------------------------------- Diode vs. LEDDiode vs. LED (laser) …………. (light)(laser) …………. (light)
Historical Historical 1900 (1900 (Max PlanckMax Planck) …quantum mechanics) …quantum mechanics 1917 (1917 (EinsteinEinstein) …… A & B Coefficients) …… A & B Coefficients 1954 (Townes)…... MASER (microwave)1954 (Townes)…... MASER (microwave) 1960 (Maiman)…… Ruby laser1960 (Maiman)…… Ruby laser 1961 (Javan, Johnson) ……. HeNe, Nd:YAG1961 (Javan, Johnson) ……. HeNe, Nd:YAG 1962 (Bennett)…….. Argon laser1962 (Bennett)…….. Argon laser 1964 (Patel) ………. CO2 laser1964 (Patel) ………. CO2 laser The laser-patent war /Gordon Gould (1997). The laser-patent war /Gordon Gould (1997).
Examples of innovation-IMPACTExamples of innovation-IMPACT
Only < 1% patents has major financial impacts !!!Only < 1% patents has major financial impacts !!! (the METHODS patents)(the METHODS patents) IBM (1983 US patent):IBM (1983 US patent): UV laser (193 nm, ArF) for all organic tissue ablationUV laser (193 nm, ArF) for all organic tissue ablation licensed to LaserSight for >$30Mlicensed to LaserSight for >$30M Steve Troke (Columbia Univ.)Steve Troke (Columbia Univ.) 1986 US Pat…ArF for PRK/LASIK1986 US Pat…ArF for PRK/LASIK value : >$2.0 Bvalue : >$2.0 B JT Lin (1991, 2000, 2004, 2006 US pat)JT Lin (1991, 2000, 2004, 2006 US pat) scanning-laser for Lasikscanning-laser for Lasik value > $500Mvalue > $500M Shue Lai (1993)Shue Lai (1993) eye-tracking device, eye-tracking device, value >$200Mvalue >$200M
JT Lin (1998)..JT Lin (1998).. laser for presbyopia laser for presbyopia value > $200M (???)value > $200M (???)
Medical products Medical products developmentdevelopment
Energy (E), Intensity (I), Power (P), fluency (F)Energy (E), Intensity (I), Power (P), fluency (F) Absorption coefficient (A), Reflection/scattering loss Absorption coefficient (A), Reflection/scattering loss
concept: F = E/ laser spot-sizeconcept: F = E/ laser spot-size
I= E/ pulse-widthI= E/ pulse-width
Thermal vs. Non-Thermal vs. Non-thermal thermal
(1) Thermal: ( most cosmetic lasers): (1) Thermal: ( most cosmetic lasers):
Laser Ablation Theory Laser Ablation Theory (1) (1) Beers law:Beers law: I(z) = I(0) Exp [-Az]I(z) = I(0) Exp [-Az]
(2) (2) Ablation depth (Ablation depth (H) is given byH) is given by H = (1/A) ln (F/F*)H = (1/A) ln (F/F*) where F*= threshold laser fluence where F*= threshold laser fluence for ablation to occur. for ablation to occur. optimal A* given by dH/dA = 0optimal A* given by dH/dA = 0 A*=2.718 (F*/F)A*=2.718 (F*/F)
(3) (3) Lin’s lawLin’s law (2005, for focused laser) (2005, for focused laser) I = B I(0) Exp(-Az)I = B I(0) Exp(-Az)
B=focusing factor for optimal depth.B=focusing factor for optimal depth.
0 F* 0 F* F F
Depth (H)Depth (H)
0 A* 0 A* A A
Depth (H)Depth (H)
Laser heating theoryLaser heating theory Laser produced tissue temperature via heat conduction Laser produced tissue temperature via heat conduction
equationequation dT/dz = k (ddT/dz = k (d22 T/dz T/dz22)) where k=temperature conductivitywhere k=temperature conductivity Laplace transform or the Green function method to Laplace transform or the Green function method to
obtainobtain T(z,t) = Integrate { S G dz dt }T(z,t) = Integrate { S G dz dt } S is the heat source and G is the Green function S is the heat source and G is the Green function
given by given by G = C exp [ -(z-z0)^2 / 4k(t – t0) ]G = C exp [ -(z-z0)^2 / 4k(t – t0) ] Thermal penetration depthThermal penetration depth d* = square root of (4kt) d* = square root of (4kt) = 0.75 = 0.75 square root [laser pulse width]square root [laser pulse width] for d (in um)m and t (in usec).for d (in um)m and t (in usec). Example: Example: for 1 usec laser, the heat conduction distance is for 1 usec laser, the heat conduction distance is
about 0.75 um.about 0.75 um.
The one-micron ruleThe one-micron rule: ( t*=1.0 usec): ( t*=1.0 usec) short pulsed laser for non-thermal process.short pulsed laser for non-thermal process. example: fiber laser (f.s.)example: fiber laser (f.s.)
Laserscope, Inc. (acq. by AMS for $1.9 B)Laserscope, Inc. (acq. by AMS for $1.9 B) high-power (50-80 W)high-power (50-80 W) cw, green (532 nm) lasercw, green (532 nm) laser fiber-coupledfiber-coupled ** side firing** side firing Other lasers: Other lasers: Er:YAG (2.9 um) Ho:YAG(2.1 um), Er:YAG (2.9 um) Ho:YAG(2.1 um),
Dental lasersDental lasers(1) Hard tissue (dentin, carries)(1) Hard tissue (dentin, carries) a) Biolase “water-laser” (Er:YSGG at a) Biolase “water-laser” (Er:YSGG at
2.78 um)2.78 um) b) Lin/ITRI, mid-IR diode laser (2.7-3.0 b) Lin/ITRI, mid-IR diode laser (2.7-3.0
um)um)(2) Diode laser (soft tissue)(2) Diode laser (soft tissue) at 808, 940, 980 nmat 808, 940, 980 nm(3) Teeth whitening(3) Teeth whitening Nd:YAG (1064) + dyeNd:YAG (1064) + dye(4) Velcope (4) Velcope Blue-light (or LED) to detect cancer tissueBlue-light (or LED) to detect cancer tissue
““Smart eye” designsSmart eye” designs (learned from nature’s evolution theory )(learned from nature’s evolution theory )
On the origin of species by means of On the origin of species by means of Natural Selection Natural Selection (Charles Darwin,1859) (Charles Darwin,1859)
““Functional adaptation” is one of the important Functional adaptation” is one of the important built -in survival mechanisms built -in survival mechanisms of all species.of all species.
Analysis of smart eyes with high power lens-accommodation Analysis of smart eyes with high power lens-accommodation (Lin, JCRS, 2007, 35, 758-759)(Lin, JCRS, 2007, 35, 758-759)
355 >> (0.6 to 1.3 um) .... BBO355 >> (0.6 to 1.3 um) .... BBO
Raman shift (SRS, SBS)Raman shift (SRS, SBS) (in methane, H2, D2 gas)(in methane, H2, D2 gas) 1064 (in CH4)>> 1.54 um (eye-safe range finder/Litton)1064 (in CH4)>> 1.54 um (eye-safe range finder/Litton) 532 (in H2) >> 460(Stokes), 682 (anti-stokes)532 (in H2) >> 460(Stokes), 682 (anti-stokes)
New Directions (The next 3-5 years trends)New Directions (The next 3-5 years trends)
- - IInnovative concepts for newnnovative concepts for new methods & methods & treatments treatments - - - - - LED for l- LED for lowow--cost light source cost light source ((replacing lasersreplacing lasers))..
- N- New optical fibers ew optical fibers (materials & structures)(materials & structures) - Real-time image monitoring (endoscope)- Real-time image monitoring (endoscope) - - More efficient, selective image detection devicesMore efficient, selective image detection devices in optical biopsyin optical biopsy - L- Lessess--toxic agentstoxic agents,, such as nanoparticles and new such as nanoparticles and new IR dyesIR dyes,, in PDT procedures. in PDT procedures.
More New DirectionsMore New Directions- - - SSolidolid--state UV laser state UV laser , , replacing the toxic excimer laser replacing the toxic excimer laser - for LASIK.for LASIK.- - Femto-second lasers for - Femto-second lasers for - PDT, cancer diagnosis,PDT, cancer diagnosis,- and blade-less LASIKand blade-less LASIK
- M- Multiple wavelength, multi-applications systemsultiple wavelength, multi-applications systems - M- Minimally invasive techniques for class II or II procedures.inimally invasive techniques for class II or II procedures.
REFERENCESREFERENCES 1. 1. J.T. Lin, Laser Applications in Ophthalmology, Jaypee J.T. Lin, Laser Applications in Ophthalmology, Jaypee
Brothers (2008), Brothers (2008), 2 2 J.T. Lin, US Patent J.T. Lin, US Patent NNo. 5144630o. 5144630 (1992).(1992). 3. 3. 久保于市久保于市 ,Medical Applications of Lasers Tokyo, Japan ,Medical Applications of Lasers Tokyo, Japan