Lasers and Optics in Medicine Israel Gannot

When the laser was invented by Mayman, in 1960 , it was classified as a solution in search of a problem, and today laser technology is applied in many different areas such as: medicine, communication, daily use, military, and industry.

LASER = Light Amplification by Stimulated Emission of Radiation.

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Properties of Laser Radiation Directionality

Radiation comes out of the laser in a certain direction, and spreads at a defined divergence angle (θ θ ) This angular spreading of a laser beam is very small compared to other sources of electromagnetic radiation, and described by a small divergence angle (of the order of milliradians).

Monochromaticity

Coherence Coherent waves are waves that maintain the relative phase between them. Figure below describes, using the same time base, 3 waves marked y1, y2, y3, and their superposition. In figure a, the waves are coherent, like the waves out of a laser. In figure b, the waves have the same wavelength, but are not coherent with each other. Light from an incandescent lamp is composed of waves at many wavelengths, and each wave appears randomly with no systematic relation between its phase and that of the other wave. Laser radiation is composed of waves at the same wavelength, which start at the same time and keep their relative phase as they advance. By adding (superposition) the wave amplitudes of the different waves, higher peaks are measured for laser radiation.

a

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b

The Meaning of "One Color" In the theoretical sense "One Color",which is called "spectral line , meansone wavelength (λ λ 0). A graph of light intensity versus wavelength for ideal "one color" is shown on the right side of the figure. The right side of the figure shows an artistic description of realistic "one color". It has a peak of its value of "the color", but include a spread around the central peak. In reality, every spectral line has a finite spectral width (∆λ ∆λ ) around its central wavelength (λ λ 0), as can be seen in the left side of figure:

Stained cells

Muscle cell mitochondria

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Cell membrane

Collagen fibers

Laser and Optics in Medicine

Tissue Laser

Interaction Crater formation Thermal Chemical plasma

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Parameters Scattering, absorption, Thermal conductivity Thermal capacity

Diagnostics Fluorescence CW, Lifetime Opto-acoustics Polarization Optical tomography OCT

Water spectra

Wieliczka 1989

Problem definition Patients with coronary diseases who have problems in blood perfusion into the myocardium

Photon path in tissue

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The heart

Transmyocardial Revascularization (TMR). In TMR, it is believed that blood is restored to the oxygen-deprived heart muscle via channels or holes created by a TMR Laser System.

TMLR

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Approximately 20 to 40 channels (each 1mm wide) are created through the wall of the heart muscle intothe left ventricle. The laser is synchronized with the heartbeat and automatically triggered to fire when the ventricle is filled with blood. The blood acts as a backstop for the laser energy and prevents it from damaging other tissue in the heart.

PTMR - percutaneous transluminal myocardial revascularization,

PTMR, or percutaneous transluminal myocardial revascularization , is an interventional procedure performed by an interventional cardiologist. PTMR is based upon the same principles as TMR, but the procedu re is much less invasive. The patient is under local anesthesia, and is treated through a catheter inserted in the femoral artery at the top of the leg. A laser transmitting catheter is threaded up the aorta into the heart chamber, where channels are created in the inner portion of the heart muscle.

The eye

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PRK LASIK

Photorefractive keratectomy with feedback system EyeShape s Control

D a CC mer Ca

Excimer Laser

PC Image Processing

Surgery s

X,Y,Z

Fringe Projector

Fringe Projector

X,Y,Z

High Intensity Low193nm Intensity 193nm grating

Florescence (300-400nm)

grating

grating

grating

cornea

USPL dentistry

Future use of the USPL for medical applications requires a laser sized for the medical suite. In this example, a dentist is removing carious material with a laser delivered through an articulated arm

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Drilling in tooth

Optical Diagnostics

Normal Oral Mucosa

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Oral M u c o s a Normal Tongue

Normal, veins

Lichen Planus

Leukoplakia

Non invasive optical diagnosis: Early diagnosis of molecular transition in diseases. Localization of tumors. Disease monitoring and response to treatment.

Final goal: Bedside monitoring

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Examined mouse tongues :

Fluorescence signal from mouse tongue

Fluorescence imaging

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Fluorescent light image and 3D matlab representation,sick mouse+cd19, 1.95 mm Agarose slab.

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