In vivo port wine stain, burn and melanin depth determination using a photoacoustic probe

• US 7,322,972 B2
• Filed: 02/07/2003
• Issued: 01/29/2008
• Est. Priority Date: 04/10/2002
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Viator, John A., Jacques, Steven L., Paltauf, Guenther, Nelson, J. Stuart
• Primary Examiner(s): Hindenburg; Max F.
• Assistant Examiner(s): SMITH, FANGEMONIQUE A
• Application Number:
  US10/359,782
• Publication Number:
  US 20040039379A1
• Time in Patent Office: 1,817 Days
• Field of Search: 600/595, 600/474, 600/300, 600/437, 600/463, 600/476, 600/473, 600/587, 600/407, 600/310, 600/306, 736/33
• US Class Current: 606/9
• CPC Class Codes: A61B 18/203 applying laser energy to the outside of the body
• CPC Class Codes: A61B 2017/0011 piezoelectric
• CPC Class Codes: A61B 2018/00452 Skin
• CPC Class Codes: A61B 2018/00458 Deeper parts of the skin, e.g. treatment of vascular disorders or port wine stains
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/443 Evaluating skin constituents, e.g. elastin, melanin, water
• CPC Class Codes: A61B 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar
• CPC Class Codes: A61B 5/445 Evaluating skin irritation or skin trauma, e.g. rash, eczema, wound, bed sore

Abstract

A photoacoustic probe for port wine stain (PWS), burn and melanin depth measurements is comprised of optical fibers for laser light delivery and a piezoelectric element for acoustic detection. The probe induced and measured photoacoustic waves in acryl amide tissue phantoms and PWS skin in vivo. Acoustic waves were denoised using spline wavelet transforms, then deconvolved with the impulse response of the probe to yield initial subsurface pressure distributions in phantoms and skin. The waves were then analyzed for epidermal melanin concentration, using a photoacoustic melanin index (PAMI) related to the amount of laser energy absorbed by melanin. Propagation time of the photoacoustic wave was used to determine the depth of blood perfusion underlying necrotic, burned tissue. Thus, the photoacoustic probe can be used for determining PWS, burn and melanin depth for most patients receiving laser therapy.

Claims

1. An apparatus for depth profiling subsurface skin structures comprising:

a handpiece for* placement against the skin;

a light source for generating a light pulse at a wavelength and intensity effective to generate an epidermal or dermal photoacoustic response;

at least one optic fiber coupled to the light source for delivering the light pulse to the skin to generate a photoacoustic signal in the skin;

an acoustic detector disposed in the handpiece for receiving photoacoustic waves from the skin; and

a circuit coupled to the acoustic detector for processing electrical signals generated by the acoustic detector,

where the acoustic detector is recessed in a probe so that it is spaced apart from the skin to provide an acoustic delay greater than the delay of electrical noise arising from the light pulse to prevent contamination of the photoacoustic signal.

2. An apparatus for depth profiling subsurface structures of burned skin comprising:

a hand piece for placement against the skin;

a light source for generating a light pulse at a wavelength and intensity effective to generate an epidermal or dermal photoacoustic response;

at least one optic fiber coupled to the light source for delivering the light pulse to the skin;

an acoustic detector disposed in the handpiece for receiving photoacoustic waves from the skin;

circuit means coupled to the acoustic detector for processing electrical signals generated by the acoustic detector to identify acoustic signatures of dermal burn damage; and

a plurality of optic fibers, each for delivering a light pulse to the skin, where the plurality of optic fibers each simultaneously deliver a light pulse to the skin at a single spot.

6. The apparatus of claim 2 where the light source generates two selected wavelengths delivered by the plurality of optic fibers to generate corresponding different dermal photoacoustic responses from skin burn sites characterized by hemoglobin and its breakdown products in coagulated blood respectively thereby discriminating healthy from thermally damaged erythrocytes.

3. An apparatus for depth profiling subsurface structures of burned skin comprising:

a hand piece for placement against the skin;

a plurality of light sources for simultaneously generating a corresponding plurality of light pulses in a corresponding plurality of wavelengths and intensities effective to generate dermal photoacoustic responses;

an acoustic detector disposed in the handpiece for receiving photoacoustic waves from the skin;

circuit means coupled to the acoustic detector for processing electrical signals generated by the acoustic detector to identify acoustic signatures of dermal burn damage; and

a plurality of optic fibers, each coupled to a corresponding one of the plurality of light sources, where each one of the plurality of optic fibers simultaneously deliver a corresponding one of the plurality of light pulses to the skin at a corresponding different wavelengths.

7. The apparatus of claim 3 where the plurality of light sources generate light at two selected wavelengths delivered by the plurality of optic fibers to generate corresponding different dermal photoacoustic responses from skin burn sites characterized by hemoglobin and its breakdown products in coagulated blood respectively thereby discriminating healthy from thermally damaged erythrocytes.

4. An apparatus for depth profiling subsurface structures of burned skin comprising:

a hand piece for placement against the skin;

a light source for generating a light pulse at a wavelength and intensity effective to generate a dermal photoacoustic response;

at least one optic fiber coupled to the light source for delivering the light pulse to the skin;

an acoustic detector disposed in the handpiece for receiving photoacoustic waves from the skin; and

circuit means coupled to the acoustic detector for processing electrical signals generated by the acoustic detector to identify acoustic signatures of dermal burn damage;

where the subsurface skin structure is a skin burn and where the electrical signals generated by the acoustic detector are interpretable as depth profiles of the skin burn.

8. The apparatus of claim 4 where the light source generates light at two selected wavelengths delivered by the optic fiber to generate corresponding different dermal photoacoustic responses from skin burn sites characterized by hemoglobin and its breakdown products in coagulated blood respectively thereby discriminating healthy from thermally damaged erythrocytes.

5. An apparatus for depth profiling subsurface melanin concentrations comprising:

a hand piece for placement against the skin;

a light source for generating a light pulse at a wavelength and intensity effective to generate an epidermal or dermal photoacoustic response;

at least one optic fiber coupled to the light source for delivering the light pulse to the skin;

an acoustic detector disposed in the handpiece for receiving photoacoustic waves from the skin; and

circuit means coupled to the acoustic detector for processing electrical signals generated by the acoustic detector to identify acoustic signatures of melanin concentrations.