Page 77 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
 Figure 41: Absorption curves of main chromophores in skin
● Haemoglobin is made up of the iron molecules contained within every blood cell. These molecules absorb oxygen in the lungs and then the cells transport it to every other cell in the body.
● There are essentially two main types of haemoglobin – oxyhaemoglobin and deoxyhaemoglobin. This first of these types has oxygen molecules attached to the iron core, while the second does not. They have similar absorption curves but generally it is the ‘combined’ curve which is used when calculating absorptions.
● Fortunately for us haemoglobin absorbs light quite strongly in certain parts of the spectrum. It absorbs blue light very strongly, but this is not a good wavelength for us to use when treating patients because it may induce unwanted changes in the melanin.
● Also, blue light cannot penetrate far into the dermis, so it would be of little use for vessels in that region.
● The next strong absorption peak is around 577 nm, which is in the yellow part of the spectrum. Because of this, many lasers were developed to produce energy at around this wavelength, originally.
● When light energy of this colour is fired into the skin the haemoglobin absorbs the energy preferentially compared with the surrounding tissues (like collagen or melanin).
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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