Melanoma - skin cancer reviewed

    There are many skin image capture methodologies developed and used. Here are short review of them:

Dermatoscopic photography

The deepest layer of skin can be reached - Papillary dermis

Resolution – depends on optical system

View of skin – Horizontal

The main disadvantage is reflections of light from skin surface – stratum cornea.

Dermatoscopic oil immersion photography

The deepest layer of skin can be reached - Papillary dermis

Resolution – depends on optical system

View of skin – Horizontal

Reflections of light from skin surface are smaller because of oil used between camera optics and skin.

Fluid free dermatoscopic photography, polarized light

This method gives similar results as using oil immersion. It is cleaner image taking method, because sin is kept dry and there is no wet contact with camera.

Trimodal light source

    The deepest layer of skin can be reached - Papillary dermis

    Resolution – depends on optical system

    View of skin – Horizontal

This is special method of light directing to deeper skin layers avoiding passing the lesion surface. It gives very good results of skin deeper layer imaging.

CSLM

    CLSM  - laser scanning microscope system. There laser beam is focused to particular skin layer and     scanned 2D image in this deep. This method is handy when taking deeper layers of skin. The deep can be from 2 to 300ukm.

Multispectral dermatoscopy

This method is described in earlier articles. There are multispectral light used to take separate pictures. Then calculation is used evaluate pigmentation of different skin layers. This is progressive methodology in diagnosis.

Optical Coherence Tomography

There is interference of two different light sources. One is directed to skin and other is reference to determine the depth. This method is more advanced and not suitable for screening. The depth can be achieved - 15 - 2 μm.

High Resolution Ultrasonic Imaging

    There is high frequency ultrasound used to determine lesion boundaries before surgery. In early skin cancer detection this method hardly can be used, as the difference between healthy and suspicious regions are minimal. But combining Ultrasound and lets say multispectral photography can show good results.

As you requested, here is a schematics of adapter. There is nothing much to tell about it. If there is any questions, don’t hesitate to ask.

There is simple system by using two perpendicular polarization films. The angle on which light should fall is called Brusters angle. This is an angle on which incident polarized lights polarization plane is turned  on 90 degrees when it is reflected.

The system of imaging looks as follows: 

 

 

To evaluate skin pigmentation in different skin layers, there is special light adapter needed in order to take multispectral pictures of skin. As there are different optical properties of skin pigments,  4 different light sources have been chosen.

blue λ= 470 nm – highly absorbed by epidermal melanin

green λ= 576 nm – hemoglobin peak

red  λ= 660nm – epidermal dermal boundary

IR λ= 865 nm – low absorption, sensitive to scattering to measure papillary dermis thickness.

There was lighting source for “Nikon Coolpix E3100” digital camera developed to take multispectral images of skin.

Making adapter

The drawing of  lighting adapter

The lighting adapter isn’t very hard to build. You just need to make circular PCB and solder LEDs with protective resistors. The PCB image:

                                    PCB Mask                                          REAL view

Then soldered LEDs symmetrically to distribute the smooth light:

LED’s are in row: Red, Green, Blue, and IR, White. White LED is optional, to make normal pictures of skin.

Then I made a hole for camera optics. It also serves as holder of PCB. As you see in front of LEDs I put polarized filter (another is put on optics of camera with polarization axis crossed to this one). This filter is used to filter light reflections from surface layer of skin to remove flares. Then you get the image of deeper skin structure.

The nice shiny LEDs are working:

 I had some problems to focus them to one spot. LEDs have not ideal characteristics and they weren’t ideally soldered to board. You can see my effort

I only needed one square centimetter ofregion to be smooth lightened.

 The finished adapter:

About skin modeling there are other topics created, you’re welcome to read them. There I will put few interesting results about taking photos of skin and lesions.

Lets make some test shoots:

Benign lesion:

Blue                                     Green

Red                                  White

I didntmake Infrared here, as this lession isbenign, and doesnt show any changes in skin structure. 

 Suspicious lesion as you can see Infrared (fig e) picture shows view from deeper skin layers:

And here you can see parametric maps generated using model with these images:

 Here are images with hair and benign lesion:

As this light adapter is hand made and calibration is poor, there still can be good results obtained. This experiment was made to prove, that handheld digital camera and simple lighting adapter can be used to show relative diagnostic results while inspecting skin lesions.

According to earlier modeling description, there were skin reflectance spectra calculated for skin with most common properties: Melanin (volume fraction 2% in Epidermis); hemoglobin HbO₂ and Hb (150 g Hb/liter ) and Thickness of collagen tissue in papillary dermis about 0.1mm.

What are the parts of this spectrum? This spectrum can be exploded in to several distinct spectra’s: Epidermis, Hemoglobin, There are also spectra’s of water and collagen substances, but they doesn’t play main role in our wavelength interval.

 As you can see melanin in epidermis absorbs the most part of blue light ~470nm; hemoglobin absorbs green light ~252nm and red light ~640nm and infrared 850 are used to define papillary dermis thickness, because these wavelengths are less absorbed by melanin and hemoglobin.

MM 

Understanding how light interacts with skin, can assist in designing physics based dermatological image processing. The key is to understand how light interacts with skin tissue. Skin consists of different layers with different spectral properties.

When incident light is applied to skin layer, the part of it absorbed and other part is scattered. The main layers of skin are as follows: Stratum cornea it practically doesn’t absorb light, but diffuses it; Epidermis consists of cells producing pigment melanin. Melanin strongly absorbs strongly absorbs light wavelengths towards ultraviolet part; Dermis is next skin layer which consists of collagen fibers. It can be split in to two sub layers: Papillary dermis and dermis itself. Papillary dermis consists of high dense of collagen fibbers who are strong scattereer of light. The main model requirement is that light has to be scattered. Stratum cornea is supposed as scattering filter. Skin can be characterized as follows:

1)      Epidermis, depending on wavelength can be characterized with melanin absorption coefficient μam_a^m(λ) and melanin concentration c^m;

2)      ed with hemoglobin absorption coefficient μ_a^h(λ), hemoglobin concentratμah c^h, collagen scattering coefficient μ_s^pd and collagen layer thickμspd d^pd;

3)      Dermis can be ddpdribed with scattering coefficient μ_s^rd and thickness of layer d^μsrd

Using those parameters drd model of skin was calculated which shows reflected light dependency on skin parameters and wavelengths of light:

 This color surface shows all awailable skin color values available. This color surface includes all races, sunburn degrees or even age. All benign lessions where melanin is only in epidermal layer also implies to this surface.

Skin is very intelligent structure of our body. It is very elastic and pretty strong to protect inner tissue. It also acts as thermo regulator of our entire body protecting from overheats when we sweat and when there is cold – the blood flow is reduced to skin tissues to save heat to inner organs of body.

Skin is pretty resistive to harmful chemicals, microorganisms and if dry it has high electrical receptivity. From biochemical side – skin can produce vitamin D when exposed to sunlight, which is essential for the growth and maintenance of our bones. The extensive network of nerves within the skin feeds information constantly to the brain concerning our surroundings. So it is full of sensors to know the external world like temperature, pressure. Don’t even let me start about skin importance in fashion industry. About how much there is attention paid to cosmetics, beauty shine. Skin can show you if you’re shy or cold or afraid. As you see, skin top layer of your body, and it can tell you so much and tell you many things, just get to know it.

Lets do it…

Mainly people used to name only two layers of skin epidermis and dermis. But in reality there more layers with own properties. In some cases dermatologists describe there even more layers of sub layers. I am going to be in the middle of this. Lets see the skin structure first:

So wee can see histological cut of skin layer. There are layers as follows:

• Stratum cornea;
• Epidermis;
• Papillary dermis;
• Reticular Dermis;
• Hypodermis.

Little bit about all of them:

It is the most top skin layer of dead cells. These cells are keratin impregnated and protect the skin surface. As well se later in my articles it also acts as light diffuser. Then follows more important skin layer

Epidermis is about 0.1mm thick. It mainly consists of connective tissue and cells so called melanosomes who produce pigment melanin. The most interesting part is melanosomes and melanin. Melanin is pigment, which protects you deeper organs from hazardous Ultraviolet light.

White people got less of them; people with dark skin have more of them. In summer time when you get sunburn, you get darker, because your skin is trying to protect you from harmful ultraviolet light. This is why you should be very careful when taking sunbathes in springtime or in the beginning of summer, because your skin isn’t ready for taking much sunlight. Little by little taking sunbathes your skin produces more melanin, then you are more protected. People in Africa have dark skin – guess why?

Lets leave Epidermis go to Dermis side.

Papillary dermis interconnects with epidermis. It consists of dense collagen tissue this is why mainly almost all light is reflected from this layer. Papillary dermis supports the epidermis with vital nutrients and secondly to provide a network for thermoregulation. There is nor or there is very little of melanin pigment on this layer.

Reticular dermis

 This layer consists of dense irregular connective tissue, which differs from the papillary dermis, which is made up of mainly loose connective tissue. The reticular layer of the dermis is important in giving the skin it overall strength and elasticity, as well as housing other important epithelial derived structures such as glands and hair follicles.

The subcutaneous tissue (hypodermis) is the deepest layer of the skin. It is missing on parts of the body where the skin is especially thin-the eyelids, nipples, genitals, and shins. Subcutaneous tissue acts both as an insu­lator, conserving body heat, and as a shock absorber, protecting in­ternal organs from injury. It also stores fat as an energy reserve in the event extra calories are needed to power the body. The blood vessels, nerves, lymph vessels, and hair follicles also cross through this layer.

That’s it skin structure diagram section this time. Follow next articles.

MM

Melanoma is one of the fastest spreading lesions. Melanoma is curable if it is diagnosed in

My articles there are only reviews form my sight, and don’t take it too serious as I am not a doctor. I don’t take any responsibilities as this information is for knowing purposes.

Welcome to Melanoma.Blogsome.com. This Site is dedicated to skin cancer and not only. It is reviewed not from doctors view but from engineers. During my masters I collected bunch of information, did a pretty good research and I would like to share it with you. You might find something interestin and helpful here. I wish you good luck and healthy skin.

MM