What is fluorescence diagnosis' simulation?

In science fiction the detection of diseases is very easy. We all have seen Dr. med. Leonard Horatio McCoy in Star Trek using a medical scanner showing all detailed information about the healthiness of his patient. On the side the image of this Tricoder, but unluckily enough it is just science fiction today.

August 1st, 2016 | OPTIS group

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The Challenges of Imaging Diagnoses

In medical imaging, the development has been going by a simple metal tube which helps to look into someone’s throat, over the development of Xray scanners, to todays most advanced MRI (magnetic resonance imagers) systems which need a lot of space and are quite bigger than the scanners from Science Fiction. Using all this imaging technology, it is still sometimes very difficult to make the difference between tumor tissue and normal tissue. On images showing brain tumors for example, it can be complicated to define the border where the tumor starts. The use of fuorescence can help make the difference, and photometric simulation tools like SPEOS can help to develop corresponding medical systems.

 

The use of fluorescence in analysis offers several advantages compared to simple white light:

  • Limitation of the operation areas: the tumor can be differentiated from sane tissue easily
  • Recognition of small tumors in the beginning of the illness: the treatment can be started earlier
  • Usage within stethoscopes: less invasive operations and clearer imaging due to data processing

How Does Fluorescence Diagnosis Work?

The optical spectrum is much larger than the visible spectrum we refer as “light”. If we refer to electromagnetic waves, the optical spectrum is only a very small part of this physical phenomenon. The visible spectrum for the human eye is also a very small part of the optical spectrum. In fluorescence diagnostics, the aim is to use non-visible light, mainly in the UV part, and make the tissue interaction visible to the human eye. Generally, there are two approaches how to use this effect in medicine:

  • First approach: a drug is given to the patient, containing chemical dyes called fluorophores, that attach to the cancer cells. This way, it is possible to detect the malignant cells using activation light and to see them in the visible.
  • Second approach:  use the so-called auto-fluorescence of living tissues. The body’s own (endogenous) fluorophores might be present in different concentrations in tumors and sane tissue and like this allow us to differentiate them more easily.

Physically, a fluorescent material first needs to be activated, mostly by using a short wavelength radiation like for example UV light. This radiation is absorbed by the fluorophore and a part of it is used to shift electrons in higher bands of this chemical structures. When these electrons fall back towards their original energy states, they will emit photons which are normally on a higher wavelength, like for example red light. The activation of the fluorophore using invisible UV light will be emitting red light which can be seen by our eyes, enabling to detect where there is a high concentration of these dyes.

Layout of the System in SPEOS

Simulations of these diagnoses have been generated with SPEOS, the optical add-on of OPTIS to mechanical design tools CATIA, SolidWorks, PTC Creo and NX. Using a ray tracing method, it is possible to show the interaction of the blue light rays with the fluorescent and scattering material. Several sensors have been set up inside SPEOS to see the energy distribution in the final simulation result. The sensors can be positioned and moved using the mechanical design tools' geometry, which makes it easy to register results from different observer views and to create a video or an image analysis, like in a real scanner system.

Advantages of the Simulation for Medical Advancement

Simulation brings several advantages in the development of medical instruments, like the reduction of real experiments which are cost extensive and time consuming. Another advantage is that virtual testing doesn't require any animal testing, and enable to limit these types of test. Due to the repeatability of simulation and the possibility to optimize optical and mechanical parameters, it is possible to reduce development cost and to bring instruments earlier to the market and such to accelerate the development of new analysis and treatments for medical applications.