Can Laser/Maser Pass Through Tissue without Interacting?

  • Context: Undergrad 
  • Thread starter Thread starter Thiago
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Discussion Overview

The discussion centers on the potential for lasers or masers to pass through biological tissue without interacting, exploring various wavelengths and their interactions with tissue. Participants consider the implications for medical imaging and treatment, as well as the limitations of different types of electromagnetic radiation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that certain medical lasers can penetrate tissue, but visible wavelengths tend to be absorbed at the skin surface.
  • One participant suggests that radio waves might pass through tissue without interaction, although they acknowledge that radio wave lasers may not exist.
  • Another participant points out that water absorbs radio waves significantly, which limits their use in certain applications.
  • There is mention of X-ray lasers, with some participants expressing concerns about potential tissue damage from such lasers.
  • Free-electron lasers (FEL) can be tuned to X-ray frequencies, but their safety and effectiveness in tissue applications remain uncertain.
  • Some participants argue that any electromagnetic radiation capable of penetrating tissue is likely energetic enough to cause harm.
  • There is a discussion about the accuracy and resolution of imaging techniques, with references to optical coherence tomography and the limitations of different wavelengths.
  • One participant expresses a desire to explore holographic imaging using lasers that can penetrate tissue, while another questions the necessity of laser solutions compared to other technologies.
  • Terahertz imaging systems are mentioned as a potential non-ionizing option for penetrating tissue.

Areas of Agreement / Disagreement

Participants express a range of views on the feasibility and safety of using lasers or masers for penetrating tissue, with no consensus reached on the best approach or the implications of different wavelengths.

Contextual Notes

Discussions include various assumptions about the interactions of different wavelengths with biological tissue, the potential for harm, and the technical requirements for imaging. Limitations regarding the effectiveness of certain wavelengths and the need for specific imaging resolutions are noted.

Who May Find This Useful

Individuals interested in medical imaging technologies, laser applications in medicine, and the interactions of electromagnetic radiation with biological tissues may find this discussion relevant.

Thiago
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Can some kind of Laser/Maser pass (not interacting) through a large amount of tissue?

I know that some medical lasers can penetrate over 10cm of tissue, and the visible ones stop almost in the skin surface.

the problem resides (til I've understood) in the problem that penetrating lasers tend to be highly absorbed by water molecules.
 
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Sure, just chose a wavelength with high transmission through a human. My guess would be radio waves. I don't think radio wave lasers exist though.

Water does absorb a lot of frequencies, but not all of them.
 


Radio waves lasers exists, but water absorbs radio waves a lot, (thats why radio can't be used by subs)

This was one of my first toughs.
 


Well, an X-ray laser would work...
 


I tend to believe that one x-ray laser will cause some kind of harm at the tissue Dave, I really can't explain why (probably some bias of my part), I also don't know if x-ray lasers exists, I know instead that FEL (free-electron lasers) can be tuned in x-ray frequencies.

Do you know some paper about the theme Dave? Tissue related experiences mostly.
 


Thiago said:
I tend to believe that one x-ray laser will cause some kind of harm at the tissue Dave,
Yes. My bet is that any EM that can pass through a thickness of tissue is also energetic enough to damage it.
 


Thiago said:
Radio waves lasers exists, but water absorbs radio waves a lot, (thats why radio can't be used by subs)

This was one of my first toughs.

Certainly in the microwave region , but I think with a long enough wave (energy below fundamental rotation transitions) it should pass straight through... wiki: "VLF even penetrates sea-water".
 


MikeyW,

True, they use VLF, but, I don't know a laser that use this kind of wave, even if it is feasible.

Don't you agree?
 


Any reason to insist for laser-like solution?
Can't be just some electronics and antenna?
 
  • #10


Resolution and accurateness, if it was just pass waves, any thing like pet scan or tomography would suffice.
 
  • #11


Thiago said:
Resolution and accurateness, if it was just pass waves, any thing like pet scan or tomography would suffice.
Can you explain what is more accurate in maser than in electronic generator with apropriate antenna running at the same frequency? Or what is more acurate in red light made with laser than with LED? And what maser does more than 'just passing waves'?
 
  • #12
  • #13


Thiago said:
why do you ask that kind of question? it's like if I've asked if a plane can travel the Atlantic? and instead of answering it you ask me why don't I go by boat?

Yeah. Maybe it is not a best metaphore, but if we live in 1920, and I would get impression that your goal is to get quickly to New York, I would wonder why you ask about airplanes, rather than thinking about steamliners or maybe zeppelines.

If you think about some kind of imaging, like you may get using optical coherence tomography, you should rather forgot about masers and hypothetic radio-lasers running at 100kHz frequencies.
You require wavelengths smaller than desired resolution of your imaging. OCT (as says the wiki page you quote) resolution is 10 times worse than wavelength. Theoretical limit is wavelength.

Such requirement redefines your original question: only waves of wavelenghts of 1mm or less should be considered.
 
  • #14


Ok I understood.

But let's go one problem at time. first I need to know if there is some kind of laser that can penetrate tissue without causing any harm.

I suppose I made a mistake radio-wave laser don't exist. Sorry.
 
  • #15


I still don't understand why you insist on laser-like solution. The resolution gain comparing to "classical" sources is not big, while restricts you to very limited range of frequencies.

Sub-milimeter microwaves won't penetrate body deeper than few mm, the same for visual band and ultraviolet. Only remaining band are X-rays and up (gamma), which, at low intensity do little harm. X-ray tomography is considered safe.
 
  • #16


the reason was that I was thinking in holograph (the real one not the movie one), then I remembered that we need one reflex of a laser, but I'm wondering if we can reconstruct the img with a laser that passed trough some thing, them since we use tomography i thought if it wouldn't be cool to have one holo of our heart ^^

If it's possible, I want my share in the patent^^
 
  • #17


TeraHz imaging systems penetrate tissue and are non-ionising
42 patents - most still applications are owned by Teraview.
 

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