I was marveling at the brightness of a mini Maglight recently. Pressed to the skin in a dark room, it is possible to transilluminate a small hand and see the bones.
This principle could be used to make a veinfinding device. It assumes that there exist very very bright lights which are not so hot as to burn the skin. Venous blood absorbs light at a particular red wavelength. Transillumination of a hand or arm with bright red light of that wavelength should make the veins stand out, as they will absorb more light than the relatively bloodless areas of fat and muscle around them.
Then the needle goes in!-- bungston, Feb 23 2005 US patent 6,424,858 http://www.google.com/patents/US6424858imaging apparatus for transillumination and visually exposing vasculature of the human anatomy by passing infrared light through it [xaviergisz, Mar 03 2005, last modified May 07 2016] If you shift the spectrum up a bit to, say, about 2nm and put an imager on the other side of the appendage you might have even better results.-- bristolz, Feb 23 2005 Saw a clever device recently: It viewed a patient's arm in infra-red, which showed up the veins really well, and then projected an image of the vein pattern back onto the arm in visible light so the doctor could see it.-- hippo, Feb 23 2005 I think blood is red because it reflects red, but your idea may work - I'll use the needle while you move the LED around a bit.-- Ling, Feb 23 2005 660 nm. penetrates 8-30 mm. of skin/fat. 830-950 nm. penetrates 30-40 mm.,into joints, tendons etc. Cells transmit light at the intensity of one candle seen 2-5 km away. Light ignites the cellular metabolism 98% through eyes, 2% skin. Research suggests looking outside into semi-shaded areas unobstructed by glass(es), min. half hr./day.
I haven't checked this recently but cells are a different colour when oxidized and therefore a tumour can show up on scans because of lack of oxygen getting to cells. Research is being done to pulse infra-red and other wavelengths of LED light into tumours/other for cell repair. Also the theory is that blood communicates with itself at a specific wavelength and pulsed frequency. Thus [Ling], blood is the colour that it communicates in.
Moreover I suggest the public be cautious of their close exposure to unresearched light sources/pulsed frequencies for health concerns.-- mensmaximus, Feb 23 2005 Baked. Can't be bothered to find a link. It just is, okay?
A mate of mine at university worked on a robot that located veins and then did the stabbing bit, too. Can't remeber the details but it worked pretty good.-- moomintroll, Feb 23 2005 [bris] - why shift the spectrum that tiny amount?
[mens] - would penetration not also be affected by brightness? For example, sunlight penetrates the ocean differently at different wavelengths, but everything penetrates farther on a bright sunny day as compared to a cloudy day. I don't know about blood communicating with itself. That is pretty trippy.
[moom] - you gotta find the link.-- bungston, Feb 23 2005 I'll search more but from the same page of my old notes I see an LED intensity of 6-8000 millicandle mentioned, equals 55 milliwatts per LED with a 266 cycles per second pulse rate, compatable with body nervous system.
Midday summer sun is 100,000 lux. Typical indoor illumination is 1000 lux.-- mensmaximus, Feb 23 2005 It's an absolute rather than a relative amount, [mens].-- bristolz, Feb 23 2005 Absolute and relative are two words I don't use so try again,[Bristolz]. I looked them up and words like that delay research for years, I'm postulating.-- mensmaximus, Feb 23 2005 Sorry to not be clear. To shift 2nm would be a relative amount. To, instead, shorten the wavelength to 2nm, is an absolute amount and is what I intended.-- bristolz, Feb 23 2005 Thank you Bristolz, I'm on a learning curve.-- mensmaximus, Feb 23 2005 I love the 'bakery. Attending this anno series counts towards credit at Halfbaked University. Oh, and the cafeteria is serving tuna casserole on a bun tonight.-- normzone, Feb 24 2005 Blood, being the body's refrigerant, should be flowing in veins relatively cooler than their less vascular substrate. Temperature differences within a limb could either be directly visualized by infrared imaging or be enhanced for imaging by local application of heat such as used to make his vas deferens stand out during a vasectomy.-- reensure, Feb 24 2005 I just posted then deleted a very similar idea after receiving a nasty subcutaneous bruise from my friendly local phlebotomist. Wish this were more widely known, thanks, [bungston].-- csea, Sep 27 2011 The blood in veins should be not only less red than the blood in arteries, but less red than the blood in capillaries, since it's less oxygenated than both. In fact, veins should be about the bluest thing in their vicinity. I wonder if that's why they look blue, despite the the dull, dark red shade of venous blood when it fills an evacuated vial. Pulse oximetry distinguishes oxygenated from unoxygenated blood by absorbtion wavelength, so the same trick ought to be possible in reverse. However, arterial flow is pulsatile, which makes discriminating signal from noise much easier than in the venous case.
Anyway, there's already a mature technology for bedside imaging of veins, and that's ultrasound.-- mouseposture, Sep 28 2011 The baked form of this idea (yes, it exists, no, I'm not going to provide a link either, because I can't remember what it's called, but every major hospital has one collecting dust in a closet) isn't actually used to find veins for flobotomy, nor does it need to be; if you've drawn blood enough times, you can literally do it with your eyes closed (of course, professional flobotomists _never_ do this, for legal purposes).-- Alterother, Sep 28 2011 random, halfbakery