Reading for November 18: Diffuse Optical Imaging and Mammography

Overview:
Here's a short, animated introduction to the idea of imaging with diffuse light. In fact, the site that it's on is full of good stuff.

The more technical aspects are outlined in a still fairly simple form here.

Papers:
1) A review article on breast imaging with diffuse light.

2) An article on a clever trick for seeing through opaque objects with light.

Additional Material:
1) Here's an article specifically on using light to image breast tumors.

2) There's a company called Imaging Diagnostic Systems trying to market a laser-based mammography technique. I don't know how much success they've had in getting their devices into clinics, but here's an article on their work from two years ago. If you're thinking of doing a presentation and/or paper on optical mammography, this might be a good company to look up. Look for their papers, check out articles on them, maybe even contact them and tell them you're doing a class project and see if there's any technical information that they share with the public.

Optical Society of Southern California Meeting

The next Optical Society of Southern California Meeting is next Wednesday, November 11. The topic is space exploration. Because of the holiday the school is closed and there's no journal club, but some of us will be going to the meeting. If you are interested in attending (it is FREE for students and includes dinner), please do the following:

1) Register here by Sunday.
2) Let me know so we can work out a car pool.

Optical Coherence Imaging: For November 4

1) A few links explaining the idea behind optical coherence tomography: A basic overview with a diagram. Pretty technical, but it's hard to find good stuff on this. A lot of the review articles that I found either have equations or are subscription-only. The wikipedia article seems to be OK, but this isn't my research field, so it's hard for me to say for 100% certain.

Here's one really good review article that I found.

2) A paper by Dr. Barbara Hoeling (who will be speaking on Nov. 4) on Optical Coherence Microscopy.

The basic idea of optical coherence imaging is to have two pulses of light interfere with each other. One of them bounces off of a mirror set at a fixed distance, and the other bounces off of a tissue. The pulses of light only interfere constructively if they travel the same distance. Because of the way these pulses are set up (I'll explain the concept in class) they don't interfere constructively if the difference in distance is lambda. It has to be zero. So, by playing with the distance, you can get an image that only has light that traveled a particular distance, e.g. only light that traveled 1 mm into the tissue. This is great for 3D imaging of the retina, for instance, and is widely used for that purpose. There's also work on using it to image arteries and blockage in arteries, although that stuff hasn't made its way to the clinic yet.

Two classes for spring

1) Dr. Abramzon is teaching Physics 410, Biophysics. This course is a combination of lecture, seminar, and journal club, focusing on biological applications of physics. This will cover all areas of physics, not just optics.

2) I will be teaching Physics 234, which will cover optics and relativity. We will focus on the mathematical theory of optics rather than the biological applications that we discuss in journal club. However, an understanding of the theory is needed to design the biomedical devices that we're talking about.

Beating the Diffraction Limit: Paper for October 28

Next week we will discuss ways to beat the diffraction limit. The basic idea is that a lens can't focus light down to a spot smaller than the wavelength of light, which means that it can't see anything smaller than the wavelength of light either. However, people have found ways to turn on light-emitting molecules just a few at a time, and thereby see things smaller than the wavelength of light. This article summarizes a lot of different approaches to solving that problem.

A few things to note:
1) There are a lot of acronyms. Similar things will get different names. If you see STORM, PALM, iPALM, FPALM, PALMEYRA, they all involve molecules that switch on and off randomly. If you see STED, GSD, or RESOLFT, they all involve molecules that switch on and off controllably (i.e. a laser beam determines if they switch on or off).
2) All of these things require using special molecules. The lenses are still the same.

This is what my research students and I work on.

Neuroimaging: Maybe useful for people doing projects

The latest issue of Nature has an article on imaging the nervous system with light. For those of you looking for a project topic, it might be good to skim this, find some topic that you find interesting, and then check out the references.

Fiber-Optic Biosensors

Next week Dr. Salik will talk about fiber-optic biosensors. Read this article to prepare. The article talks about several sensors, but Dr. Salik will focus on fibers. In the first few pages, just skim for basic concepts regarding sensitivity and applications, but don't worry about the detailed physics of plasmon resonance or photonic crystals. Focus on fibers and waveguides, since waveguides are very closely related to fibers. Also try to read up on Mach-Zender interferometer sensors if you get the chance, because they are related to Dr. Salik's work.