Physics & the Detection of Medical X-Rays
"No substance is so dense as to prevent rays from passing. The
rays of heat and sound penetrate through the walls of a vessel of
gold or brass."
--Roger Bacon, circa 1270
X-rays images are one of
the most important tools of a physician who is attempting to diagnose an
internal injury or disease. Because these "rays" can pass through human and
animal tissue and their absorption depends strongly on the density of the
material, x-ray images provide details of the internal parts of the body.
X-rays are also used in
the treatment of some diseases, particularly cancer. They are valuable for
such treatments because the x-rays interact with the atoms and molecules in
cells in such a way to alter or kill the cells. Thus, x-rays are used to
destroy tissue that is not functioning properly.
These two medical uses
of x-rays emphasize a basic problem with using x-rays to obtain images.
The same x-ray that can help the physician find out what is worn with a patient
can do damage to that patient's body. The x-rays that are being used to
help can also hurt.
This paradox as been
mostly resolved with the application of atomic physics to the recording of x-ray
images. Atomic processes such a fluorescence and the photo electric effect
are routine components of the imaging procedure. Their effective use
result in much lower doses than would otherwise be possible. Patients can
be diagnosed without putting them in significant danger.
This set of Web pages
has been prepared to provide teachers with background information so they can
teach about this successful application of physics to contemporary medicine.
Each of the links on the left of the page lead to short discussions and links to
related materials. Most of the Web pages are not written specifically for
physics students. A few of them are aimed at medical students, but most
are information about some aspect of the issue of minimizing x-ray dosage to
patients or historical and physics background about the topic.
One of our goals is to
prepared some interactive lessons for physics students on this topic.
Check back later to see how we are doing.
The links below provide broad overviews of radiology and the
physical science upon which it is founded. (This project is a joint effort
of Physik im Kontext
and Modern Miracle Medical Machines.
Thus, sites in English and German are included.)
The first chapter of a book, Naked to the bone: Medical
Imaging in the Twentieth Century, this site contains a fascinating story of
attempts by Alexander Graham Bell to find a bullet lodged in President James
Garfield. Exploring Bell's attempt to "look" inside the President's body with
electromagnetic induction would make a great physics lesson.
Fundamentals of Radiobiology
This course is divided into two sections. This first
part is "academic" and presents the basic science of x-rays that would be useful
for a medical technician and some safety and patient comfort issues. The
first eleven sections are useful for our purposes. The second part
discusses details of taking medical x-rays.
An overview of the production and detection of x-rays.
A little bit of everything including lots of images, some
for young children and many links.
Aufnahme- und Durchleuchtungstechnik
An overview that begins with some very basic physics.
This site is mosly text and qualitative. It has some very annoying pop-up
Medizinische Physik:Physikalische Grundlagen der medizinischen Bildgebung
sets of PowerPoint slides in PDF format. The basics physics related to
x-rays, CT scans and PET are included with a promise of more to come later.
The index for this set is in the lower half of the web page.
Medical X-ray Imaging
A series of book-style chapters on this topic.
Non-Destructive Testing of Humans
This site has been prepared for medical students. It has
links to lecture note, PowerPoint slides and many images. While it has
limited use for our purposes, its title made it too good to omit.
Introduction to Radiology
This interactive site is primarily to help physicians learn to
Introduction to Radiographic Testing
This site is a course develop by the Coalition for
Non-Destructive Testing. The applications are not medical but much of the
background information is quite useful.
X-rays & Gamma Rays
A series of lesson on x-rays and nuclear physics. This
site includes a variety of uses of radiation and is not limited to medical
This site contains a history and a description of the science
for x-rays, ultrasound, MRI, and nuclear imaging (using radioisotopes). In
English with one word of German.
The Art &
Science of Medical Diagnostic Imaging
This site was created by students as a part of a medical
radiation technology project at the QUEENSLAND University of Technology. It
contains qualitative information and a large number of pictures about a variety
of imaging techniques.
Physics of Medical Imaging – An Introduction
A text in PDF format which covers some of the basics physics.
the language of the Web site.