Back from RSNA

“Don't misinform your Doctor nor your Lawyer”- Benjamin Franklin

I’m back from the Radiological Society of North America (RSNA) Conference in Chicago. There were over 600 vendors with thousands of products on three giant sized convention floors. There were also over 2000 educational exhibits on a fourth floor. Plus lecture rooms, classrooms, and online-computer training.

Though targeted to Radiologists there was also in attendance technicians and physicians from other disciplines. For me, a computer programmer, the most interesting parts of the show were the medical machines and the amazing medical images. I quickly had to master an alphabet soup of machine types (or Modalities as they are called in the industry).

The oldest medical imaging, from 1895, is the is X-ray film machine. It is still used today. For example my dentist uses X-ray film although I’ve noticed over the years that the film has become much more sensitive allowing for shorter doses of x-ray radiation to look for cavities.

Computed Radiography (CR) is a X-ray machine with a removable sensor plate and was invented by Fuji in the 1960s. The imaging plate is put into the film slot, X-ray taken, then the plate removed, scanned, digitized, wiped clean and reused. The plate scanners resemble big paper shredders. FujiFilm Medical Systems now has a FCR machine where the imaging plate comes with a cable and the X-ray image can be downloaded directly into a computer; no plate scan required.

Competing with CR is Digital Radiography (DR) where the imaging plate is built into the machine and images go directly to a computer for storage. CR is popular with hospitals upgrading film X-ray machines to digital at minimal cost. DR is popular if you have the money to buy a brand new machine and you have computer cables connected to the X-ray room. Since CR does not require a computer connection, the CR machine can be more easily moved to from room to room to patients or used outside the hospital at accident sites.

Mammography (MG) is an X-ray machine specialized for Breast exams. It can be film, CR or DR. FujiMed demonstrated a 3D Mammogram using two X-ray images and 3D viewing glasses.

The ultimate in X-ray technology is computed tomography (CT, previously CAT). These machines look like a giant vertical doughnut. As the body on a table moves slowly through the doughnut hole, X-ray images are recorded. The result is dozens or hundreds of 2D body slices (called Tomograms, hence Tomography). The cutting edge today is using compture software to convert CT slices into 3D colorized images.

A variation on X-ray single exposure imaging is Fluoroscopy. These machines produce real-time images on a TV monitor using continuous low-dosage X-rays. Doctors use the monitor to help guide needles and during some surgery. Flouroscopy is also great for observing a contrast agent (like a barium drink) move through the body. Sonograms (which use sound instead of radiation) can also used for continuous imaging. I saw a sonogram demo where the monitor predicts the projected path of the needle so you can see if you’ll hit the tumor or biopsy site you’re aiming for.

MR or (MRI) MRI provides greater contrast between different soft tissues than X-ray and is useful for imaging the brain, muscles, heart, and tumors. No radiation is used. Instead powerful magnets are used to align all the water molecules in a section of your body. Then radio waves are used to knock the water molecules off balance causing them to emit a pulse that is recorded. Water rich tissue will appear brighter than drier tissue. MRI was invented in 1973 and older machines have a deep and confining tunnel for the body to fit into. Newer machines provide more space inside the tunnel. With Open or Coreless MRI the machine looks like a hamburger with the magnets as the bun and the person placed in the center as the meat. I also saw pediatric mini-MRI’s used to teach children not to be afraid of the machine.

With Positron emission tomography (PET) a short-lived radioactive tracer isotope is injected (usually into the blood). A radiation scanner then detects where the tracer moves to and where it concentrates at. PET can be combined with CT machines so both images are recorded at the same time – a dynamic & fluid image via PET with the static underlying structrues via CT.

Bottom Line
Radiology has greatly changed in the past 40 years. Science has digitized the old workhorse, X-rays, and added some new techniques:

MRI – molecular spin alignment via radio waves
PET – radioactive isotopes
Sonogram – sound
3D images – computer enhancement of CT slices
(pictured at right)

I expect we’ll see more advances in the 21st century.