Today we celebrate the birthday of Allan M. Cormack, inventor of the CAT scan, who would have turned 85 today (he died in 1998).

A CAT scan (computer assisted tomography or computed axial tomography or computed tomography, CT) is a three-dimensional (3D) image reconstructed from a series of two-dimensional X-ray images. Compared with a conventional X-ray image, a CAT scan provides better resolution, which helps identify the position, size and shape of tumors, among other medical applications.

Cormack won the Nobel Prize in medicine in 1979 for discovering the mathematical formulas that allow scientists to reconstruct an object’s cross section from a series of two-dimensional X-ray images. (Co-winner Godfrey Hounsfield constructed the first CAT scan system used in medical care.)

Other imaging methods, such as magnetic resonance imaging (MRI, Nobel Prize 2003), frequently are used in medicine today, but computed tomography is still popular among scientists. Structural biologists use cryo-electron tomography to reconstruct 3D images of proteins from multiple 2D images taken using an electron microscope. This technique is similar to a CAT scan, except the specimen is frozen and repeatedly tilted to acquire images from different angles (in a medical CAT scan, the patient lies still, at room temperature, while the X-ray source rotates around the patient).

Researchers also use a variation of the CAT scan to examine fossils. High-resolution X-ray CT can resolve much finer details than medical CAT scans, probably because radiation exposure is not an issue with animal remains.

My favorite use of CT scanning? Rather than disassembling a vintage guitar to see how it was built, scientists used CT scans to determine how the instrument’s bracing was assembled (see photo). The Gretsch model 6120 was manufactured with unique bracing from 1959-1961. Once the CT scan revealed the instrument’s exact measurements, guitar makers were able to recreate the unique bracing.

Know of other unusual applications for CT scanning?