# Paper Session III-B - Computerized Tomography (CT) Inspection of Mechanics of Granular Materials (MGM) Modules for the Study and Analysis of Phenomena such as Earthquakes

## Location

Radisson Resort at the Port, Convention Center, Salon I

## Start Date

29-4-1999 1:00 PM

## Description

Suppose someone sawed through a thick log, gathered up all the saw dust in a bag, and gave it to you requesting that you put the saw dust particles back together just as they were in the tree. And, no fair looking at the sawed ends of the log; not that would help! If you could re-assemble the particles exactly as they were in the tree, you would have a tomo- (slice) gram (picture) of just that thin section of the log. This of course would be impossible, but in the late 1960s, a fellow (G. Hounsfield) at EMI, Ltd. In England used an established mathematical theory by J. Radon (Radon's theorem) to do that task (Reference 1). Hounsfield's "saw" was x-radiation, and the saw dust grains, gathered with a powerful computer and re-assembled exactly, are called pixels. Each "saw dust grain," (pixel) is a computerized picture element representing a small (e.g. 1mm by 1mm) density region of the original object (the log). Correctly placed together, the pixels represent a density "map" of the object sliced. Now Hounsfield did not slice a log, but applied his Nobel Prize winning invention to the imaging of tissue, and the diagnosis of disease, in the human body. In the early days, the slices were all performed across the axis of the specimen (body) and thus was born the CAT scan acronym meaning Computed (computerized) Axial Tomography. Improvements in the way objects can be x-ray sliced (any plane) and subsequently reproduced into images have resulted in dropping the axial term, and the favored acronym is just "CT."

## Share

COinS

Apr 29th, 1:00 PM

Paper Session III-B - Computerized Tomography (CT) Inspection of Mechanics of Granular Materials (MGM) Modules for the Study and Analysis of Phenomena such as Earthquakes

Radisson Resort at the Port, Convention Center, Salon I

Suppose someone sawed through a thick log, gathered up all the saw dust in a bag, and gave it to you requesting that you put the saw dust particles back together just as they were in the tree. And, no fair looking at the sawed ends of the log; not that would help! If you could re-assemble the particles exactly as they were in the tree, you would have a tomo- (slice) gram (picture) of just that thin section of the log. This of course would be impossible, but in the late 1960s, a fellow (G. Hounsfield) at EMI, Ltd. In England used an established mathematical theory by J. Radon (Radon's theorem) to do that task (Reference 1). Hounsfield's "saw" was x-radiation, and the saw dust grains, gathered with a powerful computer and re-assembled exactly, are called pixels. Each "saw dust grain," (pixel) is a computerized picture element representing a small (e.g. 1mm by 1mm) density region of the original object (the log). Correctly placed together, the pixels represent a density "map" of the object sliced. Now Hounsfield did not slice a log, but applied his Nobel Prize winning invention to the imaging of tissue, and the diagnosis of disease, in the human body. In the early days, the slices were all performed across the axis of the specimen (body) and thus was born the CAT scan acronym meaning Computed (computerized) Axial Tomography. Improvements in the way objects can be x-ray sliced (any plane) and subsequently reproduced into images have resulted in dropping the axial term, and the favored acronym is just "CT."