L2. Computed Tomography

Question 1

Disadvantages of conventional radiography

Answer 1

No depth detail
Organs/structures superimposed
Difficult to distinguish soft tissue organs (liver, spleen, bowel, cerebrum)

Question 2

Cross sectional imaging

Answer 2

Sectional anatomy studied since 16th century
Slices of human body
Typically in transverse/axial plane

Question 3

CAT scan meaning

Answer 3

Computed Axial Tomography

Question 4

Axial plane

Answer 4

CT scan, slice of bread

Question 5

CT older definition

Answer 5

Tomo - greek word for cut/section
Graphia - describing

Question 6

CT modern definition

Answer 6

Using computer technology with x-ray equipment to image the body cross-sectionally

Question 7

Discovery of CT

Answer 7

1972 Godfrey Hounsfield
Non-invasive method of producing cross-sectional images using x-rays

Question 8

Cross sectional portion of the body which is scanned for the production of CT image called slice

Answer 8

Slice has width and volume
Width determined by the width of the x-ray beam

Question 9

Image represented as a matrix of numbers

Answer 9

MATRIX - two dimensional array of numbers arranged in rows and columns

Each number represents the value of the image at the location

Question 10

VOXEL

Answer 10

Each individual element or number in the image matrix represents a three dimensional volume element in the object called a VOXEL

Question 11

PIXEL

Answer 11

The voxel is represented in the image as a two-dimensional element called PIXEL (picture element)

Question 12

CT numbers

Answer 12

The numbers in the image matrix are called CT numbers

Each pixel has a number which represents the x-ray attenuation in the corresponding voxel of the object

Question 13

CT principles

Answer 13

The image is divided into small areas called pixels

Each pixel has a location
Each pixel has an attenuation value
Using this information and very complex math formulas the computer constructs image