IR

Discovery of X-rays

Wilhelm Röntgen discovered X-rays in 1895, earning the first Nobel Prize for Physics in 1901.

Conventional Radiography (CR)

Images produced using ionizing radiation without added contrast material, often called plain films or X-rays.

Latent Image

An image produced that is not visible until processed after exposure to ionizing radiation and light.

PACS system

Picture archiving communications and storage system for storing and retrieving images from all modalities.

Advantages of Conventional Radiography

Quick, inexpensive, and easy to obtain.

Disadvantages of Conventional Radiography

Relies on ionizing radiation and has a limited range of densities with potential cancer risk.

Common Uses of X-rays

Chest X-rays (cxr), abdominal films, and initial skeletal system imaging for fractures or arthritis.

Five Basic Densities

Air, fat, fluid/soft tissue, calcium, and metal.

Density of Air in X-rays

Absorbs the least X-rays and appears the blackest.

Density of Fat in X-rays

Appears gray, somewhat blacker than soft tissue.

Density of Calcium in X-rays

Most dense and opaque, as in bones, absorbs most X-rays.

Density of Metal in X-rays

Typically absorbs all X-rays and appears the whitest.

Computed Tomography (CT)

First introduced in the 1970s, involving a rotating X-ray beam and detectors to create 3D images.

Hounsfield Units

CT numbers range from -1000 to +1000, measuring how much X-ray beam is absorbed by tissues.

Hounsfield Number for Water

A Hounsfield number of 0.

Hounsfield Number for Air

A Hounsfield number of -1000.

Hounsfield Numbers for Fat

Range from about -40 to -120.

Hounsfield Numbers for Soft Tissue

Range from about +20 to +100.

Hounsfield Numbers for Bone

Range from about +400 to +600.

Hounsfield Numbers for Metal

Around +1000 or higher.

Window in CT Imaging

Preselected range of Hounsfield numbers to best demonstrate the tissues studied.

CT Advantages

Expands gray scale and reduces overlapping structures obscuring risks, safe for patients with implants.

CT Disadvantages

Uses ionizing radiation, is expensive, requires large space, and sophisticated processing.

Imaging Planes in CT

Axial/transverse, coronal, and sagittal planes used in cross-sectional imaging.

Axial Plane

Divides the body into upper and lower sections.

Coronal Plane

Divides the body into anterior and posterior sections.

Sagittal Plane

Divides the body into right and left sections, including midsagittal and parasagittal.

Role of Post-processing in CT

Allows additional manipulation of raw data to demonstrate abnormalities without reimaging.

CT and 3D Rendering

CT can display any body part in any plane, including 3D rendering in color.

Radiographic Image Processor

The chemical or digital reader that processes the latent image to become visible.

X-ray Machine Components

Source of X-rays, recorder (film, cassette), and processor (chemicals or digital reader).