Lecture 2- Image Aquisition

Question 0

What components are required for conventional radiography?

Answer 0

An X-ray film, cassettes with intensifying screens and an automatic or manual film processor, view box for film review and an archive for film filing.

Question 1

What are the three types of image acquisition?

Answer 1

Conventional radiography
Computed radiography
Digital radiography

Question 2

What is needed to process the film?

Answer 2

A developer, fixer, rinser and dryer

Question 3

What is double emulsion X-ray film?

Answer 3

There is a top protective coating, a silver halide emulsion on a polyester base and then another silver halide emulsion and another protective coating.

Question 4

What is silver halide crystal?

Answer 4

It is formed from silver and one of the halogen elements such as bromide. It is light sensitive and is used in the photographic paper in the cassette- the silver crystal turns into a speck- the image

Question 5

How is the image produced chemically?

Answer 5

The electron in the silver bromide is released by light energy, a silver atom forms at the sensitivity speck and this produces the latent image.

Question 6

What does the developer do?

Answer 6

It provides electrons to the exposed crystals. These can be viewed.

Question 7

What does an automatic film processor have?

Answer 7

A developer, fixer and wash.

Question 8

In an automatic processor, what happens at each stage?

Answer 8

The latent image catalyses the reaction which reduces the silver ion into metallic silver, the fixer prevents further development and removed undeveloped silver bromide and the wash removes fixer chemicals that will discolour the film over time.

Question 9

What are the two types of X-ray film?

Answer 9

Non-screen which is directly exposed to the ray

Screen which is single or double emulsion and 95% of exposure is due to the light coming off the screen

Question 10

What does the intensifying screen do?

Answer 10

Reduced personnel exposure
Reduces patient exposure
Increased contrast

Question 11

What does the grid do?

Answer 11

Absorbs scatter radiation to improve radiographic contrast.

Used when body part thickness is >10cm

Question 12

What is computed radiography?

Answer 12

Filmless, no chemistry and no darkroom.

Question 13

Haw re images produced in computed radiography?

Answer 13

Image is captured in cassettes containing a phosphor storage layer. It is put into a laser film reader and the computer creates the digital image in DICOM, it is stored in the server with PACS.

Question 14

What are the advantages and disadvantages of computed radiography?

Answer 14

A. It is time efficient, robust and good quality image. Lower radiation dose and cost effective.
D. The laser reader is sensitive to dust, maintain the moving part and there is still manual labour required.

Question 15

What is direct digital radiography?

Answer 15

The receptor plate contains many small elements that transform X-rays into an electrical signal. The images are stored on PACS and the cassette is built into the table.

Question 16

What are the advantages and disadvantages of DR?

Answer 16

A. Image is obtained within seconds, it is good quality, low radiation dose.
D. Very expensive and fragile.

Question 17

What is image stitching?

Answer 17

When the X-ray tube takes multiple radiographs and fuses them into an image up to 1.2m in length.

Question 18

What is dynamic DR?

Answer 18

It provides moving radiographic images instead of fluoroscopy, it allows 40 frames/second

Question 19

What is DICOM?

Answer 19

Digital imaging and communication in medicine. It is a unified standard that is vendor dependant, file format and communication protocol, it documents and prevents any manipulation of the image.

Question 20

What is a PACS.?

Answer 20

Picture archiving communication system. It is a central storing of images, replaces hard copies of film and allows remote access.