Lecture 1

Question 1

Conventional radiography involves acquisition using _______?

Answer 1

Film-screen combination

Question 2

Imaging plate contains a photostimulable______ . What does this do?

Answer 2

phosphor; stores the latent image of the body part until it is processed

Question 3

What are imaging plate phosphors made of?

Answer 3

Barium Fluorohalide doped with Europium

Question 4

Differentiate between the IP of Standard Resolution & High Resolution

Answer 4

Standard - IP has a thick phosphor layer, High - IP has thinner phosphor layer

Question 5

Due to the thinner phosphor layer, high resolution IP’s have what two characteristics?

Answer 5

Greater resolution & sharpness

Question 6

Why is the back side of the cassette lead lined?

Answer 6

To prevent back scatter radiation from reaching the IP; back scatter can cause image arteficats

Question 7

In the CR Imaging Chain
1. The IP phosphor is scanned with a _____.
2. This releases ______ in the form of _______.
3. Special electronics convert the light into an ___________ to produce the _________ on the computer screen.

Answer 7

1. laser
2. stored energy; visible light
3. electronic light; digital image

Question 8

In the CR Imaging Chain, the special electronics include the photomultiplier tube. What does this tube do?
hint: light signals

Answer 8

Converts weak visible light signals into electrical signals

Question 9

Which component in the CR imaging chain enables the IP to be reused after exposure? How is this done?

Answer 9

Erasure unit. It is exposed to an intense white light to erase the image.

Question 10

T or F. IP will absorb more low-energy scatter compared to old film/screen cassettes.

Answer 10

True

Question 11

T or F. IP is sensitive to background radiation.

Answer 11

True

Question 12

What can digital detectors be classified as?

Answer 12

Direct or Indirect

Question 13

In terms of converting x-rays, differentiate between Indirect & Direct flat panels.

Answer 13

Indirect flat panels convert x-rays to light photons that are then measured by CCD/CMOS or Si photodiode and TFT array.

Direct flat panels convert x-rays directly to electrons that are measured by a TFT.

Question 14

T or F. Indirect flat panels achieve higher spatial resolution by undergoing thorough steps.

Answer 14

False. Direct flat panels achieve higher spatial resolution by skipping the visible light step that can blur the images as the light spreads.

Question 15

What do Thin Film Transistors do?
hint: capacitor

Answer 15

Amplify electrical signals and store these in form of an electrical charge (on a capacitor).

Question 16

During direct conversion, detectors convert x-rays directly to __________ through a(n) ________ ________ detector.

When the x-rays interact with aSe what is the resulting production?

Answer 16

Detectors convert the x-rays directly to an electrical signal through an Amorphous Selenium detector.
X-rays interact with aSe to produce electrons and hole pairs.

Question 17

What is indirect conversion?

Answer 17

Indirect conversion is a two-step process in which the x-ray energy is converted into light and then converted into an electric signal.

Question 18

What device does indirect conversion use to convert the x-ray energy into light?

Answer 18

A scintillator

Question 19

What is a scintillator? What is it made of?

Answer 19

A scintillator is a device that glows when hit by high energy x-ray photons. It is made of cesium iodide.

Question 20

In indirect conversion, what is the photodiode made of? What does the photodiode do?

Answer 20

The photodiode made of Amorphous Silicon converts the light into an electric signal.

Question 21

What does CCD and CMOS stand for?

Answer 21

CCD - Charged-Coupled Device
CMOS - Complementary Metal Oxide Semiconductor

Question 22

What is the oldest type of indirect conversion detector used to acquire a digital image?

Answer 22

CCD

Question 23

Which provides a faster read out CCD or TFT arrays?

Answer 23

CCD

Question 24

T or F. Fiber optics or lenses used to spread light in CCD/CMOS detectors.

Answer 24

F. Fiber optics or lenses are used to funnel light to smaller size CCD or CMOS chip.