Gamma camera

Question 1

What are gamma rays

Answer 1

photons (high energy light). emitted from the NUCLEUS

Question 2

What is gamma radiation?

Answer 2

electromagnetic radiation that has high enough energy to knock an electron out of orbit or more. Originates from the nucleus of an atom usually from radioactive decay

Question 3

Are gamma rays the same as Xrays?

Answer 3

No. They appear like xrays at the same energy but xrays are produced by interactions with electron shells of atoms

Question 4

What is the scintillator made of?

Answer 4

thallium doped Na I that produces light when stimulated by gamma or photons

Question 5

What are the components of a gamma camera?

Answer 5

collimator crystal (scintillator) photomultiplier tubes

Question 6

What is septal penetration

Answer 6

photon/gamma ray pass through the septum of the collimator and reaches the scintillation crystal at the wrong location

Question 7

What factors influence septal penetration

Answer 7

energy of the incident gamma ray thickness of the septum

Question 8

How do you increase gamma camera resolution?

Answer 8

Reduce the diameter of the hole in the septa or increase the length of the septa

Question 9

increasing the length of the septa of a gamma camera collimator

Answer 9

increases the resolution

Question 10

If the septa in a gamma camera are not thick enough, what artifact can happen?

Answer 10

star artifact aka, lots of septal penetration

Question 11

How does star artifact happen?

Answer 11

septa are not thick enough and there is a lot of septal penetration

Question 12

How do you reduce star artifact?

Answer 12

increase septal thickness

Question 13

In a gamma camera, is thicker or thinner crystal more sensitive?

Answer 13

thicker

Question 14

Does a thicker or thinner crystal in a gamma camera result in higher resolution?

Answer 14

Thinner

Question 15

Why are collimators used in gamma cameras

Answer 15

to decrease scatter

Question 16

When do you use a parallel collimator?

Answer 16

object size = image size

Question 17

When is a diverging collimator used?

Answer 17

Object size > image size

Question 18

When are converging collimators used?

Answer 18

Object size < image size

Question 19

When are pinhole collimators used?

Answer 19

to magnify very small areas such as the thyroid

Question 20

What daily test has to be performed on gamma cameras?

Answer 20

daily flood Uniformly flood camera with radioactive source to look for nonuniformities

Question 21

What is a daily flood test

Answer 21

Uniformly flood a gamma camera with radioactive source to look for nonuniformities

Question 22

What is an intrinsic flood?

Answer 22

collimators are removed, point source is set at a distance away from the camera head

Question 23

What is extrinsic flood?

Answer 23

parallel collimators on, flat uniform source

Question 24

What weekly gamma camera test has to be performed?

Answer 24

weekly bar test Bar phantom is placed on camera head and imaged

Question 25

What is a weekly bar test for gamma cameras?

Answer 25

Bar phantom is placed on camera head and imaged (intrinsic bar test)

(spatial resolution)

Question 26

What does the weekly bar test?

Answer 26

detail resolution

Question 27

Low energy radionuclides used with thin crystal gamma camera

Answer 27

Tc-99m or TI-201

Question 28

full width half maximum (FWHM)

Answer 28

Defines the range of energies the camera will detect centered around the peak energy

Question 29

Tc-99m is detected with what window?

Answer 29

20% = 140keV with 20% window (+/- 10%)

Question 30

What range is acquired for Tc-99m imaging?

Answer 30

between 126keV (-10%) and 154 keV (+10%) peak is 140keV with a window of 20%