Lecture 2

Question 1

the energy must be converted into a form that is detectable for radiation to be detect..how

Answer 1

electrical current generated

Question 2

what are examples of radiation detectors

Answer 2

ionization chambers, proportional counters, geiger mueller counters

Question 3

what are examples of scintillation detectors

Answer 3

inorganic scintillators and organic liquid scintillators

Question 4

what are examples of semiconductor detectors

Answer 4

Ge(Li) and Si(Li) detectors and CZT detectors

Question 5

what are the basic components of a scintillation detector

Answer 5

scintillating material, light detector, voltage discriminator, and display/recording device

Question 6

what scintillator would you pick for a gamma camera

Answer 6

sodium iodide iwth thallium, bismuth germanium oxide, barium or cesium fluoride, luthetium orthoscilicate, plastic

Question 7

what is sodium iodide iwth thallium used in

Answer 7

nuclear medicine

Question 8

what is bismuth germanium oxide used in

Answer 8

PET

Question 9

what is barium or cesium fluoride used in

Answer 9

used in PET

Question 10

what is luthetium orthoscilicate used in

Answer 10

PET and SPECT systems

Question 11

what is the flow chart of gamma ray detection

Answer 11

gamma rays-scintillation crystal-light pulse-PM tube- voltage pulse

Question 12

what is proportional along the gamma ray detection

Answer 12

magnitude of voltage pulse is proportional to intensity of the light signal proportional to the energy deposited in the crystal

Question 13

what is positioning (pulse) arthmetic

Answer 13

positioning arithmetic refers to the electronic scheme used to determine the location fo the light pulse emitted when a gamma ray is absorbed in the NaI crystal. It does not tell you where the origin of the gamma ray was, but only where it got stuck in the crystal

Question 14

how do you determine where the radiation came from?

Answer 14

collimate the detector

Question 15

what is gamma camera collimation

Answer 15

it is designed to limit the detection of gamma rays whose rays are travelling in certain directions. Collimator material must be composed of dense material with high atomic number.

Question 16

what material is often used for collimation of gamma camera

Answer 16

lead

Question 17

what is the tradeoff in collimation

Answer 17

it is design is a trade off between resolution and sensitivity.

Question 18

what does high resolution mean for the sensitivity

Answer 18

it means there is low sensitivity

Question 19

what does high sensitivity mean for resolution

Answer 19

low resolution

Question 20

what does high sensitivity mean for resolution

Answer 20

low resolution

Question 21

what are things to consider when designing a collimator

Answer 21

it should have a hole length, hole diameter, and septal thickness

Question 22

what is the collimator resolution proportional to

Answer 22

diameter times source distance

Question 23

what is collimator sensitivity proportional to

Answer 23

hole diameter squared

Question 24

what is the proportionality between resolution and sensitivity

Answer 24

the resoultion is sqared in proportion to the sensitivity

Question 25

draw a semiconductor

Answer 25

gamma ray, Na/Csl crystal then hits a silicon photodiode and it generates an electrical signal

Question 26

what is a silicon photodiode

Answer 26

it converts light into a digital plse. Quantum detection efficiency of 50-80%. It is used in multi-crystal gamma camera and PET

Question 27

what are the benefits of silicon photodiodes

Answer 27

small, low noise, high speed, adn good spectral response

Question 28

what is the best semiconductor materials

Answer 28

CdTE and CZT becuase they havve a high Z, density, and bandgap with the best energy resolutioon

Question 29

CZT detector is

Answer 29

dense material with higher band gap so can be operated near room temperature and good energy resolution. 5-6 mm thickness overall

Question 30

what are the spectrum dysnamics of these scans

Answer 30

each detector only scans the region of the mycocardium, and the system emplys high sensitivity collimators nad proprietary reconstruction algorithms. Scan around 2 times per minute

Question 31

what technology does SPECT of the heart use

Answer 31

it is CZt

Question 32

what else is CZT used for

Answer 32

breast, heart, rnadom whole body

Question 33

what is the best parts of semiconductor technology

Answer 33

it has lightweight detectors that can be curved or shaped to meet clinical application. They have detectors with better energy and spatial resolution. Detectors can be used for both xray and gamma ray detection

Question 34

what is the best parts of semiconductor technology

Answer 34

it has lightweight detectors that can be curved or shaped to meet clinical application. They have detectors with better energy and spatial resolution. Detectors can be used for both xray and gamma ray detection

Question 35

what is intrinsic resolution a function of

Answer 35

crystal thickness, number of phtomultiplier tubes, design of light pipe, amount of light generated by gamma ray

Question 36

what effect does crystal thickness have on instrinsic resolution

Answer 36

the resolution degrades with increasing crystal thickness

Question 37

what effect does number of photomultiplier tubeshave on instrinsic resolution

Answer 37

it inproves with increased PMT

Question 38

what effect does number of design of light pipe on instrinsic resolution

Answer 38

it can be imporved by elimination of light pipe or by improved design

Question 39

what effect does number of amount of light generated by gamma rays have on instrinsic resolution

Answer 39

the resolution improves iwth increased energy

Question 40

what effect does number of amount of light generated by gamma rays have on intrinsic resolution

Answer 40

the resolution improves with increased energy

Question 41

what is the formula for energy resolution

Answer 41

energy resolution depends on gamma ray energy. R is proportional to 1/sqrt(E)

Question 42

what is system resolution dependent on

Answer 42

collimator resolution and intrinsic resolution

Question 43

what is the important part of collimator resolution

Answer 43

for all types of collimation, resolution degrades as the object is moved away from the collimator face

Question 44

what does it mean if low bandgap

Answer 44

same photon has higher sensitivity because more electrons

Question 45

what does high bandgap mean

Answer 45

it means they can be used at more room temperature

Question 46

if the band gap is too low

Answer 46

it needs to be cooled down too much

Question 47

what is important about energy resolution

Answer 47

reduced scatter in the image can be achieved by narrow image contrast large reduction in sensitivity. REduced scatter for accurate attenuation

Question 48

better energy resolution

Answer 48

better window

Question 49

what is better about CZT

Answer 49

it decreases dead speace