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Nuclear Medicine > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

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

A

electrical current generated

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2
Q

what are examples of radiation detectors

A

ionization chambers, proportional counters, geiger mueller counters

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3
Q

what are examples of scintillation detectors

A

inorganic scintillators and organic liquid scintillators

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4
Q

what are examples of semiconductor detectors

A

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

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5
Q

what are the basic components of a scintillation detector

A

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

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6
Q

what scintillator would you pick for a gamma camera

A

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

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7
Q

what is sodium iodide iwth thallium used in

A

nuclear medicine

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8
Q

what is bismuth germanium oxide used in

A

PET

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9
Q

what is barium or cesium fluoride used in

A

used in PET

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10
Q

what is luthetium orthoscilicate used in

A

PET and SPECT systems

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11
Q

what is the flow chart of gamma ray detection

A

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

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12
Q

what is proportional along the gamma ray detection

A

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

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13
Q

what is positioning (pulse) arthmetic

A

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

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14
Q

how do you determine where the radiation came from?

A

collimate the detector

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15
Q

what is gamma camera collimation

A

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.

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16
Q

what material is often used for collimation of gamma camera

A

lead

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17
Q

what is the tradeoff in collimation

A

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

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18
Q

what does high resolution mean for the sensitivity

A

it means there is low sensitivity

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19
Q

what does high sensitivity mean for resolution

A

low resolution

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20
Q

what does high sensitivity mean for resolution

A

low resolution

21
Q

what are things to consider when designing a collimator

A

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

22
Q

what is the collimator resolution proportional to

A

diameter times source distance

23
Q

what is collimator sensitivity proportional to

A

hole diameter squared

24
Q

what is the proportionality between resolution and sensitivity

A

the resoultion is sqared in proportion to the sensitivity

25
Q

draw a semiconductor

A

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

26
Q

what is a silicon photodiode

A

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

27
Q

what are the benefits of silicon photodiodes

A

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

28
Q

what is the best semiconductor materials

A

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

29
Q

CZT detector is

A

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

30
Q

what are the spectrum dysnamics of these scans

A

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

31
Q

what technology does SPECT of the heart use

A

it is CZt

32
Q

what else is CZT used for

A

breast, heart, rnadom whole body

33
Q

what is the best parts of semiconductor technology

A

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

34
Q

what is the best parts of semiconductor technology

A

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

35
Q

what is intrinsic resolution a function of

A

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

36
Q

what effect does crystal thickness have on instrinsic resolution

A

the resolution degrades with increasing crystal thickness

37
Q

what effect does number of photomultiplier tubeshave on instrinsic resolution

A

it inproves with increased PMT

38
Q

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

A

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

39
Q

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

A

the resolution improves iwth increased energy

40
Q

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

A

the resolution improves with increased energy

41
Q

what is the formula for energy resolution

A

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

42
Q

what is system resolution dependent on

A

collimator resolution and intrinsic resolution

43
Q

what is the important part of collimator resolution

A

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

44
Q

what does it mean if low bandgap

A

same photon has higher sensitivity because more electrons

45
Q

what does high bandgap mean

A

it means they can be used at more room temperature

46
Q

if the band gap is too low

A

it needs to be cooled down too much

47
Q

what is important about energy resolution

A

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

48
Q

better energy resolution

A

better window

49
Q

what is better about CZT

A

it decreases dead speace

Nuclear Medicine (5 decks)

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