Scintillation Camera Quality Control

Question 2

The _____ of the PHA is evaluated by
using a source that radiates the whole crystal.

Answer 2

photopeak window

Question 3

Irradiation of the whole crystal may be
achieved using a ____, or a ____ at a distance.

Answer 3

sheet source, point source

Question 4

The photopeak window is checked ____

Answer 4

daily

Question 5

____is the ability of the scintillation
camera to reproduce a uniform distribution of activity.

Answer 5

Field uniformity

Question 6

_____ and ___ in the crystal contribute to nonuniformity.

Answer 6

Differences in the PMT response, transmission of light

Question 7

Nonuniformities of greater than ___ from the mean are unacceptable for clinical imaging.

Answer 7

5%

Question 8

Modern cameras have a uniformity of better than ___ between adjacent areas

Answer 8

2%

Question 9

Field uniformity is commonly checked daily by placing a large-area disc made of ___ in front of the camera

Answer 9

57Co

Question 10

57Co emits ___ photons and has a half-life of ___

Answer 10

122 keV, 270 days

Question 11

____ are obtained with the collimator in place and will assess the system performance including the collimator.

Answer 11

Extrinsic flood images

Question 12

___ are performed without the
collimator and assess the performance of Nal crystal and associated light detectors.

Answer 12

Intrinsic floods

Question 13

the ability to separate two points

Answer 13

Resolution

Question 14

Resolution (i.e., the ability to separate two points) is checked using a ____

Answer 14

quadrant bar phantom

Question 15

Quadrant bar phantoms have four sets of parallel bars, with each rotated through ___ degrees, with
dimensions of _____.

Answer 15

90, 3.5, 3.0, 2.5, and 2.0 mm

Question 16

____ also check for linearity (i.e., ability to image straight lines).

Answer 16

Bar pattern phantoms

Question 17

• A _____ is an ionization chamber used to measure the activity of a radioisotope dose

Answer 17

dose calibrator

Question 18

Dose calibrators make measurements in ____

Answer 18

MBq or mCi

Question 19

____ is checked daily by measuring the same standard source that has a long half-life.

Answer 19

Constancy

Question 20

____ has a half-life of 30 years and is therefore ideal for measuring calibrator constancy.

Answer 20

137Cs

Question 21

____is checked at installation and annually using ____

Answer 21

Accuracy, calibrated sources

Question 22

Accuracy is checked at installation and ___ using calibrated sources

Answer 22

annually

Question 23

____ is checked quarterly by measuring the decay of 99mTc over 72 hours or more.

Answer 23

Linearity

Question 24

Linearity is checked ___ by measuring the decay of ____ over ____ hours or more.

Answer 24

quarterly, 99mTc, 72

Question 25

___can also be checked by using a source placed into a calibrated cylinder of lead that attenuates the source by a known amount.

Answer 25

Linearity

Question 26

____is the difference in intensity (counts) in any abnormality compared to the intensity in the surrounding normal anatomy (background).

Answer 26

Contrast

Question 27

____ is the difference in activities in the abnormality and surrounding normal anatomy.

Answer 27

Subject contrast

Question 28

_____is the corresponding difference in image counts in the abnormality and normal anatomy

Answer 28

Image contrast

Question 29

Excellent localization in an organ of interest is known as "_____" imaging.

Answer 29

hot spot

Question 30

The ratio of organ-specific uptake to unwanted uptake in other tissues is called the _____

Answer 30

target to background ratio

Question 31

___ is affected by septal penetration and scatter

Answer 31

Contrast

Question 32

Nuclear medicine ____ is the ability to distinguish two adjacent radioactive sources.

Answer 32

resolution

Question 33

An image of a line is known as the ____

Answer 33

line spread function

Question 34

Measurement of the ___ of the line spread function is the most common measure of resolution in nuclear medicine

Answer 34

full width half maximum (FWHM)

Question 35

____ refers to the performance of the camera without the collimator.

Answer 35

Intrinsic resolution

Question 36

____ assesses the performance of the Nal crystal, light detectors (PMT), and associated electronics.

Answer 36

Intrinsic resolution

Question 37

Intrinsic resolution of a scintillation camera is typically between ____

Answer 37

3 and 5 mm

Question 38

System resolution (R) depends on the ____ and ____.

Answer 38

intrinsic resolution of the scintillation camera (Ri), resolution of the collimator (Rc)

Question 39

FWHM in NM is generally ~ ___ with the low- energy high-resolution (LEHR) collimator most commonly used in clinical imaging.

Answer 39

8 mm

Question 40

A FWHM of 8 mm corresponds to a limiting spatial resolution of 1/(2 × 8 Ip/mm, or ___

Answer 40

0.06 Ip/mm

Question 41

Spatial resolution of commercial PET systems can approach __ FWHM when imaging a line source of activity

Answer 41

5 mm

Question 42

____is any unwanted counts in a nuclear medicine image that can interfere with the detection of abnormalities.

Answer 42

Noise

Question 43

Noise may be classified as ___

Answer 43

random or structured

Question 44

____ results from statistical variation in pixel counts and is called quantum mottle.

Answer 44

Random noise

Question 45

____ is a major factor in SPECT due to the low number of photons used to reconstruct each voxel.

Answer 45

Quantum mottle

Question 46

PET images have ___ counts and ___ levels of image mottle.

Answer 46

high, lower

Question 47

___ includes nonuniformities in the scintillation camera.

Answer 47

Structured noise

Question 48

Uptake in the gastrointestinal tract when imaging the kidneys is an example of _____

Answer 48

structured noise

Question 49

____ produce defects in the image, whose characteristics reflect the shape of the crack.

Answer 49

Cracked crystals

Question 50

____ may also produce a cold defect and shows up well on a flood image.

Answer 50

PMT failure

Question 51

____ refers to the increased brightness at the edge of the crystal.

Answer 51

Edge packing