Instrumentation

Question 1

_____ produce projection images of the distribution of radioactivity in patients

Answer 1

Scintillation cameras

Question 2

Scintillation cameras are sometimes called _____

Answer 2

gamma cameras or Anger cameras.

Question 3

are essential for providing
spatial information in planar NM
imaging

Answer 3

Collimators

Question 4

____ absorb incident gamma photons and produce many light photons.

Answer 4

Scintillators

Question 5

Approximately ____ of the absorbed gamma ray energy is converted to light.

Answer 5

10%

Question 6

Scintillation cameras typically use ___

Answer 6

55 PMTs

Question 7

___ refers to the registration of a
single gamma ray by the detector, and
~ _____ counts are acquired for a typical scintillation camera image.

Answer 7

Count, 500,000

Question 8

Scintillation cameras use computers to
________the acquired image data.

Answer 8

store, manipulate, and display

Question 9

Collimators are typically made of ___ and contain multiple holes. The lead strips between the holes are called
____.

Answer 9

lead, septa

Question 10

In general, only _____ photons emitted from the radioactive source will be accepted by the collimator and incorporated into the image.

Answer 10

0.01% (i.e., 1 in 10,000)

Question 11

Types of collimator used in nuclear medicine:

Answer 11

1. Pinhole collimator
2. Multihole collimator/ Parallel-hole collimator
3. Converging multihole collimator
4. Diverging collimator

Question 12

The simplest form collimator

Answer 12

pinhole collimator

Question 13

It consists of a single, small hole or aperture located a set distance (typically on the order of 20 cm) from the surface of the NaI crystal.

Answer 13

Pinhole collimator

Question 14

are cone shaped with a single
hole at the apex

Answer 14

Pinhole collimators

Question 15

Images generated using a pinhole collimator are normally _____

Answer 15

magnified and inverted

Question 16

can be of significant value when imaging small objects using a camera with a large field of view.

Answer 16

Magnification

Question 17

Provides substantially better geometric
sensitivity compared to the pinhole
collimator, because the object is viewed
through many small holes rather than through a single hole.

Answer 17

Multihole collimator

Question 18

The collimator spatial resolution depends on the

Answer 18

diameter
length of the collimator holes
distance from the source collimator

Question 19

provides both enhanced spatial resolution and improved sensitivity

Answer 19

converging multihole collimator

Question 20

produce a magnified image, and FOV decreases with distance

Answer 20

Converging collimators

Question 21

_____ project an image size that is smaller than the object size, and FOV increases with distance.

Answer 21

Diverging collimators

Question 22

is the fraction of gamma rays reaching it from allBdirections that pass through the holes.

Answer 22

Collimator sensitivity

Question 23

Collimator sensitivity is low with approximately ____, of
the emitted photons being detected.

Answer 23

10-4, or only 0.01%

Question 24

have larger holes and lower resolution

Answer 24

High-sensitivity collimators

Question 25

have smaller holes and lower sensitivity

Answer 25

– High-resolution collimators

Question 26

is degraded with increasing distance from the collimator.

Answer 26

Resolution

Question 27

Low-energy collimators used with ____ have thin septa.

Answer 27

99mTc and 201TI

Question 28

collimators that are most frequently used

Answer 28

Low-energy high-resolution (LEHR)

Question 29

– Used with 67Ga and 111In have thicker septa and therefore fewer holes and lower sensitivity.

Answer 29

Medium-energy collimators

Question 30

– Are required for 131I imaging and have the thickest septa.

Answer 30

High-energy collimators

Question 31

____ detect gamma rays emerging from patients and are generally rectangular.

Answer 31

NaI scintillators

Question 32

For gamma ray imaging, NaI scintillators are ____

Answer 32

10 mm thick

Question 33

• A _____ is when an incident gamma ray is completely absorbed (photoelectric effect).

Answer 33

photopeak

Question 34

is the percentage of incident gamma rays absorbed in the scintillator.

Answer 34

detection efficiency

Question 35

Light output from the NaI crystal is detected by

Answer 35

photomultiplier tubes (PMTs)

Question 36

is measured as the full width half maximum (FWHM).

Answer 36

Photopeak width

Question 37

The broadening of the photopeak (FWHM) is termed

Answer 37

energy resolution.

Question 38

is an electronic device used to determine which portion of the detected spectrum is used to create images.

Answer 38

pulse height analyzer (PHA)

Question 39

The ___, measured by percent, determines the acceptable range of energies around the peak for subsequent counting.

Answer 39

window

Question 40

It consists of a single, small hole or aperture located a set distance (typically on the order of _____) from the surface of the NaI crystal

Answer 40

20 cm

Question 41

The collimator spatial resolution of the pinhole, RPH, is determined by the diameter or the aperture, d (typically ___ mm) and the distances from both the object and the NaI crystal to the aperture.

Answer 41

4-6 mm

Question 42

A typical low-energy, parallel-hole collimator may have hole diameters and lengths of about ___ mm, respectively, and septal thicknesses between holes of about ____.

Answer 42

1 and 20 mm, 0.1 mm

Question 43

The distance from the collimator to the focal point is typically on the order of ___ and thus far beyond the boundaries of the patient.

Answer 43

50 cm

Question 44

Increasing the photon energy from 100 to 500 keV reduces detection efficiency from

Answer 44

100% to 6%

Question 45

A measured width (broadening) of 28 keV for 99mTc (140 keV) corresponds to an energy resolution of ___

Answer 45

20%

Question 46

% Photons Detected by 10-mm-Thick NaL Crystal with a photon energy of 100 keV

Answer 46

100

Question 47

% Photons Detected by 10-mm-Thick NaL Crystal with a photon energy of 140 keV

Answer 47

92

Question 48

% Photons Detected by 10-mm-Thick NaL Crystal with a photon energy of 200 keV

Answer 48

54

Question 49

% Photons Detected by 10-mm-Thick NaL Crystal with a photon energy of 300 keV

Answer 49

22

Question 50

% Photons Detected by 10-mm-Thick NaL Crystal with a photon energy of 500 keV

Answer 50

6