Planar Gamma Camera

Descrição

QC, acquisition modes, instrumentation, and image quality
Siobhan Pett
Quiz por Siobhan Pett, atualizado more than 1 year ago
Siobhan Pett
Criado por Siobhan Pett mais de 4 anos atrás
254
0

Resumo de Recurso

Questão 1

Questão
Why must a gamma camera be "peaked" every morning before use?
Responda
  • to ensure a proper correction factor is applied to each pixel
  • to ensure there is no damage to the camera system
  • to ensure the camera is performing consistently day-to-day
  • to ensure a proper correction factor is applied to each PMT and the spaces between PMTs
  • to ensure the PHA knows which energies to accept in imaging studies

Questão 2

Questão
Which is the correct order of events that occur when a gamma ray is emitted from the patient? 1. A count is added at the x,y pixel location on the image matrix 2. The photocathode produces electrons which accelerate and multiply through the dynodes 3. The scintillation travels through the light pipe to the photocathode 4. The pulse travels through the PHA 5. A gamma ray passes through the collimator 6. The position circuit determines the x & y signal locations 7. A gamma ray interacts with the NaI(Tl) crystal to produce scintillation 8. The amplifier manipulates the Z-pulse
Responda
  • 5 > 7 > 3 > 2 > 6 > 8 > 4 > 1
  • 7 > 5 > 3 > 2 > 8 > 6 > 4 > 1
  • 5 > 7 > 4 > 6 > 1 > 3 > 2 > 8
  • 5 > 7 > 3 > 2 > 6 > 1 > 8 > 4
  • 5 > 7 > 3 > 2 > 6 > 4 > 8 > 1

Questão 3

Questão
A nuclear medicine department receives a new gamma camera. The new camera has a larger number of smaller photomultiplier tubes than the older cameras currently in use. Which imaging characteristic will be most improved with the new camera?
Responda
  • uniformity
  • energy resolution
  • spatial resolution
  • sensitivity
  • minimum detectable activity

Questão 4

Questão
When determining the X and Y coordinates of a gamma event, the positional signals are divided by the energy signal (Z) to normalize the signal. Failure to normalize the positional signal may have what result on the resulting image?
Responda
  • True events may not be accepted by the pulse-height analyzer
  • An event may be mapped to the wrong location on the image matrix
  • Edge packing will be increased
  • A ring artifact may occur

Questão 5

Questão
Which of the following is the correct definition of spatial resolution as it relates to conventional nuclear medicine imaging?
Responda
  • the ability of a gamma camera to produce a uniform image in response to a uniform source of gamma rays
  • the ability of a gamma camera to use the gamma rays available to it
  • the ability of a gamma camera to reproduce the details of a nonuniform source of gamma rays
  • the ability of a gamma camera to accurately reflect the different energies of a radionuclide source
  • the ability of a gamma camera to correct for attenuation in an object

Questão 6

Questão
A static image is acquired with a 128x128 matrix. The minimum pixel value is 120 and the maximum pixel value is 18540. If using an 8-bit LUT array, what shade of grey will a pixel with a value of 18000 be assigned?
Responda
  • 248
  • 250
  • 249
  • 247
  • 245

Questão 7

Questão
To obtain high resolution images of a small organ, gland, or joint, which collimator would be most useful?
Responda
  • diverging
  • flat field
  • high-energy diverging
  • low-energy parallel-hole
  • pinhole

Questão 8

Questão
A technologist changes the collimator on a gamma camera from a LEAP to a LEHR collimator. If the same number of counts is acquired, how will the acquisition time change when the high-resolution collimator is used?
Responda
  • the acquisition time will be the same with both collimators
  • the acquisition time will decrease
  • the acquisition time will increase
  • the effect on acquisition time is unpredictable
  • the acquisition time is determined by the intrinsic sensitivity of the instrument

Questão 9

Questão
For a parallel hole collimator, the best resolution is at:
Responda
  • the collimator surface
  • 10 cm
  • 15 cm
  • 20 cm
  • the focal distance

Questão 10

Questão
Which of the following will increase the resolution of a "spot view" bone image obtained with a parallel hole collimator?
Responda
  • moving the camera closer to the patient's body
  • increasing the PHA window width
  • using a high sensitivity collimator instead of a LEAP collimator
  • using fewer shades of grey to display the image
  • using a slant hole collimator

Questão 11

Questão
A technologist forgets to change the LEAP collimator before imaging a patient who has been injected with I-131 for a whole body metastatic survey. The resulting image is most likely to be affected by:
Responda
  • a star artifact
  • partial volume averaging
  • a ring artifact
  • edge packing
  • PMT visualization

Questão 12

Questão
As a pinhole collimator is moved farther away from the thyroid, how will it affect the image?
Responda
  • the gland will appear larger
  • the image will be flipped
  • the gland will appear smaller
  • there is no change in size or orientation
  • right and left are reversed

Questão 13

Questão
A gamma camera is equipped with a parallel hole collimator. Sensitivity is affected by all of the following except:
Responda
  • PHA and window width
  • collimator design
  • thickness of the camera crystal
  • instrument deadtime
  • distance between the source and the collimator

Questão 14

Questão
The following counts-per-pixel values were obtained from a count profile across a line-spread function. If the pixel dimension is 1.6 mm, what is the FWHM?
Responda
  • 6.4 mm
  • 4 mm
  • 4.8 mm
  • 14.4 mm
  • 1.6 mm

Questão 15

Questão
The modulation transfer function (MTF) is a quantitative measure of a camera system's spatial and contrast resolution capabilities. Which of the following will result in a higher MTF value?
Responda
  • greater collimator-source distance
  • higher photon energy
  • changing the collimator from a LEHR to a LEAP
  • longer source wavelength
  • higher source frequency

Questão 16

Questão
Temporal resolution is related to which of the following acquisition parameters?
Responda
  • percentage energy window
  • matrix size
  • framing rate
  • collimator
  • crystal size

Questão 17

Questão
It would be appropriate to apply temporal smoothing in which of the following studies?
Responda
  • gated-equilibrium cardiac function study
  • SPECT study of the brain
  • SPECT study of the liver
  • thyroid image
  • whole-body bone image

Questão 18

Questão
If an image is acquired into a 128x128 matrix on a scintillation camera with a 350mm diameter field of view, what are the dimensions of each pixel?
Responda
  • 2.73x2.73
  • 3.14x3.14
  • 5.92x5.92
  • 6.51x6.51
  • 7.83x7.83

Questão 19

Questão
Static frame mode acquisition is the most appropriate type of image acquisition for which of the following procedures?
Responda
  • first phase of a 3-phase bone study
  • thyroid imaging
  • LVEF determination
  • renal function imaging
  • hepatobiliary imaging

Questão 20

Questão
Which of the following matrix sizes and acquisition modes would be most appropriate for a blood flow study of the feet?
Responda
  • 64x64 word
  • 64x64 byte
  • 256x256 byte
  • 256x256 word
  • 512x512 byte

Questão 21

Questão
When performing a whole-body bone scan, why is it important to have a 5 minute delay before the bed/detectors start(s) moving over the length of the patient after the acquisition is started?
Responda
  • To ensure counts are acquired for the same length of time over each section of the patient's body
  • Because tracer uptake in the skull is delayed due to the blood brain barrier
  • To allow time for the tracer to distribute through the patient's body
  • To visualize blood flow to the skull
  • There is no specific reason for this

Questão 22

Questão
Background correction is sometimes employed to enhance which of the following image characteristics?
Responda
  • spatial resolution
  • linearity
  • contrast resolution
  • uniformity
  • ability to detect small lesions

Questão 23

Questão
Image resolution may be improved when imaging small objects by all of the following EXCEPT:
Responda
  • Zoom applied pre-acquisition
  • Use of a pinhole collimator
  • Decreasing collimator-patient distance
  • Increasing the matrix size
  • Zoom applied post-acquisition

Questão 24

Questão
Perform a 9-point weighted smooth on the image matrix. What will be the new value of the highlighted pixel?
Responda
  • 58
  • 102
  • 62
  • 35
  • 42

Questão 25

Questão
A static image of the femur is acquired to 100k counts on a 128x128 matrix. The average pixel noise is 6%. If the technologist wants to improve resolution by repeating the image with a 256x256 matrix, how many counts must be acquired to avoid increasing the average pixel noise?
Responda
  • 100k
  • 200k
  • 50k
  • 400k
  • 800k

Questão 26

Questão
A 50 cm camera with an image matrix of 128x128 is used to acquire an image of the spine. Information density in the region of the spine is 1850 cts/cm^2. What is the average count density per pixel?
Responda
  • 722 cts/pixel
  • 1129 cts/pixel
  • 71 cts/pixel
  • 281 cts/pixel
  • 361 cts/pixel

Questão 27

Questão
The image on the left was likely acquired with:
Responda
  • A zoom factor with the image on the right having no zoom applied
  • A larger image matrix than the image on the right
  • A smaller image matrix than the image on the right
  • A pinhole collimator, and the image on the right was acquired with a parallel hole
  • A parallel hole collimator, and the image on the right was acquired with a pinhole

Questão 28

Questão
The system resolution of a gamma camera is 9.5 mm. What is the largest pixel dimension that should be used with this system if we are to take full advantage of the system resolution?
Responda
  • 19 mm
  • 9.5 mm
  • 4.75 mm
  • 2.38 mm
  • 7.8 mm

Questão 29

Questão
Which of the following statements about an image acquired with zoom is true?
Responda
  • image resolution is increased
  • background counts are increased
  • more memory is required
  • contrast is decreased
  • specificity is increased

Questão 30

Questão
In which scenario may a logarithmic grey scale enhance visualization of the organ of interest?
Responda
  • Visualization of the gallbladder in a hepatobiliary study
  • Visualization of the stomach in a gastric emptying study
  • Visualization of the kidney in a renal function study
  • Visualization of the sternum in a whole-body bone scan
  • Visualization of the myocardium in a myocardial perfusion study

Questão 31

Questão
A MUGA study is performed and the ROIs drawn by the technologist yield the following results: ED counts: 143908 ES counts: 78094 Background counts: 7564 ED ROI size: 645 pixels ES ROI size: 323 pixels Background ROI size: 102 pixels Calculate the LVEF.
Responda
  • 44%
  • 48%
  • 46%
  • 50%
  • 42%

Questão 32

Questão
How much memory will be needed for a MUGA study that is acquired in 30 frames with a 128x128 matrix in byte mode?
Responda
  • 3840 bytes
  • 16,384 bytes
  • 491,520 bytes
  • 546 bytes
  • 256 bytes

Questão 33

Questão
A daily uniformity flood for a scintillation camera should contain a minimum of how many counts?
Responda
  • 10,000
  • 1-2 million
  • 3-5 million
  • 6-10 million
  • 20-30 million

Questão 34

Questão
In quantitating scintillation camera detector uniformity, the central field of view (CFOV) is defined as the diameter of the useful field of view (UFOV) multiplied by:
Responda
  • 0.95
  • 0.75
  • 0.33
  • 0.25
  • 0.15

Questão 35

Questão
To perform pixel calibration, two capillary sources are placed on the camera surface 15 cm apart. From an image acquired using a 128x128 matrix, an activity profile is generated on the computer. If the profile shows that there are 45 pixels between the two activity peaks, the pixel size is:
Responda
  • 0.02 cm
  • 0.12 cm
  • 0.20 cm
  • 0.33 cm
  • 0.42 cm

Questão 36

Questão
If a PLES transmission phantom is used, how many images must be acquired to assess linearity over the entire field of view of a scintillation camera?
Responda
  • 1
  • 2
  • 3
  • 4
  • 5

Questão 37

Questão
Using a 125 MBq source, 30,500 cpm were collected during a camera sensitivity determination. If the background count is 1200 cpm, what is the sensitivity of the instrument?
Responda
  • 234 cpm/MBq
  • 244 cpm/MBq
  • 29,300 cpm
  • 3,662,500 cpm
  • 300,500 cpm

Questão 38

Questão
Which of the following radionuclide sources is used to acquire an extrinsic uniformity flood?
Responda
  • Tc-99m point course with collimator removed
  • Co-57 sheet source with collimator removed
  • Tc-99m point source with collimator in place
  • I-131 point source with collimator removed
  • Co-57 sheet source with collimator in place

Questão 39

Questão
Extrinsic uniformity is performed daily on a gamma camera with a Co-57 sheet source and a LEAP collimator. From the data shown here, all the following may have caused the decreased sensitivity seen on June 5 except:
Responda
  • incorrect photopeak/window setting
  • incorrect collimator
  • a cracked crystal
  • incorrect acquisition matrix
  • a malfunctioning PMT

Questão 40

Questão
Sources of intrinsic non-uniformity include all of the following except:
Responda
  • mistuned PMTs
  • regional variations in Z-pulse amplitude
  • spatial distortion
  • linearity
  • edge packing

Questão 41

Questão
Extrinsic quality control on a gamma camera means the quality control is done:
Responda
  • automatically overnight
  • without the collimator on
  • inside the camera
  • outside the camera
  • with the collimator on

Questão 42

Questão
If a technologist is preparing a Tc-99m point source for an intrinsic uniformity flood, how much activity is sufficient for the image?
Responda
  • 10 mCi
  • 5 mCi
  • 200 uCi
  • 2 mCi
  • 20 mCi

Questão 43

Questão
Linearity correction involves:
Responda
  • diagonal lines
  • horizontal lines
  • horizontal and vertical lines
  • vertical lines
  • diagonal and vertical lines

Questão 44

Questão
To repair the non-uniformity demonstrated on the intrinsic uniformity image the service engineer will need to:
Responda
  • replace the crystal
  • redo reference map calibration
  • repair the collimator
  • replace a photomultiplier tube
  • replace the x,y localization barrel

Questão 45

Questão
For the majority of physiologic studies, "cold" spots are areas on the image display that indicate:
Responda
  • necrotic tissue
  • mistuned PMTs
  • increased activity
  • nonlinearity
  • a cracked crystal

Questão 46

Questão
A 1M count extrinsic flood is acquired with a Co-57 sheet source and is uniform in appearance, but it takes 2 minutes longer to acquire than normal. What is a possible explanation?
Responda
  • The photopeak is centered on 140 keV
  • A high sensitivity collimator is installed when the extrinsic flood is usually acquired with a high resolution collimator
  • A brand new sheet source is being used
  • The technologist selected the incorrect matrix size
  • The technologist forgot to position the detectors as close as possible to the sheet source before acquiring the flood

Questão 47

Questão
Image A was acquired with a 128 x 128 matrix. What matrix size was used to acquire Image B?
Responda
  • 64 x 64
  • 32 x 32
  • 128 x 128
  • 256 x 256
  • 512 x 1024

Questão 48

Questão
The acquired thyroid image appears as shown here. The patient received 3.7 MBq of I-131. What is a possible explanation for the poor resolution?
Responda
  • Too little activity was administered
  • There is contamination on the bottom of the collimator
  • The photopeak is set on 140 keV
  • A HEGP collimator is installed
  • Uniformity corrections were not applied

Questão 49

Questão
This intrinsic uniformity flood was acquired using an asymmetric window. What is the most likely explanation for the phenomenon seen here?
Responda
  • Cracked crystal
  • Loss of automated corrections
  • Off-peak windows
  • Poor coupling of PMTs to the crystal
  • Loss of the hermetic seal

Questão 50

Questão
The non-uniformity seen here indicates:
Responda
  • a cracked crystal
  • a dented collimator
  • a malfunctioning PMT
  • the wrong energy window was selected
  • water damage to the crystal

Questão 51

Questão
This is the image acquired from the weekly bars quality control scan. What should the technologist do next?
Responda
  • Use the gamma camera for clinical studies
  • Call the repair technician
  • Apply linearity and uniformity corrections
  • Buy a new gamma camera
  • Check the collimator for damage

Questão 52

Questão
Regarding the images, which of the following is/are true? 1. The results may be due to improper energy window setting 2. Energy peaking is typically done for every individual scan 3. The energy window should be 20% and set at 160 keV 4. A collimator defect was likely present on the posterior camera head 5. The posterior camera had may be too far from the patient
Responda
  • 1, 2, and 5
  • 1, 2, and 3
  • 4 and 5
  • 1 only
  • 1 and 5

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