43-Spect/spect-Ct/image Quality

Front 1

What does SPECT stand for?

Back 1

single photon emission computed tomography

Front 2

What is the benefit of multidetector camera setup over single detector SPECT?

Back 2

Faster: They acquire data simultaneously from multiple directions.

Front 3

Components of Anger Camera

Back 3

...

Front 4

During Cardiac imaging the SPECT camera is configured in an (L, H) configuration and undergoes a rotation arc of _______ degrees

How about non-cardiac imaging?

Back 4

L position
180 degrees (better spatial resolution but more noisy)

H position
360 degrees (less spatial resolution but more homogeneous)

Front 5

Most Tc-99m clinical protocols use how many projections over 180 degrees with high resolution collimators?

over 360 degrees?

Back 5

64 projections/180 degrees
128 projections/360 degrees

Front 6

Which type of orbit provides the best signal characteristics, circular or non-circular orbit?

Back 6

non-circular: because the camera remains close to the patient throughout image acquisition resulting in better spatial resolution and signal

Front 7

Which type of SPECT detector is best? Anger cameras or solid state cameras

Back 7

solid state cameras:
better resolution, better sensitivity, requires less radiopharmaceutical, faster, lower dose to patient

Front 8

Attenuation correction can be done simply by acquiring images in 180 degree projections and then averaging the information. This is known as what?

Back 8

Geometric Mean

Front 9

How does the energy of the gamma ray emitted by the isotope relate to attenuation?

how about the size of the patient?

Back 9

lower energy = higher attenuation in patient

fat patient= more attenuation

Front 10

What clinical application is a chang attenuation correction applied?

Back 10

for attenuation correction of cylindrical bodies (ie. brain imaging)

Front 11

How does emission/transmission attenuation correction work?

Back 11

a line source emits radiation of different keV behind patient and attenuation is calculated based on the amount of radiation "transmitted" through the patient. This is then used to correct for the energy "emitted" from within the patient. This is done for both detectors for every projection throughout the arc.

Front 12

What are the pros and cons of CT attenuation correction?

Back 12

pros: better signal to noise ratio with a lower patient radiation dose.

cons: cannot be performed simultaneously with the emmision tomograms= misregistration.

Front 13

Once the data of a SPECT image has been acquired, how is the image reconstructed?

Back 13

Filtered back projection

Front 14

What is the star artifact?
How is it reduced?

Back 14

Star artifact results from filtered back projection when too few projections are used
Use more projections

Front 15

What are the effects of applying filters to the back projection?

Back 15

lower cutoff frequency = less noise at expense of spatial resolution

high cutoff frequency = more noise but better spatial resolution

Front 16

Iterative reconstruction, MLEM and OSEM?

Back 16

just know that iterative reconstruction is better than filtered back projection

Front 17

How is the resolution of a SPECT system defined?

Back 17

FWHM (full width half max)
typically 1 cm

Front 18

QC: How frequently are the following performed?
Energy Peaking
Intrinsic floods
Attenuation peaking and flood

Back 18

Daily

Front 19

QC: How frequently are the following performed?
Attenuation correction high-count maps

Back 19

Weekly

Front 20

QC: How frequently are the following performed?
High count extrinsic floods

how will a nonuniform detector response look?

Back 20

weekly-monthly

concentric rings

Front 21

QC: How frequently are the following performed?
Multipuspose plexiglas phantoms
Tomographic resolution (line source/point source)
3D testing

Back 21

quarterly

Front 22

What is COR calibration? how frequently should it be done?

Back 22

Weekly: Provides information to the reconstruction software about the way the images appear to shift as the camera rotates around the body for different collimators. If not properly calibrated, can result in significant reconstruction artifacts

Front 23

In a multidetector SPECT system, the percent variation between detectors should not exceed what value?

Back 23

10%

Front 24

What are the predictable and variable SPECT artifacts?

Back 24

Predictable:
1) COR = comet
2) Tilt = Mercedes-Benz
3) Wrong Energy = Fuzzy

Variable
1) Motion
2) Bad PM tube
3) Gating Errors

Front 25

Name this artifact

Back 25

Uncalibrated COR= comet artifact
Anterolateral and inferolateral defects

Front 26

Name this artifact

Back 26

Detector Tilt (>10 degrees) = mercedes benz

Front 27

Name this artifact

Back 27

Wrong energy peak = Fuzzy

Results in decreased count, spatial resolution and contrast

Front 28

Remember motion and motion-like artifacts

Back 28

can be seen during cines if patient moves and when dual head cameras are used as the information from 2 cameras is combined (ie. apparent increased parathyroid uptake at the end of a 180 degree acquisition)

Front 29

what are causes of concentric ring artifacts?

Back 29

Damaged collimators, faulty PM tube, inadequate counts of a correcting flood field and nonuniform detector response.

Front 30

What is this artifact?

Back 30

Magnetic field effects

Front 31

What is this artifact?

Back 31

Ringing artifact: occurs when bright uptake in an organ results in decreased apparent signal in adjacent "less-hot" organ. Like shining or mach band

Front 32

For SPECT CT, how frequently should a phangom be used to verify correct registration between CT and SPECT?

Back 32

Quarterly

Front 33

What is the most common type of scintillation crystal?

Back 33

NaI (Tl)

Front 34

Non-circular paths equals better _____________

Back 34

spatial resolution.

Front 35

Cardiac imaging angles

Back 35

-45 to +135 degrees

Front 36

Chang correction is for uniform attenuation coefficients along with uniform radioactivity concentrations

Back 36

...

Front 37

The function that convolutes or blurs each point has the particular form of 1/r

Back 37

fixed by ramp function

Front 38

at the same distance, planar images and SPECT have ___________ resolution?

Back 38

Same

Front 39

COR artifact results in Anterolateral and inverolateral defects

Back 39

...

Front 40

CT Attenuation correction calibration should be performed ____________

Back 40

daily