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NMED 251 - Clinical Procedures > MUGA > Flashcards

MUGA Flashcards

1
Q

What happens if a patient has a longer than average cardiac cycle?

A

Framing stops before end diastole which under represents EDV which decreases EF

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2
Q

What happens if a patient has a shorter than average cardiac cycle?

A

Lack of data to be recorded in the last few frames also resulting in a decrease of EDV = decrease EF

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3
Q

Too much background subtraction: effect on EF?

A

falsely increased EF = false negative results

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4
Q

Too little background subtraction: effect on EF?

A

falsely decreased EF = false positive results

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5
Q

what happens to the EF if LA overlaps LV ROI slightly?

A

overestimate ES which means more vol. at ES which means heart not doing a good job at contracting = underestimate EF

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6
Q

what are some artifacts seen in MUGAs?

A
  • arrhythmias
  • improper ROI
  • attenuation from ECG leads, pacemakers, other metals in FOV
  • poorly tagged RBCs
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7
Q

what are the advantages to MUGA?

A
  • accurate + non-invasive
  • reproducible
  • simple technique
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8
Q

what are the disadvantages to MUGA?

A
  • RVEF can’t be accurately calculated
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9
Q

what study is best to assess RVEF?

A

first pass

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10
Q

why is it difficult for us to assess RVEF?

A

RV can’t be easily separated from RA or an enlarged LV

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11
Q

what are the advantages to a gated equilibrium stress study?

A
  • more sensitive to ischemic changes
  • completed in short time period
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12
Q

what are the disadvantages to a gated equilibrium stress study?

A
  • “demanding”
  • requires considerable patient compliance
  • more patient motion, less statistics/shorter images
  • more electrical interference on ECG
  • must have qualified physician present during stress
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13
Q

downfall of echocardiography? pros?

A

-no reproducibility
+noninvasive + accurate at determining EF

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14
Q

downfall of angiography? pros?

A

-invasive+high radiation dose
+highly accurate

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15
Q

downfall of gated MRI?

A

-demanding + requires multiple breath holds

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16
Q

downfall of gated CT?

A

-single breath holds + needs contrast injection

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17
Q

T/F
The purpose of tin when labeling RBC’s is to ensure 99mTc04- is reduced intracellularly.

A

true

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18
Q

T/F
When performing an LAO view, 5-10 degrees caudal tilt improves separation between the two ventricles.

A

False
separates LV and LA

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19
Q

T/F
A 3 lead ECG is adequate for gating MUGA studies

A

true

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20
Q

T/F
500 accepted beats per image provides adequate statistics

A

true

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21
Q

what is the range for beats per image in a MUGA?

A

300-600

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22
Q

what is the set time for a MUGA?

A

10 minutes

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23
Q

what are the counts needed for a MUGA?

A

3-5M

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24
Q

T/F
Wall motion that is described as dyskinetic means that the area of myocardium is not contracting as vigorously as expected.

A

false
dyskinetic describes phasing therefore, it would mean that the area is not in phase with what it is supposed to be in phase with (eg. ventricles)

hypokinetic is the proper term

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25
Q

p wave

A

atrial contraction

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26
Q

on an ECG, which wave indicates ventricular depolarization? repolarization?

A

QRS - R wave signals for ventricles to contract
depolarization - t wave

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27
Q

indications for a MUGA

A
  • baseline and follow up measurements for Sx or chemotherapy
  • assessing valvular heart disease, cardiomyopathies
  • eval EF, global and LV regional wall motion, size and volumes
  • CAD eval + post MI eval
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28
Q

how is EF calculated?

A

EF = (EDV-ESV)/(EDV)

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29
Q

what are contraindications for MUGA?

A

severe arrhythmias (atrial fibrillation, greater than 10% PVCs)

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30
Q

dose for MUGA study

A

740-1850 MBq

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31
Q

radiopharm used for MUGA

A

99mTc-RBCs
IV infusion

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32
Q

critical organ of 99mTc-RBCs

A

Spleen

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33
Q

dosimetry in spleen?

A

1.1 mGy/37 MBq

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34
Q

excretion of 99mTc-RBCs

A

predominantly renal (25% in first 24hrs)

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35
Q

breastfeeding guidelines for 99mTc-RBCs (in vivo vs in vitro)

A
  • stop 12 hours if done in vivo
  • in vitro = halt feeding for minimum of 4 hrs (pump and discard)
36
Q

Which of the following is NOT an indication for a gated equilibrium study?

A) Assess blood flow to the heart muscle
B) Screening prior to or after chemotherapy
C) Evaluation of cardiac chamber size
D) Evaluation of the percentage of blood pumped from the heart/beat

A

A

37
Q

how do we acquire data for MUGA?

A

dynamic frame mode that is triggered by R-R intervals

38
Q

frame mode acquisition

A

data from each cardiac cycle has counts added to each frame until adequate counts are achieved or an average beat is obtained

39
Q

what % is typical beat rejection?

A

+/- 10% to 20%

40
Q

longer than average cardiac cycle = ?

A

framing to stop before end diastole
- under represents EDV therefore decreases EF

41
Q

shorter than average cardiac cycle?

A

lack of data recorded in last few frames
= decreases EF

42
Q

patients with infants?

A

limit contact to <5 hours for the first 24 hrs

43
Q

how many frames do we choose per cycle?

A

16-32 frames

44
Q

heart should occupy __% of FOV

A

50%

45
Q

how long do we wait for homogeneous mixing? what does it mean?

A

10 minutes
mixing with the rest of our blood around the body/heart evenly

46
Q

what angles do we get images from for a MUGA?

A

ANT, LAO (30-60d) and LLAT
caudal tilt (10-15d)

47
Q

what other angles can be done?

A

LPO, RAO, RLAT

48
Q

why do we do caudal tilts?

A

separation of LA/LV

49
Q

what is best separation?

A

clearly see separation of right/left ventricles

50
Q

what are some stop conditions?

A
  • 10 min/image
  • 200-250 kcts/frame
  • 300-600 heart beats
  • 3-7M total counts
51
Q

why do quantitative blood pool spect?

A
  • isolates r/l ventricles without overlap therefore able to assess LVEF and RVEF
  • less time to acquire
  • better regional wall motion assessment
52
Q

views for blood pool spect?

A

90 degrees
- one detector doing 45d RAO
- other at 45 LPO

53
Q

T/F
Setting up a MUGA acquisition with 32 frames will have greater temporal resolution than an acquisition with 16 frames.

A

true

54
Q

smoothing
spatial

A

each surrounding pixel around an individual pixel is examined and counts are averages

55
Q

smoothing
temporal

A

counts in pixel frame before and after area averaged

56
Q

best septal view

A

LAO

57
Q

where do we draw background ROI?

A

between 3 and 6 o’clock of LV

58
Q

what is produced from ROIs?

A

time activity curve

59
Q

qualitative analysis

A

visual
- cine loop: for wall motion, ventricular size + wall thickness

60
Q

quantitative analysis

A

time-activity curves, global ejection fraction, regional EF, phase + amplitude

61
Q

hypokinetic

A

wall motion - not moving as much

62
Q

akinetic

A

wall motion - not moving at all

63
Q

dyskinetic aka?

A

paradoxical
wall motion - moving the wrong way

64
Q

normal LVEF?

A

50-80%

65
Q

normal RVEF?

A

40-60%

66
Q

time-activity curve

A

time of blood volume (aka counts) changes in LV during average cardiac cycle

67
Q

how do we get a time activity curve?

A

by drawing ROI around the LV on every frame and the counts are then plotted on a graph over time

68
Q

what can be derived from a time activity curve?

A

EF, peak ejection rate and peak filling rate

69
Q

end frame drop off

A

caused by heart rate variability
the EDV is not the same as it was in the beginning

70
Q

normal stroke volume?

A

80-100ml

71
Q

how do you calculation stroke volume?

A

EDV-ESV

72
Q

normal cardiac output?

A

5-6L

73
Q

how do you calculate cardiac output?

A

stroke volume * heart rate

74
Q

normal EDV?

A

150ml

75
Q

phase

A

comparing the timing of atrial and ventricular contraction

76
Q

atria and ventricles should be contracting with the phase difference of ____

A

“180 degrees apart”

77
Q

phases can be looked at by?

A

images and histograms

78
Q

amplitude

A

degree/force of contraction
- looking at regional wall motion

79
Q

what area of the heart normally shows the least amount of contraction?

A

septal area

80
Q

what areas show less contractility than healthy myocardium?

A

areas of old infarcts and scarring

81
Q

what words are used to describe phase?

A

dissynchronous/synchronous
dyskinetic/paradoxical

82
Q

what words are used to describe amplitude?

A

hypokinetic/akinetic

83
Q

_____ of the LV shows most movement
_____ of the LV shows the least movement

A

most - lateral wall
least - interventricular septum

84
Q

for normal results, the septum ______ and moves slightly towards _____ during _____

A

septum shortens/thickens and moves slightly towards LV during systole

85
Q

during a gated equilibrium stress study, what are normal results?

A
  • increasing HR
  • minimum 5% increase in EF at max exercise
  • normal wall motion
86
Q

what view(s) are acquired for an exercise MUGA?

A

LAO - multiple, resting and at each stage of exercise

NMED 251 - Clinical Procedures (11 decks)

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