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Medical > Nuclear - Essentials of Cardiac PET, Perfusion, Viability > Flashcards

Nuclear - Essentials of Cardiac PET, Perfusion, Viability Flashcards

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USMLE® Step 1 flashcards
1
Q

Define positron range

A

distance the positron is required to travel within the tissue medium before undergoing annihilation

*

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2
Q

How does positron range correlate with image resolution?

A
  • Longer positron range = lower (worse) resolution
  • Shorter positron range = higher resolution
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3
Q

What are the benefits of cardiac PET:

  • Radiotracers
A
  • Superior extraction
  • Short t 1/2
  • Lower radiation dose
  • Wide array of tracers
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4
Q

What are the benefits of cardiac PET:

  • Image Quality
A
  • Accurate AC
  • High temporal and spatial resolution
  • 3D tomographic imaging
  • Sensitive (nano/picomolar)
  • Quantitative
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5
Q

What are the benefits of cardiac PET:

  • Evidence Base
A
  • Diagnosis
  • Risk assessment
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6
Q

What are the available Cardiac PET Radiotracers?

A
  • Perfusion
    • Rb82 and Ammonia N13
  • ​Metabolism
    • FDG18
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7
Q

Describe the features of Rb-82

  • How produced
  • Half-life
  • Positron range
  • Stress type
  • Image quality
  • FDA approval
A
  • Generator
  • 76 seconds (shortest)
  • β+ range - 1.6mm (long)
  • Phamacological
  • Very good quality
  • FDA approved
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8
Q

Describe the features of N-13

  • How produced
  • Half-life
  • Positron range
  • Stress type
  • Image quality
  • FDA approval
A
  • Cyclotron
  • 9.96 minutes
  • β+ range - 0.28mm
  • Pharm > Exercise (only tracer available for exercise)
  • Excellent quality
  • FDA approved
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9
Q

What is a cyclotron?

A

an apparatus in which charged atomic and subatomic particles are accelerated by an alternating electric field while following an outward spiral or cicrular path in a magnetic field

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10
Q

Describe the features of O-15

  • How produced
  • Half-life
  • Positron range
  • Stress type
  • Image quality
  • FDA approval
A
  • Cyclotron
  • 2.09 minutes
  • β+ range - 0.5mm
  • Pharmacological
  • Uninterpetable quality
  • Not FDA approved

****most well extracted radiotracer

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11
Q

Describe the features of FDG F-18

  • How produced
  • Half-life
  • Positron range
  • Stress type
  • Image quality
  • FDA approval
A
  • Cyclotron
  • 109.7 minutes (unit doses)
    • ​can be shipped to other sites for use
  • β+ range - 0.1 mm
  • Investigational for perfusion
  • Excellent quality
  • FDA approved
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12
Q

What are the advantages of 3D PET?

A
  • Higher sensitivity (4-6 fold higher than 2D)
    • Lower radiotracer dose
    • Lower radiation exposure
    • Potential cost savings
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13
Q

What are the challenges with 3D PET?

A
  • Higher scatter (30-40% vs. 10-15% for 2D)
    • Effective sensitivity is lower (randoms, scatter, camera dead time)
  • More processing time and disc space
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14
Q

What is one difference in 2D and 3D PET scanning?

A

no collimator used in 3D PET

  • most newer generation scanners are only 3D
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15
Q

What is the value of LVEF calculation in PET scanning?

A
  • Useful in evaluating
    • magnitude of myocardium at risk
    • extent of angiographic CAD
  • LVEF decreases (rest –> stress)
    • marker of significant LM or 3vCAD
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16
Q

What is the difference in diagnostic accuracy between PET and SPECT?

A

PET > SPECT

  • Specificity
    • PET = 81.3%
    • SPECT = 76%
  • Sensitivity
    • PET = 92.6%
    • SPECT = 88.4%
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17
Q

What is the relative radiation dose with PET?

  • F-18 FDG
  • N-13 Ammonia
  • Rb-82
  • Tc 99m
  • Tl 201`
A
  • N-13 Ammonia = 2.5 mSv
  • Rb-82 = 3.9 mSv
  • Tc 99m = 9 mSv
  • F-18 FDG = 14 mSv
  • Tl 201 = 25 mSv
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18
Q

What is the best use of CFR/MFR in clinical practice?

A
  • Excellent Negative Predictive Value
    • MFR >2 –> NPV 97%
  • Differentiating between:
    • Incomplete vasodilation
    • Balanced ishemia
    • Normal scan
      • ​CFR flow will increase from rest to stress in total and all vessels –> confirming a normal scan
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19
Q

Why is CFR/MFR useful in excluding severe CAD?

A
  • Excellent Negative Predictive Value
    • MFR >2 –> NPV 97%
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20
Q

What MFR value should be considered a high-risk feature on MPI PET?

A

MFR < 1.5

  • Angiography may be necessary
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21
Q

What MFR value portends extremely low risk in PET MPI?

A

MFR > 2

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22
Q

Define Hibernating myocardium

A
  • dysfunctional myocardium that has the potential to improve function after revascularization
  • Characterized by:
    • functionally by an improvement of contractile function with reperfusion or inotropic (dobutamine) stimulation
    • metabolically by a switch from fat to glucose metabolism, accompanied by reactivation of the fetal gene program
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23
Q

What is a hallmark of hibernating myocardium on myocardial viability assessment?

A

perfusion-metabolism mismatch

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24
Q

What does a normal perfusion study at rest in the setting of low LVEF indicate?

What is the next step?

A

presence of myocardial viability

  • low LVEF is not being driven by scar
    *
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25
Q

Describe the steps in a Rest/Stress-FDG Viability: PET-CT Protocol

A
  • Rest and/or Stress Perfusion
  • Glucose manipulation - 60-90 minutes
    • Trutol (oral glucose)
    • Based on BG levels –> IV insulin to drive glucose intracelluarly
    • Blood glucose < 150 –> proceed to next step
  • 10-15 mCi FDG injection
  • Cellular uptake - 60 minutes allowed
  • FDG imaing - 15 minutes
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26
Q

What the the optimal candidates to evaluate for myocardial viability?

A

Fixed defects on MPI

  • Perfusion/Metabolism mismatch –> Hibernating myocardium
  • Perfusion/Metabolism match –> Scarred myocardium
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27
Q

What is the next step in this patient?

What is the diagnosis?

A

Stress study (dobutamine)

  • normal resting perfusion = viable myocardium

Myocardial stunning - severe CAD

  • ​Severe defect of LAD territory - completely reversible at rest
  • may be cause of CHF
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28
Q

What are the most sensitive and specific methods for tracing cardiac metabolism?

A
  • Perfusion
    • more sensitive
    • less specific
  • Contractile function
    • more specific
    • less sensitive
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29
Q

What are the most sensitive and specific methods for imaing myocardial viability?

A
  • Sensitivity
    • Perfusion techniques > contractile assessments
  • Most sensitive: FDG PET
  • Most specific: DSE
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30
Q

If perfusion assessment is good, why metabolic imaging?

A
  • myocardial blood flow cannot distinguish viable from non-viable segments
  • among segments classificed as non-viable in the thallium study, 23-35% (R-R, or R-R-RI) are classified as viable by FDG PET
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31
Q

Describe why is FDG-F18 an excellent tracer for PET viability testing?

A
  • Hypoxia, ischemia, insulin –> overexpression of GLUT 4 receptors
    • causes increased uptake of glucose / FDG-F18
    • hibernating cells consume more glucose/FDG-F18 than normal cells
  • Fatty acid metabolism (β-oxidation) extremely sensitive to hypoxia
    • Hibernating myocytes do not utilize fatty acids –> selective overuse of glucose
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32
Q

What causes increased glucose uptake in cardiac myocytes?

A

GLUT 4 translocation/overexpression

  • hypoxia
  • ischemia
  • insulin
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33
Q

Why perform glucose loading and insulin administration?

A

to improve uptake in normal segments that serve as reference

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34
Q

Describe the glucose-loaded states in viability testing (myocardial blood flow, myocardial FDG-glucose loaded, regional function):

  • Normal
  • Hibernating myocardium
  • Scar
  • Stunning
A
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35
Q

What are factors inversely related to recovery of function following revascularization?

A
  • Baseline LVEF (lower is worse)
  • Magnitude of myocardial scar (larger is worse)
  • Degree of remodeling of the LV (larger is worse)
  • Time to revascularization (delay > 42 days is worse)
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36
Q

What is the threshold of viable myocardium at which early revascularization is more beneficial than that of medical therapy?

A

> 10% viable myocardium

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37
Q

What are the validated applications of PET MFR?

A
  • Identify microvascular dysfunction
  • Improve assessment of balanced ishcemia and extensive CAD
  • Assess response to therapy
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38
Q

What is the modality of choice for quantifying myocardial scar?

A

CMR

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39
Q

What is the reference standard for hibernating myocardium?

A

FDG F18 PET

40
Q

When utilizing Rubidium-82, what is key in the quality control process?

A

the first sample of the day eluted from the Rb-82 generator is examined for “breakthrough” of radionuclide contaminants

  • Strontium 82 and Strontium 85 can both be found as contaminants
41
Q

How is Rubidium 82 eluted?

A
  • small portable generator
  • contains Strontium-82 (“parent” radionuclide)
  • absorbed onto a SnO2 column
  • washed (eluted) off the column using normal saline
42
Q

What is the mechanism for uptake of Rb-82?

A
  • radioactive analog of potassium
  • relies upon Na-K ATPase transporter for cellular uptake
43
Q

What PET tracer can be used to quantitatively assess both myocardial perfusion and metabolism?

A

C11-acetate

  • marker of myocardial oxidative substrate metabolism
  • in clinical studies of patients with CAD
    • rates of C11-acetate clearance have proven useful for identifying dysfunctional myocardial segments
    • which will exhibit an improvement in function followin revascularization
  • Because C11-acetate has a high first pass myocardial extraction fraction
    • images obtained early following tracer injection can also be used to measure regional tissue blood flow, in mL/min/g tissue
44
Q

What is C11-hydroxyephedrine used for?

A

used to depict sympathetic innervation of the myocardium

45
Q

What is C11-heptagluconate used for?

A

tracer of myocardial fatty acid utilization

46
Q

What myocardial perfusion tracer will exhibit the highest net tissue uptake (flow x extraction) at increased myocardial blood flow?

A

Oxygen-15 water

  • freely diffusible tracer of myocardial blood flow whose net tissue uptake is near unity even at hyperemic blood flows
  • Other tracers (Tl201, N13, Tc99m) - net tissue uptake gets progressively smaller for each unit increase in tissue blood flow
47
Q

When is roll off or plateau effect seen?

A

Tc 99m tracers

  • ​greater problem with this tracer
  • especially when performed in conjunction with pharmacologic stress
    • greater increase in coronary blood flow relative to exercise
48
Q
  • What is the diagnosis in the abnormal anteroapical and basal inferior myocardial regions with the matching defects in perfusion and metabolism on PET images?
  • What finding would be expected on MR?
A
  • Prior MI / Scar or Fibrosis
    • ​severe matching perfusion and metabolic defects in the anteroapical and basal inferior regions
  • Delayed-gadolinium enhancement
    • consistent with fibrosis / scar on PET
49
Q

Describe findings consistent with viability:

  • Post-PVC
  • Tl 201 SPECT MPI
  • Cardiac MRI
A
  • Post-PVC:
    • Postextrasystolic potentiation of regiona function
  • Tl 201
    • redistribution
  • Cardiac MR
    • end-disastolic wall thickness of 8.0 - 8.5 mm
50
Q

What is the likelihood of a patient with Ca score 612 (intermediate pre-test probability) in having inducible ischemia on PET?

A

25-50%

  • Ca score > 400 - < 1000 —> almost 50% chance of ischemia in patients with intermediate likelihood of CAD
51
Q

What is the annual risk of death / MI:

  • 50 year old male
  • Intermediate likelihood of CAD
  • Ca score 689
  • Negative PET MPI for reversible ischemia
    • small fixed anterior defect
A

5%​

52
Q

Describe the defect and vessel territory

A
  • Small fixed perfusion defect
  • Basal, anterior wall - Diagonal distribution
    • ​corresponds to the loss (“jailing”) of a small 1st diagonal branch a the time of intervention
53
Q

Describe one major difference between 2D and 3D PET imaging

A
  • 2D PET - contain septa
    • lead or tungsten septa interposed between the detector rings
    • serve to reduce coincidence events between detectors in a given ring and the adjacent rings, decreasing the number of scatter events
  • 3D PET - “septa out”
    • ​permits a greater number of coincidence events between detectors in differing rings
    • serving to increase the sensitivity of the device as well as the number of scatter events
54
Q

What crystal type has the highest stopping power for annihilation photons?

A

Bismuth germanate (BGO)

  • energy and timing resolution are not as favorable
55
Q

What are examples of newer crystals used in PET?

Why?

A
  • Lutetium oxyorthosilicate (LSO)
  • Gadolinium oxyorthosilicate (GSO)
  • Lutetium yttrium orthosilicate (LYSO)
  • reduction in dead times and higher count rates
56
Q

What type of stress is an indicator of coronary artery endothelial function when used in conjunction with PET MPI?

A

cold pressor test

  • cold water stimulates release of norepinephrine from cardiac sympathetic nerve terminals, which in turn results in vasodilation of the coronary circulation via endothelium-mediated release of nitrous oxide (NO)
  • vasodilation induced by dipyridamole, adenosine, and regadenoson is largeley indepndent of endothelial function
57
Q

Describe the cold pressor test that is used in conjunction with PET MPI

A
  • involves immersion of a hand or foot into ice water (2C) for 2 minutes
  • stress perfusion tracer typically injected at 1 minute –> with imaging for an additional minute while the hand or foot remains immersed in the cold water
  • cold water stimulates release of norepinephrine from cardiac sympathetic nerve terminals, which in turn results in vasodilation of the coronary circulation via endothelium-mediated release of nitrous oxide (NO)
  • vasodilation induced by dipyridamole, adenosine, and regadenoson is largeley indepndent of endothelial function
58
Q

What are some QC measures for PET/CT?

A
  • System Sensitivity
  • Intrinsic scatter fraction
  • Accuracy of attenuation correction
59
Q

What is one QC measure that is used in SPECT MPI and not in PET/CT?

A

center of rotation

  • assesses performance of rotating SPECT MPI cameras
60
Q

When can you see artifact on myocardial PET images if XR CT is used for attenuation correction?

A

ICD with RV lead

  • objects with very high density (such as defibrillator coil) may not be adequately characterized by CT transmission images
  • XR CT transmission images overcompensate for the density of the object, resulting in hot spots on the attenuation-corrected images
61
Q

What is the energy emitted by each of the isotopes following annihilation?

  • Fluorine-18
  • Rubidium-82
  • Nitrogen-13
A

Same for each isotope

  • the energy of annihilation photons emitted by each of the isotopes –> 511 keV
  • the masses of the positron and electron are fixed, and the speed of light is a constant
  • therefore, E = mc2
62
Q

What organ receives the largest amount of radiation exposure during FDG-F18 myocardial viability testing?

A

Urinary bladder

  • for a 10-mCi dose of FDG –> urinary bladder receives ~59 mSv
  • can minimize radiation exposure by emptying their bladder frequently after the study
63
Q

Define “time of flight” in PET imaging

A

The time difference between two annihilation photons reaching their corresponding detectors

  • when two 511-keV photons are generated by the annihilation of a positron and an electron, they travel in opposite directions until each photon reaches its corresponding detector
64
Q

What do “time of flight” PET scanners use to improve localization of annihilation events?

A

slight differences in timing of the scintillation events in paired opposite detectors

65
Q

What organ receives the highest radiation dose in a rubidium-82 PET perfusion study?

A

Kidneys

  • potassium analong
  • 5.8 microGy/MBq is absorbed
  • myocardium is the second largest dose
66
Q

Define radiation hormesis

A

protective effect of exposure to low amounts of ionizing radiation

  • possibly on the basis of up-regulation of molecular cell repair mechanisms
67
Q

Describe deterministic effects of ionizing radiation

A
  • effect in which the dose is related to severity of effect
  • usually characterized by a minimal dose for the effect to be observed
68
Q

Describe stochastic effects of ionizing radiation

A
  • effect in which the probability of occurrence ( as opposed to severity of effect) is determined by the dose
  • stochastic effects may not have an apparent threshold dose
  • example: late development of a radiation-induced malignant neoplasm
69
Q

What is an example of a stochastic effect of ionizing radiation?

A

late development of a radiation-induced malignant neoplasm

70
Q

What method should be used to acquire the highest-quality images of a coronary arterial plaque in FDG PET/CT imaging?

A

Following a low-carbohydrate, high-fat meal

  • low-carbohydrate, high-fat meal –> favors myocardial utilization of free fatty acids –> reduces myocardial FDG uptake –> decreases background activity –> maximize FDG uptake and increased probability of visualizng the plaque
  • visualization of a coronary arterial plaque on FDG PET can be impaired by high background activity –> due to myocardial uptake of tracer
  • use of glucose load, glucose or insulin clamps will increase myocardial substrate utilzation and thus increase FDG background activity
71
Q

What makes visualization of coronary arterial plaque difficitul on FDG PET?

A

High background activity

  • visualization of a coronary arterial plaque on FDG PET can be impaired by high background activity –> due to myocardial uptake of tracer
  • use of glucose load, glucose or insulin clamps will increase myocardial substrate utilzation and thus increase FDG background activity
72
Q

Describe the process for visualization of atherosclerotic plaque inflammation on FDG PET imaging?

A

Activated macrophages exhibit an up-regulation of hexokinase, increasing the metabolic trapping of FDG within the plaque

  • FDG transported across the cell membrane via GLUT transport proteins (GLUT 1 and GLUT 3 in macrophages)
  • phosphorylated by the enzyme hexokinase to FDG-6-phosphate which becomes largely trapped in a phosphate moeity
    • poor substrate for further glycolytic or glycogen pathways
    • “reverse reaction” very slow under hypoxic conditions –> FDG becomes “trapped”
73
Q

Following tracer injection, when should FDG PET imaging of unstable plaques be performed?

A

2 hours following tracer injection

  • most of background activity occurs from the arterial blood iteself
  • allowing for clearance of this background activity improves imaging of unstable plaques
74
Q

Describe the findings in a patient with CHF

A

Extensive ischemia involving the LAD, CFx and RCA distributions - and scar involving the RCA

  • reversible defects of the LAD, CFx and RCA –> stress-induced ischemia
  • small fixed defect of RCA distribution –> scar
75
Q

Why does the LV myocadium appear thinner and “sharper” on the FDG images compared to RB-82 images?

A

Average kinetic energy of the RB-82 positron is greater than that of the Fluorine-18 positron

  • higher kinetic energy –> longer positron range –> lower image resolution
  • Kinetic energy of positrons: Rb-82 positrons >>> Fluorine-18
76
Q

What are forms of glucose metabolism stimulation used in PET imaging?

Which one has not been approved for use in the US?

A
  • Oral glusoe load with 50g of dextrose prior to FDG injection
  • IV glucose loading with D50W to which 20mg of hydrocortisone has been added to administra a total of 25g dextrose
  • “Priming” the patient with 50 mL of 20% dextrose and 5units of regular insulin
  • Acipimox, 250mg orally prior to FDG injection
77
Q

Explain the difference between Rb-82 and N-13 rest/stress images

A

Normal variant of myocardial uptake of N-13 ammonia

  • may see a decrease in N-13 ammonia uptake in the inferolateral region of the ventricle
  • quantification of MBF and segmental wall motion is normal
78
Q

What is a marker of myocardial viability on Rb-82 PET imaging?

A

retention of Rb-82 activity on PET images obtained 3-7 minutes following IV tracer injection

  • on the premise that nonviable tissue would not be capable of transmembranous uptake and retention of the tracer
79
Q

What does the finding of progressive diminution of tracer uptake from the base of the heart to apex on stress imaging (with a normal PET perfusion rest/stress study and LVEF) indicate?

A

Diffuse preclinical atherosclerotic disease of the coronary arteries

  • parallels findings oibtained in invasive studies using doppler flow and pressure probes
80
Q

Regadenoson stress/rest Rb-82 PET perfusion images, along with fused Rb-82 emission and CT transmission images, from an 82- year old mane with chest pain are shown. Describe the findings?

A

Reversible perfusion defect of RCA

With transmission-emission mismatch on rest images

  • Rest perfusion images
    • modest reduction in tracer activity of the basal anterolateral area of the LV
  • Rest images fused with CT for AC
    • misalignment between the image sets is noted
    • spurious decrease in tracer activity in the basal anterolateral area on stress study
81
Q

Describe the activity of N-13 ammonia?

A

N-13 Ammonia passively crosses the cell membrane and mitochondrial membrane; the tracer is then trapped within mitochondria as N13 NH4+

  • N13-NH3 is lipophilic and crosses the cell membrane
  • once inside the cell, NH3 is metabollically trapped
  • predominantly as glutamine via the glutamine synthase reaction
82
Q

What tracer is used to assess the sympathetic nervous systme of the heart with PET imaging?

A

C-11-hydroxyephedrine

  • largely reflects the uptake 1-mechanism
  • also subject to monoamine oxidase degredation and storage within vesicles within the neuron
83
Q

What is the most appropriate next step?

A

C - coronary angiography and possible revascularization

  • high risk stress test + large defect + abnormal systolic function –> Class I
  • fixed defect on rest/stress myocardial perfusion imaging does not necessarily indicate scarring. Fixed defect can indicate:
    • scar
    • hibernating myocardium
    • attenuation artifact (significant)
  • Regional wall motion abnormalities + perfusion defect –> excludes attenuation
  • Presence of chest pain –> hibernating myocardium
    *
84
Q

What can a fixed defect on rest/stress myocardial perfusion imaging indicate?

A
  • scar
  • hibernating myocardium
  • attenuation artifact (significant)
    • Perfusion defect + regional wall motion abnormalities –> rules out attenuation
85
Q

Myocardium that has been subjected to acute or chronic ischemia may become dysfunctional but remain viable. What are these findings?

A
  • Stunning
  • Hibernation

***both may be improved with revascularization

86
Q

Define myocardial stunning

A
  • reversible state of regional contractile dysfunction that occurs after transient ischemia
  • despite the absence of necrosis
  • (believed to) play an important role in the persistent contractile dysfunction seen in patients after reperfusion of acute MI and following attacks of UA
  • Perfusion/metabolism match (with positive stress perfusion)
87
Q

Define myocardial hibernation

A
  • refers to a state of persistent LV dysfunction that results from chronically reduced blood flow without infarction and necrosis
  • chronic downregulation in contractile function at rest is thought to represent a protective mechanism –> heart reduces oxygen requirements to ensure myocyte survival
    • protective mechanism may also decrease myocardial contractility –> LV dysfunction
  • Perfusion - Metabolism mismatch
  • Revascularization –> improves contractile function significantly
    • depends on:
      • chronicity of hibernation
      • degree of ventricular remodeling
      • other factors
88
Q

Given the result of the PET viability study, what is the most appropriate next step?

A

C - Surgical revascularization of the LAD and LCx arteries

  • Viability study demonstrates
    • normal Rb82 rest perfusion and thus viability in nearly the entire distribution of the LAD artery with the exception of the apex
    • mismatch between the Rb82 rest perfusion and F18-FDG metabolism images in the basal LCx distribution –> hibernating myocardium
    • modest mismatch in the remainder of the LCx distribution –> admixture of infarction and hibernating myocardium
      *
89
Q

What is the best interpretation of this assessment?

A

A - nearly the entire myocardium is viable

  • under resting conditions, the myocardium generally will oxidize free fatty acids to produce ATP
  • ischemia –> up-regulation of glucose transporters
  • in some cases (particularly insulin resistance) –> F18-FDG uptake in normal regions may remain less than that of ischemic or hibernating regions ****pattern seen in current study
90
Q

Describe findings of non-viable myocardium on viability testing:

  • PET with FDG
  • gadolinium enhanced-MRI
A
  • PET matched defect
    • decreased N13 rest perfusion and decreased F18-FDG uptake
  • transmural LGE
    • delayed clearance of gadolinium based contrast agent (GBCA) from affected myocardium
    • infusion of GBCA –> wait 10 minutes before T1-weight imaging is performed (“LGE”)
91
Q

Describe findings on contrast enhanced MRI for viability

A
  • Transmural LGE –> Non-viable
    • > 75% thickness involvement
  • No LGE or subendocardial LGE –> viability and functional recovery after revascularization
92
Q

What is the most appropriate next step?

A

B - cancel F18-FDG uptake imaging and proceed with CABG

  • normal resting perfusion –> viable myocardium
93
Q

Functional recovery after revascularization in a patient with CAD and impaired LV function may be seen up to what duration?

A

more than 12 months

  • complete recovery of hibernating myocardium may take more than 12 months
  • prior ischemia may have resulted in:
    • sarcomere loss
    • glycogen accumulation
    • disarray of mitochondria
    • fibrosis
94
Q

Based on the findings of the trial, the best approach to patient’s undergoing planned revascularization is:

A

If FDG PET is performed, then PET recommendations should be followed

  • at 1 year –> no significant difference in composite event rate in PET arm vs. Standard arm
  • However, patients that adhered to PET recommendations for revascularization, revascularization work-up, or neither, PET guided strategy –> lower event rate
  • Bottom line:
    • no significant reduction in cardiac events in patients with LV dysfunction and suspected CAD for FDG PET-assisted management vs. standard care
    • Benefits observed
      • those without recent angiography
      • PET recommendations
95
Q

65 year old man with known ischemic cardiomyopathy is scheduled for Tc99m sestamibi rest gated SPECT to assess viable myocardium.

What is the most appropriate step to enhance detection of viable segments?

A

Administer SL NTG 400mcg, 5 minutes before injection of Tc99m sestamibi

  • NTG improves ability to detect viable myocardium
    • improves flow to peri-infarct regions and enhances tracer delivery
  • Nitrate studies have been shown to be superior predictors of recovery of function after revascularization
96
Q

What are examples of Tl201 protocols that will provide sufficient information for viability assessment?

A
  • Stress, 4-hour redistribution, reinjection
  • Rest, 24-hour redistribution
  • Rest, 4-hour redistribution, reinjection
97
Q

What is the benefit of Tl201 redistribution imaging at 24 hours?

A

shows uptake in as many as 54% of the segments without uptake at 3-4 hours

****aditional waiting for redistribution after reinjection has not been found to be helpful –> less than 5% of persistent defects after reinjection showing viability

Medical (69 decks)

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