brief discussion on nuclear imaging in cardiology

1. Nuclear imaging in
Cardiology
Dr.Rahatul Quadir
MD Thesis Student
NHF&RI
rahatul.quadir@gmail.com

2. Applications of Nuclear Cardiology
• Coronary Artery Disease
• Assessment of LV /RV function
• Cardiomyopathy /Myocarditis
• Valvular Heart Disease
• Cardiac Shunts
• Secondary Hypertension
• Pulmonary Hypertension
• Assessment of Cardiac Transplant

3. Why??
Detection of CAD

4. Basic
• Uses a radioactive compound that is taken up and retained in
viable cardiac muscle
• Produces an objective, quantifiable 3-D map of myocardial
perfusion by a camera
• Radionuclide injected at rest and/or stress
• Rest images compared with stress images

5. Radionuclide
• Isotopes
• Thallium-201 or Technetium-99m sestamibi
• Both assess LV function and ischemia
• Sestamibi (MIBI) has superior imaging quality
» Good for obese or female patients
• Isotopes taken up by viable myocardial cells in quantities proportional to
perfusion,emit gamma rays which are collected by special instrumentations
called gamma camera
• Well perfused regions appear brighter
Tc-99m

6. Positron emitter
• Usually cyclotron produced-high energy,short half life
<2hr
• Expensive & not widely available
• Gold standard for detecting hibernating myocardium
• 18FDG – hibernating myocardium
• 13N ammonia-myocardial perfusion
• 15O- O2 utilization

7. Camera
• Single-photon emission tomography (SPECT)
• Gated SPECT, SPECT/CT
• Positron emission tomography (PET),and
PET/CT

8. Single Photon Emission Computed
Tomography:
• SPECT is the standard method for myocardial perfusion
scintigraphy.
• The cross-sectional images have high contrast resolution
and are displayed three-dimension along the short and long
axis of the heart.
• Providing good delineation of the various regional
myocardial perfusion beds supplied by their individual
coronary arteries

9. Camera

10. Positron Emission Tomography(PET)
• PET offers a higher spatial resolution than SPECT
• Routine use of PET is constrained by limited availability & cost

11. Contraindications
• Pregnancy
• Food within 4 hours of stress study
• Caffeine within 24 hours (for pharmaceutical stress)
• Bronchospasm or severe obstructive lung disease (for
pharmaceutical stress)
• Xanthine-containing drugs

12. The Stress: Exercise vs pharmacologic
• Exercise and pharmacologic agents are used to achieve
maximal coronary dilation and flow.
• Exercise stress gives additional information:(preferred)
– Degree of exercise tolerance
– Time to maximal heart rate
– Blood pressure response

13. Pharmacologic stress
• Agents:
– Dipyridamole (persantine)
– Adenosine
– Regadenoson
– Dobutamine

14. Stress procedure
• The patients must be fasting for 4 to 6 hours before the test
• Beta blockers may prevent achievement of maximum heart rate.
• Nitrates and calcium channel blockers may mask or prevent cardiac
ischemia.
• Assessment of drug therapy effectiveness requires the patient to
remain on medication.
• Thyophylline and caffeine also held before pharmacological test.

15. Drugs that interfere with stress
testing:recommended withdrawal
interval

16. Indications for Pharmacologic Stress
Imaging
• Inability to perform adequate exercise
• Left bundle branch block
• Ventricular pacemaker
• CCB’s or Beta blockers
• Evaluation of patients very early after acute MI
(<3 days) or very early after stenting ( <2 weeks)

17. Protocols: Same day
rest-stress/stress-rest

18. 2 day Protocol

19. 3 Views:

20. • Short axis = coronal cut (donut)
• Vertical long axis = sagittal cut (sideways “U”)
• Horizontal long axis = transaxial cut (“U”)

21. Short,H.L & V.L axis of LV walls with
corresponding coronary arteries

22. Diagnostic pattern of MPI

23. Visual scoring

24. Before application
Very clear vision
No color blindness
Good knowledge about coronary
antomy

25. Coronary Artery Disease
• Diagnosis of CAD
• Assessment of Prognosis
• Risk Stratification
• Assessment of Myocardial Viability
• Assessment of Revascularization Procedure
• Acute chest pain management in ER

26. Normal Scan

27. LAD

28. LCx

29. Left Main

30. Assessment of Intervention
Pre PTCA
Post PTCA

31. Pre-CABG
Post-CABG

32. Risk Stratification: Prognosis
• Risk of Cardiac Death:
• Normal MPI indicates good prognosis
• Low
<1% per year
• Intermediate
1-3% per year
• High
>3% per year

33. High Risk Feature of SPECT MPI
• Following features demonstrate >3% annual mortality
 Post-stress EF <35% (99m-Technetium).
 Stress induced large perfusion defect.
 Stress induced multiple perfusion defects of moderate size.
 Large, fixed perfusion defect with LV dilation or increased
lung uptake (Thallium-201).
 Stress induced moderate perfusion defect with LV dilation
or increased lung uptake (Thallium 201).

34. A Risk-based Approach to Suspected
CAD

35. Acute Chest Pain Management in ER

36. Assessment of LV Function
• Gated-SPECT study
• ECG is acquired at the time of the SPECT acquisition for
simultaneous assessment of perfusion and function of the
left ventricle in one examination
• Left ventricular end-diastolic volume, end-systolic volume,
stroke volume and ejection fraction may be calculated
automatically, although the values obtained should be
checked against initial qualitative assessment

37. Myocardial perfusion Images with 1 cardiac cycle: From
End-Diastole throuth End-Systole to End-Diastole of next
cycle

38. The computer software calculate
EF,EDV,ESV & SV by using ED & ES images

39. Assessment of Myocardial Viability
• Ischemic LVF patients can benefit from
revascularization procedures if there is
evidence of myocardial viability
• Noninvasive techniques can only identify
tissue that might benefit from
revascularization

40. Key non invasive methods to identify
viability
• Echocardiography
• Single Photon Emission Computed
Tomography (SPECT)
• Positron Emission Tomography (PET)
• Cardiac Magnetic Resonance (CMR)

41. SPECT
• 201Tl stress redistribution:
• Acquire a third set of images at 24 hours
• This would allow for redistribution of the
tracer to very ischemic (yet viable) tissue

42. Hibernating Myocardium

43. Scar Myocardium

44. Positron emission tomography (PET)
• metabolically inert—nonviable myocardium
will appear as a region of low-FDG
concentration in such images suggesting scar
• In areas of reversibly injured myocardium,
glucose utilization is normal and even above
normal

45. SPECT VS FDG PET
• Brunken et al published data from a
comparison of tomographic thallium images
with PET images; 47% of the irreversible
thallium defects were identified as viable on
PET images

46. Thank you for Listening