Methods of Nuclear Cardiology
I. heart evaluation
2 groups - myocardial imaging – perfusion, metabolism, ischemia, necrosis, sympathicus
- ventriculography
1. myocardial imaging
data acquisition – planar, tomography, gated SPECT, PET
radiopharmaceuticals
Tl 201 – distribution early after injection is proportional to perfusion
late distribution (3 to 24 hours) to metabolism (cell membrane
integrity)
Tc99m labeled - MIBI – binds to mitochondria, distribution stable with time
Myoview – faster clearance from liver
MIBG-I123 - density of sympathetic receptors
Antimyosin-In111 - necrosis
Positrons FDG-F18 – metabolism, NH3-N13 – perfusion, H2O-O15 – perfusion
Stress protocols – dynamic or pharmacologic stress – pathophysiology of myocardial
ischemia
Imaging protocols – differs according to used tracer (different pharmacokinetics)
Tl201 - data acquisition as soon as possible after stress, redistribution or reinjection
images several hours later
Tc99m – different protocols (stress-rest, rest-stress, one-day, two-days), every time
two injections are essential (during stress and rest)
Images patterns -
normal – homogenous distribution
ischemia – reversible defect (defect during stress, normal during rest)
scar – fixed defect (the same defect during stress and rest)
possibility to quantify and compare – pollar plots
Clinical indications
Diagnosis of CAD – sensitivity and specificity about 90% (influence of disease prevalnce in
population)
Prognosis of patients with CAD - bad prognosis – more than one defect, large defects,
increased accumulation of Tl201 in lungs
good prognosis – homogenous perfusion
Myocardial viability – stunned and hibernating myocardium
Risk for non-cardiac surgery
Acute chest pain
After revascularization
2. ventriculography
first-pass method – measurement of shunts in central circulation
radiopharmacetical – any labeled with Tc99m injected as a bolus, dynamic study with
high temporal resolution
steady-state (gated, MUGA) – use ECG signal for synchronization of data
radiopharmaceutical – Tc99m labeled erythrocytes
data acquisition – planar (more views – at least 2) or SPECT – synchronization by R wave
(cave atrial fibrilation)
information – measurement of heart mechanical function – EF of left and right ventricle,
regional EF, magnitude and volume of ventricles, emptying and filling rates, wall
motion (parametric images)
clinical indications
quantification of central circulation shunts
prognosis of patients with CAD (stress)
doxorubycin cardiotoxicity (excellent reproducibility of results)
evaluation of patients unsuitable for echocardiography
II. lung and vein system imaging
1. lung perfusion scintigraphy
radiopharmaceutical:
Tc99m labeled macroaggregated albumin or
microspheres of albumin – their distribution is proportional to perfusion
procedure: without any preparation, injection in supine position (perfusion
gradient), planar or SPECT images, duration of 10 to 15 minutes
image patterns:
normal – homogenous distribution
abnormal – defects of radioactivity – segmental or non-segmental shape
2. lung ventilation scintigraphy
radiopharmaceuticals: Kr81m, Tc99m labeled aerosols, Technegas Tc99m
procedure:
without any preparation, patient inhale radioactive gas or aerosol,
planar or SPECT images are acquired, duration 5 to 10 minutes using gas, 20 to 30 minutes
using aerosols
Clinical indications
Pulmonary embolism – perfusion scintigraphy has a high sensitivity (100%) but low
specificity – combination with chest radiograph or ventilation scan – PIOPED criteria
Diagnosis and follow-up
Lung cancer – prediction of operability and residual lung function after surgery
Chronic obstructive pulmonary disease, asthma
3. Vein system evaluation and thrombus imaging
radionuclide venography – imaging of deep venous system patency and perforators
insuficiency, lung perfusion scintigraphy follows
thrombus imaging – AcuTect – Tc99m labeled low molecular weight synthetic peptide that
binds to receptors on the surface of activated platelets