Introduction
Magnetic resonance imaging
Sequence | Planes | Description |
---|---|---|
Scouts | Sagittal, coronal, axial | Localizer |
Single-shot Fast spin echo | Axial | Provides overview of morphology |
Balanced Steady State Free Precession (SSFP)- Single shot | Axial | Provides overview of morphology |
Cine SSFP | 2-chamber, 3-chamber, 4-chamber, short-axis stacks | LV and RV volumes, ejection fraction, wall thickness, and motion |
Black blood spin-echo - T1-weighted, - T2-weighted, - Fat saturated | 2-chamber, 3-chamber, 4-chamber, short-axis stacks | Tissue characterization |
T2*-weighted Sequence Planes Description T1- mapping Short-axis stacks Tissue characterization (fibros is, amyloid, deposition, iron) T2- mapping Short-axis stacks Tissue characterizaton (edema) | Short axis | Iron quantification |
Diffusion | Localized to mass | Tissue characterization |
Dynamic first pass perfusion | Short-axis stacks | Ischemia/infarct/microvascular obstruction/masses |
2 min post contrast T1-weighted IR GRE | Short-axis stacks | For myocarditis, microvascular obstruction and masses |
Delayed enhancement sequences | 2-chamber, 3-chamber, 4-chamber, short-axis stacks | Evaluation of scarring and fibrosis |
MR angiography | Coronal/sagittal/axial | Vascular anatomy |
3d-whole heart SSFP | Axial/targeted to coronary arteries | Coronary artery anatomy Vascular anatomy |
Positron emission tomography
18F-FDG PET | NH4 | Rb-82 |
18F-FDG PET | |
---|---|---|---|---|
Reason | Viability study | Perfusion study | Perfusion study | Tumour/inflammatory lesion assessment |
Diet | Low carbohydrate diet | Low carbohydrate diet | Low carbohydrate diet | High-fat, protein-permitted low carbohydrate diet for 24 hours Fasting for 6–12 hours |
Check blood glucose | If blood glucose < 110 mg/dL AND not diabetic, oral glucose loading | Unfractionated heparin loading | ||
If blood glucose 130–200 mg/dL OR diabetic, administer IV insulin depending on blood glucose level | ||||
If blood glucose more than 200 mg/dL, notify physician (some institutes reschedule imaging) | If blood glucose more than 200 mg/dL, notify physician (some institutes reschedule imaging) | |||
Radiotracer administration | Administer 5–15 mCi of F-18 FDG when blood glucose below 150 mg/dL (preferable) | Administer 20 mCi NH4 | Administer 40 mCi Rb-82 | Administer 5–15 mCi of F-18 FDG |
18F-FDG during and after administration | Patient should remain seated or recumbent to avoid muscular uptake | Patient should remain seated or recumbent to avoid muscular uptake | ||
Start imaging | Wait 60 minutes, then scan for 10 minutes | Wait 10 minutes and scan for 5 minutes | Wait 10 minutes and scan for 6:30 minutes | Wait 60 minutes, then scan for 10 minutes |
Cardiac PET and MRI
Hybrid PET/MRI
Indication | PET | MRI | PET/MRI |
---|---|---|---|
Myocardial structure | Limited due to spatial resolution | Excellent due to good spatial resolution and several sequences | MRI contributes to improved spatial resolution |
Ventricular and valvular function | Limited | Highly accurate ventricular function Valvular function can be quantified | MRI component provides the ventricular function |
Metabolic activity of lesions | Excellent | No metabolic information | PET component provides information on metabolic activity |
Artifacts - Motion - Respiratory - Cardiac - Partial volume | Artifacts can limit diagnosis | Several solutions available for artifacts | The MRI component can enable reducing artifacts |
Cardiac masses | Metabolic activity | Morphological information Tissue characterization Functional quantification | Characterization of mass Localization of abnormal FDG activity in PET scan Assessment of cardiac involvement of mass seen in PET Local staging M staging Functional evaluation Response to therapy |
Inflammatory disorders | Inflammatory metabolic activity | Morphological information Activity of lesion | Complementary information provided by different mechanism Morphological, functional, and metabolic information |
Vasculitis | Metabolic activity | Disease activity Morphological information Vascular anatomy, complications | Evaluation of disease activity Comprehensive evaluation of vascular tree Lower radiation than PET/CT |
Atherosclerosis | Plaque inflammation Targeted isotopes | Plaque component characterization Luminal evaluation | MRI localizes activity of PET Perfect spatial alignment Evaluation of lumen with MRI Lower radiation than PET/CT Targeted isotopes localized with MRI |
Myocardial ischemia | Accurate Absolute quantification of MBF and CFT possible | Highly accurate Can quantify ventricular function Coronary anatomy can be evaluated | Comprehensive evaluation of perfusion along with vascular anatomy and function |
Myocardial infarction | Accurate, reliable | Highly accurate Functional evaluation Complications Prognostic value | Complementary information |
Applications of cardiac PET and MRI
Cardiac masses
Inflammatory disorders
Myocarditis
Sarcoidosis
Pericarditis
Cardiac valve abscess
Vascular disease
Vasculitis
Atherosclerotic disease
Component | T1-w | T2-w | PD | Contrast enhancement |
---|---|---|---|---|
Lipid | High | Intermediate | Intermediate | No |
Fibrocellular | High | High | High | No |
Calcium | Low | Low | Low | No |
Necrotic core | Low | High | High | No |
Fibrotic cap | Low | Low | Low | Yes |
Haemorrhage | High | Low | Intermediate | No |