Table 1.
Technical comparison of tools for the assessment of myocardial ischaemia
| Parameter | SPECT | PET | MRI | Echocardiography | CT | Invasive coronary flow and pressure measurement |
|---|---|---|---|---|---|---|
| General | ||||||
| Ionizing radiation use | Yes (radiopharmaceutical) | Yes (radiopharmaceutical) | No | No | Yes (X-rays) | Yes (X-rays) |
| Stressor | Exercise or vasodilator agents | Exercise or vasodilator agents | Mainly vasodilator agents | Exercise or vasodilator agents | Mainly vasodilator agents | Vasodilator agents |
| Contrast agent or tracer | 99mTc-sestamibi or 99mTc-tetrofosmin | 15O, 82Rb, 13NH3 or 18F-flurpiridaz | Gadolinium-based | Microbubbles | Iodine-based | None |
| Contrast agent or tracer distribution | Intracellular | Freely diffusible: intravascular, extracellular and intracellular | Intravascular and extracellular | Intravascular | Intravascular and extracellular | NA |
| Type of measurement | Static; dynamic feasible with new cameras | Dynamic bolus or static | Dynamic bolus | Clearance–reperfusion | Dynamic bolus or static | Pressure and/or flow velocity |
| Linear relationship between blood flow and tracer | No (underestimation at high flow) | Yes | No | Yes | No | NA |
| Linear relationship between tracer and image signal | Yes (radiopharmaceutical) | Yes | No | Yes | Yes | NA |
| Contrast-to-noise ratio | High | Low | High | High | Low | NA |
| Temporal resolution (acquisition time per frame) | 10 s | 1–5 s | Approximately 100–200 ms | Approximately 4–50 ms (20–250 frames per s) | Approximately 150–200 ms | NA |
| Spatial resolution (image analysis voxel size) | 10 × 10 × 10 mm³ | 4 × 4 × 4 mm³ | 1 × 2 × 6–8 mm³ | 1 × 1–3 × 3–6 mm³ (spatially varying) | 0.5 × 0.5 × 6–8 mm³ | NA |
| Isotropic left ventricle coverage | Yes | Yes | No | No | Yes | NA |
| Technical challenges | ||||||
| Stenosis quantification | NA | NA | Spatial resolution | NA | Beam hardening | Variability and projections |
| Coronary haemodynamic assessment | NA | NA | Spatial resolution | NA | Flow assumptions | Costs and availability |
| Ischaemia quantification | Spatial and temporal resolution | Spatial and temporal resolution | Contrast agent signal nonlinearity | Intravascular contrast agent | Contrast agent dynamics, noise and dose | NA |
| Types of coronary vascular component assessment by each imaging modality | ||||||
| Epicardial conductance vessel (>500 μm) | Functional assessment | Functional assessment | Functional assessment | Functional assessment | Anatomical and functional assessment | Anatomical and functional assessment |
| Resistance vessels and arterioles (<500 μm) | Functional assessment | Functional assessment | Functional assessment | Functional assessment | Functional assessment | NA |
| Capillaries | Functional assessment | Functional assessment | Functional assessment | Functional assessment | Functional assessment | NA |
| Endocardial–epicardial flow ratio | NA | NA | Yes | NA | Yes | NA |
| Collaterals | Yes (but with limitations) | Yes | Yes | Yes | Yes | Yes |
| Contraction–flow relationship | NA | NA | Yes | Yes | Yes | Yes |
| Advantages and disadvantages | ||||||
| Advantages | Wide availability and quantification now also possible in patients with a high BMI | Technically best-suited test for ischaemia quantification; novel tracers and small cyclotrons have become available | Assessment of function, perfusion and viability without ionizing radiation | Availability at the bedside for analysis without ionizing radiation | Quantitative scale and high spatial resolution for coronary stenosis and plaque analysis | Immediate treatment opportunity during the same procedure |
| Disadvantages | Low image quality owing to attenuation | Limited availability (available in specialized centres only) | Limited coronary stenosis analysis and quantification challenges | No coronary artery stenosis analysis and quantification challenges | Radiation dose, low contrast-to-noise ratio and quantification challenges | Limited use in patients without acute presentation |
Consensus ratings were performed using a Delphi process with ratings by 20 investigators (six cardiologists, four radiologists, one dual cardiologist–radiologist, one nuclear medicine physician and eight methodologists). NA, not applicable.