Characteristics of sonographic modalities used for imaging cerebrovascular circulation
| Study | Location | Frequency | Common Usage |
|---|---|---|---|
| Transcranial Doppler | Extracranial (extravascular) | Multiples of 2 MHz | Measures velocity of blood through intracranial vessels |
| Carotid duplex ultrasonography | Extracranial (extravascular) | 5–10 MHz | Duplex procedure: brightness mode (B-mode) allows imaging and Doppler imaging enables color-flow volume and directional information; spectral analysis measures blood flow velocity; measures intimal medial thickness and evaluates stenosis |
| Intravascular ultrasound | Intracranial, extracranial (intravascular) | 20–40 MHz | Determination of morphology and composition of atherosclerotic plaque within the extracranial and intracranial circulation; allows evaluation of correct stent diameter and the amount of balloon inflation pressure needed during angioplasty; enables visualization of stent apposition and expansion, mural thrombus, plaque ulceration, and aneurysm and vessel dissection |