Left Distal Internal Carotid Artery PSV

The internal carotid artery is the branch of the carotid that goes to the brain, and a narrowing in it is the carotid disease that matters for stroke. Blood moving through a narrowed segment has to speed up, the way water does through a pinched hose, so the peak velocity is the ultrasound's main measure of how tight a narrowing is. This value is from the highest part of the internal carotid artery the probe can reach, before it enters the skull; the exam samples the proximal, mid and distal segments in turn, and a narrowing shows itself wherever the velocity jumps. The highest reading along the vessel is the one the stenosis is graded from.

The bands are the 2003 Society of Radiologists in Ultrasound consensus that most accredited labs use, expressed as the percent narrowing a catheter angiogram would show (the NASCET method): under 125 cm/s is a normal vessel or one narrowed by less than half, 125 to 230 cm/s is a 50 to 69 percent narrowing, and over 230 cm/s is 70 percent or more. The velocity is read together with the ICA/CCA ratio and the end-diastolic velocity, which must agree, and with what the grayscale image shows. In 2023 the Intersocietal Accreditation Commission raised its primary velocity line from 125 to 180 cm/s while keeping the ratio at 2.0, so a value between 125 and 180 can be graded under 50 percent by a lab on the newer criteria; the report's own stenosis grade is the reading physician's call across all of it.

Velocities run higher in women, in a vessel that has to carry more blood because the other carotid is blocked, and in a tortuous or kinked artery, and a heavily calcified plaque can shadow the segment behind it, so a single high number is confirmed before anything is decided, with a repeat study or a CT or MR angiogram. A narrowing under 50 percent is treated with medication (a statin, blood pressure control, aspirin where indicated) and a repeat scan; 50 to 69 percent adds a vascular specialist and closer surveillance; 70 percent or more, with or without symptoms, is where surgery or stenting is discussed.