This is due to difficulty in obtaining a correct insonating angle, non-linear or helical flow, or increased velocityon the inside of the curve. Tortuosity can cause apparent velocity increase even although there is no stenosis.ECA waveform: High resistance Sharp systolic upstroke and relatively low velocity end diastolic flow ICA waveform: Low resistanceCCA waveform: Mixed pattern of ICA and ECA- more towards ICA.Following features differentiate ICA from ECA. At times ECA and ICA waveforms appear very similar when plaque or stenosis narrows vessel.IMT >o.8 mm: abnormal, represents earliest changes of atherosclerotic disease.Clinical importanceIMT may be superior to coronary artery calcification score for identifying pts at high risk for CVS events.Assessment of IMT provides means of assessing effectiveness of medical interventions to reduce progression of IMT or even reverse carotid wall thickening.Then passes superiorly and loops anteriorly to enter deep groove in the submandibular gland, then hooks around the middle of the inferior border of the mandible to enter the face.Occipital artery: passes posteriorly, parallel and deep to posterior belly of digastric, passes superficial to internal carotid artery and CN IX, CN XI.Posterior auricular artery: ascends posteriorly between the external acoustic meatus and the mastoid process to supply the adjacent muscles, parotid gland, facial nerve, structures in the temporal bone, auricle and scalp. Give rise to deep lingual and sublingual arteries.Facial artery: gives off tonsillar branch, branches to palate and submandibular gland. It also supplies infrahyoid muscles and SCM, also give rise to the superior laryngeal artery supplying the larynx.Lingual artery: lies on the middle constrictor muscle of the pharynx, arches superoanteriorly and passes deep to the hypoglossal nerve, the stylohyoid muscle and the posterior belly of the digastric muscle. 3 anterior, 2 posterior, 1 medial and 2 terminal branches.Ascending pharyngeal artery ascends on the pharynx deep to the internal carotid artery and sends branches to the pharynx, prevertebral muscles, middle ear, and cranial meninges.Superior thyroid artery: runs anteroinferiorly deep to the infrahyoid muscles to reach the thyroid gland.

Except for the terminal segment (C7) the odd numbered segments usually have no branches, whereas the even numbered segments (C2, C4, C6) each have two branches.

Usg carotid doppler