My take for a verbatim translation, but:
How can the lack of irregularities/the presence of normal arterial wall morphology be an indication of an 'atherosclerotic process'...?
Here, the original text is contradictory in itself, somehow.

Spectral spreading of of the Doppler signal at the site of the endarterectomy was found in 52% of the internal carotid arteries, whereas *wall irregularities* were demonstrated in 25% by intravenous digital subtraction angiography.
http://jnnp.bmj.com/content/49/2/183

Cerebral vessel angiography shows *arterial wall irregularities* and focal stenotic lesions.
http://www.pedsoncologyeducation.com/LEsCNSCerebrovasc.asp

His coronary CT showed aevere high level stenosis with *wall irregularities* of the right coronary artery. The treatment options are coronary revascularization ...
http://www.doctorsmedicalopinion.com/content/severe-right-co...

... including atherosclerotic *wall irregularities* but no hemodynamically relevant coronary artery stenoses.
http://radiology.rsna.org/content/234/3/718.figures-only

*Arterial wall irregularities* in intracranial neoplasms. The shaggy vessel brought into focus.
http://ukpmc.ac.uk/abstract/MED/4335670

Selective digital subtraction angiography of the right pulmonary artery. The angiogram shows *wall irregularities* and filling defects...
http://circ.ahajournals.org/content/103/24/2993.figures-only