彩色多普勒超声检查时，区别正常颈内动脉 和颈外动脉的有效征象是（     ）

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SQL Error: select id,body,options from ***_enewstiku where sourceid='25747' and id < 2163706 and id<>'2163706' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='25747' and id > 2163706 and id<>'2163706' order by id asc limit 5