 A very recently formed thrombus is not very solid , it will have a low echogenicity , and will be seen as a black area in the gray @-@ scale image and will be hardly visible . When the examiner uses color , the imaging is not much improved . A thrombus may not be evident in the scan . Also a vein lumen may show echoes without the presence of a thrombus . The location of the thrombus and its detail will inform of the seriousness of the condition . In a deep vein thrombosis ( DVT ) , or in a superficial vein thrombosis where the thrombus is floating , an emergency situation will be indicated . If the thrombus is near to the sapheno @-@ femoral junction there will be a high risk of a pulmonary embolism occurring . 
