Ultrasound, CTA and color ultrasound are different in imaging the presence of cancerous thrombus in the inferior vena cava (IVC), and each has its own purpose. 1. Ultrasound: it can show whether the diameter of IVC is thickened or not and whether there is a solid echogenic light mass in the lumen to determine whether there is a thrombus or not. ultrasound is easily interfered by patient’s obesity, edema, and gas factors, and it can not distinguish between cancerous thrombus and blood thrombus. 2. CTA: It can clearly show the length and size of IVC embolus and different levels of embolus, but it is difficult to distinguish embolus from thrombus. It is also difficult to distinguish between thrombus and thrombus. 3. Color ultrasound: it can show the size of the IVC diameter, the presence or absence of the thrombus in the lumen, and the position of the thrombus in the head of the IVC. If the thrombus completely blocks the IVC, color ultrasound will show that the IVC is completely blocked. Ultrasound can measure the arterial spectrum, which can indicate the arterial blood supply in the IVC thrombus and can be used to differentiate between thrombus and tumor thrombus. There are also other clinical methods such as MRA and venous angiography X-ray to detect cancerous thrombus in the inferior vena cava, which will not be repeated.