Intravascular ultrasound is an invasive procedure. You can read a summary of it here on Wikipedia. 

Change in the secondary outcome measures including apoA-I, apoB, LDL-C, HDL-C, TG, HbA1C, fasting glucose, fasting insulin, alkaline phosphatase, hsCRP, fibrinogen and estimated glomerular filtration rate (eGFR) can all be done on blood samples.

Blood sampling is safe and easy and non-invasive. IVUS.....not quite as safe and easy and requires an invasive procedure. "The physician [to steer] the guidewire from outside the body, through angiography catheters and into the blood vessel branch to be imaged."

BearDownAZ