Textbooks and credible websites are a good way to get started with your research.
Use the Fusion database to find books or you may want to refer to a textbook from one of your courses. You can limit the search in Fusion by Publication Type: Books. The library has a great collection of books. A few recently published books are listed below.
Introduction to Vascular Ultrasonography by 
Textbook of Diagnostic Sonography by 
Pathophysiology of Heart Disease by 
Porth's Pathophysiology: Concepts of Altered Health States by 
Understanding Pathophysiology by