Dear Anne Marie Kupinski
    I have lost your email address so will share this with the list.

Rabinov K, Paulin S, Roentgen Diagnosis of Venous Thrombosis in the Leg,
Arch Surg/Vol 104 Feb 1972

In their abstract they state "Pitfalls in interpretation occured when
artifacts were created by bearing weight on the leg under study, by
tourniquets, by an improper injection site, OR BY THE INCOMPLETE MIXING OF
THE CONTRAST MATERIAL AS IT FLOWS THROUGH THE VEINS>

     In the text of the paper they site certain areas such as the junction
of the superficial and deep femoral veins and at the orifice of the
internal iliac vein.

     These mixing defects could cause a false positive or false negative,
as you can imagine.

     I also have a book chapter writtten by these two authors on
venography, but I do not know what text it is from. It expands on the key
items in the article.

I hope this is helpful
Tina