In non-equilibrium contrast media injection, what is the expected HU difference between the IVC and abdominal aorta?

In non-equilibrium contrast media injection, the expected Hounsfield Unit (HU) difference between the inferior vena cava (IVC) and the abdominal aorta typically falls within the 10-30 HU range. This occurs because during the early phase of contrast enhancement, such as in non-equilibrium conditions, both the aorta and the IVC receive contrast, but the dynamics of the contrast distribution can lead to a relatively modest difference in HU values.

The abdominal aorta is commonly filled with contrast to a greater extent due to its arterial anatomy and higher flow rates, which can result in higher HU values compared to the IVC. However, the IVC, being a venous structure and having lower blood flow and pressure, receives a lesser degree of enhancement. Hence, in non-equilibrium scenarios where the contrast has not fully equilibrated between arteries and veins, a difference of about 10-30 HU is expected.

This understanding is crucial for interpreting CT images in the context of vascular studies and can provide insights into the hemodynamics and the presence of pathology in the vascular system. A more substantial difference in HU, greater than 30 HU, is typically not anticipated in non-equilibrium conditions unless there is an underlying pathology affecting contrast distribution