What is the SUV & Why is it Used?

Qualitative assessment of metabolic activity inevitably suffers from inter- and intra-observer variability. There is considerable variation as to what should be considered “significant” metabolic activity by different radiologist or even by the same radiologist on two sequential exams.  [Fig. 1]

Moreover, assessing response to therapy over sequential exams can be troublesome using purely a qualitative or subjective approach.  A radiologist’s statement that there has been “some” interval improvement is not very useful to either the patient or the treating clinician. [Fig. 2]

The SUV was created as a means to objectively quantify the metabolic activity of a region of interest, theoretically decreasing inter and intra-observer variability, and to provide an objective and reproducible means by which to assess response to therapy. [Fig. 3]  [Fig. 4]

The SUV attempts to measure focal activity, normalized for body weight and injected dose.  It is a unitless measurement (assuming 1 gram of body weight = 1.0 mL) that “quantifies” a focal concentration of metabolic activity relative to the remainder of the body.

In general, the higher the SUV of a lesion, the more probable the lesion represents active malignancy.

For many malignancies, the higher the SUV, the more aggressive the cancer.