Impact on SUV measurements: A comparison of measured vs. stated weight

Objectives At our institution we obtain the patient's weight from the doctor’s office when scheduling a PET exam. Upon arrival, the patient is questioned what their current weight is. The weight obtained from the patient is used to measure SUV values. We questioned this procedure wondering if weighing the patient would obtain a more accurate result and how this would affect SUV values.

Methods We asked 240 patients their weight then weighed them. The recorded measurements and the weight from the doctor’s office were placed in a spreadsheet. We calculated the percentage difference between the measured weight, the patient's stated weight, and the doctor’s office weight. We measured the SUV values with all three weights that were obtained.

Results Oncologic PET patients know their weight. 53% of the patients surveyed were +/- 1% of their actual weight. The doctor’s office does not know the patient's weight. 64% of the doctor’s offices could not even provide us with a patient weight. When provided they were wrong by up to 50%. SUV values are affected by wrong weight

Conclusions There are many factors that can affect the measured SUV value. Obtaining the actual patient weight is easy to do. The percent error in weight correlates directly to the error in measured SUV value. In our study the largest difference in stated weight vs. measured weight was 7%. This translates to a 7% error in SUV value. Given the fact it is easy to do, all patients should be weighed at the start of a PET examination to prevent unnecessary variability in SUV measurements.