Why FDG PET Quantification Utilizing the Conventional Standard Uptake Value SUV Metric Calculation Does NOT Work

Unique to nuclear medicine procedures and in this instance specifically, 18 fluorodeoxyglucose positron emission tomography (18 FDG PET CT) scanning features the quantification of the emissions of radiation from the source of the scan.In addition to visual evaluation of the FDG PET study is the quantification analysis of the PET scan data.Our group did a simple analysis of patients studied at both baseline with FDG PET imaging and at second timepoint during treatment intervention which consisted of cytotoxic therapy without adjuvant radiation therapy or immunotherapeutic techniques.A total of 110 patients were studied sequentially on three different manufacturer PET-CT devices at the respective imaging centers.There were 50 patients studied on a General Electric Discovery 610, 30 patients evaluated utilizing a Philips Gemini GXL, and 30 patients receiving their base and first timepoint examinations on a Siemens Biograph 16.Each individual patient scan was assessed for the numeration of the liver SUV reference value in normal hepatic parenchyma in both the baseline and initial timepoint FDG PET examination.Based on recommended guidelines regarding successive FDG PET imaging, the results were categorized according to the following criteria.Those individuals who demonstrated a difference in the liver normal reference of 3 or less SUV units were compared to the number of patients that demonstrated a greater than 3 SUV units' difference in the reference calculation.27 of the 50 patients studied with the GE Discovery DS 610 with revealed a difference of greater than 3 units, 15 of 30 patients scanned with the Philips Gemini GXL and 20 of 30 subjects examined on the Siemens Biograph PET-CT also manifest a greater than 3-unit difference in the normal liver reference value.Those patients with a greater 3-unit difference in the normal liver reference generated SUVs were by definition excluded from comparative quantitation in designated abnormal regions of glucose metabolism.In summary the results of this inquiry into frequency of individual patient biodynamic behavior when studied at the same facility on the identical vendor hardware produced a situation where comparative SUVs were not possible based on the liver reference value alone in at least 50% of the encounters.This affirms that the biological function of the individual patient is not a static phenomenon and that in order to perform chronological analysis of the patient's abnormal glucose consumption regarding a scan abnormality in any clinical scenario, the generated SUVs must be standardized in order to obtain accurate results.