PET/CT Standardized Uptake Values (SUVs) in Clinical Practice and Assessing Response to... - 0 views
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use of PET in clinical research, clinical trials, and drug discovery
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In some cases, such as Hodgkins lymphoma, quantitative PET/CT imaging may not actually be needed, as success can be defined by the complete absence of tracer uptake in the PET image following a course of standardized therapy
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The utilization of PET/CT to assess response to therapy is increasing in the US related, in part, to the creation and subsequent favorable results of the National Oncologic PET Registry (NOPR)
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Changes in size as a result of therapy may take many months to develop and any opportunity to make early decisions about therapy success or failure is often unduly delayed or lost altogether
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measures of changes in metabolic activity via FDG PET/CT can provide an alternate approach to assess response to therapy -- often very early in the course of treatment
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The true tracer uptake in a patient is composed of two components: the first being the amount of tracer uptake (e.g. FDG) associated with the disease status (the signal of interest), which can be modified by the biophysiological status of the patient. One of the more important patient parameters is the blood glucose level, which has been shown to inversely-linearly affect SUVs
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A prospective study by Crippa et al.30 in eight patients showed that as blood glucose levels were increased from 92.4 ±10.2 to 158 ± 13.8 mg/100 ml by glucose loading, the average SUV of 20 liver metastases decreased from 9.4 ± 5.7 to 4.3 ± 8.3
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chemotherapy can result in impaired renal function, significantly reducing the clearance of plasma FDG through the kidney and thus increasing tumor SUV relative to an initial PET scan
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The biological variability has been estimated in several test-retest studies7,32–35 at approximately 10% for scans repeated within a few days