About Standard Uptake Value (SUV)

Malignant cancer cells require large amounts of glucose to grow and multiply.

Malignant cancer cells have a high concentration of glucose transporter proteins, and exhibit a rapid metabolic rate (glycolysis). Glycolysis causes tumors to appear hot on PET scans.

The radioactive molecule fluorodeoxyglucose (FDG) is similar to glucose.  FDG is a radiotracer commonly used for PET scans. FDG accumulates in malignant cells because of the high rate of glucose metabolism. The dose of FDG is relative to the patient's weight, height and gender.

PET measures FDG retention per volume of tissue. Tumors and cancer cells in specific areas retain large amounts of FDG, such as in the lungs, breasts, head, and neck. Tumors and cancer cells in other areas can retain variable amounts of FDG, such as in the prostate and liver.

The standardized uptake value (SUV) is:

• a semi-quantitative index for FDG accumulation in tissue relative to the injected dose of FDG.

• the ratio of activity in tissue per millimeter to the activity in the injected radiotracer dose per patient body weight.

• (µCi/gram in tissue)/{(total µCi injected)/(body weight)}

Important: The ability to accurately reproduce the SUV measurement depends on the consistency of the clinical protocols during each study. Protocols that can vary include dose infiltration, time of imaging after the FDG administration, type of attenuation maps, size of the region of interest, changes in uptake by organs other than the tumor, and methods of analysis (maximum and mean).

WARNING Attention should be given to performing volumetric measurements on the PET/CT images for the placement of ROI. Adjust the threshold setting to be in the minimum range area (2.5 to 3 mm of minimum value) to exclude unwanted tissues within the Lesion.

For a precise volumetric measurement on the PET image, place the ROI in an appropriate area of the lesion and estimate the lesion size by scrolling through the entire volume of the ROI and confirm the lesion is fully contained inside this volume.

Adjust the threshold setting range to an approximate minimum range of 2.5 to 3.0 minimum value to exclude unwanted tissues within the volumetric area.

Enable the “Segment only a single component around the max pixel” in the application settings to avoid inclusion of unwanted lesions/tissues within the region of interest.

Important Information About SUV

When using SUV calculation during PET assessment, assumptions are made about the reference time for acquiring the data series. It is possible to interpret the requirements outlined in the DICOM Standard for determining the start reference time during acquisition and the time that the radiotracer is injected with some variability. This in turn may cause variability in the SUV values calculated by different vendors.

Due to inconsistencies throughout the industry, the acquisition time used in SUV calculation may be any of the acquisition times presented in the DICOM data. SUV is affected by several physiological factors which cause variability.

SUV can be applied as a simplified measure of radiopharmaceutical uptake. SUV has a complimentary role rather than directive role in the assessment, treatment, and staging of disease.

	WARNING Disease Specific guidelines are required when calculated SUV parameters are used for diagnostic purposes.
	WARNING Anatomy (organ) specific measurement interference is to be taken into consideration while using SUV parameters for diagnostic purposes. For example, patients with diabetes can display interference with measured brain PET SUV parameters.
	WARNING Measuring very small lesions may result in partial volume effect, caused by limited partial resolution of the PET scanner, resulting in underestimation of the SUV.

 

Formulas to Calculate SUV

The dose of FDG is relative to the patient's weight, height and gender. The types of SUV include:

• SUV-Body Weight (default)

• SUV-Body Surface Area

• SUV-Lean Body Mass (also known as SUL)

PET/CT Standard Uptake Value Formulas

See this topic:

Adjusting Patient Data for SUV