Standardized uptake value (SUV)

Standardized uptake value, SUV, (also referred to as the dose uptake ratio, DUR) is a widely used, robust PET quantifier, calculated simply as a ratio of tissue radioactivity concentration (for example in units [kBq/mL]) at time T, CPET(T), and administered dose (for example in units [MBq]) at the time of injection divided by body weight (usually in units [kg]).

If the above mentioned units are used, the unit of SUV will be [g/ml]. Tissue radioactivity and dose must be decay corrected to the same time point.

Instead of the body weight, the administered dose may also be corrected by the lean body mass (LBM), or body surface area (BSA) (Kim et al., 1994); for FDG PET studies the SUVBSA is recommended.

Verbraecken et al. (2006) review the different formulas for calculating the BSA.

Calculation of SUV does not require blood sampling or dynamic imaging. The imaging must take place at a late time point, and always at the same time point, if results are to be compared (Eckelman et al., 2000).

In FDG studies SUV can be corrected for plasma glucose level, because glucose transporters may be saturated by glucose. SUV is multiplied by plasma glucose concentration / 5.0 (5.0 represents the population average of plasma glucose concentration).

Cancer treatment responce is usually assessed with FDG PET by calculating the SUV on the highest image pixel in the tumour regions (SUVmax), because this provides lower interobserver variability than averaged SUV (SUVmean). Alternatively, tumour volume can be estimated using threshold or region growing techniques, and average SUV inside the region is reported as such or multiplied by tumour volume to calculate the total glycolytic volume, TGV (Boucek et al., 2008). Nahmias and Wahl (2008) reported that the use of SUVmax has worse reproducibility (3% ± 11%) than does the SUVmean value (1% ± 7%), and Burger et al (2012) confirmed that repeatability of SUVmean is superior to SUVmax. SUVpeak, based on a spherical volume of interest (VOI) having a volume of ~1 mL in a position that provides the maximal VOI average, avoids the noise-indused bias of SUVmax, but is less sensitive to image characteristics (Lodge et al, 2012). Combination of SUVmax and SUVpeak (Lasnon et al., 2013) should become the standard approach in multicentre FDG PET/CT studies (Boellaard, 2013).

SUV drawbacks

SUV is vulnerable to several major sources of variability (Hamberg et al. 1994; Keyes 1995; Huang 2000), and the application of SUV as a quantitative index should be discouraged. The only reason for its continuous usage is that dynamic imaging and blood sampling are not necessary.

Although SUV and Ki may correlate well over the patient population, they may provide even opposite conclusions regarding the progression of disease (Freedman et al., 2003). Image noise, poor resolution and ROI definition affect the SUV and may hamper their use, especially in multicenter trials (Boellaard et al., 2004).

In oncological (multicentre) studies variance in SUV may be reduced by dividing tumor SUVmax or SUVpeak by SUV in liver. Any calibration problems cancel out in this method, which essentially is the same as tissue-to-reference tissue ratio at a late time point. Tumour-to-blood ratio at a late time point has been shown to correlate with metabolic rate of FDG in tumors (van den Hoff et al., 2013). It is the preferred method over tumour-to-liver ratio, especially if blood activity can be determined from the same PET image; then the possible issues in calibration are again avoided. If blood or liver activity cannot be determined from the PET image, then the single venous blood sample is relatively easy to obtain.

If blood curve has been measured, a simple but quantitative alternative to SUV is fractional uptake rate (FUR), which is an approximation to the Patlak slope Ki, but does not require dynamic PET scan. FUR and SUV are proportional, related by plasma clearance rate and a dimensionless initial distribution volume (Thie, 1995).

%ID/L

In animal studies, dissected tissue samples are weighted and radioactivity is measured. Radioactivity is divided by sample weight to calculate the concentration (Bq/g). With injected dose and animal weight the SUV could be calculated similarly as from PET data. However, in animal studies the animal weight is often not taken into account: radioactivity concentration is simply divided by injected dose and multiplied by 100, and outcome is percent of injected dose per gram of tissue (%i.d./g).

Similar calculation can be done to PET data. In PET image the radioactivity concentration is measured per tissue volume (Bq/mL) instead of mass, and therefore the outcome will be in units %i.d./mL or %i.d./L. If tissue density (g/mL) is known or assumed to be 1 g/mL, it can be converted to %i.d./g.

See also:


References:

Bai B, Bading J, Conti PS. Tumor quantification in clinical positron emission tomography. Theranostics 2013; 3(10): 787-801.

Boellaard R, Krak NC, Hoekstra OS, Lammertsma AA. Effects of noise, image resolution, and ROI definition on the accuracy of standard uptake values: a simulation study. J Nucl Med 2004; 45: 1519-1527.

Boellaard R. Optimisation and harmonisation: two sides of the same coin? Eur J Nucl Med Mol Imaging. 2013; 40: 982-984.

Burger IA, Huser DM, Burger C, von Schulthess GK, Buck A. Repeatability of FDG quantification in tumor imaging: averaged SUVs are superior to SUVmax. Nucl Med Biol. 2012; 39: 666-670.

Boucek JA, Francis RJ, Jones CG, Khan N, Turlach BA, Green AJ. Assessment of tumour response with 18F-fluorodeoxyglucose positron emission tomography using three-dimensional measures compared to SUVmax - a phantom study. Phys Med Biol. 2008; 53(16): 4213-4230.

Eckelman WC, Tatum JL, Kurdziel KA, Croft BY. Quantitative analysis of tumor biochemistry using PET and SPECT. Nucl Med Biol 2000; 27: 633-635.

Freedman NMT, Sundaram SK, Kurdziel K, Carrasquillo JA, et al. Comparison of SUV and Patlak slope for monitoring of cancer therapy using serial PET scans. Eur J Nucl Med 2003; 30: 46-53.

Hamberg LM, Hunter GJ, Alpert NM, Choi NC, Babich JW, Fischman AJ. The dose uptake ratio as an index of glucose metabolism: useful parameter or oversimplification. J Nucl Med. 1994; 35: 1308-1312.

van den Hoff J, Oehme L, Schramm G, Maus J, Lougovski A, Petr J, Beuthien-Baumann B, Hofheinz F. The PET-derived tumor-to-blood standard uptake ratio (SUR) is superior to tumor SUV as a surrogate parameter of the metabolic rate of FDG. EJNMMI Res. 2013; 3: 77.

Huang S-C. Anatomy of SUV. Nucl Med Biol 2000; 27: 643-646.

Keyes JW Jr. SUV: Standard uptake or silly useless value? J Nucl Med. 1995; 36: 1836-1839.

Kim CK, Gupta NC, Chandramouli B, Alavi A. Standardized uptake values of FDG: body surface area correction is preferable to body weight correction. J Nucl Med. 1994; 35: 164-167.

Lasnon C, Desmonts C, Quak E, Gervais R, Do P, Dubois-Arvis C, Aide N. Harmonizing SUVs in multicentre trials when using different generation PET systems: prospective validation in non-small cell lung cancer patients. Eur J Nucl Med Mol Imaging. 2013; 40: 985-996.

Lodge MA. Chaudry MA, Wahl RL. Noise considerations for PET quantification using maximum and peak standardized uptake value. J Nucl Med. 2012; 53: 1041-1047.

Nahmias C, Wahl LM. Reproducibility of standardized uptake value measurements determined by 18F-FDG PET in malignant tumors. J Nucl Med. 2008; 49 (11): 1804-1808.

Shankar LK, Hoffman JM, Bacharach S, Graham MM, Karp J, Lammertsma AA, Larson S, Mankoff DA, Siegel BA, Van den Abbeele A, Yap J, Sullivan D; National Cancer Institute. Consensus recommendations for the use of 18F-FDG PET as an indicator of therapeutic response in patients in National Cancer Institute Trials. J Nucl Med. 2006; 47(6): 1059-1066.

Thie JA. Clarification of a fractional uptake concept. J Nucl Med 1995; 36:711-712.

Thie JA. Understanding the standardized uptake value, its methods, and implications for usage. J Nucl Med 2004; 45: 1431-1434.

Thie JA, Hubner KF, Isidoro FP, Smith GT. A weight index for the standardized uptake value in 2-Deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography. Mol Imaging Biol. 2007; 9(2): 91-98.

Verbraecken J, Van de Heyning P, De Backer W, Van Gaal L. Body surface area in normal-weight, overweight, and obese adults. A comparison study. Metab Clin Exp 2006; 55: 515-524.


Tags: , ,


Created at: 2008-11-20
Updated at: 2014-05-27
Written by: Vesa Oikonen