TABLE 1

Overview of Factors Affecting ¹⁸F-FDG PET Quantification

Category	Factor	Explanation	Typical range (maximum effect)^*	Reference or source
Technical errors	Relative calibration between PET scanner and dose calibrator	Systematic error in SUV is equal to error in relative calibration between PET scanner and dose calibrator	−10%−10% (±50%)	44,45
	Residual activity in syringe or administration system	Lower net administered dose results in incorrect lower uptake level and SUV	0%−5% (typically <15%, but can be much greater in worst-case situations)	Unpublished data
	Incorrect synchronization of clocks of PET/CT camera and dose calibrator	Incorrect decay correction results in incorrect SUV	0%−10% (21%, as seen in ongoing multicenter study)	Unpublished data
	Injection vs. calibration time	Incorrect time interval is used for decay correction of administered dose	0%−10% (NaN)	Unpublished data
	Paravenous administration of ¹⁸F-FDG	Rate and quantity of delivery of ¹⁸F-FDG to tumor are reduced, resulting in incorrect SUV	0%−50% or more, strongly depending on quality of administration	Estimated values based on unpublished data
Biologic factors	Blood glucose level	Lower uptake levels or SUVs occur with increasing blood glucose levels	−15%−+15% (±75%)^†	14,16,54
	Uptake period	Higher SUVs occur at increasing time intervals between injection and start of PET study	+0%−+15% at 60–90 min (±30%)	25
	Patient motion or breathing	Image artifacts result from mismatches in positions between CT-AC and PET emission scans, and lower SUV may result from respiratory motion (resolution loss)	0%−30% (±60%)	36,37
	Patient comfort	Patient stress and poor waiting conditions result in uptake of ¹⁸F-FDG in muscle or brown fat and affect SUV quantification	NaN, mainly giving rise to false-positive results (SUV_BW = 2–12) and possibly incorrect SUV in case of spillover	38
	Inflammation	Inflammatory processes near or at tumor result in false-positive increase in SUV	NaN, mainly giving rise to false-positive results and possibly incorrect SUV in case of spillover	39
Physical factors	Scan acquisition parameters	SNR of PET scan is affected, e.g., lower SNR results in upward bias of SUV	0%−15% (±15%)	26,45
	Image reconstruction parameters	Insufficient convergence and lower resolution result in lower SUV and increase in partial-volume effects; insufficient convergence makes SUV more dependent on surrounding activity distributions	−30%−0% (−30%)	26,27,43,45,49,50
	ROI	SUV outcome is strongly dependent on size and type of ROI used	0%−55% (±55%)	26,45
	Normalization factor for SUV	SUV outcomes are numerically different when body weight, body surface area, and lean body mass are used as normalization factors in SUV equation	Trivial^‡	14,22
	Blood glucose level correction	Higher serum glucose level results in underestimation of SUV; use of serum glucose level correction in SUV equation therefore results in different SUV outcomes	−15%−15% (±75%)^†	14,16,54
	Use of contrast agents during CT-AC	Overestimation of attenuation and therefore higher SUV (upward bias) may occur	0%−15% (±50%)^§	40–42

↵* Values represent estimated or approximate ranges and maximum deviations derived from published studies or unpublished data. Therefore, quoted values partly reflect personal opinions of authors. However, listed references or other reviews provide more details. For unpublished data, values were estimated or derived from my own data. NaN = not a number available; SUV_BW = SUV normalized to body weight.
↵† Very large errors may occur when blood glucose levels are very high (>11 mmol/L). Blood glucose levels should be checked before PET study; if blood glucose levels are high, PET study should be rescheduled (43).
↵‡ Use of different normalization factors (e.g., body weight [kg] and body surface area [m²]) in SUV equation yields different SUVs.
↵§ In general, use of contrast agents produces artifacts of up to about 20%. However, very large errors may occur when high-density oral contrast agents (e.g., barium) are used.