Role of advanced imaging techniques in the evaluation of oncological therapies in patients with colorectal liver metastases

Table 1 Main quantitative parameters extracted from perfusion computed tomography and magnetic resonance imaging imaging techniques to predict treatment response in patients with colorectal liver metastasis

Parameter name	Parameter definition	Parameter significance
Transfer constant (Ktrans)	Rate of contrast extraction from the blood to the interstitium	It reflects the balance between capillary permeability and BF in a tissue
Tissue interstitial volume (Ve)	Volume of extravascular and extracellular contrast agent in a certain tissue, expressed as a percentage	It is a measure of cell density
Rate contrast (Kep)	Rate at which the contrast agent returns from the extravascular-extracellular space to the vascular compartment (Kep = Ktrans/Ve)	It reflects the tissue microcirculation and contrast agent permeability
Regional BF	BF per unit volume or mass of tissue (mL of blood/min/100 mL of tissue)	It expresses the rate of the delivery of nutrients and oxygen to a certain tissue

BF: Blood flow.

Table 2 Main quantitative parameters extracted from the 18-fluorodexoyglucose positron emission tomography used in the prediction of treatment response in patients with colorectal liver metastasis

Parameter name	Parameter definition
SUVmax	Uptake value of the pixel with the highest activity inside an ROI divided by the injected dose, which must be corrected for decay and normalised to the patient’s weight or body surface
SUVmean	Average of all the uptake values of the pixels within an ROI
MTV	Volume of tumour tissues included in a tridimensional ROI with pathological FDG uptake via threshold represented by a settled absolute value or percentage of the SUVmax or SUVmean
	It includes both volumetric data and metabolic activity of the tumour
TLG	The product of multiplying SUVmean by MTV
SAM	A marker of total lesion glycolysis, calculated by drawing a volume of interest [VOI(1)] around the tumour and a larger VOI [VOI(2)] around VOI(1)
	SAM = Total SUV VOI1 − (mean BG × volume VOI1)
	Mean BG (background activity) = (total SUV VOI2 − total SUV VOI1)/(volume VOI2 − volume VOI1)

SUV_max: Standardised maximum uptake value; SUV_mean: Standardised mean uptake value; MTV: Metabolic tumour volume; TLG: Total lesion glycolysis; SAM: Standardised added metabolic activity; FDG: Fluorodexoyglucose; PET: Positron emission tomography; ROI: Region of interest; VOI: Volume of interest.