【Objective】To investigate the diagnostic value of quantitative perfusion parameters of dynamic contrast-enhanced im? aging for discriminating metastatic from non-metastatic regional lymph nodes in rectal cancer.【Methods】122 patients of our depart? ment were collected from 2015.01 to 2016.08

and 203 lymph nodes

including metastatic lymph nodes (MLNs

n=95) and non-meta? static lymph nodes (NMLNs

n=108)

were analyzed. The short-axis diameter (S)

long-axis diameter (L)

short- to long-axis diameter ratio (S/L)

volume transfer constant (K trans )

rate constant (K ep ) and extravascular extracellular space (EES) fractional volume (V e ) were compared between two groups respectively. Then using S=5 mm as a cutoff value

these parameters were compared between subgroups. Receive operating characteristic curve (ROC) was used to analyze the diagnostic efficiency and find the optimal cutoff values.【Re? sults】The metastatic group exhibited higher S and L

but lower S/L

K trans and K ep than the non-metastatic group (P<0.01). However

the V e did not differ significantly between two groups (P=0.308). Optimal cutoff values [area under the curve (AUC)

sensitivity

speci? ficity] of K trans for discriminate metastatic lymph nodes from non-metastatic were 0.088 min -1 (0.69

58.3%

78.9%). When S>/=5 mm

subgroup analysis revealed that K trans and K ep of MLNs were significant higher than those of NMLNs (P<0.001)

but V e was lower (P=0.039). Optimal cutoff values (AUC

sensitivity

specificity) of K trans were 0.088 min -1 (0.675

57.1%

77.9%). However

when S<5 mm

MLNs showed lower K trans than NMLNs (P=0.001)

but there were no significantly statistic differences of K ep and V e between these two groups (P>0.1). Optimal cutoff values (AUC

sensitivity

specificity) of K trans were 0.087 min - 1 (0.732

60.5%

81.5%).【Conclusion】 K trans can be used to discriminate regional MLNs from NMLNs in rectal cancer

especially when the short-axis diameter is less than 5 millimeters.