Pharmacokinetic analysis for the differentiation of pituitary microadenoma subtypes through dynamic contrast-enhanced magnetic resonance imaging

The value of pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in distinguishing pituitary microadenoma subtypes was investigated in the present study. Pathology and follow-up outcomes were applied as the gold standard for differentiating between 76 patients with pituitary microadenomas (38 prolactin-producing tumors, 17 adrenocorticotropic hormone adenomas and 21 growth hormone-producing tumors) and 20 patients with normal pituitary glands. DCE-MRI was conducted to obtain the following quantitative permeability parameters: Volume transfer constant (K(trans)), rate constant (K(ep)) and extracellular extravascular volume fraction (V(e)). Among the 76 cases included, 61 were visually diagnosed using conventional MRI. The K(trans), K(ep) and V(e) of the microadenoma cases were 0.472±0.292/min, 0.765±0.359/min and 0.792±0.345, respectively. The K(trans), K(ep) and V(e) of the normal control group were 0.902±0.238/min, 1.208±0.599/min and 0.928±0.378, respectively. The K(trans) and K(ep) of patients with microadenomas were significantly lower compared with those of the normal controls (P<0.05). However, the V(e) of the two groups did not significantly differ. Subtype differentiation analysis revealed that patients with growth hormone-producing tumors exhibited the highest K(trans) value (P<0.05). K(ep) significantly differed between growth hormone-producing tumors and the other two subtypes (P<0.05), but did not significantly differ among three subtypes. Receiver-operator characteristic analysis indicated that the area under the curve values of K(trans) and K(ep) were 0.884 and 0.728, respectively. Sensitivity and specificity were 95.0 and 82.6%, respectively, when K(trans) was set to 0.614/min as the cut-off value, and when the K(ep) cut-off value was set to 0.985/min, sensitivity and specificity were 60.0 and 81.3%, respectively. In conclusion, K(trans) and K(ep) derived from DCE-MRI could be applied to detect and identify microadenoma subtypes. K(trans) better reflects the blood perfusion alterations exhibited by patients with different microadenoma subtypes.