Diagnostic value of the delayed phase image for iso-attenuating pancreatic carcinomas in the pancreatic parenchymal phase on multidetector computed tomography

Abstract

Purpose: To assess the value of the delayed phase (DP) in pancreatic carcinomas which appear iso-attenuating in the pancreatic parenchymal phase (PPP).

Materials and methods: Fifty-seven preoperative MDCT studies of pancreatic carcinomas were retrospectively reviewed. The size of the tumors, and the Hounsfield unit (HU) of the tumors and pancreatic parenchyma were measured. The tumor-to-pancreas contrast (TPC: |HU [tumor]-HU [normal pancreas]|) was calculated.

Results: Eight cases (14.0%) showed iso-attenuation and 49 showed hypo-attenuation in the PPP. The DP images revealed seven of eight (87.5%) iso-attenuating tumors to be hyper-attenuating. The size of iso-attenuating tumors was smaller than that of hypo-attenuating tumors (mean+/-S.D.: 12.4+/-4.8mm vs. 30.3+/-9.0mm, p<0.0001). In hypo-attenuating tumors, TPC in the PPP (60.2+/-24.6 HU) was higher than those in the portal venous phase (PVP, 40.5+/-23.0 HU, p<0.0001) and DP (18.3+/-11.8 HU, p<0.0001). In contrast, in iso-attenuating tumors, TPC in the DP (26.0+/-4.9 HU) was higher than those in the PPP (9.2+/-3.7 HU, p=0.0003) and PVP (7.1+/-4.7 HU, p=0.001) phases.

Conclusion: The DP image is helpful in depicting small iso-attenuating pancreatic carcinomas as slightly hyper-attenuating tumors.