Detection of small (≤ 2 cm) pancreatic adenocarcinoma and surrounding parenchyma: correlations between enhancement patterns at triphasic MDCT and histologic features

BACKGROUND: The aim is to assess the time-density curves (TDCs) and correlate the histologic results for small (≤ 2 cm) PDA and surrounding parenchyma at triphasic Multidetector-row CT (MDCT). METHODS: Triphasic MDCT scans of 38 consecutive patients who underwent surgery for a small PDA were retrospectively reviewed. The TDCs were analyzed and compared with histologic examination of the PDA and pancreas upstream/downstream in all cases. Three enhancement patterns were identified: 1) enhancement peak during pancreatic parenchymal phase (PPP) followed by a rapid decline on portal venous phase (PVP) and delayed phase (DP) at 5 minutes (type 1 pattern: normal pancreas); 2) maximum enhancement in PVP that gradually decreases in DP (type 2 pattern: mild chronic pancreatitis or PDA with mild fibrous stroma); 3) progressive enhancement with maximum peak in DP (type 3 pattern: severe chronic pancreatitis or PDA with severe fibrous stroma). A p value less than 0.05 was considered statistically significant. Sensitivity was calculated for PDA detection and an attenuation difference with the surrounding tissue of at least 10 HU was considered. RESULTS: PDA showed type 2 pattern in 5/38 cases (13.2%) and type 3 pattern in 33/38 cases (86,8%). Pancreas upstream to the tumor had type 2 pattern in 20/38 cases (52,6%) and type 3 pattern in 18/38 cases (47,4%). Pancreas downstream to the tumor had type 1 pattern in 19/25 cases (76%) and type 2 pattern in 6/25 cases (24%). Attenuation difference between tumor and parenchyma upstream was higher of 10 UH on PPP in 31/38 patients (sensitivity = 81.6%), on PVP in 29/38 (sensitivity = 76.3%) and on DP in 17/38 (sensitivity = 44.7%). Attenuation difference between tumor and parenchyma downstream was higher of 10 UH on PPP in 25/25 patients (sensitivity = 100%), on PVP in 22/25 (sensitivity = 88%) and on DP in 20/25 (sensitivity = 80%). Small PDAs were isodense to the pancreas upstream to the tumor, and therefore unrecognizable, in 8 cases (8/38; 21%) at qualitative analysis and in 4 cases (4/38; 10,5%) at quantitative analysis. CONCLUSIONS: The quantitative analysis increases the sensitivity for detection of small PDA at triphasic MDCT.