Authors (including presenting author) :
Lee KYG, Cho KYF, Wong MFE
Affiliation :
Department of Radiology, Pamela Youde Nethersole Eastern Hospital
Introduction :
CT pancreas is usually the first line of investigation for detection and staging of pancreatic mass. It is one of the commonest CT requests in daily practice. Existing protocol in our department consisted of a 4 phase examination (plain, arterial, portal venous and delayed phases). Data from existing protocol showed radiation dose exceeding national reference according to “Doses from CT examinations in the United Kingdom -2011 review”.
Objectives :
To introduce new CT pancreas protocol and compare dosage and imaging quality with existing institutional average and international reference (Society of Abdominal Radiology and American Pancreatic Association) . Parameters for comparison includes (1). Pancreatic parenchymal enhancement; (2) Enhancement of the arterial circulation; which assess image quality qualitatively, and (3) Radiation dosage.
Methodology :
New CT protocol was introduced in Aug 2018. The new protocol consisted of 3 phases (Plain, late arterial and portal venous phases.) Cases of CT pancreas performed during Aug – Dec 2018 with new protocol were included (Cohort 1, new protocol). Matching cohort of existing protocol were retrieved, with examination dates from July – Dec 2017. (Cohort 2, existing protocol) Measurement for pancreatic parenchymal enhancement in Hounsfield Unit (HU)were taken arbitrarily from pancreatic head and neck region. Arterial enhancement was measured at the celiac trunk. The radiation dosage were compared in terms of CT Dose Index (CTDIvol) and Dose-Length Product (DLP). Statistical analysis was performed on SPSS (Version 25, IBM Software). Mann-Whitney U test was performed to determine statistical significance.
Result & Outcome :
Totally 94 patients (M:F=46:48, age 38-90 years) were included. 47 cases were from Cohort 1(Existing protocol) and Cohort 2(New protocol) respectively. In terms of pancreatic parenchymal enhancement, the new protocol cohort showed higher mean HU compared with existing protocol (118HU and 76HU respectively; p<0.001). In terms of enhancement of arterial circulation, the new protocol showed higher mean HU compared to existing protocol (302HU and 241HU respectively; p<0.001). The new protocol thus improves visualization of hypoenhancing tumors, and their relationship with adjacent arteries. In terms of radiation dosage, new protocol showed lower values compared to existing protocol in both mean CTDIvol and DLP (CTDIvol: 39 vs 148mGy ;p<0.001; DLP: 810 vs 1212mGy*cm ;p=0.009). The mean DLP of the new protocol was also lower than the suggested national reference dose in the United Kingdom (810 vs 910mGy*cm). The newly introduced pancreatic CT protocol generated better quality image measured by pancreatic parenchymal and arterial vascular enhancement, at reduced radiation dose comparable to international standards.
Co-location with:
