Evaluation Of Dual-energy Spectral Computed Tomography Imaging On The Diagnosis And Resectability Of Periampullary Carcinoma

Dual-energy spectral computed tomography(DESCT) is a new method with the development of computed tomography, which can help reduce beam hardening artifact, improve image quality and enhance the CNR, quantitatively analyse materials and spectral comprehensive analysis. This study was designed to investigate the value of dual-energy spectral computed tomographic imaging(DESCT) in the characteristic diagnosis, staging and resectability of carcinomas in the ampullary region. There were three parts in this research. Part one, to evaluate the difference of mixed energy mode and mono-energy mode reconstruction images on abdomen spectral CT imaging. Part two, to investigate the value of DESCT in predicting the origin of carcinomas in the ampullary region. Part three, to evaluate the application of DECT in the resectability of periampullary carcinoma.Part I Objective To evaluate the difference of mixed energy mode and mono-energy mode on reconstruction image quality in abdomen spectral CT imaging. Materials and Methods All examinations were performed under a multidetector DESCT scanner(Discovery HD750, Gemstone Spectral Imaging, GE Healthcare, USA). All 40 patients underwent routine plain/dual-phase enhanced CT scans with dual-energy spectral imaging mode(GSI mode). Images were reconstructed by two mode: mixed-energy mode, and 70 Kev mono-energy mode. The following variables were compared: signal-to-noise ratio(SNR) of liver, spleen and pancreas; organ-to-fat contrast-to-noise ratio(CNR) of liver, spleen and pancreas; noise. Paired t-test was used to compare the difference between the two modes. Two experienced radiologists evalute the artifact level of images acquired under the two reconstruction model independently. Results Compared with mixed-energy mode images, 70 ke V mono-energy images yielded significantly greater SNR, tissue-to-fat CNR and noise(p<0.01 for all comparison). Subjective score of 70 ke V mono-energy images were higher than that of mixed-energy image. Conclusion In abdominal spectral CT imaging, mono-energy reconstruction can provide higher quality of images than mixed-energy reconstruction and can replace mixed-energy images in clinical diagnosis.Part II Objective To investigate the value of dual-energy spectral computed tomographic imaging(DESCT) in predicting the origin of carcinomas in the ampullary region. Materials and Methods Eighty-eight patients with ampullary region carcinomas(39 pancreatic adenocarcinomas, 22 biliary adenocarcinomas, 27 adenocarcinomas of the ampulla) underwent DESCT prior to biopsy or surgery. We compared the CT spectral imaging features among the adenocarcinomas with the above-mentioned 3 different origins. Results During tri-phase enhanced scans, no significant difference was found in the concentration of water among three groups. The concentration of iodine, NIC and slope was highest in group of biliary adenocarcinoma, while lowest in group of pancreatic adenocarcinoma, and significant difference was found among three groups. NIC thresholds of 0.44 and 0.72 yielded a sensitivity and specificity of 89%, 85% in differentiation of common bile duct adenocarcinomas from ampullary adenocarcinoma in the portal phase(PP) and delayed phase(DP), respectively. Iodine concentration threshold at 22.50 mg/m L in the PP yielded a sensitivity of 100%, and Iodine concentration threshold at 16.46 mg/m L in the DP yielded a specificity of 100% in differentiation of common bile duct adenocarcinoma from pancreatic adenocarcinoma. Iodine concentration thresholds at 10.20 and 13.49 mg/m L yielded a sensitivity 100% in differentiation of ampullary adenocarcinoma from pancreatic adenocarcinoma in the PP and DP, respectively. Conclusion DESCT with multiple parameters can provide useful diagnostic information about the origin of masses in the ampullary region.Part III Objective To investigate the value of DESCT in the resectability of periampullary carcinoma. Materials and Methods Ninety-eight patients with periampullary carcinoma confirmed by clinical follow up or pathology underwent routine DESCT. All imaging data were analyzed retrospectively and correlated with clinical data. Results The sensitivity, specificity, accuracy, positive and negative prediction value of DESCT in the estimation of the resectability of periampullary carcinoma were 96%, 95.7%, 96%, 98.6%, 88%. Conclusion DESCT can accurately demonstrate tumor location, vessels invasion, enlarged lymph nodes and metastasis of other organ in abdomen. It has significant clinical value in the estimation of the resectability of periampullary carcinoma.