Dual-source, dual-energy multidetector CT for the evaluation of pancreatic tumours

Abstract

Objective: To investigate the potential diagnostic value of dual-energy CT (DECT) with virtual non-enhanced (VNE) and iodine-only images, and to determine the optimal mixed ratio of blended images for evaluation of pancreatic diseases. Methods: Multiphasic DECT was performed in 44 patients with focal pancreatic disease. DECT was used during the pancreatic and hepatic venous phases, and a peak kilovoltage of 120 kVp was used for both non-contrast phases. For qualitative analysis of the CT images, two radiologists assessed three image sets (VNE, iodine-only and blended images) in order to determine the acceptability of VNE in replacing true nonenhanced (TNE) images, the added value of iodine-only images and the preferred blending ratio. For quantitative analyses, the CT numbers and image noise of the pancreatic parenchyma, lesions, aorta and psoas muscle were measured. The contrastto-noise ratio of the lesion was calculated on the pancreatic phase images. The effective radiation dose for DECT and TNE images was calculated. Statistical comparisons were made using the Friedman test, the Wilcoxon test, the paired t-test and repeated measures of analysis of variation with Bonferroni correction for multiple comparisons.Results: The level of acceptance of the VNE images in replacing TNE images was 90.9%. Regarding the iodine-only images, 50% of the cases were found to have an added value. The linear-blended images with a weighting factor of 0.5 were preferred. Conclusions: DECT was able to provide high-quality VNE images that could replace TNE images and iodine-only images showing an added value. Blended images with a weighting factor of 0.5 were preferred by the reviewers. Radiological imaging is an important component in the evaluation of pancreatic disease. CT has been the initial imaging modality of choice for evaluating pancreatic pathology [1]. Recent improvements in multidetector CT (MDCT) technology, including its improved temporal and spatial resolution, facilitate the precise timing of multiphasic imaging, and have also increased the accuracy of CT for lesion detection and characterisation in the pancreas [2]. However, there are still certain problematic imaging scenarios such as the early detection of pancreatic adenocarcinoma, detection of occult neoplasms in the setting of acute or chronic pancreatitis, accuracy of pre-operative surgical staging of pancreatic malignancy and characterisation of pancreatic cystic lesions. For example, with surgical resection, a 5-year survival rate of 20% is possible only when a pancreatic cancer is small (,2 cm diameter) and there is no peripancreatic invasion [3]. Unfortunately, however, only 10-15% of pancreatic carcinomas are in this category, resulting in an overall poor survival rate [4]. These problems could be related to the inherent, limited soft-tissue contrast of MDCT or to the limited difference in vascularity between normal parenchyma and pathological lesions. Therefore, if the contrast between pancreatic lesions and pancreatic parenchyma is improved on CT scans,...

Improved Image Quality and Detectability of Hypovascular Liver Metastases on DECT with Different Adjusted Window Settings

“…In their study, the differences in CNR between the images with a weighting factor of 0.3 and the images with a weighting factor of 0.5 or 0.7 were statistically significant (different?) among the cystic lesions and solid hypovascular tumors (p: 0.05) [15]. Therefore, this might be another important parameter in addition to WS with influence on the image quality and conspicuity of hypovascular lesions.…”

An Update of Clinical CT Imaging of Pancreatic Neoplasm: Tips, Tricks, and Pitfalls

“…However, there are issues regarding detection of small and/or isodense appearing pancreatic lesions [15]. Studies have shown that the use of low tube voltage increases the attenuation value of contrast material (iodine) owing to the increased photoelectric effect [16,17]. This may increase contrast between normal pancreatic parenchyma and pancreatic lesions, thus improving lesion detection.…”

“…The more common of these include virtual noncontrast enhanced (VNE), iodine material density (which enhance the conspicuity of iodine), and mono energetic images. A variety of types of material density images can be created that allow for the identification, semi quantification, or elimination from images of a wide range of materials based on their behavior at low and high energies [16,18] (Fig. 2).…”

Pancreas

“…7.17) [58]. A calculated mean radiation dose saving of 14 % was achieved if the standard unenhanced dataset was omitted [58].…”

“…7.17) [58]. A calculated mean radiation dose saving of 14 % was achieved if the standard unenhanced dataset was omitted [58]. Another study [59] showed that virtual unenhanced images from a dualenergy dataset acquired during the pancreatic parenchymal phase demonstrated no significant difference in image quality and provided less image noise than true unenhanced imaging.…”