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Objective The extracellular volume (ECV) calculated based on contrast-enhanced computed tomography (CT) has been reported as a novel imaging parameter reflecting the morphological change of fibrosis in several parenchymal organs. Our retrospective study assessed the validity of the ECV fraction for diagnosing pancreatic fibrosis and the appropriate imaging condition as the "equilibrium phase". Methods In 27 patients undergoing multiphasic CT and subsequent pancreaticoduodenectomy, we investigated pathological fibrotic changes related to the ECV fraction and conducted analyses using the value obtained by subtracting the equilibrium CT value of the portal vein from that of the abdominal aorta (Ao-PV equilibrium ) to estimate eligibility of the equilibrium phase. Results In all patients, the ECV fraction showed a weak positive correlation with the collagenous compartment ratio (r=0.388, p=0.045). All patients were divided into two groups - the high-Ao-PV equilibrium group and low-Ao-PV equilibrium group - based on the median value. No significant correlation was found in the high-Ao-PV equilibrium group, whereas a significant correlation was observed in the low-Ao-PV equilibrium group (r=0.566, p=0.035). Conclusion The ECV fraction is a possible predictive factor for histopathological pancreatic fibrosis. In its clinical application, the eligibility of the "equilibrium phase" may affect the diagnostic capability. It will be necessary to verify the imaging conditions in order to improve the accuracy of the diagnosis.

When it comes to improving cancer therapies, one challenge is to identify key biological parameters that prevent immune escape and maintain an equilibrium state characterized by a stable subclinical tumor mass, controlled by the immune cells. Based on a space and size structured partial differential equation model, we developed numerical methods that allow us to predict the shape of the equilibrium at low cost, without running simulations of the initial-boundary value problem. In turn, the computation of the equilibrium state allowed us to apply global sensitivity analysis methods that assess which and how parameters influence the residual tumor mass. This analysis reveals that the elimination rate of tumor cells by immune cells far exceeds the influence of the other parameters on the equilibrium size of the tumor. Moreover, combining parameters that sustain and strengthen the antitumor immune response also proves more efficient at maintaining the tumor in a long-lasting equilibrium state. Applied to the biological parameters that define each type of cancer, such numerical investigations can provide hints for the design and optimization of cancer treatments., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Atsou, Khou, Anjuère, Braud and Goudon.)

Purpose: To compare abdominal equilibrium phase (EP) CT images of obese and non-obese patients to identify the reconstruction method that preserves the diagnostic value of images obtained in obese patients., Methods: We compared EP images of 50 obese patients whose body mass index (BMI) exceeded 25 (group 1) with EP images of 50 non-obese patients (BMI < 25, group 2). Group 1 images were subjected to deep learning reconstruction (DLR), hybrid iterative reconstruction (hybrid-IR), and model-based IR (MBIR), group 2 images to hybrid-IR; group 2 hybrid-IR images served as the reference standard. A radiologist recorded the standard deviation of attenuation in the paraspinal muscle as the image noise. The overall image quality was assessed by 3 other radiologists; they used a confidence scale ranging from 1 (unacceptable) to 5 (excellent). Non-inferiority and potential superiority were assessed., Results: With respect to the image noise, group 1 DLR- were superior to group 2 hybrid-IR images; group 1 hybrid-IR- and MBIR images were neither superior nor non-inferior to group 2 hybrid-IR images. The quality scores of only DLR images in group 1 were superior to hybrid-IR images of group 2 while the quality scores of group 1 hybrid-IR- and MBIR images were neither superior nor non-inferior to group 2 hybrid-IR images., Conclusions: DLR preserved the quality of EP images obtained in obese patients., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The recent success of immunotherapies for the treatment of cancer has highlighted the importance of the interactions between tumor and immune cells. Mathematical models of tumor growth are needed to faithfully reproduce and predict the spatiotemporal dynamics of tumor growth. We introduce a mathematical model intended to describe by means of a system of partial differential equations the early stages of the interactions between effector immune cells and tumor cells. The model is structured in size and space, and it takes into account the migration of the tumor antigen-specific cytotoxic effector cells towards the tumor micro-environment by a chemotactic mechanism. We investigate on numerical grounds the role of the key parameters of the model such as the division and growth rates of the tumor cells, and the conversion and death rates of the immune cells. Our main findings are two-fold. Firstly, the model exhibits a possible control of the tumor growth by the immune response; nevertheless, the control is not complete in the sense that the asymptotic equilibrium states keep residual tumors and activated immune cells. Secondly, space heterogeneities of the source of immune cells can significantly reduce the efficiency of the control dynamics, making patterns of remission-recurrence appear., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Purpose: To assess whether extracellular volume fraction (ECV) calculated from iodine(-blood) density images (I-B) of dual-energy liver CT (DECT) equilibrium phase data (EqD) is useful in estimating the degree of liver fibrosis., Materials and Methods: Consecutive 52 patients with chronic liver disease who underwent fast kV switching DECT and liver MR elastography (MRE) were retrospectively enrolled. Iodine(-water) density images (I-W) and I-B generated from EqD and ECV were calculated. As blood pools, abdominal aorta (Ao) and suprahepatic inferior vena cava (IVC) were chosen, and, therefore, 4 types of ECV (ECV I-W Ao , ECV I-W IVC , ECV I-B Ao , ECV I-B IVC ) were obtained. ECV was also calculated using conventional method (ECV conv Ao ). The correlation coefficients (R 2 or rho) of these five ECVs versus liver stiffness (MRE) or pathologically proven fibrosis grades were compared., Results: As for correlation with liver stiffness, R 2 for ECV conv.Ao , ECV I-W Ao , ECV I-B Ao , ECV I-W IVC , and ECV I-B IVC , were 0.26, 0.34, 0.44, 0.39, and 0.52, respectively (all p < 0.0001). Histopathological correlation was available in 28 patients, and rho values were 0.61, 0.60, 0.71, 0.68, and 0.76, respectively (all p < 0.001)., Conclusion: ECV I-B IVC calculated from EqD of DECT is useful in estimating the degree of liver fibrosis.

Objectives: To assess whether extracellular volume fraction (ECV) obtained from routine liver CT equilibrium phase data utilizing new subtraction algorithm is useful in estimating the degree of liver fibrosis., Materials and Methods: Consecutive 41 patients, 21 men and 20 women, with chronic liver diseases who underwent quadri-phase liver CT and MR elastography within 3 months were retrospectively enrolled. Subtraction image of unenhanced from equilibrium phase (240 s) images using conventional and new algorithms were made. We firstly assessed the quality of these subtraction algorithms using patients in whom anatomical misregistration between the two image sets were prominent. Then, ECVs were calculated using both subtraction data sets (ECV-convSub, and ECV-newSub, respectively). ECV were also calculated by traditional manual method (ECV-man). Correlation coefficients of 3 types of ECV were compared using liver stiffness (kPa) as measured by MR elastography and pathologically proven fibrosis grades as reference standards., Results: For eleven patients with prominent anatomical misregistration between the unenhanced and equilibrium phases, new algorithm provided significantly better subtraction images than the conventional one (p = 0.001, Wilcoxon's signed rank test). As for correlation with liver stiffness, R 2 for ECV-man, ECV-convSub, and ECV-newSub, were 0.57, 0.59, and 0.66, respectively (all p < 0.0001, Pearson's correlation). Histological assessment for fibrosis grades were available in 20 patients, and rho values for these three ECVs were 0.66, 0.61, and 0.71, respectively (all p < 0.01, Spearman's rank correlation)., Conclusion: ECV-newSub showed better correlation to liver stiffness and pathological fibrosis grades than ECV-convSub and ECV-man, which could be a reliable biomarker of liver fibrosis obtained from routine clinical diagnostic imaging data, where equilibrium phase delay time was set at 240 s., (Copyright © 2018 Elsevier B.V. All rights reserved.)