Young-Nyun Park

Accuracy of gadoxetic acid-enhanced magnetic resonance imaging for the diagnosis of sinusoidal obstruction syndrome in patients with chemotherapy-treated colorectal liver metastases

AbstractObjectiveTo assess whether reticular hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced magnetic resonance imaging (EOB-MRI) is a diagnostic finding of sinusoidal obstruction syndrome (SOS) in patients with hepatic metastases who have undergone chemotherapy.MethodsWe retrospectively analysed EOB-MRI of 42 patients who had undergone chemotherapy before hepatic resection of colorectal hepatic metastases. Two radiologists, who were unaware of whether or not the patients had SOS, reviewed the hepatobiliary phase images to determine the presence of hypointense reticulation in the liver using a 5-point scale. The sensitivity, specificity and area under the receiver operating characteristics curve (Az) were calculated for each reviewer.ResultsThe sensitivity, specificity and Az for the diagnosis of SOS were 75%, 100% and 0.957 for reader 1 and 75%, 96.2% and 0.936 for reader 2, respectively. In one patient who received a false-positive diagnosis by one reader, there was sinusoidal fibrosis on histological examination, but not diagnostic for SOS. False-negative diagnosis occurred in four patients for both readers; histology of these patients showed minimal and localised sinusoidal congestion and fibrosis.ConclusionsReticular hypointensity on hepatobiliary phase images of EOB-MRI is highly specific for the diagnosis of SOS in patients with treated colorectal hepatic metastases.Key Points• Gadoxetic acid enhanced magnetic resonance imaging (EOB-MRI) can identify the sinusoidal obstruction syndrome (SOS) • The diagnosis can be achieved with high specificity and good interobserver agreement. • SOS typically demonstrates diffuse hypointensity on hepatobiliary phase images on EOB-MRI. • EOB-MRI may be falsely negative in patients with minimal degree of SOS.

Position and vibration control of a flexible robot manipulator using hybrid controller

In this work, position and vibration control problem of a flexible robot arm with a voice coil type actuator is investigated. For the vibration suppression, a voice coil type actuator is designed and is implemented using H∞ control scheme, in order to guarantee the controlled system robust against unmodeled higher-order mode vibration of the arm, output sensor noise, etc. A fuzzy logic based controller is used for the position and vibration control of the joint hub. Experimental results confirm that the proposed hybrid control scheme of combining fuzzy logic and H∞ controller achieves efficient positioning and vibration suppression performances.

Robust roll control of a vehicle: Experimental study using a hardware-in-the-loop set-up

Abstract This paper presents a simcopy IMulation and experimcopy IMental study of a vehicle with an electrically actuated roll control system. The controller is designed in the framework of an output feedback H∞ control scheme based on the three-degree-of-freedom linear vehicle model. Various parameters which affect the roll dynamics are considered for robust stability and disturbance rejection. In order to investigate the feasibility of the active roll control system, its performance is evaluated by simcopy IMulation in a full vehicle model with non-linear tyre characteristics. After that, an electrically actuated roll control system is devised, which imcopy IMproves the high frequency isolation during inoperative periods. Finally, its performance is investigated by experimcopy IMental work using a hardware-in-the-loop set-up with the devised control system.

Single Hepatocellular Carcinoma: Preoperative MR Imaging to Predict Early Recurrence after Curative Resection

PURPOSE To identify magnetic resonance (MR) imaging features that enable prediction of early recurrence (<2 years) after curative resection of hepatocellular carcinoma (HCC) and to derive a preoperative prediction model. MATERIALS AND METHODS This retrospective study was approved by the institutional review board. The requirement to obtain written informed consent was waived. A total of 268 patients who underwent hepatic resection for a single HCC from January 2008 to August 2011 were divided into two cohorts: a training cohort, which was used to derive a prediction model (n = 187), and a validation cohort (n = 81). All MR images from the training cohort were reviewed by two radiologists. A prediction model was constructed by using MR imaging features that were independently associated with early recurrence with use of multiple logistic regression analysis. The performance of the prediction model in the validation cohort was evaluated with respect to discrimination (ie, whether the relative ranking of individual predictions of subsequent early recurrence is in the correct order). RESULTS In the training cohort, four MR imaging features were independently associated with early recurrence: rim enhancement (odds ratio [OR] = 3.83; 95% confidence interval [CI]: 1.39, 10.52), peritumoral parenchymal enhancement in the arterial phase (OR = 2.64; 95% CI: 1.27, 5.46), satellite nodule (OR = 4.07; 95% CI: 1.09, 15.21), and tumor size (OR = 1.66; 95% CI: 1.31, 2.09). A prediction model derived from these variables showed an area under the receiver operating characteristic curve (AUC) of 0.788 in the prediction of the risk of early recurrence in the training cohort. When applied to the validation cohort, this model showed good discrimination (AUC, 0.783). CONCLUSION The prediction model derived from rim enhancement, peritumoral parenchymal enhancement, satellite nodule, and tumor size can be used preoperatively to estimate the risk of early recurrence after resection of a single HCC.

Clinicopathologic implication of hepatic progenitor cell marker expression in hepatoblastoma.

Hepatic progenitor cells (HPCs) are thought to play a role in hepatoblastoma, as hepatoblastomas are characterized by an immature histology and a wide variety of cell lineages. We aimed to investigate the extent of expression of HPCs marker and its clinical implication in hepatoblastoma. We collected 61 hepatoblastomas and 9 childhood hepatocellular carcinomas (HCCs) and performed immunohistochemistry for HPC markers, including cytokeratin 19 (CK19), octamer-binding transcription factor 3/4 (Oct-3/4), epithelial cell adhesion molecule (EpCAM), and delta-like 1 homolog (DLK1). Of the hepatoblastoma samples, 27/61 (44.3%), 21/61 (34.4%), 51/61 (83.6%) and 56/61 (91.8%) exhibited positivity for CK19, Oct-3/4, EpCAM and DLK-1, respectively. For HCCs, the rates of expression were 22.2% (CK19), 77.8% (EpCAM) and 77.8% (DLK-1). Oct-3/4 was not expressed in HCC cells. Hepatoblastomas with a poorly differentiated epithelial component had a higher incidence of CK19 and Oct-3/4 expression than those with a well differentiated epithelial component (p=0.005 and 0.037, respectively). Higher disease stage of hepatoblastoma was correlated with CK19 expression (p=0.043). Oct-3/4-positive hepatoblastomas were associated with short disease-free survival (p=0.035). Both hepatoblastomas and childhood HCCs, therefore, exhibit characteristics of HPCs, and the poor prognosis of patients with Oct-3/4-positive hepatoblastoma suggests that stem-like properties affect hepatoblastoma pathogenicity.

Gene expression profiling of human hepatoblastoma using archived formalin-fixed and paraffin-embedded tissues

We elucidated the genetic profile of hepatoblastomas (HBLs) to identify diagnostic and prognostic markers. RNA was extracted from 32 formalin-fixed, paraffin-embedded HBLs and corresponding nonneoplastic liver (NNL) tissues, and cDNA-mediated annealing, selection, extension, and ligation (DASL) chip assays were performed. Immunohistochemistry was performed to confirm the expression of Yin Yang 1 (YY1) protein in HBL. Twenty-four genes that were associated with signal transduction, cell–cell adhesion, cell cycle regulation, and apoptosis were differentially expressed in HBL and NNL tissues. Two apoptosis-associated genes, MYCN and BIRC5, were highly upregulated in HBL. Eight genes, including YY1 and IGF1, were upregulated in HBL cases that had a poor prognosis. Thirty-eight genes, including YY1, were differentially expressed according to histologic differentiation of HBL, and the immunohistochemical expression of YY1 was correlated with poor HBL differentiation. Thus, using DASL chip assays, we report the gene expression profiles of HBL, which suggest new candidate prognostic and diagnostic genetic markers and putative therapeutic targets for HBL.

Improvement of foamed ionic polymer metal composites actuator

Research was carried out on a foamed ionic polymer metal composite (IPMC) to improve actuation performance. Foamed IPMC is manufactured from a foamed membrane with micro-sized cells formed via a microcellular foaming process, which is a technology used to form and control micro-sized cells in plastics. We measured the changes in the blocked force and free bending displacement of foamed IPMC as the applied voltage increased. The maximum change in displacement was caused by a foaming rate of 20%. Finally, thick Nafion was fabricated via casting and foaming processes, and then tested.