Strong and Stable Magnetorheological Fluids Based on Flaky Sendust-Co0.4Fe0.4Ni0.2 Nanocomposite Particles.

The magnetorheological (MR) performance of suspensions based on magnetic (flaky Sendust (FS))-magnetic (Co0.4Fe0.4Ni0.2) nanocomposite particles was investigated by using a vibrating sample magnetometer and a rotational rheometer. Flaky Sendust@Co0.4Fe0.4Ni0.2 nanocomposite particles were fabricated through wet chemical synthesis of Co0.4Fe0.4Ni0.2 on the surface of FS. The density of the resultant FS@Co0.4Fe0.4Ni0.2 was less than that of FS due to the pore/void formation in the composite particles. Because of the high saturation magnetization of Co0.4Fe0.4Ni0.2 (165 emu/g), FS@Co0.4Fe0.4Ni0.2 (145 emu/g) exhibited greater magnetization than bare FS (130 emu/g), which resulted in the good performance of FS@Co0.4Fe0.4Ni0.2-based MR fluids: the suspension exhibited a remarkably high yield stress, almost one order greater than that of MR fluids based on hierarchically structured (HS) Fe3O4 particles. In addition, the high drag coefficient of FS@Co0.4Fe0.4Ni0.2 in the liquid medium, in conjunction with its lower density, resulted in a substantially improved long-term stability, better than that of Co0.4Fe0.4Ni0.2- or FS-based suspensions. Although the density of the FS@Co0.4Fe0.4Ni0.2 nanoparticles is higher than that of HS-Fe3O4 particles, their stability is much better than the stability of HS-Fe3O4 particle's suspension. Manufactured magnetic-magnetic nanocomposite particles provide a feasible MR suspension of high MR performance and long-term stability.

High-Performance Magnetorheological Suspensions of Pickering-Emulsion-Polymerized Polystyrene/Fe3O4 Particles with Enhanced Stability.

The magnetorheological (MR) performance of suspensions based on core-shell-structured foamed polystyrene (PSF)/Fe3O4 particles was investigated by using a vibrating sample magnetometer and a rotational rheometer. Core-shell-structured polystyrene (PS)/Fe3O4 was synthesized by using the Pickering-emulsion polymerization method in which Fe3O4 nanoparticles were added as a solid surfactant. Foaming the PS core in PS/Fe3O4 particles was carried out by using a supercritical carbon dioxide (scCO2) fluid. The density was measured by a pycnometer. The densities of PS/Fe3O4 and PSF/Fe3O4 particles were significantly lowered from that of the pure Fe3O4 particle after Pickering-emulsion polymerization and foaming treatment. All tested suspensions displayed similar MR behaviors but different yield strengths. The important parameter that determined the MR performance was not the particle density but rather the surface density of Fe3O4 on the PS core surface. The morphology was observed by scanning electron microscopy and transmission electron microscopy. Most Fe3O4 particles stayed on the surface of PS/Fe3O4 particles, making the surface topology bumpy and rough, which decreased the particle sedimentation velocity. Finally, Turbiscan apparatus was used to examine the sedimentation properties of different particle suspensions. The suspensions of PS/Fe3O4 and PSF/Fe3O4 showed remarkably improved stability against sedimentation, much better than the bare Fe3O4 particle suspension because of the reduced density mismatch between the nanoparticles and the carrier medium as well as the surface topology change.

Developing an Intelligent Automatic Appendix Extraction Method from Ultrasonography Based on Fuzzy ART and Image Processing.

Ultrasound examination (US) does a key role in the diagnosis and management of the patients with clinically suspected appendicitis which is the most common abdominal surgical emergency. Among the various sonographic findings of appendicitis, outer diameter of the appendix is most important. Therefore, clear delineation of the appendix on US images is essential. In this paper, we propose a new intelligent method to extract appendix automatically from abdominal sonographic images as a basic building block of developing such an intelligent tool for medical practitioners. Knowing that the appendix is located at the lower organ area below the bottom fascia line, we conduct a series of image processing techniques to find the fascia line correctly. And then we apply fuzzy ART learning algorithm to the organ area in order to extract appendix accurately. The experiment verifies that the proposed method is highly accurate (successful in 38 out of 40 cases) in extracting appendix.

Sonographic findings of high-grade and non-high-grade ductal carcinoma in situ of the breast.

OBJECTIVE: The purpose of this study was to differentiate between high-grade and non-high-grade ductal carcinoma in situ (DCIS) of the breast on sonography. METHODS: From October 2003 to August 2009, 76 DCIS lesions in 73 women who underwent sonography and mammography were included in this study. Lesions were confirmed by mastectomy, breast-conserving surgery, or surgical biopsy. Images were analyzed by 2 radiologists with consensus and were correlated with histologic grades. RESULTS: Of the 76 lesions, 44 were classified as high--grade and 32 as non-high-grade DCIS. Fifty-seven lesions (75.0%) were identified on sonography, which revealed a mass in 30 cases, microcalcifications in 20, ductal changes in 4, and architectural distortion in 3. All cases with false-negative findings on sonography (n = 19) showed microcalcifications on mammography. On sonography, masses were more frequently found in non-high-grade (62.5%) than high-grade DCIS (22.7%; P < .01). No significant difference was seen in the sonographic features of masses between high-grade and non-high-grade DCIS. Microcalcifications were more common in high-grade (43.2%) than non-high-grade (3.1%) DCIS (P = .02). Most sonographically visible microcalcifications had associated findings such as ductal changes (n = 11), a mass (n = 7), or a hypoechoic area (n = 5). The detection rate of microcalcifications on sonography was higher in high-grade (62.9%) than non-high-grade DCIS (25.0%; P = .023). CONCLUSIONS: Microcalcifications with associated ductal changes (11 of 31 [35.5%]) were the most common sonographic findings in high-grade DCIS. An irregular hypoechoic mass with an indistinct and microlobulated margin (13 of 26 [50.0%]) was the most frequent finding in non-high-grade DCIS.

Comparison of gadoxetic acid-enhanced MR imaging versus four-phase multi-detector row computed tomography in assessing tumor regression after radiofrequency ablation in subjects with hepatocellular carcinomas.

PURPOSE: To assess the diagnostic value of gadoxetic acid-enhanced magnetic resonance (MR) imaging in follow-up of patients with hepatocellular carcinomas (HCCs) who were treated with radiofrequency (RF) ablation and to compare it with that of four-phase multi-detector row computed tomography (CT). MATERIALS AND METHODS: From July 2007 to May 2008, 36 patients (43 HCCs) were enrolled who were treated with RF ablation (tumor size, 20-47 mm; mean, 24.5 mm) and underwent gadoxetic acid-enhanced MR imaging and four-phase (precontrast, arterial, portal venous, and equilibrium) multidetector CT for follow-up. Two radiologists independently reviewed these images, and conspicuity of tumor margins and detection of residual or recurrent tumor were assessed on a five-point scale with receiver operating characteristic (ROC) curve analysis. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were evaluated. RESULTS: The mean conspicuity value of tumor margins was significantly higher on MR imaging than on multidetector CT (P < .001). The degree of differentiation between residual/recurrent tumor and hyperemia was significantly greater on MR imaging (P < .001). The mean area under the ROC curve was significantly higher with MR imaging (P = .015), as were sensitivity, specificity, PPV, NPV, and accuracy of detection rate (mean, 100%, 96.2%, 82.4%, 100%, and 96.7%, respectively, vs 41.7%, 56.8%, 13.5%, 85.7%, and 54.7% for multidetector CT). The interobserver agreement rate for MR imaging was higher (0.919) than for multidetector CT (0.672; P < .05). CONCLUSIONS: Diagnostic accuracy, conspicuity of tumor margins, and detection rate of residual or recurrent tumor were found to be better with gadoxetic acid-enhanced MR imaging than with four-phase multidetector CT.

Major complications after radio-frequency thermal ablation of hepatic tumors: spectrum of imaging findings.

Although radio-frequency (RF) ablation has been accepted as a promising and safe technique for treatment of unresectable hepatic tumors, investigation of its complications has been limited. According to the multicenter (1,139 patients in 11 institutions) survey data of the Korean Study Group of Radiofrequency Ablation, a spectrum of complications occurred after RF ablation of hepatic tumors. The prevalence of major complications was 2.43%. The most common complications were hepatic abscess (0.66%), peritoneal hemorrhage (0.46%), biloma (0.20%), ground pad burn (0.20%), pneumothorax (0.20%), and vasovagal reflex (0.13%). Other complications were biliary stricture, diaphragmatic injury, gastric ulcer, hemothorax, hepatic failure, hepatic infarction, renal infarction, sepsis, and transient ischemic attack. One procedure-related death (0.09%) occurred (due to peritoneal hemorrhage). Three important strategies for decreasing the rate of complications are prevention, early detection, and proper management. A physician who performs RF ablation of hepatic malignancies should be aware of the broad spectrum of major complications so that these strategies can be used.