Takeshi Matsumura

Gray-scale second harmonic imaging of the liver with galactose-based microbubbles

RATIONALE AND OBJECTIVESnThe authors evaluate the efficacy of SHU 508A, a galactose-based contrast agent used in gray-scale second harmonic imaging in vitro and in vivo experiments.nnnMETHODSnA Toshiba prototype harmonic imaging system (2.5/5.0 MHz) was used with SHU 508A in a phantom experiment and to image the liver in five healthy rabbits and one rabbit that had VX-2 tumors in the liver.nnnRESULTSnIn the second harmonic imaging, most of the fundamental components of the backscattered echo were eliminated, and good images with high contrast were obtained in the phantom experiment. Liver parenchyma was enhanced clearly in all rabbits at 0.3 mL/kg, an effect that lasted for 90 seconds. The tumor, which was mostly necrotic, was depicted clearly as a negative enhanced area surrounded by enhanced healthy liver.nnnCONCLUSIONSnGray-scale second harmonic imaging is a promising new method for visualization of perfusion of organs.

Gray scale second harmonic imaging of the liver: A preliminary animal study

Gray scale second harmonic imaging (2.5 MHz/5.0 MHz) was evaluated in preliminary animal studies with a new ultrasound contrast agent (FS069). FS069 was administered intravenously in 10 rabbits (6 with normal liver, and 4 with implanted VX-2 tumors) and two woodchucks with hepatocellular carcinomas. The vasculature (including tumor vessels) and liver parenchyma were clearly enhanced at a low dosage (optimal dose was from 0.1 to 0.2 mL/kg) in all cases. Enhancement was reproducible and generally dose-dependent. Tumors were enhanced well during the early phase and tumor enhancement disappeared earlier than that of surrounding normal liver. Arterial phase and portal phase were easily distinguished and patterns of enhancement were diagnostic of the tumors. Gray scale second harmonic imaging is useful in the detection of hepatic tumors and in diagnosis of their hemodynamics.

Liver targeting of human interferon-β with pullulan based on metal coordination

Abstract Although interferon (IFN)-β is widely used for the elimination of hepatitis C virus in patients with chronic liver disease, its clinical efficacy is unsatisfactory. Targeting IFN-β to the liver might enhance its efficacy without increasing its side effects. The objective of the present study was to target IFN-β to the liver to enhance its biological activity and reduce its side effects. A chelating residue, diethylenetriaminepentaacetic acid (DTPA), was introduced to pullulan, a water-soluble polysaccharide with a high affinity to the liver (DTPA-pullulan) and natural human IFN-β was coordinately conjugated with the DTPA-pullulan by mixing in an aqueous solution containing zinc ions (Zn 2+ ). Intravenous injection of the IFN-β-DTPA-pullulan conjugate with Zn 2+ coordination into mice enhanced induction of an antiviral enzyme, 2′,5′-oligoadenylate synthetase (2-5AS), specifically in the liver to a significantly greater extent than free natural IFN-β. The enhanced 2-5AS level in the liver depended on the molar mixing ratio of IFN-β, DTPA residue of the DTPA-pullulan, and Zn 2+ . Moreover, the duration of the liver 2-5AS induction by the IFN-β-DTPA-pullulan conjugate was longer than that by free natural IFN-β. Thus, human IFN-β-DTPA-pullulan conjugate appears to be applicable for clinical use, which is promising for treatment of patients with chronic hepatitis C.

Field experiment of long-distance broadband communications in TV white space using IEEE 802.22 and IEEE 802.11af

A field experiment of TV White Space (TVWS) communications was conducted using developed systems following IEEE 802.22 and IEEE 802.11af standards and succeeded to have the world first throughput, distance, and application testing. The IEEE 802.22 system achieved throughput of 4.5 Mbps for uplink and 5.2 Mbps for downlink over 12.7 km. Also, feasibility of applications such as web browsing, video streaming and video talk was confirmed in multi-hop network where the IEEE 802.22 system was a backbone link and IEEE 802.11af was access area expansion. Furthermore, aggregating bandwidth of two discontinuous TV channels, throughput of 15.5 Mbps for downlink and 9.0 Mbps for uplink was achieved over 6.3 km.

Ultrasonographic arterial portography with second harmonic imaging: Evaluation of hepatic parenchymal enhancement with portal venous flow

Ultrasonographic arterial portography was evaluated with second harmonic and conventional gray scale imaging after the administration of 0.001 to 0.1 ml/kg of FS069 (Optison) in 10 dogs (four dogs with ligation of the portal vein branch) and two woodchucks with hepatocellular carcinomas. Harmonic imaging was required to obtain good liver parenchymal enhancement for ultrasonographic arterial portography to be useful. The tumors were visible as regions of greater enhancement after intravenous injection and as hypoechoic regions after superior mesenteric artery injection. The segments with portal vein ligation were not detected after intravenous injection but were clearly seen after superior mesenteric artery injection. Doppler signal measurement verified a significant difference between the portal vein and hepatic vein after superior mesenteric artery injection and in the femoral artery after intravenous versus superior mesenteric artery injection, demonstrating that minimal levels of FS069 pass through the liver.

Bandwidth-tunable filter consisting of SAW resonators and BaSrTiO 3 varactors directly fabricated on a LiTaO 3 wafer

A prototyped bandwidth-tunable filter consisting of SAW resonators and BaSrTiO3 (BST) varactors is discussed in this paper. In general, the BST varactors require high deposition temperature (>600°C) in order to obtain good varactor performances. Thus special cared wafer integration process of BST varactors onto a 42°YX-LiTaO3 wafer was newly developed to prevent performance deterioration in SAW resonators. The bandwidth-tunable filter composed of ten pieces of both surface acoustic wave (SAW) resonators and BST varactors on the 42°YX-LiTaO3 substrate was successfully fabricated using the integration process. The measured center frequency of the filter is 1GHz, and the 3dB bandwidth is electrically tuned from 4.5 to 9.6MHz by adjusting a DC supply voltage from 0 to 10V.

Sonographic detection of tumor blood flow using a new contrast agent in woodchuck hepatomas

The aim of this study was to assess the ability of perfluoropropane‐filled albumin microspheres to visualize tumor blood flow in woodchuck hepatomas. Ten tumors in five woodchucks with hepatomas were imaged before and after intravenous injection (dosages of 0.01 ml/kg to 2.0 ml/kg) of an agent using color Doppler sonography and gray scale ultrasonography. Both enhanced imaging modalities demonstrated blood flow around and within all tumors. Enhanced gray scale ultrasonography demonstrated sonographic tumor blush in seven tumors (70%). In conclusion, tumor blood flow in woodchucks was visualized more clearly using the agent on both color Doppler and gray scale ultrasonography.

Prototype of IEEE 802.11af-Based Baseband IC Enabling Compact Device for Wireless Local Area Network Systems in TV White-Spaces

In this paper, we present the world’s first prototype of the IEEE 802.11af-based baseband (BB) integrated circuit (IC) enabling compact, low power consumption and even low cost TV white-space (TVWS) devices. Although it has been already over three years since the IEEE 802.11af was standardized in December 2013 as a wireless local area network (WLAN) system utilizing the TVWS, the IEEE 802.11af-based system has not been commercially deployed yet due to difficulties in downsizing, power saving, cost reduction, etc. As well as conventional WLAN systems, an integration of the BB signal processing circuits is one of the promising technologies that can resolve these concerns. The prototype BB IC incorporates IEEE 802.11af physical layer and low-medium access control functions, buffer memories, and interface circuits, thus enabling easy installation, and easy control by connection to a host device via the universal serial bus interface. In addition, we also develop the compact radio frequency (RF) front-end circuit with variable circuits and filters based on the direct conversion scheme by using an off-the-shelf RF IC. By incorporating the prototype BB IC and the RF front-end circuit, we successfully prototype compact card-type TVWS devices in all-in-one package including an antenna. The practicality of the prototype BB IC is demonstrated by characterizing the card-type TVWS devices in respect to transmission and reception performance and throughput.

Compact IEEE 802.22-based radio equipment enabling easy installation for regional area network system using TV white-spaces

The IEEE 802.22 system was standardized in 2011 as a fixed wireless communication system for regional area networks using TV white-spaces (TVWS). Due to its wide coverage area of 10–30 km, the IEEE 802.22 system is expected as a backbone wireless network system in developing countries as well as a public safety broadband communication system even in leading countries. This wide coverage enables a reduction of the number of base stations, resulting in the initial-cost saving compared to other communication systems. However, previously prototyped IEEE 802.22-based devices have not been deployed for social demonstrations, because there still have difficulties in cost and procurement due to the costly design such as FPGA-based baseband signal processing and specially customized RF components to comply with the strict spectrum limitations by some leading countries. In this paper, we prototype compact and lightweight IEEE 802.22-based radio equipment by applying mixed design using an FPGA and a DSP. Measured transmission spectrum conforms to Ofcom and FCC regulations with a transmit power of +30 dBm and +24 dBm, respectively. Also, measured receiver sensitivity achieves the requirement of the IEEE 802.22 system, and a maximal UDP throughput of 14.86 Mbit/s was obtained on the conditions of PHY mode 16 with a 6 MHz channel bandwidth and a 1/4 CP length.

Development of TV White-Space LTE Devices Complying with Regulation in UK Digital Terrestrial TV Band

Recently, white-space communication system has been widely promoted as one of the spectrum sharing technologies for further efficient use of spectrum resource. In particular, white-spaces in the TV bands (TVWS, TV white-spaces) have attracted attentions worldwide and regulations have been established in the U.S.A, the U.K., Singapore, etc. In the U.K., pilot program has been started based on regulations established by the Ofcom and trial operation of TVWS communication systems in cooperation with authenticated white-space databases has been performed from July 2014. In this trial, to avoid interference with primary users such as TV broadcasters and wireless microphones, draft rules established by ETSI are employed as specifications of radio characteristics. In this study, to verify the feasibility of spectrum expansion of mobile communication systems by utilizing the TVWS, the authors have developed TVWS LTE devices complying with the Ofcom rules and performed field experiment in the U.K. Prototyped devices have been licensed by the Ofcom and TVWS LTE system has been successfully demonstrated in London urban area. As a result, it is confirmed that the existing LTE system can be operated in the U.K. TVWS without interference with the primary users. This is the first report on prototype of TVWS LTE devices conforming to the ETSI draft specification.