Search

Intracholecystic papillary neoplasm (ICPN) of the gallbladder is a premalignant lesion. An ICPN arising from the cystic duct is rare. A woman in her 60s exhibited dilatation of the common bile duct on computed tomography (CT) performed for screening of respiratory disease. The CT revealed an enhancing mass, 3.3 cm in diameter, in the cystic duct. Endoscopic ultrasonography showed a well-demarcated, hyperechoic mass in the dilated cystic duct. Endoscopic retrograde cholangiography showed that the common bile duct was slightly retracted by the dilated cystic duct. Cytological analysis of the bile juice did not show any evidence of malignancy. She was diagnosed with a cystic bile duct tumor suggestive of ICPN. Cholecystectomy, resection of the extrahepatic bile duct, and lymph node dissection were performed. Macroscopically, the papillary-proliferated tumor was localized to the cystic duct. No critical lesions were evident in the common bile duct. Histologically, the tumor in the cystic duct showed intraluminal growth with a papillary configuration without malignancy. Based on these findings, the tumor was diagnosed as an ICPN. We encountered a rare case of ICPN localized to the cystic duct of the gallbladder.

Castleman’s disease (CD) arising from the hepatoduodenal ligament is extremely rare. A 32-year-old man was referred to a clinic with nausea. He was found to have an abdominal mass by ultrasonography and consulted our hospital for further examination. Computed tomography revealed an equally enhancing mass, 5.2 cm in diameter, adjacent to the duodenum. On magnetic resonance imaging, the mass revealed a slightly iso-intensity signal equal to smooth muscle on T1-weighted imaging, a slightly high-intensity signal on T2-weighted imaging, and a high-intensity signal on diffusion-weighted imaging. Endoscopic ultrasonography showed a well-demarcated hypoechoic mass adjacent to the duodenum. The Doppler echo pattern indicated abundant blood flow. The preoperative diagnosis was a duodenal gastrointestinal stromal tumor. The patient underwent laparotomy and tumor excision. The finding of the intraoperative frozen section was CD. Histologically, the lymph follicles were markedly increased in number throughout the cortex and medulla with vascular proliferation and hyalinization in the intra- or extra-follicles. The germinal centers were atrophic and surrounded by concentrically arranged layers of small lymphocytes. The histological findings were the hyaline vascular variant of CD. If a hypervascular solid mass is detected in the abdomen, CD should be considered in the differential diagnosis.

The Japanese interplanetary probe Hayabusa2 was launched on December 3, 2014 and the probe arrived at the vicinity of asteroid 162173 Ryugu on June 27, 2018. During its 1.4 years of asteroid proximity phase, the probe successfully accomplished numbers of record-breaking achievements including two touchdowns and one artificial cratering experiment, which are highly expected to have secured surface and subsurface samples from the asteroid inside its sample container for the first time in history. The Hayabusa2 spacecraft was designed not to orbit but to hover above the asteroid along the sub-Earth line. This orbital and geometrical configuration allows the spacecraft to utilize its high-gain antennas for telecommunication with the ground station on Earth while pointing its scientific observation and navigation sensors at the asteroid. This paper focuses on the regular station-keeping operation of Hayabusa2, which is called “home position” (HP)-keeping operation. First, together with the spacecraft design, an operation scheme called HP navigation (HPNAV), which includes a daily trajectory control and scientific observations as regular activities, is introduced. Following the description on the guidance, navigation, and control design as well as the framework of optical and radiometric navigation, the results of the HP-keeping operation including trajectory estimation and delta-V planning during the entire asteroid proximity phase are summarized and evaluated as a first report. Consequently, this paper states that the HP-keeping operation in the framework of HPNAV had succeeded without critical incidents, and the number of trajectory control delta-Vwas planned efficiently throughout the period.

In late 2018, the asteroid Ryugu was in the Sun’s shadow during the superior solar conjunction phase. As the Sun-Earth-Ryugu angle decreased to below 3°, the Hayabusa2 spacecraft experienced 21 days of planned blackout in the Earth-probe communication link. This was the first time a spacecraft had experienced solar conjunction while hovering around a minor body. For the safety of the spacecraft, a low energy transfer trajectory named Ayu was designed in the Hill reference frame to increase its altitude from 20 to 110 km. The trajectory was planned with the newly developed optNEAR tool and validated with real time data. This article shows the results of the conjunction operation, from planning to flight data.

Carbonaceous (C-type) asteroids1are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites2,3and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth’s atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)4onboard the spacecraft Hayabusa25, indicating that the asteroid’s boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m−2s−0.5K−1(300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites6and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect7,8. We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites6. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity9of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies10.

The present paper describes a case of hemorrhagic cholecystitis in a patient on maintenance dialysis. The patient presented with right upper quadrant abdominal pain. Computed tomography revealed swelling of the gallbladder, high- and isodensity contents of the gallbladder, and high-density stone in the gallbladder neck. He was hospitalized for suspected acute cholecystitis. After hospitalization, his levels of total bilirubin, aspartate aminotransferase, and alanine aminotransferase increased. T2-weighted magnetic resonance imaging showed low-intensity contents expanded to include a wide area from the common bile duct to the cystic duct and gallbladder neck. Endoscopic retrograde cholangiopancreatography revealed clotting from the duodenal papilla. After cannulation of the bile duct, old blood and pus began to flow from the mammary papilla, and an endoscopic nasobiliary drainage tube was placed. After his liver function had improved, the patient underwent laparoscopic cholecystectomy. His sample revealed that the gallbladder was filled with blood clots and stones. His postoperative course was uneventful and he was discharged on day 19 after the procedure. Although hemorrhagic cholecystitis is rare, it should be considered as a differential diagnosis for patients on dialysis who have acute abdominal symptoms.

In this study, we determined the alignment of the laser altimeter aboard Hayabusa2 with respect to the spacecraft using in-flight data. Since the laser altimeter data were used to estimate the trajectory of the Hayabusa2 spacecraft, the pointing direction of the altimeter needed to be accurately determined. The boresight direction of the receiving telescope was estimated by comparing elevations of the laser altimeter data and camera images, and was confirmed by identifying prominent terrains of other datasets. The estimated boresight direction obtained by the laser link experiment in the winter of 2015, during the Earth’s gravity assist operation period, differed from the direction estimated in this study, which fell on another part of the candidate direction; this was not selected in a previous study. Assuming that the uncertainty of alignment determination of the laser altimeter boresight was 4.6 pixels in the camera image, the trajectory error of the spacecraft in the cross- and/or along-track directions was determined to be 0.4, 2.1, or 8.6 m for altitudes of 1, 5, or 20 km, respectively.

The precise orbit of the Hayabusa2 spacecraft with respect to asteroid Ryugu is dynamically determined using the data sets collected by the spacecraft’s onboard laser altimeter (LIght Detection And Ranging, LIDAR) and automated image tracking (AIT). The LIDAR range data and the AIT angular data play complementary roles because LIDAR is sensitive to the line-of-sight direction from Hayabusa2 to Ryugu, while the AIT is sensitive to the directions perpendicular to it. Using LIDAR and AIT, all six components of the initial state vector can be derived stably, which is difficult to achieve using only LIDAR or AIT. The coefficient of solar radiation pressure (SRP) of the Hayabusa2 spacecraft and standard gravitational parameter (GM) of Ryugu can also be estimated in the orbit determination process, by combining multiple orbit arcs at various altitudes. In the process of orbit determination, the Ryugu-fixed coordinate of the center of the LIDAR spot is determined by fitting the range data geometrically to the topography of Ryugu using the Markov Chain Monte Carlo method. Such an approach is effective for realizing the rapid convergence of the solution. The root mean squares of the residuals of the observed minus computed values of the range and brightness-centroid direction of the image are 1.36 m and 0.0270°, respectively. The estimated values of the GM of Ryugu and a correction factor to our initial SRP model are 29.8 ± 0.3 m3/s2and 1.13 ± 0.16, respectively.