Ice front blocking of ocean heat transport to an Antarctic ice shelf.

Mass loss from the Antarctic Ice Sheet to the ocean has increased in recent decades, largely because the thinning of its floating ice shelves has allowed the outflow of grounded ice to accelerate1,2. Enhanced basal melting of the ice shelves is thought to be the ultimate driver of change2,3, motivating a recent focus on the processes that control ocean heat transport onto and across the seabed of the Antarctic continental shelf towards the ice4-6. However, the shoreward heat flux typically far exceeds that required to match observed melt rates2,7,8, suggesting that other critical controls exist. Here we show that the depth-independent (barotropic) component of the heat flow towards an ice shelf is blocked by the marked step shape of the ice front, and that only the depth-varying (baroclinic) component, which is typically much smaller, can enter the sub-ice cavity. Our results arise from direct observations of the Getz Ice Shelf system and laboratory experiments on a rotating platform. A similar blocking of the barotropic component may occur in other areas with comparable ice-bathymetry configurations, which may explain why changes in the density structure of the water column have been found to be a better indicator of basal melt rate variability than the heat transported onto the continental shelf9. Representing the step topography of the ice front accurately in models is thus important for simulating ocean heat fluxes and induced melt rates.

CuO and CeO2-doped catalytic material synthesized from red mud and rice husk ash for p-xylene deep oxidation.

CuO-CeO2 catalysts supported on material synthesized from red mud and rice husk ash (CuO-CeO2/ZRM) were prepared by co-impregnation method. The role of CeO2 additive in the improvement of physicochemical properties and catalytic activity of CuO-CeO2/ZRM catalysts were emphasized. Several techniques, including Brunauer-Emmett-Teller Nitrogen physisorption measurements, X-ray powder diffraction, hydrogen temperature programed reduction, scanning electron microscopy and transmission electron microscopy (TEM) were used to investigate the properties of catalysts. Crystallite size calculated by Scherrer' equation was 17.4 - 21.8 nm. Modification of 5 wt% CuO/ZRM catalyst with CeO2 had reduced the size of the nanoparticles leading to a significant enhancement of the catalytic activity in p-xylene deep oxidation at temperature range of 275 - 400 °C. The 5 wt% CuO/ZRM sample promoted by 3 wt% of nanoparticle CeO2 with the average size of 17.5 nm and BET surface area of 31.3 m2 g-1 exhibited the best activity for p-xylene deep oxidation. In this sample, the conversion of p-xylene reaches to 90% at 350 °C.

Seasonal variability of ocean circulation near the Dotson Ice Shelf, Antarctica.

Recent rapid thinning of West Antarctic ice shelves are believed to be caused by intrusions of warm deep water that induce basal melting and seaward meltwater export. This study uses data from three bottom-mounted mooring arrays to show seasonal variability and local forcing for the currents moving into and out of the Dotson ice shelf cavity. A southward flow of warm, salty water had maximum current velocities along the eastern channel slope, while northward outflows of freshened ice shelf meltwater spread at intermediate depth above the western slope. The inflow correlated with the local ocean surface stress curl. At the western slope, meltwater outflows followed the warm influx along the eastern slope with a ~2-3 month delay. Ocean circulation near Dotson Ice Shelf, affected by sea ice distribution and wind, appears to significantly control the inflow of warm water and subsequent ice shelf melting on seasonal time-scales.

Isolated perihepatic tuberculosis: imaging findings.

AIM: To review the imaging findings of isolated perihepatic tuberculosis without coexistent active tuberculosis elsewhere in the body. MATERIALS AND METHODS: Over a 9-year period, six patients with histopathologically proven perihepatic tuberculosis without simultaneous active tuberculosis elsewhere in the body were included in this study. Two radiologists retrospectively evaluated in consensus the location (right, left, or both perihepatic spaces), size (maximum diameter), morphology (ovoid or round), number, attenuation (low-, iso-, or high-attenuation compared with the adjacent liver parenchyma), and the presence or absence of contrast enhancement of the lesions on computed tomography (CT), and echogenicity (low-, iso-, or high-echogenicity compared with the adjacent liver parenchyma) of the lesions on ultrasonography. RESULTS: On CT, an isolated perihepatic lesion was located in the right perihepatic space in five patients, whereas three lesions were located in both perihepatic spaces in the remaining patient. The mean maximum diameter of the isolated perihepatic tuberculosis lesions was 29.7 mm. Isolated perihepatic tuberculosis appeared as an ovoid-shaped, homogeneous, and low-attenuating (n=5) or high-attenuating (n=1) lesion relative to the liver. There was peripheral rim enhancement of the lesion in two patients. On ultrasonography, isolated perihepatic tuberculosis was revealed as a homogeneous, low-echoic (n=5) or iso-echoic (n=1) lesion relative to the liver. CONCLUSION: Although various inflammatory or malignant lesions can be located in the perihepatic space, isolated perihepatic tuberculosis appears an ovoid-shaped, homogeneous, and low-attenuating or low-echoic lesion compared with the liver parenchyma on CT or ultrasonography.

MR imaging analysis of heterogeneous leiomyomas of the uterus.

Thirty-six leiomyomas from the same number of patients that were heterogeneous on MR imaging were evaluated for analyzing their MR patterns and for differentiating each type of secondary changes by means of MR imaging-pathologic correlation. The tumors with a mean diameter of 9 cm could be classified into 4 patterns depending on the morphological appearance of signal intensity: speckled (n = 14); nodular (n = 11); cystic (n = 9); or indeterminate (n = 2). Speckled pattern was associated with a mild degree of hyaline or myxoid degeneration or focal necrosis. Nodular pattern was caused by necrosis or cellular leiomyoma, and cystic pattern was related to severe hyaline or myxoid degeneration or necrosis. Each type of secondary changes within leiomyomas showed distinctive MR findings, if they were severely involved. However, use of an additional contrast-enhanced study was necessary in some instances for further clarification. MR imaging has a potential in distinguishing each type of secondary changes that occur in leiomyomas. Various degenerative changes occur in approximately 65% of uterine leiomyomas, and are caused mainly by alteration in the blood supply originating from rapid growth, pregnancy, mechanical accident, and postmenopausal atrophy. These changes include hyaline, mucoid, or myxoid degeneration, calcification, cystic changes, necrosis (red degeneration), and fatty metamorphosis. It is well known that the presence of degenerative changes within leiomyomas can be predicted on MR imaging by a heterogeneous signal intensity on T2-weighted images, although clear distinction of each type of degeneration can not be made by this modality. Recently, cellular leiomyoma, one of the variants of leiomyomas, was also reported to cause heterogeneous signal intensity. However, because various other uterine tumors can also have similar signal intensity on MR imaging, further evaluation for the heterogeneous leiomyomas appears to be necessary. The purpose of our study was to analyze the patterns of heterogeneous leiomyomas and to differentiate each type of secondary changes by means of MR imaging-pathologic correlation.

Zinc deficiency manifested by dermatitis and visual dysfunction in a patient with Crohn's disease.

We report a case of Crohn's disease with low serum zinc concentration in a 26-year-old woman. She demonstrated acrodermatitis enteropathica and decreased visual acuity during total parenteral nutrition. Subsequent intravenous zinc supplementation resulted in alleviation of the skin lesions and improvement of visual acuity. This case supports the notion that depressed serum zinc in Crohn's disease may cause clinical manifestations, such as acrodermatitis enteropathica and retinal dysfunction, which may be correctable with zinc supplementation.

Biliary ascariasis: MR cholangiography findings in two cases.

We describe the imaging features of two cases of biliary ascariasis. Ultrasonography and CT showed no specific abnormal findings, but MR cholangiography clearly demonstrated an intraductal linear filling defect that led to the correct diagnosis. MR cholangiography is thus a useful technique for the diagnosis of biliary ascariasis.

Usefulness of MR imaging for diseases of the small intestine: comparison with CT.

OBJECTIVE: To evaluate the usefulness of MR imaging for diseases of the small intestine, emphasizing a comparison with CT. MATERIALS AND METHODS: Thirty-four patients who underwent both CT and MR imaging using FLASH 2D and HASTE sequences were analyzed. All patients had various small bowel diseases with variable association of peritoneal lesions. We compared the detectabilities of CT and MR imaging using different MR pulse sequences. The capability for analyzing the characteristics of small intestinal disease was also compared. RESULTS: MR imaging was nearly equal to CT for detecting intraluminal or peritoneal masses, lesions in the bowel and mesentery, and small bowel obstruction, but was definitely inferior for detecting omental lesions. The most successful MR imaging sequence was HASTE for demonstrating bowel wall thickening, coronal FLASH 2D for mesenteric lesions, and axial FLASH 2D for omental lesions. MR imaging yielded greater information than CT in six of 12 inflammatory bowel diseases, while it was equal to CT in six of seven neoplasms and inferior in five of seven mesenteric ischemia. In determining the primary causes of 15 intestinal obstructions, MR imaging was correct in 11 (73%) and CT in nine (60%) patients. CONCLUSION: MR imaging can serve as an alternative diagnostic tool for patients with suspected inflammatory bowel disease, small intestinal neoplasm or obstruction.

CT in the early detection of strangulation in intestinal obstruction.

The role of CT in evaluating the gastrointestinal tract has increased recently because CT demonstrates pathological conditions involving the bowels, mesenteric vessels, and peritoneal cavity well. In patients who have an intestinal obstruction, the observation of both bowel loop configuration and mesenteric vessels on CT is the key to identifying the site and cause of obstruction and determining the absence or presence of intestinal strangulation. Although many clinical and radiological findings reported in the literature are not seen in the early stages of intestinal strangulation, CT might assist in its early detection. This article reviews the clinical, pathophysiological, and radiological aspects of strangulating obstruction with emphasis on the role of CT in its early diagnosis.

CT and MR diagnoses of intestinal ischemia.

CT and MR imaging have an important role in establishing the diagnosis of mesenteric ischemia. However, without specific signs such as thromboembolism in the mesenteric vessel, intramural or portal venous gas, and the absence of bowel wall enhancement, mesenteric ischemia can be confused with inflammatory or neoplastic gastrointestinal diseases. Arterial or venous occlusion or low-flow state are the main direct causes of mesenteric ischemia. Delayed diagnosis in equivocal cases can be avoided through an understanding of the patholophysiological aspects of mesenteric ischemia as they occur in a variety of other conditions, including: thromboembolism, bowel obstruction, neoplasm, vasculitis, inflammatory diseases, trauma, and drug or radiation therapy.

Medial discoid meniscus completely coalesced with the anterior cruciate ligament.

Medial discoid meniscus is an uncommon abnormality. To date, only a few reports have described the associated anomaly with discoid meniscus. However, there are no reports on medial discoid meniscus accompanied by an anomaly of the meniscus itself. The authors found that a medial discoid meniscus completely coalesced with the anterior cruciate ligament. This anomaly strongly supports the congenital development theory of discoid meniscus. Both magnetic resonance imaging and the arthroscopic findings are presented. The patient was treated successfully by saucerization of the discoid meniscus up to the torn edge. This was accomplished by closely cutting the meniscus around the anterior cruciate ligament with an electric cutter.

CT-guided liver biopsy: an update.

Computed tomography (CT)-guided liver biopsy has become an accepted part of the diagnostic evaluation of patients with benign and malignant hepatic disease The advantages of imaging guidance over blind percutaneous biopsy are now well established in the literature. Controversy continues to exist, however, over the safety and accuracy of the procedure, as well as over the proper choice of needle: large-caliber cutting needle versus small caliber aspiration needle. In 1984, our group reported the results in a preliminary set of 180 patients in whom CT-guided biopsy of focal liver lesions was performed. The study indicated that cutting-needle sampling could provide increased diagnostic accuracy over fine-needle aspiration in both benign and malignant hepatic disease without a significant increase in complications. This paper reports the results in a series of 179 new patients who underwent CT-guided liver biopsy using a variety of needles. Comparison is again made between fine-needle and cutting-needle biopsy with respect to diagnostic accuracy and safety. A detailed discussion of the proper choice of biopsy needle as well as of the causes of both biopsy failure and complications is provided.

Gastric schwannomas: radiological features with endoscopic and pathological correlation.

AIM: To describe the radiological, endoscopic, and pathological findings of gastric schwannomas in 16 patients. MATERIALS AND METHODS: The radiological, endoscopic, and pathological findings of 16 surgically proven cases of gastric schwannoma were retrospectively reviewed. All patients underwent computed tomography (CT) and four patients were evaluated with upper gastrointestinal series. Two radiologists reviewed the CT and upper gastrointestinal series images by consensus with regard to tumour size, contour, margin, and growth pattern, the presence or absence of ulcer, cystic change, and the CT enhancement pattern. Endoscopy was performed in eight of these 16 patients. Six patients underwent endoscopic ultrasonography. Pathological specimens were obtained from and reviewed in all 16 patients. Immunohistochemistry was performed for c-kit, CD34, smooth muscle actin, and S-100 protein. RESULTS: On radiographic examination, gastric schwannomas appeared as submucosal tumours with the CT features of well-demarcated, homogeneous, and uncommonly ulcerated masses. Endoscopy with endoscopic ultrasonography demonstrated homogeneous, submucosal masses contiguous with the muscularis propria in all six examined cases. On pathological examination, gastric schwannomas appeared as well-circumscribed and homogeneous tumours in the muscularis propria and consisted microscopically of interlacing bundles of spindle cells. Strong positivity for S-100 protein was demonstrated in all 16 cases on immunohistochemistry. CONCLUSION: Gastric schwannomas appear as submucosal tumours of the stomach and have well-demarcated and homogeneous features on CT, endoscopic ultrasonography, and gross pathology. Immunohistochemistry consistently reveals positivity for S-100 protein in the tumours.

Primary sclerosing lipogranuloma of the rectum: CT findings.

Sclerosing lipogranuloma is a rare, benign disease which is a peculiar granulomatous reaction of fatty tissue. This disease affects multiple organs and the majority of cases are secondary to exogenous foreign bodies. The authors report a case of primary sclerosing lipogranuloma of the rectum mimicking a submucosal rectal tumour.

Autoimmune pancreatitis: radiologic findings in 20 patients.

BACKGROUND: Autoimmune pancreatitis is a new clinical entity that is characterized by peculiar histopathologic and laboratory findings and by a dramatic clinical response to corticosteroid therapy. We evaluated the radiologic findings of autoimmune pancreatitis. METHODS: Computed tomographic, magnetic resonance imaging, endoscopic retrograde cholangiopancreatographic, and ultrasonographic findings of 20 patients with autoimmune pancreatitis in our hospital between November 2000 and December 2003 were retrospectively reviewed regarding changes and ancillary findings in the pancreatic parenchyma, the main pancreatic duct, peripancreatic vessels, and distal common bile duct. In addition, follow-up images were reviewed for changes in any abnormality seen on the initial examinations. RESULTS: Pancreatic parenchymal enlargement was invariably seen that was diffuse (n = 19) or focal (n = 1), with homogeneous contrast enhancement on computed tomography (n = 20) and magnetic resonance imaging (n = 15). Capsule-like rim enhancement was seen in six patients. There was focal (n = 18) or diffuse (n = 2) narrowing of the main pancreatic duct and it was usually multifocal (n = 17) in the former. Narrowing of the peripancreatic veins was seen in 14 patients. There was tapered (n = 15) or abrupt (n = 3) narrowing of the distal common bile duct in 18 patients, with contrast enhancement of the narrowed segment in eight. Invariably, changes in the pancreatic parenchyma, main pancreatic duct, peripancreatic vessels, and common bile duct were normalized on follow-up studies after steroid therapy. CONCLUSION: In this series, common radiologic findings of autoimmune pancreatitis were (a) diffuse pancreas enlargement, (b) multifocal narrowing of the main pancreatic duct, (c) narrowing of peripancreatic veins, and (d) tapered narrowing of the distal common bile duct with frequent contrast enhancement. These findings were usually reversible with steroid therapy.

Secretin-stimulated MRCP.

Secretin-stimulated magnetic resonance cholangiopancreatography not only facilitate the depiction of anatomic variations or morphologic changes of the pancreatic duct in the normal and diseased pancreas but also help assessing functional abnormalities of the exocrine pancreas. In this article, we illustrate findings of normal pancreas and various pancreatic diseases on magnetic resonance cholangiopancreatography after secretin stimulation.

Gastric cancer by multidetector row CT: preoperative staging.

The role of computed tomography (CT) in the preoperative staging of gastric cancer, even if controversial, may be fundamental for evaluating the local extent and nodal involvement of the disease, especially in locally advanced cases. However, previous results of CT staging have not been satisfactory for predicting the invasive depth of the tumor or possible nodal metastases. Recently introduced multidetector row CT (MDCT) and three-dimensional (3D) imaging are expected to overcome the limitations in cancer staging by offering rapid and accurate information for space perception, detailed hemodynamics, and real-time 3D processing of volumetric data sets. In particular, virtual endoscopic imaging may be helpful for detecting early gastric cancer. In our experience, T and N stagings of gastric cancer were improved with 3D MDCT when using volume rendering and virtual endoscopic imaging compared with conventional axial two-dimensional (2D) CT (accuracy of T staging with 3D vs. 2D CT images, 84% vs. 77%; accuracy of N staging, 63% vs. 61% with 3D vs. 2D images, respectively). In particular, the detection rate of early gastric cancer was markedly increased up to 96% when using 3D MDCT. Therefore, we believe that 3D MDCT of the stomach may enhance the performance of CT in the preoperative evaluation of patients who have gastric cancer by offering easy early detection of lesions and accurate tumor staging through the 3D imaging process.

Abdominal cavernous Iymphangiomas: CT findings.

Two adult patients with histopathologically proved cavernous lymphangiomas and one adult patient with lymphangiomas of strongly presumed cavernous type by cytologic and computed tomographic findings are reported. On computed tomograms, multiple, aggregated, small, and tiny cysts without a solid portion, along the lymphatic channels are characteristic computed tomographic findings for cavernous lymphangiomas.

CT interpretation of gastrointestinal tract diseases.

Most inflammatory, neoplastic and vascular disorders manifest bowel wall thickening on computed tomography (CT). Therefore, it is very important to understand the patterns of bowel wall involvement (degree, length, symmetry and contrast enhancement patterns) in each category to make a correct diagnosis. Observing extraluminal changes also help to classify the primary causes of pathological conditions involving the gastrointestinal tract. Adequate CT examinations with optimal opacification of the gastrointestinal tract are essential not only to avoid false positive findings but also to detect subtle or minimal lesions. If findings for establishing a diagnosis are equivocal, the use of combined findings increases the diagnostic accuracy of CT.

CT analysis of postoperative tumor recurrence patterns in periampullary cancer.

BACKGROUND: We analyzed postoperative tumor recurrence in periampullary cancer on computed tomography (CT). METHODS: Forty-six patients with tumor recurrence (16 pancreas head cancers, 19 distal common bile duct cancers, and 11 ampulla of Vater cancers) of 125 patients who underwent surgery for periampullary cancer were enrolled. Recurrence was diagnosed by CT findings plus elevated CA 19-9 (n = 28) or biopsy (n = 18). Two radiologists retrospectively reviewed 156 contrast-enhanced CT scans, with 7-mm slice thickness, obtained in our institution until the initial diagnosis of tumor recurrence. The modes of recurrence were classified as local recurrence, hepatic metastasis, lymph node metastasis, peritoneal carcinomatosis, or extraabdominal metastasis. We evaluated the time of recurrence, the frequency of each mode of recurrence, and the earliest mode of recurrence. The differences in tumor recurrence for the three types of periampullary cancer were evaluated. RESULTS: Half of the recurrences occurred within 6 months after surgery and 87% occurred within 12 months after surgery. Local recurrences (67%), hepatic metastases (72%), and lymph node metastases (61%) were common modes of tumor recurrence. Pancreas head cancers recurred earlier than the other types of periampullary cancer (p < 0.05). CONCLUSION: Periampullary cancer tends to recur early after surgery, usually as a local recurrence, hepatic metastasis, or lymph node metastasis.