Effects of spatial frequency on visual evoked magnetic fields

Psychophysical and visual evoked potential (VEP) studies have shown that spatial frequency of a visual stimulus affects contrast sensitivity and VEPs in humans. However, it is not clear whether and how the effect of spatial frequency varies among cortical areas. Considering that all visual inputs to the retina could be expressed as a sum of sinusoidal gratings of different spatial frequencies, the effect of spatial frequency must be clarified to separate the brain activity specific to each visual stimulus. In order to examine the effect of spatial frequency on different cortical areas, the present study compared cortical responses to sinusoidal gratings of seven different spatial frequencies using magnetoencephalography (MEG). MEG waveforms of twelve healthy adults in response to sinusoidal gratings of 0.3–18.1 cycles per degree were subjected to a multi-dipole analysis. As a result, the effect of spatial frequency was significant on the first peak latency and amplitude of the source activity around V1 and V2 but not on the source activity around V3 and V6, indicating that the effect of spatial frequency varies across different visual areas in the human brain. Our results also suggest that the responses in V1 and V2 that have a peak around 90 ms and that of V6 peaking around 120 ms should be separated to investigate the stimulus-specific cortical response, particularly when examining effects of spatial frequency on the response latency.     

Wound dressing composed of hyaluronic acid and collagen containing EGF or bFGF: comparative culture study

We developed a novel wound dressing composed of a hyaluronic acid (HA) and collagen (Col) spongy sheet containing epidermal growth factor (EGF) or basic fibrolast growth factor (bFGF) by freeze-drying method (EGF-wound dressing or bFGF-wound dressing, respectively). A wound dressing without any growth factor was prepared as a control in a similar manner as above (C-wound dressing). Intermolecular cross-linkage between Col molecules was induced by UV irradiation. The release behavior of free HA from the wound dressing was investigated using a C-wound dressing. The weight of C-wound dressing after 1 day, 3, 5, and 7?days of incubation on top of a Col gel sheet at the air–water interface (wound surface model) was 55, 36, 30, and 19% of the original weight, respectively. Most free HA and a part of Col was released from the cross-linked Col network in the wound dressing during incubation, as the original Col content in the wound dressing was 33%. Next, fibroblast proliferation was assessed in conventional culture medium preconditioned by immersion of a piece of C-, EGF-, or bFGF-wound dressing, i.e. C-conditioned medium, EGF-conditioned medium, or bFGF-conditioned medium. Cell proliferation in C-conditioned medium increased to approximately the same level as that in conventional medium. Cell proliferation in EGF- and bFGF-conditioned medium was 1.9 times and 2.6 times greater than that in conventional medium after 7?days of cultivation, respectively. Finally, cytokine production of fibroblasts was assessed in a wound surface model using a fibroblast-incorporating Col gel sheet (cultured dermal substitute [CDS]). CDS was elevated to the air–medium interface, on which each wound dressing was placed and cultured for 7?days. Fibroblasts in CDS covered with EGF-wound dressing released 3.6 times more vascular endothelial growth factor (VEGF) and 4.6 times more hepatocyte growth factor (HGF) when compared with the C-wound dressing. Fibroblasts in CDS covered with bFGF-wound dressing released 10.2 times more VEGF and 6.3 times more HGF when compared with the C-wound dressing. This finding indicates that bFGF-wound dressing can facilitate more effectively the VEGF and FGF production compared with EGF-wound dressing.     

Assessing Blood Flow in an Intracranial Stent: A Feasibility Study of MR Angiography Using a Silent Scan after Stent-Assisted Coil Embolization for Anterior Circulation Aneurysms

BACKGROUND AND PURPOSE:Blood flow in an intracranial stent cannot be visualized with 3D time-of-flight MR angiography owing to magnetic susceptibility and radiofrequency shielding. As a novel follow-up tool after stent-assisted coil embolization, we applied MRA by using a Silent Scan algorithm that contains an ultrashort TE combined with an arterial spin-labeling technique (Silent MRA). The purpose of this study was to determine whether Silent MRA could visualize flow in an intracranial stent placed in the anterior circulation.MATERIALS AND METHODS:Nine patients treated with stent-assisted coil embolization for anterior circulation aneurysms underwent MRAs (Silent MRA and TOF MRA) and x-ray digital subtraction angiography. MRAs were performed in the same session on a 3T unit. Two neuroradiologists independently reviewed the MRA images and subjectively scored flow in a stent as 1 (not visible) to 4 (excellent) by referring to the latest x-ray digital subtraction angiography image as a criterion standard.RESULTS:Both observers gave MRA higher scores than TOF MRA for flow in a stent in all cases. The mean score for Silent MRA was 3.44 ± 0.53, and for TOF MRA, it was 1.44 ± 0.46 (P < .001).CONCLUSIONS:Silent MRA was able to visualize flow in an intracranial stent more effectively than TOF MRA. Silent MRA might be useful for follow-up imaging after stent-assisted coil embolization, though these study results may be only preliminary due to some limitations.

Endovascular therapy for intracranial aneurysms has been widely used since the International Subarachnoid Aneurysm Trial.¹ The number of cases of coil embolization for aneurysms is increasing, and the stent-protection technique has widened the applicability to cases that had been otherwise difficult to treat with conventional coil embolization.² Nevertheless, there is a risk of coil compaction or in-stent restenosis after stent-assisted coil embolization. X-ray digital subtraction angiography is the optimal technique used to examine these adverse events, and it is commonly used as a follow-up tool after using an intracranial stent. However, DSA presents some unavoidable risks related to the catheter procedure, radiation, and contrast media.^3–53D time-of-flight MR angiography is widely used for the assessment of cerebral vascular diseases and has also been examined as a noninvasive substitute for DSA.^6–9 These studies generally reported difficulty in visualizing flow in a stent with TOF MRA because of magnetic susceptibility and radiofrequency shielding, though some beneficial aspects were observed in assessing the residual lumen of aneurysms. As a novel follow-up tool after stent-assisted coil embolization, we applied MRA by using a Silent Scan algorithm (GE Healthcare, Milwaukee, Wisconsin) that contains an ultrashort TE combined with an arterial spin-labeling technique (Silent MRA). In this situation, visualizing flow means visualizing arterial geometry and patency. It does not mean directly visualizing blood flow rate. The purpose of this study was to determine whether Silent MRA can visualize flow in an intracranial stent placed at the anterior circulation.     

Pancreatic Follicular Lymphoma Presenting as Acute Pancreatitis: Report of a Case

Pancreatic B-cell lymphoma is rare; it accounts for 0.2% to 2.0% of extranodal non-Hodgkin lymphoma, and constitutes less than 0.5% of all pancreatic malignancies. Most histologic types of the pancreatic lymphoma are diffuse large B-cell lymphoma, and follicular lymphoma is quite rare. We report here a case of pancreatic follicular lymphoma that was initially detected by acute pancreatitis. This is the first reported case of pancreatic follicular lymphoma presenting with acute pancreatitis. A 71-year-old woman had epigastric and left upper quadrant abdominal pain. Computed tomography (CT) revealed features of acute pancreatitis. After standard therapy for pancreatitis, enhanced CT showed a pancreatic tumor (50 × 35 mm) in the body of the pancreas with gradual enhancement. Endoscopic retrograde cholangiopancreatography and magnetic resonance cholangiopancreatography showed a complete interruption of the pancreatic duct in the body, with mild dilation of the duct in the tail of the pancreas. Endoscopic ultrasonography revealed hypervascularity of the pancreatic tumor. The patient underwent distal pancreatectomy to remove the cause of pancreatitis and to disclose the diagnosis. Histologic examination revealed follicular lymphoma of pancreas. Despite recent improvement in clinical strategies, differential diagnosis between pancreatic lymphoma and pancreatic cancer is still difficult without histologic information. Pancreatic lymphoma should be considered as a differential diagnosis in a patient who initially presents with acute pancreatitis.Key words: Pancreatic lymphoma, Acute pancreatitis, Follicular lymphomaPancreatic B-cell lymphoma is rare; it accounts for 0.2% to 2.0% of extranodal non-Hodgkin lymphoma¹ and constitutes less than 0.5% of all pancreatic malignancies.^2,3 Most histologic types of pancreatic lymphoma are diffuse large B-cell lymphoma, and follicular lymphoma is quite rare. In addition, acute pancreatitis caused by pancreatic lymphoma is also rare.Despite recent improvements in clinical strategies, differential diagnosis of pancreatic lymphoma with pancreatic cancer or autoimmune pancreatitis (AIP) is still difficult without histologic examination.We report here a rare case of a 71-year-old female with pancreatic follicular lymphoma that initially presented as acute pancreatitis.     

Spontaneous rupture of metastatic α-fetoprotein-producing gastric cancer of the liver

An 80-year-old man was admitted to our hospital because of the rupture of the liver. Laboratory data showed iron-deficiency anemia, although there was no liver dysfunction. A computed tomography scan showed large liver tumor with intraperitoneal hemorrhage, and since a serum level of α-fetoprotein (AFP) was extremely high, we initially suspected a rupture of hepatocellular carcinoma (HCC). Transarterial embolization was performed to stop bleeding from the tumor, followed by an endoscopic examination that revealed advanced gastric cancer. Histological analysis revealed that both the gastric and the hepatic tumors were moderately to poorly differentiated adenocarcinoma, as well as that both tumors were immunohistochemically positive for AFP. Finally, we diagnosed AFP-producing gastric cancer associated with liver metastasis. Rupture of metastatic liver cancer is rare, and accordingly, distinction from HCC is important, particularly for the cases of AFP-producing gastric cancer.     

Simulation analysis of three intubating supraglottic devices during infant chest compression

Current guidelines for pediatric cardiopulmonary resuscitation suggest that supraglottic devices are alternatives for tracheal intubation with minimal interruption of chest compression. We examined the utility of three intubating supraglottic devices, air‐Q® (air‐Q), Ambu® aura‐i (aura‐i), and i‐gel® (i‐gel), utilizing manikin simulation. Twenty‐two novice physicians performed securing of airway on an infant manikin with the three devices. We measured the rate of success on ventilation and the insertion time with or without chest compression. Successful ventilation rate did not significantly decrease with chest compression in the three devices (without chest compression: air‐Q, 21/22; aura‐i, 20/22; i‐gel, 20/22, during chest compression: air‐Q, 20/22; aura‐i, 20/22; i‐gel, 18/22). The insertion time with air‐Q and aura‐i did not extend significantly for chest compression. In contrast, the insertion time with i‐gel was significantly extended in chest compression (P < 0.05). Air‐Q and aura‐i are more useful for airway management during chest compression than i‐gel.     

Advances in reduced port laparoscopic liver resection

Reduced port surgery has been attracting attention in the field of minimally invasive surgery. Although the use of SILS is becoming widespread, technical difficulty has delayed its adoption for laparoscopic liver resection. Recently, advances in laparoscopic liver resection have been made in tandem with advances in surgical skill and devices. The main driver in conventional laparoscopic liver resection's evolution to become less surgically invasive seems to be single‐incision laparoscopic liver resection (SILLR). To date, most reports on SILLR have been single case reports or case series. Only a few cohort studies on conventional laparoscopic surgery and SILLR have been conducted. Recent reports have described the use of SILLR for well‐localized lesions and solitary tumors located in the anterolateral segments of the liver or left liver lobe, but its application remains limited to partial resection and left lateral sectionectomy. The feasibility and safety of SILLR have been demonstrated, but additional work is needed for standardization of the procedure.     

Multicentric Castleman's disease associated with renal amyloidosis and pure red cell aplasia

 A 50-year-old man was admitted suffering from severe anemia and renal dysfunction. He had been admitted for the first time at the age of 49, and was diagnosed with multicentric Castleman's disease (MCD) and secondary amyloidosis. At that time, marked erythroid hypoplasia was demonstrated by both aspiration and biopsy of bone marrow. A diagnosis of pure red-cell aplasia (PRCA) was made. Immunosuppressive agents improved his symptoms and laboratory data. We report here a very rare case of PRCA following MCD and amyloidosis, and with reference to the literature, we discuss the relation between MCD and related diseases. Received: February 12, 1998 / Accepted: June 17, 1998