Tolerable performance of silicon photonic optical-serial-to-parallel converter with variable power splitter.

We have proposed and investigated the tolerable performance of an optical serial-to-parallel converter with phase operation (OSPC) with lower power consumption than the conventional scheme for the purpose of achieving reduction of both the processing load and the processing latency of the high-speed packet switching systems in the data center. The target OSPC consists of Mach-Zehnder delay interferometers (MZDIs) and balanced photodetectors with silicon (Si) photonic technology. However, we have confirmed that the performance becomes degraded due to optical propagation losses of the delay lines in MZDIs. To solve this issue, unbalanced splitting ratio of a multi-mode interferometer (MMI)-type couplers in the MZDIs has been investigated, but we have found the necessity of improving the tolerance of the splitting ratio deviation. In this paper, we will analytically and experimentally demonstrate the improvement of the characteristics by using an OSPC with variable splitting ratio optical coupler (VSOC) consisting of a symmetric Mach-Zehnder interferometer (MZI). By observing the transmission spectra of the device with various applied voltage to the heater, controllability of peak-to-valley ratios of transmission spectra was observed. In addition, splitting ratio of the output symmetric MMI almost matches well with that of the optimized peak-to-valley ratios of transmission spectra by using short-optical pulse injection. We have confirmed the tolerable performance of the Si-photonic OSPC by using VSOC with the symmetric MZI.

Thoracic Intra and Extramedullary Capillary Hemangioma with Subacute Clinical Course: A Case Report and Literature Review.

Capillary hemangiomas are benign tumors comprising a lobulated proliferation of capillary vessels frequently located in the soft tissues of the neck and head. Spinal intradural capillary hemangiomas are rare, particularly intramedullary lesions. To our knowledge, only 31 cases of spinal intramedullary capillary hemangiomas have been reported. Here, we describe a rare case of a thoracic capillary hemangioma comprising extramedullary and intramedullary components. A 51-year-old male patient presented with bilateral lower extremity numbness and subsequent paraparesis, sensory disturbance, and bladder-bowel dysfunction with a subacute clinical course. Magnetic resonance imaging revealed a mass lesion with intramedullary and intradural extramedullary components at the Th9-10 vertebrae level and widespread spinal cord edema. Contrast-enhanced computed tomography revealed abnormal vessels on the dorsal spinal cord surface. Spinal angiography revealed a light-stained mass lesion fed by the radiculopial artery from the right Th11 intercostal artery. The tumor was resected en bloc, and the histological diagnosis was a capillary hemangioma. Postoperatively, the spinal cord edema diminished, and the patient was discharged from the convalescent rehabilitation ward. Although intramedullary capillary hemangioma is a rare spinal tumor and its preoperative diagnosis is difficult, it should be considered in the differential diagnosis of spinal intramedullary tumors.

Radiological features of internal carotid artery occlusion caused by pituitary apoplexy: illustrative case.

BACKGROUND: Pituitary apoplexy rarely causes internal carotid artery (ICA) occlusion and acute ischemic stroke. Some cases have been reported, but the neuroimaging findings, including cerebral angiography, have not been discussed. OBSERVATIONS: A 55-year-old male suffered the sudden onset of right cervical pain and left mild hemiparesis. Computed tomography indicated a pituitary mass, and magnetic resonance angiography showed a right ICA occlusion. The initial diagnosis was ICA occlusion caused by ICA dissection. His symptoms worsened and the region of cerebral infarction expanded, so the patient was transferred to our hospital. Magnetic resonance imaging and cerebral angiography showed the sudden stoppage of right ICA blood flow caused by local compression of the tumor near the distal dural ring. The diagnosis was acute ischemic stroke resulting from ICA pseudo-occlusion caused by pituitary apoplexy, and emergent endoscopic transsphenoidal resection was performed. Postoperatively, the right ICA was completely patent, and hemiparesis was improved with rehabilitation. LESSONS: ICA occlusion caused by pituitary apoplexy is very rare, but emergent treatment is necessary. However, the pathology is difficult to diagnose quickly. Neuroimaging findings showing that the ICA is easily stenosed or occluded if rapidly compressed by the tumor near the distal dural ring may be useful to rapidly diagnose and treat.