Hiroyuki Hagiwara

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This paper proposes a new architecture for multibit complex bandpass ∆ΣAD modulators with built-in Switched-Capacitor (SC) circuits for application to Low-IF receivers such as used for Bluetooth and WLAN. In the realization of complex bandpass ∆ΣAD modulators, we face the following problems: (i) SNR of AD converter is deteriorated by mismatches between(More)
We have designed, fabricated and measured a secondorder multibit switched-capacitor complex bandpass ∆ΣAD modulator to evaluate our new algorithms and architecture. We propose a new structure of a complex bandpass filter in the forward path with I, Q dynamic matching, that is equivalent to the conventional one but can be divided into two separate parts. As(More)
Hemangioblastoma is a benign tumor of the cerebellum, and treatment involves surgical excision, both as the initial treatment and also in case of recurrence. Recurrence of hemangioblastoma can be local due to incomplete resection or can be distant and separate from the tumor resection region. Local recurrence can largely be avoided by verifying for any(More)
A 50-year-old woman with a parietal intracerebral hematoma was initially treated by hematoma evacuation. Initial preoperative and follow-up angiograms obtained 6 months later demonstrated no pial arteriovenous malformations (AVMs). She suffered a subarachnoid hemorrhage 8 years later. Results of follow-up cerebral angiography revealed the development of(More)
We describe the clinicopathological features of 25 brainstem gliomas (BSGs). Twenty BSGs located in the pons and were all in children. Four BSGs located in the medulla oblongata were in 2 children and 2 adults. One (in a child) was located in the midbrain. Radiological findings on MR images were low-intensity on T1 weighted images and high-intensity on T2(More)
BACKGROUND Endovascular surgery is being increasingly used as an alternative to craniotomy clipping surgery, especially for aged patients and complicated cases. However, tortuous atherosclerotic arteries sometimes interfere with advancement of catheters so that direct puncture may be necessary. Short guiding catheters for use with this approach have been(More)
BACKGROUND Portable Data for Imaging (PDI) is regularly used as a guideline for sharing medical imaging data between hospitals and other medical institutions. When a patient is referred to another location, the patient almost always brings PDI media on a CD or DVD. However, problems often occur when trying to view images on PDI discs inserted into computer(More)
This paper describes Data-Weighted-Averaging (DWA) algorithms for multibit complex bandpass ∆ΣAD modulators with arbitrary signal bands. In most of bandpass ∆ΣAD modulators, their sampling frequency is chosen as four times of the center frequency of their signal band in order to simplify the following digital filter design. But with this relationship, their(More)
BACKGROUND In the pterional approach, adequate removal of the sphenoid wing is essential. For safe drilling of the medial part, the dura beside the wing is usually retracted with a metal instrument and damage to the instrument may occur. We developed an alternative retraction method that uses a cardboard shield. METHODS Before drilling the medial part of(More)