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  • Author or Editor: Akira Ogawa x
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Takashi Inoue, Yasutaka Kuzu, Kuniaki Ogasawara and Akira Ogawa

Object

This study investigated the changes in the valve pressure setting of several magnetic pressure-programmable valves after exposure to a 3-tesla magnetic field.

Methods

Five each of four types of pressure-programmable shunt valves were tested: Sophy Polaris, Sophy SM8, Codman-Hakim, and Medtronic Strata. First, the valves were advanced toward the 3-tesla static magnetic field. Second, T1-, T2-, and diffusion-weighted magnetic resonance (MR) images were generated with a radiofrequency magnetic field. Any changes in the pressure setting were observed by visual inspection with a compass or radiography.

The pressure settings were changed after exposure to the static magnetic field in all programmable valves except for the Sophy Polaris. All pressure settings studied were unchanged after exposure to both static and radiofrequency magnetic fields (T1-, T2-, and diffusion-weighted MR imaging) in the Sophy Polaris.

Conclusions

The Sophy Polaris valve allows shunt-dependent patients who need a programmable valve to undergo 3-tesla MR imaging.

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Hideki Matsuura, Takashi Inoue, Hiromu Konno, Makoto Sasaki, Kuniaki Ogasawara and Akira Ogawa

✓ Although various biomaterials such as ceramics or titanium alloy are widely used in neurosurgery, the susceptibility artifacts that appear around these materials cause problems when a magnetic resonance (MR) imager is used to assess lesions after surgery. The purpose of the present study was to quantify the susceptibility artifacts produced by various biomaterials used for neurosurgical implants.

Using a 3-tesla MR imaging unit, we obtained MR images of various biomaterials, including six types of ceramics, a cobalt-based alloy (Elgiloy), pure titanium, a titanium alloy, and stainless steel. All implants shared a uniform size and shape. In each image, a linear region of interest was defined across the center of the biomaterial in the transverse direction, and the diameter of the susceptibility artifact was calculated.

The ceramics produced a considerably smaller artifact diameter than those produced by other biomaterials. Among the types of ceramics, zirconia was found to produce the smallest artifact diameter. Among the remaining biomaterials, the diameters of the artifacts decreased in order from that associated with stainless steel to those associated with cobalt-based alloys, pure titanium, and titanium alloy. Little difference was observed between the artifact diameters associated with pure titanium and titanium alloy.

Ceramics are the most suitable biomaterials for minimizing artifacts in high-field MR imaging.

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Hiroshi Kashimura, Takashi Inoue, Kuniaki Ogasawara, Hiroshi Arai, Yasunari Otawara, Yoshiyuki Kanbara and Akira Ogawa

Object

Preoperative planning for meningiomas requires information about tumor consistency as well as location and size. In the present study the authors aimed to determine whether the fractional anisotropy (FA) value calculated on the basis of preoperative magnetic resonance (MR) diffusion tensor (DT) imaging could predict meningioma consistency.

Methods

In 29 patients with intracranial meningiomas, MR DT imaging was performed preoperatively, and the FA values of the tumors were calculated. Tumor consistency was intraoperatively determined as hard or soft, and the histological diagnosis of the tumor was established.

Results

Of the 29 tumors, 11 were classified as hard and 18 as soft. The FA values of fibroblastic meningiomas were significantly higher than those of meningothelial meningiomas (p = 0.002). The FA values of hard tumors were significantly higher than those of soft tumors (p = 0.0003). Logistic regression analysis demonstrated that the FA value was a significant independent predictor of tumor consistency (p = 0.007).

Conclusions

The FA value calculated from preoperative MR DT imaging predicts meningioma consistency.

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Takaaki Beppu, Takashi Inoue, Hideaki Nishimoto, Shinichi Nakamura, Yoichi Nakazato, Kuniaki Ogasawara and Akira Ogawa

✓Primary granulomatous angiitis of the central nervous system (CNS) is extremely rare. Its preoperative diagnosis is difficult as the condition displays nonspecific features on routine neuroimaging investigations. In this paper, the authors report findings of magnetic resonance (MR) spectroscopy and fractional anisotropy (FA) with diffusion tensor MR imaging in a case of granulomatous angiitis of the CNS.

A 30-year-old man presented with morning headaches and grand mal seizures. An MR image revealed a mass resembling glioblastoma in the right temporal lobe. Magnetic resonance spectroscopy showed a high choline/creatine (Cho/Cr) ratio indicative of a malignant neoplasm, accompanied by a slight elevation of glutamate and glutamine. The FA value was very low, which is inconsistent with malignant glioma. The mass was totally removed surgically. Histologically, the peripheral lesion of the mass consisted of a rough accumulation of fat granule cells, infiltration of inflammatory cells, and distribution of capillary vessels. Some vessels within the lesion were replaced by granulomas. The histological diagnosis was granulomatous angiitis of the CNS. The MIB-1–positive rate of the granuloma was approximately 5%. Both MR spectroscopy and FA were unable to accurately diagnose granulomatous angiitis of the CNS prior to surgery; however, elevated Cho/Cr and glutamate and glutamine shown by MR spectroscopy may indicate the moderate proliferation potential of the granuloma and the inflammatory process, respectively, in this condition. Although the low FA value in the present case enabled the authors to rule out a diagnosis of glioblastoma, FA values in inflammatory lesions require careful interpretation.

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Kuniaki Ogasawara, Keiko Yamadate, Masakazu Kobayashi, Hidehiko Endo, Takeshi Fukuda, Kenji Yoshida, Kazunori Terasaki, Takashi Inoue and Akira Ogawa

Object. Cognitive impairment occurs in 20 to 30% of patients following carotid endarterectomy (CEA). The purpose of the present study was to determine whether postoperative cerebral hyperperfusion is associated with impairment of cognitive function in patients undergoing that procedure.

Methods. Cerebral blood flow (CBF) was measured using single-photon emission computerized tomography scanning before and immediately after CEA and on the 3rd postoperative day in 92 patients with ipsilateral internal carotid artery stenosis of 70% or greater. Hyperperfusion post-CEA was defined as a 100% increase or greater in CBF compared with preoperative values. Neuropsychological testing was also performed preoperatively and at the 1-, 3-, and 6-month follow-up examinations.

At the 1-month postoperative neuropsychological assessment, 11 patients (12%) displayed evidence of cognitive impairment. In addition, the incidence of postoperative cognitive impairment in patients with post-CEA hyperperfusion (seven [58%] of 12 patients) was significantly higher than that in patients without post-CEA hyperperfusion (four [5%] of 80 patients; p < 0.0001). A logistic regression analysis demonstrated that post-CEA hyperperfusion was the only significant independent predictor of postoperative cognitive impairment. Of the seven patients in whom post-CEA hyperperfusion and cognitive impairment were identified 1 month postoperatively, four (including three patients with hyperperfusion syndrome) remained cognitively impaired at the 3- and 6-month follow-up examinations.

Conclusions. Postoperative cerebral hyperperfusion is associated with impairment of cognitive function in patients undergoing CEA. Furthermore, the development of hyperperfusion syndrome is associated with the persistence of postoperative cognitive impairment.

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Kuniaki Ogasawara, Hirotsugu Yukawa, Masakazu Kobayashi, Chiaki Mikami, Hiromu Konno, Kazunori Terasaki, Takashi Inoue and Akira Ogawa

Object. The purpose of this study was to determine whether the preoperative measurement of acetazolamide-induced changes in cerebral blood flow (CBF), which is performed using single-photon emission computerized tomography (SPECT) scanning, can be used to identify patients at risk for hyperperfusion following carotid endarterectomy (CEA). In addition, the authors investigated whether monitoring of CBF with SPECT scanning after CEA can be used to identify patients at risk for hyperperfusion syndrome.

Methods. Cerebral blood flow and cerebrovascular reactivity (CVR) to acetazolamide were measured before CEA in 51 patients with ipsilateral internal carotid artery stenosis (≥ 70% stenosis). Cerebral blood flow was also measured immediately after CEA and on the 3rd postoperative day.

Hyperperfusion (an increase in CBF of ≥ 100% compared with preoperative values) was observed immediately after CEA in eight of 12 patients with reduced preoperative CVR. Reduced preoperative CVR was the only significant independent predictor of post-CEA hyperperfusion. Forty-three patients in whom hyperperfusion was not detected immediately after CEA did not exhibit hyperperfusion on the 3rd postoperative day and did not experience hyperperfusion syndrome. In two of eight patients in whom hyperperfusion occurred immediately after CEA, CBF progressively increased and hyperperfusion syndrome developed, but intracerebral hemorrhage did not occur. In the remaining six of eight patients in whom hyperperfusion was detected immediately after CEA, the CBF progressively decreased and the hyperperfusion resolved by the 3rd postoperative day.

Conclusions. Preoperative measurement of acetazolamide-induced changes in CBF, which is performed using SPECT scanning, can be used to identify patients at risk for hyperperfusion after CEA. In addition, post-CEA monitoring of CBF performed using SPECT scanning results in the timely and reliable identification of patients at risk for hyperperfusion syndrome.

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Ryounoshin Hirooka, Kuniaki Ogasawara, Makoto Sasaki, Keiko Yamadate, Masakazu Kobayashi, Yasunori Suga, Kenji Yoshida, Yasunari Otawara, Takashi Inoue and Akira Ogawa

Object

Cerebral hyperperfusion after carotid endarterectomy (CEA) impairs cognitive function and is often detected on cerebral blood flow (CBF) imaging. The purpose of the present study is to investigate structural brain damage seen on magnetic resonance (MR) images obtained in patients with cerebral hyperperfusion and cognitive impairment after CEA.

Methods

One hundred and fifty-eight patients with ipsilateral internal carotid artery stenosis (≥ 70%) underwent CEA. Neuropsychological testing was performed preoperatively and at the 1st postoperative month. Cerebral blood flow was measured using single-photon emission computed tomography before, immediately after, and 3 days after surgery. Magnetic resonance imaging was performed before and 1 day after surgery. In patients with post-CEA hyperper-fusion (defined as a CBF increase ≥ 100% compared with preoperative values) on CBF imaging, MR images were also obtained on the 3rd postoperative day, the day on which hyperperfusion syndrome developed, and 1 month after the operation.

Results

The incidence of postoperative cognitive impairment was significantly higher in patients with post-CEA hyperperfusion on CBF imaging (12 [75%] of 16 patients) than in those without (6 [4%] of 142 patients; p < 0.0001). Only 1 of 5 patients with cerebral hyperperfusion syndrome developed reversible brain edema in the cerebral hemisphere ipsilateral to the CEA on MR images obtained on the day hyperperfusion syndrome occurred. However, postoperative cognitive impairment developed in all 5 patients with cerebral hyperperfusion syndrome regardless of the presence or absence of new lesions on MR images. In addition, postoperative cognitive impairment developed in 5 (45%) of 11 patients with asymptomatic cerebral hyperperfusion on CBF imaging despite the absence of new lesions on any postoperative MR images.

Conclusions

Although cerebral hyperperfusion syndrome after CEA sometimes results in reversible brain edema visible on MR imaging, postoperative cerebral hyperperfusion—even when asymptomatic—often results in impaired cognitive function without structural brain damage on MR imaging.

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Rob D. Dickerman, Kyle Colleb, Jonathan T. Morganb and Steve Schneiderb