Hideki Ishimaru

Diagnostic potential of short echo time MR spectroscopy of gliomas with single-voxel and point-resolved spatially localised proton spectroscopy of brain

Abstract Accurate neuroimaging grading of gliomas is useful for management, but techniques such as MRI and CT are not sufficiently reliable. Necrosis is a consistent, decisive prognostic factor and the key diagnostic criterion for glioblastoma multiforme. MR spectroscopy (MRS) allows noninvasive measurement of metabolites in brain tumours and mobile lipids reflect necrosis. However, short echo-time (TE) spectroscopy has been required for reliable assessment of lipids, since their relaxation times are very short. Recent advances have made it possible to perform short-TE MRS. We attempted to evaluate the significance of short TE spectroscopy as part of routine imaging for diagnosis and grading of gliomas. We performed TE 30 ms MRS in 25 patients with gliomas (grade II six; grade III three; grade IV, 16) and in 19 areas of healthy white matter using proton brain examination/single voxel (PROBE/SV) and point-resolved spatially localised spectroscopy (PRESS). With short-TE spectroscopy, lipid signals were detected in all 16 tumours of grade IV, one grade II (P = 0.0002) and none of grade III (P = 0.001). TE 136 ms MRS, carried out in 20 of these cases, showed lipid signals in only four of 14 grade IV tumours and in none of the other six. N-acetylaspartate/choline (NAA/Cho) ratios were always more than 1.0 in healthy tissues and less than 1.0 in all but one of the gliomas. The mean creatine (Cr)/Cho ratio in each tumour grade was significantly lower than in the healthy tissues. The mean Cr/Cho ratio was also significantly lower in grade IV than in grade II tumours (P < .0005). Considerable overlap in Cr/Cho ratio was observed between grade II and grades III and IV gliomas at long but less so at short-TE MRS. We conclude that short-TE MRS with PROBE/SV and PRESS is of value in grading gliomas.

Imaging of the patulous eustachian tube: high-resolution CT evaluation with multiplanar reconstruction technique

Objective—To evaluate the 3D anatomy of the ET and its surrounding tissues in cases with or without patulous Eustachian tube (ET) using CT with the multiplanar reconstruction (MPR) technique. Material and Methods—Twenty patients with a patulous ET and 25 without middle ear problems were investigated. After performing a temporal bone CT examination, MPR images of the ET were reconstructed and measurements were made. Results—The ET lumen and its surrounding tissues were clearly identified. In the patulous ET group, the ET lumen was open throughout the cartilaginous portion and the volume of the low-density area was smaller in size than in the controls. In unilateral patulous ET patients, the anatomical features were found to be similar on both sides, in spite of the fact that the non-involved side did not show symptoms associated with a patulous ET. Conclusion—For the first time, we were able to obtain clear reconstructed images of the patulous ET and its surrounding structure and to study its anatomical features. This method is useful for obtaining a better understanding of the ET and ET-related diseases such as patulous ET.

Proton MR spectroscopy and diffusion-weighted MR imaging for the diagnosis of intracranial tuberculomas. Report of two cases

Abstract With the current prevalence of tuberculosis, the incidence of intracranial tuberculoma may be on the rise in industrialized nations. However, clinical findings suggestive of systemic tuberculosis are frequently subtle or absent in patients with intracranial tuberculoma, and no specific neuroradiologic characteristics of tuberculoma have been defined as yet. We report two cases of ring-enhanced intracranial tuberculoma in which magnetic resonance (MR) proton spectroscopy and diffusion-weighted (DW) imaging were useful in the differential diagnosis between tuberculoma and other ring-enhanced mass lesions. Pulmonary tuberculosis had been diagnosed in one patient, but radiologic lung study and tuberculin skin test were negative in the other. DW imaging showed bright signal intensity in the core of all lesions in both patients. Malignant gliomas and metastatic brain tumors do not have this characteristic. Proton MR spectroscopy of lesion cores showed lipid peaks and a choline peak in one, and a lipid/lactate mixture pattern in the other, which differed distinctively from those of the pyogenic brain abscess. In each case, one lesion was surgically removed. Antituberculosis drugs were started before surgery for one patient and after surgery for the other. In both, the remaining lesions were reduced significantly in size. We discuss the diagnostic potential of these MR techniques and management options of intracranial tuberculoma. [Neurol Res 2002; 24: 537-543]

Local Recurrence After Chemoembolization of Hepatocellular Carcinoma: Uptake of Gadoxetic Acid as a New Prognostic Factor

OBJECTIVE The purpose of this article is to investigate whether there is a difference in susceptibility to transcatheter arterial chemoembolization between hepatocellular carcinomas (HCCs) showing high uptake and those showing low uptake of gadoxetic acid in the hepatobiliary phase of MRI. MATERIALS AND METHODS One hundred HCCs that achieved optimal chemoembolization, as assessed by immediate CT in 60 patients, were classified as having high (n = 19) or low (n = 81) uptake of gadoxetic acid on MRI performed before chemoembolization. The local recurrence rates were estimated using the Kaplan-Meier method, and differences between the groups were compared using the log-rank test. The following factors were also correlated with the local recurrence rate using the Cox proportional hazards model for a univariate analysis: high uptake of gadoxetic acid, number of feeding arteries, extrahepatic arterial supply, Child-Pugh class, clinical tumor stage, size, location, and iodized oil accumulation in the noncancerous tissue surrounding the lesion. Parameters that were significant at p < 0.05 were entered into a multivariate model. RESULTS The 1- and 3-year local recurrence-free rates were 95% in high-uptake HCCs and 66% and 54%, respectively, in low-uptake HCCs (log-rank test, p < 0.01). The low uptake of gadoxetic acid was the only significant predictor of early local recurrence (hazard ratio = 9.24; p = 0.03) by multivariate analysis. CONCLUSION HCCs showing high uptake of gadoxetic acid appear to be susceptible to chemoembolization.

Local thrombolysis for acute ischemic stroke based on findings of diffusion and perfusion MRI.

Cerebral perfusion and cerebral tissue integrity were studied in 13 patients with acute embolic stroke in the territory of the internal carotid artery by diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) within six hours after onset. PWI/DWI mismatch lesion was depicted in six patients. MCA was occluded in five of six patients, who underwent local thrombolytic therapy. In three cases, complete restoration of the cerebral circulation was obtained and enlargement of irreversible brain damage compared to initial DWI lesion was prevented. Seven patients without PWI/DWI mismatch did not undergo thrombolytic therapy. Spontaneous reopening of occluded MCA was verified with subsequent cerebral angiography in one of seven patients. CT depicted symptomatic intracerebral hemorrhage in this patient. It is concluded that DWI and PWI in combination are useful in selection of patients for thrombolytic therapy.

Cerebral lipiodol embolism related to a vascular lake during chemoembolization in hepatocellular carcinoma: A case report and review of the literature

A male patient underwent conventional transcatheter chemoembolization for advanced recurrent hepatocellular carcinoma (HCC). Even after the injection of 7 mL of lipiodol followed by gelatin sponge particles, the flow of feeding arteries did not slow down. A repeat angiography revealed a newly developed vascular lake draining into systemic veins; however, embolization was continued without taking noticing of the vascular lake. The patient’s level of consciousness deteriorated immediately after the procedure, and non-contrast computed tomography revealed pulmonary and cerebral lipiodol embolisms. The patient’s level of consciousness gradually improved after 8 wk in intensive care. In this case, a vascular lake emerged during chemoembolization and drained into systemic veins, offering a pathway carrying lipiodol to pulmonary vessels, the most likely cause of this serious complication. We should be aware that vascular lakes in HCC may drain into systemic veins and can cause intratumoral arteriovenous shunts.

Tumor Emboli from Aortic Metastasis

The patient was a 67-year-old man with cholangiocarcinoma who underwent partial hepatectomy. At 34 months after surgery, descending aortic wall thickening was observed on contrast-enhanced CT (Picture A and B). Fluorodeoxyglucose positron emission tomography (FDG-PET) scans showed an increased uptake in this lesion (Picture G). Thereafter, the aortic wall thickness gradually increased, and the wall of the superior mesenteric artery (SMA) also thickened (Picture C and D). After 6 months, a CT scan was performed because of severe abdominal pain. As wall thickening of the SMA had partly disappeared, part of the lesion was suggested to be an embolus (Picture E and F; arrow). Angiography demonstrated total occlusion of the SMA (Picture H; arrow).

Presurgical Mapping with Functional MR Imaging versus Transcranial Magnetic Stimulation Combined with Surface Anatomy Scanning

Fifteen patients, who had tumors in or near the precentral gyrus, underwent functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) combined with surface anatomy scanning (SAS) for presurgical mapping of the sensory motor cortex. TMS activated the motor cortex in all patients and fMRI demonstrated task activation of sensory motor cortex in 14 of the 15 patients. The marker of TMS superimposed on SAS and fMRI activation agreed within 0.5 cm in 11 of the 14 patients. In the remaining three, the distance of these mapped sites ranged from 1 cm to 1.5 cm, and SAS showed a deformity of the central sulcus which may cause the deviation of activated site with TMS. The cortical surface projection of TMS using SAS and fMRI has good spatial relationship and is useful in identifying a primary motor cortex in presurgical planning.