Shuhei Yamashita

Visualization of hemodynamics in intracranial arteries using time-resolved three-dimensional phase-contrast MRI.

To visualize the hemodynamics of the intracranial arteries using time‐resolved three‐dimensional phase‐contrast (PC)‐MRI (4D‐Flow).

Analysis of intrahepatic venovenous shunt by hepatic venography

BACKGROUND The necessity of preserving hepatic venous drainage in hepatectomy and liver transplantation has recently been accepted; however, the hepatic vein (HV) can be removed when an effective intrahepatic venovenous shunt (VV shunt) exists. METHODS Occlusion venography of the right HV (RHV) was performed in 51 patients to investigate the VV shunt characteristics. RESULTS Twenty patients had a shunt between the RHV and large HVs whose root diameters were >3 mm, such as the superficial or inferior RHV, or the middle HV. Twenty patients had a shunt between the RHV and small HVs with root diameters < or =3 mm. Eleven patients had no shunt. The change in anterior portal vein blood flow after RHV occlusion, evaluated by Doppler ultrasonography, was minimal (5 +/- 3%) in patients with a shunt between the RHV and large HVs, and less than in patients with a shunt between the RHV and small HVs (38% +/- 18%) or without a shunt (50% +/- 17%; P < .0001). A shunt between the RHV and large HV was less frequently seen in those patients with cirrhosis (3/20) than in those without cirrhosis (17/31; P = .0044). The existence of the shunt between the RHV and large HVs was unpredictable, however, from computed tomographic findings or laboratory data. CONCLUSION A hemodynamically significant VV shunt between the RHV and large HV was observed in fewer than half of the patients and less frequently in cirrhotic patients. Preservation of hepatic venous drainage should be considered in patients without a hemodynamically significant VV shunt in liver surgery.

Evaluation of tumor blood flow after feeder embolization in meningiomas by arterial spin-labeling perfusion magnetic resonance imaging.

Preoperative embolization changes the amount of blood flow and pattern of flow distribution in meningioma. Tumor blood flow was investigated in eight meningioma patients before and after embolization using arterial spin-labeling (ASL) perfusion imaging. Although blood flow was significantly reduced in the whole tumor after embolization, changes in flow distribution patterns varied from one case to another. The findings suggest that evaluation of post-embolization tumor blood flow by ASL perfusion imaging would be useful in the surgical planning of meningioma.

Feasibility of magnetic resonance elastography for the pancreas at 3T.

1) To assess the usefulness of an elastic belt bracing the upper abdomen for reducing the miscalculated areas of the pancreas on 3.0T magnetic resonance elastography (MRE); 2) to test whether MRE can detect difference of stiffness between normal pancreas and the focal pancreatic diseases.

Atypically enhanced cavernous hemangiomas of the liver: centrifugal enhancement does not preclude the diagnosis of hepatic hemangioma

The imaging features of an atypically enhanced hepatic hemangioma have not been well described in the literature, and the presence of such atypia may sometimes cause clinical problems in the differential diagnosis. Herein, we report a case of hepatic hemangioma demonstrating a previously unreported atypical enhancement pattern. On dynamic computed tomography during hepatic arteriography, a centrifugal enhancement pattern and subsequent peritumoral ring-shaped enhancement mimicking corona enhancement were found in cavernous hemangiomas of the liver in a 68-year-old Japanese man. Histopathological diagnosis of cavernous hemangioma of the liver was made on a biopsy specimen. Considering the importance of differentiating benign hepatic tumor from various forms of malignancy, radiologists and hepatologists should be aware of rare enhancement patterns sometimes seen in hepatic hemangioma. Establishing knowledge of the entire spectrum of atypical hepatic hemangioma may benefit the rational approach to future cases.

Visualization of spinal cord motion associated with the cardiac pulse by tagged magnetic resonance imaging with particle image velocimetry software.

Objective: The purpose of this study was to evaluate whether or not tagged magnetic resonance (MR) imaging with particle image velocimetry (PIV) software could reveal spinal cord motion clearly. Methods: Six volunteers were enrolled in this study. Tagged MR imaging using fast spoiled gradient-recalled acquisition in the steady state with spatial modulation of the magnetization technique was performed using a 1.5-T MR system. Results: Sagittal vector maps analyzed by PIV software revealed entire spinal cord motion sequentially during the cardiac cycle. The cervical spinal cord initially moved in a caudal direction and then continually oscillated from a cephalic-to-caudal direction. Each volunteer had a different cycle. In the thoracic spinal area, similar findings were observed, although they were slightly less clear than in the cervical area. Conclusion: Tagged MR imaging combined with PIV software, referred to as tagged MR image velocimetry, revealed spinal cord motion associated with the cardiac pulse, especially in the cervical spine.

Anomalous arterial ramification in the right liver

PurposeThe aim of this study was to investigate whether individual arterial and portal venous division during hepatectomy is always safe by examining the presence of the anomalous arterial ramification in the right liver.MethodsThe ramifications of the right hepatic artery (RHA) were investigated by three-dimensional (3D) reconstruction imaging using a computer software program in 87 patients undergoing computed tomography during angiography as a preoperative assessment of intrahepatic tumors.ResultsThe anterior view showed that the RHA bifurcated into the anterior and posterior sector arteries at the hilum in 76 patients. Sector-intersecting arteries from the posterior to the anterior sector and vice versa were found in 7 and 4 of those patients, respectively. The RHA in the other 11 patients was divided in a complex manner into more than 2 arteries: e.g., the first branch to the cranial part of the posterior sector, the second to the anterior sector, and the third to the caudal part of the posterior sector. A total of 22 patients showed anomalous ramification of RHA.ConclusionPreoperative observation of the hepatic artery by 3D imaging is very useful to detect anomalous ramification. Arterial dissection during the intrafascial approach should be cautiously performed based on the 3D images.

Hemorrhagic radiation gastritis successfully treated with repeated intra-arterial steroid infusions

Intra-arterial steroid infusion therapy has previously been shown to be effective for inflammatory bowel disease; however, few cases in which it has been used for the treatment of hemorrhagic radiation gastritis have been reported. We report the case of a 70-year-old Japanese man with hemorrhagic radiation gastritis induced by radiation therapy for para-aortic lymph node metastases of hepatocellular carcinoma. Two months after completing radiation therapy, acute persistent bleeding occurred in the gastric irradiation area. Although argon plasma coagulation was performed five times over a month, the bleeding continued and the patient showed persistent anemia that required 50 units of blood transfusion. Finally, the patient was given intra-arterial steroid infusions through the right gastric artery and the right gastroepiploic artery. After three intra-arterial steroid infusions, the melena stopped, and the anemia no longer progressed. Hemorrhagic radiation gastritis was successfully treated with repeated intra-arterial steroid infusions through the regional vessels to the gastric mucosa. Repeated intra-arterial steroid infusions could be a clinically useful option for the treatment of intractable bleeding from radiation gastritis.

Magnetic Resonance Angiography of the Aorta

Magnetic resonance angiography (MRA) is capable of imaging arteries in the half to whole body by a single acquisition without a nephrotoxic contrast medium, and acquired images can be reconstructed into a specific cross-sectional view in an arbitrary directions. MRA is applicable for vessels non-reachable by a catheter approach, and collateral vessels can be fully visualized. Since MRA is minimally-invasive with no exposure to ionized radiation, it can be repeatedly applied for follow-up. However, there are also disadvantages: the temporal and spatial resolutions are inferior to those of X-ray angiography, and, at present, it cannot be used as a guide for intervention. Moreover, gadolinium administrations may cause NSF in patients who have lost renal function, as a new risk. Accordingly, strict consideration is required for an indication of its application. Development of non-contrast MRA and evaluation of the wall itself may draw more attention in the future. Plaque imaging is being routinely performed nowadays, and the measurement of vascular wall shear stress, which has a close association with arteriosclerosis, may become possible by utilizing the time-resolved phase-contrast method capable of measuring the time-resolved velocity vectors of blood flow throughout the body. (*English Translation of J Jpn Coll Angiol, 2009, 49: 503-516.).

T2-weighted MRI of rectosigmoid carcinoma: Comparison of respiratory-triggered fast spin-echo, breathhold fast-recovery fast spin-echo, and breathhold single-shot fast spin-echo sequences†

To compare the abilities of T2‐weighted (T2W) imaging using respiratory‐triggered fast spin‐echo (RT‐FSE), breathhold fast‐recovery FSE (BH‐FRFSE), and BH single‐shot FSE (BH‐SSFSE) sequences without an endorectal coil to detect rectosigmoid carcinomas.