[Show abstract][Hide abstract] ABSTRACT: We performed 3-dimensional cine phase-contrast magnetic resonance-based computational fluid dynamics for a basilar artery that developed a sidewall aneurysm over a 25-month period. There was an area with high gradient oscillatory number in the location of the future aneurysm ostium and an area with high wall shear stress (WSS) and high spatial WSS gradient at the distal edge of the future aneurysm. These could be biomarkers for development of intracranial aneurysms.
Magnetic Resonance in Medical Sciences 02/2015; 14(2). DOI:10.2463/mrms.2014-0003 · 1.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Many pancreaticoduodenal artery (PDA) aneurysms are associated with celiac artery (CA) stenosis. The pathogenesis of PDA aneurysm may be associated with hemodynamic changes due to CA stenosis/occlusion. The aim of this study was to assess the hemodynamic changes of celiaco-mesenteric anastomosis in patients with PDA aneurysms concomitant with CA occlusion using four-dimensional flow-sensitive magnetic resonance imaging (4D-Flow).
4D-Flow was performed preoperatively on five patients. Seven age- and sex-matched individuals were used as controls. Hemodynamic parameters such as flow volume and maximum flow velocity in PDAs, gastroduodenal arteries, common hepatic arteries, and superior mesenteric arteries were compared between both groups. Wall shear stress (WSS) and oscillatory shear index (OSI) were mapped in both groups.
In the patient group, 4D-Flow identified retrograde flow of both gastroduodenal arteries and common hepatic arteries. Heterogeneous distribution patterns of both WSS and OSI were identified across the entire PDA in the patient group. OSI mapping showed multiple regions with extremely high OSI values (OSI > 0.3) in all patients. All PDA aneurysms, which were surgically resected, were atherosclerotic.
4D-Flow identified hemodynamic changes in celiaco-mesenteric arteries in patients with PDA aneurysms with concomitant CA occlusion. These hemodynamic changes may be associated with PDA aneurysm formation.
European journal of vascular and endovascular surgery: the official journal of the European Society for Vascular Surgery 07/2013; 46(3). DOI:10.1016/j.ejvs.2013.06.011 · 2.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: PURPOSE
To assess the feasibility of cryoablation therapy using newly developed thermosiphon system for tumor bearing rabbit model.
METHOD AND MATERIALS
Eight Japanese white rabbits bearing VX2 tumor 2 cm in diameter in the right thigh muscle were used. Before the cryotherapy, precontrast and contrast enhanced MRI was performed to confirm the location and the size of the tumor. The cryoprobe measuring 27 cm in length, its needle of 8 cm in length and 3 mm in outer diameter was used for the therapy. The cryoprobe has separate channels for the ethylene liquid and the gas. The exchange between two conditions was used as a thermosiphon. Under the ultrasound guidance, the needle was inserted into the tumor. Thirty minutes of cooling was repeated with ten minutes of thawing period in between. During the therapy, the temperature of the cryoprobe and in the tumor as well as in the surrounding muscle was continuously recorded. Right after the cryotherapy, non-contrast MRI was performed to identify the area of ice ball formation. Two days after the therapy, precontrast and contrast enhanced MRI was again repeated to assess the effect of cryoablation. The animals were then euthanized and the right thigh was removed for histopathological assessments.
Ice ball started to grow around the needle one minute after the commencement of the cooling. The temperature of the needle was maintained between -70 and -80 degrees centigrade during the cooling sessions. After the cryotherapy, the sizes (longest length x minimum length) of the ice ball were measured by MRI at 16 to 20 minutes after the cessation of the cooling, which were 52 x 38 (mm) in averages. Two days after the therapy, MRI depicted non-enhanced area of 56 x 43 (mm) in averages that reflected treated areas completely including the tumor in six cases. As for the other initial two cases, there were tumor cells at the peripheral margin of the treated area, which was considered to be misplacements of the needle. The histopathological specimen supported that there were no viable tumor in the teated area.
The animal study implicates that newly developed compact cryoprobe using thermosiphon may be a promising device for cryoablation of the localized tumor.
Our newly developed cryoprobe using thermosiphon has shown good performance in cryotherapy for the localized tumor in an animal model. The device may be used for US-guided breast cancer cryosurgery.
Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
[Show abstract][Hide abstract] ABSTRACT: Hemodynamics in intracranial aneurysms is thought to play an important role in their growth and rupture. Usual computed fluid dynamics (CFD) based on three-dimensional (3D) computed tomographic (CT) angiography requires a time-consuming process for analysis. Magnetic resonance fluid dynamics (MRFD) based on MR images is a new tool for analyzing flow dynamics and a promising method for obtaining such information more easily. We compared the data from MRFD and CFD and studied the clinical feasibility of MRFD.
A total of 15 aneurysms, including two ruptured ones, in 15 patients were investigated with MR imaging and 3D-CT angiography. The flow data of MRFD and CFD, 3D stream lines, flow velocity profile and wall shear stress (WSS) were extracted from the image reconstruction and were compared each other.
Both flow dynamics images showed quite similar 3D flow pattern and WSS map. However, the calculated value of maximum WSS was quite different and there was no significant correlation. Further, in one ruptured case, CFD showed less visualization to evaluate the intra-aneurysmal flow. Interestingly, one delayed rupture case showed a particular flow pattern with abnormal secondary flow in the bottom of the aneurysm before rupture, which might suggest the specific finding of rupture risk.
MRFD is a valuable and less invasive tool to evaluate aneurysmal fluid dynamics. It can be obtained from the usual MRI examination without contrast medium and exposure to radiation. Although there is a problem of consistency of the absolute value of WSS between MRFD and conventional CFD, it may be useful to predict the risk of enlargement or rupture of aneurysms based on the information of the similar distribution of WSS and flow patterns. The quantifiable analysis and establishment of a meaningful threshold for high risk should be further studied.
[Show abstract][Hide abstract] ABSTRACT: 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.).
Annals of Vascular Diseases 01/2011; 4(4):271-85. DOI:10.3400/avd.di.11.00822
[Show abstract][Hide abstract] ABSTRACT: To investigate the morphologic characteristics of the medial rectus muscle in patients with consecutive exotropia.
Retrospective, nonrandomized, interventional study.
Eleven eyes of 10 patients with consecutive exotropia were studied. Thirteen eyes of 13 age-matched normal subjects were studied as controls.
All of the patients underwent an advancement of a previously operated medial rectus muscle. Patients were divided into 3 groups based on the insertion of the medial rectus muscle: Normally recessed stretched scar, and slipped muscle.
A comparison was made of the clinical findings, intraoperative findings, and distance from the limbus to the medial rectus muscle measured on magnetic resonance images among the groups.
The medial rectus of 4 eyes of 3 patients had normally recessed insertions and 7 eyes had abnormal insertions (3 stretched scars, 4 slipped muscles). The clinical findings were not different among the 3 groups. The magnetic resonance images showed that the medial rectus muscle was located closest to the limbus in the control subjects and most distant in the patients with a slipped muscle (P<0.005). The clinical findings in the patients with a stretched scar and with normally recessed were indistinguishable.
Magnetic resonance images of the medial rectus muscles of the control subjects and operated groups are significantly different morphologically. A slipped medial rectus muscle has characteristic magnetic resonance findings that are distinguishable from the muscle with normally recessed and stretched scar.
[Show abstract][Hide abstract] ABSTRACT: Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to perform in vivo hemodynamic analysis of unruptured intracranial aneurysms of magnetic resonance fluid dynamics using time-resolved three-dimensional phase-contrast MRI (4D-Flow) at 1.5 T and to analyze relationships between hemodynamics and wall shear stress (WSS) and oscillatory shear index (OSI).
This study included nine subjects with 14 unruptured aneurysms. 4D-Flow was performed by a 1.5-T magnetic resonance scanner with a head coil. We calculated in vivo streamlines, WSS, and OSI of intracranial aneurysms based on 4D-Flow with our software. We evaluated the number of spiral flows in the aneurysms and compared the differences in WSS or OSI between the vessel and aneurysm and between whole aneurysm and the apex of the spiral flow.
3D streamlines, WSS, and OSI distribution maps in arbitrary direction during the cardiac phase were obtained for all intracranial aneurysms. Twelve aneurysms had one spiral flow each, and two aneurysms had two spiral flows each. The WSS was lower and the OSI was higher in the aneurysm compared to the vessel. The apex of the spiral flow had a lower WSS and higher OSI relative to the whole aneurysm.
Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall.
[Show abstract][Hide abstract] ABSTRACT: Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to compare hemodynamics of intracranial aneurysms of MR fluid dynamics (MRFD) using 3D cine PC MR imaging (4D-Flow) at 1.5 T and MR-based computational fluid dynamics (CFD).
4D-Flow was performed for five intracranial aneurysms by a 1.5 T MR scanner. 3D TOF MR angiography was performed for geometric information. The blood flow in the aneurysms was modeled using CFD simulation based on the finite element method. We used MR angiographic data as the vascular models and MR flow information as boundary conditions in CFD. 3D velocity vector fields, 3D streamlines, shearing velocity maps, wall shear stress (WSS) distribution maps and oscillatory shear index (OSI) distribution maps were obtained by MRFD and CFD and were compared.
There was a moderate to high degree of correlation in 3D velocity vector fields and a low to moderate degree of correlation in WSS of aneurysms between MRFD and CFD using regression analysis. The patterns of 3D streamlines were similar between MRFD and CFD. The small and rotating shearing velocities and higher OSI were observed at the top of the spiral flow in the aneurysms. The pattern and location of shearing velocity in MRFD and CFD were similar. The location of high oscillatory shear index obtained by MRFD was near to that obtained by CFD.
MRFD and CFD of intracranial aneurysms correlated fairly well.
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to investigate metabolite alterations in the hippocampal formation as they relate to aggression in high-functioning adults with autism. We measured concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine plus phosphocreatine (Cr+PCr) in the hippocampal formation by proton magnetic resonance spectroscopy in 12 non-medicated male subjects with autism and 12 age- and sex-matched controls. Aggression was scored in the autistic subjects using the Buss-Perry Aggression Questionnaire. The concentrations of Cho and Cr+PCr in the hippocampal formation in autistic subjects were significantly higher than the corresponding values in control subjects, and a significant positive correlation was observed between the concentrations of these metabolites in the hippocampal formation and scores on the Buss-Perry Aggression Questionnaire in autistic subjects. Results suggest that high-functioning adult subjects with autism have abnormal metabolite concentrations in the hippocampal formation, which may in part account for their aggression.
The International Journal of Neuropsychopharmacology 11/2009; 13(4):529-34. DOI:10.1017/S1461145709990952 · 4.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study proposes magnetic resonance (MR)-measurement-integrated (MR-MI) simulation, in which the difference between the computed velocity field and the phase-contrast MRI measurement data is fed back to the numerical simulation. The computational accuracy and the fundamental characteristics, such as steady characteristics and transient characteristics, of the MR-MI simulation were investigated by a numerical experiment. We dealt with reproduction of three-dimensional steady and unsteady blood flow fields in a realistic cerebral aneurysm developed at a bifurcation. The MR-MI simulation reduced the error derived from the incorrect boundary conditions in the blood flow in the cerebral aneurysm. For the reproduction of steady and unsteady standard solutions, the error of velocity decreased to 13% and to 22% in one cardiac cycle, respectively, compared with the ordinary simulation without feedback. Moreover, the application of feedback shortened the computational convergence, and thus the convergent solution and periodic solution were obtained within less computational time in the MR-MI simulation than that in the ordinary simulation. The dividing flow ratio toward the two outlets after bifurcation was well estimated owing to the improvement of computational accuracy. Furthermore, the MR-MI simulation yielded wall shear stress distribution on the cerebral aneurysm of the standard solution accurately and in detail.
[Show abstract][Hide abstract] ABSTRACT: Investigation into the whole brain morphology of early onset schizophrenia (EOS) to date has been sparse. We studied the regional brain volumes in EOS patients, and the correlations between regional volume measures and symptom severity.
A total of 18 EOS patients (onset under 16 years) and 18 controls matched for age, gender, parental socioeconomic status, and height were examined. Voxel-based morphometric analysis using the Brain Analysis Morphological Mapping (BAMM) software package was employed to explore alterations of the regional grey (GM) and white matter (WM) volumes in EOS patients. Symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS).
EOS patients had significantly reduced GM volume in the left parahippocampal, inferior frontal, and superior temporal gyri, compared with the controls. They also had less WM volume in the left posterior limb of the internal capsule and the left inferior longitudinal fasciculus. The positive symptom score of PANSS (higher values corresponding to more severe symptoms) was negatively related to GM volume in the bilateral posterior cingulate gyrus. The negative symptom score was positively correlated with GM volume in the right thalamus. As for the association with WM volume, the positive symptom score of PANSS was positively related to cerebellar WM (vermis region), and negatively correlated with WM in the brain stem (pons) and in the bilateral cerebellum (hemisphere region).
Our findings of regional volume alterations of GM and WM in EOS patients coincide with those of previous studies of adult onset schizophrenia patients. However, in brain regions that had no overall structural differences between EOS patients and controls (that is, the bilateral posterior cingulate gyrus, the right thalamus, the cerebellum, and the pons), within-subject analysis of EOS patients alone revealed that there were significant associations of the volume in these areas and the symptom severity. These findings suggest that at an early stage of the illness, especially for those with onset before brain maturation, a wide range of disturbed neural circuits, including these brain regions that show no apparent morphological changes, may contribute to the formation of the symptomatology.
Annals of General Psychiatry 01/2009; 7(1):25. DOI:10.1186/1744-859X-7-25 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Detailed and accurate information of hemodynamics is essential for clarification and advanced diagnosis of circulatory diseases.
In order to reproduce complicated real flow field, the concept of flow observer, which integrates measurement and computation
by feedback process, have been proposed. By applying the method to the MR (Magnetic Resonance) measurement, we propose MR-measurement-integrated
(MR-MI) simulation: the difference between the Phasecontrast MRI (PC MRI) data and the computational result of three-dimensional
velocity vector field is fed back to the numerical simulation. The objective in this study is to evaluate the MR-MI simulation
by numerical experiment dealing with an unsteady blood flow in a cerebral aneurysm. In the numerical experiment, we first
defined a standard solution with velocity profiles obtained by PC MRI measurement at boundaries as a model of real blood flow.
Then, MR-MI simulation was carried out by assuming a uniform velocity profile at the upstream boundary and pressure zero and
free flow conditions at the downstream boundaries. During the computation, a feedback signal being proportional to the difference
between the standard solution and the computational result was applied at each grid point in the aneurysm. As the result,
the MR-MI simulation reproduced the standard solution in the aneurysm owing to the feedback process. The error derived from
the inaccurate boundary conditions decreased to 22% in one cardiac cycle, comparing to the ordinary simulation. Consequently,
the MR-MI simulation accurately provided the wall shear stress distribution on the cerebral aneurysm as hemodynamic information.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to assess the feasibility of high spatial resolution, selective arterial phase, 3D contrast-enhanced (CE) MR angiography with first pass bolus, software-trigger, elliptical centric view ordering in the detection of intracranial aneurysms. Our study included nine consecutive patients with ten intracranial aneurysms. 3D TOF MR angiography and 3D CE MR angiography were carried out with a 1.5-T MR scanner. 3D CE MR angiography was performed with an automated bolus detection algorithm and elliptical centric view order using ultrafast SPGR with a spatial resolution of 0.63x0.83x0.5 mm and imaging time of 55 s. Observers detected seven of ten aneurysms on 3D TOF MR angiograms and nine of ten aneurysms on 3D CE MR angiograms. 3D CE MR angiography clearly revealed an IC-PC aneurysm with a relatively smaller neck, a broad-based small aneurysm originating from tortuous and dilated MCA bifurcation, and a residual aneurysm and parent vessels adjacent to metallic aneurysmal clips, which had relatively low signal intensities on 3D TOF MR angiograms. 3D CE MR angiography was found to be a good and promising technique for detecting intracranial aneurysms with small necks and slow flow, vasculature with aneurysmal clips and tortuous vasculature with disturbed flow.
European Radiology 06/2007; 17(5):1221-5. DOI:10.1007/s00330-006-0395-y · 4.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To visualize the hemodynamics of the intracranial arteries using time-resolved three-dimensional phase-contrast (PC)-MRI (4D-Flow).
MR examinations were performed with a 1.5T MR unit on six healthy volunteers (22-50 years old, average = 30 years). 4D-Flow was based on a radiofrequency (RF)-spoiled gradient-echo sequence, and velocity encoding (VENC) was performed along all three spatial directions. Measurements were retrospectively gated to the electrocardiogram (ECG), and cine series of three-dimensional (3D) data sets were generated. The voxel size was 1 x 1 x 1 mm, and acquisition time was 30-40 minutes. 4D data sets were calculated into time-resolved images of 3D streamlines, 3D particle traces, and 2D velocity vector fields by means of flow visualization software.
We were able to see the 3D streamlines from the circle of Willis to the bilateral M2 segment of the middle cerebral arteries (MCAs). Time-resolved images of 3D particle traces also clearly demonstrated intracranial arterial flow dynamics. 2D velocity vector fields on the planes traversing the carotid siphon or the basilar tip were clearly visualized. These results were obtained in all six volunteers.
4D-Flow helped to elucidate the in vivo 3D hemodynamics of human intracranial arteries. This method may be a useful noninvasive means of analyzing the hemodynamics of intracranial arteries in vivo.
Journal of Magnetic Resonance Imaging 03/2007; 25(3):473-8. DOI:10.1002/jmri.20828 · 3.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although a transient lesion in the splenium of the corpus callosum (SCC) has been reported predominantly regarding patients with epilepsia, it is of rare occurrence, and its underlying biological basis remains unknown. This is a report of an SCC lesion in a patient with anorexia nervosa (AN).
The patient was a 15-year-old girl with childhood-onset (11 years) and a protracted course of AN. On admission, the patient showed no apparent neurological abnormalities. Magnetic resonance imaging (MRI) scans revealed a circumscribed lesion in the SCC. We treated her with nutritional rehabilitation supplemented with B vitamins.
One month later, the lesion completely disappeared, but her weight was not restored.
Treatment with B-vitamin supplementation may be beneficial for the treatment of patients with AN, in cases in which the disorder develops at an early age before brain maturation (i.e., childhood-onset cases), along with an enduring course of malnutrition.
International Journal of Eating Disorders 09/2006; 39(6):527-9. DOI:10.1002/eat.20280 · 3.13 Impact Factor