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Toshio Tsuchihashi

Publications and source records attributed to Toshio Tsuchihashi.

8 recordsLinked to original sources
PubMed2004

[Examination of susceptibility artifact in three-dimensional gadolinium-enhanced chest MR angiography].

Signal loss that is sometimes found in the subclavian artery during chest MR angiography is thought to be caused by the susceptibility effect of highly concentrated contrast medium. In our research project, we examined the conditions under which signal loss occurs. We made vessel phantoms (artery phantom, vein phantom) that contained different concentrations of Gd-DTPA water solutions, and placed them in a 0.5 mmol/l Gd-DTPA water solution. We examined signal loss when the vein phantom was parallel to the magnetic field and when it was perpendicular to the magnetic field. We found that there was no signal loss in the artery phantom when the vein phantom was parallel to the magnetic field. In contrast, signal loss occurred in the artery phantom when the vein phantom was perpendicular to the magnetic field. The higher the concentration in the vein phantom, the closer the distance to the vessel phantom, and the longer the echo time (TE), the greater was the signal loss. Thus, the cause of signal loss in the subclavian artery was found to be the perpendicular orientation of the subclavian vein (through which the highly concentrated contrast medium flows) to the magnetic field. With the MRI devices currently in use, perpendicular orientation of the subclavian vein to the magnetic field cannot be avoided. Furthermore, the subclavian vein and subclavian artery are anatomically in close proximity to one another. These factors cause the susceptibility artifact, which is thought to result in signal loss in the subclavian artery.

Adult↗
PubMed2002

Fat-suppressed three-dimensional MR angiography technique with elliptical centric view order and no prolonged breath-holding time.

PURPOSE: To determine the appropriate rate of fat-suppression pulses (using spec IR-spectral selective inversion recovery) for fat-suppressed 3D magnetic resonance angiography (MRA) with an elliptical centric view order. MATERIALS AND METHODS: In abdominal 3D fast spoiled gradient echo (fast SPGR) with an elliptical centric view order, the spec IR pulse rate was changed from zero to one every 15 repetitions (in nine steps) in eight volunteers. In the equilibrium phase, abdominal contrast-enhanced 3D MRA was obtained by 3D fast SPGR using an elliptical centric view order without fat-suppression and with two spec IR, and by fat-suppressed 3D fast SPGR with a sequential-centric view order (efgre3D) in 18 cases. Fat and vascular signals were estimated. RESULTS: Although 3D fast SPGR using an elliptical centric view order with spec IR placed every 15 TR and efgre3D effectively decreased fat signals, these sequences lengthened the breath-hold by 4-6 seconds compared with non-fat-suppressed sequence. 3D fast SPGR using an elliptical centric view order and two spec IR reduced the fat signal by 30% and provided good 3D MR angiography without substantial prolongation of breath-hold. CONCLUSION: Two spec IR can be used for generation of partially fat-suppressed abdominal 3D MRA without prolongation of the breath-hold when performing 3D fast SPGR using an elliptical centric view order.

Abdomen↗
PubMed2002

[Examination of MR cholangiopancreatography using the fast recovery single shot fast spin echo sequence].

During this project, we evaluated methods to scan MRCP images with overlapping slice positions during one breath-hold using the FRSSFSE sequence. The FRSSFSE sequence is a technique to arbitrarily change the residual transverse magnetization to longitudinal magnetization. With the SSFSE sequence, the imaging field where the slice position overlaps is subject to substantial influence from the saturation effect of the water component. Therefore, one breath-hold is required for each image. However, the FRSSFSE sequence enabled the deterioration in image quality due to the saturation effect to be minimized even during a short TR. This enabled images of overlapping slice positions to be scanned during one breath-hold. We used a setting of TR=5,000 ms at our hospital, and scanned several images with overlapping slice positions during one breath-hold. The TR=5,000 ms setting was determined from image quality and breath-hold time considerations. The use of the FRSSFSE sequence with MRCP enabled 3-4 images to be scanned at overlapping slice positions during one breath-hold. This method is effective in reducing examination time and the burden on the patient.

Bile Ducts↗
PubMed2002

[Removal of high signal artifact (marching metal artifact) by the magnetic substance].

During this project, we evaluated methods to prevent high-signal artifact (marching metal artifact) that are caused by magnetic substance. Marching metal artifact is caused by the resonance frequency created by magnetic substance. Phase encoding and frequency encoding are often switched to minimize the influence that marching metal artifact have on the image. However, this method will only change the position at which marching metal artifact occur. It does not have the ability to completely prevent marching metal artifact. Our research illustrated that marching metal artifact can be prevented by changing the strength of the slice selective gradient field at the 90 degree RF pulse and 180 degree RF pulse. In other words, marching metal artifact can be prevented by changing the frequency bandwidth for the 90 degree RF pulse and 180 degree RF pulse. The incorporation of the phase correct option in the device used for our research (SIGNA LX and SIGNA CV/i) results in different slice selective gradient field strengths at the 90 degree RF pulse and the 180 degree RF pulse. This indicates that the use of phase correction enables marching metal artifact to be prevented.

Artifacts↗
PubMed2002

[Evaluation of t(1)-weighted black blood imaging using triple inversion recovery].

The black blood sequence, in which the blood signal is suppressed, fundamentally provides T(2)-weighted images. We developed a T(1)-weighted black blood sequence. This new sequence improved the triple IR sequence that uses three inversion pulses by continuously providing three inversion pulses. By so doing, the sequence lengthens the time from the third inversion pulse to data sampling. The new sequence sets the flip angle of the third inversion pulse to 95-110 degrees. Consequently, the difference in T(1) is emphasized in favor of the longitudinal magnetization component with the null point of blood. Data sampling uses the fast spin-echo sequence of a wide sampling bandwidth. The wide bandwidth shortens echo space. T(1)-weighted black blood images were obtained by these methods. Fat suppression is possible by using a CHESS pulse before data sampling.

Brain↗