Design and Construction Method of an Open-Type Magnetically Shielded Room for MRI Composed of Magnetic Square Cylinders
スポンサーリンク
概要
- 論文の詳細を見る
To shield the leakage flux densities of 3 T magnetic resonance imaging (MRI) higher than 1.5 T MRI and to reduce the degradation of magnetic properties during construction, the design of an open-type magnetically shielded room (MSR) combined with square cylinders made of magnetic and conductive materials should be improved. This paper reports on an optimal design for magnetic cylinders to improve the shielding effect, while also considering ease of construction with a view to practical use. Firstly, the structure of the magnetic cylinders, such as their opening width and the slit width were optimized using a 3D linear magnetic-field analysis. Using optimal magnetic cylinders, when the relative permeability (μ_r) of the magnetic material is larger than 10 000, the reluctance of gaps between the cylinders is the main contributor to the leakage flux. So, the required (μ_r) of the magnetic material is 10 000 and oriented silicon steel is adopted instead of the non-oriented type. Secondly, as an optimal construction method, it was determined by experiment that oriented silicon steel sheets, annealed after bending, should be laminated so that the effect of gaps on butt joints between steel sheets on the magnetic property of the cylinder becomes smaller. This enables the relative permeability of 10 000 when the maximum flux density of the material in the cylinder is less than 1.7 T. Finally, the minimum thickness of oriented silicon steel sheet of cylinders depending on the distance from a 3 T MRI is obtained using linear magnetic analysis under the condition that the maximum flux density of the material of the cylinder is less than 1.7 T. In the case of the thickness of 3.8 mm, the leakage flux density of 3 T MRI is decreased to less than a guideline (0.5 mT) when the distance between the cylinders and the center of MRI is larger than 2 750 mm. This indicates that the optimal design and construction method of an open-type MSR for 3 T MRI composed of magnetic square cylinders are realized.
論文 | ランダム
- Crossings and selections for six generations based on flower vase life to create lines with ethylene resistance or ultra-long vase life in carnations (Dianthus caryophyllus L.)
- G408 芝草害虫に対するBT剤の防除効果(昆虫病理学・微生物的防除)
- 芝草害虫の微生物的防除 (害虫の微生物的防除)
- ドウガネブイブイに対する昆虫病原糸状菌Metarhizium anisopliaeの改良菌株No.31の製剤化
- 天然アユと近自然工法(「野生生物」との共存を考える)