A Portable Unilateral Nuclear Magnetic Resonance Magnet Designed for Breast Cancer Detection

The incidence of breast cancer ranks first among female malignant tumors, which seriously threatens women's health and life. Among the existing detection methods, magnetic resonance imaging (MRI) detection has the advantages of non-destructive and non-radiation. To develop a portable magnetic resonance imaging sensor for breast cancer detection, this paper proposes a new unilateral magnet structure. Firstly, the Halbach closed-loop magnet is decomposed and a part of it is selected as the basic structure of the magnet, and a method for calculating the uniformity of the gradient magnetic field is proposed, which is conducive to subsequent optimization and adjustment. Then iron yokes are added to improve the uniformity of the magnetic field. On this basis, genetic algorithm is used to optimize the cross-sectional size, length, and spatial position of the magnetic bars and iron yokes. At the same time, a two-step optimization process is used to reduce the amount of calculation. The final magnet structure has a hemispherical target area with a radius of 5.5 cm, which can accommodate a single breast for detection. The minimum value of the magnetic field in the target area is 52mT, and the magnetic field is evenly distributed in the horizontal direction. In the vertical direction, the magnetic field has a constant small gradient of 0.4T/m, which is conducive to the detection of biological tissues. The performance of this magnet shows that it can be used as the main magnet of portable magnetic resonance imaging sensor in the future.