Methods and apparatus for operating a low-field magnetic resonance imaging (MRI) system to perform diffusion weighted imaging, the low-field MRI system including a plurality of magnetics components including a B0magnet configured to produce a low-field main magnetic field B0, at least one gradient coil configured to, when operated, provide spatial encoding of emitted magnetic resonance signals, and at least one radio frequency (RF) component configured to acquire, when operated, the emitted magnetic resonance signals. The method comprises controlling one or more of the plurality of magnetics components in accordance with at least one pulse sequence having a diffusion-weighted gradient encoding period followed by multiple echo periods during which magnetic resonance signals are produced and detected, wherein at least two of the multiple echo periods correspond to respective encoded echoes having an opposite gradient polarity.本發明揭示用於操作一低場核磁共振成像(MRI)系統以執行漫射加權成像之方法及裝置，該低場MRI系統包含複數個磁性組件，該複數個磁性組件包含：一B0磁鐵，其經組態以產生一低場主磁場B0；至少一梯度線圈，其經組態以在經操作時提供經發射核磁共振信號之空間編碼；及至少一射頻(RF)組件，其經組態以在經操作時獲取該等經發射核磁共振信號。該方法包括根據至少一脈衝序列控制該複數個磁性組件之一或多者，該至少一脈衝序列具有一漫射加權梯度編碼週期其後接著為多個回波週期，在該多個回波週期期間產生及偵測核磁共振信號，其中該多個回波週期之至少兩者對應於具有一相反梯度極性之各自經編碼回波。
