Clinical performance of a shielded diode for small field relative dosimetry in a 1.5 T MRI‐linac using measurements and simulations

This study reinforces the importance of detector choice for characterizing small fields in the presence of magnetic fields. The EDGE detector was shown to misrepresent the shape of the crossline profile for small fields in a 1.5T magnetic field. Film is recommended for determining the dose distribution shape, but it is difficult to position precisely and thus cannot be used to determine the lateral shift with high precision. The microDiamond detector was determined to most accurately characterize both the lateral shift and shape of the lateral dose distribution of the detectors investigated. The investigated ion chamber and shielded silicon diode should be used with caution for small fields in the presence of magnetic fields due to perturbances to profile shape.