Fig. 2From: Combined effect of dose gradient and rotational error on prescribed dose coverage for single isocenter multiple brain metastases in frameless stereotactic radiotherapyPaddick gradient index (GI) versus the permitted maximum dose inside the target. GI is lower (steeper gradient) as the maximum dose is higher. Arrowed GI values are those of r2.5D110 and calculated using 11-Gy volumes, not 9 Gy; therefore, they are underestimatedBack to article page