The Macdonald criteria, ¹⁾ used 2-dimensional set of measurements for assessing tumor response, measure maximal enhancing tumor diameter on a single axial contrast-enhanced T1-weighted image and the largest perpendicular diameter on the same image

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The product of these measurements is calculated, and the measurements are repeated with each scan.

RECIST ²⁾ , which has become the standard set of criteria for assessing response in systemic cancers, measures the longest single linear enhancing diameter across a lesion in the axial plane and repeats this on follow-up studies, regardless of changes in the original orientation or section