A method for evaluating radiation dose delivery to a target, comprising: using a portal imaging device to generate a digital radiation dose distribution image based on radiation delivered according to a treatment plan, wherein the generated radiation dose distribution image includes at least a first point and a second point; using a processing device to compare the generated radiation dose distribution image with a corresponding predicted radiation dose distribution image, the comparing including comparing points in the generated radiation dose distribution image with corresponding points in the predicted radiation dose distribution image; using the processing device to evaluate the compared points; and determining whether dose delivery is acceptable based on a result of the evaluation, characterized in that: said evaluating the compared points uses different evaluation criteria; and in that the first point is evaluated using a first gamma criterion and the second point is evaluated using a second gamma criterion, the first gamma criterion being different from the second gamma criterion, each of the first and second gamma criteria including a corresponding dose difference acceptance value and a spatial difference acceptance value, the evaluation including evaluating each of the first and second points for both dose and spatial differences, and determining whether the dose and spatial differences obtained for the first and second points are within the set dose and spatial difference acceptance values of their respective gamma criteria. using a portal imaging device to generate a digital radiation dose distribution image based on radiation delivered according to a treatment plan, wherein the generated radiation dose distribution image includes at least a first point and a second point; using a processing device to compare the generated radiation dose distribution image with a corresponding predicted radiation dose distribution image, the comparing including comparing points in the generated radiation dose distribution image with corresponding points in the predicted radiation dose distribution image; using the processing device to evaluate the compared points; and determining whether dose delivery is acceptable based on a result of the evaluation, characterized in that: said evaluating the compared points uses different evaluation criteria; and in that the first point is evaluated using a first gamma criterion and the second point is evaluated using a second gamma criterion, the first gamma criterion being different from the second gamma criterion, each of the first and second gamma criteria including a corresponding dose difference acceptance value and a spatial difference acceptance value, the evaluation including evaluating each of the first and second points for both dose and spatial differences, and determining whether the dose and spatial differences obtained for the first and second points are within the set dose and spatial difference acceptance values of their respective gamma criteria. said evaluating the compared points uses different evaluation criteria; and in that the first point is evaluated using a first gamma criterion and the second point is evaluated using a second gamma criterion, the first gamma criterion being different from the second gamma criterion, each of the first and second gamma criteria including a corresponding dose difference acceptance value and a spatial difference acceptance value, the evaluation including evaluating each of the first and second points for both dose and spatial differences, and determining whether the dose and spatial differences obtained for the first and second points are within the set dose and spatial difference acceptance values of their respective gamma criteria.