[Evaluation of therapeutic effect using enhanced MRI in lung cancer: evaluation of methods in terms of necrosis]

To evaluate therapeutic effect in terms of necrosis or cavity, enhanced MRI was performed in 40 lung cancer patients treated by conservative therapy. We provided the reduction ratio of the viable tumor as calculated by a volume method and a cross-sectional method. In the volume method, the volume of necrosis was subtracted from the volume of the tumor, and in the cross-sectional method, the product of the longest diameter and widest perpendicular diameter of necrosis was subtracted from the product of the longest diameter and widest perpendicular diameter of the tumor. We then examined whether we could substitute the cross-sectional method for the volume method. The reduction ratios of viable tumor calculated by the two methods were in good correlation. The limits of agreement of each method and their repeatability coefficients were considered small enough for clinical use. Therefore, we concluded that the cross-sectional method could be used in place of the volume method for clinical purposes. In evaluating therapeutic effect in terms of necrosis when using contrast-enhanced MR imaging, the reduction ratio of the viable tumor determined by the cross-sectional method can be substituted for that determined by the volume method.