Preliminary study of whole-body diffusion-weighted imaging in detecting pulmonary metastatic lesions from clear cell renal cell carcinoma: comparison with CT

Background: Whole-body diffusion-weighted imaging (DWI) has been widely used in detecting malignant metastases, including pulmonary metastases. Purpose: To evaluate the possible utility of whole-body DWI in detecting pulmonary metastases of patients with clear cell renal cell carcinoma (ccRCC) and compare the exact differences between MR and CT in detecting pulmonary lesions. Material and Methods: Whole-body DWI and chest CT examinations were performed on nine consecutive patients (8 men and 1 woman) with histologically confirmed ccRCC and possible metastatic lesions before chemotherapy. Results: CT and MR demonstrated pulmonary metastases in seven patients and no metastatic lesions in two patients. The numbers of pulmonary metastases detected on CT, DWI-only, T1WI-only and DWI in combination with T1WI were 83, 35, 34 and 39, respectively. Metastases with a diameter above 1.0 cm could all be detected by DWI and a diameter above 0.7 cm could all be detected by DWI in combination with T1WI. Significant differences were obtained both for correlationship between diameter and detection rates of DWI and T1WI by using Spearman rank correlation analysis. Conclusion: Although MR cannot be considered a replacement for CT in pulmonary metastases from ccRCC, whole-body DWI, with the combination of T1 dual echo, might be helpful for the evaluation of tumor response to chemotherapy in the follow-up of patients when the diameter of the pulmonary metastases is over 1.0 cm.