PELVIC LESIONS IN PATIENTS WITH TREATED CERVICAL-CARCINOMA - EFFICACYOF PHARMACOKINETIC ANALYSIS OF DYNAMIC MR-IMAGES IN DISTINGUISHING RECURRENT TUMORS FROM BENIGN CONDITIONS

OBJECTIVE. Dynamic MR image series were analyzed with a pharmacokineti c two-compartment model. To preserve the spatial resolution of the dyn amic MR images, the pharmacokinetic parameters were computed pixel by pixel, color coded, and superimposed on conventional MR images (pharma cokinetic mapping). The efficacies of pharmacokinetic mapping and conv entional MR imaging in distinguishing between recurrent tumors and ben ign conditions in patients who have pelvic lesions after treatment of cervical carcinoma were compared. MATERIALS AND METHODS. Twenty-one wo men with 24 suspected pelvic lesions and a history of treated cervical carcinoma (stages IB-IIIA) were included in this study. Patients had been treated before MR imaging with surgery or irradiation alone (eigh t patients) or a combination of the two (13 patients). Patients were r eferred because of findings from CT examinations and/or clinical exami nations. Of 24 suspected lesions, 17 were histologically verified as t umor recurrences and seven were classified as benign masses (histologi cally diagnosed as fibrosis and granulation tissue). T1- and T2-weight ed spin-echo images were interpreted by three observers. During and af ter constant-rate infusion of gadopentetate dimeglumine, the kinetics of lesion response were determined with a strongly T1-weighted saturat ion recovery turbo-fast low-angle shot sequence. The signal-time curve s for the suspected lesions were analyzed within the framework of a ph armacokinetic two-compartment model and displayed as color-coded image s. The calculated pharmacokinetic parameters (amplitude [A] and tissue distribution time [t(21)]) were evaluated retrospectively to obtain o ptimal threshold values for differentiating malignant lesions from ben ign lesions. RESULTS. Analysis of the pharmacokinetic mapping data sho wed significantly shorter (p < .005) and stronger (p < .001)contrast m edium enhancement of malignant lesions (t(21),24 Sec; A, 1.5 arbitrary units) than of benign lesions (t(21), 65 Sec; A,0.7), resulting in a sensitivity of 100%, a specificity of 88%, and an accuracy of 96%. Int erpretation of the lesions on conventional T2-weighted MR images resul ted in a sensitivity of 90%, a specificity of 38%, and an accuracy of 74%. CONCLUSION. Analysis of color-coded pharmacokinetic maps is more effective than conventional MR imaging in distinguishing between malig nant and benign conditions in patients who have pelvic lesions after t reatment of cervical carcinoma.