FIRST-PASS IMAGES OF MUSCULOSKELETAL LESIONS - A NEW AND USEFUL DIAGNOSTIC APPLICATION OF DYNAMIC CONTRAST-ENHANCED MRI

The purpose of this study was to evaluate the diagnostic value of parametric images which display the first-pass of Gd-DTPA after intravenous bolus injection. Single slice dynamic contrast-enhanced MRI (Turbo-FLASH) with a temporal resolution of 2.41 s was performed in 40 benign and malignant muscutoskeletal lesions, Parametric 'first-pass' images were obtained by using a new postprocessing technique, derived from a home written computer program, which calculated the steepest slope of the time-intensity curve pixel by pixel. First-pass images provided qualitative and quantitative information, which was useful for diagnosis and therapy. Demonstration of the areas with the highest vascularization was very helpful in planning the best biopsy site in 6 patients and to delineate tumor from peritumoral muscle edema in 4 patients, In 10 patients the first-pass images provided additional information, which was not visible on the conventional spin-echo images. The most promising application was the ability to evaluate the response to preoperative chemotherapy in a patient with Ewing's sarcoma. Although a highly statistically significant difference (p < 0.001) was found between the first-pass slope values of benign and malignant lesions, the sensitivity (77%) and specificity (71%) of this method were too low to permit a definite differentiation of highly vascular benign from malignant lesions. Pathologic examination of 17 lesions, performed in the plane of the first-pass image, showed a good correlation between the first-pass slope values and the vascularization of the tissues. While in lesions with a nonuniform enhancement pattern, the single slice technique is subject to sampling error, first-pass images provide useful qualitative and quantitative information for the evaluation of musculoskeletal lesions, which is often not visible on the spin-echo images.