MICROSCOPIC INTRAOSSEOUS EXTENSION OF OSTEOSARCOMA - ASSESSMENT ON DYNAMIC CONTRAST-ENHANCED MRI

Objective. This study investigated whether dynamic MRI could determine microscopic intraosseous invasion in osteosarcoma. Patients. Six pati ents with osteosarcoma who underwent total resection of the tumor afte r chemotherapy were studied. Design. The steepest slope value of the t ime-intensity curve was calculated on the basis of the first-pass meth od on dynamic MRI performed after chemotherapy. Slope value modified l og=[100.(SIb-SIa)/(T-b-T-a)/SIa], where SIa and SIb represent the sign al intensity al time points T-a and T-b when the steepest slope starte d and ended, respectively. The slope value was correlated with the his tological findings of the surgical specimens. The findings on conventi onal MRI were also reviewed. Results and conclusions. In five of six p atients microscopic tumor invasion ranging from 1 to 3.5 cm in depth w as pathologically proven. The slope value within the microscopic invas ion (-0.052+/-0.267) was significantly greater than that of tumour-fre e marrow (-0.609+/-0.220) and less than that in areas showing macrosco pic tumor invasion (0.595+/-0.483) (P<0.001). Histological examination disclosed the dilatation of small vessels within the macroscopic and microscopic invasion. Findings on conventional MRI varied among patien ts; microscopic invasion was not detected in one, underestimated in tw o, and overestimated in two. It is concluded that calculation of the s lope value on dynamic MRI can discriminate regions of microscopic inva sion from tumor-free marrow in patients with osteosarcoma after chemot herapy.