PITFALLS IN THE MR DIAGNOSIS OF PRIMARY M ALIGNANT BONE-TUMORS

MRI has gained an undisputed place in the evaluation of malignant bone tumors, not only for verifying results of conventional radiographs an d clarifying differential diagnoses; it has also become increasingly i mportant for the assessment of the malignant/benign nature of the tumo r, its growth rate, definition of adequate sites for biopsy, local pre operative staging, and evaluation of the response to chemotherapy. How ever, several pitfalls have to be observed regarding choice of technic al parameters (coils, sequences, imaging planes), tissue differentiati on, and tumor staging. When staging malignant tumors, critical aspects which have to be observed are tumor extension, integrity of the corti cal bone, soft tissue components, infiltration of a joint or neurovasc ular bundle. The use of contrast agents provides important additional information but can also give rise to misinterpretations. Thus, all fe atures of a tumor have to be observed in order to establish a final di agnosis. Particular difficulties can occur with the interpretation of MR images of osteomyelitis, osteoid osteoma, stress and insufficiency fractures, bone infarcts, myositis ossificans, hemangiomas, and aneury smal bone cysts.