[Magnetic resonance imaging of tumors of the knee using surface coils]

Fourteen patients presenting with a primary bone tumour of the knee have been assessed, in parallel with other imaging techniques, by examination using MRI with surface coils. The first examinations were made before any biopsy was made or chemotherapy given so as not to impair the interpretation of the images and to provide guidance as to the correct site for biopsy. Two sequences were made - a longitudinal sequence made with echo-spin, echo-time = 30 ms, repetition-time = 500 ms, with four impulses and a transverse sequence made with echo-spin, echo-time = 40 ms, repetition-time = 1300 ms with two impulses (+/- multi-echo). Thanks to the excellent spatial resolution using a surface aerial, we have been able to determine not only the intramedullary extent of the tumour and its relationship with healthy muscles and vessels but also, in a much more precise way than previously, evidence of extension to the skin, to the epiphysis, to the articular cartilage and to the synovium, thus allowing an objective assessment to be made of the possibility of a closed block-excision of the joint. A second MRI examination with cranial coil was made pre-operatively at the end of adjuvant chemotherapy to determine the precise progress of the tumour, and in particular, to discover the localisation of the tumour in the femoral and tibial shafts, the investigation being aided by systemic scintigraphy.