A TV-type X-ray detector using a SIT vidicon has been used for biological diffraction studies at the EMBL outstation at DESY, Hamburg, Germany. The detector converts the two-dimensional diffraction pattern to a charge pattern on the vidicon target, which is read out in the slow-scan mode. This detector has high DQE, no count-rate limit, and is simple and inexpensive to construct. Radiation from the storage ring DORIS was used to study the structure of live muscle at various phases of contraction. Typically the "count-rate" on the detector was 106 X-rays/sec and a total exposure of a few seconds was needed to record the weak diffraction from muscle. This compares with usual exposure times of several hours using a rotating anode generator and film.