A linear array (1D) detector made by monolithic silicon detector for real time high spatial resolution dosimetry in modern radiotherapy applications is described. The prototype detector consists of 128 square pixels of 250 mum connected to a dedicated read-out integrated circuit (ROIC). Results on the linearity of the system, as well as relative dosimetry measurements in the presence of high dose gradients for 6 MV X-rays by a clinical linac will be presented and compared with film
