Abstract: A multi-frequency microwave antenna (1) of the microwave image reconstruction system senses a signal which passes through an analogue connection (6) to a Dicke null-balancing radiometer (7) which detects sequentially the signal contributions at the different frequencies of the multi-frequency antenna of the system. The resulting sequential analogue signals from the radiometer are directly related to the brightness temperatures at the corresponding frequencies, and these brightness temperatures are directly related to a real intra-body temperature distribution. The system uses a PC (5) and comprises a mean to reconstruct a one-dimensional profile of real intra-body temperatures from the brightness temperatures via the outputs from the analogue-to-digital converter (15).