A system for locating lesions in a prostate during a first intervention session, and for using that lesion location information during a second intervention session, the system comprising a. a first 3D modelling module which creates a first 3D model of the prostate based at least in part on real-time ultrasound imaging of the prostate during a first intervention session; b. an intervention recording module which records positions of a plurality of biopsy samples taken during said first intervention session, position of the samples being recorded in terms of said 3D model; c. a diagnosis recording module for recording positions of at least one lesion detected by pathology examinations of said biopsy samples, the lesion positions being recorded in terms of said first 3D model; d. a second 3D modelling module which creates a second 3D model of the prostate based at least in part on real-time ultrasound imaging of the prostate during a second intervention session; e. a lesion position calculation module which calculates positions of said detected lesions with respect to said second 3D model, based on positions recorded by said diagnostic recording module and further based on positional relationships between said first 3D model and said second 3D model; and f. a display module which displays said calculated lesion positions in a context of said patient's prostate's real-time position, thereby enabling a surgeon to guide therapeutic interventions during said second intervention session according to lesion location information gleaned during said first intervention session and during analysis of biopsies taken during said first intervention session, and: g. a module for detecting and reporting the position of a prostate in real time, which module comprises one or more electronic signal transmitters positionable near a patient and a sensor for detecting and reporting the sensor's position with respect to electronic signals transmitted by said transmitters, said system being characterized in that said sensor is provided on a Foley catheter which comprises a distal balloon inflatable within a bladder for immobilizing a distal end of the catheter and a 'back-stopper' immobilization device for immobilizing a proximal portion of the catheter at the entrance to the urethra, said immobilization devices serving to immobilize said sensor within a prostate at a known and fixed position between said distal catheter end at the bladder entrance and said urethra entrance at the apex of the prostate. a. a first 3D modelling module which creates a first 3D model of the prostate based at least in part on real-time ultrasound imaging of the prostate during a first intervention session; b. an intervention recording module which records positions of a plurality of biopsy samples taken during said first intervention session, position of the samples being recorded in terms of said 3D model; c. a diagnosis recording module for recording positions of at least one lesion detected by pathology examinations of said biopsy samples, the lesion positions being recorded in terms of said first 3D model; d. a second 3D modelling module which creates a second 3D model of the prostate based at least in part on real-time ultrasound imaging of the prostate during a second intervention session; e. a lesion position calculation module which calculates positions of said detected lesions with respect to said second 3D model, based on positions recorded by said diagnostic recording module and further based on positional relationships between said first 3D model and said second 3D model; and f. a display module which displays said calculated lesion positions in a context of said patient's prostate's real-time position, thereby enabling a surgeon to guide therapeutic interventions during said second intervention session according to lesion location information gleaned during said first intervention session and during analysis of biopsies taken during said first intervention session, and: g. a module for detecting and reporting the position of a prostate in real time, which module comprises one or more electronic signal transmitters positionable near a patient and a sensor for detecting and reporting the sensor's position with respect to electronic signals transmitted by said transmitters, said system being characterized in that said sensor is provided on a Foley catheter which comprises a distal balloon inflatable within a bladder for immobilizing a distal end of the catheter and a 'back-stopper' immobilization device for immobilizing a proximal portion of the catheter at the entrance to the urethra, said immobilization devices serving to immobilize said sensor within a prostate at a known and fixed position between said distal catheter end at the bladder entrance and said urethra entrance at the apex of the prostate.