An improved method and device for accurate, efficient surgical procedures are disclosed. The disclosed system consists in simultaneously using an elongated member that conveys energy to a treatment site and imaging means to control position of the elongated member and monitor treatment progress in real-time. In a preferred embodiment, for BPH, a twister fiber with a fused cap is used and ultrasound image guidance is obtained using a rectal probe. The method consists in placing an ultrasound rectal probe, fixed by mechanical means, and an optical fiber inserted into urethra. Initial positioning of probe is done under endoscopic/ultrasound control. The twister fiber probe operates in contact-mode. Treatment is monitored, real-time, by the ultrasound device. Additional imaging technologies include Positron Emission Tomography (PET), Computed Tomography (CT) or Optical Coherence Tomography. Other applications include the removal of tumorous (hyperplasic) tissue. Sources include lasers, higher power LEDs or bright lamps and photodynamic therapy.