A tethered laparoscopic probe 100 comprising a probe head 102 on a tether 104 deployable through a trocar into a cavity where it is freely movable to detect and locate gamma radiation from a radiopharmaceutical. The probe may have a grip 108 for positioning by surgical tools. The head comprises radiation shielding 114, 116 with a detection aperture for admitting radiation from a limited field of view such that it is detected by a gamma radiation detector within the casing. The detector may comprise a scintillator 110 such as thallium activated caesium iodide, and a photodetector 112 to detect the scintillation. The detector may comprise a Cadmium Zinc Telluride semiconductor. The probe may also have a beta radiation detector or a second gamma detector. The radiation shielding may be movable to change the detector field of view, or deformable to alter the shielding thickness around the detector.
