Freehand SPECT method. (a) Data acquisition using the freehand SPECT device; radioactivity is measured with the probe from multiple directions. P is the probe, and in yellow, the detection beam of the probe. The orange cloud is an accumulation of the area where it is measured. (b) The localisation of the 125I seed after reconstruction. The 125I seed reconstruction is projected over the optical image in purple. T is the patient tracker. (c) 3D visualisation of the distance and direction of the probe tip to the 125I seed. (d) Injection of 99mTc-nanocolloid guided by freehand SPECT. I is the tracer injection localisation.