A method for spatially calibrating an ultrasound probe, comprising: placing the ultrasound probe in a first position and orientation relative to a phantom; measuring the first position and orientation of the ultrasound probe; acquiring a first ultrasound image of the phantom; determining a first spatial relationship between a phantom reference frame and a pixel reference frame, based on the first ultrasound image; repositioning the ultrasound probe in a second position and orientation relative to the phantom; measuring the second position and orientation of the ultrasound probe; acquiring a second ultrasound image of the phantom; determining a second spatial relationship between the phantom reference frame and the pixel reference frame, based on the second ultrasound image; repositioning the ultrasound probe in a third position and orientation relative to the phantom; measuring the third position and orientation of the ultrasound probe; acquiring a third ultrasound image of the phantom; determining a third spatial relationship between the phantom reference frame and the pixel reference frame, based on the third ultrasound image; and computing a probe calibration matrix by a closed form formulation based on the first position and orientation of the ultrasound probe, the first spatial relationship, the second position and orientation of the ultrasound probe, the second spatial relationship, the third position and orientation of the ultrasound probe, and the third spatial relationship, characterised in that the closed form formulation is based on homogeneous matrix equation AX=XB, in which A is the relative coordinate transformations between the locations of the respective pixels corresponding to the prominent feature points of the phantom, B is a relative coordinate transformation of an ultrasound probe reference frame at successive measured positions, and X is the probe calibration matrix R T P. placing the ultrasound probe in a first position and orientation relative to a phantom; measuring the first position and orientation of the ultrasound probe; acquiring a first ultrasound image of the phantom; determining a first spatial relationship between a phantom reference frame and a pixel reference frame, based on the first ultrasound image; repositioning the ultrasound probe in a second position and orientation relative to the phantom; measuring the second position and orientation of the ultrasound probe; acquiring a second ultrasound image of the phantom; determining a second spatial relationship between the phantom reference frame and the pixel reference frame, based on the second ultrasound image; repositioning the ultrasound probe in a third position and orientation relative to the phantom; measuring the third position and orientation of the ultrasound probe; acquiring a third ultrasound image of the phantom; determining a third spatial relationship between the phantom reference frame and the pixel reference frame, based on the third ultrasound image; and computing a probe calibration matrix by a closed form formulation based on the first position and orientation of the ultrasound probe, the first spatial relationship, the second position and orientation of the ultrasound probe, the second spatial relationship, the third position and orientation of the ultrasound probe, and the third spatial relationship, characterised in that the closed form formulation is based on homogeneous matrix equation AX=XB, in which A is the relative coordinate transformations between the locations of the respective pixels corresponding to the prominent feature points of the phantom, B is a relative coordinate transformation of an ultrasound probe reference frame at successive measured positions, and X is the probe calibration matrix R T P.