Real-Time Tumor Tracking for Four-Dimensional Computed Tomography Using SQUID Magnetometers

We present a method for real-time tumor tracking in external beam radiotherapy using superconducting quantum interference device (SQUID) magnetometers. The objective is to develop a localization algorithm and determine a cost effective sensor configuration that is capable of long-range localization, ~1000 mm, with an accuracy of 1-2 mm. We developed several algorithms to calculate the location of a magnetic dipole for geometry relevant for four-dimensional computed tomography (4DCT) to investigate sensor configuration and accuracy. We determined that two cube detectors, located diametrically opposite, are a feasible design for the localization system.