Panel-type sensor/source array assembly

A low-density sensor panel assembly system is provided for use with remote marker assemblies that generates a marker signal and for use with a radiation therapy source that generates a radiation beam during radiation therapy. The system includes a sensor array having a layer of sensor coils arranged in a selected pattern and configured to receive the marker signal from the remote marker. A support panel is connected to the sensor array and retains each of the sensor coils in a substantially fixed and unmoving position relative to the other sensor coils. The sensor panel and sensor array define a low-density panel structure configured to dwell in the radiation beam during the radiation therapy.