Magnetoresistive rotational position detection in a radiation therapy system

A method of measuring a rotational position of an assembly, the method comprising:

• applying an excitation signal to an actuator that is coupled to the assembly that includes an array of ferromagnetic teeth that are arranged circumferentially about the assembly, wherein the excitation signal causes a first rotational displacement of a first ferromagnetic tooth included in the array from a first rotational position to a second rotational position;
• measuring one or more signal outputs from the magnetoresistive sensor when the first ferromagnetic tooth is disposed at the second rotational position, wherein measuring the one or more signal outputs comprises measuring a sine signal output and a cosine signal output;
• generating one or more corrected signals by modifying each of the one or more signal outputs with a respective signal offset value;
• and
• based on the corrected signals, determining a rotational position of the assembly, wherein modifying each of the one or more signal outputs with the respective signal offset values comprises modifying the sine signal output with a sine signal offset value and the cosine signal output with a cosine signal offset value.

A radiation treatment system comprising:

• a rotatable multileaf collimator carousel;
• an array of ferromagnetic teeth that are arranged circumferentially about the carousel;
• a magnetoresistive sensor disposed proximate an edge of the carousel;
• and
• a processor configured to:
• apply an excitation signal to an actuator that is coupled to the carousel, wherein the excitation signal causes a first rotational displacement of a first ferromagnetic tooth included in the array from a first rotational position to a second rotational position;
• measure one or more signal outputs from the magnetoresistive sensor when the first ferromagnetic tooth is disposed at the second rotational position;
• generate one or more corrected signals by modifying each of the one or more signal outputs with a respective signal offset value;
• and
• based on the corrected signals, determine a rotational position of the assembly.