Intensity modulated radiation therapy (IMRT) and VMAT are the mostly widely used treatment planning and delivery techniques in radiation therapy. However, conventional IMRT (with 5-10 beams) often does not possess sufficient angular sampling required to spatially spread the dose. On the contrary, current VMAT (with 1-3 arcs) oversamples the angular space and does not provide the desired intra-beam intensity modulation in some or all directions. More specifically, conventional VMAT discretizes the angular space into equally spaced control points during planning and then optimizes the apertures and weights of the control points. The aperture at an angle in between two control points is obtained through interpolation. This approach tacitly ignores the differential need for intensity modulation of different angles. As such, multiple arcs are often required, which may oversample some angle(s) and undersample others.
What is needed is a method to differentially distribute the station points in the angular space according to the need of the specific case in order to best cover the target volume and spare the sensitive structures. In case of rotational arc therapy, this is to segmentally boost the VMAT scheme to eliminate the need for multiple arcs in VMAT treatment with improved dose distribution and/or delivery efficiency. More generally, what is needed is a method of radiation therapy planning and delivery that involves optimization of the fundamental system variables characterizing the station points (or control points) of a digital linear accelerator in unison, instead of optimization of the beam fluence parameters, which is typically a composite of a set of station parameters, or optimization of a pre-distributed set of beams.
USPTO Backgrounds
USPTO Backgrounds