Dec 20, 2012
Innovation: patent applications review
A round-up of the latest international patent applications in radiation therapy.
Cerenkov emission monitors radiation therapy
Researchers at Dartmouth College (Hanover, NH) have described a method for using Cerenkov radiation to monitor radiation therapy (WO/2012/159043). The system comprises a high-energy radiotherapy source, apparatus for excluding uncontrolled ambient light and apparatus for collecting Cerenkov and/or photoluminescent light emitted from the treated region in the subject. The system performs spectral analysis of the collected light and determines the oxygenation or metabolic function of the treated tissue. Calibration is achieved by imaging a phantom in the beam from multiple angles, and analysing the emitted light to determine the beam profile.
Collimator design reduces leakage, weight, complexity
A new design of collimator for delimiting a radiation therapy beam is detailed by Elekta of Sweden (WO/2012/146262). The collimation apparatus comprises a block that's wide enough to extend across the beam and can be moved into the beam from one side of the beam axis, plus an array of elongate narrow leaves, arranged side-by-side perpendicular to the beam, which can be moved individually into the beam from the opposing side of the beam axis. Thus, there is in effect a single bank of multileaf collimator leaves on one side of the aperture and a block collimator on the other, an arrangement that is still suitable for IMRT-based treatments. The block and the array of leaves can be the only collimation apparatus in the radiation head, offering reduced leakage and significantly reduced complexity and weight.
Compensator-based brachytherapy ramps dose conformity
A team at the University of Iowa (Iowa City, IA) has shown that compensator-based brachytherapy can increase dose conformity for non-radially symmetric tumours. The idea is to use a device to partially shield radiation emanating from a brachytherapy source (WO/2012/154762). In one aspect, this device comprises a radiation compensator that has a surface with a position-dependent thickness based on the patient's radiotherapy plan and the geometry of the region to be treated. In an alternative aspect, the device can comprise a radiation source that's movably inserted into an enclosure coupled to the radiation compensator. The source can reside at a number of locations within the compensator during a respective number of dwell times, based on the treatment plan.
Control system addresses helical therapy effects
TomoTherapy (Madison, WI) has devised a dose control system for a helical radiotherapy system, to address the effects of rotational dose variation (oscillation due to the linac rotation) and drift caused by a temperature change within the electron gun (WO/2012/149044). In one embodiment, the control system includes a monitoring device that measures the dose output from the linac, and a sensor that measures the electrical current output from the electron gun. A software program receives inputs from the dose control system and the sensor. The program then processes these inputs to determine the amount of RF power applied to the linac, based on the measured dose value, and the amount of electrical current applied to the electron gun, based on the measured electrical current.
Magnetic field correction for MR-radiotherapy
Philips Electronics of the Netherlands has developed a means of correcting the static magnetic field of a combined MRI radiotherapy apparatus, in order to minimize field perturbations due to ferromagnetic materials in the rotating radiation source (WO/2012/164527). The method involves installing a magnetic correcting element on a radial path perpendicular to the rotational axis. The element is positioned so as to reduce any change in the magnetic field within the imaging zone arising from the rotating ferromagnetic component. The method further comprises: repeatedly measuring the magnetic field within the imaging zone; determining the change in magnetic field in the imaging zone; and adjusting the position of the correcting element along the radial path if the change in magnetic field exceeds a predetermined threshold.
Simple process evaluates neutron dose
A scheme for real-time evaluation of neutron dose in patients undergoing radiotherapy is described by the Universidad de Sevilla in international patent application WO/2012/168527. The filing describes a process and detector for calculating equivalent neutron doses in a patient's organs and the associated risk of inducing secondary cancers. The calculation is carried out by associating doses in detectors placed at predetermined locations in an anthropomorphic phantom with a single effect in a semiconductor device placed in the treatment room. The researchers note that the method provides a simple and universal process for estimating the risk of secondary cancer from real-time readings of an electronic device.
About the author
Tami Freeman is editor of medicalphysicsweb.