Abstract: A method of evaluating a radiation therapy (RT) treatment plan for a treatment volume, divided into sub-volumes and having a target volume and one or more organs at risk, OAR. It includes obtaining a RT treatment plan; calculating the linear energy transfer, LET, in each sub-volume; dividing the dose distribution into doses of a first category and a second category in each sub-volume, wherein the first category comprises doses with energy depositions with an LET below a first LET threshold and the second category comprises doses with energy depositions with an LET above a second LET threshold; determining amounts of doses of the first and of the second category in each sub-volume; and performing an analysis of the quality of the RT treatment plan by metrics based on the obtained distribution of doses of the first and of the second category in the target volume and in the OAR.

Abstract: A method of performing dose calculations for ion radiotherapy compensating for tissue in which the density within a voxel may be inhomogeneous by approximating a portion of the voxel as an air cavity. For each dose voxel, the voxel is inscribed in a three-dimensional grid comprising a number of cells and the propagation of ions through the voxel is calculated based on the cell pattern in the at least one cell overlapping the voxel. Preferably, the voxel is inscribed in the three-dimensional grid in such a way that it overlaps at least one cell fully. Each cell comprises a first portion representing a first density corresponding to a density of a tissue and a second portion representing a second density corresponding to the density of air, the first and second portions forming a cell pattern.

Abstract: Accumulated path length for ions that reach a particular area of a patient is used in dose planning as an indicator of plan robustness. Also, the magnitude of the variations of the accumulated path lengths is determined for a number of beam directions, allowing beam directions to be selected for maximum robustness in treatment planning.

Abstract: A ripple filter unit comprises a first and a second ripple filter, substantially identical, are arranged so that they overlap each other in a beam, with substantially the same orientation and movable relative to each other in such a way as to vary the filter characteristics dynamically. In this way, the modulation characteristics of the ripple filter unit can be varied.

Abstract: The present disclosure generally relates to the field of radiation treatment. More specifically, the present disclosure generally relates to methods and radiation treatment systems for facilitating a multimodal radiation therapy treatment plan, in particular a multimodal radiation therapy plan employing a combined photon beam and electron beam radiation treatment. According to one example embodiment described in the disclosure, a method may comprise obtaining information related to a set of candidate beam types for the combined photon beam and electron beam radiation treatment; comparing the set of candidate beam types against a selection criterion to establish a subset of beam types from the candidate beam types; and generating the combined photon beam and electron beam radiation treatment plan utilizing the thus established subset of beam types.

Abstract: A method of correcting a first CT image for shading artefacts using another CT image as reference, comprising the steps of creating a difference image between the images and a correction map based on the difference image. The correction map is used to correct the first CT image. A method of converting a CT image to the value range of another CT image is also disclosed.

Abstract: A method of radiotherapy treatment planning for creating a plan for delivery of radiation to a patient in at least one particle-based arc is proposed. The delivery time for the plan is reduced by including a penalty in the objective function, designed to limit the number of energy layers and/or the number of energy layer changes.

Abstract: A method of evaluating a radiotherapy treatment plan for ion based radiotherapy, is proposed, comprising the steps of determining multiple elastic scattering of ions for scattering angles in a first angular interval having an upper limit at a selected cut-off angle by means of a model for Coulomb scattering; determining multiple elastic scattering of ions for scattering angles in a second angular interval having a lower limit at the selected cut-off angle; determining the scattering for angles in a range comprising at least a part of the first angular interval and at least a part of the second angular interval, based on the results obtained for the first and second angular interval, respectively. The method avoids the double counting of particles at large scattering angles that occurs when using conventional methods.

Abstract: A method of correcting a first CT image for shading artefacts using another CT image as reference, comprising the steps of creating a difference image between the images and a correction map based on the difference image. The correction map is used to correct the first CT image. A method of converting a CT image to the value range of another CT image is also disclosed.

Abstract: A method for ion based radiation therapy treatment planning for avoiding dose delivery to a distal risk organ, said risk organ being located after the target seen from a first beam angle, the method comprising defining an optimization function comprising at least one objective function related to at least one desired property of the treatment plan, wherein the objective function is related to limiting a parameter ? defining the fraction of the total number ?OAR of ions that reach the risk organ relative to the total number ?a of ions. In addition, one can assume a different density when calculating ? which will result in a plan that is more robust with respect to density perturbations.

Abstract: A method of optimizing a radiation treatment plan of ion treatment, in which the optimization procedure is interrupted, some but not all low-weight spots are discarded and the optimization procedure is resumed with a reduced set of spots. The weight of one or more remaining spots may be increased before resuming the optimization procedure, for example by adding the spot weight of one or more of the discarded spots to one or more of the remaining spots.

Abstract: A method of evaluating the robustness of a radiotherapy treatment plan for ion based radiotherapy, comprises the steps of: obtaining information related to the incident energy of ions that will stop in each voxel of the treatment volume; calculating a quantity value representative of the incident energy of these ions; and using the quantity values calculated for the first and second portion as a measure of the quality of the radiotherapy treatment plan, in particular its robustness. The information may include the mean incident energy for all ions, and/or an indication of the distribution of the energy values for all the ions.

Abstract: A method of evaluating a radiotherapy treatment plan for ion based radiotherapy, is proposed, comprising the steps of determining multiple elastic scattering of ions for scattering angles in a first angular interval having an upper limit at a selected cut-off angle by means of a model for Coulomb scattering; determining multiple elastic scattering of ions for scattering angles in a second angular interval having a lower limit at the selected cut-off angle; determining the scattering for angles in a range comprising at least a part of the first angular interval and at least a part of the second angular interval, based on the results obtained for the first and second angular interval, respectively. The method avoids the double counting of particles at large scattering angles that occurs when using conventional methods.

Abstract: A method of performing dose calculations for ion radiotherapy compensating for tissue in which the density within a voxel may be inhomogeneous by approximating a portion of the voxel as an air cavity. For each dose voxel, the voxel is inscribed in a three-dimensional grid comprising a number of cells and the propagation of ions through the voxel is calculated based on the cell pattern in the at least one cell overlapping the voxel. Preferably, the voxel is inscribed in the three-dimensional grid in such a way that it overlaps at least one cell fully. Each cell comprises a first portion representing a first density corresponding to a density of a tissue and a second portion representing a second density corresponding to the density of air, the first and second portions forming a cell pattern.

Abstract: A system for determining a treatment plan in active ion beam treatment, to minimize unwanted dose, while maintaining or improving target dose coverage, whereby a beam is split into at least two sub-beams and where each sub-beam has a range shifter of different settings.

Abstract: A method of evaluating the robustness of a radiotherapy treatment plan for ion based radiotherapy, comprises the steps of: obtaining information related to the incident energy of ions that will stop in each voxel of the treatment volume; calculating a quantity value representative of the incident energy of these ions; and using the quantity values calculated for the first and second portion as a measure of the quality of the radiotherapy treatment plan, in particular its robustness. The information may include the mean incident energy for all ions, and/or an indication of the distribution of the energy values for all the ions.