Method and apparatus for optical tracking of motions of a subject

A method of motion tracking of a subject located in a scanner, the method comprising:

• generating a baseline 3D surface representation of a surface region of the subject at a first point of time (T(0)),
• generating a subsequent 3D surface representation of the surface region of the subject at a subsequent point of time (T(s))
• determining a best-fit registration of the subsequent 3D surface representation with at least one constraint relative to the baseline 3D surface representation,
• determining at least one motion tracking parameter,
• wherein, the constraint comprises a relative restriction to provide a suppression of at least one of a false motion and a detection error, wherein the relative restriction is a function of a difference between respective locations of the baseline 3D surface representation and corresponding respective locations of the subsequent 3D surface representation, wherein the method comprises selecting at least one virtual feature and associating said at least one virtual feature to a ROI (region of interest) forming a corresponding ROI of the baseline 3D surface representation, wherein said respective location(s) comprises a location said at least one virtual feature and said corresponding ROI and wherein said constraint comprises a restriction of change of at least one parameter of said at least one virtual feature associated to said corresponding ROI of the best-fit subsequent 3D surface representation relative to the at least one parameter of the at least one virtual feature associated to the ROI of the baseline 3D surface representation, wherein the surface region comprises a surface region of a body part of the subject, wherein the virtual feature comprises a virtual point, a virtual line or a virtual bone structure, which at a first point of time is located inside a volume of the body part and wherein the parameter comprises a location parameter, an orientation parameter and/or a distance parameter, and wherein the surface region comprises a surface region of a body part of the subject, wherein the virtual feature comprises a virtual volume and/or a virtual area, which at the first point of time is located at the surface region and/or at least partly inside the volume of the body part and wherein the parameter comprises a location parameter, an orientation parameter and/or an extent parameter, wherein the method comprises selecting the at least one virtual feature with a feature spatial location at the first point of time T(0), by providing estimated movements of the subject during a scanning section and selecting the at least one virtual feature with the feature spatial location at the first point of time T(0), which is subjected to less parameter changes than other virtual features of the subject and/or to be a virtual feature with the feature spatial location subjected to parameter changes below a preselected level.

A method of motion tracking of a subject located in a scanner, the method comprising:

• generating a baseline 3D surface representation of a surface region of the subject at a first point of time (T(0)),
• generating a subsequent 3D surface representation of the surface region of the subject at a subsequent point of time (T(s)),
• determining a best-fit registration of the subsequent 3D surface representation with at least one constraint relative to the baseline 3D surface representation,
• determining at least one motion tracking parameter,
• wherein, the constraint comprises a relative restriction to provide a suppression of at least one of a false motion and a detection error, wherein the relative restriction is a function of a difference between respective locations of the baseline 3D surface representation and corresponding respective locations of the subsequent 3D surface representation, wherein the method comprises selecting at least one virtual feature and associating said at least one virtual feature to a ROI (region of interest) forming a correlated ROI of the baseline 3D surface representation, wherein said respective location(s) comprises a location said at least one virtual feature and said corresponding ROI and wherein said constraint comprises a restriction of change of at least one parameter of said at least one virtual feature associated to said corresponding ROI of the best-fit subsequent 3D surface representation relative to the at least one parameter of the at least one virtual feature associated to the ROI of the baseline 3D surface representation, wherein the at least one virtual feature as associated to the ROI of the baseline 3D surface representation is spatially located at the surface region or at a distance further from the surface region than an acquisition arrangement acquiring reflected light from the surface region for generating the respective surface representations wherein the at least one virtual feature as associated to the ROI of the baseline 3D surface representation is spatially located between the surface region and a bearing supporting the subject, and wherein the method comprises providing a trained computer comprising a method of training a computer for selecting the at least one virtual feature associated to the ROI of the baseline 3D surface representation, and the at least one constraint using sets of reference data, wherein each reference data set comprises reference data representing previously determined or modelled motions of a reference subject correlated to reference data representing determined or modelled motions of a reference surface region, wherein the reference surface region is a surface of a reference body part of said reference subject.

A method of motion tracking of a subject located in a scanner, the method comprising:

• generating a baseline 3D surface representation of a surface region of the subject at a first point of time (T(0)),
• generating a subsequent 3D surface representation of the surface region of the subject at a subsequent point of time (T(s)),
• determining a best-fit registration of the subsequent 3D surface representation with at least one constraint relative to the baseline 3D surface representation,
• determining at least one motion tracking parameter,
• wherein, the constraint comprises a relative restriction to provide a suppression of at least one of a false motion and a detection error, wherein the relative restriction is a function of a difference between respective location(s) of the baseline 3D surface representation and corresponding respective location(s) of the subsequent 3D surface representation, wherein the method comprises selecting at least one virtual feature and associating said at least one virtual feature to a ROI (region of interest) forming a correlated ROI of the baseline 3D surface representation, wherein said respective location(s) comprises a location said at least one virtual feature and said corresponding ROI and wherein said constraint comprises a restriction of change of at least one parameter of said at least one virtual feature associated to said corresponding ROI of the best-fit subsequent 3D surface representation relative to the at least one parameter of the at least one virtual feature associated to the ROI of the baseline 3D surface representation, wherein the surface region is a surface region of a body part comprising a body portion to be scanned, and wherein the at least one virtual feature comprises a cloud of points located inside the body part at locations determined by a Gaussian function around a central location of the body part, wherein the ROI of the baseline 3D surface representation corresponds to a set of locations at the surface region and wherein at least a set of points of the cloud points are associated to the ROI of the baseline 3D surface representation of the best-fit subsequent 3D surface representation relative to the at least one parameter of the at least one virtual feature associated to the ROI of the baseline 3D surface representation.