Patent ID: 12190522

DESCRIPTION OF EMBODIMENTS

FIG.1illustrates the basic steps of the method according to the first aspect, in which step S11encompasses acquiring the patient image data, step S12encompasses acquiring the atlas data, step S13encompasses acquiring the transformability model data, step S14encompasses determining the segmented image data and subsequent step S15encompasses determining the assigned transformability model data.

FIG.2illustrates deformation of a digital image representation (i.e. a depiction) of anatomical structures in the segmented patient image and boundary conditions therefor. A composite object may be defined to move multiple objects (e.g. prostate, bladder and rectum), which is moved as a whole, i.e. a deformation field is created which overlays the union of the objects. When the grid is smoothly deformed, the objects which are connected to the grid (i.e. the anatomical structures which have been assigned to the geometric transformability model) are deformed simultaneously.

However, not all objects are anatomically connected to each other. If an object is moved, adjacent structures may eitherbe simultaneously moved, orstay unchanged, orrestrict the movement of the object, ormove only when they are touched, orslide along other objects, ormove in a way which is predetermined by anatomical restrictions like sinew or joint.

One possible solution may be a bio-mechanical model which is constrained by the anatomical variability of the human being. In such a model, not only normal anatomically correct movements are possible, but also movements which correspond to anatomical variabilities, e.g. the heart cannot move in the thorax of an individual, but it can be at different positions for different individuals. Therefore, the method according to the first aspect may allow moving the heart inside the thorax. However, it may not allow to separate the bladder from the prostate, since this is not possible for any individual.

A model may be generated by statistically evaluating a set of patient images. From the statistic variability, the motion/movability parameters and the model may be received. Evaluation of different scans of one patient will lead to finding e.g. an arm in each patient image in a different position. From the resulting variability, a rotation of the arm may be determined. A computer program can do that fully automatically and on that basis calculate a model. That will then be a model. If the same is done for scans from many different patients, one will notice that the model does not only permit rotation of the respective arm but also a change of length of that arm because every human being has a different arm length. Such a model will then have been generated in the same manner as the above-mentioned biomechanical model but will be based on a different set of images.

In a given segmentation of a patient image data set, e.g. a segmented bladder, prostate, rectum and bone are present. These segmentations appear as overlays over the gray value patient image data set so that one can observe, whether there are differences between the segmentation result and the position of image representations of anatomical structures in the patient image or not. If there are differences, the user may want to correct these differences.

The method according to the first aspect includes the following approach for allowing for such a correction:

A model of the human body is defined. This can be done e.g. by defining a deformation grid, which overlays the organs but is disconnected at vertices belonging to not connected organs as shown inFIG.2.

The grid is connected to the organs. When pulling or pushing the grid (e.g. manual user interaction with a pointer tool such as a mouse or a touch screen for selecting e.g. a node of the grid for changing its position, e.g. by drag-and-drop), the organs also move accordingly. The grid has a certain elasticity (defined e.g. by a spring model or finite element model), so that the whole grid moves when pulling at some region. The coefficients of this elasticity may not be driven by the real elasticity of the tissue, but by a strength given by GUI input, which defines a kind of range of the deformation. Distant structures may be defined to move slower than nearby structures. If one pulls at the top left corner of the bladder, the bladder may be defined to move stronger than the prostate. And when changing the position of the segmentation of the rectum, only the part connected directly to the prostate moves slowly. The other rectum parts move very slowly. The bone is not connected at all and don't move. The structures may be defined to keep their position after movement (e.g. when the user releases the mouse button). The next movement may be defined to start with a new regular grid. The movement action can then be repeated several times.

The grid can be defined in the atlas and can be transferred to the patient.

There are also border conditions, which have to be taken into account, e.g. the prostate is not allowed to move into the bone. Rather, it can only slide along the bone. There are in principle two boundary conditions: 1) collision (no overlap of organs), and 2) sliding with contact (two organs are always in contact, but the contact point(s) can move, e.g. lung, liver and heart, which move simultaneously, but along the ribs).

The distorted grid can also be used to distort the registration (the atlas-patient mapping), which was the basis for the segmentation: Regnew=Distortion*Regold. This registration can be used afterwards to transfer other objects from the atlas to the patient. If the newly transferred objects are in the region of bladder, prostate or rectum, their segmentation can be as well automatically corrected.

FIG.3is a schematic illustration of the medical system1according to the sixth aspect. The system is in its entirety identified by reference sign1and comprises a computer2, an electronic data storage device (such as a hard disc)3for storing at least the patient data and a display device4(such as a monitor). The components of the medical system1have the functionalities and properties explained above with regard to the sixth aspect of this disclosure.