Method and arrangement for medical imaging
Field of the invention
The invention relates to medical imaging, such as tomographic imaging.
Prior art
In CBCT imaging, that is, Cone Beam Computed Tomography, the object is irradiated by cone beam type X-irradiation from several different imaging angles to produce CT-type (Computed Tomography) imaging data of the object being imaged, such as a patient's head region. The patent publication US 6434214 (Hitachi Medical Corporation), for example, discloses CBCT imaging.
In prior art cone beam X-ray imaging, a panoramic X-ray image of the entire dental region or images of individual teeth are produced by manually drawing guide lines in the image data obtained at the first stage and by selecting image parameters. The actual clinical image is processed by means of the guide lines drawn and image parameters selected.
In CT imaging, that is, Computed Tomography, a patient, for example, a patient's head region, is imaged using wide-angle X-ray technique. An X-ray source and an X-ray receiving means located on opposite sides of a patient's head are moved around the patient during imaging to carry out tomographic X-ray imaging in an imaging sector of 360 degrees or less. Computed tomography is disclosed in published application no. WO2007124338 Al (XORAN TECHNOLOGIES INC (US)). The position of the patient's head is seldom ideal from the point of view of imaging. When the position of the head is inclined with respect to the imaging axis, an error factor in the image data is caused by asymmetry. Brief description of the invention
The aim of the invention is to utilise the anatomic forms discernible in a patient's soft tissue or hard tissue in automatic image data processing to produce a clinically optimal image of an object of interest. This is achieved by means of a method for medical imaging, in which method is generated the radiation required for the imaging, which is directed from at least one imaging angle at the object being imaged, and the radiation that has passed through the object is received for producing the image data. In the method, the anatomy of the object being imaged is identified on the basis of image data produced by means of automatic image processing from the said at least one angle of imaging, on the basis of which identified anatomy is carried out image processing by means of an automated image processing process, where image data comprising image parameters is produced of a part of interest in the object imaged.
The invention also relates to an arrangement for medical imaging comprising a radiation source for generating the radiation required for the imaging, which is directed from at least one imaging angle at the object being imaged, and radiation receiving means for receiving the radiation that has passed through the object for producing the image data. The arrangement comprises automated image processing means for identifying the anatomy of the object being imaged on the basis of image data produced from the said at least one imaging angle and for carrying out image processing on the basis of the said identified anatomy, so that image data comprising image parameters is produced of a part of interest in the object imaged.
The invention is based on the automated identification of the anatomy of the object being imaged on the basis of image data produced from at least one angle of imaging. Identification of the anatomy is based on identifying the outlines of soft or hard tissue. The identified anatomy is utilised in automated image processing for producing an optimal clinical image of the part of interest in the object imaged for each particular purpose, respectively.
The advantage of the invention is that producing a clinical image in medical imaging is speeded up and becomes more accurate through automated image processing.
List of Figures
Figure 1 shows an arrangement for medical X-ray imaging according to a first preferable embodiment of the invention.
Detailed description of the invention
Figure 1 shows the construction of a cone beam computed tomography apparatus or CBCT apparatus for medical X-ray imaging in accordance with a first preferred embodiment of the arrangement of the invention. The cone beam computed tomography apparatus, or CBCT apparatus, is divided into an imaging unit 1 for producing image data and an image data processing unit, that is, a computer 2, which may be located in conjunction with the imaging unit or in wireless or wired data connection, which may be quite remote from the imaging unit. The control unit 3 carries out the total control of the imaging unit 1 and the computer 2.
In the imaging unit 1 is arranged an X-ray source 5 and a radiation receiving means 6 opposite one another on different sides of the object 7 being imaged. Both the X-ray source 5 and the radiation receiving means 6 are arranged in a scanning device 4 which turns around the object 7 while the axis of rotation 9 acts as the centre of rotation. The scanning device 4 is turned to each predetermined angle and the radiation receiving means 6, that is, the X-ray detector carries out the measurement of the intensity of the X-rays 8 that have passed through the object to produce image data. Pre-processing of the image data may be carried out by means of the receiver electronics comprised in the imaging unit 1, from which the image data is transmitted to the computer 2.
Further pre-processing of the image data, such as gamma correction of the X-ray detector 6, distortion correction, logarithmic conversion and non- uniformity correction are carried out with the pre-processing means 10 comprised in the computer. The reconstruction 11 means are used to reconstruct three-dimensional CBCT image data on the basis of image data which has been obtained from different imaging angles and pre-processed.
The arrangement according to the invention for CBCT-imaging shown in Figure 1 comprises a computer 2 as an automated image processing means. The method according to the invention is implemented programmatically by means of the said computer 2. Of the three-dimensional CBCT image data is automatically calculated a panoramic X-ray image of the entire dental arch in such a way that from the CBCT image data is calculated the anatomic data of the dental arch, on the basis of which is, for example automatically calculated the image data of the panoramic layer or the tangential slices or the orthogonal slices. Obtaining the anatomic data of the dental arch in a calculatory manner is preferably based on the outlines of the hard tissue, but calculations of anatomic data based on the outlines of the soft tissue can also be implemented. In a similar manner may also be automatically produced an X-ray image of a part of the teeth or of the jaw bone.
In the automated image processing method according to the invention, image parameter values such as brightness, filtering parameters and windowing may be pre-selected. The values of the image parameters are preferably dependent on the direction of viewing from which the three- dimensional image data obtained on the object is observed. The software performing the automated image processing may also be implemented in such a way that the software will automatically select optimal image parameters, in which case separate pre-selection will not be required.
A second preferred embodiment of the invention, to which Figure 1 also applies, relates to imaging the entire head region, or a part of the head region, by CBCT-imaging and also more extensively by CT-imaging, that is, by computer tomography. The imaging unit 1 carries out the imaging of the patient's head from predetermined imaging angles over a wide angle of up to 360 degrees to produce three-dimensional tomographic image data, the production of which was described in greater detail above in connection with CBCT-imaging. The arrangement and method according to the invention for computer tomography comprises a computer 2 as the processing means for automated image processing. The method is implemented programmatically by computer in such a way that the anatomy of the patient's head is identified on the basis of the outlines of the hard tissue and soft tissue comprised in the three-dimensional image data. In the method is calculatorily utilised a cubic viewing volume in such a way that by identifying the anatomy of the head, the position of the head is calculated with respect to the cubic viewing volume, and this data is used to compensate for errors of asymmetry in the three-dimensional tomographic image data. This is advantageous especially in frontal slice images, but also in sagittal and axial slice images.
In addition to compensating for errors, in the second preferred embodiment of the invention, as in the first preferred embodiment of the invention, is automatically produced the desired clinical image of the part of interest in the imaged object by means of pre-elected or automatically selected image parameters, the magnitudes of which are preferably dependent on the direction of viewing. The computer 2 used in the first and second preferred embodiments of the invention for implementing the method may be located in the same entity as the imaging unit 1 itself or in a location remote from the imaging device by means of a data link, where clinical images are processed, analysed and/or stored.
Although the invention is described above with reference to the accompanying figures and description, the invention is not, however, limited to these, but the invention may be modified within the limits allowed by the patent claims. The invention is thus also applicable to other types of medical imaging, such as gammography or ultrasonic imaging. In the applications according to the invention may also be utilised a contrast medium, which promotes the exposure of the anatomic outlines of the tissue searched for.