Patent Description:
International guidelines require that the orientation (or rotational position about a longitudinal axis) of a patient during a chest posterior-anterior (PA) or anterior-posterior (AP) x-ray acquisition be determined by measuring the projections of some anterior (clavicle heads) and posterior (spinous processes) landmarks in the image for quality checks. For example, international guidelines instruct to check whether the spinal processes of the vertebrae are positioned in the centre between the two clavicle heads. This is in order to determine if the patient's chest is orientated directly toward the X-ray source along a source to detector axis, or is twisted to a greater or lesser degree. In order to quantify the rotation angle from this underdetermined setting, it is assumed that the distances between these landmarks measured in the actual 3D body correlate with each other, i.e. that a large patient is just an isotropically scaled small patient. Thus, it is intended that a rotation angle can be estimated from the location of the three anatomical landmarks left clavicle head (Ci), right clavicle head Cr and spinal process (p), and this angle can be used to determine if a given threshold angle, either to the left or to the right, has been exceeded requiring a re-scan. Unfortunately, the distances between these three landmarks cannot easily be determined from the PA chest radiograph, especially the distances P to Ci and distances P to Cr cannot be estimated well as these lines are almost parallel to the x-rays. It has been proposed that anatomical a priori estimates be used, assuming that the patient does not vary too much from an average anatomy. The whole method is proposed to be scale invariant and would then work with small people as well as with large people as long as the ratio ρ between P to C<NUM> and Cr to C<NUM> can be taken as constant across the population. Unfortunately again, studies have shown that in a set of patients both distances P to Ci and Cr to C<NUM> do not correlate with each other [see <NPL>)]. Following that study, it is clear that the difference in body shape to be observed in a population counteracts precise estimation of the rotation angle from the projected landmarks in a PA chest radiograph. For example, for some distances measured, the angle may vary between <NUM> deg and <NUM> deg of rotation according to the individual ratio ρ as observed in the sample. This range would make the applicability of an angular threshold value difficult or quite imprecise. In other words, empirical evidence from Computer Tomography (CT) samples has shown, that the interclavicle distance does not correlate with the clavicle to spinal process distance in real patients.

It is important to determine the orientation of the patient's chest, in order to assess the quality of a chest radiograph, because rotation of the chest away from an alignment with the source to detector axis can compromise image quality for different reasons. In rotated patients, more lung parenchyma is shadowed by the mediastinum and the lung-heart-ratio is faulty, and generally these rotated images can both mimic and mask all kinds of diseases. Positioning a patient straight with respect to the source to detector axis is therefore important for the diagnostic quality, and if the patient is rotated it is required to determine by how much in order that a determination can be made if a re-scan is necessary. However, as discussed above there is no way of accurately determining this orientation of rotation angle across the population.

It would be advantageous to have improved means of determining an orientation of a patient undergoing an X-ray radiograph examination.

It should be noted that the following described aspects and examples of the invention apply also to the apparatus for determining an orientation of a patient's chest, the X-ray imaging system, the method for determining an orientation of a patient's chest, as well as to the computer program element and a computer readable medium.

In a first aspect, there is provided an apparatus for determining an orientation of a patient's chest, the apparatus comprising:.

The input unit is configured to receive an image of a patient, the image comprising image data of the patient's chest. The image being a lateral chest X-ray radiograph or an image acquired with a depth camera. The input unit is configured to receive an X-ray radiograph of the patient's chest acquired by an X-ray imaging unit with an X-ray imaging axis extending from an X-ray source to an X-ray detector. The input unit is configured to provide the image and the X-ray radiograph to the processing unit. The processing unit is configured to determine an orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis, the determination comprising utilization of the image and the X-ray radiograph.

In this manner, for example for an AP or PA X-ray radiograph of the patient's chest the quality of a chest radiograph can be assessed by determining if the patient was correctly aligned or whether he or she was rotated about their longitudinal direction with respect to the imaging axis of the X-ray imaging unit that acquired the X-ray radiograph. By determining the orientation of the patient, in terms of whether they are rotated or not, enables it to be determined if the image would impede analysis or not. For example, in rotated patients more lung parenchyma is shadowed by the mediastinum and the lung-heart-ratio is faulty, and it can be determined if the X-ray radiograph acquired is appropriate for a correct analysis, or whether a repeat scan is required. Thus, such rotated images may both mimic and mask all kinds of diseases, and the apparatus enables a determination to be made if the patient was positioned "straight" or whether they were rotated, thereby providing an important diagnostic for image quality.

Furthermore, the apparatus facilitates the meeting of international guidelines that instruct that a check be made whether the spinal processes of the vertebrae are positioned in the centre between the two clavicle heads for an AP or PA X-ray radiograph, and indeed to determine an angle of rotation away from this ideal.

The processing unit is configured to determine information relating to a clavicle to spinous process distance of the patient, the determination comprising utilization of the image. Determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to the clavicle to spinal process distance of the patient.

In other words, the clavicle to spinous process distance can be estimated from an image, such as acquired by a camera or acquired by the X-ray imaging unit itself as a lateral chest X-ray radiograph that is typically taken along with a PA or AP chest X-ray radiograph. Thus, this information of the patient is used in order to obtain a more precise estimation of the patient's rotation about their longitudinal with respect to the X-ray source to X-ray detector imaging axis.

In an example, the information relating to the clavicle to spinous process distance of the patient comprises a determined clavicle to spinal process distance of the patient.

In an example, the processing unit is configured to determine information relating to one or more of: a left clavicle head; a right clavicle head; a spinal process of the patient, the determination comprising utilization of the X-ray radiograph. Determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises locations in the X-ray radiograph of one or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises relative location information in the X-ray radiograph of two or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the left clavicle head and the right clavicle head.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the left clavicle head and the spinous process.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the right clavicle head and the spinous process.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises locations of the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph relative to each other.

In an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises distances between the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph with respect to each other.

In an example, the orientation of the patient's chest about a longitudinal axis of the patient is determined.

In this manner, an image of the patient can be used to determine the clavicle to spinal process distance for the patient, and then the relative positions of the left clavicle head to the right clavicle head and the spinal process of the patient in the X-ray radiograph in effect enables a 3D relative positioning of these three features to be determined, from which the orientation, in terms of rotation of the patient's chest about their longitudinal axis with respect to the X-ray imaging axis can be determined.

In a second aspect, there is provided an X-ray imaging system, the system comprising:.

The X-ray imaging unit comprises an X-ray source and an X-ray detector with an X-ray imaging axis extending from the X-ray source to the X-ray detector. The X-ray imaging unit is configured to acquire an X-ray radiograph of the patient's chest. The apparatus is configured to determine an orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis. The determination comprises utilization of the X-ray radiograph and an image of the patient other than the X-ray radiograph that comprises image data of the patient's chest. The image is a lateral chest X-ray radiograph or a depth image. The apparatus is configured to determine information relating to a clavicle to spinous process distance of the patient, the determination comprising utilization of the image, and wherein determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to the clavicle to spinal process distance of the patient.

In a third aspect, there is provided a method for determining an orientation of a patient's chest, the method comprising:.

According to another aspect, there is provided a computer program element for controlling one or more of the apparatuses and/or systems as previously described which, if the computer program element is executed by a processing unit, is adapted to perform one or more of the methods as previously described.

According to another aspect, there is provided a computer readable medium having stored the computer element as previously described.

The computer program element can for example be a software program but can also be a FPGA, a PLD or any other appropriate digital means.

<FIG> shows an example of an apparatus <NUM> for determining an orientation of a patient's chest. The apparatus comprises an input unit <NUM>, and a processing unit <NUM>. The input unit is configured to receive an image of a patient, the image comprising image data of the patient's chest. The input unit is configured also to receive an X-ray radiograph of the patient's chest acquired by an X-ray imaging unit with an X-ray imaging axis extending from an X-ray source to an X-ray detector. The input unit is configured also to provide the image and the X-ray radiograph to the processing unit. The processing unit is configured to determine an orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis. The determination comprises utilization of the image and the X-ray radiograph.

In an example, the orientation comprises an angle of rotation.

In an example, the the orientation comprises an angle of rotation away from an ideal AP or PA acquisition orientation.

In an example, the image of the patient is an optical image acquired by an optical depth camera.

In an example, the image of the patient is an x-ray image, which is acquired by the X-ray imaging unit, where the image is of a view of the patient that is substantially perpendicular to the view of the patient for the X-ray radiograph. Thus, for example if the X-ray radiograph is intended to be a PA or a AP radiograph of the patient's chest, then the image is of a lateral view of the patient's chest.

In an example the image of the patient is a lateral image of the patient. The processing unit is configured to determine information relating to a clavicle to spinous process distance of the patient, the determination comprising utilization of the image. Determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to the clavicle to spinal process distance of the patient.

According to an example, the information relating to the clavicle to spinous process distance of the patient comprises a determined clavicle to spinal process distance of the patient.

In an example, the determined clavicle to spinous process distance of the patient comprises a distance between one or both clavicle heads and the spinous process. In an example, the determined clavicle to spinous process distance of the patient comprises an average distance both clavicle heads and the spinous process.

According to an example, the processing unit is configured to determine information relating to one or more of: a left clavicle head <NUM>; a right clavicle head <NUM>; a spinal process of the patient <NUM>, the determination comprising utilization of the X-ray radiograph. Determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises locations in the X-ray radiograph of one or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises relative location information in the X-ray radiograph of two or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the left clavicle head and the right clavicle head.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the left clavicle head and the spinous process.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises a distance in the X-ray radiograph between the right clavicle head and the spinous process.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises locations of the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph relative to each other.

According to an example, the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises distances between the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph with respect to each other.

According to an example, the orientation of the patient's chest about a longitudinal axis of the patient is determined. In an example, the longitudinal axis of the patient is substantially perpendicular to the X-ray imaging axis.

<FIG> shows an example of an X-ray imaging system <NUM>. The system <NUM> comprises an X-ray imaging unit <NUM>, and an apparatus <NUM> for determining an orientation of a patient's chest (PC) as described with respect to <FIG>. The X-ray imaging unit comprises an X-ray source <NUM> and an X-ray detector <NUM> with an X-ray imaging axis <NUM> extending from the X-ray source to the X-ray detector. The X-ray imaging unit is configured to acquire an X-ray radiograph of the patient's chest, such as a. The apparatus is configured to determine an orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis. The determination comprising utilization of the X-ray radiograph and an image of the patient that comprises image data of the patient's chest, where this image is other than (in other words different to) the X-ray radiograph of the patient's.

<FIG> shows a method <NUM> for determining an orientation of a patient's chest in its basic steps, where essential steps are shown in solid lines and optional steps are shown in dashed lines. The method <NUM> comprises:.

The method comprises step d) determining <NUM> by the processing unit information relating to a clavicle to spinous process distance of the patient, the determining comprising utilizing the image, and wherein step f) comprises utilizing the information relating to the clavicle to spinous process distance of the patient.

In an example, in step d) determining the information relating to the clavicle to spinous process distance of the patient comprises determining a clavicle to spinous process distance of the patient.

In an example, the method comprises step e) determining <NUM> by the processing unit information relating to one or more of: a left clavicle head; a right clavicle head; a spinal process of the patient, the determining comprising utilizing the X-ray radiograph, and wherein step f) comprises utilizing the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining locations in the X-ray radiograph of one or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining relative location information in the X-ray radiograph of two or more of the left clavicle head; the right clavicle head; the spinal process of the patient.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining a distance in the X-ray radiograph between the left clavicle head and the right clavicle head.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining a distance in the X-ray radiograph between the left clavicle head and the spinous process.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining a distance in the X-ray radiograph between the right clavicle head and the spinous process.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining locations of the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph relative to each other.

In an example, in step e) determining the information relating to one or more of: the left clavicle head; the right clavicle head; the spinal process of the patient comprises determining distances between the left clavicle head, the right clavicle head, and the spinal process in the X-ray radiograph with respect to each other.

In an example, in step f) the orientation of the patient's chest is determined about a longitudinal axis of the patient.

The apparatus for determining an orientation of a patient's chest, the X-ray imaging system, and the method for determining an orientation of a patient's chest will now be discussed in specific detail, where reference is made to <FIG>.

<FIG> shows the three anatomical landmarks left clavicle head (C<NUM>), right clavicle head (Cr) and spinal process (p), and shows the projections of these landmark features on the detector for both a patient is correctly aligned along the source to detector axis, and for a patient who is slightly rotated. As seen at the detector plane, the projections of these features acquired at the detector move relative to each other as the patient rotates. As discussed above, existing methods to determine this rotation angle based on an assumed spinal process to clavicle head distance for different patients does not work, due to variability across the population. The inventors realised that information on the spinal process to clavicle head distance could be determined from an image different to the PA or AP x-ray radiograph acquired. In an x-ray scan process where a PA or AP x-ray radiograph was acquired, a lateral chest radiograph is also typically acquired. Such a lateral radiograph and PA radiograph for the same patient are shown in <FIG>. Therefore, the inventors realised that this lateral radiograph, or indeed an image acquired by a camera that could be a <NUM>-D camera, can be used to estimate or determine the spinal process to clavicle head distance.

As shown in <FIG>, the spinal process left or right clavicle head can be located in the lateral chest radiograph, enabling the spinal process to clavicle head distance to be determined. Then as indicated in <FIG> the projected distances of the three landmarks on the PA (or AP) chest radiograph are measured. The interclavicle distance (Cr to C<NUM>) is taken from the PA (or AP) while as discussed above the clavicle to spinous distance (P to Ci) is taken from the lateral radiograph. Having these distance estimates from patient measures allows for a more precise estimate of the rotation angle which is the pre requisite for working with a quantitative angular threshold in order to consistently reject images for rotation issues. This rotation angle estimation, once the spinal process to clavicle distances known, can be determined through a econometric relationships as would be appreciated by the skilled person when looking at <FIG> because the projections of the left and right clavicle head and the spinal process can be measured with respect to one another in the PA (or AP) x-ray radiograph. Moreover, the measured clavicle to spinous distance may be electronically stored such that the rotation angle can be directly estimated from a PA image for any subsequent examination of the same patient.

As discussed above, the image other than the PA (or) AP radiograph need not be a lateral x-ray radiograph, but could be acquired by an optical camera such as a depth camera. Here, information about the ratio ρ, discussed above, can be assessed from a depth camera image. Internal landmarks cannot directly be located, however the extent of the patient's upper chest can be measured both in lateral orientation and in PA orientation from a depth image. By correlating depth camera images to CT images of the same patient, one can statistically learn how to translate e.g. detected landmarks in the depth camera image to e.g. the P - Ci distance. This relationship can then be used for estimating this distance from the depth camera image alone.

This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and computer program that by means of an update turns an existing program into a program that uses the invention.

Claim 1:
An apparatus (<NUM>) for determining an orientation of a patient's chest, the apparatus comprising:
- an input unit (<NUM>); and
- a processing unit (<NUM>);
wherein, the input unit is configured to receive an image of a patient, the image comprising image data of the patient's chest, the image being a lateral chest X-ray radiograph or an image acquired with a depth camera;
wherein, the input unit is configured to receive an X-ray radiograph of the patient's chest acquired by an X-ray imaging unit with an X-ray imaging axis extending from an X-ray source to an X-ray detector;
wherein, the input unit is configured to provide the image and the X-ray radiograph to the processing unit;
wherein, the processing unit is configured to determine an orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis, the determination comprising utilization of the image and the X-ray radiograph; and
wherein the processing unit is configured to determine information relating to a clavicle to spinous process distance of the patient, the determination comprising utilization of the image, and wherein determination of the orientation of the patient's chest in the X-ray radiograph with respect to the X-ray imaging axis comprises utilization of the information relating to the clavicle to spinal process distance of the patient.