WO2020043252A1

WO2020043252A1 - An image alignment method

Info

Publication number: WO2020043252A1
Application number: PCT/DK2019/050248
Authority: WO
Inventors: Anne Dorte BLANKHOLM; Christina Carøe Ejlskov PEDERSEN
Original assignee: Region Midtjylland
Priority date: 2018-08-30
Filing date: 2019-08-28
Publication date: 2020-03-05

Abstract

The invention discloses a method for determining alignment and/or twistin the upper and/orlower part of apatient's chest in a medical imagerelative to a coronalplane of a patient, comprisingmedical imaging equipmentfor obtaining a chest x-ray of the patient, imaging analysis software,obtaining a plurality of distances43, 44, 45, 46between a midline40on an image of the patient's chest and the right and left lateral edge15, 16of the patient's ribcage 14 and comparing one or more distances 43, 44, 45, 46 so as to determine whether or not the patient is aligned in relationtothemedical imaging equipment.The inventionisadvantageous forreducingradiation exposure of a vulnerable patient group, neonates,whichare difficult to diagnose bymedical images, compared tokids and adults, and due to their high cell divisionrate,are verysensitive to radiation exposure.

Description

AN IMAGE ALIGNMENT METHOD

FIELD OF THE INVENTION

The present invention relates to a method for ensuring correct alignment of medical images in relation to the coronal or frontal plane of a patient e.g. when obtaining x-rays of a patient's chest in an anterior-posterior or posterior-anterior direction. The invention also relates to a corresponding system for ensuring aforementioned alignment.

BACKGROUND OF THE INVENTION

When diagnosing patients with the use of medical imaging, e.g. radiology, especially neonatal patients, often referred to as neonates, it is relevant to ensure that the images are provided at the correct angle relative to the patient so as to ensure that the diagnosis is based on the correct foundation. Interpreting medical images requires a highly trained specialist, typically a radiologist, and it requires skilled operators, typically radiographers, in order to obtain the images.

When obtaining a medical image, e.g. chest x-rays, one of the main challenges is ensuring that the patient is placed correctly, aligned straight in the area of interest, e.g. from the shoulder section to the hip, and that the spine is not rotated, since a correct diagnosis will be harder to make - or even not possible to make - from an incorrect image. Furthermore, the risk of misdiagnosis increases when performed based on a misaligned image.

The risk of misalignment within a medical image increases when the image is to be obtained on a neonate, as the neonate is not able to aid the operator with respect to correcting its position and might not be able to hold still during the procedure. Furthermore, neonates are more sensitive to radiation exposure because of the increased opportunity for expression of delayed radiogenic cancers as a consequence of their relative longer life expectancy. Also, the small sizes of the neonates bring all organs within or closer to the useful beam resulting in a relatively higher overall exposure per image than may be the case with adults. It is therefore important to ensure that radiation doses from radiographic examinations carried out in neonatal units are kept at a minimum while

maintaining the quality, e.g. correct alignment, of radiographic images.

It is understood that the alignment is an alignment of an object to be imaged relatively to the device providing the image.

Hence, an improved system for specifically providing information on whether or not an image is obtained correctly, in this instance, in a substantially anterior- posterior or posterior-anterior direction would be advantageous, and in particular a more reliable source of diagnosis.

OBJECT OF THE INVENTION

It is a further object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide a system for ensuring correct alignment of medical images that solves the above mentioned problems of the prior art with misaligned images and hence reduce the number of unnecessary re-imaging procedures.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by a method for determining alignment and/or twist of the patient in a coronal medical image about a cranial-caudal axis relative to a frontal plane of a patient, preferably a chest x-ray, the method comprising,

providing medical imaging equipment suitable for obtaining a chest x-ray of the patient, and hereby providing an x-ray image of the patient's chest, - providing imaging analysis software, the imaging analysis software

processing the following steps based on said image of the patient: identifying a midline in the patient's chest along a spine of the patient, and, at a first point of the midline: - identifying a lateral edge of a ribcage of the patient on a left side of said midline and identifying a lateral edge of the ribcage of the patient on a right side of said midline,

- obtaining a first transverse distance between the midline and the lateral edge of the ribcage on the left side, and obtaining a second transverse distance between the midline and the lateral edge of the ribcage on the right side, and at a second point of the midline, the second point being different from the first point of the midline:

- identifying a lateral edge of a ribcage of the patient on a left side of said midline and identifying a lateral edge of the ribcage of the patient on a right side of said midline,

- obtaining a third transverse distance between the midline and the lateral edge of the ribcage on the left side, and obtaining a fourth transverse distance between the midline and the lateral edge of the ribcage on the right side, comparing one or more of the first transverse distance and the second transverse distance with one or more of the third transverse distance and the fourth transverse distance, so as to determine a coronal alignment and/or twist of the patient about the cranial-caudal axis relative to the frontal plane of the patient.

Thus an improved image quality of chest x-rays can be provided.

The invention is particularly, but not exclusively, advantageous for reducing the amount of radiation exposure of an extraordinarily vulnerable patient group, neonates, as neonates are generally more difficult to diagnose by use of medical images, than kids and adults, and due to their high cell division are also more sensitive to radiation exposure. By reducing the need of re-imaging procedures due to misaligned images not suitable for diagnosis, it follows that radiation exposure will be reduced significantly. Furthermore, the improvement in image quality could improve the speed and accuracy of correct diagnosis and thereby reduce expenses within the health sector three-fold; through reduced wear on the imaging equipment, by way of optimal use of available health staff and shortened admission of patients as a result of fast and precise diagnosis and hence better treatment and faster recovery.

Preferably, the invention is advantageous within radiology departments and even more preferably within departments responsible for the care of neonatal patients.

In the present invention, 'Image quality' is primarily, but not limited, to be understood as an image obtained from the desired position in relation to the patient as this will improve the physicians (radiologist) ability to diagnose the patient on an informed basis.

By 'frontal plane' is understood any vertical plane, that divides the body into front and back or ventral and dorsal sections, wherein the patient is observed from the front towards the back.

By 'coronal plane' is understood any vertical plane that divides the body into front and back or ventral and dorsal sections.

By (AP) 'anterior-posterior' is understood a direction extending along a direction or axis from front to back of a patient or from anterior to posterior and within the present invention, specifically an axis perpendicular to a cranial-caudal axis in a direction from front to back so as to obtain an image directly frontal towards a frontal plane of a patient.

By (PA) 'posterior-anterior' is understood a direction extending along a direction or axis from back to front of a patient or from posterior to anterior and within the present invention, specifically an axis perpendicular to a cranial-caudal axis in a direction from back to front so as to obtain an image directly from the back towards the front of a patient in a coronal plane.

In the present invention 'Medical imaging equipment' is to be understood as equipment able to create visual representations of the internal form of a body, preferably, but not limited to electromagnetic radiation projected towards and/or through an object and obtained by either a photographic film, a digital detector or another means of generating fluoroscopic images. In the present invention 'right and left side' is to be understood as respectively the dexter and sinister side of a patient as used within medical terminology. In the present invention, 'spine' is to be understood as the spinal column within a patient and furthermore projects a central axis extending through the head of a patient towards the feet.

In the present invention 'alignment' is to be understood as a viewing direction or axis perpendicular to the two axes of a two-dimensional image, thus the plane of a two-dimensional image of an object from an anterior-posterior or posterior- anterior direction is parallel to the coronal plane of the object. In the present invention, an image is aligned when the object or patient is perfectly in situ when the image is obtained and a misalignment is to be understood as either the patient being rotated along the cranial-caudal axis within the coronal plane, or the imaging equipment not being perpendicular to the transverse and cranial-caudal axis.

In the present invention, 'twist' is to be understood as a patient being partly rotated about the cranial-caudal axis when being placed in situ on a flat surface or standing on the floor, e.g. a patient lying flat on his/hers back on a surface but having his/her shoulders rotated, both shoulders not being flat towards the same surface or having his/her leg/legs rotated and thereby rotating the spine and thorax.

By 'lateral edge of ribcage' is understood the contour or outer edge of the ribs, away from the midline, within a two-dimensional image from a coronal view, wherein the edge or contour is indicated along the ribcage from the most cranial rib extending from the first thoracic vertebrae to the most caudal rib extending from the 12'th thoracic vertebrae. In reality, in an x-ray, it is rarely possible to identify the most cranial and most caudal ribs of a ribcage and in that case, the lateral edge of the ribcage is the visual contour or outer edge of the ribs, such as from the second to the tenth ribs or from the fourth to the eighth ribs. Thus, it is from this understood that the first transverse distance between the midline and the lateral edge of the ribcage on the left side, and the second transverse distance between the midline and the lateral edge of the ribcage on the right side are lengths of the left and right side rib of a pair of ribs at a given point, such as at the fourth or the eigth ribs (costae).

It is an insight by the present disclosure that it is of importance to acknowledge that not all ribs of all patients are exactly transverse, but moreover transverse or substantially transverse, i.e. transverse or to a minor extent oblique, respectively.

Thus, it is from this disclosure understood that the first and second points of the midline are points where a given pair of ribs are positioned.

In the present invention the 'midline' is to be understood as the line dividing the right and left section of a patient defined by the spine of the patient and wherein the cranial-caudal axis and the midline is ideally, but not necessarily, identical.

In the present invention 'neonatal' is to be understood as a new-born infant, especially an ill or premature new-born infant or a new-born infant with a low birth weight, congenital malformations, sepsis, pulmonary hypoplasia etc. which are usually handled in specialized neonatal intensive care units.

It is appreciated that the invention can be implemented in any type of medical imaging equipment suitable for obtaining images of the inside of a patient including, but not limited to, a digital radiography system such as portable x-ray machine, a floor-mounted x-ray machine or a ceiling-mounted x-ray machine.

In an advantageous embodiment of the invention, the quality of an image is quantified through the comparing of one or more transverse distance(s) at the right and left side of the patient, so as to improve the accuracy of any diagnosis performed on the basis of the images, by ensuring that an image is obtained at a correct angle in relation to the patient's frontal plane or notifying an operator that another image needs to be obtained as a result of an undesirable angle or position of the patient during the imaging procedure. In an advantageous embodiment of the invention a threshold has been set on the basis of clinical guidelines in order to enable a fast assessment of the quality of an image by e.g. setting a threshold of alignment and/or twist and wherein the image is to be either above or below the threshold to be recognised as an image of sufficient quality, suitable for diagnosis processing.

In an advantageous embodiment of the invention a correctness percentage has been set on the basis of clinical guidelines in order to enable a fast assessment of the quality of an image by e.g. setting a percentage of correctness in relation to alignment and/or twist and wherein the image is to be either above or below the percentage to be recognised as an image of sufficient quality, suitable for diagnosis processing.

In an advantageous embodiment of the invention a ratio has been set on the basis of clinical guidelines, to enable a fast assessment of the quality of an image by e.g. setting a ratio in relation to alignment and/or twist and wherein the image is to be within a determined proximity of the ratio to be recognised as an image of sufficient quality, suitable for diagnosis processing.

In an advantageous embodiment of the invention, a ratio, correctness percentage or threshold has been set on the basis of clinical guidelines for alignment of an image, so as to ensure that the patient is not rotated about a cranial-caudal axis in respect to a frontal plane and the image is furthermore obtained from imaging equipment perfectly aligned in relation to the frontal plane of the patient. The ratio, correctness percentage or threshold should be based on one or more differences between at least a first and second transverse distance, preferably between a combination of first, second, third and fourth transverse distances.

In an advantageous embodiment of the invention, a ratio, correctness percentage or threshold has been set on the basis of clinical guidelines for regarding twist of the patient, so as to ensure that the patient is neither partly or fully rotated about a cranial-caudal axis and the image is furthermore obtained from imaging equipment perfectly aligned in relation to the frontal plane (i.e. also a coronal plane) of the patient. The ratio, correctness percentage or threshold should be based on one or more differences between at least a first and second transverse distance, preferably between a combination of first, second, third and fourth transverse distances.

In an embodiment of the invention, the ratio, correctness percentage or threshold could be the difference between at least a first and second area, each area being defined or formed as sections of a patient, e.g. the section defined between the midline and either the left side of the ribcage and the right side of the ribcage.

One method of calculating an area between the midline and the lateral edge of the ribcage would be describing a system of coordinates wherein the midline could represent an x-axis and a transverse axis would be the corresponding second axis and wherein the edge of the ribcage would be described as a function within the system of coordinates, hence the integral of the function would calculate the area.

In an embodiment of the invention, the medical equipment and the imaging analysis software designed for determining the midline of the patient and the lateral edge of the ribcage is specifically optimized for use with neonatal patients, such as infants with a weight less than 1.0 kilograms, less than 2.0 kilograms, less than 3.0 kilograms or less than 4.0 kilograms.

In an advantageous embodiment of the invention, the imaging analysis software designed for determining the midline of the patient and the lateral edge of the ribcage is based on empirical data from neonatal patients.

Even though the invention in preferred embodiments relates to highlighting to the operator where the patient is rotated and how much in order to let the operator adjust the patient, in advantageous embodiment of the invention, the medical imaging equipment is mounted on a motor, the motor being able to correct the angle of the imaging equipment in relation to the patient, so as to avoid adjusting the position of the patient.

In a second aspect, the invention is an apparatus or imaging system for determining alignment and/or twist of an associated patient in a coronal medical image about a cranial-caudal axis relative to a frontal plane of the associated patient, preferably a chest x-ray, the system comprising: - medical imaging equipment suitable for obtaining a chest x-ray of the patient, and hereby providing an x-ray image of the patient's chest,

- imaging analysis software, the imaging analysis software being adapted to process the following steps based on said image of the patient: identifying a midline in the patient's chest along a spine of the patient, and, at a first point of the midline: identifying a lateral edge of a ribcage of the patient on a left side of said midline and identifying a lateral edge of the ribcage of the patient on a right side of said midline,

obtaining a first transverse distance between the midline and the lateral edge of the ribcage on the left side, and obtaining a second transverse distance between the midline and the lateral edge of the ribcage on the right side, and at a second point of the midline, the second point being different from the first point of the midline:

- obtaining a third transverse distance between the midline and the lateral edge of the ribcage on the left side, and obtaining a fourth transverse distance between the midline and the lateral edge of the ribcage on the right side, comparing one or more of the first transverse distance and the second transverse distance with one or more of the third transverse distance and the fourth transverse distance, so as to determine a coronal alignment and/or twist of the patient about a cranial-caudal axis relative to a frontal plane.

In an advantageous embodiment, the invention comprises an output, such as a visual and/or audible system, preferably a display and/or means to give audible vibrations, giving feedback to an operator, so as to correct a non-alignment and/or twist of a patient about a cranial-caudal axis and/or so as to correct alignment of the medical imaging equipment about a cranial caudal axis of the patient.

If or when knowing that an X-ray tube of the medical imaging equipment is arranged perpendicular to a coronal plane of a horizontal bed, a detected misalignment seen in the image is due to a misalignment of the patient positioned in the bed.

In a third aspect, the invention is a computer program for determining alignment and/or twist of a coronal medical image relative to a cranial caudal axis of a patient, preferably a chest x-ray, the computer program, when being executed by a data processor, is adapted for controlling and/or for carrying out the methods and steps as described in the first and the second aspect of the invention and the described embodiments of the invention.

In a fourth aspect, the invention relates to a computer program product being adapted to enable a computer system comprising at least one computer having data storage means in connection therewith to control a medical imaging apparatus according to the first, second and third aspect(s) of the invention.

The fourth aspect of the invention is particularly, but not exclusively,

advantageous in that the present invention may be accomplished by a computer program product enabling a computer system to carry out the operations of the apparatus/system of the first, second and third aspect(s) of the invention when down- or uploaded into the computer system. Such a computer program product may be provided on any kind of computer readable medium, or through a network.

The individual aspects of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from the following description with reference to the described embodiments. It should be noted that the invention is not a method of treatment but a method of providing information so as to increase the information available to a physician when performing a diagnosis of a patient.

BRIEF DESCRIPTION OF THE FIGURES

The image alignment method and system according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 shows a side view of the medical imaging system in accordance with the present invention. In this particular embodiment the patient is lying on a bed but the patient could just as well be standing, sitting or otherwise be in a suitable position in regard to the imaging equipment.

Figure 2 shows an anterior-posterior view of a ribcage illustrating the lateral edges of a ribcage, in accordance with the present invention.

Figure 3 similarly shows an anterior-posterior view of a ribcage illustrating the first and second point on a midline on a ribcage, in accordance with the present invention.

Figure 4 similarly shows an anterior-posterior view of a ribcage illustrating the transverse distances between the midline and edges of a ribcage, in accordance with the present invention.

Figure 5 similarly shows an anterior-posterior view of a ribcage illustrating the at least two areas of a ribcage defined by the midline and the left and right lateral edges of a ribcage, in accordance with the present invention.

Figure 6 is a real X-ray image of a ribcage where the first, second, third and fourth transverse distances are illustrated. Figure 7 shows an anterior-posterior view of a person, in situ, illustrating a division of a left and right side of a patient on each side of a cranial-caudal axis, in accordance with the present invention.

Figure 8 is a flow-chart of a method for determining alignment and/or twist of a patient in a coronal medical image about a cranial-caudal axis, relative to a frontal plane of a patient, in accordance with the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 shows a side view of the medical imaging system 1 in accordance with the present invention. In this particular embodiment the patient 10 is lying on a bed 2 but the patient 10 could just as well be standing, sitting or otherwise be in a suitable position in regard to the medical imaging equipment 1 with respect to the part of the patient 10 which needs to be imaged. Figure 1 illustrates a situation wherein the patient 10 is lying flat on his back on the bed 2 and wherein the medical imaging equipment 1 is oriented so as to obtain an image of the patient's chest region 13, so as to obtain an image of the patient's chest 13 in an anterior-posterior direction 30. In this particular embodiment the bed 2 is depicted as being substantially flat but could be designed with curves

corresponding to the patients backside so as to ensure that the patient 10 is oriented with his/her front plane oriented straight towards the medical imaging equipment 1.

Figure 2 shows an anterior-posterior view of a ribcage 14 illustrating the lateral edges 15, 16 of a ribcage 14, in accordance with the present invention. The figure depicts how the lateral edge 15 of the left side of the ribcage 14 and the lateral edge 16 of the right side of the ribcage 14 is illustrated as a dotted line defined substantially as tangential to the outer line of the ribs, away from the midline 40. In an ideal situation, the spine of a patient 10 will follow the cranial-caudal axis 32 which would indicate that the patient's spine is straight and which would ensure that the midline 40, as defined in the present invention, would be identical to the cranial-caudal axis 32 as the midline 40 should always be defined by the spine. It should be noted that the ribcage 14 is not depicted as anatomically correct but sufficiently illustrates the general idea of the invention. Furthermore, Figure 2 illustrates the transverse axis 33.

Figure 3 shows an anterior-posterior view of a ribcage 14 illustrating a first and second point 41, 42 on a midline 40 on a ribcage 14, in accordance with the present invention. In Figure 3, the midline 40 is identical to a cranial-caudal axis 32, but the midline 40 could be arranged differently within the image depending on the position and course of the spine within the patient 10 and the first and second point 41, 42 should always be placed on the midline 40. Furthermore, the first and second point 41, 42 could be either further apart or closer together on the midline 40 than in the embodiment illustrated in Figure 3.

Figure 4 shows an anterior-posterior view of a ribcage 14 illustrating the transverse distances 43, 44, 45, 46 between the midline 40 and edges of a ribcage 15, 16 in accordance with the present invention. The transverse axis 33 should always be perpendicular to the midline 40 and each of the transverse distances 43, 44, 45, 46 should always be parallel to the transverse axis 33, so as to ensure a correct and comparable measure of the distance between the midline 40 and a lateral edge 15, 16. The transverse distances 43, 44, 45, 46 could be compared in any number of ways to determine whether the patient 10 and the medical imaging equipment 1 is oriented so as to obtain a coronal image and whether the patient 10 is twisted in e.g. the upper and/or lower part of the chest region 13 when the image is obtained.

By comparing the left transverse distance 43 at a first point 41 to the right transverse distance 44 at a first point 41, a difference would indicate that either the patient 10 is not lying flat on his/her backside on a bed 2 or that the medical imaging equipment 1 is not oriented directly towards a frontal plane 31 of the patient. By furthermore comparing the left transverse distance 44 at a second point 42 to the right transverse distance 46 at a second point 42, the difference could indicate whether the patient is not lying flat on his/her backside on a bed 2 or that the medical imaging equipment 1 is not oriented directly towards a frontal plane 31 of the patient. Whether the patient is not lying flat on his/her backside on a bed 2 or that the medical imaging equipment 1 is not oriented directly towards a frontal plane 31 of the patient could be determined by further comparing the left transverse distance 43 at a first point 41 to the left transverse distance 45 at a second point 42 and by comparing the right transverse distance

44 at a first point 41 to the right transverse distance 46 at a second point 42.

Figure 5 shows an anterior-posterior view of a ribcage 14 illustrating the at least two areas 47, 48 of a ribcage 14 defined by the midline 40 and the left and right lateral edges of a ribcage, in accordance with the present invention. In an embodiment of the invention, the areas 47, 48 could be compared and the difference of the areas 47, 48 could be used to determine whether the patient 10 is oriented ideally towards the medical imaging equipment 1 so as to obtain an aligned anterior-posterior image of the chest 13.

Figure 6 is a real X-ray image of a ribcage where the transverse distances 43, 44,

45 and 46 are illustrated. Thus, there was measured a distance from the lateral borders of the 4th rib to the centre spine to determine rotation of upper thorax related to shoulder position, and the distance from the lateral borders of the 8th rib to centre spine to determine rotation of lower thorax related to pelvis position.

It can be seen that the ribs are not exactly transverse, but has a slight

obliqueness. As seen, the length of the rib 43, 44, 45 and 46 which are measured are thus also along somewhat oblique, but straight, lines.

An example of an acceptable rotation tolerance may be determined to be < 10% deviance in measurements of left and right side transverse distance at/of the 4^th and/or at/of the 8^th rib.

An actual centring point for the image used was determined from image collimation boundaries. This was then compared to the location of the centring point if recommended collimation boundaries had been achieved and any deviation recorded in terms of vertebral level and sagittal alignment with the spine.

Figure 7 shows an anterior-posterior view of a patient 10, in situ, illustrating a division of a left and a right side 11, 12 of a patient on each side of a cranial- caudal axis 32, in accordance with the present invention. Furthermore, the figure illustrates the frontal plane 31 of the patient as seen from the optimal viewpoint, anterior-posterior 30 of the medical imaging equipment 1.

Figure 8 is a flow-chart of a method according to the invention for determining alignment and/or twist of a patient in a coronal medical image about a cranial- caudal axis 32 relative to a frontal plane 31 of a patient 10, preferably a chest x- ray, the method comprising,

- SI providing medical imaging equipment 1 suitable for obtaining a chest x- ray of the patient 10, and hereby providing an x-ray image of the patient's chest 13,

- S2 providing imaging analysis software, the imaging analysis software processing the following steps based on said image of the patient 10:

S3 identifying a midline 40 in the patient's chest 13 along a spine of the patient 10, and, at a first point 41 of the midline 40:

- S4 identifying a lateral edge 15 of a ribcage 14 of the patient 10 on a left side 11 of said midline 40 and identifying a lateral edge 16 of the ribcage 14 of the patient 10 on a right side 12 of said midline 40,

- S5 obtaining a first transverse distance 43 between the midline 40 and the lateral edge 15 of the ribcage 14 on the left side 11, and obtaining a second transverse distance 44 between the midline 40 and the lateral edge 16 of the ribcage 14 on the right side 12, and at a second point 42 of the midline 40, the second point 42 being different from the first point 41 of the midline 40:

- S6 identifying a lateral edge 15 of a ribcage 14 of the patient 10 on a left side 11 of said midline 40 and identifying a lateral edge 16 of the ribcage 14 of the patient 10 on a right side 12 of said midline 40,

- S7 obtaining a third transverse distance 45 between the midline 40 and the lateral edge 15 of the ribcage 14 on the left side 11, and obtaining a fourth transverse distance 46 between the midline 40 and the lateral edge 16 of the ribcage 14 on the right side 12,

S8 comparing one or more of the first transverse distance(s) 43 and the second transverse distance 44 with one or more of the third transverse distance(s) 45 and the fourth transverse distance 46, so as to determine an anterior-posterior 30 alignment and/or twist of the patient 10 about the cranial-caudal axis 32 relative to the frontal plane 31 of the patient 10 and

S9 generating an output to an operator of the medical imaging equipment 1.

The invention can be implemented by means of hardware, software, firmware or any combination of these. The invention or some of the features thereof can also be implemented as software running on one or more data processors and/or digital signal processors.

In short, the invention discloses a method for determining alignment and/or twist in the upper and/or lower part of a patient's chest 13 in a medical image relative to a coronal plane of a patient, comprising providing medical imaging equipment 1 for obtaining a chest x-ray of the patient 10, providing imaging analysis software, obtaining a plurality of distances 43, 44, 45, 46 between a midline 40 on an image of the patient's chest and the right and left lateral edge 15, 16 of the patient's ribcage 14 and comparing one or more of the said distances 43, 44, 45, 46 so as to determine whether or not the patient 10 is aligned in relation to the medical imaging equipment 1. The invention is advantageous for reducing radiation exposure of a particularly vulnerable patient group, neonates, which are difficult to diagnose by medical images, compared to kids and adults, and due to their high cell division rate, are very sensitive to radiation exposure.

The individual elements of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way such as in a single unit, in a plurality of units or as part of separate functional units. The invention may be implemented in a single unit, or be both physically and functionally distributed between different units and processors.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A method for determining alignment and/or twist of a patient in a coronal medical image about a cranial-caudal axis (32) relative to a frontal plane (31) of the patient (10), preferably a chest x-ray, the method comprising,

providing medical imaging equipment (1) suitable for obtaining a chest x- ray of the patient, and hereby providing an x-ray image of the patient's chest (13),

- providing imaging analysis software, the imaging analysis software

processing the following steps based on said image of the patient: identifying a midline (40) in the patient's chest along a spine of the patient, and, at a first point (41) of the midline:

- identifying a lateral edge (15) of a ribcage (14) of the patient on a left side

(11) of said midline and identifying a lateral edge (16) of the ribcage of the patient on a right side (12) of said midline,

- obtaining a first transverse distance (43) between the midline and the lateral edge of the ribcage on the left side (11), and obtaining a second transverse distance (44) between the midline and the lateral edge of the ribcage on the right side (12), and at a second point (42) of the midline, the second point being different from the first point of the midline:

- obtaining a third transverse distance (45) between the midline and the lateral edge of the ribcage on the left side, and obtaining a fourth transverse distance (46) between the midline and the lateral edge of the ribcage on the right side, comparing one or more of the first transverse distance and the second transverse distance with one or more of the third transverse distance and the fourth transverse distance, so as to determine a coronal alignment and/or twist of the patient about the cranial-caudal axis relative to the frontal plane of the patient.

2. The method according to any of the preceding claims, wherein the method comprises the step of using the coronal alignment and/or twist about the cranial-caudal axis of the patient as obtained by the method, to quantify a quality of said image.

3. The method according to any of the preceding claims, wherein the method comprises the step of using the coronal alignment and/or twist about a cranial- caudal axis of the patient as obtained by the method, so as to determine if it is necessary to obtain yet another image.

4. The method according to claim 4, wherein the determination of the necessity of obtaining yet another image results from a determination of the coronal alignment about a cranial-caudal axis being below a first threshold.

5. The method according to claim 3 and/or 4, wherein the determination of the necessity of obtaining yet another image results from a determination of the patient's twist in the coronal plane about a cranial-caudal axis being below a second threshold.

6. The method according to any of the preceding claims, wherein the coronal alignment about a cranial-caudal axis of the patient is determined by one or more of a ratio between, a difference between, a correctness percentage or a comparison of the first distance and the second distance.

7. The method according to any of the preceding claims, wherein the coronal alignment about a cranial-caudal axis of the patient is determined by a comparison of a first area (47) formed by a left side area of the ribcage and a right side area (48) of the ribcage, the left and right areas being divided by the midline.

8. The method according to claim 7, wherein a difference, ratio, or a correctness percentage between the left and right areas (47, 48) of the ribcage is/are used to determine the coronal alignment about a cranial-caudal axis of the patient.

9. The method according to any of the preceding claims 1-8, wherein the twist of the patient in the coronal plane about a cranial-caudal axis of the patient is determined by

- a ratio between a distance between the edge of the ribcage on the left side and the edge on the right side of the ribcage at a first point of the midline, and a distance between the edge of the ribcage on the left side and the edge on the right side of the ribcage at a second different point of the midline.

10. The method according to any of the preceding claims, wherein said image is obtained from a neonatal patient.

11. The method according to any of the preceding claims, wherein said midline represents a straight line from the centre of a cranial point of said spine to a centre of a caudal point of said spine and wherein said midline represents the cranial-caudal axis.

12. The method according to any one of claims 6 and/or 8, wherein said

correctness percentage is at least 80 percent, preferably at least 90 percent.

13. A system for determining alignment and/or twist of an associated patient in a coronal medical image about a cranial-caudal axis (32) relative to a frontal plane (31) of the associated patient (10), preferably a chest x-ray, the system comprising :

- medical imaging equipment (1) suitable for obtaining a chest x-ray of the patient, and hereby providing an x-ray image of the patient's chest (13),

- imaging analysis software, the imaging analysis software being adapted to process the following steps based on said image of the patient: identifying a midline (40) in the patient's chest along a spine of the patient, and, at a first point (41) of the midline:

- identifying a lateral edge (15) of a ribcage (14) of the patient on a left side (11) of said midline and identifying a lateral edge (16) of the ribcage of the patient on a right side (12) of said midline, - obtaining a first transverse distance (43) between the midline and the lateral edge of the ribcage on the left side, and obtaining a second transverse distance (44) between the midline and the lateral edge of the ribcage on the right side, and at a second point (42) of the midline, the second point being different from the first point of the midline: identifying a lateral edge of a ribcage of the patient on a left side of said midline and identifying a lateral edge of the ribcage of the patient on a right side of said midline,

obtaining a third transverse distance (45) between the midline and the lateral edge of the ribcage on the left side, and obtaining a fourth transverse distance (46) between the midline and the lateral edge of the ribcage on the right side, comparing one or more of the first transverse distance(s) and the second transverse distance with one or more of the third transverse distance(s) and the fourth transverse distance, so as to determine an coronal alignment and/or twist of the patient about a cranial-caudal axis relative to a frontal plane.

14. The system according to claim 13, wherein the system further comprises a visual and/or audible system, preferably a display and/or means to provide audible vibrations, giving feedback to an operator, so as to correct a non- alignment and/or twist of a patient about a cranial-caudal axis and/or so as to correct alignment of the medical imaging equipment about a cranial caudal axis of the patient.

15. A computer program for determining alignment and/or twist of a patient in a coronal medical image relative to a cranial caudal axis of the patient, preferably a chest x-ray, the computer program, when being executed by a data processor, is adapted for controlling and/or for carrying out the method as set forth in any one of the claims 1 to 12.