RU2576816C1 - Method for determination of left atrial myocardium contours on mr images using multi-planar reconstructions - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to medicine, x-ray diagnostics, and can be used in processing of MR images with delayed contrasting, determining the structure of the left atrial myocardium (LM) in the patients with atrial fibrillation (AF). It is necessary to perform MRT of the heart with delayed staining. On the basis of the obtained series of images one performs multi-plane reconstruction of LM in three mutually perpendicular planes: frontal, sagittal, axial. On the basis of multi-plane reconstruction data one performs searching of cardiac structures and artefacts, which can be mistaken for LM myocardium, in the following sequence. First, one determines topography of LM and adjoining structures, for which purpose it is necessary to determine topography of the mitral ring in the obtained planes, the first layer of atrial myocardium is immediately above the level of ring of mitral valve. Then, on the axial plane, one draws a longitudinal axis of the left ventricle (LV) and its transverse axis at the level of the mitral valve. Along the constructed transverse axis of LV at all axial sections of LM one draws the boundary between LV and LM. Then one determines the oesophagus and its boundary with the back wall of LM. One determines the aortic valve ring, descending aorta, differentiating these structures with LM wall in places of their closest location. One determines the route of the left coronary artery near LM loop as a band of an intensive signal migrating from layer to layer towards lateral wall of LV. Then one outlines LM contours, for which purpose it is necessary to first outline LM endocardial contour using as a reference point LM back wall. Then one outlines the atrial myocardium in the medial direction and backwards from the defined boundary between LM and LV. Front wall and LM loop are outlined above the upper boundary of the ring of mitral valve. Then one outlines LM epicardial circuit. Finally, one excludes artefacts, for which purpose he detects in LM myocardium zones with brightness more intense than brightness of the wall of the aorta in this layer. One views such zones in different planes while interpreting the zone as not related to LM myocard. Such zone is manually cut out from its boundaries.

EFFECT: this method makes its possible to accurately outline LM myocard contour and ensures standardization of procedure of working with MR-images, which allows to obtain comparable results.

3 cl, 8 dwg

Description

FIELD OF THE INVENTION

The invention relates to medicine, and more specifically to radiation diagnostics, and can be used in the processing of MP images with delayed contrast and determining the structure of the myocardium of the left atrium (LP) in patients with atrial fibrillation (MA).

MA is one of the most common cardiac arrhythmias that occurs in 1-2% of the general population and 5% of people over 65 years of age. However, the effectiveness of conservative and interventional treatment of MA is still not high enough. At the same time, the severity of the course, as well as the prognosis of the disease, are often associated with the severity of structural changes in the left atrium (LP). The improvement of modern approaches to the diagnosis and treatment of MA can be based on an assessment of the degree of structural changes in the myocardium of the atria. So, it has been demonstrated that the severity of structural changes in the atria can affect the effectiveness of drug and interventional therapy of arrhythmia.

A non-invasive assessment of the severity of structural changes in the atrial myocardium can be carried out using high-resolution magnetic resonance imaging (MRI) with delayed contrast. On the obtained MP-images, for judging the structure of the atrial myocardium, it is necessary to trace the contours of the LP myocardium. It is known that the wall thickness of a medicinal product is 1.5–3 mm, which requires high accuracy and reproducibility of encircling its contours.

State of the art

One of the analogues of the method we developed is the fully automatic determination of the walls of the LP, carried out using a special program based on mathematical modeling of the signal intensity of the myocardial LP (Veni G., Fu Zh., Awate SP et al. Bayesian Segmentation of Atrium Wall Using Globally-Optimal Graph Cuts on 3D Meshes. JC Gee et al. (Eds.): IPMI 2013, LNCS 7917, pp.656-667, 2013. Springer-Verlag Berlin Heidelberg 2013). The disadvantage of this method is the low specificity of the contour of the drug loops and the need for verification by an expert.

The closest analogue of the proposed method is a simple semi-automatic contouring of the myocardial contours of the LP without the use of the artifact search algorithm [Oakes R.S., Badger T.J., Kholmovski E.G. et al. Detection and quantification of left atrial structural remodeling with delayed-enhancement magnetic resonance imaging in patients with atrial fibrillation. Circulation. 2009 Apr 7; 119 (13): 1758-67]. However, the disadvantage of this method may be a discrepancy in the severity of the identified structural lesion of the drug when circulating its contours by various experts, due to the lack of a single system for eliminating artifacts.

Disclosure of invention

The MP-image processing technology that we developed allows us to accurately trace the contour of the myocardium of the LP. In addition, the proposed algorithm for working with images provides a standardization of the procedure for working with MP-images, allowing you to get comparable results.

To determine the left atrial myocardial contours (LP) on MR images using multi-planar reconstructions, high-resolution MRI of the heart is performed with delayed contrast, the atria are examined in free breathing, synchronizing with ECG and breathing, the average duration of atrial scanning is 10 minutes. Using the standard software of MRI workstations from the resulting series of images, multiplanar reconstruction of the LP images is performed in three perpendicular planes: frontal, axial and sagittal. When viewing and comparing the data of multiplanar reconstructions, a search is made for the structures of the heart and artifacts that may be mistaken for the myocardium of the LP.

The identification of these formations is carried out in the following sequence:

- determine the topography of the PL and adjacent structures, for which first determine the topography of the mitral ring in the obtained planes; determine the first layer of the atrial myocardium immediately above the level of the mitral valve ring, and in the case of the vertical position of the heart, the part of the mitral valve ring that stands out in the atrial septum in the form of a bright point structure is identified, then the longitudinal axis of the left ventricle (LV) is constructed on the axial plane and it the transverse axis at the level of the mitral valve, along the constructed transverse axis of the left ventricle on all axial sections of the LP draw a border between the LV and the LP;

- then the esophagus and its borders with the posterior wall of the LP are revealed;

- reveal the ring of the aortic valve, the descending aorta, differentiating these structures with the wall of the PL in the places of their closest location;

- determine the course of the left coronary artery near the ear of the PL, as a band of an intense signal migrating from layer to layer towards the lateral wall of the LV;

- further outline the contours of the patient, for which they first trace the endocardial contour of the patient, being guided by the fact that the atrial myocardium has a signal intensity exceeding the blood, and the posterior wall of the patient is most clearly visible, which is considered as a guideline when circling the contours;

- further circle the atrial myocardium more medially and posterior to a certain border between LV and PL;

- the front wall and the ear of the LP circled above the upper border of the mitral valve ring;

- then circle the epicardial contour of the medicament, which is either completed automatically by the specified thickness of the myocardium of the medicament 1.5-3.5 mm, followed by manual dressing, or is carried out manually parallel to the endocardial contour;

- then the exclusion of artifacts is carried out, for which areas with a brightness exceeding the brightness of the aortic wall in this layer are detected in the myocardium of the LP, these zones are considered in different planes, and when interpreting the zone as not related to the myocardium of the LP, such a zone is manually cut out of its borders.

The invention is illustrated by the following illustrations:

Fig 1. The topography of the mitral valve ring (arrows) on MR images of the heart in the sagittal (A), coronal (B) and axial (C) planes.

Fig 2. MP image of the left atrium. The arrow indicates the lower lateral part of the mitral ring.

Fig 3. MP image of the heart. The white arrow is the longitudinal axis of the left ventricle; the black arrow is the transverse axis of the left ventricle at the level of the mitral ring (indicates the border between the left ventricle and the left atrium).

Fig 4. MP image of the heart. The arrows indicate the esophagus at various levels.

Fig 5. MP image of the heart. The white arrow indicates the aortic valve ring, the black arrow indicates the wall of the descending aorta, and the gray arrow indicates the posterior wall of the left atrium.

Fig 6. MP-image of the heart, the coronal plane (A), axial plane (B). The white arrow indicates the ear of the left atrium, the black arrow indicates the coronary artery.

Fig 7. MP image of the heart. The yellow lines indicate the endocardial and epicardial contours of the left atrial myocardium.

Fig 8. MP image of a high resolution of the myocardium of the left atrium after ablation of the mouth of the pulmonary veins. A - axial plane (original image), B - reconstruction along the frontal plane. B-reconstruction in the sagittal plane.

The method is as follows

High-resolution MRI of the heart is performed with delayed contrast (15-20 minutes after the administration of a contrast preparation containing gadolinium). Atrial examination is performed in free breathing with synchronization with ECG and breathing, the average duration of atrial scanning is 10 minutes. On the obtained series of MR images of the heart, it is necessary to highlight the contours of the myocardium of the LP.

Tracing the borders of the myocardium of the LP can be carried out using any program that allows you to edit graphic files in the DICOM format, for example, in ImageJ (USA) or Seg3D (USA) programs. At the same time, using the standard software of MRI workstations, from the resulting series of images, a multiplanar (multi-plane) reconstruction of the LP images is performed in three perpendicular planes: frontal, axial and sagittal.

When viewing and comparing data from multiplanar reconstructions, a search is made for the structures of the heart and artifacts that may be mistaken for myocardial LP.

Identification of these formations is carried out in the following sequence:

I. Determination of the topography of the LP and adjacent structures

1. Determination of the topography of the mitral ring (Fig. 1).

2. Determination of the first layer of the atrial myocardium immediately above the level of the mitral valve ring. In the case of the vertical position of the heart, it is necessary to identify the part of the mitral valve ring that stands out in the area of the interatrial septum in the form of a point bright structure (Fig. 2).

3. On the axial plane, the longitudinal axis of the left ventricle (LV) and its transverse axis are constructed at the level of the mitral valve. On the constructed transverse axis of the left ventricle on all axial sections of the left ventricle, draw a boundary between the left ventricle and the left ventricle (Fig. 3).

4. Identification of the esophagus and its borders with the posterior wall of the PL (Fig. 4).

5. Identification of the aortic valve ring, descending aorta. Differentiation of these structures with the wall of PL in the places of their closest location (Fig. 5).

6. Determination of the course of the left coronary artery near the ear of the PL as a band of an intense signal migrating from layer to layer towards the lateral wall of the LV (Fig. 6).

In the future, the contours of the drug are circled, guided by the following rules:

II. Circulation of the endocardial contour of the LP

1. Atrial myocardium has a signal intensity exceeding the blood, the posterior wall of the LP is most clearly visible, which can be considered as a guideline when circling the contours (Fig. 5).

2. Atrial myocardial tracing is performed more medially and posterior to a certain border between the LV and the LP (Fig. 3).

3. The front wall and the ear of the LP are circled above the upper border of the mitral valve ring (Fig. 6).

III. Circulation of the epicardial contour of the LP

The epicardial contour can be automatically expanded to a predetermined thickness of the LP myocardium (usually 1.5-3.5 mm), followed by manual dressing or manually parallel to the endocardial contour (Fig. 7).

IV. Artifact exclusion

1. If zones in the myocardium of the PL are detected that have a brightness exceeding the brightness of the aortic wall in this layer, it is necessary to consider such zones in different planes in order to exclude artifacts or structures (Fig. 8) mentioned in section I.

2. When interpreting this structure as not related to the myocardium, it should be excluded from its borders (cut out manually).

The result of the application of the algorithm is the circled contour of the myocardium of the LP. Using the described technique allows you to standardize the process of circling the contours of the myocardium of the LP.

Clinical example

Patient R., who underwent cryoablation of the mouth of the pulmonary veins due to the paroxysmal form of MA.

The procedure was ineffective, which required the identification of uninsulated pulmonary veins. The patient underwent cardiac MRI with delayed contrast in order to assess postablative damage.

The use of the algorithm for circling the contours of the myocardium of the LP using multiplanar reconstructions of the heart made it possible to study the structure of the myocardium of the LP and to reveal dense circular lesions around all pulmonary veins. These data served as the basis for the identification and subsequent ablation of sources of ectopic activity that contribute to the recurrence of atrial fibrillation in the region of the posterior wall of the LP.

In Fig. 8, an example of a multiplanar reconstruction of a patient’s LP undergoing ablation of the mouths of pulmonary veins. The white arrow indicates the bright areas of contrast in the myocardium of the LP around the mouth of the right inferior pulmonary vein, which can be seen in various planes in FIG. 8A and FIG. 8B. The gray arrow marks the structure, which, when considered in FIG. 8B and FIG. 8B belongs to the anterior part of the mitral valve ring and is not part of the atrial myocardium.

Claims (3)

1. The method of determining the contours of the myocardium of the left atrium (LP) in MR images using multiplanar reconstructions, characterized in that they perform high-resolution MRI of the heart with delayed contrast,
from the obtained series of images, multiplanar reconstruction of the LP images is performed in three perpendicular planes: frontal, axial and sagittal,
on the data of multi-planar reconstructions, a search is made for the structures of the heart and artifacts that may be mistaken for a myocardium, and the identification of these formations is carried out in the following sequence:
a. determine the topography of the LP and adjacent structures, for which they determine the topography of the mitral ring in the obtained planes, the first layer of the atrial myocardium immediately above the level of the mitral valve ring, then on the axial plane, the longitudinal axis of the left ventricle (LV) and its transverse axis are constructed at the level of the mitral valve, along the constructed transverse axis of the left ventricle on all axial sections of the left ventricle, draw a boundary between the left ventricle and the left ventricle; the esophagus and its borders with the posterior wall of the LP are revealed, the aortic valve ring, the descending aorta is revealed, differentiating these structures with the LP wall in the places of their closest location, the course of the left coronary artery near the LP ear is determined as a band of an intense signal migrating from layer to layer in side of the lateral wall of the left ventricle;
b. outline the contour of the patient, for which they first trace the endocardial contour of the patient, using the posterior wall of the patient as a guideline, then trace the atrial myocardium more medially and posterior to a certain border between the left ventricle and the patient, the front wall and the ear of the patient trace above the upper border of the mitral valve ring; then circulate the epicardial contour of the LP;
from. exclude artifacts, for which areas with a brightness exceeding the brightness of the aortic wall in this layer are revealed in the myocardium of the PL, these zones are considered in different planes, and when interpreting the zone as not related to the myocardium of the PL, such a zone is manually cut out of its borders. 2. The method according to p. 1, characterized in that with the vertical position of the heart at stage a. “Determination of the topography of the LP and adjacent structures” identifies the part of the mitral valve ring that stands out in the area of the interatrial septum in the form of a bright dotted structure. 3. The method according to p. 1, characterized in that, if necessary, the epicardial contour of the medicament is either completed automatically to the prescribed thickness of the myocardium of the medicament 1.5-3.5 mm, followed by manual editing, or is carried out manually parallel to the endocardial contour.

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