RU2712310C1 - Method of diagnosing sacroiliitis on high-field magnetic resonance tomography - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: invention relates to medicine, specifically to diagnostics. A diagnostic technique for bone marrow oedema in sacroiliitis on a high-field magnetic resonance tomography involves determining the signal intensity in a skew-aligned plane using standard pulse sequences T1 and T2 DIXON. In the T2 protocol, DIXON is set in the image acquisition parameters: the interval repetition time is 3500 ms, the echo time is 82 ms, the number of cuts is 18, the thickness of cut is 4 mm, the field of view is 320 mm, the scanning matrix is 256 × 256; then performing subtraction of two series of images, in one of which there is selective inhibition of the signal from adipose tissue, and in the other - from water.EFFECT: using the given invention enables higher accuracy of diagnosing sacroiliitis.1 cl, 9 dwg, 2 ex

Description

The invention relates to medicine and can be used in radiation diagnostics and rheumatology.

A well-known method for the diagnosis of sacroileitis on a high-field magnetic resonance imager [1]. The method is based on obtaining in oblique and axial sections T1, T1 with contrast enhancement and T2 STIR weighted images (VI). On the obtained magnetic resonance tomograms, sacroileitis is defined as areas of a hyperintensive signal in the subchondral bone marrow (osteitis) in T2, T2 STIR VI, hypointensive signal in T1 VI without clear contours. An advantage of the method is an increase in the contrast of enhanced T1 tomograms and a clearer differentiation of synovitis and capsulitis. The disadvantage of this method is the need for intravenous administration of a contrast drug, an increase in time and, accordingly, the final cost of the examination. Moreover, the sensitivity of this method in identifying the main criterion for sacroiliitis - osteitis is comparable with T2 STIR VI.

A known method for the diagnosis of sacroileitis on a high-field magnetic resonance imaging scanner, based on obtaining T1 and T2 STIR images in the sagittal and coronary section [2]. On the obtained magnetic resonance tomograms, sacroileitis was determined in the form of zones of a hyperintensive signal in T2, T2 STIR VI, hypointensive in T1 VI without clear contours. In the initial stage (height), the signal homogeneity was lost in T2, T2 STIR VI. The signal inhomogeneity increased at the stage of decay. In the post-sacroileitis phase, the bone marrow edema zone decreased in size, there were signs of lipoid reconversion (hyperintensive signal in T1, T2 VI, hypointensive in T2 STIR) and subchondral osteosclerosis (hypointensive signal in T2, T1 VI), the formation of erosion. The disadvantage of this method is the inability to fully reflect the main features of sacroileitis. There is no optimal visualization of the extent and size of the zone of inflammatory changes due to the bright signal from the vessels and the sacral nerve plexus.

There is a known method for the diagnosis of sacroileitis using the T2 DIXON method, with which images are calculated from the half-sum and half-difference of two phase-sensitive MRI images - in-phase ("in phase") and antiphase ("out phase"). [3]. The result is two series of images: with selective suppression of the signal from water ("only fat") and from adipose tissue ("only water"). The procedure for the procedure is as follows. After laying the patient on his back and starting the orientation protocol, the zone of the sacroiliac joints is determined. Then load the parameters of the standard protocol. Then perform tomography in oblique and axial sections T1 and T2 DIXON image. On the obtained magnetic resonance tomograms, sacroileitis was determined in the form of zones of a hyperintensive signal on T2 DIXON VI with selective suppression of the signal from adipose tissue.

The disadvantage of this method is that when a visual comparison of the series of such images is not always possible to identify differences in contrast in the area of the alleged inflammatory changes due to the characteristics of visual perception. An additional limitation is the technical imperfection of the display device (monitor), which makes it difficult to reliably estimate the boundaries of the zone of increase in signal intensity against a background of heterogeneous bone marrow.

This method is the closest to the proposed technical essence and the achieved result, and therefore was selected as a prototype.

The purpose of the present invention is to overcome the disadvantages of the known methods and to create a new method that improves the accuracy of determining the zone of inflammatory changes in the ileosacral joints.

The goal is achieved by a technical solution, which is a method for the diagnosis of sacroiliitis on a high-field magnetic resonance imager.

FIG. 1 - MP tomogram of patient T. in T2 STIR mode in a coronal projection.

FIG. 2 - MP tomograms of patient K. (clinical example No. 1) in T2 DIXON mode in a coronal projection.

A - T2 tomogram, a series of "only fat";

B - T2 tomogram, series "only water";

B - subtraction of the series "only water" and T2 VI "only fat";

G - T2 tomogram, series "only water";

D - subtraction of the series "only water" and T2 VI "only fat".

FIG. 3 - MP-tomograms of patient P. (clinical example No. 2) in an oblique projection.

A - T2 TSE tomogram;

B - T2 DIXON tomogram, series "only water";

B - subtraction of the series "only water" and T2 VI "only fat".

The following protocol parameters are used for the T2 DIXON sequence: Time repetition (TR) - 3500 ms, Echo time (Time echo, TE) - 82 ms, Number of slices (No. slices, NS) 18, Thickness slices , SL) 3 mm, field of view (FOV) - 320 mm, matrix - 256 * 205, the time it takes to obtain one set of images (Time acquisition, TA) 3 min.

New in the proposed method is the use of additional mathematical processing (subtraction) of two series of images: "only fat" and "only water".

Thus, in a situation where there are no single standard, magnetic resonance protocols for diagnosing the initial manifestations of sacroiliitis, the protocol parameters proposed by the authors solve the problem of the most complete characterization of the zone of inflammatory changes, that is, increase the accuracy of the method.

The invention will be clear from the following description, the drawings attached to it, and the clinical cases provided.

The procedure has the following distinguishing features. After the patient’s standard laying on the back and the launch of the orientation protocol, the localizer’s usual search program is performed to determine the localization of the sacroiliac joints. Then, tomography is performed in coronal sections to obtain T2 DIXON and T1 images, and then an axial section to obtain thin sections T2 STIR images. In the course of the study, it turned out that the T2 DIXON image series in oblique section with subsequent subtraction is the most optimal than the T1 and T2 STIR image, since it most accurately and in detail characterizes the zones of osteitis, synovitis and capsulitis.

Based on the theory of magnetic resonance, the advantage of T2 images is achieved by changing the protocol parameters: reducing the time it takes to obtain one image (Time acquisition, TA) from 5 min to 3 min and reducing the thickness of the slice (Thickness slices, SL) of 3 mm. Reducing the time taken to obtain one image did not degrade image quality. Reducing the thickness of the slice led to better visualization of the minimum areas of bone marrow edema, capsule joints, ligaments, and the state of surrounding tissues.

As a result of using the standard protocol, without changing the parameters proposed by the authors, T2 STIR tomograms were obtained (Fig. 1.) As can be seen from Fig. 1, there is no optimal visualization of the swelling zone at T2 STIR, it is difficult to determine the condition of the ligaments, capsules, and also surrounding tissues.

Thus, based on the data obtained after conducting high-field magnetic resonance imaging according to the protocols proposed by the authors, we can convincingly talk about a significant increase in the accuracy of the diagnostic method.

This diagnostic method can be used in all medical centers that have at their disposal high-field magnetic resonance imaging scanners, not to mention tomographs of a similar class (Magnetom Essenza, Siemens), where this protocol can simply be transferred for use. The diagnostic method proposed by the authors was used in 27 patients with sacroiliitis and has high sensitivity and specificity, that is, it allows more accurate diagnosis of even minimal zones of inflammatory changes in the bone marrow, signs of capsulitis and ligamentitis with sacroiliitis.

The diagnostic possibilities of using the T2 DIXON image modified scan protocol are clearly visible in the following clinical examples.

Clinical example No. 1. Patient K., 36 years old, with right-sided sacroiliitis revealed a zone of bone marrow edema of the right lateral mass of the sacrum and subchondral bone marrow of the right iliac bone, capsule of the right ileosacral joint (ASC) with a hyperintense signal in T2 VI (Fig. 2A) and T2FS ( Fig. 2B). The dimensions of the edema zone (32 × 26 mm) are easily determined due to the hyper-intensive signal in T2 DIXON images obtained by the method of subtraction against the background of the surrounding intact hypo-intensive bone marrow (Fig. 2B). Additionally, it was possible to visualize similar changes in the left ASC (18 × 15 mm), which are difficult to visualize on the T2FS VI series due to fuzzy contours and low contrast (Fig. 2G). On a series of tomograms obtained by the method of subtraction, the edema zone has certain contours (Fig. 2D).

Signal intensity indicators from the osteitis and intact bone tissue in the corresponding areas on standard images with signal suppression from adipose tissue and on images obtained by subtraction were analyzed. The values of the contrast noise ratio (CNR) in tissues with inflammatory changes (osteitis) in the left ASC were higher (CNR, 241) than in standard T2 STIR images (CNR, 63), which significantly improves the perception of the differences between the two studied clinical areas.

Clinical example No. 2. Patient P., 23 years old, was admitted with complaints of severe pain in the lumbar region on the left for 2 months. An objective examination in the soft tissues of the lumbar region on the left revealed a fistulous course. An x-ray of the articular surface revealed an alteration of the articular surfaces in the left ASC. When conducting high-field magnetic resonance imaging according to the protocols proposed by the authors, the following changes were revealed. On the upper adjacent surfaces of the left sacroiliac joint, the zone of edema with a hyper-intense signal in T2 VI (Fig. 3A) and T2FS VI (Fig. 3B) is differentiated. Assessing the boundaries of the edema zone is difficult due to the heterogeneous signal from the surrounding intact bone marrow. In the image obtained by the method of subtraction, the swelling zone is clearly contoured against a uniform dark background and has dimensions 20 × 15 mm (Fig. 3B). The synovitis and fistulous course with heterogeneous fluid contents (hypointensive in T2 VI and hyperintensive in T1 FS VI), which extends to the skin surface of the left lumbar region, is also visualized. The edema of the surrounding soft tissues is clearly differentiated. This magnetic resonance picture indicates a complication of the inflammatory process in ASC and the development of a productive phase of the reaction. CNR values in tissues with inflammatory changes (osteitis, synovitis) were significantly (p <0.01) higher in images obtained by the subtraction method (CNR, 238) than on standard T2 VI (CNR, 64), T2 VI with selective signal suppression from adipose tissue (CNR, 83) and T2 STIR VI (CNR, 87).

This clinical example shows how the application of the protocols proposed by the authors allows us to characterize sacroiliitis in detail and indicate the area of spread of the inflammatory process, as well as the presence of complications (fistulous course).

List of references

1. Ӧzgen A. The Value of the T2-Weighted Multipoint Dixon Sequence in MRI of Sacroiliac Joints for the Diagnosis of Active and Chronic Sacroiliitis. Am J Roentgen (2017) 208: 603-608 https://doi.org/10.2214/AJR.16.16774

2. Ӧzgen A. Comparison of fat-saturated T2-weighted and contrast-enhanced fat-saturated T1-weighted sequences in MR imaging of sacroiliac joints in diagnosing active sacroiliitis. Eur J Radiol (2015) 84: 2593-6.10.1016 / j.ejrad.2015.08.021

3. Van der de Hooge M, Van den Berg R, Navarro-Compán V, Van Gaalen F, Van der Heijde D, Huizinga T, et al. Magnetic resonance imaging of the sacroiliac joints in the early detection of spondyloarthritis: no added value of gadolinium compared with short tau inversion recovery sequence. Rheumatology (Oxford) (2013) 52: 1220-4.10.1093 / rheumatology / ket012

Claims (1)

A method for diagnosing a bone marrow edema zone with sacroiliitis on a high-field magnetic resonance imager by determining the signal intensity in the oblique plane using standard pulse sequences T1 and T2 DIXON, characterized in that in the T2 DIXON protocol the image acquisition parameters are set: interval repetition time - 3500 ms, echo time - 82 ms, number of slices - 18, slice thickness - 4 mm, field of view - 320 mm, scan matrix - 256 * 256; then, two series of images are subtracted, one of which selectively suppresses the signal from adipose tissue, and the other from water.

Images