Feet positioning system for magnetic resonance imaging studies

Abstract

The present invention is related to a system and method to ensure the reproducibility of the position of the feet and lower parts of the legs during Magnetic Resonance Imaging (MRI) studies, and to obtain robust quantitative information through the time. The system includes a device that is inserted into the radiofrequency coils of any MRI equipment. The device includes a foot support section, a leg support section and a base adapted to allow that the abovementioned sections be fixed in it. With this device and method, and through external and internal markers, quantitative studies of the evolution of pathophysiological phenomena that affect the anatomy and physiology of the feet and lower parts of the legs are performed.

Claims

1. A magnetic resonance imaging (MRI) system to control the orientation of a foot of an individual during a MRI scanning process, the system comprising a foot positioning device, wherein said foot positioning device comprises: (a) a foot support section that includes: 1. a foot support surface to situate said foot of said individual in a fixed position relative to the foot positioning device; wherein said foot support surface comprises at least two image marker elements that are visible when MRI images are recorded; 2. an arch for a heel adapted to be positioned behind the heel of the individual and sliding regarding said foot support surface; 3. means to fix the foot of the individual on said foot support surface during the scanning process; (b) a leg support section including: 1. a leg support to situate a leg of said individual in a fixed position regarding the foot positioning device; 2. means to fix said leg of the individual to said leg support during the scanning process; (c) a foot positioning device base adapted to allow that the foot support surface and the leg support section be fixed in said base and positioned on a scanning bed; wherein said foot positioning device is adapted to be inserted into a radiofrequency (RF) coil of the MRI system for scanning in a reproducible position regarding an axis of a static magnetic field of said MRI system.

2. The system according to claim 1, wherein said foot positioning device base is adapted to allow that said foot support section could be placed in a series of fixed positions indicated on a scale regarding said foot positioning device base.

3. The system according to claim 1, wherein the at least two image marker elements are located in parallel to said foot support surface and define a plane of a magnetic resonance image.

4. The system according to claim 1, wherein said foot positioning device comprises material not visible under visualization of magnetic resonance images.

5. The system according to claim 4, wherein said material is polyvinyl chloride.

6. The system according to claim 1, wherein said foot positioning device comprises an additional foot support surface, an additional arch for an additional heel, and an additional leg support, wherein said additional foot support surface, additional arch, and an additional leg support are positioned on the foot positioning device base.

7. A method to control the orientation of a foot of an individual regarding a magnetic resonance imaging system during a magnetic resonance imaging scanning process, the method comprising: (a) situating a foot positioning device in a fixed and reproducible position in a radiofrequency coil of the magnetic resonance imaging system; (b) locating the foot of the individual in the foot positioning device while the foot positioning device is in said fixed and reproducible position with regard to image marker elements; (c) recording first images of magnetic resonance imaging to check correct foot positioning; (d) optionally correcting the foot positioning regarding the image marker elements and the foot positioning device in the magnetic resonance imaging system; and optionally (e) recording second magnetic resonance images; wherein said foot positioning device is a device comprising: a foot support section that includes a foot support surface to situate said foot of said individual in a fixed position relative to the foot positioning device; wherein said foot support surface comprises said image marker elements, wherein said image marker elements are visible when magnetic resonance imaging images are recorded; an arch for a heel adapted to be positioned behind the heel of the individual and sliding regarding said foot support surface; means to fix the foot of the individual on said foot support surface during the scanning process; a leg support section including a leg support to situate a leg of said individual in a fixed position regarding the foot positioning device; means to fix said leg of the individual to said leg support during the scanning process; a foot positioning device base adapted to allow that the foot support surface and the leg support section be fixed in said base and positioned on a scanning bed; wherein said foot positioning device is adapted to be inserted into a radiofrequency (RF) coil of a magnetic resonance imaging system for scanning in a reproducible position regarding an axis of a static magnetic field of said magnetic resonance imaging system.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1. Schematic representation of a device for positioning and fixation of the feet during MRI scanning. A. Isometric view, B. Lateral view, C. Top view of the device. In the views are shown the main parts of the device: 1. Foot support surface, 2. Leg support 3. Arch for the heel, 4. Device base, 5. Scale, 6. Means to fix feet and lower part of the legs, 7. Image markers (external), 8. Pin, and 9. Grip groove.

(2) FIG. 2. Details of leg supports in the device (2 in FIG. 2A), Foot support surface (1 in FIG. 2B), and arches for the heel (3 in FIG. 2C).

(3) FIG. 3. MRI of healthy foot. Arrows indicate the position of the external markers in coronal section (A), sagittal section (B) and in a three-dimensional image reconstruction of the feet (C).

(4) FIG. 4. Example of device positioning in a MRI head RF coil. Arrow 1 indicates the MRI magnetic system, arrow 2 shows the positioning and cramping device, and arrow 3 indicates the complete RF coil.

(5) FIG. 5. Position of the individual examined with the feet in the positioning device, inside the head coil, in the MRI equipment indicated with arrow 1. Arrow 2 indicates a pillow standing on the back of the knees of the individual.

(6) FIG. 6. Orientation of the MRI sections for foot studies. The coronal section (A) is taken parallel to the plane determined by the external markers on the surface where the foot sole is placed. The sagittal (B) and the axial (C) sections are orthogonal to the coronal section.

(7) FIG. 7. Sagittal MRI section taken at two different times (A and B), to the same healthy volunteer.

(8) FIG. 8. MRI axial section of a DFU patient, taken before and during treatment with epidermal growth factor (EGF). A. Before treatment (week 0); B. at week 9; C. at week 14; and D. at week 28 after the beginning of the treatment.

(9) FIG. 9. Variations of the area (A) and volume (B) of the DFU of a patient at weeks 0, 9, 14 and 28 of the treatment with EGF. The area and volume were measured starting from MRI.

(10) FIG. 10. Three-dimensional reconstruction of the edema volume, at three different times, starting from MRI of a DFU patient treated with EGF. The darkest area is the edema. A. Before treatment, week 0; B. at week 6; and C. at week 10 of the treatment. The thick black and white arrow indicates the DFU. The white arrow indicates the area affected by the edema.

(11) FIG. 11. Variation of the edema volume in a DFU patient. A. Before treatment; B. at week 6; and C. at week 10 of the treatment with EGF.

(12) FIG. 12. Apparent Diffusion Coefficient (ADC) measured starting from the MRI in the area of the DFU of the affected foot, compared to the equivalent area in the healthy foot and the free water ADC as a control. For the foot affected with DFU, in the figure is represented the ADC measured during the treatment with EGF.

(13) FIG. 13. MRI of the foot of a DFU patient (axial section), obtained with the system and method of the invention, during the EGF treatment. A. Before treatment; B. at week 6 of treatment; and C. at week 7 of treatment. The arrow in A and B indicates the lesion, and in C shows a hyperintense area, related to the appearance of new epithelial tissue as a consequence of treatment.

(14) FIG. 14. Temporal evolution of the calcaneus infection in a patient, studied through MRI obtained with the system and method of the invention. A. week zero; B. week 6; and C. week 8 of the study. The arrow indicates the site of infection.

EXAMPLES

(15) The following examples are shown for illustrative purposes, and should not be considered as limiting the invention.

Example 1

Positioning of the Individual

(16) The first step to ensure reproducibility of quantitative measurements for the scan of MRI was to correctly position both feet and legs of the individual in the device shown in FIG. 1, coupled to the RF coil of the MRI equipment. The individual lays face up (supine) in the equipment bed with his legs towards the entrance of the magnetic system, as illustrated in FIG. 5.

(17) The feet and the lower parts of the legs were placed and fixed, to obtain simultaneously MRI (e.g., coronal and axial sections) and Magnetic Resonance Spectra (MRS) of both feet, without changing the position. This allowed us to compare, on an equal condition, both limbs along the studies, and so that a lower member serves as reference to the other one.

(18) Each foot carefully rested on the support surfaces 1 and heels were leaned on arches 3. At unison, the lower parts of the legs were supported on supports 2, which were conveniently fitted with pins 8, according to the dimensions of the feet. The positions of the support surfaces 1 and the heel arches 3 on the scale attached to the device (denoted by 5) were recorded.

(19) People examined bent the legs slightly, as shown in FIG. 5, to feel comfortable. Below the knee backs was placed a cushion, so they could rest their legs on it. Then the means for securing the feet and lower parts of the legs were adjusted (indicated as 6) to prevent that involuntary movement of the examined person change the position of the feet or lower parts of the legs.

Example 2

Checking and/or Correction of the Position of the Feet

(20) Once positioned the feet of the individual, he was placed at the isocenter of the magnet system, and proceeded to record the planning MRI in three sections: coronal, sagittal and axial. The MRI showed the external markers 7. The correct position of the feet was checked, so that the MRI of soles appeared fully supported on the support surfaces 1, determined by the pairs of external markers 7 for each foot. In case the positioning was not correct, it was corrected as in Example 1. If the positioning was correct, the final planning of study sections proceeded.

Example 3

Planning and Orientation of the Sections

(21) The first section to be recorded was oriented parallel to the plane determined by the external markers, although it could be any plane, according to a preset angle in reference to the one determined by such markers. Other necessary sections were determined in connection with this first one, according to the study to be performed.

(22) In FIG. 6 is shown the orientation of the sections planned and applied in Examples 4 to 10. The coronal section (FIG. 6A) is taken parallel to the plane determined by the external markers, and the other two sections (sagittal, FIG. 6B and axial, FIG. 6C) are orthogonal to the initial coronal section.

Example 4

Determination of Internal Markers: Position of Anatomical Structures

(23) In addition to external markers (denoted as 7), there were established internal controls that allowed determining the position, its reproducibility and evaluation of error in the serial MRI studies. This was essential, especially for those patients with inflammatory processes, since in these cases the determination of the sizes and relative positions of the anatomical parts and their evolution, either naturally or due to treatment regimens, is difficult.

(24) As an internal marker it was defined an internal anatomical structure of the foot, which was chosen in the way that it was not affected or it was far from the pathological processes affecting the foot, in particular the inflammatory ones. In this case it was taken as an internal marker the perpendicular distance L.sub.o from the center of the tolocalcaneum interosseum ligament to the segment joining the two external markers (see FIG. 7). The L.sub.0 distance and this perpendicular segment connecting the two external markers determine exactly one plane. Both distances were measured from sagittal sections of MRI (FIG. 7). In this figure, as an example, two sagittal planes are shown taken to the same volunteer, in two separate studies, at different time moments are shown. It measures distances taken on the image between the two external markers are indicated. In this example, L.sub.0=13.2 cm in both FIGS. 7A and 7B). The L.sub.1 segment is also shown, which is perpendicular to the line L.sub.0, and runs from the intersection point of L.sub.0 with the line that connects the external markers to the furthest external marker. Furthermore, L.sub.2 is the distance in the image from the intersection of L.sub.0 to the line that connects the external markers to the posterior external marker position, as shown in FIGS. 7A and 7B. The two distances L.sub.1>L.sub.2, were selected of different sizes, to provide two different sensitivities facing a possible relative error. A change of orientation of the foot position will imply a change of distances L.sub.1 and L.sub.2. Moreover, if the deviations of L.sub.1 and L.sub.2 are small and they are known then changes above these values are attributable only to morphological variations of the foot.

(25) In Table 1 the values of L.sub.1 and L.sub.2 measured on images from 10 healthy volunteers are shown, recorded at two different times, in which the feet were always placed in identical positions. Surprisingly, as shown in Table 1, the mean changes L.sub.1 and L.sub.2 (variation between two successive positions in two different studies), are less than 1.0 mm (The maximum variation was 6.7%), which evidences how robust the device and the procedure are.

(26) TABLE-US-00001 TABLE 1 Criteria of the feet correct positioning. Measurements L.sub.1 and L.sub.2 in the sagittal MRI sections of 10 healthy volunteers studied in two separate occasions. Volunteer No 1 2 3 4 5 6 7 8 9 10 Length (mm) Study 1 (S.sub.1) L.sub.1 71 54 58 64 65 69 60 44 68 55 L.sub.2 13 5 7 7 8 20 16 31 13.5 16 Study 2 (S.sub.2) L.sub.1 70 54 57 62 65 69 58 42 66 54 L.sub.2 13 5 7 7 8 19 15 31 14 17 between L.sub.1 1 0 1 2 0 0 2 3 2 1 studies L.sub.2 0 0 0 0 0 1 1 0 1 1 (L.sub.x = L.sub.xS1 L.sub.xS2) x = 1 2 % Variation L.sub.1 1.4 0 1.8 3.2 0 0 3.4 4.5 3.0 1.9 (L.sub.x/L.sub.xS2*100) L.sub.2 0 0 0 0 0 5.3 6.7 0 3.6 5.9 L1 and L2 are variations of L.sub.1 and L.sub.2 from a single healthy volunteer from one study to another, at different times.

Example 5

Determining Internal Markers: Anatomical Structures Area

(27) Besides the external markers (indicated as 7), and the first internal marker described in Example 4, a second internal marker was defined as the area of a predetermined anatomical structure, according to MRI assessments that were required to perform.

(28) In this example, to illustrate, this second internal marker was defined as the areas of multiple calcaneus coronal sections. Five different coronal sections were chosen. The record of multiple coronal sections ensures several evaluations from different areas, located at dissimilar distances of possible inflammatory processes or changes in other regions of the foot and/or lower parts of the leg.

(29) The ratio of the measured areas in different studies, on images of different structures, was an undeniable internal control of foot positioning and orientation of the sections. This internal marker is totally conclusive, complements and is consistent with the results presented and related to the first internal marker (Example 4).

(30) In serial studies performed under the conditions described, variations in the size of different parts of the foot were below 4.5%. Any variation greater than this value is attributable solely to the evolution of pathophysiological processes of the feet. In Table 2, the coefficient of variation of the calcaneus area is shown, measured in five coronal sections, at two different times, in 10 volunteers.

(31) TABLE-US-00002 TABLE 2 Demonstration of the reproducibility of the feet position calculated from the calcaneus area as a second internal marker. Different sections of the calcaneus I II III IV V Coefficient of 1 0.86 1.48 0.54 1.21 1.32 variation % 2 0.15 0.08 0.48 0.57 1.03 (10 volunteers) 3 1.81 0.10 0.10 0.36 0.03 4 1.56 4.35 2.67 0.52 2.11 5 2.65 0.27 0.11 0.78 1.65 6 0.66 0.56 0.16 1.06 0.08 7 2.78 0.23 0.45 0.59 0.62 8 0.72 2.08 0.90 2.90 4.40 9 1.45 1.61 0.43 1.68 0.95 10 2.67 2.40 0.16 1.03 0.93

Example 6

Determination of Evolution of the Dimensions of Diabetic Foot Ulcers (DFU) Under Treatment

(32) The guarantee of proper positioning and reproducibility allowed the quantitative evaluation of the DFU cicatrization kinetics by measuring the DFU area and volume changes during the treatment with EGF. The MRI of 25 DFU patients, taken in identical positions by the system and method of the invention, allowed the measurement of the lesion sizes, with amazing accuracy.

(33) In FIG. 8 appear the axial MRI sections of one of the studied patients. The first MRI was taken before treatment with EGF, the second one was taken at week 9, the third one was taken at week 14 and the fourth one was taken in the 28th week of treatment application. Moreover, in FIG. 9 are the quantitative variations of the areas (FIG. 9A) and volumes (FIG. 9B) of the lesions during the treatment, which demonstrates the response to it. The decrease in the size of the lesion area was 6.5 times, and in the volume was 11.2 times for the referred patient.

Example 7

Determination of Evolution of the Edema Volume in the Feet of Patients with Inflammatory Processes

(34) The guarantee of the feet correct positioning, and its reproducibility with the system and method of the invention, allowed the quantitative evaluation of the kinetics of edema volume changes (swelling) due to the DFU; which is applicable to any other pathology associated with edema. For the 25 patients evaluated in Example 6, the values of the edema volumes were determined, throughout the treatment period. An example of the behavior of edema in DFU patients, treated with EGF, is shown in FIG. 10. As it can be seen, there is a noticeable decrease in the volume of edema as a result of treatment.

(35) The rate of change of edema with respect to treatment time can be calculated from the values shown in FIG. 11. At the same is seen that the volume of edema in the patient is 137 cm.sup.3 before treatment, while said volume is 54 cm.sup.3 at week 10 of treatment.

Example 8

Quantitative Evaluation by MRI of the Texture Evolution of Foot Lesions

(36) A reproducible position of the feet, as a result of the system and method of the invention, allowed recording the Diffusion MRI of patients with DFU, at different times after the beginning of treatment with EGF, and from them the Apparent Diffusion Coefficients (ADC) were calculated in the 25 patients of Example 6. ADC is a complex function of several properties, including the texture of the tissue where the measurement takes place. Only the guarantee of the position accuracy enabled to establish that the relationship of the ADC were a function depending solely on texture changes.

(37) In FIG. 12 is shown the ADC measured for both feet of a patient with DFU, and the ADC measured for the healthy and the affected foot is compared with the ADC of free water. It is observed that the ADC curve of the foot affected with DFU approaches the values of the healthy foot as the treatment take place.

(38) Quantification of changes in the molecular mobility in the lesions and their edges, through MRI, gives unexpectedly valuable information to assess the response to treatment and the onset of the granulation and epithelization processes in the DFU. In FIG. 13 are plotted three MRI (axial sections), wherein the process of wound cicatrization and the emergence of new epithelial tissue are observed. This new tissue is visualized as a hyperintense area marked with an arrow in FIG. 13C. This procedure also allows similar quantitative evaluations of other lesions, such as burns.

Example 9

Quantitative MRI Evaluation of the Evolution of In Vivo Metabolic Activity in Diabetic Foot Ulcers (DFU)

(39) The guarantee of reproducibility of the position of the feet is an essential condition to perform quantitative follow-up studies, of the metabolic activity of foot diseases, from in vivo MRS studies whether mono voxel or multi-voxel. The guarantee of the exact location of the voxel is a necessary condition to compare the spectra over serial studies, and assess the response to therapy. Once both feet and lower parts of the legs are placed, it is possible to ensure that the voxels in size, position and orientation are the same through the longitudinal studies. Two lines are highlighted in the spectra, corresponding to the Lipids (Lip) and Creatine (Cr). The MRS amplitudes of healthy foot are at least twofold the ones of the foot affected by DFU. Also, the ratio of amplitudes Lip/Cr changes from the spectrum of the healthy foot to the foot affected by DFU, which is one of the biomarkers of the status of DFU.

Example 10

Evaluation of the Evolution of an Osteomyelitis Patient

(40) In FIG. 14, the MRI of the calcaneus of a single patient are reflected, taken at three different time points, in the same positioning conditions. The volume of the bone edema was measured from the coronal MRI sections represented in said Figure. The volume of the bone infection, for the referred patient, increased from 8625 mm.sup.3 to 27049 mm.sup.3.