Ability of magnetic resonance elastography to assess taut bands

Abstract

Background: Myofascial taut bands are central to diagnosis of myofascial pain. Despite their importance, we still lack either a laboratory test or imaging technique capable of objectively confirming either their nature or location. This study explores the ability of magnetic resonance elastography to localize and investigate the mechanical properties of myofascial taut bands on the basis of their effects on shear wave propagation.

Methods: This study was conducted in three phases. The first involved the imaging of taut bands in gel phantoms, the second a finite element modeling of the phantom experiment, and the third a preliminary evaluation involving eight human subjects-four of whom had, and four of whom did not have myofascial pain. Experiments were performed with a 1.5 T magnetic resonance imaging scanner. Shear wave propagation was imaged and shear stiffness was reconstructed using matched filtering stiffness inversion algorithms.

Findings: The gel phantom imaging and finite element calculation experiments supported our hypothesis that taut bands can be imaged based on its outstanding shear stiffness. The preliminary human study showed a statistically significant 50-100% (P=0.01) increase of shear stiffness in the taut band regions of the involved subjects relative to that of the controls or in nearby uninvolved muscle.

Interpretation: This study suggests that magnetic resonance elastography may have a potential for objectively characterizing myofascial taut bands that have been up to now detectable only by the clinician's fingers.

Figures

Figure 1

(a) MRE phase image of the bovine gel phantom with taut band, showing chevron-shaped wave fronts. (b) The reconstructed stiffness image of the taut band mimicking gel phantom, showing the central band region with outstanding stiffness, 48.6±10.8KPa, versus the two lateral regions, 13.5±2.0KPa and 13.4±2.1 KPa, respectively.

Figure 1

(a) MRE phase image of the bovine gel phantom with taut band, showing chevron-shaped wave fronts. (b) The reconstructed stiffness image of the taut band mimicking gel phantom, showing the central band region with outstanding stiffness, 48.6±10.8KPa, versus the two lateral regions, 13.5±2.0KPa and 13.4±2.1 KPa, respectively.

Figure 2

(a) Finite element simulation of the wave fronts in bovine gel phantom with taut band. Chevron-shaped wave propagation was observed. (b) The reconstructed stiffness image of the taut band embedded finite element model, showing the central band region with outstanding stiffness, 36.3.6±3.7KPa, versus the two lateral regions, 13.1±4.8KPa and 13.1±5.9 KPa, respectively.

Figure 2

(a) Finite element simulation of the wave fronts in bovine gel phantom with taut band. Chevron-shaped wave propagation was observed. (b) The reconstructed stiffness image of the taut band embedded finite element model, showing the central band region with outstanding stiffness, 36.3.6±3.7KPa, versus the two lateral regions, 13.1±4.8KPa and 13.1±5.9 KPa, respectively.

Figure 3

(a) Typical MRE phase image of upper trapezius of a patient with myofascial pain superimposed to the MR image of the same subject, showing chevron-shaped wave fronts under the band-like vibration.

1. Spine of Scapula

2. MRE phase image with chevron-shaped wave fronts observed in the region of taut band palpated by the physician.

3. Myofascial taut band identified by the palpation examination.

4. Cervical Spine

(b) Typical MRE phase image of upper trapezius of a healthy human subject superimposed to the MR image of the same subject, showing planar wave propagation under the band-like vibration.

1. Spine of Scapula

2. MRE phase image with planar wave fronts observed in the upper trapezius.

3. Cervical Spine

Figure 3

(a) Typical MRE phase image of upper trapezius of a patient with myofascial pain superimposed to the MR image of the same subject, showing chevron-shaped wave fronts under the band-like vibration.

1. Spine of Scapula

2. MRE phase image with chevron-shaped wave fronts observed in the region of taut band palpated by the physician.

3. Myofascial taut band identified by the palpation examination.

4. Cervical Spine

(b) Typical MRE phase image of upper trapezius of a healthy human subject superimposed to the MR image of the same subject, showing planar wave propagation under the band-like vibration.

1. Spine of Scapula

2. MRE phase image with planar wave fronts observed in the upper trapezius.

3. Cervical Spine

Figure 4

(a) Typical MRE stiffness image of upper trapezius of a patient with myofascial pain superimposed to the MR image of the same subject, showing a significantly stiffer taut band region in the upper trapezius. The dashed line indicates the location of myofascial taut band in that subject marked by palpatory examination.

1. Spine of Scapula

2. Taut Band Region

3. Myofascial taut band identified by the palpation examination.

4. Cervical Spine

(b) Typical MRE stiffness image of upper trapezius of a healthy human subject superimposed to the MR image of the same subject, showing uniformly distributed shear stiffness.

1. Spine of Scapula

2. Upper Trapezius

3. Cervical Spine

Figure 4

(a) Typical MRE stiffness image of upper trapezius of a patient with myofascial pain superimposed to the MR image of the same subject, showing a significantly stiffer taut band region in the upper trapezius. The dashed line indicates the location of myofascial taut band in that subject marked by palpatory examination.

1. Spine of Scapula

2. Taut Band Region

3. Myofascial taut band identified by the palpation examination.

4. Cervical Spine

(b) Typical MRE stiffness image of upper trapezius of a healthy human subject superimposed to the MR image of the same subject, showing uniformly distributed shear stiffness.

1. Spine of Scapula

2. Upper Trapezius

3. Cervical Spine