Spatially resolved kinetics of skeletal muscle exercise response and recovery with multiple echo diffusion tensor imaging (MEDITI): a feasibility study

Throughout the body, muscle structure and function can be interrogated using a variety of noninvasive magnetic resonance imaging (MRI) methods. Recently, intravoxel incoherent motion (IVIM) MRI has gained momentum as a method to evaluate components of blood flow and tissue diffusion simultaneously. Much of the prior research has focused on highly vascularized organs, including the brain, kidney, and liver. Unique aspects of skeletal muscle, including the relatively low perfusion at rest and large dynamic range of perfusion between resting and maximal hyperemic states, may influence the acquisition, postprocessing, and interpretation of IVIM data. Here, we introduce several of those unique features of skeletal muscle; review existing studies of IVIM in skeletal muscle at rest, in response to exercise, and in disease states; and consider possible confounds that should be addressed for musclespecific evaluations. Most studies used segmented nonlinear least squares fitting with a b-value threshold of 200 sec/mm 2 to obtain IVIM parameters of perfusion fraction (f), pseudo-diffusion coefficient (D*), and diffusion coefficient (D). In healthy individuals, across all muscles, the average AE standard deviation of D was 1.46 AE 0.30 Â 10 À3 mm 2 /sec, D* was 29.7 AE 38.1 Â 10 À3 mm 2 /sec, and f was 11.1 AE 6.7%. Comparisons of reported IVIM parameters in muscles of the back, thigh, and leg of healthy individuals showed no significant difference between anatomic locations. Throughout the body, exercise elicited a positive change of all IVIM parameters. Future directions including advanced postprocessing models and potential sequence modifications are discussed. Level of Evidence: 2 Technical Efficacy: Stage 2

Section: Future Applicationsmentioning

confidence: 99%

Intravoxel Incoherent Motion Magnetic Resonance Imaging in Skeletal Muscle: Review and Future Directions

Englund

Reiter

Shahidi

et al. 2021

“…Mechanical loading was achieved using an MR‐compatible ergometer (Orthospect, Ergospect, Innsbruck, Austria) capable of providing static mechanical loads during the imaging session. The ergometer used pneumatic resistance provided by an external air compressor system . Control of the pneumatic force was manually set by an external controller to deliver the desired amount of load to the knee.…”

Section: Methodsmentioning

confidence: 99%

“…The ergometer used pneumatic resistance provided by an external air compressor system. 16 Control of the pneumatic force was manually set by an external controller to deliver the desired amount of load to the knee. To ensure the ergometer setup did not move during the loading condition, a vendor-provided vacuum platform was used with an external vacuum system situated outside the MR suite.…”

Section: Design Of Experimentsmentioning

confidence: 99%

In vivo tibiofemoral cartilage strain mapping under static mechanical loading using continuous GRASP‐MRI

Menon

Zibetti

Regatte

2019

Background Quantification of dynamic biomechanical strain in articular cartilage in vivo; in situ using noninvasive MRI techniques is desirable and may potentially be used to assess joint pathology. Purpose To demonstrate the use of static mechanical loading and continuous 3D‐MRI acquisition of the human knee joint in vivo to measure the strain in the tibiofemoral articular cartilage. Study Type Prospective. Subjects Five healthy human volunteers (four women, one man; age 25.6 ± 1.7) underwent MRI at rest, under static mechanical loading condition, and during recovery. Field Strength/Sequence A field strength of 3T was used. The sequence used was 3D‐continuous golden angle radial sparse parallel (GRASP) MRI and compressed sensing (CS) reconstruction. Assessment Tibiofemoral cartilage deformation maps under loading and during recovery were calculated using an optical flow algorithm. The corresponding Lagrangian strain was calculated in the articular cartilage. Statistical Tests Range of displacement and strain in each subject, and the resulting mean and standard deviation, were calculated. Results During the loading condition, the cartilage displacement in the direction of loading ranged from a minimum of –673.6 ± 121.9 μm to a maximum of 726.5 ± 169.5 μm. Corresponding strain ranged from a minimum of –7.0 ± 4.2% to a maximum of 5.4 ± 1.6%. During the recovery condition, the cartilage displacement in the same direction reduced to a minimum of –613.0 ± 129.5 μm and a maximum of 555.7 ± 311.4 μm. The corresponding strain range reduced to a minimum of –1.6 ± 7.5% to a maximum of 4.2 ± 2.6%. Data Conclusion This study shows the feasibility of using static mechanical loading with continuous GRASP‐MRI acquisition to measure the strain in the articular cartilage. By measuring strain during the loading and recovery phases, dynamic strain information in the articular cartilage might be able to be investigated. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:426–434.

“…The ergometer used pneumatic air resistance to deliver the load with air pressure hoses connecting from the ergometer to the controller and an air compressor located outside the MR scanner room. 29 To prevent movement during the loading, the ergometer was placed on a vendor-provided vacuum platform with separate hoses to an external vacuum system outside the MR suite. The schematic in Fig.…”

Section: Design Of Experimentsmentioning

confidence: 99%

Measurement of Three‐Dimensional Internal Dynamic Strains in the Intervertebral Disc of the Lumbar Spine With Mechanical Loading and Golden‐Angle Radial Sparse Parallel‐Magnetic Resonance Imaging

Menon

Zibetti

Pendola

et al. 2021

Background: Noninvasive measurement of internal dynamic strain can be potentially useful to characterize spine intervertebral disc (IVD) in the setting of injury or degenerative disease. Purpose: To develop and demonstrate a noninvasive technique to quantify three-dimensional (3D) internal dynamic strains in the IVD using a combination of static mechanical loading of the IVD using a magnetic resonance imaging (MRI)compatible ergometer. Study Type: Prospective. Subjects: Silicone gel phantom studies were conducted to assess strain variation with load and repeatability. Mechanical testing was done on the phantoms to confirm MR results. Eight healthy human volunteers (four men and four woman, age = 29 AE 5 years) underwent MRI using a rest, static loading, and recovery paradigm. Repeatability tests were conducted in three subjects. Field Strength/Sequence: MRI (3 T) with 3D continuous golden-angle radial sparse parallel (GRASP) and compressed sensing (CS) reconstruction. Assessment: CS reconstruction of the images, motion deformation, and Lagrangian strain maps were calculated for five IVD segments from L1/L2 to L5/S1. Statistical Tests: Ranges of displacement and strain in each subject and the resulting mean and standard deviation were calculated. Student t-tests were used to calculate changes in strain from loading to recovery. The correlation coefficient (CC) in the repeatability study was calculated. Results: The most compressive strain experienced by the IVD segments under loaded conditions was in the L4/L5 segment (−7.5 AE 2.9%). The change in minimum strain from load to recovery was the most for the L4/L5 segment (−7.5% to −5.0%, P = 0.026) and the least for the L1/L2 segment (−4.4% to −3.9%, P = 0.51). In vivo repeatability in three subjects shows strong correlation between scans in subjects done 6 months apart, with CCs equal to 0.86, 0.94, and 0.94 along principal directions. Data Conclusion:This study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition with CS reconstruction to measure 3D internal dynamic strains in the spine IVD. Level of Evidence: 2 Technical Efficacy Stage: 1