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

Abstract

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

Virtual Biopsy in Soft Tissue Sarcoma. How Close Are We?

“…An extension of DW-MRI is intravoxel incoherent motion (IVIM) which allows separation of perfusion from the true tissue diffusion. This allows calculation of quantitative parameters that reflect true tissue diffusivity (D), perfusion-related pseudodiffusion (D*) and perfusion fraction (f) which represents the contribution of water in capillaries (81). This could improve the accuracy of a quantitative parameter of diffusion by informing on the contribution of the microvascular circulation.…”

An Update in Imaging Evaluation of Histopathological Grade of Soft Tissue Sarcomas Using Structural and Quantitative Imaging and Radiomics

“…This may be due to the fact that elevated choline levels on MR spectra are not considered as a specific marker of malignancy grade, as elevated choline/Cr levels are occasionally seen in non-malignant lesions with increased proliferative activity. 41 The higher the histopathological grade of STSs, the more pronounced is the tumor cell proliferation, hemorrhage, necrosis, vascular proliferation in the interstitium, and cholinergic metabolism, which can be demonstrated to some extent by quantitative indices of fMRI 24,[31][32][33][34][35][36][37][38][39][40] (Table 3). ADC, D, and MD values can indirectly reflect tumor proliferation by detecting the diffusion movement of water molecules in the body from different angles.…”

“…DWI detects the diffusive motion of water molecules, but the conventional ADC values calculated by the monoexponential model integrates both diffusion and perfusion information; thus its quantitative accuracy is influenced by the microvascular circulation in living tissues, which cannot reflect the diffusion in tissues alone. Based on DWI, IVIM separates the diffusion of water molecules from the perfusion effect of capillaries, and obtains information on both the true diffusion and perfusion of water molecules in the tissue 31 . The IVIM model includes a mono‐exponential model, a double‐order mono‐exponential model (IVIM‐mono), and a double‐order bi‐exponential model (IVIM‐bi) with parameters such as Standard ADC values, Slow ADC (Dslow) values reflecting the real water molecule diffusion, Fast ADC (Dfast) values reflecting the capillary perfusion effect and perfusion fraction ( f ) values 32 .…”

“…The higher the histopathological grade of STSs, the more pronounced is the tumor cell proliferation, hemorrhage, necrosis, vascular proliferation in the interstitium, and cholinergic metabolism, which can be demonstrated to some extent by quantitative indices of fMRI 24,31–40 (Table 3). ADC, D, and MD values can indirectly reflect tumor proliferation by detecting the diffusion movement of water molecules in the body from different angles.…”

“…diffusion and perfusion of water molecules in the tissue 31. The IVIM model includes a mono-exponential model, a double-order mono-exponential model (IVIM-mono), and a double-order bi-exponential model (IVIM-bi) with parameters such as Standard ADC values, Slow ADC (Dslow) values reflecting the real water molecule diffusion, Fast ADC (Dfast)…”