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While evaluation of blood perfusion in lumbar paraspinal muscles is of interest in low back pain, it has not been performed using noncontrast magnetic resonance (MR) techniques.To introduce a novel application of a time-resolved, noncontrast MR perfusion technique for paraspinal muscles and demonstrate effect of exercise on perfusion parameters.Longitudinal.Six healthy subjects (27-48 years old, two females) and two subjects with acute low back pain (46 and 65 years old females, one with diabetes/obesity).3-T, MR perfusion sequence.Lumbar spines of healthy subjects were imaged axially at L3 level with a tag-on and tag-off alternating inversion recovery arterial spin labeling technique that suppresses background signal and acquires signal increase ratio (SIR) from the in-flow blood at varying inversion times (TI) from 0.12 seconds to 3.5 seconds. SIR vs. TI data were fit to determine the perfusion metrics of peak height (PH), time to peak (TTP), mean transit time, apparent muscle blood volume (MBV), and apparent muscle blood flow (MBF) in iliocostal, longissimus, and multifidus. Imaging was repeated immediately after healthy subjects performed a 20-minute walk, to determine the effect of exercise.Repeated measures analysis of variance.SIR vs. TI data showed well-defined leading and trailing edges, with sharply increasing SIR to TI of approximately 500 msec subsiding quickly to near zero around TI of 1500 msec. After exercise, the mean SIR at every TI increased markedly, resulting in significantly higher PH, MBV, and MBF (each P 0.001 and F 28.9), and a lower TTP (P 0.05, F = 4.5), regardless of the muscle. MBF increased 2- to 2.5-fold after exercise, similar to the expected increase in cardiac output, given the intensity of the exercise.Feasibility of an MR perfusion technique for muscle perfusion imaging was demonstrated, successfully detecting significantly increased perfusion after exercise.1 TECHNICAL EFFICACY STAGE: 1.

Author(s): Chang, Eric Y; Du, Jiang; Biswas, Reni; Statum, Sheronda; Pauli, Chantal; Bae, Won C; Chung, Christine B | Abstract: BackgroundTo determine if off-saturation ratio (OSR) measured with the ultrashort echo time magnetization transfer (UTE-MT) sequence could differentiate between tendons under different states of tensile load and to compare these changes between normal versus degenerated tendons.MethodsFourteen tendons were imaged at 3 Tesla before and during the application of 0.5-1 kg tension. A two-dimensional (2D) -UTE-MT sequence with 1.5, 3, and 5 kHz frequency offsets was used on nine tendons and a 3D-UTE-MT sequence with 1.5 kHz frequency offset was used on five tendons. OSR was calculated and compared for each condition. Histologic correlation was performed using light microscopy.ResultsIn general, OSR increased after the application of tension. Mean increase of 2D OSR was 0.035 (95% confidence interval [CI], 0.013-0.056) at 1.5 kHz offset (P l 0.01), 0.031 (95% CI, 0.023-0.040) at 3 kHz offset (P l 0.01), and 0.013 (95% CI, -0.013-0.027) at 5 kHz offset (P = 0.07) from pre- to posttension states. Mean increase of 3D OSR was 0.026 (95% CI, 0.008-0.044) at a 1.5 kHz offset (P = 0.02) from pre- to posttension states. Mean decrease of 2D OSR at 1.5 kHz offset was 0.074-0.087 when comparing normal versus degenerated tendons (P l 0.01).ConclusionOSR as measured with 2D or 3D UTE-MT sequences can detect the changes in hydration seen when tendons are placed under two different states of tensile load, but these changes are smaller than those encountered when comparing between normal versus pathologic tendons. Lower off-resonance saturation frequencies (3 kHz or less) are more sensitive to these changes than higher off-resonance saturation frequencies.

Author(s): Chang, Eric Y; Du, Jiang; Iwasaki, Kenyu; Biswas, Reni; Statum, Sheronda; He, Qun; Bae, Won C; Chung, Christine B | Abstract: BackgroundTo determine if the application of tensile force alters the single- or bi-component T2* values of human tendons as measured on a clinical MRI scanner with ultrashort echo time (UTE sequences and if single- or bi-component T2* values differ when measured with 2D-UTE, 3D-UTE, or 3D-UTE-Cones sequences.MethodsTen tendons were imaged before and during the application of tension using various UTE sequences at 3 Tesla. Single and bi-component T2* analysis was performed pre- and posttension and compared with Bonferroni-corrected paired Wilcoxon tests.ResultsRange of mean pre- and posttension T2* analysis values were: short T2* fraction (78.6-79.7% and 77.3-79.7%, respectively; P = 1.0 for all sequences), long T2* fraction (20.3-21.4% and 20.3-22.7%, respectively; P = 1.0 for all sequences), short T2* (0.9-1.0 ms and 0.9 ms, respectively; P = 1.0 for all sequences), long T2* (19.9-20.4 ms and 21.9-24.0 ms, respectively; P = 0.9 for 2D-UTE and P = 1.0 for 3D-UTE and 3D-UTE-Cones), and single-component T2* (2.3-2.5 ms and 2.5-3.2 ms, respectively; P = 1.0 for all sequences).ConclusionNo significant difference in single- or bi-component results was found after the application of tension to tendons. Results are similar regardless of UTE sequence used for acquisition.

Purpose To determine if immersion of Achilles tendon segments into various solutions improved qualitative delineation of tendon and affected quantitative MR values of T2 and T2*. Materials and Methods Six Achilles tendons were dissected, sectioned (proximal, midportion, and distal tensile pieces) and imaged at 3T both at baseline in air and after immersion into saline, Fomblin, and perfluorooctyl bromide (PFOB), respectively, for 24 h. Blinded readers qualitatively assessed the delineation of tendon boundaries and quantitatively Carr-Purcell-Meiboom-Gill (CPMG) T2 and ultrashort echo time (UTE) T2* was calculated. Comparison between images obtained in air and in solution was made. Results On qualitative evaluation, all images obtained in air had larger air-tissue susceptibility effects. Mean T2 values of saline, Fomblin, and PFOB groups were 16.1 ± 3.7, 16.6 ± 2.9, and 18.8 ± 2.6 ms at baseline in air, and 14.8 ± 4.6, 15.9 ± 3.0, and 17.7 ± 3.0 ms after immersion in the fluid, respectively. Mean T2* values of saline, Fomblin, and PFOB groups were 2.0 ± 0.8, 1.6 ± 0.5, and 1.5 ± 0.5 ms at baseline in air, and 2.1 ± 0.5, 1.6 ± 0.5, and 1.4 ± 0.5 ms after immersion in the fluid, respectively. There was no significant effect of immersion or fluid type on measured T2 or T2* (P > 0.1). Conclusion These results validate the continued use of these solutions to prevent tendon specimen dehydration and to minimize susceptibility effects. J. Magn. Reson. Imaging 2014;40:496–500. © 2013 Wiley Periodicals, Inc.