Compressed sensing acceleration of biexponential 3D‐T 1ρ relaxation mapping of knee cartilage

Sharafi

et al. 2019

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Background Measuring T1ρ in the knee menisci can potentially be used as noninvasive biomarkers in detecting early‐stage osteoarthritis (OA). Purpose To demonstrate the feasibility of biexponential T1ρ relaxation mapping of human knee menisci. Study Type Prospective. Population Eight healthy volunteers with no known inflammation, trauma, or pain in the knee and three symptomatic subjects with early knee OA. Field Strength/Sequence Customized Turbo‐FLASH sequence to acquire 3D‐T1ρ‐weighted images on a 3 T MRI scanner. Assessment T1ρ relaxation values were assessed in 11 meniscal regions of interest (ROIs) using monoexponential and biexponential models. Statistical Tests Nonparametric rank‐sum tests, Kruskal–Wallis test, and coefficient of variation. Results The mean monoexponential T1ρ relaxation in the lateral menisci were 28.05 ± 4.2 msec and 37.06 ± 10.64 msec for healthy subjects and early knee OA patients, respectively, while the short and long components were 8.07 ± 0.5 msec and 72.35 ± 3.2 msec for healthy subjects and 2.63 ± 2.99 msec and 55.27 ± 24.76 msec for early knee OA patients, respectively. The mean monoexponential T1ρ relaxation in the medial menisci were 34.30 ± 3.8 msec and 37.26 ± 11.38 msec for healthy and OA patients, respectively, while the short and long components were 7.76 ± 0.7 msec and 72.19 ± 4.2 msec for healthy subjects and 3.06 ± 3.24 msec and 55.27 ± 24.59 msec for OA patients, respectively. Statistically significant (P ≤ 0.05) differences were observed in the monoexponential relaxation between some of the ROIs. The T1ρ,short was significantly lower (P = 0.02) in the patients than controls. The rmsCV% ranges were 1.51–16.6%, 3.59–14.3%, and 4.91–15.6% for T1ρ‐mono, T1ρ‐short, and T1ρ‐long, respectively. Data Conclusion Our results showed that in all ROIs, T1ρ relaxation times of outer zones (red zones) were less than inner zones (white zones). Monoexponential T1ρ was increased in medial, lateral, and body menisci of early OA while the biexponential numbers were decreased in early OA patients. Level of Evidence: 2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2019;50:824–835.

Section: Discussionmentioning

confidence: 99%

Biexponential T_1ρ relaxation mapping of human knee menisci

Sharafi

et al. 2019

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“…In the final biexponential fitting map, the pixels that did not satisfy the following conditions were excluded from the map:

((), f_{s} > α_{s}) & ((), f_{l} > α_{l}) & ((), F_{ratio} > α_{F})

where α s and α l are the minimum short and long fractions as was set to 10% and α F = 4.32 are the threshold based on the P = 0.1 F‐distribution table for p 1 = 2 and p 2 = 4 degree of freedom in the mono‐ and biexponential models, respectively. The F ratio is calculated as:

F_{ratio} = \frac{\frac{{italicSSE}_{m} - {italicSSE}_{b}}{p_{2} - p_{1}}}{\frac{{SSE}_{b}}{L - p_{2}}}

where SSE m and SSE b are the sum of square error for the mono‐ and biexponential models, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The F ratio is calculated as:

F_{ratio} = \frac{\frac{{italicSSE}_{m} - {italicSSE}_{b}}{p_{2} - p_{1}}}{\frac{{SSE}_{b}}{L - p_{2}}}

where SSE m and SSE b are the sum of square error for the mono‐ and biexponential models, respectively. L is the number of T sl timepoints acquired for fitting …”

Section: Methodsmentioning

confidence: 99%

3D‐T_1ρ prepared zero echo time‐based PETRA sequence for in vivo biexponential relaxation mapping of semisolid short‐T₂ tissues at 3 T

Sharafi

et al. 2019

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Background: In addition to the articular cartilage, osteoarthritis (OA) affects several other tissues such as tendons, ligaments, and subchondral bone. T1ρ relaxation study of these short T2 tissues may provide a more comprehensive evaluation of OA. Purpose: To develop a 3D spin-lattice relaxation in the rotating frame (T1ρ) prepared zero echo time (ZTE)-based pointwise encoding time reduction with radial acquisition (3D-T1ρ-PETRA) sequence for relaxation mapping of semisolid short-T2 tissues on a clinical 3 T scanner. Study Type: Prospective. Population: Phantom, two bovine whole knee joint and Achilles tendon specimens, 10 healthy volunteers with no known inflammation, trauma or pain in the knee or ankle. Field Strength/Sequence: A customized PETRA sequence to acquire fat-suppressed 3D T1ρ-weighted images tissues with semisolid short T2/T2* relaxation times in the knee and ankle joints at 3 T. Assessment: Mono- and biexponential T1ρ relaxation components were assessed in the patellar tendon (PT), anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and Achilles tendon (AT). Statistical Tests: Kruskal–Wallis with post-hoc Dunn’s test for multiple pairwise comparisons. Results: Phantom and ex vivo studies showed the feasibility of T1ρ relaxation mapping using the proposed 3D-T1ρ-PETRA sequence. The in vivo study demonstrated an averaged mono-T1ρ relaxation of (median [IQR]) 15.9 [14.5] msec, 23.6 [9.4] msec, 17.4 [7.4] msec, and 5.8 [10.2] msec in the PT, ACL, PCL, and AT, respectively. The bicomponent analysis showed the short and long components (with their relative fractions) of 0.65 [1.0] msec (46.9 [15.3]%) and 37.3 [18.4] msec (53.1 [15.3]%) for PT, 1.7 [2.1] msec (42.5 [12.5]%) and 43.7 [17.8] msec (57.5 [12.5]%) for ACL, and 1.2 [1.9] msec (42.6 [14.0]%) and 27.7 [14.7] msec (57.3 [14.0]%) for PCL and 0.4 [0.02] msec (58.8 [13.3]%/) and 31.3 [10.8] msec (41.2 [13.3]%) for AT. Statistically significant (P≤ 0.05) differences were observed in the mono- and biexponential relaxation between several regions. Data Conclusion: The 3D-T1ρ-PETRA sequence allows volumetric, isotropic (0.78 × 0.78 × 0.78 mm), biexponential T1ρ assessment with corresponding fractions of the tissues with semisolid short T2/T2*.

“…Different exponential decaying time constants are observed in biological systems due to the presence of protons in different molecules. The biexponential model is usually the next step after monoexponential decaying . Nevertheless, three components had already been reported in the literature .…”

Section: Review Of Cs Mri For Compositional Mappingmentioning

confidence: 99%

“…It has been used for T 1ρ mapping and for T 1 and T 2 mapping with monoexponential models. The conjugate gradient Steihaug's trust‐region algorithm is used for monoexponential and for biexponential T 1ρ mapping. The variable projection algorithm for NLS is utilized for monoexponential T 1 and T 2 problems.…”

Section: Review Of Cs Mri For Compositional Mappingmentioning

confidence: 99%

Rapid compositional mapping of knee cartilage with compressed sensing MRI

Zibetti

et al. 2018

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More than one decade after the introduction of compressed sensing (CS) in MRI, researchers are still working on ways to translate it into different research and clinical applications. The greatest advantage of CS in MRI is the reduced amount of k-space data needed to reconstruct images, which can be exploited to reduce scan time or to improve spatial resolution and volumetric coverage. Efficient data acquisition using CS is extremely important for compositional mapping of the musculoskeletal system in general and knee cartilage mapping techniques in particular. High-resolution quantitative information about tissue biochemical composition could be obtained in just a few minutes using CS MRI. However, in order to make this goal a reality, some issues still need to be addressed. In this paper, we review the current state of the art of CS methods for rapid compositional mapping of knee cartilage. Specifically, data acquisition strategies, image reconstruction algorithms, and data fitting models are discussed. Different CS studies for T2 and T1ρ mapping of knee cartilage are reviewed, with illustrative results. Future directions, opportunities, and challenges of rapid compositional mapping techniques are also discussed.