Cross-Sectional Area of the Rotator Cuff Muscles in MRI - Is there Evidence for a Biomechanical Balanced Shoulder?

OBJECTIVE To provide in-vivo evidence for the common biomechanical concept of transverse and craniocaudal force couples in the shoulder that are yielded by both the rotator cuff muscles (RCM) and the deltoid and to quantitatively evaluate and correlate the cross-sectional areas (CSA) of the corresponding RCM as a surrogate marker for muscle strength using MRI. MATERIALS AND METHODS Fifty patients (mean age, 36 years; age range, 18-57 years; 41 male, 9 female) without rotator cuff tears were included in this retrospective study. Data were assessed by two readers. The CSA (mm2) of all rotator cuff muscles was measured on parasagittal T1-weighted FSE sequence at two different positions (at the established "y-position" and at a more medial slice in the presumably maximal CSA for each muscle, i.e., the "set position"). The CSA of the deltoid was measured on axial intermediate-weighted FSE sequences at three positions. CSA measurements were obtained using 1.5 Tesla MR-arthrographic shoulder. Pearson's correlation for the corresponding CSA of the force couple as well as was the intraclass correlation coefficient for the inter- and intra-reader agreement was calculated. RESULTS The mean CSA was 770 mm2 (±167) and 841 mm2 (±191) for the supraspinatus (in the y- and set-positions, respectively) and 984 mm2 (±241) and 1568 mm2 (±338) for the infraspinatus. The mean CSA was 446 mm2 (±129) and 438 mm2 (±128) for the teres minor (in the y- and set-positions, respectively) and 1953 mm2 (±553) and 2343 mm2 (±587) for the subscapularis. The three measurements of the deltoid revealed a CSA of 3063 mm2 (±839) for the upper edge, 3829 mm2 (±836) for the lower edge and 4069 mm2 (±937) for the middle of the glenoid. At the set position Pearson's correlation of the transverse force couple (subscapularis/infraspinatus) showed a moderate positive correlation of r = 0.583 (p<0.0001) and a strong correlation when the CSA of the teres minor was added to the infraspinatus CSA (r = 0.665, p = 0.0008) and a strong positive correlation of the craniocaudal force couple (supraspinatus/deltoid) that ranged from r = 0.565-0.698 (p<0.0001). Inter-reader agreement (ranged from 0.841 to 0.997, p = 0.0007) and intra-reader agreement were excellent (ranged from 0.863 to 0.999, p = 0.0006). CONCLUSION The significant correlation of the CSA of the RCM that form the transverse (subscapularis/infraspinatus-teres minor) and craniocaudal (supraspinatus/deltoid) force couple measured by MR-arthrography supports the biomechanical concept of a dynamically balanced shoulder in patients with an intact rotator cuff

Correction for fast pseudo-diffusive fluid motion contaminations in diffusion tensor imaging

In this prospective study, we quantified the fast pseudo-diffusion contamination by blood perfusion or cerebrospinal fluid (CSF) intravoxel incoherent movements on the measurement of the diffusion tensor metrics in healthy brain tissue. Diffusion-weighted imaging (TR/TE = 4100 ms/90 ms; b-values: 0, 5, 10, 20, 35, 55, 80, 110, 150, 200, 300, 500, 750, 1000, 1300 s/mm2, 20 diffusion-encoding directions) was performed on a cohort of five healthy volunteers at 3 Tesla. The projections of the diffusion tensor along each diffusion-encoding direction were computed using a two b-value approach (2b), by fitting the signal to a monoexponential curve (mono), and by correcting for fast pseudo-diffusion compartments using the biexponential intravoxel incoherent motion model (IVIM) (bi). Fractional Anisotropy (FA) and Mean Diffusivity (MD) of the diffusion tensor were quantified in regions of interest drawn over white matter areas, gray matter areas, and the ventricles. A significant dependence of the MD from the evaluation method was found in all selected regions. A lower MD was computed when accounting for the fast-diffusion compartments. A larger dependence was found in the nucleus caudatus (bi: median 0.86 10-3 mm2/s, Δ2b: -11.2%, Δmono: -14.4%; p = 0.007), in the anterior horn (bi: median 2.04 10-3 mm2/s, Δ2b: -9.4%, Δmono: -11.5%, p = 0.007) and in the posterior horn of the lateral ventricles (bi: median 2.47 10-3 mm2/s, Δ2b: -5.5%, Δmono: -11.7%; p = 0.007). Also for the FA, the signal modeling affected the computation of the anisotropy metrics. The deviation depended on the evaluated region with significant differences mainly in the nucleus caudatus (bi: median 0.15, Δ2b: +39.3%, Δmono: +14.7%; p = 0.022) and putamen (bi: median 0.19, Δ2b: +3.1%, Δmono: +17.3%; p = 0.015). Fast pseudo-diffusive regimes locally affect diffusion tensor imaging (DTI) metrics in the brain. Here, we propose the use of an IVIM-based method for correction of signal contaminations through CSF or perfusion

Quantitative magnetic resonance imaging of meniscal pathology ex vivo

OBJECTIVE To determine the ability of conventional spin echo (SE) T2 and ultrashort echo time (UTE) T2* relaxation times to characterize pathology in cadaveric meniscus samples. MATERIALS AND METHODS From 10 human donors, 54 triangular (radially cut) meniscus samples were harvested. Meniscal pathology was classified as normal (n = 17), intrasubstance degenerated (n = 33), or torn (n = 4) using a modified arthroscopic grading system. Using a 3-T MR system, SE T2 and UTE T2* values of the menisci were determined, followed by histopathology. Effect of meniscal pathology on relaxation times and histology scores were determined, along with correlation between relaxation times and histology scores. RESULTS Mean ± standard deviation UTE T2* values for normal, degenerated, and torn menisci were 3.6 ± 1.3 ms, 7.4 ± 2.5 ms, and 9.8 ± 5.7 ms, respectively, being significantly higher in degenerated (p  0.14). In terms of histology, we found significant group-wise differences (each p < 0.05) in fiber organization and inner-tip surface integrity sub-scores, as well as the total score. Finally, we found a significant weak correlation between UTE T2* and histology total score (p = 0.007, R$_{s}$$^{2}$ = 0.19), unlike the correlation between SE T2 and histology (p = 0.09, R$_{s}$$^{2}$ = 0.05). CONCLUSION UTE T2* values were found to distinguish normal from both degenerated and torn menisci and correlated significantly with histopathology

Added value of combined acromiohumeral distance and critical shoulder angle measurements on conventional radiographs for the prediction of rotator cuff pathology

Purpose: To investigate the role of acromiohumeral distance (AHD) and critical shoulder angle (CSA) measurements from conventional radiographs (CR) in isolation and combined (prognostic index PIAHD-CSA) as predictors of full thickness rotator cuff tendon tears (RCT) and critical fatty degeneration (CFD; i.e. as much fat as muscle). Method: In this retrospective study AHD and CSA were measured in 127 CR. MR arthrograms served as reference standard and were screened for RCT and CFD. Statistical analysis for inter-reader agreement, Spearman's rank correlation, linear stepwise regression and logistic regression for AHD and CSA with ROC analyses including PIAHD-CSA were performed. Results: In 90 subjects (17 females, mean age 36.1 ± 14.1) no RCT were found on MR imaging and served as control group. In 37 patients (13 females, mean age 58.7 ± 13.2) ≥ one RCT was found. Inter-reader agreements rated between к = 0.42-0.82 for categorical and 0.91-0.96 for continuous variables. No significant correlation of AHD and CSA with either age or sex was seen (p = 0.28 and p = 0.74, respectively). Case group had significantly smaller mean AHD (8.7 ± 3.2 vs. 10.8 ± 2.2 mm; p < 0.001) and larger mean CSA (36.5 ± 4.5° vs. 33.1 ± 4.0°; p < 0.001). PIAHD-CSA increased diagnostic performance for prediction of RCT and CFD (AUC = 0.78 and 0.71), compared to isolated AHD (0.74 and 0.71) and CSA (0.71 and 0.66). Conclusions: AHD and CSA do not depend on age or sex but differ significantly between healthy and pathologic rotator cuffs. A decreased AHD is most influenced by infraspinatus muscle atrophy and fatty degeneration. Combined PIAHD-CSA increases diagnostic performance for predicting RCT and CFD. Keywords: Acromiohumeral distance; Conventional radiography; Critical shoulder angle; Fatty degeneration; Magnetic resonance arthrography; Magnetic resonance imaging; Rotator cuff tear

The IVIM signal in the healthy cerebral gray matter: a play of spherical and non-spherical components

The intra-voxel incoherent motion (IVIM) model assumes that blood flowing in isotropically distributed capillary segments induces a phase dispersion of the MR signal, which increases the signal attenuation in diffusion-weighted images. However, in most tissue types the capillary network has an anisotropic micro-architecture. In this study, we investigated the possibility to indirectly infer the anisotropy of the capillary network in the healthy cerebral gray matter by evaluating the dependence of the IVIM signal from the direction of the diffusion-encoding. Perfusion-related indices and self-diffusion were modelled as symmetric rank 2 tensors. The geometry of the tensors was quantified pixel-wise by decomposing the tensor in sphere-like, plane-like, and line-like components. Additionally, trace and fractional anisotropy of the tensors were computed. While the self-diffusion tensor is dominated by a spherical geometry with a residual contribution of the non-spherical components, both, fraction of perfusion and pseudo-diffusion, present a substantial (in the order of 30%) contribution of planar and linear components to the tensor metrics. This study shows that the IVIM perfusion estimates in the cerebral gray matter present a detectable deviation from the spherical model. These non-spherical components may reflect the direction-dependent morphology of the microcirculation. Therefore, the tensor generalization of the IVIM model may provide a tool for the non-invasive monitoring of cerebral capillary micro-architecture during development, aging or in pathologies

Evaluation of ultrashort echo-time (UTE) and fast-field-echo (FRACTURE) sequences for skull bone visualization and fracture detection - A postmortem study

BACKGROUND AND PURPOSE CT is considered the modality of choice in the assessment of the skull due to the fast and accurate depiction of bone structures. Nevertheless, MRI has evolved into a possible alternative due to optimal soft tissue contrast and recent advances with the ability to visualize tissues with shortest T2 times, such as osseous structures. In this study we compare skull bone visualization and fracture detection across two MRI sequences to CT as reference standard. MATERIAL AND METHODS Twenty subjects underwent CT and MRI with less than 72 h between examination. The MRI protocol included a 2D ultrashort echo time (UTE) and a 3D multi-echo in-phase fast-field-echo (FRACTURE) sequence. Independent raters evaluated qualitative characteristics and fracture detectability in different skull subregions (skull vault, skull base and viscerocranium). Interrater and intermodality agreement was evaluated by calculating intraclass coefficients (ICC). RESULTS FRACTURE ICC indicated a good agreement in all subregions (ICC = 0.83 - 0.88), whereas UTE had excellent results calculated in the skull vault and viscerocranium (ICC = 0.91 - 0.94). At the skull vault, both MRI sequences received an overall good rating (UTE: 2.63 ± 0.42 FRACTURE. 2.81 ± 0.32). Fracture detection using MRI sequences for the skull vault, was highest compared to other subregions. CONCLUSIONS Both MRI sequences may provide an alternative e.g. for surgical planning or follow up exams of the osseous neurocranium; although, at the skull base and viscerocranium bone visualization with MRI bone imaging sequences perform inferior to CT standard imaging

Ultrashort Time-to-Echo Magnetic Resonance Imaging at 3 T for the Detection of Spondylolysis in Cadaveric Spines

ObjectivesThe objective of this study was to compare the diagnostic performance and confidence of conventional, optimized, and ultrashort time to echo (UTE) magnetic resonance (MR) protocols for detection of simulated lumbar spondylolysis in human cadavers. In addition, we sought to demonstrate the feasibility of the UTE technique in subjects with and without spondylolysis.Materials and methodsFour human lumbar spine specimens with 46 individual pars interarticularis were randomly left intact (n = 26) or received experimental osteotomy (n = 20) using a microsurgical saw to simulate spondylolysis. The specimens were imaged using a computed tomography (CT) scan along with 3 "Tiers" of MR protocols at 3 T: Tier 1, conventional lumbar MR protocol; Tier 2, optimized conventional protocol consisting of a sagittal oblique spoiled gradient recall echo and axial oblique T1 and short tau inversion recovery sequences; and Tier 3, a sagittal UTE MR sequence. Two blinded readers evaluated the images using a 4-point scale (1 = spondylolysis certainly absent, 2 = probably absent, 3 = probably present, 4 = certainly present) at each individual pars. For each imaging protocol, diagnostic performance (sensitivity, specificity, and area under the receiver operating characteristic curve, using the surgical osteotomy as the reference) and confidence were assessed and compared using the McNemar test. Furthermore, 2 human subjects were imaged with the conventional and UTE MR protocols to demonstrate feasibility in vivo.ResultsDiagnostic performance was moderate for Tiers 1 and 2, with a moderate sensitivity (0.70 to 0.75) and high (1.00) specificity. In contrast, CT and Tier 3 UTE MR imaging had both high sensitivity (1.00) and specificity (1.00). The sensitivities of CT or Tier 3 were statistically greater than Tier 1 sensitivity (P = 0.041) and neared statistical significance when compared with Tier 2 sensitivity (P = 0.074). Area under the receiver operating characteristic curve was also significantly greater for CT and Tier 3 (each area = 1.00), compared with the areas for Tier 1 (0.89, P = 0.037) or Tier 2 (0.873, P = 0.024). Diagnostic confidences of CT or Tier 3 were much greater than other Tiers: Both Tiers 1 and 2 had a large percentage of uncertain (&gt;60%, P &lt; 0.001) or wrong interpretations (&gt;10%, P &lt; 0.001), unlike CT or Tier 3 (0% uncertain or wrong interpretations). Preliminary in vivo UTE images clearly depicted intact and fractured pars.ConclusionsOur study demonstrated that the detection of pars fractures using a single sagittal UTE MR sequence is superior in performance and confidence to conventional and optimized MR protocols at 3 T, whereas matching those from CT evaluation. Furthermore, we demonstrated the feasibility of in vivo application of the UTE sequence in subjects with and without spondylolysis

Ultrashort Time-to-Echo Magnetic Resonance Imaging at 3 T for the Detection of Spondylolysis in Cadaveric Spines: Comparison With CT

OBJECTIVES The objective of this study was to compare the diagnostic performance and confidence of conventional, optimized, and ultrashort time to echo (UTE) magnetic resonance (MR) protocols for detection of simulated lumbar spondylolysis in human cadavers. In addition, we sought to demonstrate the feasibility of the UTE technique in subjects with and without spondylolysis. MATERIALS AND METHODS Four human lumbar spine specimens with 46 individual pars interarticularis were randomly left intact (n = 26) or received experimental osteotomy (n = 20) using a microsurgical saw to simulate spondylolysis. The specimens were imaged using a computed tomography (CT) scan along with 3 "Tiers" of MR protocols at 3 T: Tier 1, conventional lumbar MR protocol; Tier 2, optimized conventional protocol consisting of a sagittal oblique spoiled gradient recall echo and axial oblique T1 and short tau inversion recovery sequences; and Tier 3, a sagittal UTE MR sequence. Two blinded readers evaluated the images using a 4-point scale (1 = spondylolysis certainly absent, 2 = probably absent, 3 = probably present, 4 = certainly present) at each individual pars. For each imaging protocol, diagnostic performance (sensitivity, specificity, and area under the receiver operating characteristic curve, using the surgical osteotomy as the reference) and confidence were assessed and compared using the McNemar test. Furthermore, 2 human subjects were imaged with the conventional and UTE MR protocols to demonstrate feasibility in vivo. RESULTS Diagnostic performance was moderate for Tiers 1 and 2, with a moderate sensitivity (0.70 to 0.75) and high (1.00) specificity. In contrast, CT and Tier 3 UTE MR imaging had both high sensitivity (1.00) and specificity (1.00). The sensitivities of CT or Tier 3 were statistically greater than Tier 1 sensitivity (P = 0.041) and neared statistical significance when compared with Tier 2 sensitivity (P = 0.074). Area under the receiver operating characteristic curve was also significantly greater for CT and Tier 3 (each area = 1.00), compared with the areas for Tier 1 (0.89, P = 0.037) or Tier 2 (0.873, P = 0.024). Diagnostic confidences of CT or Tier 3 were much greater than other Tiers: Both Tiers 1 and 2 had a large percentage of uncertain (>60%, P 10%, P < 0.001), unlike CT or Tier 3 (0% uncertain or wrong interpretations). Preliminary in vivo UTE images clearly depicted intact and fractured pars. CONCLUSIONS Our study demonstrated that the detection of pars fractures using a single sagittal UTE MR sequence is superior in performance and confidence to conventional and optimized MR protocols at 3 T, whereas matching those from CT evaluation. Furthermore, we demonstrated the feasibility of in vivo application of the UTE sequence in subjects with and without spondylolysis