Spectrum of T2* values in knee joint cartilage at 3 T: a cross-sectional analysis in asymptomatic young adult volunteers

Objective

To establish baseline T2* values in healthy knee joint cartilage at 3 T.

Materials and Methods

Thirty-four volunteers (mean age: 24.6?±?2.7 years) with no history or clinical findings indicative of any knee joint disease were enrolled. The protocol included a double-echo steady-state (DESS) sequence for morphological cartilage evaluation and a gradient-echo multi-echo sequence for T2* assessment. Bulk and zonal T2* values were assessed in eight regions: posterior lateral femoral condyle; central lateral femoral condyle; trochlea; patella; lateral tibial plateau; posterior medial femoral condyle; central medial femoral condyle; and medial tibial plateau. Statistical evaluation comprised a two-tailed t test and a one-way analysis of variance to identify zonal and regional differences.

Results

T2* mapping revealed higher T2* values in the superficial zone in all regions (P values?≤?0.001) except for the posterior medial femur condyle (P?=?0.087), and substantial regional differences demonstrating superior values in trochlear cartilage, intermediate values in patellar and central femoral condylar cartilage, and low T2* values in posterior femoral condylar cartilage and tibial plateau cartilage.

Conclusion

Substantial regional differences in T2* measures should be taken into consideration when conducting T2* mapping of knee joint cartilage.     

An in vitro comparative study of T2 and T2* mappings of human articular cartilage at 3-Tesla MRI using histology as the standard of reference

Objective

The aim of this study was to evaluate the correlations between T2 value, T2* value, and histological grades of degenerated human articular cartilage.

Materials and methods

T2 mapping and T2* mapping of nine tibial osteochondral specimens were obtained using a 3-T MRI after total knee arthroplasty. A total of 94 ROIs were analyzed. Histological grades were assessed using the David–Vaudey scale. Spearman’s rho correlation analysis and Pearson’s correlation analysis were performed.

Results

The mean relaxation values in T2 map with different histological grades (0, 1, 2) of the cartilage were 51.9?±?9.2 ms, 55.8?±?12.8 ms, and 59.6?±?10.2 ms, respectively. The mean relaxation values in T2* map with different histological grades (0, 1, 2) of the cartilage were 20.3?±?10.3 ms, 21.1?±?12.4 ms, and 15.4?±?8.5 ms, respectively. Spearman’s rho correlation analysis confirmed a positive correlation between T2 value and histological grade (ρ?=?0.313, p?<?0.05). Pearson’s correlation analysis revealed a significant negative correlation between T2 and T2* (r?=??0.322, p?<?0.05). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, this correlation was not statistically significant in this study (ρ?=??0.192, p?=?0.129).

Conclusions

T2 mapping was correlated with histological degeneration, and it may be a good biomarker for osteoarthritis in human articular cartilage. However, the strength of the correlation was weak (ρ?=?0.313). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, the correlation was not statistically significant. Therefore, T2 mapping may be more appropriate for the initial diagnosis of articular cartilage degeneration in the knee joint. Further studies on T2* mapping are needed to confirm its reliability and mechanism in cartilage degeneration.     

T2* mapping and delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) of glenohumeral cartilage in asymptomatic volunteers at 3 T

Objectives

To establish baseline T2* and T1_Gd values of glenohumeral cartilage at 3 T.

Methods

Forty asymptomatic volunteers (mean age: 24.8?±?2.2 years) without shoulder abnormalities were included. The MRI protocol comprised a double-echo steady-state (DESS) sequence for morphological cartilage evaluation, a gradient-echo multiecho sequence for T2* assessment, and a gradient-echo dual-flip-angle sequence for T1_Gd mapping. Statistical assessment involved a one-way analysis of variance (ANOVA) to identify the differences between various regions of the glenohumeral joint and intraclass correlation (ICC) analysis comparing repetitive T2* and T1_Gd measures to assess intra- and interobserver reliability.

Results

Both techniques revealed significant differences between superior and inferior glenohumeral cartilage demonstrating higher T2* (26.2 ms vs. 23.2 ms, P value?<?0.001) and T1_Gd (750.1 ms vs. 720.2 ms, P value?=?0.014) values in the superior regions. No trend was observed in the anterior-posterior measurement (P value range: 0.279–1.000). High intra- and interobserver agreement (ICC value range: 0.895–0.983) was noted for both T2* and T1_Gd mapping.

Conclusions

T2* and T1_Gd mapping are reliable in the assessment of glenohumeral cartilage. The values from this study can be used for comparison to identify cartilage degeneration in patients suffering from shoulder joint abnormalities.

Key Points

? T2* mapping and dGEMRIC are sensitive to collagen degeneration and proteoglycan depletion. ? This study aimed to establish baseline T2*/dGEMRIC values of glenohumeral cartilage. ? Both techniques revealed significant differences between superior and inferior glenohumeral cartilage. ? High intra-/interreader agreement was noted for both T2* mapping and dGEMRIC. ? These baseline normal values should be useful when identifying potential degeneration.     

Feasibility of in vivo diffusion tensor imaging of articular cartilage with coverage of all cartilage regions

Objectives

To investigate the value of diffusion tensor imaging (DTI) of articular cartilage to differentiate healthy from osteoarthritis (OA) subjects in all cartilage regions.

Methods

DTI was acquired sagittally at 7 T in ten healthy and five OA (Kellgren-Lawrence grade 2) subjects with a line scan diffusion tensor sequence (LSDTI). Three healthy volunteers and two OA subjects were examined twice to assess the test-retest reproducibility. Averaged mean diffusivity (MD) and fractional anisotropy (FA) were calculated in each cartilage region (femoral trochlea, lateral and medial femoral condyles, patella, and lateral and medial tibia).

Results

The test-retest reproducibility was 2.9 % for MD and 5.6 % for FA. Averaged MD was significantly increased (+20 %, p?<?0.05) in the OA subjects in the lateral femoral condyle, lateral tibia and the femoral trochlea compartments. Averaged FA presented a trend of lower values in the OA subjects (-12 %), which was only significant for the lateral tibia.

Conclusions

In vivo DTI of articular cartilage with coverage of all cartilage regions using an LSDTI sequence is feasible, shows excellent reproducibility for MD and FA, and holds potential for the diagnosis of OA.

Key points

? DTI of articular cartilage is feasible at 7 T in all cartilage regions ? DTI of articular cartilage can potentially differentiate healthy and OA subjects     

Magnetic resonance transverse relaxation time T2 of knee cartilage in osteoarthritis at 3-T: a cross-sectional multicentre, multivendor reproducibility study

Objective

The transverse relaxation time (T2) in MR imaging has been identified as a potential biomarker of hyaline cartilage pathology. This study investigates whether MR assessments of T2 are comparable between 3-T scanners from three different vendors.

Design

Twelve subjects with symptoms of knee osteoarthritis and one or more risk factors had their knee scanned on each of the three vendors’ scanners located in three sites in the UK. MR data acquisition was based on the United States National Institutes of Health Osteoarthritis Initiative protocol. Measures of cartilage T2 and R2 (inverse of T2) were computed for precision error assessment. Intrascanner reproducibility was also assessed with a phantom (all three scanners) and a cohort of 5 subjects (one scanner only).

Results

Whole-organ magnetic resonance (WORM) semiquantitative cartilage scores ranged from minimal to advanced degradation. Intrascanner R2 root-mean-square coefficients of variation (RMSCOV) were low, within the range 2.6 to 6.3% for femoral and tibial regions. For one scanner pair, mean T2 differences ranged from ?1.2 to 2.8 ms, with no significant difference observed for the medial tibia and patella regions (p?<?0.05). T2 values from the third scanner were systematically lower, producing interscanner mean T2 differences within the range 5.4 to 10.0 ms.

Conclusion

Significant interscanner cartilage T2 differences were found and should be accounted for before data from scanners of different vendors are compared.     

Image registration improves human knee cartilage T1 mapping with delayed gadolinium-enhanced MRI of cartilage (dGEMRIC)

Objectives

To evaluate the effect of automated registration in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of the knee on the occurrence of movement artefacts on the T1 map and the reproducibility of region-of-interest (ROI)-based measurements.

Methods

Eleven patients with early-stage knee osteoarthritis and ten healthy controls underwent dGEMRIC twice at 3?T. Controls underwent unenhanced imaging. ROIs were manually drawn on the femoral and tibial cartilage. T1 calculation was performed with and without registration of the T1-weighted images. Automated three-dimensional rigid registration was performed on the femur and tibia cartilage separately. Registration quality was evaluated using the square root Cramér–Rao lower bound (CRLB_σ). Additionally, the reproducibility of dGEMRIC was assessed by comparing automated registration with manual slice-matching.

Results

Automated registration of the T1-weighted images improved the T1 maps as the 90% percentile of the CRLB_σ was significantly (P?<?0.05) reduced with a median reduction of 55.8 ms (patients) and 112.9 ms (controls). Manual matching and automated registration of the re-imaged T1 map gave comparable intraclass correlation coefficients of respectively 0.89/0.90 (patients) and 0.85/0.85 (controls).

Conclusions

Registration in dGEMRIC reduces movement artefacts on T1 maps and provides a good alternative to manual slice-matching in longitudinal studies.

Key Points

? Quantitative MRI is increasingly used for biomedical assessment of knee articular cartilage ? Image registration leads to more accurate quantification of cartilage quality and damage ? Movement artefacts in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) are reduced ? Automated image registration successfully aligns baseline and follow-up dGEMRIC examinations ? Reproducibility of dGEMRIC with registration is similar to that using manual slice-matching     

Bone marrow changes related to disuse

Objectives

To evaluate bone marrow changes on knee magnetic resonance imaging (MRI) in patients with 3- to 6-week-long period of unloading.

Methods

MRI knee examinations were performed in 30 patients (14 men, 16 women; aged 20–53 years) at baseline and 5–10 weeks after immobilisation of the ipsilateral lower extremity; subsets of patients were examined at additional time-points. Ten volunteers (4 men, 6 women; aged 20–50 years) were studied as control cohort at two time-points. Bone marrow signal abnormalities were analysed according to: (1) severity, (2) signal alteration relative to hyaline cartilage, (3) morphology, (4) increased vascularity in the knee joint and (5) T1-signal alteration. Spearman’s rank correlation test (SRC) and Kendall’s tau (KT) were used to compare individual scores.

Results

All 30 patients presented abnormal bone marrow findings after unloading, which reached a peak at 10–25 weeks (P <0.001). These findings decreased within 1 year (P?<?0.001). High scores of severity were associated with confluent and patchy patterns of bone marrow (SCR?=?0.923, P?<?0.001 and KT?=?0.877, P <0.001).

Conclusions

Signal abnormalities of the bone marrow related to unloading are consistent findings and most prominent 10–25 weeks following immobilisation when both confluent and patchy hyperintense patterns are present.

Key Points

? Disuse is associated with hyperintense MRI signal alteration on fluid-sensitive sequence. ? Disuse findings are more prominent at the patella and femoral epiphyses. ? Disuse MRI findings appear to be characterised by a specific chronological pattern.     

Three-dimensional topographical variation of femoral cartilage T2 in healthy volunteer knees

Objective

Quantitative knee cartilage T2 assessment on limited two-dimensional midsagittal or midcoronal planes may be insufficient to assess variations in normal cartilage composition. The purpose of this work was to reveal characteristic 3D distribution of T2 values in femoral cartilage in healthy volunteer knees.

Materials and methods

Sixteen volunteers were enrolled in this study. One knee joint in each volunteer was imaged using a 3D fast image employing steady-state acquisition cycled phases (FIESTA-C) sequence for modeling distal femoral morphology, as well as a sagittal T2 mapping of cartilage. 3D distribution of cartilage T2 values was generated for the femoral condyles. At each medial and lateral condyle, four regions of interest (ROI) were manually defined based on the cartilage covered by the 3D surface model of the medial and lateral menisci.

Results

The 3D maps showed a relatively inhomogeneous distribution of cartilage T2 on the medial and lateral condyles. Cartilage T2 values in the internal half of the weight-bearing zone were significantly higher than those in all other zones on both lateral and medial condyles.

Conclusions

Analysis of 3D distribution of femoral cartilage T2 may be valuable in determining the site-specific normal range of cartilage T2 in the healthy knee joint.     

Hip imaging of avascular necrosis at 7 Tesla compared with 3 Tesla

Objectives

To compare ultra-high field, high-resolution bilateral magnetic resonance imaging (MRI) of the hips at 7 Tesla (T) with 3 T MRI in patients with avascular necrosis (AVN) of the femoral head by subjective image evaluations, contrast measurements, and evaluation of the appearance of imaging abnormalities.

Materials and Methods

Thirteen subjects with avascular necrosis treated using advanced core decompression underwent MRI at both 7 T and 3 T. Sequence parameters as well as resolution were kept identical for both field strengths. All MR images (MEDIC, DESS, PD/T2w TSE, T1w TSE, and STIR) were evaluated by two radiologists with regard to subjective image quality, soft tissue contrasts, B1 homogeneity (four-point scale, higher values indicating better image quality) and depiction of imaging abnormalities of the femoral heads (three-point scale, higher values indicating the superiority of 7 T). Contrast ratios of soft tissues were calculated and compared with subjective data.

Results

7-T imaging of the femoral joints, as well as 3-T imaging, achieved “good” to “very good” quality in all sequences. 7 T showed significantly higher soft tissue contrasts for T2w and MEDIC compared with 3 T (cartilage/fluid: 2.9 vs 2.2 and 3.6 vs 2.6), better detailed resolution for cartilage defects (PDw, T2w, T1w, MEDIC, DESS?>?2.5) and better visibility of joint effusions (MEDIC 2.6; PDw/T2w 2.4; DESS 2.2). Image homogeneity compared with 3 T (3.9–4.0 for all sequences) was degraded, especially in TSE sequences at 7 T through signal variations (7 T: 2.1–2.9); to a lesser extent also GRE sequences (7 T: 2.9–3.5). Imaging findings related to untreated or treated AVN were better delineated at 3 T (≤1.8), while joint effusions (2.2–2.6) and cartilage defects (2.5–3.0) were better visualized at 7 T. STIR performed much more poorly at 7 T, generating large contrast variations (1.5).

Conclusions

7-T hip MRI showed comparable results in hip joint imaging compared with 3 T with slight advantages in contrast detail (cartilage defects) and fluid detection at 7 T when accepting image degradation medially.     

Magnetic resonance imaging and histology of ovine hip joint cartilage in two age populations: a sheep model with assumed healthy cartilage

Objective

To compare morphologically normal appearing cartilage in two age groups with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) and correlate magnetic resonance imaging (MRI) findings with histology.

Materials and methods

Twenty femoral head specimens collected from ten lambs (group I) and ten young adult sheep (group II) underwent dGEMRIC and histological assessment. A region of 2 cm² with morphologically normal-appearing cartilage was marked with a surgical suture for subsequent matching of MRI and histological sections. The MRI protocol included a three-dimensional (3D) double-echo steady-state sequence for morphological cartilage assessment, a B1 pre-scan with various flip angles for B1 field heterogeneity correction, and 3D volumetric interpolated breathhold examination for T1_Gd mapping (dGEMRIC). Histological analysis was performed according to the Mankin scoring system.

Results

A total of 303 regions of interest (ROI; 101 MRI reformats matching 101 histological sections) was assessed. Twenty-six ROIs were excluded owing to morphologically apparent cartilage damage or insufficient MR image quality. Therefore, 277 ROIs were analyzed. Histological analyses revealed distinct degenerative changes in various cartilage samples of group II (young adult sheep). Corresponding T1_Gd values were significantly lower in the group of sheep (mean T1_Gd?=?540.4 ms) compared with the group of lambs (mean T1_Gd?=?623.6 ms; p?<?0.001).

Conclusions

Although morphologically normal, distinct cartilage degeneration may be present in young adult sheep cartilage. dGEMRIC can reveal these changes and may be a tool for the assessment of early cartilage degeneration.     

Magnetic resonance imaging of the knee at 3 and 7 Tesla: a comparison using dedicated multi-channel coils and optimised 2D and 3D protocols

Objectives

To show the feasibility and possible superiority of two 7 Tesla knee protocols (“7?T high resolution” and “7?T quick”) using a new 28-channel knee coil compared to an optimised 3?T knee protocol using an 8-channel knee coil.

Methods

The study was approved by the ethics committee. Both 3?T and 7?T MRI of the knee were performed in 10 healthy volunteers (29.6?±?7.9?years), with two 2D sequences (PD-TSE and T1-SE) and three isotropic 3D sequences (TRUFI, FLASH and PD-TSE SPACE). Quantitative contrast-to-noise ratio (CNR) and qualitative evaluations were performed by different readers, and intra- and inter-rater agreement was assessed.

Results

The signal-to-noise ratio (SNR) as well as the CNR values for cartilage–bone, cartilage–fluid, cartilage–menisci and menisci–fluid were, in most cases, higher at 7?T compared to 3?T, and the 7?T quick measurement was slightly superior compared to the 7?T high-resolution measurement. The results of the subjective qualitative analysis were higher for the 7?T measurements compared to the 3?T measurements. Inter- and intra-observer reliability was high (0.884–0.999).

Conclusions

Through higher field strength and an optimal coil, resolution at 7?T can be increased and acquisition time can be reduced, with superior quantitative and comparable qualitative results compared to 3?T.

Key Points

? 7-Tesla MRI using a dedicated 28-channel knee coil provides high quality. ? Isotropic 3D-MR sequences benefit more from ultra-high-field than basic 2D sequences. ? At 7 T high resolution and short MR acquisition are possible. ? Dedicated coils ensure the clinical applicability of musculoskeletal MRI at ultra-high-field.     

MR relaxometry of the liver: significant elevation of T1 relaxation time in patients with liver cirrhosis

Objectives

To evaluate hepatic relaxation times T1, T2 and T2* in healthy subjects and patients with liver cirrhosis stratified by the Child-Pugh classification (CPC).

Methods

Sixty-one consecutive patients were stratified by CPC (class A?=?26; B?=?20; C?=?15) and compared with age-matched controls (n?=?31). Relaxometry measurements were performed at 1.5?T using six saturation recovery times (200–3,000?ms) to determine liver T1, six echo times (TE 14–113?ms) for T2 and eight TE (4.8–38?ms) for T2* assessment. Signal intensities in selected regions of interest in the liver parenchyma were fitted to theoretical models with least squares minimisation algorithms to determine T1, T2 and T2*.

Results

The most significant difference was the higher T1 values (852?±?132?ms) in cirrhotic livers compared with controls (678?±?45?ms, P?Conclusion Measurement of T1 relaxation time can differentiate healthy subjects from patients with liver cirrhosis, and can distinguish between mild/moderate disease (CPC A/B) and advanced disease (CPC C).

Key Points

? Significantly elevated magnetic resonance T1 relaxation times are found in liver cirrhosis. ? T1 relaxation times can distinguish healthy subjects from patients with liver cirrhosis. ? T1 relaxation times can distinguish Child–Pugh classes A and B from C.     

Correlation between apparent diffusion coefficient and viscoelasticity of articular cartilage in a porcine model

Objective

Quantitative MR imaging techniques of degenerative cartilage have been reported as useful indicators of degenerative changes in cartilage extracellular matrix, which consists of proteoglycans, collagen, non-collagenous proteins, and water. Apparent diffusion coefficient (ADC) mapping of cartilage has been shown to correlate mainly with the water content of the cartilage. As the water content of the cartilage in turn correlates with its viscoelasticity, which directly affects the mechanical strength of articular cartilage, ADC can serve as a potentially useful indicator of the mechanical strength of cartilage. The aim of this study was to investigate the correlation between ADC and viscoelasticity as measured by indentation testing.

Materials and methods

Fresh porcine knee joints (n?=?20, age 6?months) were obtained from a local abattoir. ADC of porcine knee cartilage was measured using a 3-Tesla MRI. Indentation testing was performed on an electromechanical precision-controlled system, and viscosity coefficient and relaxation time were measured as additional indicators of the viscoelasticity of cartilage. The relationship between ADC and viscosity coefficient as well as that between ADC and relaxation time were assessed.

Results

ADC was correlated with relaxation time and viscosity coefficient (R²?=?0.75 and 0.69, respectively, p?Conclusions This study found a moderate correlation between ADC and viscoelasticity in the superficial articular cartilage. Both molecular diffusion and viscoelasticity were higher in weight bearing than non-weight-bearing articular cartilage areas.     

In vivo evaluation of biomechanical properties in the patellofemoral joint after matrix-associated autologous chondrocyte transplantation by means of quantitative T2 MRI

Purpose

To determine in vivo biomechanical properties of articular cartilage and cartilage repair tissue of the patella, using biochemical MRI by means of quantitative T2 mapping.

Methods

Twenty MR scans were achieved at 3T MRI, using a new 8-channel multi-function coil allowing controlled bending of the knee. Multi-echo spin-echo T2 mapping was prepared in healthy volunteers and in age- and sex-matched patients after matrix-associated autologous chondrocyte transplantation (MACT) of the patella. MRI was performed at 0° and 45° of flexion of the knee after 0 min and after 1 h. A semi-automatic region-of-interest analysis was performed for the whole patella cartilage. To allow stratification with regard to the anatomical (collagen) structure, further subregional analysis was carried out (deep–middle–superficial cartilage layer). Statistical analysis of variance was performed.

Results

During 0° flexion (decompression), full-thickness T2 values showed no significant difference between volunteers (43 ms) and patients (41 ms). Stratification was more pronounced for healthy cartilage compared to cartilage repair tissue. During 45° flexion (compression), full-thickness T2 values within volunteers were significantly increased (54 ms) compared to patients (44 ms) (p < 0.001). Again, stratification was more pronounced in volunteers compared to patients. The volunteer group showed no significant increase in T2 values measured in straight position and in bended position. There was no significant difference between the 0- and the 60-min MRI examination. T2 values in the patient group increased between the 0- and the 60-min examination. However, the increase was only significant in the superior cartilage layer of the straight position (p = 0.021).

Conclusion

During compression (at 45° flexion), healthy patellar cartilage showed a significant increase in T2-values, indicating adaptations of water content and collagen fibril orientation to mechanical load. This could not be observed within the patella cartilage after cartilage repair (MACT) of the patella, most obvious due to a lack of biomechanical adjustment.

Level of evidence

III.     

Acoustic radiation force impulse (ARFI) in the evaluation of the renal parenchymal stiffness in paediatric patients with vesicoureteral reflux: preliminary results

Objectives

To prospectively evaluate acoustic radiation force impulse (ARFI) imaging of the kidneys in children with and without chronic renal disease.

Methods

Twenty-eight children (age range 9–16 years) with primary or secondary vesicoureteral reflux (≥ grade III) underwent scintigraphy and ultrasound with ARFI. Kidneys were divided—according to scintigraphy—into “affected” and “contralateral”; the results were compared with 16 age-matched healthy subjects. An ARFI value, expressed as speed (m/s) of wave propagation through the tissue, was calculated for each kidney through the mean of the values obtained at the upper, middle and lower third. The Wilcoxon test was used; P values <0.05 were considered statistically significant.

Results

The mean ARFI values obtained in the “affected” kidneys (5.70?±?1.71 m/s) were significantly higher than those measured in both “contralateral” (4.09?±?0.97, P?<?0.0001) and “healthy” kidneys (3.13?±?0.09, P?<?0.0001). The difference between values in the “contralateral” kidneys and “healthy” ones was significant (P?<?0.0001). The “affected” kidneys with secondary reflux had mean ARFI values (6.59?±?1.45) significantly higher than those with primary reflux (5.35?±?1.72).

Conclusions

ARFI values decrease from kidneys with secondary vesicoureteral reflux to kidneys with primary reflux to unaffected kidneys contralateral to reflux to normal kidneys.

Key points

? Acoustic radiation force impulse (ARFI) can quantify tissue elasticity during ultrasound examinations. ? Kidneys are highly heterogeneous and difficult to evaluate with ARFI. ? Kidneys damaged by vesicoureteral reflux are stiffer than normal. ? ARFI can identify initial damage in macroscopically normal kidneys.     

1H-Magnetic Resonance Spectroscopy in diffuse and focal cervical cord lesions in Multiple Sclerosis

Objectives

To investigate differences between focal and diffuse cervical lesions in multiple sclerosis (MS) by proton magnetic resonance spectroscopy (¹H-MRS) at 1.5 T in comparison to quantitative MR imaging of the upper cervical cord area and T2 relaxometry at baseline and follow-up.

Methods

Including 22 MS patients with persistent spinal cord symptoms by either diffuse or focal lesions and 17 controls, we acquired MRS, the mean cord area and the water T2 relaxation time and disability at baseline and follow-up. Cross-sectional analyses included group-level comparisons and correlation studies. Follow-up studies covered assessment of reproducibility and progression of the baseline results.

Results

Compared with focal lesions, diffuse lesions were attended by more cord atrophy, longer T2, elevated levels of creatine (Cre) and reduced N-acetyl aspartate (NAA)/Cre (focal/diffuse: 83?±?9/73?±?15 mm², 121?±?21/104?±?13 ms, 3.6?±?1.1/5.1?±?2.4 mM, 2.4?±?1.1/2.0?±?0.9). NAA/Cre at baseline was associated significantly with cord atrophy and with clinical progression during follow-up. Baseline MRS results were not significantly correlated to the clinical disability parameters. The reproducibility of MRS was 0.17-0.30. Longitudinal changes of the MRS results were not statistically significant.

Conclusions

MRS indicated differences in demyelination and gliosis between diffuse and focal cervical lesions in MS. Although longitudinal spectral and clinical changes were sparse, NAA/Cre turned out to be the most sensitive spectral parameter.

Key Points

? MR spectroscopy shows differences between focal and diffuse spinal cord MS lesions. ? MRS indicates axonal degeneration and gliosis in MS compared with controls. ? MRS results are associated with cervical cord atrophy. ? MRS may help clinicians to monitor spinal cord damage in MS.     

Prognosis of small hepatocellular nodules detected only at the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR imaging as hypointensity in cirrhosis or chronic hepatitis

Purpose

To evaluate the prognosis of “strict” high-risk nodules (small hepatocellular nodules detected only in the hepatobiliary phase of initial Gd-EOB-DTPA-enhanced MR examination) in patients with cirrhosis or chronic hepatitis.

Methods and materials

The study included thirty-three patients with 60 “strict” high-risk nodules showing hypointensity at the hepatobiliary phase that was undetectable at the vascular phase and other conventional sequences of initial Gd-EOB-DTPA-enhanced MR imaging. These nodules were observed on follow-up MR examinations until hypervascularity was detected. The potential predictive factors for hypervascular transformation were compared between two groups (group A showing hypervascular transformation, group B not showing hypervascularization).

Results

Ten (16.7 %) of 60 “strict” high-risk nodules showed hypervascular transformation during follow-up periods (group A). The growth rates of the nodules in group A (6.3?±?4.5 mm/year) were significantly higher than those in group B (3.4?±?7.2 mm/year) (p?=?0.003). Additionally, the median observation period in group A (177.5?±?189.5 day) was significantly shorter than in group B (419?±?372.2 day) (p?=?0.045). The other predictive factors were not significantly correlated with hypervascularization.

Conclusions

Subsets of “strict” high-risk nodules showed hypervascular transformation during follow-up periods in association with increased growth rates, indicating that nodule growth rate is an important predictive factor for hypervascularization.

Key Points

? “Strict” high-risk nodules are defined as hepatocellular nodules detected only in the hepatobiliary-phase. ? Subsets of “strict” high-risk nodules showed hypervascular transformation during follow-up periods. ? Increased growth rate is an important predictive factor for hypervascular transformation. ? Management of patients with “strict” high-risk nodules becomes more appropriate.     

Increasing lateral tibial slope: is there an association with articular cartilage changes in the knee?

Purpose

The geometry of the lateral tibial slope (LTS) plays an important role in the overall biomechanics of the knee. Through this study, we aim to assess the impact of LTS on cartilage degeneration in the knee.

Materials and methods

A retrospective analysis of 93 knee MRI scans (1.5 T or 3 T) for patients aged 20–45 years with no history of trauma or knee surgery, and absence of internal derangement. The LTS was calculated using the circle method. Chondropathy was graded from 0 (normal) to 3 (severe). Linear regression analysis was used for statistical analysis (p?<?0.05).

Results

In our cohort of patients, a statistically significant association was seen between increasing LTS and worsening cartilage degenerative changes in the medial patellar articular surface and the lateral tibial articular surface (p?<?0.05). There was no statistically significant association between increasing LTS and worsening chondropathy of the lateral patellar, medial trochlea, lateral trochlea, medial femoral, lateral femoral, and medial tibial articular surfaces.

Conclusions

Our results show a statistically significant association between increasing LTS and worsening cartilage degenerative changes in the medial patella and the lateral tibial plateau. We speculate that increased LTS may result in increased femoral glide over the lateral tibial plateau with subsequent increased external rotation of the femur predisposing to patellofemoral articular changes. Future arthroscopic studies are needed to further confirm our findings.     

7 Tesla quantitative hip MRI: T1, T2 and T2* mapping of hip cartilage in healthy volunteers

Objectives

To evaluate the technical feasibility and applicability of quantitative MR techniques (delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 mapping, T2* mapping) at 7 T MRI for assessing hip cartilage.

Methods

Hips of 11 healthy volunteers were examined at 7 T MRI with an 8-channel radiofrequency transmit/receive body coil using multi-echo sequences for T2 and T2* mapping and a dual flip angle gradient-echo sequence before (T1₀) and after intravenous contrast agent administration (T1_Gd; 0.2 mmol/kg Gd-DTPA^2? followed by 0.5 h of walking and 0.5 h of rest) for dGEMRIC. Relaxation times of cartilage were measured manually in 10 regions of interest. Pearson’s correlations between R1_delta?=?1/T1_Gd???1/T1₀ and T1_Gd and between T2 and T2* were calculated. Image quality and the delineation of acetabular and femoral cartilage in the relaxation time maps were evaluated using discrete rating scales.

Results

High correlations were found between R1_delta and T1_Gd and between T2 and T2* relaxation times (all p?<?0.01). All techniques delivered diagnostic image quality, with best delineation of femoral and acetabular cartilage in the T2* maps (mean 3.2 out of a maximum of 4 points).

Conclusions

T1, T2 and T2* mapping of hip cartilage with diagnostic image quality is feasible at 7 T. To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted.

Key Points

? dGEMRIC of hip cartilage with diagnostic image quality is feasible at 7 T. ? To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted. ? T2(*) mapping of hip cartilage with diagnostic image quality is feasible at 7 T. ? T2 and T2* relaxation times of cartilage were highly correlated at 7 T. ? Best delineation of femoral and acetabular cartilage was found in T2* maps.

     

Transtibial ACL reconstruction technique fails to position drill tunnels anatomically in vivo 3D CT study

Purpose

The purpose of this study was to visualize and quantify the positions of femoral and tibial tunnels in patients who underwent traditional transtibial single-bundle ACL reconstruction, as performed by multiple surgeons, utilizing 3D CT models, and to compare these positions to our previously reported anatomical tunnel positions.

Methods

Fifty-eight knee computed tomography (CT) scans were performed on patients who underwent primary or revision transtibial single-bundle ACL reconstruction, and three-dimensional reconstructions of the CT scans were aligned within an anatomical coordinate system. The position of femoral tunnel aperture centers was measured with (1) the quadrant method and (2) in the anatomic posterior-to-anterior and proximal-to-distal directions. The position of tibia tunnel aperture centers were measured similarly, in the anterior-to-posterior and medial-to-lateral dimensions on the tibial plateau. Comparisons were made to previously established anatomical tunnel positions, and data were presented as “mean value?±?standard deviation (range).”

Results

The location of tibial tunnels was at 48.0?±?5.4% (35.6–59.5%) of the anterior-to-posterior plateau depth and at 47.9?±?2.9% (42.2–57.4%) of the medial-to-lateral plateau width. The location of femoral tunnels was at 55.8?±?8.0% (41.5–79.5%) in the anatomic posterior-to-anterior direction and at 41.2?±?10.4% (15.1–67.4%) in the proximal-to-distal directions. Utilizing a quadrant method, femoral tunnels were positioned at 37.4?±?5.1% (24.9–50.6%) from the proximal condylar surface, parallel to Blumensaat line, and at 11.0?±?7.3% (?6.0–28.7%) from the notch roof, perpendicular to Blumensaat line. In summary, tibial tunnels were positioned medial to the anatomic PL position (p?p?p?Conclusion ACL reconstruction via traditional transtibial technique fails to accurately position femoral and tibial tunnels within the native ACL insertion site. To achieve anatomical graft placement, other surgical techniques should be considered.

Level of evidence

IV.