Rapid scan techniques have introduced new sequence parameters as well as novel contrast concepts into everyday magnetic resonance imaging (MRI). In particular contrast characteristics of fast-spin echo (FSE) sequences showed some significant differences when compared to conventional spin echo images. The purpose of this work was to demonstrate the capabilities of FSE MRI in identifying and characterizing the in vivo anatomy of the main cerebral associative systems. Between March and November 1995, 20 healthy adult volunteers (12 males, 8 females, mean age 35 years) were submitted to a cranial MRI examination (1.5 Philips Gyroscan NT). In all cases axial and coronal 2-dimensional FSE T2-weighted and 2-dimensional inversion recovery FSE T1-weighted images were obtained. All MRI images were examined by a neuroradiologist (G. Dal Pozzo) for the depiction of the following compact white matter fiber bundles: anterior commissure, corpus callosum, superior fronto-occipital fasciculus, cingulum, fornix, mammillothalamic tract, uncinate fasciculus, superior and inferior longitudinal fasciculus. All these associative pathways could be well identified on T2-weighted images due to a lower signal intensity with respect to the surrounding white matter. On T1-weighted images only the corpus callosum, the anterior commissure and the fornix could always be identified. Correlation with myelin-specific colorations (Luxol fast blue stains) in anatomic atlases and a review of the literature on the myelinization process during infancy indicate that the short T2 relaxation times of the aforementioned cerebral associative systems may be due to heavy myelination and high fiber density. The correct visualization of interintrahemispheric associative white matter fiber bundles may play an important role in white matter disorders like dys- and demyelinating diseases and in the spreading of vasogenic edema and/or tumor being useful for their staging.

Purpose  The aim of this study was to assess the diagnostic accuracy of magnetic resonance arthrography (MRA) in the detection of intra-articular lesions of the hip in patients affected by femoroacetabular impingement (FAI) by using arthroscopy as reference standard. Methods  Twenty-nine consecutive hip arthroscopies performed in 24 patients were considered for the study. Patients had a mean age of 38.3 years. Ultrasound-guided 1.5-T MRA was performed with precontrast short tau inversion recovery, T1-weighted and PD coronal, T1-weighted, and T2-weighted axial with 3-mm-thick slice sequences, and postcontrast T1-weighted fat saturation MRA (Fat-SAT) axial, coronal and oblique sagittal, and T1-weighted Vibe 3D coronal sequences with MPR sagittal, axial, and radial reconstructions with 2-mm-thick slice and coronal density protonil (DP) Fat-SAT. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRA were evaluated by comparison arthroscopy for the following intra-articular findings: acetabular and femoral chondral lesions, labral degeneration, labral tears, synovitis, ligamentum teres (LT) tears, CAM lesions, pincer lesions, loose bodies, and osteophytes. Results  An absolute per cent agreement (100%) was observed for all the variables in the assessment of CAM lesions. Sensitivity, specificity, PPV, and NPV of MRA were 100, 68.4, 72.7, and 100%, respectively, for acetabular chondral lesions; 100, 50, 47.3, and 100%, respectively, for femoral chondral lesions; 33, 85, 20, and 91.6%, respectively, for labral tears; 95, 71, 91.3, and 83.3%, respectively, for labral degeneration; 100, 88, 57.1, and 100%, respectively, for LT tears; 33.3, 85, 50, and 73.9%, respectively, for pincer lesions; 50, 96, 66.6, and 92.3%, respectively, for intra-articular loose bodies; and 100, 73.9, 50, and 100%, respectively, for osteophytes. Conclusion  MRA may play an important role in detecting intra-articular lesions associated with FAI. This might be helpful for the preoperative planning before hip arthroscopy. Level of Evidence  This is a Level 2, diagnostic accuracy study compared with gold standard.

Purpose (1) To investigate correlations between different types of FAI and the ratio of acetabular volume (AV) to femoral head volume (FV) on MR arthrography. (2) To assess 2D/3D measurements in identifying different types of FAI by means of cut-off values of AV/FV ratio (AFR). Materials and methods Alpha angle, cranial acetabular version, acetabular depth, lateral center edge angle, AV, and FV of 52 hip MR arthrography were measured. ANOVA test correlated different types of FAI with AFR. ROC curves classified FAI by cut-off values of AFR. Accuracy of 2D/3D measurements was calculated. Results ANOVA test showed a significant difference of AFR (p value < 0.001) among the three types of FAI. The mean values of AFR were 0.64, 0.74, and 0.89 in cam, mixed, and pincer types, respectively. Cut-off values of AFR were 0.70 to distinguish cam types from mixed and pincer types, and 0.79 to distinguish pincer types from cam and mixed types. Cut-off values identified 100%, 73.9%, and 55.6% of pincer, cam, and mixed types. 2D and 3D classifications of FAI showed accuracy of 40.4% and 73.0%. Conclusions 3D measurements were clearly more accurate than 2D measurements. Distinct cut-off values of AFR discriminated cam types from pincer types and identified pincer types in all cases. Cam and mixed types were not accurately recognized.

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