Applications of dual-energy CT in acute musculoskeletal and trauma imaging-a review.

Recent advances in computed tomography have resulted in new applications of CT scans in musculoskeletal imaging. Dual-energy CT technology involves the acquisition of data at high and low kilovolts, allowing differentiation and quantification of materials with different X-ray absorption. Newer CT scanners with a variety of post-processing options allow interesting applications of dual-energy CT in musculoskeletal and trauma imaging. This article provides an overview of the basic principles and physics of DECT. We review applications of DECT in the evaluation of the acute painful joint with suspicion of gout, metal artefact reduction in the prosthetic joint and in imaging of patients following major trauma. We present a review of literature and case examples to illustrate the strengths and limitations of this modality in the diagnosis of acute musculoskeletal conditions.

Normal values of the axial patellotrochlear overlap on MRI: Good correlation with patellotrochlear index in patients with no patellofemoral pathology.

BACKGROUND: There are several imaging-based measurements for patellofemoral height, which are obtained from sagittal images. However, these methods can be misleading with sagittal oblique slices and when the patella is tilted and/or chronically subluxated. This study aimed to describe a simple method of measuring patellar height using axial patellotrochlear overlap (APTO) on MRI. METHODS: A retrospective observational study of 97 knees from 251 patients, excluding those with fractures, massive effusion, or patellofemoral conditions. APTO was measured as follows: (1) patellar length (P) - expressed as the number of axial images showing patellar articular cartilage; (2) trochlear overlap (T) - the number of axial images showing the overlap between patellar articular cartilage and articular cartilage of the lateral trochlea. APTO is the ratio T/P. All measurements were performed independently by six raters on two separate occasions. The raters were two orthopaedic consultants, one knee surgery fellow, two consultant musculoskeletal radiologists, and one radiology fellow. The conventional patellotrochlear index (PTI) was measured as a control for all patients by a senior musculoskeletal radiologist. RESULTS: The mean APTO value was 36.7% (range 14.2-66.6; standard deviation 11.4). There was a positive correlation with the PTI, Pearson correlation coefficient: 0.76, P < 0.001. Intra-observer reliability was good (intraclass correlation coefficient(ICC): 0.66, 95% confidence interval (CI) 0.54, 0.76, P < 0.001). Inter-observer reliability was fair (ICC: 0.51, 95% CI 0.41, 0.6, P < 0.001). CONCLUSIONS: APTO was shown to be a reliable measurement of patellar height and correlated with existing PTI for patellar height. Measurement of APTO on MRI could be a reliable alternative for the evaluation of patellar height. However, further studies are required to assess its validity in patients with patellofemoral pathology.

3T MRI of wrist ligaments and TFCC using true plane oblique 3D T2 Dual Echo Steady State (DESS) - a study of diagnostic accuracy.

OBJECTIVE: This study was designed to assess the accuracy of unenhanced 3T MRI supplemented with dedicated true plane reformats of 3D T2 Dual Echo Steady State (DESS), in assessing tears of scapholunate, lunotriquetral ligaments and triangular fibrocartilage complex, using arthroscopy as gold-standard. METHODS: In a retrospective cohort review, patients who underwent wrist arthroscopy and MRI over 2 years (n=46) were identified. Dedicated axial and coronal reformats were obtained from 3D T2 DESS sequence for assessing intrinsic ligaments and triangular fibrocartilage (TFCC). At arthroscopy, tears were classified using Geissler's classification and compared to MRI findings. RESULTS: The sensitivity of unenhanced 3T MRI in detecting scapholunate ligament tears was 87%, specificity was 90% and negative predictive value of 93%. The lunate triquetral ligament was assessed with a high specificity (97%) and negative predictive value (93%), sensitivity was 63%. TFCC tears were assessed with a sensitivity of 100%. The overall diagnostic accuracy of unenhanced 3T MRI of wrist in detecting ligament tears was 91%. CONCLUSION: 3T wrist MRI with dedicated reformats from 3D T2 DESS has a high diagnostic accuracy in assessing acute intrinsic ligament and TFCC injuries. High strength 3T MRI with good technical quality isotropic 3D T2 DESS is critical for accurate wrist ligament assessment. Negative predictive values of 3T MRI of 95% can lead to reduced need for diagnostic arthroscopy of the wrist. ADVANCES IN KNOWLEDGE: This study assesses the diagnostic performance of unenhanced 3T MRI with 3D T2 DESS in assessing traumatic wrist ligament tears. The accuracy of T2 DESS in wrist imaging has not been previously reported.