The lateral aspect of the knee is stabilized by a complex arrangement of ligaments, tendons, and muscles. These structures can be demonstrated with routine spin-echo magnetic resonance (MR) imaging sequences performed in the sagittal, coronal, and axial planes. Anterolateral stabilization is provided by the capsule and iliotibial tract. Posterolateral stabilization is provided by the arcuate ligament complex, which comprises the lateral collateral ligament; biceps femoris tendon; popliteus muscle and tendon; popliteal meniscal and popliteal fibular ligaments; oblique popliteal, arcuate, and fabellofibular ligaments; and lateral gastrocnemius muscle. Injuries to lateral knee structures are less common than injuries to medial knee structures but may be more disabling. Most lateral compartment injuries are associated with damage to the cruciate ligaments and medial knee structures. Moreover, such injuries are frequently overlooked at clinical examination. Structures of the anterolateral quadrant are the most frequently injured; posterolateral instability is considerably less common. Practically all tears of the lateral collateral ligament are associated with damage to posterolateral knee structures. Most injuries of the popliteus muscle and tendon are associated with damage to other knee structures. MR imaging can demonstrate these injuries. Familiarity with the musculotendinous anatomy of the knee will facilitate accurate diagnosis with MR imaging.
Purpose. The objectives were (i) construction of a phantom to reproduce the behavior of iron overload in the liver by MRI and (ii) assessment of the variability of a previously validated method to quantify liver iron concentration between different MRI devices using the phantom and patients. Materials and Methods. A phantom reproducing the liver/muscle ratios of two patients with intermediate and high iron overload. Nine patients with different levels of iron overload were studied in 4 multivendor devices and 8 of them were studied twice in the machine where the model was developed. The phantom was analysed in the same equipment and 14 times in the reference machine. Results. FeCl3 solutions containing 0.3, 0.5, 0.6, and 1.2 mg Fe/mL were chosen to generate the phantom. The average of the intramachine variability for patients was 10% and for the intermachines 8%. For the phantom the intramachine coefficient of variation was always below 0.1 and the average of intermachine variability was 10% for moderate and 5% for high iron overload. Conclusion. The phantom reproduces the behavior of patients with moderate or high iron overload. The proposed method of calculating liver iron concentration is reproducible in several different 1.5 T systems.
Determination of liver iron concentration by magnetic resonance imaging
(MRI) is becoming the new technique of choice for the diagnosis of iron
overload in hereditary haemochromatosis and other liver iron surcharge
diseases. Determination of hepatic iron concentration obtained by liver
biopsy has been the gold standard for years. The development of MRI
techniques, via signal intensity ratio methods or relaxometry, has provided
a non-invasive and more accurate approach to the diagnosis of liver iron
overload.
This article reviews the available MRI methods for the determination of liver
iron concentration and also evaluates the technique for the diagnosis and
quantification of iron overload in different clinical practice scenarios.
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