[Imaging of knee prostheses]

The authors present a pictorial essay illustrating the different types of knee prostheses, their normal appearances, as well as the imaging features (radiographs, CT, US) of the main complications that may occur.

In vitro evaluation of 2D-digital subtraction angiography versus 3D-time-of-flight in assessment of intracranial cerebral aneurysm filling after endovascular therapy

BACKGROUND AND PURPOSE

The aim of this study was to evaluate 2D-digital subtraction angiographic (DSA) and 3D-time-of-flight (TOF) MR imaging in assessment of aneurysmal residue by using a pulsating silicon aneurysm model. For each imaging system, we studied intra- and interobserver reproducibility and the agreement between interpretations and reference measurements. We also examined how each imaging technique affected the operator's therapeutic decision.

METHODS

Two silicon aneurysm models depicting subarachnoidal aneurysms were used, one with a wide neck and one with a narrow neck. Each aneurysm model was placed in series on a pulsed flow circuit and was filled with Guglielmi detachable coils to simulate a clinical case. Each aneurysm was then gradually filled with silicon gel in increments of 10%, up to 100% to simulate different levels of occlusion (residual neck or dog ear, partial, complete) at each filling level. For each level of filling, we performed conventional 2D-DSA and 3D-TOF MR imaging. We submitted the images for examination by 2 senior medical staff with 2 readings per image. A combined reading of the 2 images was submitted to each expert to determine whether the 2 examinations were complementary.

RESULTS

The 2D-DSA analysis showed good reproducibility (k = 0.8 and k = 0.57) and agreement (k = 0.71) in describing "complete" treatments. The distinction between a "residual neck" and "partial treatment," however, was not reliable. The 2D-DSA provided a good description of the coil and silicon protrusion into the parent artery. The 3D-TOF analysis of the residual aneurysm, however, was not reproducible, though it was more effective than the 2D-DSA in evaluation of partially wide-necked aneurysms (k = 0.68 MR imaging vs k = 0.041 2D-DSA; P = .018). At the same filling level, the 2D-DSA analysis indicated repeat treatment more often than 3D-TOF analysis (P = .059).

CONCLUSION

The 2D-DSA remains the gold standard, but MR imaging is more effective in evaluating a "partial treatment." The 2D-DSA analysis indicated repeat treatment more often than the 3D-TOF for the same occlusion level. The distinction between "partial treatment" and a "residual neck" was not reliable with either method of evaluation.