Figure 5.
Images from selected volunteers showing the contrasts that can be generated with UTEDESS. (a) The S+ UTE images are T1-weighted and have high signal intensity from short-T2 tissues such as the tendons (solid arrow) and the menisci (dashed arrow). (b) The S− echo is more highly T2 weighted where the short-T2 tissues have lower signal. (c) The water-fat separation method provides spectral separation with two echo times. There is clear separation of the short-T2 tissues of the tendons (solid arrow) and the meniscus (dashed arrow) since the longest echo time used is only 1.1ms. (d) Implementing a Dixon-based water-fat separation, as opposed to using a fat-saturation RF pulse, generates a fat-only image. (e) Performing a weighted subtraction of the water S− image from the water S+ image helps suppress the longer-T2 signals. This provides a similar contrast to the high SNR water S+ image but the weightings can be modified based on the short-T2 anatomy that needs to be visualized. (f) In a different subject with fluid in the knee, the water S− image highlights the bright signal around the patellar cartilage (solid arrow) and the anterior horn of the lateral meniscus (dashed arrow). The water S− image has a T2 weighting and has a lower dynamic range relative to the non-water-fat separated S− image. (g–i) Due to the isotropic resolution of the sequence, the scan planes can be formatted in arbitrary directions to create and view T2 maps.