Relationship between pulse sequences and signal intensity of joint fluid in the gradient-echo MR imaging

To depict the labrum and meniscus in terms of contrast to joint fluid by increasing its signal intensity, we examined in vitro and in a human subject the good imaging conditions of gradient-echo magnet resonance by using a 1.0 Tesla superconducting imager (Shimadzu). In our in vitro study, 3 types of joint fluid and physiological saline were imaged together with PVA gel (as the substitute for surrounding soft tissue), by using either the STAGE, SSFP, or STERF method, and with several TR's (repetition time); and mean signal intensity was obtained. In order to confirm the findings of the in vitro study, a human study was conducted: physiological saline was injected into a shoulder joint, and axial planes were depicted under the conditions equivalent to those of the in vitro study. With the STERF method, signal intensity of the fluid was high at any flip angle, but PVS gel and the surrounding soft tissues such as muscles were rarely depicted. With the STAGE and SSFP methods, depiction of the fluid, PVA gel, and the surrounding soft tissues were possible by setting an appropriate flip angle for TR: With the STAGE method (a spoiled gradient echo sequence), good imaging was possible by selecting small flip angle, regardless TR. Therefore, because of easiness in selecting conditions, the STAGE method is considered to be the best for diagnostic scanning.