A simple analytic method for estimating T2 in the knee from DESS.

PURPOSE: To introduce a simple analytical formula for estimating T2 from a single Double-Echo in Steady-State (DESS) scan. METHODS: Extended Phase Graph (EPG) modeling was used to develop a straightforward linear approximation of the relationship between the two DESS signals, enabling accurate T2 estimation from one DESS scan. Simulations were performed to demonstrate cancellation of different echo pathways to validate this simple model. The resulting analytic formula was compared to previous methods for T2 estimation using DESS and fast spin-echo scans in agar phantoms and knee cartilage in three volunteers and three patients. The DESS approach allows 3D (256×256×44) T2-mapping with fat suppression in scan times of 3-4min. RESULTS: The simulations demonstrated that the model approximates the true signal very well. If the T1 is within 20% of the assumed T1, the T2 estimation error was shown to be less than 5% for typical scans. The inherent residual error in the model was demonstrated to be small both due to signal decay and opposing signal contributions. The estimated T2 from the linear relationship agrees well with reference scans, both for the phantoms and in vivo. The method resulted in less underestimation of T2 than previous single-scan approaches, with processing times 60 times faster than using a numerical fit. CONCLUSION: A simplified relationship between the two DESS signals allows for rapid 3D T2 quantification with DESS that is accurate, yet also simple. The simplicity of the method allows for immediate T2 estimation in cartilage during the MRI examination.

Lower genital tract infection with Chlamydia trachomatis and Neisseria gonorrhoeae in Icelandic women with salpingitis.

In a study of 225 women with acute salpingitis verified by laparoscopy or laparotomy we investigated the prevalence of gonococcal and chlamydial infection in the lower genital tract. Neisseria gonorrhoeae was isolated from 18.9% of the women and Chlamydia trachomatis from 38.5%. Women with positive cultures were significantly younger (p less than 0.01) than those with negative cultures. A trend toward more severe inflammatory changes of the tubes was found in women with positive cultures compared with those with negative cultures. The majority of women with positive cultures stated they had only one sexual partner during the preceding 6 months. Single women had more partners (mean 1.9) than those cohabiting (mean 1.2). The ratio of single/multiple partners for women with Chlamydia was 2.5:1, and for those with gonorrhea 1:1 (p less than 0.05). Of the men, 60% could be examined and about 50% had positive cultures. Microbiologic investigation of both partners is necessary in order to prevent reinfection of the woman.