Symmetric inverse consistent nonlinear registration driven by mutual information.

A nonlinear viscoelastic image registration algorithm based on the demons paradigm and incorporating inverse consistent constraint (ICC) is implemented. An inverse consistent and symmetric cost function using mutual information (MI) as a similarity measure is employed. The cost function also includes regularization of transformation and inverse consistent error (ICE). The uncertainties in balancing various terms in the cost function are avoided by alternatively minimizing the similarity measure, the regularization of the transformation, and the ICE terms. The diffeomorphism of registration for preventing folding and/or tearing in the deformation is achieved by the composition scheme. The quality of image registration is first demonstrated by constructing brain atlas from 20 adult brains (age range 30-60). It is shown that with this registration technique: (1) the Jacobian determinant is positive for all voxels and (2) the average ICE is around 0.004 voxels with a maximum value below 0.1 voxels. Further, the deformation-based segmentation on Internet Brain Segmentation Repository, a publicly available dataset, has yielded high Dice similarity index (DSI) of 94.7% for the cerebellum and 74.7% for the hippocampus, attesting to the quality of our registration method.

Social and behavioral determinants of consistent condom use among female commercial sex workers (FCSWs) in Ghana

This study aims at investigating the social and behavioral predictors of consistent condom use among female commercial sex workers (FCSWs) in Ghana. Street commercial sex workers were interviewed in Accra, Kumasi and Techiman. Whereas respondents had attained certain accurate knowledge about HIV transmission routes, misconceptions were still commonly reported. The level of condom education was very low (14%), however consistent condom use (all the time) with clients was relatively high (49.6%), 38.89% reported using condom sometimes and 11.56% reported never using condoms. ^ 277 of the respondent ants did not use condoms all the time. 163 of them reported not using condoms due to refusal by their clients, the remaining 64 respondents did not even request their clients to use condom due to cultural perception of power, lack of authority and the fear of loosing clients. ^ Significant predictive factors associated with consistency of condom use among FCSWs in a multivariate analysis were; age, level of education, religion, and number of customers. Some of the major obstacles to condom use by the FCSWs were refusal by clients, availability of free condoms, trying to communicate trust to their clients, and the lack of empowerment to negotiate safer sex with clients. Some of the respondents may have developed a false sense of safety by subjectively assessing whether their clients were well and do not look sick, but they were unaware that HIV carriers may show no obvious symptoms of illness at all. ^ In summary, this study points to an urgent need for reestablishing effective prevention intervention and some insights of what is required of such program in Ghana. ^