Towards an in-plane methodology to track breast lesions using mammograms and patient-specific finite-element simulations

In breast cancer screening or diagnosis, it is usual to combine different images in order to locate a lesion as accurately as possible. These images are generated using a single or several imaging techniques. As x-ray-based mammography is widely used, a breast lesion is located in the same plane of the image (mammogram), but tracking it across mammograms corresponding to different views is a challenging task for medical physicians. Accordingly, simulation tools and methodologies that use patient-specific numerical models can facilitate the task of fusing information from different images. Additionally, these tools need to be as straightforward as possible to facilitate their translation to the clinical area. This paper presents a patient-specific, finite-element-based and semi-automated simulation methodology to track breast lesions across mammograms. A realistic three-dimensional computer model of a patient''s breast was generated from magnetic resonance imaging to simulate mammographic compressions in cranio-caudal (CC, head-to-toe) and medio-lateral oblique (MLO, shoulder-to-opposite hip) directions. For each compression being simulated, a virtual mammogram was obtained and posteriorly superimposed to the corresponding real mammogram, by sharing the nipple as a common feature. Two-dimensional rigid-body transformations were applied, and the error distance measured between the centroids of the tumors previously located on each image was 3.84 mm and 2.41 mm for CC and MLO compression, respectively. Considering that the scope of this work is to conceive a methodology translatable to clinical practice, the results indicate that it could be helpful in supporting the tracking of breast lesions

Singlet oxygen photosensitisation by GFP mutants: Oxygen accessibility to the chromophore

Aiming at the rational development of genetically-encoded photosensitisers, the production of singlet oxygen has been assessed for a number of class-2 Green Fluorescent Protein (GFP) mutants by means of time-resolved near-infrared luminescence detection. The accessibility of molecular oxygen to the chromophore seems to play a major role in the ability of GFPs to photosensitise singlet oxygen and this can be modulated by introducing specific mutations such as replacement of His148 by a less bulky amino acid. GFPs are also good singlet oxygen quenchers, hence further developments in this area should also seek to eliminate those amino acids with the highest quenching ability, particularly those at the protein surface and in the vicinity of the chromophore