What is Molecular Imaging?
Molecular Imaging, as defined by the Society of Nuclear Medicine and Molecular Imaging, is the "visualization, characterization, and measurement of biological processes at the molecular and cellular levels in humans and other living systems." But what does that really mean?
Molecular imaging serves to diagnose diseases before symptoms occur, and to characterize therapies. Its goal is individual therapy, fine-tuned to each patient, based on their personal response to drugs or other stimuli.
In any disease, the two critical factors to success in treatment are : 1) rapid diagnosis, and 2) proper, responsive therapy. Therefore, our field serves to determine new compounds (probes) which allow us to detect a disease, and to track in real-time the progression of patients during treatment.
Bioluminescence of Streptococcus pyogenes Dissemination
Streptococcus pyogenes is a Gram positive bacteria which can cause a variety of infections in humans. The most dangerous of these infections is necrotizing fasciitis, or the "flesh eating" disease. One major determinant in these infections is streptokinase, which is produced by the bacterium as a means to break up clots and disseminate further into tissue. During a study investigating the ability of S. pyogenes to penetrate tissue in murine dissemination models, we discovered a breakdown in the correlation of bioluminescent signal released from tissues to the bacterial load present in that tissue. Our results indicate this is due to the physiological state of S. pyogenes in vivo, most importantly the glucose dependence of the bioluminescence operon.
Staphylococcus aureus Endocarditis Infections
Infections of the heart valve, termed infective endocarditis, are extremely dangerous complications of bacterial septicemia. Staphylococcus aureus is the leading bacterial cause of these infections, and results in 30-50% mortality rates, despite treatment with antibiotics. The most essential factor in patient survival is rapid and specific diagnosis, in order to ensure proper therapy. Therefore, our lab has developed a fluorescent probe which indicates the presence of S. aureus strains specifically and sensitively. Due to the large size of this initial probe, my work has investigated a related protein with similar fibrinogen-binding effects as a probe of thrombosis and endocarditis.
Multispectral Optoacoustic Tomography (MSOT) for Infectious Disease
Multi-spectral Optoacoustic Tomography (MSOT) is a new tool in imaging small animal biology. The technology works by exciting tissue using a high-powered laser, and measuring the sound released as that tissue relaxes. As in other imaging modalities, two-dimensional ultrasound images can be reconstructed into three-dimensional volumes. Due to the nature of the device, detection of probes is based on their excitation capacity, and not emission through tissue (and therefore ignores many tissue-based effects). Our lab possesses an iThera Medical MSOT imaging device, and is working to develop protocols in the detection and classification of the pathobiology of infectious diseases with this technology.