Speaker
Prof.
Claus-Christian Glüer
(UKSH and Christian-Albrechts-University Kiel)
Description
In the past decade we have seen a rapid expansion of imaging approaches for preclinical imaging in vivo, including computed tomography (CT), magnetic resonance, fluorescence and bioluminescence, ultrasound and photoacoustic and nuclear medicine approaches. Each of these techniques has strengths and limitations but multimodal assessment permits combined application for morphological, functional, and molecular imaging. However, in general, radiation dose limitation, (movement) artifacts and limited penetration depth limit the image quality and the accuracy of element- or tissue-specific analyses of these in vivo measurements. A powerful strategy thus builds on a combination of longitudinal multimodal imaging in vivo and ex vivo assessment of tissue at the final measurement time point. For the latter, synchrotron radiation (SR) approaches offer intriguing perspectives for a number of applications. I will select a few exemplary fields of study to document this potential.
In orthopedic research bone augmentation techniques are undergoing continuous refinements. For example degradable bone cements with osteoinductive potential permit improved fracture healing and fracture prevention. To document the replacement of bone cement by bone ingrowth is extremently challenging since the injected material is very similar to hydroxyapatite. Monochromatic SR techniques may permit differentiation and along with nano- or micro-tomographic morphological imaging this would permit a more objective assessment of the strength of bone tissue ingrowth, replacing the degrading injected material. Similarly, difference in mineralization status e.g. in osteogenesis imperfecta, renal disorders or due to osteoporosis medications may be differentiated using these approaches. Experience at SR facilities then may guide further development of photon counting spectral CT scanners soon to be introduced into clinical routine.
Element specific imaging can be extremely powerful if turned into truly 3D representations of tissue. SR based x-ray fluorescence imaging or energy-dispersive x-ray spectroscopy are just two options to be pursued. Multimodal imaging in vivo increasingly builds on markers that are visible on several of these modalities. Gold (nano) particles are prime candidates since they can be imaged e.g. by fluorescence, photoacoustics, optical coherence tomography, and computed tomography. As an important area of application theranostic approaches can be named. Here drug delivery nanocarriers (e.g. liposomes) loaded with drugs, markers, and activation agents safely transport drugs to the target location where the drugs are released. Element specific analysis can prove what fraction of the drug actually reaches the target tissue (usually only a few percent of the injected dose, leading to undesirable side effects of the 95+% of the drug at locations of healthy tissue elsewhere in the body) and thus can provide guidance for drug development.
Whatever the specific application there will be a need for automated 3D registration of images generate with different modalities (image fusion) or the same modality with different spatial resolution. Artificial intelligence (AI) methods have recently led to substantial progress in the field of automated image segmentation and registration and thus these techniques should be adapted to the special requirement in the setting of SR based technique. Reduction of imaging artifacts is another related area with promising AI developments.
In summary, linking SR ex vivo techniques to corresponding multimodal in vivo imaging approaches generates unique opportunities not only for experimental studies but also for refinement of clinical imaging approaches.
Primary author
Prof.
Claus-Christian Glüer
(UKSH and Christian-Albrechts-University Kiel)
