Multi-Modality Imaging

Abstract

Multi-modality imaging has emerged as a strategy that combines the strengths of different modalities and yields a hybrid imaging platform with characteristics superior to those of any of its constituents considered alone. This imaging trend has been intensified in recent years due to the emergence of molecular imaging, which brings a new dimension in the imaging sciences and requires highly synergistic visualization approaches. This is because molecular imaging, by definition, provides information that was not available in conventional radiological imaging, but regardless needs to be superimposed on more traditional images of anatomy and function to be fully understood.Collecting images from different modalities to improve diagnostic information has been always performed at some level, for example the use of ultrasound as a follow-up procedure to mammography to improve the specificity of the detection. What distinguishes current trends is the accuracy achieved in the co-registration of the images collected from different modalities. This is primarily achieved by 1) the development of true hybrid systems that collect images under the same or identical placement conditions, as seen by the recent evolution of clinical X-ray-CT/PET systems and 2) by the development of sophisticated image registration algorithms as elaborated in 8.2. An important feature of multi-modality approaches is that besides the straightforward superposition of images, it is possible to utilize the high-resolution information coming from an anatomical or functional image, in order to improve the imaging performance of the low resolution modality. This can be achieved for example by constructing attenuation maps based on anatomical or functional images which are then used to compute more accurate theoretical models of energy propagation in tissue (forward model) and therefore improve the fidelity and quantification of the reconstructed images.These trends have also propagated into the small animal imaging arena with dedicated multi-modality systems being increasingly developed for improving the in-vivo visualization capacity in pre-clinical research. This is a relatively young field but it is expected to grow significantly in the future to serve a similarly advancing field of interrogating biology and new potent drugs on transgenic animal models using novel reporter strategies developed for in-vivo biomedical research. This chapter presents the key elements of multimodality imaging in 8.1 and showcases multi-modality small animal imaging utilizing micro-CT/ micro-SPECT approaches in 8.2 and FMTmicro-MRI approaches in 8.3. These two hybrid approaches are given as implementation and utility examples of multi-modal imaging, whereas many more combinations of different synergistic modalities can improve the accuracy in imaging living systems. Concurrent imaging versus computerassisted registration Fred S. AzarMulti-modality imaging involves the integration of imaging data, which are generally complementary in nature. For example, multi-modality imagi...