Page 22 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis

Chapter 1
In SPECT, collimator design is always a compromise between spatial resolution and sensitivity. Parallel hole collimators can be used in clinical SPECT imaging and in the preclinical setting (multi)pinhole collimators are used. Preclinical multi pinhole collimators are used to obtain a much better spatial resolution compared to conventional parallel-hole collimator (83). In comparison to a parallel-hole collimator, pinhole collimators provide a smaller field of view (FOV). These collimators are suited to image focal uptake or organs in the body or the whole body, because they generate magnified images. So, smaller pinhole diameter leads to an improvement the spatial resolution, but also a loss in sensitivity (84-86). A drawback of SPECT use is that the subject is exposed to radioactivity.
CT
In computed tomography (CT) images are obtained thanks to different levels of X-ray attenuation by tissues within the body (87). Pre-clinical devices are very fast and offer ultra-high-resolution scanning at low x-ray doses. A detector rotates around the animal or patient, acquiring volumetric data (88). When associated with other imaging modalities, CT can give an anatomical reference frame for the biochemical and physiological findings that are provided by other imaging instruments. A CT is also of importance with quantification of SPECT/PET data as it is used for accurate scatter and attenuation correction (89). One of the drawbacks of the use of a CT is that it has little soft tissue in small animals, so there is a need for contrast agents. Next to that the subject is exposed to radiation.
Aim and thesis outline
This thesis describes several methods for imaging of cells in regenerative medicine, cancer and osteoarthritis. The overall aim of the studies was to label cells involved in disease, so they can be detected non-invasively with an imaging device as a means to stage the disease and to potentially interfere in the disease development. In Chapter 1, a general introduction to molecular imaging is given. We describe the imaging devices used in molecular imaging and cell labelling strategies that can be employed. In regenerative medicine the aim is to substitute damaged or aged tissue with healthy cells to regain a proper function of the tissue. To be able to visualize this process with MRI, cells can be labelled with iron particles. In Chapter 2 the efficacy of iron particles
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