A multitude of imaging techniques is available for the assessment of tissue vascu-lature on structural, functional, and molecular levels. All these methods have been successfully used preclinically and will, it is hoped, aid in antiangiogenic drug development in animal studies. At present, only the imaging of functional hemo-dyamic parameters such as Ktrans, blood flow, and blood volume is being used in the clinical arena for the evaluation of antiangiogenic and cytotoxic chemotherapies. However, the physiological meaning of the results is often hard to interpret. Concerning the imaging of molecular parameters of angiogenesis, only a few radiotracers have been used in humans up to now, and their role in the assessment of antiangiogenic therapies is still unsettled. Although avP3 is by far the most extensively studied angiogenic factor for imaging, future trials still have to show which target structure is optimal for the assessment of angiogenic activity. Concerning the optimum imaging technique, the radiotracer approach will probably be the first to be used on a wider scale in patients in the intermediate term, due to its high sensitivity and the low amounts of tracer which have to be used. In the long term, MRI might be an attractive alternative, due to its lack of ionizing radiation and high spatial resolution. However, it is likely that no one single parameter, target structure, or imaging technique will be used for the assessment of angiogenesis in the future, but that a combination of parameters will be used, which will allow for the evaluation of the angiogenic cascade in its full complexity. In summary, assessment of the different aspects of angiogenesis at the functional and molecular levels will, it is hoped, become a reality in the not too distant future and will be implemented in therapy planning and response evaluation as part of the concept of "personalized medicine".

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