The longer and the more intensively one has been working with medical imaging, the more questions of a broader, more general kind one is confronted with: How well does the image represent the truth? Can our interpretation of the imaging findings explain the patient’s disease? Which imaging appearances mean that the patient requires treatment, and if so, which treatment? When does imaging (including incidental findings) lead to unnecessary interventions – due to users not being aware of the intrinsic problems of a diagnostic method or failing to take its inherent limitations into account? These issues are relevant for all diagnostic modalities, including the traditional gold standard of angiography and more recent developments such as magnetic resonance and computed tomography angiography. Applied to diagnostic ultrasonography, the more specific question that arises is how we misinterpret echo patterns or ultrasound features and consequently make erroneous treatment decisions. These problems become particularly manifest when dealing with the morphology of internal carotid artery plaque, where the sonographic appearance of the plaque may be used as a criterion for making treatment recommendations. In the name of scientific rigor investigators sometimes end up focusing too heavily on a single aspect of a complex problem, in turn giving rise to specific assumptions and hypotheses that affect the study design and ultimately lead to wrong, contradictory, and biased results, as well as to the wrong therapeutic conclusions.
Despite these cautionary remarks, however, there is good scientific evidence that vascular duplex ultrasonography – as long as both the morphologic appearance and hemodynamic findings are taken into account and as long as the examiner remains critically aware of the methodological basis – comes very close to depicting the true clinical situation in patients with vascular disease. Although somewhat neglected by some “schools of ultrasound,” where color flow images (which are more angiography-like) are preferred, spectral Doppler analysis can provide some very valuable information. In particular it can depict the hemodynamic situation (in both normal and diseased vessels) with excellent sensitivity, making it highly useful in the diagnostic assessment of vascular disease and in solving problems of differential diagnosis. In terms of method and didactic approach this second English edition continues in the tradition of the earlier German editions and of the first English edition and emphasizes the therapeutic relevance of the diagnostic measures being taken. For details on this approach please refer to the earlier prefaces. Staying in the same pedagogical vein but seeking to advance this method further, this extensively revised edition incorporates even more diagrams and tables.