Rigor and Reproducibility in Analysis of Vascular Calcification
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Clinical and preclinical studies of cardiovascular calcification often require interpretation of images from histopathology, computed tomography, intravascular ultrasound, and positron emission tomography. To avoid potential pitfalls in biological inferences, investigators should know what happens to data in image processing algorithms, the limitations of cross-sectional images in studying mechanostability, and how smoothing algorithms can mask partial-volume artifacts in positron emission tomography.
Years ago, a head-on collision sent a motorcyclist to intensive care with multiple limb fractures. A cardiologist was paged to evaluate the unconscious patient for a dangerously low value of cardiac index, suggesting severe cardiac injury. On evaluation, pulse, blood pressure, and cardiac output were normal despite the extremely low cardiac index. How could that be? It turned out that this low value was the result of a common error: failure to scrutinize adjustments in processed data. Cardiac index is a type of processed data, which is derived from cardiac output divided by body surface area, which is, in turn, derived from height and weight. On assessing this adjustment, the cardiologist found that the patient’s weight included the casts on his arms and leg. Although it is obvious that casts do not require perfusion, this is an example of blindly following protocol, in this case resulting in a gross overestimate of weight, overestimate of body surface area, and underestimate of cardiac index. The moral of the story is that blind adherence to adjustment protocols may cause clinical errors. Does this happen in research?
Corrections, adjustments, and technical limitations are common in imaging of preclinical and clinical vascular calcification, such as x-ray computed tomography (CT), intravascular ultrasound (IVUS), and, fused positron emission tomography (PET)-CT using the bone-seeking 18F-fluoride PET tracer. There is growing interest in using such imaging methods to infer molecular and cellular mechanisms of vascular calcification. However, colleagues …