Imaging biomarker

An imaging biomarker is a biologic feature, or biomarker detectable in an image. In medicine, an imaging biomarker is a feature of an image relevant to a patient's diagnosis. For example, a number of biomarkers are frequently used to determine risk of lung cancer. First, a simple lesion in the lung detected by X-ray, CT, or MRI can lead to the suspicion of a neoplasm. The lesion itself serves as a biomarker, but the minute details of the lesion serve as biomarkers as well, and can collectively be used to assess the risk of neoplasm. Some of the imaging biomarkers used in lung nodule assessment include size, spiculation, calcification, cavitation, location within the lung, rate of growth, and rate of metabolism. Each piece of information from the image represents a probability. Spiculation increases the probability of the lesion being cancer. A slow rate of growth indicates benignity. These variables can be added to the patient’s history, physical exam, laboratory tests, and pathology to reach a proposed diagnosis. Imaging biomarkers can be measured using several techniques, such as, X-ray, CT, Electroencephalography, Magnetoencephalography, and MRI.

Imaging biomarkers are as old as the X-ray itself. A feature of a radiograph that represent some kind of pathology was first coined "Roentgen signs" after Wilhelm Röntgen, the discoverer of the X-ray. As the field of medical imaging developed and expanded to include numerous imaging modalities, imaging biomarkers have grown as well, in both quantity and complexity as finally in chemical imaging.

A Quantitative Imaging Biomarkers (QIB) is an objective characteristic derived from an in vivo image measured on a ratio or interval scale as indicators of normal biological processes, pathogenic processes or a response to a therapeutic intervention. The advantage of QIB's over qualitative imaging biomarkers is that they are better suited to be used for follow-up of patients or in clinical trials. Examples of a frequently used QIB are the RECIST criteria, measuring the evolution in tumor size to assess treatment response for patients with cancer, the Nuchal scan used for prenatal screening, or the assessment of lesion load and brain atrophy for patients with Multiple Sclerosis.

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