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Medical Imaging Methods
Imaging methods use different physical signals to answer questions about body structure or function.
#Distinguish projection from cross-sectional imaging
An X-ray image records differences in how a beam passes through the body. Structures that absorb more of the beam appear differently from those that allow more through. NIH describes the detector turning this pattern into an image. This is a physical measurement, not a photograph of every detail inside the body.
CT also uses X-rays, but collects measurements from different directions and reconstructs cross-sectional images. NIBIB describes how successive slices can be displayed individually or assembled into a three-dimensional view. A conventional X-ray and CT therefore share a kind of signal but organise the information differently.
Evidence: NIH News in Health: medical scans explained / NIBIB: computed tomography
#Separate magnetic signals from sound echoes
MRI uses a strong magnetic field and radiofrequency signals to measure responses associated with protons in the body. The response depends on the tissue environment, allowing differences between tissues to be represented in an image. Unlike X-ray and CT, MRI does not use ionizing radiation.
Diagnostic ultrasound sends sound waves and measures returning echoes. NIBIB explains how the timing of echoes supports an image of tissue boundaries; Doppler methods can also supply information about movement and blood flow. Ultrasound does not use ionizing radiation either. This page concerns diagnostic imaging, not ultrasound treatment.
Evidence: NIBIB: magnetic resonance imaging / NIBIB: ultrasound
#Match the information to the question
Imaging methods are not interchangeable versions of one universal test. NIBIB describes MRI applications in soft tissues, CT reconstruction of cross-sectional anatomy, and limitations of ultrasound when sound meets bone or air. What can be seen depends on the method and the examination, not only on how detailed an image looks.
The absence of ionizing radiation does not mean an examination has no safety considerations. NIBIB describes MRI magnetic-field hazards and potential biological effects of ultrasound. These are reasons to distinguish methods, not a personal safety clearance. This overview gives no scan selection, preparation, device setting, radiation dose or contrast advice.
Evidence: NIBIB: computed tomography / NIBIB: magnetic resonance imaging / NIBIB: ultrasound
#Read images through a report and clinical context
RadiologyInfo describes a report that records the type of exam, the clinical history or reason for it, relevant earlier imaging, the technique, findings and an impression. The findings describe observations; the impression brings the important observations together and may describe possible explanations or further assessment.
A report may not answer the original clinical question. Earlier images, symptoms and laboratory information can matter to interpretation. An image, its report and a completed care decision are different steps. This site explains the structure of imaging information; Mynd does not scan patients or interpret a personal image through this page.
Source note
The sections above were checked against the linked sources. No clinical review has been performed. This is general research education, not a clinical guideline.