Principles and safety

How each image is made, the densities, radiation, contrast and how to request a study.

10 pages

Choosing a study

• Choosing the right study: appropriateness and incidental findingsThe best scan answers the clinical question with the least risk
• Requesting a study and reading the reportA good request asks a clear question and gives the facts the radiologist needs; a good reader…

Modality

• CT: windows, Hounsfield units and contrast phasesA CT scanner spins an X-ray tube around the body and a computer builds thin slices, giving every…
• Gadolinium and the kidneyMRI contrast is removed by the kidneys
• How each imaging study makes a picture: X-ray, CT, ultrasound, MRI and nuclear medicineEach scan builds its picture from something different: X-rays passing through, sound echoes, a…
• Iodinated contrast: reactions and the kidneyThe iodine dye used in CT makes vessels and organs show up
• MRI safety: implants, metal and gadoliniumThe MRI magnet is always on and pulls on iron-containing metal
• MRI: T1, T2, FLAIR and diffusionMRI uses a strong magnet and radio waves, not X-rays
• Radiation in medical imaging: risk, ALARA and pregnancyX-rays and CT carry a small radiation risk, so each study should be needed and done with the…

Sign

• The five densities on an X-rayAn X-ray shows only five shades: air black, fat dark grey, water and soft tissue grey, bone…

A to Z

• A
• B
• C
• D
• F
• G
• H
• I
• K
• L
• M
• N
• P
• R
• S
• T
• U
• V
• W

← Radiology and diagnostic imaging

Educational content; it does not replace a radiologist's report and is not a clinical instruction. Each study is ordered on the patient's assessment and your institution's protocols.

Representative model, for educational purposes only.