EM · Imaging choice and radiation risk
Imaging choice and radiation risk in the emergency department
Also known as Modality selection · Radiation dose and ALARA · Appropriate imaging · Contrast risk and nephrogenic systemic fibrosis · Imaging in pregnancy · CT versus MRI versus ultrasound · Contrast-associated acute kidney injury · Choosing Wisely imaging
Imaging choice and radiation risk — the structured selection of the modality (X-ray, CT, MRI, ultrasound) that answers the clinical question at the lowest risk, governed by ALARA and the linear-no-threshold model. The effective doses (CXR 0.02 mSv, CT head 2 mSv, CT abdomen 10 mSv against a 2–3 mSv/yr background); the stochastic (cancer) and deterministic (skin erythema, cataract, infertility) effects; the four-modality differential with speed, cost, sensitivity and operator-dependence; the pregnancy pathway (ultrasound first, MRI second, CT last, never withhold a life-saving image on dose alone); the contrast risks — iodinated contrast-associated AKI and gadolinium-associated nephrogenic systemic fibrosis with the group I/II/III agent stratification; the appropriateness criteria and the Choosing Wisely do-not list. ACEM-primary, globally tagged.
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Meet the patient
A 28-year-old woman at 26 weeks sits in bay 1 with right-lower-quadrant pain, a fever and a positive Rovsing sign; her appendicitis is real, and she is terrified that a CT will harm the baby.[5]
In bay 4, an 82-year-old septic man with a creatinine of 240 and an eGFR of 22 needs a CT abdomen, and the registrar is asking whether to stop the metformin and whether gadolinium is banned in renal failure.[3]
Two patients, one ward round, and every principle on this page lives between them. The two questions that decide every request are the two you must hold all day: will this image change what I do? and what is the lowest-dose modality that answers it?[1]
You have read the opening of this topic. The complete unit — every section and its primary-source references — is part of the Emergency Medicine fellowship atlas.
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- [1]Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog Radiology, 2008.PMID 18566177
- [2]Mettler FA Jr. Patient Exposure from Radiologic and Nuclear Medicine Procedures in the United States: Procedure Volume and Effective Dose for the Period 2006-2016 Radiology, 2020.PMID 32181730
- [3]Weinreb JC, Rodby RA, Yee J, et al. Use of Intravenous Gadolinium-based Contrast Media in Patients with Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation Radiology, 2021.PMID 33170103
- [4]Rudnick MR, Fay K, Wahba IM Fluid administration strategies for the prevention of contrast-associated acute kidney injury Curr Opin Nephrol Hypertens, 2022.PMID 35894275
- [5]Qamar SR, Green CR, Ghandehari H, et al. CETARS/CAR Practice Guideline on Imaging the Pregnant Trauma Patient Can Assoc Radiol J, 2024.PMID 38813997
- [6]Weisbord SD, Gallagher M, Jneid H, et al. Outcomes after Angiography with Sodium Bicarbonate and Acetylcysteine N Engl J Med, 2018.PMID 29130810
- [7]Kanda T, Oba H, Toyoda K, et al. Brain gadolinium deposition after administration of gadolinium-based contrast agents Jpn J Radiol, 2016.PMID 26608061
- [8]McDonald JS, Larson NB, Kolbe AB, et al. Prevention of Allergic-like Reactions at Repeat CT: Steroid Pretreatment versus Contrast Material Substitution Radiology, 2021.PMID 34342504