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OpinionDOI Number : 10.36811/ojrmi.2021.110019Article Views : 0Article Downloads : 0

The rule of two in Radiology: An Update

Abdulwahab Alahmari

Radiology Specialist, Radiology Department, Al-Namas General Hospital, Ministry of Health, Al-Namas City, Saudi Arabia

*Corresponding Author: Abdulwahab Alahmari, Radiology Specialist, Radiology Department, Al-Namas General Hospital, Ministry of Health, Al-Namas City, Saudi Arabia, Tel: +966562428716; Email: [email protected]

ORCID ID: 0000-0002-9959-830X

Article Information

Aritcle Type: Opinion

Citation: Abdulwahab Alahmari, et al. 2021. The rule of two in Radiology: An Update. O J Radio Med Img. 4: 55-56.

Copyright: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Copyright © 2021; Abdulwahab Alahmari

Publication history:

Received date: 28 September, 2021
Accepted date: 06 October, 2021
Published date: 07 October, 2021

There are 10 rules used in medicine/radiology that taught to students so they can remember certain points that they have to do to have an accurate diagnosis. These rules are:-

1- Two views: One view is too few;
2- Two joints: Above and below the injured bone;
3- Two sides: Compare with the other normal side;
4- Two abnormalities:Find a second abnormality;
5- Two occasions: Compare the current x-ray with a previous one (especially in CXR);
6- Two visits: Repeat after an interval or a procedure;
7- Two opinions: Ask for a second opinion or use the red dot system;
8- Two records: Write down the radiographic and clinical finings;
9- Two specialists: Get a radiology report;
10- Two examinations: Ask for CT, MRI, US, NM, etc.

But, these rules are more focused for emergency physicians and it’s limited for x-ray. Therefore, these rules need to be extended to address certain radiological important points to be remembered. .

11- Two axis: On a CT scan, make a reconstitution of sagittal and coronal plans and check them during interpretation;
12- Two organs: Do not limit the brain MRI scan to the brain, but include the upper part of the spinal cord;
13- Two regions: When you do a CT chest take the upper part of the abdomen to the tip of the liver and when you do a CT abdomen take the whole pelvis in the scan;
14- Two windows: During interpretation use two windows (i.e. on chest a CT use lung window and mediastinal window or on a brain CT check the brain window and bone window);
15- Two contrasts: Use IV and oral or IV and rectal contrast -when needed- is better in trauma cases than a single contrast.
16- Two patients: In the same category for example in determining the bone age, we need to compare a pediatric patient with other pediatric patients (at least two patents) in the same age and gender;
17- Two measurements: Take the measurements twice and take the average;
18- Two scans; A plain and with contrast scans;
19- Two images: A negative (x-ray) and positive (fluoroscopy) images;
20- Two levels: The creatinine and GFR level before IV contrast media study.


1. Chan O. 2012. ABC of emergency radiology. John Wiley & Sons.

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