Welcome to Classifications and Online Calculators in Radiology

This site was build along with the Atlas of Radiology Images to support your knowledge in radiology.

You will find here:

that are used in radiology and related fields with free access.


  • Some pages are accompanied by illustrations
  • All pages contain tags for easy navigation

The concept

The concept of this website is based on a previous site that was founded in 2008 and is still up and running. The website is composed as a book, where all sources are properly referenced, according to a good practice in scientific publications.

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    C-RADS - reporting system for CT colonography

    In July 2005, Radiology published a consensus proposal for reporting in CT colonography. It has similar purpose and structure as Bi-RADS reporting system in breast imaging. According to this proposal, lesions and massess should be describes by:

    • Lesion size: the largest dimension (excluding stalk in pedunculated polyps) measures on MRP or 3D views.
    • Morphology:
      • Sessile: broad-based with height > width
      • Pedunculated: polyp with a stalk
      • Flat: polyp with height < 3mm above the surrounding mucosa
    • Location: defined by six standard colonic segments: rectum, sigmoid, desceding, transverse, ascending colon, and cecum
    • Attenuation: CT density expressed as
      • Soft tissue
      • Fat

    Categorization of colonic findings

    Category Description
    C0 Inadequate study or awaiting prior study for comparison
    • inadequate preparation, where lesions ≥10mm can not be excluded due to abundant fluid or feces
    • inadequate insufflation with one or more colonic segments collapsed on both views
    • awaiting prior study for comparison
    C1 Normal colon or benign lesion - continue routine screening
    • no abnormality of the colon found
    • no polyp ≥6mm
    • non-neoplastic findings - diverticula, inverted diverticulum, lipoma, etc.
    C2 Intermediate polyp or indeterminate finding - surveillance or colonoscopy recommended
    • <3 polyps 6 - 9mm
    • indeterminate finding where polyp ≥6mm can not be excluded despite technically adequate exam
    C3 Polyp, possibly advanced adenoma - follow-up colonoscopy recommended
    • polyp >=10mm
    • ≥3 polyps 6 - 9mm
    C4 Colonic mass, likely malignant - surgical consultation recommended
    • lesion compromises colonic lumen
    • extracolonic invasion

    Categorization of extracolonic findings

    Category Description
    E0 Limited exam - compromised by artifacts, severly limited evaluation of extracolonic soft tissues
    E1 Normal exam or anatomic variant - no extracolonic pathology found
    • ureter fissus, retroaortic renal vein as anatomic variants, etc.
    E2 Clinically unimportant finding - no workup indicated
    • simple cysts in liver or kidney
    • uncomplicated cholecystolithiasis (gallstones)
    • vertebral hemangioma, etc.
    E3 Likely unimportant finding, incompletely characterized - workup may be indicated based on local practice and patient preference
    • minimally complex or homogeneously hyperattenuating kidney cysts, etc.
    E4 Potentially important finding - further workup according to accepted practice guidelines
    • solid renal mass
    • lympadenopathy
    • aortic aneurysm
    • parenchymal nodule in lung ≥=1cm, etc.


    1. Zalis ME, Barish MA, Choi JR, Dachman AH, Fenlon HM, Ferrucci JT, et al. CT Colonography Reporting and Data System: A Consensus Proposal. Radiology. 2005 Jul 1;236(1):3–9.
    2. Summers RM. Polyp Size Measurement at CT Colonography: What Do We Know and What Do We Need to Know? Radiology. 2010 Jun;255(3):707–20

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