CT

Conversion coefficients for dose estimation from dose-length product (DLP) in CT examination

Radiation dose from a CT examination in standard body regions can be estimated from the dose-lenght product (DLP) that each CT outputs. This table shows known commonly used coefficients and their adjustment in two particular CT machines. The calculation of the efective dose estimation is:

E(mSv) = coefficient * DLP * 0.001

The most recent recommendation is based on the ICRP 103 publication (last column).
 

Scanned body region

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

Calcium score (Agatston) - risk level for significant coronary artery disease (CAD)

Coronary calcium score is an independent predictor of risk of significant coronary artery disease. It may refine overall risk of coronary artery disease estimated with conventional risk factors. It is based on CT examination and calculation of the Agatston score from the images.

Calcium score Risk of significant CAD
0 very low
≤10 low
≤100 moderate
≤400 moderately high

Maximum allowable contrast dose in adults - calculator of MACD

In healthy adult individuals, the maximum allowable volume of intravenous iodine contrast is:
≤300mL (with concentration 300mg I/mL).
In patients with renal insufficiency in particular, the volume of the contrast should be as low as reasonable. However, it should not exceed
440 x weight [kg] / creatinine [µmol/L] mL
resp.
5 x weight [kg] / creatinine [mg/dL] mL
(with concentration 300mg I/mL).

Estimate of liver volume on CT or MRI - calculator

This formula can be used to estimate volume of the liver on crossectional imaging methods by measuring its maximum dimension in three perpendicular axes - caudocranial (CC), latero-lateral (LL), antero-posterior (AP). A normal value is considered <2000mL.

Volume = CC x LL x AP x 0.31

Subarachnoid hemorrhage - Fisher CT grading scale of subarachnoid bleeding

Fisher CT grading scale is used to grade severity of intracranial subarachnoid hemorrhage associated with rupture of an intracranial aneurysm. This scale predicts the risk of subsequent arterial spasms.

Group Description
Group I no hemorrhage
Group II subarachnoid hemorrhage <1mm thick
Group III subarachnoid hemorrhage >=1mm thick
Group IV

Intracranial aneurysm - description of size and neck + calculator

Apart from giving the dimensions of an intracranial aneurysm, its size should be cathegorized according to this table.

Description Size
Small ≤5mm
Medium <15mm
Large <25mm
Giant ≥25mm

The diameter of the neck of the aneurysm is cathegorized as well.

Description Size

Germinal matrix hemorrhage - grading of intracranial bleeding in neonates

Grading of intracranial hemorrhage in neonates is based on ultrasound imaging. It has four grades with increasing mortality and decreasing outcome.

Grade Description
Grade I hemorrhage is confined to the germinal matrix
Grade II intraventricular hemorrhage without ventricular dilation
Grade III intraventricular hemorrhage with ventricular dilation
Grade IV

Shoulder impingement syndrome - Neer classification

Neer classification divides lesions of the rotator cuff into three stages that typically succeed in this order during one's life.

Stage Description Age group
Stage I actue inflammation, edema, hemorrhage in the rotator cuff younger patients <25 years
Stage II progression to fibrosis and tendinitis of the rotator cuff usually between 25 and 40 years
Stage III

Idiopathic interstitial pneumonia - classification by the American Thoracic Society (ATS) and the European Respiratory Society (ERS)

This multidisciplinary concensus was adopted in 2001 by both the American Thoracic Society (ATS) and the European Respiratory Society (ERS) in order to standardize classification of the idiopathic interstitial pneumonias.

Name Interstitial pulmonary fibrosis Non-specific interstitial pneumonia Cryptogenic organising pneumonia Acute interstitial pneumonia Desquamative interstitial pneumonia Respiratory bronchiolitis - Interstitial lung disease
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