About this CT Effective Dose
In Computed Tomography (CT), the scanner reports radiation output in terms of CTDIvol and DLP (Dose Length Product). To understand the biological risk to the patient, these numbers must be converted into Effective Dose (measured in millisieverts, mSv). This calculator applies region-specific conversion factors ('k-factors') to estimate this dose.
Who this calculator is for
- Radiology staff, medical physicists, and trainees reviewing CT dose reports.
- People who already have a DLP value from a completed CT exam.
- Learners comparing adult region-based dose estimates across CT protocols.
When to use it
- Use this calculator after a scan to estimate effective dose from the reported DLP.
- Use it when teaching how body-region k-factors change the same DLP into different mSv estimates.
- Use it to create a quick planning estimate for protocol comparisons, not for patient-specific dosimetry.
How to use this calculator
- Locate the DLP value on the CT scanner's dose report page (usually at the end of the scan).
- Select the Body Region that was scanned (e.g., Head, Chest, Abdomen).
- The calculator estimates the Effective Dose in mSv and provides a comparison to chest X-rays.
Key assumptions
- The conversion uses standard adult k-factors and does not account for pediatric scaling or SSDE.
- Effective dose is a population-level risk estimate rather than a direct absorbed-organ dose for one patient.
- Scanner model, protocol design, tube current modulation, and patient size can materially change the real exposure context.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
Inputs explained
DLP (mGy*cm)
Dose Length Product. It represents the total energy absorbed by the patient across the entire scan length.
Body Region
The anatomical area scanned. Different regions have different k-factors (e.g., Head ≈ 0.0021, Chest ≈ 0.014).
Understanding your results
Example scenarios
Head CT
DLP 1000. k-factor 0.0021. Effective Dose = 2.1 mSv.
Chest CT
DLP 400. k-factor 0.014. Effective Dose = 5.6 mSv.
Key Features
- ICRP 103 k-factors
- X-Ray Equivalent comparison
- Instant mSv conversion
Things to Keep in Mind
This tool provides an estimate based on standard adult k-factors. Patient size, scanner geometry, and tube voltage significantly affect actual absorption. Not for clinical chart recording.
Tips & Best Practices
- This is a population-based estimate. Individual patient dose varies by size (SSDE) and age.
- Pediatric patients require significantly different k-factors (usually higher).
Glossary of Terms
- mSv
- Millisievert. A measure of the health effect of low levels of ionizing radiation on the human body.
- Background Radiation
- The average person receives about 3 mSv per year from natural sources (radon, cosmic rays).