Built and fact-checked by the DocNectar team — see our editorial standards
Key Features
Instant Calculation
Get accurate results in real time with our optimized algorithm.
Mobile Friendly
Fully responsive design. Works on all devices & screen sizes.
Privacy Focused
Your data stays on your device. We don't store any inputs.
100% Free
No hidden costs. This tool is completely free forever.
Computes adrenal CT washout percentages from Hounsfield unit (HU) attenuation values at three phases, using the standard published radiology formulas (as described in Boland GW et al., "Adrenal masses: characterization with combined unenhanced and delayed enhanced CT", Radiology, 1997, and widely used since): Absolute washout % = ((enhanced HU - delayed HU) / (enhanced HU - unenhanced HU)) x 100. Relative washout % = ((enhanced HU - delayed HU) / enhanced HU) x 100, used when an unenhanced phase is unavailable. Commonly cited thresholds (absolute washout > 60%, relative washout > 40%) are suggestive of a benign adrenal adenoma. This is pure arithmetic on values you already have — a reference calculation, not a standalone diagnosis. For general reference and educational purposes only; interpretation should be done by a radiologist alongside the full imaging study.
How it works
Enter the unenhanced, enhanced (portal venous), and delayed attenuation values in Hounsfield units. The tool calculates both absolute and relative washout percentages.
- Enter unenhanced attenuation (HU).
- Enter enhanced / portal venous attenuation (HU).
- Enter delayed attenuation (HU, typically 15 min).
- Click Calculate to see your results.
Examples
Unenhanced 10 HU, enhanced 90 HU, delayed 40 HU
Absolute washout = (90-40)/(90-10) x 100 = 62.5%. Relative washout = (90-40)/90 x 100 = 55.6%.
Who should use it
- Reviewing adrenal CT washout alongside a radiology report.
- Radiology education about adrenal mass characterization.
Industry applications
- Radiology and endocrinology reference
- Radiology resident education
Advantages
- Standard, widely used radiology formula.
- Computes both washout metrics from the same three inputs.
Limitations
- Requires all three CT phases to be available.
- A reference calculation only — not a substitute for radiologist interpretation.
Common mistakes to avoid
- Measuring the region of interest (ROI) inconsistently across the three phases.
- Using relative washout thresholds when absolute washout data is actually available (they are not interchangeable).
Best practices
- Use the same ROI size and location across all three phases for consistent measurements.
Tips
- Washout is one of several features (also including unenhanced HU and imaging appearance) radiologists use together to characterize an adrenal mass.