Calculator Inputs
Example Data Table
| Case | Unenhanced HU | Enhanced HU | Delayed HU | Absolute Washout | Relative Washout | Pattern |
|---|---|---|---|---|---|---|
| Example A | 24 | 100 | 52 | 63.16% | 48.00% | Adenoma-supporting washout |
| Example B | 35 | 85 | 70 | 30.00% | 17.65% | Indeterminate or non-adenoma range |
| Example C | 8 | 55 | 32 | 48.94% | 41.82% | Lipid-rich attenuation with relative threshold met |
Formula Used
Absolute Washout Percentage:
Absolute Washout = ((Enhanced HU - Delayed HU) / (Enhanced HU - Unenhanced HU)) × 100
Relative Washout Percentage:
Relative Washout = ((Enhanced HU - Delayed HU) / Enhanced HU) × 100
Common supportive thresholds are 60% or greater for absolute washout and 40% or greater for relative washout. Unenhanced attenuation of 10 HU or lower often supports a lipid-rich adenoma pattern in a homogeneous lesion.
How to Use This Calculator
- Enter the unenhanced attenuation from the adrenal nodule ROI.
- Enter the enhanced attenuation from the contrast phase.
- Enter the delayed attenuation from the delayed phase.
- Add lesion size, delayed timing, ROI coverage, and morphology.
- Press Calculate to show the result above the form.
- Use the CSV or PDF buttons to save the report.
Advanced Adrenal Washout Review
Purpose
Adrenal nodules are often found during abdominal imaging. Many are benign adenomas. Some need closer review. A washout calculation helps compare CT attenuation across unenhanced, enhanced, and delayed phases. It measures how quickly contrast leaves the lesion.
Why Washout Matters
Adenomas often enhance and then lose contrast faster than many non-adenomas. This behavior can support a benign pattern. The calculator reports absolute washout and relative washout. Absolute washout uses the unenhanced value. Relative washout is useful when only enhanced and delayed values are considered.
Input Quality
Good measurements matter. Use the same lesion area across all phases. Avoid vessels, edges, calcification, necrosis, and hemorrhage. A larger region of interest can reduce sampling error. The delayed scan is commonly measured around fifteen minutes. Different protocols may change confidence.
Interpreting Results
An absolute washout of sixty percent or more supports an adenoma pattern. A relative washout of forty percent or more also supports that pattern. An unenhanced value of ten HU or lower suggests lipid-rich adenoma in a homogeneous lesion. These findings should not stand alone.
Important Limits
Washout can be misleading. Hypervascular metastases, pheochromocytoma, and adrenal carcinoma may overlap with adenomas. Heterogeneous lesions need careful radiology review. Known cancer history changes risk. Hormonal testing may still be needed, even when imaging appears benign.
Practical Use
This tool creates a structured report for documentation. It highlights thresholds and caution flags. It also exports results for records. Use it as a calculation aid. Final decisions should come from qualified clinicians using the full clinical picture.
FAQs
What does adrenal washout measure?
It measures how much contrast leaves an adrenal nodule between enhanced and delayed CT phases. Faster washout can support an adenoma pattern when morphology and clinical context are suitable.
What is absolute washout?
Absolute washout compares contrast loss with the enhancement above the unenhanced baseline. It needs unenhanced, enhanced, and delayed attenuation values from the same lesion.
What is relative washout?
Relative washout compares contrast loss with the enhanced attenuation value. It can be calculated without using the unenhanced value, but interpretation still needs caution.
Which threshold suggests adenoma?
Common supportive thresholds are absolute washout of at least 60% or relative washout of at least 40%. These values do not prove benign disease by themselves.
Does low unenhanced HU matter?
Yes. A homogeneous adrenal nodule measuring 10 HU or lower on unenhanced CT often supports a lipid-rich adenoma pattern. Clinical context remains important.
When is washout less reliable?
Washout is less reliable with heterogeneous, hemorrhagic, necrotic, or calcified lesions. It is also less specific in patients with known malignancy or hypervascular metastases.
Can this calculator diagnose cancer?
No. It only performs arithmetic and displays common imaging thresholds. Diagnosis requires radiology review, clinical history, laboratory testing, and follow-up when appropriate.
Why add ROI coverage?
ROI coverage helps document measurement quality. A small or poorly placed ROI can misrepresent the nodule and reduce confidence in the calculated washout result.