1. What is Adrenal Adenoma CT Washout?

Adrenal adenoma CT washout calculation is a diagnostic method used to characterize adrenal masses detected on computed tomography. It helps differentiate benign adenomas from malignant lesions based on contrast enhancement patterns.

2. How Does the Calculator Work?

The calculator uses the washout percentage formula:

Where:

• \( \text{Peak} \) — Arterial phase Hounsfield Units (HU)
• \( \text{Delayed} \) — 15-minute delayed phase Hounsfield Units (HU)
• \( \text{Unenhanced} \) — Pre-contrast Hounsfield Units (HU)

Interpretation: Washout percentage >60% is highly suggestive of benign adrenal adenoma.

3. Importance of Washout Calculation

Details: Accurate washout calculation is crucial for characterizing incidental adrenal masses, avoiding unnecessary biopsies or surgeries for benign lesions, and guiding appropriate management decisions.

4. Using the Calculator

Tips: Enter Hounsfield Unit values from unenhanced, arterial phase, and 15-minute delayed phase CT scans. Ensure measurements are taken from the same region of interest in the adrenal mass.

5. Frequently Asked Questions (FAQ)

Q1: What is the clinical significance of >60% washout?
A: Washout percentage >60% is highly specific for benign adrenal adenomas, with sensitivity of 86-98% and specificity of 92-96%.

Q2: What are the typical HU values for adrenal adenomas?
A: Most adenomas have unenhanced HU <10, but lipid-poor adenomas may have higher values requiring washout calculation.

Q3: When is absolute vs relative washout used?
A: Absolute washout is preferred when unenhanced CT is available. Relative washout is used when only contrast-enhanced phases are available.

Q4: Are there limitations to this method?
A: Limited accuracy for masses <1 cm, pheochromocytomas may show rapid washout, and some metastases can mimic washout patterns.

Q5: What if washout is between 40-60%?
A: Indeterminate range - consider additional imaging (MRI with chemical shift) or follow-up imaging in 6-12 months.