1. What is Adrenal Adenoma MRI Washout Calculation?

The adrenal adenoma MRI washout calculation is a quantitative method used to characterize adrenal lesions on contrast-enhanced CT or MRI. It helps differentiate benign adrenal adenomas from malignant lesions based on their contrast washout characteristics.

2. How Does the Calculator Work?

The calculator uses the relative washout percentage formula:

Where:

• \( \text{Pre} \) — Hounsfield Units (HU) pre-contrast
• \( 15\text{min} \) — Hounsfield Units (HU) at 15 minutes post-contrast
• \( \text{Baseline} \) — Hounsfield Units (HU) delayed phase

Interpretation: Washout percentage >40% suggests benign adrenal adenoma, while ≤40% is suspicious and may require further evaluation.

3. Importance of Washout Percentage

Details: The relative washout calculation is crucial for characterizing adrenal lesions found incidentally on imaging. It helps avoid unnecessary biopsies or surgeries for benign adenomas while identifying lesions that require further investigation.

4. Using the Calculator

Tips: Enter Hounsfield Unit values from the pre-contrast, 15-minute post-contrast, and delayed phase images. Ensure measurements are taken from the same region of interest in the adrenal lesion.

5. Frequently Asked Questions (FAQ)

Q1: What is the clinical significance of >40% washout?
A: A washout percentage greater than 40% is highly suggestive of a benign adrenal adenoma, with sensitivity and specificity exceeding 95% for lipid-rich adenomas.

Q2: Are there different types of washout calculations?
A: Yes, there are absolute washout and relative washout calculations. This calculator uses relative washout, which is more commonly used in clinical practice.

Q3: What if the washout is borderline (around 40%)?
A: Borderline cases may require additional imaging, clinical correlation, or follow-up to ensure accurate characterization of the adrenal lesion.

Q4: Can this calculation be used for all adrenal lesions?
A: The washout calculation is most reliable for lesions >1 cm. Very small lesions or those with atypical features may require different diagnostic approaches.

Q5: How accurate is MRI for adrenal lesion characterization?
A: MRI with chemical shift imaging and washout calculations has high accuracy (85-95%) for differentiating adrenal adenomas from metastases or other malignant lesions.