Adrenal Nodule MRI Calculator

Adrenal Nodule MRI Calculator for Endocrinology. The percentages describe signal behavior, not hormonal activity or definitive benignity. If opposed-phase signal exceeds in-phase signal, a negative index is retained for review rather than called malignant. No biopsy, follow-up or surgical recommendation follows automatically.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

Signal-intensity index = 100 x (lesion in-phase minus opposed-phase signal) / lesion in-phase signal. The adrenal-to-spleen phase ratio = (lesion opposed-phase / spleen opposed-phase) / (lesion in-phase / spleen in-phase). All inputs are comparable MRI signal intensities, not CT attenuation in HU.

When to use this calculator

Use to check quantitative chemical-shift arithmetic after a radiologist obtains appropriate matched regions of interest. The cited 2003 primary study evaluated these methods in a specific cohort. Its historical discrimination thresholds are not applied as universal diagnoses here.

Inputs used

  • Lesion in-phase and opposed-phase MRI signal intensities
  • Spleen in-phase and opposed-phase MRI signal intensities

Clinical interpretation

The percentages describe signal behavior, not hormonal activity or definitive benignity. If opposed-phase signal exceeds in-phase signal, a negative index is retained for review rather than called malignant. No biopsy, follow-up or surgical recommendation follows automatically.

Worked example

Lesion signals 480 in-phase and 150 opposed-phase give an index of 68.750%. With spleen signals 520 and 500 respectively, the adrenal-to-spleen phase ratio is (150/500)/(480/520) = 0.32500. Equal lesion phase signals give zero signal loss.

Limitations and safety notes

Sequence parameters, artifacts and region-of-interest placement affect measurements. This version requires all four signals and rejects zero denominators. It does not analyze images, substitute for an adrenal protocol or transfer CT washout criteria to MRI. A radiology and endocrine assessment may still be necessary.

Frequently asked questions

Can I enter CT Hounsfield units?

No. This calculator requires MRI signal intensities from matched phases; CT washout is a different calculation.

Does a large signal loss prove an inactive benign lesion?

No. Signal loss is one imaging observation. Hormonal activity and overall lesion assessment require separate evaluation.

References

  • Fujiyoshi et al. 2003 primary chemical-shift MRI study; signal-intensity index formula and adrenal-to-spleen comparison. Historical cohort thresholds are not universal diagnoses. https://pubmed.ncbi.nlm.nih.gov/12760936/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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