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Apparent Diffusion Coefficient Distinguishes Malignancy in T1-Hyperintense Small Renal Masses
Daniel R Ludwig1, David H Ballard1, Anup S Shetty1
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, Campus Box 8131, Saint Louis, MO 63110.
Abstract:
OBJECTIVE. Small renal masses (< 4 cm) can be difficult to accurately classify as benign or malignant, particularly when they appear T1 hyperintense on MRI. This intrinsic signal, potentially related to intralesional hemorrhage, may limit evaluation of signal intensity on DWI. The purpose of this study was to test whether apparent diffusion coefficient (ADC) measurements may distinguish malignancy. MATERIALS AND METHODS. This single-center retrospective study identified patients with a T1-hyperintense renal mass less than 4 cm on MRI. Malignant lesions were pathologically proven; a benign mass was established by a predefined hierarchy of pathologic proof, follow-up ultrasound, or follow-up imaging showing more than 5 years of stability. T1 hyperintensity, defined as a signal intensity equivalent to or greater than the adjacent renal cortex, was confirmed by a senior abdominal radiologist. Two additional abdominal radiologists independently measured ADC of the lesion, which was normalized to the ADC of the background ipsilateral kidney and represented as ADCratio. RESULTS. The final cohort included 58 benign and 37 malignant renal lesions in 95 patients. Interrater agreement for ADC measurements was almost perfect (κ = 0.836-0.934). ADCratio was significantly lower in malignant compared with benign lesions (0.65 ± 0.29 vs 1.03 ± 0.32; p < 0.001). Malignant lesions were significantly larger than benign lesions (2.66 ± 0.86 cm vs 1.50 ± 0.65 cm; p < 0.001); however, after controlling for lesion size, ADCratio remained a significant predictor of malignancy (p < 0.001). CONCLUSION. ADCratio was highly reproducible for T1-hyperintense small renal masses and was significantly lower in malignant compared with benign renal masses.
Insights
Apparent diffusion coefficient ratio (ADC ratio) can distinguish malignant from benign small renal masses, even those with T1 hyperintensity on MRI. Lower ADC ratios indicate malignancy, offering a reproducible diagnostic tool for these challenging lesions.
Area of Science:
- Radiology
- Oncology
- Medical Imaging
Background:
- Small renal masses (< 4 cm) pose diagnostic challenges, especially when T1 hyperintense on MRI.
- T1 hyperintensity may be due to hemorrhage, complicating diffusion-weighted imaging (DWI) analysis.
- Accurate differentiation between benign and malignant small renal masses is crucial for appropriate management.
Purpose of the Study:
- To evaluate the efficacy of apparent diffusion coefficient (ADC) measurements in differentiating malignant from benign small renal masses.
- To assess the reproducibility of ADC measurements in T1-hyperintense renal lesions.
Main Methods:
- Retrospective study of patients with T1-hyperintense renal masses (< 4 cm) on MRI.
- Pathological confirmation for malignant lesions; benign status established by pathology, ultrasound, or stable imaging for >5 years.
- ADC measurements normalized to the ipsilateral kidney (ADC ratio) were independently performed by two radiologists.
Main Results:
- The study included 95 patients with 58 benign and 37 malignant lesions.
- ADC ratio was significantly lower in malignant lesions (0.65 ± 0.29) compared to benign lesions (1.03 ± 0.32; p < 0.001).
- ADC ratio remained a significant predictor of malignancy even after controlling for lesion size, demonstrating high interrater agreement (κ = 0.836-0.934).
Conclusions:
- ADC ratio is a highly reproducible metric for small renal masses with T1 hyperintensity on MRI.
- Lower ADC ratios effectively distinguish malignant from benign renal masses.
- ADC ratio shows promise as a non-invasive tool for characterizing small, T1-hyperintense renal lesions.
