Reply to: A Comment on ‘Apparent Diffusion Coefficient (ADC) in Distinguishing Haemangiomas from Malignant Vertebral Lesions in Whole-Body Diffusion-Weighted MRI’

by Jessica Winfield (Jessica.Winfield@icr.ac.uk)

Winfield, J.M., Poillucci, G., Blackledge, M.D. et al. Eur Radiol (2018) Apparent Diffusion Coefficient (ADC) İn Distinguishing Haemangiomas From Malignant Vertebral Lesions İn Whole-Body Diffusion-Weighted MRI. Eur Radiol 28: 1687. https://doi.org/10.1007/s00330-017-5079-2

Dear Dr Kuzan,

We thank you for your letter. We agree that the phenotype of bone metastases can influence ADC. Our previously published work in this journal (1) demonstrated significant differences between tumour types and significantly lower ADC in sclerotic metastases compared to lytic metastases. We also agree that ADC in bone marrow is influenced both by cellularity and marrow fat. Hence, ADC of marrow disease increases at early treatment time points as disease cellularity falls, but can decrease at later time points due to returning normal fatty marrow. The same study demonstrated a significant correlation between ADC and fat fraction measured by 2 point Dixon (2). We also concur that Granulocyte Colony Stimulating Factor can cause marrow hypercellularity which is evident on diffusion weighted MRI (3).

We agree that the high ADC of treated metastases could potentially result in misinterpretation as haemangiomas based on diffusion weighted imaging alone. However, the clinically relevant question is differentiation of haemangiomas from active malignant deposits which our study shows is possible. We also agree that diffusion weighted MRI should be interpreted in conjunction with other sequences (3,4) which reduces false positives.

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