Re: Evaluation of hepatic hemangiomas with diffusion weighted imaging.

Dear Sir,

We are pleased to read the interesting article by Nam et al. (1) published in the November/December issue of the 2012 Korean Journal of Radiology. The authors examined the correlation between the apparent diffusion coefficient (ADC) value of hepatic cavernous hemangiomas with enhancement patterns.

Since we have a special interest on the subject (2-4) of diffusion magnetic resonance imaging (2-4), we would like to contribute to the evaluation of hepatic hemangiomas with diffusion weighted imaging (DWI).

In the results section, the authors have mentioned about the findings on hemangiomas, which have low ADC values and take on low contrast media. We find this as a valuable contribution to the literature and our practice, as hemangiomas which have low ADC values and take on low contrast media are not common (5, 6).

The authors have found a statistically significant difference between the compared b values at the well contrasted hemangiomas using b 50, 400 sequence. If it could have been possible to use smaller b values, the statistically significant difference between ADC values, noted by the authors, would have been even more significant.

When b is smaller than 200, the sequences are more sensitive to perfusion rather than diffusion. In evaluating hemangiomas with good contrast, using DWI sequences, which have b values sensitive to perfusion (b < 200), has been suggested in the literature (5, 6). Additionally, a DWI sequence with b < 200, known as a blackblood sequence, is superior to the T2 sequence in the determination of hemangiomas and metasthases (6).

Finally in the last paragraph, the authors mentioned that hypervascular solid tumors can be distinguished by their low ADC's from the rapidly enhancing hemangiomas showing high ADCs. Here, it is not very clear whether malignant or benign (or both) hypervascular solid tumors are discussed, and this may cause confusion to the reader. To further clarify this subject, it might have been better to mention that the benign hypervascular solid tumors have relatively higher ADC values than the malignant, as one would see in focal nodular hyperplasia (FNH). In FNHs, there are higher ADC values than the malignant hypervascular solid tumors (however, ADC values of FNH and hepatocellular carcinoma can overlap [6]); yet, these ADC values are still lower than the rapidly enchancing hemangiomas when b values larger than 200 are used (5).