We appreciate the interest of Dr Martins in our paper and thank him for his comments about our study. First of all we would like to state that discussion and argument are always positive in the scientific world. We agree that mean gray value (MGV), like three-dimensional power Doppler indices, is affected by attenuation. Certainly, we did not comment on this fact in our paper and we should have done. However, we would like to say that in this particular study, attenuation probably had only a small effect on the results, since the vast majority of deep infiltrating endometriosis (DIE) lesions are very close to the vaginal probe (2–3 cm). The idea of using a ratio between the MGV of DIE lesions and that of surrounding structures is certainly interesting. The cervix might be the best reference tissue and we shall analyze this concept in a future study. Regarding our comparison between Hounsfield units (HU) and MGV, the physical modalities are clearly different because computed tomographic (CT) analysis of HU is determined by the attenuation of the X-ray through the body tissues, whereas MGV is dependent on the differences in acoustic impedance of the tissues. However, it is our opinion that these two modalities can be considered similar from a conceptual point of view because of their potential in differentiating tissues quantitatively. However with both MGV and HU there are (similar) difficulties: it was well demonstrated in a recent publication1 that not only are HU values dependent on the tissue being examined but that they change markedly according to the keV (kiloelectronvolt) level used for the exam. This may produce such a big difference in HU values that the tissue might be misclassified as the wrong tissue type (e.g. fatty vs mixed). Moreover, on CT analysis of tissues, it has been demonstrated that the amount of keV applied may modify the tissue's spatial dimensions2 because of the different HU values that the tissues may show. It was for these reasons that we compared MGV with HU, knowing well each of these methods relies on different physical properties. Finally, regarding reproducibility, we agree that repeated acquisitions should be performed for proper assessment of reproducibility of the method and this can be considered as a weakness of our study. However, very few studies in the literature use repeated acquisitions, which is a very time-consuming procedure. S. Guerriero*†, L. Saba‡ and J. L. Alcazar§ †Department of Obstetrics and Gynecology, University of Cagliari, Cagliari, Italy; ‡Department of Imaging Science, Azienda Ospedaliero Universitaria di Cagliari, Cagliari, Italy; §Department of Obstetrics and Gynecology, University of Navarra, Pamplona, Spain *Correspondence. (e-mail: gineca.sguerriero@tiscali.it)