Department of Obstetrics and Gynecology, National Cheng Kung University Hospital, 138 Victory Road, Tainan 70428, Taiwan
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The valuable comments by Dr N.J.Raine-Fenning are welcome. We have answered the questions one by one below.
First, we agree that there were several studies using 2D pulsed-wave Doppler ultrasound in the assessment of ovarian stromal blood flow. Those, however, only detected one segment of the vessels within ovarian stroma and it was rather difficult to depict the same vessel or the same segment next time. In other words, the reproducibility for 2D pulsed-wave Doppler is low. In addition, there was the aliasing effect for the 2D pulsed-wave Doppler ultrasound in assessment of ovarian stromal blood flow. In our report, we emphasized that this is the first report to assess the whole ovarian stroma flow signals using the 3D power Doppler ultrasonography (3D-PDU) with the use of the Virtual Organ Computer-Aided Analysis (VOCAL) method. The results showed the whole blood flow and flow intensity of polycystic ovarian syndrome (PCOS). In this study, we did not compare these two techniques. However, we agree that a prospective study testing these two methods is necessary and it is being undertaken now at our lab.
Second, we are sorry to admit that the vascularization flow index (VFI) is the ratio of weighted colour voxels/(total voxels background voxels) (Pairleitner et al., 1999). It was cited incorrectly in the text. Thank you for your correction. However, our VFI data are correct as they were retrieved from the VOCAL software, which uses the formula defined by Pairleitner et al. (Pairleitner et al., 1999
).
Third, we have already paid attention to the reproducibility of 3D ultrasound for a long time in our lab. In this series of ovarian stromal flow assessment by 3D-PDU, all the data acquisition was undertaken by only one observer, so we did not have inter-observer reproducibility data in this paper. As for the number of scans, we scanned the ovaries by a transvaginal probe of 3D-PDU three times for each patient. The observer chose the best view of the ovary and recorded it only. During the procedure, we asked the patient to hold their breath during volume acquisition to eliminate body movement. The sweeping time only takes 23 s for an ovary. From our preliminary result, we do not consider 3DPDU to be a difficult technique to reproduce. However, we agree that the inter-observer reliability test is mandatory for the clinical setting, which is being undertaken now at our unit.
Fourth, the good reproducibility of the VOCAL method has been recently demonstrated by other investigators (Bordes et al., 2002; Raine-Fenning et al., 2002
). As you know, we cannot agree with you more that the setting of the 3D-PDU is the most important prerequisite for a 3D-PDU study, because different settings will have different results. In our study, we used the VOCAL software from the Medison-Kretz Company with the manual mode for each rotation plane with 15 degrees. In addition, we used the following setting of Voluson 530D machine with actual power: 2dB, and pulse repetition frequency: 1.0. All the rest of the setting conditions were described in the text. As mentioned in our paper, we kept the same conditions for every patient in this study. We believe our setting should be useful for further studies in different institutions.
Fifth, we agree the attenuation effect of 3D-PDU may play a role in flow indexes and have paid attention to it in our study. However, in this study we used a 7 MHz transvaginal probe, which is very close to the ovary (i.e. the distance between the ovary and the probe is minimal) and thus minimizes the attenuation effect. In other words, the environment between the probe and the ovary for each patient is similar, and therefore we could compare different groups in our study.
Finally, as Dr Raine-Fenning stated, we may be right that 3DPDU is probably more representative of total ovarian blood supply and it may well be more reproducible. We agree that we should compare the pulsed-wave Doppler and the 3D-PDU to reach the conclusion that 3D-PDU is more accurate than other methods. Nevertheless, we cannot agree with Dr Raine-Fenning that 3D-PDU may not provide substantial assistance to the management of PCOS. In our paper, we have demonstrated that 3D-PDU can be of help in differential diagnosis between PCOS patients and controls, and it is now used in our clinical practice as a helpful criterion. In our opinion, it is not appropriate to insist that 3D-PDU may be useful in a clinical setting only after we prove that 3D-PDU is better than pulsed-wave Doppler in measuring blood flow changes. In conclusion, although further studies on the reproducibility and comparison with other pulsed-wave Doppler are mandatory, we believe that the combination of 3D-PDU and VOCAL can be a good modality for the diagnosis and the management of PCOS.
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Notes |
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References |
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Pairleitner, H., Steiner, H., Hasenoehrl, G. and Staudach, A. (1999) Three-dimensional power Doppler sonography: imaging and quantifying blood flow and vascularization. Ultrasound Obstet. Gynecol., 14, 139143.[ISI][Medline]
Raine-Fenning, N., Campbell, B., Collier, J., Brincat, M. and Johnson, I. (2002) The reproducibility of endometrial volume acquisition and measurement with the VOCAL-imaging program. Ultrasound Obstet. Gynecol., 19, 6975.[ISI][Medline]