Hum. Reprod. Advance Access originally published online on February 8, 2007
Human Reproduction 2007 22(5):1327-1334; doi:10.1093/humrep/dem001
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Ultrasound-guided embryo transfer does not offer any benefit in clinical outcome: a randomized controlled trial
Centre for Reproductive Medicine, Dutch-Speaking Brussels Free University, Brussels, Belgium
1 To whom correspondence should be addressed at: Centre for Reproductive Medicine, Dutch-Speaking Brussels Free University, Brussels, Belgium. E-mail: kosmasioannis{at}gmail.com
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Abstract |
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BACKGROUND: Ultrasound-guided embryo transfer (ET) is widely suggested as a standard clinical practice that improves overall embryo implantation and pregnancy rates. Various studies of this issue suffer from methodological pitfalls, so that a randomized controlled trial, which overcomes these problems, might be valuable.
METHODS: Three hundred women aged <40, who underwent fresh ET, were included in this randomized, double-blind controlled trial. The K-J-SPPE echo tip soft catheter was used for the ultrasound-guided ET and the traditional K-Soft catheter for ETs not using ultrasound. One experienced operator performed all ETs. The primary study outcome was overall pregnancy rate (defined as the number of positive hCG results per transfer).
RESULTS: No significant differences between groups were found regarding baseline patient and embryological characteristics, except for male factor and unexplained infertility (higher in the blind and ultrasound-guided ET group, repectively, P < 0.05). Overall pregnancy rates were 53.3 and 51.3% in the ultrasound-guided and blind ET group, respectively. Two ectopic pregnancies were reported in each group. Difficulty in cervical negotiation did not differ between the two groups.
CONCLUSIONS: In patients undergoing ET by an experienced operator, ultrasound guidance did not provide any benefit in terms of overall clinical pregnancy and embryo implantation rates.
Key words: embryo transfer/implantation/IVF/pregnancy/ultrasound
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Introduction |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionAcknowledgementReferences |
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Embryo trasnfer (ET) is the final important step in IVF. A meta-analysis of eight randomized trials by Buckett (2003)
showed that embryo replacement under ultrasound guidance improves implantation and pregnancy rates. Many authors consider guidance during difficult transfers and proper placement of embryos in the uterine cavity as the two main benefits that the method offers. A disadvantage is that this method requires extra time and personnel. However, the experience of operators might account for the variable overall pregnancy rates, even without ultrasound-guided ET (Coroleu et al., 2002; Garcia-Velasco et al., 2002).
Therefore, despite wide acceptance of ultrasound as a guiding tool during ET, some controversies remain. In a study by Prapas et al. (2001), no significant difference was found in pregnancy rates for day 5 ETs using ultrasound guidance and not using ultrasound (blind). Garcia-Velasco et al. (2002) found no significant difference in the outcome of oocyte donation cycles after ET with or without ultrasound guidance. Kan et al. (1999) reported that only women 
37 years achieved higher pregnancy rates under ultrasound-guided ET.
The size of pooled studies in the meta-analysis by Buckett (2003) is large enough to show a significant difference in pregnancy rates, which favours ultrasound-guided ET. Nevertheless, one could challenge randomization and the possibility of bias in some of the studies. Only one of the randomized controlled trials (Tang et al., 2001) included in the meta-analysis had sufficient power to illustrate a 7% difference between the two groups.
So far, ultrasound-guided ET studies have been carried out on patients with a full bladder. In a recent pilot study by Lorusso et al. (2005), no difference in implantation and clinical pregnancy rates was found using ultrasound-guided ET, whether implemented with a full bladder or not. The number of patients included in this study was insufficient to achieve definite conclusions. The authors concluded that a full bladder is not a necessity for a successful outcome, although they suggested that larger randomized trials were needed.
A randomized controlled trial that would address all the issues mentioned above is therefore essential. We undertook this randomized control trial to compare pregnancy rates between ETs under ultrasound guidance using an echo-sensitive catheter (K-J-SPPE echo tip, Cook, Australia) and ETs without ultrasound guidance using the traditional catheter type (K-Soft, Cook, Australia). A full bladder was not a prerequisite.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionAcknowledgementReferences |
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Inclusion criteria
Infertility patients having IVF or ICSI treatment including preimplantation genetic diagnosis (PGD), and undergoing ET with fresh embryos, on day 3 or 5 were eligible for the study. Only patients with a body mass index of 20–30 kg m–2 were included (Table I).
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Exclusion criteria
Patients >40 years were not included in the study. Women with previous cervical surgery for cervical intraepithelial neoplasia (CIN) were also excluded because of the difficult and traumatic transfers, as reported by Aust et al. (2005)
. Patients were included in the study only once.
Treatment allocation
Patients undergoing infertility treatment in the AZ-VUB Centre for Reproductive Medicine, between August 2005 and February 2006, were prospectively randomized into two groups. In the first group, patients were scheduled for ET under ultrasound guidance using the K-J-SPPE echo tip catheter, whereas in the second group, ET was done without ultrasound using the K-soft catheter. Patients were randomized using a computer-generated sequence. The randomization list was kept in the ET room. Patient allocation was done by an accompanying nurse, not involved in the study. Significant differences have been previously observed in pregnancy rates when different providers (Hearns-Strokes et al., 2000) perform ET. Therefore, in this study, a single experienced clinician performed all transfers. The performing clinician was blinded to patient and embryo characteristics.
Follicular development was recorded with an Aloka 3500 echographic machine with 3.5 MHz probe. Blood samples were collected for hormone assessment during ovarian stimulation on days 2 and 6 and on the day of HCG administration, whereas FSH was measured once, at day 3 of the cycle. The hormones measured were LH, estradiol (E2) and progesterone. Measurements were performed with the Elecsys immunoanalyser (Roche Diagnostics, Manheim, Germany). With this method, intra- and inter-assay coefficients of variation are <3 and 4% for LH, <3 and 6% for FSH, <5 and 10% for E2 and <3 and 5% for progesterone, respectiely.
Ovulation was triggered with 10 000 IU hCG as soon as three follicles of 17 mm appeared. Oocytes were aspirated 36 h after hCG injection by vaginal ultrasonography.
Natural micronized progesterone (Utrogestan) was administered vaginally 200 mg, three times daily, as luteal support starting on the day after the oocyte retrieval. Some patients received estradiol valerate (Progynova 2 x 2 mg per day orally) and progesterone as luteal support (Table II). No other specific medication was routinely administered before or after the ET, which took place on day 3 or 5. Patients had 2 h bed rest before leaving the hospital.
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ET procedure
The main aim of the performing clinician was to achieve an atraumatic technique in both groups. No trial ET was performed in either group (Shamonki et al., 2005
). The patient was placed in the dorsal lithotomy position and the cervix was well visualized with the use of a suitably sized bivalve speculum. The pericervical area and the cervix were cleaned with gauze moistened with 0.5 M NaCl. Endocervical mucus was removed using aseptic gauze without any moisturizer.
During the insertion phase, the outer catheter sheath did not touch the vaginal walls to avoid transferring any infection inside the uterus. As the outer sheath of the ET catheter was inserted into the cervix, a nurse encouraged the patient to notify the clinician upon feeling the catheter or period like pain. If that occurred, even by a slight amount, sheath insertion was postponed until the discomfort subsided.
The embryologist on duty was responsible for the embryo scoring and final embryo selection. Embryo quality was assessed as described by Van Landuyt et al. (2005). Depending on the patients age and in accordance with Belgian legislation (Royal Decree 4 June 2003), the clinician decided on the number of embryos to be transferred.
ET without ultrasound guidance
The outer sheath of a K-soft catheter was fashioned to the cervical curvature according to the physicians' judgement and gently inserted through the cervical canal, up to the internal os. As a guide, the end-point on the outer catheter was 4 cm. Once again for standardization, the nurse focused on the patient and encouraged her to alert them of any untoward feeling during outer catheter insertion. In such instances, the outer sheath was withdrawn and the catheter insertion was repeated after 10 s. The embryologist loaded the embryos and brought the inner catheter into the transfer room when the clinician was satisfied that the outer catheter was in the correct position. The clinician inserted the inner catheter inside the outer sheath and moved it, until the catheter tip–cervical opening distance was 6 cm.
The embryos were gently expelled. Transfer fluid volume was 20–30 µl.The performing clinician immediately removed the catheter slowly with a gentle rotational movement (Martinez et al., 2001).
ET with ultrasound guidance
Until the outer catheter placement, all steps were carried out in the same way in both groups. If a patient wanted to empty her bladder, she was allowed to do so. The ultrasound guidance specific ET catheter was the K-J-SPPE echo tip.
The head of the nursing team performed abdominal ultrasound, in accordance with the training he had received before the study began. The ultrasound operator placed the probe abdominally to visualize the full length of the endometrium, the cervix and the uterine fundus.
Under visualization, the tip of the catheter was placed according to the clinicians and sonographers' judgement for the expelled embryo to be deposited at the chosen depth (15 mm from the uterine endometrial fundus). On a frozen ultrasound picture, a measurement between the embryo bubble and endometrial fundus was taken. That measurement was recorded and used for embryo placement definition inside the uterine cavity. The catheter tip was placed as close as possible to the predefined embryo deposition point when an enlarged uterus was found in the ultrasound ET group. For every ET, the advancement of the internal catheter (in centimetres) was recorded and compared with the distance of the embryo placement from the uterine endometrial fundus.
The same company with the same materials manufactures both catheters while the only difference is the echo tip on the K-J-SPPE ultrasound-guided catheter.
End points
The main study end-point was overall pregnancy rate defined as the number of positive hCG results per transfer (as defined by a rising hCG level measured on two consecutive occasions, with a minimal defined threshold of 5 IU–1 l, 2 weeks after ET). Secondary end-points included implantation rate and progression to clinical pregnancy. Implantation rate was defined as the number of sacs seen in the first scan divided by the number of embryos transferred. Clinical pregnancy rate was defined as the number of pregnancy sacs with a positive heartbeat at 7 weeks scan per transfer. Other parameters were also examined, such as the number of embryos transferred, whether PGD was performed and the embryological characteristics for each study group. It is thought that ultrasound-guided ET might achieve better results due to better cavity visualization, better negotiation of the cervical canal and embryo deposition at a predefined point.
Statistical analysis
Analyses were based on intention to treat, with patients analysed in the arm were originally randomized. Comparisons for discrete and continuous groups were performed with chi-square test and t-test, respectively. The primary and secondary end-points were analysed using the chi-square test. Interim analysis was performed when the trial included 141 and 196 patients to define whether the trial had to continue and to what extent. After no difference was found, it was decided to stop the trial at 300 patients. A P < 0.05 was considered statistically significant. Values are presented as mean ± SD.
Sample size calculations
To achieve an 80% power to show a 7% increase in overall pregnancy rates (from 35 to 42%) with 
= 0.05, a sample size of 772 patients is required. Analyses were conducted with the Statistical Package for the Social Sciences Version 12.0 (SPSS, Inc., Chicago, IL, USA). All P-values are two-tailed.
Interim analysis and decision to stop
Preset cut-off dates were used for interim analysis calculations. No decision rules based on prior information from previous studies could be applied.
The randomized controlled trial design plan excluded interaction from other factors (ET technique, age, performing clinician and clinician experience) and remained as such for the duration of the study. Since the clinician's experience is important in studies of a technical nature, this factor was controlled by allowing only one clinician and one sonographer to perform ETs and related ultrasonography. In addition, it was decided that two approaches were to be used in the interim analysis, the frequentist and the Bayesian approach. Both approaches achieved the same results.
In the first interim analysis, the first author presented results to co-authors when he was blinded to the study groups. In the first analysis, there was clearly no benefit for one of the two groups for the primary end-point (positive hCG).
At a follow-up meeting after the second interim analysis, all co-authors reviewed the results together. The results of the second interim analysis were in line with the results of the first analysis, i.e. the predefined threshold difference was not met. Therefore, it was discussed how to proceed further. Three options existed: to terminate the trial, modify it or continue as planned. The discussion centred on whether to continue the trial with subgroups only (as observed in previous trials). Specific subgroup analysis (day 3 versus 5; <37 versus >37 years old) was carried out but no specific effect was found.
In addition, the fact that no difference was observed in the incidence of adverse events (ectopic pregnancies) did not highlight a beneficial effect of one technique over the other.
Following this, the first author recommended stopping the trial, because demonstration of superior efficacy of the ultrasound group over the control group seemed highly unlikely.
Considering the recommendation of the first author, co-authors concluded that continuing or modifying this trial was not the best way to clarify the effect of ultrasound-guided ET on pregnancy rates. An additional 104 participants were enrolled after the cutoff date of the second interim analysis and the termination date. A final analysis was conducted when all participants completed their scheduled follow-up.
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Results |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionAcknowledgementReferences |
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Trial population
Three hundred patients were enrolled in this study between August 2005 and February 2006. One hundred and fifty patients were randomized in the ultrasound-guided ET group and 150 in the blind group (Figure 1).
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Patients were followed until clinical pregnancy was established. In one patient randomized in the ultrasound-guided ET group, transfer could not be performed with the catheter, first randomized.
The two groups were well balanced for baseline characteristics except for male factor and unexplained infertility (Tables I and II).
Interim analyses were run using two methods, the frequentist method and the Bayesian method. With the frequentist method, the significance for the two-sided binomial test is set at 0.05. With the Bayesian method, the criterion for deciding if the response rate of ET under ultrasound is better than ET alone is set at 0.975. On the basis of the analysis of 141 (n = 64/77 in ultrasound and no ultrasound groups, respectively) and 196 (102/94) patients using the frequentist method, the probability that the trial will end up in favour of ET under ultrasound is 0.0848 and the probability that the trial will close in favour of ET without ultrasound is 0.0652 . When using the Bayesian method for the same number of patients, the probability that the trial will end up in favour of ET under ultrasound is 0.0850 and the likelihood that the trial will decide in favour of ET without ultrasound is 0.0328. So we decided to stop the trial at 300 patients.
Primary endpoints for follow-up
Primary and secondary end-points are documented in Table III. Overall pregnancy rates were 53.3% (80 patients out of 150) and 51.3% (77 patients out of 150) in the ultrasound-guided and blind ET group, respectively, and implantation rates were 32.7% and 34.9%, respectively, whereas both the clinical pregnancy rates were 42%.
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Adverse events
Two ectopic pregnancies were reported in the ultrasound-guided ET transfer group and another two in the blind ET group.
Transfer characteristics
ET characteristics are documented in Table IV. The majority of ETs performed were easy transfers with no significant difference between both groups [143 (95.3%) and 141 (94%) in ultrasound-guided and blind group, respectively]. There were no differences between the groups with respect to the subjective degree of minor to medium clinical difficulty.
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Embryo deposition
For 14 patients, neither the clinician nor the ultrasonographer could visualize the exact embryo deposition point. When data from the other 136 patients were analysed, it was shown that a mean deposition point of 12.06 (±6.654) mm from the endometrial fundus was achieved in the ultrasound-guided ET.
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionAcknowledgementReferences |
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It has been suggested that ultrasound-guided ET facilitates ET and improves pregnancy rates, because it is thought that visualization of the cavity and the embryo deposition point have an advantage in comparison with the blind ET technique. In this study, overall pregnancy rates were compared between ultrasound-guided ET and blind ET. Operator-induced bias was reduced since a team of one experienced clinician and one sonographer performed all ETs and the intended embryo deposition point was predefined. Our data show no difference in overall pregnancy, clinical pregnancy or embryo implantation rates between patient groups randomized prospectively to ultrasound-guided versus blind ET. This finding questions the relevance of ultrasound-guided ET in experienced hands.
Previous studies have clearly commended the value of ultrasound-guided ET for improving overall pregnancy and implantation rates (meta-analysis by Prappas et al., 2001; Tang et al., 2001; Matorras et al., 2002; Sallam et al., 2002; Buckett, 2003). Our study is the first randomized controlled trial in unselected patients not to document a clear clinical benefit, when an experienced physician performs the ET and a predefined uterine point is used for embryo deposition. A randomized controlled trial (Garcia-Velasco et al., 2002) did not find any difference in pregnancy rates between ultrasound-guided and blind ET. That study included donor fresh cycles and pregnancy outcome measured in recipients. Although a single donor may provide embryos for many recipients, which might add to bias, the authors found no significant difference in all features between the two recipient groups. Four different experienced providers were involved in this study and ET was performed with a full bladder. The mean number of embryos transferred was 2.8 and the mean age was 37.8 in the ultrasound group.
In contrast, a prospective study by Tang et al. (2001) found a significant difference in implantation rates for the ultrasound group, although clinical pregnancy and ongoing pregnancy rates did not differ.
The mean number of embryos transferred in the studies included in the meta-analysis (Buckett, 2003) ranged from 2.1 to 3.5. This might add to bias because of the higher number of embryos transferred. In our study, the mean number of embryos transferred was 1.49 (±0.61) and 1.43 (±0.57) in the ultrasound-guided and control group, respectively, with no significant difference between the groups.
Prapas et al. (2001) reported a positive effect of ultrasound guidance on day 3 but not on day 5 ET . In our study, no significant difference was found in positive hCG either in day 3 or in day 5 ETs.
Randomization method is an issue for discussion in some of the randomized controlled trials undertaken previously. Pseudo-randomization methods were the randomization choice in those studies that show a significant positive effect (Buckett, 2003). Pseudo-randomization included randomization based on availability of the ultrasound machine (Prapas et al., 2001), the transfer room (Prapas et al., 2001), ultrasonographer availability (Kan et al., 1999) and randomization done by alternative allocation of patients to each group (Sallam et al., 2002). In the other two studies (Tang et al., 2001; Coroleu et al., 2002), more than one clinician performed ETs, thus contributing to bias. In one study (Tang et al., 2001), a specialized nurse was involved, performing ETs. Mattorras et al. (2002) did not mention the number of clinicians involved in his study. More than one physician was involved in the study by Garcia-Velasco that did not report statistical significant differences in pregnancy rates.
In order to optimize ET technique, effort was made to avoid uterine contractions and such an event was continuously monitored as it happened by actively encouraging the patient to report it. Also unique to this study is that only one physician and one ultrasonographer performed ET, in order to erase the physician factor contributing to bias.
The bladder was not specifically emptied, or filled, before any of the transfers. As expected, a steeper cervico-uterine axis was observed in both study groups when compared with previous studies with full bladder. Our results are in concordance with the results of the study carried out by Lorusso et al., (2005), which show that high overall pregnancy rates can be achieved when ETs are performed in patients with an empty bladder, whether they are performed under ultrasound guidance or not.
Both the traditional and the echo tip catheters used in our study were ‘soft’ catheters. No special difficulty for outer catheter placement was encountered, and therefore outer sheath placement under ultrasound guidance was not necessarily required. There is no difference between the two groups in difficult ETs and subsequent uterine contractions as perceived like ‘period-like pain’ by the patients.
Although several studies considered various points for embryo deposition (Coroleu et al., 2002, Franco et al., 2004; Frankfurter et al, 2004), we selected the study carried out by Coroleu et al., (2002) as our guide. There were a number of reasons for this. All randomized controlled trials included in the meta-analysis performed an upper uterine segment ET. Although the study by Frankfurter et al. (2004) is interesting because it adds the uterine cavity length as a variable for embryo deposition and implantation, this study does not clearly explain the presence of a biological cause responsible for the implantation results obtained, except that spontaneously conceived embryos implant preferentially in the midposterior cavity. Many operators were involved (n = 7), which add to bias in the pregnancy outcome. Study results were similar to our own results. Another prospective study performed by Oliveira et al. (2004) showed no difference in implantation and pregnancy rates, whether the embryo was deposited in the upper or lower part of the uterine cavity. Overall, our study was not designed to answer the question of the best point for embryo deposition, but to assess the usefulness of ultrasound guidance during ET, in terms of pregnancy rates.
No mock transfers or trial ET under ultrasound guidance was performed here.
A limit on the study might be the decision to discontinue the original design. After interim analysis of 141 and 196 patients, it was decided to suspend the study at 300 patients.
Four of the randomized controlled trials (Tang et al., 2001; Garcia-Velasco et al., 2002; Matorras et al., 2002; Sallam et al., 2002) reported more ectopic pregnancies in the blind group than in the ultrasound-assisted ET group. Three randomized controlled trials did not mention ectopic pregnancies. In our study, two ectopic pregnancies were reported in the ultrasound-guided ET group and two in the blind ET group.
Because of the earlier assumption, by many, of abdominal ultrasound being a tool for improving ET efficacy, several clinical investigators tried to extend the method by using 3D/4D (Gergely et al., 2005; Letterie, 2005) or vaginal ultrasound (Anderson et al., 2002) with encouraging results. In our experience, vaginal ultrasound during ET adds many time constraints and technical difficulties, whereas 3D/4D ultrasound machines are not widely available and represent a costly acquisition, so that a clearly cost-effective benefit should be demonstrated before this technique becomes widely accepted.
Although ultrasound-guided ET may not have a clear effect on increasing pregnancy rates, there are a number of positive effects of ultrasound-guided ET that cannot be ignored. As each physician tries to improve the overall pregnancy rates, ultrasound guidance may be a useful tool to achieve this, especially during the early training period.
One not so obvious advantage of using ultrasound during ET is the detection of intrauterine pathology that may arise after oocyte retrieval (Hofmann et al., 2003). This might lead to ET cancellation, embryo cryopreservation and treatment. Other authors concluded that reassessment of patient risk for ovarian stimulation is another reason for ultrasound-guided ET.
In conclusion, we cannot determine from this prospective randomized trial, whether ultrasound guidance and positioning the embryos at a certain point inside the uterine cavity has a significant effect on overall pregnancy rates. It is obvious that as long as a physician performs a standardized ET technique, while avoiding uterine contractions, high overall pregnancy rates will be achieved.
To our knowledge, this study is the first that best takes into account the real conditions found in a modern reproductive centre. One of the reasons why ultrasound-guided ET could be of some benefit is the increased concentration of the performing physician and the accountability of all the persons involved in the process. Meticulous ET technique with technique standardization and physician training is needed to increase the positive outcome.
In this randomized controlled trial, it was shown that ultrasound-guided ET does not offer any benefit in the hands of an experienced clinician, because similar overall and clinical pregnancy rates were achieved in the blind group. Ultrasound-guided ET is probably needed early in the training period of clinicians, but this needs to be proved by another randomized controlled trial.
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Acknowledgement |
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The language assistance of Mr Julian Mitchell is gratefully acknowledged.
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References |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionAcknowledgementReferences |
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Submitted on August 10, 2006; resubmitted on November 7, 2006; resubmitted on December 17, 2006; accepted on January 2, 2007.
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