| Part Ⅰ Accuracy of multimodal image fusion for oral and maxillofacial tumors:A revised evaluation method and its applicationObjectives:To develop a revised evaluation method for accuracy of multimodal image fusion for oral and maxillofacial tumors and explore its application for comparing the accuracy of three commonly used fusion algorithms,automatic fusion,manual fusion,and registration point-based fusion.Materials and Methods:Image sets of patients with oral and maxillofacial tumor were fused using the iPlan 3.0 navigation system.Fusion accuracy included two aspects:(1)overall fusion accuracy:represented by the mean value of the coordinate differences along the x-,y-,and zaxes(△x,△y,and △z),mean deviation(MD),and root mean square(RMS)of six pairs of landmarks on the two image sets;(2)tumor volume fusion accuracy:represented by Fusion Index(FI),which was calculated based on the volume of tumor delineated on the two image sets.Results:Eighteen pairs of image sets of 17 patients were enrolled in this study.The △x and△y values for the three algorithms were less than 1.5 mm.The △z values for automatic fusion,manual fusion and registration point-based fusion was 1.049 mm,1.864 mm and 1.254 mm.The MD for automatic fusion,manual fusion and registration point-based fusion was 1.978 mm,2.788 mm and 1.926 mm.Significant differences existed in △z for manual fusion and that for automatic fusion(P=0.058),in MD for manual fusion and that for automatic fusion(P=0.087),and in MD for manual fusion and that for registration point-based fusion(P=0.069).The FI for automatic fusion,manual fusion,and registration point-based fusion was 0.594,0.520,and 0.549;the inter-algorithm differences were not significant(P=0.290).Conclusions:A revised evaluation method of the accuracy of multimodal image fusion for oral and maxillofacial tumors were come out in this study.The automatic fusion and the registration point-based fusion showed higher overall fusion accuracy than manual fusion,while there was no significant difference on the tumor volume fusion accuracy among three fusion algorithms.The influencing factors of the accuracy of multimodal image fusion for oral and maxillofacial tumors needed to be explored in the following study.Part Ⅱ Multimodal image fusion for oral and maxillofacial tumors:Influencing factors of fusion accuracyObjective:To explore the factors that influence the accuracy of multimodal image fusion for oral and maxillofacial tumors,therefore to instruct the quality assurance of multimodal image fusion.Materials and Methods:Pairs of single-modality image were obtained from oral and maxillofacial tumor patients,and were fused in navigation system(iPlan 3.0,BrainLAB,Germany)by using three algorithms(automatic fusion,manual fusion and registration pointbased fusion).Fusion accuracy was evaluated including two aspects:the overall fusion accuracy and the tumor volume fusion accuracy,and were indicated by mean deviation(MD)and fusion index(FI)respectively.Image modality,fusion algorithm and other characteristics of multimodal images that may have potential influence on fusion accuracy were recorded.Univariate analysis and multivariate linear regression analysis were used to identify relevant affecting factors.Results:93 multimodal images were generated by fusing 31 pairs of single-modality images.The interaction item of image modality and fusion algorithm was shown to significantly influence the overall fusion accuracy(P<0.001),so was the thinner slice thickness(P=0.007).The tumor volume(P<0.001),the location of tumor(P=0.007)and image modality(P=0.010)were significant influencing factors of the tumor volume fusion accuracy.Conclusions:To assure high overall fusion accuracy,manual fusion was not preferred in CT/MRI image fusion,and so was automatic fusion in image fusion containing PET modality.Using image sets with thinner slice thickness could increase overall fusion accuracy.CT/MRI fusion yielded higher tumor volume fusion accuracy than fusion containing PET modality.And tumor volume fusion accuracy should be taken into great consideration during image fusion when the tumor volume was small,when the tumor was located at mandible and when the fusion modality contained PET.Part Ⅲ Treatment of mid-face tumors by computer-assisted surgical techniques based on CT/MRI multimodal image fusion:A cohort studyObjectives:To set up a treatment procedure of mid-face tumors by using computer-assisted surgical techniques based on CT/MRI multimodal image fusion,and to preliminarily explore its effect by a cohort study.Patients and Methods:Patients with mid-face tumors who were under treatment by a same surgical team from February 2019 to January 2021 were enrolled in this study as the experimental group.CT and MRI radiological examinations were performed before the operation.The DICOM data of single-modality image sets were imported into iPlan CMF 3.0(BrainLAB,Germany)for multimodal image fusion.The MD value and FI value of the multimodal image were measured to verify the fusion accuracy according to the evaluation method presented in Part I.Tumor delineation and three-dimensional reconstruction of important anatomical structures were completed based on CT/MRI multimodal image.Virtual surgical planning was then finished.Tumor resection was finished under the guidance of intraoperative navigation according to the virtual surgical planning,and intraoperative frozen section(IFS)were performed to check the status of the resection margins(RMs).Patients were requested for follow-up visits to confirm whether tumor recurred.A group of patients with mid-face tumors who were treated by the same surgical team from January 2013 to October 2014 were enrolled in this study as the control group according to the same inclusion and exclusion criteria as the experimental group,the patients of which were received surgical treatment of computer-assisted surgical techniques based on single-modality CT images.The basic characteristics of the two groups of cases were recorded.The status of IFS of RMs and the survival status during the follow-up period were compared between the two groups of cases.Fisher’s exact probability test was performed to find out whether there was significant difference between the negative rate of IFS of RMs among two groups at per patient level and at per RM level,and the significance level was P<0.05.Results:A total of 28 patients were enrolled,14 in the experimental group and 14 in the control group.The basic characteristics of patients in the two groups were similar.The mean value of MD of the experimental group was 1.34mm,and that of FI was 0.647.The accuracy of multimodal image fusion was satisfying.At per patient level,the status of RMs in the experimental group were all negative,and positive RMs existed in 3 patients in the control group,and the positive rate was 21.4%;at per RM level,66 RMs in the experimental group were all negative.Seven of the 77 RMs in the control group were positive,with a positive ratio of 9.1%.There was significant difference between the positive rate of IFS of RMs among the two groups of patients at per RM level(P=0.015).The average follow-up time of the experimental group was 12.9 months.During the follow-up period,all patients were alive and there was no tumor recurrence or distant metastasis.The average follow-up time of the control group was 35.1 months.7 patients had tumor recurrence at 28 months postoperatively on average.Conclusions:For the surgical treatment of mid-face tumors,the RMs were more likely to be tumor-free with the assistance of computer-assisted surgical techniques based on CT/MRI multimodal image fusion,which showed its potential of improving the effect of surgical treatment for mid-face tumors. |
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