Our findings show that adding DWI to DCE-MRI can improve diagnostic value in mandible and maxilla tumors. With the addition of ADC, it may be possible to avoid missing cancers and performing unnecessary surgery or biopsy for benign lesions in the jaw. DWI quantifies the diffusional mobility of water protons with apparent diffusion coefficient (ADC). DCE-MRI provides information related to the physiology of the microcirculation and vascularity. As with most DWI applications, tumor cell density is higher, and more cell membranes theoretically have a greater impediment to diffusion, consequently, a lower ADC. On the contrary, ADC is higher . Given the heterogeneous group of benign and malignant lesions, there will clearly be exceptions and overlap in ADC value as well as the WOR results. A single parameter threshold cannot be used in all circumstances, and the establishment of threshold for specific diagnosis is required. Among a wild range of head and neck lesions, previous studies have established an optimal ADC threshold of 1.3 × 10−3 mm2/s for diagnosis between benign and malignant lesions(17), and the ADC value of malignant tumors, benign solid masses, and cystic lesions of 0.93 ×10−3 mm2/s ± 0.18, 1.57 × 10−3 mm2/s± 0.26, and 2.01 × 10−3 mm2/s ± 0.21, respectively(18). For specific mandible and maxilla lesions, our results found the ADC value of benign and malignant group of 1.55×10−3mm2/s ± 0.83, 0.95×10−3mm2/s ± 0.37, respectively, which was more specific than the previous reports.
Tpeak is believed to represent microvascular counts, and in head and neck tumors, the threshold between benign and malignant tumors has been described as about 120 seconds(19). However, there is no clear data on the identification of specific jaw lesions. The data from this group showed a threshold of 75.78 seconds for the "benign and malignant tumors" group, which is more suitable for maxillary and mandibular lesions than previously reported. WOR represents a difference in medium concentration between the intravascular and extravascular phases; tumors with high cellularity exhibit higher wash out rate values(20). Previous authors reported that enhanced areas of benign lesion-fibroblastoma showed a gradual enhancement on DCE-MRI, which corresponded to solid components and/or intramural nodules, and the solid area reached 600 After s gradually disappears or maintains an enhanced level. The maximum enhancement level, our results showed that the mean WOR of benign lesions was 4.09 l / s ± 6.10, while in the malignant group, the mean WOR was 21.4 l / s ± 31.37, significantly higher than the benign group. Due to the high cell density in malignant tumors, the WOR threshold for benign and malignant groups was 4.9 l / s, corresponding to previous studies. Other parameters of DCE-MRI in our study, including maximal enhancement and relative enhancement, did not reveal significant differences in the identification of benign and malignant lesions of the jaw. By adding the ADC value, the sensitivity, specificity, and accuracy are significantly improved, which is better than using WOR alone. In addition, because DWI combined with DCE-MRI can improve the diagnostic accuracy, whether traditional MRI combined with DWI and DCE-MRI can improve the diagnostic accuracy is still to be further exploration.
Our study had the following limitations: First, due to the low incidence rate and the strict exclusion criteria of the study, we included a relatively small number of jaw lesions, thereby further prospective and multicenter studies need to validate our findings. Second, the reproducibility of ADC values between MR pulse sequences remains controversial. As such, the cutoff level for the ADC value derived from our results might not be transferable to other institutions. In addition, given the heterogeneous origin of benign and malignant lesions with jaw, data from larger studies are required to define in specific pathological entities.
In conclusion, the high WOR of DCE-MRI may have a malignant tendency, but in the evaluation of jaw disease, the addition of ADC value can improve the diagnostic value. DWI combined with DCE-MRI parameters can better distinguish benign and malignant lesions in the mandible than single parameters, which is of great significance for preoperative diagnosis of jaw lesions.