Effect of deep transfer learning with a different kind of lesion on classification performance of pre-trained model: Verification with radiolucent lesions on panoramic radiographs

Purpose@#The aim of this study was to clarify the influence of training with a different kind of lesion on the performance of a target model. @*Materials and Methods@#A total of 310 patients (211 men, 99 women; average age, 47.9±16.1 years) were selected and their panoramic images were used in this study. We created a source model using panoramic radiographs including mandibular radiolucent cyst-like lesions (radicular cyst, dentigerous cyst, odontogenic keratocyst, and ameloblastoma). The model was simulatively transferred and trained on images of Stafne’s bone cavity. A learning model was created using a customized DetectNet built in the Digits version 5.0 (NVIDIA, Santa Clara, CA). Two machines (Machines A and B) with identical specifications were used to simulate transfer learning. A source model was created from the data consisting of ameloblastoma, odontogenic keratocyst, dentigerous cyst, and radicular cyst in Machine A. Thereafter, it was transferred to Machine B and trained on additional data of Stafne’s bone cavity to create target models. To investigate the effect of the number of cases, we created several target models with different numbers of Stafne’s bone cavity cases. @*Results@#When the Stafne’s bone cavity data were added to the training, both the detection and classification performances for this pathology improved. Even for lesions other than Stafne’s bone cavity, the detection sensitivities tended to increase with the increase in the number of Stafne’s bone cavities. @*Conclusion@#This study showed that using different lesions for transfer learning improves the performance of the model.

Orthodontic tooth separation activates the hypothalamic area in the human brain / 国际口腔科学杂志·英文版

OBJECTIVES@#An animal experiment clarified that insertion of an orthodontic apparatus activated the trigeminal neurons of the medulla oblongata. Orthodontic tooth movement is known to be associated with the sympathetic nervous system and controlled by the nucleus of the hypothalamus. However, the transmission of both has not been demonstrated in humans. The purpose of this study were to examine the activated cerebral areas using brain functional magnetic resonance imaging (MRI), when orthodontic tooth separators were inserted, and to confirm the possibility of the transmission route from the medulla oblongata to the hypothalamus.@*METHODS@#Two types of alternative orthodontic tooth separators (brass contact gauge and floss) were inserted into the right upper premolars of 10 healthy volunteers. Brain functional T2*-weighted images and anatomical T1-weighted images were taken.@*RESULTS@#The blood oxygenation level dependent (BOLD) signals following insertion of a brass contact gauge and floss significantly increased in the somatosensory association cortex and hypothalamic area.@*CONCLUSION@#Our findings suggest the possibility of a transmission route from the medulla oblongata to the hypothalamus.