Our findings demonstrated that the micro-CT approach used in this study can be utilized for diagnosis in clinical settings. The equipment facilitated the collection of accurate data, as well as a rapid image processing time and reconstruction time (approximately 1 minute). Because the micro-CT device allows for reconstruction of images derived from slice image data with pixel sizes ranging from 120 μm2 to 150 μm2, the images are precise, and objects are very clear in comparison to those from conventional CT. The same performance has also been achieved with the imaging of laboratory animals. [10,12,13] While the bone structure and detailed morphological aspects of teeth in rabbits have been difficult to visualize with conventional CT, which is designed for humans, because of the inherently small size of the rabbits’ skull and teeth they are clearly depicted by micro-CT.
In this study, we attempted to compare the diagnostic utility of 2D and 3D images. 2D images allowed for a comparative study of the length, thickness, and curvature angles of teeth via numerical evaluations. These data were obtained by conducting imaging only once, minimizing the animals’ exposure to radiation. However, osteolysis and bone hyperplasia were difficult to identify with 2D imaging, hence we also utilized 3D images. Another advantage of this device is that the images generated are digitally processed in conjunction with every CT scan; consequently, they can be rotated in three dimensions, facilitating an enhanced understanding of the physical presentation of diseases or abnormalities evident in the images.
The excellent imaging capability of micro-CT allowed for the visualization of pathological images associated with diseases specific to rabbits. In the evaluation of each of the individual sites investigated, 2D images enabled the assessment of dentition in the X, Y, and Z-axes on a planar surface, and 3D images enabled the assessment of 3D structure. Thus, the advantages of the micro-CT scanning include the following: (1) Overall assessment of dentition and occlusion, and evaluation of the morphology of the upper and lower jaw, as well as abnormalities in terms of their length and angle (including abnormal angulation against the maxilla/mandible, which can worsen as the teeth continuously grow). (2) Evaluation of deformity, excessive length, and occlusion in the clinical crown. (3) Correlation between the alveolar bone and excessive elongation in the dental apices or deformities of the dental apices. (4) Changes in resorption due to bacterial infection of the dental apex, proliferative changes, fracture-related deformities, and occlusal changes in the upper and lower jaw. Furthermore, the changes identified included dental, skeletal, anatomical, and pathological abnormalities, excessive elongation, and internal and external deviation of the orientations of upper and lower jaw molars, which were difficult to detect by radiography.
The device described in this study allowed for comprehensive assessments via clear imaging of lesions such as those associated with changes in the dental apices and alveolar bones in a variety of disease contexts, including animals with chronic severe diseases. These evaluations can result in more accurate prognoses. The clear image data obtained via micro-CT facilitated the provision of informative explanations to the owners, and was extremely useful with regard to obtaining informed consent for subsequent procedures. Furthermore, the data obtained from the imaging device was useful for educating the owners about the importance of conducting routine monitoring for changes such as a refusal to eat food, spilling of food, reduced amount of stool, drooling, and nasal discharge .
According to Brodbelt et al. , the incidence rates of anesthetic and sedation-related death in healthy animals were 0.05% in dogs, 0.11% in cats, and 0.73% in rabbits. These increased to 1.33%, 1.40%, and 7.37%, respectively, in diseased animals. With regard to rabbits, it has been found that they usually remain still and calm when a net is placed over them in the manner shown in Figure 1. It was possible to acquire most of the images in this study without anesthesia. It was also possible to apply this method to rabbits with reduced cardiopulmonary function and respiratory function, for which death due to anesthesia was a distinct possibility. Also, the methods used were effective in cases where the owner agreed to CT image diagnosis but not anesthesia. Since the risk of adverse events related to anesthesia and sedation is increased in sick rabbits, it is considered an advantage that images could be acquired without anesthesia.
While dental diseases in rabbits develop gradually, we have diagnosed cases in which a failure to treat the condition during the acute phase caused the animal’s condition to deteriorate severely. To avoid such cases, the diagnosis needs to be made as early as possible. The positioning device described in this study is useful to this end, as it can be used to conduct diagnostic procedures while avoiding the risks associated with the use of anesthetics during endoscopic examination of the rabbit’s deep and narrow oral cavity.