# DeAPIR: Efficient and Enhanced Dental Arch-Guided Panoramic Image Reconstruction from CBCT Data
###### Abstract
While these methods effectively address the issue of missing teeth sections, they have the limitation of a shortened panoramic view, which not only misses the wisdom teeth but also the TMJ bones in their panoramic view. The TMJ region is crucial for the disease diagnostic procedure from the dental panoramic image of the patient. Over the past decades, several methods have been developed to generate 2D panoramic images from CT datasets [15]. Some techniques involve the manual definition of dental arch coordinates followed by Maximum Intensity Projection (MIP) over specified angles [16]. Other methods involve automatic segmentation to separate the maxilla and mandible regions, followed by spline-based reconstruction [3]. The accuracy of the dental arch has a crucial impact on the development of panoramic view from the CBCT data [17]. In [3], the author generates separate panoramic views of the upper and lower jaw and subsequently employs a hierarchical multi-step deep learning model for tooth segmentation in 3D CBCT data. In [13], the method determines the occlusal plane, generates intersection points between the teeth and an offset plane from the occlusal plane in CBCT images, and ultimately determines the dental arch form by fitting a curve to the intersection points using cubic B-spline curve approximation. The author in [18] generates a panoramic view by segmenting the bone and teeth and then detects the internal mandible curve in the segmented image, which is used to generate the panoramic image. The method is fast but results in shortened and less precise unwrapping results. The author in [19] uses teeth pulps and the entire mandible to generate a panoramic image by employing thresholding and morphological operations over the dental arches. The panoramic view generated by BlueSkyPlan software (V4.11) shows a shortened view, which skips the TMJ section [20]. These techniques have made substantial contributions to the field, providing both manual and automated methods for reconstructing panoramic images from CT data [21]. Nonetheless, each method is susceptible to various noise and artifacts caused by the presence of metallic structures and non-uniform teeth orientations [22]. The unwanted branching structure of the dental arch, resulting from these techniques, contributes to inaccuracies in panoramic image generation. Furthermore, these methods produce limited-length arches that omit the TMJ bones from the panoramic view [23]. The shortened, less enhanced, non-linear unwrapped dental panoramic view severely impacts medical image diagnostics and planning procedures. To address the limitations associated with existing software approaches, this research article introduces a novel method for panoramic image generation that leverages CBCT projection data. Given that CBCT scans offer projection data encompassing the full angular range, it is theoretically feasible to selectively extract and reconstruct panoramic projection data from these CBCT projections. In practice, an offset detector geometry is commonly employed to cover a wider field of view (FOV) in dental CBCT, with the flat-panel detector center being horizontally aligned with the system's principal X-ray. The process of extracting panoramic projection data from CBCT projection data begins by isolating an appropriate dental arch from a CBCT image, determined by slice positions where the moving average intensity exceeds a specific threshold. Subsequently, a top-view image obtained via MIP from the chosen DCM slices undergoes preprocessing involving various morphological and filtering operations to obtain the raw dental arch line. A curve fitting operation is then applied to extend the dental arch and incorporate the temporomandibular joint (TMJ) section into the panoramic image. Finally, the perpendicular angle across each dental arch point is used to rotate and extract the MIP panoramic slice at each position for the small cubic CBCT segment.