Removal of the Shadow of Cervical Vertebrae from Panoramic X-Ray Images with a Tomosynthesis Method

Koichi Ogawa,Jyunpei Yamamoto,Masatoshi Yanase,Akitoshi Katsumata

doi:10.4236/ojmi.2013.34023

Koichi Ogawa, Jyunpei Yamamoto + Show 2 more

Open Access

https://doi.org/10.4236/ojmi.2013.34023

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Abstract

The purpose of this study is to remove the shadow of cervical vertebrae from dental panoramic x-ray images with a tomosynthesis method and improve the contrast of details in both the teeth and jaw bones. To measure the shift-amount at each angular position that was required for reconstruction of panoramic x-ray images of the dental arch, strip images of a calibration phantom were acquired. Then, a shift-amount table was prepared from these images, and the other shift-amount table, which was used to reconstruct a panoramic image of the cervical vertebrae, was prepared by inverting the curve of the shift-amount table upside down. Using these two tables, images focused on the dental arch and cervical vertebrae of a patient were made with the original strip data of the patient. The shadow of the cervical vertebrae appearing on the image focused on the dental arch was removed using the two above-mentioned images and blurring functions defined at two focusing geometries. The validity of the proposed method was evaluated with clinically acquired data of two patients. The shadow of the cervical vertebrae was successfully eliminated, and the contrast of the front teeth and detailed structures of the jaw bones was improved. The results of the experiments showed that our proposed method was significantly effective in removing the shadow of the cervical vertebrae from conventional panoramic x-ray images.

Highlights

In dental imaging, many imaging techniques and imaging receptors are used in intra- and extra-oral dental radiology [1]
Two types of detector are used for this imaging: one is a scintillator with a charge coupled device (CCD) detector and the other is a semiconductor detector such as cadmium telluride (CdTe) [4]
Conventional panoramic radiography is intended to focus on the teeth and jaw bones, as a result of which a blurred shadow of the cervical vertebrae overlaps on the image, thereby reducing the image contrast at the front teeth

Summary

Introduction

Many imaging techniques and imaging receptors are used in intra- and extra-oral dental radiology [1]. Because the sensitivity and response speed of the latter detector are higher than those of the former one, we can obtain many strip images of an object acquired with slightly different angles This enables us to reconstruct an image of the teeth and jaw bones focused at a given depth with a tomosynthesis method [7,8]. A shift-amount at each angular position defined by the location of an x-ray source and detector is required in the process of the shift-and-add operation This shiftamount controls the position of a focused plane in the dental arch, and so if we use a large shift-amount in the process of focusing, we can reconstruct cervical vertebrae with the strip images originally acquired. Conventional panoramic radiography is intended to focus on the teeth and jaw bones, as a result of which a blurred shadow of the cervical vertebrae overlaps on the image, thereby reducing the image contrast at the front teeth

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