Prog Med Phys.  2015 Sep;26(3):160-167. 10.14316/pmp.2015.26.3.160.

Dosimetric Evaluation of a Small Intraoral X-ray Tube for Dental Imaging

• Ji Y
• Kim Y
• Lee R

• KMID: 2069479
• DOI: http://doi.org/10.14316/pmp.2015.26.3.160

Abstract

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was 72x72 mm with pixel size of 48 microm. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to 80 microA, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was 82.4 mGy*cm2 less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

Keyword

Miniature X-ray tube; Intraoral x-ray imaging unit; Dose measurement; ESD (Dose Area Product); DAP (Dose Area Product)

MeSH Terms

Diagnostic Imaging
Humans
Jaw
Mouth
Nuclear Energy
Radiography
Skin
Tooth

Figure

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  Fig. 1. Miniature x ray tube (Xoft, inc) without cooling (left) and with cooling (right).

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  Fig. 2. Comparison of two x-ray acquisition methods: typical settings for conventional intraoral x-ray unit (Left). Totally different settings for the new conceptual intraoral x-ray unit (Right).

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  Fig. 3. The custom-made program developed for the control of tube voltage, beam current, and filament current.

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  Fig. 4. Specification of the detector used in this study for the intensity measurements and image acquisition.

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  Fig. 5. The set-up for ESD measurements in an x-ray shielding jig: OSLDs are placed on the surface of the cylindrical phantom. The miniature x-ray tube is located 5 cm away from the OSLDs.

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  Fig. 6. The set-up for DAP measurements in an x-ray shielding jig: a DAP meter is placed from the miniature x-ray tube.

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  Fig. 7. Pig jaw phantom for the evaluation of image quality.

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  Fig. 8. X-ray image of pig mandibular molars with intensitiy profile across the image at 50 kVp, 0.051 mAs.

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  Fig. 9. X-ray images of the pig mandibular phantom obtained from (a) new system at 50 kV, 40 uA, (b) new system at 55 kV, 30uA, (c) commercial system at 60 kV, 7 mA (CS2100, &RVG digital sensor, Carestream Dental, LLC.) and (d) commercial system at 60 kV, 2 mA (EXARO&EZ digital sensor, Osstem, Inc.).

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  Fig. 10. ESD of the developed intraoral x-ray device as a function of beam current.

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  Fig. 11. DAP of the developed intraoral x-ray system as a function of beam current.

Reference

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