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Radiation dose of cone-beam computed tomography compared to conventional radiographs in orthodontics

  • Luca Signorelli
  • Raphael Patcas
  • Timo Peltomäki
  • Marc Schätzle
Original Article

Abstract

Objectives

The aim of this study was to determine radiation doses of different cone-beam computed tomography (CBCT) scan modes in comparison to a conventional set of orthodontic radiographs (COR) by means of phantom dosimetry.

Materials and methods

Thermoluminescent dosimeter (TLD) chips (3 × 1 × 1 mm) were used on an adult male tissue-equivalent phantom to record the distribution of the absorbed radiation dose. Three different scanning modes (i.e., portrait, normal landscape, and fast scan landscape) were compared to CORs [i.e., conventional lateral (LC) and posteroanterior (PA) cephalograms and digital panoramic radiograph (OPG)].

Results

The following radiation levels were measured: 131.7, 91, and 77 μSv in the portrait, normal landscape, and fast landscape modes, respectively. The overall effective dose for a COR was 35.81 μSv (PA: 8.90 μSv; OPG: 21.87 μSv; LC: 5.03 μSv).

Discussion

Although one CBCT scan may replace all CORs, one set of CORs still entails 2–4 times less radiation than one CBCT. Depending on the scan mode, the radiation dose of a CBCT is about 3–6 times an OPG, 8–14 times a PA, and 15–26 times a lateral LC. Finally, in order to fully reconstruct cephalograms including the cranial base and other important structures, the CBCT portrait mode must be chosen, rendering the difference in radiation exposure even clearer (131.7 vs. 35.81 μSv). Shielding radiation-sensitive organs can reduce the effective dose considerably.

Conclusion

CBCT should not be recommended for use in all orthodontic patients as a substitute for a conventional set of radiographs. In CBCT, reducing the height of the field of view and shielding the thyroid are advisable methods and must be implemented to lower the exposure dose.

Keywords

Radiation dosage Diagnostic techniques Organs at risk Thyroid Phantoms, imaging 

Strahlenbelastung beim digitalen Volumentomogramm im Vergleich zu konventionellen kieferorthopädischen radiologischen Unterlagen

Zusammenfassung

Zielsetzung

Unter Verwendung phantomdosimetrischer Methoden sollten die Strahlendosen unterschiedlicher DVT (Digitales Volumentomogramm; “cone-beam computed tomography”, CBCT)-Aufnahmeprotokolle mit denen beim Erstellen kompletter konventioneller radiologischer Unterlagen verglichen werden.

Material und Methoden

An einem Phantom (gewebeäquivalent einem erwachsenen Mann) wurden TLD(“thermoluminescent dosimeter”)-Chips (3x1x1 mm) verwendet, um die Verteilung der absorbierten Strahlendosis zu registrieren. Die Dosen bei 3 unterschiedlichen DVT-Aufnahmeprotokollen (Hochformat, normales Querformat, schnelles Querformat) wurden verglichen mit denen konventioneller kieferorthopädischer Aufnahmen [d. h. seitliches Fernröntgenbild, PA(posterior-anterior)-Aufnahme, und digitales Orthopantomogramm (OPT)].

Ergebnisse

Für die Protokolle Hochformat, normales Querformat und schnelles Querformat wurden 131,7, 91 bzw. 77 μSv gemessen. Die effektive Gesamtdosis für die konventionellen kieferorthopädischen Aufnahmen lag bei 35,81 μSv (PA-Aufnahme: 8,90 μSv; OPT: 21,87 μSv; seitliches Fernröntgenbild: 5,03 μSv).

Diskussion

Zwar lassen sich mit einem DVT sämtliche konventionellen kieferorthopädischen Röntgenunterlagen ersetzen, doch ein komplettes Set konventioneller Unterlagen bedeutet immer noch 2- bis 4-mal weniger Strahlung als ein DVT. Abhängig vom Aufnahmeprotokoll liegt die Strahlendosis beim DVT 3- bis 6-mal so hoch wie bei einem OPT, 8- bis 14-mal so hoch wie bei einer PA-Aufnahme und 15- bis 26-mal so hoch wie bei einem seitlichen Fernröntgenbild. Ferner erfordert eine vollständige kephalometrische Rekonstruktion einschließlich der Schädelbasis und anderer relevanter Strukturen beim DVT den Einsatz des Hochformats; damit wird der Unterschied in der Strahlenbelastung noch deutlicher: 131,7 vs. 35,81 μSv. Die Abschirmung strahlensensibler Organe kann die effektive Strahlendosis wesentlich reduzieren.

Schlussfolgerung

Zum Einsatz für alle kieferorthopädischen Patienten statt konventioneller Röntgenunterlagen ist die DVT nicht zu empfehlen. Um die Strahlenbelastung beim DVT zu verringern, sollten die Höhe des Sichtfeldes reduziert und die Schilddrüse abgeschirmt werden.

Schlüsselwörter

Strahlendosis Diagnostische Verfahren Gefährdete Organe Schilddrüse Phantome für Strahlendiagnostik 

Notes

Compliance with ethical guidelines

Conflict of interest

All the authors have no conflict of interest.

The accompanying manuscript does not include studies on humans or animals.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Luca Signorelli
    • 1
  • Raphael Patcas
    • 1
  • Timo Peltomäki
    • 2
  • Marc Schätzle
    • 1
  1. 1.Clinic for Orthodontics and Pediatric Dentistry, Center for Dental MedicineUniversity of ZurichZurichSwitzerland
  2. 2.Dental and Oral Diseases Outpatient Clinic, Department of Eye, Ear and Oral Diseases, Hospital and Department of OtolaryngologyTampere UniversityTampereFinland

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