Paper DIAGNOSTIC REFERENCE LEVELS FOR PANORAMIC AND LATERAL CEPHALOMETRIC RADIOGRAPHY OF KOREAN CHILDREN Young-Hee Kim, Byoung-Eun Yang, Suk-Ja Yoon, Byung-Cheol Kang, and Jae-Seo Lee*

Abstract—Pediatric patients are considered to be more radiosensitive than adults; thus, radiation dose evaluations based on radiologic examinations are particularly important in this population. However, no national diagnostic reference levels (DRLs) are available for pediatric patients in the Republic of Korea. Therefore, the aim of this study was to determine the usage of panoramic and cephalometric radiography under the National Health Insurance (NHI) scheme and to investigate the current DRLs for child panoramic and lateral cephalometric radiography using dose area product (DAP). DAP values were obtained for standard child exposure settings used routinely by dentists. Analysis was performed on data obtained from 28 panoramic and 20 cephalometric x-ray units for the DAP investigation. DRLs for child panoramic and cephalometric radiography were found to be 95.9 mGy cm2 and 121.3 mGy cm2, respectively. These DRLs are higher than those recommended in the UK and Germany, which indicates that further effort is required to reduce pediatric doses in the Republic of Korea. Health Phys. 107(2):111–116; 2014 Key words: children; dosimetry; exposure, radiation; radiation, medical

INTRODUCTION DENTAL RADIOLOGY accounts for 27% of all radiological examinations at the global level and 34% in countries at health care level I, such as the European countries (UNSCEAR 2008). Panoramic and cephalometric radiography is routinely used for the diagnosis of orthodontic problems; however, although radiation exposure arising from dental radiology is considered low, a child may undergo repeated dental radiological procedures throughout childhood and adolescence. Thus, the risks associated with *Dental Science Research Institute, School of Dentistry, Chonnam National University, Gawngju, Republic of Korea. The authors declare no conflicts of interest For correspondence contact: Jae-Seo Lee, Dental Science Research Institute, School of Dentistry, Chonnam National University, Gawngju, Republic of Korea, or email at [email protected]. (Manuscript accepted 18 November 2013) 0017-9078/14/0 Copyright © 2014 Health Physics Society DOI: 10.1097/HP.0000000000000071

cumulative doses should be taken into consideration (Looe et al. 2006). Diagnostic reference levels (DRLs) apply to the radiation exposure of patients as a result of medical x-ray imaging and diagnostic nuclear procedures. They should be the result of a generic optimization of protection. The values should be selected by professional medical personnel and may be specific to a country or region (ICRP 2007). National DRLs are normally set at the third quartile value of the patient dose distribution observed for a particular type of x-ray examination during a wide-scale survey (Holroyd 2011). The Korea Food and Drug Administration (KFDA) suggested the third quartile values for DRLS in dental radiography using the dose-area product (DAP). The values for adult panoramic radiography and cephalometric radiography were 110.9 mGy cm2 and 161.1 mGy cm2, respectively (Kim et al. 2009). In dental radiography, the entrance surface air kerma (ESAK), the entrance surface dose (ESD), the dose area product (DAP), and the dose width product (DWP) for different dental radiographic examinations have been recommended for setting DRLs. Several countries have reported DRLs for intraoral, panoramic, and cephalometric radiography (Holroyd 2011; Napier 1999; Helmrot and Alm, 2005; Poppe et al. 2007b; Fanning 2008; Gonzalez and Moro 2007; Han et al. 2012; Lee et al. 2010; Kim et al. 2012; Tierris et al. 2004; Looe et al. 2007). The measurement of DAP has been proven to be a convenient and easy method to quantify the dose without the presence of patients (Tierris et al. 2004). Many surveys have shown DRLs using DAP for dental radiography (Looe et al. 2006, 2007; Holroyd 2011; Kim et al. 2009; Poppe et al. 2007a; Tierris et al. 2004) However, most DRLs have been proposed for adult patients, and there is greater concern about the effects of radiation exposure in children because sensitivity to radiation damage is age dependent. Children and adolescents have a much higher risk than adults (Visser et al. 2001). Recently, DRLs for common pediatric diagnostic x-ray procedures have been established by using EASK in India (Sonawane et al. 2011) and by using DAP in Greece, 111

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Germany, and the UK (Holroyd 2011; Looe et al. 2007; Poppe et al. 2007a; Tierris et al. 2004). The third quartile DAP values for child panoramic radiography in Greece (Tierris et al. 2004) and Germany (Poppe et al. 2007a) were 77 mGy cm2 and 75.4 mGy cm2, respectively. The third quartile DAP values for pediatric patients in lateral cephalometric radiography in Germany (Looe et al. 2007) and the UK (Holroyd 2011) were 26.4 mGy cm2 and 25 mGy cm2, respectively; however, to date no attempt has been made to propose DRLs for dental radiography in Korean pediatric patients. Accordingly, the purpose of this study was to evaluate the frequency of panoramic and cephalometric radiography under the National Health Insurance (NHI) and to investigate the current DRLs for child panoramic and lateral cephalometric radiography using the DAP in the Republic of Korea.

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mean age of 5.5 y, and the analog x-ray units had a mean age of 12 y in July 2012. A DAP meter (DIAMENTOR M4‐KDK, PTW Freiburg GmbH 2012, Germany) was attached to the x-ray tube head at the exit slit of the x-ray beam. DAP values were measured three times for child (10‐y-old male) exposure settings used routinely by dentists and corrected for room temperature and pressure. Exposure parameters according to x-ray units are shown in Tables 2a and 2b. Radiography units were divided by the model. The DAP meter was calibrated by the German National Laboratory in Braunschweig. The measured DAP values were analyzed by the statistics program SPSS version 12.0 (SPSS, Inc., Chicago, IL), according to digital and analog units (Table 3). The third quartile value was proposed for DRLs for pediatric dental patients. RESULTS

MATERIALS AND METHODS Frequency of panoramic and cephalometric radiography The authors requested data from the Health Insurance Review and Assessment (HIRA) agency on the frequency of panoramic and cephalometric radiographic examinations from 2007 to 2011 (Table 1). The HIRA agency collates all information regarding treatments covered by NHI and can extract data from its nationwide database. DAP measurements DAP measurements were carried out at 27 dental clinics and one hospital, which were randomly selected in Anyang City. Radiation dose measurements made between January 2012 and July 2012 are included in the analysis. Twenty-eight panoramic radiographic machines and 20 cephalometric radiographic machines were surveyed. Twenty-four of the 28 panoramic units and 17 of the 20 cephalometric x-ray units investigated were equipped with a digital image system. These digital x-ray units had a

According to the records submitted to HIRA, dental pediatric radiographic examinations have increased annually between 2007 and 2011 (Table 1). The mean and 75th percentile DAP values obtained from the test sites in this study are shown in Table 3. For panoramic radiography, the mean DAP was 61.8 mGy cm2, and its 75th percentile value was 95.9 mGy cm2. For lateral cephalometric radiography, these values were 85.4 mGy cm2 and 121.4 mGy cm2, respectively. Fig. 1 shows the measured DAP values of the 28 panoramic x-ray units, and Fig. 2 shows the measured DAP values of the 20 cephalometric x-ray units. The horizontal bars represent 75th percentile DAP values. DISCUSSION According to records submitted to the Korean HIRA agency, the number of pediatric radiographic examinations conducted in dentistry has increased steadily (Table 1).

Table 1. Number of pediatric panoramic and cephalometric radiographic procedures (submitted to the Korean HIRA agency) from 2007 to 2011. Procedures Prescription code

Radiographic procedure

G9701

Panoramic

G9801

Cephalometric

Age (y)

2007

2008

2009

2010

2011

2–7

107,751

135,800

157,647

193,554

215,362

8–11

107,504

139,070

172,464

203,877

218,830

12–18

119,780

152,455

195,896

238,220

258,722

Total

335,035

427,325

526,007

635,651

692,914

2–7 8–11 12–18 Total

161 280 602 1,043

395 466 889 1,750

342 435 1,170 1,947

117 267 1,421 1,805

201 353 1,474 2,028

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Table 2A. Exposure parameters according to panoramic x-ray units. Panoramic units Model

Manufacturer

Orthoralix Implagraphy Kodak 8000C Pax-300 Pax-300C plus Pax-400C Pax-500 Pax-Flex3D Proline XC orthophos 3 orthophos XG5 Veraview Belmont Orthostage Auto IIIN Orthophos

Gendex Vatech Kodak Vatech Vatech Vatech Vatech Vatech Planmeca Sirona Sirona J Morita Asahi Asahi Sirona

Year of manufacture

Type

kVp

mA

time (s)

2004 2007 2007 2003 2004 2005–2009 2009 2010 2009 2000–2004 2008 2004 2003 2002 1999

digital digital digital digital digital digital digital digital digital digital digital digital analog analog analog

70 64–66 71 63 64 62–65 65 66 70 68 62 66 60 55 70

5–10 6–7 12 6 6 4–7 6 7 12 10 16 8 10 10 10

11–12 10–13 13 19 12–19 10–13 13 12 15 7–11 15 7 11 12 11

Recent reports have increased concerns about the potential association between radiation exposure and cancer and raised the use of ionizing radiation for diagnostic dental imaging as an important public health concern (Scarfe 2012). The Biological Effects of Ionizing Radiation (BEIR) VII report noted that children are at greater risk for carcinogenesis after low-dose radiation exposure than adults (NAS/NRC 2006). Stochastic effects (radiation-induced carcinogenesis) result from low levels of radiation and may become apparent over an extended period of time (Scarfe 2012). However, the probability of cancer risk at low doses is very small (Martin 2007), and there is no reason to deter any justified medical examination involving exposure to ionizing radiation (Pradhan 2013). Nevertheless, more attention has been paid to justification and optimization (As Low As Reasonably Achievable, ALARA) and the regulatory procedures to ensure the quality of equipment and the procedures to minimize

No. of units 3 4 1 1 2 6 1 1 1 2 1 1 1 1 2

any unnecessary radiation exposure (Pradhan 2013). As shown in Table 1, some dental clinics use the same x-ray units but use different exposure parameters for pediatric patients (10‐y-old boy, 35.5 kg weight). Dentists choose exposure settings based on personal experience, although it has been recommended that manufacturers should provide accurate and sufficient technical information to help optimize protection by managing the radiation doses commensurate with the imaging purpose. A review was performed to compare DRLs with those already established in other countries. The DRLs for child panoramic radiography in Greece (Tierris et al. 2004) and Germany (Poppe et al. 2007a) were 77 mGy cm2 and 75.4 mGy cm2, respectively. The third quartile DAP values for pediatric patients in lateral cephalometric radiography in Germany (Looe et al. 2007) and the UK (Holroyd 2011) were 26.4 mGy cm2 and 25 mGy cm2, respectively. The present study shows that DRLs using DAP for child

Table 2B. Exposure parameters according to cephalometric x-ray units. Cephalometric units Model

Manufacturer

Orthoralix Implagraphy Kodak 8000C Pax-400C Pax-500 Pax-Flex3D Proline XC orthophos XG Orthostage Auto IIIN Orthophos

Gendex Vatech Kodak Vatech Vatech Vatech Planmeca Sirona Asahi Sirona

Year of manufacture

Type

kVp

mA

time (s)

2004 2007 2007 2005–2009 2009 2010 2009 2008 2002 1999

digital digital digital digital digital digital digital digital analogue analogue

72 70 77 70–78 75 80 70 77 55 70

7 7 12 7–9 8 9 12 14 15 10

7 8–13 0.8 8–16 0.9 8 16 9 1.2 0.4

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Table 3. The DAP (the integral of air kerma across the entire x-ray beam emitted from the x-ray tube) values for panoramic and cephalometric radiography. Imaging system Digital panoramic (DR) Analog (film) All panoramic Digital cephalometric (DR) Analog (film) All cephalometric

No. of x-ray sets

Mean (mGy cm2)

Lowest (mGy cm2)

Highest (mGy cm2)

24 4 28 17 3 20

75.4 48.3 61.8 126.8 44.0 85.4

27.6 24.5 24.5 14 13 13

188.5 61.7 188.5 589.3 101.1 589.3

panoramic and cephalometric examination were 95.9 and 121.4 mGy cm2, respectively. The DRL for cephalometric radiography was higher than that of panoramic radiography. Although dental practices in the Republic of Korea have arranged for three yearly sets of routine checks on dental x-ray equipment to be carried out as a legislative requirement, DRL settings for children were found to be higher than those measured in other countries. These findings demonstrate an urgent need to reduce cephalometric radiography doses in the Republic of Korea. The majority of facilities surveyed in the present study were local in dental clinics that most likely lacked technical support; thus, dentists should be urged to seek appropriate help with respect to reducing exposure levels. Furthermore, the need for continuous education and training in radiation protection should be emphasized in dental schools and facilities. The highest DAP value (589.3 mGy cm2) was measured at a cephalometric unit using a longer exposure time (16 s) and mA (12 mA). Most digital cephalometric x-ray units (except Kodak 8000C and Pax‐500) use a narrow x-ray beam that scans the patient either horizontally or vertically to acquire images.

3rd quartile (mGy cm2)

95.9

121.4

For digital units, a 45.3‐fold difference was observed between the highest (589.3 mGy cm2) and lowest dose (14 mGy cm2) for cephalometric radiography. Digital radiographic machines provide a wide range of doses, which means that the dose-saving benefit provided by digital radiography is not always realized (Gijbels et al. 2005). In many cases, after making the transition from the analog to digital systems, the exposure parameters are not changed sufficiently to achieve dose optimization. Therefore, attention must be given to many factors when making the transition to digital systems. A few examples are standardization of equipment, training, privacy and security concerns, quality control, and diagnostic reference levels (DRLs) (Ann ICRP, 2004) (Vano 2005). Education in techniques for patient dose reduction, coupled with periodic review of doses to provide feedback data to individual departments, is the best way to achieve optimization (George et al. 2004) CONCLUSION In this study, DAPs at 75th percentile were 95.9 mGy cm2 for child panoramic radiography and 121.3 mGy cm2 for child cephalometric radiography. Most of the dental

Fig. 1. Distribution of dose area products (DAPs) for child panoramic radiography examinations. The horizontal bars represent the DAP value at 75th percentile. www.health-physics.com

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Fig. 2. Distribution of dose area products (DAPs) measurement for child cephalometric radiography examinations. The horizontal bars represent the DAP value at 75th percentile.

facilities included in the present study were equipped with a digital system. However, this study shows that the doses used for child panoramic and cephalometric radiography vary widely and that there is a need to improve optimization of protection in the Republic of Korea. It will be important for future research to establish criteria for optimal levels of image quality taking dose into consideration. Future studies should include DAP values outside of Anyang and image quality to establish DRLs for other image modalities, evaluate QA regimes, and image effectiveness. Acknowledgments—The author appreciates the data provided by the Policy and Information Analysis Department of the Korean HIRA agency. This work was supported by a grant (2012‐0747) from Chonnam National University.

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Diagnostic reference levels for panoramic and lateral cephalometric radiography of Korean children.

Pediatric patients are considered to be more radiosensitive than adults; thus, radiation dose evaluations based on radiologic examinations are particu...
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