|Year : 2020 | Volume
| Issue : 2 | Page : 77-81
Establishment of pediatric local diagnostic reference levels for intraoral radiography
Amal Jose, A Saravana Kumar, KN Govindarajan, P Manimaran
Department of Medical Physics, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
|Date of Submission||14-Mar-2020|
|Date of Decision||12-May-2020|
|Date of Acceptance||02-Jun-2020|
|Date of Web Publication||27-Aug-2020|
Dr. A Saravana Kumar
Department of Medical Physics, PSG Institute of Medical Sciences and Research, Coimbatore . 641 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
The objective of the present study is to propose a set of regional diagnostic reference levels (DRLs) for pediatric intraoral (IO) radiography procedures classified by IO examinations in Tamil Nadu, India. Of the 120 total units, 60 were digital and the remaining 60 units used film as image receptors. The third quartile values obtained for the selected IO examinations ranged from 1.05 mGy for the mandibular incisors to 1.48 mGy for the maxillary molars. The DRLs of the present study compare well with other International published DRLs. Following this primary study, DRLs will be proposed for other regions of the country, to arrive at national DRLs for pediatric IO dentistry.
Keywords: Diagnostic reference level, incident air kerma, optimization, radiation safety
|How to cite this article:|
Jose A, Kumar A S, Govindarajan K N, Manimaran P. Establishment of pediatric local diagnostic reference levels for intraoral radiography. Radiat Prot Environ 2020;43:77-81
|How to cite this URL:|
Jose A, Kumar A S, Govindarajan K N, Manimaran P. Establishment of pediatric local diagnostic reference levels for intraoral radiography. Radiat Prot Environ [serial online] 2020 [cited 2020 Nov 23];43:77-81. Available from: https://www.rpe.org.in/text.asp?2020/43/2/77/293629
| Introduction|| |
According to UNSCEAR 2000 Report, dental radiological examinations are one of the most common types of medical exposures performed. The most frequent imaging technique in dental radiography is intraoral (IO) imaging, either to examine single or multiple teeth. Although the radiation exposure related to IO radiography is comparatively low, a child may often need repeated dental radiological procedures during their childhood and adolescence. Children are more sensitive to radiation than adults and also have a much longer life span., Hence, more consideration should be paid to reduce unnecessary medical radiation exposure to children. To keep the patient exposure within reasonable levels, radiation doses delivered during dental examinations must be monitored regularly.
Optimizing radiation dose during IO radiography, a vital part of dental care, should be the major worry of every dentist for the safe conduct of the X-ray procedures. Diagnostic reference level (DRL) is a practical tool that can be used by dental clinics for optimizing dental exposures over a period of time, by comparing the exposures of the clinic with the DRLs set for the examinations in question, as recommended by the International Commission on Radiological Protection (ICRP)., Unnecessary radiation exposure to patients can be controlled by DRL.
Several quantities,,,,, have been used for proposing DRL in dental radiography based on the availability and modality of quantity. However, ICRP 135 has recommended Incident Air Kerma (Ka,i) as the quantity for proposing DRL in IO radiography.
A minimum patient sample size of 10–20, performing the same examination, must be chosen for establishing the regional DRLs. Larger the sample, more authentic is the DRL established. After finding Ka,i for the sample population, the median value of the distribution is calculated to set the DRL.
Many studies have reported adult DRLs for IO, panoramic, and cephalometric dental procedures.,,,, However, DRLs for IO pediatric dental radiography have been relatively very less in the published literature so far. To address this issue, the Atomic Energy Regulatory Board of India (AERB) and PSG Institute of Medical Sciences and Research have initiated a program to propose pediatric (patients who were <15 years old) DRL for IO radiography in Tamil Nadu, India for the first time. The purpose of this study was to measure Ka,i for six IO procedures and to propose regional DRL from the dose distribution.
| Materials and Methods|| |
Selection of intraoral scanners
A total of 120 IO units, both imported and indigenous, including both handheld (11 units) and wall-mounted (109 units) were selected, from Tamil Nadu state, India, for this study. The chosen IO units cover the entire state. Out of the total, 60 units were digital and the remaining 60 units used film (E/F speed films) as detectors. Before commencing the study, a questionnaire was prepared and given to the respective technologists/dentists to collect the data, namely the exposure technique factors, the detector type, availability of thyroid guards, the status of periodic quality assurance (QA), and the workload. After collecting the details, the quality assurance tests were performed on the units to ensure regulatory compliance. Parameters such as accuracy of irradiation time(s) and operating potential (kVp), linearity of tube current (mA/mAs), consistency of radiation output, and radiation leakage level from X-ray tube housing at 1 m from the focus were considered for all the units during the QA test. Only those scanners that passed the test were chosen for the study.
The dose measurements were performed for six IO procedures between 2018 and 2020; maxillary incisor, maxillary premolar, maxillary molar, mandibular incisor, mandibular premolar, and mandibular molar. The cone lengths of the X-ray units varied from 20 to 22 cm. However, the majority (115 units) of X-ray units used circular cones with a 6 cm diameter field, while the remaining 5 units used rectangular cones with an area of 16 cm2.
Most of the X-ray units selected for the present study were operating at 70 kV [Figure 1]. The study was carried out with routine pediatric exposure parameters. The average exposure parameters used for film types of detectors are higher than the digital type of units [Table 1]. The average kVp and mA used for units equipped with film types of detectors (68 kVp and 7.6 mA) are also slightly higher than the digital type of image receptors (65 kVp and 5.7 mA).
|Figure 1: Tube voltage distribution of the X-ray units used in the present study|
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Radiation dose measurements were made using the Piranha dosimeter (Piranha 557, RTI electronics, Sweden).
During the measurement, the calibrated piranha solid-state dosimeter was kept at the center of the exit cone of the tube head of the IO scanner as shown in [Figure 2]. Sensitive volume of the dosimeter is covered completely by the radiation field. Regular pediatric exposure parameters were loaded for the radiation dose measurement and exposed three times to check the reproducibility of the measurement in the absence of the patient. Measurements were made for 20 patient exposure parameters for the same examination. Total samples of 14,400 were included in the present study. The lead protection in the dosimeter protects backscatter and gives accurate Ka,i readings, by excluding the surface backscatter. Statistical parameters such as average, median, and 3rd quartile values were calculated using Microsoft Excel software.
|Figure 2: Pictorial representation of dosimeter (a) and measurement procedure (b)|
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| Results|| |
[Table 2] shows that there exists a large variation between the Ka,i values for different X-ray scanners. The minimum and maximum Ka,i was observed for units equipped with film and digital type of detectors, respectively.
[Table 3] summarizes the average of obtained median and third quartile of Ka,i values found from six different types of IO examinations calculated from 120 different X-ray units for their routine pediatric exposure settings. The average of median Ka,i and of third quartile values of digital detectors is comparatively lower than that of film type of detectors. [Figure 3] shows in graphical form, the median Ka,i in mGy measured for 120 IO units. The horizontal line in the graph shows the assessed DRL value.
|Table 3: Median Ka, i and third quartile values obtained from 120 intraoral dental units|
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|Figure 3: Summary of median Ka,imeasurements for different intraoral examinations, ordered by increasing Ka, i. The horizontal bar represents the third quartile Ka, ivalue|
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The DRL assessed in the present study was calculated from the median value as per ICRP 135 recommendations using Microsoft Excel software by the formula “PERCENTILE, (array, k),” where array represents the obtained Ka,i values and k represents the percentile value (in the present case k is 0.75).
From the findings of the present study, the proposed DRLs for Maxillary Incisor', “Maxillary Premolar,” “Maxillary Molar,” “Mandibular Incisor,” “Mandibular Premolar,” and “Mandibular Molar” examinations are 1.16, 1.25, 1.48, 1.05, 1.08, and 1.18 mGy, respectively.
| Discussion|| |
From the obtained Ka,i values, one can find a large variation between the Ka,i values among different dental hospitals/clinics [Table 2]. This shows irregularities of radiological practices performed in clinical routine. The large variation may be attributed to the difference in the type of X-ray units and their inherent filters, the type of image receptors, manufacturing year, and exposure parameters. It is remarkable that several facilities using adult exposure parameters for children. Due to the difference in their oral anatomical structures, higher exposure parameters on children sometimes may degrade the image quality on one hand and cause high radiation dose to children on the other. It can be concluded that many dentists or radiographers do not use dose optimized programs for pediatric patients.
As shown in [Table 4], it was noted that the third quartile value for child IO radiography in Cyprus ranged from 1.88 mGy to 4.75 mGy. The proposed DRL value for maxillary molar examination in UAE and mandibular examination in the UK (health protection agency) were 0.704 mGy and 0.7 mGy, respectively. The present study DRL ranges from 1.05 to 1.48 mGy.
|Table 4: Comparison of other country pediatric intraoral diagnostic reference level (Ka, i method) and the present study diagnostic reference level|
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The present study DRL is higher than UAE and the UK DRLs, are lesser than Cyprus. This difference may be ascribed to the difference in machine exposure parameters, inherent filters, and diagnostic practices. The difference in age of the units and the type of dosimeter used in the present study, may also partially contribute to the wide range of results.
The limitation of the present study is the unavailability of data regarding the reject and repeat rates in IO radiography. Although the radiation doses received by the patients are lower during a single exposure, the patient may receive a higher overall dose because of the repeated exposures. However, it is suggested to quantify retakes involved in pediatric IO radiography in future studies to estimate the overall dose received by the patients.
| Conclusions|| |
The present study reports pediatric IO DRLs for maxillary incisor, maxillary premolar, maxillary molar, mandibular incisor, mandibular premolar, and mandibular molar procedures for the first time in Tamil Nadu region, India. 120 IO units were included for the study after omitting 12 units that failed in AERB QA tests. The present study shows a large variation in Ka,i values, among the X-ray units, for the same dental examination for the routine procedures. Clinics/hospitals functioning with digital detectors are not always accompanying with lower radiation dose. The X-ray unit operator should be aware of the sensitivity of detectors and the possibility of radiation dose reduction. Periodic QA tests are suggested for monitoring the consistency of dose outputs, and timer linearity as it failed in many X-ray units. This study also suggests the scant involvement of dentists and radiographers in QA programs, which would help to familiarize common errors responsible for increases in the patient radiation dose. Dentists are advised to practice with radiation safety guards and the right techniques during pediatric radiological procedures. Periodic training and educational programs are suggested for dentists/technologists on the concept and proper use of DRLs and on the possibilities of reducing the radiation dose to patients where there exist no preset exposure parameters. These measures would bring the clinic doses closer to the established DRLs.
Financial support and sponsorship
This work was supported by the AERB of India and PSG Institute of Medical Sciences and Research, Coimbatore, India.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]