|Year : 2020 | Volume
| Issue : 1 | Page : 15-20
Assessment of frontal face radiation during panoramic and cephalometric dental radiography using miniature dosimeter
Jose Amal1, A Saravana Kumar1, KN Govindarajan1, B Devanand2
1 Department of Medical Physics, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
2 Department of Radiology, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
|Date of Submission||30-May-2019|
|Date of Decision||07-Jan-2020|
|Date of Acceptance||14-Jan-2020|
|Date of Web Publication||28-Mar-2020|
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
Aim: In this research work, radiation doses to frontal face of adult and pediatric procedures were measured from 50 panoramic and 35 cephalometric dental X-ray scanners from various regions in Tamil Nadu, India. Materials and Methods: Dose measurements were carried out using a polymethylmethacrylate tissue-equivalent phantom (10 cm diameter and 14 cm length) and two miniature electronic personnel dosimeters (PM1610). Results: Panoramic procedures and the radiation doses were measured on the frontal face of adult ranged from 80 μSv to 175 μSv and 20–66 μSv at the thyroid and eye level, respectively, and for pediatric were ranged from 52 μSv to 159 μSv and 17–58 μSv at the thyroid and eye level, respectively. For cephalometric, the frontal face dose of adult ranged from 45 μSv to 114 μSv and 45–111 μSv at the thyroid and eye level, respectively, and for pediatric, the doses were ranged from 43 μSv to 107 μSv and 43–107 μSv at the thyroid and eye level, respectively. Conclusions: Based on the detailed survey, the measured values were comparable with other literature values. It was observed that exposure parameters, beam quality, beam slit width, and beam length used in the tube head are the factors that increase facial dose during dental panoramic and cephalometric procedures.
Keywords: Cephalometric, dose assessment, eye and thyroid, panoramic, radiation safety
|How to cite this article:|
Amal J, Kumar A S, Govindarajan K N, Devanand B. Assessment of frontal face radiation during panoramic and cephalometric dental radiography using miniature dosimeter. J Dent Res Rev 2020;7:15-20
|How to cite this URL:|
Amal J, Kumar A S, Govindarajan K N, Devanand B. Assessment of frontal face radiation during panoramic and cephalometric dental radiography using miniature dosimeter. J Dent Res Rev [serial online] 2020 [cited 2020 Aug 14];7:15-20. Available from: http://www.jdrr.org/text.asp?2020/7/1/15/281505
| Introduction|| |
After the invention of X-rays in 1895, its application stretched to all fields, especially in the medical field toward the diagnosis and treatment of illness. X-rays are an unavoidable tool for the diagnosis in the medical field now. The role of radiography, which is one of the human-made sources of ionizing radiation, in producing cumulative ionizing radiation in the US was increased from 15% of total annual exposure of the population in 1987 to 50% in 2006.,,, This growth may be more in India because of the high population rate.
Dental radiography is one of the most common modes of X-ray practices when compared with other radiological techniques. Dental radiological examinations represent almost 25% of all radiological procedures carried out each year.,,
During panoramic, cephalometric, and cone-beam computed tomography procedures, the upper parts of the neck along with upper and lower jaws are also irradiated. By considering the location of the thyroid gland and the dose it may receive during the scan, the adverse effects of radiation are more probably to occur there. Exposure to radiation in early life is one of the main reasons for the cause of thyroid cancer. As no exposure to radiation can be considered as free of risks, certain safety parameters have to be considered for patient protection. This study aims to measure the frontal face dose during panoramic and cephalometric dental radiography and suggests suitable methods to reduce it.
| Materials and Methods|| |
Number of scanners participated
This study was carried out using 50 panoramic (39 digital and 11 computed radiography (CR)-based detectors) and 35 cephalometric (28 digital and 7 CR-based detectors) radiography scanners from major cities in Tamil Nadu. A questionnaire, regarding radiation safety aspects, was prepared, and data were collected. These data helped to identify the frequency of quality assurance (QA) tests, type of detectors, the status of legal registration, and the availability of safety tools for safe panoramic and cephalometric radiography practice.
Patient frontal face doses were measured using miniature polimaster personnel dosimeters (PM1610) [Figure 1].
Dedicated cylindrical polymethylmethacrylate (PMMA)[Figure 2] phantom was used to replicate the patient's head. The length and diameter of the phantom were 14 cm and 10 cm, respectively.
For ensuring the proper working of the panoramic and cephalometric scanner, QA tests were done initially using a piranha dosimeter. After doing the QA tests, by using a positioning stand, the cylindrical phantom was kept on the top of a PMMA plate, as shown in [Figure 3].
|Figure 3: Schematic representation of experimental procedure for panoramic (a) and cephalometric (b) studies|
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Dosimeters were placed on the head phantom at the eye and thyroid level and pasted with surgical tape (Transpore). The distance between two polimaster dosimeters was almost 7 cm.
[Table 1] and [Table 2] show the average exposure parameters used for panoramic and cephalometric scanners. The beam length of panoramic and cephalometric scanners at the detector side ranged from 12.94 cm to 15.1 cm and 22–30 cm, respectively. The beam length for panoramic and cephalometric scanners was obtained from the manual booklet of corresponding scanners.
| Results|| |
[Table 3] and [Table 4] show the average exposure parameters used for CR and digital types of detectors in different clinics for panoramic and cephalometric scanners, respectively.
|Table 3: Average exposure parameters used for computed radiography cassette and digital type of detectors for the panoramic study|
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|Table 4: Average exposure parameters used for computed radiography cassette and digital type of detectors for the cephalometric study|
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From [Table 5] and [Table 6], it was observed that the variation of frontal face dose at eye and thyroid level for different panoramic and cephalometric scanners, respectively. Total adult and pediatric doses were the sum of thyroid and eye doses during adult and pediatric procedures.
|Table 5: Frontal face dose measured at the eye and thyroid level during panoramic radiography|
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|Table 6: Frontal face dose measured at the eye and thyroid level during cephalometric radiography|
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[Table 7] and [Table 8] show the comparison of frontal face dose between digital and CR types of panoramic and cephalometric scanners, respectively. For adult and pediatric panoramic dental radiography, the difference between total doses of CR and digital types of detectors were 29 μSv and 46 μSv, respectively. However, for adult and pediatric cephalometric dental radiography, the difference between CR and digital type of detector's total doses was −34 μSv and −25 μSv, respectively.
|Table 7: Comparison of facial dose during panoramic radiography for digital and computed radiography cassette type of detectors|
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|Table 8: Comparison of facial face dose during cephalometric radiography for digital and computed radiography cassette type of detectors|
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[Table 9] shows the average frontal dose measured for panoramic and cephalometric radiography procedures. The eye-level doses are comparatively higher for cephalometric procedures than panoramic procedures, whereas thyroid level doses are higher in panoramic procedures.
|Table 9: Average frontal face dose measured at eye and thyroid level during panoramic and cephalometric radiography|
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| Discussion|| |
The digital detector has greater sensitivity than CR to produce better image quality with the lowest exposure parameters. For most of the CR detectors, tube current and time will be constant, and anode voltage can be adjusted in steps of ±5 kV. Minute adjustments of exposure parameters are not possible for those scanners during panoramic dental radiography. Consider, actual exposure parameters were 70 kVp, 10 mA, and 14 s, and if the image is not clear, then the next possible parameters for those scanners will be 75 kVp, 10 mA, and 14 s.
However, high exposure parameters were observed in the digital type of detectors during cephalometric procedures [Table 4]. This may be ascribed to the lower beam exposed area at the detector level for some of the digital scanners than CR type scanners [Table 2]; hence, it requires slightly higher exposure for better image quality.
The total adult dose obtained for Villa rotograph plus scanner was 241 μSv which is almost double Hyperion x7 dose [Table 5]. Exposure parameter used for Villa rotograph plus (78 kV, 10 mA, and 17s) was pretty higher than Hyperion X7 (67 kV, 5 mA, and 9s). That may be the reason for high doses for Villa rotograph plus scanner. As far as, the thyroid and eye level radiation doses were concerned, the doses at the personnel dosimeters were contributed from secondary radiation, transmitted radiation, leakage radiation from tube head, patient scattered radiation, and scattered radiation from the wall. The primary beam would not hit directly the detectors since the tube head of the panoramic scanner would not rotate 3600. The height of the tube head before scanning was fixed by the expert radiographer in the scanning center after considering the thyroid and eye level. The difference in positioning of the tube head height may also result in a variation of dose measurement. For example, if the tube head is moved toward eye level, the eye level secondary and transmitted radiation may be more.
While for cephalometric radiography, almost comparable doses were observed at the eye and thyroid level [Table 6]. Contradictory to panoramic procedures, the doses at the personnel dosimeters were also contributed from the primary radiation.
The exposure parameters and beam length used for CR type of detectors are slightly high for panoramic procedures [Table 3]. This may be the reason for higher doses in the CR type of panoramic scanners [Table 7]. For cephalometric procedures, the exposure parameters are higher for digital type detectors [Table 4]. It may be the reason for higher doses for digital cephalometric procedures [Table 8].
Dose to the thyroid can be reduced to almost 33% using a thyroid shield. Especially for children, it should make mandatory to use thyroid collars and lead aprons as they may undergo many X-ray scans during their childhood period.
In [Table 10], the comparison of the present study facial doses and the dose measured by different countries at the eye and thyroid level are summarized. The findings obtained in the present study are in agreement with other country studies.,, The present study average thyroid level dose is slightly higher than that of Gavala et al.'s study, but the maximum thyroid level doses are slightly lower than Hoseini-Zarch et al. and Bristow et al. studies. This variation may be ascribed to the difference in exposure parameter, type of dosimeter used for the study, type of phantom, time slab of measurement, and the sample size.
|Table 10: Comparison of other country mean and maximum dose with the present study|
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Considering the size of the PM1610 dosimeter, the radiation dose at a specific point and dose inside the phantom is difficult to measure, which is easy to measure with thermoluminescent dosimeter. The PMMA phantom used for the present study shows only approximate doses to the facial area during panoramic and cephalometric studies. However, to obtain more accurate results, we suggest further studies using rando phantoms or on real patients using suitable dosimeters.
| Conclusion|| |
This current research work presents the data that are an outcome of the initial survey and experiments carried out on 50 panoramic and 35 cephalometric scanners in Tamil Nadu, India, to assess the frontal face dose during panoramic and cephalometric procedures for adults and pediatric. Beam length, exposure parameters, and beam quality were the main factors that affect thyroid and eye level dose. It is advised to use a proper shielding guard to reduce the scattered radiation dose. A specially designed thyroid guard is suggested for pediatric and adult patients during panoramic and cephalometric procedures. Further, it is suggested that periodical training programs and educational sessions are to be conducted among the dental staffs/faculty, undergraduate, and postgraduate dental students to follow ALARA.
Financial support and sponsorship
This work was financially supported by the Atomic Energy Regulatory Board 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], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]