Dentistry and Oral Health-Sci Forschen

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Research Article
Dose Reduction Using the dexshield™ Rectangular Collimator in Dental Radiography

   Branets I*       Dauer LT       Quinn B       Holohan B       Branets L       Colosi DC       Goren AD   

College of Dentistry, School of Dental Medicine, New York University, New York, USA

*Corresponding author: Branets I, College of Dentistry, School of Dental Medicine, New York University, New York, USA, Tel: + 917-5898533; E-mail: iob200@nyu.edu


Abstract

Background: Rectangular collimation has been recommended by both the ADA and the NCRP to significantly reduce patient exposure to ionizing radiation. Various types of rectangular collimation devices have been devised, but the dose reduction to various organs of the head and neck and overall total dose reduction has not been evaluated.

Objective: To provide dosimetric data on four bitewing X-ray exposures to head and neck organs of a female CIRS anthropomorphic phantom using round and rectangular (DEXshield™) collimation for digital imaging.

Materials and methods: Dose measurements were obtained using Optically Stimulated Luminescent (OSL) dosimeters placed in premanufactured slots of an anthropomorphic female CIRS phantom. The phantom had removable cutouts for bilateral placement of a digital sensor at the bitewing level. Four bitewing radiographs were acquired using a Gendex 765 X-ray machine at three settings using round and rectangular (DEXshield™) collimation. All exposures were repeated 15 times for each of the four bitewing exposures. The organ fractions irradiated were determined from ICRP-89 reference phantoms according to age. kVp factors and ICRP-103 tissue weighting factors were also applied.

Results: Overall, an average of between 28-47.5% dose reductions when using the shield. The highest reductions for all exposures were for the eyes, cranium and brain. The 0.08 second exposure yielded the highest dose reduction and the 0.80 second exposure the least reduction.

Conclusion: Our data indicated that the DEXshield™ significantly reduced unnecessary radiation dose to organs of the head and neck.

Keywords

Dose measurements; DEXshield™; Dose reductions; Radiography

Background

Rectangular collimation has been recommended by the American Dental Association (ADA), the National Council on Radiation Protection and Measurement (NCRP), and the International Council on Radiation Protection (ICRP) for use in dental intraoral radiography to reduce patient exposure from ionizing radiation [1-4]. Over the past decades, various types of rectangular collimating devices have been developed to significantly reduce patient exposure [5-7]. However, organ dose reduction due to scatter of the primary radiation beam has not been evaluated for any of the rectangular collimation devices.

Optically stimulated luminescent dosimetry (OSL) technology has been shown to be at least 20% more sensitive than thermo luminescent dosimetry (TLDs) at dental radiation levels [8-10]. The Micro Star In light Nano Dot Dosimeters (Landauer, Glenwood, IL) measure radiation exposure using aluminum oxide (Al2O3 :C) detectors. The amount of light released upon stimulation of the detector by a light emitting from the array is directly proportional to the radiation dose to which the detector has been exposed.

Objective

To provide dosimetric data on four bitewing X-ray exposures to head and neck organs of a female CIRS® anthropomorphic phantom using round and rectangular (DEXshieldTM) collimation for digital imaging.

Materials and Methods

Dose measurements were obtained using Optically Stimulated Luminescent (OSL) dosimeters placed inpre-manufactured slots at the location of 27 head and neck anatomic structures of an anthropomorphic female CIRS® phantom (CIRS®, Inc. Norfolk, VA). The phantom had removable cutouts for bilateral placement of a digital sensor (Dexis) at the bitewing level (Figure 1). Four bitewing exposures were acquired using a Gendex 765DC X-ray machine (Gendex, Milan, Italy) at 65 kVp, 7 mA at three different exposure settings (0.08, 0.32 and 0.80 seconds) using round collimation alone and round collimation with the DEXshieldTM (Imaging Science International. Hatfield, PA) attached (Figure 2). All exposures were repeated 15 times for each of the four bitewing positions (60 exposures). The results were divided by 60 to evaluate the average dose. Replicate exposure conditions and positioning that the average dental practitioner would employ were created. The organ fractions irradiated were determined from ICRP-89 reference phantoms according to age. kVp factors were also applied and all OSL exposures were read on a calibrated Landauer MicroStar reader.

Figure 1: Phantom with bitewing cutouts

Figure 2: DEXshield

Results

The organ dose for the shielded and unshielded collimation using the Dex is sensor and the DEXshieldTM is shown in mrads in table 1. The highest reductions for all exposures were for the eyes, cranium and brain. Overall there was an average of between 28-47.5% reductions when all organs were considered. Table 2 shows the average per cent difference for the No Shield vs. Shield at three different exposure times. The highest dose reduction, 39.1% was for the 0.08 second exposure and the 0.80 second exposure the least reduction 36.6%. The average reduction for all three exposure times was 37.7%.

Image Receptor

DEXIS

DEXIS

DEXIS

DEXIS

DEXIS

DEXIS

Shield=S, No- Shield=NS

NS

S

NS

S

NS

S

Exposure Time (s)

0.08

0.08

0.32

0.32

0.80

0.80

kVp/mA

65/7

65/7

65/7

65/7

65/7

65/7

# of Views

4

4

4

4

4

4

Organ

Avgmrad

Avgmrad

Avgmrad

Avgmrad

Avgmrad

Avgmrad

Mandible

53.96

35.86

239.80

162.54

166.84

77.85

Brain

0.71

0.41

1.83

1.26

5.87

2.54

Cranium

0.47

0.26

1.11

0.62

2.63

0.99

C-Spine

3.21

2.33

13.54

10.49

13.64

8.46

Thyroid

1.77

1.34

7.14

5.57

13.60

9.42

Eye

14.09

4.68

42.56

9.46

231.77

30.78

Table 1: Organ dose for shielded and unshielded collimator

Type of Image Receptor

DEXIS

DEXIS

DEXIS

Shield=S, No Shield=NS

NS:S

NS:S

NS:S

Exposure Time (s)

0.08

0.32

0.80

kVp.mA

65.7

65.7

65.7

# of Reps

60

60

40

Control (mrad)

16.5

16.5

16.5

 

Avg % Difference

Avg % Difference

Avg % Difference

Mandible

-33.4

-28.2

7.8

Brain

-41.9

-31.0

-45.7

Cranium

-44.9

-42.5

-37.6

C-Spine

-22.3

-31.2

-5.4

Thyroid

-24.1

-21.7

-28.6

Eye

-67.4

-77.7

-69.7

All Locations

-39.1

-37.3

-36.6

Table 2: Per cent reduction for DEXshield at three different exposure times

Conclusion and Discussion

These data indicated that the DEXshieldTM significantly reduced unnecessary radiation dose to the organs of the head and neck. By restricting the primary and secondary radiation to which a patient is exposed, rectangular collimation is the most effective method of dose reduction a practitioner can utilize.

The DEXshield™ is a unique dental x-ray position indicating device (PID) when used during imaging procedures. It aligns the x-ray beam with desired imaging site and provides an attenuating barrier to protect the patient from unnecessary radiation. The DEXshield™ is a true all-inone positioning device that allows the dental practitioner to capture both periapical and bite wing radiographs using a single device. DEXshield™ replaces the positioning ring that comes with the PID Universal Ring and reduces the radiation to the patient by at least 30%. Also the DEXshield™ is easier to use than rectangular collimation. It also reduces the possibility of cone cuts, missed apices, and malpositioning by allowing the operator to establish correct positioning and alignment.

Conflict of Interest

This study was supported by a grant from Imaging Sciences International.

References

  1. (1993) National Council on Radiation Protection and Measurements: Limitation of exposure in ionizing radiation. NCRP Report 116.
  2. ADA Council on Scientific Affairs (2001) An update on radiographic practices: information and recommendations: ADA Council on Scientific Affairs. J Am Dent Assoc 132: 234-238. [Ref.]
  3. (2007) The 2007 Recommendations of the International Commission on Radiological Protection, ICRP publication 103. Ann ICRP 37: 1-332. [Ref.]
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  5. Thomley PH, Stewardson DA, Rout PG, Burke FJ (2004) Rectangular collimation and radiographic efficacy in eight general dental practices in the West Midlands. Prim Dent care 11: 81-86. [Ref.]
  6. White SC, Pharoh MJ (2009) Oral Radiology-Principles and Interpretation. 6th Edition, St. Louis, MO. Mosby Elsevier, United States. [Ref.]
  7. Okano T, Sur J (2010) Radiation dose and protection in dentistry. Jpn Dent Sci Rev 46: 112-121. [Ref.]
  8. Perks CA, Ray GL, Prugnaud B (2007) Introduction of the Inlight monitoring service. Radiat Prot Dosimetry 125: 220-223. [Ref.]
  9. Jursinie PA (2007) Characterization of optically stimulated luminescent dosimeters, OSLD’s for clinical dosimetric measurements. Med Phys 34: 4594-4604. [Ref.]
  10. Timilsina B, Gestell T (2008) Feasibility test for optically stimulated luminescence (OSL) dot dosimeters for environmental monitoring. The Radiation Safety Journal 95: 57.

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Article Information

Article Type: Research Article

Citation: Branets I, Dauer LT, Quinn B, Holohan B, Branets L, et al. (2016) Dose Reduction Using the dexshield™ Rectangular Collimator in Dental Radiography. Int J Dent Oral Health 2(5): doi http://dx.doi.org/10.16966/2378-7090.212

Copyright: © 2016 Branets I, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Publication history: 

  • Received date: 21 Jan 2016

  • Accepted date: 05 Jul 2016

  • Published date: 11 Jul 2016
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