SLR - December 2015 - David Bentley

Title: Fluoroscopic Radiation Exposure – Are We Protecting Ourselves Adequately?

Reference: Hoffler CE, Ilyas AM. Fluoroscopic Radiation Exposure: Are We Protecting Ourselves Adequately? J Bone Joint Surg Am. 2015 May 6;97(9): 721-725.

Scientific Literature Review

Reviewed By: David Bentley, DPM
Residency Program: Columbia Saint Mary’s Hospital Milwaukee, WI

Podiatric Relevance: While this paper was written with respect to an orthopaedic hand surgeon’s exposure to radiation in the operating room it has direct relevance to the foot and ankle surgeon. Foot and ankle specialists frequently use the same imaging techniques and exposure times as the article describes.

Purpose: (1) Examine the radiation exposure to the eyes, thyroid, chest, groin, and hands of a mannequin hand surgeon repairing a distal radial volar fracture in a sitting position with plate fixation. (2) Measure the degree at which shielding equipment can decrease exposure. (3) How exposure varies with unit size (big vs small C-arm).

Methods: An anthropomorphic surgeon model was placed in a seated position 36cm from the X-ray beam with arms extended to each side of the x-ray beam. The standard fluoroscopes were positioned 50cm vertically above the table and centered over the radial plate. The mini-fluoroscopes were positioned 25cm vertically above the table and centered over the volar radial plate. The study used three mini and three standard fluoroscopes. The standard units were set to 60 kVp and 0.8 mA. The mini units current was linked to kVp and was unable to be controlled independently. At the institution of Thomas Jefferson University in Philadelphia, PA the mean fluoroscopy time for volar plating is 60 seconds per case. However the amount of exposure generated in 60 seconds is not sufficient for measurement. Therefore each fluoroscope scanned the distal radial model for fifteen straight minutes. The fifteen minutes was chosen because on average the hand surgeon at the place of study spends approximately fifteen minutes a month exposed to ionizing radiation (15 case/month). The anthropomorphic model was fitted with radiation attenuating glasses (0.75mm equivalent at 100 kVp), a thyroid shield and apron (0.35mm lead equivalent at 100kVp), and radiation attenuating gloves (attenuation 64 percent at 60kVp).  Exposed and shielded thermoluminescent dosimeters were placed outside the protective equipment and behind the protective equipment at the level of the eyes, thyroid, chest, groin and hands. Measurements were obtained of the radiation exposures.

Results:
            Mean (standard deviation) (µSv/min)

Location Exposed Shielded P value
Eye 4.1 (4.3) 0.8 (1.1) 0.12
Thyroid 1.6 (0.8) 1.2 (0.3) 0.18
Chest 2.0 (1.7) 1.3 (0.0) 0.18
Groin 1.9 (2.1) 1.3 (0.0) 0.27
Hand 31.0 (9.2) 9.1 (2.7) 0.0001*

*Only the hand reached statistical significance

Hand exposure had the highest radiation exposure at 31 μSv/min (13 times higher than other recorded exposure levels). Eye exposure was 4 μSv/min which was 2.2 fold the exposure of the mean thyroid, chest, and groin exposure. Thyroid, chest, and groin exposure did not differ significantly from each other. Radiation reducing gloves reduced the exposure by a mean of 69.4% +/- 17.5%. The chest, thyroid, and groin shield did not significantly reduce exposure to ionizing radiation. There was overall no significant difference in exposure levels of ionizing radiation comparing the standard verse the miniature fluoroscopic units (p = 0.51).

Conclusions: The international commission on radiological protection (ICRP) recommends a maximum of 50 rem of occupational hand exposure annually – which is 10,000x the exposure generated in one minute of this study. In addition the hand exposure was reduced by almost 70 percent with the use of radiation-attenuating surgical gloves. The IRCP recommends and annual eye exposure limit of 15rem with is 35,000x a single minute of exposure in this model. Radiation attenuating glasses reduced exposure by 66 percent. Surprisingly lead thyroid shield and apron did not significantly reduce exposure. Exposures ranged from 0.16 to 0.20mrem/min when shields were not used. The ICRP recommends a limit of 2 rem of exposure averaged over five years. Ten thousand units of fluoroscopy would be needed to reach the ICRP limit.

The study makes it clear that there was not a large difference in the amount of radiation exposure of a small verses standard fluoroscope. However, this portion of the exam did not meet statistical significance. Many foot and ankle surgeons do not wear lead when using the miniature fluoroscopy due to previous articles that suggested the exposure was minimal in comparison to the large C-arm. This article questions this thought process with some evidence to suggest that there could be more exposure than what we previously thought. Though the exposure is still very low and even the busiest surgeons would have a hard time meeting the maximum ICRP recommendations.

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