- Email: [email protected]
Radiation Exposure in Hand Surgery: Mini Versus Standard C-Arm
Radiation Exposure in Hand Surgery: Mini Versus Standard C-Arm George S. Athwal, MD, London, Ontario, Canada, Reuben A. Bueno Jr, MD, Scott W. Wolfe, MD, New York, NY
Purpose: The use of intraoperative fluoroscopy in hand surgery is common. Two types of fluoroscopic units are available: the mini C-arm and the standard C-arm. There is little literature on the radiation exposure from the mini C-arm, therefore, the primary goal of this study was to quantify and compare the amount of radiation exposure to members of the surgical team (surgeon, first assistant, nurse, anesthesiologist) using both standard and mini C-arms in a simulated wrist surgery setup. Mini C-arm positioning was also examined to determine the safest configuration to minimize radiation exposure to surgeons. Methods: Radiation dosimeters were used to test 2 commercially available fluoroscopy units in a simulated wrist surgery setup with a cadaveric upper extremity. Several different configurations of the C-arms were tested to determine radiation exposure rates to surgeons and the operating room staff. Results: The mean in-beam radiation exposures with the use of the mini and standard C-arms were 3,720 mR/h and 6,540 mR/h, respectively. The mini C-arm had universally less radiation exposure than the standard C-arm in the clinical configurations tested. The safest configuration of mini C-arm use to minimize radiation exposure was with the surgeon standing on the image intensifier side of the unit as compared with the source side. Mini C-arm radiation exposure to the hands, groin, chest, and thyroid of the operating surgeons were well below the National Council of Radiation Protection and Measurement’s annual dose limits. Conclusions: In the clinical configurations tested in this study the mini C-arm had lower radiation exposures than the standard C-arm. To reduce radiation exposure maximally surgeons should stand behind the lead-encased image intensifier and should use techniques to reduce exposure. (J Hand Surg 2005;30A:1310 –1316. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Exposure, fluoroscopy, hand surgery, mini C-arm, radiation.
From the Hand and Upper Limb Centre, St. Joseph’s Health Care, University of Western Ontario, London, Ontario, Canada; and the Division of Hand Surgery, Hospital for Special Surgery, New York, NY. Received for publication February 22, 2005; accepted in revised form June 22, 2005. No benefits in any form have been received or will be received from a commerical party related directly or indirectly to the subject of this article. Corresponding author: George S. Athwal, MD, Hand and Upper Limb Centre, St. Joseph’s Health Care, University of Western Ontario, 268 Grosvenor St., London, Ontario, N6A 4L6, Canada; e-mail: [email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A06-0031$30.00/0 doi:10.1016/j.jhsa.2005.06.023
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The Journal of Hand Surgery
The use of fluoroscopy in hand surgery has become ubiquitous. In 1980 more than 15 million skeletal radiographic studies were performed per year in the United States.1 A current statistic is unavailable and likely would be impossible to calculate because of the near-universal presence of C-arm units and because some mini C-arms are used without complete usage documentation. The literature pertaining to radiation exposure with mini C-arm fluoroscopy units is in disagreement. Badman et al2 recently reported that the cumulative doses with mini C-arm fluoroscopy are relatively
Athwal, Bueno, and Wolfe / Radiation Exposure in Hand Surgery
Table 1. National Council on Radiation Protection and Measurements Annual Dose Limits Individual Circumstance
Radiation Dose Limit
Whole body Eyes Forearms Hands Gestational (embryo and fetus)
5,000 mrem per year 15,000 mrem per year 30,000 mrem per year 50,000 mrem per year 500 mrem per gestation
small and that “some of the indispensable precautions required for use of the large C-arm are not applicable to the mini C-arm.” In contrast, Singer (Presented at the 59th Annual Meeting of the American Society for Surgery of the Hand, 2004) found that the level of radiation exposure with the mini C-arm was 187 times greater than what was predicted by the manufacturer and recommended that “surgeons who use the mini C-arm use precautions to minimize radiation exposure, in particular to their hands.” In the United States the National Council on Radiation Protection and Management (NCRP) sets forth annual guidelines for radiation dose limits3 that recommend that whole-body exposures remain less than 5,000 mrem/y (Table 1). Worldwide the International Commission on Radiological Protection offers recommendations to national regulatory and advisory agencies on radiation protection4,5; it recommends a whole-body annual dose limit of 2,000 mrem/y, which is significantly lower than the NCRP’s legislated limit of 5,000 mrem/y. To investigate radiation exposure it is important to understand the origins of the dose limits set forth by the NCRP.3 Three different sources of exposure were used to extrapolate the dose limits for low-dose radiation exposure3,6: medical occupational exposures, atomic bomb survivors, and nuclear accident survivors. The methodology, albeit the only one available, inherently is flawed because 2 of the 3 sources examined are high-dose single events. The calculated low-dose limits are not based on hard science3,7 and may be clouded by results obtained from populations exposed to high-dose single-event radiation exposures.8 The fundamental point in annual dose limit determination is the calculation of health risk associated with low-dose radiation. The end point for high-dose single-event radiation exposure is death. The end point for low-dose radiation exposure is much more difficult to determine because low-dose exposure
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does not lead to death immediately but may lead to life shortening,9 somatic mutations, and heritable mutations.7 Presently there are 2 competing hypotheses on the potential risks for low-dose radiation in humans being debated among geneticists, health physicists, and radiation biologists.9 The more popular hypothesis, which is supported by most radiation biologists and geneticists, proposes that no dose of radiation can be considered completely safe and its usage must be determined on a risk-versus-benefit analysis. The second hypothesis proposes that the health risk of low-dose radiation of less than 10,000 mrem is immeasurable and may be nonexistent.7,10 Because of this dichotomy hand surgeons must be informed of the potential exposures from mini Carms and also on the safest C-arm configurations to minimize exposure. Although the literature on large C-arms is extensive11–17 there is little information on mini C-arms, especially pertaining to their usage in hand surgery during which surgeons are operating in close proximity to the devices and usually without lead protection. There were 2 goals of this study: first to determine the amount of radiation exposure to members of the surgical team (surgeon, first assistant, nurse, anesthesiologist) using both mini and standard C-arms in a simulated wrist surgery setup, and second to determine the safest configuration of mini C-arm positioning to minimize radiation exposure to surgeons.
Materials and Methods A mini C-arm (OEC MiniView 6800; OEC Medical Systems, Salt Lake City, UT) and a standard C-arm (OEC 9800 Plus; OEC Medical Systems, Salt Lake City, UT) were used to provide fluoroscopic images of a cadaver wrist in a simulated hand surgery setup. The cadaver was implanted with a 3.5-mm volar wrist T-plate (AO Synthes, Paoli, PA) and was imaged to simulate radiation scatter that may occur during surgery. The experimental setup involved 2 sitting stools and a hand table (Allen Medical, Acton, MA). The hand table was attached to a standard operating table in an operating room at our institution and placed at a standard height of 85 cm to match the nursing instrument table. The mini C-arm was tested with the C-arm horizontal, which is the position used most commonly at our institution for hand and wrist cases (Fig. 1). The mini C-arm was positioned at a height of 8 cm above the hand table. The standard C-arm was brought in to the surgical setup in the vertical position with the
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Figure 1. (A) The experimental setup involved using the mini C-arm in the horizontal fashion. Radiation measurements were taken on the source side of the C-arm (surgeon A) and on the image intensifier side of the C-arm (surgeon B). (B) The standard C-arm was tested in the vertical position with the source below the hand table and the image intensifier at the top of the C-arm.
source located below the hand table and the image intensifier at the top of the C-arm as recommended by the manufacturer (Fig. 1). The standard C-arm source was lowered to its limit, thereby bringing the image intensifier as close as possible to the cadaver wrist on the hand table: a distance of 45 cm. This position allows the greatest distance from the source to the imaged extremity to decrease direct radiation exposure, as recommended by the manufacturer. Both fluoroscopy units were set on the default automatic mode that adjusts the power level to the characteristics of the imaged object. The mini and standard C-arms’ automatic power settings for imaging of the cadaver wrist were 55 kvp/.045 mA and 55 kvp/.74 mA, respectively. Two different devices were used to measure the amount of radiation exposure during the experiment. A radiation dosimeter (Keithley Model 35000; Inovision, Cleveland, OH) was used to measure the rate of radiation exposure directly within the beam by placing the probe on the cadaver wrist during active fluoroscopy with both the mini and standard C-arms. The in-beam exposure measurement, termed entrance exposure rate, represents the amount of radiation a surgeon’s hands would be subject to if placed within the imaging field. A pressurized ion chamber survey meter (Victoreen Model 450P, Inovision, Cleveland, OH) was used to measure the rate of scatter radiation. The scatter radiation experimental setup involved obtaining measurements at locations representing the hands (immediately outside the beam), groin, chest, and
thyroid of surgeons A and B. As performed by Tremains et al13 these locations were chosen after measurements were made of one investigator (R.A.B.) positioned in the operating suite as though using the standard C-arm in the sitting position and the mini C-arm in the sitting and standing positions. Surgeon A (source-side) mini C-arm hand measurements were taken adjacent to the source as though stabilizing the C-arm over the hand table. Surgeon B (image intensifier side) mini C-arm hand measurements were taken adjacent to the image intensifier outside the beam as though stabilizing the patient’s wrist over the intensifier drum. Standard C-arm hand measurements were taken for both surgeons 5 cm outside the direct field on the hand table as though stabilizing the patient’s wrist on the hand table. Seated measurements were taken 50 cm from the center of the hand table at heights of 65, 110, and 130 cm, representing the approximate areas of the surgeon’s groin, chest, and thyroid, respectively. Standing measurements also were taken at a distance of 50 cm from the center of the hand table at heights of 90, 135, and 160 cm, representing the groin, chest, and thyroid, respectively. Radiation scatter measurements with the pressurized ion chamber survey meter also were taken at distances representing nursing (100 cm) and anesthesiology (150 cm) at chest height (135 cm). At each location (Fig. 2) radiation measurements were obtained by activating the C-arm and recording the rate on the dosimeter after it reached a steady state (3–5 s) (Fig. 3). Five measurements were taken at each location and means and SDs were calculated.
Athwal, Bueno, and Wolfe / Radiation Exposure in Hand Surgery
Figure 2. Radiation scatter measurements for the mini C-arm were taken for surgeon A (on the source side of the C-arm) and surgeon B (on the image intensifier side of the C- arm). At 1 meter from the center of the hand table at a 45° angle and at chest height, measurements were taken for nurses C and D. E1 represented the anesthesiologist at the head of the operating table 1.5 meters from the center of the hand table. E2 in setup 2 represents the anesthesiologist on the image intensifier side of the C-arm. II, image intensifier; S, source.
To estimate relevant clinical exposure the mini C-arm fluoroscopy times of 25 patients with surgically treated distal radius fractures were recorded. These cases were performed at our institution by 6 fellowship-trained hand surgeons. The mean fluoroscopy time was 138 seconds (range, 25–323 s). The data were analyzed statistically with the use of the paired and unpaired Student t tests and analysis of variance as indicated. A p value of less than .05 was considered statistically significant.
Results The in-beam radiation measurements (entrance exposure rate) for the mini and standard C-arms at the level of the cadaver wrist were 3,720 mR/h (range, 3,660 –3,780 mR/h) and 6,540 mR/h (range, 6,300 – 6,900 mR/h), respectively. The mini C-arm had significantly less in-beam radiation exposure than the
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standard C-arm (p ⬍ .01) in this surgical configuration. The radiation exposure rates obtained in all configurations are shown in Table 2. With this experimental setup the scatter radiation exposure to both surgeons’ hands, groins, chests, and thyroids were significantly less with the mini C-arm (p ⬍ .01). The scatter radiation to the nursing staff and anesthesiology staff also was significantly less with the mini C-arm (p ⬍ .01). When comparing surgeon A sitting (source side) with surgeon B sitting (image intensifier side) with the use of the mini C-arm in the horizontal position, surgeon B sitting was exposed to significantly less scatter radiation to vital areas (groin, chest, thyroid) than surgeon A (p ⬍ .01). Surgeon B, however, did receive significantly greater radiation exposure to the hands (p ⬍ .01) than surgeon A. When comparing surgeon B standing with surgeon B sitting and surgeon A with the mini C-arm, surgeon B standing (image intensifier side of the mini C-arm) received the lowest amount of scatter radiation to all vital areas (p ⬍ .01).
Discussion The results from this experimental design indicate that radiation exposure to surgeons and operating room staff with the mini C-arm are 5 to 10 times lower than the standard C-arm. This largely is because the mini C-arms operate at lower power settings (kVp and mA). The default automatic setting allows the unit to calculate and use the lowest power setting based on the specific characteristics of the object being imaged. With the mini C-arm it should be noted that the kVp and mA may be adjusted manually and increased up toward standard C-arm
Table 2. Mean Scatter Radiation With Use of the Mini and Standard C-Arms C-Arm Mini C-arm
Standard C-arm
Operating Room Staff
Chest (mR/h)
Groin (mR/h)
Thyroid (mR/h)
Hands (Adjacent to Beam)
Surgeon A sitting Surgeon B sitting Surgeon B standing Nurse C (II side) Nurse D (source side) Anesthesia E1 (source side) Anesthesia E2 (II side) Surgeon A Surgeon B Nursing* Anesthesia*
2.04 1.28 0.39 0.16 0.52 0.25 0.09 23.4 23.0 2.30 1.27
2.92 2.30 0.08 N/A N/A N/A N/A 15.1 15.2 N/A N/A
2.08 0.58 0.21 N/A N/A N/A N/A 16.6 16.4 N/A N/A
4.18 7.52 7.50 N/A N/A N/A N/A 39.6 40.0 N/A N/A
II, image intensifier; N/A, not applicable. *Because of the vertical orientation of standard C-arm only a single measurement for each operating room staff was required.
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Figure 3. Experimental setup with a cadaver arm (inset) placed on the image intensifier to mimic intraoperative radiation scatter. Surgeon A’s hand measurements were taken immediately adjacent to the source mimicking the intraoperative stabilization of the C-arm. Surgeon B’s hand measurements were taken immediately adjacent to the image intensifier mimicking stabilization of the patient’s wrist over the intensifier.
power, thereby also increasing radiation exposure. A common error with mini C-arms occurs with the scenario of a dark initial image. A frequent mistake is to increase the kVp and mA to improve the image quality. Instead we would recommend that the contrast and brightness controls on the monitor should be adjusted first to enhance the image; should this fail the power then may be increased. It is the authors’ experience that the power settings are increased far too commonly and that most imaging problems can be solved by adjusting brightness and contrast. Distance from the C-arm radiation source to the imaged object also determines the amount of direct radiation exposure.13 Surgeons should make a conscious effort to image patients as far from the source as possible; with the mini C-arm this would mean placing the imaged extremity directly onto the image intensifier. With the standard C-arm used in the recommended vertical position the source should be lowered to the floor to maximize the source to skin distance. When using the mini C-arm the lowest radiation exposures to vital areas (groin, chest, thyroid) occurred with the surgeon standing directly behind the image intensifier (surgeon B). In this position the surgeon’s groin is protected from scatter and direct radiation by the lead-encased image intensifier, creating a cone of greatest protection (Fig. 4). The surgeon seated or standing on the source side of the C-arm experiences the greatest scatter exposure be-
cause the radiation reflects off the cadaver and image intensifier back toward the source. Likewise nursing and anesthesia on the source side experience significantly higher scatter doses. Mini C-arm scatter radiation to the hands of surgeon B adjacent to the image intensifier was significantly greater than surgeon A. We hypothesize that this occurred for 2 reasons: (1) the measurement location receives a concentrated dose of scatter because it reflects off the cadaver and image intensifier and (2) the location may receive small doses of direct radiation from the periphery of the primary beam. The mean fluoroscopy time of surgically treated distal radius fractures at our institution was 138 seconds (range, 25–323 s). Therefore if a surgeon (sitting on the source side) does 10 cases a day, performs surgery 3 days per week for 52 weeks a year, and uses 138 seconds of mini C-arm fluoroscopy per case, then the annual groin exposure would be 175 mR/y, which is 3.5% of the NCRP annual total body limit of 5,000 mR (Table 1). If this same surgeon used the mini C-arm as surgeon B (standing behind the image intensifier) then they would be exposed to 23.4 mR/y, which is 0.5% of the annual recommended dose limit. The dose limit for hand exposure is much higher at 50,000 mR/y. The highest hand exposure rate obtained with the mini C-arm without entering the beam was 7.52 mR/h. Therefore by using the earlier-described scenario this would result in an exposure equivalent to 0.9% of the annual limit.
Athwal, Bueno, and Wolfe / Radiation Exposure in Hand Surgery
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Figure 4. A surgeon standing on the image intensifier side of the C-arm experiences significantly less radiation exposure to vital areas. The image intensifier drum acts as a shield to radiation creating a relative safety cone.
Mini C-arm and standard C-arm in-beam direct exposures are significantly higher at 3,720 mR/h and 6,540 mR/h, respectively, and should be avoided. If the surgeon placed his hands within the beam for 20 seconds during surgical procedure the radiation exposure would exceed 20 mR, an order of magnitude higher than that realized if care is taken to keep the hands away from the beam. The decision to use radioprotective equipment such as lead aprons, thyroid collars, eyewear, and radioresistant surgical gloves must be made on an individual basis. The mini C-arm exposure results obtained in the current study are well below the NCRP annual dose limits, therefore an argument can be made for the limited use of radioprotective equipment. One must remember, however, that the annual dose limits are predicted and that the popular hypothesis on the risk for low-dose radiation states that no dose of radiation can be considered safe. The use of these devices and the need for protective equipment must be determined on a risk-versus-benefit analysis. This study hopes to promote radiation awareness and the safe use of fluoroscopy. The use of radiation is governed by the principle of keeping exposures as low as reasonably achievable.10 Techniques to keep exposures as low as possible are the use of laser sighting to minimize images used for positioning, avoidance of image enhancement, collimation of the
beam when possible, use of the low-dose function available on both C-arms, avoidance of manual power increase, use of the last-image-hold feature, and use of single-shot fluoroscopy instead of realtime fluoroscopy. Our study had several limitations. It involved a simulated surgical setup with the use of a single cadaveric specimen. All tests were run at the same power setting, therefore all results reflect radiation exposures for imaging of the wrist. The exposure rates for imaging denser or larger specimens such as an elbow or forearm were not studied, however, logic would conclude that the doses would be higher. Another limitation was that only one manufacturer (OEC Medical Systems) was used for both mini and standard C-arm units, consequently exposure rates for other brands are unknown, if different machines are set at the same power, however, they theoretically should have the same radiation exposure. Although this study found that mini C-arm exposures universally were lower than standard C-arm exposures, it should be stated that these results reflect only the clinical configurations tested. Therefore radiation exposures from other uncommonly used configurations were not examined such as using the standard C-arm in the inverted position. The authors would like to thank Dr. I. Holodny, Mr. Michael Sheehan, and Dr. M. Peterson for their assistance with this study.
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References 1. Kereiakes JD, Rosenstein M. Handbook of radiation doses in nuclear medicine and diagnostic x-ray. Boca Raton, CRC Press 1980:241–243. 2. Badman BL, Rill L, Butkovich B, Arreola M, Vander Griend RA. Radiation exposure with use of the mini-C-arm for routine orthopaedic imaging procedures. J Bone Joint Surg Am 2005;87A:13–17. 3. National Council on Radiation Protection and Measurements. Review of the current state of radiation protection philosophy: limitation of exposure of ionizing radiation. NCRP report no. 116. Bethesda, MD, United States Government Printing Office, 1993. 4. Hendee WR. History, current status, and trends of radiation protection standards. Med Phys 1993;20:1303–1314. 5. Beral V, Gilbert ES, Mabuchi K, Sinclair WK, Tao Z. Lowdose extrapolation of radiation-related cancer risk. International Commission on Radiological Protection (ICRP) Draft Report, Available at: www.icrp.org. Accessed June 2004. 6. Herscovici D Jr, Sanders RW. The effects, risks, and guidelines for radiation use in orthopaedic surgery. Clin Orthop 2000;375:126 –132. 7. Prasad KN, Cole WC, Hasse GM. Health risks of low dose ionizing radiation in humans: a review. Exp Biol Med 2004; 229:378 –382. 8. Pochin EE. Radiation risks in perspective. Br J Radiol 1987; 60:42–50. 9. Sinclair WK. Effects of low-level radiation and comparative risk. Radiology 1981;138:1–9.
10. Health Physics Society. Radiation risk in perspective. Position statement of the health physics society. In: Health Physics Society Directory and Handbook. Health Physics Society, 2004. 11. Sanders R, Koval KJ, DiPasquale T, Schmelling G, Stenzler S, Ross E. Exposure of the orthopaedic surgeon to radiation. J Bone Joint Surg 1993;75A:326 –330. 12. Theocharopoulos N, Perisinakis K, Damilakis J, Papadokostakis G, Hadjipavlou A, Gourtsoyiannis N. Occupational exposure from common fluoroscopic projections used in orthopaedic surgery. J Bone Joint Surg 2003;85A:1698 – 1703. 13. Tremains MR, Georgiadis GM, Dennis MJ. Radiation exposure with use of the inverted-c-arm technique in upperextremity surgery. J Bone Joint Surg 2001;83A:674 – 678. 14. Mehlman CT, DiPasquale TG. Radiation exposure to the orthopaedic surgical team during fluoroscopy: “how far away is far enough?” J Orthop Trauma 1997;11:392–398. 15. Tasbas BA, Yagmurlu MF, Bayrakci K, Ucaner A, Heybeli M. Which one is at risk in intraoperative fluoroscopy? Assistant surgeon or orthopaedic surgeon? Arch Orthop Trauma Surg 2003;123:242–244. 16. Muller LP, Suffner J, Wenda K, Mohr W, Rommens PM. Radiation exposure to the hands and the thyroid of the surgeon during intramedullary nailing. Injury 1998;29:461– 468. 17. Giannoudis PV, McGuigan J, Shaw DL. Ionising radiation during internal fixation of extracapsular neck of femur fractures. Injury 1998;29:469 – 472.
Purpose: The use of intraoperative fluoroscopy in hand surgery is common. Two types of fluoroscopic units are available: the mini C-arm and the standard C-arm. There is little literature on the radiation exposure from the mini C-arm, therefore, the primary goal of this study was to quantify and compare the amount of radiation exposure to members of the surgical team (surgeon, first assistant, nurse, anesthesiologist) using both standard and mini C-arms in a simulated wrist surgery setup. Mini C-arm positioning was also examined to determine the safest configuration to minimize radiation exposure to surgeons. Methods: Radiation dosimeters were used to test 2 commercially available fluoroscopy units in a simulated wrist surgery setup with a cadaveric upper extremity. Several different configurations of the C-arms were tested to determine radiation exposure rates to surgeons and the operating room staff. Results: The mean in-beam radiation exposures with the use of the mini and standard C-arms were 3,720 mR/h and 6,540 mR/h, respectively. The mini C-arm had universally less radiation exposure than the standard C-arm in the clinical configurations tested. The safest configuration of mini C-arm use to minimize radiation exposure was with the surgeon standing on the image intensifier side of the unit as compared with the source side. Mini C-arm radiation exposure to the hands, groin, chest, and thyroid of the operating surgeons were well below the National Council of Radiation Protection and Measurement’s annual dose limits. Conclusions: In the clinical configurations tested in this study the mini C-arm had lower radiation exposures than the standard C-arm. To reduce radiation exposure maximally surgeons should stand behind the lead-encased image intensifier and should use techniques to reduce exposure. (J Hand Surg 2005;30A:1310 –1316. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Exposure, fluoroscopy, hand surgery, mini C-arm, radiation.
From the Hand and Upper Limb Centre, St. Joseph’s Health Care, University of Western Ontario, London, Ontario, Canada; and the Division of Hand Surgery, Hospital for Special Surgery, New York, NY. Received for publication February 22, 2005; accepted in revised form June 22, 2005. No benefits in any form have been received or will be received from a commerical party related directly or indirectly to the subject of this article. Corresponding author: George S. Athwal, MD, Hand and Upper Limb Centre, St. Joseph’s Health Care, University of Western Ontario, 268 Grosvenor St., London, Ontario, N6A 4L6, Canada; e-mail: [email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A06-0031$30.00/0 doi:10.1016/j.jhsa.2005.06.023
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The Journal of Hand Surgery
The use of fluoroscopy in hand surgery has become ubiquitous. In 1980 more than 15 million skeletal radiographic studies were performed per year in the United States.1 A current statistic is unavailable and likely would be impossible to calculate because of the near-universal presence of C-arm units and because some mini C-arms are used without complete usage documentation. The literature pertaining to radiation exposure with mini C-arm fluoroscopy units is in disagreement. Badman et al2 recently reported that the cumulative doses with mini C-arm fluoroscopy are relatively
Athwal, Bueno, and Wolfe / Radiation Exposure in Hand Surgery
Table 1. National Council on Radiation Protection and Measurements Annual Dose Limits Individual Circumstance
Radiation Dose Limit
Whole body Eyes Forearms Hands Gestational (embryo and fetus)
5,000 mrem per year 15,000 mrem per year 30,000 mrem per year 50,000 mrem per year 500 mrem per gestation
small and that “some of the indispensable precautions required for use of the large C-arm are not applicable to the mini C-arm.” In contrast, Singer (Presented at the 59th Annual Meeting of the American Society for Surgery of the Hand, 2004) found that the level of radiation exposure with the mini C-arm was 187 times greater than what was predicted by the manufacturer and recommended that “surgeons who use the mini C-arm use precautions to minimize radiation exposure, in particular to their hands.” In the United States the National Council on Radiation Protection and Management (NCRP) sets forth annual guidelines for radiation dose limits3 that recommend that whole-body exposures remain less than 5,000 mrem/y (Table 1). Worldwide the International Commission on Radiological Protection offers recommendations to national regulatory and advisory agencies on radiation protection4,5; it recommends a whole-body annual dose limit of 2,000 mrem/y, which is significantly lower than the NCRP’s legislated limit of 5,000 mrem/y. To investigate radiation exposure it is important to understand the origins of the dose limits set forth by the NCRP.3 Three different sources of exposure were used to extrapolate the dose limits for low-dose radiation exposure3,6: medical occupational exposures, atomic bomb survivors, and nuclear accident survivors. The methodology, albeit the only one available, inherently is flawed because 2 of the 3 sources examined are high-dose single events. The calculated low-dose limits are not based on hard science3,7 and may be clouded by results obtained from populations exposed to high-dose single-event radiation exposures.8 The fundamental point in annual dose limit determination is the calculation of health risk associated with low-dose radiation. The end point for high-dose single-event radiation exposure is death. The end point for low-dose radiation exposure is much more difficult to determine because low-dose exposure
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does not lead to death immediately but may lead to life shortening,9 somatic mutations, and heritable mutations.7 Presently there are 2 competing hypotheses on the potential risks for low-dose radiation in humans being debated among geneticists, health physicists, and radiation biologists.9 The more popular hypothesis, which is supported by most radiation biologists and geneticists, proposes that no dose of radiation can be considered completely safe and its usage must be determined on a risk-versus-benefit analysis. The second hypothesis proposes that the health risk of low-dose radiation of less than 10,000 mrem is immeasurable and may be nonexistent.7,10 Because of this dichotomy hand surgeons must be informed of the potential exposures from mini Carms and also on the safest C-arm configurations to minimize exposure. Although the literature on large C-arms is extensive11–17 there is little information on mini C-arms, especially pertaining to their usage in hand surgery during which surgeons are operating in close proximity to the devices and usually without lead protection. There were 2 goals of this study: first to determine the amount of radiation exposure to members of the surgical team (surgeon, first assistant, nurse, anesthesiologist) using both mini and standard C-arms in a simulated wrist surgery setup, and second to determine the safest configuration of mini C-arm positioning to minimize radiation exposure to surgeons.
Materials and Methods A mini C-arm (OEC MiniView 6800; OEC Medical Systems, Salt Lake City, UT) and a standard C-arm (OEC 9800 Plus; OEC Medical Systems, Salt Lake City, UT) were used to provide fluoroscopic images of a cadaver wrist in a simulated hand surgery setup. The cadaver was implanted with a 3.5-mm volar wrist T-plate (AO Synthes, Paoli, PA) and was imaged to simulate radiation scatter that may occur during surgery. The experimental setup involved 2 sitting stools and a hand table (Allen Medical, Acton, MA). The hand table was attached to a standard operating table in an operating room at our institution and placed at a standard height of 85 cm to match the nursing instrument table. The mini C-arm was tested with the C-arm horizontal, which is the position used most commonly at our institution for hand and wrist cases (Fig. 1). The mini C-arm was positioned at a height of 8 cm above the hand table. The standard C-arm was brought in to the surgical setup in the vertical position with the
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Figure 1. (A) The experimental setup involved using the mini C-arm in the horizontal fashion. Radiation measurements were taken on the source side of the C-arm (surgeon A) and on the image intensifier side of the C-arm (surgeon B). (B) The standard C-arm was tested in the vertical position with the source below the hand table and the image intensifier at the top of the C-arm.
source located below the hand table and the image intensifier at the top of the C-arm as recommended by the manufacturer (Fig. 1). The standard C-arm source was lowered to its limit, thereby bringing the image intensifier as close as possible to the cadaver wrist on the hand table: a distance of 45 cm. This position allows the greatest distance from the source to the imaged extremity to decrease direct radiation exposure, as recommended by the manufacturer. Both fluoroscopy units were set on the default automatic mode that adjusts the power level to the characteristics of the imaged object. The mini and standard C-arms’ automatic power settings for imaging of the cadaver wrist were 55 kvp/.045 mA and 55 kvp/.74 mA, respectively. Two different devices were used to measure the amount of radiation exposure during the experiment. A radiation dosimeter (Keithley Model 35000; Inovision, Cleveland, OH) was used to measure the rate of radiation exposure directly within the beam by placing the probe on the cadaver wrist during active fluoroscopy with both the mini and standard C-arms. The in-beam exposure measurement, termed entrance exposure rate, represents the amount of radiation a surgeon’s hands would be subject to if placed within the imaging field. A pressurized ion chamber survey meter (Victoreen Model 450P, Inovision, Cleveland, OH) was used to measure the rate of scatter radiation. The scatter radiation experimental setup involved obtaining measurements at locations representing the hands (immediately outside the beam), groin, chest, and
thyroid of surgeons A and B. As performed by Tremains et al13 these locations were chosen after measurements were made of one investigator (R.A.B.) positioned in the operating suite as though using the standard C-arm in the sitting position and the mini C-arm in the sitting and standing positions. Surgeon A (source-side) mini C-arm hand measurements were taken adjacent to the source as though stabilizing the C-arm over the hand table. Surgeon B (image intensifier side) mini C-arm hand measurements were taken adjacent to the image intensifier outside the beam as though stabilizing the patient’s wrist over the intensifier drum. Standard C-arm hand measurements were taken for both surgeons 5 cm outside the direct field on the hand table as though stabilizing the patient’s wrist on the hand table. Seated measurements were taken 50 cm from the center of the hand table at heights of 65, 110, and 130 cm, representing the approximate areas of the surgeon’s groin, chest, and thyroid, respectively. Standing measurements also were taken at a distance of 50 cm from the center of the hand table at heights of 90, 135, and 160 cm, representing the groin, chest, and thyroid, respectively. Radiation scatter measurements with the pressurized ion chamber survey meter also were taken at distances representing nursing (100 cm) and anesthesiology (150 cm) at chest height (135 cm). At each location (Fig. 2) radiation measurements were obtained by activating the C-arm and recording the rate on the dosimeter after it reached a steady state (3–5 s) (Fig. 3). Five measurements were taken at each location and means and SDs were calculated.
Athwal, Bueno, and Wolfe / Radiation Exposure in Hand Surgery
Figure 2. Radiation scatter measurements for the mini C-arm were taken for surgeon A (on the source side of the C-arm) and surgeon B (on the image intensifier side of the C- arm). At 1 meter from the center of the hand table at a 45° angle and at chest height, measurements were taken for nurses C and D. E1 represented the anesthesiologist at the head of the operating table 1.5 meters from the center of the hand table. E2 in setup 2 represents the anesthesiologist on the image intensifier side of the C-arm. II, image intensifier; S, source.
To estimate relevant clinical exposure the mini C-arm fluoroscopy times of 25 patients with surgically treated distal radius fractures were recorded. These cases were performed at our institution by 6 fellowship-trained hand surgeons. The mean fluoroscopy time was 138 seconds (range, 25–323 s). The data were analyzed statistically with the use of the paired and unpaired Student t tests and analysis of variance as indicated. A p value of less than .05 was considered statistically significant.
Results The in-beam radiation measurements (entrance exposure rate) for the mini and standard C-arms at the level of the cadaver wrist were 3,720 mR/h (range, 3,660 –3,780 mR/h) and 6,540 mR/h (range, 6,300 – 6,900 mR/h), respectively. The mini C-arm had significantly less in-beam radiation exposure than the
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standard C-arm (p ⬍ .01) in this surgical configuration. The radiation exposure rates obtained in all configurations are shown in Table 2. With this experimental setup the scatter radiation exposure to both surgeons’ hands, groins, chests, and thyroids were significantly less with the mini C-arm (p ⬍ .01). The scatter radiation to the nursing staff and anesthesiology staff also was significantly less with the mini C-arm (p ⬍ .01). When comparing surgeon A sitting (source side) with surgeon B sitting (image intensifier side) with the use of the mini C-arm in the horizontal position, surgeon B sitting was exposed to significantly less scatter radiation to vital areas (groin, chest, thyroid) than surgeon A (p ⬍ .01). Surgeon B, however, did receive significantly greater radiation exposure to the hands (p ⬍ .01) than surgeon A. When comparing surgeon B standing with surgeon B sitting and surgeon A with the mini C-arm, surgeon B standing (image intensifier side of the mini C-arm) received the lowest amount of scatter radiation to all vital areas (p ⬍ .01).
Discussion The results from this experimental design indicate that radiation exposure to surgeons and operating room staff with the mini C-arm are 5 to 10 times lower than the standard C-arm. This largely is because the mini C-arms operate at lower power settings (kVp and mA). The default automatic setting allows the unit to calculate and use the lowest power setting based on the specific characteristics of the object being imaged. With the mini C-arm it should be noted that the kVp and mA may be adjusted manually and increased up toward standard C-arm
Table 2. Mean Scatter Radiation With Use of the Mini and Standard C-Arms C-Arm Mini C-arm
Standard C-arm
Operating Room Staff
Chest (mR/h)
Groin (mR/h)
Thyroid (mR/h)
Hands (Adjacent to Beam)
Surgeon A sitting Surgeon B sitting Surgeon B standing Nurse C (II side) Nurse D (source side) Anesthesia E1 (source side) Anesthesia E2 (II side) Surgeon A Surgeon B Nursing* Anesthesia*
2.04 1.28 0.39 0.16 0.52 0.25 0.09 23.4 23.0 2.30 1.27
2.92 2.30 0.08 N/A N/A N/A N/A 15.1 15.2 N/A N/A
2.08 0.58 0.21 N/A N/A N/A N/A 16.6 16.4 N/A N/A
4.18 7.52 7.50 N/A N/A N/A N/A 39.6 40.0 N/A N/A
II, image intensifier; N/A, not applicable. *Because of the vertical orientation of standard C-arm only a single measurement for each operating room staff was required.
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Figure 3. Experimental setup with a cadaver arm (inset) placed on the image intensifier to mimic intraoperative radiation scatter. Surgeon A’s hand measurements were taken immediately adjacent to the source mimicking the intraoperative stabilization of the C-arm. Surgeon B’s hand measurements were taken immediately adjacent to the image intensifier mimicking stabilization of the patient’s wrist over the intensifier.
power, thereby also increasing radiation exposure. A common error with mini C-arms occurs with the scenario of a dark initial image. A frequent mistake is to increase the kVp and mA to improve the image quality. Instead we would recommend that the contrast and brightness controls on the monitor should be adjusted first to enhance the image; should this fail the power then may be increased. It is the authors’ experience that the power settings are increased far too commonly and that most imaging problems can be solved by adjusting brightness and contrast. Distance from the C-arm radiation source to the imaged object also determines the amount of direct radiation exposure.13 Surgeons should make a conscious effort to image patients as far from the source as possible; with the mini C-arm this would mean placing the imaged extremity directly onto the image intensifier. With the standard C-arm used in the recommended vertical position the source should be lowered to the floor to maximize the source to skin distance. When using the mini C-arm the lowest radiation exposures to vital areas (groin, chest, thyroid) occurred with the surgeon standing directly behind the image intensifier (surgeon B). In this position the surgeon’s groin is protected from scatter and direct radiation by the lead-encased image intensifier, creating a cone of greatest protection (Fig. 4). The surgeon seated or standing on the source side of the C-arm experiences the greatest scatter exposure be-
cause the radiation reflects off the cadaver and image intensifier back toward the source. Likewise nursing and anesthesia on the source side experience significantly higher scatter doses. Mini C-arm scatter radiation to the hands of surgeon B adjacent to the image intensifier was significantly greater than surgeon A. We hypothesize that this occurred for 2 reasons: (1) the measurement location receives a concentrated dose of scatter because it reflects off the cadaver and image intensifier and (2) the location may receive small doses of direct radiation from the periphery of the primary beam. The mean fluoroscopy time of surgically treated distal radius fractures at our institution was 138 seconds (range, 25–323 s). Therefore if a surgeon (sitting on the source side) does 10 cases a day, performs surgery 3 days per week for 52 weeks a year, and uses 138 seconds of mini C-arm fluoroscopy per case, then the annual groin exposure would be 175 mR/y, which is 3.5% of the NCRP annual total body limit of 5,000 mR (Table 1). If this same surgeon used the mini C-arm as surgeon B (standing behind the image intensifier) then they would be exposed to 23.4 mR/y, which is 0.5% of the annual recommended dose limit. The dose limit for hand exposure is much higher at 50,000 mR/y. The highest hand exposure rate obtained with the mini C-arm without entering the beam was 7.52 mR/h. Therefore by using the earlier-described scenario this would result in an exposure equivalent to 0.9% of the annual limit.
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Figure 4. A surgeon standing on the image intensifier side of the C-arm experiences significantly less radiation exposure to vital areas. The image intensifier drum acts as a shield to radiation creating a relative safety cone.
Mini C-arm and standard C-arm in-beam direct exposures are significantly higher at 3,720 mR/h and 6,540 mR/h, respectively, and should be avoided. If the surgeon placed his hands within the beam for 20 seconds during surgical procedure the radiation exposure would exceed 20 mR, an order of magnitude higher than that realized if care is taken to keep the hands away from the beam. The decision to use radioprotective equipment such as lead aprons, thyroid collars, eyewear, and radioresistant surgical gloves must be made on an individual basis. The mini C-arm exposure results obtained in the current study are well below the NCRP annual dose limits, therefore an argument can be made for the limited use of radioprotective equipment. One must remember, however, that the annual dose limits are predicted and that the popular hypothesis on the risk for low-dose radiation states that no dose of radiation can be considered safe. The use of these devices and the need for protective equipment must be determined on a risk-versus-benefit analysis. This study hopes to promote radiation awareness and the safe use of fluoroscopy. The use of radiation is governed by the principle of keeping exposures as low as reasonably achievable.10 Techniques to keep exposures as low as possible are the use of laser sighting to minimize images used for positioning, avoidance of image enhancement, collimation of the
beam when possible, use of the low-dose function available on both C-arms, avoidance of manual power increase, use of the last-image-hold feature, and use of single-shot fluoroscopy instead of realtime fluoroscopy. Our study had several limitations. It involved a simulated surgical setup with the use of a single cadaveric specimen. All tests were run at the same power setting, therefore all results reflect radiation exposures for imaging of the wrist. The exposure rates for imaging denser or larger specimens such as an elbow or forearm were not studied, however, logic would conclude that the doses would be higher. Another limitation was that only one manufacturer (OEC Medical Systems) was used for both mini and standard C-arm units, consequently exposure rates for other brands are unknown, if different machines are set at the same power, however, they theoretically should have the same radiation exposure. Although this study found that mini C-arm exposures universally were lower than standard C-arm exposures, it should be stated that these results reflect only the clinical configurations tested. Therefore radiation exposures from other uncommonly used configurations were not examined such as using the standard C-arm in the inverted position. The authors would like to thank Dr. I. Holodny, Mr. Michael Sheehan, and Dr. M. Peterson for their assistance with this study.
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