Commentary: Radiation Exposure in Hand Surgery

Commentary: Radiation Exposure in Hand Surgery Gordon Singer, MD, MS, Denver, CO In the study by Athwal et al,1 the authors compare radiation scatter from the large and the mini C-arm and conclude what may seem intuitively obvious: that the mini C-arm results in a lower exposure rate than the large C-arm. This result is, however, related to the particular experimental setup used in this study. Radiation exposure is directly related to the distance from the x-ray source. The setup used in this study had the cadaver hand directly on the intensifier and furthest from the beam source when using the mini C-arm. For the large C-arm, the cadaver hand was placed 45 cm away from the intensifier and therefore correspondingly closer to the x-ray beam source. The reader is therefore cautioned about concluding that the mini C-arm always results in a lower exposure, being that exposure rate greatly depends upon distance from the source. Radiation scatter is approximately 0.1% of the entrance exposure rate (EER) at 1 m and one quarter of 0.1% at 2 m. In a limited scatter data experiment, the same hand phantom was placed directly onto the image intensifier of both the large and small C-arm (also OEC models). Although the radiation output of the large C-arm was higher, the EER to the phantom was actually less. Because the distance from the source was greater for the large C-arm than the mini C-arm, this resulted in an overall lower exposure rate for the large C-arm when using the same hand phantom. In general, the large C-arm is used for larger body parts and will therefore result in a higher entrance and scatter rate. In the MiniView 6800 Operator’s Guide2, scatter data are available in chapter 13. The EER for a wrist is 34 mRem/min at 45 cm source-to-skin distance and increases to 684 mRem/min at 10 cm source-to-skin distance, a factor of 20. Imaging at a higher level (for example, a shoulder) and at 10 cm will result in 7928 mRem/min EER (chapter 13, page 14) or 233 times the level of a wrist further from the beam. The mini C-arm is capable of significant exposure; it depends on what is put in it to be imaged and how close it is put to the source. When the exposure rate is less (by increasing distance from the source), the scatter is correspondingly less. When the patient gets less radiation, the surgeon does as well. The surgeon can reduce scatter exposure by increasing the distance of the patient to the x-ray source, purposely minimizing fluoroscopy time, and enabling use of the low dose option.

References 1. Athwal GS, Bueno RA Jr, Wolfe, SW. Radiation exposure in hand surgery: mini versus standard C-arm. J Hand Surg 2005; 30A:1310 –1316. 2. MiniView 6800 Operator’s Guide. OE OEC Medical Systems, Inc., Salt Lake City, Utah.

From the Department of Orthopedic Surgery, Kaiser Permanente, Denver, CO. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding author: Gordon Singer MD, MS, Dept. of Orthopedic Surgery, Kaiser Permanente, 2045 Franklin Street, Denver, CO 80205; e-mail: [email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A06-0032$30.00/0 doi:10.1016/j.jhsa.2005.07.003

The Journal of Hand Surgery

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