Copyright © 2009 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Matthew J. Allen, Vet MB, PhD*,
Ohio State University, Columbus, Ohio
Posted February 2009
Despite the widely recognized dangers of ionizing radiation,
orthopaedists routinely place themselves in harm's way during the course of
their daily professional activities through the use of fluoroscopy. A number of
studies have attempted to quantify the risk of radiation exposure from the
perspectives of both surgeon and patient. The consensus from these studies has
been that the doses absorbed by the patient and the physician are relatively
low as compared with current recommended annual exposure limits1 and
may be further reduced through safe working practices that are based on the
ALARA (as-low-as-reasonably-achievable) principle2. Mini-C-arms also
offer an advantage since they permit excellent image acquisition with
concomitant reductions in the radiation dose as compared with standard C-arms3.
The authors of the current study have recognized two
important limitations in the application of these findings to current orthopaedic
practice. Firstly, most of the available literature on radiation exposure from
C-arms or mini-C-arms is based on imaging of small joints, such as the hand or
wrist. In a practical setting, there is a growing trend toward the use of
fluoroscopy to image larger bones and joints, for example in spine surgery and
minimally invasive fracture repair. Since the size of the specimen that is to
be imaged has a direct effect on the radiation dose required for imaging, the
authors sought to quantify the total radiation doses to which patients and
physicians are exposed during large-joint imaging. The second issue that they
raise is that of inadequate training in either radiation safety or in the
operation of the C-arm. Suboptimal positioning of the target tissue within the
C-arm has the potential to increase both the direct radiation dose to the patient
and the scattered radiation dose to the surgeon and assistants.
In an attempt to address these concerns, the authors
designed a simple experiment in which they quantified radiation exposure with
use of either a full-size C-arm or a mini-C-arm during fluoroscopic examination
of a cadaveric human ankle joint. Dosimeters were placed on the skin at the
level of the ankle joint (to measure the surface dose received by the patient)
and around the x-ray source and image intensifier in order to quantify x-ray
scatter to which the surgeon might be exposed.
The results from this study confirm the importance of
correctly positioning the limb within the C-arm. For a full-sized C-arm with
the ankle joint positioned 2 inches from the x-ray tube (considered the worst-case
scenario), the "patient" was exposed to a skin dose of 8988 mrem. Scattered
radiation doses varied from <10 mrem to 38 mrem, depending on the precise
location relative to the C-arm. If the same specimen configuration was used
with the mini-C-arm, the patient dose was 3912 mrem, a decrease of 56% relative
to the full-size unit, while the scattered dose ranged from <10 mrem to 18
mrem.
With the ankle joint positioned immediately above the image
intensifier (considered the best-case scenario), the patient dose with a
full-size C-arm was 850 mrem and the scattered dose ranged from <10 mrem to
17 mrem. Use of the mini-C-arm reduced the patient dose to 305 mrem but had no
significant effect on the scattered dose.
The results from this study demonstrate the range of
measurable radiation exposure to both the patient and the surgeon, depending on
the type of C-arm used and the technique. In the scenario that was modeled, the
exposure rate was on the order of 38 mrem for a five-minute exposure. These
data are consistent with exposure rates measured directly on the hands of
surgeons who are performing hand surgery under mini-C-arm fluoroscopy (5 to 80
mrem per case)4. Positioning of the imaged specimen closer to the
radiation source increased patient exposure but had relatively less effect on
surgeon exposure. For any given specimen orientation, radiation doses were
reduced with a mini-C-arm as compared with a standard C-arm.
The scattered radiation doses measured in this study were
relatively low and were roughly equivalent to the surface dose from a routine
chest x-ray (approximately 20 mrem). However, repetitive exposure of surgeons
to even low levels of scattered radiation remains a cause for concern. Medical
personnel involved in fluoroscopic procedures should be trained and certified
both in the principles of radiation safety and in the approved operating
procedures for the specific C-arm that they are using. The authors are to be
commended for this detailed and thoughtful study that reminds all of us of our obligations
with regard to the safety of the patient and the attending medical team.
*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
References
1. Singer G. Occupational radiation exposure to the surgeon. J Am Acad Orthop Surg. 2005;13:69-76.
2. Brateman L. Radiation safety considerations for diagnostic radiology personnel. Radiographics. 1999;19:1037-55.
3. Athwal GS, Bueno RA Jr, Wolfe SW. Radiation exposure in hand surgery: mini versus standard C-arm. J Hand Surg [Am]. 2005;30:1310-6.
4. Singer G. Radiation exposure to the hands from mini-C-arm fluoroscopy. J Hand Surg [Am]. 2005;30:795-7.
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