Scatter Cloud of the C-arm

Objective Investigate the radiation scatter during C-arm fluoroscopic examinations Determine the best location for the radiographer to stand to achieve the lowest dose of radiation while performing radiographic procedures

Hypothesis Radiation scatter cloud is non-uniformly distributed Scatter radiation would be higher under the examination table

“Scatter Cloud” Risk Radiation doses can vary widely Although radiation exposure is a necessary risk, protection of staff and patients require a clear understanding of how the exposure radiates The risk cannot be eliminated entirely Quantifiable and reproducible radiation is created during fluoroscopic procedures The outcome data resembles a “scatter cloud” Room set up and imaging technique variables influence scatter radiation levels

Method Digital imaging of an acrylic adult abdominal CT phantom was exposed at both anteroposterior and lateral projections

Method Dosimeters were positioned at different heights and distances Height from the floor: 2 feet, 3 feet, 4 feet, and 5 feet Distance from isocenter: 3 feet and 6 feet

Materials OEC 9900 Elite C-arm Acrylic Adult Abdominal CT Phantom RaySafe™ i2 Dosimeters (4) and Software IV Pole Lead Aprons Tape

Dosimeter RaySafe™ i2 dosomiters visualize X-ray exposure in real-time and displays exposure values Provides instant feedback to permit radiology staff to adjust their behavior to reduce unnecessary radiation exposure Measurements are simultaneously stored for analysis for furthering new behaviors and allowing comparisons over time

Data Graph of C-Arm Scatter Cloud in AP Position The scatter cloud was most intense at the 2 foot and 3 foot levels The measured values at the 4 foot and 5 foot levels diminished to almost nothing The greatest intensity of radiation was recorded at the tube end of the plane that passed through the tube and control portions of the C-Arm Data Graph of C-Arm Scatter Cloud in AP Position *Due to physical limitations, measurements could not be taken at the 3-foot distance at the control end or the 5-foot distance at the image intensifier end in this orientation.

Data Graph of C-Arm Scatter Cloud in Lateral Position The dose rate of the scatter cloud was most intense at the 2 foot and 3 foot levels The measured values at the 4 foot and 5 foot levels diminished to almost nothing The greatest intensity was to the left and right of the emitter at a distance of 3 feet away *Room constraints prevented the placement of sensors at the 6-foot point on the tube end. The values for this position have been set to zero for graphing purposes.

Discussion The results of our measurements appear to support the hypothesis that the scatter cloud produced by the C-Arm is non-uniform The intensity of the dose rate diminished greatly from the 6 foot to the 3 foot mark As anticipated based on the inverse square law

Discussion Dose rate was reduced greatly past the 3 foot height mark perhaps due to the construction of the C-Arm and the phantom used. Dose rate was particularly high near the tube end in the lateral orientation The non-uniform nature of the scatter cloud is important Knowledge of the areas of greater dose rate can help radiation workers determine where to position themselves while the C-Arm is being used

Conclusion Our data and research indicates the best place for the radiographer to stand is behind the control end of the C-arm

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