Defining the radiation "scatter cloud" in the interventional suite.

OBJECTIVE: We hypothesized that fluoroscopic imaging creates radiation fields that are unevenly scattered throughout the endovascular suite. We sought to quantify the radiation dose spectrum at various locations during imaging procedures and to represent this in a clinically useful manner. METHODS: Digital subtraction imaging (Innova 4100; GE Healthcare, Waukesha, Wisc) of the abdomen and pelvis was performed on a cadaver in anteroposterior, left lateral, and right anterior oblique 45° projections. Radiation exposure was monitored in real time with DoseAware dosimeters (Phillips, Houston, Tex) in eight radial projections at distances of 2, 4, and 6 ft from the center of the imaged field, each at 5-ft heights from the floor. Three to five consecutive data points were collected for each location. RESULTS: At most positions around the angiographic table, radiation exposure decreased as the distance from the source emitter increased; however, the intensity of the exposure varied dramatically around the axis of imaging. With anteroposterior imaging, the radiation fields have symmetric dumbbell shapes, with maximal exposure perpendicular to the table at the level of the gantry. Peak levels at 4 and 6 ft from the source emitter were 2.4 times and 3.4 times higher, respectively, than predicted based on the inverse square law. Maximal radiation exposure was measured in the typical operator position 2 ft away and perpendicular to the table (4.99 mSv/h). When the gantry was rotated 45° and 90°, the radiation fields shifted, becoming more asymmetric, with increasing radiation doses to 10.9 and 69 mSv/h, respectively, on the side of the emitter. Minimal exposure is experienced along the axis of the table, decreasing with distance from the source (<0.77 mSv/h). CONCLUSIONS: Quantifiable and reproducible radiation scatter is created during interventional procedures. Radiation doses vary widely around the perimeter of the angiography table and change according to imaging angles. These data are easily visualized using contour plots and scatter three-dimensional mesh plots. Rather than the concentric circles predicted by the inverse square law, these data more closely resemble a "scatter cloud." Knowledge of the actual exposure levels within the endovascular environment may help in mitigating these risks to health care providers.

Minimizing radiation exposure to the vascular surgeon.

OBJECTIVES: To determine radiation exposure for members of an endovascular surgery team during imaging procedures by varying technique. METHODS: Digital subtraction angiography imaging of the abdomen and pelvis (Innova 4100; GE, Fairfield, Conn) was performed on cadavers, varying positioning and technique within the usual bounds of clinical practice. Radiation exposure was monitored in real-time with dosimeters (DoseAware; Philips, Andover, Mass) to simulate the position of the operator, assistant, and anesthesiologist. The DoseAware system reports radiation exposure in 1-second intervals. Three to five consecutive data points were collected for each imaging configuration. RESULTS: Operator radiation exposure is minimized with detector-to-patient distance <5 cm (2.1 mSv/h) in contrast to 10 to 15 cm (2.8 mSv/h); source-to-image distance of <15 cm (2.3 mSv/h) in contrast to 25 cm (3.3 mSv/h). Increasing image magnification from 0 (2.3 mSv/h) to 3 (0.83 mSv/h) decreases operator exposure by 74%. Increasing linear image collimation from 0 (2.3 mSv/h) to 10 cm (0.30 mSv/h) decreases operator exposure by 87%. The anesthesiologist's radiation exposure is 11% to 49% of the operator's, greatest in the left anterior oblique (LAO) 90 degree projection. The assistant's radiation exposure is 23% to 46% of the operator's. The highest exposure to the operator was noted to be in the LAO 90 degree projection (30.3 mSv/h) and lowest exposure with 10-cm vertical collimation (0.28 mSv/h). CONCLUSIONS: Varying imaging techniques results in different radiation exposure to members of an endovascular surgery team. Knowledge of the variable intensity of radiation exposure may allow modification of the technique to minimize radiation exposure to the team while providing suitable imaging.