Radiation exposure benefit of a lead cap in invasive cardiology

Abstract

Background: Occupational head exposure to radiation in cardiologists may cause radiation induced cataracts and an increased risk of brain cancer.

Objective: To determine the effectiveness of 0.5 mm lead equivalent caps, not previously used in invasive cardiology, in comparison with a 1.0 mm lead equivalent ceiling mounted lead glass screen.

Design: An anthropomorphic Alderson-Rando phantom was used to represent the patient. Scatter entrance skin air kerma to the operator position (S-ESAK-O) was measured during fluoroscopy for all standard angulations and the S-ESAK-O per dose-area product (DAP) calculated, as applied to the phantom.

Results: Measured mean (SD) left/right anterior oblique angulation ratios of S-ESAK-O without lead devices were 23.1 (10.1), and varied as a function of tube angulation, body height, and angle of incidence. S-ESAK-O/DAP decreased with incremental operator body height by 10 (3)% per 10 cm. A 1.0 mm lead glass shield reduced mean S-ESAK-O/DAP originating from coronary angiography from 1089 (764) to 54 (29) nSv/Gy x cm2. A 0.5 mm lead cap was effective in lowering measured levels to 1.8 (1.1) nSv/Gy x cm2. Both devices together enabled attenuation to 0.5 (0.1) nSv/Gy x cm2. The most advantageous line of vision for protection of the operator's eyes was > or = 60 degrees rightward.

Conclusions: Use of 0.5 mm lead caps proved highly effective, attenuating S-ESAK-O to 2.7 (2.0) x 10(-3) of baseline, and to 1.2 (1.4) x 10(-3) of baseline where there was an additional 1.0 mm lead glass shield. These results could vary according to the x ray systems used, catheterisation protocols, and correct use of radiation protection devices.

Figures

Figure 1

Position of Rando phantom (A); image intensifier (B); articulated ceiling screen (C), lengthened by a lead flap beside the table (D); longitudinal table mounted lead drape (E), enhanced by a top shield (F); and lead cover around the phantom’s thighs (G). The detector for scatter radiation in operator’s position (H) is directed towards the left side at an angle of incidence of −40°.

Figure 2

Protective garments with 0.5 mm lead equivalency: cap, glasses, collar, and apron.

Figure 3

Position of tube, patient’s couch, and interventional operator, as well as angles of incidence of the scatter radiation to the operator: −120°, −90°, −60°, −40°, and −20° from the left side; 0°; and +20°, +40°, +60°, +90°, and +120° from the right side to the operator’s front.

Figure 4

Dependence of primary S-ESAK to the operator’s unprotected head (μSv/h) during low level fluoroscopy on tube angulation and angle of radiation incidence. LAO, left anterior oblique; PA, posterior-anterior; RAO, right anterior oblique; S-ESAK-O, scatter entrance skin air kerma to the operator.

Figure 5

Scatter ESAK-O per dose–area product, applied to the phantom during coronary angiography (nSv/Gy × cm2), as an inverse function of body height.

Figure 6

Scatter ESAK-O per dose–area product, applied to the phantom during coronary angiography (nSv/Gy × cm2), as a function of body height (140 cm (black symbols) . . . 200 cm (white symbols)) and angle of radiation incidence within −120° to +120° to the operator’s front. Effect of a 1.0 mm lead equivalent over couch shield, of a 0.5 mm lead equivalent cap, and of both devices together.

Figure 7

S-ESAK-O (nSv/h), as a function of tube angulation without lead protection (diamonds), and with the use of a 1.0 mm overcouch lead glass screen (triangles), of a 0.5 mm lead cap (squares), and of both devices together (circles). Effect of line of vision and monitor position in −40° tube direction (black), and +60° to the operator’s right side (white).