A Randomized Controlled Trial about the Levels of Radiation Exposure Depends on the Use of Collimation C-arm Fluoroscopic-guided Medial Branch Block

Abstract

Background: C-arm fluoroscope has been widely used to promote more effective pain management; however, unwanted radiation exposure for operators is inevitable. We prospectively investigated the differences in radiation exposure related to collimation in Medial Branch Block (MBB).

Methods: This study was a randomized controlled trial of 62 MBBs at L3, 4 and 5. After the patient was laid in the prone position on the operating table, MBB was conducted and only AP projections of the fluoroscope were used. Based on a concealed random number table, MBB was performed with (collimation group) and without (control group) collimation. The data on the patient's age, height, gender, laterality (right/left), radiation absorbed dose (RAD), exposure time, distance from the center of the field to the operator, and effective dose (ED) at the side of the table and at the operator's chest were collected. The brightness of the fluoroscopic image was evaluated with histogram in Photoshop.

Results: There were no significant differences in age, height, weight, male to female ratio, laterality, time, distance and brightness of fluoroscopic image. The area of the fluoroscopic image with collimation was 67% of the conventional image. The RAD (29.9 ± 13.0, P = 0.001) and the ED at the left chest of the operators (0.53 ± 0.71, P = 0.042) and beside the table (5.69 ± 4.6, P = 0.025) in collimation group were lower than that of the control group (44.6 ± 19.0, 0.97 ± 0.92, and 9.53 ± 8.16), resepectively.

Conclusions: Collimation reduced radiation exposure and maintained the image quality. Therefore, the proper use of collimation will be beneficial to both patients and operators.

Keywords: collimation; image quality; radiation absorbed dose; radiation exposure.

Fig. 1

(A) Fluoroscopic image with collimation in collimation group. (B) Conventional fluoroscopic image in control group. Rectangles: The lumbar spine area was cutted in the fluoroscope pictures to compare the exposure of image using the Photoshop program. The width was trimmed to the same as width of lower L5 body. The height was cut from bottom to top in the circular fluoroscopic image.

Fig. 2

(A) Table: effective dose at side of operating table. (B) Body: effective dose at physician's left chest.

Fig. 3

The figure indicates the histogram on the Photoshop. As the mean value approaches to 0, it indicates the picture was dark, whereas it indicates light when the mean value closes to 255. We assumed that medium value and proper exposure is 127.5.

Fig. 4

(A) Comparison between effective dose at left chest of operator, and side of the table, among group. Body: ^*P value : 0.042, Table : ^*P value : 0.025. (B) Comparsion of RAD (radiation absorbed dose) between control group and collimation group.

Fig. 5

Use of adjustable (iris) collimator to limit the field to the area of interest reduces radiation exposure to the patient and improves image resolution by decreasing the range of tissue density included in the image field.