Patient Shielding in Ultra-High-Resolution Cone-Beam CT of the Upper Extremity with a Twin Robotic X-Ray System.

Background/

Objectives

Gantry-free cone-beam CT (CBCT) allows for ultra-high-resolution (UHR) upper extremity imaging in a comfortable tableside position. The aim of this study was to assess the organ-specific radiation burden and the effect of dedicated lead shielding in the UHR-CBCT of the wrist and elbow.

Methods

A modified Alderson-Rando phantom was scanned with the tableside UHR-CBCT mode of a twin robotic X-ray system employing identical scan parameters for wrist and elbow imaging. An ion chamber was used in conjunction with an electrometer to obtain representative organ dose measurements for the eye lens, thyroid gland, breast tissue, and abdomen. All measurements were performed with and without lead shielding.

Results

Irrespective of the examined upper extremity joint, the highest absorbed dose among the assessed organs was determined for the eye lens (wrist imaging: 0.10 ± 0.01 mGy, elbow imaging: 0.12 ± 0.01 mGy). The most effective organ dose reduction by means of shielding in wrist CBCT was achieved for the thyroid gland (-17%). In elbow CBCT, the abdomen (-48%) and the ipsilateral breast (-39%) benefited particularly from shield protection.

Conclusions

Although shielding was more effective in elbow than wrist scans, the overall impact in terms of absolute dose reduction was marginal.