Impact of Shielding Strategies (Wrapping vs. Covering) on Superficial Radiosensitive Organ Doses during Wide- Detector CT Examinations

<title>Abstract</title> <p> <bold>Background</bold> Protective shielding is a standard practice in CT to reduce radiation exposure to radiosensitive organs. However, its effectiveness on wide-detector CT remains insufficiently evaluated. This study aimed to compare the protective efficacy of two shielding strategies—wrapping and covering—on superficial radiosensitive organs across various scanning protocols using a wide-detector CT scanner. <bold>Methods</bold> A total of 402 patients undergoing wide-detector CT examinations (cranial, cervical, lung, abdominopelvic, and coronary CTA) were randomized into wrapping and covering shielding groups. All scans were performed using a 256-row wide-detector CT scanner. Radiation surface doses to the eye lens, thyroid, breast, and gonads were measured using thermoluminescent dosimeters (TLD). The study evaluated internal surface doses beneath shields, external doses, and unshielded organ doses. <bold>Results</bold> In cranial axial and helical scans, the wrapping method resulted in significantly higher thyroid surface doses compared to the covering method ( <italic>P</italic>  &lt; 0.001). In lung and abdominopelvic scans using automatic tube current modulation (ATCM), the unshielded doses to the thyroid and gonads exceeded CTDI _vol by approximately 58% and 70%, respectively. A dose inversion phenomenon (internal dose &gt; external dose) was observed in cervical and abdominopelvic scans due to internal scatter accumulation. Compared to helical scans, single-rotation axial scans significantly reduced radiation doses to adjacent organs outside the scan field. <bold>Conclusions</bold> The effectiveness of shielding strategies in wide-detector CT is highly site-dependent. The covering method is superior for thyroid protection during cranial scans. Optimization of scanning modes, particularly the use of axial scanning to eliminate z-axis over-scanning, is more critical for organ protection than shielding alone. Due to ATCM and anatomical synergy, CTDI _vol alone is insufficient for assessing radiation risks to unshielded organs. </p>