探討兒童心臟電腦斷層攝影掃描程序對輻射劑量與影像品質之影響

Impact of Scan Protocol on the Relationship between Radiation Dose and Image Quality in Pediatric CT Examination

楊晴晴(Ching-Ching Yang)

《慈濟技術學院學報》 23期 (2014/09) Pp. 63-76

摘要

目的：本研究的主要目的在於探討心臟電腦斷層血管攝影（CTA）應用於兒童時輻射劑量與影像品質的對應關係。方法：我們利用64切與256切電腦斷層，針對仿1歲兒童的擬人假體進行心臟CTA掃描，掃描程序包含了無心電圖監控、回溯性心電圖監控（retrospectively ECG-gated helical, RGH）以及前導性心電圖監控（prospectively ECG-gated axial, PGA）。在劑量評估部分，我們採用熱發光劑量計量測器官劑量，並計算推得有效劑量以評估病人輻射劑量。在影像品質部份，我們利用影像雜訊大小與訊號對雜訊比值（SNR）評估重建電腦斷層影像的影像品質。結果：針對64切電腦斷層，無心電圖監控與RGH掃描所產生的有效劑量分別為1.85 ± 0.13 mSv與5.78 ± 0.41 mSv；在256切電腦斷層，無心電圖監控、RGH與PGA掃描所產生的有效劑量分別為2.66 ± 0.18 mSv、8.48 ± 0.60 mSv與1.54 ± 0.13 mSv。由影像雜訊與SNR數據發現，無心電圖監控掃描可產生出最好的影像品質，PGA掃描的影像品質較RGH掃描為佳，且PGA掃描的輻射劑量較RGH掃描有81.5%的降幅。結論：整體而言，PGA掃描在平衡兒童心臟CTA的輻射劑量與影像品質上具有良好的表現，吾人相信本研究成果將可對制定低劑量兒童心臟CTA的照影程序及參數設定上提供參考數據。

關鍵字

心臟電腦斷層血管攝影 ； 輻射劑量 ； 影像品質

並列摘要

Objective: The aim of this study was to investigate the impact of imaging protocol on the relationship between radiation exposure and image quality for pediatric cardiac CT angiography (CTA). Methods: A 64-slice CT scanner and a 256-slice CT scanner were used to perform non-gated, retrospectively ECG-gated helical (RGH) and prospectively ECG-gated axial (PGA) techniques on an anthropomorphic phantom simulating a 1-year-old child. The thermoluminescent dosimeters (TLD) were used for dose measurement. For image quality, noise and signal-to-noise-ratio (SNR) were assessed based on regions-of-interest drawn on the reconstructed CT images. Results: In 64-slice CT, the effective doses from TLD measurements were 1.85 ± 0.13 and 5.78 ± 0.41 mSv for non-gated and RGH scans, respectively. In 256-slice CT, the effective doses were 2.66 ± 0.18, 8.48 ± 0.60 and 1.54 ± 0.13 mSv for non-gated, RGH and PGA scans, respectively. The non-gated scans showed the best image quality in terms of noise and SNR. The PGA scans had better image quality than the RGH scans with 81.5% dose reduction. Conclusion: The PGA scan protocol balances radiation exposure and image quality for pediatric cardiac CTA. These results should be helpful for further investigation of dose reduction strategies in pediatric cardiac CTA.

並列關鍵字

cardiac CT angiography ； radiation dose ； image quality