| 王梦廷,梁保辉,王静,等.扫描中心对头颅CT检查器官剂量调制技术性能影响的研究[J].中华放射医学与防护杂志,2023,43(1):68-72.Wang Mengting,Liang Baohui,Wang Jing,et al.A study of the effect of scanning center on the performance of organ dose modulation in head CT[J].Chin J Radiol Med Prot,2023,43(1):68-72 |
| 扫描中心对头颅CT检查器官剂量调制技术性能影响的研究 |
| A study of the effect of scanning center on the performance of organ dose modulation in head CT |
| 投稿时间：2022-08-26 |
| DOI：10.3760/cma.j.cn112271-20220826-00352 |
| 中文关键词: 器官剂量调制技术 扫描中心 CT检查 辐射剂量 |
| 英文关键词:Organ-based tube current modulation Radiation dose CT examination |
| 基金项目:安徽省高等学校自然科学研究项目(KJ2021A0746) |
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| 中文摘要: |
| 目的 探究头颅CT检查中使用器官剂量调制(ODM)技术时,不同扫描中心对眼晶状体辐射剂量、图像质量以及剂量降低率的影响。方法 视头部模体外耳孔为等中心,开启ODM并通过调整床高分别在外耳孔及其上下2、4、6cm为扫描中心时进行CT螺旋扫描;扫描范围为颅顶至颅底。每次扫描双眼表面各放置3个热释光剂量计(TLD),计算平均值作为眼晶状体辐射剂量;记录容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP)。每次扫描后关闭ODM进行重复扫描,计算各扫描中心下ODM对剂量值的降低率。在开启ODM的各组图像中勾画感兴趣区(ROI)并评估噪声(SD)、信噪比(SNR)和对比噪声比(CNR)。结果 各扫描中心,CTDIvol和DLP相对等中心的最大变化率分别为2.46%、2.43%;眼晶状体剂量随扫描中心上移(即检查床下降)而增大,等中心上方6cm为扫描中心,眼晶状体剂量相对等中心增加了39.02%,等中心下方6cm为扫描中心相对减少了35.91%。各组扫描中心下,ODM对CTDIvol和DLP的降低率分别为7.95%~8.61%、7.91%~8.61%,差异无统计学意义(P＞0.05);眼晶状体剂量的降低率为18.09%~26.14%,等中心下方4cm为扫描中心时降低率最高,等中心次之(24.73%),差异具有统计学意义(t=0.13,P＜0.05)。随扫描中心上移,眼晶状体区域SD不断减小,SNR不断升高,等中心处CNR最高为239.79;脑实质区域SD、SNR分别为6.85~7.96、3.08~4.19,等中心处CNR最高为244.79。结论 头颅CT检查中应用ODM技术时,扫描中心偏差对眼晶状体辐射剂量和图像质量造成显著影响;同时影响ODM对眼晶状体剂量的降低率。因此,在头颅CT扫描推荐将外耳孔作为扫描中心。 |
| 英文摘要: |
| Objective To investigate the effect of different scanning centers on eye lens dose, image quality, and the dose reduction rate when using the organ dose modulation (ODM) technique in head CT.Methods The porus acusticus externus of the head phantom was considered the scanning isocenter. The ODM was initiated and the spiral scans were performed at the scanning centers with the height of porus acusticus externus and its upper and lower 2, 4, and 6 cm, respectively. The scanning range was from the top of the head to the base of the head. Three thermoluminescent dosimeters (TLD) were placed on the surface of two eyes at each scan and the average measurement value was regarded as the radiation dose to the eye lens. The volume CT dose index (CTDIvol) and dose length product (DLP) were recorded. The scans were repeated with no ODM and the dose reduction rates at each scanning center were calculated. The regions of interest (ROI) in each group of images with ODM were drawn and the noise (SD), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were evaluated.Results Compared with the isocenter, the maximum change rates of CTDIvol and DLP in each scanning center were 2.46% and 2.43%, respectively. The eye lens dose increased as the scanning centre moving upwars (i.e. the bed dropping) by 39.02% at the position of 6 cm above the isocenter and decreased by 35.91% at the position of 6 cm below the isocenter. With the seven groups of scanning centers, the reduction rates of CTDIvol and DLP caused by ODM were 7.95%-8.61%, 7.91%-8.61% respectively, and the difference in the reduction rate of each dose value was not statistically significant(P＞0.05). The reduction rate for eye lens dose ranged from 18.09% to 26.14%, with the highest reduction rate at the position of 4 cm above the isocentre and the second rate at the isocentre (24.73%). The difference in the rate of reduction at each scanning center was statistically significant(t=0.13,P＜0.05). As the scanning center moved up, the SD of the eye region decreased and the SNR increased, and the highest CNR at the isocentre was 239.79. The SD and SNR of the brain parenchyma region were 6.85-7.96 and 3.08-4.19 respectively, and the highest CNR at the isocentre was 244.79. Conclusions When ODM technique is used in head CT, the scan centre has a significant effect on the eye lens dose and image quality. Meanwhile, the reduction rate of the eye lens dose caused by ODM is also affected. Therefore, porus acusticus externus is recommended as the scanning center in head CT. |
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