乳腺X射线摄影中受检者辐射剂量评估研究进展

乳腺X射线摄影在乳腺癌的筛查和诊疗中发挥了重要作用, 但X射线的使用在提高乳腺癌检出率的同时也会增加乳腺癌的发病风险, 这种风险随着辐射剂量的增加而变大。乳房腺体组织是辐射敏感组织, 国际社会非常关注乳腺X射线摄影检查中受检者平均腺体剂量的评估。传统的二维乳腺X射线摄影和数字乳腺体层合成摄影中受检者剂量学研究已较为成熟, 较新的乳腺锥形束CT扫描中受检者剂量的评估方法尚在研究阶段。本文对不同类型乳腺X射线摄影检查设备中受检者辐射剂量的评估方法及辐射剂量相关影响因素的研究现状进行综述和探讨。     

曲面体层摄影受检者的X线辐射剂量研究

目的：测量颌骨牙列曲面体层摄影人体不同组织器官的X线吸收剂量,并计算当量剂量、有效剂量以及涎腺有效剂量。方法：使用仿真成年人体模测量颌骨牙列曲面体层摄影时腮腺、颌下腺、舌下腺、下颌骨表面、眼晶体、垂体、受照区皮肤、颈椎红骨髓、甲状腺、乳腺、卵巢以及睾丸等器官组织的X线吸收剂量,计算各器官组织的X线当量剂量、有效剂量以及涎腺有效剂量。结果：X线吸收剂量0μGy~730.50μGy,当量剂量0μSv~730.50μSv,有效剂量36.28μSv,涎腺有效剂量47.78μSv。结论：颌骨牙列曲面体层摄影受检者X线吸收剂量、当量剂量、有效剂量均较小,对眼晶体、甲状腺、性腺等敏感器官组织有较高安全性,从放射防护角度,使用曲面体层摄影观察上下颌牙列、牙槽骨的形态是合理的。     

杭州市X线诊断检查所致受检者剂量及其评价

本文报道了杭州市医用X线诊断检查所致公众剂量的估算结果.(1)1985年杭州市居民X线诊断检查的年频度为471.2人次/千人口,其中胸部(包括拍片)、消化道及腰椎片检查分别占66.45%,2.84%及4.39%:(2)6种X线诊断检查所致受检者的年群体剂量为875.6mGy/千人口,其中胸部检查为1675,smGy/千人口,占总剂量的58.3%;(3)给出了6种X线诊断检查所致受检者的平均皮肤吸收剂量、器官剂量、有遗传意义的剂量当量(GSD)、有白血病意义的剂量当量(LSD)及有恶性肿瘤意义的剂量当量(SSD)。     

乳腺X线摄影射线剂量对乳腺X线片质量的影响

目的通过调节乳腺X线摄影的曝光剂量,评价乳腺X线摄影中平均腺体剂量(average glandular dose,AGD)对图像质量的影响。资料与方法应用数字化全景乳腺机系统和PASMAM模体,手动控制条件(kV、mAs),对不同厚度的PASMAM模体在不同AGD条件下进行摄影。采用非参数统计分析不同AGD相同厚度以及相同AGD组不同厚度模体钙化和肿块的显示程度差异是否存在统计学意义,并分析图像信号噪声比(SNR)随剂量和厚度的变化。结果相同曝光剂量条件下,SNR随模体厚度的增加而下降,相同模体厚度SNR随曝光剂量的增加而增加。实验范围内的相同厚度模体组合,在不同AGD条件下,显示钙化和肿块的能力差异无统计学意义(P>0.05)。结论数字化全景乳腺X线摄影盲目提高AGD值会增加患者受辐射量,并不能提高显示钙化和肿块的能力。     

滤过板对X线剂量的影响

X线检查是一种对人体有损害的检查,随着人们对X线的不断认识,已愈来愈重视对从事放射工作人员自身防护,以及临床医务人员与被检查者的防护。国家对此也开始重视了,并以法律的形式制定了许多防护要求与规定。生产X线检查设备的厂家也正在想方设法设计生产出防护性能比较理想的设备。     

直接X线成像受检者照射剂量及图像质量的实时监测

目的 探讨利用直接X线成像(DR)图像DICOM头文件中的剂量信息实现对DR受检者照射剂量和图像质量实时监控的可行性.方法 TO.16模体进行曝光,管电流从0.5 mAs开始逐渐增加至125 mAs,分别记录TO.16模体中模拟病变A(直径11.1 mm)、D(直径4.0 mm)、J(直径0.7 mm)的显示个数,计算检测系数(H_T).设计DR受检者照射剂量及图像质量实时管理系统软件,DR摄片完成后,实时发送到工作站,实时读出每幅图像DICOM头文件中的剂量面积值(DAP)信息作为照射剂量与图像质量控制指标,设立上限值、下限值与75%分点值,当超过该部位设定的限值时,系统发出提示,及时查找原因作相应处理.结果 TO.16模体A点在低于10 mAs时、D与J在低于16 mAs,H_T随mAs增加而增加;A点在10-100 mAs、D、J点在16～100 mAs时HT没有增加.DR受检者照射剂量及图像质量实时管理系统软件共计实时监测曝光5120次,发现DAP值超过设定限值引起的提示66次,提示率为1.3%.其中超过上限值21次,包括7次为技师手动设置曝光量过高;4次自动曝光控制(AEC)点选择错误引起的剂量超标;9次为技师人为增大照射野;1次原因未明,推测可能与AEC短时不稳定有关.45次低于下限值,图像质量下降,主要是摄影部位偏离AEC探测点所致.结论 DR具有较高的曝光宽容度.此方法能及时发现人为或设备问题导致的不适当照射剂量及图像质量受损,实现DR受检者照射剂量及图像质量自动实时管理.     

Internal Mammary Lymph Node Irradiation Contributes to Heart Dose in Breast Cancer

We assessed the impact of internal mammary chain radiotherapy (IMC RT) to the radiation dose received by the heart in terms of heart dose-volume histogram (DVH). Thirty-six consecutive breast cancer patients presenting with indications for IMC RT were enrolled in a prospective study. The IMC was treated by a standard conformal RT technique (50 Gy). For each patient, a cardiac DVH was generated by taking into account the sole contribution of IMC RT. Cardiac HDV were compared according to breast cancer laterality and the type of previous surgical procedure, simple mastectomy or breast conservative therapy (BCT). The contribution of IMC RT to the heart dose was significantly greater for patients with left-sided versus right-sided tumors (13.8% and 12.8% for left-sided tumors versus 3.9% and 4.2% for right-sided tumors in the BCT group and the mastectomy group, respectively; p < 0.0001). There was no statistically significant difference in IMC contribution depending on the initial surgical procedure. IMC RT contributes to cardiac dose for both left-sided and right-sided breast cancers, although the relative contribution is greater in patients with left-sided tumors.     

Influence of Average Glandular Dose for Breast Cancer Screening and Diagnosis in Mammography

目的 通过调节乳腺X线摄影的曝光剂量,评价乳腺X线摄影中平均腺体剂量( average glandular dose,AGD)对图像质量的影响.资料与方法 应用数字化全景乳腺机系统和PASMAM模体,手动控制条件(kV、mAs),对不同厚度的PASMAM模体在不同AGD条件下进行摄影.采用非参数统计分析不同AGD相同厚度以及相同AGD组不同厚度模体钙化和肿块的显示程度差异是否存在统计学意义,并分析图像信号噪声比(SNR)随剂量和厚度的变化.结果 相同曝光剂量条件下,SNR随模体厚度的增加而下降,相同模体厚度SNR随曝光剂量的增加而增加.实验范围内的相同厚度模体组合,在不同AGD条件下,显示钙化和肿块的能力差异无统计学意义(P＞0.05).结论 数字化全景乳腺X线摄影盲目提高AGD值会增加患者受辐射量,并不能提高显示钙化和肿块的能力.     

Superiority of Equivalent Uniform Dose (EUD)-Based Optimization for Breast and Chest Wall*

We investigate whether IMRT optimization based on generalized equivalent uniform dose (gEUD) objectives for organs at risk (OAR) results in superior dosimetric outcomes when compared with multiple dose-volume (DV)–based objectives plans for patients with intact breast and postmastectomy chest wall (CW) cancer. Four separate IMRT plans were prepared for each of the breast and CW cases (10 patients). The first three plans used our standard in-house, physician-selected, DV objectives (phys-plan); gEUD-based objectives for the OARs (gEUD-plan); and multiple, “very stringent,” DV objectives for each OAR and PTV (DV-plan), respectively. The fourth plan was only beam-fluence optimized (FO-plan), without segmentation, which used the same objectives as in the DV-plan. The latter plan was to be used as an “optimum” benchmark without the effects of the segmentation for deliverability. Dosimetric quantities, such as V_20Gy for the ipsilateral lung and mean dose (D_mean) for heart, contralateral breast, and contralateral lung were used to evaluate the results. For all patients in this study, we have seen that the gEUD-based plans allow greater sparing of the OARs while maintaining equivalent target coverage. The average ipsilateral lung V_20Gy reduced from 22 ± 4.4% for the FO-plan to 18 ± 3% for the gEUD-plan. All other dosimetric quantities shifted towards lower doses for the gEUD-plan. gEUD-based optimization can be used to search for plans of different DVHs with the same gEUDs. The use of gEUD allows selective optimization and reduction of the dose for each OAR and results in a truly individualized treatment plan.