CT轴位扫描在降低腰椎间盘病变放射辐射剂量的应用价值

目的研究分析CT轴位扫描在降低腰椎间盘病变放射辐射剂量的应用价值。方法对86例成年志愿者进行不同剂量的扫描,对比分析不同剂量CT扫描的图像质量和椎间盘病变的差异性。结果和270m A系列比较,180 m A系列的DLP值明显下降了36.5%,135 m A系列的DLP值下降了54.0%。结论 CT轴位扫描可大幅度降低腰椎间盘病变放射辐射剂量,应用CT轴位扫描可行性高。

医用质子加速器扩展束流与笔形束流的感生放射性辐射剂量

目的:通过比较医用质子加速器两种不同束流引出方式的X/γ射线感生放射性辐射剂量差异,从而采取相应措施降低治疗室的环境辐射水平,减少医用质子加速器工作人员的累积辐射剂量。方法:模拟患者治疗的肿瘤辐射野,分别在质子加速器扩展束流治疗室和笔形束流治疗室进行15 CGE的质子射线照射,射线停止60 s后,进入治疗室利用两台Neutron RAE II检测仪同时对射线输出窗口和治疗床等中心这两个位置进行X/γ射线感生放射性辐射剂量测量,并记录数据。按以上出束条件和测量步骤,重复测量3次,每次间隔30 min。结果:扩展束流射线输出窗的3次测量值依次为32.3、63.2、70.1μSv/h,在治疗床等中心的3次测量值依次为4.5、5.6、7.7μSv/h,两个测量点的感生放射性辐射剂量率均随着测量次序依次增加。笔形束流射线输出窗的3次测量值依次为3.2、2.3、2.1μSv/h,在治疗床等中心的3次测量值依次为0.21、0.18、0.18μSv/h,两个测量点的感生放射性辐射剂量率均与测量次序无关。在输出窗位置,扩展束流的测量平均值是笔形束流测量平均值的21.8倍;在治疗床等中心位置,扩展束流的测量平均值是笔形束流测量平均值的31.2倍。结论:在出束剂量和时间相同的情况下,笔形束流的感生辐射剂量较小,其机房环境辐射水平远远低于扩展束流机房,对工作人员有更好的保护作用。

华东地区含煤岩系天然放射性水平与生态健康风险评价

本次研究基于地表γ辐射剂量率、氡放射性测量及^(238)U、^(232)Th、^(226)Ra、^(40)K放射性核素测试,识别华东地区含煤岩系的放射性异常地层,评价区域典型煤矿区空气、固体、水体、植物介质的天然放射性水平。结果显示:赋存于石炭系、二叠系的普通煤田与赋存于寒武系的石煤矿区呈现显著差异的天然放射性水平。普通煤田矿区地表γ辐射剂量率、氡放射性测量值总体上处于本底水平范围,矿区固体介质、水体、植物样品核素含量处于正常水平,不存在放射性污染。华东地区石煤分布带,属于放射性γ辐射高背景区,石煤矿区的原煤、煤矸石、土壤、岩石等固体介质的^(238)U、^(226)Ra核素富集明显,并显示更为显著的空间变异性。区域石煤条带监测矿区居民源于γ外照射引起的吸收剂量均超过国际标准限值1 mSv/a,总有效剂量均超过了2 mSv/a,地下水总α、总β浓度为限值的10~30倍,放射性污染不容忽视。华东地区石煤矿区公众所受辐射剂量较高,矿区的地下水、建材、植物等介质已经出现零星的放射性污染,应加强石煤矿区放射性环境监测,及时采取适当的控制措施。

呼吸时相时间长度的临床和实验观察

目的观察肺癌患者和实验犬的吸气时长、呼气时长、吸气到呼气转化时长、呼气到吸气转化时长,探讨四个呼吸时相时间长度的的规律及临床价值.方法肺癌患者5人,实验犬5只,记录X线透视下肺和肿瘤呼吸运动的录像,随机观察每只动物5个呼吸周期的吸气时长、呼气时长、吸气到呼气转化时长、呼气到吸气转化时长.结果犬及人的每次呼吸的吸气时长〉呼气时长〉呼气到吸气转化时长〉吸气到呼气转化时长.每个观察对象的5个呼吸周期间,总呼吸时长不一致,同一个呼吸时相的时长不一致.结论前期测量的呼吸时间长度不能完全代表后期的呼吸时间长度.建立在前期CT扫描基础上的放射治疗计划系统在实施时会有一定的辐射剂量误差.

甲状腺乳头状癌术后^(131)I治疗的住院时间探讨

目的探讨甲状腺乳头状癌患者术后131I治疗住院时间的相关问题。方法以38例甲状腺切除术后行131I治疗的甲状腺乳头状癌患者为研究对象,分为低剂量治疗组25例(治疗剂量为3.7 GBq)和高剂量治疗组13例(治疗剂量>3.7 GBq)。分别测量患者服药后48、72 h 1 m距离处的放射性辐射剂量,同时以0.37 GBq的131I作为参考放射源。结果低剂量治疗组和高剂量治疗组服药后48 h放射性辐射剂量差异有统计学意义(t=2.244,P=0.039)。所有患者服药后72 h的放射性辐射剂量均低于参考源,9例患者(低剂量治疗组3例,高剂量治疗组6例)服药后48 h的放射性辐射剂量高于参考源,且两组差异有统计学意义(χ2=5.520,P=0.040)。服药后放射性辐射剂量与年龄及血清Tg、Tg Ab、TSH水平无相关性。结论甲状腺乳头状癌患者行131I治疗后72 h的放射性辐射剂量迅速下降,且明显低于国家规定的0.37 GBq的辐射剂量,可出院后自行隔离。大剂量131I治疗的患者,服药后48 h的放射性辐射剂量较高。

Dosimetric study comparing photon and electron beams for boosting the tumor bed in early-stage breast cancer

Objective： The aim of our study was to assess and compare the potential dosimetric advantages and drawbacks of photon beams and electron beams as a boost for the tumor bed in superficial and deep seated early-stage breast cancer. Methods： We planned CTs of 10 women with early breast cancer underwent breast conservative surgery were selected. Tumor bed was defined as superficial and deep with a cut of point 4 cm, those with less than 4 cm were defined as superficial tumors representing 4 patients and those with depth of 4 cm or more were classified as deep tumors representing 6 patients. The clinical target volume （C＇I＇V） was defined as the area of architectural .distortion surrounded by surgical clips. The plan- ning target volume （PTV） was the C＇I＇V plus margin 1 cm. A dose of 10 Gy.in 2 Gy fractions was given concurrently at the last week of treatment. Organs at risk （OARs） were heart, lungs, contra-lateral breast and a 5 mm thick skin segment of the breast surface. Dose volume histograms were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing OARs. The following treatment techniques were assessed： photon beam with 3D-conformal technique and a single electron beam. Results： For superficial tumors better coverage for CTV and P＇I＇V with good homogeneity with better CI was found for the 3D conformal radiotherapy （3DCRT） but with no significant planning objectives over electron beam. For deep tumors, the 3DCRT met the planning objectives for C＇I＇V, PTV with better coverage and fewer hot spots with better homogeneity and CI. For superficial tumors, OARs were spared by both techniques with better sparing for the electron beam where as for deep tumors also OARs were well spared by both techniques. Conclusion： Boosting the tumor bed in early- stage breast cancer with optimized photon may be preferred to electron beam for both superficial and deep tumors. The OARs dose sparing effect may allow for a potential long-term toxicity risk reduction and better cosmesis.

Single-versus multi-fraction radiation treatment for metastatic spinal cord compression:functional outcome study

Objective:The optimal treatment of patients with metastatic spinal cord compression(MSCC) is still being debated.This randomized trial was planned to compare the functional outcome and its related prognostic factors,toxicity and in-field recurrence of the three schedules of radiotherapy.Methods:Two hundred and eighty five patients enrolled in the study of which 95 received 1 × 8 Gy,100 received 10 x 3 Gy and 90 received the radiation treatment of 20 × 2 Gy.Irradiation was performed with 6-10 Mv linear accelerators or cobalt-60 units by single posterior field or parallel opposed fields according to depth of irradiation spines.Premedication with dexamethasone was started from the first day of clinico-radiologic diagnosis till 4-5 days after the end of radiotherapy(RT) then tapered off during 10 days.Potential prognostic factors were evaluated with respect to functional outcome.Results:All groups were balanced for patient's characteristics and potential prognostic factors.No statistically significant difference was observed between the 3 groups as regard functional outcome and toxicity while single fraction was associated with higher in-field recurrences(22.8%) with statistically significant difference between the 3 groups(P = 0.01).Functional outcome was significantly better with younger age(≤ 60 y),Eastern Cooperative Oncology Group performance status(ECOG-PS) of 1-2,involved vertebra of 1-2,favorable tumor type,absence of visceral or other bone metastasis,decreased time of developing motor deficit before radiotherapy,long interval between cancer diagnosis to metastatic spinal cord compression,and normal ambulatory status.Conclusion:The three schedules provided similar functional outcome.Single-radiation dose was associated with higher in-field recurrence.To minimize treatment time and costs,the dose of 1 × 8 Gy is recommended for patients with poor predicated survival and 10 × 3 Gy for other patients.