-
核素敷贴治疗作为核医学科的常用治疗手段,对皮肤血管瘤、瘢痕增生、寻常疣等浅表性病变具有治疗彻底、不留印记、方法简单、经济、无痛无痒等特点,因而受到广大患者的欢迎[1-3]。90Sr-90Y敷贴器是目前使用较为广泛的核素治疗源, 90Sr核素衰变释放出0.55 MeV的β粒子后转变为90Y,90Y衰变成90Zr时又释放出2.28 MeV的β粒子,整个敷贴器平均能量为0.98 MeV,β粒子最大射程12.90 mm,射线综合作用深度2~3 mm[4-6]。在实际临床治疗中,由于缺乏专业设备及人员,基层医院普遍采用简易公式对90Sr-90Y敷贴治疗的时间进行估算,导致部分患者受照剂量不足或者超量,严重影响了疗效,因而急需一种快捷且方便的剂量验证手段。EBT3胶片作为全新一代的辐射自显影胶片,具有免冲洗、可裁剪、剂量范围宽和组织等效性好等优点,目前被广泛应用于临床放射治疗剂量的验证[7]。后续有研究者发现,EBT3胶片的光谱响应与兆伏级能量束流的剂量率及性质无相关性[8-10],在射线能量0.003 MeV至18 MeV范围内,其能量依赖性小于3%[11],这些特性使得EBT3胶片在光子线和电子线混合野的剂量采集中也被广泛应用[12]。
本研究通过直线加速器产生的光子线对EBT3胶片进行标准剂量照射,应用胶片扫描仪对辐照后的胶片进行透射扫描,生成灰度-剂量标准曲线。再使用敷贴器对EBT3胶片组进行定时照射,扫描测得灰度值,根据标准曲线转换即可获取实际辐照剂量和空间剂量分布。本研究以期在原始数据缺失和基层专业设备及人员缺乏的情况下直接测量出不同治疗距离的敷贴器照射源对应的剂量大小及等剂量线范围。
-
加速器出束能量为6 MeV时,纯固体水模测量结果高于换入0.5 cm厚胶片后的测量结果,偏差为−2.17%;出束能量为8、10、12、15 MeV时,换入胶片后的测量结果均高于固体水模,偏差分别为1.24%、0.50%、0.68%和0.28%(表1)。由于6 MeV射线最大剂量深度为1.3 cm,测量深度为1.5 cm,导致剂量-深度轮廓线(profile)前移,故而实测剂量低于纯固体水模所测得剂量。其余能量实测深度均在最大深度点之前,0.5 cm厚胶片替换等厚度固体水模后测量结果略高于纯固体水模,但差异无统计学意义(Z=−0.31,P=0.84)。因此,利用胶片可以较为有效地模拟人体组织密度。
模体 6 MeV 8 MeV 10 MeV 12 MeV 15 MeV $ \bar x \pm s$ Z值 P值 固体水模(cGy) 95.93 99.42 100.90 103.60 106.80 101.33±4.13 −0.31 0.84 固体水模+EBT3胶片(cGy) 93.85 100.65 101.40 104.30 107.10 101.46±4.96 偏差(%) −2.17 1.24 0.50 0.68 0.28 − − − 注:EBT3胶片为10 cm×10 cm叠加18片的胶片组,厚度为0.5 cm。−表示无此项数据 表 1 不同能量照射后2种模体接受到的剂量比较
Table 1. Comparison of the doses received by the two phantoms irradiated after different energy
-
经过90Sr-90Y敷贴器照射4 min后的胶片组扫描图见图2,从1号胶片至20号胶片,随着距离的增加,辐射显影灰度随之降低,到20号时几乎与本底一致。
-
由胶片扫描图2可见,胶片灰度在同一层面中心区域较为均匀,通过Film Analyzer分析软件进行灰度-剂量转换,测出不同深度处胶片对应的中心区域的平均剂量结果见表2。随着灰度的降低,剂量迅速下降,在0.5 cm深度处,剂量仅为7.0 cGy。
深度(mm) 剂量(cGy) 深度(mm) 剂量(cGy) 0 670.0 2.80 94.0 0.28 587.0 3.08 70.0 0.56 524.0 3.36 52.0 0.84 439.0 3.64 45.0 1.12 338.0 3.92 35.0 1.40 291.0 4.20 24.0 1.68 258.0 4.48 20.0 1.96 194.0 4.76 15.0 2.24 155.0 5.04 7.0 2.52 136.0 5.32 6.6 表 2 90Sr-90Y敷贴器照射后不同距离深度的剂量结果
Table 2. Dose results at different exposure distances after 90Sr-90Y applicator irradiation
根据表2,拟合函数y=739.07e−0.56x−44.8,其中y表示距离敷贴器某一深度处中心轴的吸收剂量,单位cGy;x表示胶片距离敷贴器底面的垂直距离,单位mm。由图3可见,随着距离敷贴器深度的增加,辐射剂量呈指数下降的趋势,曲线拟合相关参数R2=0.99576。
-
不同剂量所覆盖胶片区域的直径结果见表3。胶片的二维等剂量线示意图见图4(俯视图)。可以看出1号胶片等剂量线间隔明显,随着等剂量线的降低,相互间的间距逐渐增加,而由过中心轴的等剂量线示意图4(剖面图)可以看出同一剂量所覆盖区域的直径大小随着距离敷贴器深度的增加均呈现先增大后减小的趋势。
胶片层数
(深度,mm)50 cGy 100 cGy 150 cGy 200 cGy 250 cGy 300 cGy 1(0) 10.3 9.2 8.5 8.2 8.0 7.8 2(0.28) 10.4 9.4 8.8 8.3 8.0 7.8 3(0.56) 10.5 9.5 8.9 8.4 8.0 7.6 4(0.84) 10.6 9.5 8.8 8.0 7.5 7.0 5(1.12) 10.6 9.6 8.5 7.8 6.7 6.3 6(1.40) 10.5 9.1 8.0 7.6 5.5 0 7(1.68) 10.5 9.0 7.7 5.7 3.9 0 8(1.96) 10.1 8.3 6.5 1.5 0 0 9(2.24) 9.5 7.2 4.0 0 0 0 10(2.52) 9.3 6.5 0 0 0 0 11(2.80) 7.6 1.2 0 0 0 0 12(3.08) 6.2 0 0 0 0 0 13(3.36) 3.2 0 0 0 0 0 14(3.64) 0 0 0 0 0 0 15(3.92) 0 0 0 0 0 0 表 3 90Sr-90Y敷贴器不同剂量不同胶片层数测量的区域直 径(mm)
Table 3. The area diameter measured by the 90Sr-90Y applicator at different doses and different number of film layers (mm)
90Sr-90Y敷贴治疗的EBT3胶片剂量验证方法
EBT3 film dose verification method for 90Sr-90Y applicator
-
摘要:
目的 对90Sr-90Y敷贴治疗进行EBT3胶片剂量的测量,为临床应用提供一种快捷的剂量验证方法。 方法 选用能量响应较好的辐射直接显影EBT3胶片,并与固体水模进行比较,通过直线加速器建立0~500 cGy的胶片灰度-剂量标准曲线并检测其组织等效性。将20片6 cm×6 cm的EBT3胶片(每张胶片厚0.28 mm)重叠放置,将90Sr-90Y敷贴器放置在胶片最顶层,辐照4 min。通过灰度-剂量标准曲线计算出每张胶片中心轴附近的平均吸收剂量,根据胶片厚度计算距离敷贴器不同深度处的辐射剂量及等剂量线分布。采用非参数独立样本U检验比较不同能量的电子线照射前后所测得的吸收剂量的差异。 结果 胶片替换等厚度固体水模后测量结果略高于纯固体水模,但差异无统计学意义(Z=−0.31,P=0.84)。不同深度处胶片对应的中心区域随着灰度值的降低吸收剂量迅速下降,在0.5 cm深度处,剂量仅为7.0 cGy。4 min照射后,距离敷贴器不同深度处的吸收剂量满足拟合曲线y=739.07e−0.56x−44.8,等剂量线范围随深度的增加呈先增大后减小。 结论 EBT3胶片验证能够很好地满足90Sr-90Y敷贴治疗的剂量验证,具有简单、易行、准确的特点,适合基层医疗机构应用。 -
关键词:
- 胶片辐射剂量测定法 /
- 90Sr-90Y敷贴器 /
- EBT3胶片 /
- 剂量验证
Abstract:Objective To measure the EBT3 film dose of brachytherapy with 90Sr-90Y applicator to provide a rapid dose verification method for clinical application. Methods EBT3 films with good energy response were selected and compared with a solid water phantom. The gray scale dose curve of 0–500 cGy film was established using a linear accelerator, and its tissue equivalence was detected. Twenty 6 cm × 6 cm EBT3 films (0.28 mm thickness) were overlapped, and a 90Sr-90Y applicator was placed on the top and irradiated for 4 min. The absorbed dose near the central axis of each film was calculated using the gray scale dose curve. The radiation dose and isodose distributions at different distances from the applicator were calculated according to film thickness. Non-parametric independent sample U-test was used to compare the differences in absorbed doses measured before and after exposure to electron rays with different energies. Results The measurement results of film replacement with equal thickness solid water molds were slightly higher than those of pure solid water molds, but the difference was not statistically significant (Z=−0.31, P=0.84). The absorbed dose in the central region corresponding to different film depths decreased rapidly with decreasing gray values, and the dose at a depth of 0.5 cm was only 7.0 cGy. After irradiation for 4 min, the absorbed dose at different depths from the applicator met the fitting curve, y=739.07e−0.56x−44.8, and the range of isodose line initially increased and then decreased with the increasing depth. Conclusion EBT3 film verification can well meet the dose verification of 90Sr-90Y applicator, which is simple, easy, and accurate and is suitable of primary medical institutions. -
Key words:
- Film dosimetry /
- 90Sr-90Y applicator /
- EBT3 film /
- Dose verification
-
表 1 不同能量照射后2种模体接受到的剂量比较
Table 1. Comparison of the doses received by the two phantoms irradiated after different energy
模体 6 MeV 8 MeV 10 MeV 12 MeV 15 MeV $ \bar x \pm s$ Z值 P值 固体水模(cGy) 95.93 99.42 100.90 103.60 106.80 101.33±4.13 −0.31 0.84 固体水模+EBT3胶片(cGy) 93.85 100.65 101.40 104.30 107.10 101.46±4.96 偏差(%) −2.17 1.24 0.50 0.68 0.28 − − − 注:EBT3胶片为10 cm×10 cm叠加18片的胶片组,厚度为0.5 cm。−表示无此项数据 表 2 90Sr-90Y敷贴器照射后不同距离深度的剂量结果
Table 2. Dose results at different exposure distances after 90Sr-90Y applicator irradiation
深度(mm) 剂量(cGy) 深度(mm) 剂量(cGy) 0 670.0 2.80 94.0 0.28 587.0 3.08 70.0 0.56 524.0 3.36 52.0 0.84 439.0 3.64 45.0 1.12 338.0 3.92 35.0 1.40 291.0 4.20 24.0 1.68 258.0 4.48 20.0 1.96 194.0 4.76 15.0 2.24 155.0 5.04 7.0 2.52 136.0 5.32 6.6 表 3 90Sr-90Y敷贴器不同剂量不同胶片层数测量的区域直 径(mm)
Table 3. The area diameter measured by the 90Sr-90Y applicator at different doses and different number of film layers (mm)
胶片层数
(深度,mm)50 cGy 100 cGy 150 cGy 200 cGy 250 cGy 300 cGy 1(0) 10.3 9.2 8.5 8.2 8.0 7.8 2(0.28) 10.4 9.4 8.8 8.3 8.0 7.8 3(0.56) 10.5 9.5 8.9 8.4 8.0 7.6 4(0.84) 10.6 9.5 8.8 8.0 7.5 7.0 5(1.12) 10.6 9.6 8.5 7.8 6.7 6.3 6(1.40) 10.5 9.1 8.0 7.6 5.5 0 7(1.68) 10.5 9.0 7.7 5.7 3.9 0 8(1.96) 10.1 8.3 6.5 1.5 0 0 9(2.24) 9.5 7.2 4.0 0 0 0 10(2.52) 9.3 6.5 0 0 0 0 11(2.80) 7.6 1.2 0 0 0 0 12(3.08) 6.2 0 0 0 0 0 13(3.36) 3.2 0 0 0 0 0 14(3.64) 0 0 0 0 0 0 15(3.92) 0 0 0 0 0 0 -
[1] 赵洪伟, 阚侃, 吕茁, 等. 整形外科手术治疗瘢痕疙瘩的临床研究[J]. 中国卫生标准管理, 2020, 11(11): 43−45. DOI: 10.3969/j.issn.1674-9316.2020.11.016.
Zhao HW, Kan K, Lyu Z, et al. Clinical study of plastic surgery treatment of keloid tissue[J]. China Health Stand Manage, 2020, 11(11): 43−45. DOI: 10.3969/j.issn.1674-9316.2020.11.016.[2] 杨卷红, 张耀峰, 刘斌, 等. 核素32P简易敷贴治疗婴幼儿体表血管瘤的临床效果[J]. 临床医学研究与实践, 2020, 5(13): 109−110, 113. DOI: 10.19347/j.cnki.2096-1413.202013041.
Yang JH, Zhang YF, Liu B, et al. Clinical effect of nuclide 32P simple application in the treatment of infantile superficial hemangiomas[J]. Clin Res Pract, 2020, 5(13): 109−110, 113. DOI: 10.19347/j.cnki.2096-1413.202013041.[3] 潘展砚, 刘怡文. 32P敷贴治疗乳房外Paget病疗效评价[J]. 中国美容医学, 2017, 26(10): 77−78. DOI: 10.15909/j.cnki.cn61-1347/r.002002.
Pan ZY, Liu YW. The clinical evaluation of 32P-dressing radiotherapy in the treatment of extramammary Paget disease[J]. Chin J Aesthetic Med, 2017, 26(10): 77−78. DOI: 10.15909/j.cnki.cn61-1347/r.002002.[4] 黎凤明, 田晓东, 刘云瑛, 等. 联合整形外科手术及90Si-90Y放射性核素敷贴治疗瘢痕疙瘩的临床应用研究[J]. 中国临床医生杂志, 2016, 44(9): 32−34. DOI: 10.3969/j.issn.2095-8552.2016.09.012.
Li FM, Tian XD, Liu YY, et al. A clinical evaluation of plastic surgery combined with 90Si-90Y isotope stickers in the treatment of keloids[J]. Chin J Clin, 2016, 44(9): 32−34. DOI: 10.3969/j.issn.2095-8552.2016.09.012.[5] Rogers B, Lawrence J, Chmura J, et al. Dosimetric characterization of a novel 90Y source for use in the conformal superficial brachytherapy device[J]. Phys Med, 2020, 72: 52−59. DOI: 10.1016/j.ejmp.2020.03.002. [6] 郭晨雷, 张高龙, 钱建强. 利用磁谱仪测量90Sr-90Y放射源的β衰变能谱[J]. 物理与工程, 2011, 21(5): 10−12, 16. DOI: 10.3969/j.issn.1009-7104.2011.05.004.
Guo CL, Zhang GL, Qian JQ. Measurement of energy spectra for β decay of 90Sr-90Y by magnetic spectrometer[J]. Phys Eng, 2011, 21(5): 10−12, 16. DOI: 10.3969/j.issn.1009-7104.2011.05.004.[7] Hanušová T, Horáková I, Koniarová I. Pseudo-3D IMRT verification with EBT3 radiochromic film[J]. Radiat Prot Dosimetry, 2019, 186(2-3): 362−366. DOI: 10.1093/rpd/ncz232. [8] Sipilä P, Ojala J, Kaijaluoto S, et al. Gafchromic EBT3 film dosimetry in electron beams—energy dependence and improved film read-out[J/OL]. J Appl Clin Med Phys, 2016, 17(1): 360−373[2020-09-06]. https://aapm.onlinelibrary.wiley.com/doi/full/10.1120/jacmp.v17i1.5970. DOI: 10.1120/jacmp.v17i1.5970. [9] León-Marroquín EY, Mulrow DJ, Khan R, et al. Spectral analysis of the EBT3 radiochromic films for clinical photon and electron beams[J]. Med Phys, 2019, 46(2): 973−982. DOI: 10.1002/mp.13330. [10] Reinhardt S, Hillbrand M, Wilkens JJ, et al. Comparison of Gafchromic EBT2 and EBT3 films for clinical photon and proton beams[J]. Med Phys, 2012, 39(8): 5257−5262. DOI: 10.1118/1.4737890. [11] Hermida-López M, Lüdemann L, Flühs A, et al. Technical note: influence of the phantom material on the absorbed-dose energy dependence of the EBT3 radiochromic film for photons in the energy range 3 keV−18 MeV[J]. Med Phys, 2014, 41(11): 112103. DOI: 10.1118/1.4898598. [12] Sorriaux J, Kacperek A, Rossomme S, et al. Evaluation of Gafchromic® EBT3 films characteristics in therapy photon, electron and proton beams[J]. Phys Med, 2013, 29(6): 599−606. DOI: 10.1016/j.ejmp.2012.10.001. [13] 马俊杰, 韩寿岭, 张谦, 等. 锶-90/钇-90敷贴器γ、X射线的来源及所致医护人员的剂量[J]. 工业卫生与职业病, 2000, 26(3): 160−161. DOI: 10.3969/j.issn.1000-7164.2000.03.011.
Ma JJ, Han SL, Zhang Q, et al. Gamma-ray and X-ray from 90Sr/90Y applicator and its doses on medical staff[J]. Ind Health Occup, 2000, 26(3): 160−161. DOI: 10.3969/j.issn.1000-7164.2000.03.011.[14] 施常备, 梁晓燕, 袁彬, 等. 32P持续低剂量率辐射敷贴治疗的胶片剂量验证[J]. 现代肿瘤医学, 2009, 17(9): 1772−1774. DOI: 10.3969/j.issn.1672-4992.2009.09.061.
Shi CB, Liang XY, Yuan B, et al. The quantitative radiation dose by RC film for the continued low-dose-rate radiation of 32P[J]. J Mod Oncol, 2009, 17(9): 1772−1774. DOI: 10.3969/j.issn.1672-4992.2009.09.061.[15] Massillon-JL G, Minniti R, Mitch MG, et al. The use of gel dosimetry to measure the 3D dose distribution of a 90Sr/90Y intravascular brachytherapy seed[J]. Phys Med Biol, 2009, 54(6): 1661−1672. DOI: 10.1088/0031-9155/54/6/017. [16] Hansen JB, Culberson WS, DeWerd LA. Windowless extrapolation chamber measurement of surface dose rate from a 90Sr/90Y ophthalmic applicator[J]. Radiat Meas, 2018, 108: 34−40. DOI: 10.1016/j.radmeas.2017.11.0.