基于最优自动勾画的放疗计划剂量学评估

目的 从计算和测量层面评价MimMaestro最优自动勾画结果导致OAR受量误差。方法 利用240例鼻咽癌、乳腺癌和直肠癌数据建立Mim模板库完成76例相应部位CT数据OAR自动勾画,并从中各选出1例与原手工勾画结构最接近的“最优”病例。评价依据包括CI、适形均距(MDC)、体积差(Dv%)、相似系数(DICE)、敏感指数(Se. Idx)、包容指数(Inc. Idx)。基于自动勾画的OAR分别设计放疗计划使其表观DVH满足临床需求,然后评价该计划在计算与测量层面导致真实OAR受量的误差。配对t检验(正态分布)或秩和检验(非正态分布)差异。结果 76例自动分割与人工勾画结果不同(P<0.05),其中最优病例各器官DICE值为0.43~0.98,DICE>0.70的占73%(16/22)。由此导致OAR受量误差的理论值为(-1.15±15.94)%,95% CI为-8.21%~5.92%(平均剂量)和(-6.53±21.13)%,95% CI为-15.90%~2.84%(最大点剂量);实测值为(-2.43±24.52)%,95% CI为-13.30%~8.44%(平均剂量)和(-3.38±20.87)%,95% CI为-12.63%~5.87%(最大点剂量)。结论 在缺乏人工干预情况下,即使基于最优自动分割结果的放疗计划也无法直接满足临床需求。     

National comparison of 131I measurement among nuclear medicine clinics of eight countries

A generally applicable protocol for organizing comparisons among nuclear medicine clinics created within the IAEA project CRP E2.10.05 was tested in Brazil, Cuba, Czech Republic, India, Iran, Republic of Korea, Romania and Turkey in 2007. Comparisons of measurement of ¹³¹I were organized by local pilot laboratories with different backgrounds and levels of experience in this field. The results and experiences gained were compared and analyzed. A majority of results in each national comparison were within 10% of the reference value.     

Thermoluminescence studies of LiSrBO3:RE3+ (RE=Dy,Tb, Tm and Ce)

The polycrystalline samples of LiSrBO₃:RE³⁺ were synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy³⁺, Tb³⁺, Tm³⁺ and Ce³⁺, on thermoluminescence (TL) of LiSrBO₃ phosphor was discussed. We also investigated some dosimetric characteristics of LiSrBO₃:Tm³⁺. The effect of the concentration of Tm³⁺ on the TL intensity was investigated and the result of which showed that the optimum mole fraction of Tm³⁺ was 1%. The TL kinetic parameters of LiSrBO₃:0.01Tm³⁺ were calculated by the computer glow curve deconvolution (CGCD) method. We also studied the three-dimensional (3D) TL emission spectrum of LiSrBO₃:0.01Tm³⁺ under gamma-ray irradiation. The dose-response of LiSrBO₃:0.01Tm³⁺ to γ-ray was linear in the range from 1 to 400 m Gy.     

Activity standardization of 3H with the new TDCR system at PTB

A triple-to-double coincidence ratio (TDCR) liquid scintillation counting system (Pochwalski et al., 1988; Grau Malonda and Coursey, 1988) was set up at the Physikalisch-Technische Bundesanstalt (PTB) to be used as an additional technique for primary activity standardization. The optical chamber of the system was designed in our laboratory, expending great effort to achieve maximum light transmission to the photomultiplier tubes (PMT) and, consequently, a maximum counting efficiency and low uncertainties.A programme to compute the counting efficiencies and to analyse the measurement data was developed and tested. The software can also be used to allow for PMT asymmetries. The system and recently developed analysis procedures were used for the activity standardization of a tritiated water solution within the scope of an international comparison under the auspices of the Bureau International des Poids et Mesures (BIPM).     

便携式医用激光源检定装置的研制及测量不确定度评定

目的：设计研制便携式医用激光源检定装置。方法：该装置设计由毫瓦级激光功率探测器、瓦级激光功率探测器、激光能量探测器、激光功率/能量显示器、激光输出终端锁定装置等5部分组成。3个探测器共用一台显示器以实现便携目的。激光输出终端锁定装置用于固定激光终端和探测器的相对位置,以便于在医疗单位现场开展测量工作。对检定装置进行了性能测试和不确定度评定。结果：研制出便携式医用激光源检定装置1套,3个探测器可测量的激光功率、能量范围分别为0.1～100mW、0.1～150W、0.01～2.0J,在校准波长上的测量不确定度为1.5%、2.6%和3.3%。结论：研制的便携式医用激光源检定装置性能达到了设计指标要求,适合于在医疗单位现场开展检定工作。     

Beta spectrometry with metallic magnetic calorimeters

Metallic magnetic calorimeters are a specific type of cryogenic detectors that have been shown to enable precise measurement of the shape of low energy beta spectra. The aim of their use at LNHB is the determination of the shape factors of beta spectra. The beta source is enclosed in the detector absorber, allowing for very high detection efficiency. It has turned out that the type of source is of crucial importance for the correctness of the measured spectrum. Spectra of ⁶³Ni measured with several sources prepared by drying a NiCl₂ solution differ from one another and from theory, whereas spectra measured with electroplated sources are reproducible and agree with theory. With these latter measurements we could confirm the atomic exchange effect down to very low energy (200 eV).     

A long-term performance evaluation of the gamma-ray activity measurement laboratory in CPST,Lithuania

The quality control procedures used for two HPGe detectors (a well-type and a GAMMA-X coaxial) are described. Since 2001, check sources containing ¹³⁷Cs have been measured weekly for 7200s each, and the gamma-ray spectrometry system background was determined once per month for an acquisition time of 100,000 s. The laboratory participated in the international comparisons at environmental radioactivity level organized by the IAEA, Risø National Laboratory and NPL.     

Comparison of digital signal processing modules in gamma-ray spectrometry

Commercial digital signal-processing modules have been tested for their applicability to gamma-ray spectrometry. The tests were based on the same n-type high purity germanium detector. The spectrum quality was studied in terms of energy resolution and peak area versus shaping parameters, using a Eu-152 point source. The stability of a reference peak count rate versus the total count rate was also examined. The reliability of the quantitative results is discussed for their use in measurement at the metrological level.     

Preliminary beta spectrum measurements using a magnetic spectrometer

We report the performances of a double focusing magnetic beta spectrometer. The energy resolution was measured using conversion peaks of Cs-137 and Ba-133 at 0.73% for 624 keV, and 1.33% for 124 keV. The counting efficiency as a function of the energy was estimated using a P-32 source and was used to correct the measured spectra of Cs-137. The result was compared with the theoretical spectrum and we found a good agreement.