Comparing the biological washout of β+-activity induced in mice brain after 12C-ion and proton irradiation
Comparing the biological washout of β+-activity induced in mice brain after 12C-ion and proton irradiation
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DOI：
10.1088/0031-9155/59/23/7229
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发表时间：
2014-12-07
影响因子：
3.5
通讯作者：
Parodi, K.
中科院分区：
文献类型：
--
作者：
Ammar, C.;Frey, K.;Parodi, K.
在临床离子束治疗中，质子以及较重的离子如碳被用于治疗。对于质子，β（+）-发射体仅由靶中的碎裂反应（靶碎裂）诱导，而对于重离子，它们还由射弹的碎裂诱导（进一步称为自激活）。一种利用这些过程进行治疗验证的方法，通过将测量的正电子发射断层扫描（PET）数据与蒙特卡罗模拟的预测进行比较，已经在临床上实施。为了准确模拟，重要的是要考虑由于重要功能而导致的β（+）-发射体的生物洗脱。到目前为止，冲洗的数学表达式主要是通过使用C-10-和C-11-离子的放射性射束来确定的，这两种离子都是β（+）-发射体，以增强照射区域中的计数统计。尽管如此，如何选择射弹（自动激活或nonautoactivating）的影响的冲洗系数的问题，还没有addressed.In这种情况下，在海德堡离子束治疗中心进行了一项实验，目的是直接比较辐射诱导的生物冲洗系数在小鼠中的质子和C-12-离子。为此目的，用质子和C-12离子照射小鼠的脑区域，并在照射后用PET/CT扫描仪（Siemens Biograph mCT）测量。在适当的等待时间后，处死小鼠，然后在类似条件下再次照射和测量。尽管PET计数统计非常低，但在C-12离子和质子照射的小鼠之间可以识别出一致的差异，其中C-12数据通过具有0.50 +/-的组合的中等和缓慢洗脱分数的双组分拟合得到最佳描述0.05，质子小鼠数据通过仅具有0.73 +/- 0.06的一个（缓慢）洗脱分数的单组分拟合得到最佳描述。
In clinical ion beam therapy, protons as well as heavier ions such as carbon are used for treatment. For protons, beta(+)-emitters are only induced by fragmentation reactions in the target (target fragmentation), whereas for heavy ions, they are additionally induced by fragmentations of the projectile (further referred to as autoactivation). An approach utilizing these processes for treatment verfication, by comparing measured Positron Emission Tomography (PET) data to predictions from Monte Carlo simulations, has already been clinically implemented. For an accurate simulation, it is important to consider the biological washout of beta(+)-emitters due to vital functions. To date, mathematical expressions for washout have mainly been determined by using radioactive beams of C-10- and C-11-ions, both beta(+)-emitters, to enhance the counting statistics in the irradiated area. Still, the question of how the choice of projectile (autoactivating or nonautoactivating) influences the washout coefficients, has not been addressed.In this context, an experiment was carried out at the Heidelberg Ion Beam Therapy Center with the purpose of directly comparing irradiation-induced biological washout coefficients in mice for protons and C-12-ions. To this aim, mice were irradiated in the brain region with protons and C-12-ions and measured after irradiation with a PET/CT scanner (Siemens Biograph mCT). After an appropriate waiting time, the mice were sacrificed, then irradiated and measured again under similar conditions. The resulting data were processed and fitted numerically to deduce the main washout parameters.Despite the very low PET counting statistics, a consistent difference could be identified between C-12-ion and proton irradiated mice, with the C-12 data being described best by a two component fit with a combined medium and slow washout fraction of 0.50 +/- 0.05 and the proton mice data being described best by a one component fit with only one (slow) washout fraction of 0.73 +/- 0.06.