用于内剂量学的五种儿科头部和脑部数学模型。

Five pediatric head and brain mathematical models for use in internal dosimetry.

作者信息

Bouchet L G, Bolch W E

机构信息

Department of Nuclear and Radiological Engineering, University of Florida, Gainesville 32611-8300, USA.

出版信息

J Nucl Med. 1999 Aug;40(8):1327-36.

PMID:10450685

Abstract

UNLABELLED

Mathematical models of the head and brain currently used in pediatric neuroimaging dosimetry lack the anatomic detail needed to provide the necessary physical data for suborgan brain dosimetry. To overcome this limitation, the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine recently adopted a detailed dosimetric model of the head and brain for the adult.

METHODS

New head and brain models have been developed for a newborn, 1, 5, 10 and 15 y old for use in internal dosimetry. These models are based on the MIRD adult head and brain model and on published head and brain dimensions. They contain the same eight brain subregions and the same head regions as the adult model. These new models were coupled with the Monte Carlo transport code EGS4, and absorbed fractions of energy were calculated for 14 sources of monoenergetic photons and electrons in the energy range of 10 keV-4 MeV. These absorbed fractions were then used along with radionuclide decay data to generate S values for all ages for 99mTc, considering 12 source and 15 target regions.

RESULTS

Explicit transport of positrons was also considered with separation of the annihilation photons component to the absorbed fraction of energy in the calculation of S values for positron-emitting radionuclides. No statistically significant differences were found when S values were calculated for positron-emitting radionuclides under explicit consideration of the annihilation event compared with the traditional assumption of a uniform distribution of 0.511-MeV photons.

CONCLUSION

The need for electron transport within the suborgan brain regions of these pediatric phantoms was reflected by the relatively fast decrease of the self-absorbed fraction within many of the brain subregions, with increasing particle energy. This series of five dosimetric head and brain models will allow more precise dosimetry of radiopharmaceuticals in pediatric nuclear medicine brain procedures.

摘要

未标注

目前儿科神经影像剂量学中使用的头部和大脑数学模型缺乏为脑内亚器官剂量学提供必要物理数据所需的解剖细节。为克服这一局限性，核医学协会的医学内部辐射剂量（MIRD）委员会最近采用了一种针对成人的详细头部和大脑剂量学模型。

方法

已开发出适用于新生儿、1岁、5岁、10岁和15岁儿童的新头部和大脑模型，用于内部剂量学。这些模型基于MIRD成人头部和大脑模型以及已发表的头部和大脑尺寸。它们包含与成人模型相同的八个脑亚区域和相同的头部区域。这些新模型与蒙特卡罗传输代码EGS4相结合，计算了能量范围为10 keV - 4 MeV的14种单能光子和电子源的能量吸收分数。然后，这些吸收分数与放射性核素衰变数据一起用于生成99mTc在所有年龄段的S值，考虑了12个源区域和15个靶区域。