Average glandular dose coefficients for pendant-geometry breast CT using realistic breast phantoms.
Average glandular dose coefficients for pendant-geometry breast CT using realistic breast phantoms.
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DOI：
10.1002/mp.12477
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发表时间：
2017-10
期刊：
影响因子：
3.8
通讯作者：
Boone JM
中科院分区：
文献类型：
--
作者：
Hernandez AM;Boone JM
从乳腺CT （bCT）数据集设计体积特异性乳腺影，并使用蒙特卡罗方法估计乳腺CT相关的归一化平均腺体剂量系数。一个大队列的bCT数据集（N=215）被用来评估乳房体积的五分位数（加上前5%）。然后为六个特定于体积的组确定平均半径轮廓，并用于制造物理幻影和生成数学幻影（V1-V6；“V”表示按体积分类）。利用MCNP6蒙特卡罗代码对在我院制作的bCT原型系统进行了建模；这个模型在制作的模型中进行了物理测量验证。利用数学模型模拟了单能源光子“DgNCT(E)”（8-70 keV， 1 keV间隔）和多能x射线束“pDgNCT”（35-70 kV， 1 kV间隔）的归一化平均腺体剂量系数。使用蒙特卡罗代码研究乳腺尺寸（V1 vs. V5）和腺体分数（6.4% vs. 45.8%）对腺体剂量的影响。我们还将V1、V3和V5模型的pDgNCT系数与具有等效体积和两个几何约束的简单圆柱形模型的pDgNCT系数进行了比较；(1)在乳房虚幻胸壁“Rcw”处测定圆柱体半径；以及(2)在乳房幻像质心“RCOM”处确定的圆柱体半径。使用MCNP6的剂量估计与V1、V3和V5幻影的物理测量值（R2 = 0.995）和使用简单幻影的参考bCT剂量系数（R2 = 0.999）的一致性令人满意。对于含有1.5 mm Al滤过的49 kV频谱，腺体分数的差异（6.5%（第5百分位）vs. 45.8%（第95百分位））对V3幻象的pDgNCT有13.2%的影响，乳房大小的差异（V1 vs. V5）对由17%（中位数）纤维腺组织组成的乳房的pDgNCT有16.6%的影响。对于半径为RCOM的圆柱形幻像，与V1、V3和V5幻像相比，差异分别为1.5%、0.1%和2.1%。乳房幻影的设计使用了六种乳房尺寸范围内的大量bCT数据集。然后，这些幻象被制造出来，并用于乳腺CT中腺体剂量的估计。数学模型和相关的乳腺剂量系数范围的乳房大小（V1 - V6）和腺体分数（第5至第95百分位）可供感兴趣的用户。
To design volume-specific breast phantoms from breast CT (bCT) data sets and estimate the associated normalized mean glandular dose coefficients for breast CT using Monte Carlo methods. A large cohort of bCT data sets (N=215) was used to evaluate breast volume into quintiles (plus the top 5%). The average radius profile was then determined for each of the six volume-specific groups and used to both fabricate physical phantoms and generate mathematical phantoms (V1–V6; “V” denotes classification by volume). The MCNP6 Monte Carlo code was used to model a prototype bCT system fabricated at our institution; and this model was validated against physical measurements in the fabricated phantoms. The mathematical phantoms were used to simulate normalized mean glandular dose coefficients for both monoenergetic source photons “DgNCT(E)” (8–70 keV in 1 keV intervals) and polyenergetic x-ray beams “pDgNCT” (35–70 kV in 1 kV intervals). The Monte Carlo code was used to study the influence of breast size (V1 vs. V5) and glandular fraction (6.4% vs. 45.8%) on glandular dose. The pDgNCT coefficients estimated for the V1, V3, and V5 phantoms were also compared to those generated using simple, cylindrical phantoms with equivalent volume and two geometrical constraints including; (1) cylinder radius determined at the breast phantom chest wall “Rcw”; and (2) cylinder radius determined at the breast phantom center-of-mass “RCOM”. Satisfactory agreement was observed for dose estimations using MCNP6 compared with both physical measurements in the V1, V3, and V5 phantoms (R2 = 0.995) and reference bCT dose coefficients using simple phantoms (R2 = 0.999). For a 49 kV spectrum with 1.5 mm Al filtration, differences in glandular fraction (6.5% (5th percentile) vs. 45.8% (95th percentile)) had a 13.2% influence on pDgNCT for the V3 phantom, and differences in breast size (V1 vs. V5) had a 16.6% influence on pDgNCT for a breast composed of 17% (median) fibroglandular tissue. For cylindrical phantoms with a radius of RCOM the differences were 1.5%, 0.1%, and 2.1% compared with the V1, V3, and V5 phantoms, respectively. Breast phantoms were designed using a large cohort of bCT data sets across a range of six breast sizes. These phantoms were then fabricated and used for the estimation of glandular dose in breast CT. The mathematical phantoms and associated glandular dose coefficients for a range of breast sizes (V1 – V6) and glandular fractions (5th to 95th percentiles) are available for interested users.
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影响因子：
3.8
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