Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Med Phys. 2012 Apr;39(4):2119-28. doi: 10.1118/1.3684951.
To present a method to evaluate the dose mapping error introduced by the dose mapping process. In addition, apply the method to evaluate the dose mapping error introduced by the 4D dose calculation process implemented in a research version of commercial treatment planning system for a patient case.
The average dose accumulated in a finite volume should be unchanged when the dose delivered to one anatomic instance of that volume is mapped to a different anatomic instance-provided that the tissue deformation between the anatomic instances is mass conserving. The average dose to a finite volume on image S is defined as d(S)=e(s)/m(S), where e(S) is the energy deposited in the mass m(S) contained in the volume. Since mass and energy should be conserved, when d(S) is mapped to an image R(d(S→R)=d(R)), the mean dose mapping error is defined as Δd(m)=|d(R)-d(S)|=|e(R)/m(R)-e(S)/m(S)|, where the e(R) and e(S) are integral doses (energy deposited), and m(R) and m(S) are the masses within the region of interest (ROI) on image R and the corresponding ROI on image S, where R and S are the two anatomic instances from the same patient. Alternatively, application of simple differential propagation yields the differential dose mapping error, Δd(d)=|∂d∂eΔe+∂d∂mΔm|=|(e(S)-e(R))m(R)-(m(S)-m(R))m(R) (2)*e(R)|=α|d(R)-d(S)| with α=m(S)/m(R). A 4D treatment plan on a ten-phase 4D-CT lung patient is used to demonstrate the dose mapping error evaluations for a patient case, in which the accumulated dose, D(R)=∑(S=0) (9)d(S→R), and associated error values (ΔD(m) and ΔD(d)) are calculated for a uniformly spaced set of ROIs.
For the single sample patient dose distribution, the average accumulated differential dose mapping error is 4.3%, the average absolute differential dose mapping error is 10.8%, and the average accumulated mean dose mapping error is 5.0%. Accumulated differential dose mapping errors within the gross tumor volume (GTV) and planning target volume (PTV) are lower, 0.73% and 2.33%, respectively.
A method has been presented to evaluate the dose mapping error introduced by the dose mapping process. This method has been applied to evaluate the 4D dose calculation process implemented in a commercial treatment planning system. The method could potentially be developed as a fully-automatic QA method in image guided adaptive radiation therapy (IGART).
提出一种评估剂量映射过程引入的剂量映射误差的方法。此外，将该方法应用于评估商业治疗计划系统研究版本中对患者病例实施的 4D 剂量计算过程引入的剂量映射误差。
如果组织变形是质量守恒的，那么将一个解剖实例的剂量映射到另一个解剖实例时，该有限体积内累积的平均剂量应该保持不变。在图像 S 上的有限体积的平均剂量定义为 d(S)=e(s)/m(S)，其中 e(S) 是沉积在体积 m(S) 中的能量。由于质量和能量应该守恒，当 d(S) 映射到图像 R(d(S→R)=d(R))时，平均剂量映射误差定义为 Δd(m)=|d(R)-d(S)|=|e(R)/m(R)-e(S)/m(S)|，其中 e(R) 和 e(S) 是积分剂量（沉积的能量），m(R) 和 m(S) 是图像 R 上感兴趣区域 (ROI) 内的质量以及图像 S 上相应的 ROI 内的质量，其中 R 和 S 是同一患者的两个解剖实例。或者，应用简单的微分传播可以得到微分剂量映射误差，Δd(d)=|∂d∂eΔe+∂d∂mΔm|=|(e(S)-e(R))m(R)-(m(S)-m(R))m(R)*(2)*e(R)|=α|d(R)-d(S)|，其中 α=m(S)/m(R)。使用十相 4D-CT 肺患者的 4D 治疗计划来演示患者病例的剂量映射误差评估，其中计算了累积剂量 D(R)=∑(S=0) (9)d(S→R)，以及相关的误差值 (ΔD(m) 和 ΔD(d))，这些误差值是在一组均匀间隔的 ROI 上计算的。
对于单个样本患者剂量分布，平均累积微分剂量映射误差为 4.3%，平均绝对微分剂量映射误差为 10.8%，平均累积平均剂量映射误差为 5.0%。在大体肿瘤体积 (GTV) 和计划靶区 (PTV) 内的累积微分剂量映射误差较低，分别为 0.73%和 2.33%。
提出了一种评估剂量映射过程引入的剂量映射误差的方法。该方法已应用于评估商业治疗计划系统中实施的 4D 剂量计算过程。该方法可能会作为图像引导自适应放射治疗 (IGART) 中的全自动 QA 方法得到进一步发展。
