Kim Yusung, Tomé Wolfgang A, Bal Matthieu, McNutt Todd R, Spies Lothar
Department of Medical Physics, University of Wisconsin Medical School, Madison, 53792, USA.
Radiother Oncol. 2006 May;79(2):198-202. doi: 10.1016/j.radonc.2006.03.022. Epub 2006 May 4.
To quantify the cold or hot spot induced in IMRT treatment plans due to the presence of metal artifact in CT image data sets stemming from dental work.
Metal artifact corrected image data sets of five patients have been analyzed. IMRT plans were generated using five different planning image data sets: (a) uncorrected (UC) (b) homogeneous uncorrected (HUC), (c) sinogram completion corrected (SCC), (d) minimum value corrected (MVC), and (e) image set (d) subsequently corrected with a streak artifacts reduction algorithm (SAR-MVC). The SAR-MVC data set is assumed to be the closest approximation to the absence of metal artifacts and has therefore been taken as the reference image data set. An IMRT plan was generated for each of the image datasets (a)-(e). The resulting IMRT treatment plans for data sets (a)-(d) were then projected onto the reference data set (e) and recalculated. The reference dose distribution (e) was then subtracted from these recalculated dose distributions. Using dose difference analysis, the cold and hot spots in organs at risk (OARs) and the target volumes (TVs) were quantified.
When compared to the reference dose distribution, the UC, HUC, and SCC plans exhibited hot spots showing on average more than 1.0 Gy hot dose in the left and right parotids. For the UC, HUC, and SCC recalculated plans, subvolumes of the clinical target volumes (CTV) were under dosed on average by more than 0.9 Gy. On the other hand, the MVC plan showed less than 0.3 Gy hot dose in both parotids, and the cold dose in the CTVs were reduced by up to 0.8 Gy.
The presence of dental metal artifacts in head and neck planning CT data sets can lead to relative hot spots in OARs and relative cold spots in regions of the TVs when compared to the reference data set that more closely approximates the patient anatomy. This effect can be reduced if a simple minimum value correction (MVC) method for the dental metal artifacts is employed.
量化因牙科治疗导致的CT图像数据集中存在金属伪影而在调强放射治疗（IMRT）计划中产生的冷点或热点。
分析了五名患者的金属伪影校正图像数据集。使用五种不同的计划图像数据集生成IMRT计划：（a）未校正（UC），（b）均匀未校正（HUC），（c）正弦图完成校正（SCC），（d）最小值校正（MVC），以及（e）随后用条纹伪影减少算法（SAR-MVC）校正的图像集（d）。假设SAR-MVC数据集最接近无金属伪影的情况，因此将其作为参考图像数据集。为每个图像数据集（a） - （e）生成一个IMRT计划。然后将数据集（a） - （d）得到的IMRT治疗计划投影到参考数据集（e）上并重新计算。然后从这些重新计算的剂量分布中减去参考剂量分布（e）。使用剂量差异分析，对危及器官（OARs）和靶区（TVs）中的冷点和热点进行量化。
与参考剂量分布相比，UC、HUC和SCC计划在左右腮腺中均出现热点，平均热剂量超过1.0 Gy。对于UC、HUC和SCC重新计算的计划，临床靶区（CTV）的子体积平均剂量不足超过0.9 Gy。另一方面，MVC计划在两个腮腺中的热剂量均小于0.3 Gy，CTV中的冷剂量减少了高达0.8 Gy。
与更接近患者解剖结构的参考数据集相比，头颈部计划CT数据集中存在牙科金属伪影会导致OARs中出现相对热点，TVs区域出现相对冷点。如果采用针对牙科金属伪影的简单最小值校正（MVC）方法，这种影响可以降低。
