Bellon Maria R, Siddiqui M Salim, Ryu Samuel, Chetty Indrin J
Department of Radiation Oncology, Henry Ford Health System, 2799 West Grand Blvd, Detroit, MI 48202, USA.
J Radiosurg SBRT. 2014;3(2):149-163.
The acquisition of high-quality, anatomic images is essential for the accurate delineation of tumor volumes and critical structures used for stereotactic radiosurgery (SRS) treatment planning. This study investigates the effect of CT slice thickness and field of view (FOV), i.e., longitudinal and axial CT resolution, on volume delineation and treatment planning in SRS and suggests optimal CT acquisition parameters for brain SRS simulation. Optimization of such parameters will maximize clinical efficacy, alter data storage requirements, reduce dosimetric uncertainties, and may ultimately facilitate more favorable clinical outcomes. Changes in the extent, shape and the absolute volume of the GTV were recorded when the longitudinal and axial CT resolution were modified. These changes ultimately impacted the PTV dose coverage. Reducing CT slice thickness from 2mm to 1mm resulted in an average decrease of 8.6%±13.9% (max=52.2%) and 3.0 %±4.3% (max=13.1%) in PTV D and PTV D95, respectively. Increasing CT slice thickness from 2mm to 3mm resulted in an average decrease of 10%±9.9% (max=26.8%) and 5.8%±5.8% (max=17.4%) in PTV D and PTV D95, respectively. Similarly, on average, PTV coverage decreased when FOV decreased. The average decrease in PTV D and PTV D95 for a 350cm FOV was 5.2%±7.2% (max=21.4%) and 1.9%±3.2% (max=7.5%), respectively. Decreasing FOV to 250cm yielded similar results with the average decrease of 5.6%±5.0% (max=13.2%) and 1.6%±2.6% (max=6.3%) in PTV D and PTV D95, respectively. These results suggest that the slice thickness and FOV of CT images affect target delineation and may potentially compromise the quality of the target coverage.
获取高质量的解剖图像对于精确勾画用于立体定向放射外科（SRS）治疗计划的肿瘤体积和关键结构至关重要。本研究调查了CT层厚和视野（FOV），即纵向和轴向CT分辨率，对SRS中体积勾画和治疗计划的影响，并提出了脑部SRS模拟的最佳CT采集参数。优化这些参数将使临床疗效最大化，改变数据存储需求，降低剂量学不确定性，并最终可能促成更有利的临床结果。当纵向和轴向CT分辨率改变时，记录了GTV的范围、形状和绝对体积的变化。这些变化最终影响了PTV的剂量覆盖。将CT层厚从2mm减至1mm分别导致PTV D和PTV D95平均下降8.6%±13.9%（最大值=52.2%）和3.0%±4.3%（最大值=13.1%）。将CT层厚从2mm增至3mm分别导致PTV D和PTV D95平均下降10%±9.9%（最大值=26.8%）和5.8%±5.8%（最大值=17.4%）。同样，平均而言，当FOV减小时PTV覆盖也会降低。对于350cm FOV，PTV D和PTV D95的平均下降分别为5.2%±7.2%（最大值=21.4%）和1.9%±3.2%（最大值=7.5%）。将FOV减至250cm产生了类似结果，PTV D和PTV D95的平均下降分别为5.6%±5.0%（最大值=13.2%）和1.6%±2.6%（最大值=6.3%）。这些结果表明CT图像的层厚和FOV会影响靶区勾画，并可能潜在地损害靶区覆盖质量。
