Department of Radiation Oncology, University Hospital Wuerzburg, Wuerzburg, Germany.
Department of Radiation Oncology, University Hospital Wuerzburg, Wuerzburg, Germany.
Radiother Oncol. 2023 Oct;187:109840. doi: 10.1016/j.radonc.2023.109840. Epub 2023 Aug 1.
Objective and subjective assessment of image quality of brain metastases on dual-energy computed tomography (DECT) virtual monoenergetic imaging (VMI) and its impact on target volume delineation.
26 patients with 37 brain metastases receiving Magnetic Resonance Imaging (MRI) and DECT for stereotactic radiotherapy planning were included in this retrospective analysis. Lesion contrast (LC), contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were assessed for reconstructed VMI at 63 keV and artificial 120 kV Computed Tomography (CT). Image contrast and demarcation of metastases between 120 kV CT, VMI and MRI were subjectively assessed. Brain metastases were delineated by four radiation oncologists on VMI with a fixed or free brain window and contours were compared to solely MRI-based delineation using the Dice similarity coefficient.
LC, CNR and SNR were significantly higher in VMI than in 120 kV CT (p < 0.0001). Image contrast and lesion demarcation were significantly better on VMI compared to 120 kV CT (p < 0.0001). Mean gross tumor volume (GTV)/planning target volume (PTV) Dice similarity coefficients were 0.87/0.9 for metastases without imaging uncertainties (no artifacts, calcification or impaired visibility with MRI) but worse for metastases with imaging uncertainties (0.71/0.74). Target volumes delineated on VMI were around 5-10% smaller compared to MRI.
Image quality of VMI is objectively and subjectively superior to conventional CT. VMI provides significant advantages in stereotactic radiotherapy planning with improved visibility of brain metastases and geometrically distortion-free representation of brain metastases. Beside a plausibility check of MRI-based target volume delineation, VMI might improve reliability and accuracy in target volume definition particularly in cases with imaging uncertainties with MRI.
双能 CT（DECT）虚拟单能量成像（VMI）对脑转移瘤的客观和主观图像质量评估及其对靶区勾画的影响。
本回顾性分析纳入了 26 例接受磁共振成像（MRI）和 DECT 行立体定向放疗计划的 37 个脑转移瘤患者。评估了重建的 63keV 和人工 120kV 计算机断层扫描（CT）VMI 的病灶对比度（LC）、对比噪声比（CNR）和信噪比（SNR）。评估了 120kV CT、VMI 和 MRI 之间的转移瘤的图像对比度和边界。四位放射肿瘤学家在 VMI 上使用固定或自由脑窗进行脑转移瘤勾画，并使用 Dice 相似系数比较与仅基于 MRI 的勾画的差异。
VMI 的 LC、CNR 和 SNR 均显著高于 120kV CT（p<0.0001）。与 120kV CT 相比，VMI 的图像对比度和边界更好（p<0.0001）。无成像不确定性（无伪影、钙化或 MRI 下显示不佳）的转移瘤的总肿瘤体积（GTV）/计划靶区（PTV）Dice 相似系数为 0.87/0.9，而有成像不确定性的转移瘤的相似系数为 0.71/0.74。与 MRI 相比，VMI 勾画的靶区体积小约 5-10%。
VMI 的图像质量在客观和主观上均优于常规 CT。VMI 在立体定向放疗计划中具有明显优势，可提高脑转移瘤的可见性，并可无几何变形地呈现脑转移瘤。除了对基于 MRI 的靶区勾画进行可行性检查外，VMI 可能会提高靶区定义的可靠性和准确性，特别是在 MRI 存在成像不确定性的情况下。
