Radiography & Diagnostic Imaging, School of Medicine, University College Dublin, Dublin 4 Belfield, Ireland.
IRIS-Imaging Research Initiative Southwest, Department of Radiology & Nuclear Medicine, Esbjerg University Hospital, 6700 Esbjerg, Denmark.
Tomography. 2023 Nov 15;9(6):2089-2102. doi: 10.3390/tomography9060164.
Measuring left ventricular ejection fraction (LVEF) is important for detecting heart failure, e.g., in treatment with potentially cardiotoxic chemotherapy. MRI is considered the reference standard for LVEF, but availability may be limited and claustrophobia or metal implants still present challenges. CT has been shown to be accurate and would be advantageous, as LVEF could be measured in conjunction with routine chest-abdomen-pelvis oncology CT. However, the use of CT is not recommended due to the excessive radiation dose. This study aimed to explore the potential for dose reduction using simulation. Using an anthropomorphic heart phantom scanned at 13 dose levels, a noise simulation algorithm was developed to introduce controlled Poisson noise. Filtered backprojection parameters were iteratively tested to minimise differences in myocardium-to-ventricle contrast/noise ratio, as well as structural similarity index (SSIM) differences between real and simulated images at all dose levels. Fifty-one clinical CT coronary angiographies, scanned with full dose through end-systolic and -diastolic phases, were located retrospectively. Using the developed algorithm, noise was introduced corresponding to 25, 10, 5 and 2% of the original dose level. LVEF was measured using clinical software (Syngo.via VB50) with papillary muscles in and excluded from the LV volume. At each dose level, LVEF was compared to the 100% dose level, using Bland-Altman analysis. The effective dose was calculated from DLP using a conversion factor of 0.026 mSv/mGycm.
In the clinical images, mean CTDIvol and DLP were 47.1 mGy and 771.9 mGycm, respectively (effective dose 20.0 mSv). Measurements with papillary muscles excluded did not exhibit statistically significant LVEF bias to full-dose images at 25, 10 and 5% simulated dose. At 2% dose, a significant bias of 4.4% was found. With papillary muscles included, small but significant biases were found at all simulated dose levels.
Provided that measurements are performed with papillary muscles excluded from the LV volume, the dose can be reduced by a factor of 20 without significantly affecting LVEF measurements. This corresponds to an effective dose of 1 mSv. CT can potentially be used for LVEF measurement with minimal excessive radiation.
测量左心室射血分数（LVEF）对于检测心力衰竭很重要，例如在接受潜在心脏毒性化疗时。磁共振成像（MRI）被认为是 LVEF 的参考标准，但可用性可能有限，幽闭恐惧症或金属植入物仍然存在挑战。CT 已被证明是准确的，并且具有优势，因为可以在常规胸部-腹部-骨盆肿瘤 CT 检查的同时测量 LVEF。然而，由于辐射剂量过高，不建议使用 CT。本研究旨在探索使用模拟技术降低剂量的潜力。使用在 13 个剂量水平下扫描的人体心脏模型，开发了一种噪声模拟算法，以引入受控泊松噪声。迭代测试滤波反投影参数，以最小化心肌与心室对比度/噪声比的差异，以及在所有剂量水平下真实图像和模拟图像之间的结构相似性指数（SSIM）差异。回顾性定位了 51 例经全剂量扫描的冠状动脉 CT 血管造影术，分别在收缩末期和舒张末期进行扫描。使用开发的算法，将噪声引入与原始剂量水平的 25%、10%、5%和 2%相对应的水平。使用临床软件（Syngo.via VB50）测量 LVEF，将乳头肌包含或不包含在 LV 体积内。在每个剂量水平下，使用 Bland-Altman 分析将 LVEF 与 100%剂量水平进行比较。使用剂量长度乘积（DLP）与 0.026 mSv/mGycm 的转换因子计算有效剂量。
在临床图像中，平均 CTDIvol 和 DLP 分别为 47.1 mGy 和 771.9 mGycm（有效剂量为 20.0 mSv）。在模拟 25%、10%和 5%剂量时，不包含乳头肌的测量结果与全剂量图像无统计学显著 LVEF 偏差。在 2%剂量时，发现 4.4%的显著偏差。包含乳头肌时，在所有模拟剂量水平下都发现了较小但显著的偏差。
如果在测量 LV 体积时不包括乳头肌，剂量可以降低 20 倍，而不会对 LVEF 测量结果产生显著影响。这相当于有效剂量为 1 mSv。CT 可以潜在地用于 LVEF 测量，辐射剂量最小。
