Department of Physics, Carleton University, Ottawa, ON, Canada.
Division of Cardiology, Cardiac Imaging, University of Ottawa Heart Institute, H2258 - 40 Ruskin Street, Ottawa, ON, K1Y 4W7, Canada.
J Nucl Cardiol. 2021 Feb;28(1):225-233. doi: 10.1007/s12350-019-01664-5. Epub 2019 Mar 4.
In addition to acquired photon counts, image noise depends on the image reconstruction algorithm. This work develops patient-specific activity or acquisition time protocols to standardize the average noise in a reconstructed image for different patients, cameras, and reconstruction algorithms.
Image noise was calculated for images from 43 patients acquired on both a conventional and a multiple-pinhole cardiac SPECT camera. Functions were found to relate image noise to radiotracer activity, scan time, and body mass and were validated by normalizing the image noise in a test set of 58 patients.
There was a 3.6-fold difference in photon sensitivity between the two cameras but a 16-fold difference in activity-scan time was necessary to match the noise levels. Image noise doubled from 45 to 128 kg for the conventional camera (12.8 minutes) and tripled for the multiple-pinhole camera (5 minutes) for 350 MBq (9.5 mCi) Tc-tetrofosmin. It was 16.3% and 6.1% respectively for an average sized patient.
A linear scaling of activity with respect to the patient weight normalizes image noise but the scaling factors depend on the choice of camera and image reconstruction parameters. Therefore, equivalent numbers of acquired photon counts are not sufficient to guarantee equivalent image noise.
除了获得的光子计数外，图像噪声还取决于图像重建算法。这项工作开发了针对特定患者的活动或采集时间方案，以标准化不同患者、相机和重建算法的重建图像中的平均噪声。
从在常规和多针孔心脏 SPECT 相机上采集的 43 名患者的图像中计算图像噪声。发现了将图像噪声与示踪剂活性、扫描时间和体重相关的函数，并通过对 58 名患者的测试集进行图像噪声归一化验证。
两台相机的光子灵敏度相差 3.6 倍，但要匹配噪声水平，活动扫描时间需要相差 16 倍。对于常规相机（12.8 分钟），体重从 45 增加到 128 公斤，图像噪声增加一倍；对于多孔相机（5 分钟），体重从 45 增加到 128 公斤，图像噪声增加两倍（350 MBq [9.5 mCi] Tc-tetrofosmin）。对于平均体型的患者，分别为 16.3%和 6.1%。
根据患者体重对活动进行线性缩放可使图像噪声标准化，但缩放因子取决于相机和图像重建参数的选择。因此，获得的光子计数相等并不足以保证图像噪声相等。
