Lee Eunsin, Werner Matthew E, Karp Joel S, Surti Suleman
Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104 USA. He is now with the Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104 USA.
IEEE Trans Nucl Sci. 2013 Jun;60(3):1645-1652. doi: 10.1109/TNS.2013.2257849.
A dedicated breast positron emission tomography (PET) scanner with limited angle geometry can provide flexibility in detector placement around the patient as well as the ability to combine it with other imaging modalities. A primary challenge of a stationary limited angle scanner is the reduced image quality due to artifacts present in the reconstructed image leading to a loss in quantitative information. Previously it has been shown that using time-of-flight (TOF) information in image reconstruction can help reduce these image artifacts arising due to missing angular projections. Our goal in this work is to optimize the TOF, breast scanner design by performing studies for estimating image uniformity and lesion activity uptake as a function of system timing resolution, scanner angular coverage and shape. Our results show that (i) 1.5 × 1.5 × 15 mm lutetium oxy-orthosilicate (LSO) crystals provide a high spatial resolution and system sensitivity relative to clinical scanners, (ii) 2/3 angular coverage scanner design with TOF timing resolution less than 600 ps is appropriate for providing a tomographic image with fewer artifacts and good lesion uptake estimation relative to other partial ring designs studied in this work, (iii) a flat scanner design with 2/3 angular coverage is affected more by larger parallax error than a curved scanner geometry with the same angular coverage, but provides more uniform lesion contrast estimate over the imaging field-of-view (FOV), (iv) 2/3 angular coverage, flat, 300 ps TOF scanner design (for short, practical scan times of ≤ 5 mins per breast) provides similar precision of contrast recovery coefficient (CRC) values to a full curved, non-TOF scanner, and (v) employing depth-of-interaction (DOI) measuring detector and/or implementing resolution modeling (RM) in image reconstruction lead to improved and more uniform spatial resolution and lesion contrast over the whole FOV.
一台具有有限角度几何结构的专用乳腺正电子发射断层扫描（PET）扫描仪，在围绕患者放置探测器方面具有灵活性，并且能够与其他成像模态相结合。固定式有限角度扫描仪的一个主要挑战是，由于重建图像中存在伪影，导致图像质量下降，进而造成定量信息丢失。此前已经表明，在图像重建中使用飞行时间（TOF）信息有助于减少因角度投影缺失而产生的这些图像伪影。我们在这项工作中的目标是，通过进行研究来优化TOF乳腺扫描仪设计，以估计图像均匀性和病变活性摄取与系统定时分辨率、扫描仪角度覆盖范围和形状的关系。我们的结果表明：（i）相对于临床扫描仪，1.5×1.5×15毫米的正硅酸镥（LSO）晶体提供了高空间分辨率和系统灵敏度；（ii）与本研究中其他部分环形设计相比，具有小于600皮秒TOF定时分辨率的2/3角度覆盖扫描仪设计，适合提供伪影较少且病变摄取估计良好的断层图像；（iii）与具有相同角度覆盖范围的弯曲扫描仪几何结构相比，具有2/3角度覆盖的平板扫描仪设计受更大视差误差的影响更大，但在成像视野（FOV）上提供更均匀的病变对比度估计；（iv）2/3角度覆盖、平板、300皮秒TOF扫描仪设计（简而言之，每个乳房实际扫描时间≤5分钟）提供的对比度恢复系数（CRC）值精度与全弯曲、非TOF扫描仪相似；（v）采用相互作用深度（DOI）测量探测器和/或在图像重建中实施分辨率建模（RM），可在整个FOV上提高并使空间分辨率和病变对比度更均匀。
