Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany.
Eur J Nucl Med Mol Imaging. 2011 Sep;38(9):1691-701. doi: 10.1007/s00259-011-1842-9. Epub 2011 Jun 18.
In this study, the potential contribution of Dixon-based MR imaging with a rapid low-resolution breath-hold sequence, which is a technique used for MR-based attenuation correction (AC) for MR/positron emission tomography (PET), was evaluated for anatomical correlation of PET-positive lesions on a 3T clinical scanner compared to low-dose CT. This technique is also used in a recently installed fully integrated whole-body MR/PET system.
Thirty-five patients routinely scheduled for oncological staging underwent (18)F-fluorodeoxyglucose (FDG) PET/CT and a 2-point Dixon 3-D volumetric interpolated breath-hold examination (VIBE) T1-weighted MR sequence on the same day. Two PET data sets reconstructed using attenuation maps from low-dose CT (PET(AC_CT)) or simulated MR-based segmentation (PET(AC_MR)) were evaluated for focal PET-positive lesions. The certainty for the correlation with anatomical structures was judged in the low-dose CT and Dixon-based MRI on a 4-point scale (0-3). In addition, the standardized uptake values (SUVs) for PET(AC_CT) and PET(AC_MR) were compared.
Statistically, no significant difference could be found concerning anatomical localization for all 81 PET-positive lesions in low-dose CT compared to Dixon-based MR (mean 2.51 ± 0.85 and 2.37 ± 0.87, respectively; p = 0.1909). CT tended to be superior for small lymph nodes, bone metastases and pulmonary nodules, while Dixon-based MR proved advantageous for soft tissue pathologies like head/neck tumours and liver metastases. For the PET(AC_CT)- and PET(AC_MR)-based SUVs (mean 6.36 ± 4.47 and 6.31 ± 4.52, respectively) a nearly complete concordance with a highly significant correlation was found (r = 0.9975, p < 0.0001).
Dixon-based MR imaging for MR AC allows for anatomical allocation of PET-positive lesions similar to low-dose CT in conventional PET/CT. Thus, this approach appears to be useful for future MR/PET for body regions not fully covered by diagnostic MRI due to potential time constraints.
在这项研究中，评估了基于 Dixon 的磁共振成像（MR）与快速低分辨率屏气序列（用于 MR 衰减校正（AC）的技术）在临床 3T 扫描仪上与 PET 阳性病变的解剖相关性方面的潜在贡献，与低剂量 CT 进行比较。该技术还用于最近安装的完全集成的全身 MR/PET 系统。
35 名常规接受肿瘤分期的患者在同一天接受了（18）F-氟脱氧葡萄糖（FDG）PET/CT 和 2 点 Dixon 三维容积内插屏气检查（VIBE）T1 加权 MR 序列。使用低剂量 CT（PET（AC_CT））或模拟基于 MR 的分割（PET（AC_MR））的衰减图重建了两个 PET 数据集，用于评估局灶性 PET 阳性病变。在低剂量 CT 和 Dixon 基础 MRI 上以 4 分制（0-3）对与解剖结构的相关性进行判断。此外，比较了 PET（AC_CT）和 PET（AC_MR）的标准化摄取值（SUV）。
统计学上，与 Dixon 基础 MRI 相比，低剂量 CT 对所有 81 个 PET 阳性病变的解剖定位没有显著差异（分别为平均 2.51 ± 0.85 和 2.37 ± 0.87；p = 0.1909）。CT 对小淋巴结、骨转移和肺结节具有优势，而 Dixon 基础 MRI 对头部/颈部肿瘤和肝转移等软组织病变具有优势。对于 PET（AC_CT）和 PET（AC_MR）的 SUV（平均 6.36 ± 4.47 和 6.31 ± 4.52），发现了几乎完全一致的高度显著相关性（r = 0.9975，p < 0.0001）。
基于 Dixon 的 MR 成像用于 MR AC 可以在常规 PET/CT 中对 PET 阳性病变进行解剖分配，与低剂量 CT 相似。因此，由于潜在的时间限制，该方法似乎对于未来的身体区域的 MR/PET 有用，这些区域由于诊断 MRI 的局限性而无法完全覆盖。
