Brechtel Klaus, Klein Magnus, Vogel Monika, Mueller Marc, Aschoff Philip, Beyer Thomas, Eschmann Susanna M, Bares Roland, Claussen Claus D, Pfannenberg Anna C
Department of Diagnostic Radiology, University of Tuebingen, Tuebingen, Germany.
J Nucl Med. 2006 Mar;47(3):470-6.
The purpose of this study was to compare various PET/CT examination protocols that use contrast-enhanced single-phase or contrast-enhanced multiphase CT scans under different breathing conditions.
Sixty patients with different malignant tumors were randomized into 4 different PET/CT protocols. Single-phase protocols included an intravenous contrast-enhanced (Ultravist 370; iodine at 370 mg/mL) single-phase whole-body CT scan (90 mL at 1.8 mL/min; delay, 90 s) during shallow breathing (protocol A) or during normal expiration (NormExp; protocol B). Multiphase protocols included 2 separate CT scans in the arterial contrast enhancement phase (90 mL at 2.5-2.8 mL/min; bolus tracking; scan range, base of the skull to the kidneys) and the portal-venous contrast enhancement phase (delay, 90 s; scan range, base of the lungs to the proximal thighs) during shallow breathing (protocol C) or during NormExp (protocol D) followed by a low-dose CT scan during shallow breathing for attenuation correction and whole-body PET. Feasibility was assessed by comparing the misalignment of the upper abdominal organs quantitatively by means of the craniocaudal, lateral, and anterior-posterior differences on coregistered PET/CT images. For image quality, the occurrence of CT artifacts and mismatching of rigid body points were evaluated qualitatively.
Misalignment was significantly lower for protocol B in almost all organs and represented the best coregistration quality. Surprisingly, protocol A showed significantly better alignment than the multiphase CT scans during NormExp. Misalignment values between the multiphase protocols were not significantly different, with a trend toward lower values for protocol D. The best CT image quality, with a significantly lower occurrence of artifacts, was found for protocols B and D (NormExp). The levels of mismatching of rigid body points because of patient movement in between the transmission and emission scans were similar for all protocols.
Multiphase CT protocols presented a technical disadvantage represented by suboptimal image coregistration compared with single-phase protocols. Nevertheless, multiphase protocols are technically feasible and should be considered for patients who will benefit from a contrast-enhanced multiphase CT examination for diagnosis.
本研究的目的是比较在不同呼吸条件下使用对比增强单相或对比增强多相CT扫描的各种PET/CT检查方案。
60例患有不同恶性肿瘤的患者被随机分为4种不同的PET/CT方案。单相方案包括在浅呼吸（方案A）或正常呼气（NormExp；方案B）期间进行静脉注射对比增强（Ultravist 370；碘浓度为370mg/mL）单相全身CT扫描（90mL，流速1.8mL/min；延迟90秒）。多相方案包括在浅呼吸（方案C）或NormExp（方案D）期间分别进行动脉期对比增强CT扫描（90mL，流速2.5 - 2.8mL/min；团注追踪；扫描范围，从颅底到肾脏）和门静脉期对比增强CT扫描（延迟90秒；扫描范围，从肺底部到大腿近端），随后在浅呼吸期间进行低剂量CT扫描用于衰减校正和全身PET检查。通过在配准后的PET/CT图像上比较上腹部器官在头脚、左右和前后方向上的差异来定量评估可行性。对于图像质量，定性评估CT伪影的出现情况和刚体点的匹配情况。
方案B在几乎所有器官中的错位明显更低，代表了最佳的配准质量。令人惊讶的是，方案A显示出比NormExp期间的多相CT扫描具有明显更好的对齐效果。多相方案之间的错位值没有显著差异，方案D有值更低的趋势。方案B和D（NormExp）的CT图像质量最佳，伪影出现率显著更低。所有方案中，由于患者在透射和发射扫描之间移动导致的刚体点匹配不良水平相似。
与单相方案相比，多相CT方案存在以图像配准欠佳为表现的技术劣势。然而，多相方案在技术上是可行的，对于将从对比增强多相CT检查诊断中获益的患者应予以考虑。
