Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland.
AJNR Am J Neuroradiol. 2012 Jun;33(6):1014-9. doi: 10.3174/ajnr.A2910. Epub 2012 Feb 2.
CT protocols should aim for radiation doses being as low as reasonably achievable. The purpose of our study was to assess the image quality and radiation dose of neck CT at a tube potential of 70 kVp.
Twenty patients (7 female, mean age 51.4 years, age range 19-81 years) underwent contrast-enhanced 64-section CT of the neck at 70 kVp (ATCM, effective tube current-time product 614 eff.mAs, range 467-713 eff.mAs). All 20 patients had a previous neck CT at 120 kVp on the same scanner. Two radiologists assessed image quality and artifacts in the upper, middle, and lower neck. Image noise and attenuation were measured, and the CNR was calculated. Effective radiation dose was calculated.
Interobserver agreement regarding image quality of soft tissue for 70-kVp and 120-kVp scans was good to excellent. At 70 kVp, soft tissues were of diagnostic image quality in all scans, whereas the lower cervical spine was not of diagnostic quality in 3 and 4 scans per both readers. No difference was found among 70-kVp and 120-kVp scans for soft tissue image quality in the upper neck, while image quality was significantly better in the middle at 70 kVp (P < .05) and better in the lower third at 120 kVp (P < .05). CNR was significantly higher at 70 kVp in all levels for both readers (P < .001). Effective radiation dose at 70 kVp was significantly lower (0.88 ± 0.2 mSv) than at 120 kVp (1.33 ± 0.2 mSv, P < .001).
CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved CNR, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality.
CT 方案应尽量降低辐射剂量。本研究的目的是评估管电压为 70kVp 时颈部 CT 的图像质量和辐射剂量。
20 例患者（7 例女性，平均年龄 51.4 岁，年龄范围 19-81 岁）在同一台扫描仪上接受了管电压为 70kVp 的颈部增强 64 层 CT（ATCM，有效管电流时间乘积 614eff.mAs，范围 467-713 eff.mAs）。所有 20 例患者均有之前在同一台扫描仪上进行的 120kVp 颈部 CT。两位放射科医生评估了上、中、下颈部的图像质量和伪影。测量图像噪声和衰减，并计算 CNR。计算有效辐射剂量。
70kVp 和 120kVp 扫描的软组织图像质量的观察者间一致性为良好至极好。在 70kVp 时，所有扫描的软组织均具有诊断质量，而两位读者在 3 次和 4 次扫描中均认为下颈椎无诊断质量。上颈部 70kVp 和 120kVp 扫描的软组织图像质量无差异，而 70kVp 时中颈部的图像质量明显更好（P<.05），120kVp 时下颈部的图像质量更好（P<.05）。两位读者在所有水平上的 CNR 均明显更高（P<.001）。70kVp 的有效辐射剂量明显低于 120kVp（0.88±0.2mSv）（P<.001）。
70kVp 颈椎软组织 CT 是可行的，可提供诊断质量的图像，与 120kVp 标准方案相比，CNR 提高，辐射剂量降低约 34%。相比之下，低 kVp CT 下颈椎的图像质量较差。
