Christe Andreas, Heverhagen Johannes, Ozdoba Christoph, Weisstanner Christian, Ulzheimer Stefan, Ebner Lukas
Andreas Christe, Johannes Heverhagen, Lukas Ebner, Department of Radiology, University Hospital of Bern, Inselspital, 3010 Bern, Switzerland.
World J Radiol. 2013 Nov 28;5(11):421-9. doi: 10.4329/wjr.v5.i11.421.
To compare the computed tomography (CT) dose and image quality with the filtered back projection against the iterative reconstruction and CT with a minimal electronic noise detector.
A lung phantom (Chest Phantom N1 by Kyoto Kagaku) was scanned with 3 different CT scanners: the Somatom Sensation, the Definition Flash and the Definition Edge (all from Siemens, Erlangen, Germany). The scan parameters were identical to the Siemens presetting for THORAX ROUTINE (scan length 35 cm and FOV 33 cm). Nine different exposition levels were examined (reference mAs/peek voltage): 100/120, 100/100, 100/80, 50/120, 50/100, 50/80, 25/120, 25/100 and 25 mAs/80 kVp. Images from the SOMATOM Sensation were reconstructed using classic filtered back projection. Iterative reconstruction (SAFIRE, level 3) was performed for the two other scanners. A Stellar detector was used with the Somatom Definition Edge. The CT doses were represented by the dose length products (DLPs) (mGycm) provided by the scanners. Signal, contrast, noise and subjective image quality were recorded by two different radiologists with 10 and 3 years of experience in chest CT radiology. To determine the average dose reduction between two scanners, the integral of the dose difference was calculated from the lowest to the highest noise level.
When using iterative reconstruction (IR) instead of filtered back projection (FBP), the average dose reduction was 30%, 52% and 80% for bone, soft tissue and air, respectively, for the same image quality (P < 0.0001). The recently introduced Stellar detector (Sd) lowered the radiation dose by an additional 27%, 54% and 70% for bone, soft tissue and air, respectively (P < 0.0001). The benefit of dose reduction was larger at lower dose levels. With the same radiation dose, an average of 34% (22%-37%) and 25% (13%-46%) more contrast to noise was achieved by changing from FBP to IR and from IR to Sd, respectively. For the same contrast to noise level, an average of 59% (46%-71%) and 51% (38%-68%) dose reduction was produced for IR and Sd, respectively. For the same subjective image quality, the dose could be reduced by 25% (2%-42%) and 44% (33%-54%) using IR and Sd, respectively.
This study showed an average dose reduction between 27% and 70% for the new Stellar detector, which is equivalent to using IR instead of FBP.
比较采用滤波反投影法、迭代重建法以及配备最小电子噪声探测器的CT的计算机断层扫描（CT）剂量和图像质量。
使用3种不同的CT扫描仪对肺部模型（京都科学株式会社的胸部模型N1）进行扫描：Somatom Sensation、Definition Flash和Definition Edge（均来自德国埃尔朗根的西门子公司）。扫描参数与西门子公司THORAX ROUTINE的预设参数相同（扫描长度35 cm，视野33 cm）。检查了9种不同的曝光水平（参考毫安秒/峰值电压）：100/120、100/100、100/80、50/120、50/100、50/80、25/120、25/100和25毫安秒/80千伏峰值。SOMATOM Sensation的图像采用经典滤波反投影法重建。另外两台扫描仪采用迭代重建法（SAFIRE，第3级）。Somatom Definition Edge使用了Stellar探测器。CT剂量由扫描仪提供的剂量长度乘积（DLP）（毫希沃特厘米）表示。两名分别具有10年和3年胸部CT放射学经验的放射科医生记录了信号、对比度、噪声和主观图像质量。为确定两台扫描仪之间的平均剂量降低情况，计算了从最低到最高噪声水平的剂量差异积分。
在图像质量相同的情况下，采用迭代重建（IR）而非滤波反投影（FBP）时，骨骼、软组织和空气的平均剂量降低分别为30%、52%和80%（P < 0.0001）。最近推出的Stellar探测器（Sd）使骨骼、软组织和空气的辐射剂量分别额外降低了27%、54%和70%（P < 0.0001）。在较低剂量水平下，剂量降低的益处更大。在相同辐射剂量下，从FBP改为IR以及从IR改为Sd时，对比度与噪声的平均值分别提高了34%（22%-37%）和25%（13%-46%）。在对比度与噪声水平相同的情况下，IR和Sd的剂量分别平均降低了59%（46%-71%）和51%（38%-68%）。在主观图像质量相同的情况下，使用IR和Sd时剂量分别可降低25%（2%-42%）和44%（33%-54%）。
本研究表明，新型Stellar探测器的平均剂量降低了27%至70%，这与采用IR而非FBP相当。
