Department of Radiology, Duke University Medical Center, Durham, NC 27705, USA.
Med Phys. 2012 Oct;39(10):6048-55. doi: 10.1118/1.4752209.
To quantitatively compare noise texture across computed tomography (CT) scanners from different manufacturers using the noise power spectrum (NPS).
The American College of Radiology CT accreditation phantom (Gammex 464, Gammex, Inc., Middleton, WI) was imaged on two scanners: Discovery CT 750HD (GE Healthcare, Waukesha, WI), and SOMATOM Definition Flash (Siemens Healthcare, Germany), using a consistent acquisition protocol (120 kVp, 0.625∕0.6 mm slice thickness, 250 mAs, and 22 cm field of view). Images were reconstructed using filtered backprojection and a wide selection of reconstruction kernels. For each image set, the 2D NPS were estimated from the uniform section of the phantom. The 2D spectra were normalized by their integral value, radially averaged, and filtered by the human visual response function. A systematic kernel-by-kernel comparison across manufacturers was performed by computing the root mean square difference (RMSD) and the peak frequency difference (PFD) between the NPS from different kernels. GE and Siemens kernels were compared and kernel pairs that minimized the RMSD and |PFD| were identified.
The RMSD (|PFD|) values between the NPS of GE and Siemens kernels varied from 0.01 mm(2) (0.002 mm(-1)) to 0.29 mm(2) (0.74 mm(-1)). The GE kernels "Soft," "Standard," "Chest," and "Lung" closely matched the Siemens kernels "B35f," "B43f," "B41f," and "B80f" (RMSD < 0.05 mm(2), |PFD| < 0.02 mm(-1), respectively). The GE "Bone," "Bone+," and "Edge" kernels all matched most closely with Siemens "B75f" kernel but with sizeable RMSD and |PFD| values up to 0.18 mm(2) and 0.41 mm(-1), respectively. These sizeable RMSD and |PFD| values corresponded to visually perceivable differences in the noise texture of the images.
It is possible to use the NPS to quantitatively compare noise texture across CT systems. The degree to which similar texture across scanners could be achieved varies and is limited by the kernels available on each scanner.
使用噪声功率谱（NPS）定量比较来自不同制造商的 CT 扫描仪之间的噪声纹理。
使用一致的采集协议（120kVp、0.625/0.6mm 层厚、250mAs 和 22cm 视野）对美国放射学院 CT 认证体模（Gammex 464，Gammex，Inc.，威斯康星州 Middleton）在两台扫描仪上进行成像：Discovery CT 750HD（GE 医疗，威斯康星州 Waukesha）和 SOMATOM Definition Flash（西门子医疗，德国）。从体模的均匀部分估算每个图像集的二维 NPS。通过人眼视觉响应函数对二维谱进行归一化、径向平均和滤波。通过计算不同内核之间 NPS 的均方根差（RMSD）和峰值频率差（PFD），对制造商之间的系统内核进行比较。对 GE 和西门子内核进行比较，并确定最小化 RMSD 和|PFD|的内核对。
GE 和西门子内核的 NPS 之间的 RMSD（|PFD|）值从 0.01mm²（0.002mm⁻¹）到 0.29mm²（0.74mm⁻¹）不等。GE 内核“Soft”、“Standard”、“Chest”和“Lung”与西门子内核“B35f”、“B43f”、“B41f”和“B80f”非常匹配（RMSD<0.05mm²，|PFD|<0.02mm⁻¹）。GE“Bone”、“Bone+”和“Edge”内核与西门子“B75f”内核最为匹配，但 RMSD 和|PFD|值较大，分别高达 0.18mm²和 0.41mm⁻¹。这些较大的 RMSD 和|PFD|值对应于图像噪声纹理的视觉可察觉差异。
可以使用 NPS 定量比较 CT 系统之间的噪声纹理。在多大程度上可以在扫描仪之间实现相似的纹理受到每个扫描仪上可用内核的限制。
