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常用CT定量参数及其特点

Commonly used quantitative metrics in CT imaging

Category	Parameters	Software	Characteristics
RER: relative enhancement ratios; SD: standard deviation of CT value; ASM: angular second moment; BF: blood flow; BV: blood volume; TEF: total tumor extravascular flow; MTT: mean transit time; PS: capillary permeability surface area product; PBV: Pallak blood volume; TVV: total tumor vascular volume; IRA: iodine-related attenuation; IU: iodine uptake; AEF: arterial enhancement fraction; TDA: three-dimensional algorithm; AW: Advanced workstation; PACS: picture archiving and communication system; VNC: virtual non-contrast.
Volume	3D Volume	MEDx TDA	1. Used to measure overall tumor changes. 2. Good reproducibility, especially in those tumors with irregular shapes. 3. Lack of well-accepted standards among various processing algorithms.
Density	CT value SD RER	AW PACS ITK-SNAP	1. Capable of assessing intratumoral changes. 2. Time-consuming in comparison to traditional anatomical and morphological measurements. 3. Intraobserver and interobserver variations as well as variations due to measurement approaches.
Texture	ASM Entropy Contrast	OneCut graph ImageJ® MaZda®	1. Advantage of quantitative description of tumor heterogeneity. 2. Measurement outcome less subject to observers and methodologies. 3. Results vulnerable to scanning equipment and post-processing algorithms.
Perfusion	BF, BV, TEF MTT, PS PBV, TVV	Syngo 2008G AW Functional CT	1. Able to provide functional imaging information by assessment of vascular perfusion within tumors, which may be more accurate for evaluation of physiological changes than dimensional or volumetric methodologies, such as RECIST. 2. Be aware of the radiation dose. 3. Performance could be improved by optimization of hemodynamics models.
Energy	IRA, IU, AEF	Liver VNC, Syngo IPIPE	1. Material decomposition, especially iodine quantitation, provides biological and chemical information related to tumors, in a manner similar to PET-CT imaging. 2. Thanks to the virtual non-contrast technique, the unenhanced examination could be waivered, hence radiation dose reduced. 3. Image quality may be compromised in patients with high BMI values. 4. Unclear or inconsistent relationship between disease conditions and measurements.