影响磁共振成像(magnetic resonance imaging，MRI)图像质量的因素有：信噪比（SNR）、空间分辨率、对比度/噪声比（CNR）及伪影。
在MRI检查中只有掌握各种成像参数与MR图像质量的各种指标的相关性，并合理地加以控制，才能获得可靠的、高质量的MR图像。
1、SNR 它是组织信号与随机背景噪声的比值，信噪比与图像质量成正比。
影响信噪比的因素有：①FOV：信噪比与FOV的平方成正比；②层间距：层间距越小，层间的交叉干扰越大；③平均次数：当平均次数增加时，导致扫描时间增加，而信噪比的增加只与平均次数的平方根成正比；④重复时间。
当重复时间延长时，导致组织的纵向磁化倾向最大限度增加。
与此同时，信号强度也增加，使信噪比增加，但增加是有限的；⑤回波时间：当回波时间延长时，由于T2衰减导致回波信号减弱，引起信噪比相应减低；⑥反转时间；⑦射频线圈：它不但采集人体内的信号，而且它也接受人体内的噪声。
控制噪声的方法为选择与扫描部位合适的射频接受线圈。
2、CNR 应该看到，在评价图像质量时，SNR是一项比较重要的技术指标，但是不能把它看作是一项绝对的标准。
临床应用表明，即使SNR很高也不能保证两个相邻结构能有效地被区分开来，因此有价值的诊断图像必须在特性组织和周围正常组织间表现出足够的对比度。
图像的对比度反映了两组织间的相对信号差。
它取决于组织本身的特性。
当病灶与周围组织的图像对比度较小时，在MRI中使用顺磁性造影剂。
SNR则与设备性能有关。
对比度和SNR共同决定了图像的质量，为此定义CNR来评价两者对图像的共同作用。
其定义是：图像中相邻组织结构间SNR之差，即：CNR=SNR(A)-SNR(B)式中SNR(A)与SNR(B)分别为组织A、B的SNR。
上式表明，只有SNR不同的相邻组织，才能够表现出良好的对比度。
在实际的信号检测中，如果组织间对比度较大，但噪声也很大，则较大的对比度会被较高的噪声所淹没。
医疗器械类英语及其缩写Medical Devices and their AbbreviationsIntroduction:Medical devices, also known as medical equipment, play a critical role in healthcare. They are designed to diagnose, prevent, monitor, treat, or alleviate medical conditions. These devices are regulated and categorized based on their intended use and risk level. In the medical field, several terms and abbreviations are commonly used to refer to various medical devices and their components. This article aims to provide a comprehensive list and explanation of medical device terminology and their corresponding abbreviations.1. Diagnostic Devices:1.1 Electrocardiograph (ECG) - A device used to measure the electrical activity of the heart.1.2 Magnetic Resonance Imaging (MRI) - Uses magnetic fields and radio waves to produce detailed images of the body.1.3 Ultrasound (US) - Utilizes high-frequency sound waves to create images of internal body structures.1.4 Computed Tomography (CT) - Combines multiple X-ray images to construct cross-sectional images of the body.1.5 Positron Emission Tomography (PET) - Uses radioactive substances to produce three-dimensional images of functional processes within the body.2. Therapeutic Devices:2.1 Ventilator - Assists patients in breathing by delivering oxygen to the lungs.2.2 Insulin Pump - Provides insulin to manage blood glucose levels in diabetic patients.2.3 Dialysis Machine - Used to filter and purify the blood in patients with kidney failure.2.4 Defibrillator - Administers an electric shock to restore normal heart rhythm in cases of cardiac arrest.2.5 Prosthesis - Replaces a missing body part or functions as a support.3. Surgical Instruments:3.1 Scalpel - A sharp knife used for surgical incisions.3.2 Forceps - Used to grasp and hold tissue or objects during surgical procedures.3.3 Suture Needle - Needle used to sew together incisions or wounds during surgery.3.4 Retractor - Used to hold open incisions or separate tissues during surgery.3.5 Trocar - A sharp-pointed surgical instrument used to create access into body cavities.4. Monitoring Devices:4.1 Electroencephalogram (EEG) - Records electrical activity of the brain through electrodes placed on the scalp.4.2 Pulse Oximeter - Measures oxygen saturation levels in the blood.4.3 Blood Pressure Monitor (BPM) - Used to measure the force exerted by blood against the walls of blood vessels.4.4 Glucometer - Device used to measure glucose levels in the blood.4.5 Holter Monitor - A portable device that continuously records the electrical activity of the heart over a period of time.5. Abbreviations:5.1 FDA - Food and Drug Administration (United States)5.2 CE - Conformité Européene (Europe)5.3 ISO - International Organization for Standardization5.4 PACS - Picture Archiving and Communication System5.5 CPR - Cardiopulmonary ResuscitationConclusion:Medical devices are indispensable tools in modern healthcare. By understanding the wide array of medical devices and their associated abbreviations, healthcare professionals can effectively communicate and improve patient care. As technology advances, the development of new medical devices and their related terms will continue to expand, enhancing the overall efficiency and effectiveness of the healthcare industry.。
磁共振的英文缩写MRI：Magnetic Resonance Imaging磁共振成像NMRI：Nuclear Magnetic Resonance Imaging核磁共振成像MRA：Magnetic Resonance Angiography磁共振血管造影CE-MRA：contrast enhanced magnetic resonance angiography对比增强磁共振血管成像MRV：Magnetic Resonance Venography磁共振静脉造影VW-MRI：vessel wall magnetic resonance imaging磁共振血管壁成像MRCP：Magnetic Resonance cholangiopancreatography磁共振胰胆管成像MRM：Magnetic Resonance Myelography磁共振脊髓成像MRU：Magnetic Resonance urography磁共振尿路成像MRN：Magnetic Resonance neurography磁共振神经成像CMR：Cardiovascular MR心血管磁共振检查技术fMRI：functional magnetic resonance imaging磁共振功能成像MRE：Magnetic Resonance Elastography磁共振弹性成像T1WI：T1-weighted imagingT1加权成像T2WI：T2-weighted imagingT2加权成像PDWI：proton density weighted imaging质子密度加权成像EPI：echo planar imaging平面回波成像MS-EPI：multi shot echo planar imaging多激发平面回波成像DWI：diffusion weighted imaging扩散加权成像(小视野弥散Philips-ZOOM/Siemens-ZOOMit/GE-FOCUS)ADC：apparent diffusion coefficient表观扩散系数DWIBS：diffusion weighted imaging with background suppression背景抑制扩散加权成像RESOLVE：readout segment of long variable echo trains 基于读出方向分段K空间的多次激发弥散加权成像(Siemens)MUSE：multi-slab parallel EPI多激发节段式EPI采集空间信号敏感性编码图像重建(GE)DTI：diffusion tensor imaging扩散张量成像PWI：perfusion weighted imaging灌注加权成像BOLD：blood oxygenation level dependent血氧水平依赖RF：Radio Frequency射频TR：repetition time重复时间TE：echo time回波时间(Effective TE有效TE)Minimum TE：部分回波技术TI：inversion time反转时间ES：echo space回波间隙ETL：echo train length回波链长度BW：bandwidth带宽FA：flip angle反转角TA：Acquisition time采集时间NA：number of acquisitions采集次数NSA：number of signal averaged信号平均次数NEX：number of excitation激励次数TD：time of delay延迟时间WFS：water fat shift水脂位移FC：flow pensation流动补偿TOF：time of flight时间飞跃TRICKS：time resolved imaging of contrast Kinetics对比剂动态成像PC：phase contrast相位对比VENC：velocity encoding流速编码NPW：no phase wrap去相位卷褶IR：inversion recovery反转恢复MT：magnetization transfer磁化转移(磁化传递)FT：fourier transform傅里叶变换VPS：Views Per Segment每段视图BSP TI：blood suppression TI血夜抑制反转时间(IFIR参数)序列SE：spin echo自旋回波FSE：fast spin echo快速自旋回波TSE：turbo spin echo快速自旋回波FRFSE：fast recovery fast spin echo快速恢复快速自旋回波(GE)TSE-Restore：快速恢复快速自旋回波(Siemens)TSE DRIVE(TSE driven equilibrium DE驱动平衡)：快速恢复快速自旋回波(Philips)SSFSE：single shot fast spin echo单次激发快速自旋回波HALF-SS-TSE：half-fourier acquisition single-shot turbo spin echo半傅里叶单次激发快速自旋回波(Philips)HASTE：half-fourier acquisition single-shot turbo spin echo半傅里叶单次激发快速自旋回波(Siemens)FLAIR：fluid attenuated inversion recovery水抑制反转恢复ASL：arterial spin labeling动脉自旋标记BPAS：basi-parallel anatomical scanning平行椎基底动脉系统扫描FIR：fast inversion recovery快速反转恢复(TIR：turbo inversion recovery)DIR：dual inversion recovery(有资料译为double inversion recovery)双重反转恢复下面三个技术（VISTA/CUBE/SPACE）摘自懋氏百科全书，后面两个的中文是我瞎翻译的：VISTA(3D VIEW)：volume isotropic turbo spin echo acquisition各向同性快速自旋回波容积采集(Philips)CUBE：3D fast spin echo with an extended echo train acquisition长回波链3D快速自旋回波采集(GE)SPACE：sampling perfection with application optimized contrast using different flip angle evolution最优可变翻转角改善对比完美采样(Siemens)梯度回波GRE：gradient recalled echo梯度回波(GE)FFE：fast field echo快速场回波(Philips)GE：gradient echo梯度回波(Siemens)TFE：turbo field echo超快速场回波FISP：fast imaging with steady-state precession稳态进动快速成像(Siemens)PSIF(Siemens)：采集刺激回波的GRE序列；在时序上与FISP 相反遂命名为PSIF(Philips为T2-FFE；GE为CE-GRASS:contrast enhanced GRASS)DESS：dual spin steady state双回波稳态进动(Siemens独有3D序列，显示软骨优势；同时采集FISP信号和PSIF信号)MEDIC：multiple echo data image bination多回波数据合并成像(Siemens)MERGE：multiple echo recalled gradient echo多回波梯度回波 (GE 2D)COSMIC：coherent oscillatory state acquisition for the manipulation imaging contrast连续振荡状态采集操控成像对比(GE 3D多回波合并成像)mFFE(Philips多回波)：multiple fast field echoSWI：susceptibility weighted imaging磁敏感加权成像QSM：quantitative susceptibility mapping定量磁化率成像SSFP：steady state free precession普通稳态自由进动(GE 的GRE、Fast GRE均属该类型；西门子为FISP；在飞利浦上称为conventional FFE)Balance-SSFP：balance steady state free precession平衡式稳态自由进动(Philips)FIESTA：fast imaging employing steady stateacquisition稳态采集快速成像(GE)FIESTA-C：FIESTA-cycled phases双激发稳态采集快速成像(GE)True FISP：true fast imaging with steady state precession真稳态自由进动快速成像(Siemens)CISS：constructive interference in the steady state稳态进动结构相干(双激发)B-FFE：balance fast field echo平衡式快速场回波(Philips)TRANCE：triggered angiography non-contrast enhanced触发血管造影非对比增强(Philips; Siemens为 Native truefisp; GE为IFIR: InFlow Inversion Recovery)QISS：Quiescent-Interval Single-Shot MR血管造影-静态间隔单次激发成像是一种用于外周MRA的非增强MRA技术(Siemens)。
