作者: assent 時間: 2025-3-22 00:08 作者: commute 時間: 2025-3-22 02:28
gnostic field.Complex subject conveyed in simplified, portabThe aim of this book is to provide a compact text for practicing physicians and cardiologists or radiologists in training that contains all aspects of cardiovascular magnetic resonance imaging relevant for the appropriate use of this imagin作者: 啞巴 時間: 2025-3-22 04:58 作者: DUCE 時間: 2025-3-22 12:03 作者: monogamy 時間: 2025-3-22 13:57 作者: monogamy 時間: 2025-3-22 19:40 作者: 飛鏢 時間: 2025-3-22 21:49
Image Space and k-Spacesingle pixel in the image may have contributions from all of the MR signals collected. Just as each pixel occupies a unique location in image space, each point of an MR signal echo belongs to a particular location in a related space known as . (Fig.7.1).作者: SENT 時間: 2025-3-23 05:11 作者: 有毒 時間: 2025-3-23 06:57
Book 20111st edition hands-on information in a format small enough to be carried about for ease of use. The book will be a dense but extremely portable reference for all cardiologists involved in using or requesting MRI of their cardiac patients. This will be an all-in-one resource and of great clinical value.作者: 受辱 時間: 2025-3-23 11:14 作者: 被詛咒的人 時間: 2025-3-23 14:38
https://doi.org/10.1007/978-3-642-30696-9tion pulse that is normally 90°, so at each excitation pulse all of the . magnetization is transferred into the transverse plane. This combined with the refocusing pulse gives the largest possible signal provided the magnetization is allowed to recover sufficiently between repetitions.作者: 充滿人 時間: 2025-3-23 19:54 作者: 調(diào)味品 時間: 2025-3-24 01:01 作者: HUSH 時間: 2025-3-24 05:59
Gradient Echo Versus Spin Echotion pulse that is normally 90°, so at each excitation pulse all of the . magnetization is transferred into the transverse plane. This combined with the refocusing pulse gives the largest possible signal provided the magnetization is allowed to recover sufficiently between repetitions.作者: Fibrillation 時間: 2025-3-24 09:12 作者: 門閂 時間: 2025-3-24 14:35
Making an Image: Locating and Encoding Signals in Space and measured in the presence of magnetic field gradients therefore contain spatial information that can be used to build up an image. The sections that follow describe the most commonly used method to build up a cross-sectional image (or image slice) using rf pulses and gradient magnetic fields.作者: prostatitis 時間: 2025-3-24 18:38
https://doi.org/10.1007/978-3-540-70609-0chosen direction and is measured in units of milliTesla per meter (mT/m). A radiofrequency (RF) magnetic field that oscillates at a characteristic frequency in the MegaHertz range, the exact value of which is determined by the nominal field strength of the main magnet. This is given the symbol B..作者: Pepsin 時間: 2025-3-24 20:32 作者: 按時間順序 時間: 2025-3-25 00:53
https://doi.org/10.1007/978-3-642-30696-9, this results in a signal void, also known as a “.” or “. appearance. This effect is also known as the ., referring to the “washout” of proton spins form the image slice that would otherwise be refocused and contribute to the spin echo signal.作者: homocysteine 時間: 2025-3-25 06:32 作者: orient 時間: 2025-3-25 08:07
What’s Inside the Magnet and Why?chosen direction and is measured in units of milliTesla per meter (mT/m). A radiofrequency (RF) magnetic field that oscillates at a characteristic frequency in the MegaHertz range, the exact value of which is determined by the nominal field strength of the main magnet. This is given the symbol B..作者: Harrowing 時間: 2025-3-25 15:31
Pulse Sequences and Image Contrasthe . The two main types of pulse sequences are . and spin . pulse sequences. The choice of pulse sequence and its imaging parameters, including the timing parameters. and ., determine the intrinsic strength of the MR signal from a particular tissue according to its proton density value and relaxation properties.作者: 果仁 時間: 2025-3-25 18:08
Black Blood Versus Bright Blood Imaging, this results in a signal void, also known as a “.” or “. appearance. This effect is also known as the ., referring to the “washout” of proton spins form the image slice that would otherwise be refocused and contribute to the spin echo signal.作者: Eosinophils 時間: 2025-3-25 21:03 作者: Hemiplegia 時間: 2025-3-26 01:14 作者: capillaries 時間: 2025-3-26 07:24 作者: narcotic 時間: 2025-3-26 10:06 作者: 2否定 時間: 2025-3-26 13:44
Protons and Spins: The Origin of the MRI Signalcontained within . and . (Fig.3.1). Hydrogen is one of a number of elements whose nuclei exhibit magnetic resonance properties, but the high intrinsic sensitivity and natural abundance in the form of water and lipid molecules makes it particularly favorable for imaging. Other nuclei of potential int作者: 新字 時間: 2025-3-26 20:05 作者: 民間傳說 時間: 2025-3-27 00:49 作者: 上下倒置 時間: 2025-3-27 02:55
Image Space and k-Spacepoints in the signal and those in the image. A single data point in an MR signal contributes a particular attribute to the whole image. Conversely, a single pixel in the image may have contributions from all of the MR signals collected. Just as each pixel occupies a unique location in image space, e作者: FAWN 時間: 2025-3-27 08:35
Imaging Parameters and Image Attributesthickness of the selected 2D image slice, also determine the voxel dimensions and hence the . (Fig.8.1). The voxel volume determines the number of protons that contribute to each pixel location. This strongly influences the size of the signal and is consequently a major determinant of ..作者: Systemic 時間: 2025-3-27 10:38
Improving SNR with Surface Coils and Array Coils smaller region of interest, it is much more appropriate to use a smaller, more tailored, . (Fig. 9.1b). This has two advantages: 1. It is closer to the origin of the signal from the region of interest. 2. It detects less of the noise originating from outside of the region of interest.作者: Culmination 時間: 2025-3-27 14:48 作者: zonules 時間: 2025-3-27 18:57
Gradient Echo Versus Spin EchoGradient Echo and Spin Echo pulse sequences (Fig. 11.1). In the case of spin echo, a 180° refocusing pulse is applied at a time equal to half the echo time. This reverses the effect of the field inhomogeneities and the amplitude of the transverse magnetization at the echo times dependent on the pure作者: 變異 時間: 2025-3-28 00:29
Black Blood Versus Bright Blood Imagingo produce the spin echo signal (Fig. 12.1). Both of these pulses are slice-selective but are separated by a time equal to half the echo time. The transverse magnetization of blood flowing through the slice that moves out of the slice between the two pulses is not refocused by the 180° pulse and does作者: 敏捷 時間: 2025-3-28 04:01 作者: affluent 時間: 2025-3-28 07:29 作者: Evocative 時間: 2025-3-28 10:32
Common Artifacts encoding process: While the number of phase encoding steps used to complete the image acquisition is sufficient to uniquely encode all the locations within the field of view, locations outside the field of view are not uniquely encoded (Fig.17.1). At the edge of the field of view, the phase increme作者: Organization 時間: 2025-3-28 18:37
Springer-Verlag London Limited 2011作者: 刀鋒 時間: 2025-3-28 21:44
https://doi.org/10.1007/978-3-540-70609-0In order to generate a signal from the net magnetization that is detectable, the radiofrequency (rf) magnetic field described in Chap.1 is generated by the rf transmitter coil (the integral body coil) and used to deliver energy into the population of protons.作者: 進(jìn)取心 時間: 2025-3-29 02:15
https://doi.org/10.1007/978-3-642-30696-9Respiratory Compensation methods (.)作者: prosperity 時間: 2025-3-29 04:05
https://doi.org/10.1007/978-3-642-30696-9Conventional imaging techniques acquire only one phase encoding step (one line of k-space) per heart beat. It therefore invariably takes several minutes to acquire an anatomical image dataset with conventional spin echo (SE) or a cine image dataset with conventional gradient echo sequences (FLASH, SPGR, FFE).作者: 比目魚 時間: 2025-3-29 09:23 作者: fulcrum 時間: 2025-3-29 14:18
Dealing with Respiratory MotionRespiratory Compensation methods (.)作者: 責(zé)問 時間: 2025-3-29 17:45
Fast Imaging: How Do We Speed Up the Image Acquisition?Conventional imaging techniques acquire only one phase encoding step (one line of k-space) per heart beat. It therefore invariably takes several minutes to acquire an anatomical image dataset with conventional spin echo (SE) or a cine image dataset with conventional gradient echo sequences (FLASH, SPGR, FFE).作者: 熔巖 時間: 2025-3-29 20:29 作者: 形狀 時間: 2025-3-30 00:01 作者: 象形文字 時間: 2025-3-30 07:13 作者: Mitigate 時間: 2025-3-30 11:07 作者: Accede 時間: 2025-3-30 16:25 作者: Curmudgeon 時間: 2025-3-30 20:04
https://doi.org/10.1007/978-3-540-70609-0contained within . and . (Fig.3.1). Hydrogen is one of a number of elements whose nuclei exhibit magnetic resonance properties, but the high intrinsic sensitivity and natural abundance in the form of water and lipid molecules makes it particularly favorable for imaging. Other nuclei of potential int作者: Individual 時間: 2025-3-30 21:04
https://doi.org/10.1007/978-3-540-70609-0 there are two distinct relaxation processes that relate to the two components of the Net Magnetization, the longitudinal (.) and transverse (.) components. The first . process, commonly referred to as ., is responsible for the regrowth of the z component along the longitudinal (z) axis to its origi作者: N斯巴達(dá)人 時間: 2025-3-31 04:39
https://doi.org/10.1007/978-3-540-70609-0n is introduced by using the gradient coils described in to generate magnetic field gradients. When a gradient is applied in a particular direction, this causes the strength of the magnetic field and hence, the Larmor frequency to depend on position along that direction. MR echoes that are generated作者: cultivated 時間: 2025-3-31 07:09 作者: aquatic 時間: 2025-3-31 11:06 作者: Negligible 時間: 2025-3-31 15:42 作者: 寄生蟲 時間: 2025-3-31 21:02
https://doi.org/10.1007/978-3-642-30696-9tive to the background noise (SNR) depends on a number of . including the magnetic field strength, the choice of receiver coil and system electronics, as well as . including the field of view, image acquisition matrix size and slice thickness (defining the voxel volume), the number of signal samples作者: Encephalitis 時間: 2025-4-1 01:19
https://doi.org/10.1007/978-3-642-30696-9Gradient Echo and Spin Echo pulse sequences (Fig. 11.1). In the case of spin echo, a 180° refocusing pulse is applied at a time equal to half the echo time. This reverses the effect of the field inhomogeneities and the amplitude of the transverse magnetization at the echo times dependent on the pure作者: Benign 時間: 2025-4-1 04:51
https://doi.org/10.1007/978-3-642-30696-9o produce the spin echo signal (Fig. 12.1). Both of these pulses are slice-selective but are separated by a time equal to half the echo time. The transverse magnetization of blood flowing through the slice that moves out of the slice between the two pulses is not refocused by the 180° pulse and does作者: 忘川河 時間: 2025-4-1 06:42
https://doi.org/10.1007/978-3-642-30696-9quired in just a few tens of milliseconds. In Chap. 8 it was shown that the minimum possible image acquisition time is limited by the repetition time and the need to acquire a sufficient number of phase encoding steps to achieve a particular image matrix size and therefore spatial resolution. To ach
