Read the quick review below and download the PDF by using links given at the end of the post. We have uploaded these PDF and EPUB files to our online file repository so that you can enjoy a safe and blazing-fast downloading experience. Handbook of MRI Technique continues to be the ideal support both for radiographers new to MRI and for regular users looking for information on alternative techniques and suggestions on protocol modifications.
Fourth edition has been fully revised and updated to incorporate new technologies and developments essential to good practice. Written specifically for technologists and highly illustrated, it guides the uninitiated through scanning techniques and helps more experienced technologists to improve image quality. The first part of the book considers the main aspects of theory that relate to scanning and also includes practical tips on gating, equipment use, patient care and safety, and information on contrast media.
The second half provides step-by-step instruction for examining each anatomical area, beginning with a basic anatomy section followed by sections on indications, patient positioning, equipment, artefacts and tips on optimizing image quality. Catherine has been involved in MRI education for nearly 25 years.
Score: 5. This text is essential reading on undergraduate and postgraduate MRI courses. The book explains in clear terms the theory that underpins magnetic resonance so that the capabilities and operation of MRI systems can be fully appreciated and maximised.
This fourth edition captures recent advances, and coverage includes: parallel imaging techniques and new sequences such as balanced gradient echo. Building on the success of the first three editions, the fourth edition has been fully revised and updated. The book now comes with a companion website at www.
The website also hosts over interactive self-assessment exercises to help the reader test their understanding. The MRI Study Guide for Technologists offers comprehensive review questions covering the basic areas, principles, equipment, and terminology to help provide readers with the highest level of preparation for the Registry Exam.
Contains over multiple choice and fill-in questions. Includes a bibliography of highly recommended books for further reading. Yet if you're like many psychiatrists, you're sometimes uncertain about which studies to use in specific situations. Until now, you've had to sort through the only information available -- technical reviews in the literature -- for guidance. But no more. Essentials of Neuroimaging for Clinical Practice is an all-in-one resource that explains how to use these powerful techniques to improve outcomes.
It demystifies neuroimaging with clear, concise, and practical advice on using today's most advanced applications in the diagnostic workup of patients. The can exchange energy with the term radio wave is used to de- protons. You may not notice of the waves which you receive it, because there is no exchange in your radio. How- wave of long duration, but a ever, if someone were to pound short burst of some electro- you in the stomach, exchange magnetic wave, which is called energy with you, your alignment a radio frequency RF pulse.
And this The purpose of this RF pulse is may explain why we need a Fig. In effect the mag- with you as you are hungry, netization along the z-axis decreases, as the protons which point down the sandwiches would give you "neutralize" the same number of pro- new energy.
This energy trans- tons pointing up. The term resonance can be What happens with What speed, or illustrated by the use of tuning better, what forks.
Imagine that you are in the protons, when frequency did the a room with different kinds of they are exposed to tuning forks, tuned e. Somebody enters this RF-pulse? From all the and go from a lower to a higher lated by the Larmor equation tuning forks in the room, all of energy level. Some, which were see page So the Larmor a sudden the other "a" forks, walking on their feet, start walk- equation gives us the necessary and only those, pick up energy, ing on their hands.
And this has frequency of the RF pulse start to vibrate and to emit some effect on the patients to send in. Only when the RF sound, they show a phenomenon magnetization, as you can see in pulse and the protons have the called resonance. Let us assume that same frequency, can protons from the net sum of 6 protons pick up some energy from the pointing up, after the RF pulse radio wave, a phenomenon is sent in 2 point down.
The called resonance this is where result is that these 2 protons the "resonance" in magnetic cancel out the magnetic forces resonance comes from. But something else happens. Due to the RF pulse, the This is why it is called trans- Just look at fig. They now point in precessing protons in synch the same direction at the same and this has another important time, and thus their magnetic effect. The former results in ship then is in a normal posi- decreasing the magnetization along the tion.
Then have all passengers z-axis, the so-called longitudinal magnetization. The latter establishes a walk in equal step around the new magnetization in the x-y-plane railing; what happens?
So the RF pulse causes a trans- versal magnetization. This newly established magnetic vector naturally does not stand still, but moves in line with the precessing protons, and thus with the precession frequency, fig. Their A magnetic field in the patient, vectors now also add up in a longitudinal to the external direction transverse to the ex- field results fig. Sending In summary: the RF pulse causes in an RF pulse causes a new transversal longitudinal magnetization to magnetization while longitudinal magneti- decrease, and establishes ation decreases b.
Depending on the RF pulse, longitudinal magnetization may a new transversal magnetization even totally disappear c. Let us have a look charge of the proton, the wards the antenna, goes away electrical current, induces the from it, comes towards it again at that newly proton's magnetic field.
The re- sulting MR signal therefore versal magnetization around: a moving magnetic field also has the precession causes an electrical current, vector e. How can we know that? This The trick is really quite simple: And this is important: the can also induce an electrical we do not put the patient into magnetic vector, by constantly current in an antenna, which is a magnetic field which has the moving, constantly changing, the MRI signal.
As the transversal magnetic vec- section of the patient, which We talked about the opposite tor moves around with the we want to examine. Instead we already: the moving electrical precessing protons, it comes to- take a magnetic field, which has a different strength at each point of the patients cross sec- tion.
What does this do? We heard that the precession frequency of a proton depends on the strength of the magnetic field as the frequency of a violin string depends on the strength with which you pull it. If this strength is different from point to point in the patient, then protons in different places Fig. Thus for an external observer, transversal magnetization constantly changes its direction, and can induce a signal in an antenna.
And as they precess zation starts to disappear with different frequencies, about the MR signal a process called transversal the resulting MR signal from relaxation , and the longitudinal different locations also has If our protons rotated around magnetization grows back to a different frequency.
And by in synch, in phase, and nothing its original size a process the frequency we can assign would change, then we would called longitudinal relaxation. This, however, is not It is like with your TV: when you what happens. As soon as the The reason why the longitudinal are in the kitchen where you RF pulse is switched off, the magnetization grows back to probably do not have a TV and whole system, which was dis- its normal size is easier to ex- hear a sound from your favourite turbed by the RF pulse, goes plain, so let us start with that TV show, you know where the back to its original quiet, peace- see fig.
It comes ful state, it relaxes. The newly No proton walks on its hands from that spot in your apart- longer than it has to - sort of a ment where the TV stands. The protons that What you subconsciously do, were lifted to a higher energy is connect a certain sound to level by the RF pulse go back a certain location in space. This is illustrated "one-by-one". Note that for simplicity This is illustrated in fig. And this is why the protons were not depicted as being a group of protons.
For the this process is not only called in phase; this subject is covered in more sake of simplicity the protons longitudinal relaxation, but detail in fig. Why and how they stop pre- cessing in phase will be ex- plained a little later.
By going back on their feet, pointing upwards again, these protons no longer cancel out the magnetic vectors of the same number of protons point- ing up, as they did before. So, the magnetization in this direction, the longitudinal magnetization increases, and finally goes back to its original value fig.
If you plot the time vs. This curve is also Fig. If one plots the longitudinal magnetization vs. The time that it takes for the The " 1 " looks very much like Enough of the longitudinal magnetization to re- the , reminding you also that cover, to go back to its original it describes the spin-"l"attice longitudinal value, is described by the relaxation.
But there are more magnetization - longitudinal relaxation time, hidden hints to this: the "1" what happens with also called T1. This actually is also looks like a match. And this not the exact time it takes, match should remind you of the transversal but a time constant, describing something, which we also have magnetization?
The time off, the protons get out of step, gives you an idea of how long thermal energy, which the pro- tons emit to the surrounding out of phase again, as nobody the race may take, but not the is telling them to stay in step. Or more scientifi- lattice while returning to their lower state of energy. For the sake of simplicity this cally, T1 is a time constant com- has been illustrated for a group parable to the time constants of protons which all "point up" that for example describe radio- in fig.
We heard earlier that protons That T1 is the longitudinal precess with a frequency which relaxation time can easily be is determined by the magnetic remembered by looking at your typewriter: fig. So after the RF pulse is switch- will have made So in this field. Due to Fig. These proton has a precession fre- which is illustrated in the lower part quency of Fanning out, they point less ations are somehow charac- more. In 5 microseconds and less in the same direction, and thus teristic for a tissue.
Similar to what we did for the us of the underlying mechanism, longitudinal magnetization, a spin-spin interaction. What we the T1- and which the T2-curve? Just put both curves together, This curve is going downhill, as and you can see something like transversal magnetization dis- a mountain with a ski slope. And as you You first have to go uphill probably expect: there is also T1-curve , before you jump a time constant, describing how down T2-curve fig.
This time constant is the transversal relaxation time T2. How to remember what "T2" is? The resulting curve in figure 21 thus is Fig. Another term vs. It takes longer to climb a mountain than to slide or jump down, which helps to remember that T1 is normally longer than T2. Or in absolute that resembles the wobbling in phase.
Thus, of the external magnetic field increases again; this longi- T1 and T2 were not defined as a relationship which is de- tudinal relaxation is described the times when relaxation is scribed by the Larmor by a time constant T1, the completed. Instead T1 was de- equation. This, however, see? You see somebody to drink it, so T2 also is long. Now look at fig. What about T2? When the lattice consists of WhatisT1 medium-size molecules most Why does fat have a short T1? As we have read, fluctuating magnetic fields near effective energy transfer.
T1-relaxation has something the Larmor frequency of the And why is T1 longer in stronger to do with the exchange of precessing protons, energy can thermal energy, which is handed magnetic fields? It is easy to imagine that in a the surroundings, the lattice. Thus these ly changes directions, that ample: see page 17 handing over sandwiches i. The lattice from one car proton to the other lattice is easy and this takes longer than handing also has its own magnetic fields.
With a dif- energy. Even though it may hand energy over to the lattice seem logical, this is the wrong to relax. This can be done ference in speeds, the energy transfer will be less efficient. As we heard in very effectively, when the fluc- the beginning, the precession tuations of the magnetic fields frequency depends on magnetic in the lattice occur with a fre- field strength, a relationship quency that is near the Larmor described by the Larmor frequency.
And when for the protons to get rid of they precess faster, they their energy, as the small water have more problems handing molecules move too rapidly. And down their energy to a lattice as the protons which are on with more slowly fluctuating the higher energy level cannot magnetic fields. With impure liquids, e.
The dif- protons get out of phase, which ations in the local magnetic ferences in the surroundings - as we already know - has fields. The larger molecules do the magnetic field variations two causes: inhomogeneities of not move around as fast, so influence you considerably. These larger differences ings move very fast , you do not tissues see page As water in local magnetic fields feel the single pot holes any- molecules move around very consequently cause larger more.
Before they have a major fast, their local magnetic fields differences in precession fre- effect on you, you are already fluctuate fast, and thus kind quencies, thus protons get back on the normal street level; of average each other out, so out of phase faster, T2 is thus their effect is averaged out, there are no big net differ- shorter.
When you drive What does all this have to do inside of a tissue, the protons slow which is equal to the with what we want to know? I hope that you walks on its hands. As we know, these are the ones that have a net magnetic effect because their effects are not cancelled out. What will happen? The longitudi- nal magnetization up to now resulting from two protons point- ing up will decrease, in our example to zero one pointing up is neutralized by one point- ing down.
But: as both protons are in phase, now there is a transversal magnetization which had not been there before. Naturally, other RF pulses magnetization has disappeared, and are also possible, and are named there is only transversal magnetization due to phase coherence. The magnetic accordingly, e. For the sake up, and one down, resulting in protons pointing up; we send of simplicity, let us look at what a net longitudinal magnetization in a RF pulse, which lifts up happens step by step, and first of "4" fig.
You should What happens, when the RF up, and two pointing down. In be able to answer this: the pulse is switched off? Protons also start to precess in phase b , which causes the new transversal magnetization. After the RF pulse is switched off c-e longitudinal magnetization increases, recovers, and transversal magnetization disappears, decays. Both processes are due to entirely different mechanisms, and occur independently even though at the same time. In fig. These a tissue in general, and thus magnetic vectors add up to a can be used instead of the two sum vector.
Our represent forces of a certain magnetic sum vector during size and a certain direction. And thus the sum vector will actually perform a spiraling motion fig.
In a - before the RF pulse - there is only longitudinal magnetization. With time this transversal magnetization decreases, while longi- tudinal magnetization increases c-d , until the starting point with no trans- versal but full longitudinal magnetization is reached again e.
This sum vector performs a spiraling motion f when it changes its direction from being in the transversal x-y plane no longitudinal magnetization to its final position along the z-axis no transversal magnetization. Instead of the terms Fig. The sum vector induces an electrical current in think of the antenna as a micro- tensity" at the axis of our T1, an antenna, the MR signal. This is of phone, and the sum magnetic and T2 curves. This will hope- greatest magnitude immediately after vector as having a bell at its tip.
The further the vector goes continue reading. The fre- quency of the sound, however, remains the same because the sum vector spins with the precessing frequency fig. This type of signal is called a FID signal, from free induction decay.
This type of signal is called a FID free induction decay signal. What if we do not wait so long Using these two pulses, we can What about another from pulse to pulse?
At this time, a long time apart after a long which is illustrated in figure When we wait for a sal magnetization after the sity in this experiment depends long time TRlong the longitudinal second pulse will be the same on the difference in longitudinal magnetization of both tissues will have for both tissues, as it was in magnetization, and this means totally recovered frame 5.
Using a shorter TR, also called spin density, in- pulses - you use a so-called there was a difference in signal fluences tissue contrast, can be pulse sequence. As you can use intensity between the tissues, explained quite simply; where different pulses, e. The resulting picture is be no signal; where there are between successive pulses can called a T1-weighted picture.
We will read different pulse sequences. As of signal intensity between more about this later. The point we saw in our experiment, the tissues in that picture, the is that by using certain pulse choice of a pulse sequence will tissue contrast, is mainly due sequences, we can make certain determine what kind of signal to their difference in T1. So it is However, there is always more more or less important in the necessary to carefully chose and than one parameter influencing resulting image.
The transversal magnetization of the How did TR influence the signal As you may imagine or know al- two tissues after the second RF pulse in our experiment? Thus, by changing the time between successive With a long TR we got similar weighted images, and so-called RF pulses, we can influence and modify signals from both tissues, both proton density -weighted magnetization and the signal intensity of tissues.
By choosing a pulse sequence, Fig. All instruments para- meters , however, always play some role in the final sound signal. At the once more for a receive a signal. The T1- curve described the relationship pretty much recovered. The magnetization appears. If we, however, send in the will have recovered totally. The sum magnetic vector goes back to its original longitudinal align- ment, the signal disappears. Why does the after a very long a T2-weighted transversal magnetization dis- time TR between image?
The protons lose phase coherence, as we have heard pulses not identical? And this is illustrated This is a little more difficult to understand. Let us perform in figure 33 for three protons, We have heard the explanation which are almost exactly in another experiment, which is already.
The signal intensity phase in a but increasingly a little different from the ones depends on many parameters. The longitudinal mag- does not influence the tissue b and c. The loss of phase netization is tilted, we get a contrast any more, however, coherence results in decreasing transversal magnetization. Now we have read about T1- and proton density-weighted images.
The result is that the faster precessing protons are now be- hind the slower ones. At that time the protons are nearly in phase again, which results in a stronger trans- versal magnetization, and thus in a stronger signal again.
A little later however, the faster precessing protons will be ahead again, with the signal decreasing again. This is why bit is ahead of the turtle. Thus it is possible to run with constant speed. We naturally obtain more than one signal, more than one spin echo. A curve connecting the spin echo and another and another. If we did If we now plot time vs. A curve describing the signal intensity in that in fig.
These time. In our example with the buses constant manner, and these are Or the difference in signal this would mean that we just the constant inhomogeneities intensities, the difference in record the signals as the buses of the external magnetic field. The signals vanish Inconstant inhomogeneities from ferences of inherent properties due to extrinsic bus speed local magnetic fields inside of the two groups internal and intrinsic exhaustion of the of the tissue cannot be "evened inhomogeneities ; may be in one passengers properties under out", as they may influence bus, there are only the "party these circumstances see fig.
So some of the the other crowd. It is im- May be we should illustrate this portant to realize that with a buses will be back at the start- by an example: imagine two spin echo sequence, we cannot ing line. The signal intensity, buses full of people, e. They and proton density - weighted phone then depends only on are standing at a starting line pictures. We will get to that a inherent properties, i.
With two micro- little later. Then the buses inhomogeneities, the protons leave in the same direction. Due to this they will be Without having the buses come back out of phase faster, the trans- i. To distinguish this erties the differing shape of the shorter transversal relaxation bus passengers , or due to external influences, i. First we sent have become smaller. However, this The intensity of this echo is transversal magnetization dis- given by the T2-curve at the time appears, due to T2-effects.
How TE. And as we can transversal magnetization faster. As both T2-curves and only little static noise. So it might be reasonable to away, you may not be able With a short TE, however, there wait a very long TE; the result- to discern the music from the will be a problem fig. And this Both T2-curves in this example heavily T2-weighted. If we But and there is always a there is always some noise in only wait a very short TE, the "but" if we wait longer, the the system, however, when the difference in signal intensity total signal intensity becomes signal is strong, this does not between tissue A and tissue B smaller and smaller.
The signal matter much. However, the is very small, both tissues may to noise ratio becomes smaller, smaller the signal, the harder hardly be distinguished as there the picture appears grainy. Consequence: with signal-to-noise problem: when a short TE, differences in T2 you receive a local radio station do not influence tissue contrast in.
To figure out how much signal the starting point from which Fig. So we just attach the T2- sequence by combining the T1-and the spin echo sequence, you actual- curve at this point. How much T2-curve for that tissue. There image, also depends on TE, the as it is "tilted" 90 degrees. This trans- we have the T1 and T2-curve of time that we wait after the versal magnetization immediately starts to disappear by a rate which is deter- a certain tissue.
So we now only have mined by the transversal relaxation time, Which parameter determined to look for the signal intensity and thus by the T2-curve.
The signal the amount of longitudinal at the time TE on the T2-curve.
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