To conclude this series on Diagnostic Imaging, we will learn more about the fascinating world of Magnetic Resonance Imaging and what the "proton dance" actually means.
We will review the history and evolution of MRI technology, and include a biography of one of the most brilliant minds in science. Within the100 years since its invention, this imaging modality has changed the world of medical diagnosis, helping millions of human beings around the world. |
“…If you want to find the secrets of the universe, think in terms of energy, frequency, and vibration…” Nikola Tesla |
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MRI is a study used in diagnostic medicine, which provides high quality images, is non-invasive and does not emit radiation. It combines classical physics and quantum physics. It began to be used as a name: Magnetic Resonance Imaging, instead of Nuclear Magnetic Resonance, since the word nuclear gained during history a bad connotation. It uses the generation of static magnetic fields, and the detection of radiofrequency fields that are re-emitted from the hydrogen atoms of the cells of the body being studied.
The images produced by magnetic resonance imaging are of enormous utility as a diagnostic tool. It detects and diagnoses a variety of conditions that can put the patient's health and life at risk, such as tumors, brain, heart, digestive and joint diseases. In general, it is used for diagnosis in soft tissues, unlike others that use radiation, which are preferably used in tissues of greater density.
Are you ready to see some concepts of classical and quantum physics? What is deep inside the "proton dance" of resonance?
Let's start from the assumption that the human body is made up of 60% water. Within this general proportion our brain is made up of 70% water, the blood of 80%, and the lungs of 90%.
Why is this important in MRI? The images obtained are the result of the signal re-emitted by the protons. And in the body the most abundant protons, which in turn occur in an odd number, are mostly hydrogen protons. These can be bound to an oxygen atom forming water, or to carbon atoms forming fat.
The electric charge that each proton has in itself confers it two types of movements:
Magnetic momentum or Spin: the spin that the proton performs on its own axis.
Precession momentum: the spin that the proton makes around the axis of the external magnetic field where we have placed it.
It also has its own magnetic field, i.e. it behaves like a magnet.
The energy released between its "precession dance" and its relaxation momentum is what will produce the images (in an extremely simplified concept).
When there is no external magnetic field, the protons are randomly positioned. With magnetization some protons will adopt an alignment in favor of the field (there will always be a predominance of these), and others against it.
Magnetic resonance phenomenon: this is obtained by applying an electromagnetic wave whose frequency coincides with the frequency of the "precession dance" of the atom we want to excite. That is to say: if we had two H atoms (inside a magnetic field), and with different molecular environments (one in water and the other in fat). They will be aligned in favor of the field, but their precession dance frequencies will be different. We could say that they will rotate at different speeds.
Taking into account the above mentioned: i.e. the protons are exposed to a magnetic field, and we emit a radio wave in which dances (precession) one of these two atoms.
Sucederá que va a absorber esta energía, y, a la exposición al campo magnético:debido
It will change its orientation.
In addition, all protons dancing at the same frequency, will leave their random position and start to rotate in unison as if they were "synchronized clocks". This is called protons in phase.
Relaxation:
At the end of the radiofrequency wave, the protons in the excited state are going to return to their original position releasing the absorbed energy also in the form of radio waves. The interesting thing is that this released wave will have different characteristics with respect to the one generated from the resonator. And the revealing thing about the images is that this wave will depend on the environment where the hydrogen atom is located. For example: imagine what would happen if we emitted a sound in a cave. Its echo will be different from that sound, and it will come back to us according to the characteristics of the cave: amplitude of the cave, adjacent structures, roughness, consistency of the walls, etc.
This relaxation occurs through two components: T1 depends on the interactions of the atoms with the environment, and T2 depends on the interaction of the atoms with each other (as they stop spinning in unison and return to spinning independently as they did before being excited). In addition to other factors, the intensity of the signal will depend on T1 and T2.
And what will the images look like according to this intensity in the signals emitted by the protons?
High intensity or hyperintense: white
Intermediate intensity: light gray
Low intensity or hypointense: dark gray.
Those that do not emit anything: black
Of course, the interpretation of these colors, images, energy exchange and re-emission times, among other parameters, are much more complex than mere color classification.
Contrast medium: Gadolinium
This substance is used to produce small magnetic fields that increase the intensity of the signal emitted by some tissues such as: pituitary, vessels, abnormal tissues such as tumors that damage the blood-brain or hematotisular barrier.
In summary: when our body enters a resonator, and is exposed to the magnetic field: the hydrogen atoms that we have in the different tissues (forming water or fat), dance, that is to say, they rotate on themselves and also aligned in unison. They receive the radiofrequency that is also emitted from the resonator, and when they stop dancing, when they relax, they resend those radiofrequency waves, with characteristics that are unique for each tissue, and that is what allows us to identify the different structures and their particularities.
Let's get to know the history of the players behind the “proton dance”.
Nikola Tesla
In a village in the Austro-Hungarian Empire, Nikola Tesla was born on July 10, 1856. His mother had a magnificent ability to build handmade tools, and could neither read nor write; and his father, a priest of the Serbian Orthodox Church, was the fourth of five children. At the age of 17 he was bed ridden by cholera for 9 months and was on the verge of death on several occasions. A year later he avoided conscription into the Austro-Hungarian army and enrolled in a polytechnic school in Austria. He pursued higher studies in engineering, leaving three years later to start working as an engineering assistant for a year. He then resumed his studies in Prague.
Upon the death of his father, he abandoned his studies again, and began working as a draughtsman in a telegraph station where he was assigned as Chief Electrician after some time. Here, he befriended another inventor: Nevojsa Petrovic. Together they worked on a project to produce continuous power based on the use of twin turbines. He also developed a telephone repeater or amplifier, although for some it was the first loudspeaker.
He started a new job in Paris, as a dynamo engineer at Continental Edison Company, (a subsidiary of Edison Electric Light Co). After a year, Tesla designed the induction motor.
He received an offer to work in the US, New Jersey, where he introduced major improvements in dynamo manufacturing for Edison, as well as providing the company with numerous lucrative patents. In the meantime, he was also engaged in improving the designs of his direct current generators for almost a year. Edison refused to pay him the $50,000, which he had promised and would not increase his salary to $25/week, so Tesla finally resigned (fittingly).
In addition to transmitting electromagnetic energy without wires by creating the radio transmitter, he designed the world's first hydroelectric power plant at Niagara Falls, receiving the Order of Danilo from King Nikola of Montenegro, and was recognized worldwide as a hero for alternating current. With the Tesla Tower or Wardencly he proved that it was possible to send energy and information without the need for a wire (1880 y 1890).
He lit dozens of light bulbs that he had buried (without a wire) by producing a potential difference between the ground and the ionization in the air, which generated the high voltage of the tower.
The polyphase power supply, among more than 700 patents, not counting those he left to Edison and company. He was awarded and recognized by Yale and Columbia Universities, Franklin Institute, U.S. Postal Service, National Electric Light Association, and some cities. Ironically, he also received the Edison Medal, awarded by the Institute of Electrical Engineers, one of the most important awards in electrical engineering in the US, and at the award ceremony, the vice president of the Institute said: "If we were to eliminate from our industrial world the achievements of Nikola Tesla, the wheels of industry would stop turning, our electric trains would stop, our cities would be dark and our windmills would die".
The New York Times reported on the Nobel Prize he would have won, but declined.
Nikola Tesla's record of patents and awards is enormous, and we will do a special chapter on him in History's Heroes Who Contributed to Medicine.
Going back to the early years of the 1880’s, Nikola Tesla devised the theory of dynamic gravity, which explains the relationship of gravity and the electromagnetic force. A unified field theory combining all the fundamental forces. So he carried out experiments with high frequency and high potential currents and electromagnetism, thus discovering the rotational gravitational field.
And so, in 1882, one of the most extraordinary minds of mankind discovered the Rotational Magnetic Field, which is generated from an alternating electric current, one of the most outstanding discoveries in physics.
Isidor Rabi
55 years later, Columbia University professor Isidor Rabi was the first to develop and demonstrate the phenomenon of nuclear magnetic resonance. That is, he realized that protons and neutrons in the nucleus act like small rotating magnets. And that, by passing a beam of molecules through a magnetic field and exposed to radio waves, that direction of rotation could be changed. And that the atoms returning to their original position emitted electromagnetic radiation of characteristically unique frequencies. This is just some of what the official website nobelprize.org mentions in his name, for his Nobel Prize in physics won in 1944. But who was Isidor Rabi?
He was born in 1988, in what was then Austria, into a Jewish family. At the age of one year, he and his family emigrated to the US, where they lived on meager means. He never practiced religion as an adult since he thought that, by doing good physics, he was walking the path of God. He finished at Cornell University his degree in Chemistry and then his PhD in Physics.
He traveled to Europe to work with the greats of quantum mechanics, from where he returned fascinated by the quantum ideas he worked with, especially the Stern-Gerlach experiment. In which it was observed that when a thin beam of silver atoms was passed through a magnetic field, this beam split in two and was slightly deflected according to the direction of its magnetic moments. Returning to the U.S., he became a professor at Columbia University, and after a couple of years set up a laboratory to determine the nuclear spin (the proton dance) associated with the magnetic moment, and together with Gregory Breit devised modifications to Stern Gerlach's apparatus to find the nuclear "dance" of sodium. He was one of the leading physicists in developing the atomic bomb during World War II, as well as in the development of radar.
And finally, he was able to detect the transition of protons from an excited state to a relaxed state, a method he called: Magnetic Resonance of the molecular beam. He also realized that the energy returned by the molecule was particular and unique to that molecule, so that substances could be identified, as well as receive certain information from them.
It was this discovery that earned him the merit for the Nobel Prize in 1944.
Felix Bloch and Edward Purcell
In 1946 Felix Bloch and Edward Purcell began studying the effect of magnetic resonance on atoms and molecules in solids and liquids. Purcell studied electrical engineering at Purdue University and physics at Harvard. He also worked at MIT to develop radar during World War II. Bloch, born in Zurich, left Europe when the Nazis took power in 1933 to work at Stanford. He worked during that conflict on atomic energy and radar.
The reason for the Nobel Prize they shared in 1952 was, and I quote: "For the development of new methods of precision nuclear magnetic measurement and related discoveries", "...making it possible to study the composition of different materials".
Raymond Damadian
In 1970, Raymond Damadian, a professor at the University of New York Downstate Medical Center, was the first person to perform an MRI on a human being. While scanning bacteria, he realized that it could be useful to study different tissues of the body. After a year he concluded that cancerous tissues, since they contained a greater amount of water, could be detected by scanners covering that area of the body, and thus differentiate them from healthy tissues. He applied for a patent as: Apparatus and method for detecting cancerous tissues, which was granted in the US, and was the first patent in magnetic resonance imaging.
Damadian y prototype in the image.
Paul Lauterbur
In 1973 the English researcher Paul Lauterbur, from the University of New York, was the one who developed the technique of resonance imaging in two and three dimensions, publishing in this year the first image with these characteristics.
Peter Mansfield
Peter Mansfield, an English physicist, developed a mathematical model that made it possible to capture images with better definition, and to accelerate the capture time from hours to minutes. And he was the first in history to take an MRI of just one part of the human body: the finger of the hand of one of his students.
For these achievements, Manfield and Lauterbur were awarded the 2003 Nobel Prize in Medicine.
In our modern era, several types of resonance scans are performed, for example:
"regular" resonances of different parts of the organism: joints, cerebral, abdominal, pelvic, etc. They are of 1.5 Tesla or 2.00 Tesla. This means that the patient is subjected to a magnetic field with a 1.5 T magnet, for example, which is equivalent to 15,000 times the earth's magnetic field. Also 3T MRI, which provides images with precise anatomical detail, is preferably used to diagnose and evaluate conditions of the central nervous system: dementias, Parkinson's disease, refractory epilepsy, brain tumors. When it comes to dementias, it evidences classic patterns of hypometabolism, allowing early diagnosis of Alzheimer's disease, and other types of dementias such as frontotemporal, vascular, and Levy body dementias. 3T MRI images are used for the development of Precision Personalized Medicine. In omic sciences, according to a report by the Roche Institute, in the Trends in Future Medicine observatory, and I quote: "Computational advances and the current extensive digital development make it possible to generate information through radiomics, thus contributing medical imaging to the development of Precision Personalized Medicine (PPM)".
MRI Elastography: it is used to detect and diagnose fatty liver and fibrosis with a fairly high precision, and the resonance is performed in conjunction with ultrasound.
Three-phase MRI: to evaluate the liver in three phases: arterial, venous and simple and late.
Magnetic Resonance Spectroscopy: This is a non-invasive technique that allows an analysis of metabolism in different types of tissues.
Functional MRI: This MRI is dependent on the level of oxygen in the brain. It is used to obtain images of blood flow changes in the brain that accompany an increase in neuronal activity. This MRI produces multiple images in a few seconds.
Studies are underway in which the way brain activity is scanned has been changed to obtain images on a millisecond scale, potentially at the speed of thought. After one scan, multiple high-resolution images are obtained, very quickly, allowing researchers to see the spread of signals in the brain in a noninvasive way. They think this will be an absolutely "game-changing" study possibility that could lead to a new way of understanding how this organ works.
A portable magnetic resonator is also being researched and developed, although it is very difficult due to the size and power of the magnet and the cooling equipment that are essential in this device, it has been achieved with only a little less resolution, and weighing much less 600kg vs. 14,000 kg or more of the conventional ones. For now it would be designed to be taken to mobile hospitals, or military stations that have certain infrastructure to be able to install it.
A Magnetic Resonance Imaging (MRI) scanner is being built at the NeuroSpin Center in Saclay, France, to scan the human brain. This scanner will take images with slices every 100 nanometers, with a power and resolution of 11.7 T to develop new biomarkers for psychiatric and neurological diseases, as well as brain chemistry, metabolism and energy. It will be about 5 meters in diameter, 132 tons in weight, and have a cumulative energy of 340 MJ. They mention that it has been a challenge to solve issues such as technical decisions, configuration, protection, magnet shielding, cryogenics and cooling, among others. And it was designed and built by Tesla Engineering Limited, UK.
Who regulates this activity and these devices?
Each country has a regulatory body, for example in the United States it is the Center for Medical Devices and Radiological Health (CDRH), in Argentina the National Magnetic Resonance System SNRM, and at the international level it is the International Commission on Non-Ionizing Radiation Protection ICNIRP.
The effects of exposure to magnetic fields and radiofrequency waves on the human organism are dealt with in Environmental Health Criteria 232, jointly with the International Labour Organization, the International Commission on Non-Ionizing Radiation Protection, and the World Health Organization.
Conclusion.
From Nikola Tesla and his rotational gravitational field in the late 1800s, the first resonances in gases, liquids, solids and bacteria, to the slow resonances lasting hours during the 1970s, to the development of brain resonance at the speed of thought; Or considering the current weight of over 13 tons, to those in research and development, which are portable resonators of less than 600 kg; It has been an amazing and enriching journey for physical and medical science. And without a doubt these 130 years have presented a rapid evolution in specificity, variety, duration, and resolution, among other characteristics to the present day. It has positively and significantly impacted the lives of millions of people in just a few decades around the world. It is able to diagnose severe and complex pathologies that would be difficult or impossible to detect by other means, without radiation or undesirable effects. And as we have seen, resonance is based on a large number of principles of quantum physics and classical physics, which I have only been able to outline in this text, and which were discovered and developed by extraordinarily brilliant minds.
About the author:
Maria Soledad Gomez has more than 10 years of industry experience working in a variety of roles within regulated industry, healthcare and medicine, including food/beverage, hospitals and veterinary medicine. Maria Sole writes technical articles on a wide variety of topics in the medical field.
About the translator / editor:
Brian Hoy has over 20 years of experience in the medical device industry and business formation, supporting the full lifecycle with global scope. Brian consults for industry and provides general advisory and off-hours support.
Publication ID: PUB0009EN
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