Friday, December 31, 2010

What are radioisotopes?

Many of the chemical elements have a number of isotopes. The isotopes of an element have the same number of protons in their atoms (atomic number) but different masses due to different numbers of neutrons. In an atom in the neutral state, the number of external electrons also equals the atomic number. These electrons determine the chemistry of the atom. The atomic mass is the sum of the protons and neutrons. There are 82 stable elements and about 275 stable isotopes of these elements.

When a combination of neutrons and protons, which does not already exist in nature, is produced artificially, the atom will be unstable and is called a radioactive isotope or radioisotope. There are also a number of unstable natural isotopes arising from the decay of primordial uranium and thorium. Overall there are some 1800 radioisotopes.

At present there are up to 200 radioisotopes used on a regular basis, and most must be produced artificially.

Radioisotopes can be manufactured in several ways. The most common is by neutron activation in a nuclear reactor. This involves the capture of a neutron by the nucleus of an atom resulting in an excess of neutrons (neutron rich). Some radioisotopes are manufactured in a cyclotron in which protons are introduced to the nucleus resulting in a deficiency of neutrons (proton rich).

The nucleus of a radioisotope usually becomes stable by emitting an alpha and/or beta particle (or positron). These particles may be accompanied by the emission of energy in the form of electromagnetic radiation known as gamma rays. This process is known as radioactive decay.

Radioactive products which are used in medicine are referred to as radiopharmaceuticals.

Isotopes used in Medicine

Many radioisotopes are made in nuclear reactors, some in cyclotrons. Generally neutron-rich ones and those resulting from nuclear fission need to be made in reactors, neutron-depleted ones are made in cyclotrons. There are about 40 activation product radioisotopes and five fission product ones made in reactors.

Reactor Radioisotopes (half-life indicated)

Bismuth-213 (46 min): Used for targeted alpha therapy (TAT), especially cancers, as it has a high energy (8.4 MeV).

Chromium-51 (28 d): Used to label red blood cells and quantify gastro-intestinal protein loss.

Cobalt-60 (5.27 yr): Formerly used for external beam radiotherapy, now used more for sterilising

Dysprosium-165 (2 h): Used as an aggregated hydroxide for synovectomy treatment of arthritis.

Erbium-169 (9.4 d): Use for relieving arthritis pain in synovial joints.

Holmium-166 (26 h): Being developed for diagnosis and treatment of liver tumours.

Iodine-125 (60 d): Used in cancer brachytherapy (prostate and brain), also diagnostically to evaluate the filtration rate of kidneys and to diagnose deep vein thrombosis in the leg. It is also widely used in radioimmuno-assays to show the presence of hormones in tiny quantities.

Iodine-131 (8 d)*: Widely used in treating thyroid cancer and in imaging the thyroid; also in diagnosis of abnormal liver function, renal (kidney) blood flow and urinary tract obstruction. A strong gamma emitter, but used for beta therapy.

Iridium-192 (74 d): Supplied in wire form for use as an internal radiotherapy source for cancer treatment (used then removed).

Iron-59 (46 d): Used in studies of iron metabolism in the spleen.

Lutetium-177 (6.7 d): Lu-177 is increasingly important as it emits just enough gamma for imaging while the beta radiation does the therapy on small (eg endocrine) tumours. Its half-life is long enough to allow sophisticated preparation for use. It is usually produced by neutron activation of natural or enriched lutetium-176 targets.

Molybdenum-99 (66 h)*: Used as the 'parent' in a generator to produce technetium-99m.

Palladium-103 (17 d): Used to make brachytherapy permanent implant seeds for early stage prostate cancer.

Phosphorus-32 (14 d): Used in the treatment of polycythemia vera (excess red blood cells). Beta emitter.

Potassium-42 (12 h): Used for the determination of exchangeable potassium in coronary blood flow.

Rhenium-186 (3.8 d): Used for pain relief in bone cancer. Beta emitter with weak gamma for imaging.

Rhenium-188 (17 h): Used to beta irradiate coronary arteries from an angioplasty balloon.

Samarium-153 (47 h): Sm-153 is very effective in relieving the pain of secondary cancers lodged in the bone, sold as Quadramet. Also very effective for prostate and breast cancer. Beta emitter.

Selenium-75 (120 d): Used in the form of seleno-methionine to study the production of digestive enzymes.

Sodium-24 (15 h): For studies of electrolytes within the body.

Strontium-89 (50 d)*: Very effective in reducing the pain of prostate and bone cancer. Beta emitter.

Technetium-99m (6 h): Used in to image the skeleton and heart muscle in particular, but also for brain, thyroid, lungs (perfusion and ventilation), liver, spleen, kidney (structure and filtration rate), gall bladder, bone marrow, salivary and lacrimal glands, heart blood pool, infection and numerous specialised medical studies. Produced from Mo-99 in a generator.

Xenon-133 (5 d)*: Used for pulmonary (lung) ventilation studies.

Ytterbium-169 (32 d): Used for cerebrospinal fluid studies in the brain.

Ytterbium-177 (1.9 h): Progenitor of Lu-177.

Yttrium-90 (64 h)*: Used for cancer brachytherapy and as silicate colloid for the relieving the pain of arthritis in larger synovial joints. Pure beta emitter and of growing significance in therapy.

Radioisotopes of caesium, gold and ruthenium are also used in brachytherapy.

Cyclotron Radioisotopes

Carbon-11, Nitrogen-13, Oxygen-15, Fluorine-18: These are positron emitters used in PET for studying brain physiology and pathology, in particular for localising epileptic focus, and in dementia, psychiatry and neuropharmacology studies. They also have a significant role in cardiology. F-18 in FDG (fluorodeoxyglucose) has become very important in detection of cancers and the monitoring of progress in their treatment, using PET.

Cobalt-57 (272 d): Used as a marker to estimate organ size and for in-vitro diagnostic kits.

Copper-64 (13 h): Used to study genetic diseases affecting copper metabolism, such as Wilson's and Menke's diseases, and for PET imaging of tumours, and therapy.

Copper-67 (2.6 d): Beta emitter, used in therapy.

Fluorine-18 as FLT (fluorothymidine), F-miso (fluoromisonidazole), 18F-choline: tracer.

Gallium-67 (78 h): Used for tumour imaging and localisation of inflammatory lesions (infections).

Gallium-68 (68 min): Positron emitter used in PET and PET-CT units. Derived from germanium-68 in a generator.

Germanium-68 (271 d): Used as the 'parent' in a generator to produce Ga-68.

Indium-111 (2.8 d): Used for specialist diagnostic studies, eg brain studies, infection and colon transit studies.

Iodine-123 (13 h): Increasingly used for diagnosis of thyroid function, it is a gamma emitter without the beta radiation of I-131.

Iodine-124: tracer.

Krypton-81m (13 sec) from Rubidium-81 (4.6 h): Kr-81m gas can yield functional images of pulmonary ventilation, e.g. in asthmatic patients, and for the early diagnosis of lung diseases and function.

Rubidium-82 (1.26 min): Convenient PET agent in myocardial perfusion imaging.

Strontium-82 (25 d): Used as the 'parent' in a generator to produce Rb-82.

Thallium-201 (73 h): Used for diagnosis of coronary artery disease other heart conditions such as heart muscle death and for location of low-grade ly


You can't see them but they're everywhere. There are 60 billion in front of your nose this second. You can't smell them. You can't taste them when they touch your tongue. You can't hear them. You can't feel them when they pass through you. 10,000,000,000,000,000 will do it while you read this page and you will never know. They are neutrinos, the ``little neutral ones'' in the family of subatomic particles. Neutrinos hold secrets from the earliest days of the universe. They bring us information from deep inside exploding stars and from high energy particle collisions. Their presence may signal unexpected phenomena. Measuring their properties will help us understand how the universe will evolve.

We need large detectors to detect neutrinos, because neutrinos don't interact with matter very often. Most subatomic particles are very interactive. For example, quarks, which make up most of ordinary matter, are so active in our detectors that it is difficult to sort out the patterns that they leave. The electron is another highly evident particle -- and reliable, too. You can count on finding electrons inside your typical wall outlet and also inside your typical particle interaction. But the neutrino is different from the rest. Their interactions occur far more rarely. At the highest energy accelerator in the world, Fermilab, it is oobserved that neutrino reactions 10,000,000,000 times less often than those of quarks. They just quietly zip through the detector and go on their merry way.

Neutrino research is fascinating today because the results are full of contradictions. For fifty years, all of the evidence pointed to neutrinos being bundles of moving energy that had no mass -- a pretty weird concept for a particle. But recently we discovered a novel behavior which can only be explained if neutrinos do have mass. How do resolve this conflict?

If the neutrino has mass, it must be very, very small. It would take at least half a million neutrinos to tip the scales on the electron. Still, such a wispy particle will have a big effect in the universe. The collective mass of the neutrinos rivals the mass of all the stars! Given the discovery of mass, we can begin asking even more exciting questions. The Big Bang, for example, produced a million neutrinos in every gallon of space. The holy grail of neutrino physics is to detect these relics. Their mass may hold the key.

All of that sounds pretty esoteric, and you may ask: ``What have neutrinos done for me lately?'' Actually, they matter a lot to you. They are part of the ignition process of the sun. They play a role in heating the center of the earth, causing continental drift. So the next time you see a koala, whose evolution depended on living on an isolated continent, thank a neutrino! The tools that physicists use to create and study neutrinos have direct benefit to every one of us. One fork of the beam line for the neutrino experiment at the Fermilab goes to Neutron Therapy, a very successful cancer treatment method. The extremely clean laboratory environment of state-of-the-art solar neutrino experiments can be used for sensitive tests to monitor violations of the nuclear test ban treaty.

Saturday, December 11, 2010

Galileo Galilei

Basic Information:


Nationality: Italian

Religion: Roman Catholic 

Born: February 15, 1564

Death: January 8, 1642


Education and Academic Positions:


Born in Pisa to Vincenzo Galilei, a famous lutenist and musical theorist, Galileo was a devout Catholic who seriously considered pursuing a career in the priesthood. Instead, at his father's urging, he enrolled at the University of Pisa to study medicine, but switched to mathematics. He was appointed the chair of mathematics in 1589. In 1592 he moved to the University of Padua, teaching in the fields of mathematics, geometry, and astronomy until 1610.


Galileo - the Father of Science:


Among other things, Galileo has been called: The father of science (by Albert Einstein), The father of modern physics, The father of modern astronomy, The father of observational science


Stephen Hawking (among others) have observed that Galileo probably contributed more to the creation of the modern natural sciences, and the scientific method, than any other single figure in history.


Specifically, Galileo focused on observation and experimentation, rather than creating abstract theories that were not tested. He also was one of the first scientists to provide mathematical descriptions of the laws of physics.




Some of Galileo's most significant work was in the field of kinematics, identifying that the total distance covered is proportional to the square of the time. He also identified the parabola as the ideal trajectory for uniformly accelerated motion in a plane.


Galileo also studied the motion of a pendulum, realizing that a pendulum swing is constant regardless of amplitude (at least to small angle approximations).


He proposed a principle of inertia, which became the foundation of Newton's First Law of Motion. Though this concept had been put forth by others, Galileo was the first to formalize it mathematically.


Astronomy, the Telescope, & the Heliocentric Universe:


In 1608, the telescope was invented in the Netherlands. Over the next year, Galileo had heard about it and crafted his own improvements. With the improved telescope, he was able to observe the heavens more closely than ever before and identified three of Jupiter's moons. This, along with observing the phases of Venus, provided support for the Copernican heliocentric model of the universe over Ptolemy's geocentric model.


In addition, he made many other significant observations. He was the first to observe sunspots, the rings of Saturn (though he didn't know what to make of him), and lunar mountains and craters.


Galileo's First Controversy:


Galileo's support of a heliocentric theory was seen by the Roman Catholic Church as contradicting various scriptural passages.


In 1616, Galileo first defended himself against the Church. Galileo was ordered not to "hold or defend" the idea that the Earth moved and the Sun remained stationary at the center. For several years, Galileo was able to discuss heliocentric theory hypothetically without arousing undue ire from the Church.


Galileo's Trial:


In 1632, Galileo published Dialogue Concerning the Two Chief World Systems with the permission of Pope Urban VII, who had supported Galileo in the earlier conflict (as Cardinal Barberini).


Urban had two conditions:


Galileo was to include arguments for both heliocentric and geocentric viewpoints Urban's own views on the matter were to be included. Unfortunately, the book turned out to be biased in favor of heliocentrism and the Pope did not appreciate the perceived public ridicule. Galileo was ordered to stand trial for suspicion of heresy in 1633.


Galileo's Imprisonment:


The 1633 hearing did not go as well as the one in 1616, and Galileo was found guilty of heresy. His sentence had three parts: He was required to recant his heliocentric views. He was imprisoned (though this later got commuted to house arrest at his estate near Florence). His Dialogue was banned, and all other works written by him (or to be written by him) were forbidden, though this latter part was not enforced. While under house arrest, Galileo wrote Two New Sciences, which outlined his earlier work in kinematics and the strength of materials. This book was praised by both Sir Isaac Newton and Albert Einstein.


Galileo's Death & Redemption:


Galileo died of natural causes in 1642, after having gone blind. He was reburied at Santa Croce, sacred ground, in 1737. In 1741, Pope Benedict XIV authorized publication of Galileo's complete works. Heliocentrism was formally rescended as heresy in 1758. It was not until October 31, 1992, that the Church under Pope John Paul II expressed regret over how Galileo had been treated, in response to a Pontifical Council for Culture study.


Galileo Galilei is one of the most influential and famous scientists in human history, having contributed to a wide range of fields and establishing the mathematical and experimental foundations of modern physics and astronomy.


Some questions and answers

What is Physics?


Physics is the scientific study of matter and energy and how they interact with each other. This energy can take the form of motion, light, electricity, radiation, gravity . . . just about anything, honestly.


Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even entire galaxies.


What is Quantum Physics?


Quantum physics is the study of the behavior of matter and energy at the molecular, atomic, nuclear, and even smaller microscopic levels. In the early 20th century, it was discovered that the laws that govern macroscopic objects do not function the same in such small realms.


What Does Quantum Mean?


"Quantum" comes from the Latin meaning "how much." It refers to the discrete units of matter and energy that are predicted by and observed in quantum physics. Even space and time, which appear to be extremely continuous, have smallest possible values.


Who Developed Quantum Mechanics?


As scientists gained the technology to measure with greater precision, strange phenomena was observed. The birth of quantum physics is attributed to Max Planck's 1900 paper on blackbody radiation. Development of the field was done by Max Planck, Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schroedinger, and many others. Ironically, Albert Einstein had serious theoretical issues with quantum mechanics and tried for many years to disprove or modify it.


What's Special About Quantum Physics?


Light waves act like particles and particles act like waves (called wave particle duality). Matter can go from one spot to another without moving through the intervening space (called quantum tunnelling). Information moves instantly across vast distances. In fact, in quantum mechanics we discover that the entire universe is actually a series of probabilities. Fortunately, it breaks down when dealing with large objects, as demonstrated by the Schroedinger's Cat thought experiment.



List of various branches of physics

The different disciplines of physics are listed below. The list will be updated with new additions and definitions as appropriate.


  1. Acoustics - the study of sound & sound waves


  1. Astronomy - the study of space


  1. Astrophysics - the study of the physical properties of objects in space


  1. Atomic Physics - the study of atoms, specifically the electron properties of the atom


  1. Biophysics - the study of physics in living systems


  1. Chaos - the study of systems with strong sensitivity to initial conditions, so a slight change at the beginning quickly become major changes in the system


  1. Chemical Physics - the study of physics in chemical systems


  1. Computational Physics - the application of numerical methods to solve physical problems for which a quantitative theory already exists


  1. Cosmology - the study of the universe as a whole, including its origins and evolution


  1. Cryophysics / Cryogenics / Low Temperature Physics - the study of physical properties in low temperature situations, far below the freezing point of water


  1. Crystallography - the study of crystals and crystalline structures


  1. Electromagnetism - the study of electrical and magnetic fields, which are two aspects of the same phenomenon


  1. Electronics - the study of the flow of electrons, generally in a circuit


  1. Fluid Dynamics / Fluid Mechanics - the study of the physical properties of "fluids," specifically defined in this case to be liquids and gases


  1. Geophysics - the study of the physical properties of the Earth


  1. High Energy Physics - the study of physics in extremely high energy systems, generally within particle physics


  1. High Pressure Physics - the study of physics in extremely high pressure systems, generally related to fluid dynamics


  1. Laser Physics - the study of the physical properties of lasers


  1. Mathematical Physics - applying mathematically rigorous methods to solving problems within physics


  1. Mechanics - the study of the motion of bodies in a frame of reference


  1. Meteorology / Weather Physics - the physics of the weather


  1. Molecular Physics - the study of physical properties of molecules


  1. Nanotechnology - the science of building circuits and machines from single molecules and atoms


  1. Nuclear Physics - the study of the physical properties of the atomic nucleus


  1. Optics / Light Physics - the study of the physical properties of light


  1. Particle Physics - the study of fundamental particles and the forces of their interaction


  1. Plasma Physics - the study of matter in the plasma phase


  1. Quantum Electrodynamics - the study of how electrons and photons interact at the quantum mechanical level


  1. Quantum Mechanics / Quantum Physics - the study of science where the smallest discrete values, or quanta, of matter and energy become relevant


  1. Quantum Optics - the application of quantum physics to light


  1. Quantum Field Theory - the application of quantum physics to fields, including the fundamental forces of the universe


  1. Quantum Gravity - the application of quantum physics to gravity and unification of gravity with the other fundamental particle interactions


  1. Relativity - the study of systems displaying the properties of Einstein's theory of relativity, which generally involves moving at speeds very close to the speed of light


  1. Statistical Mechanics - the study of large systems by statistically expanding the knowledge of smaller systems


  1. String Theory / Superstring Theory - the study of the theory that all fundamental particles are vibrations of one-dimensional strings of energy, in a higher-dimensional universe


  1. Thermodynamics - the physics of heat