medical imaging.

1. Radioisopes

2. Wilhelm Conrad
Roentgen
(1845-1923)

3. On November 8, 1895, at the University
of Wurzburg….
Glowing fluorescent screen on a nearby
table.
fluorescence was caused by invisible rays
originating from the partially evacuated
glass Hittorf-Crookes tube he was using
to study cathode rays (i.e., electrons).

4. Surprisingly, these mysterious rays penetrated
the opaque black paper wrapped around the
tube. Roentgen had discovered X rays.
However, prior to his first formal correspondence
to the University Physical-Medical
Society, Roentgen spent two months thoroughly
investigating the properties of X rays.
Silvanus Thompson complained that Roentgen
left "little for others to do beyond elaborating his
work."

5. For his discovery, Roentgen
received the first Nobel Prize in
physics in 1901.

6. As a student in Holland, Roentgen was
expelled from the Utrecht Technical School
for a prank committed by another student.
Even after receiving a doctorate, his lack of
a diploma initially prevented him from
obtaining a position at the University of
Wurzburg.
He even was accused of having stolen the
discovery of X rays by those who failed to
observe them.

7. He rejected a title (i.e., von Roentgen) that would
have provided entry into the German nobility.
Donated the money he received from the Nobel
Prize to his University.
Roentgen did accept the honorary degree of
Doctor of Medicine offered to him by the medical
faculty of his own University of Wurzburg.
At the time of his death, Roentgen was nearly
bankrupt from the inflation that followed World
War I.

8. Antoine Henri
Becquerel
(1852-1908)

9. Henri Becquerel was born into a family of scientists. His
grandfather had made important contributions in the field
of electrochemistry while his father had investigated the
phenomena of fluorescence and phosphorescence.
Becquerel not only inherited their interest in science, he
also inherited the minerals and compounds studied by his
father.
And so, upon learning how Wilhelm Roentgen
discovered X rays from the fluorescence they
produced, Becquerel had a ready source of
fluorescent materials with which to pursue his
own investigations of these mysterious rays.

10. The material Becquerel chose to work with was
potassium uranyl sulfate, K2UO2(SO4)2, which he
exposed to sunlight and placed on photographic
plates wrapped in black paper.
When developed, the plates revealed an image of
the uranium crystals. Becquerel concluded "that
the phosphorescent substance in question emits
radiation which penetrates paper opaque to
light." Initially he believed that the sun's energy
was being absorbed by the uranium which then
emitted X rays.

11. Further investigation, on the 26th and 27th of
February, was delayed because the skies over
Paris were overcast and the uranium-covered
plates
Becquerel intended to expose to the sun were
returned to a drawer.

12. On the first of March, he developed the
photographic plates expecting only faint images
to appear. To his surprise, the images were clear
and strong.
This meant that the uranium emitted radiation
without an external source of energy such as the
sun.
Becquerel had discovered radioactivity, the
spontaneous emission of radiation by a
material.

13. For his discovery of radioactivity,
… Becquerel was awarded the 1903
Nobel Prize for physics.

14. Pierre Curie
(1859-1906)
Marie Curie
(1867-1934)

15. In 1880, he and his brother Jacques had
discovered piezoelectricity whereby physical
pressure applied to a crystal resulted in the
creation of an electric potential.
He also had made important investigations into
the phenomenon of magnetism including the
identification of a temperature, the curie
point, above which a material's magnetic
properties disappear.

16. After marriage with Curie…

17. Together, they began investigating the phenomenon of
radioactivity recently discovered in uranium ore.
Although the phenomenon was discovered by Henri
Becquerel, the term radioactivity was coined by Marie.
After chemical extraction of uranium from the
ore, Marie noted the residual material to be more
"active" than the pure uranium.
She concluded that the ore contained, in addition to
uranium, new elements that were also radioactive. This
led to their discoveries of the elements of polonium
and radium.

18. For their work on radioactivity, the Curies
were awarded the 1903 Nobel Prize in
physics.
Tragically, Pierre was killed three years later
in an accident while crossing a street in a
rainstorm.
Pierre's teaching position at the Sorbonne
was given to Marie. Never before had a
woman taught there in its 650 year history!

19. Her first lecture began with the very
sentence her husband had used to finish his
last.
In his honor, the 1910 Radiology Congress
chose the curie as the basic unit of
radioactivity: the quantity of radon in
equilibrium with one gram of radium
(current definition: 1 Ci = 3.7x1010 dps).

20. A year later, Marie was awarded the Nobel Prize
in chemistry for her discoveries of radium and
polonium, thus becoming the first person to
receive two Nobel Prizes.
For the remainder of her life she tirelessly
investigated and promoted the use if radium as a
treatment for cancer.
Marie Curie died July 4, 1934, overtaken by
pernicious anemia no doubt caused by years of
overwork and radiation exposure.

21. Ernest Rutherford
(1871-1937)

22. Father of nuclear physics.
Particles named and characterized by him
include the alpha particle, beta particle and
proton.
Even the neutron, discovered by James Chadwick, owes
its name to Rutherford. The exponential equation used
to calculate the decay of radioactive substances was
first employed for that purpose by Rutherford and he
was the first to elucidate the related concepts of the
half-life and decay constant.

23. Rutherford won the 1908 Nobel Prize in
chemistry.
In 1909, now at the University of
Manchester, Rutherford was bombarding a
thin gold foil with alpha particles when he
noticed that although almost all of them
went through the gold, one in eight
thousand would "bounce" (i.e., scatter)
back.

24. From this simple observation, Rutherford
concluded that the atom's mass must be
concentrated in a small positively-charged
nucleus while the electrons inhabit the farthest
reaches of the atom.
In 1919, Rutherford returned to Cambridge to become
director of the Cavendish laboratory where he had
previously done his graduate work under J.J.
Thomson.
It was here that he made his final major
achievement, the artificial alteration of nuclear
and atomic structure.

25. By bombarding nitrogen with alpha
particles, Rutherford demonstrated the
production of a different element, oxygen.
"Playing with marbles" is what he called; the
newspapers reported that Rutherford had "split
the atom."
After his death in 1937, Rutherford's remains
were buried in Westminster Abbey near those
of Sir Isaac Newton.

27. The radioisotopes have numerous
applications in
medicine, agriculture, industry
and pure research.

28. Many applications employ a special
technique known as “ tracer
technique”.
A small quantity of a radioisotope is
introduced into the substance to be
studied and its path is traced by
means of a Geiger-Muller (G. M.)
counter.

29. 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.

30. 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.

31. 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.

32. Radioisotopes in Medicine
NUCLEAR MEDICINE
This is a branch of medicine that uses radiation to
provide information about the functioning of a
person's specific organs or to treat disease. The
thyroid, bones, heart, liver and many other organs
can be easily imaged, and disorders in their
function revealed. In some cases radiation can be
used to treat diseased organs, or tumours.

33. Diagnostic techniques in nuclear medicine use
radioactive tracers which emit gamma rays from within
the body.
They can be given by injection, inhalation or orally.
The first type are where single photons are detected by
a gamma camera which can view organs from many
different angles.
The camera builds up an image from the points from
which radiation is emitted; this image is enhanced by a
computer and viewed by a physician on a monitor for
indications of abnormal conditions.

34. In a similar way, the passage of a particular
element in the body and the rate at which
it accumulates in different organs can be
studied.

35. A positron-emitting radionuclide is
introduced, usually by injection, and
accumulates in the target tissue. As it
decays it emits a positron, which promptly
combines with a nearby electron resulting
in the simultaneous emission of two
identifiable gamma rays in opposite
directions.
These are detected by a PET camera and
give very precise indication of their origin.

36. PET's most important clinical role is in
oncology, with fluorine-18 as the
tracer, since it has proven to be the most
accurate non-invasive method of detecting
and evaluating most cancers. It is also well
used in cardiac and brain imaging.

37. Positron emission tomography (PET) is nuclear
medicine imaging technique that produces a
three-dimensional image or picture of
functional processes in the body.
The system detects pairs of gamma rays emitted
indirectly by a positron-
emitting radionuclide (tracer), which is
introduced into the body on a biologically active
molecule.

38. Three-dimensional images of tracer
concentration within the body are then
constructed by computer analysis.
In modern scanners, three dimensional imaging
is often accomplished with the aid of a CT X-ray
scan performed on the patient during the same
session, in the same machine.

43. Gamma imaging by either method described provides a
view of the position and concentration of the
radioisotope within the body. Organ malfunction can be
indicated if the isotope is either partially taken up in
the organ (cold spot), or taken up in excess (hot spot). If
a series of images is taken over a period of time, an
unusual pattern or rate of isotope movement could
indicate malfunction in the organ.
A distinct advantage of nuclear imaging over x-ray
techniques is that both bone and soft tissue can be
imaged very successfully. This has led to its common
use in developed countries where the probability of
anyone having such a test is about one in two and
rising.

44. RADIOTHERAPY
Rapidly dividing cells are particularly sensitive to
damage by radiation. For this reason, some
cancerous growths can be controlled or
eliminated by irradiating the area containing the
growth.

45. External irradiation can be carried out using a
gamma beam from a radioactive cobalt-60
source, though in developed countries the much
more versatile linear accelerators are now being
utilised as a high-energy x-ray source (gamma
and x-rays are much the same).

46. Internal radiotherapy is by administering or planting a
small radiation source, usually a gamma or beta
emitter, in the target area.
Iodine-131 is commonly used to treat thyroid
cancer, probably the most successful kind of cancer
treatment. It is also used to treat non-malignant thyroid
disorders. Iridium-192 implants are used especially in the
head and breast.
They are produced in wire form and are introduced
through a catheter to the target area. After administering
the correct dose, the implant wire is removed to shielded
storage. This brachytherapy (short-range) procedure gives
less overall radiation to the body, is more localised to the

47. Targeted Alpha Therapy (TAT): especially for the control
of dispersed cancers.
The short range of very energetic alpha emissions in
tissue means that a large fraction of that radiative
energy goes into the targeted cancer cells, once a carrier
has taken the alpha-emitting radionuclide to exactly the
right place. Laboratory studies are encouraging and
clinical trials for leukaemia, cystic glioma and melanoma
are under way.

48. An experimental development of this is Boron
Neutron Capture Therapy using boron-10 which
concentrates in malignant brain tumours.
The patient is then irradiated with thermal
neutrons which are strongly absorbed by the
boron, producing high-energy alpha particles
which kill the cancer. This requires the patient to
be brought to a nuclear reactor, rather than the
radioisotopes being taken to the patient.

49. BIOCHEMICAL ANALYSIS
It is very easy to detect the presence or absence of some
radioactive materials even when they exist in very low
concentrations. Radioisotopes can therefore be used to
label molecules of biological samples in vitro (out of the
body). Pathologists have devised hundreds of tests to
determine the constituents of
blood, serum, urine, hormones, antigens and many drugs
by means of associated radioisotopes. These procedures
are known as radioimmuno assays and, although the
biochemistry is complex, kits manufactured for laboratory
use are very easy to use and give accurate results.

50. DIAGNOSTIC RADIOPHARMACEUTICALS:
Every organ in our bodies acts differently from a
chemical point of view. Doctors and chemists
have identified a number of chemicals which are
absorbed by specific organs.
The thyroid, for example, takes up iodine, the
brain consumes quantities of glucose, and so on.

51. With this knowledge, radiopharmacists are able
to attach various radioisotopes to biologically
active substances.
Once a radioactive form of one of these
substances enters the body, it is incorporated
into the normal biological processes and
excreted in the usual ways.

52. Diagnostic radiopharmaceuticals can be used to
examine blood flow to the brain, functioning of
the liver, lungs, heart or kidneys, to assess bone
growth, and to confirm other diagnostic
procedures.
Another important use is to predict the effects
of surgery and assess changes since treatment.

53. A radioisotope used for diagnosis must emit
gamma rays of sufficient energy to escape from
the body and it must have a half-life short
enough for it to decay away soon after imaging
is completed.
The radioisotope most widely used in medicine
is technetium-99m, employed in some 80% of all
nuclear medicine procedures.

54. Myocardial Perfusion Imaging (MPI) uses
thallium-201 chloride or technetium-99m and is
important for detection and prognosis of
coronary artery disease.
For PET imaging, the main radiopharmaceutical
is Fluoro-deoxy glucose (FDG) incorporating F-18
- with a half-life of just under two hours, as a
tracer.
The FDG is readily incorporated into the cell
without being broken down, and is a good
indicator of cell metabolism.

55. THERAPEUTIC RADIOPHARMACEUTICALS:
For some medical conditions, it is useful to destroy or
weaken malfunctioning cells using radiation. The
radioisotope that generates the radiation can be
localised in the required organ in the same way it is
used for diagnosis - through a radioactive element
following its usual biological path, or through the
element being attached to a suitable biological
compound.

56. In most cases, it is beta radiation which
causes the destruction of the damaged
cells. This is radiotherapy.
Short-range radiotherapy is known as
brachytherapy.