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                          Whole Body Counters


  UNITED STATES
  ATOMIC ENERGY COMMISSION

  _Dr. Glenn T. Seaborg, Chairman_
  _James T. Ramey_
  _Dr. Gerald F. Tape_
  _Dr. Samuel M. Nabrit_
  _Wilfrid E. Johnson_

                          _ONE OF A SERIES ON
                        UNDERSTANDING THE ATOM_

  Nuclear energy is playing a vital role in the life of every man,
  woman, and child in the United States today. In the years ahead it
  will affect increasingly all the peoples of the earth. It is essential
  that all Americans gain an understanding of this vital force if they
  are to discharge thoughtfully their responsibilities as citizens and
  if they are to realize fully the myriad benefits that nuclear energy
  offers them.

  The United States Atomic Energy Commission provides this booklet to
  help you achieve such understanding.

                  [Illustration: Edward J. Brunenkant]

                          Edward J. Brunenkant
                                Director
                   Division of Technical Information




                    Whole Body Counters/_{CONTENTS}


  1 SENSITIVE DETECTORS
  2 THE GENEVA COUNTER
  8 THE LIQUID SCINTILLATION COUNTER
  10 POTASSIUM-40 IN HUMAN BODIES
  13 CRYSTAL COUNTERS
  15 THE RADIUM STORY
  17 A NEW BODY CONTAMINANT
  21 PROTECTION OF LABORATORY PERSONNEL
  24 SPECIAL USES
  31 CONCLUSION
  34 SUGGESTED REFERENCES


THE COVER

                  [Illustration: Whole Body Counters]

This smiling youngster in the chute of a large whole body counter has
just emerged from the opening (beyond her feet) of a hollow tank of
scintillation liquid, where she lay while the radioactivity in her body
was being “counted.” In a minute she will step into her slippers (on the
ramp, right) and be ready for play. The sensitive, heavily shielded
radiation-detecting equipment shown has many uses that are described in
this booklet.


THE AUTHORS

                    [Illustration: John H. Woodburn]

John H. Woodburn teaches chemistry at Walter Johnson High School in
Rockville, Md. In the past he taught at Michigan State University,
Illinois State Normal University, and Johns Hopkins University. He
received his A.B. from Marietta College, his M.A. from Ohio State
University, and his Ph. D. from Michigan State University. He is the
author of the book _Radioisotopes_ (J. P. Lippincott 1962), which is a
student’s introduction to this subject.

                 [Illustration: Frederick W. Lengemann]

Frederick W. Lengemann is associate professor of radiation biology at
New York State Veterinary College, Cornell University. He received his
B.S. and M.N.S. from Cornell and his Ph. D. from the University of
Wisconsin. He has been research associate in radiation biology and
assistant professor of chemistry at the University of Tennessee and
formerly was a biochemist with the Atomic Energy Commission, Division of
Biology and Medicine.




                          Whole Body Counters


By JOHN H. WOODBURN
and FREDERICK W. LENGEMANN




                          SENSITIVE DETECTORS


Whole body counters are sensitive radiation detecting and measuring
instruments that provide information not easily obtainable otherwise
about that most important of all chemical systems, the human body. They
can do this because, strange as it may seem, every person who ever lived
is slightly radioactive.

Quickly, accurately, and painlessly, whole body counters reveal the
kinds and amounts of radioactive substances that have accumulated in the
body from natural sources, from man-made fallout, or from tracer
isotopes given for medical purposes. They count emissions from these
radioactive materials, as do other kinds of instruments known as
“counters”.

In contrast to devices that disclose concentrations of radioactivity in
a small area or a particular organ, whole body counters usually are used
to total up the burden of radioactivity in all parts of a human body.
They also are distinguished from many radiation detecting instruments
with the same general purpose by their large size, their heavy
shielding, and their sensitivity to low levels of radioactivity.

Whole body counters are useful in many studies of physiological activity
in living persons and animals. They have proved valuable in calculating
the radiation absorbed by victims of overexposure to radioactive
materials. They can show a doctor how much of his patient’s body is fat
and how much lean. Whole body counters also gave medical scientists
clues to the relation of potassium deficiency to muscular dystrophy and
other diseases. And new medical and scientific uses are being found
regularly.

The need for an instrument that would measure whole body radioactivity
was first felt in the 1920s when the hazardous nature of radium was
recognized. Other sorts of instruments had to be used to estimate the
amount of radium that some factory workers inadvertently had absorbed
while painting luminous watch dials with a radium-containing coating.
(See pages 15 and 16.) But instruments then available were without
adequate shielding to eliminate background radiation, and so the
measurement efforts were of limited value.

It was not until the 1950s that new types of radiation-detecting
instruments were designed, making use of the discovery that some
crystals, liquids, and plastics give off light when struck by gamma rays
(one form of radioactive emission). Two principal types of instruments
have been developed to detect these emissions in human tissues.

The most common whole body counter employs a sodium iodide crystal as
the radiation detector. The person being examined usually sits in a
tilted chair in a room that has thick steel walls to absorb background
radiation. During the counting period, the crystal is centered a few
inches above the subject. This type is useful for examination involving
low levels of radiation or emissions from more than one kind of
radioactive atom.

In the other type the subject is surrounded by a tank of a liquid that
detects gamma rays. This type is faster, but less sensitive, than the
crystal type.

This booklet is intended to enable you to make imaginary visits to
several whole body counters, to understand the scientific principles
that are applied in their design, to learn the interesting ways they are
used, and to appreciate the promise they hold for increasing our
knowledge of ourselves and the world we live in.




                           THE GENEVA COUNTER


In general, all whole body counters must have (1) a mechanism that
reacts to the energy emitted by some kinds of disintegrating, or
radioactive, atoms; (2) a device that displays or records these
reactions; and (3) adequate shielding to exclude unwanted rays from
other sources.

        [Illustration: Figure 1 _Types of whole body counters._]

[Illustration: A _The subject may be seated in a chair in an
iron-shielded room and under a scintillation detecting crystal._]

[Illustration: B _The subject may lie in a bed that slides into the end
of a hollow cylindrical tank filled with scintillation fluid._]

[Illustration: C _The subject may stand in a semicylindrical
double-walled tank filled with scintillation fluid._ (_See Figure 2._)]

[Illustration: D _The subject may lie on a wheeled cart and be wheeled
beneath a shielded detecting crystal._]

One of the first whole body counters was shown at an atomic science
conference in Geneva, Switzerland, in 1955 (Figures 1D and 2). While it
was on display, 4258 visitors to the meeting climbed a set of stairs to
enter a 10-ton lead-walled chamber. Here they stood still for 40 seconds
while the radioactive atoms in their bodies were being “counted”, or
recorded. This device, because it was the first one persons could walk
into, aroused great interest.

[Illustration: Figure 2 _How a “walk-in” whole body counter, such as the
one demonstrated at Geneva, works._]

  Showing:
  Signal lights
  Lead glass windows
  Lead shield
  Scintillation shield
  Photomultiplier tube
  Solution storage tank under platform

Shielding for the Geneva counter consisted of 3 inches of lead. Only the
most energetic background gamma rays and cosmic rays can penetrate this
amount of shielding, and the number that do so remain almost constant
during successive counting periods. This constant remaining “background”
radiation level, once determined, could be subtracted from the recorded
number of emissions to provide the correct radiation total from the body
of each person examined.

[Illustration: Figure 3 _Typical crystals and liquid materials used to
produce scintillations for whole body counters and other
radiation-detecting instruments. Scintillation counters provide much
faster recording of radiation than Geiger counters, and are widely used
in experiments with high-energy particle accelerators, as well as in
whole body counters._]

To detect the gamma rays emitted by radioactive atoms disintegrating
within the body, whole body counters take advantage of a property of
radiation that has been known since 1896. In that year the English
physicist William Crookes discovered that X rays react with certain
chemicals to produce fluorescence. A few years later a New Zealand-born
physicist, Ernest Rutherford (later Lord Rutherford), found that this
glow consisted of many tiny individual flashes or scintillations, each
caused by the emission of a single alpha particle. He laboriously
counted individual flashes by observing them through a magnifying glass.
If you examine a luminous watch with a hand lens in a dark room, you can
see these fascinating scintillations, just as Rutherford saw them long
ago.

Today, scientists have found several crystals, liquids, and plastics
that are especially effective in showing scintillations caused by
nuclear radiations. One of these substances, with the challenging name
2,2′-_p_-phenylene bis [5-phenyloxazole], often shortened to POPOP, was
used in the scintillating liquid of the Geneva counter. How the flashes
are detected can be appreciated by considering the infinitely small
world of individual atoms and following a single atom as it
disintegrates. (For a more complete explanation of radioactivity, see
the companion booklet _Our Atomic World_ in this series.)

Let us assume that we are looking at a single potassium-40 atom in the
body of the person to be examined and that it is about to disintegrate.
(Potassium-40 is naturally radioactive. It is the most abundant
radioisotope in our bodies.) In any sizable portion of potassium-40, we
know that half of the atoms will disintegrate over a period of 1.3
billion years, but, since this process is random, there is no way for us
to know when any particular atom will do so. However, when it does, one
of two alternative events will occur: either a beta particle (that is,
an electron) will be ejected from the nucleus, creating an atom of
nonradioactive calcium-40, or the nucleus will capture one of its own
orbital electrons, resulting in creation of an atom of stable argon-40
and the emission of a gamma ray. (The beta emission process occurs in 89
out of every 100 disintegrations. See Figure 4.)

[Illustration: Figure 4 _Comparison of potassium-40 disintegration
methods._]

Assume that the particular gamma ray is traveling in the direction of
the scintillating liquid in the counter. Remember that the gamma ray is
tiny in comparison with an atom, which is mostly empty space. Therefore,
any one gamma ray probably will miss all the material part of the atoms
in the body of the person being studied. Nor will it collide with
anything as it passes through his clothes and the stainless steel tank.
It also may fail to collide with any of the atoms in the molecules of
scintillation liquid, of course. But let us assume that the one we are
watching does make a hit there. Its total energy will be converted
instantaneously to a flash of many bits or photons of light.

These photons radiate from the collision scene and strike a
light-sensitive surface in one or more of the counter’s photomultiplier
tubes, which have been placed where they can “see” the scintillation
liquid. Energy transformations result, and a tiny pulse of electricity
is originated. These photomultiplier devices are similar to the
equipment in the familiar “electric eye” door openers. As their name
suggests, photomultiplier tubes (see Figures 6 and 9) do more than
merely respond to the light flashes produced in the scintillation
liquid. They also amplify the weak electron disturbances into electrical
pulses to operate meters that record each scintillation and count the
total.

The Geneva counter recorded about 25% of the total gamma rays emitted by
each subject. Since this sample was a constant proportion of the total
body radiation, it could be converted to whole body measurements with
about 97% reliability.

In addition to finding persons with actual body contamination among
those counted at Geneva, the 1955 counter revealed some interesting
sideline information. People who failed to remove radium-dial watches
were soon spotted. And one small boy who had picked up a sample of
uranium ore at a nearby exhibit “jammed” the instrument.

Each of the 25 persons who were found to have above-normal levels of
radiation could recall having worked with radium or some other
radioactive substance at some time in the past.


THE LIQUID SCINTILLATION COUNTER

A visit to this type of counter recalls the first glimmers of scientific
insight that the radiation in the human body could be counted. In the
early 1950s, Frederick Reines and Clyde L. Cowan, two scientists at the
Los Alamos Scientific Laboratory, Los Alamos, New Mexico, built a large
liquid scintillation counter hoping to prove or disprove that neutrinos
really existed. Neutrinos are elusive, uncharged particles with
essentially no mass. They had been predicted in theory nearly 20 years
earlier to explain how beta particles of different energy levels can be
emitted from atoms with apparently identical nuclei.

                        [Illustration: Figure 5]

[Illustration: _Dr. Frederick Reines (left) and Dr. Clyde L. Cowan
(right), co-discoverers of the neutrino, lower a fellow worker into the
first “whole body counter”, the scintillation assembly used in their
experiment. Below, Dr. Wright Lanham, inside the counter, peers from the
opening._]

                    [Illustration: Figure 5, below]

According to theory, neutrinos are created whenever negative
beta-emitting atoms are produced. On this basis, Drs. Reines and Cowan
were convinced that the fission of the nuclear fuel in the reactors of
the Hanford atomic plant at Richland, Washington, should create high
densities of neutrinos. They went to Hanford and set up an elegant
neutrino-catching experiment that hinged on detecting and counting gamma
rays of definite energy. To accomplish this, they built a large liquid
scintillation detector and shielded it from stray gamma radiation. As
their work progressed, someone realized that the equipment was large
enough to allow a person to crawl inside. After further research at the
Atomic Energy Commission’s Savannah River Plant in South Carolina, they
were successful in finding their long-sought neutrino. In doing so, they
also developed the sort of instrument that can study the human body.

Figure 6 shows a person about to enter one version of a Los Alamos
counter, the instrument’s 140-gallon tank of scintillation fluid, and 45
of its 108 photomultiplier tubes. When the instrument is in use, the
tank slides into, and is shielded by, a 20-ton barrier of 5-inch lead.

[Illustration: Figure 6 _A liquid scintillation whole body counter at
Los Alamos National Laboratory, showing (left) a subject in the chute
before it is slid into the shielded detector chamber. Below, the same
instrument’s detecting assembly, showing the photomultiplier tubes,
removed from the shielding._]

The loading chute will hold a person 6 feet 4 inches tall and weighing
up to 260 pounds. The subject lies in the chute as it slides into the
counter. A lead plug behind his head closes the end of the cylinder to
add shielding. Counters of this type have “panic buttons” with which
subjects may signal if they become uneasy on being confined. Most counts
are completed in less than 5 minutes, however, so the buttons are rarely
used.

Since the detector fluid almost completely surrounds the subject when
the chute is in place, this type of counter captures twice as large a
fraction of the emitted gamma rays as does the Geneva type.

Each radioactive substance emits gamma rays with an energy level
characteristic of that substance. Whole body counters are able to
measure this specific energy spectrum, or “fingerprint”, and so identify
the kind of atom producing the radiation.

The number of light photons produced in the scintillation fluid is
proportional to the energy transferred by the incoming gamma rays. For
example, gamma rays emitted by potassium-40 have 1.46 million electron
volts (Mev) energy; those of cesium-137 have 0.660 Mev energy. When both
these radionuclides are producing flashes of light in the scintillation
fluid at once, the photomultiplier tubes produce two different strengths
of electrical pulses. Electronic devices called multichannel
pulse-height analyzers sort and record the number of each.


POTASSIUM-40 IN HUMAN BODIES

Data from whole body counters indicate that potassium-40 is the most
abundant radionuclide in the human body. Our bodies also contain other
naturally radioactive substances but the numbers of atoms usually
present are so low (as with radium for instance) that they cannot be
detected with whole body counters. Several man-made radionuclides also
have found their way into body tissues and organs in quantities that
sometimes are large enough to be detected and counted.

Measurement of disintegrating potassium-40 atoms in the tissues of a
human body can be used to determine the total amount of potassium (both
radioactive and stable) in the body. It is known that potassium-40 makes
up 0.0119% of all potassium and that 11% of all disintegrating
potassium-40 atoms emit high-energy gamma rays that are measurable by
the counter.

The method of determining the amount of potassium in a human subject is
to compare the number of gamma rays from a known amount of potassium
placed in a phantom, or dummy body, with the number counted from the
human subject (see photo on next page). Phantoms are artificial bodies,
approximately the size, shape, and density of a human body, used for
calibrating counters. They are designed so the radioisotopes they
contain have similar distribution to the distribution of the isotopes
expected in the real body. This is how a test might work:

  Counts per minute from 140 grams of potassium in the phantom     16,800
  Counts per minute with nothing in counter (background)           12,000
  Net counts per minute from 140 grams of potassium                 4,800
  Counts per minute with a 77-pound boy in counter                 14,400
  Background cunts per minute                                      12,000
  Net count per minute from boy                                     2,400
  Calculated amount of potassium in boy                          70 grams

[Illustration: Figure 7 _Phantom used for iodine-131 studies. The
radiation spectrum from the thyroid area in the neck is being obtained
with a sodium iodide crystal, left._]

We can appreciate the sensitivity of whole body counters by comparing
the number of gamma rays recorded by the instruments with the total
number emitted from the body being counted. The following data, also
simplified, illustrate this comparison:

  Total atoms in 70 grams of potassium                 1.08 × 10²⁴[1]
  Number of atoms of potassium-40 in 70 grams of           1.3 × 10²⁰
  potassium
  Half-life of potassium-40 in minutes                     6.4 × 10¹⁴
  Number of potassium-40 atoms disintegrating
  per minute in 70 grams of potassium                         141,000
  Number of potassium-40 atoms disintegrating per              15,510
  minute with emission of measurable gamma rays
  Number of counts recorded                                     2,400
  Detection efficiency: 2,400 ÷ 15,510 = 15.5%

Fatty tissues are known to have a low potassium concentration and muscle
tissue a higher level. It is therefore apparent that potassium-40
determinations provide a way to indicate the amount of lean muscle in
any individual, and indirectly the amount of fat. Estimates of the
amount of fat based on the measurement of the specific gravity of the
subject, often used in the past, have never been satisfactory. Not only
do variable and unmeasurable air spaces change body density, but the
process of submerging a person in a tank—to determine his specific
gravity by the amount of water he displaces—is a clumsy and
uncomfortable one.

Significant variations in potassium content have been found in persons
suffering from muscle diseases or malfunctions. For example, a sharp
drop in potassium content accompanies the profound muscle weakness that
follows diabetic coma. Administration of potassium produces striking
improvement in the condition known as familial periodic paralysis.

Whole body counter data from a study of muscular dystrophy and myotonia
atrophica patients showed there is a gradual and progressive decrease of
body potassium during the unrelenting courses of these diseases.
Otherwise healthy children of muscular dystrophy patients, or their
brothers and sisters, also may be deficient in potassium. By assisting
in muscle research, whole body counters help doctors learn more of how
potassium relates to muscle function and muscle health.

Whole body counting is an improvement over potassium determination based
on chemical analysis of body fluids. If counters are not used, one way
to measure body potassium is to inject a known quantity of potassium-42
(another radioactive form of potassium), wait until this has been
uniformly mixed with the potassium already in the body, and then record
the radioactivity of a volume of blood serum. From the degree of
dilution of the injected potassium-42, the total body potassium can be
calculated. This widely used method is uncomfortable for the patient
since it involves use of syringes to inject and withdraw fluids. Because
about 95% of the body potassium is inside the cells, rather than in
fluids between the cells, this method may also be inexact if the mixing
process does not continue long enough. (See _Radioisotopes in Medicine_,
another booklet in this series, for a full discussion of medical
treatment with radioactive materials.)

[Illustration: Figure 8 _A crystal whole body counter “iron room” under
construction above, and in use._]

                    [Illustration: Figure 8, below]




                            CRYSTAL COUNTERS


When we visit a crystal counter, shown under construction in Figure 8,
walls of battleship steel 6 to 8 inches thick are the first things we
see. Rather than using shielding only around the detecting instrument,
as was done in the Geneva counter and early versions of the Los Alamos
counter, crystal counters have shielding around the entire counting
room. With this arrangement the instruments are available for adjustment
and servicing.

This type of counter also uses a different detection device: a solid,
rather than a liquid scintillator. A large crystal, usually of sodium
iodide sensitized with thallium, is used to convert gamma rays to light
photons.

Let us return to the shielding problem for a moment. Tanks of water,
bricks, stone, and lead have been tried by scientists seeking effective,
cheap, and convenient shielding. Some early counters were built deep
underground in the hope of avoiding cosmic radiation. Radioactive
elements are so widely distributed in the rocks, soil, water, and air,
however, that there is no place where background radiation does not
exist. Not even the crystals, glass, or metals used in the detection
system are free of radioactivity.

Pre-World War II surplus armor plate came to be the preferred shielding
material. Thick slabs of battleship steel were available after the war
at low cost. Furthermore, steel produced since the war may contain
unwanted radioactivity originating in fallout from nuclear tests and
make it undesirable for shielding. Sometimes cobalt-60 used as a tracer
to measure deterioration of blast furnace walls causes problems in
postwar steel, too, so old warship armor is used when possible.

Some whole body counters have additional shielding. In the counter at
the Brookhaven National Laboratory, Upton, New York, the steel room is
lined with ¼-inch lead sheets, covered by thin layers of cadmium and
copper. The lead is intended to absorb the secondary X rays produced in
the iron by the interaction of high-energy gamma and cosmic rays. The
cadmium and copper absorb the secondary radiation that is similarly
produced in the lead.

The doors of these rooms often weigh 6 tons or more. A special escape
hatch was built into the counter room at the University of California at
Los Angeles, to be used if the main door should be jammed by an
earthquake. In newer whole body counting laboratories, such as the one
at the National Institutes of Health, Bethesda, Md., the steel rooms are
concealed in the interior design and are so pleasantly furnished that
the patient scarcely is aware of the thick walls around him.

[Illustration: Figure 9 _A sodium iodide crystal, right, and a cluster
of 7 photomultiplier tubes that fit under it to record its
scintillations._]

Figure 9 shows a sodium iodide crystal used to react with the gamma rays
that traverse it. To the left of the crystal is a cluster of seven
photomultiplier tubes that “watch” for the scintillations, convert them
to electrical pulses, and amplify them so they can be sorted, counted,
and recorded. A trace of thallium added to the sodium iodide improves
its scintillation properties.

In addition to being of convenient size and easy to maintain, crystal
detectors have another advantage over liquid systems. The energy of the
incident gamma rays from crystals is more accurately indicated by the
quality of the flashes of light impinging on the photomultiplier tubes.
If two or more radionuclides are emitting gamma rays, a crystal detector
distinguishes between their energy levels with much more precision and
sensitivity than does a liquid system. Crystal instruments separate
gamma rays differing by no more than 0.05 Mev.

The energies of the gamma rays emitted by nuclides have all been
determined and are listed in handbooks. A scientist can thus identify
the data delivered by a multichannel pulse-height analyzer as coming
from potassium-40, zinc-65, or any other nuclide.

Counters using sodium iodide crystals intercept, and therefore count, a
much smaller fraction of the gammas emitted by the subject’s body than
liquid systems, but they also pick up a smaller amount of background.
When speed is important, the liquid counter is more effective, but the
crystal counter is preferred when radionuclides emitting gammas of
nearly the same energies are to be separated and counted.




                            THE RADIUM STORY


Radium-226 in the human body poses unique problems for whole body
counters. People who have accumulated this nuclide only because of the
minute amounts occurring naturally in food and water have counts of only
two or three disintegrating atoms per second, and this amount cannot be
distinguished from background radiation. Whole body counters are useful,
however, in diagnosing effects in persons who have been overexposed to
radium. These include persons who formerly were employed to paint watch
dials with a luminous paint containing radium. (See table below.)

[Illustration: Figure 10 _A group of radium dial painters at work in a
watch factory in 1922. Almost all these employees have been identified
and the living ones recently have participated in a study at Argonne
National Laboratory to determine the extent of radium accumulation in
their bodies. Whole body counters aided in their examinations._]

Excerpts from case records of one research center show the high counts
found in several patients and the source of the radium or thorium (a
closely related element) that their bodies had taken up:

  Case                                                   Body burden in
                                                   disintegrating atoms
                                                             per second
  Born 1900, drank 210 bottles of “Radithor”                     63,640
  in 1927[2]
  Born 1897, drank approximately 78 ounces of                    32,780
  “Radium Water” in 1932[2]
  Born 1925, worked as radium chemist since                      14,800
  1946
  Born 1922, radium chemist for 7 years                           7,000
  Born 1898, two injections of “Thorotrast”                       3,300
  for X-ray diagnosis
  Born 1898, radium dial painter in watch                        72,500
  factory, 1918 to 1921
  Born 1902, radium dial painter for 4½ months                    1,924
  in 1924

Scientists at the Argonne National Laboratory, Argonne, Illinois, have
attempted to improve crystal whole body counters so that they will be
more useful in determining the amount of radium-226 in humans. Rolf
Sievert at the Swedish Atomic Energy Commission also has studied the
radium-226 detection. He devised a highly accurate whole body counter
with 10 ion chambers arranged around a curved aluminum bed on which the
subject rested. The instrument was installed below ground to reduce the
interference of background radiation.

[Illustration: Figure 11 _The spectrum of gamma radiation emitted by the
body of a man three years after he accidentally inhaled radium-226. The
solid line shows the normal radiation due to potassium-40, the dotted
line the total from potassium-40 and radium-226._]

  Showing:
  COUNTS/MINUTE PER 95-KEV CHANNEL
  Subject G (total)
  Subject G (potassium-40)




                         A NEW BODY CONTAMINANT


In 1955, Charles E. Miller and L. D. Marinelli were measuring human
potassium levels with the whole body counter at the Argonne laboratory.
They were puzzled by finding several people who emitted 0.660-Mev gamma
rays. Gamma rays of this energy, which are emitted by cesium-137, had
not previously been detected in humans. To add to the perplexity, when
the same persons were examined a few months later, the count of these
gamma rays had increased. The Argonne findings indicated strongly that
radiocesium, which is known to occur in fallout from nuclear explosions,
was finding its way into people’s bodies. (See _Fallout from Nuclear
Tests_, another booklet in this series.)


INVESTIGATION OF FALLOUT CESIUM IN LAPLANDERS’ DIET

[Illustration: _Long-lived radionuclides, particularly cesium-137,
accumulate on plants._]

[Illustration: _Reindeer herds graze on lichens and mosses._]

[Illustration: _A substantial portion of the Laplanders’ diet is
reindeer meat._]

[Illustration: _Here personal data and eating habits are recorded for
each person to be counted._]

[Illustration: _A Laplander in a whole body counter._]

[Illustration: _The University of Helsinki (Finland) study revealed a
close correlation between the consumption of reindeer meal and the
Lapps’ body burdens of cesium-137. However, these levels did not exceed
acceptable limits._]

[Illustration: Figure 12 _Using a whole body counter to determine
radioactivity in milk._]

The idea that this nuclide had entered the body with food later was
tested by placing various foods in the whole body counter. All foods
tested were found to contain some cesium-137, but beef and dairy
products had highest levels. The radiation spectra of persons of the
same age but different diet habits were compared, and correlation was
found between their cesium-137 content and the amount of dairy products
they ate.

In October 1960, Kurt Liden at the University of Lund in Sweden
encountered evidence of the source of cesium-137 in humans. While he was
using the whole body counter at the University’s Radiation Physics
Department, Liden found several Norwegians whose bodies contained
quantities of cesium-137 several times higher than previously recorded.
He substantiated these data by counting 15 additional Norwegians from
Oslo and 6 from Bergen. The Oslo residents averaged 21 nanocuries
(abbreviated nc) of cesium-137 and the Bergen group 60 nc. Swedes
averaged only 8 nc. (A nanocurie is one billionth of a curie, the
standard unit of radioactivity.)

Curiosity regarding these high values in the Norwegians led him to
investigate goat cheese, which Norwegians consume in larger quantities
than Swedes. Goat cheese at that time showed a high cesium-137 content
of 41 nc per kilogram. In northern Norway, near Bergen, another main
food is reindeer meat, which was found to contain 28 nc of cesium-137
per kilogram, compared to 0.1 nc per kilogram in beef. These factors
indicated that goat cheese and reindeer meat were responsible for the
high cesium-137 count in the Norwegians.

Investigation of the soil in northern Norway revealed that it averaged
20 nc of cesium-137 per square meter. Only thin covers of lichens grow
in this region, and reindeer must graze over large areas to obtain
sufficient food. It was obvious that cesium-137 from fallout was
collecting on lichens and then was being concentrated in the bodies of
the reindeer before they were killed for meat.

Similar studies have been conducted by scientists of the Pacific
Northwest Laboratory at Richland, Washington, who since 1959 have been
measuring radioactivity of plants and animals in Alaska. When they found
high levels of cesium-137 in lichens and caribou, they became interested
in the body burdens of fallout isotopes in the Eskimos.

A portable crystal type of whole body counter was used to measure the
cesium-137 content of Eskimos at five villages. The Eskimos cooperated
willingly; in some communities nearly everyone accepted the invitation
to be counted. This table presents the results:

                                      Cesium-137 (in nanocuries)
  Village               Number of     Minimum      Maximum       Average
                        subjects
  Diomede                     12            8           35            22
  Barrow                     259            8          166            51
  Point Hope                 107            3          119            17
  Kotzebue                   132           17          518           138
  Anaktuvuk                   52           83          719           421

  (For comparison, the average body burden of cesium-137 of residents of
  Richland, Washington, during this period was between 5 and 7
  nanocuries.)

These data show that the Eskimos who lived inland at Anaktuvuk and ate
heavily of caribou meat carried cesium-137 burdens up to 20 times
greater than Eskimos who lived in the four villages along the coast and
had more variety in their food. (See pages 18 and 19 for photo story of
a similar project in Finland.)




                   PROTECTION OF LABORATORY PERSONNEL


For chemists or others working with arsenic, cyanide, or other chemical
poisons, safety depends on recognizing the materials and keeping them
where they belong. When accidents do happen and poisons are swallowed or
breathed in, successful treatment requires that someone find out exactly
what and how much of the poisonous material was involved.

In the event of accidents in nuclear laboratories or reactors, it would
be equally essential to identify accurately and quickly the quantity and
kind of unstable nuclides the victim has absorbed. A reactor accident
conceivably could add a unique hazard since neutron radiation might
change the normally stable, nonradioactive atoms in the bodies of nearby
workers into radioactive ones. Even gold or silver fillings in their
teeth might become radioactive.

[Illustration: Figure 13 _A portable whole body counter used for
research as well as routine monitoring of personnel in an atomic reactor
installation. Usually gamma-emitting radionuclides can be detected in 10
minutes. This counter is in almost constant use at the AEC’s National
Reactor Testing Station in Idaho._]

When human tissue (for example, hair) is bombarded by fast neutrons,
sulfur atoms in molecules of proteins are converted to the radionuclide
phosphorus-32. In atomic shorthand, this reaction is:

                       ³²₁₆S + ¹₀n → ³²₁₅P + ¹₁p

or, in still more abbreviated form, ³²S_{n,p}³²P. Phosphorus-32 atoms do
not emit gamma rays upon disintegration and so are not detected in
standard whole body counters. Attempts are being made, however, to adapt
some whole body counters to pick up the secondary radiations, called
bremsstrahlung, that occur when the high-energy beta particles that are
emitted by phosphorus-32 collide with other atoms.

[Illustration: Figure 14 _Whole body counter record of evidence that a
cyclotron worker has picked up higher-than-average quantities of
radioactive zinc-65. Note how the graph shows peaks at specific energy
levels identifying the radionuclides._]

[Illustration: Figure 15 _Graphic evidence that a radioactive gas
accidentally inhaled by a worker at an experimental reactor contained 3
radioactive isotopes of iodine._]

[Illustration: Figure 16 _The number of 1.38-Mev gamma rays emitted by
sodium-24 in the body of a reactor accident victim indicates he received
about 900 rads of neutron irradiation._]

  _Figures 14 through 16 illustrate the kind of data that whole body
  counters provide to help physicians care for people involved in
  accidents._

Similarly, neutron bombardment of natural sodium (²³Na) atoms in the
body produces sodium-24. This reaction is written: ²³Na(n, gamma
ray)²⁴Na. The 1.38-Mev gamma rays emitted by sodium-24 are detected
effectively by whole body counters. Since a given neutron dose converts
a known proportion of ²³Na atoms to ²⁴Na, it is possible to determine
how much neutron exposure a worker has received by obtaining his body
count of radioactive sodium.

Crystal type counters also were used in an interesting special case of
excessive radiation exposure. Seven natives of the Marshall Islands were
examined by the whole body counter at the Argonne National Laboratory in
1957. Another whole body counter, mounted in a Navy amphibious landing
ship, was taken to Rongelap Atoll in the Marshalls several times to
check on the health of all the residents of the atoll. These people had
accumulated zinc-65 in their bodies as a result of contamination of
crabs and other food items by fallout from the March 1954 atomic bomb
tests at the Pacific Proving Ground. Although normal radioactive decay
progressively reduced the total amount of radioactivity in the area, the
Marshallese still were carrying this nuclide in their bodies after
several years. (See _Atoms, Nature, and Man_, another booklet in this
series, for a more complete report of this study.)




                              SPECIAL USES


Studies of New Babies

Study of the transfer of nutrients and other substances from an
expectant mother’s body to that of her unborn child is one of the most
challenging areas of biological research. A team of scientists headed by
N. S. MacDonald has used a whole body counter at the University of
California at Los Angeles to study one aspect of this problem by
comparing the concentrations of radioactive materials in newborn
infants, in babies who are born dead, and in tissues of the
mothers-to-be.

In these studies the scintillation crystal was placed directly beneath a
plastic bassinet holding the babies. Twenty-eight infants, 6 to 24 hours
old, were counted for 45 minutes each. The only radionuclide found was
the ever-present potassium-40.

The bodies of seven stillborn babies were counted for at least 10 hours
each. More kinds of radionuclides were found than in the living babies,
although the large counting time may have affected the results.

The same counting techniques were used with placental tissues from
mothers of three of the stillborns. The placenta is the organ that
nourishes an unborn child and through which substances from the mother’s
bloodstream are exchanged with those in the baby’s blood. The graphs in
Figure 17 show data from this experiment and illustrate the method of
interpreting whole body counter data. When the counts per minute at each
band of gamma-ray energy recorded from the placental tissues (b) were
subtracted from corresponding values from the stillborns (a), it was
found (c) that the placentas contained more of the isotopes
ruthenium-103, ruthenium-106, and zirconium-95 than did the babies that
had been nurtured by these placentas. The babies’ bodies contained more
niobium-95 and potassium-40 than the placentas. Niobium-95 is produced
by the radioactive disintegration of zirconium-95. This suggested that
zirconium-95 atoms do not pass readily through the placenta, but, after
they have decayed to niobium-95, they pass into the baby’s bloodstream
easily.

Actually, the gamma-ray energies of zirconium-95 and niobium-95 are so
similar that the counter cannot distinguish between them. The two
isotopes, however, were separated chemically, and whole body spectra
were prepared from samples of the pure elements. The spectrum (d) of
pure zirconium-95 subtracted from that of pure niobium-95 was strikingly
similar to the spectrum of “stillborn baby minus placenta” on the
graphs. Cesium-137 was added to the synthetic spectrum to provide a
reference mark at the 0.660-Mev point. This revealed that the ratio of
cesium-137 to potassium-40 is lower in babies than in adults.

[Illustration: Figure 17 _Results of experiment studying transfer of
nutrients from an expectant mother to her unborn child._]


Research on Body Processes

Radioactive tracer atoms, either natural or purposefully built into
molecules of vital materials like proteins, are revealing how these
substances function in the body to produce energy or to form new
tissues. When we know accurately the normal totals and kinds of
radioactive substances in the body, we can undertake new kinds of tracer
studies without using large amounts of additional radiation. Small
instruments called scanners (see Figure 18) usually are used to track
tracer isotopes, but whole body counters are useful in special
circumstances.

[Illustration: Figure 18 _A multidetector positron scanner to record
radiations with opposed pairs of detection crystals. Scanning devices
are commonly used for noting the fate of tracer isotopes in medical
diagnosis._]

Two types of adaptations enable whole body counters to locate
accumulations of radioactive materials in specific organs or small
portions of the body. At the National Institutes of Health, Bethesda,
Md., one counter is fitted with three rows of six 12-by-12-inch plastic
blocks. Each block has four photomultiplier tubes to collect the
scintillations from the crystal. The rows are curved so as to be equally
distant from the patient’s body.

The current pulses from each of the 18 blocks can be fed individually
into the pulse sorter, counter, and recorder. Thus the kinds and numbers
of gamma rays from the sector of the patient adjacent to any block can
be studied individually. Similarly, the path and speed of the
administered materials can be followed by taking recordings from the
blocks sequentially.

At the U. S. Naval Hospital in Bethesda, Md., a whole body counter is
fitted with a crystal that can be moved at controlled speed past the
body of the person being studied (Figure 19). To increase its scanning
efficiency, the crystal is fitted with a slit and a focusing device.
Instruments record the body radioactivity visibly at timed intervals as
the crystal moves along the patient’s body. A television screen enables
the operator to observe the patient during the counting.

[Illustration: Figure 19 _The U. S. Naval Hospital whole body counter,
showing the moving crystal, left, and instruments, including the
television screen used by the operator. The moving crystal makes it
possible to use this whole body counter for scanning._]

The role of iron in preventing one form of anemia has been clarified by
using iron-59 as a tracer. Persons suffering from chronic infections or
such blood diseases as leukemia and polycythemia vera have been checked
for the amount of iron carried by their red blood cells. Cobalt-60 atoms
have been substituted for stable cobalt in molecules of vitamin B-12 so
that the way the body makes use of this vitamin can be studied.
Similarly, the body’s use of sodium can be studied by labeling sodium
chloride with sodium-22 and then administering solutions of the tagged
salt orally or by injection.

Whole body counters used in tracer studies cause a minimum of
inconvenience for the patient. Their sensitivity permits use of smaller
quantities of radioactive material than is required with small scanning
instruments.

Those are unusual jobs for whole body counters, however. Scanners or
other types of instruments are used more typically in following tracer
isotopes.


Animal Research

[Illustration: Figure 20 _Dogs about to be examined in a whole body
counter._]

How do dogs accumulate fallout isotopes in their bodies? This question
was answered effectively by placing dogs in whole body counters and
comparing the count from radioactive strontium-emitted gamma rays
originating in their bodies with the count from a masonite phantom dog
containing a known amount of radioactive strontium-85. It was found that
female dogs increase their strontium retention while they are nursing
newborn puppies. Strontium is much like calcium, which is a major
component of milk. One dog measured had broken a leg in a fight. The
counter showed above-average strontium accumulation for this dog, and it
was conjectured that strontium, a “bone-seeking” element, had followed
calcium to the point of bone repair and new bone growth.

[Illustration: Figure 21 _A wild deer under a whole body counter._]

[Illustration: Figure 22 _Graph of whole body counter survey of four
different animal species, showing differences in their retention of
orally administered radioactive zinc-65._]

  Showing RETENTION, % versus TIME, DAYS for Man, Dog, Rat, Mouse

Figure 22 shows how animals differ in their retention of orally
administered zinc-65, as revealed by a whole body counter. It is
apparent that counters can be used to determine the differences in the
metabolism of different animal species used for research. Standard data
developed in this way can serve to reduce error that may occur if
results from one species are used for interpretation of data for another
species, such as man.

A University of Illinois project to breed meat animals with a high
lean-to-fat ratio has been aided by whole body counters. The tendency to
deposit fat seems to be inherited, and breeding stock with low fat
content can be selected, using “muscle-seeking” potassium-40 to show the
proportion of muscle in each potential parent. The Illinois counter is
unique in being large enough to examine an adult steer (Figure 23). A
similar counter at Cornell University has been used to study animals
infested with internal parasites, comparing them with parasite-free
animals. The counter revealed that a positive relationship exists
between the level of parasite infestation and loss of iron-59-labeled
blood from the digestive tract. The possibility of using this method to
evaluate parasite-killing drugs is being considered. The Cornell counter
is kept clean by covering the animals with plastic sheeting. The same
counter also can serve human patients, who are positioned in a wheeled
hospital stretcher. (See Figure 1D.)




                               CONCLUSION


This booklet has presented a sample of the ways whole body counters add
to man’s knowledge and increase his ability to manage conditions and
processes important to his health and well-being. Radioactive substances
occur naturally within our own bodies and all other materials. Whole
body counters measure this radioactivity, or any which may have been
added from artificial sources.

We have seen how these sensitive instruments help to prove hypotheses
difficult to verify otherwise and how they thereby may stimulate new and
fruitful scientific experimentation. We have learned how whole body
counters add to our knowledge of normal processes in healthy bodies and
detect disease or abnormalities resulting from dangerous conditions.

[Illustration: Figure 23 _A University of Illinois counter large enough
to examine an adult steer, above. A Cornell University counter used for
animal-parasite studies, below._]

                    [Illustration: Figure 23, below]

[Illustration: Figure 24 _A trailer-mounted whole body counter used for
research. School children were examined in a project to determine
possible pathways by which radioactivity may enter the human body._]

Each fact uncovered by whole body counters seems to trigger more
penetrating research. This is how science advances. And with the advance
of science comes knowledge on which we may build intelligent behavior
and find solutions to problems affecting our lives.




                          SUGGESTED REFERENCES


Books

  _Environmental Radioactivity_, Merril Eisenbud, McGraw-Hill Book
  Company, Inc., New York. 1963, 430 pp., $13.50.

  _Radioactivity in Man: Whole Body Counting and the Effects of Internal
  Gamma Ray-Emitting Radioisotopes_, George R. Meneely (Ed.). Charles C
  Thomas, Springfield, Illinois. 1965, 672 pp., $24.50.

  _Whole Body Counting_, Proceedings of the Symposium on Whole Body
  Counting Held by the International Atomic Energy Agency at the Neue
  Hofburg, Vienna (June 12-16, 1961), National Agency for International
  Publications, 317 East 34th Street, New York 10016, 1962, 535 pp.,
  $10.00.

  _How to Detect and Measure Radiation_, Harold S. Renne, The
  Bobbs-Merrill Company, Inc., New York, 1963, 160 pp., $3.95.

  _An Introduction to Radiation Counters and Detectors_, C. C. H.
  Washtell, George Newnes Ltd., London, 1960, 115 pp., $7.50.

  _Liquid Scintillation Counting_, Proceedings of a Conference Held at
  Northwestern University (August 20-22, 1957), Carlos G. Bell, Jr., and
  F. Newton Hayes (Eds.), Pergamon Press, Inc., New York, 1958, 292 pp.,
  $10.00.


Reports

  _Fundamental Nuclear Energy Research, A Special Report of the United
  Stales Atomic Energy Commission_ (December 1963), Superintendent of
  Documents, U. S. Government Printing Office, Washington, D. C. 20402,
  407 pp., $2.50. Whole Body Counters as Medical Aids, pp. 11-13; Acute
  Whole Body Irradiation Effects, pp. 35-41; Chronic Whole Body
  Irradiation Effects, pp. 42-48.

  _Radioactive Contamination of Materials Used in Scientific Research_,
  James R. DeVoe, Nuclear Science Series Report No. 34, National Academy
  of Sciences—National Research Council, Washington, D. C. 20418, 1961,
  $2.00. Appendix VIII, The Negotiations and Developmental Work on Low
  Activity Glasses for Use in Whole Body Counters, pp. 109-115.


Articles

  Liquid Scintillation Counting of C¹⁴ and H³ Labeled Amino Acids and
  Proteins, M. Vaughan and others, _Science_, 126: 446 (Sept. 6, 1957).

  Phosphorescence in Liquid Scintillation Counting of Proteins, R. J.
  Herberg, _Science_, 128: 199 (July 25, 1958).

  Suspension Counting of Carbon-14 in Scintillation Gels, B. L. Funt and
  A. Hetherington, _Science_, 125: 986 (May 17, 1957).

  Liquid Scintillation Counting of Aqueous Solutions of Carbon-14 and
  Tritium, J. Shapira and W. H. Perkins, _Science_, 131: 414 (Feb. 12,
  1960).

  Alone in the Dark with a Panic Button: Purdue’s Whole Body Counter,
  Martin Mann, _Popular Science_, 181: 90 (October 1962).

  Counter as a Test Instrument, W. H. Bucksbaum, _Electronics World_,
  68: 48 (November 1962).

  Spiral Capillary Plastic Scintillation Flow Counter for Beta Assay, B.
  L. Funt and A. Hetherington, _Science_, 129: 1429 (May 22, 1959).


Motion Pictures

Available for loan without charge from the AEC Headquarters Film
Library, Division of Public Information, U. S. Atomic Energy Commission,
Washington, D. C. 20545 and from other AEC film libraries.

  _Understanding the Atom: Radiation Detection by Scintillation_, 30
  minutes, black and white, sound, 1962. Produced by the Educational
  Broadcasting Corporation under the direction of the AEC’s Division of
  Isotopes Development. This semitechnical film describes the
  scintillation process. Solid and liquid scintillators are shown, a
  description of a photomultiplier is given, and the pulse-height
  analyzer principle is illustrated.

  _Human Radioactivity Measurements_, 9 minutes, color and sound, 1958.
  Produced by AEC’s Los Alamos Scientific Laboratory. This film shows a
  method developed at LASL to monitor possible intake of radiation by
  personnel. The liquid scintillation counter is large enough to contain
  a man and sensitive enough to detect even the minute amounts of his
  natural gamma radioactivity.

  _Ionizing Radiation in Humans_, 15 minutes, color and sound, 1958.
  Produced by AEC’s Argonne National Laboratory. Describes the design
  and operation of ANL’s whole body counter for determining
  identification, quantity, and location of internally deposited
  radioelements. Various techniques in accumulation of data are shown.

  _Liquid Scintillation Counting_, 14 minutes, color and sound, 1958.
  Produced by the Jam Handy Organization for the U. S. Atomic Energy
  Commission. Describes the use of a liquid scintillator for counting
  low-energy beta emitters commonly used in biological and medical
  tracer experiments. Also describes counting techniques, how the
  counters work, and how a sample is prepared.


PHOTO CREDITS

  Cover            courtesy Los Alamos Scientific Laboratory (LASL)
  Figure 1         A, Argonne National Laboratory (ANL); B and C; LASL;
                   D, Cornell University.
  Figure 2         LASL
  Figure 3         Brookhaven National Laboratory (BNL)
  Figure 5         LASL
  Figure 6         LASL
  Figure 7         BNL
  Figure 8         LASL
  Figure 9         LASL
  Figure 10        Dr. Charles E. Miller, ANL
  Figure 12        LASL
  Figure 13        National Reactor Testing Station
  Figure 18        BNL
  Figure 19        National Naval Medical Center
  Figure 20        LASL
  Figure 21        Colorado State University
  Figure 23        Cornell University
  Figure 24        Pacific Northwest Laboratory
  Center-spread    Professor J. K. Miettinen, University of Helsinki


This booklet is one of the “Understanding the Atom” Series. Comments are
invited on this booklet and others in the series; please send them to
the Division of Technical Information, U. S. Atomic Energy Commission,
Washington, D. C. 20545.

Published as part of the AEC’s educational assistance program, the
series includes these titles:

  NUCLEAR POWER AND MERCHANT SHIPPING
  PLUTONIUM
  OUR ATOMIC WORLD
  NUCLEAR ENERGY FOR DESALTING
  CONTROLLED NUCLEAR FUSION
  WHOLE BODY COUNTERS
  PLOWSHARE
  POPULAR BOOKS ON NUCLEAR SCIENCE
  SNAP, NUCLEAR SPACE REACTORS
  NUCLEAR REACTORS
  ATOMS, NATURE, AND MAN
  MICROSTRUCTURE OF MATTER
  SYNTHETIC TRANSURANIUM ELEMENTS
  COMPUTERS
  RESEARCH REACTORS
  GENETIC EFFECTS OF RADIATION
  POWER FROM RADIOISOTOPES
  NONDESTRUCTIVE TESTING
  RARE EARTHS
  FOOD PRESERVATION BY IRRADIATION
  FALLOUT FROM NUCLEAR TESTS
  RADIOACTIVE WASTES
  RADIOISOTOPES IN INDUSTRY
  ATOMS AT THE SCIENCE FAIR
  RADIOISOTOPES AND LIFE PROCESSES
  ATOMIC FUEL
  ATOMIC POWER SAFETY
  DIRECT CONVERSION OF ENERGY
  CAREERS IN ATOMIC ENERGY
  RADIOISOTOPES IN MEDICINE
  ACCELERATORS
  NUCLEAR TERMS, A BRIEF GLOSSARY
  NEUTRON ACTIVATION ANALYSIS
  ATOMS IN AGRICULTURE
  NUCLEAR CLOCKS
  POWER REACTORS IN SMALL PACKAGES
  NUCLEAR POWER PLANTS
  YOUR BODY AND RADIATION

A single copy of any one booklet, or of no more than three different
booklets, may be obtained free by writing to:

           USAEC, P. O. BOX 62, OAK RIDGE, TENNESSEE    37830

Complete sets of the series are available to school and public
librarians, and to teachers who can make them available for reference or
for use by groups. Requests should be made on school or library
letterheads and indicate the proposed use.

Students and teachers who need other material on specific aspects of
nuclear science, or references to other reading material, may also write
to the Oak Ridge address. Requests should state the topic of interest
exactly, and the use intended.

In all requests, include “Zip Code” in return address.


                Printed in the United States of America
USAEC Division of Technical Information Extension, Oak Ridge, Tennessee
                             February 1967




                               FOOTNOTES


[1]This is mathematical shorthand for 1.08 followed by 24 zeros, or 1.08
    million billion billion.

[2]Medicines such as “Radithor” and “Radium Water” were manufactured and
    sold before it was known that overexposure to radioactivity was
    harmful.




                          Transcriber’s Notes


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--In the text versions only, other subscripted text is preceded by
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