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 Sealed
sources are radioactive materials
encased or "sealed" inside metal or plastic
and can take many different forms, sizes and
shapes. All forms share some type of
encapsulation that prevents their radioactive
contents from leaking or dispersing, barring
tampering or a severe accident. In some
forms, the radioactive material is an inherent
part of the source and cannot be separated.
 Almost
all "sealed sources" can be handled
without concern that the radioactive
material will rub-off or be dispersed onto
hands or clothing. There is, however,
reason to be concerned about exposure to
the radiation emitted from the sealed
source. Sealed sources are not a significant
contamination
hazard
under
normal
conditions; however, they may present an
external exposure hazard.
 Plated
sources
In this form, the radioactive
material
coats
a
disk
or
planchette. This coating may be
covered, depending upon the
type of radiation, by mylar,
aluminum, steel, or plastic.
 Capsules
 In
this form, a capsule usually
made of metal surrounds the
radioactive
material.
These
sources are often placed onto the
end of metal or plastic handling
rods. Another example of a
capsule is when a mixture of
radioactive compounds is placed
into a container and welded or
sealed closed.
 Activated

metal
In this form, a metal wire or foil has been
exposed to a neutron flux to irradiate the metal
and create a radioactive isotope from the original
material. This form of sealed source may have a
plastic or epoxy coating to protect the activated
metal. In some instances, however, the metal is
not protected.
 Many
commonly used laboratory devices
also contain sealed sources, such as gas
chromatographs with electron capture
detectors, liquid scintillation detectors,
and static eliminators.
Sealed sources present an external radiation
hazard as opposed to a contamination hazard.
Sealed sources can emit any type of ionizing
radiation, including alpha particles, beta particles,
gamma rays, x-rays, or neutrons.
 1. Do not touch electroplated sources, as this may
result in the removal of the active material.
 2. Wear gloves when working with a plated or
deposited source.
 3. Monitor hands and fingers after handling a
plated or deposited source.
 4. Do not use handling tools in such a way as to
penetrate the surface of the source.
 5. Storage containers should not have material
that abrades the surface of the electroplated
sources.

 6.
Sealed Sources shall not be opened
under any circumstances!
 7.
Only authorized individuals shall
perform the repair and cleaning of sources.
The safety and handling precautions
furnished by the manufacturer shall be
maintained in a location that is readily
available to all workers and followed.
 8. Storage containers must be properly
labeled.
 The
equipment which may contain sources of
interest in this publication varies widely in
construction and application. Descriptions of
some of the main types of equipment are
provided below
 1.1.
Brachytheraphy (therapy at a short
distance) is a term that is used to describe the
interstitial application of radioactive sources by
placing them directly in the tumour (e.g.
breast, prostate), in moulds (e.g. skin, rectum)
or in special applicators (e.g. vagina, cervix).
Originally, brachytherapy techniques involved
the use of individual needles or manual
afterloading. Relatively low activity sources
were used in these applications. Historically,
226Ra encapsulated in platinum in either needles
or tubes of a few mm in diameter and up to 5
cm in length was used (Fig).

Emission of alpha particles (helium nucleus)
leads to pressure buildup in a sealed capsule. A
buildup of pressure may eventually damage the
encapsulation, resulting in a release of
radioactivity. Remote afterloading techniques
were developed in the 1970s. 226Ra was replaced
mainly by 137Cs and 60Co and more recently by
192Ir and 252Cf. These techniques involve the use
of machines which can contain a large number of
relatively low activity sources, but which taken
together represent a significant inventory stored
in a single, relatively transportable container. An
example of brachytherapy equipment is shown in
Fig. 3. This type of equipment typically contains
activities of up to 185 GBq (usually of 137Cs).
Remote afterloading equipment is used to
arrange sources into an appropriate configuration
and to transfer them either pneumatically or on
the end of a cable into the patient applicator.
 The
other principal medical application of sealed
sources is teletherapy, where a large source
(typically 60Co but possibly 137Cs) of several
hundred TBq is used, external to the body, to
irradiate a tumour. 60Co teletherapy heads can
contain up to 500 TBq of activity.. An example of
a 60Co unit is shown in Fig. 4.
 Sealed
radioactive sources are also used in
medicine for bone densitometry (241Am, 153Gd
and 125I), for whole blood irradiation (137Co,
60Co) and as gamma radiosurgery knives
(60Co).
 In
heavy industries such as steel foundries or
fabrication, portable, mobile or fixed
radiographic equipment incorporating various
radionuclides may be installed in purpose
built enclosures. Mobile or fixed installations
incorporate heavier shielding than portable
source housing
 Typical
industrial applications with their main
isotopes are shown below:
 (a) Industrial radiography: 6oCo, 192Ir, 75Se,
170Tm, 169Yb, 137Cs (historical); 241Am/Be, 252Cf
(neutron radio-graphy);
 (b) Moisture detectors: 241Am/Be, 137Cs,
226Ra/Be, 252Cf;
 (c) Well logging: 241Am/Be, 137Cs;
 (d) Gauges: 137Cs, 6oCo, 241Am, 85Kr,
90Sr(+90Y), 32P, 147Pm;
 (e)
Static eliminators: 241Am, 210Po, 226Ra;
 (f) Lightning rods: 241Am, 85Kr, 226Ra
(historical); (g) Dredgers: 60Co
 (h) X ray fluorescence analysis: 55Fe, 109Cd,
238Pu, 241Am, 57Co;
 (i) Calibration: 60Co, 137Cs;
 (j) Smoke detectors: 241Am, 239Pu.
 Radiography
is the use of ionizing
electromagnetic radiation such as X-rays to
view objects. Although not technically
radiographic techniques, imaging modalities
such as PET and MRI are sometimes grouped
in radiography because the radiology
department of hospitals handle all forms of
imaging. Treatment using radiation is known
as radiotherapy.
 Radiography
started in 1895 with the
discovery of X-rays , a type of
electromagnetic radiation. Soon these
found various applications, from helping to
find shoes that fit, to the more lasting
medical uses.

X-rays were put to diagnostic use very early,
before the dangers of ionizing radiation were
discovered. Initially, many groups of staff
conducted radiography in hospitals, including
physicists, photographers, doctors, nurses, and
engineers. The medical specialty of radiology
grew up around the new technology, and this
lasted many years. When new diagnostic tests
involving X-rays were developed, it was natural
for the radiographers to be trained and adopt this
new technology. This happened first with
fluoroscopy, computed tomography (1960s), and
mammography
Ultrasound (1970s) and magnetic resonance
imaging (1980s) was added to the list of skills
used by radiographers because they are also
medical imaging, but these disciplines do not
use ionizing radiation or X-rays.
 Diagnostic
radiography involves the use of
both ionizing radiation and non-ionizing
radiation to create images for medical
diagnoses. The predominant test is still the Xray. X-rays are the second most commonly
used medical tests, after laboratory tests. This
application
is
known
as
diagnostic
radiography.
 Since
the body is made up of various
substances with differing densities, X-rays
can be used to reveal the internal structure
of the body on film by highlighting these
differences using attenuation, or the
absorption of X-ray photons by the denser
substances (like calcium-rich
bones).
Medical
diagnostic
radiography
is
undertaken
by
a
specially
trained
professional called a diagnostic radiographer
in the UK, or a radiologic technologist in the
USA.

The creation of images by exposing an object to X-rays
or other high-energy forms of electromagnetic
radiation and capturing the resulting remnant beam
(or "shadow") as a latent image is known as
"projection radiography." The "shadow" may be
converted to light using a fluorescent screen, which
is then captured on photographic film, it may be
captured by a phosphor screen to be "read" later by
a laser (CR), or it may directly activate a matrix of
solid-state detectors. Bone and some organs (such as
lungs) especially lend themselves to projection
radiography. It is a relatively low-cost investigation
with a high diagnostic yield.
 Projection radiography uses X-rays in different
amounts and strengths depending on what body part
is being imaged:

Hard tissues such as bone require a relatively high
energy photon source, and typically a tungsten anode
is used with a high voltage (50-150 kVp) on a 3-phase
or high-frequency machine to generate braking
radiation. Bony tissue and metals are denser than the
surrounding tissue, and thus by absorbing more of the
X-ray photons they prevent the film from getting
exposed as much. Wherever dense tissue absorbs or
stops the X-rays, the resulting X-ray film is unexposed,
and appears translucent blue, whereas the black parts
of the film represent lower-density tissues such as fat,
skin, and internal organs, which could not stop the Xrays. This is usually used to see bony fractures, foreign
objects (such as ingested coins), and used for finding
bony pathology such as osteoarthritis, infection
(osteomyelitis), cancer (osteosarcoma), as well as
growth studies (leg length, achondroplasia, scoliosis,
etc.).


Soft tissues are seen with the same machine as for hard
tissues, but a "softer" or less-penetrating X-ray beam is
used. Tissues commonly imaged include the lungs and
heart shadow in a chest X-ray, the air pattern of the
bowel in abdominal X-rays, the soft tissues of the neck,
the orbits by a skull X-ray before an MRI to check for
radiopaque foreign bodies (especially metal), and of
course the soft tissue shadows in X-rays of bony injuries
are looked at by the radiologist for signs of hidden
trauma (for example, the famous "fat pad" sign on a
fractured elbow).
Dental radiography uses a small radiation dose with high
penetration to view teeth, which are relatively dense. A
dentist may examine a painful tooth and gum using X-ray
equipment. The machines used are typically singlephase pulsating DC, the oldest and simplest sort. Dental
technicians or the dentist may run these machines—
radiologic technologists are not required by law to be
present.


Mammography is an X-ray examination of breasts and other soft
tissues. This has been used mostly on women to screen for breast
cancer, but is also used to view male breasts, and used in
conjunction with a radiologist or a surgeon to localise suspicious
tissues before a biopsy or a lumpectomy. Breast implants designed
to enlarge the breasts reduce the viewing ability of mammography,
and require more time for imaging as more views need to be
taken. This is because the material used in the implant is very
dense compared to breast tissue, and looks white (clear) on the
film. The radiation used for mammography tends to be softer (has
a lower photon energy) than that used for the harder tissues.
Often a tube with a molybdenum anode is used with about 30 000
volts (30 kV), giving a range of X-ray energies of about 15-30 keV.
Many of these photons are "characteristic radiation" of a specific
energy determined by the atomic structure of the target material
(Mo-K radiation).
Other modalities are used in radiography when traditional
projection X-ray cannot image what doctors want to see. Below are
other modalities included within radiography; they are only
summaries and more specific information can be viewed by going
to their individual pages