On September 9, 1980, Daniel Berrigan
(above), his brother Philip, and six others (the "Plowshares Eight")
began the Plowshares Movement. They illegally trespassed onto the General Electric Nuclear Missile facility in King of Prussia, Pennsylvania, where they damaged nuclear warhead nose cones and poured blood onto documents and files. They were arrested and charged with over ten different felony and misdemeanor counts.
The Plowshares movement is an anti-nuclear weapons and Christian pacifist
movement that advocates active resistance to war. The group often
practices a form of symbolic protest that involves the damaging of weapons
and military property. The movement gained notoriety in the early 1980s
when several members damaged nuclear warhead nose cones and were
subsequently convicted. The name refers to the text of prophet Isaiah
who said that weapons shall be beaten into plowshares.
And many people shall go and say, Come ye, and let us go up to the mountain of the LORD,
to the house of the God of Jacob; and he will teach us of his ways, and
we will walk in his paths: for out of Zion shall go forth the law, and
the word of the LORD
from Jerusalem. And he shall judge among the nations, and shall rebuke
many people: and they shall beat their swords into plowshares, and their
spears into pruning hooks: nation shall not lift up sword against
nation, neither shall they learn war any more.
On September 9, 1980, Daniel Berrigan, his brother Philip Berrigan, and six others (the "Plowshares Eight") began the Plowshares Movement under the premise of beating swords to ploughshares. They trespassed onto the General Electric Re-entry Division in King of Prussia, Pennsylvania, where Mark 12A reentry vehicles
for the Minuteman III missile were made. They hammered on two reentry
vehicles, poured blood on documents, and offered prayers for peace. They
were arrested and charged with more than ten different felony and
misdemeanor counts.
On April 10, 1990, after 10 years of appeals, the Berrigans' group was
re-sentenced and paroled for up to 23 and 1/2 months in consideration of
time already served in prison. Their legal battle was re-created in Emile de Antonio's 1982 film In the King of Prussia, which starred Martin Sheen and featured appearances by the Plowshares Eight as themselves.
Actions
Other actions followed. As of 2000, some 71 such actions happened on several continents.
There have been several more such actions since 2000. The vast
majority end in prison time for the actors, the longest of which were
those meted out to the 1984 group, the "Silo Pruning Hooks" (after the
Biblical verse admonishing people to turn spears into pruning hooks),
two of which were sentenced to 18 years in federal prison for entering a
Minuteman II missile silo.
Pouring of blood
Pouring of blood is a controversial symbolic act that has been traditionally conducted by Plowshares activists.
Recent actions
On April 30, 2008, three Plowshares activists entered the GCSB Waihopai base near Blenheim, New Zealand and punctured an inflated radome used in the ECHELON
signal interception program, causing $1.2 million in damages. In March
2010 the three men stood trial by jury at the District Court in
Wellington and were acquitted.
The New Zealand Attorney-General then lodged a civil claim, on behalf
of the GCSB, for $1.2 million. This claim was dropped in February 2014.
On November 2, 2009, a Plowshares action took place in the U.S. at Naval Base Kitsap-Bangor, where Trident nuclear weapons are stored or deployed on Trident submarines. These weapons constitute the largest stockpile of nuclear weapons in the US.
On July 28, 2012, three Plowshares activists, Sister Megan Rice, 82, Greg Boertje-Obed, 57, and Michael Walli, 63, who compose the Transform Now Plowshares movement, breached security at the U.S. Department of Energy'sY-12 National Security Complex in Oak Ridge, Tennessee, causing the government to temporarily shut down the weapons facility.
Once inside a "secure" area, the activists hung protest banners on a
uranium storage site, poured human blood and spray-painted the walls
with anti-war slogans.
Following a controversial trial, the three activists were convicted in
early May 2013 on the charges of damaging property in violation of 18
US Code 1363, damaging federal property in excess of $1000 in violation
of 18 US Code 1361, and intending to injure, interfere with, or obstruct
the national defense of the United States and willful damage of
national security premises in violation of 18 US Code 2155.
Megan Rice was sentenced to 35 months, or just under three years. The
other two protesters, Greg Boertje-Obed and Michael Walli, both were
sentenced to 62 months, or a little more than five years.
The National Nuclear Security Administration
has acknowledged the seriousness of the 2012 Plowshares action, which
involved the protesters walking into a high-security zone of the plant,
calling the security breach "unprecedented." Independent security
contractor, WSI, has since had a weeklong "security stand-down," a halt
to weapons production, and mandatory refresher training for all security
staff.
Non-proliferation
policy experts are concerned about the relative ease with which these
unarmed, unsophisticated protesters could cut through a fence and walk
into the center of the facility. This is further evidence that nuclear
security—the securing of highly enriched uranium and plutonium—should be
a top priority to prevent terrorist groups from acquiring nuclear
bomb-making material. These experts have questioned "the use of private
contractors to provide security at facilities that manufacture and store
the government's most dangerous military material".
On April 4, 2018, seven Plowshares activists calling themselves "Kings Bay Plowshares" were arrested at the Kings Bay Naval Submarine Base. They stated that the action had been planned to coincide with the 50th anniversary of the Assassination of Martin Luther King Jr.
The activists were arrested, handed over to local authorities, and
taken to the county jail. The Kings Bay spokesman, Scott Bennett, said
that no one had been threatened and no military personnel or assets were
endangered. The base houses 8 Ohio-class submarines, 6 of which carry ballistic missiles and are described by the Navy as "designed specifically for stealth and the precise delivery of nuclear warheads."
Different
assumptions on the extrapolation of the cancer risk vs. radiation dose
to low-dose levels, given a known risk at a high dose: (A) supra-linearity, (B) linear (C) linear-quadratic, (D) hormesis
Stochastic health effects are those that occur by chance, and whose probability is proportional to the dose, but whose severity is independent of the dose.
The LNT model assumes there is no lower threshold at which stochastic
effects start, and assumes a linear relationship between dose and the
stochastic health risk. In other words, LNT assumes that radiation has
the potential to cause harm at any dose level, and the sum of several
very small exposures is just as likely to cause a stochastic health
effect as a single larger exposure of equal dose value. In contrast, deterministic health effects are radiation-induced effects such as acute radiation syndrome,
which are caused by tissue damage. Deterministic effects reliably
occur above a threshold dose and their severity increases with dose.
Because of the inherent differences, LNT is not a model for
deterministic effects, which are instead characterized by other types of
dose-response relationships.
LNT is a common model to calculate the probability of radiation-induced cancer both at high doses where epidemiology studies support its application but, controversially, also at low doses, which is a dose region that has a lower predictive statistical confidence.
Nonetheless, regulatory bodies commonly use LNT as a basis for
regulatory dose limits to protect against stochastic health effects, as
found in many public health policies.
There are three active (as of 2016) challenges to the LNT model currently being considered by the US Nuclear Regulatory Commission. One was filed by Nuclear Medicine Professor Carol Marcus of UCLA, who calls the LNT model scientific "baloney".
Whether the model describes the reality for small-dose exposures is disputed. It opposes two competing schools of thought: the threshold model, which assumes that very small exposures are harmless, and the radiation hormesis
model, which claims that radiation at very small doses can be
beneficial. Because the current data are inconclusive, scientists
disagree on which model should be used. Pending any definitive answer to
these questions and the precautionary principle, the model is sometimes used to quantify the cancerous effect of collective doses
of low-level radioactive contaminations, even though it estimates a
positive number of excess deaths at levels that would have had zero
deaths, or saved lives, in the two other models. Such practice has been
condemned by the International Commission on Radiological Protection.
One of the organizations for establishing recommendations on radiation protection guidelines internationally, the UNSCEAR,
recommended policies in 2014 that do not agree with the LNT model at
exposure levels below background levels. The recommendation states "the
Scientific Committee does not recommend multiplying very low doses by
large numbers of individuals to estimate numbers of radiation-induced
health effects within a population exposed to incremental doses at
levels equivalent to or lower than natural background levels." This is a
reversal from previous recommendations by the same organization.
The LNT model is sometimes applied to other cancer hazards such as polychlorinated biphenyls in drinking water.
Origins
Increased Risk of Solid Cancer with Dose for A-bomb survivors,
from BEIR report. Notably this exposure pathway occurred from
essentially a massive spike or pulse of radiation, a result of the brief
instant that the bomb exploded, which while somewhat similar to the
environment of a CT scan, it is wholly unlike the low dose rate of living in a contaminated area such as Chernobyl, were the dose rate is orders of magnitude smaller. However LNT does not consider dose rate and is an unsubstantiated one size fits all approach based solely on total absorbed dose.
When the two environments and cell effects are vastly different.
Likewise, it has also been pointed out that bomb survivors inhaled
carcinogenic benzopyrene from the burning cities, yet this is not factored in.
The association of exposure to radiation with cancer had been observed as early as 1902, six years after the discovery of X-ray by Wilhelm Röntgen and radioactivity by Henri Becquerel. In 1927, Hermann Muller demonstrated that radiation may cause genetic mutation. He also suggested mutation as a cause of cancer. Muller, who received a Nobel Prize for his work on the mutagenic
effect of radiation in 1946, asserted in his Nobel Lecture, "The
Production of Mutation", that mutation frequency is "directly and simply
proportional to the dose of irradiation applied" and that there is "no
threshold dose".
The early studies were based on relatively high levels of
radiation that made it hard to establish the safety of low level of
radiation, and many scientists at that time believed that there may be a
tolerance level, and that low doses of radiation may not be harmful. A
later study in 1955 on mice exposed to low dose of radiation suggest
that they may outlive control animals. The interest in the effect of radiation intensified after the dropping of atomic bombs on Hiroshima and Nagasaki,
and studies were conducted on the survivors. Although compelling
evidence on the effect of low dosage of radiation was hard to come by,
by the late 1940s, the idea of LNT became more popular due to its
mathematical simplicity. In 1954, the National Council on Radiation Protection and Measurements (NCRP) introduced the concept of maximum permissible dose. In 1958, United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR) assessed the LNT model and a threshold model, but noted the
difficulty in acquiring "reliable information about the correlation
between small doses and their effects either in individuals or in large
populations". The United States Congress Joint Committee on Atomic Energy
(JCAE) similarly could not establish if there is a threshold or "safe"
level for exposure, nevertheless it introduced the concept of "As Low As Reasonably Achievable"
(ALARA). ALARA would become a fundamental principle in radiation
protection policy that implicitly accepts the validity of LNT. In 1959,
United States Federal Radiation Council (FRC) supported the concept of
the LNT extrapolation down to the low dose region in its first report.
By the 1970s, the LNT model had become accepted as the standard in radiation protection practice by a number of bodies. In 1972, the first report of National Academy of Sciences (NAS) Biological Effects of Ionizing Radiation
(BEIR), an expert panel who reviewed available peer reviewed
literature, supported the LNT model on pragmatic grounds, noting that
while "dose-effect relationship for x rays and gamma rays may not be a
linear function", the "use of linear extrapolation . . . may be
justified on pragmatic grounds as a basis for risk estimation." In its
seventh report of 2006, NAS BEIR VII writes, "the committee concludes
that the preponderance of information indicates that there will be some
risk, even at low doses".
Radiation precautions and public policy
Radiation precautions have led to sunlight being listed as a carcinogen at all sun exposure rates, due to the ultraviolet
component of sunlight, with no safe level of sunlight exposure being
suggested, following the precautionary LNT model. According to a 2007
study submitted by the University of Ottawa to the Department of Health
and Human Services in Washington, D.C., there is not enough information
to determine a safe level of sun exposure at this time.
If a particular dose of radiation is found to produce one extra
case of a type of cancer in every thousand people exposed, LNT projects
that one thousandth of this dose will produce one extra case in every
million people so exposed, and that one millionth of the original dose
will produce one extra case in every billion people exposed. The
conclusion is that any given dose equivalent of radiation will produce the same number of cancers, no matter how thinly it is spread. This allows the summation by dosimeters of all radiation exposure, without taking into consideration dose levels or dose rates.
The model is simple to apply: a quantity of radiation can be
translated into a number of deaths without any adjustment for the
distribution of exposure, including the distribution of exposure within a
single exposed individual. For example, a hot particle embedded in an organ (such as lung) results in a very high dose in the cells directly adjacent to the hot particle,
but a much lower whole-organ and whole-body dose. Thus, even if a safe
low dose threshold was found to exist at cellular level for
radiation-induced mutagenesis,
the threshold would not exist for environmental pollution with hot
particles, and could not be safely assumed to exist when the
distribution of dose is unknown.
The linear no-threshold model is used to extrapolate the expected number of extra deaths caused by exposure to environmental radiation, and it therefore has a great impact on public policy. The model is used to translate any radiation release, like that from a "dirty bomb", into a number of lives lost, while any reduction in radiation exposure, for example as a consequence of radon
detection, is translated into a number of lives saved. When the doses
are very low, at natural background levels, in the absence of evidence,
the model predicts via extrapolation, new cancers only in a very small
fraction of the population, but for a large population, the number of
lives is extrapolated into hundreds or thousands, and this can sway
public policy.
A linear model has long been used in health physics to set maximum acceptable radiation exposures.
The United States-based National Council on Radiation Protection and Measurements (NCRP), a body commissioned by the United States Congress,
recently released a report written by the national experts in the field
which states that, radiation's effects should be considered to be
proportional to the dose an individual receives, regardless of how small
the dose is.
A 1958 analysis of two decades of research on the mutation rate
of 1 million lab mice showed that six major hypotheses about ionizing
radiation and gene mutation were not supported by data. Its data was used in 1972 by the Biological Effects of Ionizing Radiation I
committee to support the LNT model. However, it has been claimed that
the data contained a fundamental error that was not revealed to the
committee, and would not support the LNT model on the issue of mutations
and may suggest a threshold dose rate under which radiation does not produce any mutations. The acceptance of the LNT model has been challenged by a number of scientists, see controversy section below.
Fieldwork
The
LNT model and the alternatives to it each have plausible mechanisms
that could bring them about, but definitive conclusions are hard to make
given the difficulty of doing longitudinal studies involving large cohorts over long periods.
A 2003 review of the various studies published in the authoritative Proceedings of the National Academy of Sciences
concludes that "given our current state of knowledge, the most
reasonable assumption is that the cancer risks from low doses of x- or
gamma-rays decrease linearly with decreasing dose."
A 2005 study of Ramsar, Iran
(a region with very high levels of natural background radiation) showed
that lung cancer incidence was lower in the high-radiation area than in
seven surrounding regions with lower levels of natural background
radiation. A fuller epidemiological study of the same region showed no difference in mortality for males, and a statistically insignificant increase for females.
A 2009 study by researchers that looks at Swedish children exposed to fallout from Chernobyl while they were fetuses between 8 and 25 weeks gestation concluded that the reduction in IQ
at very low doses was greater than expected, given a simple LNT model
for radiation damage, indicating that the LNT model may be too
conservative when it comes to neurological damage. However, in medical journals, studies detail that in Sweden in the year of the Chernobyl accident, the birth rate, both increased and shifted to those of "higher maternal age" in 1986. More advanced maternal age in Swedish mothers was linked with a reduction in offspring IQ, in a paper published in 2013. Neurological damage has a different biology than cancer.
In a 2009 study
cancer rates among UK radiation workers were found to increase with
higher recorded occupational radiation doses. The doses examined varied
between 0 and 500 mSv received over their working lives. These results
exclude the possibilities of no increase in risk or that the risk is 2-3
times that for A-bomb survivors with a confidence level of 90%. The
cancer risk for these radiation workers was still less than the average
for persons in the UK due to the healthy worker effect.
A 2009 study focusing on the naturally high background radiation region of Karunagappalli, India concluded: "our cancer incidence study, together with previously reported cancer mortality studies in the HBR area of Yangjiang, China, suggests it is unlikely that estimates of risk at low doses are substantially greater than currently believed."
A 2011 meta-analysis further concluded that the "Total whole body
radiation doses received over 70 years from the natural environment high
background radiation areas in Kerala, India and Yanjiang, China are
much smaller than [the non-tumour dose, "defined as the highest dose of
radiation at which no statistically significant tumour increase was
observed above the control level"] for the respective dose-rates in each
district."
In 2011 an in vitro time-lapse study of the cellular
response to low doses of radiation showed a strongly non-linear response
of certain cellular repair mechanisms called radiation-induced foci
(RIF). The study found that low doses of radiation prompted higher rates
of RIF formation than high doses, and that after low-dose exposure RIF
continued to form after the radiation had ended.
In 2012 a historical cohort study of >175 000 patients without
previous cancer who were examined with CT head scans in UK between 1985
and 2002 was published.
The study, which investigated leukaemia and brain cancer, indicated a
linear dose response in the low dose region and had qualitative
estimates of risk that were in agreement with the Life Span Study (Epidemiology data for low-linear energy transfer radiation).
In 2013 a data linkage study of 11 million Australians with
>680 000 people exposed to CT scans between 1985 and 2005 was
published.
The study confirmed the results of the 2012 UK study for leukaemia and
brain cancer but also investigated other cancer types. The authors
conclude that their results were generally consistent with the linear no
threshold theory.
Controversy
The LNT model has been contested by a number of scientists. It is been claimed that the early proponent of the model Hermann Joseph Muller
intentionally ignored an early study that did not support the LNT model
when he gave his 1946 Nobel Prize address advocating the model.
It is also argued that LNT model had caused an irrational fear of radiation. In the wake of the 1986 Chernobyl accident in Ukraine,
Europe-wide anxieties were fomented in pregnant mothers over the
perception enforced by the LNT model that their children would be born
with a higher rate of mutations. As far afield as the country of Denmark, hundreds of excess induced abortions were performed on the healthy unborn, out of this no-threshold fear. Following the accident however, studies of data sets approaching a million births in the EUROCAT
database, divided into "exposed" and control groups were assessed in
1999. As no Chernobyl impacts were detected, the researchers conclude
"in retrospect the widespread fear in the population about the possible
effects of exposure on the unborn was not justified".
Despite studies from Germany and Turkey, the only robust evidence of
negative pregnancy outcomes that transpired after the accident were
these elective abortion indirect effects, in Greece, Denmark, Italy
etc., due to the anxieties created.
In very high dose radiation therapy,
it was known at the time that radiation can cause a physiological
increase in the rate of pregnancy anomalies, however, human exposure
data and animal testing suggests that the "malformation of organs
appears to be a deterministic effect with a threshold dose" below which, no rate increase is observed. A review in 1999 on the link between the Chernobyl accident and teratology
(birth defects) concludes that "there is no substantive proof regarding
radiation‐induced teratogenic effects from the Chernobyl accident". It is argued that the human body has defense mechanisms, such as DNA repair and programmed cell death, that would protect it against carcinogenesis due to low-dose exposures of carcinogens.
Ramsar, located in Iran,
is often quoted as being a counter example to LNT. Based on preliminary
results, it was considered as having the highest natural background
radiation levels on Earth, several times higher than the ICRP-recommended radiation dose limits for radiation workers, whilst the local population did not seem to suffer any ill effects. However, the population of the high-radiation districts is small (about 1800 inhabitants) and only receive an average of 6 millisieverts per year, so that cancer epidemiology data are too imprecise to draw any conclusions. On the other hand, there may be non-cancer effects from the background radiation such as
chromosomal aberrations or female infertility.
A 2011 research of the cellular repair mechanisms support the evidence against the linear no-threshold model.
According to its authors, this study published in the Proceedings of
the National Academy of Sciences of the United States of America "casts
considerable doubt on the general assumption that risk to ionizing
radiation is proportional to dose".
However, a 2011 review of studies addressing childhood leukaemia
following exposure to ionizing radiation, including both diagnostic
exposure and natural background exposure, concluded that existing risk
factors, excess relative risk per Sv (ERR/Sv), is "broadly applicable"
to low dose or low dose-rate exposure.
Several expert scientific panels have been convened on the
accuracy of the LNT model at low dosage, and various organizations and
bodies have stated their positions on this topic:
The
assumption that any stimulatory hormetic effects from low doses of
ionizing radiation will have a significant health benefit to humans that
exceeds potential detrimental effects from the radiation exposure is
unwarranted at this time.
In 2005 the United States National Academies' National Research
Council published its comprehensive meta-analysis of low-dose radiation
research BEIR VII, Phase 2. In its press release the Academies stated:
The scientific research base shows that there is no
threshold of exposure below which low levels of ionizing radiation can
be demonstrated to be harmless or beneficial.
Until
the [...] uncertainties on low-dose response are resolved, the
Committee believes that an increase in the risk of tumour induction
proportionate to the radiation dose is consistent with developing
knowledge and that it remains, accordingly, the most scientifically
defensible approximation of low-dose response. However, a strictly
linear dose response should not be expected in all circumstances.
Underlying
the risk models is a large body of epidemiological and radiobiological
data. In general, results from both lines of research are consistent
with a linear, no-threshold dose (LNT) response model in which the risk
of inducing a cancer in an irradiated tissue by low doses of radiation
is proportional to the dose to that tissue.
Oppose
A number of organisations disagree with using the Linear no-threshold
model to estimate risk from environmental and occupational low-level
radiation exposure:
The French Academy of Sciences (Académie des Sciences) and the National Academy of Medicine (Académie Nationale de Médecine)
published a report in 2005 (at the same time as BEIR VII report in the
United States) that rejected the Linear no-threshold model in favor of a
threshold dose response and a significantly reduced risk at low
radiation exposure:
In conclusion, this report raises
doubts on the validity of using LNT for evaluating the carcinogenic risk
of low doses (< 100 mSv) and even more for very low doses (< 10
mSv). The LNT concept can be a useful pragmatic tool for assessing rules
in radioprotection for doses above 10 mSv; however since it is not
based on biological concepts of our current knowledge, it should not be
used without precaution for assessing by extrapolation the risks
associated with low and even more so, with very low doses (< 10 mSv),
especially for benefit-risk assessments imposed on radiologists by the
European directive 97-43.
The Health Physics Society's position statement first adopted in January 1996, as revised in July 2010, states:
In accordance with current
knowledge of radiation health risks, the Health Physics Society
recommends against quantitative estimation of health risks below an
individual dose of 5 rem (50 mSv) in one year or a lifetime dose of 10
rem (100 mSv) above that received from natural sources. Doses from
natural background radiation in the United States average about 0.3 rem
(3 mSv) per year. A dose of 5 rem (50 mSv) will be accumulated in the
first 17 years of life and about 25 rem (250 mSv) in a lifetime of 80
years. Estimation of health risk associated with radiation doses that
are of similar magnitude as those received from natural sources should
be strictly qualitative and encompass a range of hypothetical health
outcomes, including the possibility of no adverse health effects at such
low levels.
The American Nuclear Society
recommended further research on the Linear No Threshold Hypothesis
before making adjustments to current radiation protection guidelines,
concurring with the Health Physics Society's position that:
There
is substantial and convincing scientific evidence for health risks at
high dose. Below 10 rem or 100 mSv (which includes occupational and
environmental exposures) risks of health effects are either too small to
be observed or are non-existent.
Intermediate
The US Nuclear Regulatory Commission
takes the intermediate position that "accepts the LNT hypothesis as a
conservative model for estimating radiation risk", but noting that
"public health data do not absolutely establish the occurrence of cancer
following exposure to low doses and dose rates — below about 10,000
mrem (100 mSv). Studies of occupational workers who are chronically
exposed to low levels of radiation above normal background have shown no
adverse biological effects."
Mental health effects
The consequences of low-level radiation are often more psychological
than radiological. Because damage from very-low-level radiation cannot
be detected, people exposed to it are left in anguished uncertainty
about what will happen to them. Many believe they have been
fundamentally contaminated for life and may refuse to have children for
fear of birth defects. They may be shunned by others in their community who fear a sort of mysterious contagion.
Forced evacuation from a radiation or nuclear accident may lead
to social isolation, anxiety, depression, psychosomatic medical
problems, reckless behavior, even suicide. Such was the outcome of the
1986 Chernobyl nuclear disaster
in the Ukraine. A comprehensive 2005 study concluded that "the mental
health impact of Chernobyl is the largest public health problem
unleashed by the accident to date". Frank N. von Hippel, a U.S. scientist, commented on the 2011 Fukushima nuclear disaster,
saying that "fear of ionizing radiation could have long-term
psychological effects on a large portion of the population in the
contaminated areas".
Such great psychological danger does not accompany other
materials that put people at risk of cancer and other deadly illness.
Visceral fear is not widely aroused by, for example, the daily emissions
from coal burning, although, as a National Academy of Sciences study
found, this causes 10,000 premature deaths a year in the US. It is "only
nuclear radiation that bears a huge psychological burden — for it
carries a unique historical legacy".
The modern practice of radiology involves several different
healthcare professions working as a team. The radiologist is a medical
doctor who has completed the appropriate post-graduate training and
interprets medical images, communicates these findings to other
physicians by means of a report or verbally, and uses imaging to perform
minimally invasive medical procedures. The nurse
is involved in the care of patients before and after imaging or
procedures, including administration of medications, monitoring of vital
signs and monitoring of sedated patients. The radiographer, also known as a "radiologic technologist" in some countries such as the United States,
is a specially trained healthcare professional that uses sophisticated
technology and positioning techniques to produce medical images for the
radiologist to interpret. Depending on the individual's training and
country of practice, the radiographer may specialize in one of the
above-mentioned imaging modalities or have expanded roles in image
reporting.
Radiographs (originally called roentgenographs, named after the discoverer of X-rays, Wilhelm Conrad Röntgen)
are produced by transmitting X-rays through a patient. The X-rays are
projected through the body onto a detector; an image is formed based on
which rays pass through (and are detected) versus those that are
absorbed or scattered in the patient (and thus are not detected).
Röntgen discovered X-rays on November 8, 1895 and received the first Nobel Prize in Physics for their discovery in 1901.
In film-screen radiography, an X-ray tube generates a beam of
X-rays, which is aimed at the patient. The X-rays that pass through the
patient are filtered through a device called an grid or X-ray filter,
to reduce scatter, and strike an undeveloped film, which is held
tightly to a screen of light-emitting phosphors in a light-tight
cassette. The film is then developed chemically and an image appears on
the film. Film-screen radiography is being replaced by phosphor plate radiography but more recently by digital radiography (DR) and the EOS imaging.
In the two latest systems, the X-rays strike sensors that converts the
signals generated into digital information, which is transmitted and
converted into an image displayed on a computer screen. In digital radiography
the sensors shape a plate, but in the EOS system, which is a
slot-scanning system, a linear sensor vertically scans the patient.
Plain radiography was the only imaging modality available during
the first 50 years of radiology. Due to its availability, speed, and
lower costs compared to other modalities, radiography is often the
first-line test of choice in radiologic diagnosis. Also despite the
large amount of data in CT scans, MR scans and other digital-based
imaging, there are many disease entities in which the classic diagnosis
is obtained by plain radiographs. Examples include various types of
arthritis and pneumonia, bone tumors (especially benign bone tumors),
fractures, congenital skeletal anomalies, etc.
Fluoroscopy and angiography are special applications of X-ray imaging, in which a fluorescent screen and image intensifier tube is connected to a closed-circuit television system. This allows real-time imaging of structures in motion or augmented with a radiocontrast
agent. Radiocontrast agents are usually administered by swallowing or
injecting into the body of the patient to delineate anatomy and
functioning of the blood vessels, the genitourinary system, or the gastrointestinal tract (GI tract). Two radiocontrast agents are presently in common use. Barium sulfate (BaSO4)
is given orally or rectally for evaluation of the GI tract. Iodine, in
multiple proprietary forms, is given by oral, rectal, vaginal,
intra-arterial or intravenous routes. These radiocontrast agents
strongly absorb or scatter X-rays, and in conjunction with the real-time
imaging, allow demonstration of dynamic processes, such as peristalsis
in the digestive tract or blood flow in arteries and veins. Iodine
contrast may also be concentrated in abnormal areas more or less than in
normal tissues and make abnormalities (tumors, cysts, inflammation)
more conspicuous. Additionally, in specific circumstances, air can be
used as a contrast agent for the gastrointestinal system and carbon
dioxide can be used as a contrast agent in the venous system; in these
cases, the contrast agent attenuates the X-ray radiation less than the
surrounding tissues.
CT imaging uses X-rays in conjunction with computing algorithms to image the body.
In CT, an X-ray tube opposite an X-ray detector (or detectors) in a
ring-shaped apparatus rotate around a patient, producing a
computer-generated cross-sectional image (tomogram). CT is acquired in
the axial
plane, with coronal and sagittal images produced by computer
reconstruction. Radiocontrast agents are often used with CT for enhanced
delineation of anatomy. Although radiographs provide higher spatial
resolution, CT can detect more subtle variations in attenuation of
X-rays (higher contrast resolution). CT exposes the patient to
significantly more ionizing radiation than a radiograph.
Spiral multidetector CT uses 16, 64, 254 or more detectors during
continuous motion of the patient through the radiation beam to obtain
fine detail images in a short exam time. With rapid administration of
intravenous contrast during the CT scan, these fine detail images can be
reconstructed into three-dimensional (3D) images of carotid, cerebral,
coronary or other arteries.
The introduction of computed tomography in the early 1970s
revolutionized diagnostic radiology by providing Clinicians with images
of real three-dimensional anatomic structures. CT scanning has become
the test of choice in diagnosing some urgent and emergent conditions,
such as cerebral hemorrhage, pulmonary embolism (clots in the arteries of the lungs), aortic dissection (tearing of the aortic wall), appendicitis, diverticulitis,
and obstructing kidney stones. Continuing improvements in CT
technology, including faster scanning times and improved resolution,
have dramatically increased the accuracy and usefulness of CT scanning,
which may partially account for increased use in medical diagnosis.
Ultrasound
Medical ultrasonography uses ultrasound (high-frequency sound waves)
to visualize soft tissue structures in the body in real time. No ionizing radiation
is involved, but the quality of the images obtained using ultrasound is
highly dependent on the skill of the person (ultrasonographer)
performing the exam and the patient's body size. Examinations of larger,
overweight patients may have a decrease in image quality as their subcutaneous fat
absorbs more of the sound waves. This results in fewer sound waves
penetrating to organs and reflecting back to the transducer, resulting
in loss of information and a poorer quality image. Ultrasound is also
limited by its inability to image through air pockets (lungs, bowel
loops) or bone. Its use in medical imaging has developed mostly within
the last 30 years. The first ultrasound images were static and
two-dimensional (2D), but with modern ultrasonography, 3D
reconstructions can be observed in real time, effectively becoming "4D".
Because ultrasound imaging techniques do not employ ionizing
radiation to generate images (unlike radiography, and CT scans), they
are generally considered safer and are therefore more common in obstetrical imaging.
The progression of pregnancies can be thoroughly evaluated with less
concern about damage from the techniques employed, allowing early
detection and diagnosis of many fetal anomalies. Growth can be assessed
over time, important in patients with chronic disease or
pregnancy-induced disease, and in multiple pregnancies (twins, triplets,
etc.). Color-flow Doppler ultrasound measures the severity of peripheral vascular disease and is used by cardiologists for dynamic evaluation of the heart, heart valves and major vessels. Stenosis, for example, of the carotid arteries may be a warning sign for an impending stroke. A clot,
embedded deep in one of the inner veins of the legs, can be found via
ultrasound before it dislodges and travels to the lungs, resulting in a
potentially fatal pulmonary embolism. Ultrasounds is useful as a guide to performing biopsies to minimise damage to surrounding tissues and in drainages such as thoracentesis. Small, portable ultrasound devices now replace peritoneal lavage in trauma wards by non-invasively assessing for the presence of internal bleeding and any internal organ damage. Extensive internal bleeding or injury to the major organs may require surgery and repair.
Magnetic resonance imaging
MRI of the knee.
MRI uses strong magnetic fields to align atomic nuclei (usually hydrogenprotons) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states.
The radio signals are collected by small antennae, called coils,
placed near the area of interest. An advantage of MRI is its ability to
produce images in axial, coronal, sagittal
and multiple oblique planes with equal ease. MRI scans give the best
soft tissue contrast of all the imaging modalities. With advances in
scanning speed and spatial resolution, and improvements in computer 3D
algorithms and hardware, MRI has become an important tool in
musculoskeletal radiology and neuroradiology.
One disadvantage is the patient has to hold still for long
periods of time in a noisy, cramped space while the imaging is
performed. Claustrophobia (fear of closed spaces) severe enough to
terminate the MRI exam is reported in up to 5% of patients. Recent
improvements in magnet design including stronger magnetic fields (3 teslas),
shortening exam times, wider, shorter magnet bores and more open magnet
designs, have brought some relief for claustrophobic patients. However,
for magnets with equivalent field strengths, there is often a trade-off
between image quality and open design. MRI has great benefit in imaging
the brain, spine, and musculoskeletal system. The use of MRI is
currently contraindicated for patients with pacemakers, cochlear
implants, some indwelling medication pumps, certain types of cerebral
aneurysm clips, metal fragments in the eyes and some metallic hardware
due to the powerful magnetic fields and strong fluctuating radio signals
to which the body is exposed. Areas of potential advancement include
functional imaging, cardiovascular MRI, and MRI-guided therapy.
Nuclear medicine
Nuclear medicine imaging involves the administration into the patient
of radiopharmaceuticals consisting of substances with affinity for
certain body tissues labeled with radioactive tracer. The most commonly
used tracers are technetium-99m, iodine-123, iodine-131, gallium-67,
indium-111, thallium-201 and fludeoxyglucose (18F) (18F-FDG). The heart, lungs, thyroid, liver, brain, gallbladder, and bones are commonly evaluated for particular conditions using these techniques. While anatomical detail is limited in these studies, nuclear medicine is useful in displaying physiological
function. The excretory function of the kidneys, iodine-concentrating
ability of the thyroid, blood flow to heart muscle, etc. can be
measured. The principal imaging devices are the gamma camera
and the PET Scanner, which detect the radiation emitted by the tracer
in the body and display it as an image. With computer processing, the
information can be displayed as axial, coronal and sagittal images
(single-photon emission computed tomography - SPECT or Positron-emission
tomography - PET). In the most modern devices, nuclear medicine images
can be fused with a CT scan taken quasisimultaneously, so the physiological information can be overlaid or coregistered with the anatomical structures to improve diagnostic accuracy.
Positron emission tomography (PET) scanning deals with positrons instead of gamma rays detected by gamma cameras.
The positrons annihilate to produce two opposite traveling gamma rays
to be detected coincidentally, thus improving resolution. In PET
scanning, a radioactive, biologically active substance, most often
18F-FDG, is injected into a patient and the radiation emitted by the
patient is detected to produce multiplanar images of the body.
Metabolically more active tissues, such as cancer, concentrate the
active substance more than normal tissues. PET images can be combined
(or "fused") with anatomic (CT) imaging, to more accurately localize PET
findings and thereby improve diagnostic accuracy.
The fusion technology has gone further to combine PET and MRI similar to PET and CT. PET/MRI
fusion, largely practiced in academic and research settings, could
potentially play a crucial role in fine detail of brain imaging, breast
cancer screening, and small joint imaging of the foot. The technology
recently blossomed after passing the technical hurdle of altered
positron movement in strong magnetic field thus affecting the resolution
of PET images and attenuation correction.
Interventional radiology
Interventional radiology (IR or sometimes VIR for vascular and
interventional radiology) is a subspecialty of radiology in which
minimally invasive procedures are performed using image guidance. Some
of these procedures are done for purely diagnostic purposes (e.g., angiogram), while others are done for treatment purposes (e.g., angioplasty).
The basic concept behind interventional radiology is to diagnose or treat pathologies,
with the most minimally invasive technique possible. Minimally invasive
procedures are currently performed more than ever before. These
procedures are often performed with the patient fully awake, with little
or no sedation required. Interventional Radiologists and Interventional
Radiographers diagnose and treat several disorders, including peripheral vascular disease, renal artery stenosis, inferior vena cava filter placement, gastrostomy tube placements, biliarystents and hepatic interventions. Images are used for guidance, and the primary instruments used during the procedure are needles and catheters.
The images provide maps that allow the clinician to guide these
instruments through the body to the areas containing disease. By
minimizing the physical trauma to the patient, peripheral interventions
can reduce infection rates and recovery times, as well as hospital
stays. To be a trained interventionalist in the United States, an
individual completes a five-year residency in radiology and a one- or
two-year fellowship in IR.
Teleradiology is the transmission of radiographic images from one
location to another for interpretation by an appropriately trained
professional, usually a Radiologist or Reporting Radiographer. It is
most often used to allow rapid interpretation of emergency room, ICU and
other emergent examinations after hours of usual operation, at night
and on weekends. In these cases, the images can be sent across time
zones (e.g. to Spain, Australia, India) with the receiving Clinician
working his normal daylight hours. However at present, large private
teleradiology companies in the U.S. currently provide most after-hours
coverage employing night working Radiologists in the U.S. Teleradiology
can also be used to obtain consultation with an expert or subspecialist
about a complicated or puzzling case. In the U.S., many hospitals
outsource their radiology departments to radiologists in India due to
the lowered cost and availability of high speed internet access.
Teleradiology requires a sending station, a high-speed internet
connection, and a high-quality receiving station. At the transmission
station, plain radiographs
are passed through a digitizing machine before transmission, while CT,
MRI, ultrasound and nuclear medicine scans can be sent directly, as they
are already digital data. The computer at the receiving end will need
to have a high-quality display screen that has been tested and cleared
for clinical purposes. Reports are then transmitted to the requesting
clinician.
The major advantage of teleradiology is the ability to use different
time zones to provide real-time emergency radiology services
around-the-clock. The disadvantages include higher costs, limited
contact between the referrer and the reporting Clinician, and the
inability to cover for procedures requiring an onsite reporting
Clinician. Laws and regulations concerning the use of teleradiology vary
among the states, with some requiring a license to practice medicine in
the state sending the radiologic exam. In the U.S., some states require
the teleradiology report to be preliminary with the official report
issued by a hospital staff Radiologist. Lastly, the major benefit of
teleradiology is that it can be automated with modern machine learning
techniques.
X-ray of a hand with calculation of bone age analysis
Professional training
United States
Radiology
is a field in medicine that has expanded rapidly after 2000 due to
advances in computer technology, which is closely linked to modern
imaging techniques. Applying for residency positions in radiology is
relatively competitive. Applicants are often near the top of their
medical school classes, with high USMLE (board) examination scores.
Diagnostic radiologists must complete prerequisite undergraduate
education, four years of medical school to earn a medical degree (D.O. or M.D.), one year of internship, and four years of residency training. After residency, radiologists may pursue one or two years of additional specialty fellowship training.
The American Board of Radiology
(ABR) administers professional certification in Diagnostic Radiology,
Radiation Oncology and Medical Physics as well as subspecialty
certification in neuroradiology, nuclear radiology, pediatric radiology
and vascular and interventional radiology. "Board Certification" in
diagnostic radiology requires successful completion of two examinations.
The Core Exam is given after 36 months of residency. This
computer-based examination is given twice a year in Chicago and Tucson.
It encompasses 18 categories. A pass of all 18 is a pass. A fail on 1 to
5 categories is a Conditioned exam and the resident will need to retake
and pass the failed categories. A fail on over 5 categories is a failed
exam. The Certification Exam, can be taken 15 months after completion
of the Radiology residency. This computer-based examination consists of 5
modules and graded pass-fail. It is given twice a year in Chicago and
Tucson. Recertification examinations are taken every 10 years, with
additional required continuing medical education as outlined in the
Maintenance of Certification document.
Following completion of residency training, Radiologists may
either begin practicing as a general Diagnostic Radiologist or enter
into subspecialty training programs known as fellowships. Examples of
subspeciality training in radiology include abdominal imaging, thoracic
imaging, cross-sectional/ultrasound, MRI, musculoskeletal imaging, interventional radiology, neuroradiology, interventional neuroradiology, paediatric radiology,
nuclear medicine, emergency radiology, breast imaging and women's
imaging. Fellowship training programs in radiology are usually one or
two years in length.
Some medical schools in the US have started to incorporate a
basic radiology introduction into their core MD training. New York
Medical College, the Wayne State University School of Medicine, Weill Cornell
Medicine, the Uniformed Services University, and the University of
South Carolina School of Medicine offer an introduction to radiology
during their respective MD programs.
Campbell University School of Osteopathic Medicine also integrates
imaging material into their curriculum early in the first year.
Radiographic exams are usually performed by Radiographers. Qualifications for Radiographers vary by country, but many Radiographers now are required to hold a degree.
Veterinary Radiologists are veterinarians who specialize in the
use of X-rays, ultrasound, MRI and nuclear medicine for diagnostic
imaging or treatment of disease in animals. They are certified in either
diagnostic radiology or radiation oncology by the American College of
Veterinary Radiology.
United Kingdom
Radiology
is an extremely competitive speciality in the UK, attracting applicants
from a broad range of backgrounds. Applicants are welcomed directly
from the foundation programme,
as well as those who have completed higher training. Recruitment and
selection into training post in clinical radiology posts in England,
Scotland and Wales is done by an annual nationally coordinated process
lasting from November to March. In this process, all applicants are
required to pass a Specialty Recruitment Assessment (SRA) test.
Those with a test score above a certain threshold are offered a single
interview at the London and the South East Recruitment Office. At a later stage, applicants declare what programs they prefer, but may in some cases be placed in a neighbouring region.
The training programme lasts for a total of five years. During
this time, doctors rotate into different subspecialities, such as
paediatrics, musculoskeletal or neuroradiology, and breast imaging.
During the first year of training, radiology trainees are expected to
pass the first part of the Fellowship of the Royal College of Radiologists
(FRCR) exam. This comprises a medical physics and anatomy examination.
Following completion of their part 1 exam, they are then required to
pass six written exams (part 2A), which cover all the subspecialities.
Successful completion of these allows them to complete the FRCR by
completing part 2B, which includes rapid reporting, and a long case
discussion.
After achieving a certificate of completion of training
(CCT), many fellowship posts exist in specialities such as
neurointervention and vascular intervention, which would allow the
Doctor to work as an Interventional Radiologist. In some cases, the CCT
date can be deferred by a year to include these fellowship programmes.
UK radiology registrars are represented by the Society of
Radiologists in Training (SRT), which was founded in 1993 under the
auspices of the Royal College of Radiologists.
The society is a nonprofit organisation, run by radiology registrars
specifically to promote radiology training and education in the UK.
Annual meetings are held by which trainees across the country are
encouraged to attend.
Currently, a shortage of radiologists in the UK has created
opportunities in all specialities, and with the increased reliance on
imaging, demand is expected to increase in the future. Radiographers, and less frequently Nurses,
are often trained to undertake many of these opportunities in order to
help meet demand. Radiographers often may control a "list" of a
particular set of procedures after being approved locally and signed off
by a Consultant Radiologist. Similarly, Radiographers may simply
operate a list for a Radiologist or other Physician on their behalf.
Most often if a Radiographer operates a list autonomously then they are
acting as the Operator and Practitioner under the Ionising Radiation
(Medical Exposures) Regulations 2000. Radiographers are represented by a
variety of bodies, most often this is the Society and College of Radiographers. Collaboration with Nurses is also common, where a list may be jointly organised between the Nurse and Radiographer.
Germany
After
obtaining medical licensure, German Radiologists complete a five-year
residency, culminating with a board examination (known as Facharztprüfung).
Italy
The
radiology training program in Italy increased from four to five years in
2008. Further training is required for specialization in radiotherapy
or nuclear medicine.
The Netherlands
Dutch radiologists complete a five-year residency program after completing the 6-year MD program.
India
The radiology training course is a post graduate 3-year program (MD/DNB Radiology) or a 2-year diploma (DMRD).
Singapore
Radiologists in Singapore complete a five-year undergraduate medicine degree followed by a one-year Internship (medical)
and then a five-year residency program. Some Radiologists may elect to
complete a one or two-year fellowship for further sub-specialization in
fields such as interventional radiology.
