College of Radiology, Academy of Medicine of Malaysia position on whole body screening CT scans in healthy asymptomatic individuals (2008)
1. College of Radiology, Academy of Medicine of Malaysia; Sime Darby Specialist Centre Megah, Petaling Jaya, Malaysia
2. University Malaya Medical Centre, Kuala Lumpur , Malaysia
3. Sime Darby Medical Centre Subang, Selangor, Malaysia
4. Universiti Putra Malaysia, Selangor, Malaysia
5. Pantai Medical Centre, Kuala Lumpur, Malaysia
6. Kuala Lumpur Hospital, Kuala Lumpur, Malaysia
7. Islamic International University of Malaysia, Pahang, Malaysia
8. Sungai Buloh Hospital, Selangor, Malaysia���������������
9. Malacca Hopital, Malacca, Malaysia
10. Hospital Tuanku Ja�afar Seremban, Negeri Sembilan, Malaysia
11. Selayang Hospital, Malaysia
To date, the College of Radiology (CoR) does not see any
clear benefit in performing whole body screening computed tomography (CT)
examinations in healthy asymptomatic individuals. There are radiation risk
issues in CT and principles of screening should be adhered to. There may be a
role for targeted cardiac screening CT that derives calcium score, especially
for asymptomatic medium-risk individuals and CT colonography when used as part
of a strategic programme for colorectal cancer screening in those 50 years and
older. However, population based screening CT examinations may become
appropriate when evidence emerges regarding a clear benefit for the patient outweighing
the associated radiation risks. � 2008 Biomedical Imaging and Intervention
Journal. All rights reserved.
Keywords: Screening, computed tomography (CT), radiation
risks, cost-benefit analysis, whole body imaging
After examining the published literature to date, the College of Radiology (CoR) does not see any clear benefit in performing whole body
screening computed tomography (CT) examinations in healthy asymptomatic
individuals. This recommendation is made based on available evidence and the
points taken into consideration are discussed in the various sections below. It
does not replace case-by-case or individual clinical assessment where the need
arises. It is also not meant to be used for legal purposes.
This position provides guidance for medical and health
care professionals for appropriate radiologic care that is as effective and
safe as possible for the patient. It is recognised that many factors come into
play in the delivery of health care. This includes the patient's condition,
available resources and new information, results from studies, as well as new
All parties, i.e. the radiologist who agrees to perform
and interpret this examination, the physician prescribing the examination (if
the patient is not self-referred) as well as the patient, must fully understand
the limitations and implications of the findings, as well as the risks entailed
(from the radiation and contrast media). All must be cognisant of the fact that
there may be ensuing investigations for abnormalities found on the CT scan and
these may have potentially profound financial, psychological and physical
Sectional imaging such as Computed Tomography (CT) or
Magnetic Resonance Imaging (MRI) have revolutionised the capabilities for
medical imaging studies, image-guided therapeutic intervention, and improved
targeted radiation therapy. Unlike non-ionising ultrasound examinations, it is
not limited by gas and body habitus or conventional radiographic imaging where
there is overlapping of significant volumes of tissue. CT provides
visualisation of body structures previously not well visualised except through
open surgery. CT is much more widely available and therefore much more utilised
than MRI. CT has benefited many patients by clinching the diagnosis, guiding
surgery, staging a disease much more accurately and allowing radiation therapy
to proceed ever more precisely.
The varieties of CT scanners currently in clinical use
range from single slice to spiral, multislice and dual source technology as
well as electron beam CT (EBCT). Scans can now proceed more rapidly by
acquiring each sectional image of the body in subsecond or millisecond
acquisition times. Multislice, dual source and EBCT allow elegant multiplanar
and 3-D reconstructions as well. Virtual colonoscopy is one good example where
post processing 3-D rendering has been invaluable.
Therefore, it is not surprising that CT is now being
explored and employed in whole body screening for disease. In fact, screening
CT centres have sprouted up based on the premise of wellness screening � to
detect diseases before they become more advanced. A whole body CT is being
marketed directly to consumers (patients), and they, in turn, are now demanding
for the test.
Does Whole Body Screening CT Satisfy the Criteria of a Good Screening Test?
The following are intended as points of consideration
rather than questions. All focus on whether whole body screening CT meets the
standards of a good screening test for the target diseases (diseases generally
being marketed for are cancer and coronary artery disease) [1,2,3]. Do note
that whole body screening CT may include the head, neck, thorax, abdomen and
pelvis. In some centres or countries, this may only include the neck, thorax,
abdomen and pelvis, or just the thorax, abdomen and pelvis.
- Results from large-scale randomised clinical trials (RCT) for evaluation
of whole body screening in apparently healthy individuals has not been
published to date. These studies may be difficult to perform because of ethical
issues regarding radiation dose, being very significant in whole body CT as
well as the costs of the examination and the risks from contrast media, if
administered in routine whole body screening CT. In addition, RCTs generally
tend to be disease-specific, and interpreting results of trials where an
individual is being screened for multiple diseases at the same time may not be
straightforward. In addition, CT technology is rapidly advancing and therefore
by the time an RCT is concluded, would the results be applicable?
- Indices for whole body CT such as negative predictive rate, sensitivity,
specificity, false negative, false positive and others are unknown. Therefore
the cost-effectiveness or more comprehensively, the benefit-risk-cost
evaluation is lacking.
- Malpractice issues have to be considered in screening CT such as would
arise if there was a missed diagnosis and/or where intravenous contrast media
used resulted in a severe contrast reaction. Linked to the possibility of
missed diagnosis, is the question of whether intravenous contrast media should
be routinely used for whole body screening CT examinations. It is known that
non-enhanced CT of the abdomen is generally inadequate for lesion
- No specific guidelines exist for follow-up or further evaluation when
abnormalities are detected for general whole body screening. Currently there
are some guidelines or consensus statements for lung CT but this is because
there is a basis for the size or other pretest probabilities. Guidelines for
lung CT (relatively organ specific) are easier to establish than for abdomen CT
Principles in Screening
Screening involves a test, procedure or investigation that
is used to identify a condition of disease before it manifests with signs and
symptoms. It is based on the premise that detecting a disease at its earliest
affords the best chance of cure.
A screening test is considered effective if it produces a
statistically significant reduction in disease mortality. Screening tests can
be applied to the whole population or to a subset of the population, for
example, that is based on the risk profile of the person for a specific
Main considerations for screening are as follows :
- Does the disease merit screening? (For example, is the disease very
common in the population in question and is proving to be a major healthcare
burden to treat and care for?)
- Is there a reliable screening test for the disease in question? The
false positive and false negative rates, positive and negative predictive
values as well as accuracy are important parameters.
- Is effective intervention/treatment available for the disease in
question, if detected early? There is no point in screening for a disease if
there is no cure or effective treatment for the disease. There is also no point
in treating a disease that is slowly progressing such that treating it early
may not make a difference to the patient�s lifespan.
- Therefore, screening in general requires the careful consideration of a
number of factors including a careful cost-benefit analysis. Individuals opting
for any screening examination should be counseled as to the benefits and risks
associated with the examination.
Radiation Issues in CT
The effective doses from diagnostic CT procedures are typically
estimated to be in the range of 1 to 10 mSv. However, for a whole body CT, the
effective dose for CT head, thorax, abdomen and pelvis is easily 20 mSv . A CT examination with an effective dose of 10 mSv may be associated with an increase in the chance
of fatal cancer of approximately 1 in 2000. Therefore, a CT scan must only be
performed when the benefits outweigh the risks, and when information from the
CT scan will positively affect the management of the patient�s condition.
The amount of radiation dose received by the patient is
variable by a factor of 10 [6, 7], depending on the size of the patient, make
and type of CT scanner, scanning parameters and body part being scanned. It is
also an established fact that CT studies account for the largest population
radiation dose from medical diagnostic studies and this is increasing rapidly
with time [8,9,10]. In 1998, CT contributed 42% of the average effective dose
per capita from diagnostic exposures in the Netherlands .
According to the UNSCEAR 2000 Report on Sources and
Effects of Ionising Radiation, the percentage contribution by CT scans to
global collective dose from medical x-ray examinations have increased from
about 14% between 1955 and 1990 to about 33% between 1991 and 1996 . The growth
is phenomenal and, therefore, the collective dose to the population from
medical sources of ionising radiation is significant.
The College of Radiology, Academy of Medicine Position on Whole Body
Screening CT Scans
After examining the published literature to date, the
College of Radiology (CoR) does not see any clear benefit in performing whole
body screening computed tomography (CT) examinations in healthy asymptomatic
individuals. Indiscriminate whole body screening CT does not satisfy the
criteria needed for a good screening test. There is also no standardisation of
what constitutes a whole body CT scan and whether contrast media should be
used. There is no evidence-based consensus of the various diseases for which
morbidity and mortality are allegedly reduced. It should be noted that there is
no �one size fits all� for a properly conducted CT scan, especially so if the
whole body is involved. In addition, a CT scan examination is costly when it
involves many sections of the body (as in whole body) and contrast media is
used with attendant risks.
The false positives from the whole body screening CT will
lead to additional tests, some of which may be high risk (for example fatality
from biopsy procedures); and uncertainty from findings of unknown clinical
significance will lead to unnecessary investigations and anxiety for the
patient. All these translate to financial and psychological burden to the
patient, as well as financial and other burdens to the healthcare system. Finally
as discussed above, the risks from radiation are real and significant.
Theoretically, the perceived benefits are earlier
detection leading to earlier intervention, reduction of morbidity and mortality
for the patient, and lower overall health costs and burden to the healthcare infrastructure.
However, these benefits have not been proven yet. Therefore, the risks outweigh
the benefits in whole body screening CT at this time.
Every medical procedure must have indications and
justification for its use. Consideration must be given to the available
resources versus clinically useful information that alters management inclusive
of financial and safety issues. This is even more imperative with medical
procedures requiring the administration of ionising radiation.
Justification, optimisation and dose limitation remain the
main tenets for radiology practitioners. In clinical scenarios where benefit
exceeds risks and further management of the patient is dependent on information
gleaned from the CT scan, the examination is deemed justified. The radiologist
and the radiographer/radiologic technologist operating the CT scanner must
optimise the examination to get the most information by using scan parameters
that do not use excessive radiation (dose limitation). CT scans should be
performed keeping in mind the principle of ALARA (As Low As Reasonably
In Malaysia, all CT scans must be conducted by a trained
medical practitioner who is a qualified radiologist with a valid practicing
licence from the Malaysian Medical Council (MMC) and is preferably listed in
the National Specialist Register (currently a voluntary registration process).
The equipment must be operated by trained and qualified radiographers. The
facility providing the CT service must have in place radiation protection and
quality assurance programmes.
Special Circumstances for Targeted Screening CT Procedures
This position statement would be incomplete without also
discussing some of the results of studies done for screening CT confined to
specific areas of the body, as well as for diseases which are deemed common and
for which earlier intervention may impact positively on morbidity and
A. CT Heart for Calcium Score
Calcium scoring in cardiac CT is deemed appropriate for
patients at medium risk for coronary artery disease, as the information from
the calcium score may render the patient as high risk, requiring more intensive
risk modification . More recently, calcium scoring may prove to be
independently predictive of cardiovascular risk and adds incremental prognostic
information to the conventional risk factor scoring methods .
B. CT colonography (Other names are virtual colonoscopy and virtual
This is a CT examination of the colon, and typically
involves distending the colon with carbon dioxide or air, and then performing a
CT scan of the abdomen and pelvis, usually in both prone and supine positions.
The data is reconstructed and can provide axial images, 3-D, MPR images as well
as colon fly-through video images. The radiation dose in CT colonography ranges
from 1.8 mSv to 15 mSv with an average of 8 mSv. The radiation
dose in barium enema (barium study using x-ray fluoroscopy) is typically 7 mSv.
Recently, CT colonography was recognised as a screening
tool in the Joint Guideline of the American Cancer Society, the US
Multi-Society Task Force on Colorectal Cancer and the American College of
Radiology on Screening and Surveillance for the Early Detection of Colorectal
Cancer and Adenomatous Polyps, 2008 [12, 13]. Screening average-risk individuals
over 50 years old may reduce mortality from colorectal cancer . Screening
should proceed in a proper programme that begins with risk stratification, and
based on the findings, the results from the initial test should be followed
through appropriately. For this screening examination to be effective, the
patient must adhere to the programme and undergo good quality tests. CT
colonography must be used judiciously and existing recommendations for
screening in low, medium and high risk individuals should be factored into the
decision to proceed with screening CT colonography.
C. Screening lung CT is still controversial [14, 15, 16, 17, 18].
Although CT is probably best at detecting early lung
cancer, the evidence to suggest that treatment / intervention at this stage
reduces mortality or improves life span is not conclusive . In addition,
lung CT detects many small benign nodules, and the cost-safety-benefit analysis
is not straightforward, as lung biopsy carries significant risks. There are
ongoing trials in screening lung CT in the at-risk population, including the
National Lung Screening Trial in the USA . However, even trials are
surrounded by controversy. The International Early Lung Cancer Action Programme
was recently reported to have received some funding from a tobacco company
. The latter adds to the other questions on lead time bias, study length
and over diagnosis bias.
After an extensive review of the published literature, the
CoR at this time does not recommend whole body screening CT scans in healthy
asymptomatic individuals, as the risks (safety, psychological, cost) outweigh
the potential benefits (reduced mortality, burden and costs to healthcare
systems). The appropriateness of screening CT examinations may change with new
evidence, improvements or changes in CT technology, disease pattern, type,
treatment, and various other factors. [12-28].
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|Received 3 September 2008; received in revised form 10
November 2008, accepted 11 November 2008
Correspondence: College of Radiology, Academy of Medicine of Malaysia and Consultant Clinical Radiologist, Sime Darby Specialist Centre Megah, Petaling Jaya, Malaysia. E-mail: firstname.lastname@example.org (Evelyn Ho).
Please cite as: Ho ELM, Abdullah BJJ, Tang AAL, Nordin AJ, Nair AR, Lim GCC, Samad Cheung H, Ng KH, Ponnusamy S, Abbas SF, Bux SI, Arasaratnam S, Abdul Aziz YF, Venugopal S, Musa Z, Abdul Manaf Z,
College of Radiology, Academy of Medicine of Malaysia position on whole body screening CT scans in healthy asymptomatic individuals (2008), Biomed Imaging Interv J 2008; 4(4):e44