Radiation Risk from CT Scan and the possibility of getting cancer after receiving high dose of radiation.
Dr. Khalid Shokor Mahmood, neurosurgeon, Iraq
2. Computed tomography (CT) scans are
widely used and are an invaluable tool for
medical imaging.
However, the possible overuse of CT
scans and the variability in radiation
doses might subsequently lead to
thousands of cases of cancer.
3. Sir Godfrey Hounsfield (1919-2004),
Nobel Prize, 1979
In September 1971, CT scanning
was introduced into medical
practice
4. Radiation Absorption
The biological effect of radiation can be described
by the roentgen-equivalent man (REM) or Sievert
(Sv) where 1Sv = 100REM.
1 REM is estimated to cause about 300 aditional
cases of cancer per million persons ( one third of
which are fatal).
360 mREMAverage annual exposure to radiation
10-40 mREMA CXR
18-40 REMA CT scan of the head
1.25 REMEach slice of CT scan
10-20 REMAn angiogram
5 mREMA transcontinental airline flight
6. More than 19,500 CT scans are performed every day in
the United States; these expose each patient to the
equivalent of 30 to 442 chest radiographs per scan.
An estimated 72 millionCT scans were performed in
the United States in 2007.
researchers estimated future cancer risks from
current CT scan use in the United States, and
projected that
No. of estimated cancer cases due to CT
14,000abdomen and pelvis
4100Chest
4000Head
2700CT coronary aniography
7. The US Food and Drug Administration (FDA)
estimates that a CT examination with an effective
dose of 10 millisieverts (1Sv=100REM), for
example, 1 CT examination of the abdomen, may
be associated with an increase in the possibility of
fatal cancer of approximately 1 chance in 2000.
The comparison of organ-specific doses showed
that CT coronary angiogram delivers a dose to the
breast that is equivalent to approximately 15
mammography screenings. It also delivers a
radiation dose to the lung that is equivalent to 711
chest x-rays, the authors note.
8. The risk is higher in children and
females
Based on the highest effective dose that was
observed, a 20-year-old women who received a CT
scan for suspected pulmonary embolism, a CT
coronary angiography, or a multiphase abdomen
and pelvis CT scan could have an associated
increased risk of developing cancer of as high as 1 in
80, note the authors.
"The risks declined substantially with age and were
lower for men, so radiation-associated cancer risks
are of particular concern for the younger, female
patient.
9. What is becoming clear . . . is that the
large doses of radiation from such scans
will translate, statistically, into
additional cancers.
