Computed Tomography (CT) scans are widely used in modern medicine for accurate diagnosis of a host of diseases. But a recent study conducted in the US in 2023 and published in JAMA Internal Medicine says CT scams could cause over 1,00,000 extra cancer cases.
Why the growing use of CT scans in Indian healthcare is a cause for concern.
Radiation exposure is known to increase cancer risk. And CT scans expose patients to a much higher level of ionizing radiation than regular X-rays. A chest X-ray delivers around 0.1 mSv, (millisievert) of radiation, while a CT scan can deliver around 10 mSv, which is 70 to 100 times more radiation in one scan. Exposure to ionizing radiation can cause breaks in the DNA strands of cells, which one’s bodily mechanisms may not be able to repair perfectly, leading to mutations that can be passed on when the cells divide. Over time, these mutations can accumulate and cause cells to grow abnormally into a tumor; often leading to cancer: For a single CT scan, the risk is generally low, but cancer risk increases with repeated exposure.
The use of CT scans has increased globally, with an annual rise of about 3-4%. In 2023, 93 million scans were conducted in the US alone. The study is concerning given that the population of India is approximately four times larger than that of the US. This could mean that an indiscriminate and repeated use of CT and PET scans could potentially lead to an increase in new cancers such as lung, colon, leukemia, thyroid and breast cancer. Organs with high cell turnover rates like the colon and bone marrow, are more vulnerable to DNA damage from ionizing radiation. Tissues with rapidly dividing cells, including the ovaries and breast tissue, are especially radiosensitive and mutations in these cells can trigger abnormal growth, increasing cancer risk over time.
CT scans are often critical to monitor disease progression or detect recurrence in cancer patients. But it must be used judiciously and not as a default approach. Overuse not only leads to unnecessary radiation exposure but also to increased healthcare costs.
Ideally, all radiation exposure should be minimized. According to the International Commission on Radiological Protection, for doctors and imaging technicians, the effective dose limit is 20 mSv per year; averaged over five years, with no single year exceeding 50 mSv. Also, organs like the eyes, skin, hands and feet have different thresholds. As for others, we are naturally exposed to about 3 mSv of background radiation annually, and any radiation from CT scans or other imaging adds to that. Children are especially vulnerable to radiation as their tissues are still developing, and they have a longer lifetime during which radiation-induced effects could manifest. That’s why the American Academy of Pediatrics follows the ALARA (As Low As Reasonably Achievable) principle for safe imaging practices in pediatric care.
There are no formal governance structures in India that actively track the number of CT scans a patient undergoes, or the cumulative radiation dose over a period of time. Hospitals are expected to follow ALARA principles, but it largely depends on their discretion and awareness levels.
Yes, for certain conditions, MRI (Magnetic Resonance Imaging) uses magnetic fields and radio waves, and doesn’t involve ionizing radiation. It’s often preferred for soft tissue imaging. Ultrasound, another radiation-free option, is commonly used for imaging organs like the liver, kidneys, and in obstetrics for fetal assessments. But CT scans remains a crucial tool for specific diagnosis. A risk-benefit analysis is essential before every scan. Patient safety and clinical necessity should be the utmost priority for physicians.
Most hospitals now use dose-tracking software to track cumulative radiation exposure for every patient. Imaging centers can also get accredited by institutions such as the American College of Radiology to maintain radiation safety standards. Newer CT scanners have iterative reconstruction and dose modulation technologies that cut radiation doses as much as 50% without sacrificing image quality. If patients are made aware of these, they will force hospitals to invest in such machines.
They must ask if the scan is absolutely essential as lower-radiation alternatives might be equally effective. It’s a good idea to keep a personal record of previous X-rays, CT scans, or nuclear medicine tests, especially if they are seeing more than one doctor, to prevent unnecessary repeated scans.
TYPE OF SCANS & RADIATION IN mSv:
Bone density test+ — 0.001 mSv
X-ray, chest —- 0.1 mSv
X-ray, abdomen —– 0.7 mSv
Mammogram ——– 0.4 mSv
CT, abdomen/pelvis – 10 mSv
CT, angiogram ——— 16 mSv
Natural sources ——- 3 mSv
Long-haul flight ——— 0.03 mSv
