Can CT Scans Cause Cancer?

Picture by webMD

How many of you have had CT (computed tomography) scans done before? I have had at least 2 so far, both after each of my 2 bike accidents. They are vital to give doctors a quick and detailed look inside our bodies to diagnose internal injuries, strokes, cancer and lots more. They are a crucial part of modern medicine and are found in every hospital and many private clinics.

However a recent study suggests that CT scans performed in USA alone in 2023 could eventually lead to over 100,000 extra cancer cases. If the current rate of scanning carries on, the researchers say that CT scans can be responsible for around 5 percent of all cancers diagnosed each year.

The researchers reported that the number of CT scans done in the US has increased by 30 percent in just over a decade. In 2023, there were an estimated 93 million CT scans done on 62 million people.

Note that the risk from a single CT scan is low, but not zero. The younger the patient, the higher the risk. Children and teenagers are more vulnerable because their bodies are still growing and developing. Any damage caused by the ionising radiation may not show up until years later.

Hence it is fortunate that more than 90 percent of CT scans are done on adults, so this group will probably face the most impact.

The more common cancers linked to CT exposure are bladder, colon, leukemia, and lung. For females, breast cancer is a significant concern.

This latest estimate is much higher than a previous similar analysis. That analysis, published in 2009, projected 29,000 future cancers linked to CT scans. The current estimate  (100,000 cases) is more than 3 times higher. It not just because of more scans done but also newer research allows for a more detailed analysis of radiation to specific organs.

This study also suggested that if things stay the same, CT related cancers could match the number of cancers caused by alcohol or excess weight, 2 well known risk factors.

Note that not all CT scans carry the same levels of risk. Abdomen and pelvic CT scans are thought to contribute the most to future cases in adults. In children, it's head CTs that pose the biggest concern. This is especially for babies under one year of age.

Despite this, doctors ordering them stress that CT scans are essential in many cases and they have saved lives by catching potentially fatal conditions early and also to guide treatment. They are often crucial during emergencies. The big challenge is making sure they are used only when really needed.

Please note that this study by Smith-Bindman et al (2025) does NOT prove that CT scans cause cancers. The estimates are based on risk models, not direct evidence. The American College of Radiology released a statement to say that no study has yet linked CT scans directly to humans getting cancer, even after multiple scans.

The idea that radiation can cause cancer is not new. It is scientifically sound, especially with the huge number of scans done. Small risks do add up. 

Personally I hope that hospitals (here in Singapore) switch to photon counting CT scanners since they deliver smaller doses of radiation. The researchers also suggest using MRI's or ultrasound scans when necessary or possible instead of CT to reduce radiation.

CT scans definitely save lives, but they are not risk free. Hopefully as medical technology evolves, we too will change how we use them by cutting down unnecessary scans or use safer alternatives.

Reference

Smith-Bindman R, Chu PW, Firdaus HF et al (2025) Projective Lifetime Cancer Risks From Current Computed Tomography Imaging. JAMA Intern Med. 185(6): 710-710. DOI: 10.1001/jamainternmed.2025.0505

Super Shoes Or Super Placebo?

Thinking of buying a pair of Nike Vaporfly's (pictured above) for your next racing shoe? Or another super shoe from another brand? Here's a really interesting study I read on super running shoes.

Researchers in that study (Hebert-Losier et al, 2025) recruited 24 female recreational runners. All ran in Nike's Vaporfly Next% 2.

Here is what is so interesting, the shoe was not changed or manipulated. It was how the shoe was described. For the first shoe, the narrative was a "super shoe" description. carbon plated, energy return foam, elite level technology and expensive ($400).

For the other pair, a "basic/ knock-off" (or counterfeit) description with  no carbon plate, standard foam, lower price, ($100) and the idea that elite runners will not race in them.

Nothing changed in the shoe, just the "story" or description of the shoe.

All the participants did four 6-minute treadmill runs at 10km/h on a 1 percent incline. The researchers measured their running economy (V02 and energy cost). Cadence and contact time on the ground and perceptual responses were also investigated. These include comfort, enjoyment of run, ease, expected performance and perceived injury risk.

When the runners thought they were running with the Super shoes, perception changed noticeably. Reported comfort was significantly higher. They also felt running was easier and more enjoyable. Expected performance was higher and their perceived injury rate was lower.

To summarize, the subjective experience of running improved even though the shoes used were exactly the same.

What about the objective measures? There were NO significant differences in running economy, oxygen consumption, lactate responses or even biomechanically.

Whilst running at 10 km/h pace for 6 minutes, belief alone did nothing to translate into measurable physiological or even biomechanical differences.

Does this mean you don't have to buy a super shoes for your next attempt to beat your marathon personal best? 

Personally I don't think so. 6 minutes at 10 km/h pace using recreational runners may not be totally accurate. It shows that expectation plays a big role in how running feels even though performance metrics remained unchanged.

Comfort, confidence, enjoyment and perceived safety matter so one can train consistently and push themselves harder when there is less fear of injury. These may not show in data measuring running economy, but may still influence outcomes over time.

The message for runners is NOT that they do not need to buy super shoes. Instead it's that shoes cannot replace training and price tags do not guarantee performance. Perception changes a runner's experience, even when physiology does not change.

Technology helps sometimes. Sometimes the story helps too.

So are you buying Nike's Vaporfly or Decathlon's Kiprun (pictured above)?

Reference

Hebert-Losier K, PfisterA, Finayson SJ et al (2025). Are Super Shoes A Super Placebo? A Randomised Crossover Trial In Female Recreational Runners. Footwear Sc. 17(2): 79-88. DOI: 10.1080/19424280.2025.2458330

Is This You?

Who thinks that the above and below postures lead to neck pain or discomfort? They are a common sight now since smart phones have become widely available.

There is a general consensus that the flexed (or forward bending) posture of the neck and head while reading and typing, also known as text neck is harmful, and is related to neck pain and other physical discomfort.

This impression that neck pain is caused by excessive smartphone use started after one computational model study in 2017 suggested that the greater the neck bending forward, the greater the overload. The theory is based purely on biomechanics and does not consider that pain is multifactorial and modulated by several factors.

Previous studies did not find an association between text neck and neck pain. Bertozzi et al (2023) also did not find an association between neck posture and time spent on smartphones with neck pain or disability.

The present study aims to investigate whether text neck is a risk factor for neck pain, while considering the influence of psychosocial and lifestyle factors. This longitudinal study with a 12 month follow-up using a self reported questionnaire and objective assessment of posture while sending messages on a smartphone. 

396 participants (87 percent) completed the 1-year follow-up. Average age of the participants was 27 years. 319 (70 percent) were female. The average neck flexion angle using the smartphone was 34 degrees. Only 4 subjects (1 percent) had neck pain "very often", 20 subjects (5 percent) had neck pain "often". 129 subjects 33 percent) had neck pain "occasionally", 158 subjects (40 percent) rarely had neck pain 85 subjects (21 percent) "never" had neck pain.

The researchers concluded that neck flexion posture was not a risk factor for neck pain or frequency of neck pain. They found that psychosocial factors like low sleep quality and insufficient levels of physical activity were contributing factors of neck pain.

So it's not really just what position you neck is in or how long you spend on your phone that can cause your neck to hurt. However, if you spend a lot of your time on your phone, please make sure you get in enough exercise and sleep well to avoid neck pain.

Reference

Correia IMT, Ferreira ADS, Gomes JFM et al (2025). Cervical Flexion Posture During Smartphone Use Was Not A Risk Factor For Neck Pain, But Low Sleep Quality And Insufficient Levels Of Physical Activity Were. A Longitudinal Investigation. Braz J PT. 29(6): 101258. DOI: 10.1016j.bjpt.2025.101258

Exercises Or Manual Therapy Better For Persistent Neck Pain?

Neck exercise

Assuming you have persistent neck pain, would you prefer to very diligently do 13 exercises (pictured above) or would you prefer to have a physiotherapist treat you with hands on manual therapy? 

Manual therapy

Research by (Villanueva-Ruiz et al, 2025) shows that both help patients with chronic neck pain. Manual therapy in this case refers to both myofascial and joint mobilization techniques (Guo et al, 2022 and Zabala-Mata et al, 2024). Please read on for a twist at the end. 

The authors randomly allocated 65 patients with non specific chronic neck pain into a manual therapy or exercise group. They received 4 treatment sessions of either performing 13 specific neck exercises with supervision (plus home exercises) or manual therapy once a week for 4 weeks.

The following outcomes were measured at baseline, 2, 4 and 12 weeks post treatment. Pain intensity, disability, quality of life, patient-perceived improvement, fear of movement and also the cranio-cervical flexion test (CCFT). 

Patients were also categorized into responders or non-responders according to their pain intensity, disability and their perceived improvement at 4 and 12 weeks post treatment. Commitment to exercise was also recorded.

After reading so far, which group do you think fared better? Note that both groups of patients had 'general physio' before and not gotten better.

Ready for the results? The manual therapy group had much more responders than the exercise group at all follow up periods. Treatment outcome in the exercise group was linked to exercise adherence. So manual therapy is more effective? Here's the twist.

When the researchers looked only at patients who were ≥ 95 percent diligent at doing their home exercises (60 percent of the exercise group), the treatments were equal. 

So, a 4 week manual therapy intervention was more effective than exercises for chronic neck pain patients. However, when exercise adherence was ≥ 95 percent, both interventions were equally effective.

Manual therapy may be superior to doing strengthening exercises for chronic neck pain when patients are not able or not motivated to do their home exercises.

For healthcare professionals whose patients are motivated and are likely to do their strengthening exercises then you can dole out the exercises out and send videos to aid them. For patients who are not compliant with the exercises perhaps due to challenging home or work situations, then manual therapy is evidenced based and effective.

References

Villanueva-Ruiz I, Falla D, Saez M et al (2025). Manual Therapy And Neck-Specific Exercise Are Equally effective For Non-Specific Neck Pain But Only When Exercise Adherence Is Maximized: A Randomized Controlled Trial. Musc Sci Pract.77: 103319. DOI: 10.1016/j.msksp.2025.103319