News Excerpt:

CT (Computerised Tomography) Scan has the potential for increased cancer risks and relatively high cumulative doses from multiple scans have raised concerns among the medical and scientific community.

Key highlights of the findings:

• Researchers monitored a group of people for at least two years after their initial CT scan. 
• They discovered 790 cases of haematological malignancies, including 578 cases of lymphoid malignancies and 203 cases of myeloid malignancies and acute leukaemia (AL).
• They found a clear association between cumulative dose and risk of all haematological malignancies, with an excess relative risk of 1.96 per 100 mGy. 

• Researchers estimated that “for every 10,000 children examined today (mean dose 8 mGy), one-two persons are expected to develop a haematological malignancy attributable to radiation exposure in the subsequent 12 years.” 
• The results showed a clear dose-response between cumulative ABM dose and risk of haematological malignancies, both lymphoid and myeloid, with increased risk at doses as low as 10-15 mGy.

Impact of CT Scan:

• Radiation doses at moderate (over 100 mGy) to high (over 1 Gy) values are known to cause haematological malignancies (blood cancers) in both children and adults and other cancers. 
• There has been uncertainty about risk at low doses (less than 100 mGy) that are typically associated with diagnostic CT examinations. 
• A recent study (Nature Medicine) suggests that even low doses of radiation have a small probability of causing blood cancer.

Working of CT Scan:

• A CT scanner emits a series of narrow beams through the human body as it moves through an arc.
• This is different from an X-ray machine, which sends just one radiation beam. 
• The CT scan produces a more detailed final picture than an X-ray image.
• The CT scanner’s X-ray detector can see hundreds of different levels of density. It can see tissues within a solid organ.
• This data is transmitted to a computer, which builds up a 3-D cross-sectional picture of the part of the body and displays it on the screen.
• Sometimes, a contrast dye is used because it can help show certain structures more clearly.
• For instance, if a 3-D image of the abdomen is required, the patient may have to drink a barium meal. The barium appears white on the scan as it travels through the digestive system.