CT scanning of the chest can be a relatively high dose radiological examination. In appropriate settings this dose is warranted for investigation and management of serious medical conditions. There are times however when lower dose scans would be desirable.

The National Lung Cancer Screening Trial in the USA in the early 2000's utilised a low dose CT chest protocol for detection of lung cancer. Ultra-low dose CT, utilising the latest in technology, uses only 20% of this already low dose.

We are all exposed to environmental radiation in our daily lives, totalling about 2 millisieverts (mSv) a year. Below is a table comparing radiation doses for different examinations against our natural background exposure. Doses are illustrative, and will vary with imaging protocol, body size and available technology. Radiology SA is regularly achieving ultra-low dose CT chest doses of 0.2 - 0.3 mSv.

Ultra-low CT chest is useful in situations such as:

• CT chest imaging in young/radiation conscious patients
• Conditions requiring serial follow-up, especially when detail greater than that offered by a CXR is required
• Clarification of CXR findings
• Lung cancer screening (currently no medicare rebate without clinical indication)

It is not indicated for:

• Imaging of the chest wall and mediastinum
• Oncology staging
• Emphysema quantification
• Interstitial lung disease

At left, a conventional dose CT, radiation dose 6.7 mSv. Follow-up ultra-low dose CT on the right, radiation dose 0.2 mSv. At only 3% of the original dose the mucous filling of airways and partial collapse of the left lower lobe of lung is still clearly visible. Some textural change in the image is apparent due to the low dose technique. Despite a major reduction in radiation exposure there is only mild loss of image quality, and the study remains diagnostic.

Please contact Radiology SA if you would like further information about whether this technique might be suitable for you or your patient.