Radiological imaging is very useful in visualising the chest and lungs to establish a diagnosis.
Commonly used radiological imaging includes:
- Chest x-ray
- Computed Tomography (CT)
- Pleural / Thoracic Ultrasound
- Positron Emission Tomography (PET)
- Magnetic Resonance Imaging (MRI)
- Ventilation – Perfusion (VQ) scans
Chest x-ray
Chest x-rays can be obtained quickly and offer a rapid general view of the lungs to make an initial diagnosis or determine progress after treatment.
The radiation from a chest x-ray is 0.02 mSV and is equivalent to 5 days of background radiation.
CT scans
CT scans offer a more detailed view of the chest including the heart, blood vessels, lymph nodes, airways, lung tissue and chest wall. Usually the test takes only a few seconds. Sometimes a dye (contrast) is injected to better help visualise specific structures and scans taken before and after injection of dye. For example, injection of dye and scanning whilst the dye is in the pulmonary arteries allows the detection of clots (emboli) within the pulmonary arteries. On other occasions scans need to be taken during inspiration and expiration to help in identifying specific airways disease.
Regarding the contrast, it is important that you let Dr. Singh and Radiology department of Hospital know if you are allergic to contrast
A CT scan delivers approximately 6.1 mSV of radiation that is equivalent to 2 years of background radiation. However, in some cases, for example with lung cancer screening, low dose CT scans can be done, which reduce the radiation dose to 1.5 mSV.
Thoracic / Pleural Ultrasound
This involves no radiation . The Use of Ultrasound helps detect presence of fluid in the chest cavity / pleura and estimate its size . It also helps guide the procedure to remove fluid from the chest.
PET CT scans
PET CT scans are nuclear medicine scans where a nuclear dye is injected to demonstrate areas of the body that are more active. They imaging is combined with CT scans to offer 3D visualisation of the body and is particularly useful to detect active sights of inflammation, infection and cancer.
The scan is safe but pregnant woman should only have it in an emergency. The scan delivers approximately 22 mSV of radiation that is equivalent to 3 years of background radiation. Drinking plenty of water after the scan helps to flush the body of the radioactive tracer. As a precaution you should avoid coming in to close contact with pregnant woman and young children for 6 hours.
Ventilation-Perfusion scans
These scans use radioactive tracer to detect ventilation (airflow) and perfusion (blood flow) in the lungs. This allows detection of areas where there is a problem with ventilation or perfusion and helps make a diagnosis of pulmonary emboli (blood clots in the lungs). As the test is done in two parts it can take up to 30 min to complete.
Ventilation-Perfusion scans can be combined with CT using single-photon emission computed tomography (SPECT) to provide 3D information, with lower dose of radiation that with a CT pulmonary angiogram, and avoiding the use the contrast
This is often the investigation of choice to detect blood clots in the lungs of pregnant woman, using only the radioactive tracer to detect perfusion, as CT pulmonary angiogram delivers a higher dose of radiation to the breast tissue of pregnant woman.
● ABOUT DR ANAND SINGH
About Dr Anand Singh
Dr Anand Singh is a highly experienced Consultant Respiratory Physician with over a decade of experience in the field.
Dr Singh is a well known Chest Consultant and Sleep Consultant who provides personalised treatment plan.
Dr Anand Singh is a consultant Respiratory Physician at West Hertfordshire Teaching Hospitals NHS Trust
(Watford General and Hemel Hempstead Hospital where he leads the Sleep and Non-Invasive ventilation Service
and Respiratory High Dependency unit. He undertakes sub-speciality clinics in Interstitial Lung diseases
and Sleep Apnoea as well as conducting general respiratory medicine clinics.
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