Scans of the lungs normally require patients to hold their breath to minimise the movement of their tumours. This has limited the use of MRI in patients with lung problems, given that scans can often last for more than 30 seconds.
Researchers from The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust tested a free-breathing version of a new technique called diffusion-weighted magnetic resonance imaging (DW-MRI) in eight patients with multiple lung lesions, and found it could clearly take measurements from lung tumours while patients breathed freely.
The technique measures the microscopic movement of water in tissue, which increases in a tumour when targeted cancer treatments attack and kill cancer cells, and so its use could help speed up the development of new treatments.
The study, published in the journal European Radiology, was carried out at the Cancer Research UK Imaging Centre at The Institute of Cancer Research (ICR) and The Royal Marsden and received funding from the EU Innovative Medicines Project, Cancer Research UK and EPSRC, with additional funding from the NIHR Clinical Research Facility in Imaging.
The team at the ICR and The Royal Marsden used CT scans to identify eight patients with multiple lung lesions, before taking two DW-MRI scans per patient when patients were not receiving treatment. Two observers with experience in interpreting DW-MRI analysed the data and calculated the apparent diffusion coefficient (ADC), which measures the rate of movement of water in the lungs, as a way of recording cell death. They compared their ADC values to determine whether DW-MRI could be used to reliably monitor tumours in the lungs.
Researchers found that ADC values calculated for each tumour within a patient’s lungs were consistent on the two occasions they were measured, with less than 10% variation. The variation was even less when all the tumours in a patient were considered together. They also found that ADC values calculated by each observer agreed well with each other and varied less between each others’ measurements when tumours were larger.
They also checked to see if the motion of breathing affected the scans, and observed that the chest movement during free breathing did not affect the observers’ ability to accurately identify the lesions nor obtain a reliable ADC.
Professor Nandita deSouza, Professor of Translational Imaging at the ICR and Honorary Consultant at The Royal Marsden, said: “We looked at eight cancer patients with multiple lung tumour lesions to see if diffusion-weighted MRI could be used to monitor changes to their tumour. Other types of MRI employed in lung cancer require the patient to hold their breath for as long as 25 seconds, but often patients with tumours in their lungs can’t physically hold their breath that long. The free-breathing MRI technique we used here proved to be robust, reliable and easy to implement, so it could be used more widely in the future. ”
“This study also shows that we can use diffusion-weighted MRI to study microscopic water movement in lung tumours, where an increase in our measured ADC values was a proxy for cell death. We found that there was good agreement between two experienced observers in calculating ADC values, so DW-MRI could be used to monitor treatment effects and help develop new lung cancer treatments.”