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New technique deepens insights into asthma

10 August 2021
VU LaserLaB physicist Johannes de Boer, working with lung specialists Peter Bonta and Jouke Annema from Amsterdam UMC, has developed a new technique for determining muscle thickness in the airways of asthma patients. It is a groundbreaking study that puts Amsterdam at the international forefront in this field.

This breakthrough in imaging technology will make it possible to determine the thickness of muscle layers in the airways of asthma patients without having to remove tissue. This will make it easier to identify the patients who will benefit most from treatment. The study was published in the scientific journal Chest last week. 

“Stated simply, asthmatics have attacks of tightness in which the muscles around the airways contract, making breathing more difficult,” De Boer explains. “If you’ve had asthma for a long time, the effect is the same as regular visits to the gym: the muscles in the airway walls grow stronger, and therefore thicker, and the tightness experienced during an asthma attack becomes worse.” 

Bronchial thermoplasty
A treatment does exist to weaken the muscle layer and therefore make it thinner. Called bronchial thermoplasty, it heats the airway walls and is carried out during a bronchoscopy. The airways of the lungs are examined and treated from the inside, using a thin tube with a camera that is inserted through the mouth.

“However, it is difficult to determine how thick this layer of muscle is in asthma patients,” Bonta says. “That can only be done by taking a piece of tissue (biopsy). This is more invasive and only allows us to determine muscle thickness at that one location.” At present, patients are selected for bronchial thermoplasty based on their disease characteristics and symptoms, but not all patients benefit equally from the treatment.

New imaging technique
In their new study, De Boer, Bonta and Annema have demonstrated for the first time that a new imaging technique known as polarization-sensitive OCT (Optical Coherence Tomography) can determine the thickness of muscle layers in asthma patients, without the need to take biopsies. And it has the added advantage of determining muscle thickness not only at the site of the biopsy, but throughout the patient’s airways.

To obtain images using the new laser OCT technique, a tiny catheter with a diameter of 1.4 mm is inserted through the mouth into the airways. The polarization of the OCT light is used to determine the direction and amount of muscle fibres. This new technique can measure muscle layer thickness with an accuracy that is equivalent to biopsies.

The researchers hope that this breakthrough in imaging technology will make it easier to identify the patients who will benefit most from treatment. In addition, the technique means that the effect of bronchial thermoplasty treatment on the airways can be measured directly.

In a follow-up study, the researchers hope to discover whether their technique can allow them to measure not only the muscle layer but also the amount of connective tissue in the walls of the airways.

Photo: Alfonso Cerezo, via Pixabay