New Imaging Approach May Assess Disease Burden in Patients With SMA

A proof-of-concept trial has demonstrated that Multispectral Optoacoustic Tomography (MSOT) may be able to visualize and quantify progressive muscle degeneration in children with spinal muscular atrophy.

If further studies confirm a benefit with this novel diagnostic, the technology can help forge a path toward a noninvasive, bedside, nonionizing approach to early visualization of disease as well as evaluation of disease burden and disease progression in patients.

“There is an unmet urgent clinical need – especially among presymptomatic and very young patients – for non-invasive technologies that enable rapid and objective assessment of the disease state and progression with the lowest burden possible,” emphasized the researchers, explaining that traditional validated motor function tests and development scales may be affected by factors like general development gains, learning effects, and daytime tiredness, which may cause inaccuracies in disease and treatment monitoring.

The small study of 10 patients with SMA and 10 matched healthy volunteers completed 320 scans. The researchers documented overall higher mean signals values in the healthy volunteers compared with the patients with SMA. There were statistically significant differences for MSOT single wavelength (SWL) 715 nm, 730 nm, 760 nm, 800 nm, 850 nm, and 1064 nm, with the greatest difference of mean signal intensity being observed with SWL 800 nm.

Meanwhile, the spectrum of maximum values was higher among patients with SMA. Statistically significant differences were found for SWL 680 nm, 715 nm, 730 nm, 760 nm, 800 nm, and 850 nm.

“As a main finding, optoacoustic imaging (OAI) signals (see SWL 800 nm) in healthy muscles showed a homogenous signal band just beneath the muscle fascia,” wrote the researchers. “In muscles of SMA patients, OAI signals were found ragged in patchy scattered areas comparable to moth-eaten damage with alternating high and low signal intensities. For signal quantification, the defined ROIs included both, areas with high and low OAI signals.”

Assessing the correlation between imaging and clinical standard assessments, the researchers found that the best optoacoustic signal difference between the healthy volunteers and patients with SMA was quantified and visualized for SWL 800 nm.

According to the researchers, healthy volunteers exhibited a homogenous signal band under the muscle fascia, which starts to be disrupted in patients with SMA with preserved walking ability and becomes more scattered the SMA progresses.

Reference

Regensburger A, Wagner A, Danko V, et al. Multispectral optoacoustic tomography for non-invasive disease phenotyping in pediatric spinal muscular atrophy patients. Photoacoustics. 2021;25:100315 doi: 10.1016/j.pacs.2021.100315