Date of Award

2023

Degree Name

Doctor of Philosophy (College of Medicine)

Schools and Centres

Medicine

First Supervisor

Professor Merrilee Needham

Second Supervisor

Associate Professor Helen Keen

Abstract

Background

Ultrasound (US) modalities, shear wave elastography (SWE), B mode US and power Doppler (PD) show great potential as imaging tools in idiopathic inflammatory myopathies (IIM), but their utility requires further validation, reliability, and discrimination studies. This data are presented in five result chapters.

Methods

The initial literature review chapters set the foundation for the study. Chapter four assessed the face validity of US by comparing IIM patients and healthy controls. Chapter five aimed to establish criterion validity by comparing US with gold standard techniques. Chapter six and seven were longitudinal studies examining a non-inclusion body myositis (IBM) and IBM cohort respectively. Chapter eight documented a collaborative effort to test reliability of the defined US domains.

Results

The literature review identified fascial thickness (FT), muscle bulk, echogenicity, power Doppler (PD) and shear wave speed (SWS), as crucial US domains for exploration. In IIM patients, higher echogenicity and lower FT were observed compared to healthy controls. BMI was found to influence muscle stiffness and echogenicity in the deltoid, making it a less reliable muscle to study. In non-IBM patients, muscle echogenicity increased over time in the vastus lateralis (VL) in the prevalent group, indicating fatty infiltration. Conversely, in the incident group, muscle echogenicity in the VL showed changes towards normal from hyperechoic, and SWS increased over time with treatment, suggesting a component of reversibility. In IBM, a thinner FT at baseline was associated with those who progressed over time, which was a novel and interesting finding. FT became thicker over time, more predominantly in the deltoid compared with VL, which is a less affected muscle in IBM, suggesting other potential influences on the fascia such as sex, age and perhaps BMI. PD was not a useful US domain for monitoring in IBM. Despite lacking reliability, international collaborations reached consensus on ten xv definitions and standard operating procedures that will aid future work. Consensus on echogenicity appearance in acute inflammation has not yet been achieved and requires further exploration.

Conclusion

Despite ongoing efforts to establish reliability, US modalities have demonstrated promise as imaging tools in IIM, but further research and consensus-building efforts are necessary to establish their reliability and enhance their utility. This is best done through collaborative efforts with centres and groups that have a special interest in US and IIM.

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