Novel compact DT imaging in inflammatory arthritis: a pathway to a first-in-human trial

Professor Karen Knapp and colleagues present an expert overview of a pathway for initiating the first human trial of a new compact digital tomosynthesis system. Designed as a low-dose, portable alternative to traditional imaging, it overcomes the drawbacks of 2D X-rays by providing depth-resolved, 3D imaging that facilitates greater detail for earlier detection and monitoring of bone changes in inflammatory arthritis.

Early and accurate imaging is critical in inflammatory arthritis, where irreversible joint damage can occur early in the disease course. However, conventional two-dimensional (2D) X-rays are limited by the superimposition of anatomical structures, often obscuring subtle erosions.

While computed tomography (CT) and magnetic resonance imaging (MRI) provide greater detail, they are less accessible and, in the case of CT, involve higher radiation doses.

Digital tomosynthesis (DT) has been shown to play an important role in evaluating skeletal abnormalities.¹ Compact DT represents an evolution in musculoskeletal imaging, combining the advantages of X-rays and CT into a low-dose, portable, point-of-care modality.

It also has the potential to deliver higher-quality extremity imaging than X-rays, reducing the need for CT or MRI when 2D X-rays are equivocal.

Here, we outline the pathway to a first-in-human trial of a novel compact DT device – the Adaptix Ortho350 – designed for high‑resolution, depth‑resolved three-dimensional (3D) imaging.

The technology offers a transformative alternative to both traditional X-ray and CT scanning by capturing multiple low-dose projections from an array of positions and reconstructing them into a depth-resolved stack of planes through the subject.

This approach overcomes the limitations of X-rays by separating overlapping bony anatomical structures, which are superimposed and can obscure key structures.

Preclinical validation of compact DT imaging

The Adaptix Ortho350 device is already in use across the veterinary and non-destructive testing sectors and has shown positive results in cadaver testing.

The University of Exeter has been collaborating with Adaptix Ltd for approximately three years to develop a prototype scanner and support its preclinical validation, with funding from the company itself and Innovate UK, to deliver the first-in-human trial of this system.

After the Innovate UK grant kick off in August 2023, preclinical testing was conducted in several phases.

Initial ex vivo imaging used antique human bones, as well as poultry and ovine bone samples from the human food chain. However, these techniques proved suboptimal for long-term imaging due to reduced bone densities and poor trabecular structures in the antique bones and degradation of the ex vivo animal bones over time.

To address this, phantoms were developed to replicate varying bone densities and trabecular structures.² These provided stable, reproducible tools for iterative testing and comparison of compact DT with three established imaging modalities: microCT, dual-energy X-ray absorptiometry (DXA) and X-ray.

Subsequent evaluation used ex vivo human bone samples excised during total hip replacements under Human Tissue Authority approval and in compliance with the 2004 Human Tissue Act.

These samples enabled more clinically relevant comparisons of images across a range of imaging modalities and bone densities, as well as osteoarthritis presentations. Examples of imaging are shown in the main image above, which can be enlarged here.

Feasibility and design: the Arthritis 3D trial

Inflammatory arthritis encompasses a group of autoimmune and autoinflammatory conditions, with rheumatoid arthritis (RA) remaining the most common form.

RA affects approximately 0.5–1% of the adult population worldwide, with peak onset between the ages of 40 and 60 and a higher prevalence in women.³

Psoriatic arthritis (PsA) affects 0.1–1% of the population, typically appearing five to 10 years after the onset of psoriasis.⁴

Early identification of these diseases is important, as irreversible erosive changes often occur within the first two years of active disease.⁵ Compact DT provides an opportunity for superior imaging to identify erosive changes sooner than X-rays.

For the Arthritis 3D trial, inflammatory arthritis of the hand was selected as the initial clinical application.

Routine clinical practice for this patient group includes X-rays, which provides an opportunity for comparative imaging. In addition, hand X-rays use low-dose imaging, which is important when adding an additional source of ionising radiation to the technique with compact DT.

The trial will compare compact DT imaging with X-rays in a direct head-to-head design. A total of 30 participants with inflammatory arthritis are being recruited to the trial at the Royal Devon University Healthcare NHS Foundation Trust, under approval from the Health Research Authority and the Medicines and Healthcare products Regulatory Agency.

The first patient was enrolled in December 2025, with eligibility requirements including being at least 18 years of age, having a diagnosis of inflammatory arthritis and requiring X-ray imaging of their hands.

Patients are excluded if they have any condition that prevents them from remaining still for 15 seconds or if they are pregnant, unable to provide informed consent or lack sufficient English language proficiency to provide informed consent.

DT imaging protocol and assessment

Participants attend the University of Exeter’s Medical Imaging Centre for DT imaging within four weeks of their initial X-ray imaging to ensure that any differences between the imaging techniques are unlikely to reflect progressive bone changes.

Bilateral dorso-palmar and oblique DT scans of the hands are performed, with each image having an exposure time of approximately 13 seconds. Participants also completed an acceptability questionnaire immediately after their scan.

All compact DT scans and X-rays are reported by the study radiologist, who is blinded to the patient study identification during X-ray image review to remove any bias. Furthermore, the X-rays will be batch-reported at the end of the study to remove any recall bias from the DT scan reports, which are reported at each participant visit.

The preliminary results demonstrate that the device is well accepted by participants and delivers excellent image quality, as shown in Figures 1 and 2.

Figure 1: Six slices through the hand demonstrating tissue at different depths

Figure 2: The same six slices with areas of interest enlarged to demonstrate the detail afforded by compact DT imaging

The improved visibility of complex bone structures makes compact DT well-suited for imaging in inflammatory arthritis, where identifying sometimes subtle bone erosions is clinically important.

Compact DT imaging also enables the diagnosis of subtle fractures, joint space abnormalities, degenerative disease, and post‑traumatic changes.

The future of DT imaging

This first in-human trial represents an important milestone in the development of a compact DT system, translating preclinical validation into a real-world clinical setting.

Developed as a low-dose, portable, point-of-care solution, the technology is designed to overcome the limitations of conventional 2D X-rays, where superimposed anatomy can obscure key structures.

The approach is now being implemented in an inflammatory arthritis setting, with early work demonstrating excellent image quality and the ability to provide depth-resolved imaging at X-ray-level dose.

This makes compact DT a promising imaging approach for this patient group, where timely diagnosis and structured disease monitoring are crucial to prevent disability and optimise patient outcomes.

Further results are awaited as evaluation within clinical practice continues.

Author

Karen Knapp PhD
Professor of musculoskeletal imaging, University of Exeter

With thanks to

Junning Chen PhD
Associate professor of biomedical engineering, University of Exeter

Jingrui Hu PhD
Research fellow in evolutionary biomechanics, University College London

Sascha Kranen PhD
Postdoctoral research fellow, University of Exeter

Susie Earl BM FRCP
Consultant rheumatologist, Royal Devon University Healthcare NHS Foundation Trust

Luke Jones
Rheumatology speciality doctor

Jon Evans MBChB MD (Res) FRCS (T & O)
Clinical senior lecturer in trauma and orthopaedics, University of Exeter

Katy Knight PhD
Lecturer in medical imaging, University of Exeter

Siân Phillips MBBCh MRCP FRCR
Chief medical officer, Adaptix Ltd

Steve Wells PhD
Chief technology officer, Adaptix Ltd

References

1. Cajamarca-Baron J et al. The use of digital tomosynthesis in rheumatology: a systematic review of the literature focused on four diseases. Radiología (English Edition) 2021;63(2):127–44.
2. Hu J et al. Development of a novel anthropomorphic bone phantoms for mimicking osteoporosis in medical imaging development. Bone 2026;117803.
3. Venetsanopoulou AI et al. Epidemiology and risk factors for rheumatoid arthritis development. Mediterr J Rheumatol 2023;34(4):404.
4. Kang Z et al. Global and regional epidemiology of psoriatic arthritis in patients with psoriasis: A comprehensive systematic analysis and modelling study. J Autoimmun 2024;145:103202.
5. Gessl I et al. Tenderness and radiographic progression in rheumatoid arthritis and psoriatic arthritis. Ann Rheum Dis 2023;82(3):344–50.