Nanotechnology and photon counting ‘colour’ CT imaging join forces to revolutionise bone microcrack imaging with unprecedented clarity

Bone is a metabolically active tissue which preserves the integrity of other tissues by providing structural support. However, it also bears compressive and tensile stresses and strains, which may result in stress or fatigue-related microcracks. If undetected and untreated, they can cause serious damage to the bone to make it weaker and more susceptible to collapse under strain, leading to a complete bone fracture or macro-fracture.

X-ray imaging-based techniques are conventionally used to detect such abnormalities in the clinic; however, the dense abundance of calcium in bone makes the presence of a tiny microfracture hard to detect. Furthermore, the spatial resolution of conventional CT (approximately 0.5–0.625mm due to the large detector element size) does not allow the detection of damage on the micrometre scale. Here we show that introducing colour to these x-ray images can effectively discriminate the tiny microcracks from the healthy bone structures.

We have shown for the first time that the combination of targeted nanoparticles comprising K-edge metals and photon counting CT imaging make microfractures profoundly visible. We have developed nanoparticles that are chemically ‘trained’ to find the microcracks and become visible with CT imaging.

Because of the high surface-to-volume ratio at the nanoscale, these particles are equipped with functionalities that can differentially bind to the calcium in tiny microcracks. Photon counting CT is the newest advancement in CT imaging technology, which enhances traditional CT images with the capability to image and quantify certain elements based on their distinctive K-edge energies. K-edge imaging will recognise high accumulations of targeted elements and present them as colourised voxels against the normal grayscale x-ray background, offering promise to overcome the relatively low inherent contrast within soft tissue and distinguish the high attenuation of calcium from contrast-enhanced targets.

Distribution of hafnia NPs targeted to bone microdamage in an ex vivo human finger bone. Hafnia NPs are materially separated from bone-like material.

MARS spectral CT technology equipped with Medipix detectors is like a human eye under sunlight. Based on the unique spectral signatures of materials used in this work, i.e. hafnium (Hf), this technology produced images that can be uniquely quantified to reveal the precise location and extent of the damage. Furthermore, the state-of-the-art reconstruction techniques equipped with MARS photon counting CT produced images with unparallel clarity. Together with these clinically translatable ligand-directed particles, MARS can generate images that reveal abnormalities that usually remain undetected by conventional methods.

Dipanjan Pan, MS, PhD is Professor in Diagnostic Radiology & Nuclear Medicine, Paediatrics and Chemical, Biochemical and Environmental Engineering. He works at the Departments of Bioengineering and Beckman Institute for Advanced Science & Technology at the University of Illinois at Urbana-Champaign, the Biomedical Research Center, Carle Foundation Hospital in Urbana, USA, the Departments of Diagnostic Radiology and Nuclear Medicine and Pediatrics, University of Maryland, Baltimore and the Department of Chemical, Biochemical and Environmental Engineering, University of Maryland in Baltimore, USA.

The abstract will be presented by Dr. Mahdieh Moghiseh, PhD, a Postdoctoral Research Fellow at the Department of Radiology and Centre for Bioengineering, University of Otago, in Christchurch, New Zealand.

Research Presentation Session
RPS 1406 From hyperpolarised MRI to multimodal imaging probes

Functionalised nanoparticles for bone micro-fractures with spectral photon-counting CT
C. Lowe1, F. Ostadhossein2, M. Moghiseh1, M. Anjomrouz1, R. K. Panta1, A. Y. Raja1, A. P. H. Butler1, D. Pan3, M. Collaboration1; 1Christchurch/NZ, 2Urbana/US, 3St. Louis, MO/US

Read the full abstract in the ECR 2020 Book of Abstracts
Moghiseh M, et al. (2020) Functionalised nanoparticles for bone micro-fractures with spectral photon-counting CT. Abstract RPS 1406-8 in: ECR 2020 Book of Abstracts. Insights Imaging 11, 34 (2020). DOI 10.1186/s13244-020-00851-0