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Emerging Imaging, Affordable Imaging

Photoacoustic imaging in the neonate

Project ID: 2020_023

1st supervisor: Wenfeng Xia, King’s College London
2nd supervisor and clinical champion: David Edwards, King’s College London
Additional supervisors: Tom Vercauteren, Eli Nabavi, Virginie Meau-Petit and Iain Yardley

Aim of the PhD Project:

The aim of this pioneering project is to investigate the potential of photoacoustic imaging as a new affordable, bedside imaging modality in the neonate.

Project Description / Background:

Clinical context
Premature babies on the neonatal intensive care unit (NICU) are in an extremely fragile state and may deteriorate rapidly. Their precarious condition precludes any complex and invasive investigation requiring transport out of the NICU. Potential major morbidities include sepsis, lung pathologies, Necrotizing Enterocolitis (NEC), Persistent Ductus Arteriosus (PDA) and intraventricular haemorrhage leading to brain damage. Current investigations are limited to basic procedures performed at the bedside, including X-ray and ultrasound (US) imaging. These modalities are useful in terms of providing anatomical information, but they have significant drawbacks. X-ray only gives limited 2D images and is associated with harmful ionizing radiation, whilst US provides poor soft-tissue contrast and is highly operator-dependent.

Two clinical contexts of particular interest are discussed below.

Lung pathology: Chest X-Ray is the current “gold standard” for imaging lung pathologies at the cotside. The main challenge in preterm newborns with underlying chronic lung disease is to define the cause of consolidation which may be atelectasis, collapse or pneumonia, each of which requires a different treatment. Additionally, two or more of these factors may co-exist, further confusing the picture. There is currently a lack of parameters allowing early diagnosis of pneumonia, despite the need for rapid diagnosis and treatment. The ability to identify areas of hyperaemia or hypoperfusion could improve sensitivity and specificity in diagnosing pneumonia.

Necrotizing Enterocolitis: This is among the most devastating of neonatal diseases. It is characterized by intestinal necrosis of variable extension, leading to perforation, generalized peritonitis and death. The pathophysiology of NEC is not fully understood and its clinical presentation is varied and nonspecific, making early diagnosis challenging.  Because of its often-silent early progression, NEC is not always recognized until clinical signs are well developed. The rate of progression varies from case to case with the most extreme cases advancing to an unrecoverable state within 12 hours of presentation, emphasising the importance of early recognition and detection.

Photoacousic imaging
Photoacoustic (PA) imaging is an emerging imaging modality based on light-induced ultrasound (US) waves: Under pulsed light illuminations, specific tissue chromophores absorb light and convert optical energies into rapid rises in local temperature, resulting in the generation of US waves via thermal expansion. These US waves can be detected by US detectors to form images of optical absorption of chromophores. PA imaging inherits advantages from both optical and ultrasound imaging: it reveals spectroscopic optical contrasts of biological tissue that is originated from chemical composition, at cm-scale imaging depths. Additionally, PA imaging is capable of providing tissue functional information including blood oxygen saturation, and metabolism by optical excitation at multiple wavelengths. Using a clinical ultrasound probe, PA imaging can be performed to acquire naturally co-registered PA and US images to provide complementary functional, molecular and structural information of biological tissue.

This functional, molecular and structural information has the potential to be invaluable in the clinical evaluation of neonates at risk of NEC and lung pathologies. This project aims to investigate the potential of PA imaging as an affordable non-invasive bedside tool in the neonate.

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