Solitary pulmonary nodule imaging approaches and the role of optical fibre-based technologies

Abstract

Solitary pulmonary nodules (SPNs) are a clinical challenge, given there is no single clinical sign or radiological feature that definitively identifies a benign from a malignant SPN. The early detection of lung cancer has a huge impact on survival outcome. Consequently, there is great interest in the prompt diagnosis, and treatment of malignant SPNs. Current diagnostic pathways involve endobronchial/transthoracic tissue biopsies or radiological surveillance, which can be associated with suboptimal diagnostic yield, healthcare costs and patient anxiety. Cutting-edge technologies are needed to disrupt, and improve, existing care pathways. Optical fibre-based techniques, which can be delivered via the working channel of a bronchoscope or via transthoracic needle, may deliver advanced diagnostic capabilities in patients with SPNs. Optical endomicroscopy, an autofluorescence-based imaging technique, demonstrates abnormal alveolar structure in SPNs in vivo. Alternative optical fingerprinting approaches, such as time-resolved fluorescence spectroscopy and fluorescence-lifetime imaging microscopy, have shown promise in discriminating lung cancer from surrounding healthy tissue. Whilst fibre-based Raman spectroscopy has enabled real-time characterisation of SPNs in vivo. Fibre-based technologies have the potential to enable in situ characterisation and real-time microscopic imaging of SPNs, which could aid immediate treatment decisions in patients with SPNs. This review discusses advances in current imaging modalities for evaluating SPNs, including computed tomography (CT) and positron emission tomography-CT. It explores the emergence of optical fibre-based technologies, and discusses their potential role in patients with SPNs and suspected lung cancer.

Fibroblast Activation Protein Specific Optical Imaging in Non-Small Cell Lung Cancer

“…Label free optical imaging modalities have the potential to characterize lung cancer using both optical endomicroscopy and fluorescence lifetime imaging (FLIM) systems ( 36 ). Here we used a clinically approved fluorescence and FLIM imaging system ( 31 ) which was compatible with bronchoscopy, where a fibre can be passed through the working channel to access tumours and lung parenchyma ( Supplementary Figure S5 ).…”

Targeted detection of cancer cells during biopsy allows real-time diagnosis of pulmonary nodules

“…GGOs are the most challenging pulmonary lesions to evaluate during diagnostic biopsy because they are often early-stage adenocarcinoma spectrum lesions that have a soft tissue architecture not easily distinguishable from normal lung parenchyma [31]. GGOs, unlike solid nodules, cannot be seen using fluoroscopy and radial endobronchial ultrasound (r-EBUS), and no technique is available for real-time visualization of GGOs [3,32,33]. In all GGOs evaluated in this study, fluorescent cancer cells were identified within the lesion during biopsy.…”

“…Increasing use of computed tomography scanning in medical practice and lung cancer screening guidelines has made it commonplace to detect pulmonary nodules radiographically suspicious for malignancy [1,2]. These solitary pulmonary nodules (SPNs)-spherical radiographic opacities less than 3 cm in diameter that are surrounded by normal lung-present a significant clinical challenge, as the majority are benign but a nontrivial portion represent early-stage, curable lung cancers [3]. There is no clinical or radiological feature that definitively identifies malignant SPNs, and SPNs often require endobronchial or transthoracic tissue biopsy to rule out malignancy [2,4].…”

“…Both probebased CLE (pCLE) and needle-based CLE (nCLE) permit autofluorescence imaging as well as reverse-contrast imaging of tissues after systemic administration of fluorescein [8,12,13,18]. While promising, these approaches require image interpretation by an experienced observer and do not provide sensitive detection of malignancy at the level of individual cancer cells [3].…”

Getting innovative bronchoscopic techniques into real clinical practice

“…Optical endomicroscopy, such as fibre-based confocal laser fluorescence endomicroscopy (CLE), is a high-resolution imaging technique, which enables autofluorescence visualisation of individual cells and structures of the respiratory tract and distal lung parenchyma at a near microscopic level. Probe-based confocal laser endomicroscopy (pCLE) is available since 2008 using a thin semiflexible 1.2 mm probe (Alveoflex, Cellvizio System; Mauna Kea Technologies, Paris, France), which is inserted through the working channel of a bronchoscope 7 8. It consists of 30 000 optical fibres enabling a lateral resolution of 3 µm, confocal depth of focus of 0–50 µm and a 600 µm field of view.…”