Imaging & Diagnostics

Brain MRI volumetrics uses structural magnetic resonance imaging to quantify the volume of specific brain regions — most notably the hippocampus, lateral ventricles and total grey- and white-matter — as well as cortical thickness across parcellated regions. Automated analysis pipelines such as FreeSurfer and the GPU-accelerated FastSurfer process T1-weighted images to generate normative deviation scores; larger ventricular volumes and reduced hippocampal or cortical thickness are established markers of accelerated brain ageing, with rates of atrophy increasing substantially after age 60. Cross-sectional population studies such as UK Biobank have mapped trajectories of regional volume loss against age, lifestyle factors and disease risk, enabling the concept of a 'brain age gap' — the difference between estimated brain age and chronological age — as a potential biomarker for neurodegenerative risk and cognitive resilience.

Carotid intima-media thickness (CIMT) is the B-mode ultrasound measurement of the combined thickness of the intima and media layers of the common carotid artery wall, serving as a surrogate marker for subclinical atherosclerosis and vascular ageing. CIMT increases progressively with age and is elevated in the presence of traditional cardiovascular risk factors; population-based studies established associations with incident myocardial infarction, stroke and all-cause mortality, and it was incorporated into risk calculators in the early 2000s. However, the randomised METEOR and other statin trials showed that reductions in CIMT did not reliably translate to clinical event reduction, and subsequent meta-analyses questioned its incremental value over traditional risk models, leading major cardiology guidelines to downgrade its routine clinical use. CIMT remains widely used in cardiovascular research as an outcome measure for intervention trials and in observational studies of accelerated vascular ageing.

Coronary CT angiography (CCTA) uses multi-detector computed tomography with intravenous iodinated contrast to produce three-dimensional images of the coronary arteries, enabling assessment of both luminal stenosis and plaque composition — including non-calcified, low-attenuation (lipid-rich) plaques that are not visible on unenhanced calcium scoring. In the SCOT-HEART randomised trial (n=4,146), CCTA-guided management reduced fatal and non-fatal myocardial infarction by 41% over five years compared with standard care, partly through reclassification of risk and initiation of preventive therapy. Modern CCTA delivers effective radiation doses of approximately 1–5 mSv with iterative reconstruction, substantially lower than earlier protocols; CT-derived fractional flow reserve (CT-FFR) extends the examination to haemodynamic significance assessment without invasive catheterisation. CCTA differs from coronary artery calcium (CAC) scoring: CAC quantifies calcified plaque burden only, while CCTA reveals the full atherosclerotic plaque landscape including non-calcified disease.

FibroScan (vibration-controlled transient elastography, VCTE) measures liver stiffness in kilopascals (kPa) by propagating a low-frequency shear wave through hepatic tissue and tracking its velocity via ultrasound, with stiffer tissue reflecting more advanced fibrosis. Validated cut-offs range from approximately 7–8 kPa for significant fibrosis (F2) to >12–14 kPa for cirrhosis, though values are influenced by inflammation, congestion, food intake and BMI. In metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD) — now the commonest cause of chronic liver disease globally — VCTE is endorsed as a non-invasive alternative to biopsy for fibrosis staging and longitudinal monitoring, avoiding both sampling error and procedural risk. The controlled attenuation parameter (CAP), measured simultaneously on modern devices, quantifies hepatic steatosis in dB/m and enables a single-visit assessment of both fat content and fibrosis stage.

Positron emission tomography with amyloid-targeting tracers — florbetapir, florbetaben and flutemetamol, all FDA-approved — allows in vivo visualisation of fibrillar amyloid-beta plaques, while second-generation tau PET tracers such as flortaucipir map neurofibrillary tangle burden and staging (Braak stages) in living patients. PET amyloid and tau status have become clinically actionable since 2023–2024, following the FDA approvals of lecanemab (Leqembi) and donanemab: both anti-amyloid antibody therapies require confirmed amyloid positivity for treatment eligibility, and tau PET staging increasingly informs prognosis and likely treatment benefit. Centiloid standardisation of amyloid PET allows cross-scanner and cross-tracer comparison, though reimbursement for diagnostic use remains limited in most healthcare systems. Radiation exposure (approximately 5–7 mSv per scan) and cost are relevant constraints for population screening applications.

Pulse wave velocity (PWV) is the speed at which the pressure wave generated by ventricular ejection travels along the arterial tree, and is the non-invasive gold-standard measure of arterial stiffness. Carotid-femoral PWV (cf-PWV), measured by applanation tonometry or oscillometric devices over the aortic segment, is the most validated modality: the European Society of Hypertension threshold of >10 m/s in the context of hypertension identifies pathological aortic stiffness. Arterial wall composition, cross-linking of structural proteins, elastin fragmentation and vascular smooth-muscle tone all contribute to stiffness, which increases progressively with age and is further accelerated by hypertension, diabetes and chronic kidney disease. Large prospective studies and meta-analyses have demonstrated that cf-PWV independently predicts cardiovascular events and all-cause mortality beyond traditional risk factors, including in populations free of established cardiovascular disease.

Optical coherence tomography (OCT) of the retina generates micrometre-resolution cross-sectional images of retinal layers, enabling quantification of macular thickness, retinal nerve fibre layer (RNFL) thickness and ganglion cell layer volume, while fundus photography documents the retinal vasculature and optic disc. Because the retina shares embryological origin and vascular supply architecture with the brain, retinal parameters serve as proxies for central nervous system and systemic vascular health: RNFL thinning is an established marker of glaucoma and has been associated with Alzheimer's disease, multiple sclerosis and Parkinson's disease. Deep-learning algorithms trained on fundus images can estimate cardiovascular risk factors — including age, sex, blood pressure and HbA1c — directly from the image, and emerging 'retinal age gap' AI clocks predict mortality and morbidity beyond chronological age in large population studies. OCT angiography (OCTA) extends the examination to capillary-level flow mapping without dye injection, enabling assessment of foveal avascular zone geometry as a vascular health marker.

Whole-body MRI (WB-MRI) acquires multi-station images covering the brain, neck, thorax, abdomen and pelvis without ionising radiation, enabling simultaneous assessment of soft tissue, organs and bone marrow in a single session lasting approximately 45–90 minutes. Its clinical utility is established in specific contexts — surveillance of hereditary cancer syndromes (Li-Fraumeni, BRCA2) and staging of multiple myeloma — but evidence for benefit in asymptomatic general-population screening is lacking; randomised trial data demonstrating reduced morbidity or mortality from commercial longevity-screening offerings are not available. Incidentaloma rates are high, with studies reporting clinically significant and minor incidental findings in 30–50% of asymptomatic subjects, creating a risk of diagnostic cascades involving further imaging, biopsy and unnecessary intervention. Major radiology and oncology societies have not endorsed WB-MRI for routine preventive screening outside of defined high-risk genetic populations.