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Medical imaging is a revolutionary field that has transformed healthcare, providing clinicians with the ability to view the inside of the body without invasive procedures. This overview traces the evolution of the major medical imaging modalities from their inception to the advanced technologies used today. Starting with the serendipitous discovery of X-rays by Wilhelm Conrad Röntgen in 1895 the subsequent developments in various imaging modalities including fluoroscopy, computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine and ultrasound imaging are chronicled. The technological breakthroughs, pioneering scientists and clinicians involved, and the significant impact of these advancements on diagnostic medicine are discussed. Additionally the integration of digital imaging, artificial intelligence (AI) and machine learning technologies into medical imaging is considered together with their potential to revolutionise diagnostic procedures, enhance patient care and streamline healthcare delivery.

Our purpose is to investigate the feasibility of imaging tumor metabolism in breast cancer patients using 13C magnetic resonance spectroscopic imaging (MRSI) of hyperpolarized 13C label exchange between injected [1-13C]pyruvate and the endogenous tumor lactate pool. Treatment-naïve breast cancer patients were recruited: four triple-negative grade 3 cancers; two invasive ductal carcinomas that were estrogen and progesterone receptor-positive (ER/PR+) and HER2/neu-negative (HER2−), one grade 2 and one grade 3; and one grade 2 ER/PR+ HER2− invasive lobular carcinoma (ILC). Dynamic 13C MRSI was performed following injection of hyperpolarized [1-13C]pyruvate. Expression of lactate dehydrogenase A (LDHA), which catalyzes 13C label exchange between pyruvate and lactate, hypoxia-inducible factor-1 (HIF1α), and the monocarboxylate transporters MCT1 and MCT4 were quantified using immunohistochemistry and RNA sequencing. We have demonstrated the feasibility and safety of hyperpolarized 13C MRI in early breast cancer. Both intertumoral and intratumoral heterogeneity of the hyperpolarized pyruvate and lactate signals were observed. The lactate-to-pyruvate signal ratio (LAC/PYR) ranged from 0.021 to 0.473 across the tumor subtypes (mean ± SD: 0.145 ± 0.164), and a lactate signal was observed in all of the grade 3 tumors. The LAC/PYR was significantly correlated with tumor volume (R = 0.903, P = 0.005) and MCT 1 (R = 0.85, P = 0.032) and HIF1α expression (R = 0.83, P = 0.043). Imaging of hyperpolarized [1-13C]pyruvate metabolism in breast cancer is feasible and demonstrated significant intertumoral and intratumoral metabolic heterogeneity, where lactate labeling correlated with MCT1 expression and hypoxia.

Deuterium metabolic imaging (DMI) and hyperpolarized 13C-pyruvate MRI (13C-HPMRI) are two emerging methods for non-invasive and non-ionizing imaging of tissue metabolism. Imaging cerebral metabolism has potential applications in cancer, neurodegeneration, multiple sclerosis, traumatic brain injury, stroke, and inborn errors of metabolism. Here we directly compare these two non-invasive methods at 3 T for the first time in humans and show how they simultaneously probe both oxidative and non-oxidative metabolism. DMI was undertaken 1–2 h after oral administration of [6,6′-2H2]glucose, and 13C-MRI was performed immediately following intravenous injection of hyperpolarized [1–13C]pyruvate in ten and nine normal volunteers within each arm respectively. DMI was used to generate maps of deuterium-labelled water, glucose, lactate, and glutamate/glutamine (Glx) and the spectral separation demonstrated that DMI is feasible at 3 T. 13C-HPMRI generated maps of hyperpolarized carbon-13 labelled pyruvate, lactate, and bicarbonate. The ratio of 13C-lactate/13C-bicarbonate (mean 3.7 ± 1.2) acquired with 13C-HPMRI was higher than the equivalent 2H-lactate/2H-Glx ratio (mean 0.18 ± 0.09) acquired using DMI. These differences can be explained by the route of administering each probe, the timing of imaging after ingestion or injection, as well as the biological differences in cerebral uptake and cellular physiology between the two molecules. The results demonstrate these two metabolic imaging methods provide different yet complementary readouts of oxidative and reductive metabolism within a clinically feasible timescale. Furthermore, as DMI was undertaken at a clinical field strength within a ten-minute scan time, it demonstrates its potential as a routine clinical tool in the future.

Hyperpolarized 13C Magnetic Resonance Imaging (13C-MRI) provides a highly sensitive tool to probe tissue metabolism in vivo and has recently been translated into clinical studies. We report the cerebral metabolism of intravenously injected hyperpolarized [1–13C]pyruvate in the brain of healthy human volunteers for the first time. Dynamic acquisition of 13C images demonstrated 13C-labeling of both lactate and bicarbonate, catalyzed by cytosolic lactate dehydrogenase and mitochondrial pyruvate dehydrogenase respectively. This demonstrates that both enzymes can be probed in vivo in the presence of an intact blood-brain barrier: the measured apparent exchange rate constant (kPL) for exchange of the hyperpolarized 13C label between [1–13C]pyruvate and the endogenous lactate pool was 0.012 ± 0.006 s−1 and the apparent rate constant (kPB) for the irreversible flux of [1–13C]pyruvate to [13C]bicarbonate was 0.002 ± 0.002 s−1. Imaging also revealed that [1–13C]pyruvate, [1–13C]lactate and [13C]bicarbonate were significantly higher in gray matter compared to white matter. Imaging normal brain metabolism with hyperpolarized [1–13C]pyruvate and subsequent quantification, have important implications for interpreting pathological cerebral metabolism in future studies. [Display omitted]

Fully-quantitative MR imaging methods are useful for longitudinal characterization of disease and assessment of treatment efficacy. However, current quantitative MRI protocols have not been widely adopted in the clinic, mostly due to lengthy scan times. Magnetic Resonance Fingerprinting (MRF) is a new technique that can reconstruct multiple parametric maps from a single fast acquisition in the transient state of the MR signal. Due to the relative novelty of this technique, the repeatability and reproducibility of quantitative measurements obtained using MRF has not been extensively studied. Our study acquired test/retest data from the brains of nine healthy volunteers, each scanned on five MRI systems (two at 3.0 T and three at 1.5 T, all from a single vendor) located at two different centers. The pulse sequence and reconstruction algorithm were the same for all acquisitions. After registration of the MRF-derived M0, T1 and T2 maps to an anatomical atlas, coefficients-of-variation (CVs) were computed to assess test/retest repeatability and inter-site reproducibility in each voxel, while a General Linear Model (GLM) was used to determine the voxel-wise variability between all confounders, which included test/retest, subject, field strength and site. Our analysis demonstrated an excellent repeatability (CVs of 2–3% for T1, 5–8% for T2, 3% for normalized-M0) and a good reproducibility (CVs of 3–8% for T1, 8–14% for T2, 5% for normalized-M0) in grey and white matter.

T1 mapping and extracellular volume (ECV) have the potential to guide patient care and serve as surrogate end-points in clinical trials, but measurements differ between cardiovascular magnetic resonance (CMR) scanners and pulse sequences. To help deliver T1 mapping to global clinical care, we developed a phantom-based quality assurance (QA) system for verification of measurement stability over time at individual sites, with further aims of generalization of results across sites, vendor systems, software versions and imaging sequences. We thus created T1MES: The T1 Mapping and ECV Standardization Program. A design collaboration consisting of a specialist MRI small-medium enterprise, clinicians, physicists and national metrology institutes was formed. A phantom was designed covering clinically relevant ranges of T1 and T2 in blood and myocardium, pre and post-contrast, for 1.5 T and 3 T. Reproducible mass manufacture was established. The device received regulatory clearance by the Food and Drug Administration (FDA) and Conformité Européene (CE) marking. The T1MES phantom is an agarose gel-based phantom using nickel chloride as the paramagnetic relaxation modifier. It was reproducibly specified and mass-produced with a rigorously repeatable process. Each phantom contains nine differently-doped agarose gel tubes embedded in a gel/beads matrix. Phantoms were free of air bubbles and susceptibility artifacts at both field strengths and T1 maps were free from off-resonance artifacts. The incorporation of high-density polyethylene beads in the main gel fill was effective at flattening the B1 field. T1 and T2 values measured in T1MES showed coefficients of variation of 1 % or less between repeat scans indicating good short-term reproducibility. Temperature dependency experiments confirmed that over the range 15–30 °C the short-T1 tubes were more stable with temperature than the long-T1 tubes. A batch of 69 phantoms was mass-produced with random sampling of ten of these showing coefficients of variations for T1 of 0.64 ± 0.45 % and 0.49 ± 0.34 % at 1.5 T and 3 T respectively. The T1MES program has developed a T1 mapping phantom to CE/FDA manufacturing standards. An initial 69 phantoms with a multi-vendor user manual are now being scanned fortnightly in centers worldwide. Future results will explore T1 mapping sequences, platform performance, stability and the potential for standardization.

Hyperpolarised magnetic resonance imaging (HP  13 C-MRI) is an emerging clinical technique to detect [1- 13 C]lactate production in prostate cancer (PCa) following intravenous injection of hyperpolarised [1- 13 C]pyruvate. Here we differentiate clinically significant PCa from indolent disease in a low/intermediate-risk population by correlating [1- 13 C]lactate labelling on MRI with the percentage of Gleason pattern 4 (%GP4) disease. Using immunohistochemistry and spatial transcriptomics, we show that HP  13 C-MRI predominantly measures metabolism in the epithelial compartment of the tumour, rather than the stroma. MRI-derived tumour [1- 13 C]lactate labelling correlated with epithelial mRNA expression of the enzyme lactate dehydrogenase (LDHA and LDHB combined), and the ratio of lactate transporter expression between the epithelial and stromal compartments (epithelium-to-stroma MCT4). We observe similar changes in MCT4, LDHA, and LDHB between tumours with primary Gleason patterns 3 and 4 in an independent TCGA cohort. Therefore, HP  13 C-MRI can metabolically phenotype clinically significant disease based on underlying metabolic differences in the epithelial and stromal tumour compartments. Your paper will be accompanied by the following editor’s summary. Please let us know if there are any inaccuracies: ‘Hyperpolarised ¹³C-MRI is used to image cancer metabolism. Here the authors use this technique in prostate cancer and show that it can differentiate distinct disease states.

Objectives Hypoxia is associated with poor prognosis and treatment resistance in breast cancer. However, the temporally variant nature of hypoxia can complicate interpretation of imaging findings. We explored the relationship between hypoxia and vascular function in breast tumours through combined 18 F-fluoromisonidazole ( 18 F-FMISO) PET/MRI, with simultaneous assessment circumventing the effect of temporal variation in hypoxia and perfusion. Methods Women with histologically confirmed, primary breast cancer underwent a simultaneous 18 F-FMISO-PET/MR examination. Tumour hypoxia was assessed using influx rate constant K i and hypoxic fractions (%HF), while parameters of vascular function ( K trans , k ep , v e , v p ) and cellularity (ADC) were derived from dynamic contrast-enhanced (DCE) and diffusion-weighted (DW)-MRI, respectively. Additional correlates included histological subtype, grade and size. Relationships between imaging variables were assessed using Pearson correlation ( r ). Results Twenty-nine women with 32 lesions were assessed. Hypoxic fractions > 1% were observed in 6/32 (19%) cancers, while 18/32 (56%) tumours showed a %HF of zero. The presence of hypoxia in lesions was independent of histological subtype or grade. Mean tumour K trans correlated negatively with K i ( r  = − 0.38, p  = 0.04) and %HF ( r  = − 0.33, p  = 0.04), though parametric maps exhibited intratumoural heterogeneity with hypoxic regions colocalising with both hypo- and hyperperfused areas. No correlation was observed between ADC and DCE-MRI or PET parameters. %HF correlated positively with lesion size ( r  = 0.63, p  = 0.001). Conclusion Hypoxia measured by 18 F-FMISO-PET correlated negatively with K trans from DCE-MRI, supporting the hypothesis of perfusion-driven hypoxia in breast cancer. Intratumoural hypoxia-perfusion relationships were heterogeneous, suggesting that combined assessment may be needed for disease characterisation, which could be achieved using simultaneous multimodality imaging. Key Points • At the tumour level, hypoxia measured by 18 F-FMISO-PET was negatively correlated with perfusion measured by DCE-MRI, which supports the hypothesis of perfusion-driven hypoxia in breast cancer. • No associations were observed between 18F-FMISO-PET parameters and tumour histology or grade, but tumour hypoxic fractions increased with lesion size. • Intratumoural hypoxia-perfusion relationships were heterogeneous, suggesting that the combined hypoxia-perfusion status of tumours may need to be considered for disease characterisation, which can be achieved via simultaneous multimodality imaging as reported here.

Imaging in thyroid eye disease (TED) is used to exclude other diagnoses, assess for apical crowding and plan surgery. But to quantify TED activity objectively, subjective clinical scoring assessments remain the norm. Magnetic resonance imaging (MRI) T2-relaxation times correlate with extra-ocular muscle (EOM) inflammation, but are confounded by signal from fat. We investigated whether T2-relaxation mapping in combination with fat fraction (FF) measurements could quantify disease activity in EOMs objectively. Sixty-two TED patients and six controls were enroled for coronal short tau inversion recovery (STIR), T2 multi-echo fast-spin echo and multi-echo fast-gradient echo MRI of the orbits. STIR signal intensity ratios (SIRs), T2-relaxation times and percentage FF were derived for inferior, lateral, superior and medial recti bilaterally. Twelve patients were re-scanned following immunosuppressive treatment. The results found a positive correlation for all subjects between T2 and SIR (p < 0.001), but only mean T2 differed significantly between patients and controls (p < 0.001). We measured FF in EOMs for the first time and found it greater in TED (p < 0.001). There was also a significant reduction in mean T2 after treatment, with a corresponding reduction in the clinical activity score (CAS) in almost all patients. We show that T2-relaxation times differentiate between normal and inflamed EOMs and are responsive to treatment. Combined, uniquely, with FF measurement in EOMs, an objective, quantitative marker of inflammation in TED-affected muscles could be derived. T2-relaxation times mirrored improvements in CAS after treatment, occasionally preceding them. Rarely, they diverged, suggesting limitations in the CAS as a disease burden marker.

Objective Although certain morphological features depicted by high resolution, multi-contrast magnetic resonance imaging (hrMRI) have been shown to be different between culprit and non-culprit middle cerebral artery (MCA) atherosclerotic lesions, the incremental value of hrMRI to define culprit lesions over stenosis has not been assessed. Methods Patients suspected with MCA stenosis underwent hrMRI. Lumen and outer wall were segmented to calculate stenosis, plaque burden (PB), volume (PV), length (PL) and minimum luminal area (MLA). Results Data from 165 lesions (112 culprit and 53 non-culprit) in 139 individuals were included. Culprit lesions were larger and longer with a narrower lumen and increased PB compared with non-culprit lesions. More culprit lesions showed contrast enhancement. Both PB and MLA were better indicators than stenosis in differentiating lesion types (AUC were 0.649, 0.732 and 0.737 for stenosis, PB and MLA, respectively). Combinations of PB, MLA and stenosis could improve positive predictive value (PPV) and specificity significantly. An optimal combination of stenosis ≥ 50 %, PB ≥ 77 % and MLA ≤ 2.0 mm 2 produced a PPV = 85.7 %, negative predictive value = 54.1 %, sensitivity = 69.6 %, specificity = 75.5 %, and accuracy = 71.5 %. Conclusions hrMRI plaque imaging provides incremental information to luminal stenosis in identifying culprit lesions. Key points • High resolution MRI provides incremental information in defining culprit MCA atherosclerotic lesions. • Both plaque burden and minimum luminal area are better indicators than stenosis. • An optimal combination includes stenosis ≥ 50 %, PB ≥ 77 % and MLA ≤ 2.0 mm 2 .