This study investigated time-dependent group-level changes in chemical exchange saturation transfer (CEST) signals in a mouse model and explored utility in identifying stroke onset time. Multiparametric magnetic resonance imaging (diffusion weighted imaging, arterial spin labeling, and CEST) was conducted on 12 normal and 26 ischemic mice. Imaging findings were validated by immunohistochemical analysis. CEST parameters in infarct and penumbra were compared between strokes within 4.5 h and over 4.5 h. Correlations, regression, and receiver operating characteristic curves evaluated performance. Infarct guanidine, magnetization transfer (MT), nuclear Overhauser enhancement (NOE) (-3.5 ppm), and NOE (-1.6 ppm) significantly differed between groups and associated with onset time (P < .01). MT, NOE (-3.5 ppm), NOE (-1.6 ppm) showed significant associations with onset time in univariate logistic regression (P < .05). The NOE (-3.5 ppm) achieved an area under the curve of 0.848 (95% CI: 0.655-1.000), outperforming apparent diffusion coefficient (z = -2.397, P = .017) and cerebral blood flow (z = -2.271, P = .0271). NOE (-3.5 ppm) signals and lipid peroxidation both declined progressively with ischemic duration. These findings indicate that NOE (-3.5 ppm) signal attenuation parallels lipid peroxidation and may indicate progressive membrane lipid loss in ischemia.
Despite the increased water content in fibrotic livers, numerous studies reported a decrease in apparent diffusion coefficient (ADC) in liver fibrosis. We argue that the ADC decrease in fibrotic livers is due to the “T2 shine-through” of ADC, as the longer T2 in liver fibrosis leads to less signal decay between the low and high b -value images. The metric slow diffusion coefficient (SDC), predominantly measuring Brownian motion of water molecules, was proposed to mitigate the difficulties associated with this “T2 shine-through” of ADC. This study calculated ADC and SDC of 1 rat study with liver fibrosis induced by biliary duct ligation (BDL), and 3 sets of human liver fibrosis data. To tease out the menopausal effect on liver SDC, only the results of men's livers were analyzed for the human datasets. The rat study showed that liver ADC decreased stepwise (in weeks after BDL procedure) following fibrosis induction, and SDC increased stepwise. In human studies, all 3 datasets consistently showed that advanced fibrosis had a liver ADC lower than that of earlier stage fibrosis; advanced fibrosis had a liver SDC higher than that of earlier stage fibrosis.
Potent STING agonists are among the most promising strategies for reversing immunosuppression in “cold” tumors, but in vivo antitumor efficacy is frequently limited by dose-limiting systemic toxicity and inadequate tumor selectivity. To achieve localized STING activation and robust systemic immunity, we combined STING agonism with photodynamic therapy (PDT), creating a carrier-free nanoplatform (Ce6&SR717 NPs) through self-assembly of SR717 (STING agonist) and Ce6 (chlorin e6, photosensitizer). This excipient-free design achieves maximum drug loading, alleviates carrier-related safety issues, and realizes the spatiotemporally synchronized activation of PDT-induced immunogenic cell death and STING signaling through irradiation, which establishes an auto-amplifying cycle of on-site antigen release and systemic immune priming. In the murine breast cancer model, Ce6&SR717 NPs plus laser irradiation dramatically increased CD8 + T-cell infiltration within the tumor, triggered strong systemic antitumor immunity, and suppressed both primary and distant tumors. Collectively, these results identify Ce6&SR717 NPs as a safe and efficient modality for synergistic photo-immunotherapy of immunologically cold tumors.
Background This study aimed to evaluate the diagnostic performance of magnetic resonance imaging (MRI)-based radiomics for predicting pathological complete response (pCR) after neoadjuvant chemoradiotherapy in patients with locally advanced rectal adenocarcinoma. Methods Eligible studies developed MRI-based radiomics or deep learning models to predict pCR and reported sufficient data to reconstruct 2 × 2 contingency tables. Only validation cohorts were included in the quantitative synthesis. Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 and the Radiomics Quality Score. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio were estimated using a bivariate random-effects model. Hierarchical summary receiver operating characteristic (HSROC) analysis was performed. Results Thirty-eight studies were included. The pooled sensitivity and specificity were 0.82 (95% CI, 0.71-0.90) and 0.86 (95% CI, 0.80-0.91), respectively. The pooled PLR and NLR were 6.0 (95% CI, 4.0-8.9) and 0.21 (95% CI, 0.12-0.35), corresponding to a diagnostic odds ratio of 29 (95% CI, 14-61). HSROC analysis showed an area under the curve of 0.846. Subgroup analyses suggested improved performance for deep learning and combined clinical–radiomic models. Conclusion MRI-based radiomics demonstrates good diagnostic accuracy for predicting pCR after neoadjuvant chemoradiotherapy in rectal cancer, although methodological heterogeneity and limited prospective validation remain challenges.
The efficacy of chimeric antigen receptor (CAR)-T therapy in solid tumors is limited by the immunosuppressive microenvironment and poor T-cell infiltration. Radiotherapy offers immunomodulatory potential, yet its synergy with CAR-T via targeted internal radionuclides remains unexplored. Here, we identified protein regulator of cytokinesis 1 (PRC1) as a novel immunotherapeutic target. Through bioinformatic analysis, we engineered PRC1-specific CAR-T cells coexpressing the sodium iodide symporter (NIS) and an shRNA targeting SLC26A4, enabling enhanced iodide uptake and retention. These NIS-CAR-T cells demonstrated potent, antigen-restricted cytotoxicity and cytokine secretion upon co-culture with breast cancer cells. Low-dose 125 I selectively induced cytolysis in tumor cells without impairing CAR-T function. At low effector-to-target ratios mimicking poorly infiltrated “cold” tumors, internal irradiation via 125 I significantly boosted CAR-T killing, even against low-antigen tumors. This study introduces a multifunctional CAR-T platform that integrates internal radiotherapy to overcome key barriers in solid tumors, thereby offering a radiosensitized cellular therapy designed for the hostile tumor microenvironment.
Background:Positron emission tomography (PET) is one of the most effective imaging methods for detecting lung cancer, and artificial intelligence-based approaches are increasingly being applied to PET-based lung cancer detection. However, this typically requires a large amount of labeled data for training, while obtaining sufficient labeled PET imaging data remains challenging. Objective:To improve the accuracy of three-dimensional (3D) lung cancer detection in PET images and address the issue of scarce labeled data, this study aims to propose a novel self-supervised learning method based on the pseudo image generation. Methods:This method first uses a spatial tumor simulator to generate 3D images resembling real lung cancer lesions, and randomly implants them into the lung regions of PET images to construct pseudo-lung-cancer PET images. Subsequently, a restoration task based on pseudo-cancer images and normal images is designed as a self-supervised pretraining objective, using the 55 training cases to generate paired original and pseudo-lesion PET images, which are used to pretrain a Dual-Attention Hybrid Unet (DH-Unet) encoder-decoder integrated with a self-attention mechanism. Finally, the model is fine-tuned using real labeled PET data from these same 55 cases, along with 10 additional test cases, all pathologically confirmed as lung cancer, to complete the 3D lung cancer detection task. Results:Experimental results show that this method achieves significant performance in the lung cancer detection task, with an mAP@ 0.10 to 0.50 of 0.4616, which is 13.72% higher than that of the random initialization method and 11.1% higher than that of traditional self-supervised models. Conclusion:The proposed self-supervised learning framework, which combines pseudo image generation and a self-attention-equipped DH-Unet, provides an effective approach for improving lung cancer detection in PET imaging, especially in scenarios with limited labeled data.
The efficacy of chimeric antigen receptor (CAR)-T therapy in solid tumors is limited by the immunosuppressive microenvironment and poor T-cell infiltration. Radiotherapy offers immunomodulatory potential, yet its synergy with CAR-T via targeted internal radionuclides remains unexplored. Here, we identified protein regulator of cytokinesis 1 (PRC1) as a novel immunotherapeutic target. Through bioinformatic analysis, we engineered PRC1-specific CAR-T cells coexpressing the sodium iodide symporter (NIS) and an shRNA targeting SLC26A4, enabling enhanced iodide uptake and retention. These NIS-CAR-T cells demonstrated potent, antigen-restricted cytotoxicity and cytokine secretion upon co-culture with breast cancer cells. Low-dose 125 I selectively induced cytolysis in tumor cells without impairing CAR-T function. At low effector-to-target ratios mimicking poorly infiltrated “cold” tumors, internal irradiation via 125 I significantly boosted CAR-T killing, even against low-antigen tumors. This study introduces a multifunctional CAR-T platform that integrates internal radiotherapy to overcome key barriers in solid tumors, thereby offering a radiosensitized cellular therapy designed for the hostile tumor microenvironment.
Reporter genes are employed to improve visualization of specific tissues by creating a higher contrast in MR imaging. The genes on the magnetosome gene island (MAI) in magnetotactic bacteria have been of interest as contrast agents due to their ability to facilitate the formation of magnetic nanoparticles. In this work, we evaluated the influence of co-expressing mms6 and magA - genes within MAI- in mammalian cells and their effect on transverse relaxation rate when cultured with and without iron supplementation. A transgenic colorectal adenocarcinoma (HT-29) cell line co-expressing mms6 and magA was produced by transgene delivery using Sleeping Beauty. The iron uptake was measured using an iron assay kit and viability of cells was determined by trypan blue and MTT assays. The cells were supplemented with ferric citrate and imaged using a 3T Siemens Prisma. Data from a multiecho sequence was used to calculate R 2 (R 2 = 1/T 2 ) values by monoexponential fitting. We evaluated the R 2 of the cells co-expressing the two genes with cell lines expressing either gene individually and non-expressing control cells. The result showed dual expression of mms6 and magA lead to a significant increase in R 2 and iron uptake compared to cells expressing either gene individually.
Imprecision in breast-conserving surgery results in re-excision in 20% of cases, delaying adjuvant therapy and increasing patient anxiety and financial burden. Fluorescence-guided surgery (FGS) enables real-time tumor visualization and may improve surgical precision. This systematic review evaluates fluorophores investigated for intraoperative navigation in breast cancer. Medline, Embase, Scopus, and Web of Science were searched using "breast cancer," "surgery," "fluorophore," and "near-infrared." Eligible studies investigated in vivo fluorophores for invasive breast cancer in animals or humans. Of 1946 studies, 65 met the inclusion criteria. Extracted data included fluorophore administration, mechanism, optical properties, imaging systems, safety, and diagnostic accuracy. Dual-modality studies were excluded. 58 fluorophores were evaluated across 761 human and 520 animal subjects. Most agents emitted within the near-infrared-I (NIR-I) window (74.1%), while 11 utilized NIR-II imaging for deeper penetration. Indocyanine green (ICG) was the most widely studied fluorophore, demonstrating a pooled clinical tumor-to-background ratio (TBR) of 2.25 ± 0.74 (95% CI 2.10-2.39); sensitivity 80.8% (95% CI 72.5-89.2%); specificity 93.3% (95% CI 88.1-98.6%). IRDye800CW-trastuzumab demonstrated higher pooled TBRs of 4.83 ± 1.77 (95% CI 4.27-5.40). Nanoparticle-based fluorophores showed high contrast but remained preclinical. FGS is rapidly evolving, but no fluorophore has demonstrated optimal performance across translational endpoints; standardized reporting remains essential.
Background: Neurodegenerative diseases, characterized by progressive neuronal degeneration, are increasingly prevalent due to global aging trends and impose a significant burden on patients. No cure currently exists, with oxidative stress and inflammation serving as key drivers of disease progression. Advances in imaging technologies and artificial intelligence (AI) offer new opportunities for early diagnosis, monitoring, and treatment evaluation. This review aims to summarize the role of advanced neuroimaging modalities and AI integration in improving the diagnosis, monitoring, and management of neurodegenerative diseases, while highlighting current challenges and future directions. Material and Methods: A narrative review was conducted based on published literature on neuroimaging techniques in neurodegenerative diseases. Key modalities included structural and functional magnetic resonance imaging (MRI, fMRI), diffusion tensor imaging (DTI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). The integration of AI in image analysis was evaluated for its impact on diagnostic accuracy and workflow efficiency. Sources were selected from peer-reviewed journals focusing on clinical applications, technical advancements, and multimodal imaging strategies. Results Structural MRI, fMRI, and DTI provide detailed insights into brain atrophy and microstructural integrity, while PET and SPECT enable molecular-level assessment of metabolism and pathology. AI-enhanced analysis reduces interpretation variability and improves diagnostic precision. Despite these advances, high costs, limited accessibility, and inter-expert subjectivity remain major barriers. Emerging multimodal approaches and AI-driven tools show promise in enabling earlier detection and personalized treatment monitoring. Conclusion: The integration of advanced imaging and AI holds transformative potential for neurodegenerative disease management. Future efforts should prioritize cost reduction, improved accessibility, and seamless multimodal data fusion to translate these technologies into routine clinical practice.
Photoacoustic (PA) imaging is a promising modality for medical diagnostics and therapeutic monitoring, but accurate quantification of contrast agents (CAs) remains a challenge due to nonlinear signal responses and spectral shifts at varying concentrations. These limitations hinder its clinical utility in applications such as tumor detection and treatment monitoring. This study introduces a spectral decomposition method to improve absolute CA concentration estimation in PA imaging. By using a reference spectral library, the approach corrects for signal distortions and nonlinear behavior, overcoming key limitations of traditional intensity-based methods. Validation was performed through in vitro experiments using a prostate-specific membrane antigen (PSMA)-targeted CA in both saline and blood, as well as dynamic tracking of indocyanine green (ICG) in ex vivo tissue. The method achieved significantly lower concentration estimation errors, with average absolute errors of 1.80 µM in saline and 3.34 µM in blood. Compared to conventional techniques, the proposed method demonstrated enhanced reliability and robustness. These results underscore the potential of this spectral-based quantification technique to support more precise, clinically translatable PA imaging, enabling accurate CA measurement for early disease detection, surgical guidance, and real-time monitoring of therapeutic interventions.
Finding the rate constants (rates of transition) of radiopharmaceuticals between organs or different regions of interest (ROIs) in nuclear medicine quickly and accurately provides rich physiological data that is essential for determining drug dosages and performing precise radiation dosimetry. This article describes a novel exact analytical approach to achieving this goal. This can be done in a very short time period at the beginning of treatment with application of tracer levels of radiopharma, and using activities in the ROIs construct the rate constants. Here, using randomly chosen rate constants, time activity curves (TACs) for a four-compartment model are created, and using different sampling regimens of these TACs, the rate constants are reconstructed in a large number of simulations. The least square error (LSE) and relative LSE in the reconstructed parameters are shown to be better than 1 × 10 − 4 . While studies based on optimization methods have been described previously, this paper achieves the rate constants accurately and robustly using analytical methods, thus improving on the clinical applicability of these methods.
Purpose The kappa opioid receptor (KOR) plays a pivotal role in stress- and anxiety-related behaviors, with growing evidence linking it to stress induced by social isolation and separation. Despite this, tools for studying KOR in clinically relevant social contexts remain limited. The socially monogamous coppery titi monkey offers a translational model for investigating pair bonding. This study evaluated the feasibility of [ 11 C]GR103545 PET imaging to characterize KOR activity in vivo , and its pharmacological blockade for the first time in titi monkeys. Methods Adult titi monkeys (N = 6) underwent [ 11 C]GR103545 PET brain scans at baseline and following administration of the KOR antagonist CERC-501. Non-displaceable binding potential (BP ND ) was calculated across 14 brain volumes of interest (VOIs) implicated in social bonding, using Simplified and Logan reference tissue models (SRTM and LRTM), with the cerebellum as the reference region. Results Baseline [ 11 C]GR103545 uptake patterns across VOIs were consistent with reports in humans, other primates and published autoradiography data. CERC-501 pretreatment significantly reduced BP ND (SRTM: 55.99%, LRTM: 59.68%) across several, but not all brain VOIs. Conclusions This study establishes [ 11 C]GR103545 PET as a viable tool for assessing KOR binding dynamics in titi monkeys, providing new opportunities to explore KOR modulation in social bonding and separation.
Purpose The kappa opioid receptor (KOR) plays a pivotal role in stress- and anxiety-related behaviors, with growing evidence linking it to stress induced by social isolation and separation. Despite this, tools for studying KOR in clinically relevant social contexts remain limited. The socially monogamous coppery titi monkey offers a translational model for investigating pair bonding. This study evaluated the feasibility of [ 11 C]GR103545 PET imaging to characterize KOR activity in vivo , and its pharmacological blockade for the first time in titi monkeys. Methods Adult titi monkeys (N = 6) underwent [ 11 C]GR103545 PET brain scans at baseline and following administration of the KOR antagonist CERC-501. Non-displaceable binding potential (BP ND ) was calculated across 14 brain volumes of interest (VOIs) implicated in social bonding, using Simplified and Logan reference tissue models (SRTM and LRTM), with the cerebellum as the reference region. Results Baseline [ 11 C]GR103545 uptake patterns across VOIs were consistent with reports in humans, other primates and published autoradiography data. CERC-501 pretreatment significantly reduced BP ND (SRTM: 55.99%, LRTM: 59.68%) across several, but not all brain VOIs. Conclusions This study establishes [ 11 C]GR103545 PET as a viable tool for assessing KOR binding dynamics in titi monkeys, providing new opportunities to explore KOR modulation in social bonding and separation.
Background Ankylosing spondylitis (AS) is characterized by inflammation and osteoblastic changes in the sacroiliac joint. As a potential imaging method for the early assessment of AS, positron emission tomography (PET) can quantify systemic disease activity, which is conducive to monitoring the progression of disease activity and assisting in evaluating the efficacy of the treatment. Objective The study was to evaluate the diagnostic value of aluminium-[ 18 F]fuoride(Al 18 F)-labelled fibroblast activation protein inhibitor (FAPI) PET/computed tomography (CT) in AS and to investigate its ability to assess disease activity during the development of AS. Material and Methods Twenty AS participants who met the Assessment of SpondyloArthritis international Society criteria and were in an active disease stage were included in this study from May 2022 to April 2023. Sixteen healthy controls were also inrolled. All participants underwent Al 18 F-NOTA-FAPI-04 PET/CT imaging after collecting clinical assessment and laboratory results. The correlation between positive joint count (PJC) and systemic joint standard uptake value ratio (SUVR, the mean SUV max of the 5 highest joints/SUV max of the uninvolved sacrum) on PET and clinical disease activity assessment and various laboratory tests were analyzed. Results A total of 2820 joints were observed in 20 participants (median age 34.5,[21-61]range, 15 men), with a PJC of 1300 (46.7%), and 39 positive uptakes were found in 40 sacroiliac joints (97.5%). PET/CT images revealed FAPI-04 uptake in both sacroiliac joints in 2 participants without radiographic sacroiliitis in the early stages of AS and varying degrees of uptake in the sacroiliac joints and spinal joints in the remaining participants. PJC and SUVR were positively correlated with most clinical assessments and laboratory findings ( P < .05), and SUVR of the sacroiliac joint was positively correlated with C-reactive protein (CRP) (mg/L; r = 0.498, P = .026). Conclusion Al 18 F-NOTA-FAPI-04 PET/CT was highly sensitive to systemic arthritic changes in AS participants and correlated with clinical disease activity and laboratory tests. Keywords fibroblast activation protein , PET/CT , ankylosing spondylitis , inflammation
Purpose Elevated dopamine synthesis capacity is part of the pathophysiology of schizophrenia thought to underlie psychosis. Drugs that reduce this phenomenon could thus be potential treatments for these disorders. In this study, we evaluated the ability of the trace amine-associated receptor 1 (TAAR1) partial agonist ralmitaront to reduce presynaptic dopamine synthesis capacity. Procedures Ralmitaront (3 mg/kg, i.p.), a TAAR1 partial agonist, was evaluated using [18F]DOPA PET for its ability to modulate presynaptic dopamine synthesis capacity in naïve mice as well as mice in an induced hyperdopaminergic state following acute cocaine administration (20 mg/kg, i.p.). Results Cocaine treatment on its own did not induce elevated dopamine synthesis capacity when compared to the control group. Pretreatment with ralmitaront significantly reduced dopamine synthesis capacity when given either alone (44%) or in combination with the psychostimulant cocaine (50%) when compared to the control group. Conclusions The TAAR1 agonist ralmitaront reduces striatal dopamine synthesis capacity, indexed as KiMod, both in naïve animals and when given prior to acute cocaine. This indicates the potential of TAAR1 agonism to address disorders characterized by striatal hyperdopaminergia.
Purpose Elevated dopamine synthesis capacity is part of the pathophysiology of schizophrenia thought to underlie psychosis. Drugs that reduce this phenomenon could thus be potential treatments for these disorders. In this study, we evaluated the ability of the trace amine-associated receptor 1 (TAAR1) partial agonist ralmitaront to reduce presynaptic dopamine synthesis capacity. Procedures Ralmitaront (3 mg/kg, i.p.), a TAAR1 partial agonist, was evaluated using [ 18 F]DOPA PET for its ability to modulate presynaptic dopamine synthesis capacity in naïve mice as well as mice in an induced hyperdopaminergic state following acute cocaine administration (20 mg/kg, i.p.). Results Cocaine treatment on its own did not induce elevated dopamine synthesis capacity when compared to the control group. Pretreatment with ralmitaront significantly reduced dopamine synthesis capacity when given either alone (44%) or in combination with the psychostimulant cocaine (50%) when compared to the control group. Conclusions The TAAR1 agonist ralmitaront reduces striatal dopamine synthesis capacity, indexed as Ki Mod , both in naïve animals and when given prior to acute cocaine. This indicates the potential of TAAR1 agonism to address disorders characterized by striatal hyperdopaminergia.
Background In rodents, 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyzes the conversion of inactive 11-dehydrocorticosterone to the active hormone corticosterone. Dysregulation of intracellular glucocorticoid action is implicated in metabolic diseases. Assessing 11β-HSD1 enzyme levels in vivo may be key to understanding obesity pathophysiology. Objective We used a Zucker Fatty (ZF) rat model and [ 18 F]AS2471907 PET imaging to determine appropriate kinetic modeling methods and assess changes in 11β-HSD1 levels due to obesity in the liver, white and brown adipose tissue (WAT/BAT), and brain. Material and Methods To validate [ 18 F]AS2471907 PET in preclinical models, time-activity curves (TACs) were generated and kinetic modeling was performed with image-derived input functions (IDIFs) extracted from multiple locations. Quantitative estimates of radioligand binding were compared with ex vivo 11β-HSD1 protein expression. Validated quantitative PET kinetic modeling methods were then used to assess differences in 11β-HSD1 between lean and obese ZF rats. Metabolic disease status was confirmed with stable isotopes tracer studies of glucose and fatty acid metabolism. Results Obesity is associated with decreased brain 11β-HSD1 levels, measured by [ 18 F]AS2471907 PET, which correlated with measures of glucose and fatty acid metabolism. Conclusion We demonstrate that [ 18 F]AS2471907 PET can provide useful quantification of 11β-HSD1 levels in a rodent model of obesity.
Introduction and Purpose Radiopharmaceutical therapy (RPT) dosimetry can be challenging to perform due to sparse data measurements and variations in how the time activity curve (TAC) is determined. In this work, a single system of equations was theoretically derived to estimate the TAC. Methods A pharmacokinetic (PK) model was developed to estimate patient specific rate constants for a given set of body compartments. The PK model and an optimizer were numerically implemented to determine the rate constants and, using these physiologic data, to generate TACs and time integrated activities (TIAs) for 3 tissue systems from clinical data gathered in 5 patients. A fourth (aggregate) tissue compartment is added using conservation of activity considerations. Results Feasibility of the PK model was demonstrated by successfully generating TACs and TIAs for all patients in a manner comparable to existing methods in the literature. The data are compared to smaller sampling regimes. Differences between the 3- and 4-compartment models show that conservation of activity considerations should be part of TAC estimations. Conclusion The results here suggest a new paradigm in RPT in using the rate constants so identified as a diagnostic tool and as a vehicle to achieving individualized tumorcidal dose and/or the maximum tolerable dose to normal tissues.
The magnetosome, a membrane-bound iron biomineral formed within magnetotactic bacteria, is a unique model for a magnetic resonance imaging (MRI) reporter gene contrast agent. We are translating this technology to mammalian cells by expressing essential magnetosome genes mamI, mamL, mamB, and mamE into MDA-MB-435 human melanoma cells. Currently, these genes are individually expressed in the cell although the future goal is to express all four genes together. We examined the influence of these genes on cellular MRI relaxation rates by culturing cells in the presence and absence of iron-supplemented medium and scanning them at 3 Tesla using a gelatin phantom. Total cellular iron was measured by inductively-coupled plasma mass spectrometry and correlated with relaxation rates obtained from phantom experiments. Apart from mamE, magnetosome genes that are individually expressed in mammalian cells grown in iron supplement significantly affected cellular transverse relaxation rates compared to cells grown without iron supplement. Interestingly, mamI, mamL, mamB, and mamE (even though the latter had no effect on relaxation rate) significantly affected cellular iron content. This developing gene-based contrast agent will equip MRI with improvement to imaging sensitivity and the technology to track cellular activities long term.
