Current Role at Stanford

Associate Director of Stanford Center for Innovation in In vivo Imaging (SCi3), Radiology
Member, Molecular Imaging Program at Stanford

Professional Affiliations and Activities

  • Member, AAPM (1993 - Present)
  • Member, ISMRM (2002 - Present)

All Publications

  • Reproducibility and repeatability of quantitative T2 and T2* mapping of osteosarcomas in a mouse model. European radiology experimental Roudi, R., Pisani, L. J., Pisani, F., Liang, T., Daldrup-Link, H. E. 2024; 8 (1): 74


    New immunotherapies activate tumor-associated macrophages (TAMs) in the osteosarcoma microenvironment. Iron oxide nanoparticles (IONPs) are phagocytosed by TAMs and, therefore, enable TAM detection on T2*- and T2-weighted magnetic resonance images. We assessed the repeatability and reproducibility of T2*- and T2-mapping of osteosarcomas in a mouse model.Fifteen BALB/c mice bearing-murine osteosarcomas underwent magnetic resonance imaging (MRI) on 3-T and 7-T scanners before and after intravenous IONP infusion, using T2*-weighted multi-gradient-echo, T2-weighted fast spin-echo, and T2-weighted multi-echo sequences. Each sequence was repeated twice. Tumor T2 and T2* relaxation times were measured twice by two independent investigators. Repeatability and reproducibility of measurements were assessed.We found excellent agreement between duplicate acquisitions for both T2* and T2 measurements at either magnetic field strength, by the same individual (repeatability), and between individuals (reproducibility). The repeatability concordance correlation coefficient (CCC) for T2* values were 0.99 (coefficients of variation (CoV) 4.43%) for reader 1 and 0.98 (CoV 5.82%) for reader 2. The reproducibility of T2* values between the two readers was 0.99 (CoV 3.32%) for the first acquisitions and 0.99 (CoV 6.30%) for the second acquisitions. Regarding T2 values, the repeatability of CCC was similar for both readers, 0.98 (CoV 3.64% for reader 1 and 4.45% for reader 2). The CCC of the reproducibility of T2 was 0.99 (CoV 3.1%) for the first acquisition and 0.98 (CoV 4.38%) for the second acquisition.Our results demonstrated high repeatability and reproducibility of quantitative T2* and T2 mapping for monitoring the presence of TAMs in osteosarcomas.T2* and T2 measurements of osteosarcomas on IONP-enhanced MRI could allow identifying patients who may benefit from TAM-modulating immunotherapies and for monitoring treatment response. The technique described here could be also applied across a wide range of other solid tumors.• Optimal integration of TAM-modulating immunotherapies with conventional chemotherapy remains poorly elucidated. • We found high repeatability of T2* and T2 measurements of osteosarcomas in a mouse model, both with and without IONPs contrast, at 3-T and 7-T MRI field strengths. • T2 and T2* mapping may be used to determine response to macrophage-modulating cancer immunotherapies.

    View details for DOI 10.1186/s41747-024-00467-9

    View details for PubMedID 38872042

    View details for PubMedCentralID 6763764

  • Two-Photon Intravital Microscopy of Glioblastoma in a Murine Model. Journal of visualized experiments : JoVE Nernekli, K., Mangarova, D. B., Shi, Y., Varniab, Z. S., Chang, E., Tikenogullari, O. Z., Pisani, L., Tikhomirov, G., Wang, G., Daldrup-Link, H. E. 2024


    The delivery of intravenously administered cancer therapeutics to brain tumors is limited by the blood-brain barrier. A method to directly image the accumulation and distribution of macromolecules in brain tumors in vivo would greatly enhance our ability to understand and optimize drug delivery in preclinical models. This protocol describes a method for real-time in vivo tracking of intravenously administered fluorescent-labeled nanoparticles with two-photon intravital microscopy (2P-IVM) in a mouse model of glioblastoma (GBM). The protocol contains a multi-step description of the procedure, including anesthesia and analgesia of experimental animals, creating a cranial window, GBM cell implantation, placing a head bar, conducting 2P-IVM studies, and post-surgical care for long-term follow-up studies. We show representative 2P-IVM imaging sessions and image analysis, examine the advantages and disadvantages of this technology, and discuss potential applications. This method can be easily modified and adapted for different research questions in the field of in vivo preclinical brain imaging.

    View details for DOI 10.3791/66304

    View details for PubMedID 38497657

  • A novel mouse model of cerebral adrenoleukodystrophy highlights NLRP3 activity in lesion pathogenesis. bioRxiv : the preprint server for biology Hashemi, E., Narain Srivastava, I., Aguirre, A., Tilahan Yoseph, E., Kaushal, E., Awani, A., Kyu Ryu, J., Akassoglou, K., Talebian, S., Chu, P., Pisani, L., Musolino, P., Steinman, L., Doyle, K., Robinson, W. H., Sharpe, O., Cayrol, R., Orchard, P., Lund, T., Vogel, H., Lenail, M., Han, M. H., Bonkowsky, J. L., Van Haren, K. P. 2023


    We sought to create and characterize a mouse model of the inflammatory, cerebral demyelinating phenotype of X-linked adrenoleukodystrophy (ALD) that would facilitate the study of disease pathogenesis and therapy development. We also sought to cross-validate potential therapeutic targets such as fibrin, oxidative stress, and the NLRP3 inflammasome, in post-mortem human and murine brain tissues.ALD is caused by mutations in the gene ABCD1 encoding a peroxisomal transporter. More than half of males with an ABCD1 mutation develop the cerebral phenotype (cALD). Incomplete penetrance and absence of a genotype-phenotype correlation imply a role for environmental triggers. Mechanistic studies have been limited by the absence of a cALD phenotype in the Abcd1-null mouse.We generated a cALD phenotype in 8-week-old, male Abcd1-null mice by deploying a two-hit method that combines cuprizone (CPZ) and experimental autoimmune encephalomyelitis (EAE) models. We employed in vivo MRI and post-mortem immunohistochemistry to evaluate myelin loss, astrogliosis, blood-brain barrier (BBB) disruption, immune cell infiltration, fibrin deposition, oxidative stress, and Nlrp3 inflammasome activation in mice. We used bead-based immunoassay and immunohistochemistry to evaluate IL-18 in CSF and post-mortem human cALD brain tissue.MRI studies revealed T2 hyperintensities and post-gadolinium enhancement in the medial corpus callosum of cALD mice, similar to human cALD lesions. Both human and mouse cALD lesions shared common histologic features of myelin phagocytosis, myelin loss, abundant microglial activation, T and B-cell infiltration, and astrogliosis. Compared to wild-type controls, Abcd1-null mice had more severe cerebral inflammation, demyelination, fibrin deposition, oxidative stress, and IL-18 activation. IL-18 immunoreactivity co-localized with macrophages/microglia in the perivascular region of both human and mouse brain tissue.This novel mouse model of cALD suggests loss of Abcd1 function predisposes to more severe cerebral inflammation, oxidative stress, fibrin deposition, and Nlrp3 pathway activation, which parallels the findings seen in humans with cALD. We expect this model to enable long-sought investigations into cALD mechanisms and accelerate development of candidate therapies for lesion prevention, cessation, and remyelination.

    View details for DOI 10.1101/2023.11.07.564025

    View details for PubMedID 37986739

    View details for PubMedCentralID PMC10659266

  • Novel Clinically Translatable Iron Oxide Nanoparticle for Monitoring Anti-CD47 Cancer Immunotherapy. Investigative radiology Roudi, R., Pisani, L., Pisani, F., Kiru, L., Daldrup-Link, H. E. 2023


    A novel clinically translatable iron oxide nanoparticle (IOP) is currently being tested in phase 2 clinical trials as a magnetic resonance imaging (MRI) contrast agent for hepatocellular carcinoma diagnosis. The purpose of our study is to evaluate if this IOP can detect activation of tumor-associated macrophages (TAMs) due to CD47 mAb-targeted immunotherapy in 2 mouse models of osteosarcoma.The toxicity, biodistribution, and pharmacokinetics of IOP were evaluated in 77 female and 77 male rats. Then, 24 female BALB/c mice with intratibial murine K7M2 tumors and 24 female NOD scid gamma mice with intratibial human 143B osteosarcoma xenografts were treated with either CD47 mAb (n = 12) or control antibody (n = 12). In each treatment group, 6 mice underwent MRI scans before and after intravenous infusion of either IOP or ferumoxytol (30 mg Fe/kg). Tumor T2* values and TAM markers F4/80, CD80, CD206, and Prussian blue staining were compared between different experimental groups using exact 2-sided Wilcoxon rank sum tests.Biodistribution and safety evaluations of IOP were favorable for doses of less than 50 mg Fe/kg body weight in female and male rats. Both IOP and ferumoxytol caused negative enhancement (darkening) of the tumor tissue. Both murine and human osteosarcoma tumors treated with CD47 mAb demonstrated significantly shortened T2* relaxation times after infusion of IOP or ferumoxytol compared with controls (all P's < 0.05). Higher levels of F4/80+CD80+ were found in murine and human osteosarcomas treated with CD47 mAb compared with sham-treated controls (all P's < 0.05). In addition, murine CD47 mAb-treated tumors after infusion of either IOP or ferumoxytol showed significantly higher numbers of Prussian blue-positive cells compared with controls (P < 0.05). There was no significant difference of F4/80+CD206+ cells among any of the groups (all P's > 0.05).Iron oxide nanoparticle-enhanced MRI can be used to diagnose CD47 mAb-mediated TAM-activation in osteosarcomas.

    View details for DOI 10.1097/RLI.0000000000001030

    View details for PubMedID 37812494

  • Measurement of Tumor T2* Relaxation Times after Iron Oxide Nanoparticle Administration. Journal of visualized experiments : JoVE Ramasamy, S. K., Roudi, R., Morakote, W., Adams, L. C., Pisani, L. J., Moseley, M., Daldrup-Link, H. E. 2023


    T2* relaxometry is one of the established methods to measure the effect of superparamagnetic iron oxide nanoparticles on tumor tissues with magnetic resonance imaging (MRI). Iron oxide nanoparticles shorten the T1, T2, and T2* relaxation times of tumors. While the T1 effect is variable based on the size and composition of the nanoparticles, the T2 and T2* effects are usually predominant, and T2* measurements are the most time-efficient in a clinical context. Here, we present our approach to measuring tumor T2* relaxation times, using multi-echo gradient echo sequences, external software, and a standardized protocol for creating a T2* map with scanner-independent software. This facilitates the comparison of imaging data from different clinical scanners, different vendors, and co-clinical research work (i.e., tumor T2* data obtained in mouse models and patients). Once the software is installed, the T2 Fit Map plugin needs to be installed from the plugin manager. This protocol provides step-by-step procedural details, from importing the multi-echo gradient echo sequences into the software, to creating color-coded T2* maps and measuring tumor T2* relaxation times. The protocol can be applied to solid tumors in any body part and has been validated based on preclinical imaging data and clinical data in patients. This could facilitate tumor T2* measurements for multi-center clinical trials and improve the standardization and reproducibility of tumor T2* measurements in co-clinical and multi-center data analyses.

    View details for DOI 10.3791/64773

    View details for PubMedID 37318243

  • Tumor protease-activated theranostic nanoparticles for MRI-guided glioblastoma therapy. Theranostics Huang, C. H., Chang, E., Zheng, L., Raj, J. G., Wu, W., Pisani, L. J., Daldrup-Link, H. E. 2023; 13 (6): 1745-1758


    Rationale: As a cancer, Glioblastoma (GBM) is a highly lethal and difficult-to-treat. With the aim of improving therapies to GBM, we developed novel and target-specific theranostic nanoparticles (TNPs) that can be selectively cleaved by cathepsin B (Cat B) to release the potent toxin monomethyl auristatin E (MMAE). Methods: We synthesized TNPs composed of a ferumoxytol-based nanoparticle carrier and a peptide prodrug with a Cat-B-responsive linker and the tubulin inhibitor MMAE. We hypothesized that intratumoral Cat B can cleave our TNPs and release MMAE to kill GBM cells. The ferumoxytol core enables in vivo drug tracking with magnetic resonance imaging (MRI). We incubated U87-MG GBM cells with TNPs or ferumoxytol and evaluated the TNP content in the cells with transmission electron microscopy and Prussian blue staining. In addition, we stereotaxically implanted 6- to 8-week-old nude mice with U87-MG with U87-MG GBM cells that express a fusion protein of Green Fluorescence Protein and firefly Luciferase (U87-MG/GFP-fLuc). We then treated the animals with an intravenous dose of TNPs (25 mg/kg of ferumoxytol, 0.3 mg/kg of MMAE) or control. We also evaluated the combination of TNP treatment with radiation therapy. We performed MRI before and after TNP injection. We compared the results for tumor and normal brain tissue between the TNP and control groups. We also monitored tumor growth for a period of 21 days. Results: We successfully synthesized TNPs with a hydrodynamic size of 41 ± 5 nm and a zeta potential of 6 ± 3 mV. TNP-treated cells demonstrated a significantly higher iron content than ferumoxytol-treated cells (98 ± 1% vs. 3 ± 1% of cells were iron-positive, respectively). We also found significantly fewer live attached cells in the TNP-treated group (3.8 ± 2.0 px2) than in the ferumoxytol-treated group (80.0 ± 14.5 px2, p < 0001). In vivo MRI studies demonstrated a decline in the tumor signal after TNP (T2= 28 ms) but not control (T2= 32 ms) injections. When TNP injection was combined with radiation therapy, the tumor signals dropped further (T2 = 24 ms). The combination therapy of radiation therapy and TNPs extended the median survival from 14.5 days for the control group to 45 days for the combination therapy group. Conclusion: The new cleavable TNPs reported in this work accumulate in GBM, cause tumor cell death, and have synergistic effects with radiation therapy.

    View details for DOI 10.7150/thno.79342

    View details for PubMedID 37064879

    View details for PubMedCentralID PMC10091873

  • Multimodal In Vivo Tracking of Chimeric Antigen Receptor T Cells in Preclinical Glioblastoma Models. Investigative radiology Wu, W. E., Chang, E., Jin, L., Liu, S., Huang, C., Kamal, R., Liang, T., Aissaoui, N. M., Theruvath, A. J., Pisani, L., Moseley, M., Stoyanova, T., Paulmurugan, R., Huang, J., Mitchell, D. A., Daldrup-Link, H. E. 2022


    OBJECTIVES: Iron oxide nanoparticles have been used to track the accumulation of chimeric antigen receptor (CAR) T cells with magnetic resonance imaging (MRI). However, the only nanoparticle available for clinical applications to date, ferumoxytol, has caused rare but severe anaphylactic reactions. MegaPro nanoparticles (MegaPro-NPs) provide an improved safety profile. We evaluated whether MegaPro-NPs can be applied for in vivo tracking of CAR T cells in a mouse model of glioblastoma multiforme.MATERIALS AND METHODS: We labeled tumor-targeted CD70CAR (8R-70CAR) T cells and non-tumor-targeted controls with MegaPro-NPs, followed by inductively coupled plasma optical emission spectroscopy, Prussian blue staining, and cell viability assays. Next, we treated 42 NRG mice bearing U87-MG/eGFP-fLuc glioblastoma multiforme xenografts with MegaPro-NP-labeled/unlabeled CAR T cells or labeled untargeted T cells and performed serial MRI, magnetic particle imaging, and histology studies. The Kruskal-Wallis test was conducted to evaluate overall group differences, and the Mann-Whitney U test was applied to compare the pairs of groups.RESULTS: MegaPro-NP-labeled CAR T cells demonstrated significantly increased iron uptake compared with unlabeled controls (P < 0.01). Cell viability, activation, and exhaustion markers were not significantly different between the 2 groups (P > 0.05). In vivo, tumor T2* relaxation times were significantly lower after treatment with MegaPro-NP-labeled CAR T cells compared with untargeted T cells (P < 0.01). There is no significant difference in tumor growth inhibition between mice injected with labeled and unlabeled CAR T cells.CONCLUSIONS: MegaPro-NPs can be used for in vivo tracking of CAR T cells. Because MegaPro-NPs recently completed phase II clinical trial investigation as an MRI contrast agent, MegaPro-NP is expected to be applied to track CAR T cells in cancer immunotherapy trials in the near future.

    View details for DOI 10.1097/RLI.0000000000000946

    View details for PubMedID 36729074

  • Brain iron deposition after Ferumoxytol-enhanced MRI: A study of Porcine Brains. Nanotheranostics Theruvath, A. J., Aghighi, M. n., Iv, M. n., Nejadnik, H. n., Lavezo, J. n., Pisani, L. J., Daldrup-Link, H. E. 2020; 4 (4): 195–200


    Recent evidence of gadolinium deposition in the brain has raised safety concerns. Iron oxide nanoparticles are re-emerging as promising alternative MR contrast agents, because the iron core can be metabolized. However, long-term follow up studies of the brain after intravenous iron oxide administration have not been reported thus far. In this study, we investigated, if intravenously administered ferumoxytol nanoparticles are deposited in porcine brains. Methods: In an animal care and use committee-approved prospective case-control study, ten Göttingen minipigs received either intravenous ferumoxytol injections at a dose of 5 mg Fe/kg (n=4) or remained untreated (n=6). Nine to twelve months later, pigs were sacrificed and the brains of all pigs underwent ex vivo MRI at 7T with T2 and T2*-weighted sequences. MRI scans were evaluated by measuring R2* values (R2*=1000/T2*) of the bilateral caudate nucleus, lentiform nucleus, thalamus, dentate nucleus, and choroid plexus. Pig brains were sectioned and stained with Prussian blue and evaluated for iron deposition using a semiquantitative scoring system. Data of ferumoxytol exposed and unexposed groups were compared with an unpaired t-test and a Mann-Whitney U test. Results: T2 and T2* signal of the different brain regions was not visually different between ferumoxytol exposed and unexposed controls. There were no significant differences in R2* values of the different brain regions in the ferumoxytol exposed group compared to controls (p>0.05). Prussian blue stains of the same brain regions, scored according to a semiquantitative score, were not significantly different either between the ferumoxytol exposed group and unexposed controls (p>0.05). Conclusions: Our study shows that intravenous ferumoxytol doses of 5-10 mg Fe/kg do not lead to iron deposition in the brain of pigs. We suggest iron oxide nanoparticles as a promising alternative for gadolinium-enhanced MRI.

    View details for DOI 10.7150/ntno.46356

    View details for PubMedID 32637297

    View details for PubMedCentralID PMC7332795

  • GABA Measurement in a Neonatal Fragile X Syndrome Mouse Model Using 1H-Magnetic Resonance Spectroscopy and Mass Spectrometry. Frontiers in molecular neuroscience Reyes, S. T., Mohajeri, S. n., Krasinska, K. n., Guo, S. G., Gu, M. n., Pisani, L. n., Rosenberg, J. n., Spielman, D. M., Chin, F. T. 2020; 13: 612685


    Fragile X syndrome (FXS) is the leading monogenetic cause of autism spectrum disorder and inherited cause of intellectual disability that affects approximately one in 7,000 males and one in 11,000 females. In FXS, the Fmr1 gene is silenced and prevents the expression of the fragile X mental retardation protein (FMRP) that directly targets mRNA transcripts of multiple GABAA subunits. Therefore, FMRP loss adversely impacts the neuronal firing of the GABAergic system which creates an imbalance in the excitatory/inhibitory ratio within the brain. Current FXS treatment strategies focus on curing symptoms, such as anxiety or decreased social function. While treating symptoms can be helpful, incorporating non-invasive imaging to evaluate how treatments change the brain's biology may explain what molecular aberrations are associated with disease pathology. Thus, the GABAergic system is suitable to explore developing novel therapeutic strategies for FXS. To understand how the GABAergic system may be affected by this loss-of-function mutation, GABA concentrations were examined within the frontal cortex and thalamus of 5-day-old wild type and Fmr1 knockout mice using both 1H magnetic resonance imaging (1H-MRS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our objective was to develop a reliable scanning method for neonatal mice in vivo and evaluate whether 1H-MRS is suitable to capture regional GABA concentration differences at the front end of the critical cortical period where abnormal neurodevelopment occurs due to FMRP loss is first detected. 1H-MRS quantified GABA concentrations in both frontal cortex and thalamus of wild type and Fmr1 knockout mice. To substantiate the results of our 1H-MRS studies, in vitro LC-MS/MS was also performed on brain homogenates from age-matched mice. We found significant changes in GABA concentration between the frontal cortex and thalamus within each mouse from both wild type and Fmr1 knockout mice using 1H-MRS and LC-MS/MS. Significant GABA levels were also detected in these same regions between wild type and Fmr1 knockout mice by LC-MS/MS, validating that FMRP loss directly affects the GABAergic system. Thus, these new findings support the need to develop an effective non-invasive imaging method to monitor novel GABAergic strategies aimed at treating patients with FXS.

    View details for DOI 10.3389/fnmol.2020.612685

    View details for PubMedID 33390902

    View details for PubMedCentralID PMC7775297

  • Nanoparticle enhanced MRI can monitor macrophage response to CD47 mAb immunotherapy in osteosarcoma. Cell death & disease Mohanty, S., Yerneni, K., Theruvath, J. L., Graef, C. M., Nejadnik, H., Lenkov, O., Pisani, L., Rosenberg, J., Mitra, S., Cordero, A. S., Cheshier, S., Daldrup-Link, H. E. 2019; 10 (2): 36


    CD47 monoclonal antibodies (mAbs) activate tumor-associated macrophages (TAMs) in sarcomas to phagocytose and eliminate cancer cells. Though CD47 mAbs have entered clinical trials, diagnostic tests for monitoring therapy response in vivoare currently lacking. Ferumoxytol is an FDA-approved iron supplement which can be used "off label" as a contrast agent: the nanoparticle-based drug is phagocytosed by TAM and can be detected with magnetic resonance imaging (MRI). We evaluated if ferumoxytol-enhanced MRI can monitor TAM response to CD47 mAb therapy in osteosarcomas. Forty-eight osteosarcoma-bearing mice were treated with CD47 mAb or control IgG and underwent pre- and post-treatment ferumoxytol-MRI scans. Tumor enhancement, quantified as T2 relaxation times, was compared with the quantity of TAMs as determined by immunofluorescence microscopy and flow cytometry. Quantitative data were compared between experimental groups using exact two-sided Wilcoxon rank-sum tests. Compared to IgG-treated controls, CD47 mAb-treated tumors demonstrated significantly shortened T2 relaxation times on ferumoxytol-MRI scans (p<0.01) and significantly increased F4/80+CD80+ M1 macrophages on histopathology (p<0.01). CD47 mAb-treated F4/80+ macrophages demonstrated significantly augmented phagocytosis of ferumoxytol nanoparticles (p<0.01). Thus, we conclude that ferumoxytol-MRI can detect TAM response to CD47 mAb in mouse models of osteosarcoma. The ferumoxytol-MRI imaging test could be immediately applied to monitor CD47 mAb therapies in clinical trials.

    View details for PubMedID 30674867

  • Magnetic Resonance Imaging of Tumor-Associated Macrophages: Clinical Translation CLINICAL CANCER RESEARCH Aghighi, M., Theruvath, A. J., Pareek, A., Pisani, L. L., Alford, R., Muehe, A. M., Sethi, T. K., Holdsworth, S. J., Hazard, F. K., Gratzinger, D., Luna-Fineman, S., Advani, R., Spunt, S. L., Daldrup-Link, H. E. 2018; 24 (17): 4110–18
  • A novel theranostic strategy for MMP-14 expressing glioblastomas impacts survival Mohanty, S., Chen, Z., Li, K., Morais, G., Klockow, J., Yerneni, K., Pisani, L., Chin, F., Mitra, S., Cheshier, S., Chang, E., Gambhir, S., Rao, J., Loadman, P. M., Falconer, R. A., Daldrup-Link, H. E. AMER ASSOC CANCER RESEARCH. 2018
  • Magnetic Resonance Imaging of Tumor Associated Macrophages: Clinical Translation. Clinical cancer research : an official journal of the American Association for Cancer Research Aghighi, M. n., Theruvath, A. J., Pareek, A. n., Pisani, L. n., Alford, R. n., Muehe, A. M., Sethi, T. K., Holdsworth, S. J., Hazard, F. K., Gratzinger, D. n., Luna-Fineman, S. n., Advani, R. H., Spunt, S. L., Daldrup-Link, H. E. 2018


    Tumor associated macrophages (TAM) in malignant tumors have been linked to tumor aggressiveness and represent a new target for cancer immunotherapy. As new TAM-targeted immunotherapies are entering clinical trials, it is important to detect and quantify TAM with non-invasive imaging techniques. The purpose of this study was to determine if ferumoxytol-enhanced MRI can detect TAM in lymphomas and bone sarcomas of pediatric patients and young adults.In a first-in-patient, IRB-approved prospective clinical trial, 25 pediatric and young adult patients with lymphoma or bone sarcoma underwent ferumoxytol-enhanced MRI. To confirm ferumoxytol enhancement, five pilot patients (2 lymphoma, 3 bone sarcoma) underwent pre- and post-contrast MRI. Subsequently, 20 patients (10 lymphoma, 10 bone sarcoma) underwent ferumoxytol-enhanced MRI 24-48 hours after intravenous injection, followed by tumor biopsy/resection and macrophage staining. To determine if ferumoxytol-MRI can differentiate tumors with different TAM content, we compared T2* relaxation times of lymphomas and bone sarcomas. Tumor T2* values of 20 patients were correlated with CD68+ and CD163+ TAM quantities on histopathology.Significant ferumoxytol tumor enhancement was noted on post-contrast scans compared to pre-contrast scans (P = 0.036). Bone sarcomas and lymphomas demonstrated significantly different MRI enhancement and TAM density (P < 0.05). Within each tumor group, T2* signal enhancement on MR images correlated significantly with the density of CD68+ and CD163+ TAM (P < 0.05).Ferumoxytol-enhanced MRI is immediately clinically applicable and could be used to stratify patients with TAM-rich tumors to immune-targeted therapies and to monitor tumor response to these therapies.

    View details for PubMedID 29764855

  • Ferumoxytol Is Not Retained in Kidney Allografts in Patients Undergoing Acute Rejection. Molecular imaging and biology Aghighi, M., Pisani, L., Theruvath, A. J., Muehe, A. M., Donig, J., Khan, R., Holdsworth, S. J., Kambham, N., Concepcion, W., Grimm, P. C., Daldrup-Link, H. E. 2017


    To evaluate whether ultrasmall superparamagnetic iron oxide nanoparticle (USPIO)-enhanced magnetic resonance imaging (MRI) can detect allograft rejection in pediatric kidney transplant patients.The USPIO ferumoxytol has a long blood half-life and is phagocytosed by macrophages. In an IRB-approved single-center prospective clinical trial, 26 pediatric patients and adolescents (age 10-26 years) with acute allograft rejection (n = 5), non-rejecting allografts (n = 13), and normal native kidneys (n = 8) underwent multi-echo T2* fast spoiled gradient-echo (FSPGR) MRI after intravenous injection (p.i.) of 5 mg Fe/kg ferumoxytol. T2* relaxation times at 4 h p.i. (perfusion phase) and more than 20 h p.i. (macrophage phase) were compared with biopsy results. The presence of rejection was assessed using the Banff criteria, and the prevalence of macrophages on CD163 immunostains was determined based on a semi-quantitative scoring system. MRI and histology data were compared among patient groups using t tests, analysis of variance, and regression analyses with a significance threshold of p < 0.05.At 4 h p.i., mean T2* values were 6.6 ± 1.5 ms for native kidneys and 3.9 ms for one allograft undergoing acute immune rejection. Surprisingly, at 20-24 h p.i., one rejecting allograft showed significantly prolonged T2* relaxation times (37.0 ms) compared to native kidneys (6.3 ± 1.7 ms) and non-rejecting allografts (7.6 ± 0.1 ms). Likewise, three additional rejecting allografts showed significantly prolonged T2* relaxation times compared to non-rejecting allografts at later post-contrast time points, 25-97 h p.i. (p = 0.008). Histological analysis revealed edema and compressed microvessels in biopsies of rejecting allografts. Allografts with and without rejection showed insignificant differences in macrophage content on histopathology (p = 0.44).After ferumoxytol administration, renal allografts undergoing acute rejection show prolonged T2* values compared to non-rejecting allografts. Since histology revealed no significant differences in macrophage content, the increasing T2* value is likely due to the combined effect of reduced perfusion and increased edema in rejecting allografts.

    View details for DOI 10.1007/s11307-017-1084-8

    View details for PubMedID 28411307

  • Detection of Stem Cell Transplant Rejection with Ferumoxytol MR Imaging: Correlation of MR Imaging Findings with Those at Intravital Microscopy. Radiology Daldrup-Link, H. E., Chan, C., Lenkov, O., Taghavigarmestani, S., Nazekati, T., Nejadnik, H., Chapelin, F., Khurana, A., Tong, X., Yang, F., Pisani, L., Longaker, M., Gambhir, S. S. 2017: 161139-?


    Purpose To determine whether endogenous labeling of macrophages with clinically applicable nanoparticles enables noninvasive detection of innate immune responses to stem cell transplants with magnetic resonance (MR) imaging. Materials and Methods Work with human stem cells was approved by the institutional review board and the stem cell research oversight committee, and animal experiments were approved by the administrative panel on laboratory animal care. Nine immunocompetent Sprague-Dawley rats received intravenous injection of ferumoxytol, and 18 Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice received rhodamine-conjugated ferumoxytol. Then, 48 hours later, immune-matched or mismatched stem cells were implanted into osteochondral defects of the knee joints of experimental rats and calvarial defects of Jax mice. All animals underwent serial MR imaging and intravital microscopy (IVM) up to 4 weeks after surgery. Macrophages of Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice express enhanced green fluorescent protein (GFP), which enables in vivo correlation of ferumoxytol enhancement at MR imaging with macrophage quantities at IVM. All quantitative data were compared between experimental groups by using a mixed linear model and t tests. Results Immune-mismatched stem cell implants demonstrated stronger ferumoxytol enhancement than did matched stem cell implants. At 4 weeks, T2 values of mismatched implants were significantly lower than those of matched implants in osteochondral defects of female rats (mean, 10.72 msec for human stem cells and 11.55 msec for male rat stem cells vs 15.45 msec for sex-matched rat stem cells; P = .02 and P = .04, respectively) and calvarial defects of recipient mice (mean, 21.7 msec vs 27.1 msec, respectively; P = .0444). This corresponded to increased recruitment of enhanced GFP- and rhodamine-ferumoxytol-positive macrophages into stem cell transplants, as visualized with IVM and histopathologic examination. Conclusion Endogenous labeling of macrophages with ferumoxytol enables noninvasive detection of innate immune responses to stem cell transplants with MR imaging. (©) RSNA, 2017 Online supplemental material is available for this article.

    View details for DOI 10.1148/radiol.2017161139

    View details for PubMedID 28128708

  • Alk5 inhibition increases delivery of macromolecular and protein-bound contrast agents to tumors. JCI insight Daldrup-Link, H. E., Mohanty, S., Ansari, C., Lenkov, O., Shaw, A., Ito, K., Hong, S. H., Hoffmann, M., Pisani, L., Boudreau, N., Gambhir, S. S., Coussens, L. M. 2016; 1 (6)


    Limited transendothelial permeability across tumor microvessels represents a significant bottleneck in the development of tumor-specific diagnostic agents and theranostic drugs. Here, we show an approach to increase transendothelial permeability of macromolecular and nanoparticle-based contrast agents via inhibition of the type I TGF-β receptor, activin-like kinase 5 (Alk5), in tumors. Alk5 inhibition significantly increased tumor contrast agent delivery and enhancement on imaging studies, while healthy organs remained relatively unaffected. Imaging data correlated with significantly decreased tumor interstitial fluid pressure, while tumor vascular density remained unchanged. This immediately clinically translatable concept involving Alk5 inhibitor pretreatment prior to an imaging study could be leveraged for improved tumor delivery of macromolecular and nanoparticle-based imaging probes and, thereby, facilitate development of more sensitive imaging tests for cancer diagnosis, enhanced tumor characterization, and personalized, image-guided therapies.

    View details for PubMedID 27182558

  • Speeding up PET/MR for cancer staging of children and young adults. European radiology Aghighi, M., Pisani, L. J., Sun, Z., Klenk, C., Madnawat, H., Fineman, S. L., Advani, R., von Eyben, R., Owen, D., Quon, A., Moseley, M., Daldrup-Link, H. E. 2016: -?


    Combining (18)F-FDG PET with whole-body MR for paediatric cancer staging is practically feasible if imaging protocols can be streamlined. We compared (18)F-FDG PET/STIR with accelerated (18)F-FDG PET/FSPGR for whole-body tumour imaging in children and young adults.Thirty-three children and young adults (17.5 ± 5.5 years, range 10-30) with malignant lymphoma or sarcoma underwent a (18)F-FDG PET staging examination, followed by ferumoxytol-enhanced STIR and FSPGR whole-body MR. (18)F-FDG PET scans were fused with MR data and the number and location of tumours on each integrated examination were determined. Histopathology and follow-up imaging served as standard of reference. The agreement of each MR sequence with the reference and whole-body imaging times were compared using Cohen's kappa coefficient and Student's t-test, respectively.Comparing (18)F-FDG PET/FSPGR to (18)F-FDG PET/STIR, sensitivities were 99.3 % for both, specificities were statistically equivalent, 99.8 versus 99.9 %, and the agreement with the reference based on Cohen's kappa coefficient was also statistically equivalent, 0.989 versus 0.992. However, the total scan-time for accelerated FSPGR of 19.8 ± 5.3 minutes was significantly shorter compared to 29.0 ± 7.6 minutes for STIR (p = 0.001).F-FDG PET/FSPGR demonstrated equivalent sensitivities and specificities for cancer staging compared to (18)F-FDG PET/STIR, but could be acquired with shorter acquisition time.• Breath-hold FSPGR sequences shorten the data acquisition time for whole-body MR and PET/MR. • Ferumoxytol provides long-lasting vascular contrast for whole-body MR and PET/MR. • (18) F-FDG PET/FSPGR data provided equal sensitivity and specificity for cancer staging compared to (18) F-FDG PET/STIR.

    View details for PubMedID 27048532

  • Imaging Tumor Necrosis with Ferumoxytol. PloS one Aghighi, M., Golovko, D., Ansari, C., Marina, N. M., Pisani, L., Kurlander, L., Klenk, C., Bhaumik, S., Wendland, M., Daldrup-Link, H. E. 2015; 10 (11)

    View details for DOI 10.1371/journal.pone.0142665

    View details for PubMedID 26569397

  • Assessment of elastin deficit in a marfan mouse aneurysm model using an elastin-specific magnetic resonance imaging contrast agent. Circulation. Cardiovascular imaging Okamura, H., Pisani, L. J., Dalal, A. R., Emrich, F., Dake, B. A., Arakawa, M., Onthank, D. C., Cesati, R. R., Robinson, S. P., Milanesi, M., Kotek, G., Smit, H., Connolly, A. J., Adachi, H., McConnell, M. V., Fischbein, M. P. 2014; 7 (4): 690-696


    -Ascending aortic dissection and rupture remain a life-threatening complication in patients with Marfan syndrome (MFS). The extracellular matrix provides strength and elastic recoil to the aortic wall, thereby preventing radial expansion. We have previously shown that ascending aortic aneurysm formation in Marfan mice (Fbn1(C1039G/+)) is associated with decreased aortic wall elastogenesis and increased elastin breakdown. In this study, we test the feasibility of quantifying aortic wall elastin content using magnetic resonance imaging (MRI) with a gadolinium-based elastin-specific contrast agent (ESMA) in Fbn1(C1039G/+) mice.-Ascending aorta elastin content was measured in 32-week-old Fbn1(C1039G/+) mice and wild-type (WT) (n=9 and n=10, respectively) using 7T MRI with a T1-mapping sequence. Significantly lower enhancement (i.e., lower R1 values, where R1=1/T1) was detected post-ESMA in Fbn1(C1039G/+) compared to WT ascending aortas (1.15±0.07 vs. 1.36±0.05, p<0.05). Post-ESMA R1 values correlated with ascending aortic wall gadolinium content directly measured by inductively coupled mass spectroscopy (p=0.006).-Herein, we demonstrate that MRI with ESMA accurately measures elastin bound gadolinium within the aortic wall and detects a decrease in aortic wall elastin in Marfan mice compared to WT controls. This approach has translational potential for non-invasively assessing aneurysm tissue changes and risk, as well as monitoring elastin content in response to therapeutic interventions.

    View details for DOI 10.1161/CIRCIMAGING.114.001658

    View details for PubMedID 24814820

  • Severe Impairment of Axonal Transport in Acute Experimental Anterior Ischemic Optic Neuropathy Ma, J., Shariati, M., Pisani, L., Pestilli, F., Dougherty, B., Perry, L., Lee, G., Contag, C., Wandell, B. A., Liao, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2014
  • PET Imaging of Stroke-Induced Neuroinflammation in Mice Using [F-18]PBR06 MOLECULAR IMAGING AND BIOLOGY Lartey, F. M., Ahn, G., Shen, B., Cord, K., Smith, T., Chua, J. Y., Rosenblum, S., Liu, H., James, M. L., Chernikova, S., Lee, S. W., Pisani, L. J., Tirouvanziam, R., Chen, J. W., Palmer, T. D., Chin, F. T., Guzman, R., Graves, E. E., Loo, B. W. 2014; 16 (1): 109-117


    The purpose of this study is to evaluate the 18 kDa translocator protein (TSPO) radioligand [(18)F]N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ([(18)F]PBR06) as a positron emission tomography (PET) imaging biomarker of stroke-induced neuroinflammation in a rodent model.Stroke was induced by transient middle cerebral artery occlusion in Balb/c mice. Dynamic PET/CT imaging with displacement and preblocking using PK111195 was performed 3 days later. PET data were correlated with immunohistochemistry (IHC) for the activated microglial markers TSPO and CD68 and with autoradiography.[(18)F]PBR06 accumulation peaked within the first 5 min postinjection, then decreased gradually, remaining significantly higher in infarct compared to noninfarct regions. Displacement or preblocking with PK11195 eliminated the difference in [(18)F]PBR06 uptake between infarct and noninfarct regions. Autoradiography and IHC correlated well spatially with uptake on PET.[(18)F]PBR06 PET specifically images TSPO in microglial neuroinflammation in a mouse model of stroke and shows promise for imaging and monitoring microglial activation/neuroinflammation in other disease models.

    View details for DOI 10.1007/s11307-013-0664-5

    View details for PubMedID 23836504

  • Ferumoxytol: a new, clinically applicable label for stem-cell tracking in arthritic joints with MRI. Nanomedicine Khurana, A., Nejadnik, H., Chapelin, F., Lenkov, O., Gawande, R., Lee, S., Gupta, S. N., Aflakian, N., Derugin, N., Messing, S., Lin, G., Lue, T. F., Pisani, L., Daldrup-Link, H. E. 2013; 8 (12): 1969-1983


    Aim: To develop a clinically applicable MRI technique for tracking stem cells in matrix-associated stem-cell implants, using the US FDA-approved iron supplement ferumoxytol. Materials & methods: Ferumoxytol-labeling of adipose-derived stem cells (ADSCs) was optimized in vitro. A total of 11 rats with osteochondral defects of both femurs were implanted with ferumoxytol- or ferumoxides-labeled or unlabeled ADSCs, and underwent MRI up to 4 weeks post matrix-associated stem-cell implant. The signal-to-noise ratio of different matrix-associated stem-cell implant was compared with t-tests and correlated with histopathology. Results: An incubation concentration of 500 µg iron/ml ferumoxytol and 10 µg/ml protamine sulfate led to significant cellular iron uptake, T2 signal effects and unimpaired ADSC viability. In vivo, ferumoxytol- and ferumoxides-labeled ADSCs demonstrated significantly lower signal-to-noise ratio values compared with unlabeled controls (p < 0.01). Histopathology confirmed engraftment of labeled ADSCs, with slow dilution of the iron label over time. Conclusion: Ferumoxytol can be used for in vivo tracking of stem cells with MRI. Original submitted 28 February 2012; Revised submitted 8 November 2012.

    View details for DOI 10.2217/nnm.12.198

    View details for PubMedID 23534832

  • Evaluation of the novel USPIO GEH121333 for MR imaging of cancer immune responses. Contrast media & molecular imaging Shi, Q., Pisani, L. J., Lee, Y. K., Messing, S., Ansari, C., Bhaumik, S., Lowery, L., Lee, B. D., Meyer, D. E., Daldrup-Link, H. E. 2013; 8 (3): 281-288


    Tumor-associated macrophages (TAM) maintain a chronic inflammation in cancers, which is associated with tumor aggressiveness and poor prognosis. The purpose of this study was to: (1) evaluate the pharmacokinetics and tolerability of the novel ultrasmall superparamagnetic iron oxide nanoparticle (USPIO) compound GEH121333; (2) assess whether GEH121333 can serve as a MR imaging biomarker for TAM; and (3) compare tumor MR enhancement profiles between GEH121333 and ferumoxytol. Blood half-lives of GEH121333 and ferumoxytol were measured by relaxometry (n = 4 each). Tolerance was assessed in healthy rats injected with high dose GEH121333, vehicle or saline (n = 4 each). Animals were monitored for 7 days regarding body weight, complete blood counts and serum chemistry, followed by histological evaluation of visceral organs. MR imaging was performed on mice harboring MMTV-PyMT-derived breast adenocarcinomas using a 7 T scanner before and up to 72 h post-injection (p.i.) of GEH121333 (n = 10) or ferumoxytol (n = 9). Tumor R1 , R2 * relaxation rates were compared between different experimental groups and time points, using a linear mixed effects model with a random effect for each animal. MR data were correlated with histopathology. GEH121333 showed a longer circulation half-life than ferumoxytol. Intravenous GEH121333 did not produce significant adverse effects in rats. All tumors demonstrated significant enhancement on T1 , T2 and T2 *-weighted images at 1, 24, 48 and 72 h p.i. GEH121333 generated stronger tumor T2 * enhancement than ferumoxytol. Histological analysis verified intracellular compartmentalization of GEH121333 by TAM at 24, 48 and 72 h p.i. MR imaging with GEH121333 nanoparticles represents a novel biomarker for TAM assessment. This new USPIO MR contrast agent provides a longer blood half-life and better TAM enhancement compared with the iron supplement ferumoxytol. Copyright © 2013 John Wiley & Sons, Ltd.

    View details for DOI 10.1002/cmmi.1526

    View details for PubMedID 23606432

    View details for PubMedCentralID PMC3662997

  • Intravenous Ferumoxytol Allows Noninvasive MR Imaging Monitoring of Macrophage Migration into Stem Cell Transplants RADIOLOGY Khurana, A., Nejadnik, H., Gawande, R., Lin, G., Lee, S., Messing, S., Castaneda, R., Derugin, N., Pisani, L., Lue, T. F., Daldrup-Link, H. E. 2012; 264 (3): 803-811


    To develop a clinically applicable imaging technique for monitoring differential migration of macrophages into viable and apoptotic matrix-associated stem cell implants (MASIs) in arthritic knee joints.With institutional animal care and use committee approval, six athymic rats were injected with intravenous ferumoxytol (0.5 mmol iron per kilogram of body weight) to preload macrophages of the reticuloendothelial system with iron oxide nanoparticles. Forty-eight hours later, all animals received MASIs of viable adipose-derived stem cells (ADSCs) in an osteochondral defect of the right femur and mitomycin-pretreated apoptotic ADSCs in an osteochondral defect of the left femur. One additional control animal each received intravenous ferumoxytol and bilateral scaffold-only implants (without cells) or bilateral MASIs without prior ferumoxytol injection. All knees were imaged with a 7.0-T magnetic resonance (MR) imaging unit with T2-weighted fast spin-echo sequences immediately after, as well as 2 and 4 weeks after, matrix-associated stem cell implantation. Signal-to-noise ratios (SNRs) of viable and apoptotic MASIs were compared by using a linear mixed-effects model. MR imaging data were correlated with histopathologic findings.All ADSC implants showed a slowly decreasing T2 signal over 4 weeks after matrix-associated stem cell implantation. SNRs decreased significantly over time for the apoptotic implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 16.9, 10.9, and 6.7, respectively; P = .0004) but not for the viable implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 17.7, 16.2, and 15.7, respectively; P = .2218). At 4 weeks after matrix-associated stem cell implantation, SNRs of apoptotic ADSCs were significantly lower than those of viable ADSCs (mean, 6.7 vs 15.7; P = .0013). This corresponded to differential migration of iron-loaded macrophages into MASIs.Iron oxide loading of macrophages in the reticuloendothelial system by means of intravenous ferumoxytol injection can be utilized to monitor differential migration of bone marrow macrophages into viable and apoptotic MASIs in a rat model.

    View details for DOI 10.1148/radiol.12112393

    View details for PubMedID 22820731

  • Infection of pregnant mice with Listeria monocytogenes induces fetal bradycardia PEDIATRIC RESEARCH Hardy, J., Kirkendoll, B., Zhao, H., Pisani, L., Luong, R., Switzer, A., McConnell, M. V., Contag, C. H. 2012; 71 (5): 539-545


    Listeriosis is one of the most lethal bacterial diseases for fetuses and infants. However, pregnant women who get infected with Listeria may experience only mild symptoms, making the diagnosis difficult, even when the fetus is fatally infected.To reveal features of this infection, we conducted a multimodality imaging study of Listeria-induced miscarriage, using a pregnant mouse model. In this model, fetal morbidity and mortality can be observed in utero, noninvasively, and the timing and extent of infection can be carefully controlled. By employing in vivo bioluminescence imaging (BLI), perinatal infections were localized over time such that a correlation of infection to outcome could be determined without the need to kill the animal subject. The morbidity and viability of fetuses were assessed with ultrasound, and fetal morphology was imaged using magnetic resonance imaging (MRI).The ultrasound revealed sustained fetal bradycardia, the slowing of the fetal heartbeat, in infected fetuses, with an association between slowed fetal heart rate and strong bioluminescent signal.Uninfected fetuses showing no bioluminescent signal in the same uterine horn exhibited normal heartbeats. Thus, fetal bradycardia during infection was localized to the infected fetus and was not systemic or disseminated.

    View details for DOI 10.1038/pr.2012.2

    View details for PubMedID 22314663

  • Bioluminescence and Magnetic Resonance Imaging of Macrophage Homing to Experimental Abdominal Aortic Aneurysms MOLECULAR IMAGING Miyama, N., Dua, M. M., Schultz, G. M., Kosuge, H., Terashima, M., Pisani, L. J., Dalman, R. L., McConnell, M. V. 2012; 11 (2): 126-134


    Macrophage infiltration is a prominent feature of abdominal aortic aneurysm (AAA) progression. We used a combined imaging approach with bioluminescence (BLI) and magnetic resonance imaging (MRI) to study macrophage homing and accumulation in experimental AAA disease. Murine AAAs were created via intra-aortic infusion of porcine pancreatic elastase. Mice were imaged over 14 days after injection of prepared peritoneal macrophages. For BLI, macrophages were from transgenic mice expressing luciferase. For MRI, macrophages were labeled with iron oxide particles. Macrophage accumulation during aneurysm progression was observed by in situ BLI and by in vivo 7T MRI. Mice were sacrificed after imaging for histologic analysis. In situ BLI (n  =  32) demonstrated high signal in the AAA by days 7 and 14, which correlated significantly with macrophage number and aortic diameter. In vivo 7T MRI (n  =  13) at day 14 demonstrated T₂* signal loss in the AAA and not in sham mice. Immunohistochemistry and Prussian blue staining confirmed the presence of injected macrophages in the AAA. BLI and MRI provide complementary approaches to track macrophage homing and accumulation in experimental AAAs. Similar dual imaging strategies may aid the study of AAA biology and the evaluation of novel therapies.

    View details for DOI 10.2310/7290.2011.00033

    View details for PubMedID 22469240

  • Improvements in Parallel Imaging Accelerated Functional MRI Using Multiecho Echo-Planar Imaging MAGNETIC RESONANCE IN MEDICINE Schmiedeskamp, H., Newbould, R. D., Pisani, L. J., Skare, S., Glover, G. H., Pruessmann, K. P., Bammer, R. 2010; 63 (4): 959-969


    Multiecho echo-planar imaging (EPI) was implemented for blood-oxygenation-level-dependent functional MRI at 1.5 T and compared to single-echo EPI with and without parallel imaging acceleration. A time-normalized breath-hold task using a block design functional MRI protocol was carried out in combination with up to four echo trains per excitation and parallel imaging acceleration factors R = 1-3. Experiments were conducted in five human subjects, each scanned in three sessions. Across all reduction factors, both signal-to-fluctuation-noise ratio and the total number of activated voxels were significantly lower using a single-echo EPI pulse sequence compared with the multiecho approach. Signal-to-fluctuation-noise ratio and total number of activated voxels were also considerably reduced for nonaccelerated conventional single-echo EPI when compared to three-echo measurements with R = 2. Parallel imaging accelerated multiecho EPI reduced geometric distortions and signal dropout, while it increased blood-oxygenation-level-dependent signal sensitivity all over the brain, particularly in regions with short underlying T*(2). Thus, the presented method showed multiple advantages over conventional single-echo EPI for standard blood-oxygenation-level-dependent functional MRI experiments.

    View details for DOI 10.1002/mrm.22222

    View details for Web of Science ID 000276064300013

    View details for PubMedID 20373397

    View details for PubMedCentralID PMC2906757

  • Restricted field of view magnetic resonance imaging of a dynamic time series MAGNETIC RESONANCE IN MEDICINE Pisani, L., Bammer, R., Glover, G. 2007; 57 (2): 297-307


    A restricted field of view (rFOV) approach for imaging a dynamic time series of volumes of limited spatial extent within a larger subject is described. The shorter readout with rFOV-MRI can be exploited to either limit image artifacts or increase spatial resolution. To accomplish rFOV imaging of a multislice volume for a dynamic series, an outer volume suppression (OVS) preparation that saturates signal external to a cylinder through the subject is followed by slice-selective excitation and a spiral readout. The pass- and stopband efficiencies of the OVS in an agar gel phantom were 97% (+/-1.5%) and 3% (+/-1%), respectively. Profiles of the temporal signal-to-noise ratio (SNR) were measured in a phantom and an adult brain. The rFOV sequence reduced distortions from off-resonance signal and T2*-induced blurring compared to a conventional sequence. Sequence utility is demonstrated for high-resolution rFOV functional MRI (fMRI) in the visual cortex. The rFOV sequence may prove to be useful for other multislice dynamic and high-resolution imaging applications.

    View details for DOI 10.1002/mrm.21115

    View details for Web of Science ID 000243946300009

    View details for PubMedID 17260360

  • Assessment of MR thermometry during high intensity ultrasound ablation of the canine prostate 5th International Symposium on Therapeutic Ultrasound Pauly, K. B., Rieke, V., Pisani, L., Sommer, G., Bouley, D., Diederich, C., Ross, A., Nau, W., Kinsey, A., Dumoulin, C., Watkins, R. AMER INST PHYSICS. 2006: 76–80
  • Effects of spatial and temporal resolution for MR image-guided thermal ablation of prostate with transurethral ultrasound JOURNAL OF MAGNETIC RESONANCE IMAGING Pisani, L. J., Ross, A. B., Diederich, C. J., Nau, W. H., Sommer, F. G., Glover, G. H., Butts, K. 2005; 22 (1): 109-118


    To describe approaches for determining optimal spatial and temporal resolutions for the proton resonance frequency shift method of quantitative magnetic resonance temperature imaging (MRTI) guidance of transurethral ultrasonic prostate ablation.Temperature distributions of two transurethral ultrasound applicators (90 degrees sectored tubular and planar arrays) for canine prostate ablation were measured via MRTI during in vivo sonication, and agree well with two-dimensional finite difference model simulations at various spatial resolutions. Measured temperature distributions establish the relevant signal-to-noise ratio (SNR) range for thermometry in an interventional MR scanner, and are reconstructed at different resolutions to compare resultant temperature measurements. Various temporal resolutions are calculated by averaging MRTI frames.When noise is added to simulated temperature distributions for tubular and planar applicators, the minimum root mean squared (RMS) error is achieved by reconstructing to pixel sizes of 1.9 and 1.7 mm, respectively. In in vivo measurements, low spatial resolution MRTI data are shown to reduce the noise without significantly affecting thermal dose calculations. Temporal resolution of 0.66 frames/minute leads to measurement errors of more than 12 degrees C during rapid heating.Optimizing MRTI pixel size entails balancing large pixel SNR gain with accuracy in representing underlying temperature distributions.

    View details for DOI 10.1002/jmri.20339

    View details for PubMedID 15971190