Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Sci Rep ; 10(1): 1399, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31996701

RESUMO

Tissue oximetry can assist in diagnosis and prognosis of many diseases and enable personalized therapy. Previously, we reported the ability of hexamethyldisiloxane (HMDSO) for accurate measurements of tissue oxygen tension (pO2) using Proton Imaging of Siloxanes to map Tissue Oxygenation Levels (PISTOL) magnetic resonance imaging. Here we report the feasibility of several commercially available linear and cyclic siloxanes (molecular weight 162-410 g/mol) as PISTOL-based oxygen reporters by characterizing their calibration constants. Further, field and temperature dependence of pO2 calibration curves of HMDSO, octamethyltrisiloxane (OMTSO) and polydimethylsiloxane (PDMSO) were also studied. The spin-lattice relaxation rate R1 of all siloxanes studied here exhibited a linear relationship with oxygenation (R1 = A' + B'*pO2) at all temperatures and field strengths evaluated here. The sensitivity index η( = B'/A') decreased with increasing molecular weight with values ranged from 4.7 × 10-3-11.6 × 10-3 torr-1 at 4.7 T. No substantial change in the anoxic relaxation rate and a slight decrease in pO2 sensitivity was observed at higher magnetic fields of 7 T and 9.4 T for HMDSO and OMTSO. Temperature dependence of calibration curves for HMDSO, OMTSO and PDMSO was small and simulated errors in pO2 measurement were 1-2 torr/°C. In summary, we have demonstrated the feasibility of various linear and cyclic siloxanes as pO2-reporters for PISTOL-based oximetry.

2.
EJNMMI Res ; 8(1): 66, 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-30043115

RESUMO

BACKGROUND: Florbetaben, a 18F-labeled stilbene derivative (Neuraceq®, formerly known as BAY-949172), is a diagnostic radiopharmaceutical developed to visualize ß-amyloid plaques in the brain. Here, we report a pilot study evaluating patients with suspected cardiac amyloidosis for systemic extent of disease. METHODS: We prospectively enrolled nine patients, 61-86 year old (mean ± SD 69.4 ± 8.6), referred from the cardiac amyloid clinic. First, dynamic imaging of the heart was acquired immediately after injection of 222-318.2 MBq (mean ± SD 270.1 ± 33.3) of 18F-florbetaben using the GE SIGNA PET/MRI. This was followed by a whole-body PET/MRI scan 60-146.4 min (mean ± SD 98 ± 33.4) after injection. Cardiac MRI sequences included ECG-triggered cine SSFP, T2-weighted, and late gadolinium-enhanced imaging. Whole-body MRI sequences included MRAC and axial T1-weighted imaging. RESULTS: High early uptake and delayed high uptake in the left ventricle correlated with amyloid deposition in five patients, while low uptake on early and delayed cardiac imaging was noted in four patients. Cardiac function measurements were successfully obtained in all participants. Areas of increased abnormal 18F-florbetaben accumulation were noted on delayed whole-body imaging in the bone marrow (seven patients), stomach (diffuse in five patients and focal in one patient), brain (five patients), salivary glands (three patients), tongue (three patients), spleen (three patients), skeletal muscles (three patients), ocular muscles (two patients), thyroid (two patients), pleura (two patients), kidneys (two patients), and lungs (two patients). CONCLUSIONS: Whole-body 18F-florbetaben PET/MRI is promising for localization of systemic amyloid deposition. This technique may provide important structural and functional information regarding the organs involved by disease, with potential to guide biopsy and evaluate response to treatment. TRIAL REGISTRATION: Clinicaltrials.gov registration: NCT03119558 .

3.
AJR Am J Roentgenol ; 211(3): 655-660, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29873506

RESUMO

OBJECTIVE: Gallium-68-labeled radiopharmaceuticals pose a challenge for scatter estimation because their targeted nature can produce high contrast in these regions of the kidneys and bladder. Even small errors in the scatter estimate can result in washout artifacts. Administration of diuretics can reduce these artifacts, but they may result in adverse events. Here, we investigated the ability of algorithmic modifications to mitigate washout artifacts and eliminate the need for diuretics or other interventions. MATERIALS AND METHODS: The model-based scatter algorithm was modified to account for PET/MRI scanner geometry and challenges of non-FDG tracers. Fifty-three clinical 68Ga-RM2 and 68Ga-PSMA-11 whole-body images were reconstructed using the baseline scatter algorithm. For comparison, reconstruction was also processed with modified sampling in the single-scatter estimation and with an offset in the scatter tail-scaling process. None of the patients received furosemide to attempt to decrease the accumulation of radiopharmaceuticals in the bladder. The images were scored independently by three blinded reviewers using the 5-point Likert scale. RESULTS: The scatter algorithm improvements significantly decreased or completely eliminated the washout artifacts. When comparing the baseline and most improved algorithm, the image quality increased and image artifacts were reduced for both 68Ga-RM2 and for 68Ga-PSMA-11 in the kidneys and bladder regions. CONCLUSION: Image reconstruction with the improved scatter correction algorithm mitigated washout artifacts and recovered diagnostic image quality in 68Ga PET, indicating that the use of diuretics may be avoided.


Assuntos
Algoritmos , Ácido Edético/análogos & derivados , Imagem por Ressonância Magnética , Neoplasias/diagnóstico por imagem , Oligopeptídeos , Tomografia por Emissão de Pósitrons , Imagem Corporal Total , Idoso , Artefatos , Feminino , Radioisótopos de Gálio , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias/patologia , Estudos Retrospectivos , Espalhamento de Radiação
4.
J Cereb Blood Flow Metab ; 38(1): 126-135, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28155582

RESUMO

15O-H2O PET imaging is an accurate method to measure cerebral blood flow (CBF) but it requires an arterial input function (AIF). Historically, image-derived AIF estimation suffers from low temporal resolution, spill-in, and spill-over problems. Here, we optimized tracer dose on a time-of-flight PET/MR according to the acquisition-specific noise-equivalent count rate curve. An optimized dose of 850 MBq of 15O-H2O was determined, which allowed sufficient counts to reconstruct a short time-frame PET angiogram (PETA) during the arterial phase. This PETA enabled the measurement of the extent of spill-over, while an MR angiogram was used to measure the true arterial volume for AIF estimation. A segment of the high cervical arteries outside the brain was chosen, where the measured spill-in effects were minimal. CBF studies were performed twice with separate [15O]-H2O injections in 10 healthy subjects, yielding values of 88 ± 16, 44 ± 9, and 58 ± 11 mL/min/100 g for gray matter, white matter, and whole brain, with intra-subject CBF differences of 5.0 ± 4.0%, 4.1 ± 3.3%, and 4.5 ± 3.7%, respectively. A third CBF measurement after the administration of 1 g of acetazolamide showed 35 ± 23%, 29 ± 20%, and 33 ± 22% increase in gray matter, white matter, and whole brain, respectively. Based on these findings, the proposed noninvasive AIF method provides robust CBF measurement with 15O-H2O PET.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/irrigação sanguínea , Imagem Multimodal/métodos , Adulto , Circulação Cerebrovascular/fisiologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética , Masculino , Tomografia por Emissão de Pósitrons
5.
J Vis Exp ; (130)2017 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-29286486

RESUMO

Integrated PET/MRI is a hybrid imaging technique enabling clinicians to acquire diagnostic images for tumor assessment and treatment monitoring with both high soft tissue contrast and added metabolic information. Integrated PET/MRI has shown to be valuable in the clinical setting and has many promising future applications. The protocol presented here will provide step-by-step instructions for the acquisition of whole-body 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG) PET/MRI data in children with cancer. It also provides instructions on how to combine a whole-body staging scan with a local tumor scan for evaluation of the primary tumor. The focus of this protocol is to be both comprehensive and time-efficient, which are two ubiquitous needs for clinical applications. This protocol was originally developed for children above 6 years, or old enough to comply with breath-hold instructions, but can also be applied to patients under general anesthesia. Similarly, this protocol can be modified to fit institutional preferences in terms of choice of MRI pulse sequences for both the whole-body scan and local tumor assessment.


Assuntos
Imagem por Ressonância Magnética/métodos , Imagem Multimodal/métodos , Neoplasias/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Imagem Corporal Total/métodos , Criança , Fluordesoxiglucose F18 , Humanos , Masculino , Neoplasias/patologia , Compostos Radiofarmacêuticos , Sarcoma/diagnóstico por imagem , Sarcoma/patologia , Ensaio Tumoral de Célula-Tronco
6.
Radiology ; 285(3): 971-979, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28777701

RESUMO

Purpose To develop a positron emission tomography (PET)/magnetic resonance (MR) imaging protocol for evaluation of the brain, heart, and joints of pediatric cancer survivors for chemotherapy-induced injuries in one session. Materials and Methods Three teams of experts in neuroimaging, cardiac imaging, and bone imaging were tasked to develop a 20-30-minute PET/MR imaging protocol for detection of chemotherapy-induced tissue injuries of the brain, heart, and bone. In an institutional review board-approved, HIPAA-compliant, prospective study from April to July 2016, 10 pediatric cancer survivors who completed chemotherapy underwent imaging of the brain, heart, and bone with a 3-T PET/MR imager. Cumulative chemotherapy doses and clinical symptoms were correlated with the severity of MR imaging abnormalities by using linear regression analyses. MR imaging measures of brain perfusion and metabolism were compared among eight patients who were treated with methotrexate and eight untreated age-matched control subjects by using Wilcoxon rank-sum tests. Results Combined brain, heart, and bone examinations were completed within 90 minutes. Eight of 10 cancer survivors had abnormal findings on brain, heart, and bone images, including six patients with and two patients without clinical symptoms. Cumulative chemotherapy doses correlated significantly with MR imaging measures of left ventricular ejection fraction and end-systolic volume, but not with the severity of brain or bone abnormalities. Methotrexate-treated cancer survivors had significantly lower cerebral blood flow and metabolic activity in key brain areas compared with control subjects. Conclusion The feasibility of a single examination for assessment of chemotherapy-induced injuries of the brain, heart, and joints was shown. Earlier detection of tissue injuries may enable initiation of timely interventions and help to preserve long-term health of pediatric cancer survivors. © RSNA, 2017 Online supplemental material is available for this article.


Assuntos
Antineoplásicos/efeitos adversos , Doenças Ósseas/induzido quimicamente , Encefalopatias/induzido quimicamente , Cardiopatias/induzido quimicamente , Imagem por Ressonância Magnética/métodos , Imagem por Ressonância Magnética/estatística & dados numéricos , Tomografia por Emissão de Pósitrons/métodos , Adolescente , Doenças Ósseas/diagnóstico por imagem , Encefalopatias/diagnóstico por imagem , Sobreviventes de Câncer , Feminino , Cardiopatias/diagnóstico por imagem , Humanos , Masculino , Imagem Multimodal , Neoplasias/diagnóstico por imagem , Neoplasias/tratamento farmacológico , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Fatores de Risco , Sensibilidade e Especificidade , Integração de Sistemas , Resultado do Tratamento , Adulto Jovem
7.
Stroke ; 48(9): 2441-2449, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28765286

RESUMO

BACKGROUND AND PURPOSE: Arterial spin labeling (ASL) MRI is a promising, noninvasive technique to image cerebral blood flow (CBF) but is difficult to use in cerebrovascular patients with abnormal, long arterial transit times through collateral pathways. To be clinically adopted, ASL must first be optimized and validated against a reference standard in these challenging patient cases. METHODS: We compared standard-delay ASL (post-label delay=2.025 seconds), multidelay ASL (post-label delay=0.7-3.0 seconds), and long-label long-delay ASL acquisitions (post-label delay=4.0 seconds) against simultaneous [15O]-positron emission tomography (PET) CBF maps in 15 Moyamoya patients on a hybrid PET/MRI scanner. Dynamic susceptibility contrast was performed in each patient to identify areas of mild, moderate, and severe time-to-maximum (Tmax) delays. Relative CBF measurements by each ASL scan in 20 cortical regions were compared with the PET reference standard, and correlations were calculated for areas with moderate and severe Tmax delays. RESULTS: Standard-delay ASL underestimated relative CBF by 20% in areas of severe Tmax delays, particularly in anterior and middle territories commonly affected by Moyamoya disease (P<0.001). Arterial transit times correction by multidelay acquisitions led to improved consistency with PET, but still underestimated CBF in the presence of long transit delays (P=0.02). Long-label long-delay ASL scans showed the strongest correlation relative to PET, and there was no difference in mean relative CBF between the modalities, even in areas of severe delays. CONCLUSIONS: Post-label delay times of ≥4 seconds are needed and may be combined with multidelay strategies for robust ASL assessment of CBF in Moyamoya disease.


Assuntos
Encéfalo/diagnóstico por imagem , Circulação Cerebrovascular , Doença de Moyamoya/diagnóstico por imagem , Adolescente , Adulto , Encéfalo/irrigação sanguínea , Circulação Colateral , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Imagem Multimodal , Radioisótopos de Oxigênio , Tomografia por Emissão de Pósitrons , Marcadores de Spin
8.
J Nucl Med ; 58(12): 2004-2009, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28572487

RESUMO

The purpose of this study was to assess safety, biodistribution, and radiation dosimetry in humans for the highly selective σ-1 receptor PET agent 18F-6-(3-fluoropropyl)-3-(2-(azepan-1-yl)ethyl)benzo[d]thiazol-2(3H)-one (18F-FTC-146). Methods: Ten healthy volunteers (5 women, 5 men; age ± SD, 34.3 ± 6.5 y) were recruited, and written informed consent was obtained from all participants. Series of whole-body PET/MRI examinations were acquired for up to 3 h after injection (357.2 ± 48.8 MBq). Blood samples were collected, and standard vital signs (heart rate, pulse oximetry, and body temperature) were monitored at regular intervals. Regions of interest were delineated, time-activity curves were calculated, and organ uptake and dosimetry were estimated. Results: All subjects tolerated the PET/MRI examination well, and no adverse reactions to 18F-FTC-146 were reported. High accumulation of 18F-FTC-146 was observed in σ-1 receptor-dense organs such as the pancreas and spleen, moderate uptake in the brain and myocardium, and low uptake in bone and muscle. High uptake was also observed in the kidneys and bladder, indicating renal tracer clearance. The effective dose of 18F-FTC-146 was 0.0259 ± 0.0034 mSv/MBq (range, 0.0215-0.0301 mSv/MBq). Conclusion: First-in-human studies with clinical-grade 18F-FTC-146 were successful. Injection of 18F-FTC-146 is safe, and absorbed doses are acceptable. The potential of 18F-FTC-146 as an imaging agent for a variety of neuroinflammatory diseases is currently under investigation.


Assuntos
Azepinas/farmacocinética , Benzotiazóis/farmacocinética , Compostos Radiofarmacêuticos/farmacocinética , Adulto , Azepinas/efeitos adversos , Azepinas/síntese química , Benzotiazóis/efeitos adversos , Benzotiazóis/síntese química , Feminino , Voluntários Saudáveis , Humanos , Marcação por Isótopo , Imagem por Ressonância Magnética , Masculino , Imagem Multimodal , Radiometria , Compostos Radiofarmacêuticos/efeitos adversos , Compostos Radiofarmacêuticos/síntese química , Receptores sigma/efeitos dos fármacos , Receptores sigma/metabolismo , Distribuição Tecidual , Imagem Corporal Total
9.
Mol Imaging Biol ; 19(5): 779-786, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28280965

RESUMO

PURPOSE: Sigma-1 receptors (S1Rs) play an important role in many neurological disorders. Simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) with S1R radioligands may provide valuable information for diagnosing and guiding treatment for these diseases. Our previously reported S1R radioligand, [18F]FTC-146, demonstrated high affinity for the S1R (K i = 0.0025 nM) and excellent selectivity for the S1R over the sigma-2 receptor (S2Rs; K i = 364 nM) across several species (from mouse to non-human primate). Herein, we report the clinical-grade radiochemistry filed with exploratory Investigational New Drug (eIND) and first-in-human PET/MRI evaluation of [18F]FTC-146. PROCEDURES: [18F]FTC-146 is prepared via a direct [18F] fluoride nucleophilic radiolabeling reaction and formulated in 0.9 % NaCl containing no more than 10 % ethanol through sterile filtration. Quality control (QC) was performed based on USP 823 before doses were released for clinical use. The safety and whole body biodistribution of [18F]FTC-146 were evaluated using a simultaneous PET/MR scanner in two representative healthy human subjects. RESULTS: [18F]FTC-146 was synthesized with a radiochemical yield of 3.3 ± 0.7 % and specific radioactivity of 8.3 ± 3.3 Ci/µmol (n = 10, decay corrected to EOB). Both radiochemical and chemical purities were >95 %; the prepared doses were stable for 4 h at ambient temperature. All QC test results met specified clinical criteria. The in vivo PET/MRI investigations showed that [18F]FTC-146 rapidly crossed the blood brain barrier and accumulated in S1R-rich regions of the brain. There were also radioactivity distributed in the peripheral organs, i.e., the lungs, spleen, pancreas, and thyroid. Furthermore, insignificant uptake of [18F]FTC-146 was observed in cortical bone and muscle. CONCLUSION: A reliable and automated radiosynthesis for providing routine clinical-grade [18F]FTC-146 for human studies was established in a modified GE TRACERlab FXFN. PET/MRI demonstrated the initial tracer biodistribution in humans, and clinical studies investigating different S1R-related diseases are in progress.


Assuntos
Azepinas/química , Azepinas/síntese química , Benzotiazóis/química , Benzotiazóis/síntese química , Imagem por Ressonância Magnética , Tomografia por Emissão de Pósitrons , Adulto , Azepinas/farmacocinética , Benzotiazóis/farmacocinética , Feminino , Humanos , Masculino , Distribuição Tecidual
10.
Crit Rev Biomed Eng ; 42(6): 437-50, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25955710

RESUMO

Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) has become a valuable clinical tool for cancer diagnosis and prognosis. DCE MRI provides pharmacokinetic parameters dependent on the extravasation of small molecular contrast agents, and thus high temporal resolution and/or spatial resolution is required for accurate estimation of parameters. In this article we investigate the efficacy of 2 undersampling approaches to speed up DCE MRI: a conventional keyhole approach and compressed sensing-based imaging. Data reconstructed from variants of these methods has been compared with the full k-space reconstruction with respect to data quality and pharmacokinetic parameters Ktrans and ve. Overall, compressive sensing provides better data quality and reproducible parametric maps than key-hole methods with higher acceleration factors. In particular, an undersampling mask based on a priori precontrast data showed high fidelity of reconstructed data and parametric maps up to 5× acceleration.


Assuntos
Meios de Contraste/química , Meios de Contraste/farmacocinética , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Algoritmos , Animais , Feminino , Neoplasias Mamárias Experimentais/metabolismo , Neoplasias Mamárias Experimentais/patologia , Ratos , Ratos Endogâmicos F344
11.
Magn Reson Med ; 71(6): 2172-9, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23900942

RESUMO

PURPOSE: To investigate the efficacy of a novel respiratory motion scheme, where only the center of k-space is gated using respiratory navigators, versus a fully respiratory-gated acquisition for three-dimensional flow imaging. METHODS: Three-dimensional flow images were acquired axially using a gradient echo sequence in a volume, covering the ascending and descending aorta, and the pulmonary artery bifurcation in 12 healthy subjects (33.2 ± 15.8 years; five men). For respiratory motion compensation, two gating and tracking strategies were used with a 7-mm gating window: (1) All of k-space acquired within the gating window (fully gated) and (2) central k-space acquired within the gating window, and the remainder of k-space acquired without any gating (center gated). Each scan was repeated twice. Stroke volume, mean flow, peak velocity, and signal-to-noise-ratio measurements were performed both on the ascending and on the descending aorta for all acquisitions, which were compared using a linear mixed-effects model and Bland-Altman analysis. RESULTS: There were no statistical differences between the fully gated and the center-gated strategies for the quantification of stroke volume, peak velocity, and mean flow, as well as the signal-to-noise-ratio measurements. Furthermore, the proposed center-gated strategy had significantly shorter acquisition time compared to the fully gated strategy (13:19 ± 3:02 vs. 19:35 ± 5:02, P < 0.001). CONCLUSIONS: The proposed novel center-gated strategy for three-dimensional flow MRI allows for markedly shorter acquisition time without any systematic variation in quantitative flow measurements in this small group of healthy volunteers.


Assuntos
Aorta Torácica/fisiologia , Velocidade do Fluxo Sanguíneo/fisiologia , Imagem por Ressonância Magnética/métodos , Artéria Pulmonar/fisiologia , Adulto , Feminino , Voluntários Saudáveis , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional , Masculino , Movimento (Física) , Respiração , Razão Sinal-Ruído , Fatores de Tempo
12.
J Biol Inorg Chem ; 19(2): 271-9, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24281854

RESUMO

Tumor hypoxia is known to affect sensitivity to radiotherapy and promote development of metastases; therefore, the ability to image tumor hypoxia in vivo could provide useful prognostic information and help tailor therapy. We previously demonstrated in vitro evidence for selective accumulation of a gadolinium tetraazacyclododecanetetraacetic acid monoamide conjugate of 2-nitroimidazole (GdDO3NI), a magnetic resonance imaging T1-shortening agent, in hypoxic cells grown in tissue culture. We now report evidence for accumulation of GdDO3NI in hypoxic tumor tissue in vivo. Our data show that GdDO3NI accumulated significantly (p < 0.05) in the central, poorly perfused regions of rat prostate adenocarcinoma AT1 tumors (threefold higher concentration than for the control agent) and showed better clearance from well-perfused regions and complete clearance from the surrounding muscle tissue. Inductively coupled plasma mass spectroscopy confirmed that more GdDO3NI than control agent was retained in the central region and that more GdDO3NI was retained in the central region than at the periphery. These results show the utility of GdDO3NI to image tumor hypoxia and highlight the potential of GdDO3NI for application to image-guided interventions for radiation therapy or hypoxia-activated chemotherapy.


Assuntos
Meios de Contraste , Gadolínio/química , Imagem por Ressonância Magnética/métodos , Nitroimidazóis/química , Compostos Organometálicos/química , Neoplasias da Próstata/patologia , Animais , Transporte Biológico , Hipóxia Celular , Meios de Contraste/química , Meios de Contraste/metabolismo , Masculino , Compostos Organometálicos/metabolismo , Neoplasias da Próstata/diagnóstico , Ratos
13.
Magn Reson Imaging ; 31(6): 1006-11, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23602729

RESUMO

The quantitative assessment of gene expression and related enzyme activity in vivo could be important for the characterization of gene altering diseases and therapy. The development of imaging techniques, based on specific reporter molecules may enable routine non-invasive assessment of enzyme activity and gene expression in vivo. We recently reported the use of commercially available S-Gal(®) as a ß-galactosidase reporter for (1)H MRI, and the synthesis of several S-Gal(®) analogs with enhanced response to ß-galactosidase activity. We have now compared these analogs in vitro and have identified the optimal analog, C3-GD, based on strong T1 and T2 response to enzyme presence (ΔR1 and ΔR2~1.8 times S-Gal(®)). Moreover, application is demonstrated in vivo in human breast tumor xenografts. MRI studies in MCF7-lacZ tumors implanted subcutaneously in athymic nude mice (n=6), showed significant reduction in T1 and T2 values (each~13%) 2h after intra-tumoral injection of C3-GD, whereas the MCF7 (wild type) tumors showed slight increase. Thus, C3-GD successfully detects ß-galactosidase activity in vivo and shows promise as a lacZ gene (1)H MR reporter molecule.


Assuntos
Biomarcadores Tumorais/metabolismo , Galactosídeos/farmacocinética , Imagem por Ressonância Magnética/métodos , Imagem Molecular/métodos , Neoplasias Experimentais/metabolismo , Umbeliferonas/farmacocinética , beta-Galactosidase/metabolismo , Animais , Biomarcadores Tumorais/análise , Meios de Contraste/farmacocinética , Genes Reporter , Camundongos , Camundongos Nus , Neoplasias Experimentais/patologia , Prótons , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , beta-Galactosidase/análise
14.
Chemistry ; 18(31): 9669-76, 2012 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-22740186

RESUMO

Tissue hypoxia occurs in pathologic conditions, such as cancer, ischemic heart disease and stroke when oxygen demand is greater than oxygen supply. An imaging method that can differentiate hypoxic versus normoxic tissue could have an immediate impact on therapy choices. In this work, the gadolinium(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with a 2-nitroimidazole attached to one carboxyl group via an amide linkage was prepared, characterized and tested as a hypoxia-sensitive MRI agent. A control complex, Gd(DO3A-monobutylamide), was also prepared in order to test whether the nitroimidazole side-chain alters either the water proton T(1) relaxivity or the thermodynamic stability of the complex. The stabilities of these complexes were lower than that of Gd(DOTA)(-) as expected for mono-amide derivatives. The water proton T(1) relaxivity (r(1)), bound water residence lifetime (τ(M)) and rotational correlation time (τ(R)) of both complexes was determined by relaxivity measurements, variable temperature (17) O NMR spectroscopy and proton nuclear magnetic relaxation dispersion (NMRD) studies. The resulting parameters (r(1) =6.38 mM(-1) s(-1) at 20 MHz, τ(M) =0.71 µs, τ(R) =141 ps) determined for the nitroimidazole derivative closely parallel to those of other Gd(DO3A-monoamide) complexes of similar molecular size. In vitro MR imaging experiments with 9L rat glioma cells maintained under nitrogen (hypoxic) versus oxygen (normoxic) gas showed that both agents enter cells but only the nitroimidazole derivative was trapped in cells maintained under N(2) as evidenced by an approximately twofold decrease in T(1) measured for hypoxic cells versus normoxic cells exposed to this agent. These results suggest that the nitroimidazole derivative might serve as a molecular reporter for discriminating hypoxic versus normoxic tissues by MRI.


Assuntos
Gadolínio/química , Compostos Heterocíclicos/síntese química , Compostos Organometálicos/síntese química , Animais , Compostos Heterocíclicos/química , Hipóxia , Imagem por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Camundongos , Estrutura Molecular , Compostos Organometálicos/química , Ratos
15.
Chempluschem ; 77(5): 370-378, 2012 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-23807909

RESUMO

There is increasing interest in the development of reporter agents to reveal enzyme activity in vivo using small animal imaging. We have previously demonstrated the feasibility of detecting lacZ gene activity using the commercially available 3,4-cyclohexenoesculetin-ß-D-galactopyranoside (S-Gal™) as a 1H MRI reporter. Specifically, ß-galactosidase (ß-gal) releases the aglycone, which forms an MR contrast-inducing paramagnetic precipitate in the presence of Fe3+. Contrast was primarily T2-weighted signal loss, but T1 effects were also observed. Since T1-contrast generally provides signal enhancement as opposed to loss, it appeared attractive to explore whether analogues could be generated with enhanced characteristics. We now report the design and successful synthesis of novel analogues together with characterization of 1H MRI contrast based on both T1 and T2 response to ß-gal activity in vitro for the lead agent.

16.
Theranostics ; 2(12): 1199-207, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23382776

RESUMO

An emerging need for evaluation of promising cellular therapies is a non-invasive method to image the movement and health of cells following transplantation. However, the use of a single modality to serve this purpose may not be advantageous as it may convey inaccurate or insufficient information. Multi-modal imaging strategies are becoming more popular for in vivo cellular and molecular imaging because of their improved sensitivity, higher resolution and structural/functional visualization. This study aims at formulating Nile Red doped hexamethyldisiloxane (HMDSO) nanoemulsions as dual modality (Magnetic Resonance Imaging/Fluorescence), dual-functional (oximetry/detection) nanoprobes for cellular and molecular imaging. HMDSO nanoprobes were prepared using a HS15-lecithin combination as surfactant and showed an average radius of 71±39 nm by dynamic light scattering and in vitro particle stability in human plasma over 24 hrs. They were found to readily localize in the cytosol of MCF7-GFP cells within 18 minutes of incubation. As proof of principle, these nanoprobes were successfully used for fluorescence imaging and for measuring pO(2) changes in cells by magnetic resonance imaging, in vitro, thus showing potential for in vivo applications.


Assuntos
Imagem por Ressonância Magnética , Imagem Molecular/métodos , Nanopartículas/química , Animais , Sobrevivência Celular , Endocitose , Fibroblastos , Humanos , Células MCF-7 , Camundongos , Microscopia de Fluorescência , Células NIH 3T3 , Nanopartículas/ultraestrutura , Oxazinas/química , Tamanho da Partícula , Siloxanas/química
17.
NMR Biomed ; 24(10): 1226-34, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21412864

RESUMO

Quantitative in vivo oximetry has been reported using (19) F MRI in conjunction with reporter molecules, such as perfluorocarbons, for tissue oxygenation (pO(2) ). Recently, hexamethyldisiloxane (HMDSO) has been proposed as a promising alternative reporter molecule for (1) H MRI-based measurement of pO(2) . To aid biocompatibility for potential systemic administration, we prepared various nanoemulsion formulations using a wide range of HMDSO volume fractions and HMDSO to surfactant ratios. Calibration curves (R(1) versus pO(2) ) for all emulsion formulations were found to be linear and similar to neat HMDSO for low surfactant concentrations (<10% v/v). A small temperature dependence in the calibration curves was observed, similar to previous reports on neat HMDSO, and was characterized to be approximately 1 Torr/ °C under hypoxic conditions. To demonstrate application in vivo, 100 µL of this nanoemulsion was administered to healthy rat thigh muscle (Fisher 344, n=6). Dynamic changes in mean thigh tissue pO(2) were measured using the PISTOL (proton imaging of siloxanes to map tissue oxygenation levels) technique in response to oxygen challenge. Changing the inhaled gas to oxygen for 30 min increased the mean pO(2) significantly (p<0.001) from 39 ± 7 to 275 ± 27 Torr. When the breathing gas was switched back to air, the tissue pO(2) decreased to a mean value of 45 ± 6 Torr, not significantly different from baseline (p>0.05), in 25 min. A first-order exponential fit to this part of the pO(2) data (i.e. after oxygen challenge) yielded an oxygen consumption-related kinetic parameter k=0.21 ± 0.04 min(-1) . These results demonstrate the feasibility of using HMDSO nanoemulsions as nanoprobes of pO(2) and their utility to assess oxygen dynamics in vivo, further developing quantitative (1) H MRI oximetry.


Assuntos
Imagem por Ressonância Magnética/métodos , Sondas Moleculares/química , Nanopartículas/química , Oximetria/métodos , Prótons , Siloxanas/química , Animais , Calibragem , Morte Celular , Emulsões , Filtração , Cinética , Camundongos , Células NIH 3T3 , Oxigênio/metabolismo , Consumo de Oxigênio , Tamanho da Partícula , Ratos , Ratos Endogâmicos F344 , Temperatura
18.
Ann Biomed Eng ; 37(1): 201-9, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18923902

RESUMO

BACKGROUND: Approximately 400,000 cholecystectomies are performed annually in the United States. The most important complication of the operation is bile duct injury (BDI). Injury prevention relies mostly on an individual surgeon's skill. As of yet no technology has been introduced that will enable surgeons to visualize the bile ducts while operating. Theoretically, such a device could eliminate BDI. Near infrared (NIR) spectroscopy capitalizes on near infrared light's ability to penetrate deeply into tissues and spectroscopic capability to discern tissue's chemical properties. The purpose of this work is to characterize the NIR optical properties of bile containing structures that are needed for later development of a clinically useful probe. METHODS: NIR Spectroscopy combined with visible light spectroscopy was used to determine the spectroscopic properties of the biliary tree and its adjacent structures. Eight anesthetized pigs were used to obtain reflectance measurements using a fiber probe. Radial Basis functions (RBFs) were used to characterize the reflected light spectra. Parameters describing the RBFs were then used to classify tissues based on their observed spectra using machine automation. RESULTS: Biliary tissues, arteries and veins all had unique reflectance spectra. These spectra were characterized by their unique set of RBFs. CONCLUSION: We have developed an optical probe capable of imaging and identifying biliary tract tissues in a porcine model. In this study, we characterized the reflectance properties for bile and blood vessels such that when the probe is applied to the porta hepatis it will enable surgeons to localize important biliary structures prior to any portal dissection, potentially eliminating the risk for inadvertent BDI.


Assuntos
Doenças dos Ductos Biliares/cirurgia , Ductos Biliares/cirurgia , Sistema Biliar/fisiologia , Algoritmos , Animais , Bile/química , Ductos Biliares/química , Sistema Biliar/química , Colecistectomia , Complicações Intraoperatórias/prevenção & controle , Óptica e Fotônica/instrumentação , Óptica e Fotônica/métodos , Espectroscopia de Luz Próxima ao Infravermelho , Suínos
19.
NMR Biomed ; 21(8): 899-907, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18574806

RESUMO

Hexamethyldisiloxane (HMDSO) has been identified as a sensitive proton NMR indicator of tissue oxygenation (pO(2)) based on spectroscopic spin-lattice relaxometry. A rapid MRI approach has now been designed, implemented, and tested. The technique, proton imaging of siloxanes to map tissue oxygenation levels (PISTOL), utilizes frequency-selective excitation of the HMDSO resonance and chemical-shift selective suppression of residual water signal to effectively eliminate water and fat signals and pulse-burst saturation recovery (1)H echo planar imaging to map T(1) of HMDSO and hence pO(2). PISTOL was used here to obtain maps of pO(2) in rat thigh muscle and Dunning prostate R3327 MAT-Lu tumor-implanted rats. Measurements were repeated to assess baseline stability and response to breathing of hyperoxic gas. Each pO(2) map was obtained in 3(1/2) min, facilitating dynamic measurements of response to oxygen intervention. Altering the inhaled gas to oxygen produced a significant increase in mean pO(2) from 55 Torr to 238 Torr in thigh muscle and a smaller, but significant, increase in mean pO(2) from 17 Torr to 78 Torr in MAT-Lu tumors. Thus, PISTOL enabled mapping of tissue pO(2) at multiple locations and dynamic changes in pO(2) in response to intervention. This new method offers a potentially valuable new tool to image pO(2) in vivo for any healthy or diseased state by (1)H MRI.


Assuntos
Músculo Esquelético/metabolismo , Oximetria/métodos , Oxigênio/análise , Oxigênio/metabolismo , Siloxanas/análise , Siloxanas/metabolismo , Animais , Prótons , Ratos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA