Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 38
Filtrar
Más filtros

Banco de datos
País/Región como asunto
Tipo del documento
País de afiliación
Intervalo de año de publicación
1.
J Magn Reson Imaging ; 46(3): 663-677, 2017 09.
Artículo en Inglés | MEDLINE | ID: mdl-28067973

RESUMEN

PURPOSE: To assess the feasibility of diffusion tensor imaging (DTI) using simultaneous multislice (SMS) acquisition with blipped controlled aliasing in parallel imaging (CAIPI) for accelerated readout-segmented echo planar imaging (rs-EPI) of the mandibular nerves. DTI of the mandibular nerves using EPI is challenging due to susceptibility artifacts. Rs-EPI is less prone to artifacts but associated with longer scan durations. MATERIALS AND METHODS: Eight asymptomatic volunteers were imaged at 3T using a 64-channel head/neck coil. Conventional, 2-fold (2xSMS) and 3-fold (3xSMS) slice-accelerated rs-EPI sequences were acquired. Tractography of the mandibular nerves was performed. Signal-to-noise ratio (SNR), fractional anisotropy (FA), mean diffusivity (MD), and number of tracts were calculated. Artifacts were evaluated qualitatively on Likert scales. Parameters were compared statistically. Clinical feasibility of 2xSMS rs-EPI was tested in four patients. RESULTS: SNR was similar for conventional (mean ± SD; 8.55 ± 3.90) and 2xSMS rs-EPI (7.83 ± 3.15) but lower for 3xSMS rs-EPI (5.42 ± 2.93; analysis of variance, P = 0.004). FA was similar for all sequences (rs-EPI, 0.42 ± 0.08; 2xSMS rs-EPI, 0.43 ± 0.08; 3xSMS rs-EPI, 0.44 ± 0.06), while 3xSMS rs-EPI showed lower MD (rs-EPI, 0.0015 ± 0.0003; 2xSMS rs-EPI, 0.0014 ± 0.0001; 3xSMS rs-EPI, 0.0013 ± 0.0003) and lower number of tracts (rs-EPI, 66.56 ± 51.31; 2xSMS rs-EPI, 65.75 ± 55.40; 3xSMS rs-EPI, 37.93 ± 52.42) compared to rs-EPI and 2xSMS rs-EPI. Additionally, 2xSMS rs-EPI was feasible in four clinical patients and provided robust imaging results. CONCLUSION: 2xSMS rs-EPI yielded similar SNR, FA, and MD values compared to conventional rs-EPI at reduced scan time and is feasible in clinical patients. These findings suggest the potential clinical applicability of rs-EPI for DTI of the mandibular nerve. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:663-677.


Asunto(s)
Imagen de Difusión Tensora/métodos , Imagen Eco-Planar/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Nervio Mandibular/diagnóstico por imagen , Adulto , Estudios de Factibilidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Adulto Joven
2.
J Neuroradiol ; 44(1): 38-43, 2017 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-27836653

RESUMEN

OBJECTIVE: To determine the prevalence of simple and complex sacral perineural Tarlov cysts (TCs) in a cohort of children and adults. MATERIAL AND METHODS: Retrospective observational epidemiological study assessing 1100 consecutive sacral magnetic resonance (MR) studies, including 100 children and adolescents. All patients underwent 1.5T MR imaging with T1 and T2 weighted image acquisitions in sagittal and axial planes. All perineural cysts affecting the sacral nerve roots S1-S4 were quantitatively and qualitatively assessed. RESULTS: Two hundred and sixty-three sacral TCs were found in 132 adult patients (13.2%), with a female predominance (68%). None was found in children. The prevalence of TCs increased with age. The average number of cysts per patient was 2.0±1.2 with a maximum of 6 cysts in a single patient. Most of the cysts (87.5%) showed a homogenous central fluid collection and a parietal course of the nerve fibers. Complex patterns were present in 33 cysts (12.5%) within which 28 cysts showed endocystic crossing of nerve fibers and 5 cysts contained internal septations. Seventy cysts (26.6%) eroded the adjacent bone and 13 cysts (4.9%) extended to the pelvis. CONCLUSION: The prevalence of sacral TCs in our cohort corresponded to 13%, with a female predominance. Interestingly no TCs were found in children or adolescents (<18 years). In relation to the non-negligible percentage of complex cysts with internal septations, or endocystic crossing of nerve fibers, pre-interventional characterization of sacral TCs might help to choose an appropriate procedure in the treatment of rare symptomatic variants.


Asunto(s)
Quistes de Tarlov/epidemiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Femenino , Francia/epidemiología , Humanos , Lactante , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Retrospectivos , Sacro/diagnóstico por imagen , Sacro/patología , Quistes de Tarlov/diagnóstico por imagen , Quistes de Tarlov/patología , Adulto Joven
3.
Neuroimage ; 137: 52-60, 2016 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-27155125

RESUMEN

Dynamic changes of brain-tissue magnetic susceptibility provide the basis for functional MR imaging (fMRI) via T2*-weighted signal-intensity modulations. Promising initial work on a detection of neuronal activity via quantitative susceptibility mapping (fQSM) has been published but consistently reported on ill-understood positive and negative activation patterns (Balla et al., 2014; Chen and Calhoun, 2015a). We set out to (i) demonstrate that fQSM can exploit established fMRI data acquisition and processing methods and to (ii) better describe aspects of the apparent activation patterns using fMRI and PET as standards of reference. Under a standardized visual-stimulation paradigm PET and 3-T gradient-echo EPI-based fQSM, fMRI data from 9 healthy volunteers were acquired and analyzed by means of Independent Component Analysis (ICA) at subject level and, for the first time, at group level. Numbers of activated (z-score>2.0) voxels were counted and their mean z-scores calculated in volumes of interest (occipital lobe (Nocc_lobe), segmented occipital gray-matter (NGM_occ_lobe), large veins (Nveins)), and in occipital-lobe voxels commonly activated in fQSM and fMRI component maps. Common but not entirely congruent regions of apparent activation were found in the occipital lobe in z-score maps from all modalities, fQSM, fMRI and PET, with distinct BOLD-negatively correlated regions in fQSM data. At subject-level, Nocc_lobe, NGM_occ_lobe and their mean z-scores were significantly smaller in fQSM than in fMRI, but their ratio, NGM_occ_lobe/Nocc_lobe, was comparable. Nveins did not statistically differ and the ratio Nveins/NGM_occ_lobe as well as the mean z-scores were higher for fQSM than for fMRI. In veins and immediate vicinity, z-score maps derived from both phase and fQSM-data showed positive and negative lobes resembling dipole shapes in simulated field and phase maps with no correlate in fMRI or PET data. Our results show that standard fMRI tools can directly be used for fQSM processing, and suggest that fQSM may have the potential to detect gray-matter activation distant from large veins, to improve detection of veins with stimulus-induced venous oxygen saturation (SvO2) variations, and to better localize areas of activation. However, our results seem to clearly expose issues that phenomenologically resemble an incomplete dipolar inversion and that need to be subject to further investigation.


Asunto(s)
Mapeo Encefálico/métodos , Interpretación de Imagen Asistida por Computador/métodos , Imagen por Resonancia Magnética/métodos , Red Nerviosa/fisiología , Tomografía de Emisión de Positrones/métodos , Corteza Visual/fisiología , Percepción Visual/fisiología , Adulto , Algoritmos , Femenino , Humanos , Aumento de la Imagen/métodos , Imagenología Tridimensional/métodos , Masculino , Estimulación Luminosa/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
4.
J Magn Reson Imaging ; 44(2): 393-400, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-26854879

RESUMEN

PURPOSE: Panoramical radiographs or cone-beam computed tomography (CT) are the standard-of-care in dental imaging to assess teeth, mandible, and mandibular canal pathologies, but do not allow assessment of the inferior alveolar nerve itself nor of its branches. We propose a new technique for "MR neurographic orthopantomograms" exploiting ultrashort echo-time (UTE) imaging of bone and teeth complemented with high-resolution morphological and functional MR neurography. MATERIALS AND METHODS: The Institutional Review Board approved the study in 10 healthy volunteers. Imaging of the subjects mandibles at 3.0T (Magnetom Skyra, Siemens-Healthcare) using a 64-channel head coil with isotropic spatial resolution for subsequent multiplanar reformatting, was performed. Bone images were acquired using a 3D PETRA sequence (TE, 0.07 msec). Morphological nerve imaging was performed using a dedicated 3D PSIF and 3D SPACE STIR sequence. Functional MR neurography was accomplished using a new accelerated diffusion-tensor-imaging (DTI) prototype sequence (2D SMS-accelerated RESOLVE). Qualitative and quantitative image analysis was performed and descriptive statistics are provided. RESULTS: Image acquisition and subsequent postprocessing into the MR neurographic orthopantomogram by overlay of morphological and functional images were feasible in all 10 volunteers without artifacts. All mandibular bones and mandibular nerves were assessable and considered normal. Fiber tractography with quantitative evaluation of physiological diffusion properties of mandibular nerves yielded the following mean ± SD values: fractional anisotropy, 0.43 ± 0.07; mean diffusivity (mm(2) /s), 0.0014 ± 0.0002; axial diffusivity, 0.0020 ± 0.0002, and radial diffusivity, 0.0011 ± 0.0001. CONCLUSION: The proposed technique of MR neurographic orthopantomogram exploiting UTE imaging complemented with high-resolution morphological and functional MR neurography was feasible and allowed comprehensive assessment of osseous texture and neural microarchitecture in a single examination. J. Magn. Reson. Imaging 2016;44:393-400.


Asunto(s)
Imagen por Resonancia Magnética/métodos , Mandíbula/diagnóstico por imagen , Mandíbula/inervación , Neuroimagen/métodos , Radiografía Panorámica/métodos , Diente/diagnóstico por imagen , Diente/inervación , Adulto , Estudios de Factibilidad , Femenino , Humanos , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Imagenología Tridimensional/métodos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Procesamiento de Señales Asistido por Computador
5.
Neuroradiology ; 58(9): 929-35, 2016 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-27278377

RESUMEN

INTRODUCTION: The study aims to assess the influence of neck extension on water diffusivity within the cervical spinal cord. METHODS: IRB approved the study in 22 healthy volunteers. All subjects underwent anatomical MR and diffusion tensor imaging (DTI) at 1.5 T. The cervical cord was imaged in neutral (standard) position and extension. Segmental vertebral rotations were analyzed on sagittal T2-weighted images using the SpineView® software. Spinal cord diffusivity was measured in cross-sectional regions of interests at multiple levels (C1-C5). RESULTS: As a result of non-adapted coil geometry for spinal extension, 10 subjects had to be excluded. Image quality of the remaining 12 subjects was good without any deteriorating artifacts. Quantitative measurements of vertebral rotation angles and diffusion parameters showed good intra-rater reliability (ICC = 0.84-0.99). DTI during neck extension revealed significantly decreased fractional anisotropy (FA) and increased radial diffusivity (RD) at the C3 level and increased apparent diffusion coefficients (ADC) at the C3 and C4 levels (p < 0.01 Bonferroni corrected). The C3/C4 level corresponded to the maximal absolute change in segmental vertebral rotation between the two positions. The increase in RD correlated positively with the degree of global extension, i.e., the summed vertebral rotation angle between C1 and C5 (R = 0.77, p = 0.006). CONCLUSION: Our preliminary results suggest that DTI can quantify changes in water diffusivity during cervical spine extension. The maximal differences in segmental vertebral rotation corresponded to the levels with significant changes in diffusivity (C3/C4). Consequently, kinetic DTI measurements may open new perspectives in the assessment of neural tissue under biomechanical constraints.


Asunto(s)
Agua Corporal/química , Médula Cervical/química , Médula Cervical/diagnóstico por imagen , Vértebras Cervicales/diagnóstico por imagen , Imagen de Difusión Tensora/métodos , Interpretación de Imagen Asistida por Computador/métodos , Rango del Movimiento Articular/fisiología , Adulto , Vértebras Cervicales/química , Difusión , Femenino , Humanos , Cinética , Masculino , Persona de Mediana Edad , Proyectos Piloto , Valores de Referencia , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
6.
J Stroke Cerebrovasc Dis ; 24(5): 965-71, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25813061

RESUMEN

BACKGROUND: Moyamoya disease (MMD) is an idiopathic intracranial angiopathy with a progressive spontaneous occlusion of the circle of Willis resulting in repeated ischemia if not diagnosed and treated early, especially in children. Prevention of stroke is achieved by revascularization of the affected cerebral regions. Functional imaging techniques such as H2[(15)O]-Positron emission tomography (PET) allow quantification of cerebral perfusion/blood flow (CBF) and in particular cerebrovascular response after acetazolamide (AZA) challenge. The cerebrovascular reserve (CVR) can then be calculated and used to identify regions at risk of infarct, hence allowing surgery to be specifically targeted and personalized. METHODS: Pediatric patients with diagnosed MMD underwent initial H2[(15)O]-PET scans at baseline and after stimulation with AZA. Indication for surgery was then based collectively on the extent of disease observed clinically and on magnetic resonance imaging, on the arterial territories involved, as seen in angiography and the respective regional CVR observed in PET. Cerebral revascularization surgeries were subsequently performed, tailored to the individual patient. Postoperative assessment of clinical outcome was augmented with follow-up PET (median duration after surgery, 10.4 months). CBF at baseline, after AZA and CVR were compared between presurgery and postsurgery scans in the areas supplied by the major cerebral arteries. RESULTS: Parametric images reflecting CBF, response to AZA and CVR clearly showed deficits in cortical but not subcortical regions or cerebellum. AZA-CBF and CVR deficits were most clear in middle cerebral artery and anterior cerebral artery (ACA) regions. In addition to the clinical symptomatology, angiography, AZA-CBF, and CVR images allowed the laterality of deficits to be clearly visualized for tailored surgery and the indication for targeted ACA or posterior cerebral artery revascularization to be assessed. Comparison of baseline CBF, AZA-CBF, and CVR between presurgery and postsurgery scans in revascularized areas revealed a significant improvement in baseline and AZA-CBF after surgery. Although no significant differences in CVR after revascularization surgery were found, a clear improvement of the deficits apparent in AZA-CBF in revascularized regions was found. CONCLUSIONS: We demonstrate that quantitative H2[(15)O]-PET is a highly useful tool to direct surgical intervention in MMD. Detailed quantitative analysis of CBF changes and CVR after surgery supports a targeted surgical approach.


Asunto(s)
Revascularización Cerebral/métodos , Enfermedad de Moyamoya/diagnóstico por imagen , Enfermedad de Moyamoya/terapia , Tomografía de Emisión de Positrones , Acetazolamida/farmacología , Inhibidores de Anhidrasa Carbónica/farmacología , Angiografía Cerebral , Circulación Cerebrovascular/efectos de los fármacos , Niño , Preescolar , Femenino , Estudios de Seguimiento , Humanos , Procesamiento de Imagen Asistido por Computador , Lactante , Masculino , Radioisótopos de Oxígeno , Tomografía Computarizada por Rayos X
7.
Radiology ; 273(3): 859-69, 2014 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-25102372

RESUMEN

PURPOSE: To assess the diagnostic performance of whole-body non-contrast material-enhanced positron emission tomography (PET)/magnetic resonance (MR) imaging and PET/computed tomography (CT) for staging and restaging of cancers and provide guidance for modality and sequence selection. MATERIALS AND METHODS: This study was approved by the institutional review board and national government authorities. One hundred six consecutive patients (median age, 68 years; 46 female and 60 male patients) referred for staging or restaging of oncologic malignancies underwent whole-body imaging with a sequential trimodality PET/CT/MR system. The MR protocol included short inversion time inversion-recovery ( STIR short inversion time inversion-recovery ), Dixon-type liver accelerated volume acquisition ( LAVA liver accelerated volume acquisition ; GE Healthcare, Waukesha, Wis), and respiratory-gated periodically rotated overlapping parallel lines with enhanced reconstruction ( PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction ; GE Healthcare) sequences. Primary tumors (n = 43), local lymph node metastases (n = 74), and distant metastases (n = 66) were evaluated for conspicuity (scored 0-4), artifacts (scored 0-2), and reader confidence on PET/CT and PET/MR images. Subanalysis for lung lesions (n = 46) was also performed. Relevant incidental findings with both modalities were compared. Interreader agreement was analyzed with intraclass correlation coefficients and κ statistics. Lesion conspicuity, image artifacts, and incidental findings were analyzed with nonparametric tests. RESULTS: Primary tumors were less conspicuous on STIR short inversion time inversion-recovery (3.08, P = .016) and LAVA liver accelerated volume acquisition (2.64, P = .002) images than on CT images (3.49), while findings with the PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction sequence (3.70, P = .436) were comparable to those at CT. In distant metastases, the PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction sequence (3.84) yielded better results than CT (2.88, P < .001). Subanalysis for lung lesions yielded similar results (primary lung tumors: CT, 3.71; STIR short inversion time inversion-recovery , 3.32 [P = .014]; LAVA liver accelerated volume acquisition , 2.52 [P = .002]; PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction , 3.64 [P = .546]). Readers classified lesions more confidently with PET/MR than PET/CT. However, PET/CT showed more incidental findings than PET/MR (P = .039), especially in the lung (P < .001). MR images had more artifacts than CT images. CONCLUSION: PET/MR performs comparably to PET/CT in whole-body oncology and neoplastic lung disease, with the use of appropriate sequences. Further studies are needed to define regionalized PET/MR protocols with sequences tailored to specific tumor entities.


Asunto(s)
Imagen Multimodal , Neoplasias/patología , Imagen de Cuerpo Entero , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Artefactos , Medios de Contraste , Femenino , Humanos , Metástasis Linfática , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Tomografía de Emisión de Positrones , Tomografía Computarizada por Rayos X
8.
Eur J Nucl Med Mol Imaging ; 41(6): 1066-75, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24577950

RESUMEN

PURPOSE: Positron emission tomography (PET)/MRI combines the functional ability of PET and the high soft tissue contrast of MRI. The aim of this study was to assess contrast-enhanced (ce)PET/MRI compared to cePET/CT in patients with suspected recurrence of head and neck cancer (HNC). METHODS: Eighty-seven patients underwent sequential cePET/CT and cePET/MRI using a trimodality PET/CT-MRI set-up. Diagnostic accuracy for the detection of recurrent HNC was evaluated using cePET/CT and cePET/MRI. Furthermore, image quality, presence of unclear (18)F-fluorodeoxy-D-glucose (FDG) findings of uncertain significance and the diagnostic advantages of use of gadolinium contrast enhancement were analysed. RESULTS: cePET/MRI showed no statistically significant difference in diagnostic accuracy compared to cePET/CT (91.5 vs 90.6%). Artefacts' grade was similar in both methods, but their location was different. cePET/CT artefacts were primarily located in the suprahyoid area, while on cePET/MRI, artefacts were more equally distributed among the supra and infrahyoid neck regions. cePET/MRI and cePET/CT showed 34 unclear FDG findings; of those 11 could be solved by cePET/MRI and 5 by cePET/CT. The use of gadolinium in PET/MRI did not yield higher diagnostic accuracy, but helped to better define tumour margins in 6.9% of patients. CONCLUSION: Our data suggest that cePET/MRI may be superior compared to cePET/CT to specify unclear FDG uptake related to possible tumour recurrence in follow-up of patients after HNC. It seems to be the modality of choice for the evaluation of the oropharynx and the oral cavity because of a higher incidence of artefacts in cePET/CT in this area mainly due to dental implants. However, overall there is no statistically significant difference.


Asunto(s)
Carcinoma/diagnóstico por imagen , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Imagen por Resonancia Magnética , Imagen Multimodal , Tomografía de Emisión de Positrones , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma/diagnóstico , Femenino , Fluorodesoxiglucosa F18 , Estudios de Seguimiento , Neoplasias de Cabeza y Cuello/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Estudios Prospectivos , Radiofármacos
9.
Eur J Nucl Med Mol Imaging ; 41(12): 2212-21, 2014 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-25091219

RESUMEN

OBJECTIVE: The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers. METHODS: Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar's test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference. RESULTS: One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8%) were malignant and 70 (37.2%) were benign. PET/MRI without DWI had a higher accuracy in detecting malignant lesions than DWI alone (86.8% vs. 60.6%, p < 0.001). PET/MRI combined with DWI detected 120 concurrent lesions (89 malignant and 31 benign), PET/MRI alone identified 48 additional lesions (20 malignant and 28 benign), and DWI alone detected 20 different lesions (nine malignant and 11 benign). However, lesions detected on DWI did not change overall staging. SUV maximum and mean were significantly higher in malignant lesions than in benign lesions. DWI parameters between malignant and benign lesions were not statistically different. CONCLUSION: The use of DWI as part of PET/MRI to evaluate head and neck cancers does not provide remarkable information. Thus, the use of DWI might not be needed in clinical PET/MRI protocols for the staging or restaging of head and neck cancers.


Asunto(s)
Imagen de Difusión por Resonancia Magnética , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Tomografía de Emisión de Positrones , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Neoplasias de Cabeza y Cuello/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Imagen Multimodal , Valor Predictivo de las Pruebas , Tomografía Computarizada por Rayos X
10.
Eur J Nucl Med Mol Imaging ; 40(1): 44-51, 2013 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-22955547

RESUMEN

PURPOSE: PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions. METHODS: A total of 100 oncological patients underwent sequential whole-body (18)F-FDG PET with CT-based attenuation correction (AC), 40 mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization. RESULTS: From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p < 0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40 % of lesions, equal to CT in 49 %, and inferior to CT in 11 %. CONCLUSION: Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust.


Asunto(s)
Abdomen/diagnóstico por imagen , Imagen por Resonancia Magnética , Imagen Multimodal , Tomografía de Emisión de Positrones , Tomografía Computarizada por Rayos X , Adulto , Anciano , Femenino , Fluorodesoxiglucosa F18 , Humanos , Masculino , Persona de Mediana Edad , Neoplasias/diagnóstico por imagen , Neoplasias/patología , Radiofármacos , Imagen de Cuerpo Entero
11.
MAGMA ; 26(1): 25-35, 2013 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-23053712

RESUMEN

Tri-modality PET/CT-MRI includes the transfer of the patient on a dedicated shuttle from one system into the other. Advantages of this system include a true CT-based attenuation correction, reliable PET-quantification and higher flexibility in patient throughput on both systems. Comparative studies of PET/MRI versus PET/CT are readily accomplished without repeated PET with a different PET scanner at a different time point. Additionally, there is a higher imaging flexibility based on the availability of three imaging modalities, which can be combined for the characterization of the disease. The downside is a somewhat higher radiation dose of up to 3 mSv with a low dose CT based on the CT-component, longer acquisition times and potential misalignment between the imaging components. Overall, the tri-modality PET/CT-MR system offers comparative studies using the three different imaging modalities in the same patient virtually at the same time, and may help to develop reliable attenuation algorithms at the same time.


Asunto(s)
Imagen por Resonancia Magnética/métodos , Tomografía de Emisión de Positrones/métodos , Tomografía Computarizada por Rayos X/métodos , Diseño de Equipo , Humanos , Imagen por Resonancia Magnética/instrumentación , Tomografía de Emisión de Positrones/instrumentación , Tomografía Computarizada por Rayos X/instrumentación
12.
Eur J Nucl Med Mol Imaging ; 39(7): 1154-60, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-22526955

RESUMEN

PURPOSE: Accurate attenuation correction (AC) is essential for quantitative analysis of PET tracer distribution. In MR, the lack of cortical bone signal makes bone segmentation difficult and may require implementation of special sequences. The purpose of this study was to evaluate the need for accurate bone segmentation in MR-based AC for whole-body PET/MR imaging. METHODS: In 22 patients undergoing sequential PET/CT and 3-T MR imaging, modified CT AC maps were produced by replacing pixels with values of >100 HU, representing mostly bone structures, by pixels with a constant value of 36 HU corresponding to soft tissue, thereby simulating current MR-derived AC maps. A total of 141 FDG-positive osseous lesions and 50 soft-tissue lesions adjacent to bones were evaluated. The mean standardized uptake value (SUVmean) was measured in each lesion in PET images reconstructed once using the standard AC maps and once using the modified AC maps. Subsequently, the errors in lesion tracer uptake for the modified PET images were calculated using the standard PET image as a reference. RESULTS: Substitution of bone by soft tissue values in AC maps resulted in an underestimation of tracer uptake in osseous and soft tissue lesions adjacent to bones of 11.2 ± 5.4% (range 1.5-30.8%) and 3.2 ± 1.7% (range 0.2-4%), respectively. Analysis of the spine and pelvic osseous lesions revealed a substantial dependence of the error on lesion composition. For predominantly sclerotic spine lesions, the mean underestimation was 15.9 ± 3.4% (range 9.9-23.5%) and for osteolytic spine lesions, 7.2 ± 1.7% (range 4.9-9.3%), respectively. CONCLUSION: CT data simulating treating bone as soft tissue as is currently done in MR maps for PET AC leads to a substantial underestimation of tracer uptake in bone lesions and depends on lesion composition, the largest error being seen in sclerotic lesions. Therefore, depiction of cortical bone and other calcified areas in MR AC maps is necessary for accurate quantification of tracer uptake values in PET/MR imaging.


Asunto(s)
Neoplasias Óseas/diagnóstico por imagen , Fluorodesoxiglucosa F18 , Radiofármacos , Adulto , Anciano , Neoplasias Óseas/metabolismo , Neoplasias Óseas/patología , Fluorodesoxiglucosa F18/farmacocinética , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Tomografía de Emisión de Positrones/métodos , Radiofármacos/farmacocinética , Estudios Retrospectivos , Tomografía Computarizada por Rayos X
13.
BMJ Case Rep ; 14(8)2021 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-34404638

RESUMEN

A male refugee from the Middle East was diagnosed with pulmonary tuberculosis and Pott's disease with paravertebral abscess. After starting the standard regimen, the sputum culture converted to negative and the patient's general condition improved. Six weeks later, the patient presented with clinical worsening of known symptoms, new appearance of focal neurological deficits and progress of radiological features showing progression of the paravertebral abscess. Immune reconstitution inflammatory syndrome with Mycobacterium tuberculosis (TB-IRIS) was presumed, and treatment with high-dose steroids was started. Due to recurrent relapses while tapering, corticosteroids had to be given over a prolonged period. After treatment completion, the patient was in a good general condition, abscesses had decreased and neurological deficits were in complete remission. This case presents the rare manifestation of TB-IRIS in HIV-negative patients and its management in a high-income country.


Asunto(s)
Infecciones por VIH , Síndrome Inflamatorio de Reconstitución Inmune , Mycobacterium tuberculosis , Tuberculosis Pulmonar , Tuberculosis de la Columna Vertebral , Infecciones por VIH/complicaciones , Infecciones por VIH/tratamiento farmacológico , Humanos , Síndrome Inflamatorio de Reconstitución Inmune/complicaciones , Síndrome Inflamatorio de Reconstitución Inmune/diagnóstico , Síndrome Inflamatorio de Reconstitución Inmune/tratamiento farmacológico , Masculino
14.
Magn Reson Med Sci ; 18(2): 150-157, 2019 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-30416178

RESUMEN

PURPOSE: Diffusion tensor imaging (DTI) adds functional information to morphological magnetic resonance neurography (MRN) in the assessment of the brachial nerve plexus. To determine the most appropriate pulse sequence in scan times suited for diagnostic imaging in clinical routine, we compared image quality between simultaneous multi-slice readout-segmented (rs-DTI) and conventional single-shot (ss-DTI) echo-planar imaging techniques. METHODS: Institutional Review Board (IRB) approved study including 10 healthy volunteers. The supraclavicular brachial plexus, covering the nerve roots and trunks from C5 to C7, was imaged on both sides with rs-DTI and ss-DTI. Both sequences were acquired in scan times <7 min with b-values of 900 s/mm2 and with isotropic spatial resolution. RESULTS: In rs-DTI image, the overall quality was significantly better and distortion artifacts were significantly lower (P = 0.001-0.002 and P = 0.001-0.002, respectively) for both readers. In ss-DTI, a trend toward lower degree of ghosting and motion artifacts was elicited (reader 1, P = 0.121; reader 2, P = 0.264). No significant differences between the two DTI techniques were found for signal-to-noise ratios (SNR), contrast-to-noise ratios (CNR) and fractional anisotropy (FA) (P ≥ 0.475, P ≥ 0.624, and P ≥ 0.169, respectively). Interreader agreement for all examined parameters and all sequences ranged from intraclass correlation coefficient (ICC) 0.064 to 0.905 and Kappa 0.40 to 0.851. CONCLUSION: Incomparable acquisition times rs-DTI showed higher image quality and less distortion artifacts than ss-DTI. The trend toward a higher degree of ghosting and motion artifacts in rs-DTI did not deteriorate image quality to a significant degree. Thus, rs-DTI should be considered for functional MRN of the brachial plexus.


Asunto(s)
Plexo Braquial/diagnóstico por imagen , Imagen de Difusión por Resonancia Magnética , Imagen de Difusión Tensora , Imagen Eco-Planar , Neuroimagen/métodos , Adulto , Anisotropía , Artefactos , Plexo Braquial/patología , Medios de Contraste , Femenino , Voluntarios Sanos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Masculino , Estudios Prospectivos , Reproducibilidad de los Resultados , Relación Señal-Ruido
15.
J Cereb Blood Flow Metab ; 38(5): 847-856, 2018 05.
Artículo en Inglés | MEDLINE | ID: mdl-28421854

RESUMEN

Fluctuations in blood-oxygenation level dependent (BOLD) signal and perfusion affect the quantification of changes in cerebral blood flow (CBF), coupled to neuronal activity, in arterial spin labeling (ASL). Subtraction methods for control and labeled MR images (i.e. pair-wise, surround subtraction, and subtraction of sinc-interpolated images), postulated to mitigate this interference in pseudo-continuous ASL (pCASL), were evaluated by comparison with quantitative 15O-water PET. At rest, a good agreement in the CBF values was found between PET and MRI for each of the subtraction methods. Stimulation of the visual system resulted in a regional CBF increase in the occipital lobe, which was detectable in both modalities. Bland-Altman analysis showed a systematic underestimation of the CBF values during activation in MRI. Evaluation of the relative CBF change induced by neuronal stimulation showed good inter-modality agreement for the three subtraction methods. Perfusion data obtained with each subtraction method followed the stimulation paradigm without significant differences in the correlation patterns or in the time lag between stimulation and perfusion response. Comparison to the gold standard confirmed the detectability of a neuronal stimulation pattern by pCASL. The results indicate that the combined use of background suppression and short TE reduces the BOLD-weighting in the pCASL signal.


Asunto(s)
Encéfalo/diagnóstico por imagen , Procesamiento de Imagen Asistido por Computador/métodos , Imagen por Resonancia Magnética/métodos , Neuroimagen/métodos , Adulto , Algoritmos , Encéfalo/irrigación sanguínea , Circulación Cerebrovascular , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tomografía de Emisión de Positrones , Adulto Joven
16.
Heliyon ; 4(10): e00853, 2018 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-30364500

RESUMEN

PURPOSE: To compare conventional single-shot echo planar imaging (ss-EPI) and simultaneous multi-slice (SMS) readout-segmented EPI (rs-EPI) for magnetic resonance diffusion tensor imaging (DTI) of the ulnar nerve. MATERIALS AND METHODS: This study was approved by the local ethics committee. Ten healthy volunteers (mean age 30.4 ± 4.01 years; range 25-36 years) underwent 3T DTI of the ulnar nerve at the level of the cubital tunnel. DTI was performed based on ss-EPI as well as SMS rs-EPI sequences. Signal-to-noise ratio (SNR), image quality, and DTI parameters in the ulnar nerve (fractional anisotropy, FA; mean diffusivity, MD) were compared between the two sequences by two independent radiologists. RESULTS: Acquisition time was 5:12 min for ss-EPI and 5:18 min for SMS rs-EPI. Between the two sequences, no significant differences were found for derived DTI measures FA (p = 0.11) and MD values (p = 0.93). Compared to conventional ss-EPI, SMS rs-EPI yielded significantly less ghosting artifacts (p = 0.04) but inferior nerve depiction (p = 0.001) and worse overall image quality (p = 0.008). CONCLUSION: SMS rs-EPI is not advantageous over ss-EPI in DTI of the ulnar nerve at the level of the cubital tunnel.

17.
Magn Reson Imaging ; 47: 147-153, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29221966

RESUMEN

BACKGROUND AND PURPOSE: Quantitative susceptibility mapping has been previously used to differentiate lesions in patients with brain tumors. The aim of this work was to characterize the response of magnetic susceptibility differences in malignant brain tumors and surrounding edema to hyperoxic and hypercapnic respiratory challenges. METHODS: Images of malignant brain tumor patients (2 glioblastoma multiforme, 2 anaplastic astrocytoma, 1 brain metastasis) with clinical MRI exams (contrast-enhanced T1w) were acquired at 3T. 3D multi-gradient-echo data sets were acquired while the patients inhaled medical-air (21% O2), oxygen (100% O2), and carbogen (95% O2, 5% CO2). Susceptibility maps were generated from real and imaginary data. Regions of interest were analyzed with respect to respiration-gas-induced susceptibility changes. RESULTS: Contrast-enhancing tumor regions with high baseline magnetic susceptibility exhibited a marked susceptibility reduction under hyperoxic challenges, with a stronger effect (-0.040 to -0.100ppm) under hypercapnia compared to hyperoxia (-0.010 to -0.067ppm). In contrast, regions attributed to necrotic tissue and to edema showed smaller changes of opposite sign, i.e. paramagnetic shift. There was a correlation between malignant tumor tissue magnetic susceptibility at baseline under normoxia and the corresponding susceptibility reduction under hypercapnia and - to a lesser degree - under hyperoxia. CONCLUSION: In this small cohort of analysis, quantification of susceptibility changes in response to respiratory challenges allowed a complementary, functional differentiation of tumorous sub-regions. Those changes, together with the correlations observed between baseline susceptibility under normoxia and susceptibility reduction with challenges, could prove helpful for a non-invasive characterization of local tumor microenvironment.


Asunto(s)
Astrocitoma/diagnóstico por imagen , Neoplasias Encefálicas/diagnóstico por imagen , Encéfalo/diagnóstico por imagen , Dióxido de Carbono/química , Glioblastoma/diagnóstico por imagen , Oxígeno/química , Microambiente Tumoral , Adulto , Biomarcadores , Encéfalo/patología , Neoplasias Encefálicas/patología , Femenino , Humanos , Hipercapnia , Hiperoxia , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Metástasis de la Neoplasia , Estudios Prospectivos
19.
Invest Radiol ; 52(8): 482-487, 2017 08.
Artículo en Inglés | MEDLINE | ID: mdl-28291025

RESUMEN

OBJECTIVE: The aim of this study was to evaluate the reproducibility of 3 T magnetic resonance imaging diffusion tensor imaging (DTI) of the brachial plexus in healthy subjects. METHODS: Ten healthy volunteers were included, and morphological and DTI sequences of the nerve roots of the brachial plexus from C5 to T1 of both sides were repeatedly acquired on a 3 T magnetic resonance system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). A prototype diffusion-weighted single-shot echo-planar imaging sequence-enabling slice-specific shim adjustments was performed with b-values of 0 and 800 s/mm in 30 gradient directions, resulting in an acquisition time of about 6 minutes each in axial orientation. Between scans, subjects were moved and repositioned in the scanner, coils were reinserted, and new localizers were acquired. Image analysis was performed using MITK Diffusion software toolkit. Two independent readers performed diffusion data postprocessing, and regions of interest (ROIs) were set on the proximal postganglionic trunk at each spinal level, bilaterally to obtain values for fractional anisotropy (FA) and mean diffusivity (MD). Interreader and intrareader agreement as well as test-retest reproducibility of DTI metrics were assessed. RESULTS: Intraclass correlation coefficients (ICCs) for interreader and intrareader agreement did not differ significantly between measurements for FA and MD. In particular, ICCs for interreader agreement of FA ranged from 0.741 to 0.961 and that of MD ranged from 0.802 to 0.998, and ICCs for intrareader agreement of FA ranged from 0.759 to 0.949 and that of MD ranged from 0.796 to 0.998. The test-retest reproducibility of DTI metrics showed an overall moderate to strong correlation (r > 0.707), with few minor exceptions, for both FA and MD values. CONCLUSIONS: Diffusion tensor imaging metrics in the brachial plexus are reproducible. Future applications of DTI for a possible clinical use should be further investigated.


Asunto(s)
Plexo Braquial/anatomía & histología , Imagen de Difusión Tensora/métodos , Adulto , Plexo Braquial/diagnóstico por imagen , Imagen Eco-Planar/métodos , Femenino , Humanos , Masculino , Valores de Referencia , Reproducibilidad de los Resultados , Adulto Joven
20.
Clin Imaging ; 42: 232-239, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28129606

RESUMEN

PURPOSE: To compare the diagnostic accuracy of PET+MR with PET/CT in the initial staging of head and neck cancer. MATERIALS AND METHODS: Contrast-enhanced PET/CT+MR was performed in 27 patients with newly diagnosed head and neck cancer. PET/CT and PET+MR were evaluated separately, and the TNM stage and factors influencing treatment were assessed. RESULTS: The TNM staging by PET+MR was comparable to PET/CT (T: p=0.331, N: p=0.453, M: p=0.034). The sensitivity/specificity/accuracy of treatment-influencing factors by PET/CT and PET+MR were 0.68/0.99/0.97, and 1.00/1.00/0.99, respectively. CONCLUSIONS: Whole-body staging with PET+MR yields at least equal diagnostic accuracy as PET/CT in head and neck cancer.


Asunto(s)
Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Imagen por Resonancia Magnética , Tomografía Computarizada por Tomografía de Emisión de Positrones , Tomografía de Emisión de Positrones , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Fluorodesoxiglucosa F18 , Humanos , Masculino , Persona de Mediana Edad , Imagen Multimodal , Estadificación de Neoplasias , Estudios Prospectivos , Radiofármacos , Sensibilidad y Especificidad
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA