GRAPPA-based susceptibility-weighted imaging of normal volunteers and patients with brain tumor at 7 T (original) (raw)
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The British Journal of Radiology, 2010
The purpose of this study was to determine the benefit of high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient for brain tumour imaging, and to assess the clinical feasibility of using a non-contrast MR protocol at 3 T. 73 patients with intra-axial tumours were enrolled into the study. Two experienced neuroradiologists reviewed three MRI sessions: (i) a non-contrast protocol including high-resolution susceptibility-weighted images and apparent diffusion coefficient; (ii) a contrast protocol including MR perfusion images; and (iii) combined contrast and non-contrast protocols. The two observers categorised tumours as glial or non-glial tumours, and then subcategorised the gliomas into low-grade or high-grade tumours. For semi-quantitative analysis, a scoring system based on the degree of intratumoral susceptibility signals and the visual apparent diffusion coefficient was used. The two observers diagnosed accurate tumour pathology in 52 (71%) of 73 tumours in the first review, 55 (75%) of 73 tumours in the second review and 61 (84%) of 73 tumours in the third review. The addition of the non-contrast protocol to the contrast protocol significantly differentiated glioblastoma multiforme and metastatic tumours, which was not possible with the contrast protocol alone. The sensitivity, specificity, positive predictive value and negative predictive value for glioma grading with the non-contrast protocol were 83.2%, 100%, 100% and 79.3%, respectively. The addition of both high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient improved the diagnostic performance of the contrast MR protocol for brain tumour imaging and could be feasible in selected patients who cannot tolerate a contrast agent.
T he initial development of MR venography by Reichenbach et al. 90 laid the foundation for Haacke et al. to apply the principles of MR venography in conventional MRI for broader usage in clinical and research settings. By utilizing magnitude and phase information, both of which are normally acquired from conventional MRI data, susceptibility weighted imaging (SWI) has an enhanced ability to detect microhemorrhages and microvasculature. It is a highly sensitive imaging modality able to depict magnetic substances, such as deoxygenated hemoglobin, with high contrast 42 and to help investigate neurological diseases, 82 grade tumors, 25,63 and assist in determining treatment or prognosis. Over the past years, the SWI technique has found applications in the different fields of neurosurgery, namely neurooncology, vascular neurosurgery, neurotraumatol-abbreviatioNs AVM = arteriovenous malformation; CCM = cerebral cavernous malformation; CMB = cerebral microbleed; CVS = cortical vessel sign; DAI = diffuse axonal injury; DBS = deep brain stimulation; DWI = diffusion-weighted imaging; GBM = glioblastoma multiforme; GCS = Glasgow Coma Scale; GPe = external globus pallidus; GPi = internal GP; GRE = gradient-recalled echo; ITSS = intratumoral susceptibility signal; mIP = minimum intensity projection; MRA = MR angiography; MS = multiple sclerosis; PD = proton density; PQ = percentagewise quantification; PWI = perfusion-weighted imaging; SN = substantia nigra; STN = subthalamic nucleus; SWI = susceptibility weighted imaging; TBI = traumatic brain injury; VM = vascular malformation. Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.
Magnetic Resonance in Medicine, 1999
The aim of this work was to evaluate the potential of T 2-weighted, steady-state susceptibility-enhanced contrast magnetic resonance imaging (MRI), to characterize brain tumor heterogeneity and tumor vascularization. In vivo T 2-weighted MRI experiments were carried out on normal rats (n ؍ 11) and rats bearing C6 glioma (n ؍ 17), before and after the injection of a remanent superparamagnetic contrast agent. The ⌬R 2 variations of the transverse relaxation rate due to the injection of the contrast agent were used to generate relative cerebral blood volume (CBV) maps. Contrast enhancement of the tumor was shown to reflect tissue vascularization rather than leakage of the blood-brain barrier. The quantitative results clearly show the heterogeneity of tumor vascularization and reveal a high vessel density in the peripheral area (CBV per ϰ ϰ 17.2 ؎ 2.3 sec ؊1) and a low vessel density in the central area of the tumor (CBV cen ϰ ϰ 2.5 ؎ 0.5 sec ؊1). Magn
BMC Medical Imaging, 2009
The work presented here investigates parallel imaging applied to T1-weighted high resolution imaging for use in longitudinal volumetric clinical studies involving Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI) patients. This was in an effort to shorten acquisition times to minimise the risk of motion artefacts caused by patient discomfort and disorientation. The principle question is, "Can parallel imaging be used to acquire images at 1.5 T of sufficient quality to allow volumetric analysis of patient brains?" Methods: Optimisation studies were performed on a young healthy volunteer and the selected protocol (including the use of two different parallel imaging acceleration factors) was then tested on a cohort of 15 elderly volunteers including MCI and AD patients. In addition to automatic brain segmentation, hippocampus volumes were manually outlined and measured in all patients. The 15 patients were scanned on a second occasion approximately one week later using the same protocol and evaluated in the same manner to test repeatability of measurement using images acquired with the GRAPPA parallel imaging technique applied to the MPRAGE sequence.
La radiologia medica, 2011
Magnetic resonance imaging (MRI) with a dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) sequence to study brain tumours provides information on the haemodynamic characteristics of the neoplastic tissue. Brain perfusion maps and calculation of perfusion parameters, such as relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV) and mean transit time (MTT) allow assessment of vascularity and angiogenesis within tumours of the central nervous system (CNS), thus providing additional information to conventional MRI sequences. Although DSC-PWI has long been used, its clinical use in the study of brain tumours in daily clinical practice is still to be defined. The aim of this review was to analyse the application of perfusion MRI in the study of brain tumours by summarising our personal experience and the main results reported in the literature. Keywords Perfusion • Magnetic resonance imaging • Neuroradiology • Brain tumours Riassunto L'utilizzo della sequenza dinamica di perfusione con mezzo di contrasto (DSC-PWI) in risonanza magnetica (RM) nello studio dei tumori cerebrali fornisce informazioni sulle caratteristiche emodinamiche del tessuto neoplastico. L'elaborazione delle mappe di perfusione cerebrale ed il calcolo dei parametri di perfusione, come il flusso ematico cerebrale relativo (rCBF), il volume ematico cerebrale relativo (rCBV) ed il tempo di transito medio (MTT), consentono di studiare la vascolarizzazione ed i processi angiogenetici presenti nel contesto dei tumori del sistema nervoso centrale (CNS), fornendo informazioni aggiuntive alle sequenze RM convenzionali. Nonostante abbia un impiego diagnostico diffuso, l'esatto ruolo assunto dalla metodica nello studio delle neoplasie cerebrali, nella pratica clinica quotidiana, non è esattamente definito. Lo scopo di questa revisione è quello di analizzare le applicazioni della sequenza di perfusione nello studio dei tumori cerebrali riassumendo l'esperienza personale ed i principali risultati emergenti dalla letteratura. Parole chiave Perfusione • Risonanza magnetica • Neuroradiologia • Tumori cerebrali NEURORADIOLOGY NEURORADIOLOGIA Clinical applications of dynamic susceptibility contrast perfusionweighted MR imaging in brain tumours Impiego clinico della sequenza RM di perfusione con tecnica dinamica contrastografica nei tumori cerebrali
American Journal of Neuroradiology, 2009
BACKGROUND AND PURPOSE: It has been reported that high-resolution susceptibility-weighted imaging (HR-SWI) may demonstrate brain tumor vascularity. We determined whether the degree of intratumoral susceptibility signal intensity (ITSS) on HR-SWI correlates with maximum relative cerebral blood volume (rCBVmax) and to compare its diagnostic accuracy for glioma grading with that of dynamic susceptibility contrast (DSC) perfusion MR imaging. MATERIALS AND METHODS: Forty-one patients with diffuse astrocytomas underwent both non-contrast-enhanced HR-SWI and DSC at 3T. We correlated the degree and morphology of ITSS with rCBVmax within the same tumor segment. The degree of ITSS and rCBVmax were compared among 3 groups with different histopathologic grades. Spearman correlation coefficients were determined between the degree of ITSS, rCBVmax, and glioma grade. Receiver operating characteristic (ROC) curve analyses were performed to determine the diagnostic accuracy for glioma grading. RESULTS: The degree of ITSS showed a significant correlation with the value of rCBVmax in the same tumor segments (r ϭ 0.72, P Ͻ .0001). However, the areas of densely prominent ITSSs did not accurately correspond with those of rCBVmax. Spearman correlation coefficients between ITSS degree and glioma grade were 0.88 (95% confidence interval, 0.79-0.94). In the ROC curve analysis of histopathologic correlation by using the degree of ITSS, the optimal sensitivity, specificity, positive predictive value, and negative predictive value for determining a high-grade tumor were 85.2%, 92.9%, 95.8%, and 76.5%, respectively. CONCLUSIONS: The degree of ITSS shows a significant correlation with the value of rCBVmax in the same tumor segments, and its diagnostic performance for glioma grading is comparable with that of DSC.