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Suitability of Pharmacokinetic Models for Dynamic Contrast-Enhanced MRI of Abdominal Aortic Aneurysm Vessel Wall: A Comparison  [PDF]
V. Lai Nguyen, M. Eline Kooi, Walter H. Backes, Raf H. M. van Hoof, Anne E. C. M. Saris, Mirthe C. J. Wishaupt, Femke A. M. V. I. Hellenthal, Rob J. van der Geest, Alfons G. H. Kessels, Geert Willem H. Schurink, Tim Leiner
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075173
Abstract: Purpose Increased microvascularization of the abdominal aortic aneurysm (AAA) vessel wall has been related to AAA progression and rupture. The aim of this study was to compare the suitability of three pharmacokinetic models to describe AAA vessel wall enhancement using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Materials and Methods Patients with AAA underwent DCE-MRI at 1.5 Tesla. The volume transfer constant (Ktrans), which reflects microvascular flow, permeability and surface area, was calculated by fitting the blood and aneurysm vessel wall gadolinium concentration curves. The relative fit errors, parameter uncertainties and parameter reproducibilities for the Patlak, Tofts and Extended Tofts model were compared to find the most suitable model. Scan-rescan reproducibility was assessed using the interclass correlation coefficient and coefficient of variation (CV). Further, the relationship between Ktrans and AAA size was investigated. Results DCE-MRI examinations from thirty-nine patients (mean age±SD: 72±6 years; M/F: 35/4) with an mean AAA maximal diameter of 49±6 mm could be included for pharmacokinetic analysis. Relative fit uncertainties for Ktrans based on the Patlak model (17%) were significantly lower compared to the Tofts (37%) and Extended Tofts model (42%) (p<0.001). Ktrans scan-rescan reproducibility for the Patlak model (ICC = 0.61 and CV = 22%) was comparable with the Tofts (ICC = 0.61, CV = 23%) and Extended Tofts model (ICC = 0.76, CV = 22%). Ktrans was positively correlated with maximal AAA diameter (Spearman’s ρ = 0.38, p = 0.02) using the Patlak model. Conclusion Using the presented imaging protocol, the Patlak model is most suited to describe DCE-MRI data of the AAA vessel wall with good Ktrans scan-rescan reproducibility.
Pharmacokinetic Changes Induced by Focused Ultrasound in Glioma-Bearing Rats as Measured by Dynamic Contrast-Enhanced MRI  [PDF]
Feng-Yi Yang, Chia-En Ko, Sheng-Yao Huang, I-Fang Chung, Gin-Shin Chen
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092910
Abstract: Focused ultrasound (FUS) combined with microbubbles has been shown to be a noninvasive and targeted drug delivery technique for brain tumor treatment. The purpose of this study was to measure the kinetics of Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) in glioma-bearing rats in the presence of FUS-induced blood-brain barrier disruption (BBB-D) by magnetic resonance imaging (MRI). A total of ten glioma-bearing rats (9–12 weeks, 290–340 g) were used in this study. Using dynamic contrast-enhanced (DCE)-MRI, the spatial permeability of FUS-induced BBB-D was evaluated and the kinetic parameters were calculated by a general kinetic model (GKM). The results demonstrate that the mean Ktrans of the sonicated tumor (0.128±0.019 at 20 min and 0.103±0.023 at 24 h after sonication, respectively) was significantly higher than (2.46-fold at 20 min and 1.78-fold at 24 h) that of the contralateral (non-sonicated) tumor (0.052±0.019 at 20 min and 0.058±0.012 at 24 h after sonication, respectively). In addition, the transfer constant Ktrans in the sonicated tumor correlated strongly with tissue EB extravasation (R = 0.95), which suggests that DCE-MRI may reflect drug accumulation in the brain. Histological observations showed no macroscopic damage except for a few small erythrocyte extravasations. The current study demonstrates that DCE-MRI can monitor the dynamics of the FUS-induced BBB-D process and constitutes a useful tool for quantifying BBB permeability in tumors.
The Use of Dynamic Tracer Concentration in Veins for Quantitative DCE-MRI Kinetic Analysis in Head and Neck  [PDF]
Jing Yuan, Steven Kwok Keung Chow, Qinwei Zhang, David Ka Wai Yeung, Anil T. Ahuja, Ann D. King
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0059885
Abstract: Background Head and neck Magnetic Resonance (MR) Images are vulnerable to the arterial blood in-flow effect. To compensate for this effect and enhance accuracy and reproducibility, dynamic tracer concentration in veins was proposed and investigated for quantitative dynamic contrast-enhanced (DCE) MRI analysis in head and neck. Methodology 21 patients with head and neck tumors underwent DCE-MRI at 3T. An automated method was developed for blood vessel selection and separation. Dynamic concentration-time-curves (CTCs) in arteries and veins were used for the Tofts model parameter estimations. The estimation differences by using CTCs in arteries and veins were compared. Artery and vein voxels were accurately separated by the automated method. Remarkable inter-slice tracer concentration differences were found in arteries while the inter-slice concentration differences in veins were moderate. Tofts model fitting by using the CTCs in arteries and veins produced significantly different parameter estimations. The individual artery CTCs resulted in large (>50% generally) inter-slice parameter estimation variations. Better inter-slice consistency was achieved by using the vein CTCs. Conclusions The use of vein CTCs helps to compensate for arterial in-flow effect and reduce kinetic parameter estimation error and inconsistency for head and neck DCE-MRI.
Average arterial input function for quantitative dynamic contrast enhanced magnetic resonance imaging of neck nodal metastases
Amita Shukla-Dave, Nancy Lee, Hilda Stambuk, Ya Wang, Wei Huang, Howard T Thaler, Snehal G Patel, Jatin P Shah, Jason A Koutcher
BMC Medical Physics , 2009, DOI: 10.1186/1756-6649-9-4
Abstract: Twenty patients (mean age 50 years [range 27–77 years]) with neck nodal metastases underwent pretreatment DCE-MRI studies with a temporal resolution of 3.75 to 7.5 sec on a 1.5T clinical MRI scanner. Eleven individual AIFs (Ind-AIFs) met the criteria of expected enhancement pattern and were used to generate Avg-AIF. Tofts model was used to calculate pharmacokinetic DCE-MRI parameters. Bland-Altman plots and paired Student t-tests were used to describe significant differences between the pharmacokinetic parameters obtained from individual and average AIFs.Ind-AIFs obtained from eleven patients were used to calculate the Avg-AIF. No overall significant difference (bias) was observed for the transfer constant (Ktrans) measured with Ind-AIFs compared to Avg-AIF (p = 0.20 for region-of-interest (ROI) analysis and p = 0.18 for histogram median analysis). Similarly, no overall significant difference was observed for interstitial fluid space volume fraction (ve) measured with Ind-AIFs compared to Avg-AIF (p = 0.48 for ROI analysis and p = 0.93 for histogram median analysis). However, the Bland-Altman plot suggests that as Ktrans increases, the Ind-AIF estimates tend to become proportionally higher than the Avg-AIF estimates.We found no statistically significant overall bias in Ktrans or ve estimates derived from Avg-AIF, generated from a limited population, as compared with Ind-AIFs.However, further study is needed to determine whether calibration is needed across the range of Ktrans. The Avg-AIF obtained from a limited population may be used for pharmacokinetic modeling of DCE-MRI data in larger population studies with neck nodal metastases. Further validation of the Avg-AIF approach with a larger population and in multiple regions is desirable.A broad range of tumors [1-3] have been studied clinically by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) which monitors the passage of intravenously administered Gadolinium (Gd) contrast agent through tumor tissu
Magnetic resonance imaging staging of nasopharyngeal carcinoma in the head and neck  [cached]
Ann Dorothy King, Kunwar Suryaveer Singh Bhatia
World Journal of Radiology , 2010,
Abstract: Magnetic resonance imaging (MRI) is the modality of choice for staging nasopharyngeal carcinoma in the head and neck. This article will review the patterns of primary and nodal spread on MRI with reference to the latest 7th edition of the International Union Against Cancer/American Joint Committee on Cancer staging system.
Biocompatible Nanocomplexes for Molecular Targeted MRI Contrast Agent  [cached]
Chen Zhijin,Yu Dexin,Wang Shaojie,Zhang Na
Nanoscale Research Letters , 2009,
Abstract: Accurate diagnosis in early stage is vital for the treatment of Hepatocellular carcinoma. The aim of this study was to investigate the potential of poly lactic acid–polyethylene glycol/gadolinium–diethylenetriamine-pentaacetic acid (PLA–PEG/Gd–DTPA) nanocomplexes using as biocompatible molecular magnetic resonance imaging (MRI) contrast agent. The PLA–PEG/Gd–DTPA nanocomplexes were obtained using self-assembly nanotechnology by incubation of PLA–PEG nanoparticles and the commercial contrast agent, Gd–DTPA. The physicochemical properties of nanocomplexes were measured by atomic force microscopy and photon correlation spectroscopy. The T1-weighted MR images of the nanocomplexes were obtained in a 3.0 T clinical MR imager. The stability study was carried out in human plasma and the distribution in vivo was investigated in rats. The mean size of the PLA–PEG/Gd–DTPA nanocomplexes was 187.9 ± 2.30 nm, and the polydispersity index was 0.108, and the zeta potential was 12.36 ± 3.58 mV. The results of MRI test confirmed that the PLA–PEG/Gd–DTPA nanocomplexes possessed the ability of MRI, and the direct correlation between the MRI imaging intensities and the nano-complex concentrations was observed (r = 0.987). The signal intensity was still stable within 2 h after incubation of the nanocomplexes in human plasma. The nanocomplexes gave much better image contrast effects and longer stagnation time than that of commercial contrast agent in rat liver. A dose of 0.04 mmol of gadolinium per kilogram of body weight was sufficient to increase the MRI imaging intensities in rat livers by five-fold compared with the commercial Gd–DTPA. PLA–PEG/Gd–DTPA nanocomplexes could be prepared easily with small particle sizes. The nanocomplexes had high plasma stability, better image contrast effect, and liver targeting property. These results indicated that the PLA–PEG/Gd–DTPA nanocomplexes might be potential as molecular targeted imaging contrast agent.
Automatic Characterization of Myocardial Perfusion in Contrast Enhanced MRI  [cached]
Positano Vincenzo,Santarelli Maria Filomena,Landini Luigi
EURASIP Journal on Advances in Signal Processing , 2003,
Abstract: The use of contrast medium in cardiac MRI allows joining the high-resolution anatomical information provided by standard magnetic resonance with functional information obtained by means of the perfusion of contrast agent in myocardial tissues. The current approach to perfusion MRI characterization is the qualitative one, based on visual inspection of images. Moving to quantitative analysis requires extraction of numerical indices of myocardium perfusion by analysis of time/intensity curves related to the area of interest. The main problem in quantitative image sequence analysis is the heart movement, mainly due to patient respiration. We propose an automatic procedure based on image registration, segmentation of the myocardium, and extraction and analysis of time/intensity curves. The procedure requires a minimal user interaction, is robust with respect to the user input, and allows effective characterization of myocardial perfusion. The algorithm was tested on cardiac MR images acquired from voluntaries and in clinical routine.
Nanoparticles as contrast agents for MRI of atherosclerotic lesions
Juan Carlos Frías,Michael Joseph Lipinski,María Teresa Albelda,Borja Ibá?ez
Clinical Medicine : Cardiology , 2008,
Abstract: Nanoparticle contrast agents for MRI may aid in identifying atherosclerotic lesions that give rise to ischemic events by means of penetration and retention in the plaque. These imaging agents may provide valuable information regarding plaque characteristics which can help determine the risk of plaque rupture. By increasing molecular flexibility or adding a means of specifically targeting ligands via antibody or peptide, nanoparticles can enhance certain regions of the atherosclerotic plaque. The development of single contrast agents detectable with multiple imaging modalities may further improve our ability to detect and characterize atherosclerosis in clinical and preclinical applications. These exciting developments may help in the realization of MRI as a powerful tool in the prevention of cardiovascular morbidity and mortality.
Utility of MRI Diffusion Techniques in the Evaluation of Tumors of the Head and Neck  [PDF]
José Pablo Martínez Barbero,Inmaculada Rodríquez Jiménez,Teodoro Martin Noguerol,Antonio Luna Alcalá
Cancers , 2013, DOI: 10.3390/cancers5030875
Abstract: The use of diffusion-weighted imaging in the head and neck is an increasingly used technique that requires adaptation of the acquisition parameters. Parallel imaging and emerging techniques such as IVIM are playing a new role. The main indications for performing DWI are tissue characterization, nodal staging and therapy monitoring. Lower apparent diffusion coefficients have been reported in this region for malignant lesions such as SCC, lymphoma and metastatic lymph node, as opposed to higher ADC in benign lesions and lymph nodes. Follow-up and early response to treatment are reflected in an ADC increase in both primary tumor and nodal metastasis.
Predicting Neck Abscess with Contrast-Enhanced Computed Tomography  [PDF]
Melisa Lim Seer Yee,Noraini Abdul Rahim,Ning Ajleaa Ngah,Yang Faridah Abdul Aziz,Sethu Subha
Advances in Otolaryngology , 2014, DOI: 10.1155/2014/896831
Abstract: Neck abscesses are difficult to diagnose and treat. Currently, contrast-enhanced computed tomography (CECT) is the imaging modality of choice. The study aims to determine the predictive value of CECT findings in diagnosing neck abscess, causes of neck abscess and the most common neck space involved in the local population. 84 consecutive patients clinically suspected to have neck abscess who underwent CECT and surgical confirmation of pus were included. Demographic and clinical data were recorded. 75 patients were diagnosed as having neck abscess on CECT; out of those 71 patients were found to have pus. Overall CECT findings were found to have a high sensitivity (98.6%) and positive predictive value (PPV) (94.7%) but lower specificity (67.2%) in diagnosing neck abscess. The CECT diagnostic criterion with the highest PPV is the presence of rim irregularity (96%). The most common deep neck space involved is the submandibular compartment, which correlates with the finding that odontogenic cause was the most common identifiable cause of abscess in the study population. Thus, in a patient clinically suspected of having neck abscess, CECT findings of a hypodense mass with rim irregularity are helpful in confirming the diagnosis and guiding clinical management. 1. Introduction Neck abscesses are still commonly encountered in the era of widespread antibiotic usage. Neck abscesses are usually sequelae of upper respiratory tract infection, odontogenic infection, or even direct trauma [1–5]. These abscesses may spread into adjacent compartments of the neck or into the mediastinum via the retropharyngeal, parapharyngeal, carotid, or prevertebral spaces [1, 2]. The potentially life-threatening complications associated with neck abscess include respiratory embarrassment, mediastinitis, internal jugular vein thrombosis, pseudoaneurysm, fulminant sepsis, and even death. Therefore, neck abscess poses significant morbidity and mortality risks such that any patient suspected to have it should be assessed and treated immediately [1, 3, 6, 7]. However, it is recognized that neck abscesses are difficult to diagnose and treat. Currently, contrast-enhanced computed tomography (CECT) of the neck is the imaging modality of choice in determining the presence of neck abscess and the neck spaces involved. In clinical routine, the examination of the neck should be extended to include the evaluation of the mediastinum in order to exclude the presence of a descending necrotizing mediastinitis as one of the complications aforementioned. The classical radiological description of an
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