Influence of bolus volume and dose of gadolinium chelate for first-pass myocardial perfusion MR imaging studies

First-pass MR myocardial perfusion measurements require a well-defined left ventricular (LV) blood pool input function. We used a peripheral intravenous (IV) injection of a gadolinium (Gd) chelate to obtain a well-characterized LV time-intensity curve. Using a strongly T1-weighted subsecond MR sequence, we performed cardiac MR imaging after administering an IV bolus injection of one of three different doses of the Gd chelate: a standard dose (0.1 mmol/kg, group I, n = 8); a low dose with two bolus volumes (0.01 mmol/kg, l/10e bolus volume, group n, n = 7, and 0.01 mmol/kg diluted in saline, same bolus volume as group I, group III, n = 3); and an intermediate dose (0.05 mmol/kg, group IV, n = 5). Unlike in group I (high dose), in groups n and m (low dose), the LV curve had a well-defined first peak, followed by a downslope and a recirculation peak. With the intermediate dose (group IV), a saturation effect still remained on the LV curve. The signal intensity (SI) enhancement of the myocardium was respectively 580 ± 77% at 0.1 mmol/kg, 362 ± 95% at 0.05 mmol/kg, and at 0.01 mmol/kg, it was 184 ± 33% in group II and 272 ± 8% in group m. In conclusion, with subsecond T1-weighted MR imaging and a low dose of Gd chelate (i.e., 0.01 mmol/kg). the LV input function is a well-defined first step for MR perfusion modeling.     

Mice lacking αβ T cells are resistant to the induction of experimental autoimmune encephalomyelitis

T cells of the γδ subset have been found to localise to demyelinated lesions in both multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) and have been implicated in the pathogenesis of both diseases. We have assessed mice carrying a targeted mutation of the T cell receptor-α locus which consequently lack T cell receptor (TCR) αβ cells but have an intact γδ⁺-T cell population for their susceptibility to EAE. No disease was found in any of the mutant mice, nor was any infiltration of the CNS detected. These data show that, at least in the absence of TCR-αβ cells, TCR-γδ cells are not able to elicit the pathology associated with EAE.     

2 cases of coronary embolism. Angiographic diagnosis and anatomopathological confirmation

The authors report two cases selected from a series of 61 cases of coronary embolism observed over an 18 year period at the Cardiovascular Hospital (Lyon) out of 4,860 autopsies of adult patients who died of cardiovascular causes. These two cases underwent coronary angiography, the results of which correlated with the autopsy findings. The authors review the causes and clinical manifestations of coronary embolism and compare their results with previously reported data, to establish the radiological features of coronary embolism. They notice the regular appearance of obstruction due to embolism and underline the importance of the associated negative signs (normality of the rest of the coronary circulation, absence of collateral vessels...) which makes the angiographic diagnosis one of elimination.     

Quantification of multicontrast vascular MR images with NLSnake,an active contour model: In vitro validation and in vivo evaluation

Vessel‐wall measurements from multicontrast MRI provide information on plaque structure and evolution. This requires the extraction of numerous contours. In this work a contour‐extraction method is proposed that uses an active contour model (NLSnake) adapted for a wide range of MR vascular images. This new method employs length normalization for the purpose of deformation computation and offers the advantages of simplified parameter tuning, fast convergence, and minimal user interaction. The model can be initialized far from the boundaries of the region to be segmented, even by only one pixel. The accuracy and reproducibility of NLSnake endoluminal contours were assessed on vascular phantom MR angiography (MRA) and high‐resolution in vitro MR images of rabbit aorta. An in vivo evaluation was performed on rabbit and clinical data for both internal and external vessel‐wall contours. In phantoms with 95% stenoses, NLSnake measured 94.3% ± 3.8%, and the accuracy was even better for milder stenoses. In the images of rabbit aorta, variability between NLSnake and experts was less than interobserver variability, while the maximum intravariability of NLSnake was equal to 1.25%. In conclusion, the NLSnake technique successfully quantified the vessel lumen in multicontrast MR images using constant parameters. Magn Reson Med 51:370–379, 2004. © 2004 Wiley‐Liss, Inc.     

Computer-assisted analysis of three-dimensional MR angiograms.

The software tools required for postprocessing of magnetic resonance (MR) angiograms include the following functions: data handling, image visualization, and vascular analysis. A custom postprocessing software called Magnetic Resonance Angiography Computer Assisted Analysis (MARACAS) has been developed. This software combines the most commonly used three-dimensional visualization techniques with image processing methods for analysis of vascular morphology on MR angiograms. The main contributions of MARACAS are (a) implementation of a fast method for stenosis quantification on three-dimensional MR angiograms, which is clinically applicable in a personal computer-based system; and (b) portability to the most widespread platforms. The quantification is performed in three steps: extraction of the vessel centerline, detection of vessel boundaries in planes locally orthogonal to the centerline, and calculation of stenosis parameters on the basis of the resulting contours. Qualitative results from application of the method to data from patients showed that the vessel centerline correctly tracked the vessel path and that contours were correctly estimated. Quantitative results obtained from images of phantoms showed that the computation of stenosis severity was accurate.     

What is the future of magnetic nanoparticles in the axillary management of breast cancer?

Magnetic nanoparticles (MNPs) possess unique properties, which make them highly attractive for medical applications. The use of MNPs in surgery has mainly been focused on their role in the identification of metastatic lymph node involvement. There have been developments within this field, including ongoing and newly conducted clinical trials. The current published evidence for the use of MNPs in assessing metastatic lymph node spread using sentinel lymph node biopsy and non-invasive imaging modalities is reviewed and future applications considered.