Breathhold‐regulated blood oxygenation level‐dependent (BOLD) MRI of human brain at 3 tesla

Purpose:

To investigate the cerebrovascular response to repeated breathhold challenges using blood oxygenation level‐dependent (BOLD) MRI at 3T and compare the results with previous data at 1.5T.

Materials and Methods:

Six normal volunteers and six patients with brain tumors were recruited for this 3T study. For the normal group, BOLD MRI during repeated breathholds of different durations (five to 30 seconds) were acquired. Maximum signal change, full‐width at half‐maximum (FWHM) and onset time (defined as the time to the first half‐maximum) were determined by curve fitting. The fractional activation volume was also calculated. Patients performed a 10‐ or 15‐second breathhold paradigm according to individual capability.

Results:

Significant BOLD signal increases in the gray matter for a breathhold period as short as 5 seconds at 3T, instead of 10 seconds at 1.5T. The fractional activation volume vs. breathhold duration reached a plateau of 49.54 ± 7.26% at 15 seconds at 3T, which was higher and shorter than that at 1.5T. The maximum signal changes were significantly larger (a 69% increase) at 3T than at 1.5T. In the patient group, there were BOLD signal increases in gray matter but not in tumor bulk or perifocal edema, which agreed with the results previously found at 1.5T.

Conclusion:

BOLD MRI at 3T is more sensitive for detecting breathhold‐regulated signal changes than at 1.5T, which allows a shorter and more feasible breathhold paradigm for clinical applications in patients with brain tumors. J. Magn. Reson. Imaging 2010;31:78–84. © 2009 Wiley‐Liss, Inc.     

Functional brain mapping at 9.4T using a new MRI‐compatible electrode chronically implanted in rats

There is a need for acute and chronic stimulation of the brain within the MRI for studies of epilepsy, as well as deep brain stimulation for movement and behavioral disorders. This work describes the production and characteristics of carbon fiber–based electrodes for acute and chronic stimulation in the brain. Increasing MRI field strengths are making it increasingly difficult to introduce foreign objects without a susceptibility artifact. We describe the production of, and the characteristics of carbon fiber–based electrodes. These are biocompatible and can be implanted for chronic studies. We show the use of these electrodes at 9.4T for studying functional activation. Data are presented showing regional connectivity. Activation not only occurs near the electrode, but at sites distant and often contralateral to the electrode. In addition, there were sites showing strong negative activation to stimulation both with direct stimulation and during a kindling‐associated seizure. Magn Reson Med 61:222–228, 2009. © 2008 Wiley‐Liss, Inc.     

A one‐season prospective study of injuries and illness in elite junior tennis

The objective of this study was to estimate the incidence and prevalence of injury and illness among elite junior tennis players. A cohort of 73 players (11–14 years) in the 2012–2013 Dutch national high‐performance program was followed for 32 weeks; all participants completed the study. The OSTRC Questionnaire on Health Problems was used to record self‐reported injuries and illnesses and to record training and match exposure. Main outcome measures were average prevalence of overuse injury and illness and incidence density of acute injury. On average, players practiced 9.1 h/week (SD 0.6; range 2.3–12.0) and had 2.2 h of match play (SD 0.6; range 2.3–12.0). During the course of the study, 67 players reported a total of 187 health problems. The average weekly prevalence of all health problems was 21.3% (95% CI: 19.2–22.9), of which 12.1% (95% CI: 10.9–13.3) constituted overuse injuries and 5.8% (95% CI: 4.6–6.9) illnesses. The incidence of acute injuries was 1.2/1000 h of tennis play (95% CI: 0.7–1.7). The high occurrence of overuse injuries among elite junior tennis players suggests that an early focus on preventative measures is warranted, with a particular focus on the monitoring and management of workload.     

Experimental protocol for activation‐induced manganese‐enhanced MRI (AIM‐MRI) based on quantitative determination of Mn content in rat brain by fast T1 mapping

In activation‐induced manganese‐enhanced MRI (AIM‐MRI) experiments, differential accumulation of Mn in activated and silent brain areas is generally assessed using T₁‐weighted images and quantified by the enhancement of signal intensity (SI), calculated with reference to SI before Mn administration or to SI of brain regions unaffected by the specific stimulus. However, SI enhancement can be unreliable when animals are removed from and reinserted into the magnet. We have developed an experimental protocol based on repeated intraperitoneal (i.p.) injections of Mn, quantitative determination of T₁, and coregistration of images to a rat brain atlas that allows absolute quantification of Mn concentration in selected brain areas. Results showed that interanimal variability of postcontrast T₁ values was very low (compared to the experimental error in T₁ determinations) allowing detection of differential regional Mn uptake in stimulated and unstimulated animals. In addition we have determined in vivo relaxivity of Mn in brain tissue and its frequency dependence. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

On the measurement of absolute cerebral blood volume (CBV) using vascular‐space‐occupancy (VASO) MRI

Recently, a vascular‐space‐occupancy (VASO) MRI technique was developed for quantitative assessment of cerebral blood volume (CBV). This method uses the T₁‐shortening effect of gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA) with imaging parameters chosen that null the precontrast blood magnetization but allow the postcontrast blood magnetization to recover to equilibrium. A key advantage of VASO CBV estimation is that it provides a straightforward procedure for converting MR signals to absolute physiologic values. However, as with other T₁‐based steady‐state approaches, several important factors need to be considered that influence the accuracy of CBV values obtained with VASO MRI. Here, the transverse relaxation (T₂/T) effect in VASO MRI was investigated using multiecho spin‐echo and gradient‐echo experiments, resulting in underestimation of CBV by 14.9% ± 1.1% and 16.0% ± 2.5% for spin echo (TE = 10 ms) and gradient echo (TE = 6 ms), respectively. In addition, the influence of contrast agent clearance was studied by acquiring multiple postcontrast VASO images at 2.2‐min intervals, which showed that the concentration of Gd‐DTPA in the first 14 min (single dose) was sufficient for the blood magnetization to fully recover to equilibrium. Finally, the effect of vascular Gd‐DTPA leakage was assessed for scalp tissue, and signal extrapolation as a function of postinjection time was demonstrated to be useful in minimizing the associated errors. Specific recommendations for VASO MRI acquisition and processing strategies are provided. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.     

Feasibility of T mapping for the evaluation of hip joint cartilage at 1.5T using a three‐dimensional (3D), gradient‐echo (GRE) sequence: A prospective study

This study defines the feasibility of utilizing three‐dimensional (3D) gradient‐echo (GRE) MRI at 1.5T for T mapping to assess hip joint cartilage degenerative changes using standard morphological MR grading while comparing it to delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC). MRI was obtained from 10 asymptomatic young adult volunteers and 33 patients with symptomatic femoroacetabular impingement (FAI). The protocol included T mapping without gadolinium‐enhancement utilizing a 3D‐GRE sequence with six echoes, and after gadolinium injection, routine hip sequences, and a dual‐flip‐angle 3D‐GRE sequence for dGEMRIC T₁ mapping. Cartilage was classified as normal, with mild changes, or with severe degenerative changes based on morphological MRI. T₁ and T findings were subsequently correlated. There were significant differences between volunteers and patients in normally‐rated cartilage only for T₁ values. Both T₁ and T values decreased significantly with the various grades of cartilage damage. There was a statistically significant correlation between standard MRI and T (T₁) (P < 0.05). High intraclass correlation was noted for both T₁ and T. Correlation factor was 0.860 to 0.954 (T‐T₁ intraobserver) and 0.826 to 0.867 (T‐T₁ interobserver). It is feasible to gather further information about cartilage status within the hip joint using GRE T mapping at 1.5T. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Dural sinus malformation (DSM) in fetuses. Diagnostic value of prenatal MRI and follow-up

Dural sinus malformations (DSM) are rare malformations mainly reported after birth. The objectives of this study are to describe their prenatal patterns and to focus on their possible favorable outcome. This multicenter retrospective study reported 13 cases of DSM prenatally diagnosed. The admission criterion was a dural mass posterior to the vermis. In 12 patients, MRI was performed after US. Follow-up in 10 born babies (mean: 8 months) and three neuropathological examinations were available. In all fetuses, DSM presented as a well-delimited round mass involving the torcular. The follow-up examinations (n = 10) revealed progressive thrombosis of the DSM marked by a heterogeneous pattern (US and MRI) with concentric rings. The volume of the mass decreased, with complete regression in seven patients (five before and two after birth). One child died at the age of 5 months in the context of major hydrocephalus and another developed atrophy of the frontal lobes. The eight other babies were doing well (5 days to 3 years) without any treatment (n = 6) or following treatment for hydrocephalus (n = 2). Prenatal DSM may have a typical MR pattern, and the prognosis might not be as bad as has previously been reported. In the absence of criterion to predict the hydrovenous cerebral imbalance, it is mandatory to check the parenchyma and the ventricles during the pregnancy.     

Dynamic contrast-enhanced (DCE) derived transfer coefficient (ktrans) is a surrogate marker of matrix metalloproteinase 9 (MMP-9) expression in brain tuberculomas

PURPOSE: To correlate dynamic contrast-enhanced (DCE) MRI derived perfusion indices with immunohistochemically obtained vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) in a cellular fraction of brain tuberculomas (BT). MATERIALS AND METHODS: Thirteen BT patients underwent DCE MRI. Perfusion indices (cerebral blood volume [CBV], transfer coefficient [ktrans] and leakage [ve]) maps were generated for the quantitative analysis. The CBV was corrected for the leaky blood-brain barrier (BBB). The relative CBV (rCBV), ktrans, and ve were calculated by placing 10 regions of interest (ROIs) showing the highest values in the lesion. The percentage area of VEGF and percentage area of MMP-9 and microvessel density (MVD) were quantified from 10 fields per lesion with maximal expression of the excised BT. Pearson correlation analysis between physiological indices and quantitative VEGF, MMP-9, and MVD was performed for each ROI. RESULTS: The average value of rCBV, ktrans, ve, VEGF, MMP-9, and MVD were 3.53+/-0.37, 2.04+/-0.40 min(-1), 0.71+/-0.09, 12.51+/-2.56, 18.09+/-2.06, 10.87+/-1.99, respectively. The ktrans (r=0.918, P<0.001) and ve (r=0.899, P<0.001) showed significant correlation with MMP-9, while rCBV correlated significantly with MVD (r=0.962, P<0.001) and VEGF (r=0.868, P<0.001). CONCLUSION: We conclude that the expression of MMP-9, a marker of BBB disruption and disease activity in BT correlates with DCE-derived ktrans and thus has the potential to be used as its surrogate marker.