Altered cerebrovascular reactivity velocity in mild cognitive impairment and Alzheimer's disease.

Interindividual variation in neurovascular reserve and its relationship with cognitive performance is not well understood in imaging in neurodegeneration. We assessed the neurovascular reserve in amnestic mild cognitive impairment (aMCI) and Alzheimer's dementia (AD). Twenty-eight healthy controls (HC), 15 aMCI, and 20 AD patients underwent blood oxygen level-dependent imaging for 9 minutes, breathing alternatively air and 7% carbon dioxide mixture. The data were parcellated into 88 anatomic regions, and carbon dioxide regressors accounting for different washin and washout velocities were fitted to regional average blood oxygen level-dependent signals. Velocity of cerebrovascular reactivity (CVR) was analyzed and correlated with cognitive scores. aMCI and AD patients had significantly slower response than HC (mean time to reach 90% of peak: HC 33 seconds, aMCI and AD 59 seconds). CVR velocity correlated with Mini Mental State Examination in 35 of 88 brain regions (p = 0.019, corrected for multiple comparisons), including 10 regions of the default-mode network, an effect modulated by age. This easily applicable protocol yielded a practical assessment of CVR in cognitive decline.

Globe restriction in a severely myopic patient visualized through oculodynamic magnetic resonance imaging (od-MRI).

Different mechanisms have been hypothesized as contributing to abduction deficit in high myopia: the size of the eye within the orbit, tightness of the medial rectus muscles, decompensation of longstanding esotropia, and inferior displacement of the lateral rectus muscle. Using oculodynamic magnetic resonance imaging, enhanced by computer-aided visualization, we demonstrate globe restriction by the medial orbital wall on abduction in a patient with high myopia.

Therapy-induced plasticity of cognitive functions in MS patients: insights from fMRI.

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system whose pathological mechanisms are still not completely understood. Physical as well as cognitive deterioration are consequences within the disease process that have an extensive impact on the patient's quality of life. Therefore, understanding the functional background of spontaneous as well as induced remission is of high relevance. Studies on visualization of therapeutic effects of pharmacological or cognitive treatment by functional magnetic resonance imaging (fMRI) are still rare. From fMRI studies on focal brain lesions hypotheses on mechanisms of brain reorganization can be derived. This contribution will first give an overview of the existing studies using fMRI in MS, on cognitive decline, on cognitive treatment studies and its therapeutic effects on behavioural readouts in MS, and on therapy-induced brain plasticity and its possible visualization by fMRI. Results of a study on correlating the effects of cognitive training with changes in brain organization in patients with mild to severe cognitive impairment will be reported.

Optimizing brain MRI protocols in the follow-up of patients with multiple sclerosis T2-weighted MRI of the brain after the administration of gadopentetate dimeglumine.

The aim of our study was to determine whether T2-weighted (T2w) MRI of the brain could be performed immediately after the administration of gadopentetate dimeglumine (gadolinium DTPA) in patients with multiple sclerosis (MS) without a loss in image quality or diagnostic reliability. Sixteen patients with clinically diagnosed MS were included in the study. Twenty-four patients with various cerebral pathologies (14 patients with multiple lacunar lesions) were examined in order to exclude masking of T2 hyperintense lesions other than MS lesions. Images of 10 patients without pathological changes served as a control condition for the qualitative analysis. In these 50 patients, T1w and T2w MRI was performed before and after the administration of gadolinium DTPA. Signal intensities were measured within T2 hyperintense cerebral lesions, in T1-enhancing lesions and in normal appearing brain tissue on T2w turbo spin-echo (TSE) sequences. Both quantitative and qualitative analysis did not show significant differences between T2w pre- and postcontrast series. T2w MRI performed prior to and after the administration of gadolinium DTPA provides similar information in patients with MS. With a TR of 3.2 s, not a single lesion was obscured on T2w postcontrast series. Acquisition of T2w MR images immediately after the administration of gadolinium DTPA allows for shorter examination time and assures sufficient time for contrast enhancement in cerebral lesions with a disrupted blood-brain barrier.

PET imaging drug distribution after intratumoral injection: the case for (124)I-iododeoxyuridine in malignant gliomas.

UNLABELLED: Locoregional administration may yield higher tumor drug concentrations compared with intravenous injection and may reduce the risk of systemic adverse effect. Furthermore, in the case of brain tumors, it may circumvent limited drug delivery imposed by the blood-brain barrier. We used PET to study the retention and spatial distribution of iododeoxyuridine (IUdR), which has been used as a DNA-targeting radiosensitizing drug and which can be charged with therapeutic nuclides. METHODS: Locoregional (resection cavity, tumor) instillation of 5-19 MBq (124)I-IUdR was achieved in 7 postoperative patients with malignant gliomas through a reservoir implanted in the skull. Patients were scanned with PET during the first hour and at 2, 24, and 48 h after (124)I-IUdR instillation. (124)I-IUdR metabolism was measured in the reservoir fluid in the presence or absence of a degradation inhibitor (5'-butyryl-IUdR [butyryl-IUdR]). Region-of-interest analysis was applied to calculate intratumoral retention (K(local)) of (124)I-IUdR from the PET images after a 24-h washout phase using an autoradiographic method. RESULTS: At 24 h, radioactivity concentration in the reservoir was approximately 1% of the concentration 5 min after tracer instillation. The major metabolite of (124)I-IUdR in the reservoir was (124)I-iodouracil. (124)I-IUdR degradation could be partially inhibited by butyryl-IUdR. In the plasma, radioactivity peaked between 2 and 6 h. The area of tissue radioactivity increased with time up to 3-fold compared with the initial distribution. Tumor (124)I-IUdR retention (K(local)) ranged from 0.006 to 0.017 micro L/g/min, which is substantially lower compared with the IUdR-DNA incorporation reported recently after intravenous injection of (124)I-IUdR (K(i), 3.9 +/- 2.3 micro L/g/min, where K(i) is the DNA incorporation rate of (124)I-IUdR after intravenous tracer injection). CONCLUSION: Although a single injection of (124)I-IUdR resulted in radioactivity distribution over the tumor, retention at 24 h was substantially lower compared with intravenous injection of (124)I-IUdR. Slow diffusion after locoregional administration, in contrast to fast delivery via tumor capillaries after intravenous injection, may account for our findings, resulting in a low amount of drug incorporation into DNA before degradation and washout from tissue.