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At least 163 records · Page 9Linked to original sources
PubMed1993

MRI pallidal hyperintensity and brain atrophy in cirrhotic patients: two different MRI patterns of clinical deterioration?

In cirrhotic patients, even in a stable nonencephalopathic state, MRI may show cerebral atrophy and increased signal in globus pallidus on T1-weighted sequences. We investigated the relationship between cerebral atrophy and increased pallidal signal and the clinical status of 30 cirrhotic patients. We found a weak association between the two MRI findings. There were different patterns of clinical variables related to the imaging findings. Performance on motor tasks involving speed correlated with the pallidal signal and plasma ammonia levels but not with atrophy. Test results for memory and frontal-premotor function were associated with brain atrophy but not with the pallidal signal or with ammonia.

Aged↗
PubMed2000

Cladribine and progressive MS: clinical and MRI outcomes of a multicenter controlled trial. Cladribine MRI Study Group.

OBJECTIVE: To evaluate the safety and efficacy of two doses of cladribine in patients with progressive MS. BACKGROUND: Treatment of progressive MS patients with cladribine in a previous single-center, placebo-controlled clinical trial was associated with disease stabilization. METHODS: In the current study, 159 patients with a median baseline Kurtzke's Expanded Disability Status Scale (EDSS) score of 6.0 were randomly assigned to receive placebo or cladribine 0.07 mg/kg/day for 5 consecutive days every 4 weeks for either two or six cycles (total dose, 0.7 mg/kg or 2.1 mg/kg, respectively), followed by placebo, for a total of eight cycles. Thirty percent had primary progressive MS (PPMS) and 70% had secondary progressive MS (SPMS). EDSS and Scripps Neurologic Rating Scale (SNRS) scores were assessed bi-monthly and MRI was performed every 6 months. The primary outcome measure was disability (mean change in EDSS). RESULTS: Mean changes in disability did not differ among the groups at the end of the 12-month double-blind phase. Both cladribine treatments were superior to placebo for the proportion of patients having gadolinium-enhanced T1 lesions and for the mean volume and number of such lesions (p < or = 0.003). Differences were statistically significant at the 6-month evaluation time, with < or =90% reduction in volume and number of enhanced T1 lesions, which was maintained through final evaluation. This effect segregated largely with the SPMS group. The T2 burden of disease showed a modest improvement in cladribine-treated patients and worsened in placebo-treated patients. Most adverse events were mild or moderate in severity and not treatment limiting. CONCLUSION: No significant treatment effects were found for cladribine in terms of changes in EDSS or SNRS scores. Both doses of cladribine produced and sustained significant reductions in the presence, number, and volume of gadolinium-enhanced T1 brain lesions on MRI, and cladribine 2.1 mg/kg reduced the accumulation of T2 lesion load. Cladribine at doses up to 2.1 mg/kg was generally safe and well tolerated.

Adult↗
PubMed1995

Estimation of spinal bone density using conventional MRI. Comparison between MRI and DXA in 32 subjects.

We evaluated the usefulness of MRI T1 and T2 relaxation times in assessing bone mineral status. T1 and T2 relaxation times of L3 were measured in 16 pairs of identical twins (24 men, 8 women), aged 25-69 years. Bone mineral density (BMD), bone mineral content (BMC) and apparent volumetric bone mineral density (BMDvol) of L3 were measured from the same subjects using dual x-ray absorptiometry (DXA). T2 relaxation time correlated inversely with BMD and BMC (r -0.40 and r -0.47, respectively), whereas a significant positive correlation between T1 relaxation time and BMDvol was found (r 0.36). The measurement of T1 may give some information on bone mineral status in clinical MRI measurements when DXA is not available. It is possible that T1 and T2 reflect not only bone density, but also other factors related to bone structure.

Absorptiometry, Photon↗
PubMed2004

Comparison of MRI graded cartilage and MRI based volume measurement in knee osteoarthritis.

OBJECTIVES: The aim of this study was to investigate the relationship between the femoral, tibial and patellar cartilage volume and MRI grading of the articular cartilage in patients with knee OA. METHODS: Articular cartilage volumes of 65 postmenopausal women were determined by processing images acquired in the sagittal plane using a fast spin echo proton density-weighted sequence. The articular cartilages were divided into 5 compartments including lateral and medial tibial, lateral and medial femoral and patellar compartments. The articular cartilages were graded using a modified Outerbridge classification. Grade 0 indicated intact cartilage, grade 1 chondral softening with normal contour, grade 2 superficial fraying, grade 3 surface irregularity and thinning and grade 4 full thickness cartilage loss. The grades of articular cartilage were compared with cartilage volume measurements. RESULTS: In medial femoral cartilage, grade 1 had more volume compared to grade 0 cartilage (p: 0.017). In medial tibial cartilage, grade 1 had more volume compared to grade 0 and grade 2 cartilage (p: 0.045 and p: 0.027, respectively). In patellar cartilage, grade 1 cartilage had significantly more volume than grade 0 cartilage (p: 0.007). In lateral tibial and femoral cartilages, no significant difference was observed between grade 0 and grade 1 cartilage. CONCLUSIONS: Cartilage volume correlates well with MR grading of articular cartilage. The higher the grade of the cartilage the less the volume, with the exception of grade 1 lesions. Grade 1, reflects oedema in the cartilage and has a conflicting effect on volume measurement. The combination of MRI based volume measurement and grading of articular cartilage may provide an accurate method for the non-invasive evaluation and follow-up of articular cartilage.

Cartilage, Articular↗
PubMed1988

[Clinical application of MRI for urological malignancy. 3: A new trial of MRI for bladder cancer and prostatic cancer; surface coil and GD-DTPA].

We performed MRI in several recent cases of bladder cancer and prostatic cancer using a general coil or a 5-inch general purpose surface coil with or without Gd-DTPA. The surface coil improves the spacial resolution, density resolution and signal to noise ratio but reduces the field and the signal detection drops off as the depth from the surface increases. Moreover, additional time is required for patient positioning. In Gd-DTPA enhanced images of bladder cancer, the muscle layer became more distinct, and the images of tumor and bladder mucosa were enhanced, suggesting that facilitates evaluation of the extent of bladder wall invasion of the tumor. In Gd-DTPA enhanced images of prostatic cancer, the area conside to correspond to the tumor was enhanced. MRI using a surface coil and Gd-DTPA is considered to provide detailed information of bladder and prostatic cancer.

Contrast Media↗
PubMed1995

[Non-granulomatous prostatitis: MRI image with endorectal surface coil ("Endo-MRI")].

Inflammatory conditions of the prostate are often difficult to distinguish from early stages of prostate cancer with imaging techniques. The use of an endorectal surface coil in MRI of the prostate gland has been reported to provide superior resolution and better imaging of details than MRI with a body coil in the diagnosis of early prostate cancer. We report a 34-year-old patient with nonspecific non-granulomatous prostatitis in whom T2-weighted endorectal surface coil magnetic resonance imaging (ESCMRI) showed a region of markedly decreased signal intensity in the periphery of the gland. The low signal intensity of the lesion, its sharp demarcation from the normal part of the peripheral zone of the prostate and the marked bulge of the surface contour without capsular breach of the organ were interpreted as evidence of a bioptically proven benign inflammatory condition.

Adult↗
PubMedDate not supplied

MRI of pseudocoarctation of the aorta: morphological and cine-MRI findings.

We report a case of pseudocoarctation of the thoracic aorta diagnosed by magnetic resonance imaging. Morphological spin-echo findings and cine-MRI performed by gradient-echo multiphase images are reported. No other more invasive examinations were needed to establish the diagnosis of pseudocoarctation and to differentiate from other aortic abnormalities.

Aorta, Thoracic↗
PubMed2002

Atypical X-linked adrenoleukodystrophy: new MRI observations with FLAIR, magnetization transfer contrast, diffusion MRI, and proton spectroscopy.

An 11-year-old boy with an atypical form of X-linked adrenoleukodystrophy is reported predominantly involving the frontal lobes, and later spreading to temporal lobes. Magnetization transfer contrast T1-weighted, and FLAIR images without intravenous paramagnetic contrast medium, clearly identified the leading edge of a central necrotic zone, as well as a splenial lesion. Zonal differences were identified on ADC maps of an echo-planar diffusion MRI sequence that the ADC value of central zone (2.06 x 10(-3) mm(2)/sec) was higher than that of the peripheral zone (1.67 x 10(-3) mm(2)/sec). On proton spectroscopy, besides changes in the peaks of NAA, choline, and myoinositol, prominent peaks between 0.9 and 1.4 ppm were shown belonging to macromolecules, probably to very long chain fatty acids, a diagnostic feature of adrenoleukodystrophy. In addition, a distinct and prominent glycine peak was observed at 3.50 ppm, reflecting excitotoxic brain damage.

Adrenoleukodystrophy↗
PubMed1996

Magnetic resonance imaging (MRI) detection of the murine brain response to light: temporal differentiation and negative functional MRI changes.

Using a 9.4 T MRI instrument, we have obtained images of the mouse brain response to photic stimulation during a period between deep anesthesia and the early stages of arousal. The large image enhancements we observe (often >30%) are consistent with literature results extrapolated to 9.4 T. However, there are also two unusual aspects to our findings. (i) The visual area of the brain responds only to changes in stimulus intensity, suggesting that we directly detect operations of the M visual system pathway. Such a channel has been observed in mice by invasive electrophysiology, and described in detail for primates. (ii) Along with the typical positive response in the area of the occipital portion of the brain containing the visual cortex, another area displays decreased signal intensity upon stimulation.

Animals↗
PubMedDate not supplied

The utility of contrast-enhanced MRI in diagnosis of muscle injuries occult to conventional MRI.

PURPOSE: Our goal was to define the utility of contrast-enhanced MRI in the diagnosis of occult muscle injuries on T2 and STIR sequences. METHOD: We retrospectively reviewed the pre- and postcontrast MR studies of four professional athletes with a clinical diagnosis of suspected muscle injuries. RESULTS: The four cases demonstrated muscle strain injuries not visualized on the conventional T2 and STIR sequences but visualized on the postcontrast MR studies as areas of localized enhancement. CONCLUSION: We recommend the intravenous administration of gadolinium in the setting of clinically suspected muscle injuries not visualized on T2 and STIR sequences.

Adult↗
PubMed2006

Finite volume analysis of temperature effects induced by active MRI implants: 2. Defects on active MRI implants causing hot spots.

BACKGROUND: Active magnetic resonance imaging implants, for example stents, stent grafts or vena cava filters, are constructed as wireless inductively coupled transmit and receive coils. They are built as a resonator tuned to the Larmor frequency of a magnetic resonance system. The resonator can be added to or incorporated within the implant. This technology can counteract the shielding caused by eddy currents inside the metallic implant structure. This may allow getting diagnostic information of the implant lumen (in stent stenosis or thrombosis for example). The electro magnetic rf-pulses during magnetic resonance imaging induce a current in the circuit path of the resonator. A by material fatigue provoked partial rupture of the circuit path or a broken wire with touching surfaces can set up a relatively high resistance on a very short distance, which may behave as a point-like power source, a hot spot, inside the body part the resonator is implanted to. This local power loss inside a small volume can reach (1/4) of the total power loss of the intact resonating circuit, which itself is proportional to the product of the resonator volume and the quality factor and depends as well from the orientation of the resonator with respect to the main magnetic field and the imaging sequence the resonator is exposed to. METHODS: First an analytical solution of a hot spot for thermal equilibrium is described. This analytical solution with a definite hot spot power loss represents the worst case scenario for thermal equilibrium inside a homogeneous medium without cooling effects. Starting with this worst case assumptions additional conditions are considered in a numerical simulation, which are more realistic and may make the results less critical. The analytical solution as well as the numerical simulations use the experimental experience of the maximum hot spot power loss of implanted resonators with a definite volume during magnetic resonance imaging investigations. The finite volume analysis calculates the time developing temperature maps for the model of a broken linear metallic wire embedded in tissue. Half of the total hot spot power loss is assumed to diffuse into both wire parts at the location of a defect. The energy is distributed from there by heat conduction. Additionally the effect of blood perfusion and blood flow is respected in some simulations because the simultaneous appearance of all worst case conditions, especially the absence of blood perfusion and blood flow near the hot spot, is very unlikely for vessel implants. RESULTS: The analytical solution as worst case scenario as well as the finite volume analysis for near worst case situations show not negligible volumes with critical temperature increases for part of the modeled hot spot situations. MR investigations with a high rf-pulse density lasting below a minute can establish volumes of several cubic millimeters with temperature increases high enough to start cell destruction. Longer exposure times can involve volumes larger than 100 mm3. Even temperature increases in the range of thermal ablation are reached for substantial volumes. MR sequence exposure time and hot spot power loss are the primary factors influencing the volume with critical temperature increases. Wire radius, wire material as well as the physiological parameters blood perfusion and blood flow inside larger vessels reduce the volume with critical temperature increases, but do not exclude a volume with critical tissue heating for resonators with a large product of resonator volume and quality factor. CONCLUSION: The worst case scenario assumes thermal equilibrium for a hot spot embedded in homogeneous tissue without any cooling due to blood perfusion or flow. The finite volume analysis can calculate the results for near and not close to worst case conditions. For both cases a substantial volume can reach a critical temperature increase in a short time. The analytical solution, as absolute worst case, points out that resonators with a small product of inductance volume and quality factor (Q V(ind) < 2 cm3) are definitely save. Stents for coronary vessels or resonators used as tracking devices for interventional procedures therefore have no risk of high temperature increases. The finite volume analysis shows for sure that also conditions not close to the worst case reach physiologically critical temperature increases for implants with a large product of inductance volume and quality factor (Q V(ind) > 10 cm3). Such resonators exclude patients from exactly the MRI investigation these devices are made for.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging (MRI) of primary liver cancer--MRI-pathologic correlation.

In seven primary liver cancers (HCC 5, CCC 1, mixed 1), MR images (0.35 Tesla super-conducting) were compared with macroscopic appearances, and relaxation times (T1 and T2) with microscopic characteristics. MRI was able to reveal the gross appearance of five nodular lesions, but did not reveal one diffuse HCC and one nodular HCC with marked extracapsular extension. T2-weighted SE images could not demonstrate fibrous capsules around the tumor in four nodular HCCs. The T1 and T2 values of the tumors were longer than those of the surrounding liver parenchyma, and the T1 elongation corresponded roughly to the degree of necrosis and fibrosis within the tumors.

Adult↗
PubMed1996

Ultrafast perfusion-weighted MRI of functional brain activation in rats during forepaw stimulation: comparison with T2 -weighted MRI.

A fast version of the arterial spin tagging technique for the detection of cerebral perfusion is presented. Based on adiabatic spin inversion in combination with snapshot FLASH imaging, our technique allows the recording of perfusion changes with a temporal resolution of about 3 s. Differences of cerebral perfusion dependent on the choice of anesthesia were observed in rat brain. Furthermore, with this arterial spin tagging method we demonstrated perfusion increases in the somatosensory cortex of anaesthetized rats during forepaw stimulation. Comparison of the activated areas in the T2 -weighted BOLD images and the perfusion-weighted images showed good spatial correspondence, but the sensitivity to the functional activation was more than ten times higher in the perfusion technique.

Anesthesia↗
PubMed2004

Towards targeted MRI: new MRI contrast agents for sialic acid detection.

The detection of sialic acid in living systems is of importance for the diagnosis of several types of malignancy. We have designed and synthesized two new lanthanide ion ligands (L1 and L2) that are capable of molecular recognition of sialic acid residues. The basic structure of these ligands consists of a DTPA-bisamide (DTPA, diethylenetriamine pentaacetic acid) whose amide moieties each bear both a boronic function for interaction with the diol groups in the side chain of sialic acid, and a functional group that is positively charged at physiologic pH values and is designed to interact with the carboxylate anion of sialic acid. The relaxometric properties of the Gd3+ complexes of these two ligands were evaluated. The relaxivity of the GdL1 complex has a significant second-sphere contribution at pH values above the pKa of its phenylboronic acid moiety. The interaction of the Gd3+ complexes of L1 and L2 with each of several saccharides was investigated by means of a competitive fluorescent assay. The results show that both complexes recognize sialic acid with good selectivity in the presence of other sugars. The adduct formed by GdL2 with sialic acid has the higher conditional formation constant (50.43+/-4.61 M(-1) at pH 7.4). The ability of such complexes to recognize sialic acid was confirmed by the results of a study on the interaction of corresponding radiolabeled complexes (153SmL1 and 153SmL2) with C6 glioma rat cells. 153SmL2 in particular is retained on the cell surface in significant amounts.

Boronic Acids↗
PubMed2004

Development of brain infarct volume as assessed by magnetic resonance imaging (MRI): follow-up of diffusion-weighted MRI lesions.

PURPOSE: To investigate the development of ischemic brain lesions, as present in the acute stroke phase, by diffusion-weighted magnetic resonance imaging (DWI), and in the subacute and chronic phases until up to four months after stroke, in fluid-attenuated inversion recovery (FLAIR)- and T2-weighted (T2W) magnetic resonance (MR) images. MATERIALS AND METHODS: Twelve consecutive patients with their first middle cerebral artery (MCA) infarction were included. Lesion volumes were assessed on T2W images recorded with a turbo spin echo (TSE) and on images recorded with the FLAIR sequence on average on day 8 and after about four months. They were compared with acute lesion volumes in perfusion and DWI images taken within 24 hours of stroke onset. RESULTS: On day 8, lesion volumes in images obtained with FLAIR exceeded the acute infarct volumes in DWI. The chronic lesion volumes were almost identical in T2W and FLAIR images but significantly reduced compared with the acute DWI lesions. The lesion volumes assessed on DWI images correlated highly with the lesions in the images obtained with TSE or FLAIR, as did the lesions in the images obtained with FLAIR and TSE. The secondary lesion shrinkage was accompanied by ventricular enlargement and perilesional sulcal widening, as most clearly visible in the images obtained with FLAIR. CONCLUSION: Our results show that the acute DWI lesions are highly predictive for the infarct lesion in the chronic stage after stroke despite a dynamic lesion evolution most evident in MR images obtained with FLAIR.

Acute Disease↗