SE MRI Research Articles

Combined evaluation of conventional MRI, dynamic contrast-enhanced MRI and diffusion weighted imaging for response evaluation of patients with multiple myeloma

PurposeTo evaluate the value of the combined evaluation of SE MRI, dynamic contrast enhanced MRI (DCE-MRI) and diffusion weighted imaging (DWI) in multiple myeloma (MM) patients after treatment compared to the international myeloma working group (IMWG) response criteria. Materials and methodsThe retrospective study includes 27 newly diagnosed patients, providing 99 MRI-investigations. Patients were categorized according to the IMWG response criteria. Quantitative assessment was based on signal intensities (SI) of T1-weighted, fat-saturated T2-weighted and b1000 images, apparent diffusion coefficients (ADC) and parameters from time-intensity-curves (TIC) derived from L3. Qualitative visual analysis of conventional MRI-images, b1000-images and TICs, providing a “combined skeletal score”, was used to create MRI response criteria. ResultsThe combined skeletal score could significantly differentiate between subgroups based on IMWG response criteria (p=0.016). The gold standard plasmacytosis could significantly differentiate between subgroups based on MRI response criteria (p<0.001), as well as slope (p<0.001) and ADC (p=0.006). There is a good agreement between IMWG and MRI response criteria (Kendall’s coefficient=0.761). ConclusionResponse evaluation of MM-patients based on the combination of anatomical information from conventional MRI with functional information from DCE-MRI and DWI, is useful for monitoring therapy.

Use of contrast-enhanced MRI of the heart in detection of risk of supraventricular tachyarrhythmias in patients with recent myocardial infarction

Methods Twenty persons (all males but two, as old as 57 ± 7 years) with recent (< 4 months) myocardial infarction of left ventricle were included. Paramagnetic contrast-enhanced T1weighted SE (TR=450-600 ms, TE=15-20 ms) MRI of the heart has been employed for visual detection of risk as well of anatomic locations of atrial arrhythmias in twenty patients with previous myocardial infarction. Contrast enhancement was carried out using intravenous injection of widely available extracellular paramagnetics in a dose as high as 2 ml of 0,5 M solution per 10 kg of body mass (BM). Two groups were separated in accordance with the electrophysiologic and clinical data. The Group 1 included eight persons without supraventricular tachycardias (SVT) in the course of follow-up for four months, and the Group 2 comprised twelve patients with frequent SVT paroxysms, all were later suggested for maze procedure. Also eight persons were recruited to the control group, all without cardiac pathology.

High-resolution(18)F-fluorodeoxyglucose positron emission tomography and magnetic resonance imaging for pituitary adenoma detection in Cushing disease.

OBJECT High-resolution PET (hrPET) performed using a high-resolution research tomograph is reported as having a resolution of 2 mm and could be used to detect corticotroph adenomas through uptake of(18)F-fluorodeoxyglucose ((18)F-FDG). To determine the sensitivity of this imaging modality, the authors compared(18)F-FDG hrPET and MRI detection of pituitary adenomas in Cushing disease (CD). METHODS Consecutive patients with CD who underwent preoperative(18)F-FDG hrPET and MRI (spin echo [SE] and spoiled gradient recalled [SPGR] sequences) were prospectively analyzed. Standardized uptake values (SUVs) were calculated from hrPET and were compared with MRI findings. Imaging findings were correlated to operative and histological findings. RESULTS Ten patients (7 females and 3 males) were included (mean age 30.8 ± 19.3 years; range 11-59 years). MRI revealed a pituitary adenoma in 4 patients (40% of patients) on SE and 7 patients (70%) on SPGR sequences.(18)F-FDG hrPET demonstrated increased(18)F-FDG uptake consistent with an adenoma in 4 patients (40%; adenoma size range 3-14 mm). Maximum SUV was significantly higher for(18)F-FDG hrPET-positive tumors (difference = 5.1, 95% CI 2.1-8.1; p = 0.004) than for(18)F-FDG hrPET-negative tumors.(18)F-FDG hrPET positivity was not associated with tumor volume (p = 0.2) or dural invasion (p = 0.5). Midnight and morning ACTH levels were associated with(18)F-FDG hrPET positivity (p = 0.01 and 0.04, respectively) and correlated with the maximum SUV (R = 0.9; p = 0.001) and average SUV (R = 0.8; p = 0.01). All(18)F-FDG hrPET-positive adenomas had a less than a 180% ACTH increase and(18)F-FDG hrPET-negative adenomas had a greater than 180% ACTH increase after CRH stimulation (p = 0.03). Three adenomas were detected on SPGR MRI sequences that were not detected by(18)F-FDG hrPET imaging. Two adenomas not detected on SE (but no adenomas not detected on SPGR) were detected on(18)F-FDG hrPET. CONCLUSIONS While(18)F-FDG hrPET imaging can detect small functioning corticotroph adenomas and is more sensitive than SE MRI, SPGR MRI is more sensitive than(18)F-FDG hrPET and SE MRI in the detection of CD-associated pituitary adenomas. Response to CRH stimulation can predict(18)F-FDG hrPET-positive adenomas in CD.

An integrative model for neuronal activity-induced signal changes for gradient and spin echo functional imaging

Gradient and spin echo (GRE and SE, respectively) weighted magnetic resonance images report on neuronal activity via changes in deoxygenated hemoglobin content and cerebral blood volume induced by alterations in neuronal activity. Hence, vasculature plays a critical role in these functional signals. However, how the different blood vessels (e.g. arteries, arterioles, capillaries, venules and veins) quantitatively contribute to the functional MRI (fMRI) signals at each field strength, and consequently, how spatially specific these MRI signals are remain a source of discussion. In this study, we utilize an integrative model of the fMRI signals up to 16.4 T, exploiting the increasing body of published information on relevant physiological parameters. Through simulations, extra- and intravascular functional signal contributions were determined as a function of field strength, echo time (TE) and MRI sequence used. The model predicted previously reported effects, such as feasibility of optimization of SE but not the GRE approach to yield larger micro-vascular compared to macro-vascular weighting. In addition, however, micro-vascular effects were found to peak with increasing magnetic fields even in the SE approach, and further increases in magnetic fields imparted no additional benefits besides beyond the inherent signal-to-noise (SNR) gains. Furthermore, for SE, using a TE larger than the tissue T 2 enhances micro-vasculature signal relatively, though compromising SNR for spatial specificity. In addition, the intravascular SE MRI signals do not fully disappear even at high field strength as arteriolar and capillary contributions persist. The model, and the physiological considerations presented here can also be applied in contrast agent experiments and to other models, such as calibrated BOLD approach and vessel size imaging.

In vivo 3D MRI of insect brain: cerebral development during metamorphosis of Manduca sexta

High-resolution 3D MRI of male pupae of Manduca sexta was performed at 2.35 T in order to evaluate its potential for an in vivo characterization of insect brain during metamorphosis. T1-weighted 3D FLASH (TR/TE = 20/7.8 ms, 25 degrees flip angle) and T2-weighted 3D fast SE MRI data sets (TR/TEeff = 3000/100 ms) were acquired at different developmental stages with an isotropic resolution of 100 microm. Both T1- and T2-weighted 3D MRI allowed for the identification of cerebral structures such as the antennal nerve, antennal and optical lobe, and central brain. Pronounced developmental alterations of the morphology were observed during metamorphosis. The results demonstrate the feasibility of 3D MRI at nanoliter resolution to identify major brain systems of M. sexta and respective changes during pupal development from caterpillar to sphinx moth. Together with the use of suitable contrast agents, this approach may provide new ways for studying the axonal connectivity and neural function of the developing insect brain.

Splenic imaging with ultrasmall superparamagnetic iron oxide ferumoxtran-10 (AMI-7227): preliminary observations.

Ferumoxtran-10 (ultrasmall superparamagnetic iron oxide; Combidex, AMI-7227) is a long-circulating MR contrast agent with reticuloendothelial uptake known to enhance tissue T1 and T2 relaxation rates. The purpose of this study was to assess the effect of ferumoxtran-10-enhanced MRI in evaluating focal splenic lesions. Eighteen patients underwent MR evaluation of the spleen. Two of these patients with exophytic normal splenic tissue (splenules) and 13 of these patients with 24 focal splenic lesions (7 cysts, 2 hemangiomas, 7 metastases, 1 infarct, 7 lymphoma) were assessed by T1-weighted gradient echo and T2-weighted fast SE MRI following intravenous administration of ferumoxtran-10 (1.1 mg of Fe/kg). Qualitative analysis involving improved lesion detection and/or characterization, additional information from postcontrast images affecting staging, and patient management was performed. Quantitative measurements of lesion-to-spleen contrast-to-noise ratio were also performed. Additional information was provided by ferumoxtran-10-enhanced images in 15 of 18 patients. In 8 of 15 (53%) patients, improved lesion detection (i.e., number of lesions) was obtained on contrast-enhanced images. Improved lesion visualization (i.e., conspicuity) was noted in 11 of 15 (73%) of patients. In 10 of 15 (67%) patients, postcontrast imaging provided additional information leading to lesion characterization. Staging of disease and patient management were affected in 5 of 15 (33%) and 6 of 15 (40%) patients, respectively. Ferumoxtran-10 is a promising contrast agent for the evaluation of focal splenic lesions.

Effect of slice acquisition direction on image quality in thoracic MRI.

We tested the basic observation that imaging the heart and pericardium in systole improves image quality compared with that in diastole. Twenty consecutive patients and two volunteers underwent sequential ECG-gated short TE transaxial prospective multislice SE MRI with both caudocranially and craniocaudally directed slice prescriptions, keeping other imaging parameters constant. Images of the heart and pericardium were obtained in systole and diastole and examined by three independent reviewers for image quality. In the lower mediastinum, cardiac structures and the pericardium were better seen in 49 of 57 individual evaluations when imaged in systole, 15 of which were judged markedly better. Vascular structures and the pericardium in the upper mediastinum were imaged equally well with both prescriptions. The findings suggest that in systole, the more mobile heart can maintain a more consistent shape during the acquisition of successive phase-encoding steps and preserve luminal flow void, factors critical to optimizing image quality in the transaxial plane.

Entry tears of thoracic aortic dissections: MR appearance on gated SE imaging.

The purpose of this study was to assess the ability of gated SE MR to demonstrate entry tears of thoracic aortic dissections and to elucidate their MR appearance. Gated SE MR images of nine consecutive patients with nonthrombosed aortic dissection on aortography were retrospectively analyzed. Magnetic resonance consistently depicted an intimal flap and a double lumen in all nine patients. A focal intimal flap discontinuity suggesting an intimal tear was shown in eight patients. This intimal flap discontinuity was confirmed to be the entry tear by operation in five patients and by aortography in three. In five of eight patients with a focal intimal flap discontinuity, rapid influx of blood across an intimal defect produced a localized signal void area within the false lumen, which was surrounded by slow flow signal showing even-echo rephasing. This MR sign of a localized jet of flow void within the false lumen was very useful in determining the significance of a focal intimal flap discontinuity. Familiarity with these MR appearances of entry tears may enable their preoperative localization in a large proportion of aortic dissections on routine gated SE MRI.

Gd-DTPA enhanced MR of the lumbar spinal canal in patients with claudication.

The purpose of this work was to study the findings on intravenous gadolinium-enhanced MRI of the lumbar spinal canal in patients with clinically suspected neurogenic claudication. A prospective gadolinium-enhanced MR evaluation of seven adult patients presenting with clinical claudication thought to be related to the lumbosacral spine was undertaken. Of seven consecutive enhanced conventional SE MRI examinations of the lumbosacral spine in patients presenting with lower extremity claudication, five patients (71.4%) revealed abnormal intrathecal enhancement on MR at and extending craniad from the level(s) of severe spinal stenosis. Each of the seven patients (100%) showed relatively severe central stenosis of the lumbar spinal canal. The enhancement pattern was linear, curvilinear, punctate, and/or diffuse in configuration. Two of the five patients with intrathecal enhancement also showed similar abnormal intrathecal enhancement extending caudal to the severely stenotic levels. The clinically significant intrathecal enhancement on intravenous gadolinium-enhanced MRI identified above the level of a severely stenotic lumbar spinal canal hypothetically might represent enhancement of dilated, obstructed venous structures serving the cauda equina. More likely, however, the major factor in such enhancement at, above, and/or below the stenosis signals blood-nerve barrier breakdown associated with mechanical injury, inflammatory response, and wallerian degeneration/regeneration of axons within chronically compressed nerve roots.