Showed Signal Intensity Changes Research Articles

Real-time monitoring of inertial cavitation effects of microbubbles by using MRI: In vitro experiments.

To investigate the feasibility of half-Fourier acquisition single-shot turbo spin-echo (HASTE) for real-time monitoring of signal changes because of water flow induced by inertial cavitation (IC) during microbubbles (MBs)-present focused ultrasound (FUS) exposure. Strong turbulence produced in MB solution at the onset of IC results in the difficulty to refocus signal echoes and thus the decrease in signal intensity (SI). Fundamental investigations were conducted using an agar phantom containing MB dilutions exposed to 1.85-MHz FUS. The effects of various experimental conditions including MB concentrations, imaging slice thicknesses, chamber diameters, acoustic pressures, duty cycles, and pulse repetition frequencies (PRFs) were discussed. Continuous 2.8 MPa FUS exposure resulted in SI changed from 11% to 55% when MBs concentrations increased from 0.025% to 0.1%. When slice thickness increased from 3 mm to 6 or 8 mm, smaller SI changes were observed (84%, 59%, and 46%). Images acquired with chamber diameter of 6 and 3 mm showed SI changes of 84% and 35%, respectively. In burst modes, higher duty cycles exhibited higher SI changes, and lower PRFs exhibited smaller and longer SI decrease. Under various conditions, substantial signal changes were observable, suggesting the feasibility of applying HASTE to real-time monitor IC effect under FUS exposure. Magn Reson Med 77:102-111, 2017. © 2015 Wiley Periodicals, Inc.

Arteriovenous malformation mimicking tuberculosis of spine with myelitis

Abstract Arteriovenous malformations of the spinal cord are a rare cause of neurological impairment and they represent 5% of all intraspinal pathology. They can occur anywhere in the spinal cord from occiput to coccyx and they can present in any way. Here we report a case of AV malformation of the spinal cord which was diagnosed as tuberculosis of the spine and presented as paraperesis. A 27 year old male presented to us with gradually progressive weakness of both lower limbs for 5 months and difficulty in micturition and defaecation for 5 days. He was investigated at his local place and was diagnosed as tuberculosis spine with myelitis and was on antitubercular therapy (ATT) for 5 months. However the symptoms worsened and at the time of presentation to us he had grade 1 power in bilateral lower limbs with decreased sensation below D12 and with bowel and bladder involvement. MRI showed signal intensity changes in multiple vertebrae which was hyperintense in both T1 and T2 weighted images and signal intensity changes in the spinal cord. An urgent digital subtraction angiogram was performed which revealed type I AV malformation at D11 level which was treated surgically by laminectomy and cauterization of the fistula. The power increased to grade 4 on the 5th postoperative day but however the bladder and bowel symptoms persisted. Spinal AV malformations should be entertained in the differential diagnosis of progressive myelopathy of uncertain etiology and when the clinical findings are not correlating with imaging findings. Advanced imaging studies like spinal MRA or CTA should be used to screen these lesions and spinal digital subtraction angiogram is the gold standard for diagnosing AV malformations. Early and prompt diagnosis and management in these cases in the form of complete occlusion of the fistula will prevent any further neurological deterioration.

Do quantitative magnetic resonance imaging parameters correlate with the clinical presentation and functional outcomes after surgery in cervical spondylotic myelopathy? A prospective multicenter study.

A prospective multicenter cohort study. To establish the relationship between preoperative quantitative magnetic resonance imaging (MRI) parameters and clinical presentation and postoperative outcomes in patients with cervical spondylotic myelopathy. Correlation of magnetic resonance imaging with clinical presentation and outcomes in cervical spondylotic myelopathy is poorly understood. A total of 134 magnetic resonance imaging scans were reviewed from 12 sites across North America. The transverse area (TA) of the spinal cord at the site of maximal compression was computed, and spinal cord signal intensity (SI) changes on T1-/T2-weighted imaging (WI) were evaluated. Detailed clinical assessments--neurological signs, symptoms, Nurick grade, modified Japanese Orthopaedic Association, segmental-tract score, and long-tract score of modified Japanese Orthopaedic Association, 30-m walk test, Short-Form 36 questionnaire, and neck disability index were performed at admission, 6 months, and 12 months postoperatively. The total number of neurological signs in a patient correlated with TA (P = 0.01) and SI changes on T1-/T2WI (P = 0.05). Pre- and postoperative Nurick grade (P = 0.03, P = 0.02), modified Japanese Orthopaedic Association score (P = 0.005, P = 0.001), segmental-tract score (P = 0.05, P = 0.006), and long-tract score (P = 0.006, P = 0.002), 30-m walk test (P = 0.002, P = 0.01) correlated with TA. There was no significant difference in pre- and postoperative clinical scores in patients with/without SI changes. Patients with severe cord compression showed SI changes on T1-/T2WI more frequently (r =-0.27, r =-0.38). Pyramidal signs--plantar response, Hoffmann reflex and hyper-reflexia correlated with TA (P = 0.003, P = 0.0004, P = 0.024, respectively) and SI changes on T1/T2WI (P = 0.02). TA closely mirrors the clinical presentation of cervical spondylotic myelopathy and may be used in predicting surgical outcomes. Pyramidal signs correlated with TA and/or SI changes on T1-/T2WI. The total number of neurological signs in a patient correlated with TA. There was no significant relationship between TA, age and duration of symptoms. 3.

Left ventricular remodeling in swine after myocardial infarction: a transcriptional genomics approach

Despite the apparent appropriateness of left ventricular (LV) remodeling following myocardial infarction (MI), it poses an independent risk factor for development of heart failure. There is a paucity of studies into the molecular mechanisms of LV remodeling in large animal species. We took an unbiased molecular approach to identify candidate transcription factors (TFs) mediating the genetic reprogramming involved in post-MI LV remodeling in swine. Left ventricular tissue was collected from remote, non-infarcted myocardium, 3 weeks after MI-induction or sham-surgery. Microarray analysis identified 285 upregulated and 278 downregulated genes (FDR < 0.05). Of these differentially expressed genes, the promoter regions of the human homologs were searched for common TF binding sites (TFBS). Eighteen TFBS were overrepresented >two-fold (p < 0.01) in upregulated and 13 in downregulated genes. Left ventricular nuclear protein extracts were assayed for DNA-binding activity by protein/DNA array. Out of 345 DNA probes, 30 showed signal intensity changes >two-fold. Five TFs were identified in both TFBS and protein/DNA array analyses, which showed matching changes for COUP-TFII and glucocorticoid receptor (GR) only. Treatment of swine with the GR antagonist mifepristone after MI reduced the post-MI increase in LV mass, but LV dilation remained unaffected. Thus, using an unbiased approach to study post-MI LV remodeling in a physiologically relevant large animal model, we identified COUP-TFII and GR as potential key mediators of post-MI remodeling.Electronic supplementary materialThe online version of this article (doi:10.1007/s00395-011-0229-1) contains supplementary material, which is available to authorized users.

Mouse model mimics multiple sclerosis in the clinico‐radiological paradox

The value of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, in deriving novel diagnostic and therapeutic input has been subject to recent debate. This study is the first to report a disseminated distribution of plaques including cranial nerves, prior to or at early stages of disease in murine adoptive transfer EAE, irrespective of the development of clinical symptoms. We induced EAE by adoptive proteolipid protein-specific T-cell transfer in 26 female SJL/J mice, and applied high-field-strength magnetic resonance imaging (MRI) scans longitudinally, assessing blood-brain barrier (BBB) disruption by gadopentate dimeglumine enhancement. We visualized inflammatory nerve injury by gadofluorine M accumulation, and phagocytic cells in inflamed tissue by very small anionic iron oxide particles (VSOP-C184). MRI was correlated with immunohistological sections. In this study, we discovered very early BBB breakdown of white and grey brain matter in 25 mice; one mouse developed exclusively spinal cord inflammation. Widely disseminated contrast-enhancing lesions preceded the onset of disease in 10 animals. Such lesions were present despite the absence of any clinical disease formation in four mice, and coincided with the first detectable symptoms in others. Cranial nerves, predominantly the optic and trigeminal nerves, showed signal intensity changes in nuclei and fascicles of 14 mice. At all sites of MRI lesions we detected cellular infiltrates on corresponding histological sections. The discrepancy between the disease burden visualized by MRI and the extent of disability indeed mimics the human clinico-radiological paradox. MRI should therefore be implemented into evaluational in vivo routines of future therapeutic EAE studies.

Functional magnetic resonance imaging in children with Asperger's syndrome.

Asperger's syndrome is a pervasive developmental disorder of unknown etiology. We evaluated children with this syndrome (n = 9) and control (n = 8) children by functional magnetic resonance imaging (MRI) during a task involving social judgment. All control and 5 of 9 subjects with Asperger's syndrome showed signal intensity changes in frontal regions. Four patients with Asperger's syndrome, including one case with right frontal dysplasia, had no signal intensity change during the task. In this first functional MRI study of childhood Asperger's syndrome, frontal activation patterns demonstrated some differences between patients and normal subjects. Further studies using other functions frequently impaired in Asperger's syndrome are warranted.

Symptomatic fibroleiomyomata: MR imaging of the uterus before and after uterine arterial embolization.

To determine the magnetic resonance (MR) imaging features of uterine fibroleiomyomata after uterine arterial embolization (UAE) and identify pretreatment MR imaging features that may be predictive of successful UAE. T1- and T2-weighted and dynamic gadolinium-enhanced T1-weighted images were obtained before and 3 months after UAE in 31 patients. Up to five fibroleiomyomata (total of 125) were evaluated for volume, location, signal intensity characteristics, and vascularity. Region-of-interest curves were used to assess the vascular enhancement pattern of each fibroleiomyoma and adjacent myometrium. Each patient completed a questionnaire on symptoms 3 months after UAE. UAE resulted in significant reductions in mean uterine volume (from 588.6 to 393.1 cm(3)) and mean fibroleiomyoma volume (from 69.4 to 41.4 cm(3)) (P <.005). After UAE, lesions showed signal intensity changes consistent with hemorrhagic infarction. The vascularity of fibroleiomyomata was decreased (P <.001), with no significant change in myometrial vascularity. Submucosal location was a strong positive predictor of fibroleiomyoma volume reduction (P < 001). When a reduction in vascularity was the measure of success, hypervascularity was a strong indicator of success (P <. 005). MR imaging is useful for quantitative assessment of signal intensity and morphologic changes before and after UAE. Pretreatment MR imaging findings may help predict the success of the procedure.

MR Imaging of Skeletal Muscle Injury in Rabbit: Comparison bet ween Diffusion and T2-weighted MR Images

Purpose : The purpose of this study was to apply the diffusion-weighted MR imaging technique to the early detection of skeletal muscle injury and to evaluate the usefulness of this imaging sequence. Materials and Methods : Thirty rabbits, divided into two groups, were included in this study. Skeletal muscle injury was experimentally induced in the right thigh muscles of each rabbit by clamping with a hemostat for one minute. Four-stage clamping was applied to the rabbits in group I, but for group II there was only one stage. Diffusion and T2-weighted MR images were obtained using a 1.5T MR unit. Serial 5-and 30-minute, and 2-, 24-, and 48- hour delayed images were obtained after injury. The initial time of signal intensity change was recorded and the signal intensities of the injured sites and corresponding normal sites were measured and compared. Results : On 5-minute delayed images in group I, diffusion-weighted MR images showed signal intensity changes in injured muscle in all 15 cases, but on T2-weighted images, change was not detected in three cases. In group II, 5-minute delayed T2-weighted images failed to depict the lesion in six cases, but on diffusion-weighted images, all lesions were detected. In addition, one lesion was not detected on 30-minute delayed T2- weighted images. In group II, the sensitivity of lesion detection was significantly higher on diffusion-weighted than on T2-weighted images (p = 0.0169). Conclusion : Diffusion-weighted MR imaging was shown to be more sensitive than T2-weighted imaging for the detection of signal intensity changes immediately after artificial injury, especially when this was of a lesser degree. These results suggest that diffusion-weighted MR imaging may be useful for the detection of early stage skeletal muscle injury.

Magnetic resonance imaging of lateral epicondylitis of the elbow with a 0.2-T dedicated system.

The purpose of this study was to evaluate MR imaging findings of the common extensor tendon in patients with lateral epicondylitis and asymptomatic volunteers studied on a 0.2-T dedicated system. In 23 patients (age range 29-58 years, mean age 47 years) with clinical symptoms of lateral epicondylitis MR imaging was performed using T1-, T2- and contrast-enhanced T1-weighted spin-echo sequences. In addition, the elbows of seven healthy volunteers (age range 22-29 years, mean age 25 years) and the symptom-free contralateral elbow of 11 of the 23 patients (age range 29-58 years, mean age 47 years) were studied as controls. Five patients were surgically treated after the MR examination and the results of histopathology were correlated with MR findings. Of the patients, 95.6 % showed intratendinous signal intensity changes on T1-weighted images on the symptomatic side. In 69.6 % signal alterations were observed on T2-weighted sequences and in 56.5 % an intratendinous contrast enhancement was present. Histopathology showed fibrovascular proliferation and fatty degeneration in patients with distinct signal intensity changes and contrast enhancement. Patients with only minor signal intensity changes on T1- and T2-weighted sequences and no contrast enhancement demonstrated fibrosclerotic degeneration and intratendinous cartilage formation in histopathology. The contralateral elbow showed signal intensity changes in 6 of 11 (54.5 %) cases on T1-weighted images and in 3 of 11 (27.3 %) on T2-weighted images. In the group of healthy volunteers minor signal intensity changes of the common extensor tendon could be seen in only 1 case. In patients with lateral epicondylitis of the elbow the type and extent of pathologic changes within the common extensor tendon can be evaluated using a dedicated low-field MR system. On the basis of MR imaging findings a more specified therapy planning among the variety of treatment modalities can be achieved.

Oxygen-induced MR signal changes in murine tumors

Breathing of 100% oxygen was used to challenge vascular autoregulation in 14 mice with either osteosarcomas ( n = 6) or mammary carcinomas ( n = 8). Reproducible and statistically significant signal intensity changes of –29 ± 6% to +35 ± 3% were observed on heavily T 2∗-weighted images in the tumors during the oxygen challenge. No significant changes were observed in muscle. For the mammary carcinomas a higher percentage of tumor voxels showed significant signal-intensity decrease (31 ± 8%) compared to the percentage of voxels showing a signal-intensity increase (22 ± 3%). In contrast, for the osteosarcomas, a higher percentage of tumor voxels showed signal-intensity increase (52 ± 9%) compared to the percentage of voxels showing signal-intensity decrease (27 ± 9%). The regional distribution of these signal intensity changes did not correlate with the signal pattern on T 1-, T 2-,and T 2∗-weighted and Gd-DTPA enhanced images acquired without breathing 100% oxygen. Most likely, the signal intensity changes represented the inability of the tumor’s neovascularization for autoregulation during the oxygen challenge, particularly in hypoxic regions. Although further investigation is needed, the findings that malignant tumor tissue showed signal intensity changes, whereas normal muscle tissue did not, suggests that this technique may prove useful in distinguishing benign from malignant tissue.

Intramural hematoma of the thoracic aorta: MR image findings and their prognostic implications.

To evaluate magnetic resonance (MR) imaging findings of intramural hematoma of the thoracic aorta and their relationship to prognosis. MR images of 22 patients with intramural hematoma of the thoracic aorta were reviewed retrospectively. Site, thickness, degree of mural involvement, and signal intensity on spin-echo (SE) and cine gradient-echo (GRE) images of the hematoma were noted. MR findings of patients who did and those who did not develop complications were compared. Hematoma site was the only MR finding that correlated significantly with patient outcome. Complication frequencies in four (80%) of five patients with hematoma of the ascending aorta (type A) and in two (12%) of 17 patients with hematoma of the descending aorta (type B) were significantly different (P = .009). There were moderately strong correlations between days after symptom onset and signal intensity of the hematoma on SE (r = 0.78) and GRE (r = 0.72) images. MR images of two of three patients who developed early-subacute complications showed signal intensity changes of the hematoma that were consistent with recurrent bleeding. Patients with MR findings consistent with type A intramural hematoma of the thoracic aorta should undergo surgery. In cases of type B intramural hematoma of the thoracic aorta, MR imaging can be useful for detecting complete resolution or impending complications of the hematoma.

MRI demonstration of Wallerian degeneration in various intracranial lesions and its clinical implications

Dynamic signal intensity changes of Wallerian degeneration (WD) are well documented in cases of stroke. These changes have been staged I–IV, depending on time-specific signal intensity changes in corticospinal tract with magnetic resonance imaging (MRI). We performed both prospective and retrospective evaluation of various intracranial lesions to look for evidence of WD and to assess its prognostic implications. Eighteen patients of acute stroke were studied prospectively. Their functional disability was evaluated by using a modified Barthel index of activity of daily living (ADL) at presentation, at 1 month and at 4 months, and was correlated with presence or absence of WD on MRI. 10 18 patients showed signal intensity changes of WD on MRI and their mean ADL score changed from 9.1 at 1 month to 11.4 at 4 months duration suggestive of moderate to severe disability after 4 months of stroke. The rest of the eight patients, where MRI did not reveal signal intensity changes of WD, the mean ADL score improved from 10.37 at 1 month to 17.5 at 4 months, suggesting significant improvement in their clinical disability, 520 patients were studied retrospectively, out of whom 31 showed signal intensity changes of WD in various intracranial lesions, i.e. infarcts ( 14 220 ), intracranial haematoma ( 4 147 ), arterio-venous malformation ( 1 20 ), tumour ( 6 98 ), multiple sclerosis ( 5 20 ) and encephalitis ( 1 15 ). Presence of WD in these intracranial lesions correlated well with persistent clinical disability. This observation has immense prognostic value, particularly in relapsing and remitting disease like multiple sclerosis. We conclude that WD can be seen secondary to any CNS insult with MRI and its presence correlates well with persistent functional disability. It thus has prognostic value. © 1997 Elsevier Science B.V. All rights reserved.