Volume-targeted and whole-heart coronary magnetic resonance angiography using an intravascular contrast agent.

PURPOSE: To compare volume-targeted and whole-heart coronary magnetic resonance angiography (MRA) after the administration of an intravascular contrast agent. MATERIALS AND METHODS: Six healthy adult subjects underwent a navigator-gated and -corrected (NAV) free breathing volume-targeted cardiac-triggered inversion recovery (IR) 3D steady-state free precession (SSFP) coronary MRA sequence (t-CMRA) (spatial resolution = 1 x 1 x 3 mm(3)) and high spatial resolution IR 3D SSFP whole-heart coronary MRA (WH-CMRA) (spatial resolution = 1 x 1 x 2 mm(3)) after the administration of an intravascular contrast agent B-22956. Subjective and objective image quality parameters including maximal visible vessel length, vessel sharpness, and visibility of coronary side branches were evaluated for both t-CMRA and WH-CMRA. RESULTS: No significant differences (P = NS) in image quality were observed between contrast-enhanced t-CMRA and WH-CMRA. However, using an intravascular contrast agent, significantly longer vessel segments were measured on WH-CMRA vs. t-CMRA (right coronary artery [RCA] 13.5 +/- 0.7 cm vs. 12.5 +/- 0.2 cm; P < 0.05; and left circumflex coronary artery [LCX] 11.9 +/- 2.2 cm vs. 6.9 +/- 2.4 cm; P < 0.05). Significantly more side branches (13.3 +/- 1.2 vs. 8.7 +/- 1.2; P < 0.05) were visible for the left anterior descending coronary artery (LAD) on WH-CMRA vs. t-CMRA. Scanning time and navigator efficiency were similar for both techniques (t-CMRA: 6.05 min; 49% vs. WH-CMRA: 5.51 min; 54%, both P = NS). CONCLUSION: Both WH-CMRA and t-CMRA using SSFP are useful techniques for coronary MRA after the injection of an intravascular blood-pool agent. However, the vessel conspicuity for high spatial resolution WH-CMRA is not inferior to t-CMRA, while visible vessel length and the number of visible smaller-diameter vessels and side-branches are improved.

Improved three-dimensional free-breathing coronary magnetic resonance angiography using gadocoletic acid (B-22956) for intravascular contrast enhancement.

PURPOSE: To evaluate gadocoletic acid (B-22956), a gadolinium-based paramagnetic blood pool agent, for contrast-enhanced coronary magnetic resonance angiography (MRA) in a Phase I clinical trial, and to compare the findings with those obtained using a standard noncontrast T2 preparation sequence. MATERIALS AND METHODS: The left coronary system was imaged in 12 healthy volunteers before B-22956 application and 5 (N = 11) and 45 (N = 7) minutes after application of 0.075 mmol/kg of body weight (BW) of B-22956. Additionally, imaging of the right coronary system was performed 23 minutes after B-22956 application (N = 6). A three-dimensional gradient echo sequence with T2 preparation (precontrast) or inversion recovery (IR) pulse (postcontrast) with real-time navigator correction was used. Assessment of the left and right coronary systems was performed qualitatively (a 4-point visual score for image quality) and quantitatively in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, visible vessel length, maximal luminal diameter, and the number of visible side branches. RESULTS: Significant (P < 0.01) increases in SNR (+42%) and CNR (+86%) were noted five minutes after B-22956 application, compared to precontrast T2 preparation values. A significant increase in CNR (+40%, P < 0.05) was also noted 45 minutes postcontrast. Vessels (left anterior descending artery (LAD), left coronary circumflex (LCx), and right coronary artery (RCA)) were also significantly (P < 0.05) sharper on postcontrast images. Significant increases in vessel length were noted for the LAD (P < 0.05) and LCx and RCA (both P < 0.01), while significantly more side branches were noted for the LAD and RCA (both P < 0.05) when compared to precontrast T2 preparation values. CONCLUSION: The use of the intravascular contrast agent B-22956 substantially improves both objective and subjective parameters of image quality on high-resolution three-dimensional coronary MRA. The increase in SNR, CNR, and vessel sharpness minimizes current limitations of coronary artery visualization with high-resolution coronary MRA.

Is magnetic resonance imaging of hepatic hemangioma any different in liver fibrosis and cirrhosis compared to normal liver?

PURPOSE: To compare qualitative and quantitative magnetic resonance (MR) imaging characteristics of hepatic hemangiomas in patients with normal, fibrotic and cirrhotic livers. MATERIALS AND METHODS: Retrospective, institutional review board approved study (waiver of informed consent). Eighty-nine consecutive patients with 231 hepatic hemangiomas who underwent liver MR imaging for lesion characterization were included. Lesions were classified into three groups according to the patients' liver condition: no underlying liver disease (group 1), fibrosis (group 2) and cirrhosis (group 3). Qualitative and quantitative characteristics (number, size, signal intensities on T1-, T2-, and DW MR images, T2 shine-through effect, enhancement patterns (classical, rapidly filling, delayed filling), and ADC values) were compared. RESULTS: There were 160 (69%), 45 (20%), and 26 (11%) hemangiomas in groups 1, 2 and 3, respectively. Lesions were larger in patients with normal liver (group 1 vs. groups 2 and 3; P=.009). No difference was found between the groups on T2-weighted images (fat-suppressed fast spin-echo (P=.82) and single-shot (P=.25)) and in enhancement patterns (P=.56). Mean ADC values of hemangiomas were similar between groups 1, 2 and 3 (2.11±.52×10(-3)mm(2)/s, 2.1±.53×10(-3)mm(2)/s and 2.14±.44×10(-3)mm(2)/s, P=87, respectively). T2 shine-through effect was less frequently observed in cirrhosis (P=.02). CONCLUSION: MR imaging characteristics of hepatic hemangioma were similar in patients with normal compared to fibrotic and cirrhotic livers. Smaller lesion size was observed with liver disease and less T2 shine-through effect was seen in hemangiomas developed on cirrhosis, the latter being an important finding to highlight in these patients at risk of developing hepatocellular carcinoma.

Postmortem magnetic resonance imaging of the heart ex situ: development of technical protocols.

Postmortem MRI (PMMR) examinations are seldom performed in legal medicine due to long examination times, unfamiliarity with the technique, and high costs. Furthermore, it is difficult to obtain access to an MRI device used for patients in clinical settings to image an entire human body. An alternative is available: ex situ organ examination. To our knowledge, there is no standardized protocol that includes ex situ organ preparation and scanning parameters for postmortem MRI. Thus, our objective was to develop a standard procedure for ex situ heart PMMR examinations. We also tested the oily contrast agent Angiofil® commonly used for PMCT angiography, for its applicability in MRI. We worked with a 3 Tesla MRI device and 32-channel head coils. Twelve porcine hearts were used to test different materials to find the best way to prepare and place organs in the device and to test scanning parameters. For coronary MR angiography, we tested different mixtures of Angiofil® and different injection materials. In a second step, 17 human hearts were examined to test the procedure and its applicability to human organs. We established two standardized protocols: one for preparation of the heart and another for scanning parameters based on experience in clinical practice. The established protocols enabled a standardized technical procedure with comparable radiological images, allowing for easy radiological reading. The performance of coronary MR angiography enabled detailed coronary assessment and revealed the utility of Angiofil® as a contrast agent for PMMR. Our simple, reproducible method for performing heart examinations ex situ yields high quality images and visualization of the coronary arteries.

Automatic Segmentation of the Eye in 3D Magnetic Resonance Imaging: A Novel Statistical Shape Model for Treatment Planning of Retinoblastoma.

PURPOSE: Proper delineation of ocular anatomy in 3-dimensional (3D) imaging is a big challenge, particularly when developing treatment plans for ocular diseases. Magnetic resonance imaging (MRI) is presently used in clinical practice for diagnosis confirmation and treatment planning for treatment of retinoblastoma in infants, where it serves as a source of information, complementary to the fundus or ultrasonographic imaging. Here we present a framework to fully automatically segment the eye anatomy for MRI based on 3D active shape models (ASM), and we validate the results and present a proof of concept to automatically segment pathological eyes. METHODS AND MATERIALS: Manual and automatic segmentation were performed in 24 images of healthy children's eyes (3.29 ± 2.15 years of age). Imaging was performed using a 3-T MRI scanner. The ASM consists of the lens, the vitreous humor, the sclera, and the cornea. The model was fitted by first automatically detecting the position of the eye center, the lens, and the optic nerve, and then aligning the model and fitting it to the patient. We validated our segmentation method by using a leave-one-out cross-validation. The segmentation results were evaluated by measuring the overlap, using the Dice similarity coefficient (DSC) and the mean distance error. RESULTS: We obtained a DSC of 94.90 ± 2.12% for the sclera and the cornea, 94.72 ± 1.89% for the vitreous humor, and 85.16 ± 4.91% for the lens. The mean distance error was 0.26 ± 0.09 mm. The entire process took 14 seconds on average per eye. CONCLUSION: We provide a reliable and accurate tool that enables clinicians to automatically segment the sclera, the cornea, the vitreous humor, and the lens, using MRI. We additionally present a proof of concept for fully automatically segmenting eye pathology. This tool reduces the time needed for eye shape delineation and thus can help clinicians when planning eye treatment and confirming the extent of the tumor.

Magnetic properties of an Fe/Cu granular multilayer

A Cu/Fe granular film, formed from a multilayer film and composed of particles of Fe imbedded in Cu, has had several of its important properties investigated. Measurements include ferromagentic resonance, magnetoresistance, Mössbauer effect, magnetic viscosity, and magnetization. The two‐phase behavior of these immiscible alloy systems, and the effect of multilayering on the shape of the magnetic precipitates, can explain some of these properties. An explanation of the ferromagnetic resonance line shape is proffered. An extraordinary macroscopic quantum tunneling effect is found to govern the magnetic relaxation at the lowest temperatures.

Sintesi i caracteritzacio dels materials multiferroics BiFeO3, La: BiFeO3 i Sr: BiFeO3

Recentment, ha crescut un notable interès pels materials multiferroics (o materials que presenten simultàniament propietats elèctriques i magnètiques), a causa de les seves múltiples aplicacions, sobretot en el camp de l"electrònica. Aquest article pretén donar a conèixer els materials multiferroics, tant des del punt de vista de la física fonamental com de la química de l"estat sòlid. Tanmateix, es presentarà un dels materials multiferroics actualment més estudiats i s"exposaran els detalls de la seva síntesi i caracterització habituals en la química de l"estat sòlid.

Syntheses of niobium oxide in the presence of magnetic field and determination of physical properties

Now when the technology fast developing it is very important to control the formation of materials with better properties. In the scientific literature there is a number of works describing the influence of magnetic field on the properties and process of formation of materials. The goal of this master's thesis is to analyze the process of electrochemical synthesis of niobium oxide in the present of magnetic field, to compare properties of formed oxide films and to estimate the influence of magnetic field on the process and on the result of synthesis.

Magnetic resonance imaging findings of disc-related epidural cysts in nonsurgical and postoperative microdiscectomy patients

OBJECTIVE: To demonstrate five discal cysts with detailed magnetic resonance imaging findings in nonsurgical and following postoperative microdiscectomy. MATERIALS AND METHODS: Five discal cysts in four patients who underwent magnetic resonance imaging were found through a search in our database and referral from a single orthopedic spine surgeon. Computed tomography in two cases and computed tomography discography in one case were also performed. RESULTS: Five discal cysts were present in four patients. Three patients had no history of previous lumbar surgery and the other patient presented with two discal cysts and recurrent symptoms after partial laminectomy and microdiscectomy. All were oval shaped and seated in the anterior epidural space. Four were ventrolateral, and the other one was centrally positioned in the anterior spinal canal. One showed continuity with the central disc following discography. Three were surgically removed. CONCLUSION: Magnetic resonance imaging can easily depict an epidural cyst and the diagnosis of a discal cyst should be raised when an homogeneous ventrolateral epidural cyst contiguous to a mild degenerated disc is identified.

Incidental enchondromas at knee magnetic resonance imaging: intraobserver and interobserver agreement and prevalence of imaging findings

Objective To evaluate intra- and interobserver agreement in the identification of incidental enchondromas at knee magnetic resonance imaging, and to assess the prevalence of imaging findings. Materials and Methods Retrospective study reviewing 326 knee magnetic resonance images acquired in the period between November 2009 and September 2010. The images were independently and blindly analyzed by two specialists in musculoskeletal radiology, with the objective of identifying incidental enchondromas, presence of foci with signal similar to bone marrow and foci of signal absence suggestive of calcifications within the enchondromas. Inter- and intraobserver agreements were analyzed. Results Eleven lesions compatible with enchondromas (3.3%) were identified. The interobserver agreement for the presence of enchondroma was high. Prevalence of foci of bone marrow signal inside the enchondromas was of 54.55%, and foci suggestive of calcification corresponded to 36.36%. The intraobserver agreement for foci of bone marrow signal in enchondromas was perfect, and interobserver agreement was high. Conclusion The prevalence of incidental enchondromas in the current study was compatible with data in the literature. Excellent agreement was observed in the identification of enchondromas and in the assessment of imaging findings. A higher prevalence of fat signal foci was observed as compared with signal absence suggestive of calcifications.

Prevalence of simple liver cysts and hemangiomas in cirrhotic and non-cirrhotic patients submitted to magnetic resonance imaging

Objective To determine the prevalence of liver cysts and hemangiomas in the general population and in cirrhotic patients. Materials and Methods Retrospective, observational, and cross-sectional study selecting consecutive magnetic resonance imaging studies performed in the period from February to July 2011. A total of 303 patients (187 women and 116 men) with mean age of 53.3 years were included in the present study. Patients with previously known liver lesions were excluded. The images were consensually analyzed by two observers in the search for simple liver cysts and typical liver hemangiomas, according to universally accepted imaging criteria. Lesions prevalence, diameters and location were determined in both cirrhotic and non-cirrhotic individuals. Results The authors observed prevalence of 8.6% for hemangiomas and 14.5% for simple cysts. No statistically significant difference was observed in relation to prevalence of hemangiomas and cysts among cirrhotic and non-cirrhotic patients (p = 0.954; p = 0.472). Conclusion In the present study, the prevalence of cysts and hemangiomas was higher than the prevalence reported by autopsy series. No influence of cirrhosis was observed on the prevalence and appearance of such incidental lesions.

Cardiac magnetic resonance imaging in clinical practice

Objective To evaluate and describe indications, mainly diagnoses and cardiac magnetic resonance imaging findings observed in clinical practice. Materials and Methods Retrospective and descriptive study of cardiac magnetic resonance performed at a private hospital and clinic in the city of Niterói, RJ, Brazil, in the period from May 2007 to April 2011. Results The sample included a total of 1000 studies performed in patients with a mean age of 53.7 ± 16.2 years and predominance for male gender (57.2%). The majority of indications were related to assessment of myocardial perfusion at rest and under pharmacological stress (507/1000; 51%), with positive results in 36.2% of them. Suspected myocarditis was the second most frequent indication (140/1000; 14%), with positive results in 63.4% of cases. These two indications were followed by study of arrhythmias (116/1000; 12%), myocardial viability (69/1000; 7%) and evaluation of cardiomyopathies (47/1000; 5%). In a subanalysis, it was possible to identify that most patients were assessed on an outpatient basis (58.42%). Conclusion Cardiac magnetic resonance has been routinely performed in clinical practice, either on an outpatient or emergency/inpatient basis, and myocardial ischemia represented the main indication, followed by investigation of myocarditis, arrhythmogenic right ventricular dysplasia and myocardial viability.

Effects of iodinated contrast agent, xylocaine and gadolinium concentration on the signal emitted in magnetic resonance arthrography: a samples study

Objective:To investigate the effects of dilution of paramagnetic contrast agent with iodinated contrast and xylocaine on the signal intensity during magnetic resonance arthrography, and to improve the paramagnetic contrast agent concentration utilized in this imaging modality.Materials and Methods:Samples specially prepared for the study with three different concentrations of paramagnetic contrast agent diluted in saline, iodinated contrast agent and xylocaine were imaged with fast spin echo T1-weighted sequences with fat saturation. The samples were placed into flasks and graphical analysis of the signal intensity was performed as a function of the paramagnetic contrast concentration.Results:As compared with samples of equal concentrations diluted only with saline, the authors have observed an average signal intensity decrease of 20.67% for iodinated contrast agent, and of 28.34% for xylocaine. However, the increased gadolinium concentration in the samples caused decrease in signal intensity with all the dilutions.Conclusion:Minimizing the use of iodinated contrast media and xylocaine and/or the use of a gadolinium concentration of 2.5 mmol/L diluted in saline will improve the sensitivity of magnetic resonance arthrography.

Magnetic resonance imaging and BMB score in the evaluation of bone involvement in Gaucher’s disease patients

AbstractObjective:To evaluate by magnetic resonance imaging changes in bone marrow of patients undergoing treatment for type I Gaucher’s disease.Materials and Methods:Descriptive, cross-sectional study of Gaucher’s disease patients submitted to 3 T magnetic resonance imaging of femurs and lumbar spine. The images were blindly reviewed and the findings were classified according to the semiquantitative bone marrow burden (BMB) scoring system.Results:All of the seven evaluated patients (three men and four women) presented signs of bone marrow infiltration. Osteonecrosis of the femoral head was found in three patients, Erlenmeyer flask deformity in five, and no patient had vertebral body collapse. The mean BMB score was 11, ranging from 9 to 14.Conclusion:Magnetic resonance imaging is currently the method of choice for assessing bone involvement in Gaucher’s disease in adults due to its high sensitivity to detect both focal and diffuse bone marrow changes, and the BMB score is a simplified method for semiquantitative analysis, without depending on advanced sequences or sophisticated hardware, allowing for the classification of the disease extent and assisting in the treatment monitoring.

Accuracy of computer-aided ultrasound as compared with magnetic resonance imaging in the evaluation of nonalcoholic fatty liver disease in obese and eutrophic adolescents

AbstractObjective:To compare the accuracy of computer-aided ultrasound (US) and magnetic resonance imaging (MRI) by means of hepatorenal gradient analysis in the evaluation of nonalcoholic fatty liver disease (NAFLD) in adolescents.Materials and Methods:This prospective, cross-sectional study evaluated 50 adolescents (aged 11–17 years), including 24 obese and 26 eutrophic individuals. All adolescents underwent computer-aided US, MRI, laboratory tests, and anthropometric evaluation. Sensitivity, specificity, positive and negative predictive values and accuracy were evaluated for both imaging methods, with subsequent generation of the receiver operating characteristic (ROC) curve and calculation of the area under the ROC curve to determine the most appropriate cutoff point for the hepatorenal gradient in order to predict the degree of steatosis, utilizing MRI results as the gold-standard.Results:The obese group included 29.2% girls and 70.8% boys, and the eutrophic group, 69.2% girls and 30.8% boys. The prevalence of NAFLD corresponded to 19.2% for the eutrophic group and 83% for the obese group. The ROC curve generated for the hepatorenal gradient with a cutoff point of 13 presented 100% sensitivity and 100% specificity. As the same cutoff point was considered for the eutrophic group, false-positive results were observed in 9.5% of cases (90.5% specificity) and false-negative results in 0% (100% sensitivity).Conclusion:Computer-aided US with hepatorenal gradient calculation is a simple and noninvasive technique for semiquantitative evaluation of hepatic echogenicity and could be useful in the follow-up of adolescents with NAFLD, population screening for this disease as well as for clinical studies.