Abdominal Coil Research Articles

Empirical evaluation of human fetal fMRI preprocessing steps.

Increased study and methodological innovation have led to growth in the field of fetal brain fMRI. An important gap yet to be addressed is optimization of fetal fMRI preprocessing. Rapid developmental changes, imaged within the maternal compartment using an abdominal coil, introduce novel constraints that challenge established methods used in adult fMRI. This study evaluates the impact of (1) normalization to a group mean-age template versus normalization to an age-matched template; (2) independent components analysis (ICA) denoising at two criterion thresholds; and (3) smoothing using three kernel sizes. Data were collected from 121 fetuses (25–39 weeks, 43.8% female). Results indicate that the mean age template is superior in older fetuses, but less optimal in younger fetuses. ICA denoising at a more stringent threshold is superior to less stringent denoising. A larger smoothing kernel can enhance cross-hemisphere functional connectivity. Overall, this study provides improved understanding of the impact of specific steps on fetal image quality. Findings can be used to inform a common set of best practices for fetal fMRI preprocessing.

Application of intensity transfer function (ITF) on MRI ekstremity with soft tissue tumor to improve image quality

MRI examination of extremities with soft tissue tumors are constrained in insufficient coils with enlarged objects. Recently the solution used with a larger coil such as the abdominal coil. The use of inappropriate coils will have an impact on the deterioration of image quality. The way to improve image quality is to increase Number of Exitation (NEX), but it will increase scan time and have an impact on patient comfort. Patients who are uncomfortable during the examination will make movements that can cause artifacts. Intensity Transfer Functin (ITF) is carried out to help improve image quality without increasing NEX. The purpose was to improve the image quality of Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR). This research is a quasi experimental with a Pre Post Test Only Group Design. MRI image of the extremity obtained with the specified inclusion criteria and then the ITF is implemented. Data were analyzed by statistical tests Paired T Test. The results of the application of ITF on MRI Extremities can improve the SNR with p-value <0,001, and CNR with p-value <0,047.

CT-based attenuation correction of whole-body radiotherapy treatment positioning devices in PET/MRI hybrid imaging

Objective.To implement computed tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. Materials and Methods. The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization device. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. Results. The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between −8.3 ± 2.1% (mean ± SD) (head and neck coil holder with coils) to −1.0 ± 0.5% (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to −2.0 ± 1.2% and −0.6 ± 0.5%, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2%. Conclusion. The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.

Influence of the abdominal coil position in children magnetic resonance imaging

A quality of received signal in magnetic resonance imaging (MRI) depends, among the other, on the correct use of radiofrequency (RF) coils. The problem of quality decrease is especially relevant when scanning children, because in some cases, coils of unsuitable size or position are used. In this work, we demonstrated that the position of the abdominal coil affects the presence of signal-to-noise homogeneity. Based on the results of the work, it is reasonable to give recommendations to children’s clinics on the correct use of radio frequency coils.

A Dedicated 36-Channel Receive Array for Fetal MRI at 3T.

Due to a lack of fetal imaging coils, the standard commercial abdominal coil is often used for fetal imaging, the performance of which is limited by its insufficient coverage, element number, and Signal-to-noise ratio (SNR). In this paper, a dedicated 36-channel coil array, of which size can best fit the body sizes of pregnancy gestation from 20 to 37+ weeks, was designed for fetal imaging at 3T. SNR with full phase encoding and G-factor denoted as noise amplification for parallel imaging were quantitatively evaluated by phantom studies. Compared with a commercial abdominal coil array, the proposed 36-channel fetal array provides not only SNR improvements in full phase encoding (with 10% in the region where the whole fetal body was located, and up to 40% in the edge region where the fetal brain and heart may appear) but also an augmented parallel imaging capability and remarkable SNR improvements at high acceleration factors.

Magnetic resonance enterography in refractory iron deficiency anemia: a pictorial overview.

To highlight magnetic resonance enterography (MRE) for diagnosis of patients with refractory iron deficiency anemia and normal endoscopy results. Fifty-three patients diagnosed with iron deficiency anemia refractory to treatment and normal gastroscopy and colonoscopy results were admitted to this prospective study between June 2013 and December 2013. All patients underwent a standardized MRE examination with a 1.5 Tesla magnetic resonance imaging system using two six-channel phased-array abdominal coils. Adequate bowel distention and fast imaging sequences were utilized to achieve diagnostic accuracy. All segments of the small bowel, duodenum, jejunum, and ileum were examined in detail. All cases were examined independently by two radiologists with > 5 years of experience in abdominal magnetic resonance imaging. A consensus reading was performed for each patient following image examination. Both radiologists were blinded to patient history, laboratory findings, and endoscopy results. Twenty (37.7%) male and 33 (62.3%) female patients were included in the study. The mean age of the patients was 52.2 ± 13.6 years (range: 19-81 years, median 51.0). The age difference between the male and female patient groups was not statistically significant (54.8 ± 16.3 years vs 50.7 ± 11.7 years). MRE results were normal for 49 patients (92.5%). Four patients had abnormal MRE results. One patient with antral thickening was diagnosed with antral gastritis in the second-look gastroscopy. One patient had focal wall thickening in the 3(rd) and 4(th) portions of the duodenum. The affected areas were biopsied in a subsequent duodenoscopy, and adenocarcinoma was diagnosed. One patient had a fistula and focal contrast enhancement in the distal ileal segments, consistent with Crohn's disease. One patient had focal wall thickening with luminal narrowing in the mid-jejunum that was later biopsied during a double-balloon enteroscopy, and lymphoma was diagnosed. MRE is a non-invasive and effective alternative for evaluating possible malignancies of the small intestines and can serve as a guide for a second-look endoscopy.

Mo1226 Magnetic Resonance Imaging (MRI) Has the Sensitivity to Detect Changes in Colonic Gas Content After Fiber Supplementation in Health

Introduction: Increased abdominal gas content induces distension and can lead to abdominal discomfort and functional symptoms such as an altered intestinal motor activity. Still, the effects of abdominal bloating remain only partially described and understood. In order to study abdominal bloating and its effects on human physiology, methods are required that allow the non-invasive quantification of abdominal gas content. The aim of this study was to noninvasively determine changes in colonic gas content in health by means of Magnetic Resonance Imaging (MRI) after a one-week fiber supplementation. Methods: 15 healthy volunteers (7 female, 8 male, mean BMI 23.0) appeared each on two study days (day 1, day 8) for a 4 hours MRI session. During the 7 day treatment period, all subjects were asked to ingest 7 g of Normacol® (Norgine, Middlesex, UK) fiber supplement together with their breakfast. An additional dose of 7 g Normacol® was ingested on the evening prior to day 8. On both study days, subjects were asked to have a defined light breakfast 5 hours prior to study start. On day 8, subjects were asked to add 7 g Normacol® to their breakfast. At the beginning and at the end of the MRI session, high-resolution anatomic scans of the abdomen were acquired using a dedicated abdominal coil array (T2 weighted single-shot turbo spin-echo sequence; 1526/80; flip angle, 90°). Colonic structures were segmented in all volunteers. A pixel-by-pixel comparison of the image signal intensity with a predefined signal intensity threshold allowed labeling individual pixels as gas or solid. The predefined threshold was set to the background noise level (mean + 2 × stdev). Gas content inside the segmented areas was computed as gas/(gas+solid). Relative gas content was calculated as the average gas content on day 8 divided by the average gas content on day 1. A paired Wilcoxon signed rank test was performed to test the null hypothesis that gas content remained unchanged between study day 1 and study day 8. Results: Gas content was reduced in 12 out of 15 healthy volunteers after fiber supplementation. Gas content change was significant (p , 0.04). One prominent outlier (volunteer number 13) was detected, perhaps due to an improper intake of the prescribed fiber supplement. Overall, gas content on study day 8 was 73% ± 50% (mean ± stdev) relative to study day 1. Conclusion & Discussion: MRI has the sensitivity to noninvasively detect changes in colonic gas content after fiber supplementation in health. By providing the means for a noninvasive detection of colonic gas content in health, MRI shows potential for further studies on abdominal gas content in patient groups such as IBS.

3.0 T proton magnetic resonance spectroscopy of the liver: Quantification of choline

To investigate the normal hepatic magnetic resonance spectroscopy findings choline/lipid2 (Cho/Lip2) associated with age and body mass index (BMI). A total of 58 single-voxel proton spectra of the liver were acquired at 3.0 T using the eight-channel phased array abdominal coil as the receiver coil. Consecutive stacks of breath-hold spectra were acquired using the point resolved spectroscopy technique at a short echo time of 30 ms and a repetition time of 1500 ms. The spectra were processed with the SAGE software package. Areas and heights for metabolite resonance were obtained. Student's t test for unpaired data was used for comparisons of shimming, Cho/Lip2, and lipid content. There were significant negative correlations between the Cho/Lip2 peak height ratios and BMI (r = -0.615) and age (r = -0.398) (all P < 0.01). Compared with the high-BMI group, the low-BMI group was younger (39.1 ± 13.0 years vs 47.6 ± 8.5 years, t = -2.954, P = 0.005); had better water suppression (93.4% ± 1.4% vs 85.6% ± 11.6%, t = 2.741, P = 0.014); had higher Cho/Lip2 peak heights ratio (0.2 ± 0.14 vs 0.05 ± 0.04, t = 6.033, P < 0.000); and had lower lipid content (0.03 ± 0.08 vs 0.29 ± 0.31, t = -3.309, P = 0.004). Compared with the older group, the younger group had better shimming effects (17.1 ± 3.6 Hz vs 22.0 ± 6.8 Hz, t = -2.919, P = 0.008); higher Cho/Lip2 peak heights ratios (0.03 ± 0.05 vs 0.09 ± 0.12, t = 2.4, P = 0.020); and lower lipid content (0.05 ± 0.11 vs 0.23 ± 0.32, t = -2.337, P = 0.031). Compared with the low-choline peak group, the high-choline peak group had lower lipid content (0.005 ± 0.002 vs 0.13 ± 0.23, t = -3.796, P < 0.000); lower BMI (19.6 ± 2.4 vs 23.9 ± 3.0, t = -4.410, P < 0.000); and younger age (34.7 ± 10.0 years vs 43.2 ± 12.5 years, t = -2.088, P = 0.041). Lipid accumulation could result from the increased fat in the body depending on age and BMI. Lipid can mask the resonance signal of choline.

An evaluation of a superfast MRI sequence in the diagnosis of suspected acute appendicitis.

A lack of typical symptoms in acute appendicitis may delay the appropriate therapy. We hypothesized that a superfast MRI sequence with fat suppression could assist in the diagnosis of acute appendicitis. To evaluate the sensitivity and specificity of MRI in the diagnosis of suspected acute appendicitis especially in the early stages and before surgery. Subject images were acquired with a 1.5-T clinical MRI scanner (Achieva Nova Dual, Philips, Netherlands) with a four-element phased array abdominal coil with a SENSE factor of 1.8. A total of 41 cases with suspected acute appendicitis were recruited. SENSE-BTFE-SPIR sequence, sensitivity encoding (SENSE) with balanced turbo field echo (BTFE) and spectral presaturation and inversion recovery (SPIR), was adopted in this study. The sensitivity and specificity were 91.7% and 100%, respectively, in the diagnosis of acute appendicitis by SENSE-BTFE-SPIR in this series. Cases with simple acute appendicitis showed a higher T2 signal in the appendiceal wall, with local fluid surrounding appendix. Cases with purulent appendicitis showed an increased T2 signal within the cavity of the appendix, along with appendiceal wall thickening, or increased T2 signals around effusions in cases with gangrenous appendicitis. A periappendiceal abscess showed a localized, high-signal fluid collection that may have had extensive effects on the adjacent bowel loops, into which the entire appendix may disappear. The fast SENSE-BTFE-SPIR sequence is capable of demonstrating the location and position of the appendix, the presence of acute appendicitis and its complications, and the clinical stages.

Two-dimensional radial sodium heart MRI using variable-rate selective excitation and retrospective electrocardiogram gating with golden angle increments

Two-dimensional projection reconstruction methods provide advantages over three-dimensional techniques because of higher flexibility regarding the resolution and shorter scan time needed. To optimize a two-dimensional radial sequence with respect to signal-to-noise ratio, variable-rate selective excitation and retrospective electrocardiogram gating is investigated. The minimal radiofrequency pulse duration is simulated in dependence of the flip angle and coil parameters using sinc waveforms with two different variable-rate selective excitation approaches and a Fermi pulse. Retrospectively electrocardiogram-gated imaging with Golden Angle incremented projections was implemented to allow for continuous data acquisition enabling the possibility of dynamic electrocardiogram-gated heart imaging. Especially for abdominal coils with high transmitter voltages required, variable-rate selective excitation strongly reduces the radiofrequency pulse duration and echo time resulting in a signal-to-noise ratio gain up to 15.5% (if the fast relaxation component of sodium is in the order of the radiofrequency pulse duration) compared with standard sinc-shaped radiofrequency pulses. Retrospective electrocardiogram gating shows higher flexibility with regard to the trigger delay enabling the trade-off between heart motion artifacts and signal-to-noise ratio. A two-dimensional radial sequence is optimized for sodium heart imaging regarding signal-to-noise ratio. Different sodium contrasts of the human heart are shown, which can give additional information on heart diseases.

Nonrigid motion correction in 3D using autofocusing withlocalized linear translations

AbstractMR scans are sensitive to motion effects due to the scan duration. To properly suppress artifacts from nonrigid body motion, complex models with elements such as translation, rotation, shear, and scaling have been incorporated into the reconstruction pipeline. However, these techniques are computationally intensive and difficult to implement for online reconstruction. On a sufficiently small spatial scale, the different types of motion can be well approximated as simple linear translations. This formulation allows for a practical autofocusing algorithm that locally minimizes a given motion metric — more specifically, the proposed localized gradient‐entropy metric. To reduce the vast search space for an optimal solution, possible motion paths are limited to the motion measured from multichannel navigator data. The novel navigation strategy is based on the so‐called “Butterfly” navigators, which are modifications of the spin‐warp sequence that provides intrinsic translational motion information with negligible overhead. With a 32‐channel abdominal coil, sufficient number of motion measurements were found to approximate possible linear motion paths for every image voxel. The correction scheme was applied to free‐breathing abdominal patient studies. In these scans, a reduction in artifacts from complex, nonrigid motion was observed. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

High Field Open MRI: Correlation with Fetal Ultrasound in the Evaluation of Central Nervous System Abnormalities

Background and Aims: MRI is a valuable alternative diagnostic tool for the assessment of the fetal central nervous system1, which frequently offers additional information to ultrasound that may change patient counselling and occasionally management2. Traditionally these studies were performed at 1.5Tesla. Open MRI is better tolerated by pregnant women and only recently it was made technically possible to achieve high magnetic field strength of 1.0Tesla3 for improved image quality. To date and to our knowledge this is the first systematic study aiming to correlate fetal brain Ultrasound to high field open-MRI.Methods: Informed parental consent and research ethics committee approval were obtained.128 fetal CNS scans (median GA 27w+2, range 19w+2 to 37w+0) were performed at a 1.0Tesla open-MRI system (Philips, Best, the Netherlands) during a 40-month period using a standard abdominal coil. These patients were referred for MRI within one week of suspected sonographic abnormality (52.4% ventriculomegaly, 20.63% posterior fossa abnormalities, 15.87% other abnormalities 8.7% callosal abnormalities and 2.4% combination) using state-of-the art ultrasound in the referring centres. Multiplanar T2W single-shot FSE, axial T1W breath-hold GRE, axial DWI and T2* sequences were applied.Results: In 57.3% of the cases ultrasound and MRI were in complete agreement, in 20.9% MRI correctly provided additional information to ultrasound and in 21.8% it changed diagnosis. Pregnancy management was altered in 31% of the cases.Conclusions: Open-MRI at 1.0Tesla is a valuable complementary diagnostic tool to US for the evaluation of fetal CNS abnormalities, with images comparable to 1.5Tesla conventional MRI scanners

MR imaging of Crohn's disease: The experience at the Royal Melbourne Hospital

AbstractUntil recently, magnetic resonance imaging (MRI) has had little to offer the physician or surgeon in the area of small bowel gastro‐intestinal (GI) imaging. Long scan times leading to motion artifacts and poor image quality as well as a lack of good quality imaging coils have all contributed to this fact. However, in the last 5–10 years, these problems have been overcome by the creation of very fast sequences enabling breath‐hold scan times, as well as increases in surface coil technology (phased‐array abdominal coils) to increase signal‐to‐noise ratio and image quality. In the light of these new advances, MRI is being used increasingly to aid in the diagnosis of certain GI tract diseases. This paper looks at the ability of MRI to diagnose the chronic inflammatory bowel condition known as Crohn's disease, with a discussion on the experience of our department to date.