Female genitalia: dynamic MR imaging with use of MS-325 initial experiences evaluating female sexual response

PURPOSE: To determine whether magnetic resonance (MR) imaging with MS-325, a recently developed blood pool contrast agent, can depict sexual arousal response in healthy women. MATERIALS AND METHODS: Serial MR imaging of the external genitalia was performed in 12 healthy sexually functional women before and after administration of MS-325. MR images were obtained every 3 minutes during a 45-minute examination. During the examination, the subjects viewed neutral and erotic video material while they were in the magnet bore. MR image analysis at each interval consisted of vaginal wall, vaginal mucosa, and clitoris assessments; femoral vein signal intensity measurements; relative regional blood volume (rRBV) calculations; and clitoral volume measurements. Statistical analysis of the results was performed with a t test. RESULTS: On subjective questionnaires, all subjects in the test group reported being sexually aroused. MS-325-enhanced MR images showed strong contrast enhancement of the external genitalia. The rRBV in the glans clitoris of seven of 10 subjects and in the clitoral body of eight of these subjects increased significantly (P <.05) during erotic visual stimulation. All 10 subjects had a significant (P <.05) increase in clitoral size. There were no significant differences in any measures between the pre- and postmenopausal study groups. CONCLUSION: The sexual arousal response in healthy women can be monitored at serial MR imaging with MS-325. This examination holds promise for future studies of sexual arousal dysfunction in women.     

Functional brain imaging using a long intravenous half-life gadolinium-based contrast agent

PURPOSE: We describe a technique for functional MR imaging (fMRI) with high spatial and temporal resolution using a long intravascular half-life gadolinium-based contrast agent, MS-325. METHODS: All fMRI measurements used a rat model of sensory cortex activation with forepaw electrical stimulation under alpha-chloralose anesthesia. Standard blood oxygen level-dependent (BOLD) fMRI measurement was initially performed. MS-325 was then intravenously administered and a MS-325 fMRI measurement was performed by using a 3D gradient-echo sequence. RESULTS: We found that a dose of 0.1 mmol/kg MS-325 produced adequate signal intensity changes in rat sensory cortex to demonstrate activations. Using a boxcar stimulation pattern with a standard correlation analysis, the locations of the most significantly activated voxels (ie, highest Z score) in the MS-325 and BOLD fMRI measurements were not significantly different. CONCLUSIONS: MS-325 fMRI has the advantage of using a T1-weighted sequence, rather than the highly T2*-weighted sequences used in other common fMRI techniques. This could reduce the susceptibility artifacts associated with fMRI.     

MR angiography of aortoiliac occlusive disease: a phase III study of the safety and effectiveness of the blood-pool contrast agent MS-325

PURPOSE: To evaluate prospectively the safety and effectiveness of aortoiliac magnetic resonance (MR) angiography enhanced with MS-325 (gadofosveset trisodium) at a dose of 0.03 mmol/kg; effectiveness was defined as accuracy relative to the reference standard, conventional angiography. MATERIALS AND METHODS: Study was approved by institutional review boards of participating institutions, and required national approvals were obtained. Study protocol conformed to Good Clinical Practice guidelines, and informed patient consent was obtained. Patients with known or suspected peripheral vascular disease received 0.03 mmol/kg MS-325 for aortoiliac MR angiography. They were also examined with conventional angiography. MS-325-enhanced MR was evaluated for safety and effectiveness. Along with unenhanced two-dimensional time-of-flight MR angiography, it was compared with conventional angiography for presence of vascular stenosis. Student t tests were used to identify significant improvement in diagnostic sensitivity, specificity, and accuracy, as well as quantitative characterization of stenoses by three blinded readers. Correlations between readers of conventional angiograms were calculated and compared with MR results. RESULTS: In 174 patients, MS-325-enhanced MR angiography showed significant improvement (P < or = .001) in sensitivity, specificity, and accuracy for diagnosis of clinically significant (> or =50%) stenosis, compared with unenhanced MR. For all readers, areas under the receiver operating characteristic curve for both quantitative and qualitative measures of significant disease increased (P < .001) for MS-325-enhanced MR compared with time-of-flight MR. All readers also expressed higher confidence in diagnosis (P < .001) and found fewer images uninterpretable with MS-325 enhancement. All measures of interpretation accuracy approached corresponding measures of correlation between readers of conventional angiograms. Incidence of severe and serious adverse events with MS-325 was low. No patients were withdrawn from study due to adverse events or abnormalities in laboratory results. There were no clinically important trends in findings at hematology, blood chemistry, urinalysis, electrocardiography, or physical examination. CONCLUSION: MR angiography with MS-325 provides significant improvement in effectiveness over unenhanced MR (and minimal and transient side effects) at a dose of 0.03 mmol/kg and was safe and effective for MR evaluation of patients with aortoiliac occlusive disease.     

MRI detection of myocardial perfusion defects due to coronary artery stenosis with MS-325

PURPOSE: To assess the value of an intravascular, albumin-targeted contrast agent, MS-325, in visualizing myocardial ischemia with magnetic resonance imaging (MRI). MATERIALS and METHODS: Left anterior descending coronary artery (LAD) stenosis was created in 19 pigs using a closed-chest modified angioplasty technique. Myocardial ischemia was detected by first-pass, contrast-enhanced MRI at peak dipyridamole stress and was compared to Technetium-99m (Tc-99m) sestamibi single photon emission computed tomography (SPECT). Regional coronary blood flow was determined using microspheres. RESULTS: Inducible myocardial ischemia with >40% reduction in stress myocardial blood flow was created in eight animals. An MRI defect, classified as > or=75% reduction in peak myocardial signal intensity in the affected territory, was detected in 92.3% of these animals. In the presence of mild coronary stenosis, there was uniform enhancement with MRI and tracer uptake by SPECT. Concordance of MRI and SPECT for detecting perfusion defects was 85%. CONCLUSION: The pattern of prolonged and persistent MR hypoenhancement of the ischemic myocardial bed using MS-325, which is retained primarily in the vascular bed due to its albumin-binding properties, facilitates the detection of myocardial perfusion defects.     

Comparison of MS-325- and gadodiamide-enhanced MR venography of iliocaval veins

PURPOSE: To compare conventional extracellular and blood-pool magnetic resonance (MR) contrast agents in "indirect" contrast-enhanced three-dimensional (3D) MR venography of the iliocaval veins. MATERIALS AND METHODS: Twenty-nine gadodiamide-enhanced 3D MR (Gd-MR) angiography studies and 12 MS-325-enhanced 3D MR (MS-325-MR) angiography studies were reviewed retrospectively. Abnormalities of the inferior vena cava (IVC) or iliac veins were not suspected before MR imaging. The MR angiography studies were reviewed with and without subtraction. Diagnostic conspicuity and subjective contrast of the various iliocaval venous segments (suprarenal IVC, infrarenal IVC, and iliac veins) and the presence of artifacts were subjectively scored by two blinded observers. RESULTS: In the Gd-MR angiography group, the infrarenal IVC and iliac veins were visualized with good conspicuity in only 55% of segments compared to 92%-100% of segments in the MS-325-MR angiography group. Although subtraction improved subjective conspicuity and contrast relative to background in the Gd-MR angiography group, it resulted in increased artifacts and luminal blurring. Subtraction offered little diagnostic advantage in the MS-325-MR angiography group. CONCLUSION: Indirect contrast-enhanced 3D MR venography with use of MS-325 offered significantly improved diagnostic conspicuity and contrast in iliocaval venous opacification compared to gadodiamide-enhanced studies.     

Species dependence on plasma protein binding and relaxivity of the gadolinium-based MRI contrast agent MS-325

RATIONALE AND OBJECTIVES: We sought to determine whether there is a species dependence on plasma protein and serum album binding and/or relaxivity of the MR contrast agent MS-325. METHODS: Equilibrium binding of MS-325 to plasma proteins or purified serum albumin was determined as a function of chelate concentration. T1 and T2 values were determined at 0.47 and 1.41 T, and NMRD profiles were measured to determine the changes in relaxivity over varying field strengths from 0.002 to 1.2 T. RESULTS: The binding of MS-325 to either animal plasma or serum albumin plateaus at chelate concentrations less than 0.1 mM with human, pig, and rabbit plasmas showing maximum binding. Human and pig plasmas show the greatest observed relaxivity enhancement in the presence of MS-325. CONCLUSIONS: MS-325 exhibits increased relaxivity in blood plasma as the result of plasma protein binding. Binding ranged from 64% to 91% and was species dependent: human > pig approximately rabbit > dog approximately rat approximately mouse.     

Serial MR imaging with MS-325 for evaluating female sexual arousal response: determination of intrasubject reproducibility

PURPOSE: To determine if a similar sexual arousal response in normal, healthy women could be obtained and monitored by serial magnetic resonance (MR) imaging at two separate sessions. MATERIALS AND METHODS: Serial imaging of the external genitalia was performed on nine healthy, sexually functional women at two separate MR sessions after administration of the contrast agent, MS-325. Images were obtained every three minutes during a 45-minute study period during each MR session. The second MR session began approximately 45 minutes after the end of the first MR session. While undergoing imaging, subjects viewed videotapes that contained neutral and sexually-explicit material through an audiovisual system. Analysis performed at each time point consisted of visual evaluation of the images, clitoral and femoral vein signal intensity measurements, relative regional blood volume calculations, and clitoral volume measurements. Statistical analysis of the results consisted of calculating correlation coefficients of the two MR sessions by using the least square fit method. RESULTS: All nine subjects reported sexual arousal on subjective questionnaires at each MR session. Post-contrast MS-325 MR images showed strong enhancement of the external genitalia at each session. There was excellent correlation between the two sessions for the clitoral volume measurements of all nine subjects. The correlation coefficient, r(2), was 0.95. CONCLUSION: The sexual arousal response in normal, healthy women can be monitored by serial imaging combined with the use of the contrast agent, MS-325, and similar results can be reproduced at two different MR sessions. This method holds promise for future studies of women with female sexual arousal dysfunction.     

Whole‐heart contrast‐enhanced coronary magnetic resonance angiography using gradient echo interleaved EPI

Whole‐heart coronary MR angiography (MRA) is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (on the order of 10–15 min). Such a long imaging time may result in patient discomfort and compromise the robustness of whole‐heart coronary MRA due to increased respiratory and cardiac motion artifacts. The goal of this study was to optimize a gradient echo interleaved echo planar imaging (GRE‐EPI) acquisition scheme for reducing the imaging time of contrast‐enhanced whole‐heart coronary MRA. Numerical simulations and phantom studies were used to optimize the GRE‐EPI sequence parameters. Healthy volunteers were scanned with both the proposed GRE‐EPI sequence and a 3D TrueFISP sequence for comparison purposes. Slow infusion (0.5 cc/sec) of Gd‐DTPA was used to enhance the signal‐to‐noise ratio (SNR) of the GRE‐EPI acquisition. Whole‐heart images with the GRE‐EPI technique were acquired with a true resolution of 1.0 × 1.1 × 2.0 mm³ in an average scan time of 4.7 ± 0.7 min with an average navigator efficiency of 44 ± 6%. The GRE‐EPI acquisition showed excellent delineation of all the major coronary arteries with scan time reduced by a factor of 2 compared with the TrueFISP acquisition. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Carotid MR angiography: phase II study of safety and efficacy for MS-325

PURPOSE: To evaluate the safety and efficacy of MS-325 in patients suspected of having carotid arterial disease. MATERIALS AND METHODS: Fifty carotid arteries in 26 patients were imaged with three-dimensional spoiled gradient-recalled-echo magnetic resonance (MR) angiography at 5 and 50 minutes after injection of MS-325. MS-325 was administered intravenously as a single dose of 0.01, 0.03, or 0.05 mmol per kilogram of body weight as determined with a dose randomization scheme for four, nine, and 13 patients, respectively. Safety, including clinical laboratory changes and electrocardiographic monitoring, was assessed until approximately 3 days after injection. Conventional contrast agent-enhanced angiography was used as the standard of reference. Independent readers blinded to the dose interpreted the MR angiographic and conventional images. Images were assessed for location and extent of carotid arterial stenosis. RESULTS: There were no severe or serious adverse events. For the determination of clinically significant stenosis (>70%) on the 5-minute images, sensitivity, specificity, and accuracy (P =.07, three-way comparison) were 100%, 100%, and 100%; 63%, 100%, and 88%; and 40%, 75%, and 55% at 0.01, 0.03, and 0.05 mmol/kg, respectively. Sensitivity and specificity for images at 50 minutes after MS-325 administration showed the same trends as the 5-minute images. CONCLUSION: Overall accuracy for MS-325-enhanced carotid MR angiography performed during steady-state conditions of circulating contrast agent approximately 5 minutes after injection was high (88%-100%) at 0.03 and 0.01 mmol/kg. MS-325 was well tolerated at all evaluated doses.     

Contrast-enhanced magnetic resonance imaging (MS-325) in a murine model of systemic lupus erythematosus

RATIONALE AND OBJECTIVES: To investigate whether inflammatory activity can be evaluated by MRI with an intravascular compound (MS-325) in Desoxyribonuclease I (Dnase1)-deficient mice, which show classical symptoms of systemic lupus erythematosus. METHODS: Dnase1-deficient and normal mice (both groups n = 10) underwent MRI with a body weight adapted dose of MS-325 on a 1.5 T whole body scanner equipped with a dedicated surface coil. MR images of the kidneys and the aorta and signal to noise ratios prior and post contrast administration were compared with histopathology in all animals. RESULTS: Dnase1-knockout mice demonstrated aortic-wall enhancement and inhomogeneous-renal enhancement with significantly higher SNR values corresponding to microscopically proved inflammatory changes (P < 0.05). CONCLUSION: MS-325-enhanced MRI appears to be a sensitive tool for the detection of renal and vascular involvement in this animal model. In addition, this method may facilitate assessment of therapeutic approaches in patients with SLE in the future.     

First-pass renal perfusion imaging using MS-325, an albumin-targeted MRI contrast agent.

RATIONALE AND OBJECTIVES: MR angiography is proving to be a useful clinical study for the diagnosis of vascular disorders of renal arteries. However, its utility in terms of stenosis characterization is still limited. Renal perfusion could provide supplemental information that could allow for a comprehensive evaluation of renal artery stenosis by MR imaging. METHODS: MS-325 is a small-molecule blood pool agent that reversibly binds with serum albumin and hence leads to higher relaxivity and longer residence times in the blood. In this study, the authors evaluated the use of MS-325 to perform first-pass perfusion imaging and contrast-enhanced MR angiography in the characterization of renal artery stenosis in an animal model. RESULTS: Quantitative perfusion estimates were obtained in the renal cortex (258 +/- 19.8 mL/min/100 g) and are comparable to microsphere measurements (198 +/- 12.2 mL/min/100 g), given the practical constraints. Based on these measurements, perfusion showed minimal changes even when the diameter reductions reached 75%. CONCLUSIONS: MS-325 could provide quantitative perfusion estimates that when combined with MR angiography may lead to comprehensive evaluation of renal artery stenosis.     

Contrast agent-enhanced, free-breathing, three-dimensional coronary magnetic resonance angiography.

For free-breathing, high-resolution, three-dimensional coronary magnetic resonance angiography (MRA), the use of intravascular contrast agents may be helpful for contrast enhancement between coronary blood and myocardium. In six patients, 0.1 mmol/kg of the intravascular contrast agent MS-325/AngioMARK was given intravenously followed by double-oblique, free-breathing, three-dimensional inversion-recovery coronary MRA with real-time navigator gating and motion correction. Contrast-enhanced, three-dimensional coronary MRA images were compared with images obtained with a T2 prepulse (T2Prep) without exogenous contrast. The contrast-enhanced images demonstrated a 69% improvement in the contrast-to-noise ratio (6.6 +/- 1.1 vs. 11.1 +/- 2.5; P < 0.01) compared with the T2Prep approach. By using the intravascular agent, extensive portions (> 80 mm) of the native left and right coronary system could be displayed consistently with sub-millimeter in-plane resolution. The intravascular contrast agent, MS-325/AngioMARK, leads to a considerable enhancement of the blood/muscle contrast for coronary MRA compared with T2Prep techniques. The clinical value of the agent remains to be defined in a larger patient series. J. Magn. Reson. Imaging 1999;10:790-799.     

Magnetically labeled cells can be detected by MR imaging

To determine the feasibility of MR imaging of magnetically labeled cells, different cell lines were labeled with monocrystalline iron oxide (MION) particles. Phantoms containing MION labeled cells were then assembled and imaged by MR at 1.5 T using T1-weighted and T2-weighted pulse sequences. MION uptake ranged from 8.5 × 10⁴ to 2.9 × 10⁵ particles/cell for tumor cells (9L and LX1, respectively) to 1.5 × 10⁶ to 4.8 × 10⁸ particles/cell for “professional phagocytes” (J774 and peritoneal macrophages, respectively). On the T1-weighted images, cell-internalized MION appeared hyperintense relative to agar and similar to MION in aqueous solution. On T2-weighted images, signal intensity varied according to concentration of MION within cells. Cell-internalized MION caused similar MR signal changes of cells as did free MION; however, at a dose that was an order of magnitude lower, depending on the pulse sequence used. The detectability of MION within cells was approximately 2 ng Fe, which corresponded to 10⁵ tumor cells/well or 5 × 10³ macrophages/well. We conclude that a variety of cells can be efficiently labeled with MION by simple incubation. Intracellular labeling may be used for MR imaging of in vivo cell tracking.     

Contrast-enhanced magnetic resonance angiography of carotid arterial wall in pigs

This study was designed to investigate the effects of contrast agents on MR images of balloon-injured carotid arteries containing atherosclerotic-like lesions. We have evaluated an intravascular contrast agent, MS-325 (METASYN INC., Cambridge, MA) and an extra-vascular contrast agent, Optimark, (Mallinckrodt Medical Inc., St. Louis, MO) on MR angiograms obtained 4 weeks after balloon hyperinflation-induced injury of the left common carotid artery in 12 hypercholesterolemic minipigs. High in-plane resolution (.8 × .4 mm²), thin slice (1 mm) time-of-flight gradient echo sequences were used to acquire the MR angiographic images. Vascular lumen definition was compared before and after a single bolus intravenous injection of a contrast agent. Digital subtraction angiograms were obtained from all pigs after MR imaging. High grade stenosis developed in 1 of the 12 pigs and five pigs had complete occlusion of the injured vessel. The remaining pigs exhibited essentially no visible stenoses as assessed either by MR angiography or digital subtraction angiography. The vessel walls of the stenosed and occluded vessels were visible after the injection of either intravascular or extravascular contrast agent. Histologic analyses showed well developed neovascularization in the neointima or occlusive thrombosis. We conclude that the observed contrast-enhanced vessel wall is caused by an increased vascular supply associated with thrombosis and neointimal thickening that leads to an accumulation of contrast agent in the abnormal vessel walls after the injection of the T1-shortening paramagnetic contrast agent.     

Interstitial MR lymphography with MS-325: characterization of normal and tumor-invaded lymph nodes in a rabbit model

OBJECTIVE: The aim of our study was to evaluate the performance of a new blood-pool contrast agent, MS-325, in depicting regional lymph nodes when injected interstitially and in allowing the subsequent classification of the lymph nodes as normal or tumor-bearing (VX2 tumor). MATERIALS AND METHODS: Six New Zealand white rabbits underwent adapted fast three-dimensional (3D) MR imaging before implantation of VX2 tumor cells in the flank and again 3 weeks after the implantation. For each imaging session, 0.5 mL of undiluted MS-325 was injected subcutaneously into both dorsal foot pads. For more than 120 min, the rabbits underwent repeated 3D MR imaging. The size of the individual lymph nodes and the amount of contrast agent uptake in the nodes were measured 5, 10, 15, 30, 60, and 120 min after the injection. After the rabbits had been sacrificed, their lymph nodes were removed and histopathologically analyzed. RESULTS. In normal as well as tumor-bearing hindlegs, the subcutaneous administration of MS-325 resulted in rapid delineation of popliteal, inguinal, iliac, and paraaortal lymph nodes. Tumor invasion into lymph nodes presented as circumscribed signal voids in the areas infiltrated by tumor, whereas the surrounding residual lymphatic tissue showed enhancement identical to that of normal nodes. CONCLUSION: In addition to providing a safe means of displaying the normal lymphatic system, MS-325-enhanced 3D MR lymphography depicts direct tumor invasion in lymph nodes.     

Studies on bromobenzene-induced hepatotoxicity using in vivo MR microscopy with surgically implanted RF coils

Using surgically implanted RF coils at 300 MHz, three-dimensional microscopic MR images of rat liver were obtained in vivo to follow the development of pathology induced by bromobenzene exposure. Formalin fixed specimens of liver from these animals were also imaged using in vitro MR microscopy, followed by conventional optical microscopy. All MR images were acquired using a spin-warp pulse sequence with TR = 950 ms and TE= 23 ms. The in vivo images were reconstructed as 256² × 32 arrays with a voxel size of (50 μm)² × 219 pm, while the in vitro images were reconstructed as 256² × 128 arrays, giving an isotropic resolution at (39 μm)². Based on results from six animals, we have found in all animals exposed to bromobenzene, image intensity decreased in specific hepatic tissue regions. These regions were well correlated to low signal intensity areas observed in in vitro MR images at higher resolution. Conventional optical microscopy indicated that the low signal intensity regions corresponded to areas of necrosis. The decrease in signal intensity is consistent with increased local diffusion coefficients as a result of necrosis. This study demonstrates that MR microscopy with implanted RF coils can be successfully used to follow tissue pathological changes in living tissues.     

van der Knaap syndrome: MR imaging findings including FLAIR, diffusion imaging, and proton MR spectroscopy

A patient is reported with diffuse leukoencephalopathy associated with cystic degeneration of the white matter of the brain (van der Knaap syndrome). The changes were studied by fluid attenuated inversion recovery (FLAIR), and diffusion-weighted MR imaging. The FLAIR sequence revealed suppressed signal of the cysts, and widespread high-signal white matter changes associated with thinned cortices. On diffusion-weighted MR imaging, apparent diffusion coefficient (ADC) values ranged from 3.0 × 10^–3 to 2.7 × 10^–3 mm²/s in the temporal cysts, similar to that of CSF. The ADC values within the parenchyma ranged between 2 × 10^–3 and 2.1 × 10^–3 mm²/s, a value falling between normal parenchyma and cerebrospinal fluid, compared with a control group of three healthy subjects. The changes were also evaluated by proton MR spectroscopy, and were compared with a control group of 12 cases. Magnetic resonance spectroscopy revealed apparently increased NAA/Cr ratios in most parts of the brain. The NAA/Cho ratios were either high or low, and the Cho/Cr ratios were increased or normal in different regions. Received: 27 October 1999; Revised: 9 December 1999; Accepted: 20 December 1999     

Monitoring tissue coagulation during thermoablative treatment by using a novel magnetic resonance imaging contrast agent

INTRODUCTION: We tested the feasibility of using a novel contrast agent, MS-325, as a marker of coagulating tissue during thermoablative treatment. MATERIALS AND METHODS: In vivo, we created coagulated lesions in porcine muscle tissue under 3 different conditions: MS-325 (n = 5), gadolinium-DTPA (n = 5), or no contrast agent (n = 9) present during laser thermoablation. At the same time, we performed continuous T1-weighted magnetic resonance imaging at 1.5 T. We quantified the change in signal intensity during treatment expressed as relative enhancement, and compared the 3 groups by using Mann-Whitney analysis. RESULTS: MS-325 resulted in a more than 3.2-fold increase in relative enhancement over the gadolinium-DTPA and noncontrast control groups (P < 0.008). CONCLUSION: MS-325 appears to be a valid marker for coagulating tissue and significantly increased relative enhancement of the treated lesions when compared with both Gd-DTPA and noncontrast-enhanced conditions. MS-325 thus has potential for monitoring of thermoablative treatment.     

Diffusion MRI and spectroscopy in Rasmussen's encephalitis

The purpose of this study was to evaluate the diffusion MRI and proton MR spectroscopy findings in a rare disorder, Rasmussen's encephalitis. Diffusion MRI studies of 3 cases of Rasmussen's encephalitis were performed using the echo-planar trace sequence (TR=5700 ms, TE=139.03 ms). The gradient-echo diffusion sequence, PSIF (TR=21.6 ms, TE=5 ms), which is a reverse FISP sequence, and proton MR spectroscopy (TR=1500 ms, TE=40 ms) were applied in two patients. The trace sequence revealed high apparent diffusion coefficient values at the diseased regions (1.21±0.13×10^–3 mm²/s), compared with normal parenchymal values in 12 control cases (0.84±0.09×10^–3 mm²/s), indicating increased motion of water molecules (disintegration of the tissue) in these regions. The PSIF sequence revealed pixel value differences between the two hemispheres. Proton MR spectroscopy revealed decreased N-acetyl aspartate peaks, compared with five control cases.     

A combined solenoid‐surface RF coil for high‐resolution whole‐brain rat imaging on a 3.0 tesla clinical MR scanner

Rat brain models effectively simulate a multitude of human neurological disorders. Improvements in coil design have facilitated the wider utilization of rat brain models by enabling the utilization of clinical MR scanners for image acquisition. In this study, a novel coil design, subsequently referred to as the rat brain coil, is described that exploits and combines the strengths of both solenoids and surface coils into a simple, multichannel, receive‐only coil dedicated to whole‐brain rat imaging on a 3.0 T clinical MR scanner. Compared with a multiturn solenoid mouse body coil, a 3‐cm surface coil, a modified Helmholtz coil, and a phased‐array surface coil, the rat brain coil improved signal‐to‐noise ratio by approximately 72, 61, 78, and 242%, respectively. Effects of the rat brain coil on amplitudes of static field and radiofrequency field uniformity were similar to each of the other coils. In vivo, whole‐brain images of an adult male rat were acquired with a T₂‐weighted spin‐echo sequence using an isotropic acquisition resolution of 0.25 × 0.25 × 0.25 mm³ in 60.6 min. Multiplanar images of the in vivo rat brain with identification of anatomic structures are presented. Improvement in signal‐to‐noise ratio afforded by the rat brain coil may broaden experiments that utilize clinical MR scanners for in vivo image acquisition. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.