Journal of Magnetic Resonance Imaging

Published by Wiley
Online ISSN: 1522-2586
Publications
Article
To validate the feasibility of using a newly designed MR imaging-guidewire (MRIG) to guide angioplasty balloon placement in coronary arteries. A custom gold/sliver/Nitinol/MP35N-based, 0.014-inch MRIG was manufactured. To test its mechanical performance we used the new MRIG to catheterize the left coronary arteries of three dogs under x-ray fluoroscopy. To further validate the feasibility of using the MRIG to generate intracoronary MR imaging, we positioned the MRIG, along with a dilation-perfusion balloon catheter, into the left coronary arteries of an additional three dogs. Longitudinal and four-chamber views of cine cardiac MR images were obtained using a fast gradient recalled echo (FGRE) sequence (TR/TE/FA = 5.2 msec/1.6 msec/20 degrees , field of view [FOV] = 32 x 32 cm, thickness = 5 mm, space = 2 mm, matrix = 256 x 160, number of excites [NEX] = 0.5, and bandwidth [BW] = 32 kHz). Then three-dimensional (3D) MR coronary angiography of the left coronary arteries was obtained using a fast imaging employing steady-state acquisition (FIESTA) sequence. We subsequently used the MRIG, at a receive-only mode, to generate intracoronary MR images using FGRE (TR/TE/FA = 7.2 msec/3.5 msec/20 degrees , FOV = 18 x 18cm, thickness = 3 mm, space = 0.5 mm, matrix = 256 x 256, NEX = 0.5, and BW = 32 kHz). In all six animals the left main coronary arteries were successfully catheterized. 3D MR imaging displayed left coronary artery branches. Intracoronary MR imaging demonstrated the inflated balloons as a "train track" or a bright, thick ring at different views. This study demonstrates the potential of using this newly designed gold/sliver/Nitinol/MP35N-based, 0.014-inch MRIG to catheterize coronary arteries and, thus, generate intracoronary MR imaging with balloon inflation.
 
Article
To develop an "active" (receiver-coil) clinical-grade guidewire with enhanced visibility for magnetic resonance imaging (MRI) and favorable mechanical characteristics for interventional MRI procedures that require conspicuous intravascular instruments distinguishable from surrounding tissues. We designed a 0.035-inch guidewire combining two antenna designs on separate channels. A loop antenna visualizes the tip and a dipole antenna visualizes the whole shaft. We compared mechanical characteristics of this guidewire with x-ray alternatives and tested MRI performance at 1.5T in vitro and in vivo in swine. Images reflected tip position within 0.97 +/- 0.42 mm and afforded whole-shaft visibility under expected conditions without sacrificing device size or handling. We report tip stiffness, torquability, and pushability comparable to commercial interventional guidewires. Our clinical-grade 0.035-inch active guidewire is conspicuous under MRI and has mechanical performance comparable to x-ray interventional guidewires. This may enable a range of interventional procedures using real-time MRI.
 
Article
To determine the appropriate dose of contrast medium for moving-table MR angiography (MT-MRA) from the abdominal aorta to the ankle by comparing visualization with different doses of meglumine gadopentetate (Gd-DTPA) administered in crossover fashion to normal volunteers. Twelve healthy adults underwent imaging after crossover administration of 0.1 and 0.2 mmol/kg of Gd-DTPA in random order. Continuous MT-MRA was performed with a fast 3D spoiled gradient echo sequence without parallel imaging technique. Visualization was evaluated in a total of 252 arteries by three blinded readers who independently rated arterial visualization using a 5-grade scale. Signal intensity was determined and the blood concentration of Gd-DTPA was estimated. Arterial visualization in the lower leg region was significantly better with a dose of 0.2 mmol/kg than with 0.1 mmol/kg (P<0.001). For all regions assessed the estimated blood Gd-DTPA level was significantly higher with 0.2 mmol/kg than with 0.1 mmol/kg (abdominal aorta, P=0.030; superficial femoral artery, P<0.001; posterior tibial artery, P=0.039). The vascular signal enhancement ratio and artery-to-muscle signal ratio were significantly higher in the upper leg and lower leg regions at 0.2 mmol/kg. With continuous MT-MRA imaging from the abdomen to the ankle in normal volunteers, better arterial visualization and superior contrast were achieved with 0.2 mmol/kg of Gd-DTPA.
 
Article
The objective of this study was to compare the diagnostic performance of a dedicated orthopedic magnetic resonance (MR) imaging system (0.18 T) and a conventional MR imaging system (1.0 T) in the detection of articular cartilage lesions. Fifty knee joint specimens of pigs with artificially created articular cartilage lesions of different diameters, grades (2-3), and localizations, as well as 50 joints with intact articular cartilage, were imaged at 0. 18 and 1.0 T. Diagnostic performance was determined by means of receiver operating characteristics (ROC) analysis with three independent observers. For none of the pulse sequences used at 0.18 T or 1.0 T areas under ROC curves (A(z)) showed significant differences between the three observers. A(z) values from averaged data were as follows: a) 0.18 T: T1-weighted spin echo (SE): 0.70, proton-density-weighted SE: 0.59, T2-weighted SE: 0.61, two-dimensional (2D) gradient-echo (GRE): 0.73, 3D GRE: 0.75; and b) 1.0 T: T1-weighted SE: 0.73, fat-suppressed T2-weighted turbo-SE: 0. 79, 2D fast low-angle shot (FLASH): 0.79, fat-suppressed 3D FLASH: 0. 96, and water-excited 3D double-echo steady state (DESS): 0.96. With the use of 3D pulse sequences, the high-field system demonstrated a significantly better diagnostic performance than the low-field system in the detection of grades 2 and 3 articular cartilage lesions (P < 0.001).
 
Article
The objective of this study was to demonstrate in an animal model the feasibility of a passive tracking technique for catheter visualization of magnetic resonance (MR)-guided endovascular procedures. All experiments were performed in a 0.2 Tesla open MR system. Susceptibility-based catheters and guide wires were introduced into the aorta and were advanced selectively into the splenic and renal arteries under MR guidance. Based on a previously acquired contrast-enhanced magnetic resonance angiography (MRA) data set, the catheter positioning was performed by using a single-slice true fast imaging with steady state precession (FISP) sequence with a frame rate of 1.3 seconds. Contrast-enhanced MRA was performed in all animals. All catheters were advanced without complications into the aorta and were introduced into the proximal parts of the right renal and splenic arteries under MR guidance. Catheter manipulations were more difficult in the distal parts of these vessels due to the more complex anatomy. Passive catheter tracking is a valuable and technically robust alternative to active tracking methods, because it does not require additional hardware and, thus, can be implemented and used easily with any open MR imaging system. J. Magn. Reson. Imaging 1999;10:841-844.
 
Article
To investigate and measure apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values using data obtained with line-scan diffusion-weighted imaging (DWI) of human brains on a 0.2 Tesla MR imager. Diffusion-tensor imaging (DTI) was performed on eight healthy volunteers. The signal-to-noise ratios (SNRs) of white matter and cerebrospinal fluid were measured. ADC and FA were also measured from the data obtained from all subjects. Three-dimensional corticospinal fiber tracts were reconstructed from the DT images and a qualitative evaluation was done. The total scan time was 52 minutes 30 seconds for 18 slices with full-tensor images covering the whole brain. The ADCs and FAs show the appropriate values, in comparison with values obtained at high field strength in previous studies. Corticospinal fibers were demonstrated more clearly on images obtained at 0.2 T than at 1.5T. DTI at low field strength may be feasible for clinical use to estimate the white matter of brain with limited coverage, which often may be sufficient.
 
Article
Lung ventilation imaging using inhaled oxygen as a contrast medium was performed using both a 0.2 and a 1.5 T clinical magnetic resonance (MR) scanner in eight volunteers. Signal-to-noise-ratios (SNRs) of the ventilation images as well as T1 values of the lung acquired with inhalation of 100% oxygen and room air were calculated. The SNR was 9.7 +/- 3.0 on the 0.2 T MR system and 69.5 +/- 28.8 on the 1.5 T system (P < 0.001). The mean T1 value on the 0.2 T MR system with subjects breathing room air was 632 +/- 54 msec; with 100% oxygen, it was 586 +/- 41 msec (P < 0.01). At 1.5 T, the mean values were 904 +/- 99 msec and 790 +/- 114 msec, respectively (P < 0.0001). We conclude that MR oxygen-enhanced ventilation imaging of the lung is feasible with an open configured 0.2 T MR system.
 
Article
Acoustic noise levels for fast MRI pulse sequences were surveyed on 14 systems with field strengths ranging from 0.2 T to 3 T. A microphone insensitive to the magnetic environment was placed close to the magnet isocenter and connected via an extension cable to a sound level meter outside the scan room. Measured noise levels varied from 82.5 +/- 0.1 dB(A) for a 0.23 T system to 118.4 +/- 1.3 dB(A) for a 3 T system. Further measurements on four of the closed-bore systems surveyed showed that: 1) pulse sequence parameters (particularly FOV and TR) were more influential in determining noise level than field strength, 2) the noise level was found to vary along the z-direction with a maximum near the bore entrance, and 3) in one of two systems tested there was a significant increase in noise with a volunteer present instead of a test object. The results underline the importance of hearing protection for patients and for staff spending extended periods in the scan room.
 
Article
The purpose of this study was to compare the contrast between radiofrequency (RF) thermal liver lesions and surrounding tissue in T2-weighted turbo spin-echo sequences (TSE T2), short TI inversion recovery techniques (STIR), and contrast-enhanced (CE) T1-weighted spin-echo images. Nineteen RF thermal ablations were performed on eight patients with metastatic liver tumors. After ablation, contrast-to-noise ratios (CNRs) were calculated between mean signal amplitudes from three regions of interest (ROI) (lesion, surrounding edema, and normal tissue) using TSE T2-weighted, STIR, and contrast-enhanced T1-weighted (CE T1) sequences for each lesion. CNRs between the thermal lesion and normal liver tissue for both TSE T2-weighted (mean 0.9) and STIR (2.0) images were significantly lower than for CE T1-weighted (8.4) images (t-test, alpha = 0.05). However, CNRs between edema rim and the core of the thermal lesion for both TSE T2-weighted (8.1) and STIR images (7.2) were not significantly different (t-test, alpha = 0.05) from CNRs between lesion and normal tissue for CE T1-weighted images (8.4), nor was the CNR between edema rim and normal tissue for both TSE T2-weighted (10.3) and STIR (9.8) images. Although the edema was not visible on CE T1-weighted images, 18 of 19 lesions (94.7%) were surrounded by a hyperintense rim on TSE T2-weighted or STIR images. Both TSE T2-weighted and STIR sequences represent valid techniques for repeatable assessment of RF thermal lesions.
 
Article
To evaluate the feasibility and technique effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation of hepatic malignancies. In 64 patients, 100 primary (N = 19) or secondary (N = 81) liver tumors (mean diameter = 24.7 mm; range = 4-60 mm) were treated with 87 sessions of MR-guided RF ablation. The entire ablation procedure was carried out at an 0.2-T open MR system by using MR-compatible internally cooled electrodes. T2-weighted turbo spin echo sequences (TR/TE = 3500 msec/110 msec) were used to monitor thermally induced coagulation. Technique effectiveness was assessed four months after the last RF ablation by dynamic MR imaging at 1.5-T. MR-guided RF ablation procedures were technical successful in 85 of 87 (97.7%) assessed at the end of each session. Complete coagulation was intended in 99 of 100 tumors. Technique effectiveness was observed in 92 of 99 (92.9%) of these tumors. To achieve complete coagulation 82 of 92 (89.1%) tumors required a single session. T2-weighted sequences were accurate to monitor the extent of coagulation and were supportive to guide overlapping ablation. There were two of 87 (2.3%) major and seven of 87 (8.0%) minor complications. MR-guided RF ablation is a safe and effective therapy in the treatment of hepatic malignancies. MR imaging offers an accurate monitoring of thermally-induced coagulation, thus enabling complete tumor coagulation in a single session.
 
Article
To develop and analyze the performance of the variation correction algorithm (VCA), a phase correction technique that mitigates the contribution of background phase variations by combining accurate alignment of echoes, K-space-based phase correction (as opposed to spatial polynomials), and extraction of alias-free phase difference images. A series of echo-shifted gradient-recalled echo (GRE) images was processed with K-space alignment and phase corrected with increasing sizes of M x M masks of central K-space coefficients. The extent of background phase variation suppression due to magnet field drift was assessed. Further, a simulated thermal profile was superimposed on the same data in a related experiment. Residual errors in reconstructed simulated thermal profiles were quantitatively characterized to estimate algorithm performance. Using a 3 x 3 K-space mask, the VCA was able to 1) maintain the typical mean background error in a 35 x 35 pixel region of interest (ROI) at -0.1 degrees C; and 2) reconstruct, relative to the applied thermal profile, a phase-corrected profile that typically contains a 1.7 degrees C underestimation of peak temperature difference and a mean error along the 60 degrees C line of -0.8 degrees C. The results suggest that thermal profiles can be accurately reconstructed at 0.2 T using the VCA, even in the presence of over 1 ppm spatially and temporally dependent field drift over a 1-hour time frame.
 
Article
An inversion recovery true fast imaging with steady precession (FISP) pulse sequence was developed to carry out fast imaging of the lungs at 0.2 T. Using this sequence, oxygen-enhanced magnetic resonance (MR) lung imaging was performed on healthy volunteers. The lungs showed signal enhancement (11.7% +/- 3.8%) when breathing 100% oxygen. Using inversion recovery, true FISP at low field may prove promising for MR lung imaging.
 
Article
The purpose of this investigation was to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI) performed using a dedicated-extremity MR system in detecting lesions of the rotator cuff and glenoid labrum. This retrospective study compared the MR results obtained in 47 patients that underwent MRI using a 0.2-Tesla extremity MR system (E-scan) to the surgical findings. MR images of the shoulder were obtained as follows: shoulder coil, T1-weighted, coronal-oblique and axial images; short Tau inversion recovery (STIR), coronal-oblique images; and T2-weighted, coronal-oblique, sagittal-oblique, and axial images. The MR examinations were interpreted by three highly experienced, musculoskeletal radiologists. Open surgical (N = 26) or arthroscopic (N = 21) procedures were performed within a mean time of 33 days after MRI. The surgical findings revealed rotator cuff tears in 28 patients and labral lesions in 9 patients. For the rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 100%, 100%, and 90%, respectively. For the labral lesions, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 95%, 80%, and 97%, respectively. The findings indicated that there was good agreement comparing the MR results obtained using the low-field extremity MR system to the surgical findings for determination of lesions of the rotator cuff and glenoid labrum. Notably, the statistical values determined for the use of this MR system were comparable to those reported in the peer-reviewed literature for the use of whole-body, mid- and high-field-strength MR systems.
 
Article
To evaluate the diagnostic performance of a newly developed single-scan phase-contrast water-fat imaging technique for fat suppression at 0.23T open magnet, compared to the conventional chemical shift selective fat suppression method at 1.5T, in the detection of experimental articular cartilage lesions. Sixty regions of 20 knee joint specimens of pigs with artificially created articular cartilage lesions were examined with 0.23T and 1.5T MR scanners. Sagittal fat-suppressed three-dimensional gradient-echo (3D GRE) images, obtained with the phase-contrast method at 0.23T, and fat-suppressed three-dimensional spoiled gradient recalled echo (3D SPGR) images, obtained with a chemical shift selective method at 1.5T, were evaluated. Diagnostic performance was analyzed. The conspicuity of the lesions, the amount of artifacts, and the uniformity of fat suppression were evaluated. The contrast-to-noise (CNR) values of cartilage-to-bone marrow, and cartilage-to-infrapatellar fat were calculated. At 0.23T, sensitivity and specificity were 80% and 95% for partial cartilage lesions (grade 2), and 91% and 100% for full-thickness lesions (grade 3). At 1.5T, sensitivity and specificity were 85% and 95% for grade 2 lesions, and 96% and 97% for grade 3 lesions. No significant difference was detected in the conspicuity of lesions. The uniformity of fat suppression was more constant with 3D SPGR images compared to 3D GRE images. More susceptibility artifacts, derived from the procedure of creating lesions, were detected at 1.5T. The cartilage-to-fat CNRs were significantly higher with high-field images. Phase-contrast method for fat suppression at 0.23T is a useful technique in detecting articular cartilage lesions.
 
Article
To test the correlation between manually assessed volumes of magnetic resonance (MR) signal-enhancing regions in postcontrast images and MRI-based rheumatoid arthritis scoring system (RAMRIS) synovitis scores in 0.2T MR data. The low-field (0.2T) extremity MRI scans were acquired in 32 patients (37 study cases) as a part of the rheumatoid arthritis diagnostic procedure in accordance with Outcome Measures in Rheumatology Clinical Trials MRI working group (OMERACT) recommendations. The synovitis in joint regions was assessed based on RAMRIS. Regions of enhanced signals in postcontrast MR images were outlined manually. Spearman's rank-order correlations between RAMRIS scores and both absolute and relative volumes of signal-enhancing regions were equal to 0.68, 0.78 (moderately positive) and 0.84 (strongly positive) for distal radioulnar joint (DRUJ), intercarpal-carpometacarpal joints (ICCMJ), and radiocarpal joint (RCJ), respectively. Absolute and relative volumes of signal-enhancing regions grow significantly with RAMRIS scores. Development of algorithms for automated detection of signal-enhancing regions in 0.2T MR images is a reasonable direction of forthcoming studies on computer-aided diagnosis (CAD) systems supporting low-field extremity MR-based diagnosis of rheumatoid arthritis by identifying its symptoms.J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
 
Article
The purpose of this work is to describe our experience with single-session percutaneous ethanol injection (PEI) under the guidance of 0.2-T open MRI for hepatocellular carcinomas (HCC) that were not suitable for ablation under ultrasound (US) or computed tomography (CT) guidance. None of the lesions (N = 7) were detectable on US. MRI was chosen over CT as the guidance modality because the nodules were located in the hepatic dome (N = 4) or were invisible on noncontrast CT (N = 3). All of the nodules were targeted successfully, and apparently complete tumor necrosis was achieved in six nodules (86%). During a follow-up of one to 41 months, only one patient developed local recurrence four months after PEI. MR-guided PEI is feasible and effective for treating HCC when other imaging guidance methods are not appropriate.
 
Article
To perform a quantitative and qualitative comparison of gadobutrol and gadoterate in three-station contrast enhanced magnetic resonance angiography (CE-MRA) of the lower limbs. In this prospective randomized controlled trial, 52 patients with leg ischemia were randomly assigned to one of two groups receiving either gadobutrol (1.0 mmol Gd/mL, 15 mL) or gadoterate (0.5 mmol Gd/mL, 30 mL). Three-station 3D CE-MRAs from the pelvis to the ankles were performed with moving-table technique on a 1.5T MR scanner. Injection time was identical in both groups. Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated for 816 arteries. Contrast quality in 1196 vessel segments was evaluated separately by two blinded readers on a three-point scale. Mean SNR (61.8 +/- 7.8 for gadobutrol vs. 61.9 +/- 9.1 for gadoterate, P = 0.257), CNR (52.8 +/- 9.1 vs. 52.8 +/- 10.7, P = 0.154), and qualitative ranking (1.41 vs. 1.44, P = 0.21) for all vessels did not differ significantly between the two patient groups. The overall quality was good in 90.4% with gadoterate and 94.2% with gadobutrol (P = 0.462). High-concentration gadobutrol allows neither a higher CNR nor any qualitative advantage over the ordinary unspecific Gd agent gadoterate when the same Gd load and injection times are used in multistation CE-MRA of the peripheral arteries.
 
Article
To compare image quality and diagnostic accuracy of 0.5 molar gadobenate dimeglumine and 1.0 molar gadobutrol in contrast-enhanced (CE) magnetic resonance angiography (MRA) of the lower extremities interindividually. The study was approved by our Institutional Review Board. Written informed consent was obtained from all patients before enrollment in the study. We prospectively included 74 patients (21 women, 53 men; mean age ± SD: 67.9 ± 11.0 years) with suspected peripheral occlusive vascular disease. All patients underwent a contrast-enhanced MRA of both lower extremities with either 0.1 mL/kg body weight gadobutrol or gadobenate dimeglumine. Image quality, stenosis grade, and artifacts were assessed by two blinded, independent investigators. Signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured by a third investigator. Contrast agent groups were compared to each other using a two-sided Student's t-test. The results did not show significant differences for SI, SNR, or CNR. Both investigators were in significant accordance (P < 0.05) with regard to stenosis detection. We conclude that application of standard clinical doses (0.1 mL/kg body weight) of both contrast agents provides similar diagnostic results and gadolinium dose could be reduced by the application of a single dose of gadobenate dimeglumine for CE run-off MRA.
 
Article
To compare contrast characteristics and image quality of 1.0 M gadobutrol with 0.5 M Gd-DTPA for time-resolved three-dimensional pulmonary magnetic resonance angiography (MRA). Thirty-one patients and five healthy volunteers were examined with a contrast-enhanced time-resolved pulmonary MRA protocol (fast low-angle shot [FLASH] three-dimensional, TR/TE = 2.2/1.0 msec, flip angle: 25 degrees, scan time per three-dimensional data set = 5.6 seconds). Patients were randomized to receive either 0.1 mmol/kg body weight (bw) or 0.2 mmol/kg bw gadobutrol, or 0.2 mmol/kg bw Gd-DTPA. Volunteers were examined three times, twice with 0.2 mmol/kg bw gadobutrol using two different flip angles and once with 0.2 mmol/kg bw Gd-DTPA. All contrast injections were performed at a rate of 5 mL/second. Image analysis included signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in lung arteries and veins, as well as a subjective analysis of image quality. In patients, significantly higher SNR and CNR were observed with Gd-DTPA compared to both doses of gadobutrol (SNR: 35-42 vs.17-25; CNR 33-39 vs. 16-23; P < or = 0.05). No relevant differences were observed between 0.1 mmol/kg bw and 0.2 mmol/kg bw gadobutrol. In volunteers, gadobutrol and Gd-DTPA achieved similar SNR and CNR. A significantly higher SNR and CNR was observed for gadobutrol-enhanced MRA with an increased flip angle of 40 degrees. Image quality was rated equal for both contrast agents. No relevant advantages of 1.0 M gadobutrol over 0.5 M Gd-DTPA were observed for time-resolved pulmonary MRA in this study. Potential explanations are T2/T2*-effects caused by the high intravascular concentration when using high injection rates.
 
Article
To measure uterine artery and vein blood velocity and flow rate profiles using MRI during normal pregnancy. A two-shot velocity magnitude-encoded echo planar imaging (EPI) sequence is used at a magnetic field 0.5T. Data analysis procedures, necessary to overcome problems associated with low signal to noise ratio (SNR), and a spatial resolution comparable to the vessel size were used. The measured blood flow values averaged over nine volunteers for the mean velocity are 5.33 and 3.97 cm/s and for the unilateral flow rate are 203 and 274 mL/min (for the arteries and veins respectively). Values for the flow rate are consistent with ultrasound Doppler studies. Arterial velocity measurements are more pulsatile than venous ones and validation calculations performed on average velocity values would suggest that the nature of blood flow in the uterine vessels is laminar. This study presents the first report of noninvasive quantitative measurements of uterine artery and vein blood velocity and flow rate profiles using MRI during normal pregnancy. Consistent and reproducible measurements have been obtained by subject specific sequence optimization and data analysis procedures.
 
Article
To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.
 
Article
Preliminary experience with phase-contrast magnetic resonance (MR) angiography at 0.5 T applied in 12 cases of vascular malformations of the spinal cord is reported. There were six intramedullary arteriovenous malformations (AVMs), four perimedullary fistulas, and two dural arteriovenous fistulas with perimedullary drainage, all proved with x-ray angiography. The small size of the vessels and their location within a bony structure presented a technical challenge. Serpentine vascular signal patterns were identified within the spinal canal in all cases, showing good correlation with the x-ray angiographic pattern. Relative to spin-echo images, MR angiograms allowed better visualization of the venous drainage. The nidus of intramedullary AVMs was more difficult to recognize. The ability to manipulate the velocity-encoding value allows better characterization of flow speed. The results underline the two dimensions of the phase-contrast technique, which provides both anatomic images and dynamic information about vascular malformations. MR angiography does not replace selective x-ray angiography, which is indispensable for therapeutic strategy (endovascular procedure or surgery), but it can be considered a valuable alternative to x-ray angiography during follow-up.
 
Article
The authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor-liver signal intensity ratios on T1-, T2-, and T2*-weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21 of 23, 91%) than on T2-weighted images (15 of 23, 65%). T1-weighted images were not useful for this distinction. In conclusion, T2*-weighted images were better than routine T2-weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*-weighted images because of an out-of-phase effect.
 
Article
Intraoperative line scan diffusion imaging (LSDI) on a 0.5 Tesla interventional MRI was performed during neurosurgery in three patients. Diffusion trace images were obtained in acute ischemic cases. Scan time per slice was 46 seconds and 94 seconds, respectively, for diffusion tensor images. Diagnosis of acutely developed vascular occlusion was confirmed with follow-up scans. White matter tracts were displayed with the principal eigenvectors and provided guidance for the tumor surgery. In all cases, the diagnostic utility of LSDI was established. J. Magn. Reson. Imaging 2001;13:115-119.
 
Article
To compare the signal characteristics and bolus dynamics of 1.0 M gadobutrol and 0.5 M Gd-DTPA for time-resolved, three-dimensional, contrast-enhanced (CE) MRA of the upper torso. Ten healthy volunteers were examined with time-resolved three-dimensional CE-MRA (scan time per three-dimensional data set: 0.86 second; voxel size: 3.6 x 2 x 6.3 mm(3)). Each volunteer underwent eight individual examinations after intravenous injection of 0.05 and 0.1 mmol/kg body weight (b.w.) of 1.0 M gadobutrol and 0.5 M Gd-DTPA using two injection rates (2.5 and 5 mL/second). The data analysis included quantitative measurements of the peak signal-to-noise ratio (SNR) and bolus dispersion (full width at half maximum (FWHM)) in the pulmonary artery, left atrium, and thoracic and abdominal aortas. No significant differences in the peak SNR and bolus dispersion were observed between gadobutrol and Gd-DTPA for all dose levels and injection rates in any of the vascular segments. For both contrast agents a dose of 0.1 mmol/kg b.w. injected with 5 mL/second achieved the highest SNR in all vascular segments. For the imaging parameters used in this study, higher-concentrated gadolinium chelates offer no relevant advantages for time-resolved three-dimensional CE-MRA of the upper torso.
 
Article
To utilize a microwave coagulator for MR-guided interstitial thermal therapy of liver tumors as a clinically feasible heating device. MR-guided microwave thermocoagulation therapy was carried out 34 times in 30 patients with liver tumors (eight hepatocellular carcinoma, 22 metastatic tumors) using a 0.5 T open configuration MR system. Percutaneous puncture could be accomplished both accurately and safely while monitoring real-time magnetic resonance imaging (MRI). Using a notch filter, MR images could be observed without electromagnetic interference even during microwave ablation. Temperature monitoring during ablation was possible using the proton resonance frequency method. All procedures could be successfully carried out without any complications, and the therapeutic effects were deemed satisfactory. MR-guided microwave thermocoagulation therapy could be one promising procedure of minimally invasive treatment for liver tumors.
 
Article
To evaluate the diagnostic efficacy of macrocyclic paramagnetic gadolinium (Gd) chelates gadoterate (0.5 mmol/mL) and gadobutrol (1.0 mmol/mL) for the diagnosis of clinically significant abdominal/lower limb arterial diseases at 3.0T. This study was conducted as a prospective, single-center, randomized, double-blind, intraindividual study comparing single dose (0.1 mmol/kg) gadoterate enhanced-MRA (magnetic resonance angiography) with gadobutrol enhanced-MRA at 3.0T for their diagnostic potential in patients with peripheral artery disease. A total of 20 patients were included in this trial. Fourteen patients were eligible for the final efficacy analysis. The overall image quality (excellent/more than adequate) was better rated with gadoterate than with gadobutrol (100% vs. 78.6%, 100% vs. 92.9%, 100% vs. 85.7%, 100% vs. 85.7% for readers 1, 2, 3, 4, respectively). Diagnostic confidence was rated high/excellent in 100% (readers 1, 2, and 3) and 92.9% (reader 4) with gadoterate compared to 92.9% (readers 1 and 2) and 85.7% (readers 3 and 4) with gadobutrol. Higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values were obtained for gadobutrol compared to gadoterate (26.1/23.4, P = 0.01, and 22.7/20.2, P = 0.01). For the secondary criteria, no differences between groups were reported. No adverse events were reported. Gadobutrol yielded significantly higher SNR/CNR while gadoterate was better rated in terms of overall image quality and diagnostic confidence (P > 0.05). J. Magn. Reson. Imaging 2012;36:1213-1221. © 2012 Wiley Periodicals, Inc.
 
Article
To determine whether MR-guided anorectal surgery is feasible, and to develop techniques for MR-guided anal fistula surgery. Six patients with pilonidal sinus (PNS), and 21 with suspected anal fistulae were operated on in the GE Signa SPIO 0.5T interventional MRI unit. Procedures were performed with magnet-safe Lockhart-Mummery fistula probes. Preprocedural and intra-operative MRI (IOMRI) techniques were used to identify the extent of the fistula tracts and septic foci, and to ensure the adequacy of the surgical procedure. IOMRI demonstrated the PNS lesions and the adequacy of excision. Imaging failed to demonstrate a fistula in two patients, as confirmed by surgical examination. No images were obtained in one patient due to his size (weight in excess of 100 kg). In 18 patients a fistula tract or abscess was demonstrated and IOMRI was used to assess the adequacy of the surgical procedure. In three patients this demonstrated incomplete drainage of septic foci, which was not obvious on inspection of the surgical field. We believe that in these patients IOMRI prevented an incomplete procedure and the potential requirement for a second operation. Further surgery was performed to rectify this situation. The fistula tract was laid open in 13 patients, and a Seton drain was inserted in five. MRI-guided surgery for anal fistula is feasible. IOMRI demonstrates the exact anatomy of the tracts and abscesses, and confirms that all have been adequately treated. We believe it may become particularly useful in surgery for recurrent and complex anal fistulae, and may lead to fewer recurrences.
 
Article
To compare endovaginal with pelvic phased array coil magnetic resonance imaging (MRI) in detection of Stage I cervical carcinoma by correlating the findings with histopathology. Patients and Forty consecutive patients with Stage I cervical carcinoma confirmed histologically were studied using an endovaginal coil alone immediately followed by a pelvic phased array coil. T1-W transverse and T2-W FSE sagittal images made with each coil were analyzed independently by two radiologists noting the presence and size of a mass within the cervix and any parametrial extension or involvement of adjacent organs. Tumor volumes were measured using the electronic calliper to compute tumor area on each slice and multiplying by the slice thickness. Thirty patients underwent radical hysterectomy, one a trachylectomy, one simple hysterectomy and four extended cone biopsies. Four patients had radiotherapy to the primary tumor. Following surgery, histopathologic findings were recorded and tumor volumes measured. Tumor volumes ranged from 0-106 cm(3)(median 1.4 cm(3), mean 9 +/- 19.4 cm(3)). Thirty-six patients had correlation of the primary site with the surgical specimen. Agreement between observers was excellent for both endovaginal (k = 0.90) and pelvic phased array (k = 0.96) techniques. Combined sensitivity and specificity for both observers of endovaginal MR imaging for detection of tumor was 96% and 70%, respectively; for pelvic phased array imaging sensitivity was substantially less at 54%. Specificity was higher at 83.7%, probably because small abnormalities were seldom visible. In patients treated surgically, early parametrial involvement in four women on endovaginal MRI was confirmed histologically in two. Pelvic phased array imaging showed early parametrial involvement in four women and was confirmed in one. Endovaginal MRI adds substantially to information from pelvic phased array images in the preoperative assessment of patients with early cervical cancer. J. Magn. Reson. Imaging 2000;12:1020-1026.
 
Article
The growing use of highly sensitive but only moderate specific breast MRI requires the development of both minimal-invasive as well as precise biopsy systems. The aim of the study was to prove the accuracy and feasibility of a biopsy procedure carried out in prone position in a vertically opened MR imager. The biopsies were carried out in 21 women with lesions visible on MRI alone using an open breast coil with an integrated biopsy device. A 14 G coaxial needle was placed under near real-time MRI-guidance. After the tip of this needle was verified in contact with the lesion, we used a non MR-compatible, but MR-safe biopsy gun with a 16 G canula to take four to eight cores. We found eight malignant and 12 benign lesions. In one patient the procedure was not successful. In case of malignancy, the operation confirmed the diagnosis in all cases. The 12/21 patients with benign lesions have been followed without evidence of lesions growth over eight to 28 months. The described procedure allows MRI-guided minimal invasive core biopsy of small breast lesions (five to 17 mm) with a high degree of accuracy.
 
Article
Glioblastoma is a malignant World Health Organization (WHO) grade IV glioma with a poor prognosis in humans. New therapeutics are desperately required. The nitrone OKN-007 (2,4-disulfophenyl-PBN) has demonstrated effective anti-glioma properties in several rodent models and is currently being used as a clinical investigational drug for recurrent gliomas. We assessed the regional effects of OKN-007 in the tumor necrotic core and non-necrotic tumor parenchyma. An F98 rat glioma model was evaluated using proton magnetic resonance spectroscopy ((1) H-MRS), diffusion-weighted imaging (DWI), morphological T2-weighted imaging (T2W) at 7 Tesla (30 cm-bore MRI), as well as immunohistochemistry and microarray assessments, at maximum tumor volumes (15-23 days following cell implantation in untreated (UT) tumors, and 18-35 days in OKN-007-treated tumors). (1) H-MRS data indicates that Lip0.9/Cho, Lip0.9/Cr, Lip1.3/Cho, and Lip1.3/Cr ratios are significantly decreased (all P < 0.05) in the OKN-007-treated group compared with UT F98 gliomas. The Cho/Cr ratio is also significantly decreased in the OKN-007-treated group compared with UT gliomas. In addition, the OKN-007-treated group demonstrates significantly lower ADC values in the necrotic tumor core and the nonnecrotic tumor parenchyma (both P < 0.05) compared with the UT group. There was also an increase in apoptosis following OKN-007 treatment (P < 0.01) compared with UT. OKN-007 reduces both necrosis and tumor cell proliferation, as well as seems to mediate multiple effects in different tumor regions (tumor necrotic core and nonnecrotic tumor parenchyma) in F98 gliomas, indicating the efficacy of OKN-007 as an anti-cancer agent and its potential clinical use. J. Magn. Reson. Imaging 2015. © 2015 Wiley Periodicals, Inc.
 
Article
To compare two different injection rates for gadoxetic acid-enhanced hepatic arterial phase images on hepatic dynamic MRI. Hepatic arterial phase images were obtained after an intravenous bolus injection of gadoxetic acid at a rate of 1 mL/second in 62 patients and 2 mL/second in 64 patients on a 3 Tesla MR scanner using a test-bolus injection method. The signal-to-noise ratios (SNR) of the liver, portal vein, hepatic vein, aorta, spleen and pancreas were measured. The contrast-to-noise ratio (CNR) of hypervascular hepatic tumors was calculated. Two radiologists independently scored items to evaluate image quality of hepatic arterial phase and detected hypervascular hepatocellular carcinoma (HCC). The SNR of the aorta on the arterial phase images was significantly higher in the 1 mL/second group (235.43 +/- 82.59) than in the 2 mL/second group (190.94 +/- 96.90, P < 0.05). The SNRs of the liver, spleen and pancreas, the CNRs of hypervascular hepatic tumors, the detection rate of hypervascular HCC and subjective ratings for the optimal arterial enhancement were comparable between the two groups. Injection rates of 2 mL/second and 1 mL/second provided comparable image qualities on arterial phase images of hepatic dynamic MRI using gadoxetic acid.
 
Rectal carcinoma in a 69-year-old male patient. T2-weighted transverse image (a), b800 DWIs (b,c), and ADC maps (d,e) from the first MRI scan with two diffusion-weighted sequences. The arrow indicates the tumor.
Bland-Altman plot of intraobserver repeatability of ADC. The horizontal dashed line represents the bias, and the dotted lines represent the 95% confidence interval.
Bland-Altman plot of repeatability of ADC within the MRI protocol for the rectal tumor. The horizontal dashed line represents the bias, and the dotted lines represent the 95% confidence interval.
Bland-Altman plot of repeatability of ADC within the MRI protocol for the prostate central gland in the first 10 male patients. The horizontal dashed line represents the bias, and the dotted lines represent the 95% confidence interval.
Article
Serial diffusion-weighted MRI (DW-MRI) measurements of the apparent diffusion coefficient (ADC) of rectal tumors are used for rectal cancer response evaluation after neo-adjuvant treatment. In this study, we determined the repeatability of DW-MRI to distinguish therapy-related response from measurement variations. In 18 patients with rectal cancer on five consecutive days, 1.5 Tesla (T) MR imaging was performed including two identical DW-MRI sequences. The repeatability of the tumor ADC measurements and the intraobserver ADC variation were depicted in a Bland-Altman plot. The repeatability coefficient was calculated as the range of ADC values of two identical DWI measurements for 95% of subjects. It was expressed as percentage of the mean ADC value. Three females and 15 males were included. The mean tumor ADC value was 1.15 × 10(-3) mm(2) /s (SD 0.07 × 10(-3) mm(2) ). The repeatability coefficient of the ADC value was 9.8% and for the intraobserver repeatability 4.7%. In serial DW-MRI for rectal cancer treatment response evaluation, a repeatability coefficient of 9.8% has to be considered to account for measurement variations in rectal tumor ADC. These variations represent observer judgement and patient and MR spectrometer induced variations. J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
 
Article
The purpose of this study was to determine the diagnostic value of the superparamagnetic iron oxide NSR 0430 for the detection of focal liver lesions in the presence of advanced cirrhosis. Cirrhosis and growth of cholangiofibromas were induced in 22 rats by administration of thioacetamide. Sixteen non-cirrhotic animals served as controls. T1 and T2 relaxation times of liver and tumor tissue of 12 animals were measured spectroscopically. In 10 animals in vivo MRI was performed before and 1 hour after contrast administration, and then the tumor-to-liver contrast-to-noise ratio (CNR) was calculated. All specimens were evaluated histologically. After contrast administration, T1 and T2 values of liver tissue showed a significant decrease of 18% (P = 0.01) and 31% (P = 0.009), respectively, whereas relaxation times of tumor tissue did not change. On precontrast turbo spin-echo images, 40 tumors could be identified; after contrast administration, 95 lesions were visible. CNR increased significantly after contrast administration by 297% at a TE of 50 msec and by 254% at a TE of 90 msec. In conclusion, our in vitro and in vivo results demonstrate that administration of NSR 0430 substantially improves liver-to-tumor CNR and lesion detection on T2-weighted magnetic resonance images even in the presence of severe cirrhosis.
 
Article
To examine the effects of the alkylating anticancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) on (23)Na MRI and the water apparent diffusion coefficient (ADC) in subcutaneously- (sc-) implanted 9L glioma in rats. (23)Na MRI and (1)H water ADC measurements were performed on sham-treated control (N = 6) and BCNU-treated (N = 15) Fisher rats one day before BCNU injection and then one, three, and five days after BCNU injection. The BCNU-treated tumors were divided into BCNU-responsive (R(BCNU)) and BCNU-nonresponsive (NR(BCNU)) groups depending on the tumor volume changes that occurred after therapy. The pretreatment (23)Na MRI signal intensity (SI) and water ADC values were higher in R(BCNU) tumors compared to NR(BCNU) tumors. (23)Na MRI SI and water ADC increased with tumor growth in control and NR(BCNU) groups, but these changes were interrupted by BCNU therapy in R(BCNU) group. (23)Na MRI and water ADC measurements may be useful for predicting and monitoring response to chemotherapy in some tumors. However, the changes that occurred in (23)Na MRI SI and water ADC in sc-implanted 9L tumors are in contrast to previously published results for BCNU therapy of orthotopic 9L tumors. This may have important implications for monitoring therapy response in tumors.
 
Article
Ten cases of hepatic focal nodular hyperplasia (FNH) were studied with magnetic resonance (MR) imaging. Proof of diagnosis was by needle biopsy or follow-up of as long as 5 years. Both short TR/TE and long TR/TE images were obtained. The most common finding was isointensity of the lesion relative to liver parenchyma with all pulse sequences. A central scar was seen in only one patient and was hyperintense on long TR/TE images. Slight hyperintensity of the lesion on short TR/TE and long TR/TE images was seen in two cases. Textural heterogeneity was present in only one of these. The most common presentation in our series was a visually isointense lesion relative to liver on short TR/TE images and an isointense or slightly hyperintense lesion on long TR/TE images. A review of the literature and the present findings suggest that FNH has a variable appearance on MR images.
 
Article
To demonstrate the noninferiority of gadobutrol-enhanced magnetic resonance imaging (MRI) compared with gadopentetate dimeglumine-enhanced MRI in Asian patients referred for contrast-enhanced imaging of the body or extremities. A multicenter, parallel-group comparison study of Asian adults referred for contrast-enhanced MRI were randomized (1:1) to either gadobutrol or gadopentetate dimeglumine. Lesions were assessed for three primary visualization variables: degree of contrast enhancement, border delineation, and internal morphology. Secondary efficacy variables included number of lesions detected, match of MRI diagnosis with final clinical diagnosis, and sensitivity and specificity for malignant lesion detection. Safety was monitored for 24 ± 4 hours after contrast agent administration. A total of 363 patients received either gadobutrol (n = 168) or gadopentetate dimeglumine (n = 178). Mean total scores for three primary visualization variables were 9.39 and 9.34 for gadobutrol and gadopentetate dimeglumine, respectively. The proportion of patients with matched MRI and final diagnosis and sensitivity for malignant lesion detection was greater for unenhanced versus combined images (gadobutrol: 72.2% vs. 81.7%; gadopentetate dimeglumine: 76.2% vs. 82.2%, respectively). Both contrast agents were well tolerated. Gadobutrol (0.1 mmol/kg BW) was well tolerated and effective in Asian patients referred for contrast-enhanced MRI of the body or extremities.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
 
Article
Echo-planar imaging (EPI) on the authors' 1-T prototype imager provides high-quality 100-msec images of the central nervous system. Contrast parameters can be chosen freely. Three-dimensional EPI sequences provide isotropically resolved data sets with 1-mm resolution. Brain perfusion and blood-brain barrier disruption can be assessed in time-course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.
 
Article
Gadobutrol is a 1.0 M macrocyclic magnetic resonance imaging (MRI) contrast agent. A study was performed to evaluate the efficacy and safety of gadobutrol-enhanced versus unenhanced imaging for central nervous system (CNS) lesion visualization and detection. An international, multicenter, open-label, Phase III clinical trial. Patients underwent unenhanced and gadobutrol 1.0 M-enhanced (0.1 mmol/kg BW) MR imaging using a standardized protocol. Unenhanced and combined unenhanced/gadobutrol-enhanced images were scored by three independent, blinded readers for degree of lesion enhancement, border delineation, internal morphology, and total number of lesions detected (primary efficacy variables). Exact match of the MR diagnoses with the final clinical diagnosis, detection of malignant CNS lesions, and confidence in diagnosis were secondary efficacy variables. Of 343 enrolled patients, 321 were evaluated for efficacy. All primary efficacy endpoints were met: superiority was demonstrated for gadobutrol-enhanced versus unenhanced MR images (P < 0.0001 in all cases) for lesion enhancement, border delineation, and internal morphology. Noninferiority was met for mean number of lesions detected. There were improvements in the sensitivity of malignant lesion detection, without a loss in specificity, exact-match diagnostic accuracy, and reader confidence. Treatment-related adverse events were reported in 4.1% (n = 14); all were nonserious. Gadobutrol 1.0M is an effective and well-tolerated contrast agent for CNS MRI.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
 
Article
To validate an unspoiled gradient-recalled echo pulse sequence with dual echo acquisition as a means to increase temperature sensitivity while monitoring intradiscal laser ablation therapy. Phantom experiments as well as in vitro thermal ablation simulations were performed in an open 1.0T magnetic resonance (MR) scanner. Three methods of noninvasive MR-thermometry based on the signal void decrease caused by T1-relaxation time increase (T1), the temperature-dependent proton resonance frequency (PRF) shift, and a combination of both methods with complex differences (CD) were compared. Temperature accuracy and reliability of temperature distribution were the main assessment criteria. The optimum temperature sensitivity was found using CD in phantom experiments. During in vitro experiments the PRF showed the smallest margin of error (T1: +/-1.64 degrees C, PRF: +/-1.23 degrees C, CD: +/-1.29 degrees C) and the best qualitative evaluation of temperature. Intradiscal temperature monitoring with an unspoiled dual-echo sequence is most accurate with PRF-thermometry in combination with the long echo time. Magnitude images with an initial short echo time permit high image detail of the heat-induced lesion.
 
Top-cited authors
Scott Reeder
  • University of Wisconsin–Madison
Paul Stephen Tofts
  • University of Sussex
Ferenc A Jolesz
  • Harvard Medical School
Richard Semelka
  • University of North Carolina at Chapel Hill
Frank Shellock
  • University of Southern California