Open High-field MRI Research Articles

MR-guided percutaneous biopsy of solitary pulmonary lesions using a 1.0-T open high-field MRI scanner with respiratory gating.

To prospectively evaluate the feasibility, safety and accuracy of MR-guided percutaneous biopsy of solitary pulmonary lesions using a 1.0-T open MR scanner with respiratory gating. Sixty-five patients with 65 solitary pulmonary lesions underwent MR-guided percutaneous coaxial cutting needle biopsy using a 1.0-T open MR scanner with respiratory gating. Lesions were divided into two groups according to maximum lesion diameters: ≤2.0cm (n = 31) and >2.0cm (n = 34). The final diagnosis was established in surgery and subsequent histology. Diagnostic accuracy, sensitivity and specificity were compared between the groups using Fisher's exact test. Accuracy, sensitivity and specificity of MRI-guided percutaneous pulmonary biopsy in diagnosing malignancy were 96.9%, 96.4% and 100%, respectively. Accuracy, sensitivity and specificity were 96.8%, 96.3% and 100% for lesions 2.0cm or smaller and 97.1%, 96.4% and 100%, respectively, for lesions larger than 2.0cm. There was no significant difference between the two groups (P > 0.05). Biopsy-induced complications encountered were pneumothorax in 12.3% (8/65) and haemoptysis in 4.6% (3/65). There were no serious complications. MRI-guided percutaneous biopsy using a 1.0-T open MR scanner with respiratory gating is an accurate and safe diagnostic technique in evaluation of pulmonary lesions. • MRI-guided percutaneous lung biopsy using a 1.0-T open MR scanner is feasibility. • 96.9% differentiation accuracy of malignant and benign lung lesions is possible. • No serious complications occurred in MRI-guided lung biopsy.

Feasibility of high dose dobutamine stress and scar imaging in high field open MRI in patients with suspected coronary artery disease

Feasibility of high dose dobutamine stress and scar imaging in high field open MRI in patients with suspected coronary artery disease

Osteoid Osteoma with a Multicentric Nidus: Interstitial Laser Ablation under MRI Guidance

Osteoid osteoma (OO) is a common benign tumor of the bone and is typically treated by thermal ablation with computed tomography (CT) guidance. Only a few cases of multicentric OO have been described. We here report the case of an 11-year-old boy with multicentric OO of the right femur treated with laser ablation under open high-field MRI guidance. The steps of the interventional MRI procedure are described, discussing the benefits and disadvantages of MRI versus CT guidance especially with regard to younger patients.

Feasibility of high dose dobutamine stress and scar imaging in high field open MRI in patients with suspected coronary artery disease

Background High-dose dobutamine-stress magnetic resonance (DSMR) and late gadolinium enhanced cardiac magnetic resonance (LGE-CMR) imaging are well established for the detection of significant cardiovascular disease (CAD) and infarction for cylindrical 1.5 T or 3T. Due to the narrow bore, patients (pts) with obesity or claustrophobia usually cannot be studied with conventional MRI scanners. 1.0T high field open (HFO) is a non-cylindrical MRI system offering significantly more space but has only rarely been utilized for diagnostic cardiac MRI so far. In this pilot study we sought to investigate the performance of 1.0T HFO DSMR and LGE-CMR in pts with suspected CAD and low to intermediate risk profile.

Maximum instrument length for MR-guided minimal-invasive interventions of the lumbar spine in open high-field MRI

Maximum instrument length for MR-guided minimal-invasive interventions of the lumbar spine in open high-field MRI

Heating of conductive wires in an open high field MRI environment: Effect of different wire positions in the MR scanner room

Heating of conductive wires in an open high field MRI environment: Effect of different wire positions in the MR scanner room

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

Comparison of temperature measurements of pacemaker leads in a 1.0T high field open MRI and a 1.5T classic cylindrical MRI: initial results

As of today, the use of MRI procedures on patients with implanted cardiac pacemakers is prohibited due to safety issues. The implants can interact with the RF fields of the MRI device. The most hazardous effect is heating at the tip of the lead, less dangerous are sensing errors and malfunctions of the devices, because they disappear completely after the procedure. The majority of the previous studies used classic cylindrical whole-body MRI systems. The influence of different alignments of the pacemaker/lead system and the RF fields were evaluated by comparing temperature changes occurring in a cylindrical device with the effects induced in a high field open MRI (HFO) system.

Recurrent osteoid osteoma: interstitial laser ablation under magnetic resonance imaging guidance

Thermal ablation has become a therapy of choice in the treatment of osteoid osteomas. To date, computed tomography has been the standard imaging modality for minimally invasive treatment regimes. We report a case of a 46-year-old man with a recurrent osteoid osteoma in the right tibial head after CT-guided drill excision and repeat treatment with laser ablation under open high-field MRI guidance. We describe the steps of the interventional MRI procedure and discuss related innovative guidance and monitoring features, and potential benefits of MRI compared with CT-guided techniques. In conclusion, MR-guided laser ablation was proved to be safe and effective.

Laser-induced thermotherapy (LITT)—evaluation of a miniaturised applicator and implementation in a 1.0-T high-field open MRI applying a porcine liver model

To evaluate the feasibility and safety of a novel LITT applicator for thermal ablation of liver malignancies in 1.0-T high-field open MRI. A miniaturised 6-F double-tubed protective catheter with a closed cooling circuit was used with a flexible laser fibre, connected to a 1,064-nm Nd:YAG laser and evaluated in non-perfused porcine livers (18-30W for 10-20min, 2-W and 2-min increments; n = 210/applicator) in reference to an established 9-F system. As a proof of concept, MR-guided LITT was performed in two healthy domestic pigs in high-field open MRI. Ex-vivo, the coagulation volumes induced by the 6-F system with maximum applicable power of 24W for 20min (33.0 ± 4.4cm(3)) did not differ significantly from those set with the 9-F system at 30W for 20min (35.8 ± 4.9cm(3)) (p = 0.73). A flow-rate of 15ml/min of the cooling saline solution was sufficient. MR navigation and thermometry were feasible. The miniaturised 6-F applicator can create comparable coagulation sizes to those of the 9-F system. Applicator guidance and online-thermometry in high-field open MRI are feasible.

MR-guided liver tumor ablation employing open high-field 1.0T MRI for image-guided brachytherapy

To determine the feasibility and safety of image-guided brachytherapy employing a modified open high-field MR system. This is a follow-up study of a development project enabling technologies for interventional use of 1.0T open MRI. Modifications included coils and in-bore visualization, fluoroscopic sequences and user interfaces. We recruited 104 patients with 224 liver malignancies to receive MR-guided brachytherapy. Interventions were performed >20 min after Gd-EOB-DTPA. We recorded interventional parameters including the intervention time (from acquisition of the first scout until the final sequence for brachytherapy treatment planning). Two reviewers assessed MR-fluoroscopic images in comparison to plain CT as used in CT intervention, applying a rating scale of 1-10. Statistical analysis included Friedman and Kendall's W tests. We employed freehand puncture with interactive dynamic imaging for navigation. Technical success rate was 218 complete ablations in 224 tumours (97%). The median intervention time was 61 min. We recorded no adverse events related to the use of MRI. No major complications occurred. The rate of minor complications was 4%. Local control at 3 months was 96%. Superiority of MR-fluoroscopic, Gd-EOB-DTPA-enhanced images over plain CT was highly significant (P < 0.001). MR-guided brachytherapy employing open high-field MRI is feasible and safe.

Image-guided spinal injection procedures in open high-field MRI with vertical field orientation: feasibility and technical features

We prospectively evaluated the feasibility and technical features of MR-guided lumbosacral injection procedures in open high-field MRI at 1.0 T. In a CuSO(4).5H(2)O phantom and five human cadaveric spines, fluoroscopy sequences (proton-density-weighted turbo spin-echo (PDw TSE), T1w TSE, T2w TSE; balanced steady-state free precession (bSSFP), T1w gradient echo (GE), T2w GE) were evaluated using two MRI-compatible 20-G Chiba-type needles. Artefacts were analysed by varying needle orientation to B(0), frequency-encoding direction and slice orientation. Image quality was described using the contrast-to-noise ratio (CNR). Subsequently, a total of 183 MR-guided nerve root (107), facet (53) and sacroiliac joint (23) injections were performed in 53 patients. In vitro, PDw TSE sequence yielded the best needle-tissue contrasts (CNR = 45, 18, 15, 9, and 8 for needle vs. fat, muscle, root, bone and sclerosis, respectively) and optimal artefact sizes (width and tip shift less than 5 mm). In vivo, PDw TSE sequence was sufficient in all cases. The acquisition time of 2 s facilitated near-real-time MRI guidance. Drug delivery was technically successful in 100% (107/107), 87% (46/53) and 87% (20/23) of nerve root, facet and sacroiliac joint injections, respectively. No major complications occurred. The mean procedure time was 29 min (range 19-67 min). MR-guided spinal injections in open high-field MRI are feasible and accurate using fast TSE sequence designs.

Imaging sequences for intraoperative MR-guided laparoscopic liver resection in 1.0-T high field open MRI

The aim of this study was to identify suitable interactive (dynamic) magnetic resonance (MR) sequences for real-time MR-guided liver dissection in a 1.0-T high field open MRI system. Four dynamic sequences encompassing balanced steady state free precession (bSSFP), T1W gradient echo (GRE), T2W GRE and T2W fast spin echo (FSE) were analysed regarding the image quality, artefact susceptibility and the performance of SNR and CNR. The T2W FSE sequence (1.5 s/image) was considered superior because of an intraoperative SNR of 6.9 (+/-0.7) and CNR (vessel to parenchyma) of 5.6 (+/-1.7) in the interventional setting. As a proof of concept, MR-guided laparoscopic liver resection was performed in two healthy domestic pigs by using the T2W FSE sequence. The additional MR images offered simultaneous multiplanar real-time visualisation of the liver vessels during the intervention and thereby increased the anatomical orientation of the surgeon.

Three-Dimensional Optimization of Correction Iron Pieces for Open High Field MRI System

We have developed a new magnet for open high field (0.7 T) MRI systems. In order to homogenize magnetic fields in the field of view, an optimization method to determine initial configurations of large correction iron pieces was developed. In our method, we combined linear programming (LP) and 3D magnetic FEA and, using analytic formulae for LP, we computed field harmonics due to the volume of magnetized iron.

Shielding Stray Magnetic Fields of Open High Field MRI Magnets

We have developed a new magnet for open high field (0.7 T) MRI systems. Since MRI systems are installed in hospital sites, it is important to reduce stray magnetic fields of the magnets. We studied passive, active and hybrid shielding methods and compared them. In order to study feasibility of active shielding, we considered higher order multipole stray fields. We present details of the calculation method and the results.

Shielding stray magnetic fields of open high field MRI magnets

We have developed a new magnet for open high field (0.7 T) MRI systems. Since MRI systems are installed in hospital sites, it is important to reduce stray magnetic fields of the magnets. We studied passive, active and hybrid shielding methods and compared them. In order to study feasibility of active shielding, we considered higher order multipole stray fields. We present details of the calculation method and the results.

MRI is nondiagnostic in cervical spine imaging of the helmeted football player with shoulder pads.

It is currently recommended that helmet and shoulder pads remain in place during the initial clinical and radiographic evaluation of the helmeted athlete with a potential cervical spine injury. The objective of this prospectively designed, single-subject study was to determine whether MRI may play a role in the initial evaluation and management of the helmeted football player with a cervical spine injury. One male athlete was fitted using equipment (football helmet [Riddell], shoulder pads [Douglas]) worn during the collegiate season at Lehigh University. Standard MRI using a routine clinical 0.7 T high field open MRI scanner (GE Signa System, Milwaukee, WI) was employed for the evaluation using standard clinical parameters (sagittal T1, fast spin echo [FSE] T2, STIR, and axial FSE T2 series). A single board-certified, fellowship-trained neuroradiologist reviewed all series. Studies were evaluated for image clarity and diagnostic capability in this clinical setting. All standard MRI series were of extremely limited quality, even using sequences and slice selection designed to minimize artifact associated with metals (FSE T2-weighted series). When all MRI series were reviewed as a whole, sufficient evidence was not available to allow clinical decision making. The amount and type of metal within the standard football helmet and shoulder pads result in sufficient field inhomogeneity and SKEW artifact to preclude adequate evaluation of the cervical structures, rendering MRI evaluation in this setting not clinically useful. This study shows that current MRI techniques play no role in the clearance of the cervical spine (with currently available brands of helmet and shoulder pads in place) without prior equipment removal or manipulation.