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Purpose: To reduce the inter‐scanner variability of diffusion MRI (dMRI) measures between scanners from different vendors by developing a vendor‐neutral dMRI pulse sequence using the open‐source vendor‐agnostic Pulseq platform. Methods: We implemented a standard EPI based dMRI sequence in Pulseq. We tested it on two clinical scanners from different vendors (Siemens Prisma and GE Premier), systematically evaluating and comparing the within‐ and inter‐scanner variability across the vendors, using both the vendor‐provided and Pulseq dMRI sequences. Assessments covered both a diffusion phantom and three human subjects, using standard error (SE) and Lin's concordance correlation to measure the repeatability and reproducibility of standard DTI metrics including fractional anisotropy (FA) and mean diffusivity (MD). Results: Identical dMRI sequences were executed on both scanners using Pulseq. On the phantom, the Pulseq sequence showed more than a 2.5× reduction in SE (variability) across Siemens and GE scanners. Furthermore, Pulseq sequences exhibited markedly reduced SE in‐vivo, maintaining scan‐rescan repeatability while delivering lower variability in FA and MD (more than 50% reduction in cortical/subcortical regions) compared to vendor‐provided sequences. Conclusion: The Pulseq diffusion sequence reduces the cross‐scanner variability for both phantom and in‐vivo data, which will benefit multi‐center neuroimaging studies and improve the reproducibility of neuroimaging studies. [ABSTRACT FROM AUTHOR]

Abstract Background Image-guided surgery with an open magnetic resonance imaging (MRI) system is applied for brain tumors in the neurosurgery field, but has rarely been reported in pediatric surgery. We report our initial experience of intraoperative confirmation of precision rectal pull-through during laparoscopically assisted anorectoplasty (LAARP) in an open MRI operating theater for pediatric patients with anorectal malformation (ARM). Case presentation A 3.0 kg term male neonate was delivered with anorectal malformation. An invertogram revealed the intermediate type. Transverse colostomy was made on the left upper abdomen. The recto-bulbar urethral fistula (RBUF) was diagnosed by a distal colostogram and voiding cystourethrogram. LAARP was planned at 6 months of age. Because this was the first procedure in which the pediatric abdomen had been scanned in an open MRI operating theater in our institution, we scanned his pelvic floor under sedation 3 weeks before the operation using the open MRI system in our operation room. We performed the operation with 4 trocars. The peritoneal reflection was carefully incised and the rectum was dissected. The RBUF was resected. The center of the muscle complex was detected at the perineal skin with an electrical nerve stimulator, and a 7-mm longitudinal skin incision was made on the perineal lesion for anoplasty. The muscle complex and the pubo-rectal sling were confirmed laparoscopically using a 3.5-mm bipolar forceps connected to the electrical nerve stimulator. Anoplasty was performed between the rectal stump and perineal skin. After anoplasty, the patient was scanned with open MRI under general anesthesia. We attached the quadrature-detection (QD) head coil around the patient’s pelvis and inserted him in the gantry. A 0.45-T open MRI clearly revealed that the pulled through rectum was located in the center of the muscle complex on T2-weighted images. The postoperative course was uneventful. Oral intake was started on post-operative day 1. Postoperative dynamic urography showed no complication (e.g., leakage or residual fistula). Conclusions We successfully performed LAARP for ARM, with intraoperative confirmation of precision rectal pull-through in an open MRI operating theater. Further cases are required to evaluate the application of open MRI systems in pediatric surgery.

Awake craniotomy with intraoperative open magnetic resonance imaging (MRI) requires special anesthesia management, wherein the use of an anesthesia information management system (AIMS) is important. However, automatic recording using AIMS is generally difficult because of potential noise from electronic devices affecting magnetic resonance images and device malfunction due to magnetic fields emitted during MRI. At our hospital, we have confirmed that wireless local area network (LAN) radio waves do not cause noise during MRI, and have designed a shielded box to house the wireless transmitter and electronic devices that allow a wireless LAN to pass through but shield the electronic devices from noise, thus enabling AIMS recording via a wireless LAN, even during MRI. We demonstrated the usefulness of this system with a wireless LAN connection in three cases of awake craniotomy with open MRI.

Purpose: To introduce a framework for rapid prototyping of MR pulse sequences. Methods: We propose a simple file format, called “TOPPE”, for specifying all details of an MR imaging experiment, such as gradient and radiofrequency waveforms and the complete scan loop. In addition, we provide a TOPPE file “interpreter” for GE scanners, which is a binary executable that loads TOPPE files and executes the sequence on the scanner. We also provide MATLAB scripts for reading and writing TOPPE files and previewing the sequence prior to hardware execution. With this setup, the task of the pulse sequence programmer is reduced to creating TOPPE files, eliminating the need for hardware‐specific programming. No sequence‐specific compilation is necessary; the interpreter only needs to be compiled once (for every scanner software upgrade). We demonstrate TOPPE in three different applications: k‐space mapping, non‐Cartesian PRESTO whole‐brain dynamic imaging, and myelin mapping in the brain using inhomogeneous magnetization transfer. Results: We successfully implemented and executed the three example sequences. By simply changing the various TOPPE sequence files, a single binary executable (interpreter) was used to execute several different sequences. Conclusion: The TOPPE file format is a complete specification of an MR imaging experiment, based on arbitrary sequences of a (typically small) number of unique modules. Along with the GE interpreter, TOPPE comprises a modular and flexible platform for rapid prototyping of new pulse sequences. Magn Reson Med 79:3128–3134, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Purpose: Recurrent patellar dislocation is currently treated with anatomical reconstruction of the medial patellofemoral ligament (MPFL), and favourable postoperative outcomes have been reported. However, it is uncertain if healthy MPFL function is restored by anatomical reconstruction. The hypothesis in this study was that stabilization of the patella following MPFL reconstruction would be improved compared with that before surgery, but that function of the grafted tendon would differ from that of a healthy MPFL. The objective was to analyse the length change patterns of the MPFL before surgery and the grafted tendon after surgery in patients with recurrent patellar dislocation treated with anatomical MPFL reconstruction.Methods: The subjects were 12 patients (13 knees) in whom recurrent patellar dislocation was treated with anatomical MPFL reconstruction. The length change patterns of the MPFL and reconstructed ligament were analysed at extension and flexion of the knee joint using open MRI.Results: The postoperative grafted tendon length was significantly shorter than that of the preoperative MPFL at knee extension, and significantly longer at 90° and 120° of knee flexion. The postoperative length of the grafted tendon only changed slightly from 0° to 30° of knee flexion, and then significantly decreased at flexion of 30° or more. The morphology of the grafted tendon was linear until 60° knee flexion, but became convex toward the extraarticular side at flexion of 90° or more.Conclusion: The grafted tendon length at knee extension was shorter than that of the preoperative MPFL, but there was no significant difference at 30° flexion. These findings suggest that the effect of damping of the patella with a grafted tendon after MPFL reconstruction may differ from that in a healthy knee. In addition, the morphology at 60° knee flexion was improved to linear after surgery, suggesting that ligament morphology at this flexion was normalized by MPFL reconstruction.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: To design planar gradient coil for MRI applications without discretization of continuous current density and loop-loop connection errors.Methods: In the new design method, the coil current is represented using a spiral curve function described by just a few control parameters. Using a proper parametric equation set, an ensemble of spiral contours is reshaped to satisfy the coil design requirements, such as gradient linearity, inductance and shielding.Results: In the given case study, by using the spiral coil design, the magnetic field errors in the imaging area were reduced from 5.19% (non-spiral design) to 4.47% (spiral design) for the transverse gradient coils, and for the longitudinal gradient coil design, the magnetic field errors were reduced to 5.02% (spiral design). The numerical evaluation shows that when compared with conventional wire loop, the inductance and resistance of spiral coil was reduced by 11.55% and 8.12% for x gradient coil, respectively.Conclusion: A novel spiral gradient coil design for biplanar MRI systems, the new design offers better magnetic field gradients, smooth contours than the conventional connected counterpart, which improves manufacturability. [ABSTRACT FROM AUTHOR]

Existing open magnetic resonance imaging (MRI) systems use biplanar gradient coils for the spatial encoding of signals. We propose using novel oval gradient coils for an open vertical-field MRI. We designed oval gradients for a 0.3 T open MRI system and showed that such a system could outperform a traditional biplanar gradient system while maintaining adequate gradient homogeneity and subject accessibility. Such oval gradient coils would exhibit high efficiency, low inductance and resistance, and high switching capability. Although the designed oval Y and Z coils showed more heat dissipation and less cooling capability than biplanar coils with the same gap, they showed an efficient heat-dissipation path to the surrounding air, which would alleviate the heat problem. The performance of the designed oval-coil system was demonstrated experimentally by imaging a human hand. [ABSTRACT FROM AUTHOR]

ABSTRACT Open MRI in functional positions has potential to directly and non-invasively assess cam femoroacetabular impingement (FAI). Our objective was to investigate whether open MRI can depict intrusion of the cam deformity into the intra-articular joint space, and whether intrusion is associated with elevated acetabular contact force. Cadaver hips (9 cam; 3 controls) were positioned in an anterior impingement posture and imaged using open MRI with multi-planar reformatting. The β-angle (describing clearance between the femoral neck and acetabulum) was measured around the entire circumference of the femoral neck. We defined a binary 'MRI cam-intrusion sign' (positive if β < 0°). We then instrumented each hip with a piezoresistive sensor and conducted six repeated positioning trials, measuring acetabular contact force (F). We defined a binary 'contact-force sign' (positive if F > 20N). Cam hips were more likely than controls to have both a positive MRI cam-intrusion sign ( p = 0.0182, Fisher's exact test) and positive contact-force sign ( p = 0.0083), which represents direct experimental evidence for cam intrusion. There was also a relationship between the MRI cam-intrusion sign and contact-force sign ( p = 0.033), representing a link between imaging and mechanics. Our findings indicate that open MRI has significant potential for in vivo investigation of the cam FAI mechanism. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:205-216, 2016. [ABSTRACT FROM AUTHOR]

Purpose: A bilateral filter (BF) has the property of de-noising digital images while preserving edges. This paper investigates the impact of selecting the BF variables in order to diminish the deterioration of SNR due to reducing the number of excitations (NEX) per image in magnetic resonance imaging (MRI) technique. The paper studies the behavior of the BF on the axial, sagittal, and coronal MRI orientations acquired by spin echo (SE), turbo spin echo (TSE), and the fluid attenuated inversion recovery (FLAIR) pulse sequences from an open MRI device. Method: a set of MRI head images where acquired at different NEXs. The BF was applied at various values of window sizes, filter domains, and filter ranges. The comparison between the high NEX and the BF low NEX MR images was calculated using the peak signal-to-noise ratio (PSNR), the mean-square error (MSE), and the normalized absolute error (NAE). Results: Numerically, the BF is able to achieve up to 29, 44, and 59 % noise suppression from the T2 axial, T1 sagittal, and coronal MR views, respectively. Conclusions: The BF can successfully compensate a part of the SNR decrease due to reduce NEX. The behavior of the BF varies with the type of MR view and the type of pulse sequence. The BF is a successful tool to enhance the appearance of low NEX MR images acquired from open MR devices. This means that BF can contribute in shortening the MRI scan time. [ABSTRACT FROM AUTHOR]

The evaluation of the glenohumeral joint laxity requires the estimate of displacements of the humeral head centre (HHC) with respect to the glenoid. To the authors? knowledge, several studies have been conducted to estimate HHC translations in vivo but data under anterior loading conditions has not been collected yet. Aim of this study was to develop a non-invasive experimental methodology based on magnetic resonance (MR) imaging for the in vivo evaluation of the HHC translations due to an anteriorly directed force. Fourteen asymptomatic shoulders were acquired using a horizontal open MR scanner with the subjects in the supine position both at 15° and 90° of arm abduction with and without an anterior force of 20 N applied at the HHC level. When no load was applied, from 15° to 90° of arm abduction, the HHC moved, anteriorly (1.5±1.3 mm) and superiorly (1.8±1.3 mm) while smaller displacements were observed medio-laterally (0.4±0.7 mm). Under the application of the anterior force the 3D displacement of the HHC with respect to the glenoid was 1.6±1.2 mm and 1.3 ±0.7 mm, respectively at 15° and 90° of arm abduction. The level of precision associated to the GHJ translation was less than 0.33 mm along all directions i.e. one order of magnitude smaller than the relevant translations. In conclusion, the MRI-based methodology allowed for the analysis of HHC displacements under conditions of anterior loads within an acceptable level of reliability. [ABSTRACT FROM AUTHOR]

Background In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant. Methods Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior–posterior meniscal movement, radial displacement, and meniscal height. Findings No difference ( P > 0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height ( P > 0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference ( P ≤ 0.05) in anterior–posterior movement during flexion was observed between the two groups. Interpretation In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior–posterior movement was slightly different between the implant and the normal meniscus. [ABSTRACT FROM AUTHOR]

Abstract: Open-configuration magnetic resonance imaging (MRI) systems are becoming increasingly desirable for musculoskeletal imaging and image-guided radiotherapy because of their non-claustrophobic configuration. However, geometric image distortion in large fields-of-view (FOV) due to field inhomogeneity and gradient nonlinearity hinders the practical applications of open-type MRI. We demonstrated the use of geometric distortion correction for increasing FOV in open MRI. Geometric distortion was modeled and corrected as a global polynomial function. The appropriate polynomial order was identified as the minimum difference between the coordinates of control points in the distorted MR image space and those predicted by polynomial modeling. The sixth order polynomial function was found to give the optimal value for geometric distortion correction. The area of maximum distortion was<1 pixel with an FOV of 285mm. The correction performance error was increased at most 1.2% and 2.9% for FOVs of 340mm and~400mm compared with the FOV of 285mm. In particular, unresolved distortion was generated by local deformation near the gradient coil center. [Copyright &y& Elsevier]

Purpose: To evaluate the accuracy, safety, and efficacy of cervical nerve root injection therapy using magnetic resonance guidance in an open 1.0 T MRI system. Methods: Between September 2009 and April 2012, a total of 21 patients (9 men, 12 women; mean age 47.1 ± 11.1 years) underwent MR-guided cervical periradicular injection for cervical radicular pain in an open 1.0 T system. An interactive proton density-weighted turbo spin echo (PDw TSE) sequence was used for real-time guidance of the MR-compatible 20-gauge injection needle. Clinical outcome was evaluated on a verbal numeric rating scale (VNRS) before injection therapy (baseline) and at 1 week and 1, 3, and 6 months during follow-up. Results: All procedures were technically successful and there were no major complications. The mean preinterventional VNRS score was 7.42 and exhibited a statistically significant decrease ( P < 0.001) at all follow-up time points: 3.86 ± 1.53 at 1 week, 3.21 ± 2.19 at 1 month, 2.58 ± 2.54 at 3 months, and 2.76 ± 2.63 at 6 months. At 6 months, 14.3 % of the patients reported complete resolution of radicular pain and 38.1 % each had either significant (4-8 VNRS score points) or mild (1-3 VNRS score points) relief of pain; 9.5 % experienced no pain relief. Conclusion: Magnetic resonance fluoroscopy-guided periradicular cervical spine injection is an accurate, safe, and efficacious treatment option for patients with cervical radicular pain. The technique may be a promising alternative to fluoroscopy- or CT-guided injections of the cervical spine, especially in young patients and in patients requiring repeat injections. [ABSTRACT FROM AUTHOR]

Objectives: To assess the feasibility, safety and efficacy of real-time MR guidance and thermometry of percutaneous laser disc decompression (PLDD). Methods: Twenty-four discs in 22 patients with chronic low-back and radicular pain were treated by PLDD using open 1.0-T magnetic-resonance imaging (MRI). A fluoroscopic proton-density-weighted turbo spin-echo (PDw TSE) sequence was used to position the laser fibre. Non-spoiled gradient-echo (GRE) sequences were employed for real-time thermal monitoring based on proton resonance frequency (PRF). Radicular pain was assessed over 6 months with a numerical rating scale (NRS). Results: PLDD was technically successful in all cases, with adequate image quality for laser positioning. The PRF-based real-time temperature monitoring was found to be feasible in practice. After 6 months, 21 % reported complete remission of radicular pain, 63 % at least great pain relief and 74 % at least mild relief. We found a significant decrease in the NRS score between the pre-intervention and the 6-month follow-up assessment ( P < 0.001). No major complications occurred; the single adverse event recorded, moderate motor impairment, resolved. Conclusions: Real-time MR guidance and PRF-based thermometry of PLDD in the lumbar spine under open 1.0-T MRI appears feasible, safe and effective and may pave the way to more precise operating procedures. Key Points: • Percutaneous laser disc decompression ( PLDD) is increasingly used instead of conventional surgery. • Open 1. 0- T MRI with temperature mapping seems technically successful in monitoring PLDD. • Pain relief was at least ' great' in 64 % of patients. • No major complications occurred. • Open 1. 0- T MRI appears a safe and effective option for patient- tailored PLDD. [ABSTRACT FROM AUTHOR]

Background: The recent development of open magnetic resonance imaging (MRI) has provided an opportunity for the next stage of image-guided surgical and interventional procedures. The purpose of this study was to evaluate the feasibility of laparoscopic surgery under the pneumoperitoneum with the system of an open MRI operating theater. Methods: Five patients underwent laparoscopic surgery with a real-time augmented reality navigation system that we previously developed in a horizontal-type 0.4-T open MRI operating theater. Results: All procedures were performed in an open MRI operating theater. During the operations, the laparoscopic monitor clearly showed the augmented reality models of the intraperitoneal structures, such as the common bile ducts and the urinary bladder, as well as the proper positions of the prosthesis. The navigation frame rate was 8 frames per min. The mean fiducial registration error was 6.88 ± 6.18 mm in navigated cases. We were able to use magnetic resonance-incompatible surgical instruments out of the 5-Gs restriction area, as well as conventional laparoscopic surgery, and we developed a real-time augmented reality navigation system using open MRI. Conclusions: Laparoscopic surgery with our real-time augmented reality navigation system in the open MRI operating theater is a feasible option. [ABSTRACT FROM AUTHOR]

The in vivo pain treatment was successfully performed with the patient in a prone position. The PD-weighted TSE with echo time = 10 ms rendered contrast-to-noise-ratio values of 27 ± 10 for needle/fat, 1.6 ± 5 for needle/muscle, and 4 ± 4.7 for needle/nerve tissue. The mean diameter of the needle artifact was 1.2 ± 0.2 mm. In the T1-weighted gradient echo, the needle's artifact diameter was 6 ± 2 mm; the needle's contrast-to-noise ratio relative to muscle tissue was 4 ± 2, 7.6 ± 1.5 for needle/fat, and 5 ± 1 for needle/nerve tissue. With the PD-weighted TSE (echo time = 10 ms) and the T1-weighted gradient echo, the needle was imaged reliably throughout the intervention. The butterfly surface coil is feasible for the guidance of spinal interventions in a prone patient. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The article presents a study which assesses the grade of piphyseal fusion by T2* weighted images (T2*WI) compared to the results from T1 weighted image (T1WI). It examines a total of 87 subjects who were all junior football players ages between 12 and 17. Results suggest that T1WI is a better sequence compared to T2*WI in assessing bone fusion following the Federation Internationale de Football Associations (FIFA) protocol.

Purpose: To report the safety and diagnostic performance of magnetic resonance (MRI)-guided core biopsy of osseous lesions in children with chronic recurrent multifocal osteomyelitis (CRMO) that were visible on MRI but were occult on radiography and computed tomography (CT). Materials and Methods: A retrospective analysis of MRI-guided osseous biopsy performed in seven children (four girls and three boys; mean age 13 years (range 11 to 14) with CRMO was performed. Indication for using MRI guidance was visibility of lesions by MRI only. MRI-guided procedures were performed with 0.2-Tesla (Magnetom Concerto; Siemens, Erlangen, Germany; n = 5) or 1.5-T (Magnetom Espree; Siemens; n = 2) open MRI systems. Core needle biopsy was obtained using an MRI-compatible 4-mm drill system. Conscious sedation or general anesthesia was used. Parameters evaluated were lesion visibility, technical success, procedure time, complications and microbiology, cytology, and histopathology findings. Results: Seven of seven (100%) targeted lesions were successfully visualized and sampled. All obtained specimens were sufficient for histopathological analysis. Length of time of the procedures was 77 min (range 64 to 107). No complications occurred. Histopathology showed no evidence of malignancy, which was confirmed at mean follow-up of 50 months (range 28 to 78). Chronic nonspecific inflammation characteristic for CRMO was present in four of seven (58%) patients, and edema with no inflammatory cells was found in three of seven (42%) patients. There was no evidence of infection in any patient. Conclusion: MRI-guided osseous biopsy is a safe and accurate technique for the diagnosis of pediatric CRMO lesions that are visible on MRI only. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Verification of MR-guidance with image acquisitions slower than 1 image per second as it is inevitable for some interventions. Therefore, we quantified solely the effect of acquisition-time on the efficiency of MR-guided interventions in a static phantom study. Materials and methods: We measured the duration, accuracy and error rate of simulated interventions for different acquisition-times using a simplified interventional setup. All measurements were performed in a 1.0T open MRI scanner. Imaging was performed with a gradient-echo sequence (flipangle=20°; TR/TE=12/6ms; voxelsize=1mm×1mm; slicethickness=5mm; FOV=230mm×200mm; acquisition-time=1s). Variable acquisition times were simulated with intermediate pauses of 0, 1, 2, 3, 4 and 5s. The interventions were performed by a total of 20 volunteers including 7 experienced interventionalists. Results: The mean duration of the intervention was 2min. Significant differences between experienced and unexperienced volunteers were limited to the localization of the image plane and corrections made. The mean accuracy was 5.6mm. The time to localize the image plane increased with deceleration of imaging from 24s to 49s. A similar increase was observed for the intervention time (55–108s). A significant influence of the acquisition-time on durations and corrections was only found with acquisition-times greater than 4s per image. Conclusion: Even image rates of several seconds per image are sufficient enough for efficient interventions in static organs. Thus, the main attention has to be turned on the visibility of the needle when sequences are optimized for MR-guidance. The minimization of imaging speed is rather of secondary interest. [Copyright &y& Elsevier]

The article presents a study which aims at evaluating the potential of kinematic magnetic resonance imaging (KMRI). It explains the methodology of this pilot study in which a superconducting, high-field open-magnet magnetic resonance (MR) system is used to perform KMRI on the knee and lumbar spine of healthy volunteers. It concludes the effectiveness of KMRI in kinematic diagnosis of sports injuries.

Background: Deep tissue injury is the new acceptable term for deep pressure ulcers. Deep tissue injury of the buttocks is typically caused by sustained soft tissue deformations under the ischial tuberosities. Wheelchair users are at high risk, and although usually laterally tilted, the effect of tilts on tissue deformations is unknown. This has brought us to investigate buttocks tissue compressive deformations between the ischial tuberosities and skin during sitting in various body tilts, utilizing weight-bearing Magnetic resonance imaging (MRI). Methods: Ten healthy volunteers underwent sitting MRI, in six postures including neutral with/without weight-bearing, 10° and 20° lateral-tilts, and 20° and 40° anterior tilts. Studies utilized a coronal T1-weighted sequence. Images were evaluated for thickness of tissues between the skin and the lowest point of the ischial tuberosity, of fat between the skin and the gluteus muscle and of muscle between the ischial tuberosity and fat. Measurements in weight-bearing positions were compared to the non-weight-bearing for calculation of compressive tissue deformations in each trunk tilt. Statistical analysis was obtained utilizing multiple pairwise t-tests with Bonferroni corrections. Findings: Muscle and soft tissue compressive deformations, from highest to lowest, were 20°-lateral-tilt (87%, 72%), lateral-10° (85%, 70%), anterior-20° (79%, 67%), anterior-40° (74%, 64%), and neutral (72%, 59%). For the fat, highest was anterior-tilts (42%), followed by lateral-20°-tilt (41%), lateral-10° (39%) and neutral (35%). Interpretation: For lateral tilts, the higher the angle was, the higher the compressive deformation was. However, the most profound change in compressive deformation occurred at the small angle tilts. [Copyright &y& Elsevier]

Deep tissue injury (DTI) is a severe type of pressure ulcer, in which damage initiates under intact skin, in soft tissues that are mechanically deformed by load-bearing bony prominences. Sitting-acquired DTI typically occurs in the gluteus muscles that could sustain deformations by the weight-bearing ischial tuberosities (ITs). No clinical method currently exists for measuring internal tissue deformations; so design and selection of wheelchair cushions are based mostly on meas-uring sitting pressures. Our objective was to evaluate the influence of different commercial cushions on internal soft-tissue deformations under the ITs, using weight-bearing magnetic resonance imaging (MRI). We specifically compared muscle, superficial fat, and effective (muscle and fat together) tissue deformations while subjects (n = 10) sat on four cushions (two viscoelastic and two foam) and directly on a rigid support. Deformations were maximal in muscle tissue (mean ∼70%), twice more the amount than in fat (∼30%). Effective soft-tissue deformations were ∼50% to ∼60%. Although cushions mildly reduced muscle deformations in the order of 10%, theoretically, our interpretation suggests that this deformation level adds safe sitting time. This study demonstrated that weight-bearing MRI is applicable for evaluating wheelchair cushions and, in the future, may be a tool to systematically support cushion design and selection. [ABSTRACT FROM AUTHOR]

As minimally invasive treatments for liver cancers, percutaneous ablation therapies represent a valid alternative to liver resections, especially in patients with poor liver function. Recently, image-guided surgical and interventional procedures using open magnetic resonance imaging (MRI) have been introduced. We performed percutaneous ablation therapy for 51 nodules of liver cancer in 34 patients using a navigation system based on open MRI. During the ablation therapy, the ultrasonography (US) probe, needle, and tumor were displayed on the MR image. Immediately after the procedure, the therapeutic effect was evaluated by open MRI. In all cases, percutaneous puncture into the tumors was successful, even in the case of tumor undetectable by US. Mean fiducial registration error was approximately 3 mm. MR images captured after the procedure clearly demonstrated the ablated area. No mortality or major complications occurred, except for mild hemorrhage, pyrexia, and ascites. We developed a novel navigation system integrating US and MR images using open MRI for percutaneous ablation therapy of liver cancers. The presented system allows a safe and accurate approach to liver cancers, especially certain tumors that cannot be adequately visualized by US, and an evaluation of therapeutic results immediately after the procedures. [ABSTRACT FROM AUTHOR]

Developments in open magnetic resonance imaging (MRI) magnets have made possible the use of reproducible thermosensitive sequences to determine temperature distribution inside biological tissue. This study aimed to compare MR thermal mapping during laser-induced interstitial thermal therapy (LITT) with macroscopically observed thermal lesions in order to estimate the 3D size of the coagulative necrosis. Laser irradiation was performed ex vivo with a 980-nm laser in pig liver in an open low-magnetic field (0.2 T) scanner. Laser light was transmitted through a 1,040/600 μm (outer/core diameter) bare-tipped silica fiber. Laser energy was applied in a pulsed mode (10 s laser-on, 10 s laser-off) for 12 min, power 6 W, energy 2,160 J. Gradient-echo images acquired during laser irradiation were used for real-time temperature mapping by the MR-T1 method. The method was then validated by a comparison between calculated 60°C isotherm and macroscopic lesion size. Temperature accuracy was 2.2°C, temporal resolution was 20 s. and spatial resolution was 2.5 × 2.5 × 2.5 mm3 (0.8% of the mean volume of coagulative necrosis). The mean lesion volume was 1830 mm3 ± 189 (standard error), σ (standard deviation) = 499 and range (min = 1281; max = 2591) mm3. Volumes calculated from MRI isotherms were correlated (correlation coefficient r 2 = 0.70) significantly ( P = 0.08) to lesion size determined from macroscopic measurements. Using fast gradient-echo sequence, laser monitoring is achieved efficiently with fast temperature mapping. T1-weighted images appear promising in monitoring lesion size evolution in future low magnetic field in vivo studies. [ABSTRACT FROM AUTHOR]

Abstract: MRI of the knee has become an indispensable clinical tool in the management of chronic knee conditions. MRI for acute knee injuries is less well established but is becoming increasingly prevalent. MRI in acute ACL injuries is particularly useful for identifying associated injuries that will influence the early management of the patient. The aim of this paper is to describe the MRI findings of acute ACL tears, their commonly associated, and less common but serious associated injuries. Where available, the evidence for the sensitivity and specificity of these MRI features is presented. The contribution of these MRI findings to the management of the patient is discussed. [Copyright &y& Elsevier]

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In prostate cancer treatment, there is a move toward targeted interventions for biopsy and therapy, which has precipitated the need for precise image-guided methods for needle placement. This paper describes an integrated system for planning and performing percutaneous procedures with robotic assistance under MRI guidance. A graphical planning interface allows the physician to specify the set of desired needle trajectories, based on anatomical structures and lesions observed in the patient’s registered pre-operative and pre-procedural MR images, immediately prior to the intervention in an open-bore MRI scanner. All image-space coordinates are automatically computed, and are used to position a needle guide by means of an MRI-compatible robotic manipulator, thus avoiding the limitations of the traditional fixed needle template. Automatic alignment of real-time intra-operative images aids visualization of the needle as it is manually inserted through the guide. Results from in-scanner phantom experiments are provided. [ABSTRACT FROM AUTHOR]

The debate is to which extent external skin markers represent true underlying vertebral position and motion. Skin markers and lumbar vertebrae L3 and L4 were examined by vertically open magnetic resonance imaging (MRI) within different postures to investigate whether, and to which extent the position and orientation of skin markers represent the corresponding information of assigned underlying vertebra. Nine healthy volunteers sat within an open MRI scanner in five different seating postures: upright, low flexion, heavy flexion, upright left turn and upright right turn. Skin markers were fixed at lumbar levels L3 and L4. A set of landmarks defines corresponding positions on the vertebrae. Translation-vectors quantify the change of co-ordinates while changing position. Orientation (Cardan-angles) of each level in space was calculated from co-ordinates of three skin-markers and the corresponding vertebral landmarks respectively. The close relation between the position of the individual skin marker and its corresponding landmark on the vertebrae is conserved through all postures (regression coefficients: 0.720< b<0.972, 0.916< r<0.993, p<0.0001). Despite the high sensitivity to measurement errors there is a strong relation between the translation-vectors of external markers and the corresponding translation of the landmark on the vertebrae (0.68< r<0.99, p<0.0001). Within the resolution of the MR-imaging the orientation of the vertebrae can be predicted from the external markers (regression coefficients: 0.936< b<1.189, 0.769< r<0.959, p<0.0001). Positions and motions of skin markers can be taken as a first estimate to calculate the position and spatial orientation of underlying vertebrae. The use of skin markers may help to investigate spinal positions in daily life situations where internal imaging is not possible. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Ex vivo studies have suggested that cartilage contact areas and pressure are of high clinical relevance in the etiology of osteoarthritis in patients with patellar subluxation. The aims of this study were therefore to validate in vivo measurements of contact areas with 3D open magnetic resonance imaging (MRI), and to study knee joint contact areas in patients with patellar subluxation at different angles of knee flexion in comparison with healthy subjects. Methods: 3D-MRI data sets of 12 healthy volunteers and eight patients with patellar subluxation were acquired using a standard clinical (1.5T) and an open (0.2T) MRI scanner. We compared femoro-patellar and femoro-tibial contact areas obtained with two different sequences from open MRI [dual-echo-steady-state (DESS) and fast-low-angle-shot (FLASH) sequences] with those derived from standard clinical 1.5T MRI. We then analyzed differences in joint contact areas between healthy subjects and patients with patellar subluxation at 0°, 30°, and 90° of knee flexion using open MRI. Results: The correlation of the size of contact areas from open MRI with standard clinical MRI data ranged from r=0.52 to 0.92. Open-MRI DESS displayed a smaller overestimation of joint contact areas (+21% in the femoro-patellar, +12% in the medial femoro-tibial, and +19% in the lateral femoro-tibial compartment) than FLASH (+40%, +37%, +30%, respectively). The femoro-patellar contact areas in patients were significantly reduced in comparison with healthy subjects (−47% at 0°, −56% at 30°, and −42% at 90° of flexion; all ), whereas no significant difference was observed in femoro-tibial contact areas. Conclusions: Open MRI allows one to quantify joint contact areas of the knee with reasonable accuracy, if an adequate pulse sequence is applied. The technique permits one to clearly identify differences between patients with patellar subluxation and healthy subjects at different flexion angles, demonstrating a significant reduction and lateralization of contact areas in patients. In the future, application of this in vivo technique is of particular interest for monitoring the efficacy of different types of surgical and conservative treatment options for patellar subluxation. [Copyright &y& Elsevier]

Abstract: When performing surgery for malignant brain tumor that is close to pyramidal tract, it is an important issue how to preserve motor function. While diffusion tensor (DT) imaging on magnetic resonance imaging (MRI) can visualize course of nerve bundle, surgical navigation based on preoperative image may have considerable position error because of brain shift. We visualized pyramidal tract by intraoperative diffusion weighted (DW) imaging using 0.3T open MRI in tumor removal close to the fiber and performed surgery using the navigation based on the image. The surgeon was able to perform surgery confirming pyramidal tract localization corresponding to brain shift demonstrated on the navigation image. [Copyright &y& Elsevier]

The purpose of this study was (1) to demonstrate a computer-assisted gait analysis system that can visualize the locus of the dynamic loading axis on the proximal tibia joint surface, and (2) to assess the accuracy of this system in a patient with bilateral knee osteoarthritis (OA). This system uses force plate data, CT skeletal structure data and motion capture data obtained from an infrared position sensor. The relative positions between bones and markers were used to calculate skeletal model movement based on movement of the markers. The locus of the dynamic loading axis on the knee joint was defined as the point on the proximal tibia joint surface that intersected with the loading axis of the lower limb, which passed through the centre of the femoral head and the centroid of multiple points surrounded by the distal tibia joint surface contour. To assess the accuracy of this system, open MRI was used to evaluate positions of skin markers against bones in six healthy volunteers. The locus in a patient was affected by differences between the varus knee with medial compartment OA on the non-operative side and the knee treated with high tibial osteotomy (HTO) on the opposite side. At knee flexion angles of 0°, 15° and 30°, the mean value of measurement error for point locations on the locus was within 5.6% of joint width in the lateral direction (JWLD) on the proximal tibia joint. This system can provide clinically useful information for evaluation of the dynamic loading axis on the knee joint surface. [Copyright &y& Elsevier]