Reduced cross-scanner variability using vendor-agnostic sequences for single-shell diffusion MRI.

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.

TOPPE: A framework for rapid prototyping of MR pulse sequences.

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.

Length change patterns and shape of a grafted tendon after anatomical medial patellofemoral ligament reconstruction differs from that in a healthy knee.

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.

Comparative analysis of medial patellofemoral ligament length change pattern in patients with patellar dislocation using open-MRI.

PURPOSE: Medial patellofemoral ligament (MPFL) reconstruction has become a common form of treatment for recurrent patellar dislocation. This study was performed using open-MRI to compare the length change pattern of MPFL in patients with a history of patellar dislocation to that in healthy subjects. METHODS: The subjects comprised 10 knees of 8 males and 13 knees of 12 females with a history of one or more patellar dislocations. The length of the MPFL was measured using open-MRI in both the leg-extended position and knee-flexed positions to analyse the length change pattern. RESULTS: The average MPFL lengths were 58.6 ± 6.5 mm and 52.0 ± 4.6 mm for males and females in the extended knee position, respectively. The length change pattern of the MPFL showed slight variation up to a flexion angle of 30° and a clear decrease above 30°. This pattern differed from that of normal MPFL. In terms of morphology, the fibre bundle of the damaged MPFL followed a convex course towards the side of the patellofemoral joint surface at a knee flexion angle of 60°, whereas that of the normal MPFL followed a straight course. CONCLUSION: The in vivo damaged MPFL length change pattern was specific and differed distinctly from that of normal MPFL. The results of the present study suggested that MPFL fibres with a history of patellar dislocation lack sufficient tension at knee flexion angles of 0°-60°. However, further studies are needed to obtain a better understanding of cases with a patellar dislocation or postsurgical cases of MPFL reconstruction. LEVEL OF EVIDENCE: III.

Magnetic resonance imaging (MRI) of the lumbar spine with dedicated G-scan machine in the upright position: a retrospective study and our experience in 10 years with 4305 patients.

PURPOSE: To evaluate the pathological changes of the lumbar spine and the instability of the lumbar intervertebral joints observed in patients with low back pain, with the study of the transition from supine to orthostatic position through the use of dedicated MRI-G-scan machine. MATERIALS AND METHODS: Within 10 years, 4305 patients, aged between 21 and 80 years old, with history of low back pain with or without sciatica, underwent MRI examinations in upright and in supine position. The open MRI-scanner used is Esaote G-scan, which enables the acquisition of images in supine and standing positions. The used sequences were sagittal T2-weighted FSE, T1-weighted SE and axial 3D HYCE. Patients were divided into two groups: "negatives", with no changes in the two positions (supine and upright), and "positives", with MRI modifications of imaging in upright position. RESULTS: Orthostatic examination showed MRI changes in 2870 out of 4305 (66.6%) patients, including 1252 males and 1618 females. CONCLUSIONS: The G-scan is useful to assess instability of the lumbar spine detecting hidden modifications of protrusions and/or herniated discs already present in the supine position. It is also helpful in assessing the presence or modification of spondylolisthesis and lumbar canal stenosis.

MRI-guided percutaneous transhepatic cholangiodrainage: feasibility study in a porcine model.

BACKGROUND AND STUDY AIMS: MRI-guided procedures combine high-quality imaging with lack of radiation. Percutaneous transhepatic cholangiodrainage under real-time MRI guidance (MRI-PTCD) seems promising, allowing targeted puncture and avoiding multiple blind passes and use of contrast, which are associated with standard PTCD's heaviest complications. PATIENTS AND METHODS: Aim of this study was to investigate the feasibility of MRI-PTCD in three outbred piglets. Obstructive cholestasis was induced by common bile duct ligation. Two days later, MRI-PTCD was performed (open MRI, 1.0 Tesla) with prototype MRI-compatible accessories. Visualization was achieved with a balanced steady-state free precession real-time sequence (bSSFP: 0.75 frames/s, TR/TE [ms]: 7.2/3.6; flip angle: 45°; 200 × 200 matrix size; resolution: 1.3 × 1.3 mm(2), slice thickness: 7 mm). Cannulation of the bile ducts was followed by placement of Yamakawa drainages. RESULTS: Twelve punctures were performed (four per animal, 10/12 successful); in 2/10 the bile ducts could not be cannulated. Animal survival was 100% and no significant complications occurred. CONCLUSIONS: Initial data show that MRI-PTCD can be successfully performed. This may lead to establishment of a new optimized PTCD technique compared to the standard approach under fluoroscopy.

Proposed Safety Guidelines for Patient Assistants in an Open MRI Environment.

The wide-open side of an open magnetic resonance imaging (MRI) system allows a patient to easily contact the patient assistant during MRI scans. A wide-open-shaped magnet is highly effective when interventional procedures are necessary. Patient assistants can provide comfort by holding a part of the patient's body. Because current regulations or guidelines are concerned with only patient radio frequency (RF) safety, investigations on the safety of patient assistants exposed to high-magnetic field MRI (up to 1.2 T) are required. In this study, five different poses of patient assistants were numerically simulated at a 1.2 T open MRI system to determine the impact of poses on the RF exposure level. The 10-g averaged specific absorption rate (SAR) levels were analyzed for the poses of each patient assistant wearing gloves. Compared with the patient, up to 29.8% of the patient SAR was observed in the patient assistant. When the patient assistant wore latex gloves, a 63.7% reduction in the 10-g averaged SAR level was observed, which could be a remedy to minimize possible RF hazards. To prevent possible RF hazards during MRI scans, certain clauses regarding the patient assistant's poses or wearing gloves must be added to the existing MRI screening forms.

MR-guided lumbar facet radiofrequency denervation for treatment of patients with chronic low back pain in an open 1.0 Tesla MRI system.

BACKGROUND: To evaluate the feasibility, safety and efficacy of magnetic resonance imaging (MRI)-guided lumbar facet joint radiofrequency denervation (FRD) in patients with chronic low back pain. METHODS: The study consisted of two parts. First, a preclinical analysis using an ex vivo animal model was performed to define optimal technical parameters for ablation. Then, 17 patients with chronic lumbar facet joint pain syndrome were prospectively included and underwent MRI-guided FRD in an open 1.0-Tesla MRI. We analyzed technical feasibility and complications as well as clinical outcome in terms of subjective pain assessed on a numerical visual analogue scale (VAS) before and after 1 week/6 months after FRD. Clinical assessment was complemented by measurement of paravertebral muscle volume and fat content before the intervention and at 6-month follow-up. RESULTS: All interventions were technically successful without major complications. Initial VAS scores (median: 8, IQR: 1, range: 6-9, CI: 7.14-8.04) decreased significantly both after one week (median: 4, IQR: 5, range: 0-7, CI: 1.9-4.69, P=0.003) and after 6 months (median: 1, IQR: 6, range: 0-7, CI: 1.06-4.23, P<0.001). Mean multifidus muscle volume increased significantly in the patient population (from 366.8±130.8 cm3 before to 435.4±146.7 cm3 after FRD, P=0.031). CONCLUSIONS: This proof of principle study shows MRI-guided FRD in an open 1.0-Tesla MRI system to be a potential therapy option for patients with chronic low back pain.

Image-guided confirmation of a precision pull-through procedure during laparoscopically assisted anorectoplasty in an open MRI operating theater: first application in an infantile case with anorectal malformation.

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.

Quantitative identification and segmentation repeatability of thoracic spinal muscle morphology.

OBJECTIVE: MRI derived spinal-muscle morphology measurements have potential diagnostic, prognostic, and therapeutic applications in spinal health. Muscle morphology in the thoracic spine is an important determinant of kyphosis severity in older adults. However, the literature on quantification of spinal muscles to date has been limited to cervical and lumbar regions. Hence, we aim to propose a method to quantitatively identify regions of interest of thoracic spinal muscle in axial MR images and investigate the repeatability of their measurements. METHODS: Middle (T4-T5) and lower (T8-T9) thoracic levels of six healthy volunteers (age 26 ± 6 years) were imaged in an upright open scanner (0.5T MROpen, Paramed, Genoa, Italy). A descriptive methodology for defining the regions of interest of trapezius, erector spinae, and transversospinalis in axial MR images was developed. The guidelines for segmentation are laid out based on the points of origin and insertion, probable size, shape, and the position of the muscle groups relative to other recognizable anatomical landmarks as seen from typical axial MR images. 2D parameters such as muscle cross-sectional area (CSA) and muscle position (radius and angle) with respect to the vertebral body centroid were computed and 3D muscle geometries were generated. Intra and inter-rater segmentation repeatability was assessed with intraclass correlation coefficient (ICC (3,1)) for 2D parameters and with dice coefficient (DC) for 3D parameters. RESULTS: Intra and inter-rater repeatability for 2D and 3D parameters for all muscles was generally good/excellent (average ICC (3,1) = 0.9 with ranges of 0.56-0.98; average DC = 0.92 with ranges from 0.85-0.95). CONCLUSION: The guidelines proposed are important for reliable MRI-based measurements and allow meaningful comparisons of muscle morphometry in the thoracic spine across different studies globally. Good segmentation repeatability suggests we can further investigate the effect of posture and spinal curvature on muscle morphology in the thoracic spine.

A spiral, bi-planar gradient coil design for open magnetic resonance imaging.

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.

Oval gradient coils for an open magnetic resonance imaging system with a vertical magnetic field.

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 0.3T 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.

Open-MRI measures of cam intrusion for hips in an anterior impingement position relate to acetabular contact force.

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 ß-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 ß < 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.

Neuroimaging of Spinal Instability.

The human spine is a complex biomechanical system composed of multiple articular structures controlled by muscles. Spine diseases are frequently related to a loss of stability. Dedicated imaging protocols have been developed to evaluate spinal instability. Dynamic radiography with lumbar flexion-extension is used most often; however, in traumatic instability, computerized tomography provides better diagnostic accuracy for fracture detection. Novel technology improvements allow acquisition of dynamic MRI with axial load or upright standing techniques to simulate a more pathologic condition compared with conventional supine scans. This article reviews the basic concepts of spinal instability and describes the role of different imaging techniques in its assessment.

In-vivo evaluation of the kinematic behavior of an artificial medial meniscus implant: A pilot study using open-MRI.

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.

In vivo glenohumeral translation under anterior loading in an open-MRI set-up.

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 20N applied at the HHC level. When no load was applied, from 15° to 90° of arm abduction, the HHC moved, anteriorly (1.5±1.3mm) and superiorly (1.8±1.3mm) while smaller displacements were observed medio-laterally (0.4±0.7mm). Under the application of the anterior force the 3D displacement of the HHC with respect to the glenoid was 1.6±1.2mm and 1.3 ±0.7mm, respectively at 15° and 90° of arm abduction. The level of precision associated to the GHJ translation was less than 0.33mm 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.

Characteristics of geometric distortion correction with increasing field-of-view in open-configuration MRI.

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.

A Preliminary In Vivo Assessment of Anterior Cruciate Ligament-Deficient Knee Kinematics With the KneeM Device: A New Method to Assess Rotatory Laxity Using Open MRI.

BACKGROUND: Methods of objectively measuring rotational knee laxity are either experimental or difficult to use in daily practice. A new method has been developed to quantitatively assess rotatory laxity using an open MRI system and new tool, the KneeM device. PURPOSE/HYPOTHESIS: To perform a preliminary evaluation of a novel knee rotation measurement device to assess knee kinematics during flexion in an MRI field, in both anterior cruciate ligament (ACL)-deficient and healthy contralateral knees. The hypothesis was that the KneeM device would allow in vivo reproduction and analysis of knee kinematics during flexion in healthy and ACL-deficient knees. STUDY DESIGN: Controlled laboratory study. METHODS: Ten subjects (7 men and 3 women; mean age ± standard deviation, 32.3 ± 9.4 years) with ACL-deficient knees and contralateral uninjured knees participated in the study. An open MRI was performed with the KneeM device at a mean 4.9 months (range, 3.0-7 months) after ACL injury. The device exerted on the knee an anterior drawer force of 100 N, with an internal rotation of 20°, through the range of flexion (0°, 20°, 40°, and 60°). Both ACL-deficient and healthy contralateral knees were analyzed using the Iwaki method. RESULTS: There was no statistical difference of anterior translation in the medial compartment between intact and ACL-deficient knees at all degrees of flexion. However, significant differences in the anterior translation of the lateral compartment were observed between ACL-deficient and intact contralateral knees at 0° and 20° of flexion (P = .005 and P = .002, respectively). Between 20° and 40°, the lateral plateau of ACL-deficient knees translated 7.7 mm posteriorly, whereas the medial compartment remained stable, reflecting a sudden external rotation of the lateral plateau under the femoral condyle. CONCLUSION: This preliminary study suggests that measurement of tibiofemoral movements in both compartments during flexion using the KneeM device was useful for quantifying rotatory laxity in ACL-deficient knees. Moreover, this device seemed to allow a "mechanized pivot shift" and allowed reproduction of the "pivot" phase in the MRI field between 20° and 40° of flexion. CLINICAL RELEVANCE: This device could be used for diagnostic purposes or to investigate the outcomes of ACL reconstructions.

Comparison of MR images for age determination; T1 weighted images (T1WI) versus T2* weighted images (T2*WI).

PURPOSE: T1WI (T1 weighted image) was acquired in order to grade bone fusion following the studies by FIFA (Federation Internationale de Football Associations). Research using images other than T1WI has not been reported. The aim of this study is to evaluate the grade of epiphyseal fusion by T2* weighted images (T2*WI) and to investigate new findings on T2*WI as compared with T1WI. METHODS: A total of 87 subjects, all junior football players between the ages of 12 and 17 years old, were examined. T1 and T2* WI were obtained using a 1.2T Open type MR system. The T1WI and T2*WI were rated twice randomly by four radiologists using the FIFA grading system. RESULTS: The intra-rater reliability for grading was higher in T1WI (The Intraclass Correlation Coefficient (ICC)=0.949-0.985) than in T2*WI (ICC=0.917-0.943). The inter-rater reliability for grading was also higher in T1WI (ICC=0.923) than in T2*WI (ICC=0.867). CONCLUSIONS: This research showed that T1WI is a better sequence than T2*WI to evaluate bone fusion following FIFA protocol. It was speculated that the reason for this is that T1WI has higher tissue contrast resolution and enables clearer images of the epiphyseal fusion than T2*WI and the grading system by T1WI was not suitable for T2*WI.

A pilot trial on kinematic magnetic resonance imaging using a superconducting, horizontally opened, 1.2 T magnetic resonance system.

PURPOSE: This study was performed to introduce and evaluate the potential of kinematic magnetic resonance imaging (KMRI) using a high-field open-magnet magnetic resonance (MR) system. METHODS: We attempted to perform KMRI of healthy volunteers' lumbar spine and knee in the lateral position and ankle in the supine position utilizing the superconducting, horizontally opened, 1.2 T MR system (OASIS, HITACHI, Tokyo, Japan). For the KMRI of the lumbar spine, the volunteer had to lie on one side while maintaining maximally anteflexed, neutral, and maximally retroflexed positions and remain still for the duration of the acquisition time for each posture. In the same way, KMRI of the knee was performed with the volunteer's knee flexed at 0°, 30°, 60°, 90°, and 120° in the lateral position, and KMRI of the ankle was performed with the volunteer's ankle in maximally dorsiflexed, neutral, and maximally plantarflexed positions while lying in the supine position. RESULTS: We could acquire higher quality kinematic MR images than those acquired using low-field MR systems. The spinal canal, intervertebral discs and foramina, and facet joints in lumbar spine KMRI; the ligaments, menisci and patellofemoral joint in knee KMRI; and the tibiotalar articulation and peroneal tendon in ankle KMRI were clearly depicted. CONCLUSION: The results of our pilot trial indicated that a superconducting horizontally opened, 1.2 T MR system offers high-quality KMRI images and can be utilized for the kinematic diagnosis and evaluation of sports injuries.