Open Magnetic Resonance Imaging Scanner Research Articles

Percutaneous Magnetic Resonance Imaging-Guided Coaxial Cutting Needle Biopsy of Pancreatic Lesions: Diagnostic Accuracy and Safety.

To appraise the diagnostic performance of magnetic resonance imaging-guided percutaneous coaxial cutting needle biopsy of pancreatic lesions using a 0.4-T open magnetic resonance imaging scanner with optical tracking navigation. This retrospective study included 158 patients who underwent magnetic resonance imaging-guided pancreatic lesion biopsy procedures from May 2019 to December 2020. Two to four specimens were collected from each patient. Pathological diagnosis and clinical follow-ups were conducted to establish the final diagnosis. The procedures were evaluated for sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and complications. The Cardiovascular and Interventional Radiological Society of Europe guidelines were used to classify complications. Biopsy pathology revealed 139 pancreatic tumor malignancies and 19 benign pancreatic lesions. Finally, 151 patients were diagnosed with pancreatic malignancy and 7 with benign disease confirmed by surgery, re-biopsy, and clinical follow-up. The sensitivity, specificity, positive and negative predictive value, and accuracy for diagnosis of pancreatic diseases were 92.1%, 100%, 100%, 36.8%, and 92.4%, respectively. The biopsy accuracy was significantly related to the size (≤ 2cm, 76.2%; 2-4cm, 94.0%; > 4cm, 96.2%, P = .02) and not the lesion's location (head of pancreas, 90.7%; neck of pancreas, 88.9%; body of pancreas, 94.3%; tail of pancreas, 96.7%, P = .73). Minor complications included two patients experiencing mild abdominal pain and two with a minor occurrence of hemorrhage. Percutaneous magnetic resonance imaging-guided pancreatic lesion biopsy combined with optical navigation has high diagnostic accuracy and is safe for clinical practice. Level of Evidence Level 4, Case-series.

Muscle activity with 0.5 T upright MRI-DESS to measure T2 in biceps and triceps.

The purpose of this study was to determine if muscle activity of the biceps followed by isometric flexion changes T2 measured in the biceps. It is hypothesized that an increase in T2 will be observed in the biceps but not in the triceps after flexion exercise. Ten healthy volunteers were imaged with a one-channel neck coil while seated in a 0.5 T upright open magnetic resonance imaging (MRI) scanner using a three-dimensional double echo steady-state (DESS) sequence. Volunteers were imaged while relaxing their arm for 10, 20, and 30 minduring an isometric biceps flexion immediately following performance of biceps curls to exhaustion, and again after relaxing for 10 and 20 min. Voxel-wise T2 was calculated by fitting to a DESS signal equation in regions segmented at muscle centers to determine mean T2 . During isometric biceps flexion immediately following biceps curls, mean T2 increased (average 33%, p < 0.05) in the biceps but not in the triceps. By 20 min after curls, mean T2 decreased (p < 0.05), and was near preactivity values. In contrast, there was no change in triceps T2 across any activity or postactivity time points. Intra-rater repeatability was excellent (ICC: 0.90-0.97). This study demonstrated that measuring T2 in an active muscle is feasible using a DESS sequence in an upright open MRI scanner. This could enable the study of muscle function while the muscle is working and weight-bearing, rather than of the "fatigue" of the muscles after activity. In comparison to electromyography, MRI also enables the study of deep muscles and allows simultaneous assessment of activity and function.

Image Performance Characterization of an In-Beam Low-Field Magnetic Resonance Imaging System During Static Proton Beam Irradiation

Image guidance using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-beam</i> real-time magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy for moving tumors, by reducing treatment margins, detecting interfractional and intrafractional anatomical changes and enabling beam gating. The aim of this study is to quantitatively characterize the static magnetic field and image quality of a 0.22T open MR scanner that has been integrated with a static proton research beamline. The magnetic field and image quality studies are performed using high-precision magnetometry and standardized diagnostic image quality assessment protocols, respectively. The magnetic field homogeneity was found to be typical of the scanner used (98ppm). Operation of the beamline magnets changed the central resonance frequency and magnetic field homogeneity by a maximum of 16Hz and 3ppm, respectively. It was shown that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-beam</i> MR scanner features sufficient image quality and influences of simultaneous irradiation on the images are restricted to a small sequence-dependent image translation (0.1–0.7mm) and a minor reduction in signal-to-noise ratio (1.3%–5.6%). Nevertheless, specific measures have to be taken to minimize these effects in order to achieve accurate and reproducible imaging which is required for a future clinical application of MR integrated proton therapy.

The Application of Magnetic Resonance Imaging in Skeletal Age Assessment.

Method The study includes 80 patients identified from an endocrine clinic, two males and two females from each of 5 age groups (<5, 5 to 7, 8 to 10, 11 to 13, and 14 to 16 years). Skeletal age as determined from an open MRI scanner and radiographs performed on the same day was compared for each child. Two observers assess the skeletal age from radiographs and MRI images independently. After a period of at least three weeks, observers determined the skeletal age of all patients independently. All of the images were in different and random orders, on both of the assessment occasions. The agreement was assessed using the interclass correlation coefficient and Bland Altman plots. Problem Statement. The recurrent use of left-hand radiography in children with chronic conditions might result in the patient being exposed to the same image several times throughout the course of their lives. Use of radiation-free methods such as magnetic resonance imaging (MRI) may be able to assist in reducing the risks associated with radiation exposure, if done properly. Results Patients' age ranged from 3 to 16 years, in which the mean of the chronological age was 9.3 years (±2.9) and 9.8 years (±2.7) in girls and boys, respectively. The interrater agreement for skeletal age determination was 0.984 for radiographs and 0.976 for MRI scans. Using the G&P technique, for Observer 1, intraobserver agreement for radiographs and DXA was 0.993 and 0.983, respectively, and 0.995 and 0.994, respectively, for Observer 2. Plotting the rater readings against the line of equality shows no significant differences between readings acquired from radiographs and MRI scans. Conclusion For the study contribution, it is possible to employ open compact MRI to determine the skeletal age of a person. Our results showed that left-hand MRI scans were of better quality than the radiographs.

Automated Segmentation of Spinal Muscles From Upright Open MRI Using a Multiscale Pyramid 2D Convolutional Neural Network.

Randomized trial. To implement an algorithm enabling the automated segmentation of spinal muscles from open magnetic resonance images in healthy volunteers and patients with adult spinal deformity (ASD). Understanding spinal muscle anatomy is critical to diagnosing and treating spinal deformity.Muscle boundaries can be extrapolated from medical images using segmentation, which is usually done manually by clinical experts and remains complicated and time-consuming. Three groups were examined: two healthy volunteer groups (N = 6 for each group) and one ASD group (N = 8 patients) were imaged at the lumbar and thoracic regions of the spine in an upright open magnetic resonance imaging scanner while maintaining different postures (various seated, standing, and supine). For each group and region, a selection of regions of interest (ROIs) was manually segmented. A multiscale pyramid two-dimensional convolutional neural network was implemented to automatically segment all defined ROIs. A five-fold crossvalidation method was applied and distinct models were trained for each resulting set and group and evaluated using Dice coefficients calculated between the model output and the manually segmented target. Good to excellent results were found across all ROIs for the ASD (Dice coefficient >0.76) and healthy (dice coefficient > 0.86) groups. This study represents a fundamental step toward the development of an automated spinal muscle properties extraction pipeline, which will ultimately allow clinicians to have easier access to patient-specific simulations, diagnosis, and treatment.

Tibiofemoral Contact Measures During Standing in Toe-In and Toe-Out Postures.

Knee osteoarthritis is thought to result, in part, from excessive and unbalanced joint loading. Toe-in and toe-out gait modifications produce alterations in external knee joint moments, and some improvements in pain over the short- and long-term. The aim of this study was to probe mechanisms of altered joint loading through the assessment of tibiofemoral contact in standing with toe-in and toe-out positions using an open magnetic resonance scanner. In this study, 15 young, healthy participants underwent standing magnetic resonance imaging of one of their knees in 3 foot positions. Images were analyzed to determine contact in the tibiofemoral joint, with primary outcomes including centroid of contact and contact area for each compartment and overall. The centroid of contact shifted laterally in the lateral compartment with both toe-in and toe-out postures, compared with the neutral position (P < .01), while contact area in the medial and lateral compartments showed no statistical differences. Findings from this study indicate that changes in the loading anatomy are present in the tibiofemoral joint with toe-in and toe-out and that a small amount of lateralization of contact, especially in the lateral compartment, does occur with these altered lower limb orientations.

Audio-guided self-hypnosis for reduction of claustrophobia during MR imaging: results of an observational 2-group study

ObjectivesTo evaluate the influence of audio-guided self-hypnosis on claustrophobia in a high-risk cohort undergoing magnetic resonance (MR) imaging.MethodsIn this prospective observational 2-group study, 55 patients (69% female, mean age 53.6 ± 13.9) used self-hypnosis directly before imaging. Claustrophobia included premature termination, sedation, and coping actions. The claustrophobia questionnaire (CLQ) was completed before self-hypnosis and after MR imaging. Results were compared to a control cohort of 89 patients examined on the same open MR scanner using logistic regression for multivariate analysis. Furthermore, patients were asked about their preferences for future imaging.ResultsThere was significantly fewer claustrophobia in the self-hypnosis group (16%; 9/55), compared with the control group (43%; 38/89; odds ratio .14; p = .001). Self-hypnosis patients also needed less sedation (2% vs 16%; 1/55 vs 14/89; odds ratio .1; p = .008) and non-sedation coping actions (13% vs 28%; 7/55 vs 25/89; odds ratio .3; p = .02). Self-hypnosis did not influence the CLQ results measured before and after MR imaging (p = .79). Self-hypnosis reduced the frequency of claustrophobia in the subgroup of patients above an established CLQ cut-off of .33 from 47% (37/78) to 18% (9/49; p = .002). In the subgroup below the CLQ cut-off of 0.33, there were no significant differences (0% vs 9%, 0/6 vs 1/11; p = 1.0). Most patients (67%; 35/52) preferred self-hypnosis for future MR examinations.ConclusionsSelf-hypnosis reduced claustrophobia in high-risk patients undergoing imaging in an open MR scanner and might reduce the need for sedation and non-sedation coping actions.Key Points• Forty percent of the patients at high risk for claustrophobia may also experience a claustrophobic event in an open MR scanner.• Self-hypnosis while listening to an audio in the waiting room before the examination may reduce claustrophobic events in over 50% of patients with high risk for claustrophobia.• Self-hypnosis may also reduce the need for sedation and other time-consuming non-sedation coping actions and is preferred by high-risk patients for future examinations.

Effect of posture and femoral neck osteochondroplasty on femur-acetabulum clearance in patients with cam-type femoroacetabular impingement.

It is not clear whether femoral neck osteochondroplasty achieves its objective of increasing femoroacetabular clearance. We used an upright open magnetic resonance imaging scanner to image the hip joint in multiple postures to explore the effect of posture and femoral neck osteochondroplasty on femur-acetabulum clearance in patients with cam-type femoroacetabular impingement. We recruited 13 consecutive patients scheduled to undergo arthroscopic femoral neck osteochondroplasty and completed assessments on 10 patients. We scanned each subject before surgery and at 6 months post-op in supine and 3 other physiological postures: supine 90° flexion with adduction and internal rotation (FADIR), sitting deep (maximal flexion with internal rotation and adduction), and sitting crossed leg (maximal adduction with flexion and internal rotation). We measured the alpha angle, which describes the severity of cam deformity, and the beta angle, which defines joint clearance. We also evaluated hip flexion, internal rotation, and adduction before and after surgery. Femoral neck osteochondroplasty significantly decreased alpha angle by 23.9° ± 4.6° (p = 0.001) and increased beta angle across all postures by 28.1° ± 6.3° (p = 0.002). An increase in beta angle represented a decreased chance of impingement. Femoral neck osteochondroplasty significantly increased flexion by an average of 8.6° in the sitting deep posture after surgery (p = 0.007) which might indicate an improvement of joint function. These findings lend support to the hypothesis that arthroscopic osteochondroplasty accomplishes its stated goals of increasing bone-bone clearance in the hip joint and improving joint mechanics for the static postures assessed.

Needle artifact characteristics and insertion accuracy using a 1.2 T open MRI scanner: A phantom study

PurposeTo evaluate the characteristics of needle artifacts and the accuracy of needle insertion using a 1.2 Tesla open magnetic resonance imaging (MRI) system in a phantom. Materials and methodsFirst, the apparent width of the needle on the MRI and the needle tip position error of 16- and 18-gauge MRI-compatible introducer needles and a 17-gauge cryoneedle were examined with different needle angles (0°, 30°, 45°, 60°, and 90°) to the main magnetic field (B0), sequence types (balanced steady-state acquisition with rewound gradient echo [BASG] and T2-weighted fast spin echo [FSE] sequence), and frequency encoding directions. Second, the accuracy of needle insertion was evaluated after 10 MRI fluoroscopy-guided insertions in a phantom. ResultsThe apparent needle widths was larger when the angle of the needle axis relative to B0 was larger. The needles appeared larger on BASG than on T2-weighted FSE images, with the largest apparent widths of 16-, 17-, and 18-gauge needles of 14.3, 11.6, and 11.0mm, respectively. The apparent needle tip position was always more distal than the actual position on BASG images, with the largest longitudinal error of 4.0mm. Meanwhile, the 16- and 18-gauge needle tips appeared more proximal on T2-weighted FSE images with right-to-left frequency encoding direction. The mean accuracy of MRI fluoroscopy-guided needle insertion was 3.1mm. ConclusionThese experiments clarify the characteristics of needle artifacts in a 1.2 Tesla open MRI. With this system, the MRI fluoroscopy-guided needle insertion demonstrated an acceptable accuracy for clinical use.

The Efficacy of 0.2 Tesla Open Magnetic Resonance Imaging Scanner in the Diagnosis of Anterior Cruciate Ligament Injury

The Efficacy of 0.2 Tesla Open Magnetic Resonance Imaging Scanner in the Diagnosis of Anterior Cruciate Ligament Injury

Integrating a low-field open MR scanner with a static proton research beam line: proof of concept

On-line image guidance using magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy. However, to date no combined system exists. In this study, for the first time a low-field open MR scanner was integrated with a static proton research beam line to test the feasibility of simultaneous irradiation and imaging. The field-of-view of the MR scanner was aligned with the beam by taking into account the Lorentz force induced beam deflection. Various imaging sequences for extremities were performed on a healthy volunteer and on a patient with a soft-tissue sarcoma of the upper arm, both with the proton beam line switched off. T1-weighted spin echo images of a tissue-mimicking phantom were acquired without beam, with energised beam line magnets and during proton irradiation. Beam profiles were acquired for the MR scanner’s static magnetic field alone and in combination with the dynamic gradient fields during the acquisition of different imaging sequences. It was shown that MR imaging is feasible in the electromagnetically contaminated environment of a proton therapy facility. The observed quality of the anatomical MR images was rated to be sufficient for target volume definition and positioning. The tissue-mimicking phantom showed no visible beam-induced image degradation. The beam profiles depicted no influence due to the dynamic gradient fields of the imaging sequences. This study proves that simultaneous irradiation and in-beam MR imaging is technically feasible with a low-field MR scanner integrated with a static proton research beam line.

Modified technique for imaging the wrist and elbow in obese and claustrophobic patients using a non-open standard MRI scanner.

It is challenging to image extremely obese and claustrophobic patients using a standard, non-open, magnetic resonance imaging (MRI) scanner. On the other hand, installing an additional upright or open MRI scanner may not be cost-effective for most practices. Our technique with a patient in a sitting or standing position behind the standard MRI scanner may be helpful in the MR examination of the wrist/elbow in these patients using a standard wrist/elbow coil. We performed wrist and elbow MRI of extremely obese and claustrophobic patients by using our modified technique with the patient sitting or standing outside the standard non-open MRI scanner. A total number of 20 cases with the following diagnosis were examined: triquetral and scaphoid bone contusions and fractures, scapholunate ligament tears, triangular fibrocartilage complex tear, and biceps tear. Comparison of image quality for diagnostic information between the standard technique and our technique showed no significant difference, which is necessary for making the diagnosis. Our technique enables wrist and elbow imaging of extremely obese and claustrophobic patients who cannot otherwise be imaged using a standard MRI scanner without compromising the image quality that is essential for making a diagnosis.

Evaluation of low back pain with low field open magnetic resonance imaging scanner in rural hospital of Southern India.

Background:Low back pain (LBP) is the most common symptom which is associated with limitation of normal activities and work-related disability. Imaging techniques are often essential in making the correct diagnosis for prompt management. Plain Radiography though remain a first imaging modality, magnetic resonance imaging (MRI) due to its inherent softtissue contrast resolution and lack of ionizing radiation remains invaluable modality in the evaluation of LBP.Aim:To find the common causes of LBP in different age groups and the role of MRI in detecting the spectrum of various pathological findings.Materials and Methods:This is a prospective study done in the Department of Radiodiagnosis during a period of 2 years from July 2013 to July 2015. The study population includes all the cases referred to our department with complaints of LBP. Patients with ferromagnetic metallic implants and uncooperative cases were excluded. HITACHI 0.4 Tesla open MRI machine was used for imaging.Results and Conclusion:This study involved a total of 235 cases. There were 121 males and 114 females. The age of the patient ranged from 21 to 68 years with an average of 41.3 years. Back pain was commonly observed in the third to fifth decade. The common causes for back pain are disc herniations (disc bulge – 35.3%, disc protrusion – 39.6%, disc extrusion – 7.2%) accounting to 82.1%, followed by normal study (10.2%), vertebral collapse (traumatic – 2.1%, osteoporotic – 1.7%), infections (2.1%), and neoplasm (1.7%). MRI provides valuable information regarding the underlying causes of LBP, especially in disc and marrow pathology.

Decoupling and shielding numerical optimization of MRI phased-array coils

Receiver array coils in magnetic resonance imaging systems are used to pick up the signals emitted by the nuclei with high signal-to-noise ratio and a large region of sensitivity. Especially in low-field magnetic resonance systems, receiver coil performance plays a significant role in image quality. Moreover, since the magnetic resonance scanner shielding system strongly modifies resonance frequencies and field distribution, the array coils performance should be evaluated in dependence on the shield position.In this paper, we describe the use of a numerical solver based on finite-difference time-domain method to evaluate coil performances also considering the presence of radiofrequency shields.In particular, this paper deals with coupling and shielding in phased array coils at low field: we analyzed a classic two circular elements array and a novel two elements array coil both designed for the application in a 0.5T open magnetic resonance scanner. The prototypes of the arrays were tested by laboratory workbench in order to validate the simulated data and experiments were also done in real low field magnetic resonance scanner by using the novel coil.

The triangle zone as a femoral attachment location in medial patellofemoral ligament reconstruction: An in vivo three-dimensional analysis using an open MRI scanner

BackgroundThe exact isometric points for medial patellofemoral ligament (MPFL) fixation during MPFL reconstruction remain a matter of debate. PurposeThe aim of this study was to characterize the functional length changes of various patellar and femoral fixation sites using in vivo three-dimensional (3D) movement patterns and to determine the ideal fixation sites at which the graft remains largely isometric. MethodsTwelve right knees of healthy volunteers were examined at early flexion angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) with a horizontal-type open magnetic resonance scanner, and 3D models were reconstructed using the marching cubes algorithm. Six points on the femoral condyle and three points on the medial aspect of the patella were simulated. The matching points represented the MPFL, which crossed the bony obstacle. The MPFL length changes were analyzed at various flexion degrees. ResultsThe lengths from the dome of Blumensaat's line (G), the point 10mm inferior to the adductor tubercle (H), to the midpoint between the adductor tubercle and the medial epicondyle (I) were more isometric than other points. The lengths between the dome of Blumensaat's line and the superior pole of the patella changes significantly between 20° and 60° of flexion (p=0.040). ConclusionsThe femoral fixation site may be more accurately located during MPFL reconstruction at the G, H, and I points to restore the native biomechanical function of the MPFL. The dome of Blumensaat's line should be avoided during MPFL reconstruction with the superficial quad technique. Clinical relevanceA triangular region composed of the dome of Blumensaat's line, 10mm inferior to the adductor tubercle, and the midpoint between the adductor tubercle and medial epicondyle is recommended as the femoral fixation site.

High-resolution small field-of-view magnetic resonance image acquisition system using a small planar coil and a pneumatic manipulator in an open MRI scanner.

Low-field open magnetic resonance imaging (MRI) is frequently used for performing image-guided neurosurgical procedures. Intraoperative magnetic resonance (MR) images are useful for tracking brain shifts and verifying residual tumors. However, it is difficult to precisely determine the boundary of the brain tumors and normal brain tissues because the MR image resolution is low, especially when using a low-field open MRI scanner. To overcome this problem, a high-resolution MR image acquisition system was developed and tested. An MR-compatible manipulator with pneumatic actuators containing an MR signal receiver with a small radiofrequency (RF) coil was developed. The manipulator had five degrees of freedom for position and orientation control of the RF coil. An 8-mm planar RF coil with resistance and inductance of 2.04[Formula: see text] and 1.00[Formula: see text] was attached to the MR signal receiver at the distal end of the probe. MR images of phantom test devices were acquired using the MR signal receiver and normal head coil for signal-to-noise ratio (SNR) testing. The SNR of MR images acquired using the MR signal receiver was 8.0 times greater than that of MR images acquired using the normal head coil. The RF coil was moved by the manipulator, and local MR images of a phantom with a 2-mm grid were acquired using the MR signal receiver. A wide field-of-view MR image was generated from a montage of local MR images. A small field-of-view RF system with a pneumatic manipulator was integrated in a low-field MRI scanner to allow acquisition of both wide field-of-view and high-resolution MR images. This system is promising for image-guided neurosurgery as it may allow brain tumors to be observed more clearly and removed precisely.

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.

High-Field Open versus Short-Bore Magnetic Resonance Imaging of the Spine: A Randomized Controlled Comparison of Image Quality

BackgroundThe purpose of the present study was to compare the image quality of spinal magnetic resonance (MR) imaging performed on a high-field horizontal open versus a short-bore MR scanner in a randomized controlled study setup.MethodsAltogether, 93 (80% women, mean age 53) consecutive patients underwent spine imaging after random assignement to a 1-T horizontal open MR scanner with a vertical magnetic field or a 1.5-T short-bore MR scanner. This patient subset was part of a larger cohort. Image quality was assessed by determining qualitative parameters, signal-to-noise (SNR) and contrast-to-noise ratios (CNR), and quantitative contour sharpness.ResultsThe image quality parameters were higher for short-bore MR imaging. Regarding all sequences, the relative differences were 39% for the mean overall qualitative image quality, 53% for the mean SNR values, and 34–37% for the quantitative contour sharpness (P<0.0001). The CNR values were also higher for images obtained with the short-bore MR scanner. No sequence was of very poor (nondiagnostic) image quality. Scanning times were significantly longer for examinations performed on the open MR scanner (mean: 32±22 min versus 20±9 min; P<0.0001).ConclusionsIn this randomized controlled comparison of spinal MR imaging with an open versus a short-bore scanner, short-bore MR imaging revealed considerably higher image quality with shorter scanning times.Trial RegistrationClinicalTrials.gov NCT00715806

A Prototype MR Compatible Positioning Device for Guiding a Focused Ultrasound System for the Treatment of Abdominal and Thyroid Cancer

A prototype magnetic resonance imaging (MRI)-compatible positioning device that navigates a high intensity focused ultrasound (HIFU) transducer is presented. The intended application is to treat eventually tumours in the abdominal and thyroid. The positioning device has 3 user-controlled stages that allow access to various targets using a top to bottom coupling approach. Materials and Methods. The positioning device incorporates only MRI compatible materials such as piezoelectric motors, ABS plastic, brass screws, and brass rack and pinion. Results The MRI compatibility and the accuracy of the system were successfully demonstrated in an open MRI scanner. The robot has the ability to accurately move the transducer thus creating discrete and overlapping lesions in rabbit liver in vivo. This simple, cost effective positioning device can be placed mostly on the structure of an open MRI gantry. Due to the size of this positioning device, the proposed prototype in its current form cannot be used in any closed MRI system. The novelty of this positioning device is the MRI compatible design and its intended application which is the treatment of tumors in the abdominal area using focused ultrasound. This system can be utilized in the future to treat patients with cancer in the liver, kidney, pancreas and thyroid provided that the accuracy of the positioning device is greatly improved.

MRI-guided biopsy and fine needle aspiration biopsy (FNAB) in the diagnosis of musculoskeletal lesions

ObjectivesThe purpose of this study was to evaluate the diagnostic performance of magnetic resonance imaging (MRI) guided musculoskeletal biopsy and the value of fine needle aspiration biopsy (FNAB) when combined with histologic biopsy. Materials and methodsA total of 172 biopsies were performed under MRI guidance, 170 were histologic biopsies. In 112 cases, a fine needle aspiration biopsy was also performed. In two cases, a stand-alone FNAB was performed. The diagnostic performance was evaluated retrospectively by comparing the histopathologic and cytologic diagnosis with the current or final diagnosis after at least one year of clinical and imaging follow-up. A 0.23T open MRI scanner with an interventional stereotactic guidance system was used. ResultsThe overall diagnostic accuracy of MRI guided biopsy was 0.95, sensitivity 0.91, specificity 0.98, positive predictive value (ppv) 0.97 and negative predictive value (npv) 0.93. The diagnostic accuracy of trephine biopsy alone was 0.93, sensitivity 0.89, specificity 0.98, ppv 0.97 and npv 0.91 and accuracy for FNAB alone was 0.85, sensitivity 0.80, specificity 0.90, ppv 0.89 and npv 0.82. ConclusionsMRI guidance is a feasible and accurate tool in percutaneous musculoskeletal biopsies. Fine needle biopsy is a useful low-cost supplement to histologic biopsy.