Dedicated Extremity Magnetic Resonance Imaging Research Articles

Using a Dedicated Extremity MRI Scanner for Depicting Anatomic Structures of Common Wrist Pathologies: A Pilot Comparison with a 3-Tesla MRI Scanner.

Background This pilot study explored the value of a dedicated extremity magnetic resonance imaging (MRI) scanner by focusing on the qualitative depiction of important wrist structures in common wrist pathologies, the overall image quality, artifacts, and participant experience in undergoing the examinations. Methods Images of the right wrist of 10 healthy adult volunteers were acquired with a 0.31-Tesla (T) dedicated extremity MRI and a 3-T MRI system, using a dedicated wrist coil. Images were separately evaluated by three radiologists. Paired images were randomized and graded for the visibility of anatomical details, including the triangular fibrocartilage complex (TFCC; central disc, meniscus homolog, and ulnar attachment), carpal ligaments (scapholunate [SL] and lunotriquetral [LT] ligaments), intercarpal cartilage, and median and ulnar nerves. Mean values and standard deviations of evaluation results were calculated for each sequence. Participants' experience in undergoing the examination in both MRI scanners was explored using a questionnaire. Results The mean values of anatomic structures and overall image quality were significantly in favor of the 3-T MRI scanner, compared with the dedicated extremity MRI scanner. With respect to patient satisfaction in undergoing the examination, the overall trend suggested that patients were more in favor of the dedicated extremity MRI scanner. Conclusion For defining the real clinical value of the dedicated MRI scanner in the treatment of hand and wrist pathology, studies focused on pathologies are needed, which is certainly warranted, considering the important benefits of these devices including lower costs and higher accessibility for both patients and health care providers.

Using an Office-Based, Dedicated Extremity MRI Scanner for Depicting Important Structures in Common Wrist Pathologies: A Pilot Comparison with a Conventional MRI Scanner.

Background Compared with the conventional magnetic resonance imaging (MRI), dedicated MRI scanners are more accessible. Images of a dedicated 1.0-T MRI specifically developed for the hand and wrist were compared with images of a conventional 1.5-T MRI. Methods Paired images of the right wrist were randomized and separately graded by two experienced radiologists for the quality of anatomical details, including the triangular fibrocartilage complex, carpal ligaments, intercarpal cartilage, median and ulnar nerves, overall image quality, and artifacts. Interrater reliability was measured with the percentage of exact agreement and agreement within a range of ± 1 score point. Participant experience of undergoing the examination in both MRI scanners was evaluated using a questionnaire. Results The overall image quality of all sequences was considered to be moderate to high. In 25 of 38 paired images, no statistically significant difference was found between the MRI scanners. Ten scores were found to be in favor of the dedicated extremity MRI. Within a range of ± 1 score point, the extremity MRI and the conventional MRI demonstrated an interrater agreement of 67 to 100% and 70 to 100%, respectively. Among the respondents of the questionnaire, the extremity MRI scored better for participant satisfaction when compared with the conventional MRI. Conclusions In healthy volunteers, the dedicated extremity MRI generally is similar or superior to the conventional MRI in the depiction of anatomical structures of the wrists, image quality, and artifacts, and significantly scored better on participant satisfaction. Future clinical studies should focus on defining the diagnostic value of the extremity MRI in wrist pathologies.

Design, fabrication and test of superconducting magnet for 1.5 T dedicated extremity magnetic resonance imaging system

Magnetic resonance imaging (MRI) has been a primary diagnostic technique due to its high imaging quality, noninvasion and non-radiation capacity. However, the application of conventional whole body MRI is restricted by its massive size, high installation and management cost. Dedicated MRI overcomes the shortcomings of whole body MRI and has great importance in medical diagnosis. The challenge is that the design of superconducting magnet for extremity MRI is largely constrained by physiological structure of human body. As a result, a limited longitudinal length with high field homogeneity in a 160 mm diameter sphere volume (DSV) is required for superconducting magnet of extremity MRI. In this article, a non-shielded 1.5 T extremity dedicated superconducting magnet is designed by using both 0-1 integer programming and genetic algorithm and fabricated with a comprehensive consideration of superconductivity wire consumption, central magnetic field intensity and imaging region homogeneity. The NbTi superconducting wire is chosen for coil winding, and copper-to-superconducting ratio of the wire is 1.3. The sizes of cross-section of the bare wire and the insulated wire are 0.75 mm×1.20 mm and 0.83 mm×1.28 mm respectively, and the critical currents at 4.2 K and 5 T are both about 935 A.According to the size constraint of the magnet, we first calculate the current carrying zone of the superconducting coils and divide it into grid elements with parallel current. The size of each grid element is equal to that of the superconducting wire, and the distribution of non-rectangular coils is obtained by using 0-1 integer programming. In order to obtain a higher homogeneity of magnetic field, a reverse current zone is manually created in the wide blank area of the feasible current carrying zone. Using the results above, we then optimize the distribution of coils and build a rectangular model which facilitates the fabrication by using genetic algorithm. The inductance of the magnet is 1.8094 H, the operating current is 402.09 A, the stored energy is 146.27 kJ and the peak magnetic field of current carrying zone is 5.48 T. The calculated peak-to-peak homogeneity in 160 mm DSV is about 22 ppm. Taking into consideration the factors such as mechanical error and cold shrinkage, the estimated homogeneity would reach 60 ppm (peak-to-peak) with passive shimming.The 1.5 T extremity dedicated superconducting magnet is successfully fabricated through a series of processes such as winding, curing, assembly and welding. The prototype magnet has a room temperature bore of 280 mm in diameter and a total length of 520 mm, and the volume of liquid helium vessel is about 30 liters. To reduce the evaporation of liquid helium, a 1.5 Watt two-stage Gifford-McMahon refrigerator is employed to cool the system and maintain the evaporation rate of Helium at zero level. The range of 5 Gauss line of the magnet is 3.2 m in the radial direction and 2.6 m in the axial direction. Moreover, the magnet is magnetized to 1.5 T after being conditioned three times and the measured homogeneity in 160 mm DSV achieves 55 ppm (peak-to-peak) and 3.4 ppm (Vrms) after passive shimming using silicon steel pieces.

Gamekeeper’s Thumb—A Treatment-Oriented Magnetic Resonance Imaging Classification

To investigate by magnetic resonance imaging the degree of ulnar collateral ligament (UCL) displacement in order to create a simple classification to aid in determining which UCL injuries require surgery. We evaluated 43 cases of UCL injury with a dedicated extremity magnetic resonance imaging and measured the degree of ligament displacement. This was correlated to clinical outcome with planned surgical intervention reserved for patients with a Stener lesion. By collating results we could generate 4 types of injury based on the appearances of the UCL. Partial and minimally displaced UCL tears (type 1) and tears displaced less than 3 mm (type 2) typically healed by immobilization alone, whereas 90% of tears displaced more than 3 mm (type 3) failed immobilization and required surgery as did all of those with a Stener lesion (type 4). Our 4-stage, treatment-oriented classification of thumb UCL injury is based on the degree of UCL displacement in, with correlation with the likelihood of success with either immobilization or operative intervention. Tears of the UCL with more than 3 mm of displacement are likely to require operative repair even in the absence of a true Stener lesion.

Feasibility and reproducibility of the PsAMRIS-H score for psoriatic arthritis in low-field-strength dedicated extremity magnetic resonance imaging

Objectives: The psoriatic arthritis magnetic resonance imaging scoring system (PsAMRIS-H) for the evaluation of inflammatory and destructive changes in PsA hands was validated on 0.6-T scanners. The applicability of the PsAMRIS-H on a low-field MRI system as a well-accepted, low-cost imaging modality was evaluated.Method: In 65 consecutive patients (31 males, median age 52 years), 73 scans on a 0.2-T dedicated extremity MRI system were obtained for evaluation of PsA. Images were scored for synovitis, tenosynovitis, periarticular enhancement, bone erosion, bone oedema, and proliferation, and the PsAMRIS-H score was calculated. The intraclass correlation coefficient (ICC) was calculated and the paired t-test conducted.Results: Intra-reader reliability for the total PsAMRIS-H score was good, with an ICC of 0.81 and 0.77 for readers 1 and 2, respectively, and inter-reader agreement was moderate (0.57 for each reader). However, the PsAMRIS-H score differed significantly between the two readers (22 vs. 31; p < 0.05). When individual components of the PsAMRIS were evaluated, intra- and inter-reader agreement was poor to moderate, especially for tenosynovitis and periarticular inflammation.Conclusions: Low-field 0.2-T MRI is capable of quantifying the PsAMRIS-H with good intra-reader reproducibility. However, low signal-to-noise ratio (SNR), low spatial resolution, and system artefacts limit the application of the PsAMRIS-H, leading to low inter- and intra-reader agreement for individual features.

Comparison of low-field dedicated extremity magnetic resonance imaging with articular ultrasonography in patients with rheumatoid arthritis

To compare magnetic resonance imaging (MRI) and ultrasonography (US) in the detection of joint inflammation of rheumatoid arthritis (RA), 6 patients with RA were examined by US and low-field 0.3-T nonenhanced dedicated extremity MRI (compacTscan). All patients were females, with mean age of 50.2 years, mean disease duration of 13.5 years, and mean disease activity score (DAS)28-CRP of 1.78. Each patient was treated with either infliximab, etanercept, adalimumab, or tocilizumab. Intercarpal joints, radioulnar joints, second through fifth proximal interphalangeal (PIP) joints, and first through fifth metacarpophalangeal (MCP) joints (a total of 132 joints, 22 joints in each patient) were assessed by MRI for presence of joint inflammation. A total of 156 joints (24 first interphalangeal and radiocarpal joints plus the above 132 joints), were assessed by grayscale US (GS-US) and power Doppler US (PD-US) for presence of joint inflammation by two trained ultrasonographers. We assessed correlations between joint inflammations on MRI and GS-US/PD-US, and also interobserver correlation between the two ultrasonographers by calculating intraclass correlation coefficients (ICC). Synovial hypertrophy and/or synovial fluid was detected in 74/156 joints on GS-US, and synovitis was detected in 10/156 joints on PD-US and in 38/132 joints on MRI. Using PD-US as a reference, sensitivity of MRI in detection of synovitis was 80%. Using MRI as a reference, sensitivity of PD-US was 21%. Specificity of PD-US was higher than that of MRI. Overall agreement between GS-US and MRI and between PD-US and MRI was 0.56 and 0.76, respectively, suggesting that results of PD-US are close to those of MRI. ICC was 0.545 for GS-US and 0.807 for PD-US, suggesting specificity of PD-US in detecting joint inflammation. Our results show that findings of PD-US correlated with those of MRI. Low-field MRI and PD-US are useful tools for assessment of patients with RA.

Comparison of low-field dedicated extremity magnetic resonance imaging with articular ultrasonography in patients with rheumatoid arthritis

To compare magnetic resonance imaging (MRI) and ultrasonography (US) in the detection of joint inflammation of rheumatoid arthritis (RA), 6 patients with RA were examined by US and low-field 0.3-T nonenhanced dedicated extremity MRI (compacTscan). All patients were females, with mean age of 50.2 years, mean disease duration of 13.5 years, and mean disease activity score (DAS)28-CRP of 1.78. Each patient was treated with either infliximab, etanercept, adalimumab, or tocilizumab. Intercarpal joints, radioulnar joints, second through fifth proximal interphalangeal (PIP) joints, and first through fifth metacarpophalangeal (MCP) joints (a total of 132 joints, 22 joints in each patient) were assessed by MRI for presence of joint inflammation. A total of 156 joints (24 first interphalangeal and radiocarpal joints plus the above 132 joints), were assessed by grayscale US (GS-US) and power Doppler US (PD-US) for presence of joint inflammation by two trained ultrasonographers. We assessed correlations between joint inflammations on MRI and GS-US/PD-US, and also interobserver correlation between the two ultrasonographers by calculating intraclass correlation coefficients (ICC). Synovial hypertrophy and/or synovial fluid was detected in 74/156 joints on GS-US, and synovitis was detected in 10/156 joints on PD-US and in 38/132 joints on MRI. Using PD-US as a reference, sensitivity of MRI in detection of synovitis was 80%. Using MRI as a reference, sensitivity of PD-US was 21%. Specificity of PD-US was higher than that of MRI. Overall agreement between GS-US and MRI and between PD-US and MRI was 0.56 and 0.76, respectively, suggesting that results of PD-US are close to those of MRI. ICC was 0.545 for GS-US and 0.807 for PD-US, suggesting specificity of PD-US in detecting joint inflammation. Our results show that findings of PD-US correlated with those of MRI. Low-field MRI and PD-US are useful tools for assessment of patients with RA.

Reducing Invasiveness, Duration, and Cost of Magnetic Resonance Imaging in Rheumatoid Arthritis by Omitting Intravenous Contrast Injection — Does It Change the Assessment of Inflammatory and Destructive Joint Changes by the OMERACT RAMRIS?

Gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) provides highly sensitive assessment of inflammatory and destructive changes in rheumatoid arthritis (RA) joints, but intravenous (IV) Gd injection prolongs examination time and increases cost, invasiveness, and patient discomfort. We explored to what extent RA joint pathologies in wrists and metacarpophalangeal (MCP) joints can be reliably assessed by unenhanced MRI images compared with Gd-enhanced MRI as the reference method. MRI data sets from 2 RA substudies were scored according to preliminary OMERACT RA MRI scoring system (RAMRIS): Substudy A included 1.0 T/1.5 T MR images from 40 RA patients, which were scored twice by 2 experienced readers. Substudy B included 0.2 T dedicated extremity MRI (E-MRI) images from 55 patients, scored twice by one experienced reader. The first reading included only unenhanced images, whereas complete image sets were available for the second reading. Gd contrast injection appeared unimportant to MRI scores of bone erosions and bone edema in RA wrist and MCP joints. However, when post-Gd MRI was considered the standard reference, MRI without Gd provided only moderate to high agreement concerning assessment of synovitis, and omitting the post-Gd acquisitions increased the interreader variation on synovitis scores. Low-field (0.2 T) E-MRI in these exercises provided a lower sensitivity of unenhanced imaging for synovitis than MRI using higher-field strengths. Omitting IV contrast injection did not change scores of bone erosions and bone edema, but decreased the reliability of synovitis scores. However, this disadvantage may for some purposes be outweighed by the possibility to assess more joints and/or greater feasibility.

Conventional radiography requires a MRI-estimated bone volume loss of 20% to 30% to allow certain detection of bone erosions in rheumatoid arthritis metacarpophalangeal joints

The aim of this study was to demonstrate the ability of conventional radiography to detect bone erosions of different sizes in metacarpophalangeal (MCP) joints of rheumatoid arthritis (RA) patients using magnetic resonance imaging (MRI) as the standard reference. A 0.2 T Esaote dedicated extremity MRI unit was used to obtain axial and coronal T1-weighted gradient echo images of the dominant 2nd to 5th MCP joints of 69 RA patients. MR images were obtained and evaluated for bone erosions according to the OMERACT recommendations. Conventional radiographs of the 2nd to 5th MCP joints were obtained in posterior-anterior projection and evaluated for bone erosions. The MRI and radiography readers were blinded to each other's assessments. Grade 1 MRI erosions (1% to 10% of bone volume eroded) were detected by radiography in 20%, 4%, 7% and 13% in the 2nd, 3rd, 4th and 5th MCP joint, respectively. Corresponding results for grade 2 erosions (11% to 20% of bone volume eroded) were 42%, 10%, 60% and 24%, and for grade 3 erosions (21% to 30% of bone volume eroded) 75%, 67%, 75% and 100%. All grade 4 (and above) erosions were detected on radiographs. Conventional radiography required a MRI-estimated bone erosion volume of 20% to 30% to allow a certain detection, indicating that MRI is a better method for detection and grading of minor erosive changes in RA MCP joints.

Acute Knee Trauma: Value of a Short Dedicated Extremity MR Imaging Examination for Prediction of Subsequent Treatment

To assess the predictive value of a short magnetic resonance (MR) imaging examination, in addition to or instead of radiography, performed in patients with acute knee trauma to identify those who require additional treatment versus those who do not and can be discharged without further follow-up. The randomized controlled trial and use of collected data for prediction modeling were approved by the institutional review board; informed consent was obtained. Patients with recent knee injury were included in the trial if radiography was ordered. They were randomized into a group undergoing only radiography and a group undergoing radiography plus immediate MR imaging. A 0.2-T dedicated extremity MR imager and four short pulse sequences were used. Univariable and multivariable logistic regression analysis was used to evaluate patient characteristics, trauma mechanism, and findings at radiography and MR imaging for their value in prediction of need for subsequent treatment within the 6-month follow-up. Data in 189 patients (123 male patients, 66 female patients; mean age, 33.4 years), 109 of whom underwent treatment after their initial visit, were analyzed. Age of 30 years or older, indirect trauma mechanism, radiographic results, and MR imaging results were significant predictors of need for treatment in univariable and multivariable analyses (P < .05). In the multivariable analysis, only abnormal MR imaging results were significantly predictive of need for treatment, and only when MR imaging replaced radiography (odds ratio, 2.61; 95% confidence interval: 1.12, 6.06). Implementation of a dedicated extremity MR imaging examination, in addition to or instead of radiography, performed in patients with traumatic knee injury improves prediction of the need for additional treatment but does not significantly aid in identification of patients who can be discharged without further follow-up. Value of a short MR imaging examination in the initial stage after knee trauma is limited.

Acute Wrist Trauma: Value of a Short Dedicated Extremity MR Imaging Examination in Prediction of Need for Treatment

To assess predictive value of a short magnetic resonance (MR) imaging examination in addition to or instead of radiography in patients with acute wrist trauma to identify patients who require additional treatment versus those who do not and can be discharged without further follow-up. Informed consent was obtained from all participating patients; the institutional review board approved the randomized controlled trial and use of data to create prediction models. Of 90 patients (37 female, 53 male; mean age, 40.0 years), 87 with acute wrist trauma were randomized to undergo radiography (n = 43) or radiography and a short MR imaging examination with low-field-strength dedicated extremity MR system (n = 44). Age, sex, trauma mechanism, presence of tenderness of the anatomic snuffbox, radiographic results, MR imaging results, and treatment data were collected. Univariable and multivariable logistic regression analysis was used to create four models for prediction of treatment need. Thirty-six patients had one or more fractures; one patient had a marked soft-tissue lesion. In univariable analysis, age (odds ratio, 1.02; 95% confidence interval: 1.00, 1.05), anatomic snuffbox tenderness (odds ratio, 2.31; 95% confidence interval: 0.90, 5.96), radiographic results (odds ratio, 31.2; 95% confidence interval: 8.90, 109), and positive MR imaging results versus MR imaging not performed (odds ratio, 1.86; 95% confidence interval: 0.57, 6.06) were significantly predictive of treatment need. In multivariable analysis, radiographic results (odds ratio, 24.7; 95% confidence interval: 6.59, 93.1) and positive MR imaging results (odds ratio, 6.28; 95% confidence interval: 1.27, 31.0) were significantly predictive of treatment need. Negative MR imaging results were not significantly predictive (odds ratio, 0.87; 95% confidence interval: 0.20, 3.82). A short MR imaging examination with a low-field-strength MR imaging system following radiography in initial evaluation of patients with acute wrist trauma has additional value in prediction of treatment need; it does not have value in identification of patients who can be discharged without further follow-up.

Acute Ankle Trauma: Value of a Short Dedicated Extremity MR Imaging Examination in Prediction of Need for Treatment

To assess predictive value of a short magnetic resonance (MR) imaging examination with or instead of radiography performed in patients with acute ankle trauma to identify those who require additional treatment versus those who do not and can be discharged without further follow-up. Informed consent was obtained from all participating patients, and the institutional review board approved the randomized controlled trial and use of data to create prediction models. In a prospective controlled trial, 197 patients with recent ankle trauma (92 women, 105 men) were randomized into two groups: those who underwent radiography and those who underwent a combination of radiography and MR imaging. Data about side of injury, trauma mechanism, and results of radiography and MR imaging were collected. Additional treatment was necessary in 109 of 197 patients after their initial hospital visit. With univariable and multivariable regression analysis, four models were created for prediction of treatment. In univariable analysis, age (odds ratio [OR], 1.02; 95% confidence interval: 1.00, 1.04), radiographic results (OR, 7.92; 95% confidence interval: 3.17, 19.8), and positive or uncertain results in patients who underwent MR imaging versus patients who did not (OR, 2.42; 95% confidence interval: 1.25, 4.70) were predictive of treatment. In the multivariable analysis, positive or uncertain MR imaging results (OR, 2.61; 95% confidence interval: 1.28, 5.30) contributed significantly to prediction of subsequent treatment. Negative MR imaging results did not contribute significantly (OR, 0.66; 95% confidence interval: 0.27, 1.61). A limited MR imaging examination in initial evaluation of acute ankle injury with radiography has additional predictive value in identification of patients who need treatment but does not add significant information in identification of those who can be discharged without further follow-up. A limited MR imaging examination cannot replace radiography for prediction of need for additional treatment.

Diagnosis of scaphoid fracture and dedicated extremity MRI.

We evaluated the value of dedicated extremity magnetic resonance imaging (E-MRI) in patients with clinical suspicion of a scaphoid fracture and normal initial radiographs. 52 patients underwent E-MRI within a mean of 4 (2-10) days after trauma. Follow-up radiographs were performed at average 11 (8-14) weeks after trauma, and these images were used as the "gold standard". A T1-weighted turbo gradient echo 3D and a tau short inversion recovery STIR were performed, both in coronal planes. The imaging time was less than 10 min. The images were evaluated independently by two radiologists. E-MRI detected occult fractures of the scaphoid in 9 patients, and of the distal radius in a further 6 patients. All these fractures were confirmed at follow-up radiographs. Furthermore, E-MRI revealed a fracture of the capitate bone in 1 patient, and of the triquetrum in 2 patients, and in 8 patients, bone bruise in 1 or more of the carpal bones. However, these fractures and bone lesions could not be confirmed by the follow-up radiographs. The agreement between the two examiners was high (kappa = 0.8) for E-MRI detection of fractures. E-MRI seems to be better than radiographs in the early diagnosis of occult fractures of the scaphoid bone and the wrist.

Prenatal diagnosis of galactosaemia.

We have monitored two pregnancies from families at risk for galactosaemia. The fetus was diagnosed as having galactosaemia in one and to be unaffected in the other. The accuracy of the predictions was confirmed postnatally. Assays for galactose 1-phosphate uridyl transferase involving the reduction of the coenzymes NAD or NADP are unsuitable for amniotic cells whereas estimation of (14)C-UDP-galactose produced from (14)C-galactose 1-phosphate detected the homozygous mutant fetus.