Benjamin Fritz

Three-Dimensional CAIPIRINHA SPACE TSE for 5-Minute High-Resolution MRI of the Knee.

ObjectiveThe aim of this study was to prospectively test the hypothesis that a 2-dimensional (2D) CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration) sampling pattern facilitates 5-minute high spatial resolution 3-dimensional (3D) sampling perfection with application optimized contrast using different flip angle evolutions (SPACE) magnetic resonance imaging (MRI) of the knee with image quality similar or better than current 2D turbo spin echo (TSE) and 3D SPACE standards. Materials and MethodsThe study was approved by our institutional review board. Twenty asymptomatic subjects (12 men, 8 women; mean age, 42 years; age range, 24–65 years) underwent 3 T MRI of the knee. A 4-fold accelerated 3D SPACE TSE prototype with 2D CAIPIRINHA sampling pattern and 5-minute acquisition time was compared with commercially available 2-fold and 4-fold accelerated 3D SPACE and 2D TSE pulse sequences with acquisition times of 11 minutes and 15 seconds, 6 minutes and 30 seconds, as well as 9 minutes and 48 seconds, respectively. Outcome variables included image quality, anatomic visibility, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Statistical analysis included Friedman, repeated measures analysis of variances, and Cohens weighted &kgr; tests. Bonferroni-corrected P values of 0.005 and less were considered statistically significant. ResultsOverall, image quality, visibility of anatomic structures, SNR, and CNR of 3D CAIPIRINHA SPACE were statistically similar to 2-fold accelerated 3D SPACE and significantly better than 4-fold accelerated 3D SPACE, which exhibited degrading parallel imaging artifacts. Compared with 2.5-mm 2D TSE images, 0.5-mm 3D CAIPIRINHA SPACE images showed statistically similar good edge sharpness and very good contrast resolution, and significantly less partial volume as well as absent chemical shift and pulsatile flow artifacts. Visibility of menisci, anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and lateral collateral ligament was good to very good on 0.5-mm 3D CAIPIRINHA SPACE images as compared with good on 2.5-mm 2D TSE image (P < 0.005). The SNR of fat, fluid, and cartilage as well as CNR between cartilage, fluid, fat, posterior cruciate ligament, and menisci were minimally higher on 2.5-mm 2D TSE image (P < 0.005). Image quality, visibility of anatomic structures, SNR, and CNR of 2.5-mm 3D CAIPIRINHA SPACE and 2.5-mm 2D TSE images were good to very good without significant differences. ConclusionsThree-dimensional SPACE with 2D CAIPIRINHA sampling pattern enables high-quality 3D TSE MRI of the knee at an acquisition time of 5 minutes and image quality, visibility of anatomic structures, SNR, and CNR similar to conventional 3D SPACE and 2D TSE, both of which require approximately 10-minute acquisition times.

Simultaneous Multislice Accelerated Turbo Spin Echo Magnetic Resonance Imaging: Comparison and Combination With In-Plane Parallel Imaging Acceleration for High-Resolution Magnetic Resonance Imaging of the Knee

Purpose We prospectively quantified the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of integrated parallel acquisition technique (PAT) and simultaneous multislice (SMS) acceleration and various combinations thereof, and we further compared two 4-fold–accelerated (PAT2-SMS2) high-resolution turbo spin echo (TSE) magnetic resonance imaging (MRI) protocols of the knee against a clinical 2-fold–accelerated (PAT2-SMS1) TSE standard. Materials and Methods Institutional review board approval was obtained, and all subjects gave informed consent. Fourteen knee MRI examinations were obtained (8 men, 6 women; mean age, 46 years; age range, 28–62 years) using a 3 T MRI system and a TSE pulse sequence prototype that allowed for the combination of PAT and SMS acceleration. Predicted whole-body specific absorption rates were recorded for all pulse sequences. For quantitative analysis, the difference method was used to calculate SNR and CNR analysis of 6 different TSE acceleration schemes (PAT2-SMS1, PAT3-SMS1, PAT1-SMS2, PAT1-SMS3, PAT2-SMS2, and PAT2-SMS3). For qualitative analysis, sagittal intermediate-weighted and axial fat-suppressed T2-weighted MR images were obtained with PAT2-SMS1 and PAT2-SMS2 acceleration schemes using similar parameters. One faster PAT2-SMS2 acceleration scheme with decreased repetition time and longer echo train was labeled with the addition SPEED for the purpose of this report. Two readers rated the data sets for image quality, structural visibility, and overall observer satisfaction using equidistant 5-point Likert scales. Readers additionally noted the presence of cartilage defects, meniscal tears, tendons and ligament tears, and bone marrow edema pattern. Friedman and Kruskal-Wallis tests were used. P values of less than 0.01 were considered significant. Results All pulse sequences were successfully executed and reconstructed inline. Whole-body specific absorption rates ranged between 1.4 and 3.9 W/kg for all acquisitions and remained within mandated limits. Quantitatively, mean SNR and CNR were significantly higher for SMS than those for PAT and similar for PAT2-SMS2 and PAT2-SMS1. Fluid was brightest on PAT2-SMS1, whereas noise, edge sharpness, contrast resolution, and fat suppression were similar on PAT2-SMS1 and SMS2-PAT2 and mildly inferior on PAT2-SMS2 SPEED. Articular cartilage received mildly higher ratings on PAT2-SMS1, whereas visibility of menisci was mildly inferior on PAT2-SMS2 SPEED. Observer preferences were similarly high for PAT2-SMS1 and PAT2-SMS2 and mildly inferior for the faster PAT2-SMS2 SPEED images. Four cartilage defects and 2 meniscal tears were seen by both readers on all sequences. Conclusions We demonstrate the signal preservation capabilities of SMS over PAT acceleration, which allow for similar SNR and CNR of 4-fold PAT2-SMS2 and 2-fold PAT2-SMS1 acceleration. Four-fold–accelerated TSE through the combination of PAT2 and SMS2 enables approximately 50% shorter acquisition times compared with regular PAT2 acceleration, similar quantitative and qualitative image quality, and holds promise for a meaningful increase of the efficiency of clinical 2-dimensional MRI of the knee.

Metal artifact reduction MRI of total ankle arthroplasty implants

AbstractObjectivesTo assess high-bandwidth and compressed sensing-(CS)-SEMAC turbo spin echo (TSE) techniques for metal artifact reduction MRI of total ankle arthroplasty (TAA) implants.MethodsFollowing institutional approval and consent, 40 subjects with TAA implants underwent 1.5-T MRI prospectively. Evaluations included bone-implant interfaces, anatomical structures, abnormal findings and differential diagnoses before and after MRI. AUCs of P-P plots were used to determine superiority. Statistical differences were evaluated with McNemar and chi-square tests. P-values ≤ 0.05 were considered significant.ResultsCS-SEMAC TSE was superior to high-bandwidth TSE in showing the bone-implant interfaces (AUC=0.917), periprosthetic bone, tendons and joint capsule (AUC=0.337–0.766), bone marrow oedema (43 % difference, p=0.041), interface osteolysis (63 %, p=0.015), tendinopathy (62 %, p=0.062), periprosthetic fractures (60 %, p=0.250), synovitis (43 %, p=0.250), as well as reader confidence for bone marrow oedema (p=<0.001), fracture (p=0.001), interface osteolysis (p=0.003), synovitis (p=0.027) and tendinopathy (p=0.034). The number of differential diagnoses in symptomatic subjects after the MRI with CS-SEMAC decreased from 3 (1–4) to 1 (1–2) (p<0.001).ConclusionsMRI of TAA implants with CS-SEMAC improves the diagnosis of interface osteolysis, periprosthetic bone marrow oedema, fractures and tendinopathy when compared to high-BW TSE, and has a positive effect on patient management.Key Points• High-bandwidth TSE and compressed sensing SEMAC improve MRI of ankle arthroplasty implants.n • Compressed sensing SEMAC improves bone-implant interfaces, periprosthetic bone, tendons and joint capsule visibility.n • Compressed sensing SEMAC improves the diagnosis of osteolysis, tendinopathy, fractures and synovitis.n • MRI decreases the number of clinical differential diagnoses of painful ankle arthroplasty implants.

Prevalence of vitamin D insufficiency in radiologists: a cross-sectional study

ObjectiveTo compare the prevalence of vitamin D insufficiency between radiologists and a control group of non-radiologists.Materials and methodsThis prospective cross-sectional study was conducted at the Swiss Congress of Radiology in May of 2016. Attendees (radiologists and non-radiologists) were asked to give a venous blood sample to measure vitamin D (25-hydroxyvitamin D) blood serum level. Vitamin D insufficiency was defined as <xa050xa0nmol/l (30xa0ng/ml). We collected information on profession, age, gender, vitamin D supplements, recent sunny vacation, and eating fish. We compared vitamin D between radiologists and non-radiologists.ResultsA total of 137 radiologists (mean age, 38u2009±u200910xa0years) and 164 non-radiologists (mean age, 40u2009±u200912xa0years) participated in the study. Prevalence of vitamin D insufficiency in both groups was similar (58.4% (80/137) vs. 53.7% (88/164); pu2009=u20090.240). Forty-three participants were under vitamin D supplementation. In those without supplementation, we found no difference in vitamin D between groups (44.0u2009±u200916.2xa0nmol/l (17.6u2009±u20096.5xa0ng/ml) vs. 44.4u2009±u200916.9xa0nmol/l (17.8u2009±u20096.8xa0ng/ml); pu2009=u20090.757). Average vitamin D levels for radiologists were slightly lower (−0.98xa0nmol/l (0.39xa0ng/ml), 95% confidence intervalu2009−u20095.96 to 4.00 (−xa02.38 to 1.6xa0ng/ml); pu2009=u20090.699), when adjusting for the potential confounders, but not statistically significant. The odds ratio of vitamin D insufficiency for radiologists versus non-radiologists was 1.7 (95%xa0CIu2009=u20090.94–3.06; pu2009=u20090.078) after adjusting for the other independent variables.ConclusionsThe prevalence of vitamin D insufficiency in radiologists was high (58.4%), but not substantially higher than in non-radiologists.

Synthetic MRI of the Knee: Phantom Validation and Comparison with Conventional MRI

Purpose To test the hypothesis that synthetic MRI of the knee generates accurate and repeatable quantitative maps and produces morphologic MR images with similar quality and detection rates of structural abnormalities than does conventional MRI. Materials and Methods Data were collected prospectively between January 2017 and April 2018 and were retrospectively analyzed. An International Society for Magnetic Resonance in Medicine-National Institute of Standards and Technology phantom was used to determine the accuracy of T1, T2, and proton density (PD) quantification. Statistical models were applied for correction. Fifty-four participants (24 men, 30 women; mean age, 40 years; range, 18-62 years) underwent synthetic and conventional 3-T MRI twice on the same day. Fifteen of 54 participants (28%) repeated the protocol within 9 days. The intra- and interday agreements of quantitative cartilage measurements were assessed. Contrast-to-noise (CNR) ratios, image quality, and structural abnormalities were assessed on corresponding synthetic and conventional images. Statistical analyses included the Wilcoxon test, χ2 test, and Cohen Kappa. P values less than or equal to .01 were considered to indicate a statistically significant difference. Results Synthetic MRI quantification of T1, T2, and PD values had an overall model-corrected error margin of 0.8%. The synthetic MRI interday repeatability of articular cartilage quantification had native and model-corrected error margins of 3.3% and 3.5%, respectively. The cartilage-to-fluid CNR and menisci-to-fluid CNR was higher on synthetic than conventional MR images (P ≤ .001, respectively). Synthetic MRI improved short-tau inversion recovery fat suppression (P ˂ .01). Intermethod agreements of structural abnormalities were good (kappa, 0.621-0.739). Conclusion Synthetic MRI of the knee is accurate for T1, T2, and proton density quantification, and simultaneously generated morphologic MR images have detection rates of structural abnormalities similar to those of conventional MR images, with similar acquisition time.

10-Min 3D Turbo Spin Echo MRI of the Knee in Children: Arthroscopy-Validated Accuracy for the Diagnosis of Internal Derangement: 10-Min Pediatric Knee 3D MRI

Ten‐minute MRI of the pediatric knee can add value through increased cost‐effectiveness and decreased sedation needs but requires validation of its clinical efficacy.

The external obturator footprint as a landmark in total hip arthroplasty through a direct anterior approach: a CT-based analysis

Background: Anatomical landmarks for templating of total hip arthroplasty (THA) that are visible both during surgery and on radiographs are rare. If surgery is performed through a direct anterior approach the external obturator tendon (EO) is consistently visible. To use this point as a reference the exact position and dimensions of the footprint need to be known. Aim: To determine the location and dimension of the EO footprint on pelvic radiographs by correlating the EO anatomy in CT scans with conventional radiographs. Methods: CT scans and radiographs of 200 patients were analysed. The EO tendon was identified on CT scans; the height of its footprint, and its distance to the tip of the greater trochanter and to the anatomical axis of the femur was measured. The accuracy and inter-rater reliability in the identification of the EO footprint was determined. Results: The EO tendon was visible on all CT scans and it’s footprint was identifiable on all corresponding radiographs. It’s cranio-caudal dimension was 6.4 ± 1.4 mm. It’s distance to the tip of the greater trochanter was 16.0 ± 3.1 mm. The EO footprint was located 5.2 ± 3.7 mm lateral to the femoral anatomical axis. There was no significant difference regarding the accuracy of EO footprint localisation on radiographs among the 2 readers. Conclusion: The EO footprint on the greater trochanter is consistently visible on CT scans and radiographs. As the variability of the footprint dimension is small, this structure may serve as a useful landmark in THA, particularly when performed through a direct anterior approach.

CAIPIRINHA-accelerated 10-min 3D TSE MRI of the ankle for the diagnosis of painful ankle conditions: Performance evaluation in 70 patients

ObjectivesTo test the hypothesis that MRI of the ankle with a 10-min 3D CAIPIRINHA SPACE TSE protocol is at least equivalent for the detection of painful conditions when compared to a 20-min 2D TSE standard of reference protocol.MethodsFollowing institutional review board approval and informed consent, 70 symptomatic subjects underwent 3T MRI of the ankle. Six axial, sagittal and coronal intermediate-weighted (IW) and fat-saturated T2-weighted (T2FS) 2D TSE (total acquisition time, 20 min), and two sagittal isotropic IW and T2FS 3D CAIPIRINHA TSE (10 min) pulse sequence prototypes were obtained. Following randomization and anonymization, two musculoskeletal radiologists evaluated the 2D and 3D datasets independently. Descriptive statistics, inter-reader reliability, inter-method concordance, diagnostic definitiveness tests were applied. P-values < 0.05 were considered significant.ResultsRaters diagnosed 116 cartilage defects with 2D and 109 with 3D MRI, 35 ligament tears with 2D and 65 with 3D MRI, 18 tendon tears with 2D and 20 with 3D MRI, and 137 osseous abnormalities with 2D and 149 with 3D MRI. The inter-reader agreement was high for 2D (Kendall W, 0.925) and 3D MRI (W, 0.936) (pu2009<u20090.05), as was the inter-method concordance (W, 0.919). The diagnostic definitiveness of readers was higher for 3D MRI than 2D MRI in 10-27% of the time, while the reverse was true in 7-11% of the time (pu2009<u20090.01).ConclusionsThe performance of 10-min 3D CAIPIRINHA SPACE MRI for the detection of painful ankle conditions is similar to that of a 20-min 2D TSE MRI reference standard.Key Points• CAIPIRINHA Acceleration facilitates isotropic 3D MRI of the Ankle in 10 min.• 10-min 3D CAIPIRINHA MRI and 20-min 2D TSE MRI have similar performance.• 3D CAIPIRINHA SPACE MRI afforded higher diagnostic definitiveness of readers.

MRI Assessment of Supra- and Infratrochanteric Femoral Torsion: Association With Femoroacetabular Impingement and Hip Dysplasia

OBJECTIVEnThe objective of our study was to evaluate a novel measurement technique for assessing the supra- and infratrochanteric components of femoral torsion, establish reference values in healthy volunteers, and compare supra- and infratrochanteric torsion angles in patients with hip dysplasia and patients with femoroacetabular impingement (FAI) with those in healthy volunteers.nnnMATERIALS AND METHODSnFemoral torsion was assessed in 380 patients and 61 healthy volunteers on MRI. For assessing supra- and infratrochanteric torsion, three measurement techniques (i.e., Kim, simplified Kim, and centroid methods) were evaluated by two readers on 100 patients. The technique with the highest interreader reliability was selected to perform measurements on all patients and volunteers. Supra- and infratrochanteric torsion angles of patients were stratified by hip disorders, which were diagnosed by specialized hip surgeons, and were compared with reference values of healthy volunteers. Statistical analysis included the independent t test, Mann-Whitney U test, and intraclass correlation coefficient (ICC).nnnRESULTSnThe centroid method showed the highest interreader reliability for measuring supra-and infratrochanteric torsion with an ICC of 0.979. The supra- and infratrochanteric torsion values of the volunteers were 31.5° ± 7.4° (mean ± SD) and -18.3° ± 9.9°, respectively. In comparison with the volunteers, patients with hip dysplasia had significantly higher supraand infratrochanteric torsion values of 37.5° ± 10.3° (p = 0.001) and -9.6° ± 11.7° (p < 0.001) and patients with pincer-type FAI had significantly higher supratrochanteric torsion values of 37.8° ± 8.0° (p = 0.002).nnnCONCLUSIONnThe supra- and infratrochanteric components of femoral torsion differ substantially between hip disorders: Patients with hip dysplasia have predominantly increased infratrochanteric torsion, whereas patients with pincer-type FAI have increased supratrochanteric torsion. Quantification of separate supra- and infratrochanteric torsion angles allows a more detailed analysis of hip disorders and may influence treatment planning.

Sacrotuberous Ligament Healing following Surgical Division during Transgluteal Pudendal Nerve Decompression: A 3-Tesla MR Neurography Study.

Pelvic pain due to chronic pudendal nerve (PN) compression, when treated surgically, is approached with a transgluteal division of the sacrotuberous ligament (STL). Controversy exists as to whether the STL heals spontaneously or requires grafting. Therefore, the aim of this study was to determine how surgically divided and unrepaired STL heal. A retrospective evaluation of 10 patients who had high spatial resolution 3-Tesla magnetic resonance imaging (3T MRI) exams of the pelvis was done using an IRB-approved protocol. Each patient was referred for residual pelvic pain after a transgluteal STL division for chronic pudendal nerve pain. Of the 10 patients, 8 had the STL divided and not repaired, while 2 had the STL divided and reconstructed with an allograft tendon. Of the 8 that were left unrepaired, 6 had bilateral surgery. Outcome variables included STL integrity and thickness. Normative data for the STL were obtained through a control group of 20 subjects. STL integrity and thickness were measured directly on 3 T MR Neurography images, by two independent Radiologists. The integrity and thickness of the post-surgical STL was evaluated 39 months (range, 9–55) after surgery. Comparison was made with the native contra-lateral STL in those who had unilateral STL division, and with normal, non-divided STL of subjects of the control group. The normal STL measured 3 mm (minimum and maximum of absolute STL thickness, 2–3 mm). All post-operative STL were found to be continuous regardless of the surgical technique used. Measured at level of Alcock’s canal in the same plane as the obturator internus tendon posterior to the ischium, the mean anteroposterior STL diameter was 5 mm (range, 4–5 mm) in the group of prior STL division without repair and 8 mm (range, 8–9 mm) in the group with the STL reconstructed with grafts (p<0.05). The group of healed STLs were significantly thicker than the normal STL (p<0.05). We conclude that a surgically divided STL will heal spontaneously and will be significantly thicker after healing.