Faculty Bibliography

During the past 2 decades, the number of spinal surgeries performed annually has been steadily increasing, and these procedures are being accompanied by a growing number of postoperative imaging studies to interpret. CT is accurate for identifying the location and integrity of implants, assessing the success of decompression and intervertebral arthrodesis procedures, and detecting and characterizing related complications. Although postoperative spinal CT is often limited owing to artifacts caused by metallic implants, parameter optimization and advanced metal artifact reduction techniques, including iterative reconstruction and monoenergetic extrapolation methods, can be used to reduce metal artifact severity and improve image quality substantially. Commonly used and recently available spinal implants and prostheses include screws and wires, static and extendable rods, bone grafts and biologic materials, interbody cages, and intervertebral disk prostheses. CT assessment and the spectrum of complications that can occur after spinal surgery and intervertebral arthroplasty include those related to the position and integrity of implants and prostheses, adjacent segment degeneration, collections, fistulas, pseudomeningoceles, cerebrospinal fluid leaks, and surgical site infections. Knowledge of the numerous spinal surgery techniques and devices aids in differentiating expected postoperative findings from complications. The various types of spinal surgery instrumentation and commonly used spinal implants are reviewed. The authors also describe and illustrate normal postoperative spine findings, signs of successful surgery, and the broad spectrum of postoperative complications that can aid radiologists in generating reports that address issues that the surgeon needs to know for optimal patient management.^©RSNA, 2019.

The majority of peripheral musculoskeletal soft tissue masses encountered in routine clinical practice are benign and associated with an excellent prognosis, whereas a small proportion of soft tissue masses are malignant and are associated with higher morbidity and mortality. Owing to the excellent tissue contrast resolution provided, magnetic resonance imaging (MRI) is a primary modality for the diagnostic evaluation of soft tissue masses, particularly for defining the anatomic extent. MRI is also useful for the characterization of soft tissue masses; however, after the exclusion of cysts and lipomas, it is challenging to accurately categorize neoplastic lesions as benign or malignant with conventional anatomic MRI. Quantitative MRI biomarkers obtained with nonconventional pulse sequences are becoming increasingly available, and can improve the accuracy of determining the character of soft tissue masses. In this article we discuss established qualitative and emerging quantitative MRI-based biomarkers available with dynamic contrast-enhanced MRI, diffusion-weighted imaging, and MR spectroscopy and their utility for the characterization of untreated soft tissue masses. Level of Evidence: 5 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:11-27.

Promising outcomes of hip replacement interventions in this era of aging populations have led to higher demands for hip arthroplasty procedures. These require effective methods and techniques for the detection of postoperative outcomes and complications. Based on the presence or absence of radiographic findings, magnetic resonance imaging (MRI) and computed tomography (CT) may be required to detect and further characterize different causes of failing implants. Yet metal-related artifacts degrade image quality and pose significant challenges for adequate image quality. To mitigate such artifacts in MRI, a set of techniques, collectively known as metal artifact reduction sequence (MARS) MRI, were developed that optimize the framework of the conventional pulse sequences and exploit novel multispectral and multispatial imaging methods such as Slice Encoding for Metal Artifact Correction (SEMAC) and Multi-Acquisition Variable-Resonance Image Combination (MAVRIC). Metal-induced artifacts on CT can be effectively reduced with virtual monochromatic reconstruction of dual-energy CT data sets, metal artifact reduction reconstruction algorithms, and postprocessing image visualization techniques.

BACKGROUND: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. PURPOSE/OBJECTIVE:To determine the arthroscopy-based diagnostic accuracy and interreader reliability of 10-min 3D Controlled Aliasing In Parallel Imaging Results In Higher Acceleration (CAIPIRINHA) turbo spin echo (TSE) MRI with two isotropic pulse sequences for the diagnosis of internal derangement in children with painful knee conditions. STUDY TYPE/METHODS:Prospective. SUBJECTS/METHODS:Sixty children. FIELD STRENGTH/SEQUENCE/UNASSIGNED:3T, gradient echo-based scout with automatic anatomical landmark recognition and plane prescription, 3D CAIPIRINHA SPACE TSE. ASSESSMENT/RESULTS:Three fellowship-trained musculoskeletal radiologists evaluated the MRI studies independently and resolved discrepancies through consensus. Outcome variables included image quality, motion artifacts, meniscal abnormalities, anterior and posterior cruciate ligament tears, and cartilage lesions. Arthroscopic surgery served as the standard of reference, which was performed after 37 (range, 1-143) days post-MRI. STATISTICAL TESTS/UNASSIGNED:Diagnostic accuracy analysis of MRI with arthroscopic surgery as the standard of reference. Reliability analysis through calculation of interreader agreements with kappa statistics. RESULTS:All studies were suitable for diagnostic interpretation with good-to-very-good image quality ratings and little-to-no motion degradation ratings in the majority of cases. The sensitivities/specificities/accuracies of 3D CAIPIRINHA TSE MRI were 0.93/0.96/0.94 for 15/60 (25%) medial meniscal tears, 0.95/0.92/0.94 for 21/60 (35%) lateral meniscal tears, 0.83/1.00/0.92 for 6/60 (17%) discoid menisci, 1.00/0.98/0.99 for 16/60 (27%) anterior cruciate ligament tears, 1.0/1.0/1.0 for 2/60 (3%) posterior cruciate ligament tears, 1.00/1.00/1.00 for 5/60 (8%) osteochondritis dissecans lesions, 0.71/0.96/0.84 for 48 (13%) defects in 360 cartilage segments, and 0.85/0.97/0.91 overall. The interreader agreements were overall good-to-very-good (kappa, 0.72-1.00). DATA CONCLUSION/UNASSIGNED:The clinical use of 10-min 3D CAIPIRINHA TSE MRI of the knee in children with painful knee conditions yields an overall high arthroscopy-validated diagnostic accuracy of 91% and good-to-very good interreader reliability for the diagnosis of internal knee derangements. LEVEL OF EVIDENCE/METHODS:1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019;49:e139-e151.

BACKGROUND:Pulmonary involvement is common in several infectious and non-infectious diagnostic settings. Imaging findings consistently overlap and are therefore difficult to differentiate by chest-CT. The aim of this study was to evaluate the role of CT-textural features(CTTA) for discrimination between atypical viral (respiratory-syncitial-virus(RSV) and herpes-simplex-1-virus (HSV1)), fungal (pneumocystis-jirovecii-pneumonia(PJP)) interstitial pneumonias and alveolar hemorrhage. METHODS:By retrospective single-centre analysis we identified 46 consecutive patients (29 m) with RSV(n = 5), HSV1(n = 6), PJP(n = 21) and lung hemorrhage(n = 14) who underwent unenhanced chest CTs in early stages of the disease between 01/2016 and 02/2017. All cases were confirmed by microbiologic direct analysis of bronchial lavage. On chest-CT-scans, the presence of imaging features like ground-glass opacity(GGO), crazy-paving, air-space consolidation, reticulation, bronchial wall thickening and centrilobular nodules were described. A representative large area was chosen in both lungs and used for CTTA-parameters (included heterogeneity, intensity, average, deviation, skewness). RESULTS:Discriminatory CTTA-features were found between alveolar hemorrhage and PJP consisting of differences in mean heterogeneity(p < 0.015) and uniformity of skewness(p < 0.006). There was no difference between CT-textural features of diffuse alveolar hemorrhage and viral pneumonia or PJP and viral pneumonia. Visual HRCT-assessment yielded great overlap of imaging findings with predominance of GGO for PJP and airspace consolidation for pneumonia/alveolar hemorrhage. Significant correlations between HRCT-based imaging findings and CT-textural features were found for all three disease groups. CONCLUSION:CT-textural features showed significant differences in mean heterogeneity and uniformity of skewness. HRCT-based imaging findings correlated with certain CT-textural features showing that the latter have the potential to characterize structural properties of lung parenchyma and related abnormalities.

RATIONALE AND OBJECTIVES:This study aimed to test the hypothesis that ultrastructural wall abnormalities of lymphoma vessels correlate with perfusion computed tomography (PCT) kinetics. MATERIALS AND METHODS:), and electron microscopy was used to determine the presence or absence of tight junctions, endothelial fenestration, basement membrane, and pericytes, and to measure extracellular matrix thickness. RESULTS:(P = .038, r = 0.695). CONCLUSION:k-Trans values of PCT do not correlate with ultrastructural microvessel features, whereas endothelial fenestrations correlate with increased intra-tumoral BVs.

OBJECTIVES/OBJECTIVE:To 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. METHODS:Following 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. RESULTS:Raters 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) (p < 0.05), 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 (p < 0.01). CONCLUSIONS:The 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/CONCLUSIONS:• 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.

PURPOSE:The aim of this study to evaluate the role of frequency-selective nonlinear blending (FS-NLB) for the detectability of brain metastases with contrast-enhanced computed tomography (CECT) using magnetic resonance imaging (MRI) as standard of reference. MATERIALS AND METHODS:A retrospective patient data search at our institution yielded 91 patients who underwent both brain CECT and MRI for screening of brain metastases (n = 173) between 2014 and 2016 (mean time interval, 29 ± 37 [malignant: 15 ± 16/benign: 42 ± 47] days). A recently introduced FS-NLB postprocessing technique was applied to CECT images. Two readers interpreted all CT images in an independent fashion. The conventional, linear blending (LB) CT images were evaluated first. After a washout period, the same readers evaluated the FS-NLB CT images. The standard of reference was established by a consensus interpretation of the brain MRI studies. Outcome variables included determination of best performing FS-NLB settings, region of interest (ROI)-based calculation of contrast-to-noise ratios (CNRs), size, and number of brain metastases. Based on the number of metastases, we classified patients in 5 therapeutically relevant categories (0, no metastasis; 1, singular metastasis; 2, less than 4 metastases; 3, >4 and <10 metastases; 4, >10 metastases). Statistical comparison and diagnostic performance tests were applied. RESULTS:A center of 47 Hounsfield units (HU), delta of 5 HU, and slope of 5 resulted in the best delineation of hyperdense brain metastases, whereas for hypodense brain metastases, a center of 32 HU, delta of 5 HU, and slope of 5 showed best delineation. Frequency-selective nonlinear blending significantly increased CNR in hyperdense cerebral metastases (CECT: 9.11 [6.9-10.9], FS-NLB: 18.1 [11.9-22.8]; P < 0.0001) and hypodense cerebral metastases (CECT: 6.3 [5.2-8], FS-NLB: 17.8 [14.5-19.7]; P < 0.0001). Sensitivity, specificity, negative predictive values, positive predictive values, and accuracy for LB, and FS-NLB were 40%, 98%, 99%, 31%, and 52%, and 62%, 94%, 97%, 40%, and 69%, respectively. Magnetic resonance imaging, LB, and FS-NLB classification of metastatic patients were group 0 (47, 47, 46), group 1 (14, 8, 11), group 2 (16, 12, 15), group 3 (8, 7, 8), and group 4 (6, 4, 6). CONCLUSIONS:Frequency-selective nonlinear blending postprocessing of CECT significantly increases the detection of brain metastases over conventional CECT; however, the sensitivity remains lower than MRI. Frequency-selective nonlinear blending is slightly inferior in the categorization of patients into therapeutically relevant groups, when compared with MRI.

Purpose To investigate the diagnostic performance of three-dimensional (3D) MRI for depicting meniscal injuries of the knee by using surgery as the standard of reference. Materials and Methods A literature search was performed to identify original studies published between 1985 and 2017. Summary receiver operating characteristic curve and sensitivity analyses were performed to compare the diagnostic performance of 3D versus two-dimensional (2D) MRI for the assessment of knee meniscal injuries and to evaluate the impact of relevant covariates on the diagnostic performance for assessment of knee meniscal injuries. Results Of identified records, 31 studies (1743 3D knee MRI examinations) were included (23 studies also reported the results of 2D MRI). All studies before 2008 used gradient-echo (GRE) sequences, whereas all studies after 2011 used fast spin-echo (FSE) sequences. By comparing FSE and GRE sequences with 2D MRI, pooled estimate of sensitivity (90.0%; P = .2 and 90.1%; P = .2 vs 88.5%) and pooled estimate of specificity (91%; P = .3 and 89.8% vs 90.1%; P = .7) were comparable. The 3D FSE sequences demonstrated similar diagnostic performance as 3D GRE sequences, except for slightly improved sensitivity for depicting lateral meniscal injuries (FSE, 84.6%; GRE, 75%; P = .01). The specificity of 3D sequences improved when multiplanar reformatting was performed (P = .02). Conclusion Both three-dimensional (3D) fast spin-echo (FSE) and 3D gradient-echo (GRE) sequences had similar diagnostic performance as two-dimensional sequences, with slight superior sensitivity of 3D FSE sequences compared with 3D GRE sequences for depicting lateral meniscal injuries of the knee. © RSNA, 2018 Online supplemental material is available for this article.

OBJECTIVES/OBJECTIVE:We aimed to test the hypothesis that the spleen-to-liver-attenuation ratio on portal-venous enhancement phase CT images can identify diffuse splenic infiltration in subjects with lymphoma. METHODS:A database search yielded 70 subjects with malignant haematological diseases who underwent contrast-enhanced CT (CECT) between December 2010 and March 2018. Additionally, consecutive control subjects were evaluated. We compared the splenic volume, splenic attenuation, spleen-to-liver, spleen-to-aorta and spleen-to-musculature ratios on portal-venous phase CECT images, pre- to post-treatment and between the different lymphoma entities. The standard of reference for splenic involvement was normalisation of the spleen volume following chemotherapy or normalisation of FDG-uptake. RESULTS:; p < .001). Spleen-to-liver ratio significantly increased in lymphoma patients after therapy, inversely correlating with the decline in FDG-uptake (n=10) even in patients with normal-sized spleens (2/10), staying unchanged at follow-up. The outcome variables were not significantly different between the lymphoma subtypes. CONCLUSIONS:We suggest the additional use of spleen-to-liver attenuation ratio to splenic volume alone for detection of diffuse splenic infiltration in subjects with lymphoma. The course of spleen-to-liver attenuation ratio inversely correlated with that of FDG-uptake in a subgroup of patients working accurately in normal-sized diffusely involved spleens. KEY POINTS/CONCLUSIONS:• Involvement of the spleen is frequent in haematological malignancies and is important for staging and appropriate treatment. • Diffuse splenic infiltration often results in only homogeneous splenomegaly without a focal lesion, but even no or only minimal increase in splenic volume is possible. In these cases diagnosis of spleen involvement is a challenge for the radiologist. • Our data support the use of the spleen-to-liver attenuation ratio in addition to size measurements for the detection of diffuse splenic infiltration in subjects with lymphoma.