3D zero-echo time and 3D T1-weighted gradient-echo MRI sequences as an alternative to CT for the evaluation of the lumbar facet joints and lumbosacral transitional vertebrae.

BACKGROUND: Computed tomography (CT) is the reference standard for assessment of the bone. Magnetic resonance imaging (MRI) developments enable a CT-like visualization of the osseous structures. PURPOSE: To assess the diagnostic performance of 3D zero-echo time (3D-ZTE) and 3D T1-weighted gradient-echo (3D-T1GRE) MRI sequences for the evaluation of lumbar facet joints (LFJs) and the detection of lumbosacral transitional vertebrae (LSTV) using CT as the reference standard. MATERIAL AND METHODS: In total, 87 adult patients were included in this prospective study. Evaluation of degenerative changes of the facet joints at the L3/L4, L4/L5, and L5/S1 levels on both sides was performed by two readers using a 4-point Likert scale. LSTV were classified according to Castelvi et al. Image quality was quantitatively measured using the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Intra-reader, inter-reader, and inter-modality reliability were calculated using Cohen's kappa statistic. RESULTS: Intra-reader agreement for 3D-ZTE, 3D-T1GRE, and CT was 0.607, 0.751, and 0.856 and inter-reader agreement was 0.535, 0.563, and 0.599, respectively. The inter-modality agreement between 3D-ZTE and CT was 0.631 and between 3D-T1GRE and CT 0.665. A total of LSTV were identified in both MR sequences with overall comparable accuracy compared to CT. Mean SNR for bone, muscle, and fat was highest for 3D-T1GRE and mean CNR was highest for CT. CONCLUSION: 3D-ZTE and 3D-T1GRE MRI sequences can assess the LFJs and LSTV and may serve as potential alternatives to CT.

Ultrashort time-to-echo MR morphology of cartilaginous endplate correlates with disc degeneration in the lumbar spine.

PURPOSE: Using ultrashort echo time (UTE) MRI, we determined prevalence of abnormal cartilaginous endplate (CEP), and the relationship between CEP and disc degeneration in human lumbar spines. MATERIALS AND METHODS: Lumbar spines from 71 cadavers (age 14-74 years) were imaged at 3 T using sagittal UTE and spin echo T2 map sequences. On UTE images, CEP morphology was defined as "normal" with linear high signal intensity or "abnormal" with focal signal loss and/or irregularity. On spin echo images, disc grade and T2 values of the nucleus pulposus (NP) and annulus fibrosus (AF) were determined. 547 CEPs and 284 discs were analysed. Effects of age, sex, and level on CEP morphology, disc grade, and T2 values were determined. Effects of CEP abnormality on disc grade, T2 of NP, and T2 of AF were also determined. RESULTS: Overall prevalence of CEP abnormality was 33% and it tended to increase with older ages (p = 0.08) and at lower spinal levels of L5 than L2 or L3 (p = 0.001). Disc grades were higher and T2 values of the NP were lower in older spines (p < 0.001) and at lower disc level of L4-5 (p < 0.05). We found significant association between CEP and disc degeneration; discs adjacent to abnormal CEPs had high grades (p < 0.01) and lower T2 values of the NP (p < 0.05). CONCLUSION: These results suggest that abnormal CEPs are frequently found, and it associates significantly with disc degeneration, suggesting an insight into pathoetiology of disc degeneration.

Deep-Learning-Aided Evaluation of Spondylolysis Imaged with Ultrashort Echo Time Magnetic Resonance Imaging.

Isthmic spondylolysis results in fracture of pars interarticularis of the lumbar spine, found in as many as half of adolescent athletes with persistent low back pain. While computed tomography (CT) is the gold standard for the diagnosis of spondylolysis, the use of ionizing radiation near reproductive organs in young subjects is undesirable. While magnetic resonance imaging (MRI) is preferable, it has lowered sensitivity for detecting the condition. Recently, it has been shown that ultrashort echo time (UTE) MRI can provide markedly improved bone contrast compared to conventional MRI. To take UTE MRI further, we developed supervised deep learning tools to generate (1) CT-like images and (2) saliency maps of fracture probability from UTE MRI, using ex vivo preparation of cadaveric spines. We further compared quantitative metrics of the contrast-to-noise ratio (CNR), mean squared error (MSE), peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM) between UTE MRI (inverted to make the appearance similar to CT) and CT and between CT-like images and CT. Qualitative results demonstrated the feasibility of successfully generating CT-like images from UTE MRI to provide easier interpretability for bone fractures thanks to improved image contrast and CNR. Quantitatively, the mean CNR of bone against defect-filled tissue was 35, 97, and 146 for UTE MRI, CT-like, and CT images, respectively, being significantly higher for CT-like than UTE MRI images. For the image similarity metrics using the CT image as the reference, CT-like images provided a significantly lower mean MSE (0.038 vs. 0.0528), higher mean PSNR (28.6 vs. 16.5), and higher SSIM (0.73 vs. 0.68) compared to UTE MRI images. Additionally, the saliency maps enabled quick detection of the location with probable pars fracture by providing visual cues to the reader. This proof-of-concept study is limited to the data from ex vivo samples, and additional work in human subjects with spondylolysis would be necessary to refine the models for clinical use. Nonetheless, this study shows that the utilization of UTE MRI and deep learning tools could be highly useful for the evaluation of isthmic spondylolysis.

Detailed bone assessment of the sacroiliac joint in a prospective imaging study: comparison between computed tomography, zero echo time, and black bone magnetic resonance imaging.

OBJECTIVES: To compare the value of zero echo time (ZTE) and gradient echo "black bone" (BB) MRI sequences for bone assessment of the sacroiliac joint (SI) using computed tomography (CT) as the reference standard. MATERIALS AND METHODS: Between May 2019 and January 2021, 79 patients prospectively underwent clinically indicated 3-T MRI including ZTE and BB imaging. Additionally, all patients underwent a CT scan covering the SI joints within 12 months of the MRI examination. Two blinded readers performed bone assessment by grading each side of each SI joint qualitatively in terms of seven features (osteophytes, subchondral sclerosis, erosions, ankylosis, joint irregularity, joint widening, and gas in the SI joint) using a 4-point Likert scale (0 = no changes-3 = marked changes). Scores were compared between all three imaging modalities. RESULTS: Interreader agreement was largely good (k values: 0.5-0.83). Except for the feature "gas in SI joint" where ZTE exhibited significantly lower scores than CT (p < 0.001), ZTE and BB showed similar performance relative to CT for all other features (p > 0.52) with inter-modality agreement being substantial to almost perfect (Krippendorff's alpha coefficients: 0.724-0.983). When combining the data from all features except for gas in the SI joint and when binarizing grading scores, combined sensitivity/specificity was 76.7%/98.6% for ZTE and 80.8%/99.1% for BB, respectively, compared to CT. CONCLUSIONS: The performance of ZTE and BB sequences was comparable to CT for bone assessment of the SI joint. These sequences may potentially serve as an alternative to CT yet without involving exposure to ionizing radiation.

Evaluation of ultrashort echo-time (UTE) and fast-field-echo (FRACTURE) sequences for skull bone visualization and fracture detection - A postmortem study.

BACKGROUND AND PURPOSE: CT is considered the modality of choice in the assessment of the skull due to the fast and accurate depiction of bone structures. Nevertheless, MRI has evolved into a possible alternative due to optimal soft tissue contrast and recent advances with the ability to visualize tissues with shortest T2 times, such as osseous structures. In this study we compare skull bone visualization and fracture detection across two MRI sequences to CT as reference standard. MATERIAL AND METHODS: Twenty subjects underwent CT and MRI with less than 72 h between examination. The MRI protocol included a 2D ultrashort echo time (UTE) and a 3D multi-echo in-phase fast-field-echo (FRACTURE) sequence. Independent raters evaluated qualitative characteristics and fracture detectability in different skull subregions (skull vault, skull base and viscerocranium). Interrater and intermodality agreement was evaluated by calculating intraclass coefficients (ICC). RESULTS: FRACTURE ICC indicated a good agreement in all subregions (ICC = 0.83 - 0.88), whereas UTE had excellent results calculated in the skull vault and viscerocranium (ICC = 0.91 - 0.94). At the skull vault, both MRI sequences received an overall good rating (UTE: 2.63 ± 0.42 FRACTURE. 2.81 ± 0.32). Fracture detection using MRI sequences for the skull vault, was highest compared to other subregions. CONCLUSIONS: Both MRI sequences may provide an alternative e.g. for surgical planning or follow up exams of the osseous neurocranium; although, at the skull base and viscerocranium bone visualization with MRI bone imaging sequences perform inferior to CT standard imaging.

Comparison of MR Ultrashort Echo Time and Optimized 3D-Multiecho In-Phase Sequence to Computed Tomography for Assessment of the Osseous Craniocervical Junction.

BACKGROUND: To assess changes of the craniocervical junction (CCJ), computed tomography (CT) is considered the reference standard. Recent advances in bone depiction on magnetic resonance imaging (MRI) enable high-quality visualization of osseous structures. Consequently, MRI may serve as an alternative to CT, without the use of ionizing radiation. PURPOSE: To compare two MRI sequences optimized for bone visualization to the CT reference standard in the assessment of the osseous CCJ. STUDY TYPE: Prospective. POPULATION/SUBJECTS: Twenty-seven decedents and five healthy volunteers. FIELD STRENGTH/SEQUENCE: 3T/ultrashort-echo time gradient echo (UTE) and optimized 3D-multiecho in-phase gradient echo sequences (FRACTURE). ASSESSMENT: All decedents were scanned with both MRI sequences and CT. Three observers rated degeneration to obtain a score for the upper (atlanto-dental and left/right atlanto-occipital joint) and for the lower part of the CCJ (left and right atlanto-axial joint). Two reader rated the following quantitative parameters: basion-axial-interval, atlanto-dental-interval, atlanto-occipital-interval, Powers-ratio, and signal/contrast-to-noise-ratio. As a proof of concept, five healthy volunteers were scanned with both MRI sequences. STATISTICAL TESTS: Degeneration was assessed on a Likert scale by three independent observers. Interrater and intermodality reliability were calculated using an intraclass correlation coefficient. To compare distance measurements between examination methods, a Friedman test, between-degenerative ratings, and a Kruskal-Wallis test were performed. RESULTS: Degenerative ratings of the CCJ between MRI sequences and CT showed a good interrater and intermodality agreement. MRI sequences tended to underestimate the degree of degeneration compared to CT, and this became more marked with increasing degeneration severity. There were no significant relationships between distance measurements and the degree of degeneration (PCT = 0.62, PUTE = 0.64, PFRACTURE = 0.67). The in vivo examination proved the feasibility of both MRI methods in a clinical setting. DATA CONCLUSION: Quantitative and qualitative ratings on MR images were comparable to CT images; thus, MRI may be a valid alternative to CT assessing the CCJ. LEVEL OF EVIDENCE: 1. TECHNICAL EFFICACY STAGE: 3.

Quantitative magnetic resonance imaging of meniscal pathology ex vivo.

OBJECTIVE: To determine the ability of conventional spin echo (SE) T2 and ultrashort echo time (UTE) T2* relaxation times to characterize pathology in cadaveric meniscus samples. MATERIALS AND METHODS: From 10 human donors, 54 triangular (radially cut) meniscus samples were harvested. Meniscal pathology was classified as normal (n = 17), intrasubstance degenerated (n = 33), or torn (n = 4) using a modified arthroscopic grading system. Using a 3-T MR system, SE T2 and UTE T2* values of the menisci were determined, followed by histopathology. Effect of meniscal pathology on relaxation times and histology scores were determined, along with correlation between relaxation times and histology scores. RESULTS: Mean ± standard deviation UTE T2* values for normal, degenerated, and torn menisci were 3.6 ± 1.3 ms, 7.4 ± 2.5 ms, and 9.8 ± 5.7 ms, respectively, being significantly higher in degenerated (p < 0.0001) and torn (p = 0.0002) menisci compared to that in normal. In contrast, the respective mean SE T2 values were 27.7 ± 9.5 ms, 25.9 ± 7.0 ms, and 35.7 ± 10.4 ms, without significant differences between groups (all p > 0.14). In terms of histology, we found significant group-wise differences (each p < 0.05) in fiber organization and inner-tip surface integrity sub-scores, as well as the total score. Finally, we found a significant weak correlation between UTE T2* and histology total score (p = 0.007, Rs2 = 0.19), unlike the correlation between SE T2 and histology (p = 0.09, Rs2 = 0.05). CONCLUSION: UTE T2* values were found to distinguish normal from both degenerated and torn menisci and correlated significantly with histopathology.

Speed of sound ultrasound: comparison with proton density fat fraction assessed with Dixon MRI for fat content quantification of the lower extremity.

OBJECTIVES: To compare speed of sound (SoS) ultrasound (US) of the calves with Dixon magnetic resonance imaging (MRI) for fat content quantification. MATERIALS AND METHODS: The study was approved by the local ethics committee. Fifty calf muscles of 35 women (age range 22-81 years) prospectively underwent an US and subsequent MRI (Dixon sequence) examination as well as body weight and impedance fat measurements. SoS (in m/s) was calculated positioning a reflector on the opposite side of a conventional US machine probe with the calf in between. Fiducial nitroglycerin markers were placed on the calf at the reflector and US probe end positions for later registration of the US sonification volumetric section. An automatic segmentation algorithm separated MRI adipose tissue, muscle and bone regions. MRI fat fraction of the entire leg slice (total) and intramuscular and adipose tissue fat fraction were calculated and correlation analysis and correlation coefficient comparison were performed. RESULTS: Median SoS demonstrated a very strong (r = - 0.83 (95% CI - 0.90; - 0.72); p < 0.001) correlation with MRI total fat fraction, a strong (r = - 0.61 (95% CI - 0.76; - 0.40); p < 0.001) correlation with MRI adipose tissue fat fraction and a moderate (r = - 0.54 (95% CI - 0.71; - 0.31); p < 0.001) correlation with MRI intramuscular fat fraction. Impedance body fat percentage correlated strongly with SoS (r = - 0.72 (95% CI - 0.85; - 0.51); p < 0.001) and MRI total fat fraction (r = 0.61 (95% CI 0.34; 0.78); p < 0.001). For electrical impedance, significantly lower correlations (p = 0.033) were found for MRI total fat fraction compared with SoS. CONCLUSIONS: Correlations of SoS with Dixon MRI fat fraction measurements were very strong to moderate. KEY POINTS: • Correlations of speed of sound with Dixon MRI fat fraction measurements of the same body location were very strong to moderate. • Speed of sound measurements showed a high repeatability. • Speed of sound provides a sufficient discrimination range for fat fraction estimates.

Vertebral body insufficiency fractures: detection of vertebrae at risk on standard CT images using texture analysis and machine learning.

PURPOSE: To evaluate the diagnostic performance of bone texture analysis (TA) combined with machine learning (ML) algorithms in standard CT scans to identify patients with vertebrae at risk for insufficiency fractures. MATERIALS AND METHODS: Standard CT scans of 58 patients with insufficiency fractures of the spine, performed between 2006 and 2013, were analyzed retrospectively. Every included patient had at least two CT scans. Intact vertebrae in a first scan that either fractured ("unstable") or remained intact ("stable") in the consecutive scan were manually segmented on mid-sagittal reformations. TA features for all vertebrae were extracted using open-source software (MaZda). In a paired control study, all vertebrae of the study cohort "cases" and matched controls were classified using ROC analysis of Hounsfield unit (HU) measurements and supervised ML techniques. In a within-subject vertebra comparison, vertebrae of the cases were classified into "unstable" and "stable" using identical techniques. RESULTS: One hundred twenty vertebrae were included. Classification of cases/controls using ROC analysis of HU measurements showed an AUC of 0.83 (95% confidence interval [CI], 0.77-0.88), and ML-based classification showed an AUC of 0.97 (CI, 0.97-0.98). Classification of unstable/stable vertebrae using ROC analysis showed an AUC of 0.52 (CI, 0.42-0.63), and ML-based classification showed an AUC of 0.64 (CI, 0.61-0.67). CONCLUSION: TA combined with ML allows to identifying patients who will suffer from vertebral insufficiency fractures in standard CT scans with high accuracy. However, identification of single vertebra at risk remains challenging. KEY POINTS: • Bone texture analysis combined with machine learning allows to identify patients at risk for vertebral body insufficiency fractures on standard CT scans with high accuracy. • Compared to mere Hounsfield unit measurements on CT scans, application of bone texture analysis combined with machine learning improve fracture risk prediction. • This analysis has the potential to identify vertebrae at risk for insufficiency fracture and may thus increase diagnostic value of standard CT scans.

Patterns of cartilage degeneration in knees with medial tibiofemoral offset.

OBJECTIVE: To determine if radiographic medial tibiofemoral offset (MTFO) is associated with: (1) magnetic resonance imaging (MRI) pathology of cartilage, meniscus, and ligament; and (2) a distinct pattern of lateral cartilage degeneration on MRI. MATERIALS AND METHODS: Three hundred consecutive adult knee MRIs with anteroposterior (AP) radiographs were retrospectively reviewed, and 145 studies were included. MTFO was defined as a medial extension of the medial femoral condyle beyond the articular surface of the medial tibial plateau on weight-bearing AP radiographs. The patients were then divided into the MTFO (n = 61) or no-offset (n = 84) groups. On MRI data obtained on a 1.5-Tesla system, articular cartilage of the femoral condyle and tibial plateau were graded using a modified Outerbridge classification (36 sub-regions similar to whole-organ MRI Score (WORMS) system). In addition, MR pathology of the ACL, MCL, LCL, medial and lateral menisci, were determined. RESULTS: Significantly increased (ANOVA p < 0.007) MR grade of the ligaments, menisci, and cartilage in the MTFO group (ranging from 0.3 to 2.5) compared to the control group (0.2 to 1.1). Color maps of the cartilage grades suggested a marked difference in both severity of degeneration and regional variations between the groups. MTFO group exhibited focally increased cartilage grades in the central, non-weight regions of lateral compartment (region p = 0.07 to 0.12, interaction p = 0.05 to 0.1). CONCLUSIONS: MTFO is associated with overall degeneration of the knee and features a distinct lateral cartilage degeneration pattern, which may reflect non-physiologic contact of the cartilage between the lateral tibial eminence and lateral central femoral condyle.

Investigation of the pulsatility of cerebrospinal fluid using cardiac-gated Intravoxel Incoherent Motion imaging.

The quantitative and non-invasive monitoring of cerebrospinal fluid (CSF) dynamics and composition may have high clinical relevance in the management of CSF disorders. In this study, we propose the use of the Intravoxel Incoherent Motion (IVIM) MRI for obtaining simultaneous measurements of CSF self-diffusion and fluid circulation. The rationale for this study was that turbulent fluid and mesoscopic fluid fluctuations can be modeled in a first approximation as a fast diffusion process. In this case, we expect that the fast fluid circulation and slower molecular diffusion dynamics can be quantified, assuming a bi-exponential attenuation pattern of the diffusion-weighted signal in MRI. IVIM indexes of fast and slow diffusion measured at different sites of the CSF system were systematically evaluated depending on both the phase of the heart cycle and the direction of the diffusion-encoding. The IVIM measurements were compared to dynamic measurements of fluid circulation performed by phase-contrast MRI. Concerning the dependence on the diffusion/flow-encoding direction, similar patterns were found both in the fraction of fast diffusion, f, and in the fluid velocity. Generally, we observed a moderate to high correlation between the fraction of fast diffusion and the maximum fluid velocity along the high-flow directions. Exploratory data analysis detected similarities in the dependency of the fraction of fast diffusion and of the velocity from the phase of the cardiac cycle. However, no significant differences were found between parameters measured during different phases of the cardiac cycle. Our results suggest that the fraction of fast diffusion may reflect CSF circulation. The bi-exponential IVIM model potentially allows us to disentangle the two diffusion components of the CSF dynamics by providing measurements of fluid cellularity (via the slow-diffusion coefficient) and circulation (via the fraction of fast-diffusion index).

The Calcaneal Crescent in Patients With and Without Plantar Fasciitis: An Ankle MRI Study.

OBJECTIVE: The bundled, crescent-shaped trabeculae within the calcaneal tuberosity-which we term and refer to here as the "calcaneal crescent"-may represent a structural adaption to the prevailing forces. Given Wolff law, we hypothesized that the calcaneal crescent would be more robust in patients with plantar fasciitis, a syndrome in part characterized by overload of the Achilles tendon-calcaneal crescent-plantar fascia system, than in patients without plantar fasciitis. MATERIALS AND METHODS: MR images of 37 patients (27 women and 10 men; mean age ± SD, 51 ± 13 years; mean body mass index [BMI, weight in kilograms divided by the square of height in meters], 26.8 ± 6.3) referred for workup of foot or ankle pain were retrospectively evaluated by two blinded readers in this study. Patients were assigned to two groups: group A, which was composed of 15 subjects without clinical signs or MRI findings of Achilles tendon-calcaneal crescent-plantar fascia system abnormalities, or group B, which was composed of 22 patients with findings of plantar fasciitis. The thickness and cross-sectional area (CSA) of the Achilles tendon, calcaneal crescent, and plantar fascia were measured on proton density (PD)-weighted MR images. The entire crescent volume was manually measured using OsiriX software on consecutive sagittal PD-weighted images. Additionally, contrast-to-noise ratio (CNR) as a surrogate marker for trabecular density and the mean thickness of the calcaneal crescent were determined on PD-weighted MR images. The groupwise difference in the morphologic measurements were evaluated using ANOVA with BMI as a covariate. Partial correlation was used to assess the relationships of measurements for the group with plantar fasciitis (group B). Intraclass correlation coefficient (ICC) statistics were performed. RESULTS: Patients with plantar fasciitis had a greater CSA and volume of the calcaneal crescent and had lower CNR (i.e., denser trabeculae) than those without Achilles tendon-calcaneal crescent-plantar fascia system abnormalities (CSA, 100.2 vs 73.7 mm2, p = 0.019; volume, 3.06 vs 1.99 cm3, p = 0.006; CNR, -28.40 vs -38.10, p = 0.009). Interreader agreement was excellent (ICC = 0.85-0.99). CONCLUSION: In patients with plantar fasciitis, the calcaneal crescent is enlarged compared with those without abnormalities of the Achilles tendon-calcaneal crescent-plantar fascia system. An enlarged and trabeculae-rich calcaneal crescent may potentially indicate that abnormally increased forces are being exerted onto the Achilles tendon-calcaneal crescent-plantar fascia system.

Cardiac-gated intravoxel incoherent motion diffusion-weighted magnetic resonance imaging for the investigation of intracranial cerebrospinal fluid dynamics in the lateral ventricle: a feasibility study.

PURPOSE: Intravoxel incoherent motion (IVIM) in diffusion-weighted magnetic resonance imaging (DW-MRI) attributes the signal attenuation to the molecular diffusion and to a faster pseudo-diffusion. Purpose of the study was to demonstrate the feasibility of IVIM for the investigation of intracranial cerebrospinal fluid (CSF) dynamics. METHODS: Cardiac-gated DW-MRI images with fifteen b-values (0-1300s/mm2) along three orthogonal directions (mediolateral (ML), anteroposterior (AP), and craniocaudal (CC)) were acquired during maximum systole and diastole in 10 healthy volunteers (6 males, mean age 36 ± 15 years). A pixel-wise bi-exponential fitting with an iterative nonparametric algorithm was carried out to calculate the following parameters: diffusion coefficient (D), fast diffusion coefficient (D*), and fraction of fast diffusion (f). Region of interest measurements were performed in both lateral ventricles. Comparison of IVIM parameters was performed among two cardiac cycle acquisitions and among the diffusion-encoding directions using a paired Student's t test. RESULTS: f significantly (p < 0.05) depended on the diffusion-encoding direction and on the cardiac cycle (diastole AP 0.30 ± 0.13, ML 0.22 ± 0.12, CC 0.26 ± 0.17; systole AP 0.45 ± 0.17, ML 0.34 ± 0.15, CC 0.40 ± 0.21). Neither a cardiac cycle nor a direction dependency was found among mean D values (which is in line with the expected intraventricular isotropic diffusion) and D* values (p > 0.05 each). CONCLUSION: The fraction of fast diffusion from IVIM is feasible to detect a direction-dependent and cardiac-dependent pulsatile CSF flow within the lateral ventricles allowing for quantitative monitoring of CSF dynamics. This technique might provide opportunities to further investigate the pathophysiology of various neurological disorders involving altered CSF dynamics.

Correlation of listhesis on upright radiographs and central lumbar spinal canal stenosis on supine MRI: is it possible to predict lumbar spinal canal stenosis?

OBJECTIVE: To investigate whether upright radiographs can predict lumbar spinal canal stenosis using supine lumbar magnetic resonance imaging (MRI) and to investigate the detection performance for spondylolisthesis on upright radiographs compared with supine MRI in patients with suspected lumbar spinal canal stenosis (LSS). MATERIALS AND METHODS: In this retrospective study, conventional radiographs and MR images of 143 consecutive patients with suspected LSS (75 female, mean age 72 years) were evaluated. The presence and extent of listhesis (median ± interquartile range) were assessed on upright radiographs and supine MRI of L4/5. In addition, the grade of central spinal stenosis of the same level was evaluated on MRI according to the classification of Schizas and correlated with the severity/grading of anterolisthesis on radiographs. RESULTS: Anterolisthesis was detected in significantly more patients on radiographs (n = 54; 38%) compared with MRI (n = 28; 20%), p < 0.001. Pairwise comparison demonstrated a significantly larger extent of anterolisthesis on radiographs (9 ± 5 mm) compared with MRI (5 ± 3 mm), p < 0.001. A positive correlation was found regarding the extent of anterolisthesis measured on radiographs and the grade of stenosis on MRI (r = 0.563, p < 0.001). Applying a cutoff value of ≥5 mm anterolisthesis on radiographs results in a specificity of 90% and a positive predictive value of 78% for the detection of patients with LSS, as defined by the Schizas classification. CONCLUSION: Upright radiographs demonstrated more and larger extents of anterolisthesis compared with supine MRI. In addition, in patients with suspected LSS, the extent of anterolisthesis on radiographs (particularly ≥5 mm) is indicative of LSS and warrants lumbar spine MRI.

The IVIM signal in the healthy cerebral gray matter: A play of spherical and non-spherical components.

The intra-voxel incoherent motion (IVIM) model assumes that blood flowing in isotropically distributed capillary segments induces a phase dispersion of the MR signal, which increases the signal attenuation in diffusion-weighted images. However, in most tissue types the capillary network has an anisotropic micro-architecture. In this study, we investigated the possibility to indirectly infer the anisotropy of the capillary network in the healthy cerebral gray matter by evaluating the dependence of the IVIM signal from the direction of the diffusion-encoding. Perfusion-related indices and self-diffusion were modelled as symmetric rank 2 tensors. The geometry of the tensors was quantified pixel-wise by decomposing the tensor in sphere-like, plane-like, and line-like components. Additionally, trace and fractional anisotropy of the tensors were computed. While the self-diffusion tensor is dominated by a spherical geometry with a residual contribution of the non-spherical components, both, fraction of perfusion and pseudo-diffusion, present a substantial (in the order of 30%) contribution of planar and linear components to the tensor metrics. This study shows that the IVIM perfusion estimates in the cerebral gray matter present a detectable deviation from the spherical model. These non-spherical components may reflect the direction-dependent morphology of the microcirculation. Therefore, the tensor generalization of the IVIM model may provide a tool for the non-invasive monitoring of cerebral capillary micro-architecture during development, aging or in pathologies.

Degenerative lumbar spinal canal stenosis: intra- and inter-reader agreement for magnetic resonance imaging parameters.

PURPOSE: To assess the inter- and intra-reader agreement of commonly used quantitative and qualitative image parameters for the assessment of degenerative lumbar spinal canal stenosis (LSS) by magnetic resonance imaging (MRI). METHODS: In this ethical board approved cross-sectional multicenter study, MRI of 100 randomly selected patients (median age 72.5 years, 48 % female) of the prospective Lumbar Stenosis Outcome Study (LSOS) were evaluated by two independent readers. A set of five previously published core imaging parameters as well as nine qualitative and five quantitative additional parameters regarding LSS and degenerative changes of the lumbar spine were assessed to calculate κ and intraclass correlation coefficients (ICC) for the inter-reader agreement. Additional repeated image evaluations were performed by one reader to calculate the intra-reader agreement. RESULTS: κ values for the core image parameters ranged between 0.42 (compromise of the foraminal zone) and 0.77 (relation between fluid and cauda equina) for inter-reader agreement and between 0.59 (compromise of the foraminal zone) and 0.8 (compromise of the central zone) for intra-reader agreement. The inter-reader agreement for the non-core parameters showed κ values of 0.27-0.69 and ICC values of 0.46-0.85. The intra-reader agreement showed κ values of 0.53-0.69 and ICC values of 0.81-0.88. CONCLUSIONS: The inter- and intra-reader agreement of commonly used quantitative and qualitative image parameters for the assessment of LSS showed quite a variability with previously defined core parameters having good to excellent inter- and intra-reader agreements.

Gouty arthritis: the diagnostic and therapeutic impact of dual-energy CT.

OBJECTIVES: To determine the diagnostic and therapeutic impact of dual-energy computed tomography (DECT) in gout. METHODS: Forty-three patients with (n = 20) and without a history of gout (n = 23) showing non-specific soft tissue deposits underwent DECT after unrewarding arthrocentesis. Two blinded, independent readers evaluated DECT for the presence of urate crystals. Clinical diagnosis, clinically suspected urate crystal locations, diagnostic thinking and therapeutic decisions were noted before and after DECT. Clinical 1-month follow-up was obtained. RESULTS: DECT showed urate in 26/43 patients (60 %). After DECT, clinical diagnosis of gout was withdrawn in 17/43 (40 %) and was maintained in 16/43 patients (37 %). In 10/43 patients (23 %) the diagnosis was maintained, but DECT revealed urate in clinically unsuspected locations. In 23/43 patients (53 %), a treatment-change based on DECT occurred. Changes in diagnostic thinking occurred more frequently in patients without a history of gout (p < 0.001), changes in therapeutic decisions more frequently in patients with a history of gout (p = 0.014). Clinical follow-up indicated beneficial effects of DECT-based diagnoses in 83 % of patients. CONCLUSIONS: In patients with or without a history of gout and a recent suspicion for gouty arthritis with an unrewarding arthrocentesis, DECT has a marked diagnostic and therapeutic impact when hyperdense soft-tissue deposits are present. KEY POINTS: • This study evaluates the concept of evidence-based radiology • In patients with suspected gout, DECT can help clinicians make the diagnosis • DECT has a marked impact on therapy • Clinical follow-up after 1 month indicated reliable results of DECT.

Performances of low-dose dual-energy CT in reducing artifacts from implanted metallic orthopedic devices.

OBJECTIVES: The objective was to evaluate the performances of dose-reduced dual-energy computed tomography (DECT) in decreasing metallic artifacts from orthopedic devices compared with dose-neutral DECT, dose-neutral single-energy computed tomography (SECT), and dose-reduced SECT. MATERIALS AND METHODS: Thirty implants in 20 consecutive cadavers underwent both SECT and DECT at three fixed CT dose indexes (CTDI): 20.0, 10.0, and 5.0 mGy. Extrapolated monoenergetic DECT images at 64, 69, 88, 105, 120, and 130 keV, and individually adjusted monoenergy for optimized image quality (OPTkeV) were generated. In each group, the image quality of the seven monoenergetic images and of the SECT image was assessed qualitatively and quantitatively by visually rating and by measuring the maximum streak artifact respectively. RESULTS: The comparison between SECT and OPTkeV evaluated overall within all groups showed a significant difference (p <0.001), with OPTkeV images providing better images. Comparing OPTkeV with the other DECT images, a significant difference was shown (p <0.001), with OPTkeV and 130-keV images providing the qualitatively best results. The OPTkeV images of 5.0-mGy acquisitions provided percentages of images with scores 1 and 2 of 36 % and 30 % respectively, compared with 0 % and 33.3 % of the corresponding SECT images of 10- and 20-mGy acquisitions. Moreover, DECT reconstructions at the OPTkeV of the low-dose group showed higher CT numbers than the SECT images of dose groups 1 and 2. CONCLUSIONS: This study demonstrates that low-dose DECT permits a reduction of artifacts due to metallic implants to be obtained in a similar manner to neutral-dose DECT and better than reduced or neutral-dose SECT.

Impact of acceleration on bone depiction quality by ultrashort echo time magnetic resonance bone imaging sequences in medication-related osteonecrosis of the jaw.

Objectives: To assess the impact on bone depiction quality by decreasing number of radial acquisitions (RA) of a UTE MR bone imaging sequence in MRONJ. Material and methods: UTE MR bone imaging sequences using pointwise encoding time reduction with RA (PETRA) with 60'000, 30'000 and 10'000 RA were acquired in 16 patients with MRONJ and 16 healthy volunteers. Blinded readout sessions were performed by two radiologists. Qualitative analysis compared the detection of osteolytic lesions and productive bony changes in the PETRA sequences of the patients with MRONJ. Quantitative analysis assessed the differences in image artifacts, contrast-to-noise ratio (CNR) and image noise. Results: Acquisition times were reduced from 315 to 165 and 65 s (60'000, 30'000, 10'000 RA, respectively), resulting in a fewer number of severe motion artifacts. Bone delineation was increasingly blurred when reducing the number of RA but without any trade-off in terms of diagnostic performance. Interreader agreement for the detection of pathognomonic osteolysis was moderate (κ = 0.538) for 60'000 RA and decreased to fair (κ = 0.227 and κ = 0.390) when comparing 30'000 and 10'000 RA, respectively. Image quality between sequences was comparable regarding CNR, image noise and artifact dimensions without significant differences (all P > 0.05). Conclusions: UTE MR bone imaging sequences with a lower number of RA provide sufficient image quality for detecting osteolytic lesions and productive bony changes in MRONJ subjects at faster acquisition times compared to the respective standard UTE MR bone imaging sequence.

Added value of combined acromiohumeral distance and critical shoulder angle measurements on conventional radiographs for the prediction of rotator cuff pathology.

Purpose: To investigate the role of acromiohumeral distance (AHD) and critical shoulder angle (CSA) measurements from conventional radiographs (CR) in isolation and combined (prognostic index PIAHD-CSA) as predictors of full thickness rotator cuff tendon tears (RCT) and critical fatty degeneration (CFD; i.e. as much fat as muscle). Method: In this retrospective study AHD and CSA were measured in 127 CR. MR arthrograms served as reference standard and were screened for RCT and CFD. Statistical analysis for inter-reader agreement, Spearman's rank correlation, linear stepwise regression and logistic regression for AHD and CSA with ROC analyses including PIAHD-CSA were performed. Results: In 90 subjects (17 females, mean age 36.1 ± 14.1) no RCT were found on MR imaging and served as control group. In 37 patients (13 females, mean age 58.7 ± 13.2) ≥ one RCT was found. Inter-reader agreements rated between к = 0.42-0.82 for categorical and 0.91-0.96 for continuous variables. No significant correlation of AHD and CSA with either age or sex was seen (p = 0.28 and p = 0.74, respectively). Case group had significantly smaller mean AHD (8.7 ± 3.2 vs. 10.8 ± 2.2 mm; p < 0.001) and larger mean CSA (36.5 ± 4.5° vs. 33.1 ± 4.0°; p < 0.001). PIAHD-CSA increased diagnostic performance for prediction of RCT and CFD (AUC = 0.78 and 0.71), compared to isolated AHD (0.74 and 0.71) and CSA (0.71 and 0.66). Conclusions: AHD and CSA do not depend on age or sex but differ significantly between healthy and pathologic rotator cuffs. A decreased AHD is most influenced by infraspinatus muscle atrophy and fatty degeneration. Combined PIAHD-CSA increases diagnostic performance for predicting RCT and CFD.