MRI Gadolinium-Based Contrast Media: Meeting Radiological, Clinical, and Environmental Needs.

Gadolinium-based contrast agents (GBCAs) are routinely used in magnetic resonance imaging (MRI). They are essential for choosing the most appropriate medical or surgical strategy for patients with serious pathologies, particularly in oncologic, inflammatory, and cardiovascular diseases. However, GBCAs have been associated with an increased risk of nephrogenic systemic fibrosis in patients with renal failure, as well as the possibility of deposition in the brain, bones, and other organs, even in patients with normal renal function. Research is underway to reduce the quantity of gadolinium injected, without compromising image quality and diagnosis. The next generation of GBCAs will enable a reduction in the gadolinium dose administered. Gadopiclenol is the first of this new generation of GBCAs, with high relaxivity, thus having the potential to reduce the gadolinium dose while maintaining good in vivo stability due to its macrocyclic structure. High-stability and high-relaxivity GBCAs will be one of the solutions for reducing the dose of gadolinium to be administered in clinical practice, while the development of new technologies, including optimization of MRI acquisitions, new contrast mechanisms, and artificial intelligence may help reduce the need for GBCAs. Future solutions may involve a combination of next-generation GBCAs and image-processing techniques to optimize diagnosis and treatment planning while minimizing exposure to gadolinium. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 3.

Use of a Dual Artificial Intelligence Platform to Detect Unreported Lung Nodules.

OBJECTIVE: To investigate the performance of Dual-AI Deep Learning Platform in detecting unreported pulmonary nodules that are 6 mm or greater, comprising computer-vision (CV) algorithm to detect pulmonary nodules, with positive results filtered by natural language processing (NLP) analysis of the dictated report. METHODS: Retrospective analysis of 5047 chest CT scans and corresponding reports. Cases which were both CV algorithm positive (nodule ≥ 6 mm) and NLP negative (nodule not reported), were outputted for review by 2 chest radiologists. RESULTS: The CV algorithm detected nodules that are 6 mm or greater in 1830 (36.3%) of 5047 cases. Three hundred fifty-five (19.4%) were unreported by the radiologist, as per NLP algorithm. Expert review determined that 139 (39.2%) of 355 cases were true positives (2.8% of all cases). One hundred thirty (36.7%) of 355 cases were unnecessary alerts-vague language in the report confounded the NLP algorithm. Eighty-six (24.2%) of 355 cases were false positives. CONCLUSIONS: Dual-AI platform detected actionable unreported nodules in 2.8% of chest CT scans, yet minimized intrusion to radiologist's workflow by avoiding alerts for most already-reported nodules.

Clinical quantitative susceptibility mapping (QSM): Biometal imaging and its emerging roles in patient care.

Quantitative susceptibility mapping (QSM) has enabled magnetic resonance imaging (MRI) of tissue magnetic susceptibility to advance from simple qualitative detection of hypointense blooming artifacts to precise quantitative measurement of spatial biodistributions. QSM technology may be regarded to be sufficiently developed and validated to warrant wide dissemination for clinical applications of imaging isotropic susceptibility, which is dominated by metals in tissue, including iron and calcium. These biometals are highly regulated as vital participants in normal cellular biochemistry, and their dysregulations are manifested in a variety of pathologic processes. Therefore, QSM can be used to assess important tissue functions and disease. To facilitate QSM clinical translation, this review aims to organize pertinent information for implementing a robust automated QSM technique in routine MRI practice and to summarize available knowledge on diseases for which QSM can be used to improve patient care. In brief, QSM can be generated with postprocessing whenever gradient echo MRI is performed. QSM can be useful for diseases that involve neurodegeneration, inflammation, hemorrhage, abnormal oxygen consumption, substantial alterations in highly paramagnetic cellular iron, bone mineralization, or pathologic calcification; and for all disorders in which MRI diagnosis or surveillance requires contrast agent injection. Clinicians may consider integrating QSM into their routine imaging practices by including gradient echo sequences in all relevant MRI protocols. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:951-971.

Diffusion-weighted imaging outside the brain: Consensus statement from an ISMRM-sponsored workshop.

The significant advances in magnetic resonance imaging (MRI) hardware and software, sequence design, and postprocessing methods have made diffusion-weighted imaging (DWI) an important part of body MRI protocols and have fueled extensive research on quantitative diffusion outside the brain, particularly in the oncologic setting. In this review, we summarize the most up-to-date information on DWI acquisition and clinical applications outside the brain, as discussed in an ISMRM-sponsored symposium held in April 2015. We first introduce recent advances in acquisition, processing, and quality control; then review scientific evidence in major organ systems; and finally describe future directions. J. Magn. Reson. Imaging 2016;44:521-540.

Contrast-Enhanced Dixon Fat-Water Separation Imaging of the Spine: Added Value of Fat, In-Phase and Opposed-Phase Imaging in Marrow Lesion Detection.

OBJECTIVE: Beyond fat suppression (FS), the efficacy of (fat-water separation or Dixon [FWD]) Dixon imaging in gadolinium-enhanced spine imaging has yet to be validated. This study evaluated enhanced opposed-phase (OP) and fat-only (FO) images along with water-only (WO; FS) images against traditional unenhanced techniques and rated the incremental value of in-phase imaging in patients with presumed neoplastic focal spine lesions. METHODS: A retrospective cohort study of 36 subjects with focal spine lesions imaged with FWD was evaluated qualitatively and quantitatively. RESULTS: Enhanced OP, WO, and FO images were of significant value in detection of osseous lesions, surpassing the lesion conspicuity with conventional techniques both qualitatively and quantitatively, although the impact of in-phase imaging was limited. Water-only imaging performed well for FS. CONCLUSIONS: Contrast-enhanced FO, WO, and OP outperform traditional techniques, providing reliable lesion characterization and highest conspicuity. In-phase imaging offered limited impact on the subjective assessment of enhancement. The added value and robustness of FWD, particularly the unique contrast provided by FO imaging, suggests consideration for routine use for postgadolinium spine imaging.

Acute ischaemia after subarachnoid haemorrhage, relationship with early brain injury and impact on outcome: a prospective quantitative MRI study.

OBJECTIVE: To determine if ischaemia is a mechanism of early brain injury at the time of aneurysm rupture in subarachnoid haemorrhage (SAH) and if early MRI ischaemia correlates with admission clinical status and functional outcome. METHODS: In a prospective, hypothesis-driven study patients with SAH underwent MRI within 0-3 days of ictus (prior to vasospasm) and a repeat MRI (median 7 days). The volume and number of diffusion weighted imaging (DWI) positive/apparent diffusion coefficient (ADC) dark lesions on acute MRI were quantitatively assessed. The association of early ischaemia, admission clinical status, risk factors and 3-month outcome were analysed. RESULTS: In 61 patients with SAH, 131 MRI were performed. Early ischaemia occurred in 40 (66%) with a mean DWI/ADC volume 8.6 mL (0-198 mL) and lesion number 4.3 (0-25). The presence of any early DWI/ADC lesion and increasing lesion volume were associated with worse Hunt-Hess grade, Glasgow Coma Scale score and Acute Physiology and Chronic Health Evaluation II physiological subscores (all p<0.05). Early DWI/ADC lesions significantly predicted increased number and volume of infarcts on follow-up MRI (p<0.005). At 3 months, early DWI/ADC lesion volume was significantly associated with higher rates of death (21% vs. 3%, p=0.031), death/severe disability (modified Rankin Scale 4-6; 53% vs. 15%, p=0.003) and worse Barthel Index (70 vs. 100, p=0.004). After adjusting for age, Hunt-Hess grade and aneurysm size, early infarct volume correlated with death/severe disability (adjusted OR 1.7, 95% CI 1.0 to 3.2, p=0.066). CONCLUSIONS: Early ischaemia is related to poor acute neurological status after SAH and predicts future ischaemia and worse functional outcomes. Treatments addressing acute ischaemia should be evaluated for their effect on outcome.

Three-Tesla imaging of the pituitary and parasellar region: T1-weighted 3-dimensional fast spin echo cube outperforms conventional 2-dimensional magnetic resonance imaging.

OBJECTIVE: We explored how a novel T1-weighted 3-dimensional (3D) fast spin echo (FSE) sequence (Cube; GE, Waukesha, Wis) might outperform conventional 2-dimensional (2D) FSE techniques for contrast-enhanced imaging of the pituitary and parasellar region. METHODS: Ninety-one patients were imaged with 3D Cube and conventional 2D FSE on a 3.0-T magnetic resonance scanner. Two neuroradiologists independently assessed images for anatomical delineation (infundibulum, optic apparatus, and cavernous sinus), degree of artifact, and confidence in lesion definition or exclusion using a 5-point scale. In addition, the readers were asked to rank overall preference. RESULTS: Readers A and B found 3D Cube to be better or equal to 2D FSE in 84% and 86% of the cases. Three-dimensional Cube provided significantly better images than 2D FSE with respect to delineation of the infundibulum (P < 0.0001), cavernous sinus (P < 0.0001), optic apparatus (P = 0.002 for reader A and P = 0.265 for reader B), and fewer artifacts at the sellar floor (P < 0.0001). Three-dimensional Cube provided greater lesion conspicuity or confidence in lesion exclusion (P < 0.0001). CONCLUSIONS: Three-dimensional Cube provides superior quality with thinner slices as well as diminished artifact and can replace conventional 2D FSE sequences for routine evaluations of the pituitary and parasellar region.

New treatments and imaging strategies in degenerative disease of the intervertebral disks.

Magnetic resonance (MR) imaging in patients with persistent low back pain and sciatica effectively demonstrates spine anatomy and the relationship of nerve roots and intervertebral disks. Except in cases with nerve root compression, disk extrusion, or central stenosis, conventional anatomic MR images do not help distinguish effectively between painful and nonpainful degenerating disks. Hypoxia, inflammation, innervation, accelerated catabolism, and reduced water and glycosaminoglycan content characterize degenerated disks, the extent of which may distinguish nonpainful from painful ones. Applied to the spine, "functional" imaging techniques such as MR spectroscopy, T1ρ calculation, T2 relaxation time measurement, diffusion quantitative imaging, and radio nucleotide imaging provide measurements of some of these degenerative features. Novel minimally invasive therapies, with injected growth factors or genetic materials, target these processes in the disk and effectively reverse degeneration in controlled laboratory conditions. Functional imaging has applications in clinical trials to evaluate the efficacy of these therapies and eventually to select patients for treatment. This report summarizes the biochemical processes in disk degeneration, the application of advanced disk imaging techniques, and the novel biologic therapies that presently have the most clinical promise.

Spine Oncology: Imaging and Intervention.

Osseous metastases are the most common spine tumor and increasingly prevalent as advances in cancer treatments allow patients to live longer with their disease. Evidence-based algorithms derive the majority of their data from imaging studies and reports; the radiologist should understand the most current treatments and report in the language of the treatment team for efficient and effective communication and patient care. Advanced imaging techniques such as diffusion-weighted imaging and dynamic contrast-enhanced MRI are increasingly used for diagnosis and problem solving. Radiologists have a growing role in treatment of patients with metastatic disease, performing cement augmentation and tumor ablation.

Clinical application of CT angiography in acute ischemic stroke.

OBJECTIVE: To evaluate the contribution of CT angiography (CTA) in predicting clinical outcome in a broad spectrum of patients presenting with acute neurological deficits suggestive of brain ischemia, to assess its strengths and limitations in this setting, and examine its influence on selection of patients for thrombolytic treatment. PATIENTS AND METHODS: Prospective, observational outcome study of 54 consecutive patients with acute neurological deficits suggestive of brain ischemia who received immediate CTA. Clinical outcome was compared for patients presenting with and without arterial occlusion on CTA. Treatment decisions made by a vascular neurologist blinded to CTA results were compared to CTA cognizant treatment. RESULTS: For patients presenting with slight to moderate neurological deficits, the sensitivity and specificity for predicting good clinical outcome was 0.62 and 0.79, respectively, using the initial NIH Stroke Scale (NIHSS) score alone, and 0.38 and 0.92 if additionally, CTA showed no occlusion. For patients presenting with more severe deficits, the sensitivity and specificity for predicting poor clinical outcome using the NIHSS score alone was 0.79 and 0.60, compared to 0.67 and 0.92 if CTA showed vessel obstruction. CTA correctly identified six stroke mimickers. Selection of patients for thrombolysis made with knowledge of CTA results were more often conservative, and corresponded to CTA blinded decisions in 42/50 cases (84%, r=0.72). CONCLUSIONS: Combining CTA results with the neurological exam allows increased specificity for predicting clinical outcome as compared to predictions based on admission NIH Stroke Scale score alone. Awareness of CTA results was occasionally associated with less aggressive treatment and testing decisions.

Clinical 3T MR imaging: mastering the challenges.

3T MRI is ready to meet the needs of clinical practice. SAR limitations are minimized by technical advances and surface coils are available for all core applications. With appropriate adjustments to scanning protocols, one can master the challenges of scanning at 3T; studies of the brain, spine, chest, abdomen, pelvis, vasculature, and extremities can be consistently higher in quality than are those obtained at 1.5T. The superior studies that are obtainable at 3T have great appeal to clinicians who are sophisticated about MR technology in areas, such as neurology, orthopedics, vascular surgery, and oncology,and encourage a shift in referrals toward practices that invest in higher field technology. The greater sensitivity to magnetic susceptibility offers unique benefits in functional neuroimaging, and available software/hardware packages enhance clinical setting feasibility, which adds a source of new referrals. The greater overall signal of 3T can be manipulated to make scanning more comfortable and with less motion artifact because scan times could be half as long. Spectacular anatomic delineation that is provided by high-definition scanning at true 1024 resolution can improve preoperative assessment and may improve sensitivity to smaller lesions. 3T provides practices with an advantage that is sought increasingly by high field strength purchasers in a competitive market. Only cost considerations stand in the way of the eventual domination of 3T systems in the high field strength market.

Relationship between timed 25-foot walk and diffusion tensor imaging in multiple sclerosis.

OBJECTIVE/BACKGROUND: The majority of multiple sclerosis patients experience impaired walking ability, which impacts quality of life. Timed 25-foot walk is commonly used to gauge gait impairment but results can be broadly variable. Objective biological markers that correlate closely with patients' disability are needed. Diffusion tensor imaging, quantifying fiber tract integrity, might provide such information. In this project we analyzed relationships between timed 25-foot walk, conventional and diffusion tensor imaging magnetic resonance imaging markers. DESIGN/METHODS: A cohort of gait impaired multiple sclerosis patients underwent brain and cervical spinal cord magnetic resonance imaging. Diffusion tensor imaging mean diffusivity and fractional anisotropy were measured on the brain corticospinal tracts and spinal restricted field of vision at C2/3. We analyzed relationships between baseline timed 25-foot walk, conventional and diffusion tensor imaging magnetic resonance imaging markers. RESULTS: Multivariate linear regression analysis showed a statistically significant association between several magnetic resonance imaging and diffusion tensor imaging metrics and timed 25-foot walk: brain mean diffusivity corticospinal tracts (p = 0.004), brain corticospinal tracts axial and radial diffusivity (P = 0.004 and 0.02), grey matter volume (p = 0.05), white matter volume (p = 0.03) and normalized brain volume (P = 0.01). The linear regression model containing mean diffusivity corticospinal tracts and controlled for gait assistance was the best fit model (p = 0.004). CONCLUSIONS: Our results suggest an association between diffusion tensor imaging metrics and gait impairment, evidenced by brain mean diffusivity corticospinal tracts and timed 25-foot walk.

CT angiography in acute ischemic stroke: preliminary results.

BACKGROUND AND PURPOSE: We sought to evaluate the ability of CT angiography (CTA) to determine vessel occlusion before acute stroke treatment and to predict its impact on patient outcome. METHODS: Consecutive patients with acute focal neurological deficits received immediate brain CTA. Occlusion on CTA was correlated with other neuroimaging studies and clinical outcome. RESULTS: Diagnostic CTA was obtained in 54 patients: catheter angiography (digital subtraction angiography) confirmed the CTA findings in 12 of 14 patients (86%). CTA results were consistent with at least 1 other neuroimaging study in 40 of 50 patients (80%). Patients with occlusion on CTA had significantly worse discharge National Institutes of Health Stroke Scale (NIHSS) score (mean 14.3 versus 4.5, P=0.0023). In multivariate analysis, both CTA-determined presence of occlusion and admission NIHSS score were independent predictors of clinical outcome. CONCLUSIONS: In our study there was good agreement between acute CTA interpretation and subsequent imaging studies. CTA evidence of occlusion correlated strongly and independently with poor clinical outcome. CTA provides relevant data regarding vessel patency in acute stroke, which may be of value in selecting patients for aggressive treatment.

Computed tomography angiographic correlates of early computed tomography signs in acute ischemic stroke.

BACKGROUND AND PURPOSE: Early computed tomography (CT) signs of stroke signify major arterial occlusion. CT angiogram (CTA) is useful in detecting major arterial occlusion and may help triaging patients for intra-arterial thrombolysis. The correlation between the early signs of stroke and arterial occlusion on CTA was studied. METHODS: Consecutive patients with suspected acute anterior circulation ischemic stroke presenting within 6 hours of symptom onset underwent noncontrast CT of the head followed by CTA. The scans were later reviewed for evidence of early signs of stroke on CT scan and intracranial arterial occlusion on CTA. RESULTS: Sixteen of 65 patients had arterial occlusion on CTA; 12 (75%) of these showed the early CT signs of stroke. All the early signs except M2 "dot" sign significantly correlated with middle cerebral artery (MCA) occlusion on CTA. Hyperdense MCA sign was the only independent predictor of a MCA occlusion. CONCLUSION: In a small sample, early CT signs of stroke strongly correlated with arterial occlusion, with hyperdense MCA sign being the most predictive of a MCA occlusion.

Effect of iterative reconstruction algorithms on peripheral MDCT angiography virtual histology plaque volumes: have we been overestimating disease burden?

Our objective was to compare plaque volumes of multidetector computed tomographic images reconstructed using adaptive statistical iterative reconstruction (ASIR), model-based iterative reconstruction (MBIR), and filtered back projection (FBP). We reviewed 25 patients for a total of 50 extremities imaged on the same scanner. Calcified plaque FBP volume (3468.2 ± 2634.8 mm(3)) was higher than ASIR (2548.1 ± 2166.5 mm(3)). Calcified plaque FBP volume was higher than MBIR (mean=2345.7 ± 1935.4 mm(3)). Our findings suggest that traditional FBP methods overestimate disease compared to newer reconstruction methods.

State of the art imaging of multiple myeloma: comparative review of FDG PET/CT imaging in various clinical settings.

18-Flurodeoxyglucose Positron Emission Tomography with computed tomography (FDG PET/CT) and Magnetic Resonance Imaging (MRI) have higher sensitivity and specificity than whole-body X-ray (WBXR) survey in evaluating disease extent in patients with multiple myeloma (MM). Both modalities are now recommended by the Durie-Salmon Plus classification although the emphasis is more on MRI than PET/CT. The presence of extra-medullary disease (EMD) as evaluated by PET/CT imaging, initial SUVmax and number of focal lesions (FL) are deemed to be strong prognostic parameters at staging. MRI remains the most sensitive technique for the detection of diffuse bone marrow involvement in both the pre and post-therapy setting. Compression fractures are best characterized with MRI signal changes, for determining vertebroplasty candidates. While PET/CT allows for earlier and more specific evaluation of therapeutic efficacy compared to MRI, when signal abnormalities persist years after treatment. PET/CT interpretation, however, can be challenging in the vertebral column and pelvis as well as in cases with post-therapy changes. Hence, a reading approach combining the high sensitivity of MRI and superior specificity of FDG PET/CT would be preferred to increase the diagnostic accuracy. In summary, the established management methods in MM, mainly relying on biological tumor parameters should be complemented with functional imaging data, both at staging and restaging for optimal management of MM.

Optimized imaging of the postoperative spine.

Few tasks in imaging are more challenging than that of optimizing evaluations of the instrumented spine. The authors describe how applying fundamental and more advanced principles to postoperative spine computed tomography and magnetic resonance examinations mitigates the challenges associated with metal implants and significantly improves image quality and consistency. Newer and soon-to-be-available enhancements should provide improved visualization of tissues and hardware as multispectral imaging sequences continue to develop.

Clinical applications of diffusion imaging in the spine.

As in the brain, the sensitivity of diffusion-weighted imaging (DWI) to ischemic damage in the spinal cord may provide early identification of infarction. Diffusion anisotropy may enhance the detection and understanding of damage to the long fiber tracts with clinical implications for diseases such as multiple sclerosis and amyotrophic lateral sclerosis and may also yield insight into damage that occurs with spondylotic and traumatic myelopathy. This article reviews the basis for DWI for the evaluation of the spinal cord, osseous, and soft tissues of the spine and reviews the imaging appearance of a variety of disease states.