Specific MRI Sequences Research Articles

Diagnostic evaluation of deep learning accelerated lumbar spine MRI.

Deep learning (DL) accelerated MR techniques have emerged as a promising approach to accelerate routine MR exams. While prior studies explored DL acceleration for specific lumbar MRI sequences, a gap remains in comprehending the impact of a fully DL-based MRI protocol on scan time and diagnostic quality for routine lumbar spine MRI. To address this, we assessed the image quality and diagnostic performance of a DL-accelerated lumbar spine MRI protocol in comparison to a conventional protocol. We prospectively evaluated 36 consecutive outpatients undergoing non-contrast enhanced lumbar spine MRIs. Both protocols included sagittal T1, T2, STIR, and axial T2-weighted images. Two blinded neuroradiologists independently reviewed images for foraminal stenosis, spinal canal stenosis, nerve root compression, and facet arthropathy. Grading comparison employed the Wilcoxon signed rank test. For the head-to-head comparison, a 5-point Likert scale to assess image quality, considering artifacts, signal-to-noise ratio (SNR), anatomical structure visualization, and overall diagnostic quality. We applied a 15% noninferiority margin to determine whether the DL-accelerated protocol was noninferior. No significant differences existed between protocols when evaluating foraminal and spinal canal stenosis, nerve compression, or facet arthropathy (all p > .05). The DL-spine protocol was noninferior for overall diagnostic quality and visualization of the cord, CSF, intervertebral disc, and nerve roots. However, it exhibited reduced SNR and increased artifact perception. Interobserver reproducibility ranged from moderate to substantial (κ = 0.50-0.76). Our study indicates that DL reconstruction in spine imaging effectively reduces acquisition times while maintaining comparable diagnostic quality to conventional MRI.

Multiple sclerosis imaging in clinical practice: a European-wide survey of 428 centers and conclusions by the ESNR Working Group.

To evaluate compliance with the available recommendations, we assessed the current clinical practice of imaging in the evaluation of multiple sclerosis (MS). An online questionnaire was emailed to all members and affiliates. Information was gathered on applied MR imaging protocols, gadolinium-based contrast agents (GBCA) use and image analysis. We compared the survey results with the Magnetic Resonance Imaging in MS (MAGNIMS) recommendations considered as the reference standard. A total of 428 entries were received from 44 countries. Of these, 82% of responders were neuroradiologists. 55% performed more than ten scans per week for MS imaging. The systematic use of 3T is rare (18%). Over 90% follow specific protocol recommendations with 3D FLAIR, T2-weighted and DWI being the most frequently used sequences. Over 50% use SWI at initial diagnosis and 3D gradient-echo T1-weighted imaging is the most used MRI sequence for pre- and post-contrast imaging. Mismatches with recommendations were identified including the use of only one sagittal T2-weighted sequence for spinal cord imaging, the systematic use of GBCA at follow-up (over 30% of institutions), a delay time shorter than 5min after GBCA administration (25%) and an inadequate follow-up duration in pediatric acute disseminated encephalomyelitis (80%). There is scarce use of automated software to compare images or to assess atrophy (13% and 7%). The proportions do not differ significantly between academic and non-academic institutions. While current practice in MS imaging is rather homogeneous across Europe, our survey suggests that recommendations are only partially followed. Hurdles were identified, mainly in the areas of GBCA use, spinal cord imaging, underuse of specific MRI sequences and monitoring strategies. This work will help radiologists to identify the mismatches between their own practices and the recommendations and act upon them. • While current practice in MS imaging is rather homogeneous across Europe, our survey suggests that available recommendations are only partially followed. • Several hurdles have been identified through the survey that mainly lies in the areas of GBCA use, spinal cord imaging, underuse of specific MRI sequences and monitoring strategies.

394 R2* and QSM Reliability for Measuring Brain Tissue Iron Concentrations

INTRODUCTION: Pathologic levels of iron have been implicated in various neurological disease states, such as Parkinson’s, Multiple Sclerosis, Amyotrophic Lateral Sclerosis, and Stroke (hemorrhagic & ischemic). Using brain tissue iron concentration as a biomarker for disease progression has great potential for clinical translation; however, measuring iron concentrations non-invasively remains challenging. MRI based R2* and quantitative susceptibility mapping (QSM) values have been shown to correlate with iron levels in previous cadaveric studies. METHODS: Ten normal human subjects (ages 35-73) underwent test and retest MRI scans approximately 10 minutes apart. T1 and gradient-echo images were used to segment 7 regions of the brain bilaterally. The gradient-echo sequences were used to calculate the R2* and QSM for each region of interest. Iron concentrations were calculated from the R2* values based on R2* calibrated with a phantom. RESULTS: R2* values ranged from 19.45 Hz in the hand homunculus to 38.81 Hz in the substantia nigra and were consistent across 8-echo and 6-echo sequences. Mean QSM values ranged from -0.041 in the internal capsule to 0.046 in the globus pallidus. Calculated iron concentrations ranged from 52.1 mg/kg in the centrum semiovale to 104.6 mg/kg in the substantia nigra. Test and retest values showed consistency across brain regions for R2* with weighted coefficient variation percent of 3.9-9.6%. White matter iron concentrations ranged from 52.1-59.5 mg/kg, while deep grey nuclei iron concentrations ranged from 72.5-104.6 mg/kg. CONCLUSIONS: Our study demonstrates the ability of gradient-echo MRI to reliably measure tissue iron levels in non-disease states in healthy human subjects. Further research is needed to validate the ability of specific MRI sequences to be a surrogate biomarker in disease states.

Abstract WP49: Mri Based Thrombolysis For Unwitnessed Stroke Patients Is Feasible At Primary Stroke Centers

Background: The 2018 WAKE-UP Trial established the safety and efficacy of administering IV-tPA in patients who presented within 4.5 hours of symptom discovery based on specific MRI sequences. Implementation of the study results remains limited at Primary Stroke Centers (PSCs). We assessed the feasibility of a Comprehensive Stroke Center (CSC) MRI based unwitnessed thrombolysis protocol at 13 PSCs. Methods: A committee consisting of vascular neurologists, neuroradiologists and MRI technologists developed the protocol. The protocol was utilized at the CSC for one year, and subsequently expanded to the PSCs. A specific "WAKE-UP MRI”" order was created which consisted of only DWI, GRE and FLAIR sequences. MRI technologists were trained to ensure that the "WAKE-UP MRI” would take priority over other patients; eg: if there was no one in MRI, it would be held for the stroke patient, and if MRI was occupied, the stroke patient would be next. The acute stroke care was managed by an integrated telestroke system at the PSCs. All telestroke providers were educated on the protocol. Standard stroke time metrics were collected and analyzed over 2 years. Data from the CSC was compared with its 13 PSC spokes. A student’s t-test was used for data analysis. Results: A total of 190 patients who arrived with 4.5 hours of symptom discovery were screened; 62 at CSC and 128 at PSCs. Forty underwent emergent MRI at CSC and 29 at PSCs. Median door to MRI time was longer for patients presenting to PSC compared to CSC (78 vs 53.5 mins; p = 0.0002). Twenty-one vs 9 patients received tPA at CSC and PSC hospitals respectively. Median door to needle (DTN) times were longer for patients at PSC vs CSC (106 vs 67 mins; p = .018). The most common reasons for not administering IV-tPA was a negative MRI (40% at PSCs vs 47% at CSC) and a lack of DWI and FLAIR mismatch (40% at PSCs vs 42% at CSC). Conclusion: Use of emergent MRI in unwitnessed stroke for thrombolysis is feasible at PSCs. There remain barriers to implementation, with PSCs showing more delayed access to MRI and thrombolysis compared to CSC.

Deep Learning-Based Localization of EEG Electrodes Within MRI Acquisitions.

The simultaneous acquisition of electroencephalographic (EEG) signals and functional magnetic resonance images (fMRI) aims to measure brain activity with good spatial and temporal resolution. This bimodal neuroimaging can bring complementary and very relevant information in many cases and in particular for epilepsy. Indeed, it has been shown that it can facilitate the localization of epileptic networks. Regarding the EEG, source localization requires the resolution of a complex inverse problem that depends on several parameters, one of the most important of which is the position of the EEG electrodes on the scalp. These positions are often roughly estimated using fiducial points. In simultaneous EEG-fMRI acquisitions, specific MRI sequences can provide valuable spatial information. In this work, we propose a new fully automatic method based on neural networks to segment an ultra-short echo-time MR volume in order to retrieve the coordinates and labels of the EEG electrodes. It consists of two steps: a segmentation of the images by a neural network, followed by the registration of an EEG template on the obtained detections. We trained the neural network using 37 MR volumes and then we tested our method on 23 new volumes. The results show an average detection accuracy of 99.7% with an average position error of 2.24 mm, as well as 100% accuracy in the labeling.

Global mean diffusivity: A radiomarker discriminating good outcome long term after traumatic brain injury.

Traumatic brain injury (TBI) is a chronic pathology responsible for cognitive disorders impacting outcome. Global clinical outcome several years after TBI may be associated with anatomical sequelae. Anatomical lesions are not well described because characterizing diffuse axonal injury and brain atrophy require using specific MRI sequences with quantitative measures. The best radiologic parameter to describe the lesions long term after TBI is not known. We aimed to first, assess the global volumetric and diffusion parameters related to long-term outcome after TBI and second, define the most discriminating parameter. In this observational study, we included 96 patients with severe TBI and 22 healthy volunteers. The mean delay after TBI was 63.2 months [range 31-119]. The Glasgow Outcome Scale Extended (GOS-E) was used to assess the global long-term clinical outcome. All patients underwent multimodal MRI with measures of brain volume, ventricle volume, global fractional anisotropy (FA) and global mean diffusivity (MD). All 96 participants had significant impairment in global FA, global MD, brain volume and ventricle volume as compared with the 22 controls (P<0.01). Only global MD significantly differed between the "good recovery" group (GOS-E score 7-8) and the other two groups: GOS-E scores 3-4 and 5-6. Brain volume significantly differed between the GOS-E 7-8 and 3-4 groups. Global MD was the most discriminating radiological parameter for the "good recovery" group versus other patients, long term after TBI. FA appeared less relevant at this time. Global atrophy was higher in patients than controls but lacked reliability to discriminate groups of patients. Global mean diffusivity seems a more promising radiomarker than global FA for discriminating good outcome long term after TBI. Further work is needed to understand the evolution of these long-term radiological parameters after TBI.

Reporting Guidelines, Review of Methodological Standards, and Challenges Toward Harmonization in Bone Marrow Adiposity Research. Report of the Methodologies Working Group of the International Bone Marrow Adiposity Society.

The interest in bone marrow adiposity (BMA) has increased over the last decade due to its association with, and potential role, in a range of diseases (osteoporosis, diabetes, anorexia, cancer) as well as treatments (corticosteroid, radiation, chemotherapy, thiazolidinediones). However, to advance the field of BMA research, standardization of methods is desirable to increase comparability of study outcomes and foster collaboration. Therefore, at the 2017 annual BMA meeting, the International Bone Marrow Adiposity Society (BMAS) founded a working group to evaluate methodologies in BMA research. All BMAS members could volunteer to participate. The working group members, who are all active preclinical or clinical BMA researchers, searched the literature for articles investigating BMA and discussed the results during personal and telephone conferences. According to the consensus opinion, both based on the review of the literature and on expert opinion, we describe existing methodologies and discuss the challenges and future directions for (1) histomorphometry of bone marrow adipocytes, (2) ex vivo BMA imaging, (3) in vivo BMA imaging, (4) cell isolation, culture, differentiation and in vitro modulation of primary bone marrow adipocytes and bone marrow stromal cell precursors, (5) lineage tracing and in vivo BMA modulation, and (6) BMA biobanking. We identify as accepted standards in BMA research: manual histomorphometry and osmium tetroxide 3D contrast-enhanced μCT for ex vivo quantification, specific MRI sequences (WFI and H-MRS) for in vivo studies, and RT-qPCR with a minimal four gene panel or lipid-based assays for in vitro quantification of bone marrow adipogenesis. Emerging techniques are described which may soon come to complement or substitute these gold standards. Known confounding factors and minimal reporting standards are presented, and their use is encouraged to facilitate comparison across studies. In conclusion, specific BMA methodologies have been developed. However, important challenges remain. In particular, we advocate for the harmonization of methodologies, the precise reporting of known confounding factors, and the identification of methods to modulate BMA independently from other tissues. Wider use of existing animal models with impaired BMA production (e.g., Pfrt−/−, KitW/W−v) and development of specific BMA deletion models would be highly desirable for this purpose.

The effects of volume of interest delineation on MRI-based radiomics analysis: evaluation with two disease groups

BackgroundManual delineation of volume of interest (VOI) is widely used in current radiomics analysis, suffering from high variability. The tolerance of delineation differences and possible influence on each step of radiomics analysis are not clear, requiring quantitative assessment. The purpose of our study was to investigate the effects of delineation of VOIs on radiomics analysis for the preoperative prediction of metastasis in nasopharyngeal carcinoma (NPC) and sentinel lymph node (SLN) metastasis in breast cancer.MethodsThis study retrospectively enrolled two datasets (NPC group: 238 cases; SLN group: 146 cases). Three operations, namely, erosion, smoothing, and dilation, were implemented on the VOIs accurately delineated by radiologists to generate diverse VOI variations. Then, we extracted 2068 radiomics features and evaluated the effects of VOI differences on feature values by the intra-class correlation coefficient (ICC). Feature selection was conducted by Maximum Relevance Minimum Redundancy combined with 0.632+ bootstrap algorithms. The prediction performance of radiomics models with random forest classifier were tested on an independent validation cohort by the area under the receive operating characteristic curve (AUC).ResultsThe larger the VOIs changed, the fewer features with high ICCs. Under any variation, SLN group showed fewer features with ICC ≥ 0.9 compared with NPC group. Not more than 15% top-predictive features identical to the accurate VOIs were observed across feature selection. The differences of AUCs of models derived from VOIs across smoothing or dilation with 3 pixels were not statistically significant compared with the accurate VOIs (p > 0.05) except for T2-weighted fat suppression images (smoothing: 0.845 vs. 0.725, p = 0.001; dilation: 0.800 vs. 0.725, p = 0.042). Dilation with 5 and 7 pixels contributed to remarkable AUCs in SLN group but the opposite in NPC group. The radiomics models did not perform well when tested by data from other delineations.ConclusionsDifferences in delineation of VOIs affected radiomics analysis, related to specific disease and MRI sequences. Differences from smooth delineation or expansion with 3 pixels width around the tumors or lesions were acceptable. The delineation for radiomics analysis should follow a predefined and unified standard.

Development and implementation of algorithms with diffusion tensor images to evaluate brain connectivity

Diffusion-weighted magnetic resonance imaging (DWI) is the use of specific MRI sequences, which uses the diffusion of Hydrogen atoms to generate contrast and it allows the mapping of the diffusion process of molecules in vivo and reflects interactions with macromolecules, fibers, and membranes among other. Hydrogen atom diffusion patterns (quantification of anisotropy) can reveal microscopic details about tissue architecture, either normal or in a diseased state. A special kind of DWI, diffusion tensor imaging (DTI), has been used extensively to map white matter tractography in the brain. Tractography is a procedure that is used to highlight neural tracts (axon), its fibers position estimation in brain areas has broad potential implications in cognitive neuroscience fields. An algorithm based on diffusion tensor Image is developed and implemented in order to evaluate brain connectivity in different regions of interest. The major objective of this work is represent two-dimensional and three-dimensional connectivity between areas thereby show the potential of the DTI. Results shows how Connectivity Matrix provides statistical data on the pattern of anatomical relationships, this connectivity pattern is formed by synapses that represent the cross correlations and the flow of information.

Cardiac MRI Evaluation of Myocarditis.

Cardiac MRI (CMR) is the non-invasive test of choice for the assessment of myocarditis. In 2009, the Lake Louise Criteria for the diagnosis of myocarditis using CMR were first released. The decade since that time has vastly improved our understanding of CMR's strengths and limitations. Traditional CMR methods including T2-weighted imaging and late gadolinium enhancement have proven their diagnostic value, but diagnostic performance is dependent on patient presentation. Newer parametric mapping techniques have begun to be more comprehensively studied and may improve diagnostic accuracy of CMR in an expanded set of clinical scenarios. Additionally, the prognostic value of CMR has begun to solidify. These advances culminated in an update to the Lake Louise Criteria at the end of 2018. In this review, we discuss the evolution of the diagnostic criteria for CMR in the assessment of myocarditis. We also discuss the pathophysiologic premises behind the use of specific MRI sequences and an up-to-date summary of their individual utility.

European Ultrahigh-Field Imaging Network for Neurodegenerative Diseases (EUFIND)

IntroductionThe goal of European Ultrahigh-Field Imaging Network in Neurodegenerative Diseases (EUFIND) is to identify opportunities and challenges of 7 Tesla (7T) MRI for clinical and research applications in neurodegeneration. EUFIND comprises 22 European and one US site, including over 50 MRI and dementia experts as well as neuroscientists. MethodsEUFIND combined consensus workshops and data sharing for multisite analysis, focusing on 7 core topics: clinical applications/clinical research, highest resolution anatomy, functional imaging, vascular systems/vascular pathology, iron mapping and neuropathology detection, spectroscopy, and quality assurance. Across these topics, EUFIND considered standard operating procedures, safety, and multivendor harmonization. ResultsThe clinical and research opportunities and challenges of 7T MRI in each subtopic are set out as a roadmap. Specific MRI sequences for each subtopic were implemented in a pilot study presented in this report. Results show that a large multisite 7T imaging network with highly advanced and harmonized imaging sequences is feasible and may enable future multicentre ultrahigh-field MRI studies and clinical trials. DiscussionThe EUFIND network can be a major driver for advancing clinical neuroimaging research using 7T and for identifying use-cases for clinical applications in neurodegeneration.

Use of magnetic resonance imaging in severe pediatric traumatic brain injury: assessment of current practice.

There is no consensus on the optimal timing and specific brain MRI sequences in the evaluation and management of severe pediatric traumatic brain injury (TBI), and information on current practices is lacking. The authors performed a survey of MRI practices among sites participating in a multicenter study of severe pediatric TBI to provide information for designing future clinical trials using MRI to assess brain injury after severe pediatric TBI. Information on current imaging practices and resources was collected from 27 institutions participating in the Approaches and Decisions after Pediatric TBI Trial. Multiple-choice questions addressed the percentage of patients with TBI who have MRI studies, timing of MRI, MRI sequences used to investigate TBI, as well as the magnetic field strength of MR scanners used at the participating institutions and use of standardized MRI protocols for imaging after severe pediatric TBI. Overall, the reported use of MRI in pediatric patients with severe TBI at participating sites was high, with 40% of sites indicating that they obtain MRI studies in > 95% of this patient population. Differences were observed in the frequency of MRI use between US and international sites, with the US sites obtaining MRI in a higher proportion of their pediatric patients with severe TBI (94% of US vs 44% of international sites reported MRI in at least 70% of patients with severe TBI). The reported timing and composition of MRI studies was highly variable across sites. Sixty percent of sites reported typically obtaining an MRI study within the first 7 days postinjury, with the remainder of responses distributed throughout the first 30-day postinjury period. Responses indicated that MRI sequences sensitive for diffuse axonal injury and ischemia are frequently obtained in patients with TBI, whereas perfusion imaging and spectroscopy techniques are less common. Results from this survey suggest that despite the lack of consensus or guidelines, MRI is commonly obtained during the acute clinical setting after severe pediatric TBI. The variation in MRI practices highlights the need for additional studies to determine the utility, optimal timing, and composition of clinical MRI studies after TBI. The information in this survey describes current clinical MRI practices in children with severe TBI and identifies important challenges and objectives that should be considered when designing future studies.

2-deoxy-2-[18]fluoro-D-glucose PET/CT (18FDG PET/CT) may not be a viable biomarker in Pompe disease

BackgroundPompe disease (PD) is an autosomal recessive, lysosomal storage disease due to a mutation of the acid α-glucosidase (GAA) gene. In adult patients, PD is characterized by slowly progressive limb-girdle and trunk myopathy and restrictive respiratory insufficiency. Enzyme replacement therapy (ERT) is available, improving or stabilizing muscle-function in some and slowing deterioration in other patients. Unfortunately, there is no biomarker available to indicate therapeutic efficacy and/or disease activity. Whole body MRI depicts all skeletal muscles demonstrating foci of atrophic muscles, i.e., late and irreversible pathological changes. Any method indicating the localizations of increased muscle glycogen storage, muscle inflammation and/or degradation could possibly help identifying newly afflicted tissue and may be of prognostic value. We therefore investigated 2-deoxy-2-[18]fluoro-D-glucose (FDG) PET, a biomarker for glucose-metabolism, as a tool to evaluate disease activity and prognosis in PD.MethodsIn a pilot study, we investigated four patients by FDG dynamic PET/CT while on ERT. One patient had FDG-PET/CT twice, before and after 12 months on ERT. Dynamic FDG-PET/CT quantifies the metabolic rate of glucose utilisation in mg/ml/min. MRI was performed in parallel with pelvic and thigh muscles semi-quantitatively scored for atrophy and disease-activity.ResultsNone of the muscles analysed showed a focally increased FDG-uptake. Thus, quantification of muscle glucose metabolism could not be calculated. However, increased FDG-uptake, i.e., increased glucose utilisation, was observed in the respiratory muscles of one patient with severe, restrictive respiratory failure. In contrast, specific MRI sequences showed oedematous as well as atrophic muscle areas in PD.ConclusionsOur pilot study demonstrates that FDG-uptake does not correlate with glycogen storage in vivo. In contrast, MRI is an excellent tool to demonstrate the extent of muscle involvement. Specific MRI sequences may even demonstrate early changes possibly allowing prognostic predictions or localization of early stages of PD.

Importance of functional diagnostics in gastroenterology

In this review article important and frequently used investigation methods for gastrointestinal functional diagnostics are presented. Some other rarely used special investigations are also explained. The hydrogen breath test is simple to carry out, ubiquitously available and enables the detection of lactose, fructose and sorbitol malabsorption. Furthermore, by the application of glucose, the test can be carried out when there is a suspicion of abnormal intestinal bacterial colonization and using lactulose for measuring small intestinal transit time. The 13C urea breath test is applied for non-invasive determination of Helicobacter pylori infections and assessment of gastrointestinal transit time, liver and exocrine pancreas functions. The secretin cholecystokinin test was the gold standard for the detection of exocrine pancreas insufficiency. However, measurement of pancreatic elastase in stool is less invasive but also less sensitive. Scintigraphy and capsule investigations with pH and temperature probes constitute important methods for determination of gastric emptying, intestinal and colon transit times. For evaluation of constipation panoramic abdominal images are taken after intake of radiologically opaque markers (Hinton test). For the diagnosis of functional esophageal diseases manometry is indispensable. In addition, manometry is only occasionally used for diagnosing a dysfunction of the sphincter of Oddi, due to the danger of inducing pancreatitis. A24 h pH-metry is applied for the detection of non-erosive gastroesophageal reflux disease and, if necessary, with impedance measurements. Recent investigation procedures, e. g. specific MRI sequences, sonographic determination of gall bladder ejection fraction, analysis of gastric accomodation or real-time lumen imaging, require further evaluation prior to clinical application.

Bone marrow lesions detected by specific combination of MRI sequences are associated with severity of osteochondral degeneration.

BackgroundBone marrow lesions (BMLs) are useful diagnostic and prognostic markers in knee osteoarthritis (OA), but what they represent at the tissue level remains unclear. The aim of this study was to provide comprehensive tissue characterization of BMLs detected using two specific MRI sequences.MethodsTibial plateaus were obtained from 60 patients (29 females, 31 males), undergoing knee arthroplasty for OA. To identify BMLs, MRI was performed ex vivo using T1 and PDFS-weighted sequences. Multi-modal tissue level analyses of the osteochondral unit (OCU) were performed, including cartilage volume measurement, OARSI grading, micro-CT analysis of bone microstructure, routine histopathological assessment and quantitation of bone turnover indices.ResultsBMLs were detected in 74 % of tibial plateaus, the remainder comprising a No BML group. Of all BMLs, 59 % were designated BML 1 (detected only by PDFS) and 41 % were designated BML 2 (detected by both PDFS + T1). The presence of a BML was related to degeneration of the OCU, particularly within BML 2. When compared to No BML, BML 2 showed reduced cartilage volume (p = 0.008), higher OARSI scores (p = 0.004), thicker subchondral plate (p = 0.002), increased trabecular bone volume and plate-like structure (p = 0.0004), increased osteoid volume (p = 0.002) and thickness (p = 0.003), more bone marrow oedema (p = 0.03), fibrosis (p = 0.002), necrosis (p = 0.01) and fibrovascular cysts (p = 0.04). For most measures, BML 1 was intermediate between No BML and BML 2.ConclusionsBMLs detected by specific MRI sequences identify different degrees of degeneration in the OCU. This suggests that MRI characteristics of BMLs may enable identification of different BML phenotypes and help target novel approaches to treatment and prevention of OA.

Recognition and treatment of endometriosis involving the sacral nerve roots.

Endometriosis involving the sacral plexus is still poorly understood or neglected by many surgeons. Looking at that scenario, we have designed this educational video to explain and describe the symptoms suggestive of endometriotic involvement of the sacral plexus in addition to the technique for the laparoscopic treatment of this condition. Retrospective analysis of 13 consecutive cases of endometriotic entrapment of nerves of the lumbosacral plexus. Paired t test revealed a statistically significant (p < 0.0000001) reduction in pain VAS score, from preoperative average 9.1 (±1.98) to postoperative 1.46 (±1.66). Twelve out of 13 patients (92.3%) experienced a reduction of 50% or more in VAS score and 6 (46.15%) became completely pain-free. The signs suggestive of intrapelvic nerve involvement include perineal pain or pain irradiating to the lower limbs, lower urinary tract symptoms, tenesmus or dyschezia associated with gluteal pain. Whenever deeply infiltrating lesions are present, the patient must be asked about those symptoms and specific MRI sequences for the sacral plexus must be taken, so that the equipment and team can be arranged and proper treatment performed.

Impact of skull base development on endonasal endoscopic surgical corridors

Scarce morphometric data exist on the developing skull base as a corridor for endonasal endoscopic approaches (EEAs). Furthermore, the impact of skull base lesions on its development has not been assessed. The authors describe a novel set of anatomical parameters characterizing the developmental process as well as the utility of these parameters in preoperative planning and a feasibility assessment of EEAs for neurosurgical treatment of skull base lesions in children. Based on specific MRI sequences in 107 pediatric patients (2-16 years of age) without skull base lesions (referred to here as the normal population), 3 sets of anatomical parameters were analyzed according to age group and sex: drilling distance, restriction sites, and working distance parameters. A separate set of patients undergoing EEAs was analyzed in similar fashion to address the impact of skull base lesions on the developmental process. The volume of the sphenoid sinus significantly increases with age, reaching 6866.4 mm(3) in the 14-16 years age group, and directly correlates with the pneumatization type (r = 0.533, p = 0.0001). The pneumatization process progresses slowly in a temporal-posterior direction, as demonstrated by the growth trend of the sellar width (r = 0.428, p = 0.0001). Nasal restriction sites do not change significantly with age, with little impact on EEAs. The intercarotid distance is significantly different only in the extreme age groups (3.9 mm, p = 0.038), and has an important impact on the transsphenoidal angle and the intracranial dissection limits (r = 0.443, p < 0.0001). The 14.9° transsphenoidal angle at 2-4 years has a 37.6% significant increase in the 11-13 years age group (p = 0.001) and is highly dependent on pneumatization type. Age-dependent differences between working parameters are mostly noted for the extreme age groups, such as the 8.6-mm increase in nare-vomer distance (p = 0.025). The nare-sellar distance is the only parameter with significant differences based on sex. Skull base lesions induce a high degree of variance in skull base measurements, delaying development and decreasing parameter values. Skull base parameters are interdependent. Nare-sellar distance can be used to assess global skull base development because it highly correlates with the intercarotid distance in both the normal population and in patients harboring skull base lesions. Skull base development is a slow, gradual, age-dependent, sex-independent process significantly altering endonasal endoscopic corridors. Preoperative MRI measurements of the pediatric skull base are thus a useful adjunct in choosing the appropriate corridor and in assessing working angles and limits during dissection or reparative surgery. Skull base lesions can significantly impact normal skull base development and age-dependent growth patterns.

SU-D-WAB-02: MRI-Based Treatment Planning in Brain Radiation Therapy: Validation of An Atlas-Based Pseudo-CT Generation Method

Purpose: To quantify the dosimetric accuracy of an atlas‐based pseudo‐CT (p‐CT) generation method in MRI‐based treatment planning, and to evaluate the influence of specific MRI sequences on p‐CT quality. Methods: For six brain IMRT patients, a p‐CT was generated from an MR image set previously used for target delineation. A research version of Advantage SIM™ software (GE Healthcare) was used to produce the p‐CT. The software uses body segmentation and bone enhancement on the input MRI, to produce a p‐CT image with a contrast similar to that of a bone atlas generated offline. The IMRT plan including the isocenter was copied on to the p‐CT and the dose was calculated in Pinnacle™. The two dose distributions were compared using (1) gamma analysis, and (2) differences between the average DVH for the target volume, and tissue contour. Results: The p‐CT visually co‐registered well with both the MRI and conventional CT in four cases where Axial T1 Spin Echo or Fast Spoiled Gradient‐Recalled Echo images were used. For these cases, the average Gamma Index 3%/3mm pass rates were 96.85%, 95.58% and 95.40%, in the axial, coronal and sagittal planes. On average, the absolute value difference between the average DVHs was 1.74 (max: 6.97) and 0.95 (max: 16.7) percentage points, for the tissue contour and target volume, respectively. Two of the MR image sequences (Axial T2 Flair and Axial T1 Fat Sat images) resulted in poor quality p‐CTs and were not used for dose comparison. Conclusion: A good agreement was seen between the p‐CT and CT dose distributions in this preliminary study, showing the potential for using MRI for both target delineation and dose calculation for brain treatments, with the clinical integration of an automated p‐CT generation method, and appropriate MRI sequences.

Sodium ( 23 Na) MRI detects elevated muscular sodium concentration in Duchenne muscular dystrophy

In boys with Duchenne muscular dystrophy (DMD), (1)H MRI suggested muscular edema before fatty degeneration. Using specific (23)Na MRI sequences, we tested the hypothesis that the edema is caused by an osmotic effect due to increased myoplasmic Na(+) content rather than inflammation that would lead to extracellular edema. Eleven patients with DMD (mean age, 10 ± 5 years) and 16 healthy volunteers of similar age were examined on a 3-T system with (1)H MRI and (23)Na density-adapted 3-dimensional radial MRI sequences. The muscle edema was quantified on short-tau inversion recovery images using background noise as reference. Fatty degeneration was quantified on T1-weighted images using subcutaneous fat as reference. Na(+) was quantified by a muscular tissue sodium concentration (TSC) sequence. A novel inversion recovery (IR) sequence allowed us to determine mainly the myoplasmic Na(+) by suppression of the extracellular (23)Na signal from vasogenic edema. A reference tube containing 51.3 mmol/L Na(+) with agarose gel was used for standardization. The normalized muscular signal intensity of (23)Na as assessed by the IR sequence was significantly higher for patients with DMD than for volunteers. TSC was markedly increased at 38.4 ± 6.8 mmol/L in patients with DMD compared with 25.4 ± 2.1 mmol/L in volunteers. The muscular edema-like changes were much more prominent in patients with DMD than in volunteers. In addition, the muscular fat content was significantly higher in patients with DMD than in volunteers. The elevated myoplasmic Na(+) concentration in DMD is osmotically relevant and causes a mainly intracellular muscle edema that contributes to the pathogenesis of DMD.

Modeling the Distribution of New MRI Cortical Lesions in Multiple Sclerosis Longitudinal Studies

ObjectiveRecent studies have shown the relevance of the cerebral grey matter involvement in multiple sclerosis (MS). The number of new cortical lesions (CLs), detected by specific MRI sequences, has the potential to become a new research outcome in longitudinal MS studies. Aim of this study is to define the statistical model better describing the distribution of new CLs developed over 12 and 24 months in patients with relapsing-remitting (RR) MS.MethodsFour different models were tested (the Poisson, the Negative Binomial, the zero-inflated Poisson and the zero-inflated Negative Binomial) on a group of 191 RRMS patients untreated or treated with 3 different disease modifying therapies. Sample size for clinical trials based on this new outcome measure were estimated by a bootstrap resampling technique.ResultsThe zero-inflated Poisson model gave the best fit, according to the Akaike criterion to the observed distribution of new CLs developed over 12 and 24 months both in each treatment group and in the whole RRMS patients group adjusting for treatment effect.ConclusionsThe sample size calculations based on the zero-inflated Poisson model indicate that randomized clinical trials using this new MRI marker as an outcome are feasible.