Whole-Brain Dynamics in Aging: Disruptions in Functional Connectivity and the Role of the Rich Club.

Normal aging causes disruptions in the brain that can lead to cognitive decline. Resting-state functional magnetic resonance imaging studies have found significant age-related alterations in functional connectivity across various networks. Nevertheless, most of the studies have focused mainly on static functional connectivity. Studying the dynamics of resting-state brain activity across the whole-brain functional network can provide a better characterization of age-related changes. Here, we employed two data-driven whole-brain approaches based on the phase synchronization of blood-oxygen-level-dependent signals to analyze resting-state fMRI data from 620 subjects divided into two groups (middle-age group (n = 310); age range, 50-64 years versus older group (n = 310); age range, 65-91 years). Applying the intrinsic-ignition framework to assess the effect of spontaneous local activation events on local-global integration, we found that the older group showed higher intrinsic ignition across the whole-brain functional network, but lower metastability. Using Leading Eigenvector Dynamics Analysis, we found that the older group showed reduced ability to access a metastable substate that closely overlaps with the so-called rich club. These findings suggest that functional whole-brain dynamics are altered in aging, probably due to a deficiency in a metastable substate that is key for efficient global communication in the brain.

Brain BOLD MRI O2 and CO2 stress testing: implications for perioperative neurocognitive disorder following surgery.

BACKGROUND: Mechanical ventilation to alter and improve respiratory gases is a fundamental feature of critical care and intraoperative anesthesia management. The range of inspired O2 and expired CO2 during patient management can significantly deviate from values in the healthy awake state. It has long been appreciated that hyperoxia can have deleterious effects on organs, especially the lung and retina. Recent work shows intraoperative end-tidal (ET) CO2 management influences the incidence of perioperative neurocognitive disorder (POND). The interaction of O2 and CO2 on cerebral blood flow (CBF) and oxygenation with alterations common in the critical care and operating room environments has not been well studied. METHODS: We examine the effects of controlled alterations in both ET O2 and CO2 on cerebral blood flow (CBF) in awake adults using blood oxygenation level-dependent (BOLD) and pseudo-continuous arterial spin labeling (pCASL) MRI. Twelve healthy adults had BOLD and CBF responses measured to alterations in ET CO2 and O2 in various combinations commonly observed during anesthesia. RESULTS: Dynamic alterations in regional BOLD and CBF were seen in all subjects with expected and inverse brain voxel responses to both stimuli. These effects were incremental and rapid (within seconds). The most dramatic effects were seen with combined hyperoxia and hypocapnia. Inverse responses increased with age suggesting greater risk. CONCLUSIONS: Human CBF responds dramatically to alterations in ET gas tensions commonly seen during anesthesia and in critical care. Such alterations may contribute to delirium following surgery and under certain circumstances in the critical care environment. TRIAL REGISTRATION: ClincialTrials.gov NCT02126215 for some components of the study. First registered April 29, 2014.

Collateral Automation for Triage in Stroke: Evaluating Automated Scoring of Collaterals in Acute Stroke on Computed Tomography Scans.

Computed tomography angiography (CTA) collateral scoring can identify patients most likely to benefit from mechanical thrombectomy and those more likely to have good outcomes and ranges from 0 (no collaterals) to 3 (complete collaterals). In this study, we used a machine learning approach to categorise the degree of collateral flow in 98 patients who were eligible for mechanical thrombectomy and generate an e-CTA collateral score (CTA-CS) for each patient (e-STROKE SUITE, Brainomix Ltd., Oxford, UK). Three experienced neuroradiologists (NRs) independently estimated the CTA-CS, first without and then with knowledge of the e-CTA output, before finally agreeing on a consensus score. Addition of the e-CTA improved the intraclass correlation coefficient (ICC) between NRs from 0.58 (0.46-0.67) to 0.77 (0.66-0.85, p = 0.003). Automated e-CTA, without NR input, agreed with the consensus score in 90% of scans with the remaining 10% within 1 point of the consensus (ICC 0.93, 0.90-0.95). Sensitivity and specificity for identifying favourable collateral flow (collateral score 2-3) were 0.99 (0.93-1.00) and 0.94 (0.70-1.00), respectively. e-CTA correlated with the Alberta Stroke Programme Early CT Score (Spearman correlation 0.46, p < 0.001) highlighting the value of good collateral flow in maintaining tissue viability prior to reperfusion. In conclusion, -e-CTA provides a real-time and fully automated approach to collateral scoring with the potential to improve consistency of image interpretation and to independently quantify collateral scores even without expert rater input.

Resting-State Functional Connectivity Magnetic Resonance Imaging and Outcome After Acute Stroke.

Background and Purpose- Physiological effects of stroke are best assessed over entire brain networks rather than just focally at the site of structural damage. Resting-state functional magnetic resonance imaging can map functional-anatomic networks by analyzing spontaneously correlated low-frequency activity fluctuations across the brain, but its potential usefulness in predicting functional outcome after acute stroke remains unknown. We assessed the ability of resting-state functional magnetic resonance imaging to predict functional outcome after acute stroke. Methods- We scanned 37 consecutive reperfused stroke patients (age, 69±14 years; 14 females; 3-day National Institutes of Health Stroke Scale score, 6±5) on day 3 after symptom onset. After imaging preprocessing, we used a whole-brain mask to calculate the correlation coefficient matrices for every paired region using the Harvard-Oxford probabilistic atlas. To evaluate functional outcome, we applied the modified Rankin Scale at 90 days. We used region of interest analyses to explore the functional connectivity between regions and graph-computation analysis to detect differences in functional connectivity between patients with good functional outcome (modified Rankin Scale score ≤2) and those with poor outcome (modified Rankin Scale score >2). Results- Patients with good outcome had greater functional connectivity than patients with poor outcome. Although 3-day National Institutes of Health Stroke Scale score was the most accurate independent predictor of 90-day modified Rankin Scale (84.2%), adding functional connectivity increased accuracy to 94.7%. Preserved bilateral interhemispheric connectivity between the anterior inferior temporal gyrus and superior frontal gyrus and decreased connectivity between the caudate and anterior inferior temporal gyrus in the left hemisphere had the greatest impact in favoring good prognosis. Conclusions- These data suggest that information about functional connectivity from resting-state functional magnetic resonance imaging may help predict 90-day stroke outcome.

Good clinical and MRI outcome after arthroscopic autologous chondrocyte implantation for cartilage repair in the knee.

PURPOSE: To analyze the clinical outcome and cartilage regeneration after all-arthroscopic Autologous Chondrocyte Implantation (ACI) using chondrospheres® (ACT3D) for the treatment of full-size articular cartilage lesions at the knee. METHODS: Thirty consecutive patients treated by all-arthroscopic ACI for full-size articular cartilage lesions in an otherwise healthy knee were enrolled. The defects were located on the femoral condyles (n = 18), in the trochlea (n = 7) and at the patella (n = 5). Follow-up consisted of a clinical evaluation with assessment of subjective scores. Patient satisfaction was evaluated on a visual analog scale (VAS). 3-Tesla MRI and T2 mapping of the operated and the contralateral healthy knees were included to control the quality of the regenerated cartilage. The MOCART score was assessed by three blinded independent radiologists. RESULTS: At the mean follow-up of 3 years ± 10.2 months 26 of the 30 patients (86.6%) were subjectively highly satisfied with the surgical result and assured they would undergo the same procedure again. The mean Lysholm score increased to 77.7 ± 14.6, the mean subjective IKDC significantly to 84.2 ± 5.6 (p < 0.05) and all five subgroups of the KOOS improved significantly (p < 0.05). The subjective outcome was not influenced by the duration of symptoms, age, location, size of defects nor dose of spheroids. The modified MOCART score was a mean of 60 ± 21 (0-80) points. Twenty-four patients (82.7%) were rated higher than 60 points. T2 mapping documented similar cartilage quality of the area of the ACI and the same location at the contralateral knee. Three patients had a MOCART score of 0 with few or no cartilage regeneration on MRI and were considered as failure of the ACI. CONCLUSION: In this small cohort of 30 patients, minimal invasive all-arthroscopic ACT 3D using spheroids led to convincing clinical short-to-mid-term results with a significant increase in patients quality of life, satisfaction, reduction of pain, and improvement in knee function. The high morphologic integrity and quality of the ACI was reconfirmed by the Mocart Score and T2 mapping. LEVEL OF EVIDENCE: IV.

Prospective intraindividual comparison of gadoterate and gadobutrol for cervical and intracranial contrast-enhanced magnetic resonance angiography.

PURPOSE: Gadobutrol (GB) is reported to provide improved relaxivity and concentration compared to gadoterate (GT). This study was designed to intraindividually compare quantitative and qualitative enhancement characteristics of GB to GT in cervicocranial magnetic resonance angiography (MRA) of patients with cerebrovascular disease (CVD). METHODS: Patients (n = 54) with CVD underwent two identical contrast-enhanced magnetic resonance angiography (CE-MRA) examinations of the cervical and intracranial vasculature in randomized order, using GB and GT in equimolar dose. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were obtained by two independent neuroradiologists, blinded to the applied contrast agents. Qualitative assessment was performed using a three-point scale with a focus on M1/M2 segments. RESULTS: One thousand and twenty-six vessel segments were analyzed. GB revealed a significantly higher SNR (p = 0.032) and CNR (p = 0.031) in all vessel segments. GB featured a significantly higher SNR and CNR in thoracic (p = 0.022; p = 0.016) and cervical vessels (p = 0.03; p = 0.038), as well as in the posterior circulation (p = 0.012; p = 0.005). In blinded qualitative assessment, overall preference was given to GB (p = 0.02), showing a significant better delineation of the M1/M2 segments (p = 0.041). CONCLUSION: Compared to GT, the use of GB results in a significantly higher SNR and CNR in cervical and cerebral CE-MRA, leading to a better delineation of the intracranial vasculature. Present results underline the potential of GB for improved CE-MRA assessment of vasculature in CVD patients.

Multidisciplinary Management of Pediatric Sports-Related Concussion.

OBJECTIVES: To summarize the clinical characteristics and outcomes of pediatric sports-related concussion (SRC) patients who were evaluated and managed at a multidisciplinary pediatric concussion program and examine the healthcare resources and personnel required to meet the needs of this patient population. METHODS: We conducted a retrospective review of all pediatric SRC patients referred to the Pan Am Concussion Program from September 1st, 2013 to May 25th, 2015. Initial assessments and diagnoses were carried out by a single neurosurgeon. Return-to-Play decision-making was carried out by the multidisciplinary team. RESULTS: 604 patients, including 423 pediatric SRC patients were evaluated at the Pan Am Concussion Program during the study period. The mean age of study patients was 14.30 years (SD: 2.32, range 7-19 years); 252 (59.57%) were males. Hockey (182; 43.03%) and soccer (60; 14.18%) were the most commonly played sports at the time of injury. Overall, 294 (69.50%) of SRC patients met the clinical criteria for concussion recovery, while 75 (17.73%) were lost to follow-up, and 53 (12.53%) remained in active treatment at the end of the study period. The median duration of symptoms among the 261 acute SRC patients with complete follow-up was 23 days (IQR: 15, 36). Overall, 25.30% of pediatric SRC patients underwent at least one diagnostic imaging test and 32.62% received referral to another member of our multidisciplinary clinical team. CONCLUSION: Comprehensive care of pediatric SRC patients requires access to appropriate diagnostic resources and the multidisciplinary collaboration of experts with national and provincially-recognized training in TBI.

High-resolution blood-pool-contrast-enhanced MR angiography in glioblastoma: tumor-associated neovascularization as a biomarker for patient survival. A preliminary study.

INTRODUCTION: The objective of the study was to determine whether tumor-associated neovascularization on high-resolution gadofosveset-enhanced magnetic resonance angiography (MRA) is a useful biomarker for predicting survival in patients with newly diagnosed glioblastomas. METHODS: Before treatment, 35 patients (25 men; mean age, 64 ± 14 years) with glioblastoma underwent MRI including first-pass dynamic susceptibility contrast (DSC) perfusion and post-contrast T1WI sequences with gadobutrol (0.1 mmol/kg) and, 48 h later, high-resolution MRA with gadofosveset (0.03 mmol/kg). Volumes of interest for contrast-enhancing lesion (CEL), non-CEL, and contralateral normal-appearing white matter were obtained, and DSC perfusion and DWI parameters were evaluated. Prognostic factors were assessed by Kaplan-Meier survival and Cox proportional hazards model. RESULTS: Eighteen (51.42 %) glioblastomas were hypervascular on high-resolution MRA. Hypervascular glioblastomas were associated with higher CEL volume and lower Karnofsky score. Median survival rates for patients with hypovascular and hypervascular glioblastomas treated with surgery, radiotherapy, and chemotherapy were 15 and 9.75 months, respectively (P < 0.001). Tumor-associated neovascularization was the best predictor of survival at 5.25 months (AUC = 0.794, 81.2 % sensitivity, 77.8 % specificity, 76.5 % positive predictive value, 82.4 % negative predictive value) and yielded the highest hazard ratio (P < 0.001). CONCLUSIONS: Tumor-associated neovascularization detected on high-resolution blood-pool-contrast-enhanced MRA of newly diagnosed glioblastoma seems to be a useful biomarker that correlates with worse survival.

Retirement-from-sport considerations following pediatric sports-related concussion: case illustrations and institutional approach.

The decision to advise an athlete to retire from sports following sports-related concussion (SRC) remains a persistent challenge for physicians. In the absence of strong empirical evidence to support recommendations, clinical decision making must be individualized and should involve a multidisciplinary team of experts in concussion and traumatic brain injury. Although previous authors have advocated for a more conservative approach to these issues in child and adolescent athletes, there are few reports outlining considerations for this process among this unique population. Here, the authors use multiple case illustrations to discuss 3 subgroups of clinical considerations for sports retirement among pediatric SRC patients including the following: those with structural brain abnormalities identified on neuroimaging, those presenting with focal neurological deficits and abnormalities on physical examination, and those in whom the cumulative or prolonged effects of concussion are suspected or demonstrated. The authors' evolving multidisciplinary institutional approach to return-to-play and retirement decision making in pediatric SRC is also presented.

Disk displacement, eccentric condylar position, osteoarthrosis - misnomers for variations of normality? Results and interpretations from an MRI study in two age cohorts.

BACKGROUND: Clinical decision-making and prognostic statements in individuals with manifest or suspected temporomandibular disorders (TMDs) may involve assessment of (a) the position of articular disc relative to the mandibular condyle, (b) the location of the condyle relative to the temporal joint surfaces, and (c) the depth of the glenoid fossa of the temporomandibular joints (TMJs). The aim of this study was twofold: (1) Determination of the prevalence of these variables in two representative population-based birth cohorts. (2) Reinterpretation of the clinical significance of the findings. METHODS: From existing magnetic resonance imaging (MRI) scans of the TMJs that had been taken in 2005 and 2006 from 72 subjects born between 1930 and 1932 and between 1950 and 1952, respectively, the condylar position at closed jaw was calculated as percentage displacement of the condyle from absolute centricity. By using the criteria introduced by Orsini et al. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 86:489-97, 1998), a textbook-like disc position at closed jaw was distinguished from an anterior location. TMJ morphology of the temporal joint surfaces was assessed at open jaw by measuring the depth of the glenoid fossa, using the method proposed by Muto et al. (J Oral Maxillofac Surg 52:1269-72, 1994). Frequency distributions were recorded for the condylar and disc positions at closed jaw. Student's t-test with independent samples was used as test of significance to detect differences of condylar positions between the age cohorts (1930 vs. 1950) and the sexes. The significance levels were set at 5%. First, the results from the measurement of the age cohorts were compared without differentiation of sexes, i.e., age cohort 1930-1932 versus age cohort 1950-1952. Subsequently, the age cohorts were compared by sex, i.e., men in cohort 1930-1932 versus men in cohort 1950-1952, and women in cohort 1930-1932 women men in cohort 1950-1952. RESULTS: In both cohorts, condylar position was characterized by great variability. About 50% of the condyles were located centrically, while the other half was either in an anterior or in a posterior position. In both female cohorts, a posterior position predominated, whereas a centric position prevailed among men. Around 75% of the discs were positioned textbook-like, while the remaining forth was located anteriorly. Age had no statistically significant influence on condylar or on disc position. Conversely, comparison between the age groups revealed a statistically significant decrease of the depth of the glenoid fossa in both older cohorts. This age-dependent changes may be interpreted as flattening of the temporal joint surfaces. CONCLUSIONS: We call for a re-interpretation of imaging findings because they may insinuate pathology which usually is not present. Instead, anterior or posterior positions of the mandibular condyle as well as an anterior location of the articular disc should be construed as a variation of normalcy. Likewise, flattening of articular surfaces of the TMJs may be considered as normal adaptive responses to increased loading, rather than pathological degenerative changes. TRIAL REGISTRATION: Not applicable.

Traumatic Optic Neuropathy: A Potentially Unrecognized Diagnosis after Sports-Related Concussion.

Traumatic optic neuropathy is a rare cause of visual disturbance after head injury that can be difficult to distinguish from coexisting vestibulo-ocular dysfunction because of the overlap in presenting symptoms in patients with these conditions. We present a case report of a 13-year-old girl who sustained a head injury during a ringette game leading to blurred vision and diplopia persisting 5 months after injury. Clinical history and physical examination findings were consistent with a traumatic optic neuropathy, convergence insufficiency, and postconcussion syndrome. Neuroimaging was normal. The patient was managed using a multidisciplinary approach. At 6 months of follow-up, neuro-ophthalmological examination demonstrated evidence of permanent partial optic nerve injury, and formal neuropsychological testing fell primarily within normal limits. The patient was advised to retire from collision sports. The authors discuss the value of a comprehensive multidisciplinary approach to the evaluation and management of concussion patients presenting with persistent visual symptoms.

Principles of T2 *-weighted dynamic susceptibility contrast MRI technique in brain tumor imaging.

Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) is used to track the first pass of an exogenous, paramagnetic, nondiffusible contrast agent through brain tissue, and has emerged as a powerful tool in the characterization of brain tumor hemodynamics. DSC-MRI parameters can be helpful in many aspects, including tumor grading, prediction of treatment response, likelihood of malignant transformation, discrimination between tumor recurrence and radiation necrosis, and differentiation between true early progression and pseudoprogression. This review aims to provide a conceptual overview of the underlying principles of DSC-MRI of the brain for clinical neuroradiologists, scientists, or students wishing to improve their understanding of the technical aspects, pitfalls, and controversies of DSC perfusion MRI of the brain. Future consensus on image acquisition parameters and postprocessing of DSC-MRI will most likely allow this technique to be evaluated and used in high-quality multicenter studies and ultimately help guide clinical care.

Association of cortical thickness and neurological soft signs in patients with chronic schizophrenia and healthy controls.

BACKGROUND: Neurological soft signs (NSS), i.e. subtle neurological abnormalities, have been frequently found in schizophrenia. Neuroimaging studies in schizophrenia have shown abnormal cortical thickness changes across the cortical mantle. However, few studies have examined relationships between NSS and cortical thickness abnormalities in schizophrenia. METHOD: A sample of 18 patients with chronic schizophrenia and 20 age-matched healthy controls were included. Cortical thickness was assessed on high-resolution 3-tesla magnetic resonance imaging by using FreeSurfer software and NSS were rated on the Heidelberg Scale. RESULTS: Significant negative correlations between NSS and cortical thickness were found in the prefrontal, inferior temporal, superior parietal, postcentral, and supramarginal cortices in the schizophrenia patients. In the controls, however, this negative correlation was found in the anterior cingulate, pericalcarine and superior/middle temporal regions. CONCLUSION: Our results not only confirmed the association between NSS and cortical thickness in chronic schizophrenia but also indicated that patients and controls have different anatomical substrates of NSS.

Impact of the Novel MRI Contrast Agent Gadopiclenol on Radiotherapy Decision Making in Patients With Brain Metastases.

PURPOSE: The aim of this study was to assess the effect of gadopiclenol versus gadobenate dimeglumine contrast-enhanced magnetic resonance imaging (MRI) on decision-making between whole-brain radiotherapy (WBRT) and stereotactic radiosurgery (SRS) for treatment of brain metastases (BMs). METHODS: Patients with BMs underwent 2 separate MRI examinations in a double-blind crossover phase IIb comparative study between the MRI contrast agents gadopiclenol and gadobenate dimeglumine, both administered at 0.1 mmol/kg. The imaging data of a single site using identical MRI scanners and protocols were included in this post hoc analysis. Patients with 1 or more BMs in any of both MRIs were subjected to target volume delineation for treatment planning. Two radiation oncologists contoured all visible lesions and decided upon SRS or WBRT, according to the number of metastases. For each patient, SRS or WBRT treatment plans were calculated for both MRIs, considering the gross target volume (GTV) as the contrast-enhancing aspects of the tumor. Mean GTVs and volume of healthy brain exposed to 12 Gy (V12), as well as Dice similarity coefficient scores, were obtained. The Spearman rank (ρ) correlation was additionally calculated for assessing linear differences. Three different expert radiation oncologists blindly rated the contrast enhancement for contouring purposes. RESULTS: Thirteen adult patients were included. Gadopiclenol depicted additional BM as compared with gadobenate dimeglumine in 7 patients (54%). Of a total of 63 identified metastatic lesions in both MRI sets, 3 subgroups could be defined: A, 48 (24 pairs) detected equal GTVs visible in both modalities; B, 13 GTVs only visible in the gadopiclenol set (mean ± SD, 0.16 ± 0.37 cm3); and C, 2 GTVs only visible in the gadobenate dimeglumine set (mean ± SD, 0.01 ± 0.01). Treatment indication was changed for 2 (15%) patients, 1 from no treatment to SRS and for 1 from SRS to WBRT. The mean GTVs and brain V12 were comparable between both agents (P = 0.694, P = 0.974). The mean Dice similarity coefficient was 0.70 ± 0.14 (ρ = 0.82). According to the readers, target volume definition was improved in 63.9% of cases (23 of 36 evaluations) with gadopiclenol and 22.2% with gadobenate dimeglumine (8 of 36), whereas equivalence was obtained in 13.9% (5 of 36). CONCLUSIONS: Gadopiclenol-enhanced MRI improved BM detection and characterization, with a direct impact on radiotherapy treatment decision between WBRT and SRS. Additionally, a more exact target delineation and planning could be performed with gadopiclenol. A prospective evaluation in a larger cohort of patients is required to confirm these findings.

Albumin-binding MR blood pool contrast agent improves diagnostic performance in human brain tumour: comparison of two contrast agents for glioblastoma.

OBJECTIVE: We qualitatively and quantitatively compared MRI enhancement obtained with gadofosveset, an albumin-binding blood-pool contrast agent, and with gadobutrol, an extracellular contrast agent, in patients with glioblastoma. METHODS: Thirty-five patients (25 men; 64 ± 14 years) with histologically proven glioblastoma underwent MRI including pre- and post-contrast T1-weighted SE images acquired 5 min after gadobutrol (0.1 mmol/kg) and, 48 h later, images acquired with identical parameters 5 min and 3, 6, and 24 h after gadofosveset (0.03 mmol/kg). Lesion extent, delineation, internal morphology, multifocality, and global diagnostic preference were evaluated quantitatively for the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and contrast enhancement (CE). RESULTS: Mean values of SNR, CNR, and tumour CE were highest 6 h after gadofosveset. Multifocality was seen in 17 (48.6 %) patients; additional lesions had stronger enhancement 6 h after gadofosveset in 12 patients (70.6 %). In 21 (60 %) patients, radiologists' global preference was highest in images acquired 6 h after gadofosveset (kappa = 0.764). In 22 patients (62.8 %), all qualitative endpoints were better at 5 min after gadobutrol than in images acquired 5 min after gadofosveset injection. CONCLUSIONS: Gadobutrol gives significant tumour enhancement in early postcontrast imaging. However, images acquired 6 h after gadofosveset injection have significantly better diagnostic information endpoints and contrast enhancement.

Perfusion MRI: the five most frequently asked clinical questions.

OBJECTIVE: This article addresses questions that radiologists frequently ask when planning, performing, processing, and interpreting MRI perfusion studies in CNS imaging. CONCLUSION: Perfusion MRI is a promising tool in assessing stroke, brain tumors, and neurodegenerative diseases. Most of the impediments that have limited the use of per-fusion MRI can be overcome to allow integration of these methods into modern neuroimaging protocols.

Perfusion MRI: the five most frequently asked technical questions.

OBJECTIVE: This and its companion article address the 10 most frequently asked questions that radiologists face when planning, performing, processing, and interpreting different MR perfusion studies in CNS imaging. CONCLUSION: Perfusion MRI is a promising tool in assessing stroke, brain tumors, and patients with neurodegenerative diseases. Most of the impediments that have limited the use of perfusion MRI can be overcome to allow integration of these methods into modern neuroimaging protocols.

Characterization and therapy monitoring of head and neck carcinomas using diffusion-imaging-based intravoxel incoherent motion parameters-preliminary results.

INTRODUCTION: Using the intravoxel incoherent motion (IVIM) model, diffusion-related coefficient (D) and perfusion-related parameter (f) can be measured. Here, we used IVIM imaging to characterize squamous cell carcinomas of head and neck (HNSCC) and evaluated its application in follow-up after nonsurgical organ preserving therapy. METHODS: Twenty-two patients with locally advanced HNSCC (clinical stage III to IVb) were examined before treatment using eight different b values (b = 0, 50, 100, 150, 200, 250, 700, 800 s/mm(2)). All patients were followed for at least 7.5 months after conclusion of therapy. In 16 of these patients, follow-up MRI was available. Using the IVIM approach, f and D were extracted using a bi-exponential fit. For comparison, ADC maps were calculated. RESULTS: The initial values of f before therapy were located between 5.9 % and 12.9 % (mean: 9.4 ± 2.4 %) except for two outliers (f = 17.9 % and 18.2 %). These two patients exclusively displayed poor initial treatment response. Overall, high initial f (13.1 ± 4.1 % vs. 9.1 ± 2.4 %) and ADC (1.17 ± 0.08 × 10(-3) mm(2)/s vs. 0.98 ± 0.19 × 10(-3) mm(2)/s) were associated with poor short term outcome (n = 6) after 7.5 months follow-up. D values before treatment were 0.98 × 10(-3) ± 0.18 mm(2)/s and ADC values were 1.03 × 10(-3) ± 0.18 mm(2)/s. At follow-up, in all primary responders, D (69 ± 52 %), f (65 ± 46 %), and ADC (68 ± 49%) increased. CONCLUSIONS: Our preliminary evaluation indicates that an initial high f may predict poor prognosis in HNSCC. In responders, a significant increase of all IVIM parameters after therapy was demonstrated.

Perspectives of 3 T magnetic resonance imaging in radiosurgical treatment planning.

The introduction of 3 T magnetic resonance imaging (MRI) scanners for neuro-oncological diagnostics showed a general improvement of image quality, especially in terms of the detection and differentiation of intracranial tumors. Among the advantages of 3 T scanners compared to 1.5 T scanners are the possibility of higher spatial image resolution or shorter investigation times and the availability of functional imaging in sufficient quality. Consequently, the use of 3 T MRI for radiosurgery planning is highly desired. Functional MRI techniques (perfusion-weighted imaging, dynamic contrast-enhanced MRI, MR spectroscopy, diffusion-weighted imaging, and diffusion tensor imaging) available at 3 T scanners provide not only better detection and differentiation but also significantly better delineation of intracranial tumors, which is a crucial feature for successful radiosurgical treatment planning. The use of multimodal morphological and functional MRI methods allows identification of the biologically most active parts of the tumors with consecutive changes in therapy planning. On the other hand, there are increased geometric distortions on MRI scans obtained at 3 T compared to 1.5 T, which makes their use limited for now. However, the newest studies show an acceptable degree of geometric distortion on the 3 T planning images using special imaging protocols, while additional investigations on this issue are needed to find the optimal technical solution.