Imaging In Neurology Research Articles

0.35 Tesla magnetic resonance imaging findings in a cohort of 399 seizure patients. Experience from a single centre in Nigeria

Epilepsy/seizures are major indications for brain imaging in clinical neurology. Structural lesions that may cause seizures are numerous and are defined using various neuroimaging techniques, including magnetic resonance imaging. The resolution of MRI allows for better fine ultra-structural lesions delineation. The aim of this study was to describe the pattern and frequency of structural brain lesions in MRI of patients with seizures and no clinically evident focal neurological signs. This was a retrospective, descriptive study carried out in a private hospital in Enugu, South East Nigeria to review all MRI results of patients who presented with seizures without clinical evidence of focal neurologic deficits. The MRI reports of two-third of the patients (47.9%) revealed focal lesions and about a third of the patients (32.2%) had normal findings. The structural lesions reported were mostly brain tumors (16%), stroke (9.5%), central nervous system infections (6.5%), brain malformation (6%) and encephalomalacia/gliosis (5%). Frequency of focal lesions clearly increased with age. Young patients were mostly associated with normal findings. Brain tumors and stroke were noted to occur more in the middle and aged patients respectively. Brain Magnetic Resonance Imaging remains a useful tool in the workup of patients with seizures without neurologic deficits. Treatable lesions can easily be revealed using this imaging modality.

Bibliometric Analysis of Functional Magnetic Resonance Imaging Studies on Acupuncture Analgesia Over the Past 20 Years.

BackgroundResearches on the central mechanisms of acupuncture analgesia have been widely conducted worldwide. However, there is no bibliometric analysis of functional magnetic resonance imaging (fMRI) studies on acupuncture analgesia. This study visualized the current status, hot spots and frontiers of fMRI studies on acupuncture analgesia in the past 20 years to provide a theoretical basis for its clinical application.MethodsAll publications were obtained from Science Citation Index-Expanded (SCI-E) of Web of Science (WOS). We used CiteSpace to analyze publications, journals, cited journals, authors, cited authors, institutions, countries, references, and keywords. We also analyzed collaborative network maps and co-occurrence network maps.ResultsWe retrieved a total of 797 articles. Regarding the volume of publications, the total number of annual publications showed a fluctuating but overall increasing trend. Evidence-based Complementary and Alternative Medicine (21 articles) was the most productive journal, and Pain (225 articles) was the most cited journal. The most productive author was Qin W (16 articles), and the most co-cited author was Hui KKS (111). The most prolific institution and country were Massachusetts General Hospital (34 articles) and USA (212 articles). “Pain” was the top-ranked for keyword frequency and centrality. “Functional connectivity” was the frontier hotspot for 2018–2021.ConclusionFirst, fMRI researches on acupuncture analgesia involved several countries (regions) and institutions, mainly located in the USA, China and Korea, and most of them were universities. In addition, the USA was a major contributor in this field. Second, in terms of disciplinary distribution, the literatures were mainly from clinical neurology, neuroscience, and radiology nuclear medicine medical imaging. Third, the keyword co-occurrence analysis showed that the hot keywords included pain, fMRI, and lower back pain. Fourth, through keyword clustering analysis, the hot disease was found to be lower back pain, and the hot contents were acupuncture specificity and frequency specificity. Fifth, a timeline analysis of the references identified that chronic low back pain and specificity will remain a hot topic for future research.

Comparison of Whole-Head Functional Near-Infrared Spectroscopy With Functional Magnetic Resonance Imaging and Potential Application in Pediatric Neurology

BackgroundChanges in cerebral blood flow in response to neuronal activation can be measured by time-dependent fluctuations in hemoglobin species within the brain; this is the basis of functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRS). There is a clinical need for portable neural imaging systems, such as fNIRS, to accommodate patients who are unable to tolerate an MR environment. ObjectiveOur objective was to compare task-related full-head fNIRS and fMRI signals across cortical regions. MethodsEighteen healthy adults completed a same-day fNIRS-fMRI study, in which they performed right- and left-hand finger tapping tasks and a semantic-decision tones-decision task. First- and second-level general linear models were applied to both datasets. ResultsThe finger tapping task showed that significant fNIRS channel activity over the contralateral primary motor cortex corresponded to surface fMRI activity. Similarly, significant fNIRS channel activity over the bilateral temporal lobe corresponded to the same primary auditory regions as surface fMRI during the semantic-decision tones-decision task. Additional channels were significant for this task that did not correspond to surface fMRI activity. ConclusionAlthough both imaging modalities showed left-lateralized activation for language processing, the current fNIRS analysis did not show concordant or expected localization at the level necessary for clinical use in individual pediatric epileptic patients. Future work is needed to show whether fNIRS and fMRI are comparable at the source level so that fNIRS can be used in a clinical setting on individual patients. If comparable, such an imaging approach could be applied to children with neurological disorders.

Performance of a Pediatric Stroke Alert Team Within a Comprehensive Stroke Center.

Childhood stroke is rare, and diagnosis is frequently delayed. The use of pediatric stroke teams has the potential to decrease time to neurology evaluation and imaging, hastening appropriate diagnosis and treatment for acute neurologic presentations in children. We performed a retrospective analysis of our institutional pediatric stroke or "brain attack" team (pedsBAT) activations from October 2014 to July 2017. Clinical characteristics and timing parameters were compared between pedsBAT activations in the inpatient vs emergency department (ED) / outpatient settings as well as between pediatric and adult BAT activations in the same time period. We identified 120 pedsBAT activations (75% in the ED/outpatient setting) during the study time period. Inpatient pedsBAT activations were more likely than outpatient activations to have heart disease as a risk factor for ischemic stroke and presented more frequently with altered mental status, but there were no differences in the proportion of cerebrovascular diagnoses or timing parameters between the 2 groups. When compared with adult BAT activations, outpatient pedsBAT activations had a longer time from symptom discovery to arrival at the ED, and inpatient pedsBAT activations had longer time from symptom discovery to BAT activation. Compared with adults, the interval leading up to stroke team activation was longer in children, suggesting delays in symptom recognition. Future interventions should be aimed at reducing these delays in presentation to care and stroke alert activation in pediatric patients.

Modified NEMA NU-2 performance evaluation methods for a brain-dedicated PET system with a hemispherical detector arrangement**This study is partially supported by ATOX Co., Ltd., Japan.

Brain PET imaging has important roles in neurology, neuro-oncology and molecular imaging research. We have developed a helmet-type PET prototype and have shown that the proposed hemispherical geometry had high potential for realizing high-sensitivity and low-cost brain imaging. However, there is no standard performance evaluation method for helmet-type PET, which would be a bottleneck to its commercialization. Therefore, we investigated appropriate performance evaluation methods for a helmet-type PET based on the NEMA NU 2-2018 standards. For those measurement methods that are not applicable to the helmet-type PET, we changed them while keeping the basic concept of the original NEMA standards. We measured spatial resolution, sensitivity, scatter fraction, count rate characteristics, accuracy of corrections for count losses and randoms, and image quality. We partially changed the measurement methods by making brain-size phantoms and by optimizing the length or the position of radioactive sources. The spatial resolution was 2.8 mm at 1-cm offset position by the filtered back-projection method. Sensitivities measured by the NEMA original setup and the proposed setup were 13.4 and 57.1 kcps/MBq. The respective values measured with our developed brain-size scatter phantom and with the conventional whole-body-size scatter phantom were: scatter fractions of 35% and 35%; peak NECRs of 25.1 kcps at 3.2 kBq/ml and 19.8 kcps at 2.6 kBq/ml ; and maximum absolute biases of 5.5% and 16.0%. The image quality was evaluated with the developed brain-size phantom, and good image quality was obtained. The helmet-type PET prototype showed high-sensitivity even with the small number of 54 detectors. The spatial resolution was better than 4.0 mm over the field-of-view. In conclusion, we proposed the performance evaluation methods for a brain-dedicated PET system with a hemispherical geometry. The proposed method could facilitate evaluation of performance characteristics of brain-dedicated PET scanners and optimization of its scanning and reconstruction parameters.

Radiology review for neurologists

Effective utilisation of imaging in neurology is facilitated by knowledge of technical background and a systematic approach in reading neuroradiological cases. The cooperation between neurologist and radiologist has the potential to improve neuroradiological patient care. In radiology pattern recognition plays an important role. Case reports are presented to help to recognise some common and uncommon pathology.

Delayed Intravenous Thrombolysis in Patients with Minor Stroke

Background: The actions and responses of the hospital personnel during acute stroke care in the emergency department (ED) may differ according to the severity of a patient’s stroke symptoms. We investigated whether the time from arrival at ED to various care steps differed between patients with minor and non-minor stroke who were treated with intravenous tissue plasminogen activator (IV tPA). Methods: We included consecutive patients who received IV tPA during a 1.5 year-period in 5 hospitals. Minor stroke was defined as a National Institutes of Health Stroke Scale (NIHSS) score < 5. We compared various intervals from arrival at the ED to treatment between patients with minor stroke and those with non-minor stroke (NIHSS score ≥5). Delayed treatment was defined as a door-to-needle time > 40 min. Results: During the study period, 356 patients received IV tPA treatment. The median door-to-needle time was significantly longer in the minor stroke group than it was in the non-minor stroke group (43 min [interquartile range [IQR] 35.5–55.5] vs. 37 min [IQR 30–46], p < 0.001). The minor stroke group had a significantly longer door-to-notification time (7 min [IQR 4.5–12] vs. 5 min [IQR 3–8], p < 0.001) and door-to-imaging time (20 min [IQR 15–26.5] vs. 16 min [IQR 11–21], p < 0.001) than did the non-minor stroke group. However, the imaging-to-needle time was not different between the groups. Multivariable analyses revealed that minor stroke was associated with delayed treatment (OR 2.54 [95% CI 1.52–4.30], p = 0.001). Conclusions: Our findings show that the door-to-needle time was longer in patients with minor stroke than it was in those with non-minor stroke, mainly owing to delayed action in the initial steps of neurology notification and imaging. Our findings suggest that some quality improvement initiatives are necessary for patients with suspected stroke with minor symptoms.

Nuclear Medicine Imaging in Pediatric Neurology.

Nuclear medicine imaging can provide important complementary information in the management of pediatric patients with neurological diseases. Pre-surgical localization of the epileptogenic focus in medically refractory epilepsy patients is the most common indication for nuclear medicine imaging in pediatric neurology. In patients with temporal lobe epilepsy, nuclear medicine imaging is particularly useful when magnetic resonance imaging findings are normal or its findings are discordant with electroencephalogram findings. In pediatric patients with brain tumors, nuclear medicine imaging can be clinically helpful in the diagnosis, directing biopsy, planning therapy, differentiating tumor recurrence from post-treatment sequelae, and assessment of response to therapy. Among other neurological diseases in which nuclear medicine has proved to be useful are patients with head trauma, inflammatory-infectious diseases and hypoxic-ischemic encephalopathy.

PET/MR - a rapidly growing technique of imaging in oncology and neurology.

The combination of positron emission tomography (PET) and magnetic resonance (MR) has become a subject of interest for researchers in the recent several years. Positron emission tomography in combination with magnetic resonance (PET/MR) is the most recent imaging technique classified in the so called hybrid systems category. This review briefly discusses the development history of PET/MR scanners, the principle of their operation, of tandem systems, as well as fully integrated devices. Further, it summarizes recent reports on the application of PET/MR scans and their possible future role in oncological and non-oncological diagnostics. Recent reports regarding the application of PET/MR scanners show huge potential of simultaneously received images, which exceed the advantages of either of those scans used separately. However, the results so far remain uncertain and require further investigations, especially in terms of clinical studies, not only for scientific purposes.

Chapter 12 - Positron emission tomography: ligand imaging

Since it was first used to image the brain in 1976, positron emission tomography (PET) has been utilized in a wide range of neurologic and psychiatric applications. From cerebral metabolism to receptor concentration, various PET imaging techniques involving a host of radiopharmaceuticals have provided insight into countless facets of both the normal and diseased brain. Although the majority of these radiopharmaceuticals are still limited to the realm of research, one PET ligand in particular has gained widespread clinical use: (18)F-fluorodeoxyglucose, a radiolabeled analog of glucose, has become an exceedingly prevalent clinical tool for the measurement of metabolism in organs throughout the body, including the brain. In recent years, a number of novel PET ligands have also made it through the US Food and Drug Administration approval process and been used clinically. However, gaining approval is by no means the only challenge facing these radiopharmaceuticals. Traversing the blood-brain barrier is a formidable obstacle in drug delivery, and accurately modeling tracer kinetics and correcting for the partial-volume effect are among the difficult tasks that remain once the ligand reaches its intended target. Even so, the use of PET imaging in neurology and psychiatry can be expected to expand in the coming years as novel radiopharmaceuticals continue to be developed.

Combined PET/MRI: Multi-modality Multi-parametric Imaging Is Here: Summary Report of the 4th International Workshop on PET/MR Imaging; February 23-27, 2015, Tübingen, Germany.

This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from February 23 to 27, 2015. Specifically, we summarise the three days of invited presentations from active researchers in this and associated fields augmented by round table discussions and dialogue boards with specific topics. These include the use of PET/MRI in cardiovascular disease, paediatrics, oncology, neurology and multi-parametric imaging, the latter of which was suggested as a key promoting factor for the wider adoption of integrated PET/MRI. Discussions throughout the workshop and a poll taken on the final day demonstrated that attendees felt more strongly that PET/MRI has further advanced in both technical versatility and acceptance by clinical and research-driven users from the status quo of last year. Still, with only minimal evidence of progress made in exploiting the true complementary nature of the PET and MRI-based information, PET/MRI is still yet to achieve its potential. In that regard, the conclusion of last year's meeting "the real work has just started" still holds true.

PET imaging in neurology: Alzheimer's and Parkinson's diseases.

PET studies play an important role in the early detection of Alzheimer's and Parkinson's diseases (AD and PD). Fluorine-18 fluorodeoxyglucose (F-FDG) PET imaging of regional cerebral glucose metabolism and PET amyloid imaging are the two major PET studies for AD. F-FDG PET is highly sensitive for the early diagnosis of AD, in predicting conversion from mild cognitive impairment to AD, and in differentiating AD from other dementias. PET amyloid imaging is positive in the majority of patients with AD. Negative amyloid PET reduces the likelihood of AD. The main limitations of PET amyloid imaging is its high positivity in the normal elderly population and in other medical conditions with amyloid pathologies. Various PET tracers are available to assess motor and cognitive dysfunctions in PD. PET tracers targeting presynaptic dopaminergic function (F-DOPA, radiolabeled PET tracers assessing the availability of dopamine transporters and vesicular monoamine transporters) and postsynaptic dopamine receptors are used to assess motor dysfunction in PD. PET tracers, particularly dopamine transporters, are highly sensitive in the early diagnosis of PD. Uptake of PET tracers in the striatum is inversely correlated with disease severity. PET is valuable in differentiating PD from other movement disorders. PET studies, particularly F-FDG PET, help to evaluate cortical metabolism in PD patients with cognitive dysfunction and dementia.

Hybrid SPECT/CT imaging in neurology.

In recent years, the SPECT/CT hybrid modality has led to a rapid development of imaging techniques in nuclear medicine, opening new perspectives for imaging staff and patients as well. However, while, the clinical role of positron emission tomography-computed tomography (PET-CT) is well consolidated, the diffusion and the consequent value of single-photon emission tomography-computed tomography (SPECT-CT) has yet to be weighed, Hence, there is a need for a careful analysis, comparing the "potential" benefits of the hybrid modality with the "established" ones of the standalone machine. The aim of this article is to analyze the impact of this hybrid tool on the diagnosis of diseases of the central nervous system, comparing strengths and weaknesses of both modalities through the use of SWOT analysis.

Editorial Review of 2014

Editorial Review of 2014

From PET/CT to PET/MRI: advances in instrumentation and clinical applications.

Multimodality imaging of positron emission tomography/computed tomography (PET/CT) provides both metabolic information and the anatomic structure, which is significantly superior to either PET or CT alone and has greatly improved its clinical applications. Because of the higher soft-tissue contrast of magnetic resonance imaging (MRI) and no extra ionizing radiation, PET/MRI imaging is the hottest topic currently. PET/MRI is swiftly making its way into clinical practice. However, it has many technical difficulties to overcome, such as photomultiplier tubes, which cannot work properly in a magnetic field, and the inability to provide density information on the object for attenuation correction. This paper introduces the technique process of PET/MRI and summarizes its clinical applications, including imaging in oncology, neurology, and cardiology.

RADIOLOGY REVIEW FOR NEUROLOGISTS

Effective utilisation of imaging in neurology is facilitated by knowledge of technical background and a systematic approach in reading neuroradiological cases. The cooperation between neurologist and radiologist has the potential to improve neuroradiological patient care. In radiology pattern recognition plays an important role. Case reports are presented to help to recognise some common and uncommon pathology.

Modern imaging in neurology and psychiatry

Modern imaging in neurology and psychiatry

Thalamic Activation in the Kleine-Levin Syndrome

The objective of this study was to investigate if combined measures of activation in the thalamus and working memory capacity could guide the diagnosis of Kleine-Levin Syndrome (KLS). A second objective was to obtain more insight into the neurobiological causes of KLS. Matched group and consecutive recruitment. University hospital neurology department and imaging center. Eighteen patients with KLS diagnosed according to the International Classification of Sleep Disorders and 26 healthy controls were included. N/A. Working memory capacity was assessed by the listening span task. A version of this task (reading span) was presented to the participants during functional magnetic resonance imaging (fMRI). Activation in the thalamus was measured in a region of interest analysis. A combination of the working memory capacity and the thalamic activation measures resulted in 80% prediction accuracy, 81% sensitivity, and 78% specificity regarding the ability to separate KLS patients from healthy controls. The controls had an inverse relation between working memory capacity and thalamic activation; higher performing participants had lower thalamic activation (r = -0.41). KLS patients showed the opposite relationship; higher performing participants had a tendency to higher thalamic activation (r = -0.35). This study shows that functional neuroimaging of the thalamus combined with neuropsychological assessment of working memory function provides a means to guide diagnosis of Kleine-Levin Syndrome. Results in this study also indicate that imaging of brain function and evaluation of cognitive capacity can give insights into the neurobiological mechanisms of Kleine-Levin Syndrome.

Combined PET/MR imaging in neurology: MR-based attenuation correction implies a strong spatial bias when ignoring bone

AimCombined PET/MR systems have now become available for clinical use. Given the lack of integrated standard transmission (TX) sources in these systems, attenuation and scatter correction (AC) must be performed using the available MR-images. Since bone tissue cannot easily be accounted for during MR-AC, PET quantification can be biased, in particular, in the vicinity of the skull. Here, we assess PET quantification in PET/MR imaging of patients using phantoms and patient data. Materials and methodsNineteen patients referred to our clinic for a PET/CT exam as part of the diagnostic evaluation of suspected dementia were included in our study. The patients were injected with 200MBq [18F]FDG and imaged with PET/CT and PET/MR in random sequence within 1h. Both, PET/CT and PET/MR were performed as single-bed acquisitions without contrast administration. PET/CT and PET/MR data were reconstructed following CT-based and MR-based AC, respectively. MR-AC was performed based on: (A) standard Dixon-Water–Fat segmentation (DWFS), (B) DWFS with co-registered and segmented CT bone values superimposed, and (C) with co-registered full CT-based attenuation image. All PET images were reconstructed using AW-OSEM, with neither resolution recovery nor time-of-flight option employed. PET/CT (D) or PET/MR (A–C) images were decay-corrected to the start time of the first examination. PET images following AC were evaluated visually and quantitatively using 10 homeomorphic regions of interest drawn on a transaxial T1w-MR image traversing the central basal ganglia. We report the relative difference (%) of the mean ROI values for (A)–(C) in reference to PET/CT (D).In a separate phantom experiment a 2L plastic bottle was layered with approximately 12mm of Gypsum plaster to mimic skull bone. The phantom was imaged on PET/CT only and standard MR-AC was performed by replacing hyperdense CT attenuation values corresponding to bone (plaster) with attenuation values of water. PET image reconstruction was performed with CT-AC (D) and CT-AC using the modified CT images corresponding to MR-AC using DWFS (A). ResultsPET activity values in patients following MR-AC (A) showed a substantial radial dependency when compared to PET/CT. In all patients cortical PET activity was lower than the activity in the central region of the brain (10–15%). When adding bone attenuation values to standard MR-AC (B and C) the radial gradient of PET activity values was removed.Further evaluation of PET/MR activity following MR-AC (A) relative to MR-AC (C) using the full CT for attenuation correction showed an underestimation of 25% in the cortical regions and 5–10% in the central regions of the brain.Observations in patients were replicated by observations from the phantom study. ConclusionOur phantom and patient data demonstrate a spatially varying bias of the PET activity in PET/MR images of the brain when bone tissue is not accounted for during attenuation correction. This has immediate implications for PET/MR imaging of the brain. Therefore, refinements to existing MR-AC methods or alternative strategies need to be found prior to adopting PET/MR imaging of the brain in clinical routine and research.

5-Fluoro-[β-11C]-L-tryptophan is a functional analogue of 5-hydroxy-[β-11C]-L-tryptophan in vitro but not in vivo

5-Hydroxy-[β-(11)C]-L-tryptophan ([(11)C]HTP) is an established positron emission tomography (PET) imaging agent for neuroendocrine tumors (NETs). It has also been used for other clinical research purposes in neurology and diabetes. However, its widespread use is limited by the short physical half-life of the radionuclide and a difficult radiosynthesis. Therefore, a Fluorine-18 labeled analogue, 5-[(18)F]Fluoro-L-tryptophan ([(18)F]FTRP), has been proposed as a functional analogue. There is no published method for the synthesis of L-[(18)F]FTRP. We have therefore developed a synthesis of 5-fluoro-[β-(11)C]-L-tryptophan ([(11)C]FTRP), based on the existing chemo-enzymatic method for [(11)C]HTP and evaluated the potential usefulness of radiolabeled FTRP as a substitute for [(11)C]HTP. The in vitro and in vivo behavior of [(11)C]FTRP, including the dependence of key enzymes in the serotonergic metabolic pathway, was investigated in NET cell lines, NET xenograft carrying immunodeficient mice, normal rats and in non-human primate. [(11)C]HTP was used for direct comparison. Uptake of [(11)C]FTRP in NET cell lines in vitro was mediated by enzymes involved in serotonin synthesis and metabolism, similar to [(11)C]HTP. In vivo biodistribution, either in rodent or non-human primate, was not affected by selectively inhibiting enzymatic steps in the serotonergic metabolic pathway. [(11)C]FTRP has in vitro biological function similar to that of [(11)C]HTP. However, this function is not retained in vivo as shown by biodistribution and PET/CT studies. Radiolabeled FTRP is thus not likely to provide an advantage over [(11)C]HTP in PET imaging in oncology, neurology or diabetes.