The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA's F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600  ms - 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes - B1, provided by the Japanese space agency, JAXA, and B2 - that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission's science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.

Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector

In this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285 m long, high-finesse, near-detuned optical resonator. With about 8.5 dB of generated squeezing, up to 5.6 dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2 dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6 Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5 dB and 2 dB, respectively.

Stuck in a Rut of Thought-That Is Just a Barrier: Dysfunctional Metacognitive Beliefs, Limitation on Individual Freedom and Well-Being of Adolescents during COVID-19 Lockdown

BACKGROUND

The aim of the cross-sectional study was to conduct an exploratory analysis of identifying factors related to mood, metacognitive beliefs, and limitation on individual freedom associated with lockdown restrictions during COVID-19, and to determine whether they may be relevant to the deteriorating well-being of adolescents.

METHODS

A total of 387 adolescents (M = 15.37; SD = 1.62): 85 with depression (DG) and 302 without any psychiatric diagnosis group (WPDG) were examined using the health survey and the CDI-2 questionnaire to assess the symptoms and severity of depression and MCQ-A to measure the intensity of dysfunctional metacognitive beliefs.

RESULTS

The feeling of restriction of freedom had an influence on worsened well-being in the whole group of responders OR = 4.15; p < 0.001 but was more in the DG than the WPDG (OR = 20.00; p < 0.001 vs. OR = 4.77; p < 0.001). Positive metacognitive beliefs were related to well-being (DG), but no effect was observed in the WPDG (OR = 0.88; p < 0.05 vs. OR = 1.05; p = 0.136). The lower age of the WPDG negatively impacted well-being (OR = 1.20; p < 0.05).

CONCLUSIONS

Dysfunctional metacognitive beliefs and the feeling of restriction of freedom are important in the deterioration of adolescents' well-being, but these factors have a stronger impact on well-being in the DG.

Search for Subsolar-Mass Binaries in the First Half of Advanced LIGO's and Advanced Virgo's Third Observing Run

We report on a search for compact binary coalescences where at least one binary component has a mass between 0.2  M_{⊙} and 1.0  M_{⊙} in Advanced LIGO and Advanced Virgo data collected between 1 April 2019 1500 UTC and 1 October 2019 1500 UTC. We extend our previous analyses in two main ways: we include data from the Virgo detector and we allow for more unequal mass systems, with mass ratio q≥0.1. We do not report any gravitational-wave candidates. The most significant trigger has a false alarm rate of 0.14  yr^{-1}. This implies an upper limit on the merger rate of subsolar binaries in the range [220-24200]  Gpc^{-3} yr^{-1}, depending on the chirp mass of the binary. We use this upper limit to derive astrophysical constraints on two phenomenological models that could produce subsolar-mass compact objects. One is an isotropic distribution of equal-mass primordial black holes. Using this model, we find that the fraction of dark matter in primordial black holes in the mass range 0.2  M_{⊙}<m_{PBH}<1.0  M_{⊙} is f_{PBH}≡Ω_{PBH}/Ω_{DM}≲6%. This improves existing constraints on primordial black hole abundance by a factor of ∼3. The other is a dissipative dark matter model, in which fermionic dark matter can collapse and form black holes. The upper limit on the fraction of dark matter black holes depends on the minimum mass of the black holes that can be formed: the most constraining result is obtained at M_{min}=1  M_{⊙}, where f_{DBH}≡Ω_{DBH}/Ω_{DM}≲0.003%. These are the first constraints placed on dissipative dark models by subsolar-mass analyses.

Sleeping Disorders in Healthy Individuals with Different Dietary Patterns and BMI, Questionnaire Assessment

The COVID-19 pandemic and abiding restrictions have affected every life domain. Sleep disturbances are a major health issue that is linked with a higher prevalence of metabolic syndrome, obesity, and psychological burdens. Research of sleeping disorders among vegetarian and non-vegetarian subpopulations is limited. The aim of the study was to assess the prevalence of sleeping disorders during the COVID-19 pandemic among people with different dietary patterns. Using a web-based cross-sectional survey, data were collected from 1987 people. A total of 1956 respondents met all study conditions. The questionnaire consisted of sociodemographic information, assessment of dietary habits, and assessment of the prevalence of insomnia and sleepiness, based on the Athens Insomnia Scale (AIS) and Epworth Sleepiness Scale (ESS). A total of 36.04% (n = 705) respondents declared that they noticed a change in the quality of their sleep during the last year. According to AIS and ESS, non-vegetarians suffered from insomnia or sleepiness more often than vegetarians. Insomnia and sleepiness were also more prevalent among those respondents who declared consumption of fruit and vegetables less often than once a day compared with those who consumed fruit and vegetables daily. Respondents with BMI within the recommended limit (18.5–24.99) suffered from insomnia less often when compared with underweight (BMI < 18.5) or obese (BMI ≥ 25) respondents. Those results may be useful for public health workers and medical professionals in terms of establishing new instruments that help treat sleeping disorders.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Severe course of neuromyelitis optica in a female patient with chronic C hepatitis

Neuromyelitis optica (NMO) is a rare, disabling, recurring inflammatory demyelinating disease affecting the spinal cord and optic nerves with predominance in women. We present the case of a female patient with chronic C hepatitis, who, despite treatment, developed severe symptoms of NMO during pregnancy and postpartum.

Symptoms of degeneration of the pyramidal tracts in conventional magnetic resonance imaging and diffusion tensor imaging in a young woman with primary lateral sclerosis

Primary lateral sclerosis (PLS) is one of the forms of motor neuron disease (MND), affecting only upper motor neurons. The diagnosis of PLS should be made on different diagnostic criteria, for example, Pringle or Gordon, but it is usually a diagnosis of exclusion. There are no characteristic findings in standard laboratory and electrophysiological assessment. We present details of a 31-year-old woman who had suffered from progressive paraparesis with right-side predominance. Conventional MRI of brain and spinal cord and diffusion tensor imaging (DTI) studies showed Hyperintense lesions in the upper part of the cervical spinal cord at the level C1 in lateral funicules, in the medulla oblongata at the pyramidal decussation and in the midbrain. Brain DTI revealed changes along the corticospinal tracts on fractional anisotropy (FA) maps. MRI of the thoracic spinal cord showed in T2-weighted images hyperintensive regions in the course of the lateral corticospinal tracts. This aided in PLS recognition.

Value of perfusion-weighted MR imaging in the assessment of early cerebral alterations in neurologically asymptomatic HIV-1-positive and HCV-positive patients

Background and Purpose

Asymptomatic central nervous system (CNS) involvement occurs in the early stage of the human immunodeficiency virus (HIV) infection. It has been documented that the hepatitis C virus (HCV) can replicate in the CNS. The aim of the study was to evaluate early disturbances in cerebral microcirculation using magnetic resonance (MR) perfusion-weighted imaging (PWI) in asymptomatic HIV-1-positive and HCV-positive patients, as well as to assess the correlation between PWI measurements and the clinical data.

Materials and Methods

Fifty-six patients: 17 HIV-1-positive non-treated, 18 HIV-1-positive treated with combination antiretroviral therapy (cART), 7 HIV-1/HCV-positive non-treated, 14 HCV-positive before antiviral therapy and 18 control subjects were enrolled in the study. PWI was performed with a 1.5T MR unit using dynamic susceptibility contrast (DSC) method. Cerebral blood volume (CBV) measurements relative to cerebellum (rCBV) were evaluated in the posterior cingulated region (PCG), basal ganglia (BG), temporoparietal (TPC) and frontal cortices (FC), as well as in white matter of frontoparietal areas. Correlations of rCBV values with immunologic data and liver histology activity index (HAI) were analyzed.

Results

Significantly lower rCBV values were found in the right TPC and left FC as well as in PCG in HIV-1-positive naïve (p = 0.009; p = 0.020; p = 0.012), HIV-1 cART treated (p = 0.007; p = 0.009; p = 0.033), HIV-1/HCV-positive (p = 0.007; p = 0.027; p = 0.045) and HCV-positive patients (p = 0.010; p = 0.005; p = 0.045) compared to controls. HIV-1-positive cART treated and HIV-1/HCV-positive patients demonstrated lower rCBV values in the right FC (p = 0.009; p = 0.032, respectively) and the left TPC (p = 0.036; p = 0.005, respectively), while HCV-positive subjects revealed lower rCBV values in the left TPC region (p = 0.003). We found significantly elevated rCBV values in BG in HCV-positive patients (p = 0.0002; p<0.0001) compared to controls as well as to all HIV-1-positive subjects. There were no significant correlations of rCBV values and CD4 T cell count or HAI score.

Conclusions

PWI examination enables the assessment of HIV-related as well as HCV-related early cerebral dysfunction in asymptomatic subjects. HCV-infected patients seem to reveal the most pronounced perfusion changes.

In vivo evaluation of brain damage in the course of systemic lupus erythematosus using magnetic resonance spectroscopy, perfusion-weighted and diffusion-tensor imaging

Twenty-two neuropsychiatric (NPSLE) and 13 systemic lupus erythematosus (SLE) patients with a normal appearing brain on plain magnetic resonance (MR) as well as 20 age-matched healthy controls underwent MR spectroscopy (MRS), perfusion-weighted (PWI) and diffusion-tensor imaging (DTI). In MRS NAA/Cr, Cho/Cr and mI/Cr ratios were calculated from the posterior cingulate cortex and left parietal white matter. In PWI, values of cerebral blood volume (CBV) were assessed from 14 regions, including gray and white matter. In DTI fractional anisotropy (FA) values were obtained from 14 white matter tracts including projection, commissural and association fibers. All MR measurements were correlated with clinical data. SLE and NPSLE patients showed significantly (p < 0.05) lower NAA/Cr ratios within both evaluated regions and FA values within the cingulum, as well as a tendency to cortical hypoperfusion. Compared to SLE, NPSLE subjects revealed lower FA values within a wide range of association fibers and corpus callosum. Advanced MR techniques are capable of in vivo detection of complex microstructural brain damage in SLE and NPSLE subjects regarding neuronal loss, mild hypoperfusion and white matter disintegrity. MRS and DTI seem to show the highest usefulness in depicting early changes in normal appearing gray and white matter in SLE patients.

Evaluation of early cerebral metabolic, perfusion and microstructural changes in HCV-positive patients: a pilot study

BACKGROUND & AIMS

The aim of the study was to evaluate early metabolic perfusion, and microstructural cerebral changes in patients with the hepatitis C virus (HCV) infection and normal appearing brain on plain MR using advanced MR techniques, as well as to assess correlations of MR measurements with the liver histology activity index (HAI).

METHODS

Fifteen HCV-positive patients and 18 control subjects underwent single voxel MR spectroscopy (MRS), perfusion weighted imaging (PWI), and diffusion tensor imaging (DTI), using a 1.5T MR unit. MRS metabolite ratios (NAA/Cr, Cho/Cr, mI/Cr) were calculated. PWI values of relative cerebral blood volume (rCBV) were assessed from 8 areas including several cortical locations, basal ganglia, and fronto-parietal white matter. DTI fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were obtained from 14 white matter tracts.

RESULTS

Compared to controls, HCV-positive patients showed significantly (p < 0.05) lower NAA/Cr ratios within frontal and parietal white matters, lower rCBV values within frontal and temporo-parietal cortices, decreased FA values, as well as increased ADC values in several white matter tracts. We also found elevated rCBV values in basal ganglia regions. The increase in mI/Cr and Cho/Cr ratio was correlated with a higher HAI score.

CONCLUSIONS

The results of advanced MR techniques indicate neurotoxicity of HCV reflected by neuronal impairment within white matter, cortical hypoperfusion, and disintegrity within several white matter tracts. Hyperperfusion in basal ganglia may be an indicator of brain inflammation in HCV patients. Our findings may suggest a biologic link between HCV-related liver disease and cerebral dysfunction.

Quantitative MR evaluation of atrophy, as well as perfusion and diffusion alterations within hippocampi in patients with Alzheimer's disease and mild cognitive impairment

Background

The aim of this study was to evaluate atrophy rates, perfusion, and diffusion disturbances within the hippocampus, which is the site of characteristic changes in Alzheimer’s disease (AD) and mild cognitive impairment (MCI).

Material/Methods

Thirty patients with AD (mean age 71.2 yrs) – 34 with MCI (mean age 67.7 yrs) and 20 healthy controls (mean age 68.1 yrs) – underwent structural MR examination followed by perfusion and diffusion-weighted imaging on a 1.5 T scanner. Visual rating of hippocampal atrophy, planimetric measurements of hippocampal formation (HF) and perihippocampal fluid spaces (PFSs), and values of relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) were assessed. The results were correlated with the MMSE scores.

Results

In AD we found decreased size of HF and increased diameters of PFSs and ADC values, compared to MCI and control group. Compared to normal controls, the MCI group showed decreased HF size and increased diameters of only medial PFS. There were no differences in rCBV values among all the subject groups. Planimetric measurements of hippocampal atrophy showed the highest accuracy in diagnosing AD and MCI. In all patients, the increased rates of hippocampal atrophy correlated with the increased ADC values. In MCI, MMSE scores correlated with the HF size and ADC values.

Conclusions

In AD and MCI, hippocampal atrophy is associated with decreased tissue integrity without coexisting perfusion disturbances. Of all evaluated hippocampal measurements, atrophy rates seem to be the most useful parameters in detecting changes among AD, MCI, and control subjects.

Evaluation of metabolic changes within the normal appearing gray and white matters in neurologically asymptomatic HIV-1-positive and HCV-positive patients: magnetic resonance spectroscopy and immunologic correlation

OBJECTIVE

The aim of the study was to evaluate early metabolic changes using proton MR spectroscopy (MRS) in asymptomatic HIV-1-positive and HCV-positive patients without abnormalities in the structural MR examination.

METHODS

Sixty-five asymptomatic patients: 21 HIV-1-positive naive, 20 HIV-1-positive with combination antiretroviral therapy (cART), 9 HIV-1/HCV-positive naive, 15 HCV-positive naive and 18 normal subjects were enrolled in the study. The MRS examinations were performed with a 1.5T MR scanner. Voxels were located in the following regions: posterior cingulate gyrus (PCG), anterior cingulate gyrus (ACG), parietal white matter (PWM), left basal ganglia (BG) and frontal white matter (FWM). The NAA/Cr, Cho/Cr, mI/Cr ratios and correlations of MRS measurements with the immunologic data were analyzed.

RESULTS

There was a significant decrease (p<0.05) of the NAA/Cr ratios in PCG, ACG and PWM regions in HIV-1-positive cART treated patients compared to the normal subjects. The significantly decreased NAA/Cr ratios in PWM and FWM were observed in HCV infected patients. The subjects with HIV-1/HCV co-infection revealed significantly lower NAA/Cr ratios in the ACG area. Other metabolite ratios in all analyzed regions, as well as the NAA/Cr ratios in BG showed no significant differences. The decrease of CD4n T cell count was associated with the decease of the NAA/Cr ratio in the PCG area and the increase of Cho/Cr ratio in the FWM region.

CONCLUSIONS

The metabolic changes - reduction of NAA/Cr ratios are most pronounced in HIV-1-positive patients using cART. The low CD4n T cell count is a risk factor for neurocognitive impairment in HIV-1-positive patients.

Application of diffusion tensor imaging (DTI) in pathological changes of the spinal cord

We review the current knowledge concerning clinical applications of the advanced technique of magnetic resonance imaging (MRI): diffusion tensor imaging (DTI) of the spinal cord. Due to technical difficulties, DTI has rarely been used in spinal cord diseases. However, in our opinion it is potentially a very useful method in diagnosis of the different pathological processes of the spinal cord and spinal canal. We discuss the physical principles and technical aspects of DTI, as well as current and future applications. DTI seems to be a very promising method for assessment of spinal cord trauma, spinal canal tumors, degenerative myelopathy, as well as demyelinating and infectious diseases of the spinal cord. DTI enables both qualitative and quantitative (by measuring of the fractional anisotropy and apparent diffusion coefficient parameters) assessment of the spinal cord. The particular applications are illustrated by the examples provided in this article.

Quantitative Evaluation of Changes in the Selected White Matter Tracts Using Diffusion Tensor Imaging in Patients with Alzheimer's Disease and Mild Cognitive Impairment

This study evaluated the damage to the extensive range of white matter tracts in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). Thirty-four patients with AD (mean age 71.5 yrs, MMSE 17.6), 23 patients with MCI (mean age 66 yrs, MMSE 27.4) and 15 normal controls (mean age 69 yrs, MMSE 29.8) were enrolled. Diffusion tensor imaging (DTI) was performed in 25 directions on 1.5 T MR scanner. Fractional anisotropy (FA) values were obtained with a small ROI method in several association tracts including posterior cingulum fibers, in commissural tracts (genu and splenium of corpus callosum) and projection tracts (middle cerebellar peduncles and posterior limbs of internal capsules). In MCI significant reductions of FA were found in the inferior longitudinal fascicles, left superior longitudinal fascicle and posterior cingulum fibers compared to normal controls. In AD significantly decreased FA values were detected in the same fascicles as in MCI and additionally in inferior fronto-occipital tracts and commissural tracts. In both AD and MCI the most severe changes were found within posterior cingulum fibers. No abnormalities were detected in projection tracts in both groups. Accuracy of DTI in detecting AD and MCI reached 0.95 and 0.79, respectively. FA measurements strongly correlated with neuropsychological tests. DTI is capable of depicting microstructural changes within white matter fiber tracts in dementia and may aid the differential diagnosis of AD and MCI.

Parry-Romberg syndrome: clinical, electrophysiological and neuroimaging correlations

Parry–Romberg syndrome (PRS) is a rare disorder, described in the nineteenth century by Caleb Parry and Moritz Romberg, characterized by acquired and slowly progressive atrophy of one side of the face. The pathogenesis of PRS is still unclear. Immune-mediated processes are thought to be a basic factor in PRS etiology, but autonomic nervous system might also be impaired. A case of PRS in a 26-year-old woman with coexisting disturbances in the lower left limb is presented. The multimodal electrophysiological studies were done, including electroencephalography, visual, brain auditory, somatosensory and trigeminal somatosensory evoked potentials, blink reflex, standard neurographic and electromyographic examinations, quantitative sensory tests and autonomic tests. Neuroimaging studies consisted of brain MR, single voxel proton MR spectroscopy, diffusion tensor imaging with fiber tractography. Based on multimodal electrophysiological and neuroimaging studies, it was concluded that the impairment in PRS is multisystemic, i.e., motor, sensory, and autonomic. A cortical origin of the symptoms is possible.

Management of bladder neck leiomyoma during pregnancy

A 29-year-old primigravida was admitted to the urology ward with acute urinary retention. The patient underwent cystoscopy, MRI (magnetic resonance imaging), and tissue biopsy, which consequently led to the diagnosis of bladder neck leiomyoma that obstructed urine outflow. Subsequent to a cesarean section, a successful transurethral resection was performed. Here the diagnostic complexity in the pregnant patient, clinical course, and outcome are described. One year after successful treatment both mother and daughter are in good condition.

Analysis of metabolic changes of brain in HIV-1 seropositive patients with proton magnetic resonance spectroscopy

BACKGROUND

Asymptomatic central nervous system involvement may occur in the early stages of the HIV infection. The aim of the study was to evaluate early brain metabolic changes by means of proton MR spectroscopy (H1MRS) in the HIV-1 seropositive patients without neurological deficits or significant abnormalities in the plain MR study.

MATERIAL/METHODS

The H1MRS examinations were performed with the use of a MR GE Signa 1,5T system. There were 39 subjects examined, aged 21 to 57 years (mean age 35 years) were examined, including 25 patients infected with HIV-1 and 14 healthy volunteers who constituted a control group. The examinations were performed using the Single Voxel Spectroscopy technique with the PRESS sequence, with following parameters: TR=1500 ms, TE=35 ms, number of acquisitions =128, time of acquisition =3 min. 43 sec. Voxels of 8 cm(3) (20×20×20 mm) in size were located in the following 5 regions: posterior cingulate gyrus, grey matter of the frontal area, left basal ganglia, white matter of the left parietal area and white matter of the frontal area. The NAA/Cr, Cho/Cr, mI/Cr ratios in the defined regions of interest were statistically analyzed.

RESULTS

There was a statistically significant decrease (p<0.05) in the NAA/Cr ratios in the posterior cingulate area and white matter of the left parietal area in HIV-1 seropositive patients, as compared to the control group. Other metabolite ratios in all the above mentioned locations showed no statistically significant differences, as was also the case for NAA/Cr ratios in grey matter of the frontal area, left basal ganglia and white matter of the frontal area.

CONCLUSIONS

The reduction of NAA/Cr values revealed in H1MRS studies suggests loss of neurons/neuronal activity in the posterior cingulate area and white matter of the left parietal area, in patients with HIV-1 at the stage before clinical manifestations of retroviral infection and structural changes in the plain MR study. This may reflect a direct neurotropic activity of HIV.

Assessment of degradation of the selected projectile, commissural and association brain fibers in patients with Alzheimer's disease on diffusion tensor MR imaging

BACKGROUND

Pathological examinations and the increasingly popular diffusion tensor imaging (DTI) show that in Alzheimer's disease (AD), the pathology involves not only the cortical and hippocampal structures, but also the white matter of the brain. DTI is a well recognized technique for evaluation of the integrity of white matter fibers. The aim of this study was to assess with the use of DTI some selected brain tracts in patients with AD, as well as to analyze the severity and distribution of the identified changes.

MATERIAL/METHODS

Thirty-five patients with AD (mean age of 71.6 years, MMSE 17.6), and a control group of 15 healthy volunteers (mean age of 69.1 years, MMSE 29.8) were enrolled in the study. All patients were subjected to a thorough psychiatric examination and psychological tests. DTI examinations (TE 8500, TR 100) were performed using a 1.5T MR scanner. Fractional anisotropy (FA) measurements in the selected areas of interest (ROI) of the white matter fibers were performed under the control of color FA maps. The following fibers were evaluated - the middle cerebellar peduncles (MCP), the inferior longitudinal fasciculi (ILF), inferior frontooccipital fasciculi (IFO), genu (GCC) and splenium of the corpus callosum (SCC), posterior limbs of internal capsules (PLIC), superior longitudinal fasciculi (SLF) and posterior cingula (CG).

RESULTS

There was a statistically significant decrease in FA in patients with AD, comparing to the control group. It was particularly strongly expressed in both CG (P<0.0001), followed by both ILF, right IFO, and left SLF. Less pronounced changes were found in GCC, SCC, and left IFO. In both PLICs and MCPs and in the right SLF, there was no significant change of FA.

CONCLUSIONS

In Alzheimer's disease, there is a significant decrease in FA, which suggests degradation of the majority of the assessed white matter tracts. Distribution of these changes is not uniform. They involve the selected association fibers mainly and, to a lesser extent, the commissural fibers, while they are not found in the pyramidal tracts or medial cerebellar peduncles. Definitely, the most pronounced changes were found in the posterior cingula, the assessment of which (in the process of AD diagnostics) seems to be particularly promising.

Herniation to foramen magnum in the course of cerebellitis in a 4-year-old boy, as shown by CT and MRI - case report

BACKGROUND

Acute cerebellitis is an uncommon but dangerous complication of infectious diseases. Besides neurological examination, neuroimaging (especially MR imaging) is very useful for diagnosing cerebellitis.

CASE REPORT

A 4-year-old boy was admitted to the hospital with a 1-week history of fever, vomiting and headache. His past medical history was unremarkable. The physical examination revealed disturbance of consciousness and truncal ataxia. He underwent urgent CT and MRI examinations which demonstrated isolated swelling of the cerebellar hemispheres and the vermis, with increased signal intensity in T2-weighted, FLAIR, and DWI sequence and a significant mass effect associated with tonsillar herniation. An emergent life-saving suboccipital craniectomy was performed with removal of the C1 vertebral arch. There was a gradual clinical improvement, and a follow-up brain MRI revealed disappearance of cerebellar swelling and of mass effect.

CONCLUSIONS

Magnetic resonance (MR), including diffusion-weighted imaging (DWI) sequence, plays an important role in the diagnostic work-up of cerebellitis in children. This imaging method is very useful for detecting cerebellitis, evaluating its severity and monitoring the disease.

Analysis of the brain proton magnetic resonance spectroscopy - differences between normal grey and white matter

BACKGROUND

The proton magnetic resonance spectroscopy (HMRS) is a non-invasive diagnostic method that allows for an assessment of the metabolite concentration in tissues. The sources of the strongest resonance signals within the brain are N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myoinositol (mI) and water. The aim of our study was to analyse the ratios of metabolite signals within the brain in HMRS in the healthy population, to define the differences between the grey and white matter spectra.

MATERIAL/METHODS

We studied prospectively 90 subjects aged from 8 to 80 years (mean 43.3 years, SD=17.9), without neurological symptoms or abnormalities in magnetic resonance imaging. In all patients, brain HMRS with Signa HDx 1.5 T MR unit (GE Healthcare) was performed with PRESS sequence, using a single voxel method, at TE of 35 ms and TR of 1500 ms. Spectroscopic evaluation involved voxels placed in the white matter of parietal lobe (PWM) and the grey matter of posterior cingulate gyrus (PGM). On the basis of the intensity of NAA, Cr, Cho, mI and water signals, the proportions of these signals were calculated, as well as the ratio of the analyzed metabolite signal to the sum of signals of NAA, Cho, Cr and mI (%Met) in the PGM and PWM voxels. We compared the proportions in the same patients in PGM and PWM voxels.

RESULTS

There has been a statistically significant difference between the proportions of a majority of the metabolite ratios evaluated in PGM and PWM, indicating the higher concentration of NAA, Cr and mI in grey matter, and higher concentration of Cho in white matter.

CONCLUSIONS

HMRS spectra of the brain grey and white matter differ significantly. The concentrations of NAA, Cr and mI are higher in grey matter, while of choline - in the white matter.

Parallel-opposed fields versus four fields, and two- versus three-dimensional radiotherapy planning in thin patients with gynecological malignancies

Conformal radiotherapy constitutes the standard management of pelvic malignancies, yet its role in thin patients remains debatable. This study compares dose distribution for 2D and 3D treatment techniques for cobalt (60Co) and high energy photons from linear accelerator (LA) in cervical and endometrial cancer patients with antero-posterior diameter of less than 20 cm. CT-based 3D treatment planning and 2D simulation were performed in 10 patients. Particular techniques were compared in terms of treatment portal areas, coverage of planning target volume (PTV) and sparing of critical organs. For 60Co beams, PTV was not covered adequately with 2D fields in nine patients and with conformal fields in seven. For LA, PTV was not adequately covered with 2D two-field and 2D four-field ("box") technique in three and one patients, respectively. Mean bladder dose was comparable for all plans. Both 2D "box" and 3D "box" technique spared additional portion of the rectum volume included in 95% isodose, compared to two-field plan. 3D treatment planning better protected the small intestine. Use of multiple field techniques and 3D planning allows for some improvement of PTV coverage and normal tissue sparing, although the magnitude of this benefit must be weighted against savings of time and labour related to use of simpler treatment techniques.

Rectal doses in intracavitary brachytherapy of gynecological malignancies: comparison of two dosimetric methods

PURPOSE

To compare calculated rectal doses obtained by two dosimetric methods in intracavitary brachytherapy of gynecological malignancies.

MATERIALS AND METHODS

This analysis included 124 intracavitary applications performed in 102 patients with cervical or endometrial cancer. The pelvic dose distribution based on orthogonal intracavitary placement films was calculated with the computer planning system. In each application the rectal dose was defined in the specific rectal point determined by both the use of a wire marker inserted into the rectum (R1) and by packing the vagina with radio-opaque gauze - the method recommended by the ICRU Report 38 (R2). The comparison included R1 and R2 doses as well as the respective radiobiological equivalent doses determined by the linear-quadratic model (r1 and r2).

RESULTS

In 83% of applications the absolute value of R1 was lower than R2. The mean difference between R1 and R2 was 3.7 Gy (95% CI 3.03-4.41 Gy) and between r1 and r2 7.2 Gy (95% CI 5.77-8.56 Gy). These differences were significant (P<0.001 for both comparisons). The difference between the doses was not influenced by the type of applicator and remained significant even when a systemic+/-10% error of method was assumed.

CONCLUSION

The rectal point dose determined with the use of rectal wire marker may be underestimated, therefore this method should be discouraged in gynecological brachytherapy.

[Prosthesis to reconstruction of transmissive system in the middle ear]

Authors have described prothesis to reconstruction of transmissive system in middle ear, which has received using patent no PL 54142 Y1.

[Plastic tracheostomy tube of Luer's type]

The authors describe a plastic tracheostomy tube which has been accepted as the registered model No: PL 54620 Y1. The presented tube is applied in patients in I ENT Department of the Silesian Medical Academy in Katowice. The authors presented advantages of plastic tracheostomy tube.

Fluorometric studies on the blood-retinal barrier in experimental animals

Fluorophotometry was used to evaluate the blood-ocular barrier in rats following streptozocin-induced diabetes, experimental systemic hypertension, sodium iodate treatment, diet-induced galactosemia, and aldose reductase inhibitors. After administration of intravenous (IV) fluorescein sodium, diabetes, hypertension, or sodium iodate treatment resulted in an increased vitreous accumulation of IV fluorescein. Accumulation of dextran-labeled fluorescein (3,000 and 19,000 molecular weight [mol wt]) was not increased in diabetic or sodium iodate-treated animals. However, 3,000-mol wt dextran-labeled dye accumulated in the vitreous of hypertensive rats. The disappearance of fluorescein injected into the vitreous was significantly delayed in diabetic and sodium iodate-treated rats, whereas this rate was normal in hypertension animals. Galactosemia did not alter vitreous fluorophotometric measurements. Pretreatment for systemic effects with aldose reductase inhibitors did not correct the vitreous fluorophotometric measurements of diabetic rats.