Temporal Trends in the Epidemiology of HIV in Turkey.

OBJECTIVE: The aim of this study was to analyze the temporal trends of HIV epidemiology in Turkey from 2011 to 2016. METHODS: Thirty-four teams from 28 centers at 17 different cities participated in this retrospective study. Participating centers were asked to complete a structured form containing questions about epidemiologic, demographic and clinical characteristics of patients presented with new HIV diagnosis between 2011 and 2016. Demographic data from all centers (complete or partial) were included in the analyses. For the cascade of care analysis, 15 centers that provided full data from 2011 to 2016 were included. Overall and annual distributions of the data were calculated as percentages and the Chi square test was used to determine temporal changes. RESULTS: A total of 2,953 patients between 2011 and 2016 were included. Overall male to female ratio was 5:1 with a significant increase in the number of male cases from 2011 to 2016 (p<0.001). The highest prevalence was among those aged 25-34 years followed by the 35-44 age bracket. The most common reason for HIV testing was illness (35%). While the frequency of sex among men who have sex with men increased from 16% to 30.6% (p<0.001) over the study period, heterosexual intercourse (53%) was found to be the most common transmission route. Overall, 29% of the cases presented with a CD4 count of >500 cells/mm3 while 46.7% presented with a CD4 T cell count of <350 cells/mm3. Among newly diagnosed cases, 79% were retained in care, and all such cases initiated ART with 73% achieving viral suppression after six months of antiretroviral therapy. CONCLUSION: The epidemiologic profile of HIV infected individuals is changing rapidly in Turkey with an increasing trend in the number of newly diagnosed people disclosing themselves as MSM. New diagnoses were mostly at a young age. The late diagnosis was found to be a challenging issue. Despite the unavailability of data for the first 90, Turkey is close to the last two steps of 90-90-90 targets.

Diagnosis of chronic brucellar meningitis and meningoencephalitis: the results of the Istanbul-2 study.

No detailed data exist in the literature on the accurate diagnosis of chronic brucellar meningitis or meningoencephalitis. A multicentre retrospective chart review was performed at 19 health centres to determine sensitivities of the diagnostic tests. This study included 177 patients. The mean values of CSF biochemical test results were as follows: CSF protein, 330.64 ± 493.28 mg/dL; CSF/ blood-glucose ratio, 0.35 ± 0.16; CSF sodium, 140.61 ± 8.14 mMt; CSF leucocyte count, 215.99 ± 306.87. The sensitivities of the tests were as follows: serum standard tube agglutination (STA), 94%; cerebrospinal fluid (CSF) STA, 78%; serum Rose Bengal test (RBT), 96%; CSF RBT, 71%; automated blood culture, 37%; automated CSF culture, 25%; conventional CSF culture, 9%. The clinician should use every possible means to diagnose chronic neurobrucellosis. The high seropositivitiy in brucellar blood tests must facilitate the use of blood serology. Although STA should be preferred over RBT in CSF in probable neurobrucellosis other than the acute form of the disease, RBT is not as weak as expected. Moreover, automated culture systems should be applied when CSF culture is needed.

Outbreak of adenovirus serotype 8 conjunctivitis in preterm infants in a neonatal intensive care unit.

BACKGROUND: Adenovirus keratoconjunctivitis outbreaks have rarely been reported in preterm infants. An outbreak of adenovirus conjunctivitis occurred between 15 January and 25 February at a neonatal intensive care unit of a university hospital in Turkey. AIM: To describe the evolution, investigation and management of the outbreak. METHODS: Adenovirus type 8 was identified in 14 samples by polymerase chain reaction analysis. A case-control study was performed to determine the risk factors. FINDINGS: Fifteen preterm neonates, five healthcare workers (HCWs) and four parents suffered from conjunctivitis signs such as lacrimation, swelling and redness of the eye. A retinopathy of prematurity (ROP) examination was found to be the most important risk factor for adenovirus conjunctivitis (odds ratio: 17.5; 95% confidence interval: 1.9-163.0; P=0.012). The eyelid speculum (blepharostat) used during the ROP examination was not sterilized between each patient and was found to be the cause of contamination. CONCLUSION: The outbreak was controlled by measures such as barrier precautions, hand hygiene, sterilization of the blepharostat, suspending patient transfer to other units, and excluding infected HCWs for at least 15 days.

FMRI of working memory in patients with mild cognitive impairment and probable Alzheimer's disease.

The goals of this study were to evaluate brain activation in patients with probable Alzheimer's disease (AD), mild cognitive impairment (MCI), and controls while performing a working memory (WM) task. Eleven AD patients, ten MCI subjects, and nine controls underwent functional magnetic resonance imaging (fMRI) while performing a visual WM task. Statistical parametric maps of brain activation were obtained in each group, and group activation difference maps were generated. Ability to perform the task did not differ among the groups. Activation was observed in the parahippocampal region, superior-middle-inferior frontal gyri, parietal region, anterior-posterior cingulate, fusiform gyrus, and basal ganglia. MCI and AD groups showed more activation than the controls in the right superior frontal gyrus, bilateral middle temporal, middle frontal, anterior cingulate, and fusiform gyri. Activation in the right parahippocampal gyrus, left inferior frontal gyrus, bilateral cingulate and lingual gyri, right lentiform nucleus, right fusiform gyrus, and left supramarginal gyrus in the AD group was less than in the MCI group. The WM task evoked activation in widely distributed regions, consistent with previous fMRI studies. AD and MCI patients showed an increased extent of activation and recruitment of additional areas.

Brucellar breast abscess.

Brucellosis is an endemic disease seen in many countries. It may affect different organ systems. Brucellar breast abscess is a rare entity. We report the radiological findings of breast abscess due to brucella. A 63-year-old female was investigated with mammography, ultrasonography, magnetic resonance imaging (MRI), and magnetic resonance spectroscopy (MRS). A mass measuring 25 x 20 x 15 mm was detected in the left breast on mammography and ultrasonography. The mass was homogenously hyperintense on T1- and T2-weighted MRI images. On contrast-enhanced T1-weighted images, peripheral capsular enhancement was found. MR spectroscopic analysis of the mass revealed elevated lipid and acetate peaks. The diagnosis was provided by fine needle aspiration biopsy and specimen culture. The lesion had diminished in size after 12 months' treatment with combined tetracycline and rifampicine.

Spatio-temporal analysis of auditory cortex activation as detected with silent event related fMRI.

Functional magnetic resonance imaging (fMRI) allows neuroscientists to assess brain function by evaluating haemodynamic activity (blood flow) when a stimulus is present or absent. In clinical practice, the hearing levels of individuals are determined using an audiometer that allows presentation of a pure-tone of specific intensity and frequency. Functional images of the auditory nervous system have been obtained using stimuli such as pure-tone, speech, noise, etc. However, the observed activation evoked by the stimulus is confounded with the neuronal response evoked by scanner noise generated during imaging. Hence, researchers have been developing fMRI techniques to overcome the inadvertent effect of scanner noise on fMRI studies of the auditory cortex. Silent event related fMRI is a recently reported fMRI technique diminishing the confounding effects of background scanner noise. A drawback of sfMRI is that it requires long acquisition times (30-40 min) to achieve statistically significant activation. An additional complication associated with all fMRI data is that measurements obtained at consecutive times tend to exhibit substantial temporal correlation. Such correlation structure complicates the identification of brain locations (voxels) demonstrating statistically significant activation. We propose an approach for detecting activation with high statistical power and low false-positive rate. To accomplish these goals of high power and low type I error rate in sfMRI with shorter acquisition times, we describe a statistical model that accounts for the spatial and temporal correlation structure of the haemodynamic response. Temporal dependence within each voxel's measurements is modelled, and a regional measurement-error-free kriging predictor is used to combine information from neighbouring voxels when assessing voxel activation. Instead of simply applying a post hoc smoothing to thevoxelwise test statistics (e.g. t statistics), we attempt to make optimal use of information in the locality of each voxel when estimating the voxel's mean, variance, and temporal dependence parameters. The primary advantage to this spatial modelling approach is that the degree to which voxel parameters are smoothed is driven by the data. Thus, we are not subjectively smoothing noisy data, but objectively estimating the noise-free version of the spatial processes associated with the response. The resulting voxel activation maps exhibit substantially more spatial continuity than other currently used approaches, while exhibiting desirable inferential properties including a lower false-positive rate and high power for detection of activated regions. Minimal computational resources are necessary to carry out the approach, which yielded voxel activation maps for our experiment in only minutes.

Silent functional magnetic resonance imaging (FMRI) of tonotopicity and stimulus intensity coding in human primary auditory cortex.

OBJECTIVES: The aims of this study were to determine the feasibility of obtaining auditory cortex activation evoked by pure tones presented at threshold and suprathreshold hearing levels, to evaluate tonotopicity of the primary auditory cortex, and to determine the effect of stimulus intensity on auditory cortex activation using silent functional magnetic resonance imaging (fMRI). METHODS: Sixteen subjects with normal hearing underwent silent fMRI. An audiometer was used to deliver pure tones of 1000, 2000, and 4000 Hz to the left ear. Two levels of acoustic stimulation were used: 1). threshold, hearing level determined in the scanner room and 2). suprathreshold, 70 dB hearing loss (HL). Tonotopicity and stimulus intensity coding was assessed on the basis of the location, extent, and amount of the auditory cortex activation. RESULTS: The localization of activation moved to more medial and posterior regions of the primary auditory cortex as the frequency of the pure tone increased. Compared with a threshold stimulus, a suprathreshold stimulus evoked the same regions with increased spatial extent. The average increase in the right auditory cortex activation in response to suprathreshold stimulus was 57% at 1000, 51% at 2000, and 45% at 4000 Hz compared with that activated by the threshold stimulus. CONCLUSIONS: Silent fMRI can be used to evaluate auditory cortex activation using low-intensity stimuli. The level of stimulus intensity increases the amount of auditory cortex activation and influences the fMRI mapping of the tonotopic organization of the primary auditory cortex.

Functional magnetic resonance imaging of activation in subcortical auditory pathway.

OBJECTIVES: Functional magnetic resonance imaging (fMRI) has been used to investigate activation of the auditory cortex; however, assessment of activation in the subcortical auditory pathway has been challenging. The aim of this study was to examine neural correlates of cortical and subcortical auditory activation evoked by pure-tone stimulus using silent fMRI. STUDY DESIGN: Prospective analysis. METHODS: Seventeen normal-hearing volunteers (7 male, 10 female; age range, 14-37 yrs) underwent silent fMRI. An audiometer was used to deliver pure tones of 1000 Hz to the left ear. Pure tones were presented at hearing thresholds determined in the scanner. Brain regions showing increased activation during pure-tone stimulus presentation were mapped and auditory activations exceeding P <.001 were included in the analysis. RESULTS: Pure-tone stimuli evoked bilateral activation in cortical regions of the transverse and superior temporal gyri and the planum temporale. Activation in subcortical structures included the medial geniculate body, inferior colliculus, lateral lemniscus, superior olivary complex, and cochlear nucleus. CONCLUSIONS: Silent functional magnetic resonance imaging findings documented the feasibility of detecting activation elicited by pure tone along the cortical and subcortical auditory pathway. The use of this technique in the assessment of disorders with auditory dysfunction merits further investigation.

Evaluation of auditory cortex activation by using silent FMRI.

PURPOSE: To evaluate auditory cortex activation evoked by pure-tone stimulus using silent functional magnetic resonance imaging (FMRI). MATERIAL AND METHODS: Nine volunteers with normal hearing as determined with pure-tone audiometry were studied. Auditory cortex activation was evoked by pure-tone stimuli presented monaurally at 1,000, 2,000, and 4,000 Hz. Images of auditory cortex activation were obtained using silent and conventional FMRI techniques. Heschl's gyrus activation was evaluated by the number of voxels exceeding a predetermined significance level (P <.0001). RESULTS: In both techniques, all subjects showed activation in the Heschl's gyrus. Silent FMRI detected more activation in all studied frequencies compared with the conventional FMRI. The observed difference in the Heschl's gyrus activation between the techniques reached statistical significance for 1,000 Hz frequency (P <.05). CONCLUSIONS: The amount of Heschl's gyrus activation detected with silent FMRI is greater than that of conventional FMRI. Silent FMRI technique can be used to acquire functional images of the auditory cortex without the confounding effects of scanner noise.

Hypoxia imaging in brain tumors.

Assessment of the oxygenation status of brain tumors has been studied increasingly with imaging techniques in light of recent advances in oncology. Tumor oxygen tension is a critical factor influencing the effectiveness of radiation and chemotherapy and malignant progression. Hypoxic tumors are resistant to treatment, and prognostic value of tumor oxygen status is shown in head and neck tumors. Strategies increasing the tumor oxygenation are being investigated to overcome the compromising [figure: see text] effect of hypoxia on tumor treatment. Administration of nicotinamide and inhalation of various high oxygen concentrations have been implemented. Existing methods for assessment of tissue oxygen level are either invasive or insufficient. Accurate and noninvasive means to measure tumor oxygenation are needed for treatment planning, identification of patients who might benefit from oxygenation strategies, and assessing the efficacy of interventions aimed to increase the radiosensitivity of tumors. Of the various imaging techniques used to assess tissue oxygenation, MR spectroscopy and MR imaging are widely available, noninvasive, and clinically applicable techniques. Tumor hypoxia is related closely to insufficient blood flow through chaotic and partially nonfunctional tumor vasculature and the distance between the capillaries and the tumor cells. Information on characteristics of tumor vasculature such as blood volume, perfusion, and increased capillary permeability can be provided with MR imaging. MR imaging techniques can provide a measure of capillary permeability based on contrast enhancement and relative cerebral blood volume estimates using dynamic susceptibility MR imaging. Blood oxygen level dependent contrast MR imaging using gradient echo sequence is intrinsically sensitive to changes in blood oxygen level. Animal models using blood oxygen level-dependent contrast imaging reveal the different responses of normal and tumor vasculature under hyperoxia. Normobaric hyperoxia is used in MR studies as a method to produce MR contrast in tissues. Increased T2* signal intensity of brain tissue has been observed using blood oxygen level-dependent contrast MR imaging. Dynamic blood oxygen level-dependent contrast MR imaging during hyperoxia is suggested to image tumor oxygenation. Quantification of cerebral oxygen saturation using blood oxygen level-dependent MR imaging also has been reported. Quantification of cerebral blood oxygen saturation using MR imaging has promising clinical applications; however, technical difficulties have to be resolved. Blood oxygen level dependent MR imaging is an emerging technique to evaluate the cerebral blood oxygen saturation, and it has the potential and versatility to assess oxygenation status of brain tumors. Upon improvement and validation of current MR techniques, better diagnostic, prognostic, and treatment monitoring capabilities can be provided for patients with brain tumors.

Assessment of auditory cortex activation with functional magnetic resonance imaging.

OBJECTIVE: The goal was to assess auditory cortex activation evoked by pure-tone stimulus with functional MRI. METHODS: Five healthy children, aged 7 to 10 years, were studied. Hearing evaluation was performed by pure-tone audiometry in a sound-treated room and in the MRI scanner with the scanner noise in the background. Subjects were asked to listen to pure tones (500, 1000, 2000, and 4000 Hz) at thresholds determined in the MRI scanner. Functional image processing was performed with a cross-correlation technique with a correlation coefficient of 0.5 (P < 0.0001). Auditory cortex activation was assessed by observing activated pixels in functional images. RESULTS: Functional images of auditory cortex activation were obtained in 3 children. All children showed activation in Heschl's gyrus, middle temporal gyrus, superior temporal gyrus, and planum temporale. The number of activated pixels in auditory cortexes ranged from 4 to 33. CONCLUSIONS: Functional images of auditory cortex activation evoked by pure-tone stimuli are obtained in healthy children with the functional MRI technique.

Functional magnetic resonance imaging of auditory cortex in children.

OBJECTIVE: TO obtain images of auditory cortex activation in children by using functional magnetic resonance imaging (FMRI). METHODS: Seven healthy children (three girls and four boys), ages 6 to 10 years, were studied. Hearing evaluation was performed by puretone audiometry on the day of FMRI study. Brain imaging was performed on a commercial 1.5 T imager using a three-axis local gradient coil. During scanning the children were instructed to lie still and avoid any lip, eye, jaw, or other facial movements. Subjects were asked to listen to a standard text presented in on-off sequences. Functional images of the auditory cortex were acquired with FMRI technique. Functional imaging processing was done using cross-correlation techniques with a coefficient of 0.5 (P < .0001). RESULTS: Functional correlation images of the auditory cortex activation were obtained in six of seven children after image processing. All children showed activation in the superior temporal gyrus, Heschl's gyrus, planum temporale, frontal lobe, and parietal regions. There was no significant difference in the number and percentage of activated pixels on right and left auditory cortices. CONCLUSIONS: Functional images of auditory cortex activation were obtained in healthy children following binaural text presentation. Consistent activation was observed in primary and secondary auditory cortices with no hemispheric dominance. FMRI characteristics of the auditory cortex activation in healthy children should be established in order to study those with hearing impairment.

Functional MR of frontal lobe activation: comparison with Wada language results.

PURPOSE: Our purpose was to determine the utility of functional MR imaging in conjunction with a word-generation paradigm in the assessment of language lateralization. METHODS: Functional MR imaging and Wada testing for language lateralization was performed in patients with complex partial seizures during the performance of word-generation tasks. A language lateralization quotient was calculated from the number of activated pixels in the right and left hemispheres. A language laterality score was derived from the Wada results as the percentage of correct responses during right internal carotid artery injection minus the percentage of correct responses during left internal carotid injection. A correlation coefficient between the functional MR imaging results and the Wada language laterality scores was calculated. RESULTS: In 13 patients, hemispheric dominance based on Wada testing was confirmed by functional MR imaging during silent word generation. The Wada laterality scores varied from 100 to -100 and the functional MR imaging scores varied from 100 to -10. The language lateralization scores determined by functional MR imaging correlated significantly with the language lateralization scores derived from Wada testing. CONCLUSION: Functional MR imaging performed during word generation is an accurate method for lateralizing language function in patients with complex partial epilepsy.

Cortical activation response to acoustic echo planar scanner noise.

PURPOSE: Our goal was to determine the distribution of auditory and language cortex activation in response to acoustic echo planar scanner noise with functional MRI (fMRI). METHOD: Acoustic scanner noise and spoken text, reproduced on high output cassette tape, were separately delivered at equivalent intensities to six normal hearing adult volunteers through earphones during fMRI data acquisition. In nine other subjects, taped scanner noise was delivered in five successive iterations of the task to assess the consistency of cortical activation to the noise stimulus. Gyri of the auditory and language system were divided into 10 different subregions for analysis of cortical activation. The number of activated pixels and proportion of volunteers activating each cortical subregion were determined using a cross-correlation analysis. RESULTS: Cortical activation to taped acoustic scanner noise was present within the transverse temporal gyrus (primary auditory cortex) in all subjects, but activation was highly variable between subjects in auditory association and language relevant cortex. Auditory association cortex activation was seen in the planum polari, planum temporali, and middle temporal gyrus/superior temporal sulcus regions in one-half to two-thirds of the volunteers. There was no significant difference in the distribution of cortical activation within individual subjects across five successive iterations of the scanner noise task. Listening to spoken text consistently activated primary and association auditory cortex bilaterally as well as language relevant cortex in some cases. The mean number of activated pixels was significantly greater for text listening than acoustic scanner noise in auditory association and language relevant cortical subregions (p < 0.01), although the distribution of activity was similar between the two tasks. CONCLUSION: This preliminary investigation suggests that the complex sounds produced by the echo planar pulse sequence can activate relatively large regions of auditory and language cortex bilaterally, with the extent of activation outside the primary auditory cortex being variable between subjects. However, the distribution of activation within individual subjects was relatively constant across several iterations of the scanner noise stimulus.

Hemispheric language dominance studied with functional MR: preliminary study in healthy volunteers and patients with epilepsy.

PURPOSE: We used functional MR imaging to compare hemispheric language dominance in healthy volunteers and in patients with epilepsy. METHODS: We retrospectively reviewed the functional MR images of 23 healthy volunteers and 16 patients with epilepsy obtained by using an echo-planar technique designed for whole-brain imaging. The activation paradigm used was a silent word generation task. Hemispheric language dominance was assessed as the percentage of activated pixels in the left hemisphere minus the percentage of activated pixels in the right hemisphere x 100. RESULTS: We found no significant difference in language lateralization between right-handed male and right-handed female volunteers. However, a statistically significant difference in language distribution was found between left- and right-handed female volunteers. The left-handed female volunteers showed a more bilateral hemispheric language lateralization. Language lateralization in right-handed male epilepsy patients with early age at seizure onset and seizure locus in the left temporal lobe was not significantly different from that of healthy right-handed male volunteers. Similarly, we found no difference in language lateralization between right-handed female volunteers and right-handed female epilepsy patients with late age at seizure onset and seizures in the left temporal lobe. CONCLUSION: Handedness has a significant influence on hemispheric language dominance in healthy volunteers. Sex has no influence on hemispheric language dominance, regardless of the task used to assess such dominance, nor does age at seizure onset influence language lateralization in patients with left temporal lobe epilepsy. Therefore, hemispheric language dominance can be assessed and compared effectively with functional MR imaging.

Functional MR activation correlated with intraoperative cortical mapping.

PURPOSE: To evaluate the spatial specificity of functional MR imaging by comparing it with intraoperative electrocortical mapping. METHODS: Functional MR imaging was performed in 28 patients before awake craniotomy and intraoperative electrocortical mapping. Activation was mapped for finger movement, lip movement, tongue movement, word generation, and counting paradigms. During surgery, finger movement, lip movement, tongue movement, counting, and/or speaking were mapped. The functional images and the photographic recordings of the brain functions mapped during surgery were converted to bit maps and coregistered by a computer program. The distance between the intraoperatively mapped function site and the MR activation site for a comparable function was measured. RESULTS: Forty-six functions were recorded on MR images and intraoperative maps. In 100% of correlations, the intraoperative site and the MR activation site were within 20 mm; in 87% of correlations they were within 10 mm. For each paradigm, 67% or more of the intraoperative stimulation maps correlated within 10 mm of the MR activation site. CONCLUSIONS: For the tasks used in this study, the activation site on functional MR images correlated well with the site at which intraoperative stimulation identified function.

Functional magnetic resonance imaging of the somatosensory cortex.

Functional magnetic resonance (fMR) imaging, like positron emission tomography (PET), shows regions of activation in the brain resulting from the neuronal activity associated with cognitive, sensory, or motor function. An advantage of fMR imaging is that the functional and the reference anatomic images are acquired simultaneously. Additionally, fMR imaging is generally more available than PET or magnetoencephalography. This article reviews the applications of fMR imaging for studying the sensorimotor cortex prior to craniotomy.

Functional MR of the primary auditory cortex: an analysis of pure tone activation and tone discrimination.

PURPOSE: To use functional MR imaging to measure the effect of frequency (pitch), intensity (loudness), and complexity of auditory stimuli on activation in the primary and secondary auditory cortexes. METHODS: Multiplanar echo-planar images were acquired in healthy subjects with normal hearing to whom auditory stimuli were presented intermittently. Functional images were processed from the echo-planar images with conventional postprocessing methods. The stimuli included pure tones with a single frequency and intensity, pure tones with the frequency stepped between 1,000, 2,000, 3,000, or 4,000 Hz, and spoken text. The pixels activated by each task in the transverse temporal gyrus (TTG) and the auditory association areas were tabulated. RESULTS: The pure tone task activated the TTG. The 1,000-Hz tone activated significantly more pixels in the TTG than did the 4,000-Hz tone. The 4,000-Hz tone activated pixels primarily in the medial TTG, whereas the 1,000-Hz tone activated more pixels in the lateral TTG. Higher intensity tones activated significantly more pixels than did lower intensity tones at the same frequency. The stepped tones activated more pixels than the pure tones, but the difference was not significant. The text task produced significantly more activation than did the pure tones in the TTG and in the auditory association areas. The more complex tasks (stepped tones and listening to text) tended to activate more pixels in the left hemisphere than in the right, whereas the simpler tasks activated similar numbers of pixels in each hemisphere. CONCLUSION: Auditory stimuli activate the TTG and the association areas. Activation in the primary auditory cortex depends on frequency, intensity, and complexity of the auditory stimulus. Activation of the auditory association areas requires more complex auditory stimuli, such as the stepped tone task or text reading.

Hypercapnia reversibly suppresses low-frequency fluctuations in the human motor cortex during rest using echo-planar MRI.

Using magnetic resonance (MR) echo-planar imaging (EPI), we recently demonstrated the presence of low-frequency fluctuations (< 0.1 Hz) in MR signal intensity from the resting human brain that have a high degree of temporal correlation (p < 10(-3)) within and across associated regions of the sensorimotor cortex. These fluctuations in MR signal intensity are believed to arise from fluctuations in capillary blood flow and oxygenation. A substantial overlap between the activation map generated by bilateral finger tapping and temporally-correlated voxels from the sensorimotor cortex obtained during rest was observed. In the work reported here, we investigated whether respiratory hypercapnia, which is known to suspend spontaneous oscillations in regional cerebral blood flow, influences these low-frequency fluctuations. The magnitude of low-frequency fluctuations was reversibly diminished during hypercapnia, resulting in a substantial decrease of the temporal correlation both within and across contralateral hemispheres of the sensorimotor cortex. After the breathing mixture was returned to ambient air, the magnitude and spatial extent of the temporal correlation of low-frequency fluctuations returned to normal. Results of this study support the hypothesis that low-frequency physiological fluctuations observed by MR in the human cortex and spontaneous flow oscillations observed in early studies by laser-Doppler flowmetry (LDF) in the cortex of the rat are identical and are secondary to fluctuations in neuronal activity.

Functional imaging in treatment planning of brain lesions.

PURPOSE: Explore the use of functional imaging data in radiation treatment planning of brain lesions. METHODS AND MATERIALS: Compare the treatment-planning process with and without the use of functional brain imaging for clinical cases where functional studies using either single photon emission computed tomography or magnetic resonance imaging are available. RESULTS: A method to register functional image data with planning image studies is needed for functional treatment planning. Functional volumes are not simply connected regions. One activation study may produce many isolated functional areas. After finding the functional volumes and registering the functional information with the planning imaging data, the tools used for conventional three-dimensional treatment planning are sufficient for functional treatment planning. However, the planning system must provide dose-volume histograms for volumes of interest that consist of isolated pieces. Treatment plans that spare functional brain while providing identical target coverage can be constructed for lesions situated near the functional volume. However, the dose to other areas of the brain may be increased. CONCLUSIONS: Functional imaging will make determination of dose response of eloquent areas of the brain possible when combined with volumetric dose information and neuropsychological evaluation prior to and after radiation therapy. Realizing the full potential of functional imaging studies will require improved delineation of activated volumes and determination of the uncertainties in functional volume delineation. Optimization of treatment plans by minimizing dose to volumes activated during functional imaging studies should be used cautiously, because the dose to "silent," but possibly eloquent, brain may be increased.