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Biomedical subjects

R Kikinis

Publications and source records attributed to R Kikinis.

At least 19 recordsLinked to original sources
PubMed2000

Serial magnetic resonance imaging in multiple sclerosis: correlation with attacks, disability, and disease stage.

Serial MRI and clinical testing was performed on 45 well-defined untreated multiple sclerosis patients in different categories of disease (relapsing-remitting, progressive, stable). Up to 24 MRIs were scheduled over a 1-year period for each patient. Clinical evaluation was performed monthly and at times of attacks using the Expanded Disability Status Scale (EDSS) and the Ambulation Index (AI). MRI scans were performed both with and without gadolinium enhancement. MRI lesion volume was determined by computerized analysis and gadolinium-enhancing lesions were counted by radiologists. We observed an increase in lesion volume over 1 year in all patient groups except those classified clinically as stable. In relapsing-remitting patients there were correlations between increases in the number of gadolinium enhancing lesions and increases in EDSS and the occurrence of attacks. In chronic progressive patients, increases in lesion volume were correlated with both increases in EDSS and AI. These results demonstrate a linkage between MRI and clinical disease that depends both on the stage of MS and the MRI measures used and support the use of MRI as a surrogate marker of clinical disability in the study of multiple sclerosis.

Adult↗
PubMed2000

Disruption of attention to novel events after frontal lobe injury in humans.

OBJECTIVE: To investigate whether frontal lobe damage in humans disrupts the natural tendency to preferentially attend to novel visual events in the environment. METHODS: Nine patients with chronic infarctions in the dorsolateral prefrontal cortex (DLPFC) and 23 matched normal controls participated in a study in which subjects viewed repetitive background stimuli, infrequent target stimuli, and novel visual stimuli (for example, fragmented or "impossible" objects). Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at the different kinds of stimuli, and the target detection accuracy and speed served as dependent variables. RESULTS: Overall, normal controls spent significantly more time than frontal lobe patients looking at novel stimuli. Analysis of responses across blocks showed that initially frontal lobe patients behaved like normal controls by directing more attention to novel than background stimuli. However, they quickly began to distribute their viewing time evenly between novel and background stimuli, a pattern that was strikingly different from normal controls. By contrast, there were no differences between frontal lobe patients and normal controls for viewing duration devoted to background and target stimuli, target detection accuracy, or reaction time to targets. Frontal lobe patients did not differ from normal controls in terms of age, education, estimated IQ, or mood, but were more apathetic as measured by self report and informants' judgments. Attenuated responses to novel stimuli significantly correlated with degree of apathy. CONCLUSIONS: This study demonstrates that DLPFC injury selectively impairs the natural tendency to seek stimulation from novel and unusual stimuli. These data provide the first quantitative behavioural demonstration that the human frontal lobes play a critical part in directing and sustaining attention to novel events. The impairment of novelty seeking behaviour may contribute to the characteristic apathy found in patients with frontal lobe injury.

Aged↗
PubMed2000

MR-based three-dimensional modeling of the normal pelvic floor in women: quantification of muscle mass.

OBJECTIVE: Our objective was to use a combination of axial MR source images and three-dimensional (3D) models to describe the anatomy of the normal pelvic floor in young nulliparous women and to measure the volume of the levator ani. SUBJECTS AND METHODS: Ten healthy nulliparous female volunteers (average age, 27 years) underwent T2-weighted MR imaging of the pelvis. Three-dimensional color-coded models of the pelvic bones and organs and the three major components of the levator ani--puborectalis, iliococcygeus, and coccygeus--were created. Source images were used to measure muscle width and signal intensity and to identify ligamentous structures. Using 3D models, we measured the volume of the levator ani, the angle of the levator plate, the posterior urethrovesical angle, and the distance of the bladder neck from the symphysis pubis and the pubococcygeal line. RESULTS: In all volunteers, the signal intensity of the puborectalis exceeded that of the obturator externus. The average volume of the levator ani was 46.6 ml, the average width of the levator hiatus was 41.7 mm, and the average posterior urethrovesical angle was 143.5 degrees. Vaginal shape in the volunteers followed no recognizable pattern. CONCLUSION: Muscle morphology, signal intensity, and volume is relatively uniform among healthy young women.

Adult↗
PubMed2000

Use of structural magnetic resonance imaging to predict who will get Alzheimer's disease.

We used magnetic resonance imaging (MRI) measurements to determine whether persons in the prodromal phase of Alzheimer's disease (AD) could be accurately identified before they developed clinically diagnosed dementia. Normal subjects (n = 24) and those with mild memory difficulty (n = 79) received an MRI scan at baseline and were then followed annually for 3 years to determine which individuals subsequently met clinical criteria for AD. Patients with mild AD at baseline were also evaluated (n = 16). Nineteen of the 79 subjects with mild memory difficulty "converted" to a diagnosis of probable AD after 3 years of follow-up. Baseline MRI measures of the entorhinal cortex, the banks of the superior temporal sulcus, and the anterior cingulate were most useful in discriminating the status of the subjects on follow-up examination. The accuracy of discrimination was related to the clinical similarity between groups. One hundred percent (100%) of normal subjects and patients with mild AD could be discriminated from one another based on these MRI measures. When the normals were compared with the individuals with memory impairments who ultimately developed AD (the converters), the accuracy of discrimination was 93%, based on the MRI measures at baseline (sensitivity = 0.95; specificity = 0.90). The discrimination of the normal subjects and the individuals with mild memory problems who did not progress to the point where they met clinical criteria for probable AD over the 3 years of follow-up (the "questionables") was 85% and the discrimination of the questionables and converters was 75%. The apolipoprotein E genotype did not improve the accuracy of discrimination. The specific regions selected for each of these discriminations provides information concerning the hierarchical fashion in which the pathology of AD may affect the brain during its prodromal phase.

Aged↗
PubMed1999

Changes in serum levels of ICAM and TNF-R correlate with disease activity in multiple sclerosis.

OBJECTIVE: To study the change in serum levels of soluble intercellular adhesion molecule 1 (sICAM-1) and soluble tumor necrosis factor receptors (sTNF-Rs) in MS patients in relation to clinical disease activity and changes on brain MRI. BACKGROUND: Circulating forms of adhesion molecules or soluble receptors may be released from cells as a consequence of activation and may be useful markers for inflammation. METHODS: During a prospective longitudinal study over 1 year, 40 patients with MS underwent frequent imaging of the brain (22 MR images per patient) at the time of blood sampling as well as monthly neurologic examinations, and scoring on Kurtzke's Expanded Disability Status Scale (EDSS) and ambulation index (AI). RESULTS: Patients with relapsing-progressive disease had the highest levels of sICAM-1 whereas patients with progressive disease had the highest levels of sTNF-Rs. Fluctuations in sICAM-1 correlated with the occurrence of attacks in patients with relapsing and relapsing-progressive disease. In patients with relapsing-progressive MS, an increase in sICAM-1 level preceded the appearance of new gadolinium (Gd) enhancing lesions on MRI. In patients with progressive disease, an increase in sTNF-R p55 level preceded the appearance of new Gd enhancing lesions on MRI, whereas a decrease in sICAM-1 levels correlated with the appearance of new Gd enhancing lesions. CONCLUSIONS: These results demonstrate a linkage between sICAM-1 and sTNF-R levels and disease activity in MS. Furthermore, patients with progressive disease appear to have a different immunologic stage of disease in which immune changes are tightly linked with changes on MRI. The demonstration of a correlation in individual patients between immunologic events and changes in disease activity has implications for monitoring patients undergoing treatment and for monitoring disease progression.

Adult↗
PubMed1999

Schizotypal personality disorder and MRI abnormalities of temporal lobe gray matter.

BACKGROUND: Structural MRI data indicate schizophrenics have reduced left-sided temporal lobe gray matter volumes, especially in the superior temporal gyrus (STG) and medial temporal lobe. Our data further suggest a specificity to schizophrenia spectrum disorders of STG volume reduction. Interpretation of research studies involving schizophrenics may be complicated by the effects of exposure to neuroleptics and chronic illness. Sharing the same genetic diathesis of schizophrenics, subjects with schizotypal personality disorder (SPD) offer a unique opportunity to evaluate commonalities between schizophrenia and SPD, particularly as SPD subjects are characterized by cognitive and perceptual distortions, an inability to tolerate close friendships, and odd behavior, but they are not psychotic and so have generally not been prescribed neuroleptics nor hospitalized. Evaluation of brain structure in SPD may thus offer insight into the "endophenotype" common to both disorders. In addition, differences between groups may suggest which are the brain structures of schizophrenics that contribute to the development of psychosis. METHODS: To test the hypothesis of whether SPD subjects might show similar STG abnormalities, STG and medial temporal lobe regions of interest (ROI) were manually drawn on high resolution coronal MRI 1.5 mm thick slices. Images were derived from 16 right-handed male SPD subjects, without regard to family history, and 14 healthy, right-handed, comparison males who did not differ from the SPD group on parental socio-economic status, age, or verbal IQ. RESULTS: As predicted, SPD subjects showed a reduction in left STG gray matter volume compared with age and gender matched comparison subjects. SPD subjects also showed reduced parahippocampal left/right asymmetry and a high degree of disordered thinking. Comparisons with chronic schizophrenics previously studied by us showed the SPD group had a similarity of left STG gray matter volume reduction, but fewer medial temporal lobe abnormalities. CONCLUSIONS: These abnormalities strengthen the hypothesis of a temporal lobe abnormality in SPD, and the similarity of STG findings in schizophrenia and SPD suggest that STG abnormalities may be part of the spectrum "endophenotype." It is also possible that presence of medial temporal lobe abnormalities may help to differentiate who will develop schizophrenia and who will develop the less severe schizophrenia spectrum disorder, SPD.

Adult↗
PubMed1999

Left planum temporale volume reduction in schizophrenia.

BACKGROUND: The planum temporale, located on the posterior and superior surface of the temporal lobe, is a brain region thought to be a biological substrate of language and possibly implicated in the pathophysiology of schizophrenia. To investigate further the role of planum temporale abnormalities in schizophrenia, we measured gray matter volume underlying the planum temporale from high spatial resolution magnetic resonance imaging techniques. METHODS: Sixteen male patients with chronic schizophrenia and 16 control subjects were matched for age, sex, handedness, and parental socioeconomic status. Magnetic resonance imaging images were obtained from a 1.5-T magnet. RESULTS: Gray matter volume was significantly reduced in the left planum temporale (28.2%) in schizophrenic patients compared with normal controls. Schizophrenic patients showed a reversal of the left greater than right planum temporale asymmetry found in normal controls. Heschl's gyrus (primary auditory cortex) showed no differences between the left and right sides in either group. Of note, the Suspiciousness/Persecution subscale score of the Positive and Negative Syndrome Scale was associated with reduced left planum temporale volume in schizophrenic patients. CONCLUSIONS: Patients with schizophrenia have reduced left planum temporale gray matter and a reversal of planum temporale asymmetry, which may underlie an impairment in language processing and symptoms of suspiciousness or persecution characteristic of schizophrenia.

Adult↗
PubMed1999

AnatomyBrowser: A novel approach to visualization and integration of medical information.

In this article, we present a novel technique for visualization of three-dimensional (3D) surface models, as well as its implementation in a system called AnatomyBrowser. Using our approach, visualization of 3D surface models is performed in two separate steps: a pre-rendering step, in which the models are rendered and saved in a special format, and an actual display step, in which the final result of rendering is generated using information from the prerendering step. Whereas prerendering requires high-end graphics hardware, the final image generation and display can be implemented efficiently in software. Moreover, our current implementation of AnatomyBrowser interface uses the Java programming language and can therefore be readily run on a wide range of systems, including low-end computers with no special graphics hardware. In addition to visualization of 3D models and 2D slices, AnatomyBrowser provides a rich set of annotation and cross-referencing capabilities. We demonstrate several possible applications for AnatomyBrowser, including interactive anatomy atlases, surgery planning, and assistance in segmentation.

Anatomy↗
PubMed1999

Impingement simulation of the hip in SCFE using 3D models.

OBJECTIVE: Affecting as it does the geometry of adolescent hips, slipped capital femoral epiphysis (SCFE) and its evaluation represent a major three-dimensional problem. The current methods of clinical assessment-geometric measurements of the femur on plain radiographs or on axial computed tomographic (CT) cross-sections-address only one of the two joint components. MATERIALS AND METHODS: We have developed a system to simulate motion of hip joints with physiologic joint contact. In our system, CT-based computer models of the femur, pelvis, etc., are fitted with oriented bounding boxes (OBBs) and manipulated. Collision detection algorithms control the hip motion, which, in this virtual joint, is based on the surface geometry of the joint partners rather than on a predefined fixed rotation center. RESULTS: An illustrative case is presented to show the advantages of the new biomechanical evaluation method over conventional radiological assessments for SCFE. The proposed system provides remarkably high speed, and the necessary data can be prepared in a reasonable time. CONCLUSION: The range-of-motion assessment provides the surgeon with information about the site and the impact of nonphysiologic contact in the hip joint. The information thus obtained can be valuable for indication and planning of corrective surgery in cases of SCFE.

Adolescent↗
PubMed1999

Quantitative follow-up of patients with multiple sclerosis using MRI: reproducibility.

The reproducibility of an automated method for estimating the volume of white matter abnormalities on brain magnetic resonance (MR) images of multiple sclerosis (MS) patients was evaluated. Twenty MS patients underwent MR imaging twice within 30 minutes. Measurement variability is introduced mainly by MRI acquisition and image registration procedures, which demonstrate significantly worse reproducibility than the image segmentation. The correction of partial volume artifacts is essential for sensitive measurements of overall lesion burden. The average lesion volume difference (bias) between two MR exams of the same MS patient (N = 20) was 0.05 cm3, with a 95% confidence interval between -0.17 and +0.28 cm3, suggesting that the proposed measurement system is suitable for clinical follow-up trials, even in relatively small patient cohorts. The limits of agreement for lesion volume were between -1.3 and +1.5 cm3, implying that in individual patients changes in lesion load need to be at least this large to be detected reliably. This automated method for estimating lesion burden is a reliable tool for the evaluation of MS progression and exacerbation in patient cohorts and potentially also in individual patients.

Adjuvants, Immunologic↗
PubMed1999

Quantitative follow-up of patients with multiple sclerosis using MRI: technical aspects.

A highly reproducible automated procedure for quantitative analysis of serial brain magnetic resonance (MR) images was developed for use in patients with multiple sclerosis (MS). The intracranial cavity (ICC) was identified on standard dual-echo spin-echo brain MR images using a supervised automated procedure. MR images obtained from one MS patient at 24 time points in the course of a 1-year follow-up were aligned with the images of one of the time points. Next, the contents of the ICC in each MR exam were segmented into four tissues, using a self-adaptive statistical algorithm. Misclassifications due to partial voluming were corrected using a combination of morphologic operators and connectivity criteria. Finally, a connectivity detection algorithm was used to separate the tissue classified as lesions into individual entities. Registration, classification of the contents of the ICC, and identification of individual lesions are fully automatic. Only identification of the ICC requires operator interaction. In each MR exam, the program estimated volumes for the ICC, gray matter (GM), white matter (WM), white matter lesions (WML), and cerebrospinal fluid (CSF). The reproducibility of the system was superior to that of supervised segmentation, as evidenced by the coefficient of variation: CSF supervised 45.9% vs. automated 7.7%, GM 16.0% vs. 1.4%, WM 15.7% vs. 1.3%, and WML 39.5% vs 52.0%. Our results demonstrate that this computerized procedure allows routine reproducible quantitative analysis of large serial MRI data sets.

Adult↗
PubMed1999

Partial wavelet encoding: a new approach for accelerating temporal resolution in contrast-enhanced MR imaging.

We propose a new approach using wavelet encoding to improve temporal resolution in contrast-enhanced magnetic resonance (MR) imaging. Exploiting the unique property of wavelets localized in space and frequency, we construct an efficient encoding scheme to capture signal changes due to contrast agent uptake, which in general is spatially localized with low- and mid-range frequency components. On the basis of space-frequency analysis, we describe mathematical formulations of our method and discuss its theoretical advantages over Fourier-based phase-encoding methods (the keyhole and reduced-encoding imaging by generalized-series reconstruction [RIGR] techniques). The results obtained in computer simulations and a phantom study demonstrate the feasibility and practical advantages of our approach.

Computer Simulation↗
PubMed1999

Periventricular white matter injury in the premature infant is followed by reduced cerebral cortical gray matter volume at term.

Periventricular white matter injury, that is, periventricular leukomalacia (PVL), the dominant form of brain injury in the premature infant, is the major neuropathological substrate associated with the motor and cognitive deficits observed later in such infants. The nature of the relationship of this lesion to the subsequent cognitive deficits is unclear, but such deficits raise the possibility of cerebral cortical neuronal dysfunction. Although cortical neuronal necrosis is not a prominent feature of brain injury in premature infants, the possibility of a deleterious effect of PVL on subsequent cerebral cortical development has not been investigated. An advanced quantitative volumetric three-dimensional magnetic resonance imaging technique was used to measure brain tissue volumes at term in premature infants with earlier ultrasonographic and magnetic resonance imaging evidence of PVL (mean gestational age at birth, 28.7 +/- 2.0 weeks; n = 10), in premature infants with normal imaging studies (mean gestational age at birth, 29.0 +/- 2.1 weeks; n = 10), and in control term infants (n = 14). Premature infants with PVL had a marked reduction in cerebral cortical gray matter at term compared with either premature infants without PVL or normal term infants (mean +/- SD: PVL, 157.5 +/- 41.5 ml; no PVL, 211.7 +/- 25.4 ml; normal term, 218.8 +/- 21.3 ml). As expected, a reduction in the volume of total brain myelinated white matter was also noted (mean +/- SD: PVL, 14.5 +/- 4.6 ml; no PVL, 23.1 +/- 6.9 ml; normal term, 27.6 +/- 10.3 ml). An apparent compensatory increase in total cerebrospinal fluid volume also was found (mean +/- SD: PVL, 64.5 +/- 15.2 ml; no PVL, 52.0 +/- 24.1 ml; normal term, 32.9 +/- 13.5 ml). PVL in the premature infant is shown for the first time to be followed by impaired cerebral cortical development. These findings may provide insight into the anatomical correlate for the intellectual deficits associated with PVL in the premature infant.

Basal Ganglia↗
PubMed1999

On the Laplace-Beltrami operator and brain surface flattening.

In this paper, using certain conformal mappings from uniformization theory, we give an explicit method for flattening the brain surface in a way which preserves angles. From a triangulated surface representation of the cortex, we indicate how the procedure may be implemented using finite elements. Further, we show how the geometry of the brain surface may be studied using this approach.

Brain↗
PubMed1999

Intraoperative MR imaging guidance for intracranial neurosurgery: experience with the first 200 cases.

PURPOSE: To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures. MATERIALS AND METHODS: A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed. RESULTS: There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery. CONCLUSION: Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.

Adolescent↗
PubMed1999

Superior temporal gyrus volume abnormalities and thought disorder in left-handed schizophrenic men.

OBJECTIVE: Studies of schizophrenia have not clearly defined handedness as a differentiating variable. Moreover, the relationship between thought disorder and anatomical anomalies has not been studied extensively in left-handed schizophrenic men. The twofold purpose of this study was to investigate gray matter volumes in the superior temporal gyrus of the temporal lobe (left and right hemispheres) in left-handed schizophrenic men and left-handed comparison men, in order to determine whether thought disorder in the left-handed schizophrenic men correlated with tissue volume abnormalities. METHOD: Left-handed male patients (N = 8) with DSM-III-R diagnoses of schizophrenia were compared with left-handed comparison men (N = 10) matched for age, socioeconomic status, and IQ. Magnetic resonance imaging (MRI) with a 1.5-T magnet was used to obtain scans, which consisted of contiguous 1.5-mm slices of the whole brain. MRI analyses (as previously defined by the authors) included the anterior, posterior, and total superior temporal gyrus in both the left and right hemispheres. RESULTS: There were three significant findings regarding the left-handed schizophrenic men: 1) bilaterally smaller gray matter volumes in the posterior superior temporal gyrus (16% smaller on the right, 15% smaller on the left); 2) a smaller volume on the right side of the total superior temporal gyrus; and 3) a positive correlation between thought disorder and tissue volume in the right anterior superior temporal gyrus. CONCLUSIONS: These results suggest that expression of brain pathology differs between left-handed and right-handed schizophrenic men and that the pathology is related to cognitive disturbance.

Cognition Disorders↗
PubMed1999

Subgenual cingulate cortex volume in first-episode psychosis.

OBJECTIVE: Gray matter volume and glucose utilization have been reported to be reduced in the left subgenual cingulate of subjects with familial bipolar or unipolar depression. It is unclear whether these findings are secondary to recurrent illness or are part of a familial/genetic syndrome. The authors' goal was to clarify these findings. METHOD: Volumetric analyses were performed by using magnetic resonance imaging in 41 patients experiencing their first episode of affective disorder or schizophrenia and in 20 normal comparison subjects. RESULTS: The left subgenual cingulate volume of the patients with affective disorder who had a family history of affective disorder was smaller than that of patients with affective disorder with no family history of the illness and the normal comparison subjects. Patients with schizophrenia did not differ from comparison subjects in left subgenual cingulate volume. CONCLUSIONS: Left subgenual cingulate abnormalities are present at first hospitalization for psychotic affective disorder in patients who have a family history of affective disorder.

Adult↗