Biomedical subjects

P Fransson

Publications and source records attributed to P Fransson.

At least 19 recordsLinked to original sources

PubMed2005

Functional magnetic resonance imaging at 3T as a clinical tool in patients with intracranial tumors.

PURPOSE: To investigate the potential of functional magnetic resonance imaging (fMRI) at 3T as a clinical tool in the preoperative evaluation of patients with intracranial tumors. High magnetic field strength such as 3T is of benefit for fMRI because signal-to-noise ratio and sensitivity to susceptibility changes are field-strength-dependent. MATERIAL AND METHODS: Twenty patients with tumors close to eloquent sensorimotor or language areas were studied. Motor, sensory, and two language paradigms (word generation, rhyming) were used; their effectiveness was determined as the percentage of patients in whom the functional area of interest was activated. Activation maps were calculated and their quality rated as high, adequate, or insufficient. The influence of fMRI on the neurosurgical decision regarding operability, surgical approach, and extent of the resection, was assessed. RESULTS: Paradigm effectiveness was 90% for motor and 95% for sensory stimulation, and varied from 79% to 95% for word generation and rhyming in combination. Ninety percent of the activation maps held high or adequate quality. fMRI proved useful: in the decision to operate (9 patients), in the surgical approach (13 patients), and in extent of the resection (12 patients). CONCLUSION: fMRI at 3T is a clinically applicable tool in the work-up of patients with intracranial tumors.

Adult↗

PubMed2001

Quality of life and symptoms in a randomized trial of radiotherapy versus deferred treatment of localized prostate carcinoma.

BACKGROUND: Treatment of localized prostate carcinoma (LPC) using radiotherapy (RT) can induce disturbances in a patient's quality of life (QOL) and urinary and intestinal function. Late symptoms and QOL were evaluated in a randomized trial between RT and deferred treatment (DT). METHODS: Quality of life was evaluated with European Organization for Research and Treatment of Cancer's QLQ-C30 (+3) formula. Urinary and intestinal problems were evaluated with a validated symptom specific self-assessment questionnaire, QUFW94. The questionnaires were sent to 108 randomized patients with LPC and to an age-matched control group (n = 68). Mean age was 72 years. Mean total dose was 65 grays (Gy; 62.3-70 Gy). The median follow-up time from randomization was 40.6 months for the RT group and 30.4 months for the DT group. RESULTS: Social functioning was the only QOL scale in which a significant difference was found between the two patient groups and compared with the control group. Multivariate regression analysis showed that hematuria, incontinence, mucus, and planning of daily activities in response to intestinal problems caused this decrease in QOL in the RT group. A significant increase of intestinal problems was observed in the RT versus DT groups regarding mucus, stool leakage, intestinal blood, and planning of daily activity in response to intestinal problems. CONCLUSIONS: The RT patients showed increased levels of minor intestinal side effects compared with the DT patients and the controls, but the RT patients reported no decreased QOL except for decreased social functioning. This could be because this group developed coping skills or because of a low magnitude of side effects to influence the QOL.

Adaptation, Psychological↗

PubMed2001

Functional MRI with reduced susceptibility artifact: high-resolution mapping of episodic memory encoding.

Visual episodic memory encoding was investigated using echoplanar magnetic resonance imaging at 2.0 x 2.0 mm2 resolution and 1.0 mm section thickness, which allows for functional mapping of hippocampal, parahippocampal, and ventral occipital regions with reduced magnetic susceptibility artifact. The memory task was based on 54 image pairs each consisting of a complex visual scene and the face of one of six different photographers. A second group of subjects viewed the same set of images without memory instruction as well as a reversing checkerboard. Apart from visual activation in occipital cortical areas, episodic memory encoding revealed consistent activation in the parahippocampal gyrus but not in the hippocampus proper. This finding was most prominently evidenced in sagittal maps covering the right hippocampal formation. Mean activated volumes were 432 +/- 293 microl and 259 +/- 179 microl for intentional memory encoding and non-instructed viewing, respectively. In contrast, the checkerboard paradigm elicited pure visual activation without parahippocampal involvement.

Adult↗

PubMed2001

Modulation of cerebral blood oxygenation by indomethacin: MRI at rest and functional brain activation.

The modulation of blood oxygenation level-dependent (BOLD) cerebral MRI contrast by the vasoconstrictive drug indomethacin (i.v. 0.2 mg/kg b.w.) was investigated in 10 healthy young adults without and with functional challenge (repetitive and sustained visual activation). For comparison, isotonic saline (placebo, 20 mL) and acetylsalicylate (i.v. 500 mg) were investigated as well, each in separate sessions using identical protocols. After indomethacin, dynamic T2*-weighted echo-planar MRI at 2.0 T revealed a rapid decrease in MRI signal intensity by 2.1%-2.6% in different gray matter regions (P < or = 0.001 compared to placebo), which was not observed for acetylsalicylate and the placebo condition. Regional signal differences were not significant within gray matter, but all gray matter regions differed significantly from the signal decrease of only 1.2% +/- 0.7% observed in white matter (P = 0.001). For the experimental parameters used, a 1% MRI signal decrease in response to indomethacin was estimated to correlate with a decrease of the cerebral blood flow by about 12 ml/100 g/minute, and an increase of the oxygen extraction fraction by about 15%. Responses to visual activation were not affected by saline or acetylsalicylate, and yielded 5.0%-5.5% BOLD MRI signal increases both before and after drug application. In contrast, indomethacin reduced the initial response strength to 82%-85% of that obtained without the drug. The steady-state response during sustained activation reached only 47% of the corresponding pre-drug level (P < 0.01). During repetitive activation the BOLD contrast was reduced to 66% of that observed for control conditions (P < 0.001). In conclusion, indomethacin attenuates the vasodilatory force at functional brain activation, indicating different mechanisms governing neurovascular coupling.

Adult↗

PubMed2001

Functional MRI of the human amygdala?

In view of an increasing number of publications that deal with functional mapping of the human amygdala using blood oxygenation-level-dependent (BOLD) magnetic resonance imaging, we reevaluated the underlying image quality of T2*-weighted echoplanar imaging (EPI) and fast low angle shot (FLASH) sequences at 2.0-T with regard to susceptibility-induced signal losses and geometric distortions. Apart from the timing of the gradient echoes, the degree of susceptibility influences is controlled by the image voxel size. Whereas published amygdala studies report voxel sizes ranging from 22 to 125 microl, the present results suggest that reliable imaging of the amygdala with BOLD sensitivity requires voxel sizes of 4 to 8 microl or less. Preferentially, acquisitions should be performed with a coronal section orientation. Although high-resolution BOLD MRI is at the expense of temporal resolution and volume coverage, it seems to provide the only solution to this physical problem.

Amygdala↗

PubMed2001

Reliability and responsiveness of a prostate cancer questionnaire for radiotherapy-induced side effects.

Few self-assessment cancer-specific questionnaires/modules have yet been developed for radiotherapy-induced side effects. The aim of the present study was to test the reliability and responsiveness of a prostate cancer (PC)-specific questionnaire. Thirty-one patients with PC graded their urinary and intestinal symptoms and their sexual function on the questionnaire. A doctor and a nurse performed a structured interview and graded the patient's symptoms with the same questions. The procedure was performed at both the start and the end of the treatment. A high concordance regarding symptom detection was seen between the patient, nurse and the doctor. The inter-rater test shows intraclass correlation coefficient (ICC) values above 0.60 in all scales. The internal reliability exceeded the lower limit (Cronbach a >0.70) for all scales. The test-retest gave acceptable reliability for all scales (ICC > or = 0.60). All scales indicated increased problems during radiotherapy. The questionnaire was proven to be valid for the evaluations of urinary and intestinal problems and for sexual function in PC patients.

Aged↗

PubMed2001

Acute side effects after dose-escalation treatment of prostate cancer using the new urethral catheter BeamCath technique.

Acute side effects after dose-escalated radiotherapy for prostate cancer with different treatment techniques were evaluated, using a daily diary recorded by the patients. Dose escalation was performed using the urethral catheter BeamCath' technique. Side effects were evaluated in 267 patients by means of a daily diary during the treatment and at 3-months' follow-up. The patients' evaluations were compared with those of patients treated with conventional or conformal techniques. Looser stools were reported in the conventional (placebo) and 76 Gy groups at 3-months' follow-up compared with at week 1. No other obvious increase in rectal or bladder morbidity was seen in the 76 Gy group. The catheter did not increase the urinary frequency in comparison to the other groups. The reported urgency and starting problems at the beginning of treatment seemed to improve in all groups at 3-months' follow-up. External beam radiotherapy dose escalation using the BeamCath technique did not result in a dose-dependent increase in acute side effects.

Adult↗

PubMed2001

A 4D approach to the analysis of functional brain images: application to FMRI data.

This paper presents a new approach to functional magnetic resonance imaging (FMRI) data analysis. The main difference lies in the view of what comprises an observation. Here we treat the data from one scanning session (comprising t volumes, say) as one observation. This is contrary to the conventional way of looking at the data where each session is treated as t different observations. Thus instead of viewing the v voxels comprising the 3D volume of the brain as the variables, we suggest the usage of the vt hypervoxels comprising the 4D volume of the brain-over-session as the variables. A linear model is fitted to the 4D volumes originating from different sessions. Parameter estimation and hypothesis testing in this model can be performed with standard techniques. The hypothesis testing generates 4D statistical images (SIs) to which any relevant test statistic can be applied. In this paper we describe two test statistics, one voxel based and one cluster based, that can be used to test a range of hypotheses. There are several benefits in treating the data from each session as one observation, two of which are: (i) the temporal characteristics of the signal can be investigated without an explicit model for the blood oxygenation level dependent (BOLD) contrast response function, and (ii) the observations (sessions) can be assumed to be independent and hence inference on the 4D SI can be made by nonparametric or Monte Carlo methods. The suggested 4D approach is applied to FMRI data and is shown to accurately detect the expected signal.

Brain Chemistry↗

PubMed2000

Methods for evaluation of postural control adaptation.

New methods were developed to determine the dynamic changes of postural control during the initial exposure to large perturbances of stance. The adjustments of postural control over time in measured anteroposterior torque, were investigated in ten normal subjects. Perturbations of stance were evoked by two high intensity vibrators applying pseudorandom stimulation either to the calf muscles or the paravertebral muscles of the neck. The new methods use a system identification approach, which distinguishes between feedback control, adaptation of postural responses and adaptation to stimulus. This approach makes it possible to quantify motion dynamics and complexity, stimulus impact and adjustments of postural control. Quantification of the different adaptive responses could be useful for diagnostic purposes, in evaluating treatment efficacy and patient progress in rehabilitation programs.

Adaptation, Physiological↗

PubMed1999

Does stimulus quality affect the physiologic MRI responses to brief visual activation?

We studied the effect of stimulus quality on the basic physiological response characteristics of oxygenation-sensitive MRI signals. Paradigms comprised a contrast-reversing checkerboard vs. darkness or vs. gray light as well as gray light vs. darkness in a 2 s/52 s protocol (nine subjects). MRI was performed at 2.0 T using single-shot gradient-echo EPI (TR/TE = 500/54 ms, flip angle 30 degrees). All paradigms elicited almost identical signal intensity time courses comprising a latency period (1-2s), an activation-induced signal increase (4-4.5% at about 6-7 s after stimulus onset) and a post-stimulus signal undershoot (-1%) that slowly recovered to baseline (about 50 s). Thus, in contrast to findings for sustained stimulation, brief presentations of distinct visual stimuli exhibit similar physiological response characteristics that support the use of a uniform response profile for the evaluation of event related paradigms.

Adult↗

PubMed1999

Late side effects unchanged 4-8 years after radiotherapy for prostate carcinoma: a comparison with age-matched controls.

BACKGROUND: The authors of this study previously evaluated pelvic irradiation-induced late side effects in patients with localized prostatic carcinoma 4 years after external irradiation by administering a validated self-assessment questionnaire (QUFW94), and compared the results with those of age-matched controls. The current study was designed to evaluate prospectively the patients' problems 8 years after radiotherapy and to compare them with those reported by the same controls. METHODS: The questionnaire was sent out at a mean of 8 years (range, 72-104 months) after irradiation to 120 patients and 125 controls. For analysis of sexual function, the patient group was divided into two subgroups, one treated with radiotherapy only (RT) and one group treated with radiotherapy plus castration (RT+A). A value of >1 on a 0-10 scale indicated that the patient was having a problem. RESULTS: The mean age was 73 years for both patients and controls. No changes in urinary problems were seen between the 4-year and the 8-year follow-up in the 2 groups. Sixty percent and 54% of the patients (P = 0.096) and 24% and 31% of the controls (P = 0.988) reported urinary problems at the 4-year and 8-year follow-ups, respectively. No changes in gastrointestinal late side effects in the patient group were seen between the 4-year (65%) and the 8-year (62%) follow-ups (P = 0.490). However, there was a decrease in intestinal problems in the control group between the 4-year (12%) and the 8-year (9%) follow-ups (P = 0.001). The sexual problems did not change during the two periods, in the patient groups or in the control groups. Fifty-six percent and 65% of the RT group (P = 0.052), 67% and 54 % of the RT + A group (P = 0.555), and 27% and 33 % of the control group (P = 0.243) indicated some kind of sexual problem at the 4-year and 8-year follow-ups, respectively. CONCLUSIONS: The amount of pelvic irradiation-induced urinary late side effects, intestinal late side effects, and sexual function, evaluated with a self-assessment questionnaire, did not change between 4 and 8 years after RT. The age-matched controls reported no change in urinary or sexual problems despite advanced age, but there was a reported decrease in intestinal problems.

Activities of Daily Living↗

PubMed1999

MRI of functional deactivation: temporal and spatial characteristics of oxygenation-sensitive responses in human visual cortex.

Magnetic resonance imaging (MRI) of neuronal "activation" relies on the elevation of blood flow and oxygenation and a related increase of the blood oxygenation level-dependent (BOLD) MRI signal. Because most cognitive paradigms involve both switches from a low degree of activity to a high degree of activity and vice versa, we have undertaken a baseline study of the temporal and spatial characteristics of positive and negative BOLD MRI responses in human visual cortex. Experiments were performed at 2.0 T using a multislice gradient-echo EPI sequence (TR = 1 s, mean TE = 54 ms, flip angle 50 degrees) at 2x2-mm2 spatial resolution. Activation and "deactivation" processes were accomplished by reversing the order of stimulus presentations in paradigms using homogeneous gray light and an alternating checkerboard as distinct functional states. For sustained stimulation (> or = 60 s) the two conditions resulted in markedly different steady-state BOLD MRI signal strengths. The transient responses to brief stimulation (< or = 18 s) differed insofar as activation processes temporally separate positive BOLD and negative undershoot effects by about 10 s, whereas negative BOLD effects and undershoot contributions overlap for deactivation processes. Apart from differences in stimulus features (e.g., motion) the used activation and deactivation protocols revealed similar maps of neuronal activity changes.

Adult↗

PubMed1999

Temporal and spatial MRI responses to subsecond visual activation.

The temporal and spatial characteristics of oxygenation-sensitive MRI responses to very brief visual stimuli (five Hz reversing black and white checkerboard pattern versus darkness) were investigated (nine subjects) by means of serial single-shot gradient-echo echo-planar imaging (2.0 T, TR=400 ms, mean TE=54 ms, flip angle 30 degrees). The use of a 0.2-s stimulus and a 90-s control phase resulted in an initial latency phase (about 2 s, no signal change), a positive MRI response (2.5% signal increase peaking at 5 s after stimulus onset), and a post-stimulus undershoot (1% signal decrease peaking at 15 s after stimulus onset) lasting for about 50-60 s. The finding that a subsecond visual stimulus elicits both a strong positive MRI response and a long-lasting undershoot provides further evidence for the neuronal origin of slow signal fluctuations seen in the absence of functional challenge and their utility for mapping functional connectivity. The additional observation that a reduction of the inter-stimulus control phase from 90 s to 9.8 s does not seem to affect the spatial extent of cortical activation in pertinent maps is of major relevance for the design and analysis of "event-related" MRI studies.

Adult↗

PubMed1998

Physiologic aspects of event related paradigms in magnetic resonance functional neuroimaging.

In order to substantiate event related paradigms in magnetic resonance functional neuroimaging, we assessed the temporal and spatial characteristics of oxygenation-sensitive MRI responses to 1 s periods of visual activation in repetitive protocols. A main finding is a reduction of the functional contrast between conditions (reversing checkerboard vs. darkness) for decreasing interstimulus intervals yielding 4.5% signal change for 89 s, 4% for 9 s, 3% for 6 s, and 1% for 3 s, respectively. Although rapid repetitions of identical stimuli preclude the development of the full positive and negative MRI signal deflections, pertinent responses leave the spatial pattern of activated brain regions unaffected and result in identical maps. These findings suggest the use of interstimulus intervals of the order of the response time from stimulus onset to maximum signal strength (5-6 s in the visual system). The resulting distinction in time will allow for separate mapping of stimulus-related responses with spatially overlapping cortical representations.

Adult↗

PubMed1998

Analysis of adaptation in anteroposterior dynamics of human postural control.

To quantify the postural adjustments over time, twelve normal subjects were investigated with posturography during vibration either toward the calf or the paraspinal neck muscles; with eyes open vs. eyes closed. The stimulus response adjustments over time were found to be almost identical for all test conditions, though the responses were smaller during eyes open conditions. To determine the response adjustments and thus the dynamics of postural control, a system identification methodology incorporating both step response and dynamic feedback components was developed. This methodology can be used to quantify both short-term stimulus response and postural adaptive adjustments when evaluating postural control performance. Copyright 1998 Elsevier Science B.V.

Journal Article↗

PubMed1998

Temporal characteristics of oxygenation-sensitive MRI responses to visual activation in humans.

Series of single-shot blipped echo-planar images with spin-density weighting and T2* sensitivity (2.0 T, TR = 400 ms, TE = 54 ms, flip angle = 30 degrees) were used to study the temporal response profiles to repetitive visual activation (5 Hz, reversing black and white checkerboard versus darkness) for protocols comprising multiple cycles of a 1.6-s stimulus in conjunction with a 8.4-s or 90-s recovery phase and a 10-s stimulus with a 20-s or 90-s recovery phase. Analysis of the real-time data from all activated pixels resulted in a strong positive MRI response (mean values 3-6%) as well as a marked poststimulus undershoot (mean values 1-2%, duration 60-90 s) for all paradigms. Repetitive protocols with insufficient recovery periods of 8.4 s or 20 s gave rise to a wraparound effect when analyzing time-locked averages from multiple activation cycles. This problem may lead to an early signal decrease that originates from the ongoing undershoot of preceding activations folded back into the initial latency phase of a subsequent activation. When ensuring complete decoupling of responses to successive stimuli by using a 90-s recovery period, the wraparound effect vanished and an initial dip was observed in one of seven subjects for a 10-s/90-s protocol.

Adult↗

PubMed1998

The pelvis after surgery and radio-chemotherapy for rectal cancer studied with Gd-DTPA-enhanced fast dynamic MR imaging.

The aim of this work was to study the gadolinium-enhancement of malignant and benign pathology in the pelvis after surgery for rectal cancer. Thirty patients with either local recurrence (n = 17) or benign changes related to treatment for rectal cancer (n = 13) were studied with pelvic MR imaging. T2-weighted fast spin-echo as well as T1-weighted spin- or gradient-echo imaging before and after intravenous contrast was performed and referred to as contrast-enhanced MRI (CEMRI). In addition, between the pre- and postcontrast images, dynamic contrast-enhanced MRI (DCEMRI) was performed using a single-slice, multi-phase, contrast-enhanced T1-weighted fast spoiled gradient-echo sequence. The time between the start of contrast injection to the beginning of enhancement, the duration and rate of enhancement as well as enhancement amplitude were recorded. The data were compared with the clinical diagnosis according to biopsy in 8 patients and surgery in 6 patients. In the remaining 16 patients, the clinical diagnosis was obtained by clinical or radiological follow-up. DCEMRI did not improve the diagnostic information compared with CEMRI. None of the examined parameters were found to help discriminating malignant from benign changes. Characterisation of lesions in the pelvis after rectal cancer surgery was not improved by a dynamic gadolinium-enhanced sequence.

Adult↗

PubMed1998

Gender differences and the Defense Mechanism Test: a comparative study of adolescents in psychiatric care and healthy controls.

The aim of this paper was to study gender differences in the percept-genetic method Defense Mechanism Test (DMT) among a group of 60 adolescent subjects. Three subgroups were used: patients with psychotic disorders (Axis 1); borderline personality disorder (Axis 2) according to the DSM-IV classification system, and a non-patient group. The test protocols were scored with respect to 124 DMT variables and analyzed by means of the multivariate projection method Partial Least Squares (PLS) in latent structures. The overall results showed considerable gender differences in the whole group as well as in the subgroups. The most striking finding was that girls compared to boys were characterized by the perceptual defense identification with the opposite sex, which means that they perceived male gestalts instead of females in the stimulus picture. When both gender and diagnostic group membership were considered simultaneously, the influence of diagnostic group membership seemed to be stronger than gender even if there was an interaction between diagnoses and gender. It was concluded that gender must be considered when the DMT is used on adolescent populations.

Adolescent↗