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Biomedical subjects

S Savolainen

Publications and source records attributed to S Savolainen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Auditory event-related potentials differentiate patients with normal pressure hydrocephalus and patients with concomitant Alzheimer's disease verified by brain biopsy.

We studied 51 patients with clinical symptoms and CT findings suggesting normal pressure hydrocephalus (NPH). Tests included head MRI, auditory event-related potentials (ERPs), thorough neuropsychological testing and intraventricular intracranial 24 h pressure recording and infusion testing. A brain biopsy was also obtained to verify a concomitant dementing process (Alzheimer's disease; AD). Patients were divided into subgroups according to the need of shunt and the biopsy findings, and their ERPs were analysed blindly. The present results suggest that non-invasive ERPs aid in the differentiation of pure NPH from NPH with concomitant AD.

Aged↗
PubMed2001

Contextual clustering for analysis of functional MRI data.

We present a contextual clustering procedure for statistical parametric maps (SPM) calculated from time varying three-dimensional images. The algorithm can be used for the detection of neural activations from functional magnetic resonance images (fMRI). An important characteristic of SPM is that the intensity distribution of background (nonactive area) is known whereas the distributions of activation areas are not. The developed contextual clustering algorithm divides an SPM into background and activation areas so that the probability of detecting false activations by chance is controlled, i.e., hypothesis testing is performed. Unlike the much used voxel-by-voxel testing, neighborhood information is utilized, an important difference. This is achieved by using a Markov random field prior and iterated conditional modes (ICM) algorithm. However, unlike in the conventional use of ICM algorithm, the classification is based only on the distribution of background. The results from our simulations and human fMRI experiments using visual stimulation demonstrate that a better sensitivity is achieved with a given specificity in comparison to the voxel-by-voxel thresholding technique. The algorithm is computationally efficient and can be used to detect and delineate objects from a noisy background in other applications.

Algorithms↗
PubMed2001

Application of the new MultiTrans SP3 radiation transport code in BNCT dose planning.

Dose planning in boron neutron capture therapy (BNCT) is a complex problem and requires sophisticated numerical methods. In the framework of the Finnish BNCT project, new deterministic three-dimensional radiation transport code MultiTrans SP3 has been developed at VTT Chemical Technology, based on a novel application of the tree multigrid technique. To test the applicability of this new code in a realistic BNCT dose planning problem, cylindrical PMMA (polymethyl-methacrylate) phantom was chosen as a benchmark case. It is a convenient benchmark, as it has been modeled by several different codes, including well-known DORT and MCNP. Extensive measured data also exist. In this paper, a comparison of the new MultiTrans SP3 code with other methods is presented for the PMMA phantom case. Results show that the total neutron dose rate to ICRU adult brain calculated by the MultiTrans SP3 code differs less than 4% in 2 cm depth in phantom (in thermal maximum) from the DORT calculation. Results also show that the calculated 197Au(n,gamma) and 55Mn(n,gamma) reaction rates in 2 cm depth in phantom differ less than 4% and 1% from the measured values, respectively. However, the photon dose calculated by the MultiTrans SP3 code seems to be incorrect in this PMMA phantom case, which requires further studying. As expected, the deterministic MultiTrans SP3 code is over an order of magnitude faster than stochastic Monte Carlo codes (with similar resolution), thus providing a very efficient tool for BNCT dose planning.

Adult↗
PubMed2000

Transmission imaging for registration of ictal and interictal single-photon emission tomography, magnetic resonance imaging and electroencephalography.

A method developed for registration of ictal and interictal single-photon emission tomography (SPET), magnetic resonance imaging (MRI) and electroencephalography (EEG) is described. For SPET studies, technetium-99m ethyl cysteinate dimer (ECD) was injected intravenously while the patient was monitored on video-EEG to document the ictal or interictal state. Imaging was performed using a triple-head gamma camera equipped with a transmission imaging device using a gadolinium-153 source. The images (128x128 pixels, voxel size 3.7x3.7x3.6 mm3) were reconstructed using an iterative algorithm and postfiltered with a Wiener filter. The gold-plated silver electrodes on the patient's scalp were utilized as markers for registration of the ictal and interictal SPET images, as these metallic markers were clearly seen on the transmission images. Fitting of the marker sets was based on a non-iterative least squares method. The interictal SPET image was subtracted from the ictal image after scaling. The T1-weighted MPRAGE MR images with voxel size of 1.0x1.0x1.0 mm3 were obtained with a 1.5-T scanner. For registration of MR and subtraction SPET images, the external marker set of the ictal SPET study was fitted to the surface of the head segmented from MR images. The SPET registration was tested with a phantom experiment. Registration of ictal and interictal SPET in five patient studies resulted in a 2-mm RMS residual of the marker sets. The estimated RMS error of registration in the final result combining locations of the electrodes, subtraction SPET and MR images was 3-5 mm. In conclusion, transmission imaging can be utilized for an accurate and easily implemented registration procedure for ictal and interictal SPET, MRI and EEG.

Adolescent↗
PubMed2000

Comparison of ultrasound, radiography, and clinical examination in the diagnosis of acute maxillary sinusitis: a systematic review.

The objective of this study was to assess the discriminative properties of the methods for diagnosing acute maxillary sinusitis (AMS) in unselected patients. The study design was a systematic review of evaluation studies identified by using Medline, by searching reference lists, by hand searches, and by contacting investigators. Evaluation studies were conducted anywhere in the world. Subjects were adults with suspected AMS. Main outcome measures were: sensitivity, specificity, positive and negative likelihood ratios of the primary studies, weighted means of these parameters in each comparison (clinical examination, radiography, and ultrasound compared to a reference standard in diagnosing AMS), and summary ROC curves and their Q* points where sensitivity equals specificity. For the years from 1962 to present, 49 study reports were found; 11 articles on studies that included a total of 1144 patients were eligible. Compared to sinus puncture, radiography was the most accurate method for diagnosing AMS: the Q* point on the summary ROC curve was 0.82 (95% confidence interval, CI, 0.78-0.85). Ultrasound was slightly less accurate than radiography compared to sinus puncture (Q* 0.80, 95% CI 0.76-0.83). Only two articles reported clinical examination compared to sinus puncture and the Q* for them was 0.75 (95% 0.58-0.86). Clinical examination is a rather unreliable method for diagnosing AMS, even in the hands of experienced specialists. Using radiography or ultrasound improves the accuracy of diagnosis. The diagnosis of AMS is rarely studied in primary care settings. Future comparative trials should preferably combine diagnosis and treatment, evaluating the two aspects of clinical management as unit.

Acute Disease↗
PubMed2000

MR imaging of the hippocampus in normal pressure hydrocephalus: correlations with cortical Alzheimer's disease confirmed by pathologic analysis.

BACKGROUND AND PURPOSE: MR studies have shown hippocampal atrophy to be a sensitive diagnostic feature of Alzheimer's disease (AD). In this study, we measured the hippocampal volumes of patients with a clinical diagnosis of normal pressure hydrocephalus (NPH), a potentially reversible cause of dementia when shunted. Further, we examined the relationship between the hippocampal volumes and cortical AD pathologic findings, intracranial pressure, and clinical outcomes in cases of NPH. METHODS: We measured hippocampal volumes from 37 patients with a clinical diagnosis of NPH (27 control volunteers and 24 patients with AD). The patients with NPH underwent biopsy, and their clinical outcomes were followed for a year. RESULTS: Compared with those for control volunteers, the findings for patients with NPH included a minor left-side decrease in the hippocampal volumes (P < .05). Compared with those for patients with AD, the findings for patients with NPH included significantly larger hippocampi on both sides. Although not statistically significant, trends toward larger volumes were observed in patients with NPH who had elevated intracranial pressure, who benefited from shunting, and who did not display cortical AD pathologic findings. CONCLUSIONS: Measurements of hippocampal volumes among patients with a clinical diagnosis of NPH have clear clinical implications, providing diagnostic discrimination from AD and possibly prediction of clinical outcome after shunting.

Aged↗
PubMed2000

Noise attenuation of hearing protectors against heavy weapon noise.

This study evaluated the noise attenuation of earplugs and earmuffs or their combined use against heavy weapon noise in field conditions for military personnel. The noise attenuation was measured with a miniature microphone inserted into the ear canal. The subjects (13) were tested against pink noise and against the noise of explosions and bazooka, mortar, cannon, and howitzer. The attenuation (insertion loss) was 16 to 23 dB for earplugs, 10 to 20 dB for earmuffs, and 24 to 34 dB for the combined use of plugs and muffs. The transfer function of an open ear was 5 to 7 dB when measured as the C-weighted peak level. The combined use of earplugs and earmuffs gave smaller attenuation values than expected. If the limit for the C-weighted peak level is 140 dB for unprotected ears, then protection against low-frequency noise is provided for up to 156 dB by earplugs, up to 150 dB by earmuffs, and up to 165 dB by the combined use of plugs and muffs.

Ear Protective Devices↗
PubMed1999

Prevalence of Alzheimer's disease in patients investigated for presumed normal pressure hydrocephalus: a clinical and neuropathological study.

During 1991-1995, 223 patients were investigated in the Department of Neurosurgery, Kuopio University Hospital because of a clinical and CT diagnosis of NPH. All patients underwent intracranial pressure measurements and were formed into 3 biopsy groups. Group A included incidentally biopsied patients (104 patients, 34 biopsies) seen during 1991-1992; Group B was a prospective study group from 1993-1995 (all 51 patients biopsied); and Group C patients excluded from Group B (68 patients, 34 biopsies) by age and concomitant diseases. A cortical biopsy was taken before intracranial pressure recording altogether in 118 of the 223 patients. The biopsy revealed normal brain tissue in 66 patients. Prevalence of Alzheimer's disease (AD) in biopsied patients was 42% in Group A, 31.3% in Group B and 50% in Group C. A shunt was placed according to pressure measurement in 110 patients; of these, 8 had both AD and raised ICP. Two patients with both AD and raised ICP improved after shunt placement during the first follow-up year, 4 patients deteriorated and the condition of 2 was similar to that before shunting. The frequency of haematomas after biopsy was 2.9% in groups A and C; in Group B patients had no postoperative haematomas. There was no difference in the incidence of complications in patients who had or did not have a biopsy. The relatively high prevalence of AD in patients with NPH may explain the unsuccessful recovery of many patients after shunt placement. Cortical biopsy is an effective and safe method for finding the co-existence of AD and thus improving the diagnosis of NPH and may prevent unnecessary shunt surgery.

Aged↗
PubMed1999

111In-labelled bleomycin complex for the differentiation of high- and low-grade gliomas.

The aim of this study was to evaluate 111In-labelled bleomycin complex (111In-BLMC) SPET in the differentiation of high- and low-grade gliomas. Nineteen glioma patients, 14 with high-grade and five with low-grade tumours, were studied 1, 4 and 24 h after the injection of 111In-BLMC. In the high-grade glioma group, there was significant uptake of 111In-BLMC in 12 patients and no uptake in two patients based on the visual classification of SPET images at 4 and 24 h. In the low-grade glioma group, one patient had low uptake at 4 and 24 h, but the other four patients showed no visible uptake. The mean tumour to extracerebral circulation activity ratio (T/Cr) at 4 h was 0.13 +/- 0.10 (n = 5) in low-grade gliomas and 1.7 +/- 1.0 (n = 14) in high-grade gliomas. At 24 h the T/Cr ratios were 0.56 +/- 0.21 and 3.4 +/- 1.7, respectively. The mean tumour to contralateral normal brain activity ratios (T/Br) were 5.0 +/- 3.9 (4 h) and 3.0 +/- 2.8 (24 h) in low-grade gliomas, and 37.2 +/- 37.3 (4 h) and 8.3 +/- 8.2 (24 h) in high-grade gliomas. These higher T/Br ratios did not, however, result in improved differentiation between the two groups of gliomas; at 4 h the T/Cr and T/Br ratios were of equal value, as two high-grade gliomas would have been misclassified as low-grade, but at 24 h the T/Br ratio resulted in more misclassifications. Our results show that 111In-BLMC can be used in the differentiation of high- and low-grade gliomas and that the selection of the reference area for calculating tumour to non-tumour ratios is important.

Adult↗
PubMed1999

Low-altitude overflights of fighters and the risk of hearing loss.

BACKGROUND AND OBJECTIVE: Much data are available on noise properties which cause hearing loss. There are not, however, reports on the effects of low-altitude overflight noise on the permanent threshold shift (PTS). METHODS: Low-altitude overflight noise generated by the Finnish Air Force's jet fighters and an advanced jet trainer was measured with flight distances varying from 50-310 m from the measurement point. The aircraft were always subsonic, velocities being usually 0.9 Mach or less. The measurements were undertaken because of two claims for the compensation of hearing loss caused by overflights of jet fighters on cross-country training missions. RESULTS: Peak noise levels (LCpeak) varied from 109-150 dB depending on aircraft type and the use of afterburner. The 1-s single A-weighted exposure levels (ASEL) during these overflights were 95-135 dB which correspond to daily (8 h) exposure levels of 50-90 dB. CONCLUSIONS: According to these results and the principles of noise evaluation, there should be no risk of permanent hearing loss when the distance to an overflying jet fighter is more than 200 m. However, we have received two claims, and the audiometric analyses of two subjects who had suffered hearing loss in one ear in Finland during the 1990s may indicate that there is very likely a connection between the incidents and the hearing losses.

Acceleration↗
PubMed1999

Influence of strict regulations on the use of hearing protectors in the Finnish Defence Forces.

The regulations concerning hearing protection during military training in the Finnish Defence Forces were renewed in 1989. The material of this prospective study concerns 912 consecutive conscripts (463 before and 449 after the new regulations) who were referred to the Central Military Hospital for acute acoustic trauma (AAT). We focused on three issues: (1) general habits regarding the use of hearing protection during shooting drills and combat training; (2) hearing protection at the moment of AAT; and (3) the cause of AAT. In combat training, the use of any hearing protectors was only 50% before the new regulations, but after they came into force the proportion was greater than 90%, and more effective protectors were used. However, at the time of AAT the hearing protection was absent in more than 80% of cases in both groups. The most common cause of AAT was small arms in both groups (83%).

Adult↗
PubMed1998

Comparative immunohistochemical study of group II (synovial-type) and group IV (cytosolic) phospholipases A2 in disc prolapse tissue.

Phospholipase A2 (PLA2) has been suggested to be present in herniated disc tissue and it could possibly be involved in sciatica/ discogenic back pain mechanisms. In the present study the occurrence of two different phospholipase A2 enzymes, (1) low molecular weight (14 kDa) group II synovial-type (sPLA2) and (2) high molecular weight (85 kDa) group IV cytosolic (cPLA2), were compared. Fifty-three disc prolapses obtained at disc operations were analyzed by immunohistochemistry, using anti-human monoclonal antibodies to sPLA2 and cPLA2, respectively. Only cell-associated (disc cells, hyaline cartilage chondrocytes) sPLA2 and cPLA2 immunoreactivity could be observed. The results showed that sPLA2 was more common (25/53, 47%) than cPLA2 (13/53, 25%). sPLA2 and cPLA2 were simultaneously present in 13 of 53 samples (25%). However, both PLA2 enzymes were predominantly present in hyaline cartilage cells (sPLA2: 16/53, cPLA2: 5/53), being less commonly observed in disc cells (sPLA2: 6/53, cPLA2: 3/53). In addition, three samples for sPLA2 and two samples for cPLA2 exhibited immunoreactivity in cartilage and disc cells simultaneously. sPLA2 was observed in no other locations, but in 3 of 53 samples cPLA2 was observed more diffusely in areas of granulation tissue, possibly in macrophages. No gender- or age-related dependence for either type of PLA2 enzyme immunoreactivity could be observed. Neither did their occurrence relate to clinical data such as straight leg raising or neurological deficit. The results do not support a major role for either of the two disc-cell-associated PLA2s in disc pathophysiology. For both enzymes, the major pool appears to reside in cartilage tissue cells, presumably in dislodged end-plate fragments. Disc cells are apparently unlikely candidates for major PLA2 storage.

Adult↗
PubMed1998

Multiphase segmented k-space velocity mapping in pulsatile flow waveforms.

The aim of the present study was to obtain the precision of flow measurement in breath-hold segmented k-space flow sequences. The results are based on studies of pulsatile flow in a phantom tube. The ultimate purpose is to use these sequences to measure coronary flow. In abdominal and cardiothoracic magnetic resonance imaging the image quality is degraded due to respiratory motion. In the segmented k-space acquisition method, one obtains many phase-encoding steps or views per cardiac phase. This shortens imaging time in the order of phase-encoding lines and makes it possible to image in a single breath-hold, thereby eliminating respiratory artefacts and improving edge detection. With breath-hold multiframe cine flow images it is possible to evaluate flow in all abdominal and cardiothoracic areas, including the coronary arteries. Our study shows that velocity curves shift in time when the number of k-space ky-lines per segment (LPS) are varied; this shift is linear as a function of LPS. The mean velocity Vmean in the center of mass of the pulsatile peak is constant (Vmean = 40.1 +/- 2.9 cm/s) and time t = -10.1 x LPS + 268 (r = 0.993, p < 0.0001). Correlation between theoretical and experimental flow curves is also linear as a function of LPS: C = -0.977 * LPS (r = 0.987, p < 0.0001). It is concluded that velocity curves move with LPS and are smoothed when the breath-hold velocity mapping is used. The more LPS is gathered the more inaccurate results are. LPS 7 or more cannot be considered clinically relevant.

Artifacts↗
PubMed1998

A prospective randomized study of anterior single-level cervical disc operations with long-term follow-up: surgical fusion is unnecessary.

OBJECTIVE: After 40 years of experience with anterior cervical operations, whether to fuse is still controversial. This study seeks to answer this question. METHODS: In this prospective randomized study, we operated on 91 patients with single-level cervical root compression using three different methods: 1) discectomy without fusion, 2) fusion with autologous bone graft, and 3) fusion with autologous bone graft plus plating. RESULTS: After 4 years of follow-up, the radiological results indicated that complete bony union was achieved in almost all cases. A slight kyphosis developed in 62.5% of the patients who had undergone discectomy, 40% of the patients who had undergone fusion, and 44% of the patients who had undergone fusion plus plating (not significant). The clinical outcomes were good for 76% of the patients who had undergone discectomy, 82% who had undergone fusion, and 73% who had undergone fusion plus plating. The outcomes were poor in 0, 4, and 4%, respectively (not significant). CONCLUSION: According to this study, satisfactory results can be achieved by performing simple discectomy to treat single-level cervical root compressive disease.

Adult↗
PubMed1998

Future developments in nuclear medicine instrumentation: a review.

This review article forecasts developments in nuclear medicine instrumentation which are on the horizon. Special attention is paid to the physical properties of detectors and multiple-processor parallel processing systems needed for fast and high-quality imaging in emission tomography. Advances in detector technology will improve imaging resolution below 5 mm and will increase sensitivity and quantitative accuracy. In addition, high count rate list-mode acquisition enables 'true' four-dimensional data-sets. A sandwich-like construction of two different crystals allows the simultaneous use of conventional tracers and positron tracers (multiple emission tomography, MET). Transmission-based attenuation and scatter compensation with fast iterative reconstruction methods will further improve image quality. The clinical and scientific importance of improved images and the limits on advances in instrumentation are also reviewed.

Equipment Design↗