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Biomedical subjects

T Lahtinen

Publications and source records attributed to T Lahtinen.

At least 19 recordsLinked to original sources
PubMed2006

Measurement of oedema in irritant-exposed skin by a dielectric technique.

BACKGROUND: Easily applicable water-specific instruments measuring local oedema in skin are not available. The aim of this study is to demonstrate quantitative assessment of skin oedema with the dielectric technique by measuring increase of skin water content related to sodium lauryl sulphate (SLS)-induced irritant contact dermatitis. METHODS: Irritant skin reaction and resulting oedema were induced by an irritant patch test on volar forearms in 12 healthy volunteers with the application of 1% SLS for 6 h. After occlusion the volunteers were divided into two groups: the patch test site of group I (six volunteers) received no treatment other than a base cream for the skin reaction, while for group II (six volunteers) a strong corticosteroid (clobetasol propionate) was applied on the irritant skin. During a follow-up of 72 h, erythema was scored visually, and irritant-induced oedema was measured with a novel water-specific instrument MoistureMeter-D. RESULTS: In the untreated irritant skin, a maximum increase of 45% in skin water content was found at 10 h postocclusion and water content was still elevated at 72 h. With these persons, the degree of oedema agreed well with the ultrasound-measured skin thickness (P=0.053). In the corticosteroid-treated skin, an increase of 8% in water content was measured during 72 h but there was no correlation between oedema and skin thickness. There was no correlation between erythema and oedema in untreated or corticosteroid-treated skin. CONCLUSION: The new instrument can easily be applied for noninvasive quantitative evaluation of local oedema and fluid retention in irritant-exposed skin.

Adult↗
PubMed2005

Red blood cell and tissue water content in experimental thermal injury.

UNLABELLED: Oedema formation and changes in local blood flow are known phenomena in burns. The relationship between these two is not clearly described. The aim of this study was firstly to examine both the contents of red blood cells and tissue water in skin and subcutaneous fat after experimental burns of different depths in pigs, and secondly, to confirm our recent findings of the increased dielectric constant of skin and subcutaneous fat reflecting considerable oedema formation, especially in fat after thermal injury. METHODS: Superficial, partial and full thickness contact burns were created to pigs and followed for 24h. Radioactive Cr-51 labelling of red cells was used to estimate the number of red cells in tissue, and the absolute amount of water was determined by lyophilization. RESULTS: A decreased number of labelled red cells in skin and an increase in tissue water in subcutaneous fat were found regardless of burn depth. The highest water amount in fat was found in the partial thickness burns. CONCLUSION: All burn depths resulted in a diminished number of labelled red blood cells in skin and a significant increase in the absolute water amount in subcutaneous fat at 24h post injury. The findings in fat support our recent findings of highly elevated dielectric constants measured by the new in vivo method of dielectric measurements.

Adipose Tissue↗
PubMed2005

Microdialysis for detection of dynamic changes in tissue histamine levels in experimental thermal injury.

Histamine is an important mediator contributing to oedema formation after thermal injury. Tissue histamine concentrations have been previously determined by analyzing tissue biopsies. The microdialysis method enables continuous collection of samples from the extracellular tissue fluid. In this experimental burn study on pigs samples from the extracellular fluid for histamine analysis were collected from superficial, partial thickness and full thickness burn sites during a 24-h period. There was a burn depth-related increase in histamine concentrations during the first 2 h post injury. Deep burns induced a more profound initial increase in tissue histamine concentration than the partial thickness and superficial burns. Histamine concentrations at all burn sites declined until 12 h post injury. There was a second rise in tissue histamine concentrations between 12 and 24 h post injury without a rise in plasma histamine concentrations. Histamine concentrations at all burn sites were higher than at the non-burned control sites. The microdialysis technique is an easily applicable method of collecting on-line samples from burned tissue. This method provides a useful tool in investigating the effects of different treatment modalities on the secretion of substances into interstitial fluid within burned tissue.

Animals↗
PubMed2004

The progression of burn depth in experimental burns: a histological and methodological study.

UNLABELLED: This study was designed to create a reproducible model for experimental burn wound research in pigs. Previously, the thicker paraspinal skin has been used. We used the more human-like ventral skin to create burns of different depths. Contact burns were created to 11 pigs using a brass plate heated to 100 degrees C in boiling water. Different contact times were used to create burns of different depths. In pigs 1-6, the follow-up time was 72 h and in pigs 7-11 24 h. Burn depth was determined by histology. Histologically, samples were classified into five anatomical layers: epidermis, upper one-third of the dermis, middle third of the dermis, deepest third of the dermis and subcutaneous fat. The location of both thromboses and burn marks were evaluated, respectively. The 1 s contact time lead to a superficial thermal injury, 3 s to a partial thickness and 9 s to a full thickness injury. A progression of burn depth was found until 48 h post-injury. The intra-observer correlation after repeated histological analyses of burn depths by the same histopathologist and the repeatability of burn depth creation yielded kappa coefficients 0.83 and 0.92, respectively. CONCLUSION: a reproducible burn model for further research purposes was obtained.

Animals↗
PubMed2004

Validation of a new dielectric device to assess changes of tissue water in skin and subcutaneous fat.

Easily applicable and inexpensive water-specific techniques to evaluate local oedema, swollen tissue problems and fluid retention in humans are not available. In the present investigation a recently constructed non-invasive device for a local measurement of changes in tissue water in human skin and subcutaneous fat (SSF) was validated. The instrument transmits an ultra high-frequency electromagnetic (EM) wave of 300 MHz into a coaxial line and further into an open-ended coaxial probe which is in contact with the skin. Due to the dimensions of the applied probe the penetration of the EM field extends to subcutaneous fat. A major part of the EM energy is absorbed by tissue water while the rest is reflected back into a coaxial line. From the information of the reflected wave an electrical parameter, directly proportional to tissue water content, called a dielectric constant of SSF, was calculated. For system validation, the decrease of water content in SSF measured with the dielectric technique in the volar forearm of seven patients during haemodialysis treatment was compared with the decrease of the circumference of the forearm and the amount of fluid removed. Statistically highly significant correlations were obtained between the decreasing dielectric constant (i.e. water content) of the SSF and the fluid removed during haemodialysis treatment (r = -0.99, p < 0.01) and between the decreasing dielectric constant and the circumference of the arm (r = 0.97, p < 0.05). The sensitivity of the dielectric method was four-fold compared with the circumferential measurement. The repeatability 3.0% was not dependent on the phase of haemodialysis. The new device allows an easy and non-invasive measurement technique to assess changes of tissue water in SSF.

Adipocytes↗
PubMed2003

Changes in abdominal subcutaneous fat water content with rapid weight loss and long-term weight maintenance in abdominally obese men and women.

OBJECTIVE: Insulin resistance decreases blood flow and volume in fat tissue. We hypothesised that fat tissue nutritive blood flow and volume, and thereby water content, would increase during weight loss and weight maintenance in obese persons. DESIGN: Longitudinal clinical intervention with a 9-week very-low-calorie diet (VLCD) followed by one year of weight maintenance. SUBJECTS: Obese men (n=13) and women (n=14) with the metabolic syndrome. MEASUREMENTS: Water content of abdominal subcutaneous fat tissue as estimated by a sensor on the skin surface measuring the dielectric constant at 300 MHz. Anthropometric measures of fatness and fat distribution. Biochemical measures related to insulin resistance. RESULTS: Subjects lost 14.5+/-3.4% of body weight during the VLCD, and generally sustained this weight loss during weight maintenance. Insulin sensitivity as estimated by an index (qualitative insulin sensitivity check index) increased during the VLCD, and remained increased throughout weight maintenance. The dielectric constant increased from 23.3+/-2.3 to 25.0+/-2.1 (P<0.001) during the VLCD, and further to 27.8+/-1.9 (P<0.001) during weight maintenance, indicating an increase in the water content of subcutaneous fat. The increase in subcutaneous fat water content did not correlate with weight loss and other measures of adiposity during the VLCD, but there was an inverse correlation that strengthened in significance from baseline to 6, 9 and 12 mo (r=-0.32 to -0.64, P=0.079-0.002). Increases in subcutaneous fat water content also correlated with improvements in insulin sensitivity at 6, 9 and 12 months of weight maintenance (r=0.34-0.54, P=0.094-0.006). CONCLUSIONS: Water content of abdominal subcutaneous adipose tissue increases with weight loss in obese persons with the metabolic syndrome, and may reflect increased subcutaneous fat tissue nutritive blood flow. The increase in water content correlates with the increase in insulin sensitivity, suggesting that weight loss and consequent improved insulin sensitivity could mediate the increase in abdominal subcutaneous fat hydration.

Abdomen↗
PubMed2001

Brachial arterial access: endovascular treatment of failing Brescia-Cimino hemodialysis fistulas--initial success and long-term results.

PURPOSE: To evaluate safety and efficacy of endovascular interventions in failing antebrachial Brescia-Cimino hemodialysis fistulas in consecutive patients. MATERIALS AND METHODS: Altogether, 103 interventions were performed in 53 Brescia-Cimino shunts in 51 patients by means of antegrade brachial arterial access. Twelve interventions were initiated with pharmacomechanical thrombolysis and/or thromboaspiration. All interventions included balloon angioplasty that was completed with stent placement in eight cases and with endovascular brachytherapy with an iridium 192 source in five cases. RESULTS: The technical success rate of the primary interventions was 92% (49 of 53) and that for all interventions was 95% (98 of 103). The rate of major complications was 4% (four of 103). Clinical success was achieved in 92% (95 of 103) of the interventions. By including the initial failures, 58% +/- 7 (standard error of the estimate), 44% +/- 8, 40% +/- 8, and 32% +/- 10 primary and 90% +/- 5, 85% +/- 5, 79% +/- 7, and 79% +/- 7 secondary clinical patency rates were registered at 6 months and 1, 2, and 3 years, respectively, by means of Kaplan-Meier analysis. The location of the main treated lesion at the arteriovenous anastomosis (P =.03) was a predictor of poorer long-term patency. CONCLUSION: Endovascular interventions with antegrade brachial arterial access are highly effective in restoring function in failing Brescia-Cimino fistulas.

Adult↗
PubMed2001

Effects of mobile phone radiation on X-ray-induced tumorigenesis in mice.

The increased use of mobile phones has raised the question of possible health effects of such devices, particularly the risk of cancer. It seems unlikely that the low-level radiofrequency (RF) radiation emitted by them would damage DNA directly, but its ability to act as a tumor promoter is less well characterized. In the current study, we evaluated the effect of low-level RF radiation on the development of cancer initiated in mice by ionizing radiation. Two hundred female CBA/S mice were randomized into four equal groups at the age of 3 to 5 weeks. The mice in all groups except the cage-control group were exposed to ionizing radiation at the beginning of the study and then to RF radiation for 1.5 h per day, 5 days a week for 78 weeks. One group was exposed to continuous NMT (Nordic Mobile Telephones)-type frequency-modulated RF radiation at a frequency of 902.5 MHz and a nominal average specific absorption rate (SAR) of 1.5 W/kg. Another group was exposed to pulsed GSM (Global System for Mobile)-type RF radiation (carrier-wave frequency 902.4 MHz, pulse frequency 217 Hz) at a nominal average SAR of 0.35 W/kg. The control animals were sham-exposed. Body weight, clinical signs, and food and water consumption were recorded regularly. Hematological examinations and histopathological analyses of all lesions and major tissues were performed on all animals. The RF-radiation exposures did not increase the incidence of any neoplastic lesion significantly. We conclude that the results do not provide evidence for cancer promotion by RF radiation emitted by mobile phones.

Animals↗
PubMed2000

Radiobiological depth of subcutaneous induration.

The incidence of subcutaneous induration in 23 breast cancer patients with postmastectomy radiotherapy was investigated. The patients were treated with three different radiotherapy schedules 7. 9-9.8 years ago. The incidence was correlated with the biological effective dose (BED) at different depths from the skin surface and a best fit was obtained using an alpha/beta ratio of 2 Gy. The most representative depth at which to assess dose for subcutaneous induration was 2 mm which is near the subcutaneous fat/dermis interface.

Aged↗
PubMed1999

Quantitative assessment of protein content in irradiated human skin.

PURPOSE: Radiation-induced fibrosis is a common late reaction of radiation therapy. Due to a lack of feasible noninvasive techniques to assess this reaction, the long-term development of radiation fibrosis is not well described. In order to develop quantitative means for the purpose, subcutaneous fibrosis of breast cancer patients after postmastectomy radiotherapy was evaluated by clinical scoring and a new technique based on dielectric properties of the skin. METHODS AND MATERIALS: Dielectric properties of biological tissues at radiofrequencies are principally determined by tissue water content. The major skin components are proteins, proteoglycans, and water either free or bound to the surface of proteins and proteoglycans. Since the MR studies have shown that bound water is tightly attached onto the surface of collagen, a dielectric measurement sensitive to bound water could be related to the protein content. Therefore, the dielectric constant of human skin was measured in vivo with an open-ended coaxial probe at electromagnetic (EM) frequencies in the range of delta-dispersion. Since the in vitro experiments with protein-water solutions have indicated that the slope of the dielectric constant vs. the EM frequency is a measure of the protein concentration, a respective slope was determined with irradiated skin of 14 breast cancer patients 2 years after postmastectomy radiotherapy at 63, 100, 300, and 500 MHz. Irradiated skin sites were clinically scored for subcutaneous fibrosis using a scale: none, slight, moderate, or severe fibrosis. RESULTS: A statistically significant correlation was found between the slope and the clinical score of subcutaneous fibrosis at 63, 100, and 300 MHz but not at 500 MHz. The correlation was best at 100 and 300 MHz. CONCLUSIONS: Considerable changes in the dielectric constant of the irradiated skin were found. The correlation between the dielectric constant and clinical score suggests that this novel technique is a potential tool for the follow-up and quantitative assessment of radiation-induced subcutaneous fibrosis.

Adult↗
PubMed1999

Penetration of electromagnetic fields of an open-ended coaxial probe between 1 MHz and 1 GHz in dielectric skin measurements.

An open-ended coaxial probe is often used for investigating the dielectric properties of biological tissues. The present study indicates that in addition to the probe size, the penetration of the electromagnetic (EM) fields of an open-ended coaxial probe in contact with the skin is dependent on the applied frequency between 1 MHz and 1 GHz. At high frequencies, above 100 MHz, the measured dielectric parameters are functions of the dielectric properties of different cutaneous layers and subcutaneous fat. At lower frequencies, less than 10 MHz, the measurement is mainly dependent on the dielectric properties of superficial structures of the skin. The reason for this is that the probe, the surface of the skin, mainly stratum corneum, and underlying skin form a capacitance where the stratum corneum with low water content lies between the well-conducting dermis and the probe. The situation is equivalent to the frequency-dependent Maxwell-Wagner interfacial polarization. This result is verified by experimental dielectric measurements and with human skin in vivo.

Electromagnetic Fields↗
PubMed1998

Different patterns of DNA copy number changes in gastrointestinal stromal tumors, leiomyomas, and schwannomas.

It is not uniformly agreed whether gastrointestinal stromal tumors (GISTs) are phenotypical variants of leiomyomas (cellular leiomyomas) or whether they represent a separate, genotypically definable entity. In an attempt to solve this question, we examined immunohistochemically defined leiomyomas from the esophagus and uterus, gastric schwannomas, and benign gastrointestinal stromal tumors (GIST) by comparative genomic hybridization (CGH). All 14 leiomyomas (nine esophageal, five uterine) were actin- and desmin-positive but negative for CD34 and S100-protein. Changes in DNA copy numbers were seen only in three esophageal leiomyomas. Gains were observed in chromosomes 3, 4, 5, 8, and 17, whereas losses were seen in 16p. All schwannomas were positive for S100-protein and negative for actin, desmin, and CD34. In schwannomas, the only change by CGH was a gain in 11q in one case. The benign GISTs, all from the stomach, were positive for CD34 but negative for desmin and S100-protein; two cases were positive for actin. The CGH findings in the GISTs differed markedly from those in leiomyomas and schwannomas. Ten of the 13 cases (77%) showed DNA copy number losses in 14q, and additional or other losses were found in eight cases, most often in chromosome 22 (seven cases), 15 (three cases), and 1p (two cases). Furthermore, two of the GISTs showed gains in 5q. These results indicate that phenotypically undifferentiated GISTs are also genetically different from leiomyomas and schwannomas and support their classification apart from leiomyomas.

Actins↗
PubMed1998

A dielectric method for measuring early and late reactions in irradiated human skin.

BACKGROUND AND PURPOSE: To measure the dielectric constant of irradiated human skin in order to test the feasibility of the dielectric measurements in the quantitation of acute and late radiation reactions. MATERIALS AND METHODS: The dielectric constant of irradiated breast skin was measured at an electromagnetic frequency of 300 MHz in 21 patients during postmastectomy radiotherapy. The measurements were performed with an open-ended coaxial line reflection method. The irradiation technique consisted of an anterior photon field to the lymph nodes and a matched electron field to the chest wall using conventional fractionation of five fractions/week to 50 Gy. Fourteen out of the 21 patients were remeasured 2 years later and the skin was palpated for subcutaneous fibrosis. RESULTS: At 5 weeks the dielectric constant had decreased by 31 and 39% for the investigated skin sites of the photon and electron fields, respectively. There was a statistically significant inverse correlation between the mean dielectric constant and the clinical score of erythema. An unexpected finding was a decrease of the dielectric constant of the contralateral healthy skin during radiotherapy. Two years later a statistically significant positive correlation was found between the dielectric constant at the irradiated skin sites and the clinical score of subcutaneous fibrosis. CONCLUSIONS: Dielectric measurements non-invasively yield quantitative information concerning radiation-induced skin reactions.

Adult↗
PubMed1998

Demonstration of increased collagen synthesis in irradiated human skin in vivo.

Fibrosis is a common side-effect of radiation therapy. As a complex network of cytokines and other mediators plays a central role in the process leading to fibrosis, we used an in vivo method to measure skin collagen synthesis, taking into account the physiological conditions. We determined suction blister (i.e. interstitial) fluid concentrations of types I and III procollagen propeptides, reflecting types I and III collagen synthesis, in irradiated and unirradiated skin of breast cancer patients 1-5 years after surgery and radiation therapy, hence using the patients as their own controls. The mean concentrations of the measured collagen markers were approximately two times higher in the irradiated skin than in the unirradiated contralateral breast skin. The difference slowly diminishes with time. These results indicate that abundant collagen synthesis in the irradiated skin continues several years after discontinuation of the radiation therapy, leading to fibrosis. The method outlined here offers a new in vivo perspective to study events leading to radiation fibrosis.

Aged↗
PubMed1998

Measurement of dielectric properties of subcutaneous fat with open-ended coaxial sensors.

A three-layer model of stratum corneum, epidermis/dermis and subcutaneous fat has been developed for the capacitance of an open-ended coaxial line in contact with human skin. Applying the model, the electrical properties of subcutaneous fat can be calculated from skin dielectric measurements with three probes of different sizes. The three-layer model is based on a variational formula for the capacitance of the coaxial probe. An accurate approximation for the dielectric constant of the multilayer cutaneous structure is presented for the inverse problem of solving the dielectric constants of various layers. The method was tested at 300 MHz with breast cancer patients who often have radiotherapy-induced late alterations in the structure of subcutaneous fat due to the development of subcutaneous fibrosis. Measurements from 206 sites yielded a good agreement between the dielectric constant of subcutaneous fat and the clinical score for subcutaneous fibrosis.

Adipose Tissue↗
PubMed1998

Use of the Cimmino algorithm and continuous approximation for the dose deposition kernel in the inverse problem of radiation treatment planning.

An approximate continuous data fitting model for the dose deposition kernel was developed. The model uses a discrete Fourier transform to interpolate dose values in patient space and intensity distribution in treatment space. The continuous kernel was applied to the inverse problem of radiation treatment planning. In the problem a prescribed dose distribution was to be created using intensity modulation of several fields. The Cimmino algorithm suitable for solving large systems of inequalities was adapted. Upper and lower dose constraints for planning target volume (PTV) and organs at risk (OAR) can be implemented into the algorithm. Using continuous and discrete kernels an intensity modulation was computed in a two-dimensional phantom with a PTV and low-dose region, and in the real three-dimensional patient planning. Intensity modulations obtained using continuous and discrete kernels were in good agreement.

Algorithms↗
PubMed1998

Active conservative treatment of atlantoaxial subluxation in rheumatoid arthritis.

Twenty patients with rheumatoid atlantoaxial subluxation (AAS) underwent an active conservative treatment programme, aiming at relieving the symptoms and influencing the natural course of AAS. The treatment consisted of intensive multiprofessional intervention in the hospital for a fortnight, and control and motivational visits 6 and 12 months later. The patients self-evaluated the symptoms several times, and the cervical spine radiographs were taken at the first and last visit. Seventeen of the 20 patients adopted the instructions well and undertook the exercise programme at least weekly, even after a 12 month follow-up. Cervical pain was significantly reduced (P < 0.001) during the first intervention, and the favourable effect continued at least 12 months. Promising changes were also seen in some cervical radiographs. It is possible to educate and motivate AAS patients to take active care of their neck, and to relieve their chronic neck pain significantly. Atlantoaxial instability may also be reduced during active conservative treatment.

Adult↗