[Laser Doppler technique makes measurement of microvascular blood flow changes possible].
Explore the source record for details and available documents.
Blood Flow Velocity↗
Biomedical subjects
H Svensson
Publications and source records attributed to H Svensson.
Cooperative image workstation based on explicit models of diagnostic information requirements.
A medical image workstation designed to act as a cooperative dialogue partner in diagnostic radiology has been conceived, and a prototype has been made. The system can automatically select relevant information (eg, from current and previous examinations) and generate a meaningful and appropriate image arrangement on the display screen. For a number of routinely performed tasks in radiology, the users' interaction may be as simple as switching from one patient to the next. This is shown to considerably simplify and speed up radiological image access and presentation, saving the user time and effort. The cooperative system response is based on explicit (formalized and computer-accessible) models of diagnostic information requirements. These models are context dependent and take into account that diagnostic information needs vary with radiological work procedures, workstation users, and patient cases. Initial models have been acquired from expert radiologists in two European hospitals and were integrated in a cooperative workstation prototype. For the representation of models, rule-based and object-oriented techniques were applied. The rule base was designed with a distinct modular structure, separating between rule sets for general, task-dependent, and user-dependent information requirements. The installed rule-based mechanism also offers a solution for the automatic prefetching of images to avoid transmission delays in the course of diagnostic work sessions. The first part of the report reviews the objectives for the design of cooperative workstation user interfaces and explains the benefits from the users' point of view. In the second part, the acquisition, structuring, formalization, and representation of context-dependent information requirement models is described. The rule-based model is explained using examples. A layered workstation architecture consisting of model, object, and real-time layers is presented. Difficulties in the implementation of cooperative workstations are discussed that point to future research topics and standardization efforts.
Diagnostic Imaging↗
[Quality work gives appetite in Halmstad. Interview by Carina Roxström].
Explore the source record for details and available documents.
Diet↗
Thermography and laser-Doppler flowmetry for monitoring changes in finger skin blood flow upon cigarette smoking.
Haemodynamic changes after smoking two 1.1 mg nicotine cigarettes were monitored in 24 smokers on two different occasions. Smoking caused an increase in heart rate and arterial blood pressure, whereas finger temperature as measured by thermography and finger skin blood flow as measured by laser-Doppler flowmetry (LDF) decreased. Lowest values were seen within 15 min by LDF, and after 30 min by thermography. Changes in the two methods correlated closely, however, when maximum responses during a 45-min period after smoking were compared. The wider distribution of LDF values would seem to be due to the small measuring volume which is susceptible to differences in vascular anatomy and reactivity. In both methods, responses showed a high degree of reproducibility.
Adult↗
Effect of hepatic artery or portal vein occlusion on liver tumour blood flow.
To study the blood flow in normal liver tissue and in liver malignancies after occlusion of the hepatic artery or the portal vein, an adenocarcinoma was inoculated in the left liver lobe of 10 rats. Eight days postoperatively, blood flow in normal hepatic tissue and tumour was estimated by laser Doppler flowmetry (LDF). In both normal tissue and tumour, occlusion of the hepatic artery reduced LDF values by approximately 30%, whereas occlusion of the portal vein reduced LDF values by approximately 70%. These findings indicate that changes of hepatic blood flow can be monitored by LDF, and that the portal blood flow is dominating also in liver metastasis.
Adenocarcinoma↗
Tendon blood flow assessed by laser Doppler flowmetry.
Laser Doppler flowmetry was applied to the surface of both achilles tendons in 10 mature albino rats. A prompt decline in flux values by about 60% was noted when the blood supply to the limb was interrupted by clamping the femoral artery. Increased values, indicating a hyperaemic reaction, often followed release of the clamp. Flux values reached a minimum after death, and this was used as a baseline measurement to eliminate Doppler signals generated by factors unrelated to flow. Although readings in two animals had to be omitted for technical reasons, the present study shows that reliable laser Doppler flow readings can be obtained from the surface of a tendon. The response to reversible ischaemia is prompt and reproducible. Laser Doppler flowmetry may offer a new approach to the assessment of tendon blood flow at the microvascular level.
Achilles Tendon↗
Leg showering therapy in patients with intermittent claudication.
Ten patients with intermittent claudication were treated using a recently constructed "chair" in which the seated patient has alternately warm and cool water flushed over the legs and feet. A trial treatment was given for 25 minutes, three times a week for 5 weeks. Ankle/arm index, skin perfusion pressure and calf blood flow all remained unchanged immediately after such a series of treatment. Even at follow-up 6 months later, values were unchanged but for a minute increase in ankle/arm index in the poorer leg. Walking capacity was additionally measured and an improvement was seen, also after 6 months. The role of the contrast temperature treatment in this improvement is, however, unclear.
Aged↗
Skin perfusion pressure assessed by measuring the external pressure required to stop blood cell flux.
Laser Doppler flowmetry (LDF) was used to determine the point at which blood flow cessation is achieved under circumferentially applied external counter pressure at the ankle level. In 13 individuals with a normal ankle index, the flow of cessation external pressure (FCEP) was, on average, 28 mmHg lower than the systolic ankle pressure (range: 7-62). In 19 patients with an ankle index below 1.0, FCEP correlated with the ankle pressure (rs = 0.76) and even more closely with the ankle index (rs = 0.82). In patients with a more pronounced degree of arterial occlusive disease, FCEP can be equal to or even higher than the ankle pressure. This may be due to a release of sympathetic vasoconstrictor tone and possibly to the presence of a collateral circulation supplying the skin. Individual LDF values from the skin at rest do not reflect the degree of peripheral circulatory insufficiency.
Adult↗
The IAEA/WHO TL dosimetry service for radiotherapy centres 1969-87.
The International Atomic Energy Agency (IAEA) started a postal dosimetry service in 1966 using lithium fluoride (LiF) thermoluminescent dosimeters (TLD). The World Health Organization (WHO) joined the programme in 1968. Dosimeters were sent on 29 occasions to primary standards laboratories or to the 'Bureau International des Poids et Measures' to guarantee the traceability to primary standards of absorbed dose. The mean deviation was -0.26 +/- 0.18% (1% SD of the mean). One SD for a single result was about 1%. The number of intercomparisons made during the whole period is about 2,000 from about 700 radiotherapy centres in 89 countries. To date only 60Co machines have been included. The mean deviation of all the results from the centres was -0.25, and 1% SD for a single result 6.7%. About 5% of the centres had deviations larger than 30%, at least on one occasion. It is shown that the accuracy in dosimetry improves considerably for those departments participating more than once in the TL dosimetry service.
Calibration↗
Absorbed dose in water. Comparison of several methods using a liquid ionization chamber.
In the present investigation a liquid ionization chamber has been used as a transfer instrument for the quantity absorbed dose in water in a cobalt-60 gamma-ray beam. The characteristics of the liquid ionization chamber are described. The transferred dosimetric information has been compared with absorbed-dose determination using air-ionization-chamber dosimetry, water calorimetry and ferrous-sulphate dosimetry. The agreement between the different measured absorbed-dose values is very good, i.e. within 0.2%. This is an indication that the consistency in the methods used to determine absorbed dose in water is good. The impact of the new standard for air kerma in air, introduced in 1986 by the BIPM, on the air-ionization-chamber dosimetry is investigated. It is shown that any differences in the dosimetry when using the old or the new set of data cancel out for the cobalt-60 beam. The investigation also shows that the value of epsilon mG for the ferrous-sulphate dosimeter recommended in ICRU 35 for electrons can be used also in cobalt-60 beams.
Calibration↗
[Abuse of laxatives as the cause of obscure prolonged diarrhea].
Although concealed abuse of cathartic laxatives is probably an unusual cause of severe longstanding diarrhoea, nevertheless, it is presumably a more frequent cause of such diarrhoea than are endocrine pancreatic tumours. The patient often undergoes extensive and expensive investigations before the diagnosis can be reached if indeed it ever is. The condition is almost exclusive to women, often those employed in medical care. A psychiatric background is usual, frequently with anorectic traits. The abuse often continues even after 'disclosure' and commonly defies psychotherapy.
Adult↗
Comparison of 133Xe clearance and laser Doppler flowmetry in assessment of blood flow changes in human masseter muscle induced by isometric contraction.
Changes induced by 30 s of isometric contraction at 10% and 50% of the maximum voluntary contraction were assessed in 10 healthy subjects; there was a median increase of 1.8 and 0.3 times in 133Xe clearance and 5.3 and 2.7 times in laser Doppler flowmetry. In the first minute after 10% maximum voluntary contraction, 133Xe clearance increased 12.1 times in relation to the initial resting level, and flowmetry values decreased to become 3.5 times higher than the basal flow; corresponding values after 50% maximum voluntary contraction were 24.3 times and 3.7 times. From the second minute after contraction, there was a rapid decrease in 133Xe clearance and a slow decrease in flowmetry values. Five minutes after biting at 10% maximum voluntary contraction, both methods showed a total net increase of about 15 times; after biting at 50% maximum voluntary contraction the corresponding values were 38 and 23 times. Thus laser Doppler flowmetry can be used to assess changes in blood flow in the masseter; it registers a greater increase in flow during isometric contraction than does 133Xe clearance. The significant difference between methods immediately after either chosen level of contraction disappears when the total net post-contraction hyperaemia is assessed over a period of 2 and 5 min, respectively.
Adult↗
The 6th Klaas Breur memorial lecture, 1987. The Chernobyl accident--impact Western Europe.
Explore the source record for details and available documents.
Accidents↗
On expander pressure and skin blood flow during tissue expansion in the pig.
The structural and circulatory dynamics of expanded skin in connection with expander fillings were assessed in pigs following 7, 14, and 21 days of expansion by measuring the pressure of te fluid in the expander (Pexp) and the dermal blood flow. The results differed consistently on thoracic and abdominal sites. It was suggested that the stimulus to expansion be defined as the relative increase in extensible surface area of the expander. When plotting this value against Pexp, as measured at the end of injection, there was a good fit to an exponential curve. The area/Pexp relation was used to assess the connective tissue reaction around the expander; the reaction was most pronounced at 21 days. The decrease in Pexp after injection of fluid to 100 mm Hg showed that the tissue adapted rapidly during the first hour. Blood flow in the skin covering the expander was lower than on adjacent normal skin, and there was no increase during the three weeks of expansion. The decreases in blood flow were moderate even after injection of fluid until Pexp reached 100 mm Hg. It was suggested that the connective tissue capsule might protect the dermis from flow decrease.
Animals↗
Laser-Doppler flowmetry for estimating liver blood flow.
Whether laser-Doppler flowmetry can be used to monitor liver blood flow was evaluated in a porcine model in which portal venous blood flow was followed indirectly by electromagnetic flowmetry applied to the superior mesenteric artery, and total hepatic venous outflow was measured directly by using an extracorporeal circuit. Hepatic venous outflow at rest was 23.5 +/- 5.7 ml.kg body wt-1.min-1. Occlusion of the hepatic arterial supply reduced hepatic laser-Doppler blood flow to 22%, but hepatic venous outflow only to 80%. Portal venous blood flow remained unchanged or increased slightly. Occlusion of the portal vein, on the other hand, decreased hepatic laser-Doppler blood flow values to 37% and hepatic venous outflow to 13%. Increased hepatic venous outflow pressure, caused by a positive end-expiratory pressure or elevation of the draining cannula, reduced flow and caused approximately equal changes in the three variables, as did reduced flow by step-wise bleeding. From these experiments in the pig it is concluded that laser-Doppler flowmetry on the liver surface clearly reflects relative changes of the total liver blood flow, as exemplified in this study, during venous stasis and bleeding. The technique is, however, more sensitive to blood flow changes in the hepatic artery as compared with the portal vein.
Animals↗
The Chernobyl accident. Transport of radionuclides to man living in northern Sweden.
The pathways of 131I, 134Cs and 137Cs from the Chernobyl fallout to man were followed in the county of Västerbotten, Sweden. Reported airplane measurements had shown that the ground deposition of 137Cs was 3-40 kBq/m2 with hot spots with more than 80 kBq/m2. Multiplying with a factor of 0.6 gave the 134Cs deposition and an approximate factor of 20 the 131I ground deposition. The effective dose equivalent from 131I became low, less than 0.1 mSv, as the cows were stabled. The 137Cs activity concentration in different types of food was measured in approximately 8,000 samples. The most important sources of Cs intake in man were lake fish, elk (European moose) and reindeer. Variations with time was studied in detail for four types of lake fish. Whole-body measurements on more than 250 persons showed that no group of people on average received more than 1 mSv from food during the first year after the Chernobyl accident. However, single persons eating large amounts of reindeer meat received up to 2.5 mSv. People buying all their food in ordinary provision-shops got less than 0.1 mSv from the food during the first year. The present level of 90Sr activity concentration in man will only give an effective dose equivalent of 0.004 mSv/year, most of it being a result of the atmospheric nuclear bomb tests.
Accidents↗
Laser Doppler flowmetry during hyperaemic reactions in the skin.
Laser Doppler flowmetry (LDF) was used to study skin blood flow in the finger tip and on the dorsum of the hand in healthy volunteers. Vasodilatation in the finger tip was induced by immersing the arm in water at 42 degrees C, and vasodilatation in the dorsum of the hand by intracutaneous injection of dihydralazine. Simultaneous measurements were performed using venous occlusion plethysmography (finger tip) and 133Xe clearance (dorsum of hand). Three output signals from the laser Doppler flowmeter were recorded. The LDFPf-1 value is linearly related to the blood flow, provided the concentration of blood cells in the scattering volume is low. The LDFPf-2 value is generated by a signal processor designed to give linearity even at higher concentrations of moving blood cells (CMBC), the latter quantity being reflected by the CMBC value. During vasodilatation by immersion, all laser Doppler values from the finger tip increased but less than the total finger blood flow as measured using venous occlusion plethysmography. Intracutaneous injection of dihydralazine in the dorsum of the hand caused markedly increased CMBC values and the increase in LDFPf-2 was significantly greater than that of LDFPf-1. The increase in 133Xe clearance was less pronounced. The results indicate that capillary blood flow as well as blood flow in vessels below the capillary level contribute to the Doppler signal. However, flow through the arteriovenous shunts in the finger tip seems to be only partially registered by the laser Doppler technique. The higher the CMBC value, the more obvious is the difference between LDFPf-1 and LDFPf-2 values. When using laser Doppler flowmetry, the addition of CMBC value registration may be helpful in clarifying changes in microvascular blood flow.
Adult↗
Recent developments in basic dosimetry.
CCEMRI(I) (1985) has recommended that from January 1st 1986 the Primary Standard Dosimetry Laboratories (PSDLs) should adopt new values for W/e (33.97 J/C), stopping powers for electrons (ICRU Report 37, 1984), g value in air for 60Co (3.2 X 10-3), and energy absorption coefficients [17]. The consistency of the whole dosimetric chain requires the same basic physical data at the users' beam quality and PSDLs, but most of the existing dosimetry protocols are not generally based on such a set of data and in some cases old and new data have been employed together. A review of the basic data included in the dosimetry protocols is presented here, together with a comparison with experimental data. The most recent data include the recommendations of CCEMRI(I) and at the same time, some of the inconsistencies existing in dosimetry protocol have been eliminated. The new set of data is presented in this work. New dosimetry protocols and updated versions of protocols published before 1986 are discussed in terms of their basic data.
Clinical Protocols↗