Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics最新文献_第4页

Electrical impedance tomography with cortical or scalp electrodes during global cerebral ischaemia in the anaesthetised rat. 麻醉大鼠全脑缺血时皮质或头皮电极电阻抗断层扫描。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-02-01 DOI: 10.1088/0143-0815/13/1/008

D S Holder

{"title":"Electrical impedance tomography with cortical or scalp electrodes during global cerebral ischaemia in the anaesthetised rat.","authors":"D S Holder","doi":"10.1088/0143-0815/13/1/008","DOIUrl":"https://doi.org/10.1088/0143-0815/13/1/008","url":null,"abstract":"The performance of a prototype impedance imaging (Electrical Impedance Tomography, EIT) system using cortical or scalp electrodes has been assessed in a model of global cerebral ischaemia in the anaesthetised rat. In preliminary calibration experiments using a circular array of electrodes around a tank of saline, the centre of a polythene rod could be localised with a mean error of 4% of the tank diameter, and two such rods could be discriminated when separated by 22% of the tank diameter. Cerebral ischaemia was produced by diathermy of the vertebral arteries and reversible occlusion of the common carotid arteries for 15 min. A bimodal impedance increase of about 50-200% was recorded with a ring of cortical electrodes in the fronto-occipital plane. With a similarly oriented ring of scalp electrodes, a unimodal impedance increase of about 10% was observed. In both cases, impedance reversed after cerebral reperfusion. Similar but irreversible changes were observed post mortem. As the reconstruction algorithm assumes constant initial resistivity, this suggests that modifications to allow for initial conditions would be needed for more accurate imaging with scalp electrodes.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 1","pages":"87-98"},"PeriodicalIF":0.0,"publicationDate":"1992-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/1/008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12731194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 51

99Tcm HMPAO-labelled leucocyte imaging in Crohn's disease: a subtraction technique for the quantification of disease activity. 克罗恩病中医hpao标记白细胞成像:一种量化疾病活动性的减法技术。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-02-01 DOI: 10.1088/0143-0815/13/1/004

W B Tindale, D C Barber, M H Giaffer, S Senior, C D Holdsworth

{"title":"99Tcm HMPAO-labelled leucocyte imaging in Crohn's disease: a subtraction technique for the quantification of disease activity.","authors":"W B Tindale, D C Barber, M H Giaffer, S Senior, C D Holdsworth","doi":"10.1088/0143-0815/13/1/004","DOIUrl":"https://doi.org/10.1088/0143-0815/13/1/004","url":null,"abstract":"A new technique for the quantitative analysis of labelled leucocyte images from patients with inflammatory bowel disease is described. The method involves the computer generation of a 'background' image which, after appropriate registration, is subtracted from the patient's image to leave a residue which represents abnormal uptake in the bowel. Quantification of the residual activity yields a scan score which can be related to the level of disease activity in patients with Crohn's disease. In 54 investigations on 33 patients the scan scores correctly agreed with a clinical assessment of disease activity in 16 of 20 cases with inactive disease and 32 out of 34 cases with active disease. Most of the discrepancies reflected inaccuracies in the clinical assessment of activity rather than shortcomings of the imaging technique.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 1","pages":"37-50"},"PeriodicalIF":0.0,"publicationDate":"1992-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/1/004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12731190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Detection of cortical spreading depression in the anaesthetised rat by impedance measurement with scalp electrodes: implications for non-invasive imaging of the brain with electrical impedance tomography. 用头皮电极阻抗测量检测麻醉大鼠皮质扩张性抑制:电阻抗断层成像对无创脑成像的意义。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-02-01 DOI: 10.1088/0143-0815/13/1/007

D S Holder

{"title":"Detection of cortical spreading depression in the anaesthetised rat by impedance measurement with scalp electrodes: implications for non-invasive imaging of the brain with electrical impedance tomography.","authors":"D S Holder","doi":"10.1088/0143-0815/13/1/007","DOIUrl":"https://doi.org/10.1088/0143-0815/13/1/007","url":null,"abstract":"The possible use of impedance measurement with scalp electrodes to detect intracranial events non-invasively was investigated by measuring the localised impedance changes during cortical spreading depression (CSD) in anaesthetised rats. Impedance was measured over ipsilateral fronto-parietal cortex by a four electrode method operating at 50 kHz with electrodes spaced 0.5 mm apart. Cortical impedance increased by 39% of the resting level during CSD. With scalp electrodes placed on abraded skin, an unexpected impedance decrease of 0.8% occurred, which correlated spatially and temporally with CSD. CSD was accompanied by a small rise in temperature; when scalp temperature was held constant by warming the scalp, no impedance change greater than baseline variability (+/- 0.1% of the resting impedance level) was observed. The non-invasive detection of CSD in migraine in humans may be possible by measuring the characteristic temperature-related impedance changes with Electrical Impedance Tomography and scalp electrodes.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 1","pages":"77-86"},"PeriodicalIF":0.0,"publicationDate":"1992-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/1/007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12731193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 26

Electrical impedance tomography. An improved design of voltmeter for semi-parallel data acquisition. 电阻抗断层扫描。半并联数据采集电压表的改进设计。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/001

C Trillaud, J Jossinet

{"title":"Electrical impedance tomography. An improved design of voltmeter for semi-parallel data acquisition.","authors":"C Trillaud, J Jossinet","doi":"10.1088/0143-0815/13/a/001","DOIUrl":"https://doi.org/10.1088/0143-0815/13/a/001","url":null,"abstract":"The design and implementation of high performance differential voltmeters for semi-parallel data acquisition are described. The general requirements and specific conditions encountered in electrical impedance tomography (EIT) for accurate measurements are analysed. The major parameters are common-mode rejection and bandwidth. A specific implementation of the voltmeters, with separate DC supplies and independent signal references, is described. This arrangement, in which each voltmeter follows the input signal, automatically cancels any common-mode voltage present at the input. The signal is fed to the remainder of the instrumentation through a transformer. The use of a reduced number of components contributes to the minimisation of the inter-channel variations. Furthermore, the geometrical distribution of the voltmeters around the object minimises the length of electrode wires, also reducing the input capacitance. The number of modular voltmeters and DC/DC converters is 32. The common-mode rejection of these voltmeters is greater than 72 dB in the frequency range 3.6-560 kHz. In conclusion, the proposed solution ensures a minimisation of common-mode errors and enables the use of a 250 kHz frequency.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 Suppl A ","pages":"5-10"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/a/001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12754113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

Experimental assessment of electrical impedance imaging for hyperthermia monitoring. 电阻抗成像对热疗监测的实验评估。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/036

J Conway, M Hawley, Y Mangnall, H Amasha, G C van Rhoon

{"title":"Experimental assessment of electrical impedance imaging for hyperthermia monitoring.","authors":"J Conway, M Hawley, Y Mangnall, H Amasha, G C van Rhoon","doi":"10.1088/0143-0815/13/a/036","DOIUrl":"https://doi.org/10.1088/0143-0815/13/a/036","url":null,"abstract":"Two experimental studies are presented that attempt to assess the use of electrical impedance tomography (EIT) to map thermal changes deep in the body. The first was a joint study between our group in Sheffield and the Daniel den Hoed Cancer Center in Rotterdam, funded by the COMAC-BME Hyperthermia project. Phantom and in vivo experiments were conducted with a deep heating ring-capacitive hyperthermia device; the results highlighted some of the inherent problems (electromagnetic interference, nonuniform sensitivity) that remain to be solved for this application. The second experimental study involved heating the stomachs of volunteers by pumping known quantities of liquid (a salt/glucose solution, conductivity 5 mS) at controlled temperatures (25, 37 and 47 degrees C) in and out of the stomach via a nasogastric tube. Results indicated that the level of thermal change induced by these liquids could be reproducibly measured by impedance imaging. Both studies were a further step in assessing the capabilities of EIT for noninvasive monitoring of deep body hyperthermia. The results are encouraging and indicate the value of continued development of EIT for non-invasive thermometry.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 Suppl A ","pages":"185-9"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/a/036","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12754203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 29

Electrical impedance tomography systems based on voltage drive. 基于电压驱动的电阻抗层析成像系统。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/008

W Sansen, B Geeraerts, W Van Petegem, M Steyaert

引用次数: 9

Electrical impedance tomography. Solving anisotropic mixed boundary value problems by means of the boundary element method. 电阻抗断层扫描。用边界元法求解各向异性混合边值问题。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/025

H Zhou, A van Oosterom

引用次数: 2

A broadband system for multifrequency static imaging in electrical impedance tomography. 电阻抗断层成像中用于多频静态成像的宽带系统。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/013

P J Riu, J Rosell, A Lozano, R Pallàs-Areny

{"title":"A broadband system for multifrequency static imaging in electrical impedance tomography.","authors":"P J Riu, J Rosell, A Lozano, R Pallàs-Areny","doi":"10.1088/0143-0815/13/a/013","DOIUrl":"https://doi.org/10.1088/0143-0815/13/a/013","url":null,"abstract":"A widely accepted method for static imaging in electrical impedance tomography (EIT) is to measure at two frequencies. The choice of measurement frequencies is application-dependent because some different tissues cannot be distinguished when using two fixed frequencies. We have developed a system that generates signals from 8-10(3) kHz and applies two of these signals simultaneously to the body through a broadband current mirror. Great care has been taken in the design of the current injection multiplexer in order to keep the current source output capacitance as low as possible. Furthermore design of the layout of the patient interface board, in order to reduce feedthrough capacitances, also needs great care. Other parameters for driving and detection sections have been designed according to our results from FEM and circuit simulations including skin and electrode effects. Simulations using FEM with available tissue impedance data and preliminary measurements in a discrete phantom show that static imaging is possible for both the real and imaginary parts of the impedance.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 Suppl A ","pages":"61-5"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/a/013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12754116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 31

Monitoring body fluid distribution in microgravity using impedance tomography (APT (applied potential tomography)). 利用阻抗层析成像(应用电位层析成像)监测微重力下体液分布。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/035

E J Lindley, B H Brown, D C Barber, D Grundy, R Knowles, F J McArdle, A J Wilson

{"title":"Monitoring body fluid distribution in microgravity using impedance tomography (APT (applied potential tomography)).","authors":"E J Lindley, B H Brown, D C Barber, D Grundy, R Knowles, F J McArdle, A J Wilson","doi":"10.1088/0143-0815/13/a/035","DOIUrl":"https://doi.org/10.1088/0143-0815/13/a/035","url":null,"abstract":"For an astronaut, the excitement of going into orbit is accompanied by a shift of 1 to 1.5 l of fluid from the legs into the upper body. Information on the way the redistributed fluid is handled by the body is very useful to space physiologists studying the process of adaptation to zero-gravity. Applied potential tomography (APT) can be used to image changes in fluid distribution. To ensure that the technique was capable of measuring fluid shifts induced by changing gravitational forces on the body, a standard Sheffield APT system was used to study several subjects during the eight ESA parabolic flight campaign. The results clearly demonstrated the feasibility of using APT for monitoring fluid redistribution during space flight. A battery-powered, body-worn APT system has now been developed for use in space. The equipment was tested on the eleventh parabolic flight campaign. The data collected with the miniaturised system was comparable to that obtained in the earlier experiment. Ergonomic tests indicated that the equipment is no more difficult to operate and maintain under weightless conditions than on earth. The system is undergoing space qualification tests in Munich. If no problems arise it will be used by German astronauts on missions to MIR and Skylab.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 Suppl A ","pages":"181-4"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/a/035","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12754202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Pulmonary perfusion and ventricular ejection imaging by frequency domain filtering of EIT (electrical impedance tomography) images. 肺动脉灌注和心室射血成像的频域滤波(电阻抗断层扫描)图像。

Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics Pub Date : 1992-01-01 DOI: 10.1088/0143-0815/13/a/037

M Zadehkoochak, B H Blott, T K Hames, R F George

{"title":"Pulmonary perfusion and ventricular ejection imaging by frequency domain filtering of EIT (electrical impedance tomography) images.","authors":"M Zadehkoochak, B H Blott, T K Hames, R F George","doi":"10.1088/0143-0815/13/a/037","DOIUrl":"https://doi.org/10.1088/0143-0815/13/a/037","url":null,"abstract":"While EIT images can produce clinically useful qualitative information, the extraction of quantitative data is essential in clinical monitoring. In the case of imaging of the thorax the parameters available relate to cardiac activity and pulmonary perfusion. Imaging the relatively small changes in the resistivity of the lungs due to pulmonary perfusion in the presence of noise and the larger ventilation component is difficult. Suggested solutions involve multiple time averaging of cardiac gated data or reconstructed images. The required number of data frames for this type of processing is large (at least 100 cardiac cycles). Because the ventilation and perfusion components of the resistivity signals are well separated in the frequency domain, they can be differentiated by filtering. We report the results of this analysis which requires a data collection period of typically 15 s.","PeriodicalId":77070,"journal":{"name":"Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics","volume":"13 Suppl A ","pages":"191-6"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0143-0815/13/a/037","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12754205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 58