Triple-frequency method for measuring blood impedance.

A method was developed for simultaneously measuring plasma resistance, cell interior resistance and cell membrane capacitance of blood. A three-element circuit model for simulating the impedance of blood was evaluated by comparing measured and calculated impedance frequency curves and was found feasible. The values of the three elements of the model could be determined by measuring the impedance amplitudes at three different frequencies. The cell membrane capacitance (Cm) was independent of temperature in the range 25-40 degrees C and was significantly higher for blood with ethylenediaminetetraacetic acid (EDTA) as anticoagulant than that for blood with sodium citrate and acid citrate dextrose (ACD). The Cm value of blood from patients with high erythrocyte sedimentation rate (ESR) was found to be significantly higher than that of blood from patients with low ESR. This suggests that the membrane capacitance might be a potential parameter for clinical applications.

A computerized method for clinical gait analysis of floor reaction forces and joint angular motion.

A method for clinical studies of ground reaction forces during gait is presented. A walkway consisting of two force measuring platforms, each five meter long, allows the recording from several consecutive steps from both feet. Signals from photocells and goniometers have been added and a microcomputer system for on line recording and processing have been developed. The accuracy of the system is tested.

A method of stereotaxic localization adopted for conventional and digital radiography.

A method for the determination of stereotaxic coordinates in radiography, e.g. angiography, pneumoencephalography or digital vascular radiography, is described. A special localization frame containing radiopaque structures and scales defines a diagnostic coordinate system. This frame is fixed to the X-ray-table prior to the radiographic procedure and two projections are obtained at arbitrary angles to each other. The focus-film distances do not how to be fixed. The target coordinates are then determined either by a simple graphical procedure or with the use of a digitizing x-y-table, by a computer. With the computer method the films are placed on the digitizing table and the target and a few reference points are marked using a cursor. From the relative positions the computer calculates the coordinates. With the special head fixation system, coordinates of structures visualized in radiographic examinations can be transferred to various therapeutic or diagnostic stereotaxic devices.

An adaptor to the Leksell stereotaxic instrument for digital coordinate determination in radiography.

Special perspex adaptors with radiopaque reference structures have been constructed to fit to the Leksell stereotaxic instrument. These structures are visualized on X-ray film in a radiographic examination like angiography or encephalography. The films obtained in two projections at arbitrary angles and focus-film-distances are placed on a digitizing table for the determination of the stereotaxic coordinates of selected targets. The reference structures and the targets are marked with a cursor whereupon a desk top computer performs the calculation of the stereotaxic coordinates. The system allows a rapid, simple and accurate coordinate determination in stereotaxic radiography using the Leksell stereotaxic instrument.

Mobility of the pubic symphysis. Measurements by an electromechanical method.

Two pins were inserted, one on each side of the symphysis in 15 volunteers and four cadavers. Movements between the pins were registered by two transducers. Symphyseal movements were small. Translations in the transverse and sagittal directions were around or below 1 mm. Rotations in the frontal and sagittal planes were below 1.5 degrees. Movements in the vertical direction were around 2 mm in both sexes. Higher values were observed in multiparous than in nulliparous volunteers.

Vertical ground reaction force feedback to enhance stroke patients' symmetrical body-weight distribution while rising/sitting down.

A force platform with an auditory output consisting of two electronic balances was used to reinforce symmetrical body-weight distribution in stroke patients. Forty patients randomly assigned to an experimental group or a control group practised rising and sitting down for 15 min, thrice daily, 5 days a week for 6 weeks. The experimental group but not the control group received ground reaction force feedback through the auditory output. Vertical ground reaction forces under each foot were measured with two force plates. Mean difference in improvement of body weight distribution on the paretic leg was 13.2 +/- 10.7 (M, SD) per cent total body weight in the experimental group and 5.1 +/- 6.7 per cent in the control group in rising (p < 0.01) and 12.7 +/- 7.5 per cent total body weight and 4.6 +/- 6.6 per cent in sitting down tests (p < 0.001). The patients in the experimental group achieved in average close to a symmetrical body-weight distribution while rising and sitting down. Improvements in physical performance and sit-stand tests were greater in the experimental group (p < 0.05 and p < 0.01, respectively). No differences were seen in improvement in performance of activities of daily living. Symmetry in body-weight distribution in rising and sitting down correlated with high scores in physical performance, motor function in rising, and with functional ability.

CT localization of stereotactic surgery.

A stereotactic system is described. It is built around a baseplate which is fastened to the head of the patient and to various diagnostic and therapeutic modalities. In principle this system can function as an interface between most diagnostic (CT scanners, PET scanners, conventional X-ray instrumentation for angiograms and pneumoencephalograms) and therapeutic (stereotactic instruments, linear accelerators) instruments. It has been in practical use since 1976 and used in a number of 'diagnostic-therapeutic' combinations.

Continuous monitoring of irrigating fluid absorption during transurethral surgery.

We have designed an automatic detector system for noninvasive monitoring of irrigating fluid absorption during transurethral resection of the prostate. Ethanol, which is used as a tracer for the fluid, is measured in the expired breath of the patient. The breath ethanol monitor can be used both in the awake patient and during general anaesthesia. A lap-top computer controls the monitor and calculates the fluid absorption 1-3 times per min and uses the pattern of ethanol changes to indicate whether the fluid is being taken by the intra- and/or extravascular route. The monitor has been used in routine operations for one year. The interpretation of absorption routes was checked by control methods or by evaluation of the postoperative breath-ethanol curve. We found the indicated absorption to be correct in all resections with absorption large enough for the monitor to present an interpretation.

Motion of the pubic symphysis in pelvic instability.

Pelvic instability is a term widely used to describe a clinical entity characterized by pain localized to the pubic symphysis and/or sacroiliac joints. The pain often radiates down the leg. Hypermobility of the pelvic joints has been suggested as the cause of pain. Apart from several clinical stress tests, attempts at establishing objective evidence of such mobility have mainly consisted in radiologic measurement of motion of the pubic symphysis by a method which allowed only vertical movement to be recorded (5). In the present study symphyseal mobility was measured by an electromechanical method by which direct interosseous movement could be recorded in three directions and two different planes. Measurements were performed in a series of 15 patients with a tentative diagnosis of pelvic instability and the results compared to the results of radiologic measurement and to the normal values obtained in an earlier study of healthy volunteers (31). The results of this study would seem to refute the theory of symphyseal hypermobility being pathognomonic of so-called pelvic instability. It has moreover shown that radiologic measurement may be used for rough screening purposes, but is not sufficiently reliable for more exact measurements.

Head fixation system for integration of radiodiagnostic and therapeutic procedures.

A head fixation system is described enabling exact transfer of positions between neuroradiological and therapeutic procedures. The key item of the system is a base plate that is rigidly attached to the patient's head, either by a plastic mould or screws onto the calvarium. The base plate may easily and accurately be attached to diagnostic or therapeutic units. Coordinates of target points in the various units are directly related through the exact application of the base plate. Procedures for the exact comparison of spatial information have been worked out. The system has been used for diagnostic procedures such as plain skull radiography, cerebral angiography, CT scanning, position emission tomography, and gamma camera examinations, as well as for therapeutic procedures such as stereotaxic biopsy and radiation treatment.

Titanium clips in neurosurgery for elimination of artefacts in computer tomography (ct) a technical note.

To eliminate the occurrence of artefacts produced by clips on the CT images, the use of titranium clips is suggested. Tests in vitro and in vivo indicate that clips manufactured from 0.2 mm thick 99.9 per cent titanium do not cause artefacts. They are resistant to corrosion, nontoxic, effective, easy to handle, relatively cheap, and are visible on plain X-ray films.

Head fixation device for reproducible position alignment in transmission CT and positron emission tomography.

A head-positioning device allowing accurate position transference between computed tomography and positron emission tomography is described. A base plate is fixed to the patient's head through either an individual mold or screws into the calvarium. This base plate fits onto the headholders of the two devices, thus ensuring that scans are taken at the same level. Using the regular software, the coordinates of an anatomic structure may be determined and transferred between the two images.

Assessment of mouth-to-mask ventilation in resuscitation of asphyxic newborn babies. A pilot study.

The aim of the study was to compare the effectiveness of mouth-to-mask ventilation (MM) in neonatal asphyxia with bag-and-mask ventilation (BM). A new mouth-to-mask infant resuscitation system was constructed. The study was performed in two university clinics with different resources. The KEM Hospital in Bombay was well equipped and neonatologists took part in all resuscitations; Muhimbili Medical Centre in Dar es Salaam was understaffed and had no physicians available at resuscitation. Therefore, different protocols had to be used. In Bombay, the study period was limited to 5 minutes. If needed, mask ventilation was then replaced by intubation. In Dar es Salaam, MM ventilation was continued for up to 10 minutes, the inspiratory pressure was adjusted to 30 cmH2O and the ventilation was slow (8-10 breaths/min). In Bombay, 30 babies were allocated to the BM and 24 to the MM groups. In Dar es Salaam 56 were in the BM and 64 in the MM groups. The results for term babies in Bombay and both term and pre-term babies in Dar es Salaam showed no significant differences between the two groups of treatment, as determined by Apgar score > or = 4 at 5 and 10 minutes, number of babies with their first gasp, heart rate > 130 beats/min or pulse oximeter values above 75%, all at 5 minutes. An Apgar score > or = 4 at 5 minutes was achieved in more than 75% of all infants, irrespective of treatment. The rates of early neonatal mortality and neonatal convulsions did not differ between the two methods of resuscitation. In Dar es Salaam, the low respiratory frequency used in both groups was associated with a slow increase in heart rate above 130 beats per min. This result indicates that further studies will be needed before such slow respiratory frequencies are used. We conclude that, if adequate training is provided and the respiratory frequency is kept within the normal range, MM ventilation is an alternative to assisted ventilation when no bag and mask is available. However, further studies are necessary, since this method has proved to be tiring and uncomfortable for the resuscitating health personnel.

Stereotactic radiation therapy of intracranial lesions. Methodologic aspects.

A technique for stereotactic radiation therapy of cerebral tumours and arteriovenous malformations using a linear accelerator (6 MV photons) is proposed. Treatment relies on a fixation system that permits a precise use of the coordinates estimated at stereotactic angiography or stereotactic computed tomography. The field of treatment can be exactly outlined in the CT images during repeat examinations, thus facilitating the recognition of changes induced by radiation. The system also allows the extent of the arteriovenous malformation, as seen at angiography, to be accurately traced in the CT sections thus enabling evaluation of possible radiation damage to surrounding brain structures. The precision of the method as well as its hypothetical merits and disadvantages are discussed. The number of patients treated is still small and the follow-up time is too short in the majority of cases to allow definite conclusions. Examples of preliminary results are given.