A Simplified Roentgen Stereophotogrammetric Method

A simplified roentgen stereophotogrammetric method is described. It is based on the use of a 50 mm thick reference plate consisting of a carbon-fibre-reinforced polyester box. The patient is placed directly on this box, which makes the methods less cumbersome and more suitable for routine use. The method has been tested in a model experiment designed for detecting small movements between femur and prosthesis at an early stage after total hip replacement. The head and two hemispheres on the prosthesis and three small tantalum balls inserted in the femur serve as reference points. The model experiment now reported shows that the method has acceptable precision.

Half-time re-warm up increases performance capacity in male elite soccer players

This study investigated the acute effects of a half-time re-warm up on performance and movement patterns in soccer match play. Using a crossover design, 22 professional male players performed traditional passive rest (CON) or a low-intensity re-warm up (RW) during the half-time period of two soccer matches. Before and after the first half and before the second half, maximal sprint and jump performance were evaluated. Time-motion analysis of the first 15 min of each half was conducted. Sprint and jump performance were reduced (P < 0.05) by 2.6% and 7.6%, respectively, during the half-time period in CON, whereas sprint performance was maintained and the decrement in jump performance (3.1%; P < 0.05) was lower after RW. No significant interaction for high-intensity running was observed, but less defensive high-intensity running was observed after RW than CON (0.14 ± 0.06 vs 0.22 ± 0.07 km; P < 0.01). Moreover, RW had more possession of the ball in the beginning of the second half. In conclusion, traditional passive half-time rest leads to impaired sprint and jump performance during the initial phase of the second half in professional soccer players whereas a re-warm up effectively attenuates such deteriorations. Less defensive high-intensity running and more ball possession were observed after RW, indicating a game advantage at the onset of the second half.

Inherent limitations in ectomography

Ectomography, a general tomographic method currently being implemented in nuclear medicine, is described. The object is viewed from different directions from the same projection angle, and the reconstruction process can be described as a two-dimensional filtered back-projection technique. One limitation of this limited-angle approach is that a three-dimensional Fourier representation of the acquired projections has a cone where data are missing. This empty cone can cause distortions in the tomogram by insufficient elimination of details outside the reconstructed tomographic section and by distortion of details in the section. The degree of distortion is dependent on the extension of the object in all directions and on the projection angle. Despite these limitations ectomography can be superior to single-photon-emission computed tomography for imaging sections that are close and parallel to the surface of the object, as in imaging of the hip joint or the heart.

A simplified roentgen stereophotogrammetric method. Analysis of small movements between the prosthetic stem and the femur after total hip replacement

A simplified roentgen stereophotogrammetric method is described. It is based on the use of a 50 mm thick reference plate consisting of a carbon-fibre-reinforced polyester box. The patient is placed directly on this box, which makes the methods less cumbersome and more suitable for routine use. The method has been tested in a model experiment designed for detecting small movements between femur and prosthesis at an early stage after total hip replacement. The head and two hemispheres on the prosthesis and three small tantalum balls inserted in the femur serve as reference points. The model experiment now reported shows that the method has acceptable precision.

Stability of union after tibial shaft fracture. Analysis by a non-invasive technique

The stability of union following the conservative treatment of tibial shaft fractures has been examined in 157 patients by a non-invasive method. With this technique it is possible to ascertain when the fragments are united and whether the strength of union is sufficient for full weight-bearing without protection. The mean time required for union was 14.0 +/- 9.2 weeks, with a range of 4 to 48 weeks. In 31 cases union was judged to be delayed; in 22 of these, intended operations were avoided because repeated stability determinations indicated progressive union. Of nine fracture variables examined, the only ones which significantly affected the time required to achieve union were the age and the weight of the patient. Irrelevant factors were the type and level of the fracture, the energy of trauma, soft-tissue injury and the presence of multiple injuries.

The stability of union in tibial shaft fractures: its measurement by a non-invasive method

The stability of the union in tibial shaft fractures was followed by repeated non-invasive radiographic measurement of a deflection induced in the area of the fracture. By means of a Shift Comparator the difference in the angle between the two fragments before and during application of the deflecting force can be measured. The relative measure of the strength of the union is furnished by a quantity, the deflection ratio, which is based on the quotient of the induced deflection by the magnitude of the applied bending moment. When this ratio falls below a certain value the union is considered to be stable enough for full weight bearing during walking. A plot of the deflection ratio against time, with logarithmic scales on both axes had a negative slope and was more or less linear. This graph can serve as an aid in detecting the course of union, in deciding when the cast should be removed, and in detecting any irregularity in the process of union. In the management of 207 fractures of the tibial shaft 508 such deflection measurements were performed.

Comparison of radiographic images. A new method for analysis of very small movements

A new method, shift comparisoN, for comparing 2 radiographic images is described. The method may be used for many purposes, but is particularly suitable for detecting small provoked motions between skeletal parts. Defective union in fractures or osteotomies is easily diagnosed by such a comparison. Films are exposed before and during the application of force to one of the fragments. By examining the films in the Shift Comparator small movements caused by the force may be detected. The technique has also been used for measuring the development of stability of union of tibial fractures by determining th deflection of the fracture caused by a bending moment.

Boundaries in the radiographic image. II. Principles for the representation of the object as boundary circuits in the image

The interpretation of images is mostly performed by effective intuitive mechanisms in the visual system. These mechanisms are well adapted for the interpretation of ordinary images but less capable of interpreting radiographic images. These contain boundaries of a type not found in ordinary images. The interpretive mechanism cannot utilize them and so a large part of the information contained in radiographic boundaries is not utilized. A simple analysis has been made of the geometric relations between the shape of an object and the boundaries in the radiographic image. These relationships are simple and regular. A knowledge of them enables a more complete extraction of the information contained in the boundaries.

Methods for assessing fixation and residual angulation in intracapsular hip fractures

Methods are described for assessing the angulation and the position of the pins in the femoral head after reduction and internal fixation with the Deyerle device in intracapsular hip fractures. Graphs are prepared that combine and display the relevant geometric information from the a.p. and lateral volume films. The methods have been applied in a series of 48 fractures.

Boundaries in the radiographic image. I. General principles for perception of boundaries and their application to the image

Mechanisms underlying the perception of boundaries are discussed. The boundaries seen in the radiographic image are analysed and grouped in a limited number of types according to their information. Their perception, identification and evaluation are discussed. Possible sources of error are pointed out.

Measurement of the shortening of the femur following immobilization of intracapsular hip fractures with the Deyerle device

A method is described for measuring the shortening of the femur occurring in intracapsular hip fractures immobilized with the Deyerle device. The method is based on the appearance of the Deyerle instrument on routine films, but it can be adapted for use with other immobilizing techniques in intracapsular hip fractures.

Ectomography. A new radiographic method for reproducing a selected slice of varying thickness

The mathematical basis is described of a new radiographic method by which an arbitrarily thick layer of the patient may be reconstructed. The reconstruction is performed from at least 60 images of the volume under examination. Each of these images, which have to be in digital form, is subjected to a special filtration process of its spatial frequencies. The combination of all the images will form the resulting image of the layer--the ectomogram. The method has been analysed and tested in experiments simulated with a computer.

Transverse tomography with incoherent optical reconstruction

A thin layer of an object can be imaged by reconstruction from a so-called sinogram. It is produced by an x-ray fan beam rotating around the object while a recording film is moved in a direction perpendicular to the plane of the fan beam. Before reconstruction the sinogram image is convoluted according to a special function to remove artifacts consisting of spurious shadows between different object elements. The reconstruction is done from the convoluted sinogram by means of a back projector, which operates according to a prinicple that is the reverse of the recording of the original sinogram. Tomograms of phantoms, pork chops and the head of a dog show that the process is capable of high spatial resolution but is limited by low contrast.

Knee instability and tibial osteotomy. A clinical study

Twenty-one gonarthrosis patients were preoperatively assessed according to a newly developed orthoradiographic technique ("three-point measurement") and followed up for 2-3 years postoperatively using this technique. The medio-lateral instability of the knee joints was not influenced by the operation. The varus/valgus deviation was under-corrected, on average, but the deviation did not increase significantly with time after the operation. Judging from this pilot study the three-point measurement technique supplies relevant information and it is now being used in a prospective study on high tibial osteotomy in gonarthrosis.

Computed tomography - a new technique in diagnostic radiology

An attempt is made briefly to outline the medical potentials of computed tomography. Examinations with this new and very promising X-ray technique are made without discomfort, pain or risks for the patient. The examination does not require highly trained personnel. It permits a number of pathological conditions to be reproduced directly in an image representing a transverse section of the body. Different soft tissues are visualized directly and the shape of internal organs can be accurately perceived. Opacifying media may be used to enhance the visibility of certain organs or tissues changed by pathological processes. Computed tomography might be used to make function tests of various organs where it will be possible to follow the function not only of the whole organ, but of each elementary volume of it. In radiation therapy, computed tomography offers a much higher precision in the planning of the radiation treatment of a tumour. From the tomogram a computer can readily find the optimal directions and intensities of the radiation in order to obtain the required effect on the tumour while sparing the healthy organs. This new technique will give us fresh insight into many common and serious disorders having unknown mechanisms and causes.

Knee instability. An orthoradiographic study

An orthoradiographic method for preoperative assessment of mediolateral instability and varus/valgus deviation in gonarthorsis is presented. A special definition of the varus/valgus deviation is given. The examination technique has been tested on 15 young, healthy subjects with no clinical signs or symptoms in their knee joints. To test the accuracy of the method, seven of the subjects were re-examined at a later date.

Attenuation equalizing filter in diagnostic radiography. Advantages calculated by a Monte Carlo technique

The value of an attenuation equalizing filter (equalizer) has been examined by calculation using a Monte Carlo technique. The contrast enhancement caused by the equalizer is the net result of three factors: (1) The first factor arises from the contrast change caused by the difference in detector characteristics at the different energies absorbed in the detector with and without equalizer. (2) The second factor is due to the contrast change caused by the different ratios of primary to total radiation reaching the detector. (3) Finally, the third factor describes how the transparency of the object is changed by the different primary filtration with equalizer. An example is given of the reduction in radiation energy absorbed by the patient and the question of how far the attenuation equalization can be driven is discussed.