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Results for “Radiographic Magnification”

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At least 19 recordsLinked to original sources
PubMedDate not supplied

Resolution in radiographic magnification.

Radiographic resolution and image sharpness are analyzed as a function of magnification for a few screen/film systems and a microfocal spot x-ray tube. Resolution and sharpness are described in terms of both MTF and effective aperture. The analysis demonstrates advantages of magnification for any combination of radiographic screen/film system and x-ray focal spot, and, in addition, allows one to compare different screen/film systems each used at different magnifications. Such an analysis is applicable to any radiographic system and may serve as a guide in selecting screen/film systems for use in magnification procedures.

Radiographic Magnification↗
PubMed1994

[Follow-up of fracture healing--indications and clinical relevance of direct radiographic magnification in comparison with conventional roentgen imaging].

Comparison of 83 magnification radiographs with corresponding conventional X-rays showed that direct radiographic magnification (DIMA) yielded additional information in 39 cases (47%), which had implications for the treatment in 19 cases (22.9%). In 11 cases callus was first visualized in magnification radiography; the earliest evidence of callus was found 14 days after surgery. Since magnification radiography means the region that can be examined is smaller, conventional radiographs were necessary in 32.5% of cases to find the position of the fracture in long bones. For statistical evaluation interobserver analysis was performed, anatomical and pathological structures being graded according to four levels. Magnification radiography proved superior in all structures examined. Magnification radiography can be recommended as an additional method to monitor fracture healing. Computed radiography was used together with magnification radiography to reduce the radiation dose and to perform image processing including simulation of conventional technique and edge enhancement. DIMA is a valuable tool in the evaluation of fracture stability and in the adjustment of distraction rates in limb-lengthening procedures.

Adult↗
PubMed1991

[Direct radiographic magnification and radiation exposure].

The advantage of microfocal X-ray units is the production of high-resolution magnification radiographs. Up to a magnification of x 4 the exposure equals that of a conventional radiograph. Some filter materials have been tested, aluminium filtration was found to be the best choice.

Aluminum↗
PubMed1982

Direct radiographic magnification: evaluation of three microfocus x-ray tubes.

Three microfocus x-ray tubes (RSI, Siemens, and Eimac) were evaluated for their focal and imaging characteristics. The RSI and Siemens focal spots had similar homogeneous radiation intensity distributions. The Eimac tube had an asymmetric intensity distribution. Because of their focal spot characteristics, the RSI and Siemens tubes provided superior magnification radiographs for small objects. The Siemens and Eimac tubes were preferable for magnification of thick objects because their larger object-film air gap reduced scattered radiation reaching the film.

Humans↗
PubMed1986

[Direct radiographic magnification of the hand: study of erosions in rheumatoid arthritis].

Plain films and direct magnification radiographs of the hands were performed in 34 patients affected by rheumatoid arthritis, using mammographic x-ray tube, achieved with 0.1 mm microfocus, and 1.85 X magnification factor. Direct magnification radiography has provided essential or useful diagnostic data in 44% of cases, particularly in recognizing early skeletal erosions. Nevertheless direct magnification radiography must be used only in those cases in which traditional mammographic techniques do not supply satisfactory results.

Adult↗
PubMed1982

In vivo demonstration of small intestinal villi in dogs and monkeys using radiographic magnification.

Direct radiographic magnification (3.6 x) and a microfocal spot radiographic tube (0.13 mm) were used in double contrast studies of intestinal villi in adult dogs and monkeys. The villi appeared as lucent lines surrounded by barium in profile, and as lucent dots en face; this was verified by specimen radiographic and histological analysis. The use of fast screen-film combination, motility depressant, microfocal spot tube, and air-gap technique produced a radiograph of greater detail than that obtained with conventional focal spot, source-image distance, and film-screen combination. The advantages and limitations of microfocal direct magnification radiography of the small intestine are discussed.

Air↗
PubMed1986

Radiographic magnification of colon polyps.

Radiographic magnification was evaluated on conventional and remote control machinery using a phantom with steel rods positioned at different levels. Depending on the rod-film distance, the range of magnification was 8-47% on remote control and conventional overhead films and 11-82% on conventional fluoroscopic spot-films. Extrapolation to the colon based on cross-sectional anatomic correlation showed a 14-27% variation in the radiographic magnification depending on the machinery used, the segment of the colon considered, and the position of the patient. This implies that substantial inaccuracy in the measurement of colonic polyps is common by barium enema examination, particularly when a conventional fluoroscope is used.

Colonic Polyps↗
PubMed1984

The value of conventional views and radiographic magnification in evaluating early rheumatoid arthritis.

Fifty-four patients with suspected early rheumatoid arthritis had radiographs taken of their hands and wrists in 4 views (posteroanterior [PA], oblique, reverse oblique, and Brewerton) using conventional techniques and, in the PA view, using radiographic magnification. The radiographs were "masked" and presented in random order to 2 radiologists specializing in bone and joint radiology who interpreted them for malalignment, erosions, joint space narrowing, and soft tissue swelling. The PA was the best conventional view for demonstrating malalignment, joint space narrowing, and soft tissue abnormalities; the Brewerton view was better for detecting erosive disease. Radiographic magnification was more sensitive than conventional films for evaluating erosive disease, but otherwise was no better than the conventional PA view. These results help the physician choose the radiologic technique or combination of techniques that is most likely to detect specific abnormalities.

Arthritis, Rheumatoid↗
PubMed1976

Comparison of image quality obtained with optical and radiographic magnification techniques in fine-detail skeletal radiography: effect of object thickness.

High-resolution radiography may be done using either optical or radiographic magnification. In the former technique, industrial Type M film was used without screens and the image was viewed with 4-10X optical magnification. In the latter technique, RP film was used with Detail screens and 4X geometric magnification together with a microfocus x-ray tube having a nominal focal spot size of 50 mum. The imaging properties of both techniques were evaluated by means of H & D curves, modulation transfer functions, and Wiener spectra. It was found that for thin objects such as the hand, optical magnification provides better bone images than radiographic magnification; whereas for thicker parts such as the knee, radiographic magnification is superior.

Bone and Bones↗
PubMed1977

[Radiographic magnification technique with a high-speed rare-earth screen-film system (author's transl)].

The advantages of radiographic magnification technique - better detail recognition and improved contrast with an enlarged field of vision - should prove an important supplement to the properties of a high-speed rare-earth system - low-current intensity, low voltage, short exposure time and, consequently, lower irradiation dosage. Physical measurements of the Wiener spectral value, MTF and HD curve proved the superiority of the radiographic magnification technique in combination with a rare-earth screen-film system as compared with a conventional system (Dupont Par speed screen, RP films). Phantom radiographs confirmed these results. The clinical usefulness of this method was assessed with respect to the detection rate of gall-stones by means of oral cholecystography. Two out of 25 cases showed gallstones only following implementation of the radiographic magnification technique. This method seems to be particularly valuable in angiography. In 7 out of 18 abdominal angiograms and 4 out of 14 renal angiograms the number of visible vessel ramifications was greater with the magnification technique. In 5 cases valuable diagnostic information was revealed only by means of the magnification technique. Despite two-fold or 1.7-fold magnification, measurements of skin irradiation exposure showed a reduction of about half in comparison with conventional techniques. Reduced exposure to irradiation combined with improved detail resolution should ensure that this method receives an established place in routine radiodiagnosis.

Angiography↗
PubMed1987

Direct radiographic magnification with computed radiography.

Computed radiography was combined with a 0.1-mm microfocus radiographic tube to obtain radiographic magnification of a x3 to x5. Gray-scale image processing compensated for the loss of radiographic contrast associated with the high-kilovoltage, short-exposure technique. The high-pass spatial frequency filtering capability of the computed radiography resulted in enhanced edges and increased displayed latitude. The improved image quality obtained by magnification computed radiography allowed delineation of subtle abnormalities and small anatomic structures not apparent on conventional screen-film contact or magnification radiographs.

Humans↗
PubMed1994

Optimal radiographic magnification for portal imaging.

Two approaches to estimate the optimal radiographic magnification for a TV camera-based portal imaging system and portal films have been used. The first approach optimizes signal transfer while the second optimizes signal-to-noise ratio (SNR) transfer. In order to perform these optimization calculations, the physical characteristics of the imaging system (modulation transfer function and noise power spectrum) as well as the sizes of the radiation sources of our medical linear accelerators have been measured. Using these data, the optimal magnification considering signal transfer alone (M signal) has been calculated to range between 2.0 and 2.3 for the TV camera-based imaging system and is about 1.0 for portal films. Conversely, the optimal magnification considering SNR transfer (MSNR) has been calculated to range between 1.5 and 1.7 for the TV camera-based imaging system and is about 1.0 for portal films. The results suggest that most portal imaging systems are operated close to their optimal radiographic magnification.

Humans↗
PubMed1986

Stomach and duodenum: radiographic magnification using computed radiography (CR).

We performed direct radiographic magnification (X3) using a 0.1-mm microfocal tube and computed radiography (CR) in air-barium double-contrast studies of the stomach and duodenum. To eliminate blurring of the image due to motion, we used the maximum kilovolt peak rate possible (102 kVp), the maximum milliampere second rate possible (64 mAs), the shortest possible exposure time (0.1 second), and a horizontal x-ray beam. With the patients in the supine position, CR provided the wide image reproduction range required to obtain satisfactory radiographs. Image processing in the CR system produced radiographs with increased radiographic contrast and enhanced edge definition of anatomic borders or pathologic processes. The duodenal villi were clearly visible in 45% of the cases.

Computers↗
PubMed1977

Direct radiographic magnification for skeletal radiology. An assessment of image quality and clinical application.

Recent advances in technology have made radiographic magnification of the skeleton clinically feasible. A new electron gun micro-focal tube combined with new high-resolution recording systems were used to perform magnification radiography which was then compared with conventional contact radiography. Quantitative evaluation included measurements of speed, contrast, resolution, and noise. Qualitative evaluation included an analysis of 215 clinical cases in which both techniques were used. The superior image quality of direct radiographic magnification is confirmed and the clinical areas in which it proved most helpful are defined.

Arthritis↗
PubMed1975

[Optimal distances for direct radiographic magnification].

This paper deals with the theoretical basis for radiographic magnification. In particular, the relationship between focal size and optimal magnification for various systems is discussed. Maximal resolution was chosen as the criterion for best results. It has been shown that resolution (Lp-mm) can be improved by the reciprocal of the focal spot and for optimal magnification (see article) where f is focal spot size and AVBW is resolution of the imaging system.

Humans↗
PubMedDate not supplied

Optical versus radiographic magnification for fine-detail skeletal radiography.

Fine-detail radiographic techniques for peripheral skeletal imaging have gained wide clinical acceptance. In this study, the imaging properties and clinical applications of the optical magnification technique, which employs fine-grain industrial film and a large focal spot, are compared quantitatively and qualitatively with those of three slow screen-film techniques, namely, contact exposure with a large focal spot, 2 times radiographic magnification with a 0.3 mm focal spot, and 4 times radiographic magnification with a 50 mu focal spot. The modulation transfer functions (MTF's) of the recording systems and focal spots are obtained and film sensitometry performed. Clinical comparisons are made for patients with metabolic, arthritic, and neoplastic skeletal disorders. The results illustrate the superiority of the optical magnification technique over contact or 2 times magnification techniques using slow screen-film systems. If a microfocus tube is used, however, direct radiographic magnification may provide images comparable in resolution, noise and contrast to those made with the optical magnification technique, and at lower radiation exposure to the patient.

Arthritis, Rheumatoid↗