Direct Magnification Radiography Research Articles

Spinal cerebrospinal fluid pathways and their significance for the compensation of kaolin-hydrocephalus.

To study the mechanisms of CSF-outflow in hydrocephalus we used radiological and histological methods to examine pathways of CSF absorption. Two, four and six weeks after occlusion of the cisterna magna by kaolin solution, CSF-dynamics were determined. Direct magnification radiography was used to visualize the outflow of X-ray contrast. Ten rats in each group were sacrificed for histological analysis following ventricular perfusion with marker proteins. ICP was increased to 15 +/- 1 mmHg (mean +/- SD) compared to control animals (7 +/- 2 mmHg) in the four week group. Six weeks following kaolin injection no increase in ICP (6 +/- 1 mmHg) could be demonstrated. Outflow resistance was markedly raised in all animals (1074 +/- 315 mmHg min-1 ml-1) displaying highest values (2160 +/- 960) in the four week group as compared to control animals (504 +/- 71). Cisternography demonstrated blocked cranial absorption and CSF-outflow along lumbosacral nerve roots. Histological examination showed syrinx formation in the cervical and thoracic spinal cord. Marker proteins left the subarachnoid space along thoracic and lumbo-sacral spinal rootlets. The radiological and histological findings and the normalisation of ICP after six weeks at doubled CSF-outflow resistance indicated a recruitment of spinal perineural CSF outflow pathways for the compensation of the disturbed cranial CSF-absorption.

Dynamic properties of lymphatic pathways for the absorption of cerebrospinal fluid

To study the dynamics of the outflow of cerebrospinal fluid (CSF) into the cervical lymphatic system, X-ray contrast medium or Indian ink was infused into the cisterna magna of rats at moderately increased intracranial pressure (40-50 mmHg). In the first series of experiments, while the contrast medium was being infused, the animal's head was examined using X-ray-microscopy (x4-20 direct magnification radiography) and conventional radiography. Within the first minutes of infusion, the flow of CSF was directed from the posterior fossa to the olfactory bulb. Reaching the cribriform plate approximately 7 min after starting the infusion, the contrast medium leaked into the nasal cavities. Some minutes later, it opacified the subarachnoid space (SAS) of the optic nerve, the perilymphatic space of the inner ear, the cortical SAS, and the transverse sinuses. Leakage from the optic nerve SAS into the orbit was seen after 30 min infusion. In the second series of experiments, the Indian ink was infused after microsurgical exposure of the cervical lymph vessels. During the infusion the cervical lymph ducts were observed microscopically (x40 magnification). Single dye particles draining through the cervical lymph ducts appeared 20 min after the start of cisternal infusion. Their transport was rapid, and dependent on the respiratory cycle: during inspiration the particles moved at a speed of 10-20 mm/s, during expiration the movement stopped. Thus, rapid kinetics are demonstrated for the outflow of CSF and particles from the SAS into the cervical lymphatics.

Direct radiographic magnification mammography with a new microfocus tube. Experimental studies of resolution and radiation exposure

A recently developed X-ray unit for mammography using microfocal (spot size 0.12-0.05 mm) direct magnification radiography will soon be introduced into clinical practice. Unit arrangement and tube construction have been demonstrated. Mean surface dose was measured using PMMA-phantoms. A dose reduction of up to 50% was obtained in 1.7-fold magnification mammography (full sized views) compared with conventional techniques. The image quality was almost equivalent. However, in comparison with 1.7-fold magnification mammography, a comparable dose range for 4-fold magnifications with the microfocus system was measured with a substantial gain in spatial resolution. These findings satisfy the demands of a modern mammographic unit.

Intravascular ultrasound, computed tomography, magnetic resonance imaging, and direct magnification radiography for in vitro evaluation of peripheral artery morphology and dimensions

Objective: The aim of this in vitro study was to validate five imaging modalities (12.5- and 20-MHz intravascular ultrasound, computed tomography, spin- and gradient-echo magnetic resonance imaging) for their potential to depict peripheral vessel wall calcifications, to estimate calcified plaque area and to measure luminal areas using direct magnification radiography as a reference. Methods: Forty-three postmortem, human iliac segments were consecutively examined by intravascular ultrasound (12.5- and 20-MHz mechanical system), computed tomography and magnetic resonance (MR) imaging. In each specimen, the presence of calcified regions was assessed by independent observers. Luminal area and plaque area were quantitatively estimated. All specimens were finally examined using direct magnification radiography as a reference. Results: The sensitivity was 73% using a 20-MHz probe for the identification of calcification (vs. 59% with a 12.5-MHz transducer), specificity was 97% (with 12.5-MHz 96%). Positive predictive value with 20-MHz was 90% (with 12.5-MHz 91%); negative predictive value was 87% (81% with 12.5-MHz) and accuracy 87% with 20-MHz and 84% with 12.5-MHz. With magnetic resonance imaging, the sensitivity of the gradient-echo technique to identify calcified areas was 94% (vs. 75% with the spin-echo technique) and specificity was 86% (vs. 93% with spin-echo technique). Computed tomography reached a sensitivity level of 88%, specificity was 88%. No significant difference was found for luminal area estimated by 20-MHz intravascular ultrasound and direct magnification radiography. Computed tomography, spin-echo MR and gradient-echo MR were significantly different from reference measurement ( p < 0.005). Plaque area estimated by direct magnification was 8.3 ± 6.5 mm 2 (mean and standard deviation); computed tomography, spin-echo MR and gradient-echo MR showed significant overestimation ( p < 0.008) in comparison to the reference. The correct identification of regional vessel wall calcifications by intravascular ultrasound strongly depended on both morphology and plaque thickness. Conclusion: In an in vitro setting, intravascular ultrasound, computed tomography and MR imaging of peripheral vessel wall calcifications may lead to misinterpretation.

Comparison between direct radiographic enlargement and mammography technique in detection of osseous changes of the hand skeleton in hyperparathyroidism

To compare direct magnification radiography and mammographic film-screen systems in osseous changes of the hand in hyperparathyroidism. The hands of 60 patients who were suspected to have primary (5), secondary or tertiary (both 55) hyperparathyroidism were evaluated with direct magnification radiography and a mammographic film-screen system (S12.5). Posterior-anterior views of each hand were obtained with both techniques. The magnification radiographs were made with a focal spot size of 40 or 60 microns, digital luminescence radiography (S600/1200), and a x 6 or 8 magnification. The 240 films were evaluated for subperiosteal, intracortical and endosteal resorptive changes by five radiologists using a grading according to five levels of confidence. A significant improvement (p < 0.05) in the diagnosis of periosteal and intracortical bone resorption was shown, but no significant changes in endosteal resorption with direct magnification radiography. As compared to mammographic film-screen systems, magnification radiography improved the diagnostic accuracy (24%). The time needed for the evaluation of periosteal and intracortical bone resorption was shortened with direct magnification radiography (-4%/ -15%), and the time for giving the diagnosis decreased (-10%).

Radiographic assessment of structural defects in Björk-Shiley convexo-concave prostheses.

Following the implantation of Björk Shiley 60 degrees convexo-concave (BS-CC) prostheses, outlet strut fracture rates up to 2.5% per year have been reported. According to experimental results and clinical observations, single leg separations are regarded as the primary mechanisms leading to complete outlet strut fracture after a certain interval. In an experimental study the question was addressed, whether single leg separation can be identified by especially developed radiographic means, before outlet strut fracture occurs. Five BS-CC mitral prostheses (29-31 mm) with intentionally made single leg separations of defined gas sizes (0-75 microns) and one intact mitral prostheses were implanted in sheep in a double-blind study design. Repeat non-invasive investigations were then performed applying a recently developed fluoroscopy imaging technique with direct radiographic magnification (DIMA COR C22). Single leg separations with gap sizes of more than 25 microns were properly detected using DIMA COR C22. Separations 25 microns or less could not be detected with certainty but were evaluated as probable or possible as a result of multiple investigations. The intact prosthesis was correctly identified, but was investigated on only one occasion. Non-invasive control of Björk-Shiley CC mitral prostheses applying especially developed direct radiographic magnification may allow for a reliable assessment of single leg separation with gap sizes of more than 25 microns in sheep. Using this technique of non-invasive serial investigations on particular patients with high probability of outlet strut fracture appears feasible, anticipating single leg separation detectability in humans. This has to be assessed in a second step.(ABSTRACT TRUNCATED AT 250 WORDS)

In Vitro Correlation of Intravascular Ultrasound and Direct Magnification Radiography for Calcified Arterial Lesions

Intravascular ultrasound (IVUS) is an adjunct to contrast angiography that gives additional information concerning the morphology of the vascular wall. The authors examined the accuracy of intravascular ultrasound (IVUS) in the evaluation of calcified lesions within the abdominal aorta and the iliac artery. Forty-nine human specimens (iliac artery, 26; abdominal aorta, 23) were examined using a 20-MHz 6.0-F ultrasound catheter, followed by magnification radiography of the same specimens using a newly developed microfocus x-ray tube. Magnification radiographs and ultrasound images were divided into identical sectors to analyze the morphology of calcified arteriosclerotic lesions. A total of 644 sectors was analyzed. Sensitivity of intravascular sonography was 70%, specificity 53%. Sensitivity strongly depended on the morphology of the calcified lesions. The detection of calcified arteriosclerotic lesions by means of IVUS revealed a sensitivity of 70% in an in vitro study using human specimens. However, the specificity of IVUS was only 53%, which is basically a random chance occurrence.

Fracture healing: direct magnification versus conventional radiography

The aim of the study was to evaluate the potential of magnification radiography in diagnosing fracture healing and assessing its complications. Seventy-three patients with fractures or who had undergone osteotomy were radiographed with both conventional (non-magnified) and magnification (5-fold) techniques. Since 10 patients were radiographed twice and 1 three times, 83 radiographs using each technique were obtained. All radiographs were analysed and the findings correlated with the patients' follow-up studies. The microfocal X-ray unit used for magnification radiography had a focal spot size of 20–130 μm. As an imaging system, digital luminescence radiography was employed with magnification, while normal film-screen systems were used with conventional radiography. Manification radiography proved superior to conventional radiography in 47% of cases: endosteal and periosteal callus formations were sen earlier and better in 26 cases, and osseous union could be evaluated with greater certainty in 33 cases. In 49% of cases magnification radiography was equal and in 4% inferior to conventional radiography. Additionally an “inter-observer analysis” was carried out. Anatomical and pathological structures were classified into one of four grades. Results were significantly (P < 0.01) better using magnification radiography. We conclude that the magnification technique is a good method for monitoring fracture healing in its early stages.

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.

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.

Methods of assessing radiographic change in rheumatoid arthritis

The first attempt at standardization in the evaluation of rheumatoid arthritis was reported by Steinbrocker in 1949. Subsequently, Kellgren in the late 1950s, Sharp in 1971, and Larsen in 1973 reported detailed techniques for semiquantitative evaluation of radiographic changes and indicated that joint films may be the most accurate and reproducible basis for assessing the severity and progression of rheumatoid arthritis. High-resolution magnification radiography, achieved by optical magnification of fine-grain film or direct radiographic magnification, has proved particularly valuable for the reliable and sensitive evaluation of articular abnormalities in arthritis. Studies have supported the clinical usefulness of these techniques in assessing early rheumatoid arthritis. A semiquantitative radiographic approach recently used in a multicenter clinical trial is illustrated herein. Results indicate a high interobserver correlation for grades of erosion and joint-space narrowing. The sensitivity with which observers graded the findings, however, varied among observers despite the use of reference standards. There was poor correlation among observers for assessing changes in grade with time so that evaluation of clinical response was limited. Observations from this analysis provide the basis for improved methods in the design of clinical therapeutic trials.

Direct radiological magnification of thin objects compared with contact exposures and mammographic techniques (author's transl)

Image quality of phantom objects examined by direct radiographic magnification was analysed. The following results were obtained. Improvement in image quality by direct x 2 magnification of fine, but contrasted, details is very limited. Contact examination using suitable imaging systems provides images of equal quality. Course detail with poor contrast is poorly rendered by direct radiographic magnification. Mammographic techniques are better suited for this purpose. Exposures, using mammographic techniques, produce the same dose rates as direct magnification. In view of the improved image quality, this method is therefore to be preferred. It also appears that the dose rate for comparable image quality for different techniques (direct magnification, mammography, contact exposures) is approximately the same.

Application of direct magnification radiographic technique to the jaws

Direct magnification radiography is widely applicable to situations in which enhanced definition and enlarged images are desirable. This technique is capable of providing high subject resolution when conventional radiography is not definitive. It serves as a valuable supplementary radiograph for the diagnosis of conditions in the oral and maxillofacial region. The general mechanics of the technique as well as its possible use as a supplementary high detail film are discussed. Three cases are reported in which this technique was applied in the diagnosis of oral and maxillofacial surgery patients.

Direct magnification radiography of the newborn infant.

Recent advances in technology have made direct radiographic magnification of the newborn infant clinically feasible. A microfocus radiographic tube and a rare-earth, high-speed recording system were combined to obtain more than 2,000 radiographs at magnifications of 2-2.5. Special positioning devices permitted imaging of even those infants confined to incubators and connected to life-supporting systems. When quantitatively compared with three conventional contact radiographic systems with respect to resolution, contrast, and noise, magnification radiography showed overall superiority of image characteristics. Definition of subtle abnormalities and anatomically small structures permitted diagnoses which could not be made from conventional images. Furthermore, infant radiation exposure was markedly less (15 mR [3.9 mC/kg] maximum skin exposure) as compared with conventional contact radiographic systems (24 mR [6.1 mC/kg] to 45 mR [11.6 mC/kg]).

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.

Finger arthrography.

The use of arthrography in patients with chronic finger complaints is discussed. Magnification arthrography was performed to assist the clinical evaluation of 15 patients with pain in the metacarpal-phalangeal or proximal interphalangeal joints. Conditions detected include collateral ligament laxity, extravasation around the volar plate, and fibrous ankylosis. Demonstration of normal articular cartilage was important for clinical management in some patients. Direct radiographic magnification was considered useful for best visualization, but tomography was not helpful.

Direct magnification radiography using conventional radiographic equipment.

Direct magnification radiography provides superior image quality with a resultant increase in diagnostic accuracy [1]. An x-ray tube with a nominal focal spot size of 0.1 mm is necessary for twofold or greater magnification [2]. Most recent reports on magnification radiography have used a 0.09 mm nominal focal spot x-ray tube consisting of an electron gun and a 45#{176} stationary anode (RSI MFT 1, Radiologic Sciences). Because of the cost, exposure limitations, examination limitations, and additional space needed for this dedicated unit, we recently installed a conventional notating anode microfocal spot x-ray tube in a skeletal radiography room. We describe the advantages and disadvantages of this system after our initial 6 months of experience.

Evaluation of magnification radiography in bone tumors.

The additional information obtained by direct radiographic magnification is examined in comparison to standard exposures of 50 bone tumors. A diagnostically significant increase in information is obtained in 84% of these cases. This is distributed at an irregular rate over the various decisive phases of the tumor diagnosis. In 24% of the cases the magnification exposure was helpful excluding other diseases, in 40% it permitted a differentiation between benign and malignant lesions and in 20% it permitted a classification of the type. The clinical importance of the magnification technique is relevant.

The fork-lift infant elevator for neonatal magnification radiography.

A new device permitting direct radiographic magnification (2.2 X) of the newborn infant without patients transfer from the protective environment of an incubator is described.

The Many Advantages of Direct Microfocus Roentgenographic Magnification in Pediatric Radiology

Direct radiographic magnification as a means of complementing diagnostic imaging is not a new concept.1 The technique has been used widely, but never applied generally because a bigger image was not necessarily a better image. The physics of direct roentgenographic imaging is a complex marriage of x-ray beam geometry and the physicochemistry of photon absorption within a cassette. Until the time of development of the Radiological Sciences Inc (RSI) x-ray tube, virtually all medical x-ray tubes depended on a hot tungsten filament as the initial source of electrons for the generation of x-ray photons (ie, since 1913, when Coolidge2introduced the first filament x-ray tube). Detail in magnification is adversely affected by imperfections in the beam source. The standard filament x-ray tubes usually produce two point sources and a trailing edge of radiation off their axes. The resultant images are blurred, and this blurring is amplified by magnification. Therefore, the