Magnification Technique Research Articles

Use of the direct magnification technique in dental radiology

Use of the direct magnification technique in dental radiology

Mammography grid performance.

To measure directly the grid performance of mammography units for the range of breast thicknesses and x-ray tube potentials encountered in clinical practice. Contrast improvement factors and Bucky factors were determined for four mammographic units as a function of x-ray tube potential (25, 30, and 35 kVp), phantom thickness (2, 4, and 8 cm) and, on one unit, three target-filter combinations. Three units used a linear grid; one, a cellular grid. Two methods were used for nongrid measurements. For all units tested, contrast improvement factor increased with increased phantom thickness and with increased kilovolt peak level for the 8-cm-thick phantom and changed little with kilovolt peak level for 2- and 4-cm-thick phantoms. At 25 and 30 kVp, contrast improvement factor performance with the linear grids was comparable; with the cellular grid, it was 5%-10% higher. In all cases, the Bucky factor increased with increased phantom thickness and decreased with increased tube potential. Differences in grid performance exist. At 25 and 30 kVp, the cellular grid exhibited superior contrast improvement factor performance, whereas one of the linear grids exhibited superior Bucky factor performance. Measured contrast improvement and Bucky factors are dependent on nongrid technique. Cassette tunnels introduce scatter and should not be used with nongrid or magnification techniques.

Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry (SEM/EDS): The Last Step in the Microanalysis of Particulate Matter Isolates

Abstract The SEM/EDS is a valuable tool in the pharmaceutical industry for aiding in the identification of isolated particles. It is a part of our systematic approach which proceeds from lower magnification techniques, e.g., stereomicroscope, to higher magnification techniques, eg., polarized light microscopy, and finally to the high magnification of SEM/EDS. Particles associated with pharmaceutical product rejects are due to a variety of sources, often due to the ubiquitous use of some materials, e.g., stainless steel alloys, in the manufacturing arena. Our particles of interest range in size from submicron to ≥ 50 μm (visible with the unaided eye), appearing in numerous shapes and/or colors. Any particles contained in a drug product or associated with the package are objectionable. Detection during production operations and/or during the terminal 100% inspection prior to market release will cause product rejection. In any case, foreign particles are not tolerated. Their identification leads to their source and thus proper corrective action.

Scatter rejection by air gaps in diagnostic radiology. Calculations using a Monte Carlo collision density method and consideration of molecular interference in coherent scattering

The air gap technique is an old method for scatter rejection. It is still used in lung examinations and may be reconsidered for use in digital radiography. Using magnification techniques, for example in mammography, the air gap thereby introduced simultaneously yields scatter rejection. A Monte Carlo collision density method is exploited to investigate the physical parameters relevant to this technique. Radiation quantities of scattered photons at points behind a water slab both on and laterally displaced from the central axis are calculated and their dependence on field area, slab thickness, air gap length and detector type is derived. Values of `scatter-to-primary' ratios of the plane energy fluence (the energy imparted to a totally absorbing detector) are given for perpendicularly incident 30, 70 and 130 kV energy spectra, slab thicknesses of 0.05 and 0.2 m (30 kV: 0.05 m), air gaps of length 0.002 - 1.0 m and field areas from to . Contrast degradation factors are derived for both totally absorbing and thin detectors. The influence on the scatter-to-primary ratios of using divergent instead of parallel beams and of neglecting molecular interference in coherent scattering is analysed.

The renal axes in spina bifida: issues of confusion and fusion.

The occurrence of horseshoe kidneys in myelodysplasia has been suggested to be overestimated because of the concurrent prevalence of kyphotic spine in the spina bifida population. Pseudohorseshoe kidneys result from the actual medial migration and apposition of the lower renal poles in the deep fossa created by the gibbus deformity. The presence of a lumbosacral kyphosis, however, does not imply there is not a true horseshoe kidney. In our myelodysplasia population of 189 patients, occurrence of true horseshoe kidneys (13 patients) and pseudohorseshoe kidneys (14 patients) was increased. The finding of lumbosacral kyphosis was twice as common in the pseudohorseshoe population as in the true horseshoe population. True horseshoe kidneys were three times more commonly seen in association with congenital vertebral anomalies cephalad to the dysraphic spine. Diagnosis in this study was predominantly based on renal cortical scintigraphy with the posterior pin-hole magnification technique.

Measurement System for Electric Field-Induced Strain by Use of Displacement Magnification Technique

A new, simple, and precise method has been developed for the measurement of electric field-induced strain, which is based on the displacement magnification technique. This technique is stable against environmental vibration noises, and is able to measure strains with 6 to 10 times higher resolution than that of a displacement sensor itself. Using this method, I constructed a novel measurement system which simultaneously collects data of field-induced strain, strain rate, polarization, current and acoustic emission (AE) under high electric field drive for piezoelectric and electrostrictive materials. The system reveals, for soft tetragonal lead zirconate titanate (PZT) ceramics, that 180 deg domain walls move before 90 deg domain walls move at around the coercive electric field strength under ±1500 V/mm electric field drive at a frequency of 0.05 Hz. AE is not generated around the coercive electric field, but is at high strain state. Some discussions are given about the origins of these phenomena.

Blind Tests of Inter-analyst Correspondence and Accuracy in the Identification of Cut Marks, Percussion Marks, and Carnivore Tooth Marks on Bone Surfaces

We show through blind tests that marks inflicted on bone surfaces by carnivore teeth, hammerstone percussion, and metal knife cutting and scraping can be distinguished with near perfect reliability without scanning electron microscopy or consideration of only conspicuous marks. Using low-cost and high-volume hand lens and low-power light microscope techniques, we determined the presence or absence of conspicuous and inconspicuous marks with 97% three-way correspondence, and diagnosed marks of known origin to actor and effector with 99% accuracy. Novices with less than 3 h training on control collections correctly diagnosed 86% of classic but mainly inconspicuous marks. Novices spending several more hours studying control specimens elevated their diagnostic accuracy on morphologically representative marks to near-expert levels of 95%. Our results show that published cautions about mimicry among cut marks, percussion marks, and carnivore tooth marks are overstated. All types of marks examined can be identified reliably, regardless of conspicuousness. As such, fully standardized comparisons of mark frequencies can be drawn among assemblages, even those documented by different analysts. However, such robust interpretations can be attained only if analysts base diagnoses on (a) a firm familiarity with bones marked under strictly controlled conditions, (b) the systematic application of published morphological and contextual criteria, and (c) the use of prescribed low-power magnification techniques.

High-definition radiography of tube-to-tubesheet welds of steam generator of prototype fast breeder reactor : Venkatraman, B.; Sethi, V.K.; Jayakumar, T.; Raj, B. Insight, Vol. 37, No. 3, pp. 189–192 (Mar. 1995)

In the steam generator of the Prototype Fast Breeder Reactor (PFBR), steam is generated by the transfer of heat from secondary sodium to water. Due to the inherent dangers of sodium-water reaction, the integrity of weld joints separating sodium and water/steam is of paramount importance. This is particularly true and very important for the tube-to-tubesheet joints. This paper discusses the use of projective magnification technique by microfocal radiography for the quality evaluation and optimisation of the welding parameters of such small tube-to-tubesheet welds of the steam generator of PFBR. It should be mentioned here that in a recent article on microfocus radiography (1) , Dr Halmshaw observed that little had been published on the application of projective magnification techniques using microfocal radiography for similar small-bore pipe welds.

An improved mode of operation of a transmission electron microscope for wide field off-axis holography

An improved mode of operation for low magnification off-axis electron holography is presented which permits a significant increase of the field of view over that obtained by the standard low magnification technique in a standard field emission transmission electron microscope. This improvement is achieved by a weak excitation of the objective lens. Ray diagrams for the different low magnification modes are discussed and verified on a Hitachi HF-2000 transmission electron microscope operated in free lens control mode.

233. 乳房撮影における1.2倍準拡大撮影の有用性 : 臨床における微小石灰化の描出比較

233. 乳房撮影における1.2倍準拡大撮影の有用性 : 臨床における微小石灰化の描出比較

Bedside fluoroscopy for the detection of foreign bodies.

To determine the sensitivity and specificity of portable fluoroscopy for foreign-body detection using an ex-vivo experimental model. A prospective, randomized masked investigation was performed to characterize foreign-body detection in cubes of beef. Three emergency physicians (EPs) independently used a portable fluoroscope to determine the presence or absence of various foreign bodies in ten cubes of beef (approximately 6 cm on each side). Six different groups of foreign bodies were examined: glass, wood, graphite (pencil lead), metal (needle), plastic, and gravel. An independent observer placed the six objects randomly into each set of ten beef cubes. One hundred observations were made by each physician using sets of ten beef cubes at a time. Fluoroscopy detected 117 of 180 foreign bodies (sensitivity 65%; 95% CI 58-72%), including all cubes of beef embedded with gravel, metal, and glass. Graphite was detected 27 of 30 times (sensitivity 90%; 95% CI 74-98%). None of the plastic or wooden foreign bodies was identified despite magnification techniques and real-time imaging (sensitivity 0%; 95% CI0-12%, each). Of the 120 cubes of meat with no foreign body, two false-positives were recorded (specificity 98%; 95% CI 94-100%). The overall positive predictive value and negative predictive value of fluoroscopy were 98% and 65%, with 95% CIs of 94-100% and 58-72%, respectively. Interobserver agreement between the three EPs was considered excellent (kappa = 0.75). Bedside fluoroscopy lacks sufficient sensitivity to rule out many foreign bodies in the ED. Its use should be limited to suspected gravel, glass, pencil lead, and metallic objects, which are known to be radiopaque.

Alternative procedure for failed reconstruction of a right replaced hepatic artery in liver transplantation.

A right replaced hepatic artery (RRHA) arising from the superior mesenteric artery (SMA) is the most frequent variation of the hepatic arterial supply requiring backtable reconstruction. There are several widely used techniques for backtable reconstruction of the RRHA to a single conduit. If these reconstructions fail, due to technical reasons or size discrepancies, an alternative method of rearterialization is needed. We describe six cases in which an RRHA was anastomosed to the donor's gastroduodenal artery (GDA) stump utilizing a loupe magnification technique. In four cases the reconstruction was performed at the time of the backtable procedure and in two after reperfusion and failure of the original RRHA to splenic artery (SA) reconstruction. In all cases, the anastomoses remained patent. All patients had Doppler sonography and two had subsequent arteriograms that verified anastomotic patency. This method of reconstruction is more demanding technically but obviates the awkward 90-degree twist of the hepatic artery when an RRHA is anastomosed to the SA stump.

Alternative procedure for failed reconstruction of a right replaced hepatic artery in liver transplantation

Abstract A right replaced hepatic artery (RRHA) arising from the superior mesenteric artery (SMA) is the most frequent variation of the hepatic arterial supply requiring backtable reconstruction. There are several widely used techniques for backtable reconstruction of the RRHA to a single conduit. If these reconstructions fail, due to technical reasons or size discrepancies, an alternative method of rearterialization is needed. We describe six cases in which an RRHA was anastomosed to the donor's gastroduodenal artery (GDA) stump utilizing a loupe magnification technique. In four cases the reconstruction was performed at the time of the backtable procedure and in two after reperfusion and failure of the original RRHA to splenic artery (SA) reconstruction. In all cases, the anastomoses remained patent. All patients had Doppler sonography and two had subsequent arteriograms that verified anastomotic patency. This method of reconstruction is more demanding technically but obviates the awkward 90-degree twist of the hepatic artery when an RRHA is anastomosed to the SA stump.

Computed VS. Film-Screen Magnification Radiography of Fingers in Hyperparathyroidism

One hundred randomly selected patients with suspected or known hyperparathyroidism were examined in a prospective study of the 2nd and 3rd fingers with film-screen and digital luminescence radiographs using magnification technique. The digital images were displayed on a work-station and printed as hard-copies. Two radiologists evaluated the film-screen images regarding subperiosteal and intracortical resorption and their results were defined as "gold standard" regarding the absence or presence of these changes. Four radiologists evaluated these changes in the 3 image forms and an ROC analysis was performed. Comparing the areas under the ROC curves no significant difference was found between the film-screen images and the 2 digital display forms. These results suggest that currently available digital systems provide adequate diagnostic accuracy for evaluation of subtle skeletal changes.

Computed Vs. Film-Screen Magnification Radiography of Fingers in Hyperparathyroidism

One hundred randomly selected patients with suspected or known hyperparathyroidism were examined in a prospective study of the 2nd and 3rd fingers with film-screen and digital luminescence radiographs using magnification technique. The digital images were displayed on a work-station and printed as hard-copies. Two radiologists evaluated the film-screen images regarding subperiosteal and intracortical resorption and their results were defined as “gold standard” regarding the absence or presence of these changes. Four radiologists evaluated these changes in the 3 image forms and an ROC analysis was performed. Comparing the areas under the ROC curves no significant difference was found between the film-screen images and the 2 digital display forms. These results suggest that currently available digital systems provide adequate diagnostic accuracy for evaluation of subtle skeletal changes.

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.

The role of bone scintigraphy in detecting child abuse

This review of diagnostic imaging in cases of suspected child abuse characterizes the significant differences between bone scintigraphy and x-ray evaluation, describes the advantages and disadvantages of each modality, postulates on the specific mechanisms of injury that produce the characteristic scintigraphic findings, and emphasizes the influences that scintigraphic studies have on the medical, social, and legal aspects of child abuse. The major advantages of bone scintigraphy are its increased sensitivity (25% to 50%) in detecting evidence of soft tissue as well as bone trauma in child abuse. Furthermore, it is postulated that the specific mechanisms of inflicting the trauma relate to the patient's size and are characterized by bone scintigraphy. During fits of anger or frustration, the perpetrator of child abuse grasps the small infant or child by the thorax during the shaking activity. This produces characteristic rib injuries. The older and heavier child is more likely to be grabbed by the extremities, which produces periosteal injuries manifested as characteristic abnormal localizations in the diaphyses of the extremities. The roentgenograms of these injuries are frequently normal. The importance of bone scintigraphy is its complementary nature in defining and characterizing the extent and severity of trauma from child abuse. Such findings have direct bearing on the medical, social, and legal outcomes for the abused child. The quality of scintigraphic imaging is important, requiring the use of magnification techniques in the infant. The interpretation of the scintigraphic images depends on an understanding of the mechanisms by which the radionuclide localizes in bone. The same traumatic incident can lead to decreased, normal, or increased localization at the trauma site. Radionuclide scintigraphy is a complementary rather than competitive imaging modality to X-ray evaluation in the diagnosis and management of physical child abuse.

41. ハウレットチャートを用いた DSA の画像評価 : 第 2 報 最適な拡大撮影を選択するための簡便法(応用撮影 DSA)

41. ハウレットチャートを用いた DSA の画像評価 : 第 2 報 最適な拡大撮影を選択するための簡便法(応用撮影 DSA)

Preoperative needle localization of subtle breast calcifications: magnification technique.

The authors adapted a windowed needle localization compression plate to allow performance of mammography with magnification technique, facilitating preoperative needle localization of subtle breast calcifications. The technique has been successfully used in 20 needle localization procedures.

Phosphor plate mammography: contrast studies and clinical experience

Mammography and accurate microcalcification detection require very good spatial resolution. We have compared the diagnostic capabilities of reduced-exposure, third-generation, 5 cycles/mm computed radiography (CR) phosphor plates with conventional screen-film in 67 patients. No difference in diagnostic accuracy was detected. The digital characteristics of storage phosphor plates erabled us to study the relationship between contrast and spatial resolution. We developed a computer program to identify a single 100 μm pixel in a digital image and assign various gray levels to that pixel. Using this model, we determined that, for our 5 cycles/mm CR system, the imaged contrast of a 100 μm object was 62% of the original contrast. Current 5 cycles/mm phosphor plate systems cannot adequately detect microcalcifications that approximate 100 μm or smaller unless a magnification technique is used.