Comparison of testing of collimator and beam alignment, focal spot size with slit camera, and tube current consistency using computed radiography and conventional screen-film systems.

Conversion to a filmless technique of physical performance testing is becoming a topic of much interest to researchers. We assessed the use of a computed radiography (CR) system with postprocessing software as an alternative tool for performing the three physical performance tests of an x-ray tube. Collimator and beam alignment, focal spot size, and milliampere second (mAs) linearity, were performed using a CR system. Results were then compared with those obtained from a conventional screen-film (SF) system. The distances of collimator misalignment measured by the SF system were decreased while peak tube voltage (kVp) was increased (mAs was fixed), whereas those measured by CR were independent of exposure level. The degrees of beam collimator misalignment measured by the CR system were not different from those measured by the SF system. The differences in focal spot dimensions measured by SF and CR systems were less than 4% for large and small focal spot size in both width and length. The mAs linearity evaluated by the SF system agreed with those evaluated by the dose measurement at 50 kVp and 4 mAs, as well as 55 kVp and 3.2 mAs, while the mAs linearity test using the CR system agreed with those using the dose measurement method for all exposure levels. In summary, a CR system could be utilized to assess the three physical performance tests of a single x-ray tube, but required more time than an SF system. Medical physicists with image processing skills were needed to perform the analyses.

Inaccuracies in the Use of Magnification Markers in Digital Hip Radiographs.

BACKGROUND: With the ubiquity of digital radiographs, the use of digital templating for arthroplasty has become commonplace. Although improved accuracy with digital radiographs and magnification markers is assumed, it has not been shown. QUESTIONS/PURPOSES: We wanted to (1) evaluate the accuracy of magnification markers in estimating the magnification of the true hip and (2) determine if the use of magnification markers improves on older techniques of assuming a magnification of 20% for all patients. METHODS: Between April 2013 and September 2013 we collected 100 AP pelvis radiographs of patients who had a THA prosthesis in situ and a magnification marker placed per the manufacturer's instructions. Radiographs seen during our standard radiographic review process, which met our inclusion criteria (AP pelvic view that included a well-positioned and observed magnification marker, and a prior total hip replacement with a known femoral head size), were included in the analysis. We then used OrthoView(TM) software program to calculate magnification of the radiograph using the magnification marker (measured magnification) and the femoral head of known size (true magnification). RESULTS: The mean true magnification using the femoral head was 21% (SD, 2%). The mean magnification using the marker was 15% (SD, 5%). The 95% CI for the mean difference between the two measurements was 6% to 7% (p < 0.001). The use of a magnification marker to estimate magnification at the level of the hip using standard radiographic techniques was shown in this study to routinely underestimate the magnification of the radiograph using an arthroplasty femoral head of known diameter as the reference. If we assume a magnification of 20%, this more closely approximated the true magnification routinely. With this assumption, we were within 2% magnification in 64 of the 100 hips and off by 4% or more in only four hips. In contrast, using the magnification marker we were within 2% of true magnification in only 20 hips and were off by 4% or more in 59 hips. CONCLUSION: We found the use of a magnification marker with digital radiographs for preoperative templating to be generally inaccurate, with a mean error of 6% and range from -5% to 15%. Additionally, these data suggest that the use of a magnification marker while taking preoperative radiographs of the hip may be unnecessary, as simply setting the software to assume a 20% magnification actually was more accurate. LEVEL OF EVIDENCE: Level III, diagnostic study.

The use of digital magnification to reduce radiation dose in the cardiac catheter laboratory.

OBJECTIVES: To audit whether using magnification of images by use of a large viewing screen using digital matrix magnification which enlarges the image by 33% without using the X-ray machine zoom magnification protocols on a Siemens Artis Zee X-ray machine in a cardiac catheter laboratory results in a reduction of kerma-area product (KAP) for both diagnostic and interventional procedures. This reduction was predicted in an in vitro study in our laboratory, which has previously shown a 20.4% reduction in KAP. METHODS: A retrospective analysis was conducted of the radiation exposure to compare the measured KAP recorded during the period when conventional magnification with automatic brightness and dose control was used on a Siemens Artis Zee X-ray machine with a flat panel detector and when magnification settings were avoided by using a large screen to enlarge and project a non-magnified image by digital magnification. The analysis was carried out for patients having a diagnostic coronary angiogram and those having an interventional coronary procedure. RESULTS: For diagnostic coronary angiograms the median KAP per procedure in the period using conventional magnification was 2124.5 µGy.m2 compared to 1401 µGy.m2 when image matrix magnification was used, a 34% reduction (p < 0.0001). For interventional coronary procedures, the median KAP per procedure in the period using conventional magnification was 3791 µGy.m2 compared to 2568.5 µGy.m2 when image matrix magnification was used, a 32% reduction (p < 0.0001). CONCLUSION: Avoiding using conventional magnification in the cardiac catheter laboratory and using a large screen to magnify images was associated with a statistically significant greater than 30% reduction in KAP. ADVANCES IN KNOWLEDGE: This paper is the proof in clinical practice of a theoretical conclusion that radiation dose (KAP) is reduced by use of Image matrix magnification using a large viewing screen without the need to use X-ray tube magnification without significant loss of image resolution in interventional cardiology. The same approach will be useful in interventional radiology.

Calibration of radiographs by a reference metal ball affects preoperative selection of implant size.

The aim was to evaluate the impact of a reference ball for calibration of periapical and panoramic radiographs on preoperative selection of implant size for three implant systems. Presurgical digital radiographs (70 panoramic, 43 periapical) from 70 patients scheduled for single-tooth implant treatment, recorded with a metal ball placed in the edentulous area, were evaluated by three observers with the intent to select the appropriate implant size. Four reference marks corresponding to the margins of the metal ball were manually placed on the digital image by means of computer software. Additionally, an implant with proper dimensions for the respective site was outlined by manually placing four reference marks. The diameter of the metal ball and the unadjusted length and width of the implant were calculated. Implant size was adjusted according to a "standard" calibration method (SCM; magnification factor 1.25 in panoramic images and 1.05 in periapical images) and according to a reference ball calibration method (RCM; true magnification). Based on the unadjusted as well as the adjusted implant dimensions, the implant size was selected among those available in a given implant system. For periapical radiographs, when comparing SCM and RCM with unadjusted implant dimensions, implant size changed in 42% and 58%, respectively. When comparing SCM and RCM, implant size changed in 24%. For panoramic radiographs, comparing SCM and RCM changed implant size in 48%. The use of a reference metal ball for calibration of periapical and panoramic radiographs when selecting implant size during treatment planning might be advantageous.

Trends in image quality in high magnification digital specimen cabinet radiography.

Advances in microfocus X-ray tube design together with the availability of high resolution charge coupled device (CCD) detectors have led to the introduction of high magnification digital specimen cabinets for the examination of tissue samples. This paper explores the effect that the high magnification geometry permitted by such units has upon image quality in terms of phase contrast edge enhancement, spatial resolution and the appearance of test phantom images. Phase contrast effects and spatial resolution were studied using a previously established method (using edge profiles) and by computing the system spatial frequency response at various geometries. It was demonstrated that the magnitude of the phase contrast enhancement effect reaches a stable maximum at a magnification of x 4. It has also been shown that a continual increase in both the spatial resolution together with an improved signal to noise ratio occurs up to the maximum permissible magnification geometry, with effects of focal spot blur being negligible. In practice, the limited size of the digital detector and the difficulty of object alignment can constrain the use of the very high magnification option.

A comparative evaluation of rare-earth screen-film systems. System speed, contrast, sensitometry, RMS noise, square-wave response function, and contrast-dose-detail analysis.

We evaluated the physical characteristics and contrast-dose-detail performance of 11 rare-earth and three calcium tungstate screen-film systems. Measurements included system speed, contrast, sensitometry, RMS noise, square-wave response function, and contrast-dose-detail analysis. The major differences in physical characteristics among systems were system speed and RMS noise. Square-wave response differences were more subtle. For contrast-dose-detail analysis, the rare-earth screen-film systems and the calcium tungstate system responses were significant over a limited subject contrast range as a function of detail diameter. Relative dose efficiency in the noise-limited region is a function of the properties of the screen only and is independent of the film.

Optimal sampling interval and edge detection algorithm for measurement of blood vessel diameter on a cineangiogram.

RATIONALE AND OBJECTIVES: The authors studied the effects of image magnification and the type of edge detection filter on the precision of measuring blood vessel diameters on coronary angiograms. METHOD: A blood vessel phantom containing five channels of various diameters filled with contrast medium was filmed. The magnifications examined were x4, x10, and x20, and the edge detection filters used were the first derivative, second derivative, composite, and entropy filters. The regression line y = a+bx was introduced, where x represents the nominal diameter and y the diameter measured by the edge-detection filters. Determination criteria were the offset, slope, and residual variance from the regression equation. RESULTS: The best value among three criteria was obtained with a magnification of x10 or x20. The entropy filter gave the best value of slope and residual variance. The composite filter gave the best value of offset. CONCLUSION: The most precise measurement is obtained when the entropy filter and a magnification of x10 or x20 are applied.

Film-screen magnification versus electronic magnification and enhancement of digitized contact mammograms in the assessment of subtle microcalcifications.

RATIONALE AND OBJECTIVES: To compare information drawn from magnification mammography with that extracted from electronic magnification, processing, and display of the digitized contact images. METHODS: Contact and magnification images of a mammographic statistical phantom were obtained. The magnification films versus the computer-enhanced, digitized images of the corresponding contact mammograms were separately presented to three observers. Receiver operating characteristic analysis was used to compare lesion detectability. The contact and magnification mammograms of 86 patients with subtle microcalcifications were also studied. The breast imaging reporting and data system (BI-RADS) scheme was used to compare the magnification patient films versus the corresponding digitized contact images. Differences in mammographic assessment were evaluated by using the kappa statistic. The dose to breast tissue from contact and magnification mammography was measured to evaluate dose reduction in instances where magnification mammography was to be avoided. RESULTS: Lesion detectability was found to be similar when either the digitized film image or the magnification hard-copy film was inspected. Interpretation of patient images by inspection of the contact and magnification screen-film mammograms on a view-box was in excellent agreement with that yielded by inspection of the contact image on a view-box and the computer-enhanced, digitized contact image on a display monitor. CONCLUSIONS: Electronic magnification and processing of the digitized contact image may provide valuable information concerning subtle microcalcifications, rendering magnification mammography unnecessary for many patients with such lesions.

Image-guided or needle-localized open biopsy of mammographic malignant-appearing microcalcifications?

BACKGROUND: The evaluation and initial management of abnormalities detected on screening mammography have evolved substantially over the last decade. This study was designed to evaluate the most appropriate initial diagnostic biopsy technique for patients presenting with malignant-appearing microcalcifications on screening or diagnostic mammography. STUDY DESIGN: An institutional review of a prospective database was performed to compare initial image-guided breast biopsy (IGBB) and needle-localized open biopsy (NLOB) in patients presenting with malignant-appearing microcalcifications. Patients with atypical hyperplasia (AH) or carcinoma in situ (CIS) were identified and reviewed separately. Measures of outcomes included the total number of procedures, time from initial biopsy to definitive treatment, charges, and percentages of patients who required both procedures. RESULTS: A total of 17,121 patients underwent mammography from July 1994 to December 1996 at Gundersen Lutheran Medical Center. Indeterminate microcalcifications were found in 167 patients and were the reason for IGBB in 112 and NLOB in 55 patients. Histologic results included 81 patients (48%) with benign lesions, 25 (15%) with invasive cancers, and 61 (37%) having a proliferative finding including AH or CIS. Ductal CIS was present in 42 (72%) of the 61 proliferative lesions. Comparisons were made between the groups of patients with CIS or AH who underwent initial NLOB (n = 25) versus those having initial IGBB that was followed by a secondary NLOB (n = 25). The median elapsed time to definitive therapy was 20 days (range 0 to 336 days) for initial IGBB followed by NLOB and 7 days (range 0 to 79 days) for an initial NLOB performed for suspicious microcalcifications (p = 0.0367). The total number of procedures performed on each patient and total costs were also less for patients having an initial NLOB. CONCLUSIONS: The time to definitive local therapy, the number of procedures, and overall charges were less for patients with AH or CIS having initial NLOB as opposed to initial IGBB. Careful initial evaluation of microcalcifications may identify some patients for whom an initial NLOB remains the most appropriate procedure. Such patients desiring breast-conserving therapy may benefit in terms of time to definitive treatment, total number of procedures performed, and cost if a careful NLOB is the initial procedure performed as a formal lumpectomy.

Stereoscopic magnification in spinal angiography.

This technique combines the advantages of magnification and stereoscopic angiography. A heavy-duty x-ray tube oscillating between two positions (25 mm apart) allows serial spinal angiograms to be produced in stereo magnification (factor 2.0) using the 0.2 mm, 12 kW focal spot. The x-ray tube can be rapidly changed for normal serial angiography with a 0.6 mm, 50 kW focus. The technique is easy to use for spinal phlebography and arteriography. Vessels can be observed clearly in three dimensions. Difficulties relating to localization of veins (e.g., intra- or extraspinal) are eliminated. The feeding vessels, the draining system, and the exact location of spinal angiomas are more easily recognized. In many cases, only one injection of contrast medium is needed and the use of photographic subtraction radiography is unnecessary.

Application of an x-ray image magnifier to the microradiography of dental specimens.

A highly parallel incident x-ray beam combined with x-ray image magnification was used to obtain high-resolution microradiographs of dental specimens. Preliminary results obtained using a rotating anode x-ray generator show that limitations associated with conventional contact microradiography regarding spatial resolution, sample thickness, and sample orientation, relative to the film, were significantly reduced.

Size estimation and magnification error in radiographic imaging: implications for classification of arteriovenous malformations.

PURPOSE: To assess magnification error in digital subtraction angiography as it pertains to arteriovenous malformation (AVM) size. METHODS: A rectangular grid phantom with equally spaced markers mounted in a stereotactic frame was imaged with digital angiographic equipment. The location and orientation of the grid was altered relative to the central plane of the phantom. Both linear and area measurements were made according to the perceived location of phantom markers using a standard catheter calibration technique and compared with stereotactically derived estimates. Finally, a single case example of an angiographically imaged rolandic AVM was used to compare linear dimensions obtained with both described techniques. RESULTS: The determination of location and size with standard angiographic imaging is subject to error because of the divergent geometry of the incident x-ray beam. The resulting nonconstant geometric magnification causes errors in linear measurements of 10% to 13% at depths of 7 cm from the calibration plane. Errors in area measurements at the same position increase by 20% to 25%. Measurements of maximum diameter or cross-sectional area may have an additional error when nonspherical objects are inclined to the viewing direction (40% at 45 degrees inclination). These errors are reduced to less than 1 mm using the stereotactic technique. Some commercial angiographic systems have internal software to enable a spatial calibration based on known distances in the image or on the diameter of a catheter. The catheter technique was accurate in the calibration direction (perpendicular to the catheter axis) but had a 12% error in the direction parallel to the catheter because of a nonunity aspect ratio in the video system. Measurement of the dimensions of a rolandic AVM using the catheter calibration technique had an error that ranged from -3% to +26% (standard error, 20%) with respect to the stereotactic technique. CONCLUSIONS: Numerous nonstereotactic referential systems for determining linear distances are inherently erroneous by varying degrees compared with the stereotactic technique. Area and volume determinations naturally increase this error further. To the extent that no standardized method for determining linear distances exists, significant variations in estimation of AVM size result. Classification schemes for AVMs have been hampered by this technical error.

Effects of quantum noise and binocular summation on dose requirements in stereoradiography.

In the case of a quantum-noise limited detector, signal detection theory suggests that stereoradiographic images can be acquired with one half of the per-image dose needed for a standard radiographic projection, as information from the two stereo images can be combined. Previously, film-screen stereoradiography has been performed using the same per-image dose as in projection radiography, i.e., doubling the total dose. In this paper, the assumption of a possible decrease in dose for stereoradiography was tested by a series of contrast-detail experiments, using phantom images acquired over a range of exposures. The number of visible details, the effective reduction of the dose, and the effective decrease in the threshold signal-to-noise ratio were determined using human observers under several display and viewing conditions. These results were averaged over five observers and compared with multiple readings by a single observer and with the results of an additional observer with limited stereoscopic acuity. Experimental results show that the total dose needed to produce a stereoradiographic image pair is approximately 1.1 times the dose needed for a single projection in standard radiography, indicating that under these conditions the human visual system demonstrates almost ideal binocular summation.

Magnification and high-resolution radiography in sports-related injuries.

Magnification, or high-resolution radiography, is a widely accepted technique and is currently used in angiography, mammography and pediatric chest radiographs. Small avulsion fractures of the bones of the hand and stress fractures of th tibia are examples of two areas where the fracture may not be apparent on conventional films, although in many cases magnification radiography will demonstrate the lesions. Six representative case histories are provided to illustrate the use of magnification radiography in sports-related injuries.

[Image quality from direct radiological magnification (author's transl)]. / Bildgüteuntersuchung zur direkten röntgenologischen Vergrösserung.

An assessment of image quality from a direct radiological magnification method with a microfocus was carried out. It was found that direct magnification has advantages for the magnification of thin objects (5 cm. thickness). Because of the marked radiation scarrer in thick objects an improvement in picture quality is not possible. Scatter, despite the Groedel effect, is too large. Optimum results are obtained with a microfocus tube using universal screens. Comparable image quality is not possible with high intensification screens. High definition screens are not suitable for magnification. Dose measurements revealed unexpectedly low levels, particularly for thin objects. The reasons for this were examined and are described.

[Direct digital magnification mammography with a large-surface detector made of amorphous silicon]. / Direkt digitale Vergrösserungsmammographie mit einem grossflächigen Detektor aus amorphem Silizium.

PURPOSE: To investigate the image quality of a new direct digital mammography system using a large-area amorphous silicon X-ray detector in a phantom study. MATERIALS AND METHODS: The contrast-detail resolution as a function of the tube voltages, the magnification factors and the mean glandular doses were investigated using dedicated test objects. RESULTS: The contrast-detail resolution was significantly improved in comparison with conventional screen-film mammography. Usually, the doses necessary to obtain these high-quality survey mammograms were smaller. CONCLUSIONS: By combining the direct magnification technique and a digital flat panel detector the limited spatial resolution of such image receptors can be overcome. With this direct digital mammography technique, a digital image was directly captured without an intermediate step of optical or mechanical scan.

[A new specimen radiography device with a maximum 20-fold magnification for breast diagnosis]. / Ein neues Präparatradiographiegerät mit maximal 20facher Vergrösserung für die Mammadiagnostik.

PURPOSE: A radiography system specially developed for specimen radiography and allowing maximal 20-fold magnification is presented. The efficiency of the system was tested and compared with that of conventional magnification mammography systems. METHODS: 23 surgical and 90 core biopsies of the breast were examined for detection of microcalcifications. As criteria the number of identifiable calcifications, their shape and configuration as well as tissue contrast were chosen. RESULTS: The new technique detected about 400% more microcalcifications, 200% more core and 50% more surgical biopsies containing calcifications. Thus, in a few cases, additional core biopsies were unnecessary. Moreover, this new system yielded additional information for the pathologist and surgeon concerning the exact localisation of suspicious lesions that facilitated working up specimens, or indicated additional surgical removal in special cases. CONCLUSIONS: By identification of malignant lesions not detectable with conventional magnification radiography systems, as well as a more exact localisation of suspicious lesions, false negative results may be reduced.

[Stereo magnification angiography--its application in neuroradiology (author's transl)]. / Stereovergrösserungsangiographie--ihre Anwendung in der Neuroradiologie.

The article discusses the stereo magnification technique using the Stereolix system and explains its clinical application in neuroradiology. The special advantage of the Stereolix tube is that it can be used in routine procedure, since it is suitable both for normal serial angiography and--by pressing a button--for stereo magnification angiography. The emphasis of trials was on the applicability for spinal angiography and in the diagnosis of cerebral aneurysms and arteriovenous angiomas.