Pairs Of Radiographs Research Articles

Detection of pneumothorax with lateral shoot-through digital radiography

The aim of this study was to compare the performance of digital frontal radiographs vs digital lateral shoot-through radiographs for the diagnosis of pneumothoraces in supine patients. A total of 146 pairs of radiographs were performed on 32 ventilated patients on the Intensive Care Unit. Each radiograph was independently assessed by three observers for the presence or absence of a pneumothorax. A degree of confidence was assigned to each observation and an image quality score was given to each radiograph. At least two out of three observers positively diagnosed a pneumothorax in 13/146 (8.9%) of the frontal radiographs compared to 43/146 (29.4%) of the lateral radiographs (P < 0.0001), but suboptimal images were obtained more often with lateral shoot-through radiographs than with frontal radiographs. We conclude that digital lateral shoot-through radiographs are significantly more sensitive than digital frontal radiographs for the diagnosis of pneumothoraces in supine patients.

Prediction of the progression of joint space narrowing in osteoarthritis of the knee by bone scintigraphy.

To test the hypothesis that bone scintigraphy will predict the outcome of osteoarthritis (OA) of the knee joint. Ninety four patients (65 women, 29 men; mean age 64.2 years) with established OA of one or both knee joints were examined in 1986, when radiographs and bone scan images (early and late phase) were also obtained. The patients were recalled, re-examined, and had further radiographs taken in 1991. Paired entry and outcome radiographs were read by a single observer, blinded to date order and other data. Scan findings and other entry variables were related to outcome. Progression of OA of the knee was defined as an operation on the knee or a decrease in the tibiofemoral joint space of 2 mm or more. Over the five year study period 10 patients died and nine were lost to follow up. Fifteen had an operation on one or both knees (22 knees). Of the remaining 120 knees (60 patients) analysed radiographically, 14 (12%) had progressed in the manner defined. Of 32 knees with severe scan abnormalities, 28 (88%) showed progression, whereas none of the 55 knees with no scan abnormality at entry progressed. The strong negative predictive power of scintigraphy could not be accounted for by disease severity or any combination of entry variables. Pain severity predicted a subsequent operation, but age, sex, symptom duration, and obesity had no predictive value. Scintigraphy predicts subsequent loss of joint space in patients with established OA of the knee joint. This is the first description of a powerful predictor of change in this disease. The finding suggests that the activity of the subchondral bone may determine loss of cartilage.

Pneumoconiosis: comparison of digitized and conventional radiographs.

The classification of pneumoconiosis on 108 paired radiographs obtained in coal miners was compared by using conventional radiograph film images and digitized images of those conventional film images. Conventional film images and digitized images were each independently read in a random order in two separate sessions by three radiologists certified as "B" readers. Overall, the digitized images were perceived as being of better quality than the conventional film images (radiograph quality grade 1, 48% [617 of 1,292 classifications] vs 37% [482 of 1,296], respectively; P < .001). The mean International Labour Office (ILO) scores for small-opacity profusion were similar between the digitized images and conventional film images (3.14 vs 3.24, respectively; P = .19). The mean absolute differences in small-opacity profusion score between radiograph pairs were also similar (0.74 vs 0.77, respectively; P = .50). No difference in the ILO type of opacity was noted between the display modes. Interpretation of digitized images for pneumoconiotic small opacities was shown to be an acceptable alternative to interpretation of conventional film images; the important problem of reader variability affects both display modes.

Systematic and random errors associated with Johnston's cephalometric analysis.

This study examined intra- and interexaminer systematic and random errors associated with Johnston's cephalometric method of assessing skeletal and dental changes from pairs of radiographs. Data were obtained from the tracings of radiographs of 30 mixed dentition subjects, who had been treated to correct a Class II malocclusion. Measurements included molar and incisor crown movements relative to basal bone, apical base change, maxillary and mandibular displacement relative to the cranial base, and total molar and overjet reduction. In addition, the change in axial inclination of the incisors and molars was determined. A paired t-test for each pair of replicates for each measure was performed to examine inter- and intra-examiner bias. Estimates of the random error, the coefficient of reliability, and confidence limits (95 per cent level) of a single determination were undertaken. No systematic errors occurred between/within examiners for any linear or angular measure. Interexaminer random errors, based on the standard deviation of the mean difference between replicates, were greater than intra-examiner random errors for 12 out of 13 parameters. Measures assessing molar correction and overjet reduction had the least amount of random error variance within and across judges, while changes in mandibular position had the greatest. Because considerable random errors occurred, the Johnston analysis when used to assess skeletal changes, as well as individual molar and incisor movements, may have limited utility in clinical practice for the individual case.

Time‐Related Changes of In Vivo Projection Errors in Standardized Radiographs

Subtraction radiography requires radiographs made with identical projection geometry. Recently a new radiographic aiming device and an x-ray beam manipulator made it possible to repeat radiographic exposures in vivo with small angular errors and to measure the angular errors occurring. The purpose of the present investigation was to study in vivo the measuring error and the angular errors produced by this new method at different time points (0, 6, and 12 months) and to assess the effect of different time intervals between exposures (0, 6, and 12 months). Ten sites were investigated. At each time point 2 exposures were made, resulting in 6 radiographs per site. For each pair of radiographs the measuring errors occurring during analysis and the projection errors were determined for each time point and for each time interval. Friedman's test and t-test were used to evaluate the errors. A difference in the measuring error of the system and in the angular errors at the time points 0, 6, and 12 months could not be detected. A time interval between exposures also did not have an effect on the measuring error. Time did not affect the vertical and horizontal angular errors measured between the radiographs producing the smallest oblique error. A combination of radiographs producing the largest oblique angular error showed an increase of the horizontal and vertical angular errors when the time interval increases. These effects, however, were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed equalization radiography: preliminary clinical evaluation.

Computed Equalization Radiography (CER) was designed to increase visualization of mediastinal structures without affecting lung contrast. CER optimizes the image by obtaining two 1-second fan beam scans. The initial low-dose prescan determines the location of the lungs by means of a stationary krypton gas detector. During the equalization scan, this information is used to position 35 beam attenuators in real time so as to increase exposure of the mediastinum while maintaining ideal optical density over the lungs. Eight observers analyzed 20 pairs of posteroanterior (PA) and lateral radiographs obtained on conventional and CER units. On the PA images, three of four mediastinal areas analyzed were visualized better in CER images, while there was no difference in lung detail. There were no appreciable differences in the lateral projection between the CER and conventional images. Contrast on the PA radiograph was preferred on the CER image. CER provided modest improvement in visualization of mediastinal structures and maintained lung contrast without degrading lung detail on the PA image. CER had no major effect on visualization in the lateral images.

Use of uncalibrated biplanar radiography for the measurement of skeletal coordinates around the shoulder girdle

Mechanical modelling of the musculoskeletal system is dependent upon information regarding the bony attachments of the relevant muscles; in order to study the biomechanics of the shoulder girdle the authors have identified the muscle attachments in three embalmed cadavers. A simple biplanar radiographic technique was then used to determine the attachment coordinates using frames of reference defined for each bone. This technique, using hand positioning without special fixtures was believed to be sufficiently accurate, bearing in mind the likely degree of biological variation. In order to test this assumption, the accuracy of the technique has been studied by measuring the agreement between the two measurements of the common coordinate in the pairs of radiographs. it was found that for the trunk, the errors in the common coordinate were always less than the natural variation; for the scapula they were of a similar magnitude but, for the humerus, the measurement errors frequently exceeded the variation in the coordinates of muscle attachments. It was concluded that, in general, uncalibrated biplanar radiography was sufficiently accurate for the determination of the spatial coordinates of muscle attachments.

Fungal pulmonary infections after bone marrow transplantation: evaluation with radiography and CT.

The authors reviewed 55 pairs of chest radiographs and computed tomographic (CT) studies obtained in 33 febrile bone marrow transplant (BMT) recipients. The images were read separately, without knowledge of the clinical diagnosis. Twenty-one episodes of fungal infection were documented. One chest radiograph showed a pneumonia-like opacity, and 17 showed nodular opacities, five with cavitation. In 20 of 21 episodes, CT showed nodules with cavitation (n = 7), halo (n = 4), hazy margin (n = 5), air bronchogram (n = 2), cluster of fluffy nodules (n = 1), or sharp margin (n = 1). In none of the nine bacteremic episodes, however, were there opacities on chest radiographs or CT studies. CT studies demonstrating complicated nodules in febrile BMT patients strongly suggest a fungal infection, whereas negative CT studies suggest bacteremia or non-filamentous fungal infection of nonpulmonary origin. CT appears to add useful information to radiographic analysis during the assessment of febrile episodes in BMT patients, especially when invasive diagnostic procedures pose a high risk.

Effect of region‐of‐interest in computerized densitometric analysis of radiographs

The region-of-interest (ROI) in computer-assisted densitometric image analysis (CADIA) is defined by its size and location. This study evaluated the effects of these variables on two quantitative parameters, the change in density and the area with change in density. Pairs of radiographs for these analyses were obtained from sites with "no change" or "known loss" in Cynomolgus monkeys during a study of ligature-induced periodontitis. The size and location of the ROI had clear effects on the two CADIA parameters. To reduce these effects, a corrective procedure hypothesizing a linear relationship between the ROI size and the area with change in density was tested. While this procedure was sufficient to correct for ROI size-dependent differences among "no change" images, it was not effective in images with "known loss". In such images, additional adjustments by increasing threshold levels for the registered change in density were found to reduce but not to eliminate differences between ROIs of different size and location. When densitometric radiographic analysis is used for quantitative comparison of different sites, it is primarily recommended to select ROIs of similar size and location. Application of corrective procedures should follow only after careful evaluation of their effects on sensitivity and specificity.

Silicon carbide pneumoconiosis: A radiographic assessment

Interstitial lung disease and airflow limitation have been reported in silicon carbide workers but it is uncertain whether these recent observations reflect past working conditions alone (30 years ago) or both past and present conditions even if the latter have improved. To investigate this, we analyzed pairs of chest radiographs obtained in 1977 and 1984 in 128 silicon carbide plant workers. Three indices, related to density of small opacities, profusion of opacities, and presence of pleural plaques, were obtained. Student t-tests on results obtained in each time period showed the mean density (1.02 in 1977 and 0.56 in 1984) and profusion (4.27 in 1977 and 2.13 in 1984) indices to be significantly different. However, the pleural plaque index was not different in 1984 (0.34) as compared with 1977 (0.32). There was no deterioration of the radiographic image even in groups with density ratios equal or greater than 1/1. We concluded that the actual environmental working conditions did not influence the integrity of the lung radiographic image in these workers within a time span of 6 or 7 years.

Can treatment with methotrexate influence the radiological progression of rheumatoid arthritis ?

We have recently reported that methotrexate (MTX) is an effective treatment of patients with refractory rheumatoid arthritis (RA) to second line medication. We showed that 54% of our patients continued having clinical benefit after 24 months therapy with MTX. In this study we evaluated pairs of hand radiographs from 35 patients taken before and after 24 months treatment. We used a scale scoring similar to Larsen's standard radiographs with minor modifications. No significant changes were observed in the overall scoring of the radiographs before (14.84 +/- 13.05) and after treatment (18.77 +/- 15.60) (p greater than 0.5). Of these 35 patients, 23 had a clinical remission and 12 had a good response. Twenty patients have shown a stabilization of erosions in radiographs while 15 showed a deterioration. No correlation was found between clinical response and radiological changes. We conclude that MTX does not appear to be a disease modifying agent, but may inhibit joint damage progression.

Differences between the hand–wrist and the knee in assigned skeletal ages

Skeletal ages were assessed for 4,902 pairs of hand-wrist and knee radiographs of children aged 2-17 years. The FELS method was used to assess the hand-wrist, and the RWT method was used to assess the knee. These methods have the same conceptual and statistical basis. The mean absolute differences, within age- and sex-specific groups, ranged from 0.34 to 0.87 years. The SD of the differences ranged from 0.31 to 0.68 years and, like the means, tended to increase with age until about 8-11 years. The means and SD were generally larger for the boys than for the girls, except after 14 years. Within age- and sex-specific groups, the maximum absolute differences were from 1.45 to 2.99 years. These maximum differences changed irregularly with age but tended to increase until 11 years in the boys and 9 years in the girls. These large absolute differences between the skeletal ages of the hand-wrist and the knee cannot be explained completely by the effects of observer errors. The means of the relative (signed) differences between the skeletal ages of the hand-wrist and the knee were all close to zero, but there was a wide range within age- and sex-specific groups. These skeletal ages of the hand-wrist and the knee are not interchangeable. The 95th percentiles of the absolute differences show that, in at least 5% of children, the choice of the area for skeletal age assessment will markedly influence the evaluation of individuals. They also demonstrate that descriptions of populations based on distributions of skeletal ages from one part of the skeleton may be misleading.

Evaluating regional body surface motion during breathing using stereophotogrammetry

The stereophotometric analysis of biological forms in medicine has been usefully employed for many years. Generally, the methods adopted have involved the use of stereo pairs of traditional photographs or radiographs. Although very successful, the traditional methods are time-consuming. Developments in solid-state and videoscan cameras, in computer hardware and in image processing technology have lead to real-time photogrammetry (RTP) or near-real-time photogrammetry (NRTP). It is anticipated that RTP and NRTP will play a vital role in biostereometric studies. This paper discusses the development of a low-cost PC-based NRTP system and the possibility of using NRTP in an ongoing biostereometric study which has been developed for studying regional body surface motion in the evaluation of respiratory muscle function and in which digital cameras will be substituted for analogue cameras and computer digitisation will be substituted for manual observation.

The diagnostic value of subtraction radiography in the assessment of granular hydroxylapatite implants

Although histologic analysis of osseous changes around hydroxylapatite (HA) implants can be highly accurate, it is of limited use in human beings. Digital subtraction radiography may provide a noninvasive alternative. Ten patients with bony lesions were operated on and nine of the iatrogenic defects were filled with granulated HA. In one patient, the defect was left unfilled for reference. Customized film holders provided standardized radiography. Follow-up images after 4 to 6 months were subtracted from immediately obtained postoperative images, and changes around the implants were noted. From ten pairs of radiographs, eight could be successfully subtracted, whereas two pairs required corrective image transformation before subtraction. Although no bone loss was observed in any of the patients, the implants did not appear to enhance physiologic bone regeneration either. Hence, subtraction radiography holds the potential of clinical utility for the follow-up of HA implants. However, technical improvements are necessary to yield quantitative data.

Evaluation of Euler's angles with a least squares method for the study of lumbar spine motion

To analyse intervertebral movements, methods with a high level of accuracy are required. Stereoradiographic methods have been used for a number of years to describe intervertebral movements, but their major problem is to identify the same anatomical landmarks, not only on the pair of radiographs used for three-dimensional reconstruction, but also on all the pairs used to analyse the displacements. To minimize the errors due to the incorrect identification of anatomical landmarks, a least squares method to resolve the parameters of Euler's angles was validated by means of measurements made on a spine obtained from a cadaver. The accuracy of this method varied between 0.69° and 0.71° in rotation and between 0.28 mm and 0.77 mm in translation. In addition, this method significantly corrected the position of the anatomical landmarks. Euler's angles, used with a least squares estimate, can provide accurate and precise results.

Comparison of chest radiograph reading methods for assessing progress of pneumoconiosis over 10 years in Wittenoom crocidolite workers.

Thirty three pairs of chest radiographs taken up to 10 years apart were obtained for 33 subjects suffering from asbestosis who had applied for compensation to the Pneumoconiosis Medical Board of Western Australia. Multiple films from the period before the first radiograph in each pair, from the intervening period between the two, and from the period subsequent to the second radiograph were also available and all films were read by two independent readers according to the 1980 ILO classification of pneumoconiosis. Films were read twice as side by side pairs ten years apart, twice as two separate randomly ordered films ten years apart, and once as part of the full series of all available chest radiographs on each subject to assess which method provided the best consistency (between reader variation) and repeatability (within reader variation). Judging by consistency, the full series method performed as well as either of the other methods when assessing radiographic changes and significantly better when assessing the level of profusion of small opacities. There was little to choose between the other two methods either judging by consistency or repeatability, which could not be estimated for the full series method. Use of all available films for a subject is recommended for assessing single films, as in a prevalence study, as well as for documenting change in a longitudinal study.

The influence of the lordotic projection on the interpretation of the chest radiograph

The advantages of the lordotic projection, particularly in elucidating suspected pathology at the lung apex, are well known. However, the distortion and artefact of the images of thoracic structures produced by this projection can lead to diagnostic errors. In order to determine the differences in the images produced we compared 14 pairs of lordotic and standard chest radiographs, taken within 24 h of each other, in the same patients. The main artefacts seen in the lordotic views were apparent elevation of the diaphragm, poor visualisation of the lung bases, loss of definition of the aortic knuckle, and apparent widening of the superior mediastinum. These artefacts were greatly exaggerated when lordosis coexisted with pathology, or technical factors such as patient rotation or inadequate respiration. Caution should be exercised to avoid misinterpretation of lordotic films.

The Effects of Aging on the Comparability of Antemortem and Postmortem Radiographs

To study the effects of aging on the ability to make positive identifications from radiographs of the postcranial axial skeleton, we collected early and later exposed abdominal X-rays from five patients whose period of treatment spanned from ten to twenty-three years. Corresponding lumbar vertebrae from each pair of radiographs were compared for similarities and differences in several of the criteria that have been reported as useful for individualization. These include shapes of the bodies, spinous processes, transverse processes, pedicles, and osteophytic extrusions. It is our conclusion that even though bone is a flexible tissue and changes constantly during life, aspects of the criteria chosen are quite stable and that even after two-and-a-half decades the ability to make positive identifications from postcranial axial material is not necessarily diminished.

Determination of the relative angle between orthogonal films for radioactive implants

Dose calculations for radioactive seed implants require knowledge of the three-dimensional source coordinates. These are usually determined from a pair of orthogonal radiographs. However, occasionally localization films are taken with portable, and/or nonisocentric x-ray units, and no assurances can be made as to whether or not the films were truly exposed in an orthogonal geometry. A three-dimensional magnification ring is described (consisting of three mutually orthogonal rings) which permits the treatment planner to accurately establish the exact source rotation angle used when exposing the films. This angle can in turn be used when reconstructing source coordinates, to insure accuracy in treatment planning.

Accuracy of visually estimated bone mineralization in routine radiographs of the lower extremity.

In order to determine the accuracy of reports of demineralization based on observations of routine radiographs of the peripheral skeleton, pairs of radiographs with known difference in bone mineral density (BMD) were shown to a panel of medically qualified observers. No significant difference in the rate of correct identification of osteopenia of metaphyseal and diaphyseal bone was observed. Experienced observers were more accurate than their juniors. The probability of correct identification was greater than 0.5 at all levels of BMD difference, and in general increased with increasing BMD differences, reaching a probability of 0.7 at a BMD difference of 30%. The probability increased considerably when the assessment relied on the majority vote of three or more observers. It is concluded that it is inadvisable for a single observer to judge BMD when studying routine X-ray studies of the peripheral skeleton.