Detection of emphysema with computed tomography. Correlation with pulmonary function tests and chest radiography

We studied 60 male patients who had concurrent chest films (CXR), computed tomography scans (CT) and pulmonary function tests (PFT) to assess the sensitivity of CT and conventional films in detecting emphysema compared with PFT. We also sought to determine whether emphysema could be diagnosed by CT in patients with normal pulmonary function. Using a method similar to that proposed by Bergin, we scored the severity of emphysema depicted by CT, and using arterial deficiency and bullae as criteria, we estimated the degree of emphysema on CXR. There was a significant inverse correlation between CT scores for emphysema and percentage predicted values of DLco/VA (r = -0.650), FEV1 (r = -0.552), and FVC (r = -0.409), (P less than 0.001). A significant but smaller correlation also was noted with the CXR scores and percentage predicted: DLco/VA (r = -0.564), FEV1 (r = -0.454), and FVC (r = -0.355), (P less than 0.005). When decreased diffusion capacity and airway obstruction were used as functional criteria of emphysema, CT was as sensitive as PFT and more sensitive than CXR in detecting emphysema (96% vs. 68%). There was CT evidence of emphysema in 69% (24/35) of patients who did not have functional findings of emphysema. In 12 pathologic specimens available for review, 11 had emphysema by CT and pathologic examination; one patient had centrilobular emphysema undetected by CT. We conclude that CT is as sensitive as PFT in detecting emphysema and more sensitive than conventional radiography. CT may be more sensitive than PFT in detecting mild emphysema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Large-screen image intensifier photofluorography compared with full-size screen-film technique in chest radiography

Large-screen image intensifier photofluorography revealed a radiation dose and exposure time of about one third of those of a medium speed rare-earth screen/film (Trimax T4/XD) combination for full-size chest radiography. The resolving power of the former technique is somewhat poorer and there is a moderate electron-òptical distortion in the peripheral field. In clinical chest radiography photospot films showed excellent demonstration of the central areas of the image but slight deterioration in peripheral parts. The minification effect of the photofluorographic films is advantageous for visual perception of many anatomic details on chest radiographs. The type of viewing device for photospot films is important.     

Comparison of computed tomography with conventional radiography for midfacial fractures.

OBJECTIVE: To compare the clinical effectiveness of computed tomography (CT) with conventional radiography in midfacial fractures. METHODS: The conventional radiographs (CM) and CT scans of 40 consecutive patients with complex midfacial fractures were assessed independently by two examiners. The number and site of fractures of the orbit, zygoma and maxilla were compared by the Wilcoxon Matched Pairs Signed Rank test. The best method for classification of the fracture was determined. RESULTS: Coronal CT (CCT) proved superior in the diagnosis of orbital fractures (P<0.001). There was no significant difference between any of the imaging methods for fractures of the zygoma. Axial CT (ACT) was the most effective method in imaging of maxillary fractures (ACT-CM; P<0.001, ACT-CCT; P<0.01). CCT was the most useful in classification of orbital and maxillary fracture. CONCLUSION: CCT is superior to CM for the assessment of complex midface fractures     

Variability in densitometric assessment of pulmonary emphysema with computed tomography

OBJECTIVES: The objectives of this study were to investigate whether computed tomography (CT) densitometry can be applied consistently in different centers; and to evaluate the reproducibility of densitometric quantification of emphysema by assessment of different sources of variation, ie, intersite, interscan and inter- and intraobserver variability, in comparison with intersubject variability. MATERIALS AND METHODS: In 5 different hospitals, 119 patients with emphysema were scanned using standardized protocols. In each site, an observer performed a quantitative densitometric analysis (including blood recalibration) on the corresponding patient group (n=23-25) and one observer analyzed the entire group of 119 patients. After several months, the latter observer analyzed all data for a second time. Subsequently, different sources of variation were assessed by variance component analysis with and without volume correction of the data. RESULTS: Inter- and intraobserver variability marginally contributes to the total variability (<0.001%). The interscan variability was 0.02% of the total variation after application of volume correction. The intersite variability was 48% as a result of one deviating CT scanner. Air recalibration normalized deviating air densities in CT scanners. Within sites, the intersubject variability ranged between 93% and 99% based on the analysis of 2 subsequent CT scans of the patients. CONCLUSIONS: Almost all variability in the density measurement of emphysema originates from differences between scanners and from differences in severity of emphysema between patients. Lung densitometry with multislice CT scanners is a highly reproducible measurement, especially if corrected for lung volume, because this reduces interscan variability.     

The value of conventional radiography and computed tomography (CT) in diagnosis of pulmonary hamartoma

No radiologic features are pathognomonic for hamartoma of the lung. Punctate or popcorn calcification, umbilication sign and CT density measurements should be helpful but are not diagnostic. Evidence of fat may suggest pulmonary hamartoma and CT density measurements may be helpful to detect this. A low CT number, however, may be the result of either the partial volume averaging or the presence of fat in the tumour. The definite diagnosis can be made only by histological examination after thoracotomy or transthoracic puncture.     

Pulmonary scintigraphy in elastase-induced emphysema in pigs. Correlation with high-resolution computed tomography and histology.

OBJECTIVES. The objective of this study is to evaluate the mild physiologic changes of elastase-induced pulmonary emphysema in the pig by radionuclide scintigraphy and to correlate these findings with high-resolution computed tomography (HRCT) and histologic examination. METHODS. Eight 7- to 12-week-old Yorkshire pigs were studied. Perfusion and ventilation studies were performed in six pigs at 1- or 2-week intervals after elastase instillation. HRCT was simultaneously performed for correlation with radionuclide scintigraphy. For the perfusion scans, technetium 99m (99mTc) macroaggregated albumin (MAA) was used, and both planar and single-photon emission CT (SPECT) images were obtained. Ventilation studies were performed with xenon-133 gas with dynamic sequential imaging. RESULTS. Histopathologic findings demonstrated dilatation and destruction of the alveoli and were similar to those previously reported by the authors. The SPECT perfusion images showed significantly impaired perfusion of the involved segment of the lung, corresponding to the region where elastase was instilled. The planar xenon-133 ventilation scintigraphy did not show abnormal air trapping. The mild emphysema induced with elastase manifested as decreased and impaired perfusion with no detectable ventilation abnormalities. The sensitivity of SPECT perfusion studies for the detection of the mild changes of elastase-induced pulmonary emphysema were higher than that of HRCT. CONCLUSIONS. The perfusion studies reflect functional or physiologic changes in contrast to structural changes seen on HRCT. This pig model was valuable to study the scintigraphic manifestation of elastase-induced pulmonary emphysema.     

Image-intensifier photofluorography and conventional chest radiography: comparison of diagnostic efficacy

Photofluorography with a large image intensifier, which provides an image field of 40 x 40 cm, reduces both the radiation dose and the imaging costs in chest radiography as compared with the film-screen technique. The two techniques were evaluated in a clinical study of 135 patients with suspected chest abnormalities. Photofluorographs and film-screen chest radiographs were interpreted independently by three radiologists. The diagnoses were confirmed by CT, follow-up radiographs, and clinical records. Among the 135 patients, 75 had primary lung cancer, 39 had pulmonary nodules, 52 had hilar or mediastinal abnormalities, 17 had pleural fluid, and 45 had pneumonic or atelectatic changes. Twenty-three normal subjects were included. Differences in diagnostic accuracy, measured by sensitivity and specificity, were not statistically significant. A larger number of true-positive cases (65%) with peripheral lung nodules were found by photofluorography than by film-screen radiography (54%) (p less than .05). The results suggest that the diagnostic accuracy of chest images made by photofluorography is sufficient to warrant using it instead of the film-screen technique in routine chest radiography, especially to detect lung tumors and metastases.     

Evaluation of heart size and pulmonary vasculature. Conventional chest roentgenography and image intensifier photofluorography compared.

Inter- and intraobserver variation and diagnostic accuracy in estimation of heart size and pulmonary vasculature were evaluated for conventional film-screen technique and image intensifier photofluorography. Interpretation of 218 p.a. and lateral chest films by both imaging techniques was performed independently by 4 readers. Heart size relative to body surface area measured from the plain chest films was used as the reference in cardiac size determination. Overall diagnostic accuracies of conventional radiography and image intensifier photofluorography for cardiomegaly were close to each other, 0.70 vs 0.68, respectively. Specificity of film-screen radiography was better than that of photofluorography (0.92 vs 0.84, p less than 0.05). Interobserver agreement was poor both in assessment of the heart size and pulmonary vasculature (range of kappa coefficients 0.18-0.59) while the intraobserver consistency (kappa coefficients 0.60-0.85) was good to excellent. The results suggest a limited usefulness of visual assessment of heart size and pulmonary vasculature in chest roentgenographs.     

Evaluation of the pulmonary hilum: comparison of conventional radiography, 55 degrees posterior oblique tomography, and dynamic computed tomography

In 84 patients with suspected intrathoracic neoplasms we compared the accuracy of conventional radiography, 55 degrees posterior oblique tomography, and contrast-enhanced dynamic incremental computed tomography (CT) in evaluation of the pulmonary hilum. We found dynamic incremental CT to be better than either conventional radiography or oblique tomography in hilar evaluation. In addition, significant information was detected in extrahilar and extramediastinal locations by CT in 21% of patients. This study, unlike earlier reports, indicates a role for CT in hilar evaluation.     

Acute knee trauma: analysis of multidetector computed tomography findings and comparison with conventional radiography

Purpose: To evaluate the multidetector computed tomography (MDCT) findings of acute knee trauma and to compare radiography with MDCT in patients referred to a level 1 trauma center.

Material and Methods: During a 5-year period, a total of 415 MDCT examinations were performed on 409 patients with acute knee trauma to reveal complex fracture anatomy or rule out a fracture. MDCT and primary radiographs were re-evaluated with respect to fracture location and trauma mechanism. Tibial plateau fractures were further analyzed depending on anatomical location: anterior-medial, anterior-lateral, posterior-lateral, and posterior-medial regions. Maximal depression of the tibial articular surface was measured. Findings on the primary knee radiographs were compared with MDCT findings.

Results: Of the 409 patients, 356 (87%) had a knee fracture. A total of 451 fractures were found in all anatomic regions: distal femur (n = 49), proximal tibia (n = 307), patella (n = 23), and proximal fibula (n = 72). Primary radiographs were available in 316 (76%) cases. Of these, 225 (71%) had MDCT in order to reveal the fracture anatomy better, and 91 (29%) had a subsequent MDCT after negative plain radiographs. Overall sensitivity of radiography was 83%, while negative predictive value was 49%. On radiography, tibial plateau articular depression was underestimated in all regions except when the fracture consisted of the whole half of the anterior or posterior plateau. The three main injury mechanisms were traffic accident, a simple fall, and sport. In 49 cases (15%), primary radiographs were suboptimal due to positioning.

Conclusion: In severely injured patients, diagnostically sufficient radiographs are difficult to obtain, and therefore a negative radiograph is not reliable in ruling out a fracture. In these patients, MDCT is a fast and accurate examination and is also recommended in patients with tibial plateau fractures or complex knee injuries in order to evaluate the fracture adequately.     

Effect of spinal immobilisation devices on radiation exposure in conventional radiography and computed tomography

Trauma patients at risk for, or suspected of, spinal injury are frequently transported to hospital using full spinal immobilisation. At the emergency department, immobilisation is often maintained until radiological work-up is completed. In this study, we examined how these devices influence radiation exposure and noise, as a proxy for objective image quality. Conventional radiographs (CR) and computer tomography (CT) scans were made using a phantom immobilised on two types of spineboard and a vacuum mattress and using two types of headblocks. Images were compared for radiation transmission and quantitative image noise. In CR, up to 23 % and, in CT, up to 11 % of radiation were blocked by the devices. Without compensation for the decreased transmission, noise increased by up to 16 % in CT, depending on the device used. Removing the headblocks led to a statistically significant improvement in transmission with automatic exposure control (AEC) enabled. Physicians should make an informed decision whether the increased radiation exposure outweighs the risk of missing a clinically significant injury by not making a CR or CT scan. Manufacturers of immobilisation devices should take radiological properties of their devices into account in the development and production process.     

Tomosynthesis for the early detection of pulmonary emphysema: diagnostic performance compared with chest radiography, using multidetector computed tomography as reference

Objectives

To compare the diagnostic performance of tomosynthesis with that of chest radiography for the detection of pulmonary emphysema, using multidetector computed tomography (MDCT) as reference.

Methods

Forty-eight patients with and 63 without pulmonary emphysema underwent chest MDCT, tomosynthesis and radiography on the same day. Two blinded radiologists independently evaluated the tomosynthesis images and radiographs for the presence of pulmonary emphysema. Axial and coronal MDCT images served as the reference standard and the percentage lung volume with attenuation values of ?950 HU or lower (LAA_?950) was evaluated to determine the extent of emphysema. Receiver-operating characteristic (ROC) analysis and generalised estimating equations model were used.

Results

ROC analysis revealed significantly better performance (P < 0.0001) of tomosynthesis than radiography for the detection of pulmonary emphysema. The average sensitivity, specificity, positive predictive value and negative predictive value of tomosynthesis were 0.875, 0.968, 0.955 and 0.910, respectively, whereas the values for radiography were 0.479, 0.913, 0.815 and 0.697, respectively. For both tomosynthesis and radiography, the sensitivity increased with increasing LAA_?950.

Conclusions

The diagnostic performance of tomosynthesis was significantly superior to that of radiography for the detection of pulmonary emphysema. In both tomosynthesis and radiography, the sensitivity was affected by the LAA_?950.

Key Points

? Tomosynthesis showed significantly better diagnostic performance for pulmonary emphysema than radiography. ? Interobserver agreement for tomosynthesis was significantly higher than that for radiography. ? Sensitivity increased with increasing LAA _?950 in both tomosynthesis and radiography. ? Tomosynthesis imparts a similar radiation dose to two projection chest radiography. ? Radiation dose and cost of tomosynthesis are lower than those of MDCT.     

Quantitative and qualitative assessment of closed fracture healing using computed tomography and conventional radiography

RATIONALE AND OBJECTIVES: Development of new agents to induce fracture healing requires more sensitive methods to detect early changes in fracture repair. The aims of this study were to determine quantitative and qualitative features of fracture healing using volumetric computed tomography (CT) and to compare them with conventional radiography during the weeks following uncomplicated fractures of the appendicular skeleton. MATERIALS AND METHODS: 39 otherwise healthy men and women with acute, closed fractures of the distal radius, tibial and/or fibular malleoli, or tibial shaft, were enrolled and underwent CT and X-ray imaging at 1, 2, 4, 8, 12, and 16 (tibial shaft only) weeks post fracture. Qualitative assessment included fracture line/margins, fracture gap, external callus appearance, callus-to-cortex ratio, bridging, and radiologic union. Quantitative assessment of CT density changes (Hounsfield units [HU]) in the fracture gap was performed in a subset of 8 fracture patients using MEDx multimodality image analysis software (Sterling,VA). The analysis was performed by drawing free form regions of interest (ROI) covering the fracture gap on baseline (week 1) images and by automated registration of the follow-up images to the baseline co-ordinate system. RESULTS: The mean time to achieve radiologic union on CT was slightly shorter than on X-rays for radial and tibial shaft fractures (7.3 vs. 8.0 weeks, P = .1). Blurring of the fracture margins and reactive sclerosis were the earliest signs of healing in both modalities. External callus formation was evident in 11 cases and was detected earlier with CT technique. Overall, CT images allowed for more complete and detailed visualization of healing compared with conventional X-rays, which were limited by cast and fixation hardware superimposition, especially in subjects with malleolar and distal radial fractures. Quantitative evaluation showed good intraobserver and interobserver reproducibility and a statistically significant correlation to qualitative changes. CONCLUSION: Our methods of fracture healing assessment are reliable tools that are able to detect early changes in normal bone healing and may serve as useful additions to subjective image analysis in monitoring fracture healing in clinical trials. CT shows some advantages over conventional X-rays in evaluation of early fracture healing.     

Single-exposure conventional and computed radiography image acquisition

A technique for simultaneously acquiring a conventional film-screen radiographic image and a digital computed radiography (CR) image with a single x-ray exposure is described. Measurements of image contrast, spatial resolution, and signal-to-noise ratios demonstrate that a modified film cassette in which the first intensifier screen has been replaced with a CR imaging plate permits dual-image, single-exposure imaging with only nominal degradation in film and CR image quality relative to the two standard image counterparts. This technique may be used to acquire matched image pairs for research or as a way to provide full-size conventional film images in the clinical environment, while retaining the advantages offered by computed radiography systems.     

The internal calcar septum (femoral thigh spur) in computed tomography and conventional radiography

Objective. The femoral ”thigh spur”, a cortical septum in the region of the lesser trochanter of the human femur, was first described and named by the German anatomist Merkel in 1874, but it was never examined in detail. To evaluate the frequency and the shape of this structure, a combined anatomical and radiological study was performed using saw-cuts from specimens, high-resolution CT and conventional radiography. Design. Thirty human cadaveric femora of central European origin were analyzed by high-precision computed tomography (CT) using thin slices and high-resolution imaging. The CT data were image processed with thresholding to obtain a reconstruction of high-density bone formations and for three-dimensional imaging. Additionally three macerated femur specimens were cut exactly corresponding to the CT slices. The computed images were validated with the anatomical saw-cuts. Results. A dense trabecular ridge protruding endosteally from the posteromedial cortex was found in all femora. This cortical septum reaching from the femoral neck to the distal part of the lesser trochanter separated the femoral cavity from the cancellous bone inside the lesser trochanter. On conventional radiography the femoral thigh spur could be visualized best in the frog-lateral view of the hip. Conclusion. The internal calcar septum is a constant cortical structure. It should be recognized when radiographs or CT images of the proximal femur are interpreted. It could be of importance for metaphyseal fitting of an endoprosthetic stem. Received: 19 June 2000 Revision requested: 9 August 2000 Revision received: 5 October 2000 Accepted: 30 October 2000