Reliability and Validity of Soft Copy Images Based on Flat-panel Detector in Pneumoconiosis Classification

Rationale and Objectives

The aim of this study was to evaluate the reliability and validity of soft copy images based on flat-panel detector of digital radiography (DR-FPD soft copy images) compared to analog radiographs (ARs) in pneumoconiosis classification and diagnosis.

Materials and Methods

DR-FPD soft copy images and ARs from 349 subjects were independently read by four-experienced readers according to the International Labor Organization 2000 guidelines. DR-FPD soft copy images were used to obtain consensus reading (CR) by all readers as the gold standard. Reliability and validity were evaluated by a κ and receiver operating characteristic analysis, respectively.

Results

In small opacity, overall interreader agreement of DR-FPD soft copy images was significantly higher than that of ARs, but it was not significantly different in large opacity and costophrenic angle obliteration. In small opacity, agreement of DR-FPD soft copy images with CR was significantly higher than that of ARs with CR. It was also higher than that of ARs with CR in pleural plaque and thickening. Receiver operating characteristic areas were not different significantly between DR-FPD soft copy images and ARs.

Conclusions

DR-FPD soft copy images showed accurate and reliable results in pneumoconiosis classification and diagnosis compared to ARs.

Pneumoconiosis develops as a result of exposure to dusts, and chest radiography remains the first diagnostic step for the evaluation of lung parenchymal and pleural diseases . Chest analog radiographs based on film with screen (ARs) have been used as the standard method for recognizing pneumoconiosis according to the International Labor Organization (ILO) 2000 guidelines by referring to the 22 standard analog radiographs (SARs) . This is because they have relatively lower costs, good image quality, and high spatial resolution.

Since digital technology was first introduced in the early 1980s , chest digital radiography (DR) has resulted in a significant reduction of radiation dose without loss of image quality compared with ARs , as well as improvement of diagnostic performance and work flow. Consequently, it offers an instant image display, a wide dynamic range, an exposure latitude, postprocessing, and greater imaging efficiency .

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Materials and methods

Subjects

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Table 1

Equipment and Exposure Conditions of Chest Radiography Used in This Study

Parameters Digital Radiography Analog Radiography Korean Guidelines ∗ Model Digital Diagnost, Philips MXO-15B, Toshiba – Generator 150 kVp, 1100 mA 150 kVp, 500 mA >125 kVp, 300 mA Tube voltage (kVp) 125 124 ≥120 Tube current (mA) 640 500 ≥300 Phototimer (sec) AEC 0.005 <0.03 Filtration 1.0 mm Al + 0.1 mm Cu 1.2 mm Al 1.0 mm Al + 0.1 mm Cu Grid ratio (moving) 12:1 12:1 >10:1 Detector type/film Amorphous silicon Fuji HR-C type Medium sensitivity ‡ Pixels/screen 300l × 300l (9 million) Fuji Grenex HR-4 medium Medium speed ‡ Pixel size/auto processor 143 μm (3.5 lp/mm) 90 sec/cycle † <90 sec ‡

AEC, automatic exposure control.

Exposure conditions (tube voltage and current, phototimer) were for the standard size of subject (weight 75 kg).

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Radiological Examinations

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Pneumoconiosis Classification According to ILO Guidelines

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Statistical Analysis

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Ethics Statement

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Results

Effect of Technical Image Quality for Inter-reader Agreement

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Table 2

Interreader Agreement for Small Opacity According to Technical Image Quality

Technical Image Quality Overall κ Value (SE) 95% CI DR-FPD with CR Satisfied 0.66 (0.23) 0.62 to 0.70 Unsatisfied 0.45 (0.21) 0.41 to 0.49 ARs with CR Satisfied 0.52 (0.21) 0.48 to 0.56 Unsatisfied 0.34 (0.21) 0.30 to 0.38

DR-FPD, soft copy images based on flat-panel detector of digital radiography; ARs, analog radiographs; CR, consensus reading; SE, standard error; CI, confidence interval.

Technical image quality of DR-FPD soft copy images and ARs was divided as either satisfied group (grade 1 and 2) or unsatisfied group (grade 3), and small opacity was classified as four categories according to the ILO guidelines.

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Reliability of DR-FPD Soft Copy Images and ARs in Pneumoconiosis Classification

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Table 3

Intrareader Agreement of DR-FPD Soft Copy Images with ARs for Small and Large Opacities and CPAO

Reader Small Opacity Large Opacity CPAO R1 0.54 (0.46 to 0.61) 0.69 (0.58 to 0.79) 0.58 (0.33 to 0.82) R2 0.51 (0.43 to 0.59) 0.60 (0.47 to 0.71) 0.59 (0.47 to 0.69) R3 0.46 (0.38 to 0.52) 0.51 (0.40 to 0.62) 0.61 (0.42 to 0.79) R4 0.59 (0.51 to 0.67) 0.48 (0.37 to 0.57) 0.34 (0.23 to 0.45) Overall 0.52 (0.48 to 0.56) 0.57 (0.51 to 0.61) 0.49 (0.42 to 0.55)

DR-FPD, soft copy images based on flat-panel detector of digital radiography; ARs, analog radiographs; CPAO, costophrenic angle obliteration.

Small opacity was classified as four categories according to the ILO 2000 guidelines. Data are expressed as κ value with 95% confidence interval.

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Table 4

Comparison of Interreader Agreement between DR-FPD Soft Copy Images and ARs for Small and Large Opacity and CPAO

Finding DR-FPD ARs Small opacity 0.50 (0.47 to 0.53) 0.39 (0.36 to 0.41) Large opacity 0.47 (0.42 to 0.51) 0.51 (0.46 to 0.55) CPAO 0.42 (0.37 to 0.46) 0.37 (0.31 to 0.43)

DR-FPD, soft copy images based on flat-panel detector of digital radiography; ARs, analog radiographs; CPAO, costophrenic angle obliteration.

Small opacity was classified as four categories according to the ILO 2000 guidelines. Data are expressed as overall κ value with 95% confidence interval by four readers.

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Validity of DR-FPD Soft Copy Images and ARs in Pneumoconiosis Classification

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Table 5

Comparison of Overall κ Values between DR-FPD Soft Copy Images with CR and ARs with CR for Parenchymal and Pleural Findings

Finding DR-FPD with CR ARs with CR Parenchymal Small opacity 0.66 (0.61 to 0.67) 0.51 (0.47 to 0.54) Large opacity 0.63 (0.57 to 0.68) 0.63 (0.57 to 0.68) Pleural CPAO 0.38 (0.31 to 0.45) 0.39 (0.31 to 0.47) PP Left 0.26 (0.17 to 0.36) 0.14 (0.05 to 0.22) Right 0.37 (0.29 to 0.45) 0.18 (0.11 to 0.24) DPT Left 0.29 (0.16 to 0.42) 0.21 (0.10 to 0.32) Right 0.20 (0.10 to 0.30) 0.11 (0.01 to 0.21)

DR-FPD, soft copy images based on flat-panel detector of digital radiography; ARs, analog radiographs; CR, consensus reading; CPAO, costophrenic angle obliteration; PP, pleural plaque; DPT, diffuse pleural thickening.

Small opacity was classified as four categories according to the ILO guidelines. Data are expressed as overall κ value with 95% confidence interval by four readers.

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Comparison of Diagnostic Performance between DR-FPD Soft Copy Images and ARs for Pneumoconiosis

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Discussion

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Acknowledgments

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References

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Reliability and Validity of Soft Copy Images Based on Flat-panel Detector in Pneumoconiosis Classification

Rationale and Objectives

Materials and Methods

Results

Conclusions

Materials and methods

Subjects

Radiological Examinations

Pneumoconiosis Classification According to ILO Guidelines

Statistical Analysis

Ethics Statement

Results

Effect of Technical Image Quality for Inter-reader Agreement

Reliability of DR-FPD Soft Copy Images and ARs in Pneumoconiosis Classification

Validity of DR-FPD Soft Copy Images and ARs in Pneumoconiosis Classification

Comparison of Diagnostic Performance between DR-FPD Soft Copy Images and ARs for Pneumoconiosis

Discussion

Acknowledgments

References

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