Study Syllabus for Classification of Radiographs of Pneumoconioses
Section 1: Image Quality
Assessment of image technical quality is critically important prior to performing an ILO classification. Quality appraisals are therefore appropriately the first items recorded on the classification form. Historically, variations in image quality have been shown to have an important effect on the small opacity profusion category selected by the reader. The quality of modern digital chest radiographs is often better than film images, especially with appropriate use of window and level functions. However, regardless of the imaging modality, readers completing ILO classifications should assess the quality of the image in each lung zone. Depending on the type of opacities being evaluated, the appearance and perception may be altered, accentuated, or diminished. Quality effects may be generalized throughout the image, or limited to specific lung zones.
Factors that can influence perception of opacities may be related to the image contrast, resolution, exposure, or gray scale, as well degree of inflation, body position, or movement during the examination. Localized effects may be due to superimposed bony structures, soft tissues, or foreign bodies (e.g., pacemakers, tubing, clothing, etc.). Digital radiographic systems should be monitored to avoid linear artifacts, or noise/mottle, which can suggest small pneumoconiotic opacities, and post processing software functions should be set to the minimum edge enhancement permitted by the system, to facilitate comparisons to ILO digital standard radiographs.
After selecting the one or two standard images that visually appear to most closely match the subject radiograph, the reader should weigh the potential impact of any quality factors on the appearance of parenchymal opacities. When deemed necessary, an adjustment of the profusion category may be appropriate, based upon the anticipated influence of quality factors on the comparison of the subject radiograph and the ILO standard. If more than a minor adjustment is judged necessary, consideration should be given, whenever possible, to obtaining a better quality radiograph, and classifying the imperfect image as unreadable.
There are four grades of radiographic quality:
- good–free of technical imperfections or artifacts;
- acceptable with no technical defects or artifacts likely to impair classification of the radiograph for pneumoconiosis;
- acceptable, with technical defects or artifacts but still adequate for classification purposes;
- “U/R”, unreadable or unacceptable for classification purposes.
Minor errors in positioning and handling artifacts that do not overlie the heart or lungs would usually be classified “2.” Minor degrees of over- or underexposure and minor departures from proper radiographic contrast that do not preclude the classification of the radiograph should be classified as “3.” Images with gross over- or underexposure, gross unsharpness, and gross departures from proper radiographic contrast should all be classified “U/R” (see appended reprint from the Federal Register for radiographic quality standards). If the technical quality is not grade 1, an indication of the technical defect(s) must be made.
Check the box (“1,” “2,” “3,” or “U/R”) that best indicates the quality of the radiograph. You may wish to wait until you have attempted to classify the radiograph before deciding whether its “quality” is such that it may affect your interpretation. If boxes “2,” “3,” or “U/R” are checked, indicate the reason(s) by marking all boxes that apply, and specify “other defects” on the adjacent lines.