Artifacts in chest radiographs with a third-generation computed radiography system

Computed radiography image artifacts revisited

OBJECTIVE

Computed radiography (CR) has provided a ready cost-effective transition from screen film to digital radiography and a convenient entrance to PACS. This article revisits artifacts encountered in CR systems. These artifacts may obscure abnormalities, mimic a clinical entity, or hamper image quality.

CONCLUSION

With the new-generation CR systems, software- and hardware-related artifacts have decreased, making operator errors more evident. The purpose of this study is to establish the current trend of CR artifacts and the new facets in identifying and resolving problems quickly that will help prevent future occurrences. This article also brings to light the importance of constant review required of this extensively studied topic to avoid diagnostic misadventures.

Durability of imaging plates in clinical use

In many X-ray clinics, the traditional photographic film has been replaced by an imaging plate (IP). The IP is re-usable and the purpose of this study was to test if image deterioration occurred after successive uses of the IP. The emphasis is placed on the efficiency of image formation and on image uniformity. In a cross-sectional study, 21 clinically used IPs were exposed with a standardized phantom imaging protocol. These IPs were in clinical use between one month and two years and the IPs were exposed between 191 and 3787 times. After digitizing, the mean pixel value (MPV) in a predefined image area was determined. The relation between MPV and IP uses was assessed. In a second experiment, image uniformity of 30 other clinically used IPs was visually inspected for artifacts on a diagnostic monitor. These IPs were in clinical use between one week and two years and exposed between 76 and 5373 times. The first experiment showed that no significant deterioration of the MPV with increasing usage count of the IP was present (p = 0.15). The second experiment showed the appearance of clinically relevant artifacts on the IP before 3000 uses. It was concluded that the efficiency of the image formation process does not significantly deteriorate after successive use of IPs and is therefore not expected to limit their life span. Mechanical handling in the digitizer of the used system seems to set a limit to IP durability. Uniformity should therefore be checked regularly in clinical quality control.

Artifacts found during quality assurance testing of computed radiography and digital radiography detectors

A series of artifact images, obtained over 5 years of performance testing, of both computed radiography (CR) and integrated digital radiographic X-ray imaging detectors are presented. The images presented are all either flat field or test object images and show artifacts previously either undescribed in the existing literature or meriting further comment. The artifacts described are caused by incorrect flat field corrections, a failing amplifier, damaged detector lines affecting their neighbors, lost information between neighboring detector tiles, image retention, delamination of a detector, poor setup of mechanical movements in CR, suckers damaging a CR plate, inappropriate use of grid suppression software, inappropriate use of a low pass spatial frequency filter, and unsharp masking filters. The causes and significance of the artifacts are explained and categorized as software or hardware related. Actions taken to correct the artifacts are described and explained. This work will help physicists, radiographers, and radiologists identify various image quality problems and shows that quality assurance is useful in identifying artifacts.

Juxtaposition artefact in a forearm radiograph: a cautionary note in the interpretation of a multiply exposed radiographic plate

This case report outlines the risks associated with double plate exposure radiographs in follow up images of a child's forearm fracture. Protocols need to be established between radiology and orthopaedic departments for adequate imaging techniques of children's forearms.

Evaluation of an automatic-mode image processing method in chest computed radiography

RATIONALE AND OBJECTIVES

The automatic image processing mode of the storage phosphor computed radiography system was evaluated.

MATERIALS AND METHODS

A dedicated chest unit designed for erect view was used to examine a chest phantom. Lucite plates 1, 2, and 3 cm thick that conformed to the shape of the lung were attached to the phantom, and images were obtained in automatic and manual image processing modes. The changes in the optical density of the lung, rib, and heart and the changes in contrast were measured. The degree of diffuse opacity due to the plates and the visibility of superimposed simulated nodular and honeycomb opacities were evaluated.

RESULTS

The decrease in optical density and contrast caused by increasing thickness of the Lucite plates was less pronounced in the automatic mode compared with the manual mode. When plates were placed only on the right lung, the optical density and the contrast on the contralateral side either increased or remained unchanged with the automatic mode. The degree of diffuse opacity was rated higher in the manual mode, and the visibility of superimposed simulated opacities was considered relatively constant in the automatic mode.

CONCLUSION

The automatic image reading mode used in the computed radiography chest system may mask the detection of abnormalities such as diffuse homogeneous lung opacity.