Regina Peer

Comparative reject analysis in conventional film-screen and digital storage phosphor radiography.

Abstract. The aim of this study was comparative analysis of rejected radiographs in conventional and digital radiology under the aspects number of rejected images and reasons for rejection. During 2 months waste films of conventional radiography were collected; in digital radiography each image-delete command at the postprocessing workstation was documented. Rejected images were analysed and assigned to four categories. The overall reject rate was 27.6 % in the conventional and 2.3 % in the digital department. Whereas in the conventional department the main reason for rejection was “exposure” and “others” (i. e. problems related to film handling), the main reason in the digital environment was “positioning”. The high exposure tolerance of digital systems markedly reduces the amount of faulty images. This is not only economically rewarding, but may also reduce unnecessary X-ray exposure of patients due to image retake.

Comparison of low-contrast detail perception on storage phosphor radiographs and digital flat panel detector images

A system for the computerized analysis of images obtained from epiluminescence microscopy (ELM) has been developed to enhance the early recognition of malignant melanoma. As an initial step, the binary mask of the skin lesion is determined by several basic segmentation algorithms together with a fusion strategy. A set of features containing shape and radiometric features as well as local and global parameters is calculated to describe the malignancy of a lesion. Significant features are then selected from this set by application of statistical feature subset selection methods. The final kNN classification delivers a sensitivity of 87% with a specificity of 92%.A contrast detail analysis was performed to compare perception of low-contrast details on X-ray images derived from digital storage phosphor radiography and from a flat panel detector system based on a cesium iodide/amorphous silicon matrix. The CDRAD 2.0 phantom was used to perform a comparative contrast detail analysis of a clinical storage phosphor radiography system and an indirect type digital flat panel detector unit. Images were acquired at exposure levels comparable to film speeds of 50/100/200/400 and 800. Four observers evaluated a total of 50 films with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. The overall results show that low-contrast detail perception with digital flat panel detector images is better than with state of the art storage phosphor screens. This is especially true for the low-exposure setting, where a nearly 10% higher correct observation ratio is reached. Given its high detective quantum efficiency the digital flat panel technology based on the cesium iodide scintillator/amorphous silicon matrix is best suited for detection of low-contrast detail structures, which shows its high potential for clinical imaging.

Resolution requirements for monitor viewing of digital flat-panel detector radiographs: a contrast detail analysis

Abstract. With the introduction of digital flat-panel detector systems into clinical practice, the still unresolved question of resolution requirements for picture archiving communication system (PACS) workstation monitors has gained new momentum. This contrast detail analysis was thus performed to define the differences in observer performance in the detection of small low-contrast objects on clinical 1K and 2K monitor workstations. Images of the CDRAD 2.0 phantom were acquired at varying exposures on an indirect-type digital flat-panel detector. Three observers evaluated a total of 15 images each with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. No significant difference in the correct detection ratio was detected among the observers; however, the difference between the two types of workstations (1K vs 2K monitors) despite less than 3% was significant at a 95% confidence level. Slight but statistically significant differences exist in the detection of low-contrast nodular details visualized on 1K- and 2K-monitor workstations. Further work is needed to see if this result holds true also for comparison of clinical flat-panel detector images and may, for example, exert an influence on the diagnostic accuracy of chest X-ray readings.

Sophisticated hospital information system/radiology information system/picture archiving and communications system (PACS) integration in a large-scale traumatology PACS.

Picture archiving and communications system (PACS) in the context of an outpatient trauma care center asks for a high level of interaction between information systems to guarantee rapid image acquisition and distribution to the surgeon. During installation of the Innsbruck PACS, special aspects of traumatology had to be realized, such as imaging of unconscious patients without identification, and transferred to the electronic environment. Even with up-to-date PACS hardware and software, special solutions had to be developed in-house to tailor the PACS/hospital information system (HIS)/radiology information system (RIS) interface to the needs of radiologic and clinical users. An ongoing workflow evaluation is needed to realize the needs of radiolgists and clinicians. These needs have to be realized within a commercially available PACS, whereby full integration of information systems may sometimes only be achieved by special in-house solutions.

Storage phosphor radiography of wrist fractures: a subjective comparison of image quality at varying exposure levels

Abstract. Image quality of storage phosphor radiographs acquired at different exposure levels was compared to define the minimal radiation dose needed to achieve images which allow for reliable detection of wrist fractures. In a study on 33 fractured anatomical wrist specimens image quality of storage phosphor radiographs was assessed on a diagnostic PACS workstation by three observers. Images were acquired at exposure levels corresponding to a speed classes 100, 200, 400 and 800. Cortical bone surface, trabecular bone, soft tissues and fracture delineation were judged on a subjective basis. Image quality was rated according to a standard protocol and statistical evaluation was performed based on an analysis of variance (ANOVA). Images at a dose reduction of 37% were rated sufficient quality without loss in diagnostic accuracy. Sufficient trabecular and cortical bone presentation was still achieved at a dose reduction of 62%. The latter images, however, were considered unacceptable for fracture detection. To achieve high-quality storage phosphor radiographs, which allow for a reliable evaluation of wrist fractures, a minimum exposure dose equivalent to a speed class of 200 is needed. For general-purpose skeletal radiography, however, a dose reduction of up to 62% can be achieved. A choice of exposure settings according to the clinical situation (ALARA principle) is recommended to achieve possible dose reductions.