Automated detection of changes in patient exposure in digital projection radiography using exposure index from DICOM header metadata.

PURPOSE: Automated collection of image data from DICOM headers enables monitoring of patient dose and image quality parameters. Manual monitoring is time consuming, owing to the large number of exposure scenarios, thus automated methods for monitoring needs to be investigated. The aim of the present work was to develop and optimise such a method. MATERIAL AND METHODS: Exposure index values from digital systems in projection radiography were collected over a period of five years, representing data from 1.2 million projection images. The exposure index values were converted to detector dose and an automated method for detection of sustained level shifts in the resulting detector dose time series was applied using the statistical analysis tool R. The method combined handling of outliers, filtering and estimation of variation in combination with two different statistical rank tests for level shift detection. A set of 304 time series representing central body parts was selected and the level shift detection method was optimised using level shifts identified by ocular evaluation as the gold standard. RESULTS: Two hundred and eighty-one level changes were identified that were deemed in need of further investigation. The majority of these changes were abrupt. The sensitivity and specificity of the optimised and automated detection method concerning the ocular evaluation were 0.870 and 0.997, respectively, for detected abrupt changes. CONCLUSIONS: An automated analysis of exposure index values, with the purpose of detecting changes in exposure, can be performed using the R software in combination with a DICOM header metadata repository containing the exposure index values from the images. The routine described has good sensitivity and acceptable specificity for a wide range of central body part projections and can be optimised for more specialised purposes.

Dual-headed coincidence PET vs. dedicated PET/CT in the evaluation of thoracic malignancies.

UNLABELLED: The aim of this study was to evaluate the usefulness of coincidence PET imaging as compared with dedicated PET/CT in cancer staging. PATIENTS AND METHODS: Sixteen patients with thoracic malignancies referred to a PET/CT examination accepted to repeat the acquisition with a coincidence PET system. One experienced nuclear medicine physician compiled a report from the PET/CT examinations and the coincidence PET images. The reports were compared and evaluated according to the degree of agreement: no agreement, unsatisfactory, acceptable or satisfying agreement. RESULTS: Satisfying or acceptable agreement between the PET/CT and the coincidence PET examination was found in 14 out of 16 patients (88%). The main issue for the examining physician was to anatomically locate the FDG uptake in the mediastinum in the coincidence PET images. CONCLUSION: The data from this small study imply that the staging results obtained with coincidence PET are in most cases concordant with those obtained with dedicated PET/CT.

DICOM Metadata repository for technical information in digital medical images.

UNLABELLED: The diagnostic medical image contains, apart from the pixel data, a detailed description of how the image was produced. The information reveals details on image geometry, radiation data as well as more complex quality index in a varying degree, mostly dependent on the age of the equipment. There is no simple way to retrieve, process and display this data in a general image workstation. MATERIAL AND METHODS: Since November 2004 a DICOM metadata repository has been used to record image header parameters. The automated data extraction, storage and display are based on simple standard programming and have performed without malfunction since the start, today containing metadata from 18 million images. RESULTS: The data in the metadata repository has been used in dose optimization for a Computed Radiography image plate system, analyzing the exposure index and making use of the possibilities to organize the data in examinations, projections as well as examination rooms. Analysis of exposure index in the context of these parameters shows promising qualities as it makes detection of dosimetric problems as well as follow-up of dose adjustments simpler. Current work is aimed at creating a vendor independent platform and to further develop methods to support dose optimization for flat panel direct digital detectors and computed tomography (CT) systems. The possibilities to detect equipment malfunction will be further investigated.