José Luis Oliveira
Universidade de Aveiro, DETI / IEETA
3810-193 Aveiro, Portugal
(+351) 234 370 500
The medical imaging digitalization and implementation of PACS (Picture Archiving and Communication Systems) systems increases practitioner’s satisfaction through improved faster and ubiquitous access to image data. Besides, it reduces the logistic costs associated to the storage and management of image data and also increases the intra and inter institutional data portability. Echocardiography is a rather demanding medical imaging modality when regarded as digital source of visual information. The date rate and volume associated with a typical study poses several problems. They are hard to keep “online” (in centralized servers) and difficult to access (in real-time) outside the institutional broadband network infra-structure. For example, an uncompressed echocardiography study size can typically vary between 100 and 500Mbytes.
The innovation of our approach is the implementation of a DICOM private transfer syntax designed to support any video encoder installed on the operating system. This structure provides great flexibility concerning the selection of an encoder that best suits the specifics of a particular imaging modality or working scenario. To ultrasound studies we are using the highly efficient MPEG4 codec that takes full advantage of object texture, shape coding and inter-frame redundancy. More than 40.000 studies have been performed so far. For example, a typical Doopler color run (RGB) with an optimized time-acquisition (15-30 frames) and a sampling matrix (480*512), rarely exceed 200-300kB. Typical compression ratios can go from 65 for a single cardiac cycle sequence to 100 in multi- cycle sequences. With these averaged figures, even for a heavy work-loaded echolab, it is possible to have all historic procedures online or distribute them with reduced transfer time over the network, which is a very critical issue when dealing with costly or low bandwidth connections. The solution is actually installed in one public Central Hospital (CHVNG) and one private laboratory of cardiac images. Because the solution front-end is fully Web-based, the clinical specialists are using the platform to provide decision support remotely, accessing over Internet in a secure way (i.e. over SSL). Moreover, the solution is changing the work methods. The process workflow is fully digital where reviewing and reporting procedures can be done at physician’s home (i.e. telework).
- Visualization – view dicom medical images
- Report Module – edit and export a image report, with customizable layout, to Word.
- Burning Module – to export the study to CD/DVD in DICOM default transfer syntax, including a standalone viewer.
- Communications Module – send a study to a external server.
Two studies were carried on assessing the DICOM cardiovascular ultrasound image quality. In a simultaneous and blind display of the original against the compressed cine-loops, 37% of the trials have selected the compressed sequence as the best image. This suggests that other factors related with viewing conditions are more likely to influence observer performance than the image compression itself.