Going Digital [continued]

BMP, JPEG and TIF: Where To Begin

When fully understood, PACS systems can make the efforts of the laboratory staff more efficient. Most PACS systems have the ability to store, edit, retrieve, generate reports and transfer images to storage media. A powerful tool, considering the plethora of images and information generated by the busy and often space-restricted vascular laboratory. However, in many cases the ultrasound machine itself also employs many of these abilities, making such technology accessible for smaller labs that have the desire to provide the highest quality images and services, but lack the budget, staff or overall need for a larger PACS system.

Both PACS systems and ultrasound machines can produce, store, convert and export multiple file types, meaning that digital information can and does exist in multiple formats. Files can exist in a sophisticated VR, Implicit Little Endian format or a Binary format so basic as to be called raw data, very similar to that from a digital camera. There are also Bitmapped (BMP) and Joint Photographic Experts Group (JPEG) file formats. There are also clips, loops, or movie files that demonstrate short strings of recorded moving ultrasound studies. Which one is suitable to export? Ask yourself: what do you want to do with the file? Will you export it for a journal article or PowerPoint presentation? Or, are you working on the compilation of diagnostic case studies for accreditation?

There are a few universal file types used throughout the field of ultrasound. Often, digital files are thought of in terms of how they are compressed, or not compressed. Additional considerations include the programs or operating systems with which the digital files are compatible, and whether they work with information systems. Medical imaging standards are very focused on compression rates. Images consist of pixels, the small blocks of grayscale or color information in a raster image that, when compiled in a specified way (algorithm), form a picture. Some pictures contain a huge amount of information and are cumbersome to store and work with. To compensate, lossy compressed files have a portion of redundant pixels deleted to make the image file size smaller, yet still recognizable. However, less is not always better. This large amount of data compression will cause a reduction in image resolution, and often the resulting image quality is not considered diagnostic, as only a portion of the total information remains. All medical imaging modalities have a set level or threshold for compression that allows the image to remain diagnostic, yet efficient in size. Ultrasound has a recommended compression threshold of about 25:1. There are lossless DICOM files (e.g.: Tagged Image Files [TIF] and JPG 2s) that cut back on file sizes but do not lose data as a lossy file would, thus maintaining most of the resolution. There are multiple techniques to achieve this type of compression. Simply put, it works because the DICOM viewer mathematically redefines the order in which the pixel data is written.

Taking into account the needs of the laboratory and the intended use of the obtained ultrasound data, the system administrator is required to make important choices when deciding what types of files to allow on their networks. It is important for the administrator to consult with the medical device manufacturer as well as the PACS manufacturer to choose file types that will work best for both systems.

Compiling Case Study Images For Accreditation

When copying a DICOM patient file from a PACS system to submit for accreditation, it is important to include an appropriate viewer with the images, if proprietary components are included in the DICOM files. As a safeguard, it is recommended that the file be opened on a PC to ensure that the files will display. Cases copied from an ultrasound machine should be exported to a CD-R in DICOM, if possible. The effect of compression should be observed when preparing case studies for accreditation. Such is the case of later model ultrasound machines that are able to produce quality images, primarily due to the expert skill of an experienced technologist. Once compressed, the images may appear completely undiagnostic, and would likely result in a delay in the laboratory's accreditation, necessitating additional case study submission.

Please remember, when submitting images on disk, to include all cases for each type of testing application on one disk. The disk should be clearly labeled with case type, patient identification, and laboratory name. Please note that the ICAVL does not require loops and videotapes of exams. The ICAVL continues to accept thermal images, videotape, DICOM laser images, films, and CDs. Applicant laboratories are encouraged to submit images using the format that best reflects the current practices which they perform. Labs with questions are always encouraged to contact the ICAVL staff by phone at 800-838-2110, or via the website at www.icavl.org/icavl/contact/staff.htm.

The transition into the digital age can be challenging. But the use of this progressive piece of technology can have a dramatic impact on your laboratory's efficiency and, ultimately, the level of patient care provided.