Understanding The Scalability Of A VNA Solution

A VNA is Scalable.

It is hard to estimate a facility’s required storage capacity. Most users underestimate what is required, while others over-estimate and do not make good use of their investment.

Factors that impact a growth in storage utilization are:

  • Purchasing new modalities: The increasing popularity of the latest generation of multi-slice CT scanners has had a big impact on the amount of data generated
  • New imaging protocols: A new MR protocol might suddenly generate thousands instead of hundreds of images
  • Equipment upgrades: Upgrading a digital room with a high-definition imaging subsystem, from a 512 to 1,024 acquisition matrix, would quadruple the storage requirement
  • New departments online: Most administrators are wary when cardiology comes online because of that specialty’s generation of large cine runs consisting of thousands of images. Mammography is also a killer; a typical mammography exam of four images could be 160 megabytes in size
  • New specialties: Everyone is apprehensive about the storage requirements of digital pathology. Their data generation is much larger than any current imaging modality.

There are several factors that impact the growth in storage utilization:

  • Purchasing new modalities
  • New imaging protocols
  • Equipment upgrades
  • New departments online
  • New specialties

Scalability is Difficult to Define

In general, scalability is a difficult and somewhat vague requirement, as the upper limit of the scale and corresponding performance requirements are hard to define. Imagine that the VNA supports the storage of all images taken by a 300-facility chain of hospitals. Another good example would be all images of patients residing in a certain metropolitan area or a state. One can imagine that this database could easily encompass many millions of people, with the amount of images and related information a multiple of that. Therefore, it is hard to specify an upper limit.

  • The upper limit of the scale and requirements are hard to define
  • On a large scale, it is difficult to imagine the number of patients and records

Scalability and Performance

In many cases, a new procedure is scheduled in advance and required comparison studies can be pre-fetched and made available by the local PACS within a few seconds. However, in the case of an unscheduled procedure, where the information has to be retrieved from the VNA archive in real time, the retrieval rate could be 5-10 seconds, or more. The good news is that these occurrences should be infrequent and will not have a major impact on productivity.

Another key to scalability is that the information can be preserved and should not have to be migrated when the data exceeds certain limits, like 1 million images. Note that the scalability requirement does not mean that the database might not have to be ported, as this might be needed to facilitate a larger number of database records.

  • Most new procedures are scheduled in advance
  • Unscheduled procedures could introduce a data retrieval rate of several seconds
  • Most unscheduled procedures are infrequent
  • A key to scalability is the preservation of data
  • The database may still have to be migrated to facilitate larger number of records

For more information about developing a Vendor Neutral Archive, the VNA Institute of Technology, or to enroll for CPHIMS (CE) Continuing Education Hours, visit http://www.vnait.org

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