MiniPACS packs big punch in volumetric CT data storage

Not all institutions are large enough to expand their main PACS storage to accommodate the constant stream of incoming multislice CT data sets. For smaller institutions, a miniPACS can provide cost-effective additional storage for thin-section volumetric CT data sets, according to researchers in Seoul.

Investigators at Seoul National University Hospital offloaded over 72% of their CT data and 32.8% of total data for all modalities from their main PACS to the miniPACS.

"Although volumetric data sets are larger, they are rarely retrieved by radiologists once they are interpreted, and they are often accessed by a limited number of users," said lead author Dr. Kyoung Ho Lee, a clinical instructor of diagnostic imaging at the hospital.

Lee and colleagues examined the effects of pushing thin-section volumetric data for every CT examination to the miniPACS instead of the main PACS.

Only thick-section reconstructed data sets, which are the images that radiologists often prefer reviewing, were pushed to the main PACS, Lee said.

During February 2004, 867 CT exams, which had been compressed and represented 26.8 GB of data, were stored in the main PACS. Of these, researchers stored volumetric data from 604 exams in the miniPACS, accounting for 78.1 GB of data.

Thin-section volumetric data sets were not constructed for the remaining 263 exams.

For all 867 data sets, investigators broke out the percentage of reconstruction data sets:

• volumetric: 74.4%

• thick axial: 15.9%

• standardized 3D: 7%

• 3D images added by radiologists: 2.3%

• scan planning data sets: 0.5%

Just under a quarter of the examinations stored in the miniPACS were accessed at least once by a radiologist.

The researchers also studied the changes in cumulative data volume in the main PACS and miniPACS over a five-month period. Over this period, 1.48 TB of data were stored in the main PACS, with 278 GB of the data coming from CT exams.

Volumetric data sets made up 72.6% of these CT exams. They were successfully stored in the miniPACS, according to Lee.

After the five months, all data on the main PACS were kept online. For the miniPACS, 245 GB (representing 1892 exams) were kept online and 650 GB (5162 exams) were kept in nearline storage.

The 245 GB of data kept online for the miniPACS will eventually be moved onto digital linear tapes, which are less expensive then maintaining online storage on the main PACS, Lee said.