Jessica Lee Nute MS, Presenter: Nothing to Disclose

Megan Jacobsen, Abstract Co-Author: Nothing to Disclose

Jim W. Pennington, Abstract Co-Author: Nothing to Disclose

Adam Grant Chandler PhD, Abstract Co-Author: Employee, General Electric Company

Yasuhiro Imai MS, Abstract Co-Author: Employee, General Electric Company

Dianna D. Cody PhD, Abstract Co-Author: In-kind support, General Electric Company

A prototype quality control (QC) phantom and analysis process has been designed specifically to monitor dual-energy CT and address the current lack of quantitative oversight of the spectral capabilities of these scanners.

A prototype solid water phantom was designed with multiple material inserts, and to support both head and body protocols. Inserts included tissue equivalent and material rods (iodine, iron, calcium) at various concentrations. The oval body phantom, measuring 30cmx40cmx15cm, was scanned using four dual-energy protocols with CTDIvol ranges of 19.6-62mGy (0.516 pitch) and 10.3-32.5mGy (0.984 pitch), and rotation times ranging from 0.5-1sec. The circular head phantom, measuring 22cm in diameter by 15cm, was scanned using three dual-energy protocols with CTDIvol ranges of 67-132.6mGy (0.531 pitch) and 36.7-72.7mGy (0.969 pitch), and rotation times ranging from 0.5-0.9sec. All images were reconstructed at 50, 70, 110 and 140 keV, and using a water-iodine material basis pair. The images were evaluated for iodine quantification accuracy and stability of monoenergetic reconstructions. The phantom was scanned twice on ten GE 750HD CT scanners to evaluate inter-scanner agreement, as well as ten times on a single scanner over a one-week period to evaluate intra-scanner repeatability.

Preliminary analysis revealed consistent (inter- and intra-scanner) iodine quantification accuracy within 10% was only achieved for protocols in the upper half of dose levels assessed when grouped by pitch. Although all scanners undergo rigorous daily single-energy QC, iodine quantification accuracy from one scanner unexpectedly deviated from the other nine substantially. In general, inter-scanner agreement and intra-scanner repeatability varied with dose, rotation time and reconstructed keV.

Preliminary results indicate the need for a dual-energy QC process to ensure inter-scanner agreement and intra-scanner repeatability. In particular, iodine quantification accuracy should be monitored, particularly for lower dose techniques. Future plans include longer term dual-energy CT QC data collection.

DECT is quickly becoming a critical part of routine exams. QC such as quantitative accuracy and long term stability haven’t been addressed but are essential to ensuring confidence in this application.

Nute, J, Jacobsen, M, Pennington, J, Chandler, A, Imai, Y, Cody, D, Preliminary Results of a Prototype Quality Control Process for Spectral CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014486.html