Franz Edward Boas MD, PhD, Presenter: Nothing to Disclose

Roland Bammer PhD, Abstract Co-Author: Founder, iSchemaView, Inc Director, iSchemaView, Inc Stockholder, iSchemaView, Inc

Dominik Fleischmann MD, Abstract Co-Author: Research support, Siemens AG Research support, General Electric Company

Many current CT metal artifact reduction methods suffer from various limitations, including: only working on certain types of implants, not reducing motion artifact, requiring access to raw data, or requiring a large amount of processing time. We developed and tested a new algorithm to address these limitations.

We optimized the speed and image quality of the Metal Deletion Technique (MDT) for metal artifact reduction, by testing 84 variations of the MDT algorithm on a diverse test set of 23 DICOM images. The optimal algorithm was then tested on 90 full scans. Raw projection data was estimated by forward projecting the image reconstructed by the scanner. Metal artifact reduction was set up as a scalable (tested up to 40 CPU cores in parallel) cloud application, which was integrated with PACS.

The optimal MDT algorithm is 6 times faster than the original algorithm, with a processing time of 15 minutes per slice per CPU core. It has improved performance compared to the original algorithm for aneurysm coils in the same slice as the mastoids. This is a particularly difficult case for metal artifact reduction algorithms, due to the motion of the coil and the fine bony details in the mastoids. Of the 90 scans examined, image quality was improved compared to the image generated by the scanner in 86% (77 scans). The most common cause of worsened image quality was resolution loss around implants measuring > 5 cm in the axial plane, such as pedicle screws. In 13 scans (14%), MDT changed the diagnosis, improved visualization of key findings, or improved diagnostic confidence. These cases include: new visualization of an obstructing ureteral stone obscured by bilateral hip replacements (1 case); improved visuaization of hemorrhage or infarct obscured by an intracranial aneurysm coil or clip (6 cases); and improved visualization of a pelvic mass, periprosthetic fluid collection, or traumatic urethral injury obscured by hip hardware (3 cases).

MDT reduces metal artifacts in a wide range of different implants, reduces motion artifacts involving metal implants, and can affect the diagnosis. It works by processing DICOM files, and does not require access to raw data.

MDT can be helpful in the clinical evaluation of patients with metal implants. In 14% of cases, it changed the diagnosis, improved visualization of key findings, or improved diagnostic confidence.

Boas, F, Bammer, R, Fleischmann, D, Optimized CT Metal Artifact Reduction Using the Metal Deletion Technique (MDT).  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12025294.html