Yuichi Murasaki, Presenter: Nothing to Disclose

Katsuhiro Ichikawa PhD, Abstract Co-Author: Nothing to Disclose

Shota Ito, Abstract Co-Author: Nothing to Disclose

Nagaso Daisuke, Abstract Co-Author: Nothing to Disclose

Current multi-detector row computed tomography (MDCT) systems have sufficient temporal resolutions which enable cardiac scans, and however do not have sufficient spatial resolutions to visualize fine anatomical structures such as trabecular bones because of their detector pitches of approximately 0.5 mm. This study aimed to investigate the possibility of super high resolution CT for extremities with a significantly higher resolution than current MDCT systems.

A flat panel detector system with a 0.148-mm detector pitch for general x-ray imaging (Luminous dRF, Siemens) and a handmade phantom rotation mechanism comprising a stepper motor with a minimum degree step of 0.15 were employed. Projection data of an Alderson foot phantom were acquired by fan x-ray beams with a 20-mm width narrow z-collimation and exposure parameters of 70 kV and 2 mAs. 300 projections were acquired with a rotation step of 1.2 º. To reduce the geometrical blurring as possible, a long geometry (source - detector distance = 1500 mm) with a minimal available distance between the phantom and the detector surface was used. CT images were reconstructed by using a filter back projection algorithm. The CT images were compared with images obtained by a MDCT system, Siemens Somatom-Emotion (Emotion) using its highest resolution mode. The resolution property was evaluated using a 0.1-mm thin metal wire phantom.

The trabecular bones in the foot phantom were clearly visualized by the developed system, while Emotion could not visualize them. The 10% modulation transfer function was 3.0 cycles/mm with a normal reconstruction kernel, and this was significantly higher than that of Emotion (1.5 cycles/mm). Streak artifacts appeared in the image due to the insufficient projection number. Estimated CT dose index value was approximately 10 mGy.

The potential possibility of the super high resolution CT for extremities was demonstrated through the preliminary study using a general x-ray system and a phantom rotation mechanism. Further investigations for reducing the dose and artifacts was desired. Further investigations for reducing the dose and artifacts are required.

If this super high resolution CT will be realized, this system might contribute to diagnosis of diseases with fine anatomical changes (e.g. early rheumatoid cartilage destruction and early structural change of trabecular bone in osteoporosis).

Murasaki, Y, Ichikawa, K, Ito, S, Daisuke, N, Development of Super High Resolution Computed Tomography for Extremities: Preliminary Study Using a Phantom Rotation Mechanism.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012612.html