Gil Kovalski MS, Presenter: Employee, General Electric Company

Shai Attia BS, Abstract Co-Author: Employee, General Electric Company

Ora Israel MD, Abstract Co-Author: Consultant, General Electric Company

Zohar Keidar MD, PhD, Abstract Co-Author: Nothing to Disclose

Haim Azhari DSc, Abstract Co-Author: Nothing to Disclose

Several studies reported on the non-uniform blurring of myocardial perfusion scans due to respiration. The objective of this paper is to report on several technical considerations when performing respiratory gating on patient studies as opposed to phantom studies using enhanced LIST mode functionality synchronized with respiration signal acquisition.

The respiratory signals of 10 male and 4 female volunteers were recorded while running a SPECT acquisition protocol on a GE Infinia™ without the administration of a radiopharmaceutical, using an experimental LIST mode functionality which supports synchronization with an external respiratory strap. The strap was placed on the volunteer’s abdomen. In six scans, a second strap was placed on the chest for comparison. Scans were repeated with various degree of strap tightness

A looser strap resulted in truncation of the lower portion of the signal which greatly affected the binning of signal to projections. The strap placed on the chest had a much lesser degree of sensitivity compared with the strap placed on the abdomen. This was true for male and female with various breast sizes. The respiratory signal histogram showed that the time interval spent per respiratory cycle was not uniform in all scans. This indicates that a non-uniform binning algorithm is needed. Moreover, the total count of each projection bin fluctuated as a result of the non-uniform breathing pattern. This complicates the correction of respiratory motion using the reconstructed transaxial slices.

When one attempts to correct for motion blurring due to respiration using respiratory gating, several technical limitations must be considered. Unlike the ECG signal, the respiratory cycles are not uniform in their amplitude and shape resulting in non-uniform projections per detector angle for each respiratory bin. Also, strap tightness and position should be carefully set to ensure proper respiratory signal acquisition. The binning process, which is the first step towards respiratory motion correction, must therefore account for the non-linearity of the respiration process.

Technical issues must be addressed when performing respiratory gating

Kovalski, G, Attia, S, Israel, O, Keidar, Z, Azhari, H, Towards Respiratory Gating and Correction of Clinical Myocardial Perfusion SPECT Scans.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4432548.html