Contact

Porträt Dr. Maus, Jens; FWPM

Dr. Jens Maus
Research Associate / Head IT
Positron Emission Tomography
j.mausAthzdr.de
Phone: +49 351 260 - 2757, +49 351 4585056
Fax: +49 351 260 - 12757

Correction of motion-based image artefacts in whole body PET-acquisitions

Motivation

With PET-scanner ECAT EXACT HR+ data acquisition of a bed position takes about 8-10 minutes. During acquisition motions like respiration or other body motions are inavoidable, which leads to artefacts in PET-images. Like shown in figure 1 a tumor volume is apparently increased, thus the appropriate tumor activity concentration is apparently decreased. When motion is disregarded there will be potential errors in diagnose and consistently in therapy. Our aim is a clinical routine based acquisition of patient motions and their correction in wholy body PET-acquisitions.

   
 

unkorrigiertes PET-Bild
Ein Gate einer PET-Studie
Figure 1: Effect of respiratory motion on representation of a lung metastasis. Top: Average over all respiratory phases. Bottom: exhalation phase.

     

Methods

Infrared tracking cameras are used to acquire motions of a infrared reflecting target. To track patient motion a capable target was designed which is fixed on patient's chest with elastic band during acquisition. The acquired motion data contains both respiratory motion and other body motions of the patient. The form of periodic respiratory motion fundamentally differs from other body motion. So correction of respiratory motion and body motion has to be done in seperate ways. Therefore algorithms were developed to separate both type of motions.

   
 

Infrarottracking KamerasAtemtarget
Figure 2 : Figure shows the infrared tracking cameras (left) and the patient target fixed on patient's chest (right).

     

Results

The development of a motion target enables a clinical routine based acquisition of patient motions with infrared tracking cameras. Separation of acquired patient motions into respiratory motion and other body motions allows an independent correction of both types of motion. A clinical routine based correction of patient motions makes an event based acquisition of PET data necessary. Sofar this was impossible with the original whole body protocol of the ECAT EXACT HR+. So a software was developed to enable list-mode based whole body acquisitions.

   
   
   
  Atemdaten
Figure 3: Figure shows motion data of a patient during a 6 minute lasting PET-acquisition.
     

Outlook

On the base of acquired respiratory motion a list-mode dataset can be divided into different respiratory phases (gates). The division depends on different strategies which have to be analysed. Mapping of all respiratory phases onto a reference phase enables correction of respiratory motion. Correction of other body motions will be done with methods established at PET-center Rossendorf [1].

   

[1] Bühler, P. et al., An accurate method for correction of head movement in PET. IEEE Trans Med Img (2004) 23:1176-1185


Contact

Dr. Jens Maus
Research Associate / Head IT
Positron Emission Tomography
j.mausAthzdr.de
Phone: +49 351 260 - 2757, +49 351 4585056
Fax: +49 351 260 - 12757