Purpose/Objective(s): The purpose of this work is to assess the potential of advanced amplitude-based gating techniques with continuous bed motion PET/CT to improve the use of dose painting in regions where there exists a high probability for motion artifacts.The hypothesis is that advanced amplitude-based gating techniques used in conjunction with continuous bed motion PET/CT imaging will enable increased visibility of lesion topography that may indicate regions that could benefit from special treatment during radiation therapy planning. This study uses an amplitude-based gating method known as optimal respiratory gating that examines the respiratory cycle and chooses data points where the least amount of motion was observed during the scan time.Materials/Methods: A patient with suspected lung cancer was imaged for initial staging using PET/CT. The patient was fitted with a standard respiratory belt for recording the respiratory cycle during the imaging sequence. Following the scan, data were processed as a standard PET/CT image and using optimal respiratory gating. Both image sets were sent to radiation therapy planning software for assessment and for drawing of dose contours. Countours were drawn for both the standard PET/CT images as well for the images created using optimal respiratory gating.Results: Images reviewed using standard PET/CT indicated a large lesion with a small necrotic core of dimensions 2.4 cm x 1.1 cm x 1.3 cm. This necrotic center was not large enough to draw accurate contours or warrant additional review for customized radiation therapy planning and so the entire tumor volume would have been treated to 100% dose. The images processed using optimal respiratory gating showed a significant increase in the size of the necrotic core measuring 2.6 cm x 2.7 cm x 2.4 cm. This indicated a dramatic increase of over 4x the measured volume of the necrotic core using standard PET/CT. This increase in the size of the necrotic area of the lesion enabled accurate contouring of the area so that a customized dose plan could be applied to the motion affected region. For contoured regions inside the designated necrotic area, delivered dose was increased to 130%. Data showing the change in image quality and contoured regions will be shown.Conclusions: Use of optimal respiratory gating enables improved image quality by significantly reducing the impact of motion on PET/CT images. These techniques enable visualization of motion-free imaging that may lead to improved use of dose painting techniques in areas of significant motion and subsequently improved patient outcomes.
Osborne, D,
Use of Optimal Respiratory Gating with Continuous Bed Motion PET/CT to Improve Personalized Radiation Therapy Planning. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14045817.html
