Positron Emission Tomography Phantom Studies for Radiation Therapy Target Delineation

Bioanatomic imaging is becoming more prevalent in radiation treatment planning (RTP). Positron Emission Tomography (PET) is one form of bioanatomic imaging that is readily used for RTP of non-small-cell lung cancer (NSCLC) and head and neck cancer (H&N). PET utilizes a radiotracer, such as fluro-deoxy glucose (FDG), to detect tumors. An issue with incorporating FDG-PET into RTP is what imaging parameters should be used to contour PET based gross tumor volumes (GTVs). The purpose of this work was to investigate what imaging parameters should be used to contour PET volumes, and how these parameters are related to target shape, volume, and heterogeneity. For this study the threshold method was used to contour PET volumes. Thresholds matching PET target volume to known target volume were investigated for cylindrical, spherical, cubic, and geodesic phantoms at various signal to background ratios (SBRs). Phantom studies revealed that as the SBR decreases the required threshold increases. Also, smaller phantom volumes required a larger threshold than larger phantom volumes. Phantom studies revealed that more spherical targets require a higher threshold. Phantom studies also revealed that the required threshold decreases as PET targets become more heterogeneous. Phantom data was modeled to produce thresholds for clinical targets based on target volume and SBR. These models were applied to a clinical case, and the resulting GTVs differed from the original treatment plans. This study shows that PET threshold changes as a function of target shape, size, SBR, and heterogeneity. These relationships can be modeled to yield thresholds for clinical PET targets.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2009

Author dc:creator

• Lawrence, Michael

• Medical Imaging

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10339/14839

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/14839