Differences in gross tumor volumes for pancreatic cancer: a comparison of ungated positron emission tomography and contrast-enhanced four-dimensional computed tomography
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We assessed differences in gross tumor volumes (GTVs) for pancreatic cancer between respiratory-ungated positron emission tomography (3D-PET) and contrast-enhanced four-dimensional computed tomography (CE-4DCT).
Materials and methods
We evaluated the GTVs in 21 patients. The sum of the GTVs, which was individually delineated by observers 1 and 2 on the CE-4DCT images from all respiratory phases, was used as GTV-4DCT. The GTVs on the 3D-PET images were extracted with three thresholds: 20%, 30%, and 40% of maximum activity concentration (GTV-n%). We selected one of the GTV-n%, which mostly resembled GTV-4DCT in size, as GTV-PET. Differences in the GTVs were analyzed.
Median values of GTV-4DCT for observers 1, 2, and GTV-PET were 55.0 mL, 45.7 mL, and 14.6 mL, respectively. GTV-PET was smaller than GTV-4DCT for observers 1 and 2 (p < 0.01 each). Differences of median values of maximum diameters between GTV-4DCT and GTV-PET were 1.7–1.8 cm, 1.4–1.6 cm, and 1.9–2.1 cm in the left–right, anterior–posterior, and craniocaudal directions, respectively.
GTV-PET based on 3D-PET images was smaller than GTV-4DCT for pancreatic cancer. When we refer to 3D-PET images without CE-4DCT images, we need to pay attention to the above-mentioned finding to contour the GTV.
KeywordsDelineation Contouring Ungated 3D-PET 4D-CT
This study was supported by JSPS KAKENHI (Grant number 15K19798).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable institutional and national guidelines for the care were followed.
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