Assessing margin expansions of internal target volumes in 3D and 4D PET: a phantom study
- PDF / 1,337,182 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 20 Downloads / 163 Views
ORIGINAL ARTICLE
Assessing margin expansions of internal target volumes in 3D and 4D PET: a phantom study Shyam S. Jani • James M. Lamb • Benjamin M. White Magnus Dahlbom • Clifford G. Robinson • Daniel A. Low
•
Received: 28 July 2014 / Accepted: 2 October 2014 / Published online: 8 October 2014 Ó The Japanese Society of Nuclear Medicine 2014
Abstract Background and Purpose To quantify tumor volume coverage and excess normal tissue coverage using margin expansions of mobile target internal target volumes (ITVs) in the lung. Materials and methods FDG-PET list-mode data were acquired for four spheres ranging from 1 to 4 cm as they underwent 1D motion based on four patient breathing trajectories. Both ungated PET images and PET maximum intensity projections (PET-MIPs) were examined. Amplitude-based gating was performed on sequential list-mode files of varying signal-to-background ratios to generate PETMIPs. ITVs were first post-processed using either a Gaussian filter or a custom two-step module, and then segmented by applying a gradient-based watershed algorithm. Uniform and non-uniform 1 mm margins were added to segmented ITVs until complete target coverage was achieved. Results PET-MIPs required smaller uniform margins (4.7 vs. 11.3 mm) than ungated PET, with correspondingly
S. S. Jani (&) J. M. Lamb B. M. White D. A. Low Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA e-mail: [email protected] B. M. White Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA M. Dahlbom Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA C. G. Robinson Department of Radiation Oncology, Siteman Cancer Center, Washington University in St. Louis, St. Louis, MO, USA
123
smaller over-coverage volumes (OCVs). Non-uniform margins consistently resulted in smaller OCVs when compared to uniform margins. PET-MIPs and ungated PET had comparable OCVs with non-uniform margins, but PET-MIPs required smaller longitudinal margins (4.7 vs. 8.5 mm). Non-uniform margins were independent of sphere size. Conclusions Gated PET-MIP images and non-uniform margins result in more accurate ITV delineation while reducing normal tissue coverage. Keywords
4D-PET Lung cancer
Introduction Radiotherapy for lung cancer has evolved considerably over the last decade, with recent advances in technology, staging, and image guidance leading to improved patient outcomes [1–3]. One standing challenge remains as intrafraction target motion, which affects tumor sites in both the abdomen and thorax [4]. Clinical evidence has shown improved local control and survival using increased dose levels in lung cancer, although the risks of complication are also increased [2, 5–7]. The advent of respiratory-correlated (4D) imaging in computed tomography (CT) and positron emission tomography (PET) has improved the accuracy of detecting a mobile target’s actual motion e
Data Loading...
