Journal article
Quantitation of the reconstruction quality of a four-dimensional computed tomography process for lung cancer patients
Medical physics (Lancaster), Vol.32(4), pp.890-901
03/16/2005
DOI: 10.1118/1.1870152
PMID: 15895571
Abstract
We have developed a four-dimensional computed tomography (4D CT) technique for mapping breathing motion in radiotherapy treatment planning. A multislice CT scanner (1.5 mm slices) operated in ciné mode was used to acquire 12 contiguous slices in each couch position for 15 consecutive scans (0.5 s rotation, 0.25 s between scans) while the patient underwent simultaneous quantitative spirometry measurements to provide a sorting metric. The spirometry-sorted scans were used to reconstruct a 4D data set. A critical factor for 4D CT is quantifying the reconstructed data set quality which we measure by correlating the metric used relative to internal-object motion. For this study, the internal air content within the lung was used as a surrogate for internal motion measurements. Thresholding and image morphological operations were applied to delineate the air-containing tissues (lungs, trachea) from each CT slice. The Hounsfield values were converted to the internal air content (V). The relationship between the air content and spirometer-measured tidal volume (v) was found to be quite linear throughout the lungs and was used to estimate the overall accuracy and precision of tidal volume-sorted 4D CT. Inspection of the CT-scan air content as a function of tidal volume showed excellent correlations (typically r > 0.99) throughout the lung volume. Because of the discovered linear relationship, the ratio of internal air content to tidal volume was indicative of the fraction of air change in each couch position. Theoretically, due to air density differences within the lung and in room, the sum of these ratios would equal 1.11. For 12 patients, the mean value was 1.08±0.06, indicating the high quality of spirometry-based image sorting. The residual of a first-order fit between v and V was used to estimate the process precision. For all patients, the precision was better than 8%, with a mean value of 5.1 % ± 1.9%. This quantitative analysis highlights the value of using spirometry as the metric in sorting CT scans. The 4D reconstruction provides the CT data required to measure the three-dimensional trajectory of tumor and lung tissue during free breathing
Details
- Title: Subtitle
- Quantitation of the reconstruction quality of a four-dimensional computed tomography process for lung cancer patients
- Creators
- Wei Lu - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Parag Parikh - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Issam El Naqa - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Michelle Nystrom - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110James Hubenschmidt - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Sasha Wahab - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Sasa Mutic - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Anurag Singh - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Gary Christensen - Department of Electrical and Computer Engineering, University of Iowa, Iowa City, Iowa 52242Jeffrey Bradley - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110Daniel Low - Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110
- Resource Type
- Journal article
- Publication Details
- Medical physics (Lancaster), Vol.32(4), pp.890-901
- Publisher
- American Association of Physicists in Medicine
- DOI
- 10.1118/1.1870152
- PMID
- 15895571
- ISSN
- 0094-2405
- eISSN
- 2473-4209
- Language
- English
- Date published
- 03/16/2005
- Academic Unit
- Electrical and Computer Engineering; Radiation Oncology; Radiation Research Laboratory
- Record Identifier
- 9984046829502771
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