Journal article
Effect of atelectasis changes on tissue mass and dose during lung radiotherapy
Medical physics (Lancaster), Vol.43(11), pp.6109-6117
11/2016
DOI: 10.1118/1.4965807
PMCID: PMC5085974
PMID: 27806593
Abstract
To characterize mass and density changes of lung parenchyma in non-small cell lung cancer (NSCLC) patients following midtreatment resolution of atelectasis and to quantify the impact this large geometric change has on normal tissue dose.
Baseline and midtreatment CT images and contours were obtained for 18 NSCLC patients with atelectasis. Patients were classified based on atelectasis volume reduction between the two scans as having either full, partial, or no resolution. Relative mass and density changes from baseline to midtreatment were calculated based on voxel intensity and volume for each lung lobe. Patients also had clinical treatment plans available which were used to assess changes in normal tissue dose constraints from baseline to midtreatment. The midtreatment image was rigidly aligned with the baseline scan in two ways: (1) bony anatomy and (2) carina. Treatment parameters (beam apertures, weights, angles, monitor units, etc.) were transferred to each image. Then, dose was recalculated. Typical IMRT dose constraints were evaluated on all images, and the changes from baseline to each midtreatment image were investigated.
Atelectatic lobes experienced mean (stdev) mass changes of -2.8% (36.6%), -24.4% (33.0%), and -9.2% (17.5%) and density changes of -66.0% (6.4%), -25.6% (13.6%), and -17.0% (21.1%) for full, partial, and no resolution, respectively. Means (stdev) of dose changes to spinal cord D
, esophagus D
, and lungs D
were 0.67 (2.99), 0.99 (2.69), and 0.50 Gy (2.05 Gy), respectively, for bone alignment and 0.14 (1.80), 0.77 (2.95), and 0.06 Gy (1.71 Gy) for carina alignment. Dose increases with bone alignment up to 10.93, 7.92, and 5.69 Gy were found for maximum spinal cord, mean esophagus, and mean lung doses, respectively, with carina alignment yielding similar values. 44% and 22% of patients had at least one metric change by at least 5 Gy (dose metrics) or 5% (volume metrics) for bone and carina alignments, respectively. Investigation of GTV coverage showed mean (stdev) changes in V
, D
, and D
of -5.5% (13.5%), 2.5% (4.2%), and 0.8% (8.9%), respectively, for bone alignment with similar results for carina alignment.
Resolution of atelectasis caused mass and density decreases, on average, and introduced substantial changes in normal tissue dose metrics in a subset of the patient cohort.
Details
- Title: Subtitle
- Effect of atelectasis changes on tissue mass and dose during lung radiotherapy
- Creators
- Christopher L Guy - Virginia Commonwealth UniversityElisabeth Weiss - Virginia Commonwealth UniversityNuzhat Jan - Virginia Commonwealth UniversityLeonid B Reshko - Virginia Commonwealth UniversityGary E Christensen - University of IowaGeoffrey D Hugo - Virginia Commonwealth University
- Resource Type
- Journal article
- Publication Details
- Medical physics (Lancaster), Vol.43(11), pp.6109-6117
- DOI
- 10.1118/1.4965807
- PMID
- 27806593
- PMCID
- PMC5085974
- NLM abbreviation
- Med Phys
- ISSN
- 0094-2405
- eISSN
- 2473-4209
- Grant note
- R01 CA166119 / NCI NIH HHS
- Language
- English
- Date published
- 11/2016
- Academic Unit
- Electrical and Computer Engineering; Radiation Oncology; Radiation Research Laboratory; The Iowa Institute for Biomedical Imaging; Advanced Pulmonary Physiomic Imaging Laboratory; Holden Comprehensive Cancer Center
- Record Identifier
- 9984197309702771
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