Radiation Physics

PV QA 3 - Poster Viewing Q&A 3

TU_19_3303 - Analysis of Heart Substructures Motion and Changes Using 4DCT Dataset and Heart Atlas in Lung Cancer Patients

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Analysis of Heart Substructures Motion and Changes Using 4DCT Dataset and Heart Atlas in Lung Cancer Patients
N. Mohammed1, S. Currie1, M. Glegg1, Y. Flanagan1, E. Miguel1, P. Kelso1, K. MacLellan2, and M. Sankaralingam1; 1Beatson West of Scotland Cancer Centre, Glasgow, United Kingdom, 2Edinburgh Cancer Centre, Edinburgh, United Kingdom

Purpose/Objective(s): Lung cancer has high mortality and cardiac toxicity with radiotherapy warrants investigation. Studies have investigated radiation dose to the whole heart and left ventricle but found contradictory results. The heart is a complex organ with multiple sub-structures, therefore it is unlikely that one, whole-heart structure and its correspondent dose-volume histogram (DVH) parameters will represent different types of acute and late cardiac toxicity. We developed a detailed atlas to contour heart sub-structures on computed tomography (CT) scans. The atlas was utilised on 4-dimensional computed tomography (4DCT) scans in order to investigate changes of heart substructures that could affect the radiation dose to those sub-structures in patients treated with thoracic radiotherapy.

Materials/Methods: 11 lung cancer patients with 4DCT were selected retrospectively. Structures of the heart were outlined by an experienced clinician following the proposed atlas, on inhalation (inh) and exhalation (exh) CT scan datasets. In total 36 structures were outlined on each scan. The heart structures changes were investigated using the tool “Statistics” from the image registration workspace in a treatment planning system.

Results: Analysis showed that all heart substructures’ volumes changed between the 2 CT scan datasets. The changes in volume were marked in the valvular, conduction and left ventricular territories. The sino-atrial node (SA Node) mean volumes ranged between 5.6cc (inh) to 6.3cc (exh) demonstrating a difference of 11.1%. The left ventricle demonstrated a change of mean volume 275.2cc (inh) and 276.1cc (exh) with difference of 0.3%. Table 1 The mean displacement of the centre of mass in the X and Y dimension moved by (-0.1 – 0.2 cm) for all structures. The Z direction displacement was increased for all structures in a consistent manner. The SA Node and left ventricle structures had a mean Z direction displacement of 0.5. Table 1. The DICE coefficient results varied markedly between structures. The mean DICE coefficient result for the SA Node was 0.6 (range 0.3-0.8) suggesting a large change and left ventricle was 0.9 (range 0.8-0.9) in keeping with the anatomy of the left ventricle. Table 1.

Conclusion: This analysis of heart substructures within a group of lung cancer patients shows consistent changes in volume, shape and position during inhalation and exhalation and warrants further investigation. These results suggest that the implementation of sub-structures outlining is relevant for treatment planning studies.
Structure Mean Inhalation Volume (cc) Relative Mean Inhalation Volume Change (%) z-shift (cm) Dice Coefficient
SA Node 5.6 (3.1 -9.3) +11.1 0.5 0.6
Left Atrium 128.1 (81.7 - 177.1) -2.6 0.6 0.8
Right Atrium 114.7 (63.8 -209.3) -1.6 0.4 0.8
Left Ventricle 275.2 ( 162.5 -350.2) +0.3 0.5 0.9
Right Ventricle 161.6 ( 104.4 -213.4) -5.1 0.4 0.8
LAD 22.8 ( 15.4 - 32.0) +0.4 0.4 0.4
LCX 17.5 (12.2 - 24.2) +6.4 0.5 0.4
RCA 18.1 (12.3 - 23.7) -0.6 0.5 0.4

Author Disclosure: N. Mohammed: None. S. Currie: None. M. Glegg: None. K. MacLellan: None. M. Sankaralingam: None.

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