Abstract
Purpose: Develop four-dimensional (4D) radiotherapy to incorporate breathing motion in thorax, covering PTV adequately and reducing mean lung dose and V20 for lung. Analyze tumor and thoracic structures motion using the 4D-CT images. Method and Materials: Motion of tumor and thoracic structures of twenty lung cancer patients are studies, using a retrospective respiratory gating 4D-CT and external respiratory signal generator system. Breathing was synchronized with cine image acquisition, and retrospectively correlated based on respiratory phases. For 4D-delivery, MLCs were synchronized with respiratory motion and followed tumor with a safe margin selected based on reliability of patient breathing ranging from 100% largest static field to 0% the smallest dynamic field. Results: 4D-CT provides tumor motion in different phases of breathing cycle. The GTV/CTV delineated on helical CT without incorporating breathing motion underestimates GTV/CTV by 25–50% compare to the 4D-GTV/CTV delineated on 4D-CT image sets. The 4D radiotherapy reduces the mean lung dose by 16–32% (average 23%) and V20 reduction for ipsi lung by 16–26% (average 21%) compare to the standard protocol. The volume changes of apex, mid and inferior regions of the lung during breathing are 11%, 24%, and 65%. The motion of tumors varies with the location. Tumors located in the apex move by 3–5mm, 2–4mm, and 2–3.5mm in superior/inferior, anterior/posterior, and right/left directions. Those located in mid lobe move by 6.5–9mm, 3.5–5mm, and 4–5mm, and those in lower lobe move by 7.5–12mm, 4–8mm, and 3.5–6.5mm. The superior/inferior motions of diaphragm, rib and carina range from 7–25mm, 2–7mm, and 3.5–13mm. On 4D delivery, we tested MLC synchronization with breathing motion on phantom. Lung volume coverage is minimized by a 20% safe margin. Conclusion: 4D-CT provides tumor motion in different phases of breathing cycle. 4D delivery synchronized with respiration-induced motion reduces mean lung dose and were synchronized with respiratory motion V20 for lung.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
