A standardized workflow for respiratory‐gated motion management decision‐making

Abstract

Purpose Motion management of tumors within the lung and abdomen is challenging because it requires balancing tissue sparing with accuracy of hitting the target, while considering treatment delivery efficiency. Physicists can play an important role in analyzing four‐dimensional computed tomography (4DCT) data to recommend the optimal respiratory gating parameters for a patient. The goal of this work was to develop a standardized procedure for making recommendations regarding gating parameters and planning margins for lung and gastrointestinal stereotactic body radiotherapy (SBRT) treatments. In doing so, we hoped to simplify decision‐making and analysis, and provide a tool for troubleshooting complex cases. Methods Factors that impact gating decisions and planning target volume (PTV) margins were identified. The gating options included gating on exhale with approximately a 50% duty cycle (Gate3070), exhale gating with a reduced duty cycle (Gate4060), and treating for most of respiration, excluding only extreme inhales and exhales (Gate100). A standard operating procedure was developed, as well as a physics consult document to communicate motion management recommendations to other members of the treatment team. This procedure was implemented clinically for 1 year and results are reported below. Results Identified factors that impact motion management included the magnitude of motion observed on 4DCT, the regularity of breathing and quality of 4DCT data, and ability to observe the target on fluoroscopy. These were collated into two decision tables—one specific to lung tumors and another for gastrointestinal tumors—such that a physicist could answer a series of questions to determine the optimal gating and PTV margin. The procedure was used clinically for 252 sites from 213 patients treated with respiratory‐gated SBRT and standardized practice across our 12‐member physics team. Conclusion Implementation of a standardized procedure for respiratory gating had a positive impact in our clinic, improving efficiency and ease of 4DCT analysis and standardizing gating decision‐making amongst physicists.

Intra‐ and inter‐fractional variations of tumors with fiducial markers measured using respiratory‐correlated computed tomography images for respiratory gated lung stereotactic body radiation therapy

“… 8 , 9 , 10 To reduce geometric uncertainty and adverse event risk, SBRT for lung tumors with severe respiratory motion requires appropriate motion management. 11 Several respiratory motion management methods have been used, including breath holding, respiratory gating, and dynamic tumor tracking. 12 , 13 , 14 In these respiratory motion management methods, fiducial markers (FMs), inserted either in the tumor itself or in close proximity, are often used as internal surrogates to localize the tumor.…”

“…However, a large target volume can increase the irradiation dose to the surrounding normal tissue and increase the risk of adverse events such as radiation pneumonitis 8–10 . To reduce geometric uncertainty and adverse event risk, SBRT for lung tumors with severe respiratory motion requires appropriate motion management 11 . Several respiratory motion management methods have been used, including breath holding, respiratory gating, and dynamic tumor tracking 12–14 .…”

Motion-correction strategies for enhancing whole-body PET imaging

“…As such, one of the essential techniques employed in PET imaging is gating, which helps further minimize motion artifacts caused by involuntary patient movement (5,8). This technique allows patients to breathe freely and increase comfort and accessibility (9). Furthermore, this technique can be applied in conjunction with physical constraints to help improve image quality.…”