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Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
Fluoroscopy as a surrogate for lung tumour motion
H A McNair1, A Kavanagh, C Powell
1Radiotherapy Department, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton, UK. Helen.McNair@rmh.nhs.uk
The British Journal of Radiology
|August 11, 2011
Summary
This study shows that using simple pixel density from fluoroscopy images can effectively gate radiotherapy for non-small cell lung cancer patients. This method accurately identifies breathing phases, potentially improving tumor targeting during treatment.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image Analysis
Background:
- Radiotherapy for non-small cell lung cancer requires precise tumor targeting.
- Tumor motion due to respiration can reduce treatment accuracy.
- Gated radiotherapy aims to deliver radiation only during specific phases of the breathing cycle.
Purpose of the Study:
- To evaluate a novel, simple method for gated radiotherapy using fluoroscopy image pixel density.
- To assess the feasibility of using pixel density variations to determine breathing phases (inhale/exhale).
- To determine the potential of this technique as a surrogate for tumor position during radiotherapy.
Main Methods:
- Fluoroscopy images (anterior and lateral) were acquired from 18 non-small cell lung cancer patients.
- Breathing patterns were analyzed by tracking pixel value variations within defined regions.
- Inhale and exhale phases were identified based on the greatest and lowest 30% of pixel values.
Main Results:
- The method successfully captured a median of eight breathing cycles per patient.
- Mean tumor motion ranged from 4.7 mm to 7.2 mm across different directions.
- Gating margins were established (e.g., 5.5 mm in RL direction for exhale gating), with greater benefit for motions exceeding 5 mm.
Conclusions:
- The pixel density-based gating approach was successfully applied to all patients.
- This technique offers a simple and potentially accurate method for real-time tumor tracking.
- It may serve as a valuable surrogate for tumor position in gated radiotherapy.
