Target localization errors from fiducial markers implanted around a lung tumor for dynamic tumor tracking

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Accurate tumor localization is critical for effective radiation therapy.
• Implanted fiducial markers are commonly used to guide radiation delivery.
• Assessing localization errors is essential for treatment precision.

Purpose of the Study:

• To compare the accuracy of target localization errors (TLEs) using three centers of gravity (CG) and three multiple regression analysis (MRA) methods.
• To evaluate the intrafraction and interfraction TLEs for each approach.

Main Methods:

• Three-dimensional positions of fiducial markers were analyzed in 15 lung cancer patients.
• Target position was estimated using CG and MRA techniques based on marker positions.
• TLEs were calculated as the root-mean-square error between the actual and estimated target positions.

Main Results:

• MRA approaches yielded intrafraction TLEs within 1.5 mm (mean + 2 SD).
• CG approaches resulted in intrafraction TLEs up to 4.3 mm (mean + 2 SD).
• Interfraction TLEs did not exceed 1.7 mm for either approach.

Conclusions:

• Multiple regression analysis (MRA) is a more accurate method for estimating target positions than centers of gravity (CG).
• MRA provides improved precision in localizing targets using implanted fiducial markers.