Multiple Breath-hold Volumetric Modulated Arc Therapy Under Fluoroscopic Image Guidance with an Implanted Fiducial Marker: An Advanced Technique

Abstract

An advanced technique for multiple breath-hold volumetric modulated arc therapy (VMAT) has been proposed under fluoroscopic image guidance with a fiducial marker implanted close to a tumor. The marker coordinates on a digitally reconstructed radiography image at a gantry start angle, under a planned breath-hold condition, were transferred to the fluoroscopic image window. Then, a reference lateral line passing through the planned breath-hold marker position was drawn on the fluoroscopic image. Additional lateral lines were further added on both sides of the reference line with a distance of 3 mm as a tolerance limit for the breath-hold beam delivery. Subsequently, the patient was asked to breathe in slowly under fluoroscopy. Immediately after the marker position on the fluoroscopic image moved inside the tolerance range, the patient was asked to hold the breath and the VMAT beam was delivered. During the beam delivery, the breath-hold status was continuously monitored by checking if the deviation of the marker position exceeded the tolerance limit. As long as the marker stayed within the tolerance range, a segmented VMAT delivery continued for a preset period of 15 to 30 seconds depending on the breath-hold capability of each patient. As soon as each segmented delivery was completed, the beam interrupt button was pushed; subsequently, the patient was asked for free breathing. This procedure was repeated until all the segmented VMAT beams were delivered. A lung tumor case is reported here as an initial study. The proposed technique may be clinically advantageous for treating respiratory moving tumors including lung tumor, liver cancer, and other abdominal cancers.

Initial validation of a diaphragm tracking system for multiple breath‐hold volumetric modulated arc therapy of abdominal tumors: A phantom study

“…1 Most of the breath-hold techniques are based on motion monitoring of body surface [2][3][4] or embedded metal markers. [5][6][7] Body surface may be a good surrogate for a near-surface target, but the accuracy was reduced for deep-seated tumors in some patients. 8 On the other hand, metal markers may cause migration and complications, and therefore risk assessment would be required for each patient.…”

“…The breath‐hold radiotherapy has been increasingly used to mitigate interfractional and intrafractional breathing impact on treatment planning and beam delivery, thereby reducing the dose to organs‐at‐risk (OARs) 1 . Most of the breath‐hold techniques are based on motion monitoring of body surface 2–4 or embedded metal markers 5–7 . Body surface may be a good surrogate for a near‐surface target, but the accuracy was reduced for deep‐seated tumors in some patients 8 .…”