Intrafraction tumor motion during deep inspiration breath hold pancreatic cancer treatment

Abstract

Purpose Beam gating with deep inspiration breath hold (DIBH) has been widely used for motion management in radiotherapy. Normally it relies on some external surrogate for estimating the internal target motion, while the exact internal motion is unknown. In this study, we used the intrafraction motion review (IMR) application to directly track an internal target and characterized the residual motion during DIBH treatment for pancreatic cancer patients through their full treatment courses. Methods and Materials Eight patients with pancreatic cancer treated with DIBH volumetric modulated arc therapy in 2017 and 2018 were selected for this study, each with some radiopaque markers (fiducial or surgical clips) implanted near or inside the target. The Varian Real‐time Position Management (RPM) system was used to monitor the breath hold, represented by the anterior‐posterior displacement of an external surrogate, namely reflective markers mounted on a plastic block placed on the patient's abdomen. Before each treatment, a cone beam computed tomography (CBCT) scan under DIBH was acquired for patient setup. For scan and treatment, the breath hold reported by RPM had to lie within a 3 mm window. IMR kV images were taken every 20° or 40° gantry rotation during dose delivery, resulting in over 5000 images for the cohort. The internal markers were manually identified in the IMR images. The residual motion amplitudes of the markers as well as the displacement from their initial positions located in the setup CBCT images were analyzed. Results Even though the external markers indicated that the respiratory motion was within 3 mm in DIBH treatment, significant residual internal target motion was observed for some patients. The range of average motion was from 3.4 to 7.9 mm, with standard deviation ranging from 1.2 to 3.5 mm. For all patients, the target residual motions seemed to be random with mean positions around their initial setup positions. Therefore, the absolute target displacement relative to the initial position was small during DIBH treatment, with the mean and the standard deviation 0.6 and 2.9 mm, respectively. Conclusions Internal target motion may differ from external surrogate motion in DIBH treatment. Radiographic verification of target position at the beginning and during each fraction is necessary for precise RT delivery. IMR can serve as a useful tool to directly monitor the internal target motion.

Positional repeatability and variation in internal and external markers during volumetric-modulated arc therapy under end-exhalation breath-hold conditions for pancreatic cancer patients

“…Zeng et al . showed that the mean motion of an internal marker was −0.6 ± 2.3 mm in the SI direction, observed intermittently under inhalation BH conditions on kV X-ray images [ 11 ]. However, there have neither been any reports assessing the positions of pancreatic tumors on a continuous basis, nor about the relationship between internal and external marker motion during VMAT under EE–BH conditions.…”

Accuracy and efficiency of respiratory gating comparable to deep inspiration breath hold for pancreatic cancer treatment

“…studied the reproducibility of organ movement under active breathing control in eight patients with liver cancer by repeating fluoroscopy before each treatment 24 . Very recently, we tracked the internal targets using kV images triggered during each DIBH treatment throughout the treatment course 30 …”

Positional repeatability and variation in internal and external markers during volumetric-modulated arc therapy under end-exhalation breath-hold conditions for pancreatic cancer patients

“…Of these techniques, BH is one of the most commonly used owing to its versatility (2). Some researchers reported that BH was clinically useful in cases with disease sites such as the lung, breast, liver, and pancreas (6)(7)(8)(9)(10)(11). At our institution, VMAT has been used clinically under BH conditions at the end-exhalation (EE) phase for pancreatic cancer (9,12).…”

“…Several investigators have assessed positional uncertainties in pancreatic cancer under BH conditions (9)(10)(11)(12). Nakamura et al showed that the positional reproducibility of the pancreas under EE-BH conditions was 0.6 ± 3.3 mm in the superior-inferior (SI) direction, using a visual feedback technique based on daily cone-beam computed tomography (CBCT) (9).…”

“…Lens et al concluded that the motion of pancreatic tumors under inhalation BH conditions was 4.2 ± 2.3 mm in the SI direction, as shown by intratumoral fiducial markers and kilovoltage (kV) X-ray fluoroscopic images (10). Zeng et al showed that the mean motion of an internal marker was − 0.6 ± 2.3 mm in the SI direction, observed intermittently under inhalation BH conditions on kV X-ray images (11). However, there have been no reports assessing the positions of pancreatic tumors on a continuous basis, nor on the relationship between internal and external marker motion during VMAT under EE-BH conditions.…”