Dosimetric assessment of patient‐specific breath‐hold reproducibility on liver motion for SBRT planning

Abstract

To investigate the impact of breath-hold reproducibility on liver motion using a respiratory motion management device. Methods: Forty-four patients with hepatic tumors, treated with SBRT with breathhold, were randomly selected for this study. All patients underwent three consecutive computed tomography (CT) scans using active breath-hold coordinator (ABC) with three repeated single breath-hold during simulation. The three CT scans were labeled as ABC1-CT, ABC2-CT, and ABC3-CT. Displacements of centroids of the entire livers among the three ABC-CTs were measured as a surrogate for intrafractional motion. For each patient, two different treatment plans were prepared: (a) a clinical plan using a 5-mm expansion of an ITV that encompassed all three GTVs from each of the three ABC-CTs, and (b) a research plan using a 5-mm expansion of the GTV from only ABC1-CT to create PTV. The clinical plan acceptance criteria were that 95% of the PTV and 99% of the GTV received 100% of the prescription dose. Dosimetric endpoints were analyzed and compared for the two plans. Results: All shifts in the medial-lateral direction (range: −3.9 to 2.0 mm) were within 5 mm while 7% of shifts in the anterior-posterior direction (range: −10.5 to 16.7 mm) and 11% of shifts in the superior-inferior direction (range: −17.0 to 8.7 mm) exceeded 5 mm. Six patients (14%) had an intrafraction motion greater than 5 mm in any direction. For these six patients, if a plan was created based on a PTV from a single CT (ex. ABC1-CT), 5 of 12 GTVs captured from other ABC-CTs would fail to meet the clinical acceptance criteria due to poor breath-hold reproducibility. Conclusions: Non-negligible intrafractional motion occurs in patients with poor breath-hold reproducibility. To identify this subgroup of patients, acquiring three CTs with active breath-hold during simulation is a feasible practical method.

Influence of intra- and interfraction motion on planning target volume margin in liver stereotactic body radiation therapy using breath hold

“…In contrast, the kV cone beam CT images used herein likely resulted in improved image quality and soft tissue contrast, potentially allowing for more accurate patient positioning. Lu et al 5 investigated the reproducibility of DIBH using ABC, considering liver centroid displacement across 3 CT images acquired using 3 separate breath holds. The researchers reported SDs for AP, SI, and RL of 2.51, 2.61, and 0.71 mm.…”

“…In contrast, breath hold techniques retain reasonably good treatment delivery efficiency while minimizing liver motion and allowing for treatment on a conventional C-arm linac. However, not all patients are capable of reproducible breath holds, and variations can lead to errors in treatment delivery [1], including target underdosage [5]. Pre-treatment imaging and subsequent repositioning shifts have been shown to be necessary to ensure accurate patient positioning [6,7].…”

“…However, not all patients are capable of reproducible breath holds, and variations can lead to errors in treatment delivery, 1 including target underdosage. 5 Pretreatment imaging and subsequent repositioning shifts have been shown to be necessary to ensure accurate patient positioning. 6 , 7 …”

Novel Clinically Weight-Optimized Dynamic Conformal Arcs (WO-DCA) for Liver SBRT: A Comparison with Volumetric Modulated Arc Therapy (VMAT)

“…The GI was calculated, where V Rx is the volume of the prescription isodose line, V 50%Rx is the volume of the 50% of prescription isodose line, and V PTV is the volume of the PTV (GI= V 50%Rx/ V Rx ). 19 , 20 GI is used to evaluate dose sparing in the healthy liver volume. The smaller GI values represent faster dose fall‐off.…”

“…[14][15][16] Motion management embodies a significant challenge in abdominal SBRT like its thoracic counterpart, which might get further complicated in larger target volumes. [17][18][19] The customary ways to deal with motion have entailed the expansion of the gross or clinical target volume to include the entire range of motion after Wolthaus et al's portrayal of 5 strategies for motion management; 10 defined as the internal target volume (ITV). However, in any case, there is a lack of consensus for the SBRT treatment planning or delivery technique despite the implementation of a wide range of software and hardware systems in the last decade.…”