Spirometer-guided breath-hold breast VMAT verified with portal images and surface tracking

Abstract

Background and purpose: Fast rotating closed-bore gantry linacs are ideally suited for breath-hold treatments due to reduced imaging and delivery times. We evaluated the reproducibility and stability of spirometer-guided breath-hold breast treatments, using intra-bore surface monitoring and portal imaging on Halcyon (Varian Medical Systems). Materials and methods: Seven left-sided breast cancer patients were treated in breath-hold using the SDX spirometer (Dyn'R) with an integrated boost volumetric arc protocol on Halcyon. A dual depth-camera surface scanning system monitored the left breast. The interfraction, intrafraction and intrabreath-hold motion was determined in the anterior-posterior (AP) and superior-inferior (SI) direction. Portal images (PI), acquired at a tangential gantry angle were manually registered to the planning-CT to determine inter-and intrafraction breath-hold errors for the SI and tangential-anterior-posterior (''AP") axis. Correlations between PI and surface imaging deviations were investigated. To evaluate workflow efficiency, the total time and the number of breath-holds were recorded. Results: Systematic and random variability of breath-hold amplitude was below 0.7 mm for the AP and below 1.2 mm for the SI component as detected by surface monitoring (N = 130). Systematic and random errors retrieved from portal images (N = 140) were below 1.2 mm for the ''AP" and 2.1 mm for SI axis. A limited correlation was found between PI and surface monitoring deviations for both the SI and ''AP" axes (R 2 = 0.27/0.38, p < 0.01). 75% of fractions were completed using four breath-holds and 82% within 10 min. Conclusion: Surface imaging indicated spirometer-guided breath-hold VMAT breast radiotherapy can be accurately and quickly performed on a closed-bore gantry linac. Intra-bore surface scanning proved a valuable technique for monitoring breathing motion in closed-bore systems.

Intra-fraction motion monitoring during fast modulated radiotherapy delivery in a closed-bore gantry linac

“…Monitoring was initiated within two seconds after execution of the couch shift. This surface scanning system is described in detail in Delombaerde et al [16,19] but the basics are reiterated here. The system consists of two Kinect™ for Windows cameras (Microsoft, Redmond, VA, USA) mounted at the back of the Halcyon bore to image the patient while at the treatment isocenter.…”

“…Due to limited access to the patient by the radiotherapy technologists (RTT) inside the bore, patient setup is performed in front of the linac after which the couch automatically translates to the treatment isocenter. Setup can be performed either guided by the built-in lasers or using a surface scanning system [15,16], however after translation to the treatment isocenter, the patient falls outside the reach of the ceilingmounted surface monitoring systems [17,18]. To investigate the potential added value, we have developed an intra-bore surface scanning system to monitor patient motion during treatment [16,19] to be able to assess motion during the image guidance (IGRT) procedures (e.g.…”

“…Setup can be performed either guided by the built-in lasers or using a surface scanning system [15,16], however after translation to the treatment isocenter, the patient falls outside the reach of the ceilingmounted surface monitoring systems [17,18]. To investigate the potential added value, we have developed an intra-bore surface scanning system to monitor patient motion during treatment [16,19] to be able to assess motion during the image guidance (IGRT) procedures (e.g. kV-CBCT acquisition and evaluation) and treatment delivery.…”

A method for beam’s eye view breath-hold monitoring during breast volumetric modulated arc therapy

“…For VMAT delivery there are further challenges as the anatomy projected in the BEV will change with gantry angle, and treatment planning system (TPS) optimisers typically provide MLC patterns that obscure a larger portion of the BEV. One group [15] has utilised EPID imaging on a closed-bore linac for analysing breast VMAT DIBH treatments at a single gantry angle with manual registration to extract the CW position. This approach is limited as monitoring of the CW position is only performed for a small number of time points during the treatment and the reported CW position may be subject to inter-user variability during manual registration.…”

A system for real‐time monitoring of breath‐hold via assessment of internal anatomy in tangential breast radiotherapy

“…1,2 Deep inspiration expands the lung and displaces the upper abdominal organs away from the chest wall. The quality of DIBH is currently assessed by various techniques,for example,by tracking an external marker block placed on the patient's chest or abdomen, 3 by monitoring the patient's skin surface with optical surface monitoring systems, 4 by controlling the breathing, 5,6 or by employing the treatment room lasers and tattoos on the patient's abdomen. 7 A low-cost in-house system for monitoring DIBH with an industrial laser distance meter was reported by Jensen et al 8 All such systems have in common is that they are not assessing the clinically relevant part of the patient's anatomy but a more or less motion correlated surrogate.…”