Online verification of breath‐hold reproducibility using kV‐triggered imaging for liver stereotactic body radiation therapy

Abstract

PurposeTo introduce a new technique for online breath‐hold verification for liver stereotactic body radiation therapy (SBRT) based on kilovoltage‐triggered imaging and liver dome positions.Material and MethodsTwenty‐five liver SBRT patients treated with deep inspiration breath‐hold were included in this IRB‐approved study. To verify the breath‐hold reproducibility during treatment, a KV‐triggered image was acquired at the beginning of each breath‐hold. The liver dome position was visually compared with the expected upper/lower liver boundaries created by expanding/contracting the liver contour 5 mm in the superior‐inferior direction. If the liver dome was within the boundaries, delivery continued; otherwise, beam was held manually, and the patient was instructed to take another breath‐hold until the liver dome fell within boundaries. The liver dome was delineated on each triggered image. The mean distance between the delineated liver dome to the projected planning liver contour was defined as liver dome position error edome. The mean and maximum edome of each patient were compared between no breath‐hold verification (all triggered images) and with online breath‐hold verification (triggered images without beam‐hold).ResultsSeven hundred thirteen breath‐hold triggered images from 92 fractions were analyzed. For each patient, an average of 1.5 breath‐holds (range 0–7 for all patients) resulted in beam‐hold, accounting for 5% (0–18%) of all breath‐holds; online breath‐hold verification reduced the mean edome from 3.1 mm (1.3–6.1 mm) to 2.7 mm (1.2–5.2 mm) and the maximum edome from 8.6 mm (3.0–18.0 mm) to 6.7 mm (3.0–9.0 mm). The percentage of breath‐holds with edome >5 mm was reduced from 15% (0–42%) without breath‐hold verification to 11% (0–35%) with online breath‐hold verification. online breath‐hold verification eliminated breath‐holds with edome >10 mm, which happened in 3% (0–17%) of all breath‐holds.ConclusionIt is clinically feasible to monitor the reproducibility of each breath‐hold during liver SBRT treatment using triggered images and liver dome. Online breath‐hold verification improves the treatment accuracy for liver SBRT.

SBRT for Liver Tumors: What the Interventional Radiologist Needs to Know

“…81 Intra-fractional motion monitoring can be performed by obtaining kilovoltage-triggered imaging during treatment delivery and verifying alignment with fiducials and/or the liver dome. 82 Emerging technical advances include MRI-guided adaptive radiotherapy and proton therapy. MRI-guided radiotherapy treatment systems permit highly accurate tumor tracking and facilitate daily treatment adaptation in response to anatomic changes, which can result in decreased dose to normal tissues while maximizing dose to the tumor.…”

“…81 Intra-fractional motion monitoring can be performed by obtaining kilovoltage-triggered imaging during treatment delivery and verifying alignment with fiducials and/or the liver dome. 82…”