Respiratory Motion Management and Cone-Beam CT Localization for Lung SBRT with Amplitude-gated Breath-Hold and 4D-MIP Techniques

"Purpose/Objective(s): Both amplitude-gated breath-hold and 4D maximum intensity projection (MIP) techniques have been used in our clinic to account for respiratory motion with lung stereotactic body radiation therapy (SBRT). This study investigates the impact of these two different motion management techniques on dosimetry and target localization, in order to help select an optimal motion management technique for the treatment of an individual patient.""Materials/Methods: The RPM system was used for patient respiratory motion management. Seven patients with lung lesions were scanned with a multi-slice CT scanner. For each patient, a set of phase-gated 4D CT scan was acquired first with free breathing. CT images at 10 different respiratory phases were obtained to evaluate tumor motion and reconstruct MIP images. A CT scan of the same patient was then acquired under amplitude-gated breath-hold. Both CT data sets were transferred to the Eclipse planning system for treatment planning. For amplitude-gated breath hold, both IMRT and 3D conformal techniques were used for planning. For free-breathing with 4D-MIP, only the 3D conformal technique was used for planning. Either an amplitude-gated breath-hold or a free-breathing 4D-MIP based plan was selected for treatment. For target localization for breath-hold treatment, amplitude-gated breath hold cone-beam CT (CBCT) images were acquired with the same thresholds as amplitude-gated planning CT. 3D matching between CBCT and planning CT was used to localize the target. For target localization for free breathing treatment, CBCT images were acquired with free breathing. 3D matching between CBCT and internal target volume (ITV) contours was used to localize the target."Results: The mean lung dose was lower with amplitude-gated breath hold technique than with 4D-MIP. The average reduction in mean lung dose was 28.7% with 3D conformal and 37.2% with IMRT techniques. The treatment time was longer for amplitude-gated breath hold technique with an estimated average increase of about 40%. The CBCT images with amplitude-gated breath-hold images provided a better visualization of the target than those with free breathing."Conclusions: Amplitude-gated breath hold technique provides a better dose distribution and makes IMRT feasible by reducing the MLC leaf interplay effect, but requires longer treatment time than the 4D-MIP technique and also requires patients to hold breath consistently. The selection of motion management technique should be based on the motion ranges, patient condition and target size."

SSM23-06

Respiratory Motion Management and Cone-Beam CT Localization for Lung SBRT with Amplitude-gated Breath-Hold and 4D-MIP Techniques