Reproducibility of diaphragm position assessed with a voluntary breath-holding device

To evaluate the reproducibility of diaphragm position in our new breath-holding radiotherapy for abdominal tumors using image-guided radiation therapy (IGRT) and a voluntary breath-holding device, Abches.

Patients treated with abdominal tumors using IGRT with Abches were enrolled. Twenty patients without dementia or severe lung disease were analyzed. Each fraction of all patients was set up with kV cone-beam CT with reference to the vertebral bodies. Before daily treatment, electronic portal imaging device (EPID) images of the diaphragm at breath-holding exhale phase were acquired. The difference in the diaphragm position relative to the vertebral body was analyzed by comparing EPID images and the digitally reconstructed radiograph of the planning CT. We evaluated the reproducibility of two axes: superior-inferior (S-I) and right-left (R-L) with the EPID measurements.

The 443 irradiation data sets were analyzed. The interfractional reproducibility of the diaphragm relative to vertebral bodies was 1.7 ± 1.4 mm in the S-I and 1.4 ± 1.2 mm in the R-L direction.

This technique has good interfractional reproducibility and visibility of the diaphragm during irradiation. Its use is feasible in the routine clinical setting and irradiation.