Preliminary study on the RadCalc system for monitoring in vivo dosimetry in lung cancer radiotherapy

"The in vivo dose monitoring of the RadCalc system can reflect the actual dose changes in lung cancer patients during radiotherapy in real time."

Authors

HAN Ce, YIN Xujin, ZHANG Ji, WANG Zhiwei, LIN Li, JIN Wenwen, JIN Xiance, JIN Juebin

Objective

To explore the clinical application value of the RadCalc system based on electronic portal imaging device (EPID) for in vivo dose monitoring of lung cancer volumetric modulated arc therapy (VMAT).

Methods

Thirteen lung cancer patients who underwent VMAT at the First Affiliated Hospital of Wenzhou Medical University from January 1, 2025 to August 31, 2025 were selected. Cone-beam CT (CBCT) was performed once a week before treatment. After modeling and testing the RadCalc system, secondary dose verification was performed for all plans. The fractionated in vivo dose of patients was monitored in real time based on EPID images and log files through the three-dimensional dose reconstruction algorithm of the RadCalc system; and the 3D γ (3% / 3 mm) index was used for evaluation.

Results

Under the 3D γ (3% / 3 mm) criteria, the γ values of secondary dose verification were >99%, and those for 3DMap phantom planning verification were all >95%. The mean γ across the 13 patients ranged from a minimum of (65.25 ± 4.28)% to a maximum of (95.75 ± 3.99)%, with 9 patients having values ≥ 90% and 2 patients < 80%. Among 365 fractional in vivo dose verification data, there were 130 and 61 fractions with γ values ≤ 90% and ≤ 80%, respectively. The fractions with γ ≤ 80% mainly occurred in patient No. 8 and patient No. 10. There was a large variation in the in vivo dose of lung cancer patients, with some patients being affected by multiple factors such as tumor location, tension, and respiratory motion.

Conclusion

The in vivo dose monitoring of the RadCalc system can reflect the actual dose changes in lung cancer patients during radiotherapy in real time. The 3D γ index combined with CBCT can provide important dose information for clinicians and has significant clinical value.