Room: Track 2
We developed and clinically implemented Kilovoltage Intrafraction Monitoring (KIM), a software device that converts standard cancer radiotherapy systems into real-time IGRT systems. We report on the first-in-human prospective use of real-time target tracking for liver cancer SABR.
The KIM system was adapted to meet the requirements of liver SABR. A commissioning and quality assurance program developed using a robot measured geometric accuracy of KIM under static motion, dynamic motion and treatment interruption conditions. A patient with colorectal metastases in the liver to be treated with SABR (50Gy in 5fractions) was enrolled in the TROG 17.03 Liver Ablative Radiotherapy with KIM (LARK) clinical trial. The patient was treated at end-exhale breath-hold with a VMAT 6FFF plan on a Varian TrueBeam. A margin of 5mm in all direction was applied to the CTV to create the PTV. Three gold fiducial markers (3x1mm) were implanted around the patient’s tumours and used as tracking surrogate. During treatment, an optical signal (Varian RPM) was used to monitor the patient’s breath-hold with a gating threshold of 2mm. The patient internal motion was monitored by KIM using fluoroscopic imaging at 10Hz (120kV, 40mA, 10ms). Couch shifts were performed following kV pair imaging if the internal motion exceeded the gating threshold of 3mm in two consecutive breath-holds.
KIM was successfully clinically implemented for liver SABR treatments on a standard linac. During the five fractions, a total of 10 intrafraction shifts were triggered by KIM. The largest couch shifts were 7mm in the superior/inferior direction and 3mm in the anterior/posterior direction.
The first treatment demonstrated the importance of real-time internal tracking, with large internal motion detected that was not observed by surface tracking. The successful first in human use of KIM for liver cancer SABR paves the way for the broader adoption of KIM.
Funding Support, Disclosures, and Conflict of Interest: This work is funded by Cancer Australia. DTN is supported by Australian NHMRC and Cancer Institute NSW Early Career Fellowships. PJK received funding from an NHMRC Fellowship. Conflict: PJK is an inventor of licensed and PJK, RO, DTN are inventors of unlicensed patents related to the KIM technology.