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The first aim of our study was to optimize our patient appointment schedule by comparing the estimated treatment times of the Precision treatment planning system to the real, measured door-to-door treatment times on our CyberKnife M6 system. The second aim of the study was to investigate the time reducing efficiency of the newly introduced VOLO optimizer algorithm. 

Estimated treatment times of 80 patients were calculated and then compared in the following tumour localisations: cranial with one target, cranial with multiple (2-3) targets, spine, lung, breast and prostate. First, treatment times estimated by the planning system were calculated, then the door-to-door times were measured. Later, the treatment times estimated by the VOLO algorithm were compared with the sequential algorithm for another group of 78 patients. T-test was used in both methods for statistical analysis.

There were significant differences between the calculated and the measured treatment times in all regions (p<0,05) except for the breast (p=0,087). In all cases, the measured treatment time was higher. The average increase of treatment time by localisations were the following: cranial with one target by 4 minutes (20%), cranial with multiple targets by 4 minutes (13%), prostate by 11 minutes (37%), spine by 13 minutes (33%), lung by 12 minutes (32%), breast by 13 minutes (19%).

The VOLO optimizer reduced the estimated treatment time in the following regions: prostate by 6 minutes (20%), spine by 3 minutes (14%), lung by 3 minutes (8%), breast by 2 minutes (4%). In case of the skull region, treatment times of one and multiple target plans are estimated longer by 2 minutes (8%) and 1 minute (2%), respectively. However, we found no significance between the differences except in the prostate region.

The estimated treatment times were always shorter than the measured ones on the Cyberknife. The system cannot precisely calculate the real time of patient setup and the additional time caused by the intrafractional motion, machine errors or emergencies.

The VOLO optimizer could not reduce the treatment time in the cranial region, but was very effective for prostate. The low patient number in the examined regions of spine (7), lung (9) and breast (5) results in the high p-value. We plan to evaluate the differences between the estimated treatment times of the VOLO plans and the real measured times.