Results of a 12 Year Survey of Workload for 10 Linear Accelerators at a High-Throughput Comprehensive Cancer Center
Z Saleh*, L Dauer, J Mechalakos, J St. Germain, Memorial Sloan Kettering Cancer Ctr, New York, NYSU-E-T-290 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
To report on the workload for 10 different treatment machines in terms of number of patients (pts), monitor units delivered (MUs), dose at isocenter (Gys), use factors (U) and modulation factors (C).
The survey was performed for 10 treatment machines in the years from 2001 to 2012. The machines represented different generations of Varian linear accelerators (6EX, 600C, 2100C, 2100EX, and True Beam) operating at different electron and photon energies (6, 9, 12, 16 and 20 MeV electrons and, 6 and 15MV photons).
An IRB approval was acquired to perform this study. Data regarding patient workload, number of monitor units delivered, dose at isocenter, beam energies, gantry angles, and techniques were exported from ARIA treatment management system (Varian Medical Systems) into excel spreadsheets. Data analysis was performed in Matlab (R2011a).
The number of patients, dose at isocenter, and number of monitor units delivered per week in 2002 was on average 92±32 pts, 267±34 Gys, and (49.2±10) x 10³ MUs respectively. Meanwhile, the average workload in 2012 was 106±38 pts, 326±69 Gys, and (110.7±34) x 10³ MUs. The photon beam energies predominantly used were the 6 and 15 MV. The modulation factors for SBRT (CS) and IMRT (CI) were 4.1 and 3.4. Use factor (30° bin angles) varied considerably among different techniques and ranged between 0.06 and 0.35.
The workload, in terms of monitor units (MUs), has been steadily increasing over the past decade. However, the patient workload and consequently the dose at isocenter remained relatively constant. This increase can be attributed to the emergence of treatment techniques (SBRT, IMRT) which require more MUs per Gy as compared to more conventional treatment (3DCRT). The findings of this report show that variables are still within the recommendation of NCRP Report 151.
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