Table 1.
Major Assumptions for CTgRT vs MRgRT in Prostate SBRT
| Assumption | CT-guided Linac SBRT | MR-guided Linac SBRT | Shared by CTgRT and MRgRT |
|---|---|---|---|
| Machine (Manufacturer) | TrueBeam STx (Varian) with ExacTrac (BrainLab) | MRIdian Linac (ViewRay) | |
| Real-time imaging of soft tissue | No | Yes | |
| Type of simulation required | CT simulation only (Diagnostic MRI may be done prior) | CT simulation and MR simulation |
|
| Technique | VMAT | Fixed-gantry, step-and-shoot IMRT | |
| Fiducials placed | Yes - for image guidance | No | |
| Annual time spent on machine QA (minutes) | 8,760 | 15,660 | |
| Construction costs for linac vault | $1,000 / sq ft | $1,265 / sq ft | |
| List price of machine | $4,750,000 | $7,800,000 | |
| Annual maintenance costs of machine | $417,500 | $550,000 | |
| Space of linac vault | 686 sq ft | 1134 sq ft | |
| Space/equipment cost of linac vault | $6.43/minute | $9.62/minute | |
| Number of fractions | 5 | ||
| Dose per fraction | 8 Gy | ||
| Time machine is clinically available during year, excluding QA (minutes) | 141,930 | ||
| Personnel CCR (Attending Physician) | $5.16/minute | ||
| Personnel CCR (Technologist) | $1.32/minute | ||
| Personnel CCR (Physicist) | $2.56/minute | ||
| Personnel CCR (Dosimetrist) | $2.27/minute | ||
| Personnel CCR (Radiation Therapist) | $2.11/minute | ||
| Personnel CCR (Nurse) | $2.42/minute | ||
| Personnel CCR (Hospital Assistant) | $1.09/minute | ||
| Personnel CCR (Front Desk Staff) | $0.97/minute |
Key: CTgRT = computed-tomography-guided radiation therapy, MRgRT = MR-guided radiation therapy, SBRT = stereotactic body radiation therapy, VMAT = volumetric-modulated arc therapy, QA = linear accelerator, CCR = capacity cost rates