title: Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit.
abstract: OBJECTIVE
  The objective of this work was to characterize the performance of the WOmed T-200-kilovoltage (kV) therapy machine.
  
  
  METHODS
  Mechanical functionality, radiation leakage, alignment and interlocks were investigated. Half-value layers (HVLs) (first and second HVLs) from X-ray beams generated from tube potentials between 30 and 200 kV were measured. Reference dose was determined in water. Beam start-up characteristics, dose linearity and reproducibility, beam flatness, and uniformity as well as deviations from inverse square law were assessed. Relative depth doses (RDDs) were determined in water and water-equivalent plastic. The quality assurance program included a dosimetry audit with thermoluminescent dosemeters.
  
  
  RESULTS
  All checks on machine performance were satisfactory. HVLs ranged between 0.45-4.52 mmAl and 0.69-1.78 mmCu. Dose rates varied between 0.2 and 3 Gy min(-1) with negligible time-end errors. There were differences in measured RDDs from published data. Beam outputs were confirmed with the dosimetry audit. The use of published backscatter factors was implemented to account for changes in phantom scatter for treatments with irregularly shaped fields.
  
  
  CONCLUSIONS
  Guidance on the determination of HVL and RDD in kV beams can be contradictory. RDDs were determined through measurement and curve fitting. These differed from published RDD data, and the differences observed were larger in the low-kV energy range.
  
  
  CONCLUSIONS
  This article reports on the comprehensive and novel approach to the acceptance, commissioning and clinical use of a modern kV therapy machine. The challenges in the dosimetry of kV beams faced by the medical physicist in the clinic are highlighted.
authors.affiliation: Institute of Radiation Oncology, Cantonal hospital of Lucerne, Lucerne, Switzerland.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Aspradakis
authors.affiliation: Institute of Radiation Oncology, Cantonal hospital of Lucerne, Lucerne, Switzerland.
authors.forename: Paolo
authors.initials: P
authors.lastname: Zucchetti
mesh_terms: D004867:Equipment Design; D006801:Humans; D011786:Quality Control; D011874:Radiometry; D011879:Radiotherapy Dosage; D012015:Reference Standards; D014964:X-Ray Therapy / Q000295:instrumentation* / Q000592:standards