Multi‐institutional dosimetric and geometric commissioning of image‐guided small animal irradiators. Issue 3 (3rd March 2014)

• Record Type: Journal Article
• Authors: Lindsay, P. E.; Granton, P. V.; Gasparini, A.; Jelveh, S.; Clarkson, R.; van Hoof, S.; Hermans, J.; Kaas, J.; Wittkamper, F.; Sonke, J.‐J.; Verhaegen, F.; Jaffray, D. A.
• Is Part Of: Medical physics. Volume 41:Issue 3(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-03-03
• Subjects: Collimators -- Field size -- Therapeutic applications, including brachytherapy -- Conformal radiation treatment -- Dose‐volume analysis -- Dosimetry/exposure assessment; collimators -- copper -- dosimetry -- liquid ionisation chambers -- radiation therapy -- X‐ray tubes; small animal irradiation -- pre‐clinical -- kV dosimetry -- image‐guidance; Radiation therapy -- Measurement of nuclear or x‐radiation -- Using diaphragms, collimators -- X‐ray tubes -- Tubes for determining the presence, intensity, density or energy of radiation or particles -- Devices sensitive to very short wavelength, e.g. x‐rays, gamma‐rays or corpuscular radiation -- Transforming x‐rays -- X‐ray technique -- Scintigraphy -- with scintillation detectors -- Ionisation chambers; Dosimetry -- Collimators -- Field size -- Vacuum tubes -- Medical imaging -- Image detection systems -- Ionization chambers -- Image sensors -- Medical X‐ray imaging -- Calibration; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4866215
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : To compare the dosimetric and geometric properties of a commercial x‐ray based image‐guided small animal irradiation system, installed at three institutions and to establish a complete and broadly accessible commissioning procedure. Methods: : The system consists of a 225 kVp x‐ray tube with fixed field size collimators ranging from 1 to 44 mm equivalent diameter. The x‐ray tube is mounted opposite a flat‐panel imaging detector, on a C‐arm gantry with 360° coplanar rotation. Each institution performed a full commissioning of their system, including half‐value layer, absolute dosimetry, relative dosimetry (profiles, percent depth dose, and relative output factors), and characterization of the system geometry and mechanical flex of the x‐ray tube and detector. Dosimetric measurements were made using Farmer‐type ionization chambers, small volume air and liquid ionization chambers, and radiochromic film. The results between the three institutions were compared. Results: : At 225 kVp, with 0.3 mm Cu added filtration, the first half value layer ranged from 0.9 to 1.0 mm Cu. The dose‐rate in‐air for a 40 × 40 mm 2 field size, at a source‐to‐axis distance of 30 cm, ranged from 3.5 to 3.9 Gy/min between the three institutions. For field sizes between 2.5 mm diameter and 40 × 40 mm 2, the differences between percent depth dose curves up to depths of 3.5 cm were between 1% and 4% on average, with the maximum difference being 7%. The profiles agreed very well for fields >5 mm diameter. The relative output factors differed by up to 6% for fields larger than 10 mm diameter, but differed by up to 49% for fields ≤5 mm diameter. The mechanical characteristics of the system (source‐to‐axis and source‐to‐detector distances) were consistent between all three institutions. There were substantial differences in the flex of each system. Conclusions: : With the exception of the half‐value layer, and mechanical properties, there were significant differences between the dosimetric and geometric properties of the three systems. This underscores the need for careful commissioning of each individual system for use in radiobiological experiments.