Table 1 Some variables that may affect measurement reproducibility
From: Dosimetry in brain tumor phantom at 15 MV 3D conformal radiation therapy
Categories | Variables |
|---|---|
Dose calibration in solid water phantom | PDD calibration (0.8% uncertainty [30]) |
and beam calibration | Ionizing chamber dosimeter calibration (0.6% uncertainty [30]) |
Beam radiation calibration (1.4% uncertainty [30]) | |
Radiochromic film conditions | Differences in lots or sheets of film |
Film manipulation | |
Environmental conditions (manipulation and storage) | |
Calibration film irradiation | Size and number of samples |
Film placement in the water phantom | |
Beam orientation and isocenter positioning | |
Scanning procedure | Post-irradiation waiting period |
Film batch | |
Environmental conditions during scan | |
Multiple scan passes count | |
Scanner type and equipment conditions | |
Resolution of the scanned image | |
Physical phantom | Homogeneity and heterogeneity of the equivalent tissues and tumor |
Positioning and repositioning of the phantom on the irradiation table | |
and support | |
Positioning of the affixed external reference points | |
Film affixing inside the synthetic brain and tumor | |
Phantom Tomography | Phantom positioning and repositioning |
Reference points | |
Image capture and resolution | |
Calibration and curve fitting | Film set count / dataset size |
Choice of calibration method / equation | |
Adjustment method | |
Experimental irradiation measurements | Irradiation procedure |
Reproducibility of LINAC conditions | |
TPS planning | Mathematical method |
Dose image representation | |
Inhomogeneity in CT application | |
Image processing | Discrepancies in image scaling |
Resolution, contrast, uniformity of a region of interest (ROI) | |
Noise | |
Imaging and treatment of coordinate coincidences |