Evaluation of effective energy for QA and QC: measurement of half-value layer using radiochromic film density.
The effective energy of diagnostic X-rays is important for quality assurance (QA) and quality control (QC). However, the half-value layer (HVL), which is necessary to evaluate the effective energy, is not ubiquitously monitored because ionization-chamber dosimetry is time-consuming and complicated. To verify the applicability of GAFCHROMIC XR type R (GAF-R) film for HVL measurement as an alternative to monitoring with an ionization chamber, a single-strip method for measuring the HVL has been evaluated. Calibration curves of absorbed dose versus film density were generated using this single-strip method with GAF-R film, and the coefficient of determination (r2) of the straight-line approximation was evaluated. The HVLs (effective energies) estimated using the GAF-R film and an ionization chamber were compared. The coefficient of determination (r2) of the straight-line approximation obtained with the GAF-R film was more than 0.99. The effective energies (HVLs) evaluated using the GAF-R film and the ionization chamber were 43.25 keV (5.10 mm) and 39.86 keV (4.45 mm), respectively. The difference in the effective energies determined by the two methods was thus 8.5%. These results suggest that GAF-R might be used to evaluate the effective energy from the film-density growth without the need for ionization-chamber measurements.
Gotanda
T
T
Okayama University, Graduate School of Health Sciences, Okayama, Japan. tat51826@yahoo.co.jp
Katsuda
T
T
Gotanda
R
R
Tabuchi
A
A
Yamamoto
K
K
Kuwano
T
T
Yatake
H
H
Takeda
Y
Y
D000042:Absorption; D002138:Calibration; D004307:Dose-Response Relationship, Radiation; D011786:Quality Control; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D013816:Thermodynamics; D013997:Time Factors