Open AccessEvaluation of MVCT imaging dose levels during helical IGRT: comparison between ion chamber, TLD, and EBT3 films
Author(s) -
Mege JeanPierre,
Wenzhao Sun,
Veres Attila,
Auzac Guillaume,
Diallo Ibrahima,
Lefkopoulos Dimitri
Publication year - 2016
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1120/jacmp.v17i1.5774
Subject(s) - tomotherapy , imaging phantom , thermoluminescent dosimeter , image guided radiation therapy , nuclear medicine , ionization chamber , dosimetry , dose profile , medicine , thermoluminescent dosimetry , medical imaging , medical physics , materials science , radiation therapy , radiology , dosimeter , physics , ion , quantum mechanics , ionization
The purpose of this investigation was to evaluate the dose on megavoltage CT (MVCT) images required for tomotherapy. As imaging possibilities are often used before each treatment and usually used several times before the session, we tried to evaluate the dose delivered during the procedure. For each scanning mode (fine, normal, and coarse), we first established the relative variation of these doses according to different technical parameters (explored length, patient setup). These dose variations measured with the TomoPhant, also known as Cheese phantom, showed the expected variations (due to the variation of scattered radiation) of 15% according to the explored length and ± 5 % according to the phantom setup (due to the variation of the point of measurement in the bore). In order to estimate patient doses, an anthropomorphic phantom was used for thermoluminescent and film dosimetry. The degree of agreement between the two methods was very satisfactory (the differences correspond to 5 mGy per imaging session) for the three sites studied (head & neck, thorax, and abdomen). These measurements allowed us to estimate the delivered dose of between 1 cGy and 4 cGy according to the site and imaging mode. Finally, we attempted to investigate a way to calculate this delivered dose in our patients from the study conducted on a cylindrical phantom and by taking into account data from the initial kV‐CT scan. The results we obtained were close to our measurements, with discrepancies below 5 mGy per MVCT. PACS numbers: 87.53.Bn, 87.55.km, 87.55.Qr