TY - JOUR
T1 - Effect of jaw size in megavoltage CT on image quality and dose
AU - Jung, Jae Hong
AU - Cho, Kwang Hwan
AU - Kim, Yong Ho
AU - Moon, Seong Kwon
AU - Min, Chul Kee
AU - Kim, Woo Chul
AU - Kim, Eun Seog
AU - Chang, Ah Ram
AU - Kim, Tae Ho
AU - Yoon, Jai Woong
AU - Suh, Tae Suk
AU - Huh, Hyun Do
N1 - Funding Information:
This research was supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology(MEST)(K20901000001-09E0100-00110) and the program of Basic Atomic Energy Research Institute (BAERI) which is a part of the Nuclear R and D programs (No.20120004886) funded by the Ministry of Education, Science and Technology (MEST).
PY - 2012/8
Y1 - 2012/8
N2 - Purpose: Recently, the jaw size for the TomoTherapy Hi-Art II ® (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal (IEC-Y) resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye, which is a highly radiosensitive tissue. Methods: MVCT image quality (image noise, uniformity, contrast linearity, high-contrast resolution, and full width at half-maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. Results: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high-contrast resolution. However, the full-width at half-maximum reduced from approximately 7.2 at J4 to 4.5 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69-2.32 cGy (peripheral: 0.83-2.49 cGy) at J4 to 0.85-2.81 cGy (peripheral: 1.05-2.86 cGy) at J1. The measured lens dose increased from 0.92-3.36 cGy at J4 to 1.06-3.91 cGy at J1. Conclusions: The change in jaw size improved longitudinal resolution. The MVCT imaging dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15 increase in lens dose over that with J4 should be provided with J1.
AB - Purpose: Recently, the jaw size for the TomoTherapy Hi-Art II ® (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal (IEC-Y) resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye, which is a highly radiosensitive tissue. Methods: MVCT image quality (image noise, uniformity, contrast linearity, high-contrast resolution, and full width at half-maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. Results: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high-contrast resolution. However, the full-width at half-maximum reduced from approximately 7.2 at J4 to 4.5 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69-2.32 cGy (peripheral: 0.83-2.49 cGy) at J4 to 0.85-2.81 cGy (peripheral: 1.05-2.86 cGy) at J1. The measured lens dose increased from 0.92-3.36 cGy at J4 to 1.06-3.91 cGy at J1. Conclusions: The change in jaw size improved longitudinal resolution. The MVCT imaging dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15 increase in lens dose over that with J4 should be provided with J1.
KW - image quality
KW - lens
KW - megavoltage computed tomography (MVCT)
KW - multiple scan average dose (MSAD)
KW - photoluminescence glass dosimeters (PLDs)
UR - http://www.scopus.com/inward/record.url?scp=84864682109&partnerID=8YFLogxK
U2 - 10.1118/1.4736951
DO - 10.1118/1.4736951
M3 - Article
C2 - 22894422
AN - SCOPUS:84864682109
SN - 0094-2405
VL - 39
SP - 4976
EP - 4983
JO - Medical physics
JF - Medical physics
IS - 8
ER -