Cone-beam breast computed tomography (CBBCT) of the pendant breast with dedicated scanners is an experimental X-ray 3-D imaging technique for breast cancer diagnosis under evaluation in comparison to conventional two-view 2-D mammography of the compressed breast. In CBBCT it is generally assumed that a more uniform distribution of the radiation dose to the breast volume can be obtained, with respect to mammography, at equal mean glandular dose (MGD) levels. In fact, in CBBCT the X-ray beam rotates for 360 deg around the breast, while in a mammography view the breast is irradiated from one side only. Using a CBBCT laboratory scanner developed by our group, we have measured the distribution of the radiation dose in a hemi-ellipsoidal PMMA breast phantom of 14 cm diameter simulating the average uncompressed breast, using radiochromic films type XR-SP inserted at mid-plane in the phantom. The technique factors were 80 kVp (5.6 mm Al half value layer), tube load 23-100 mAs, for an air kerma at isocenter in the range 4.7-20 mGy, corresponding to a MGD of 3.3-15.8 mGy for a 14 cm diameter breast of 50% glandularity. Results indicate a relative dose variation ¿ = ((edge-center)/center) up to 25% at a distance of 50 mm from the nipple. As for the relative dose variation along the phantom longitudinal axis, the maximum value measured is ¿ = ((nipple-chest wall)/chest wall) = -15%, indicating that the dose decreases from the chest wall toward the nipple. The values of the parameters ¿ and ¿ depend also on the height of the X-ray tube focal spot with respect to the phantom vertex (nipple).
Distribution of Absorbed Dose in Cone-Beam Breast Computed Tomography: a Phantom study with Radiochromic Films / Russo, Paolo; T., Coppola; Mettivier, Giovanni; Montesi, MARIA CRISTINA; Lauria, Adele. - (2009), pp. 3463-3470. (Intervento presentato al convegno Nuclear Science Symposium and Medical Imaging Conference tenutosi a Orlando, Florida, USA nel 24 Oct- 1 Nov, 2009) [10.1109/NSSMIC.2009.5401788].
Distribution of Absorbed Dose in Cone-Beam Breast Computed Tomography: a Phantom study with Radiochromic Films
RUSSO, PAOLO;METTIVIER, GIOVANNI;MONTESI, MARIA CRISTINA;LAURIA, ADELE
2009
Abstract
Cone-beam breast computed tomography (CBBCT) of the pendant breast with dedicated scanners is an experimental X-ray 3-D imaging technique for breast cancer diagnosis under evaluation in comparison to conventional two-view 2-D mammography of the compressed breast. In CBBCT it is generally assumed that a more uniform distribution of the radiation dose to the breast volume can be obtained, with respect to mammography, at equal mean glandular dose (MGD) levels. In fact, in CBBCT the X-ray beam rotates for 360 deg around the breast, while in a mammography view the breast is irradiated from one side only. Using a CBBCT laboratory scanner developed by our group, we have measured the distribution of the radiation dose in a hemi-ellipsoidal PMMA breast phantom of 14 cm diameter simulating the average uncompressed breast, using radiochromic films type XR-SP inserted at mid-plane in the phantom. The technique factors were 80 kVp (5.6 mm Al half value layer), tube load 23-100 mAs, for an air kerma at isocenter in the range 4.7-20 mGy, corresponding to a MGD of 3.3-15.8 mGy for a 14 cm diameter breast of 50% glandularity. Results indicate a relative dose variation ¿ = ((edge-center)/center) up to 25% at a distance of 50 mm from the nipple. As for the relative dose variation along the phantom longitudinal axis, the maximum value measured is ¿ = ((nipple-chest wall)/chest wall) = -15%, indicating that the dose decreases from the chest wall toward the nipple. The values of the parameters ¿ and ¿ depend also on the height of the X-ray tube focal spot with respect to the phantom vertex (nipple).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.