3D dose distribution in two clinical digital breast tomosynthesis - PowerPoint PPT Presentation

3D dose distribution in two clinical digital breast tomosynthesis units: a phantom study G. Mettivier, A. Sarno , F. Di Lillo, H. Bosmans, L. Cockmartin, K. Bliznakova, P. Russo sarno@na.infn.it 1

“ Mean ” glandular dose as reference in X-ray breast imaging 2

Layered breast phantoms PMMA homogeneous phantom BR 50/50 heterogeneous phantom 5 circular slabs CIRS Phantom, BR3D mod. 020 Single slab thickness = 10 mm Single slab thickness = 10 mm 3

DBT scanners and technique factors Breast Breast kVp mAs kVp mAs thickness (cm) thickness (cm) 2 26 39.0 2 26 61.8 3 28 41.0 3 27 88.0 4 29 53.0 4 28 125.8 5 31 59.0 5 29 178.5 Siemens Mammomat Prime Hologic Selenia Dimensions Anode/filter: W/Rh Anode/filter: W/Al Scan angle: 50° Scan angle: 15° Source-detector distance: 65 cm Source-detector distance: 70 cm 4 *Both scanners are located at the Katholieke University of Leauven

Dose measurements via radiochromic films XRQA2 type Calibrated GafChromic films placed within the layered phantoms 5

GafChromic film calibration 20 Y = a + b * X a= -0.37747 + 0.1742 16 b= 167.33741 + 3.00209 Air Kerma (mGy) 2 = 0.99647 R 12 8 3  3 cm 2 GafChromic pieces Hologic Selenia 4 29KVp; HVL=0.49mmAl irradiated at known exposure XR-QA2 lot#:07051601 0 levels 0.00 0.02 0.04 0.06 0.08 0.10 0.12 net  R 15 Relative uncertainty (%) Hologic Selenia 24 cm 29KVp; HVL=0.49mmAl 10 XR-QA2 lot#:07051601 5 0 0 2 4 6 8 10 12 14 16 18 20 Air Kerma (mGy) 6

Dose map CIRS phantom – 5 cm thick -3 x10 30 d: 0cm Siemens Mammomat Prime #Dose level occurrence 25 d: 1cm d: 2cm Distance from the 20 compression paddle, d: 5cm d: 3cm d: 4cm 15 10 5 0 0 2 4 6 8 10 Aik kerma (mGy) -3 x10 30 Hologic Selenia Dimension #Dose level occurrence d: 3cm 25 d: 2cm 20 d: 1cm Distance from the d: 4cm d: 0cm compression paddle, 15 d: 5cm 10 5 0 0 2 4 6 8 10 7 Aik kerma (mGy)

In-plane Dose Profile 8 Dose profile at 10 mm from the compression paddle CIRS phantom - 50 mm thick 7 Air Kerma (mGy) Siemens Mammomat Prime 6 5 Hologic Selenia Dimension 4 0 30 60 90 120 150 180 Position (mm) 8

Vertical Dose Profile 12 Siemens Mammomat Prime 10 Phantom thickness = 50 mm Air Kerma (mGy) 8 ROIs 6 4 2 PMMA CIRS 0 0 1 2 3 4 5 12 Distance from the compression paddle, d (mm) Hologic Selenia Dimension 10 Phantom thickness = 40 mm Air Kerma (mGy) 8 6 4 2 PMMA CIRS 0 0 1 2 3 4 9 Distance from the compression paddle, d (mm)

Conclusion 1)We measured, via GafChromic films XR-QA2 type, dose distributions (dose map) within two breast phantoms for two clinical DBT scanners; 2)We showd the differences between the measured dose and dose distributions which depend on the scanner protocol and spectrum; 3)We have been developing a Monte Carlo code for dose estimated in DBT and it will be validated vs measurement data presented in this work. 10

Thank you!!! Any questions? sarno@na.infn.it 11