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

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sarno@na.infn.it

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

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Layered breast phantoms

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

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DBT scanners and technique factors

*Both scanners are located at the Katholieke University of Leauven Siemens Mammomat Prime Anode/filter: W/Rh Scan angle: 50° Source-detector distance: 65 cm Hologic Selenia Dimensions Anode/filter: W/Al Scan angle: 15° Source-detector distance: 70 cm

Breast thickness (cm) kVp mAs 2 26 61.8 3 27 88.0 4 28 125.8 5 29 178.5 Breast thickness (cm) kVp mAs

2 26 39.0 3 28 41.0 4 29 53.0 5 31 59.0

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Dose measurements via radiochromic films XRQA2 type

Calibrated GafChromic films placed within the layered phantoms

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GafChromic film calibration

0.00 0.02 0.04 0.06 0.08 0.10 0.12 4 8 12 16 20

Y = a + b * X a= -0.37747 + 0.1742 b= 167.33741 + 3.00209 R

2= 0.99647

Hologic Selenia 29KVp; HVL=0.49mmAl XR-QA2 lot#:07051601

Air Kerma (mGy) netR 2 4 6 8 10 12 14 16 18 20 5 10 15

Hologic Selenia 29KVp; HVL=0.49mmAl XR-QA2 lot#:07051601

Relative uncertainty (%) Air Kerma (mGy)

33 cm2 GafChromic pieces irradiated at known exposure levels 24 cm

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Dose map

CIRS phantom – 5 cm thick

2 4 6 8 10 5 10 15 20 25 30

d: 0cm d: 1cm d: 2cm d: 4cm d: 3cm

x10

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#Dose level occurrence Aik kerma (mGy)

Distance from the compression paddle,

d: 5cm

Hologic Selenia Dimension

2 4 6 8 10 5 10 15 20 25 30

Siemens Mammomat Prime

#Dose level occurrence Aik kerma (mGy) x10

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Distance from the compression paddle,

d: 5cm d: 4cm d: 3cm d: 2cm d: 1cm d: 0cm

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In-plane Dose Profile

30 60 90 120 150 180 4 5 6 7 8

Hologic Selenia Dimension

Air Kerma (mGy) Position (mm)

Siemens Mammomat Prime

Dose profile at 10 mm from the compression paddle CIRS phantom - 50 mm thick

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Vertical Dose Profile

ROIs

1 2 3 4 5 2 4 6 8 10 12 Siemens Mammomat Prime Phantom thickness = 50 mm Air Kerma (mGy) Distance from the compression paddle, d (mm)

PMMA CIRS

1 2 3 4 2 4 6 8 10 12 Hologic Selenia Dimension Phantom thickness = 40 mm Air Kerma (mGy) Distance from the compression paddle, d (mm)

PMMA CIRS

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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.

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Thank you!!! Any questions?

sarno@na.infn.it