EVALUATION OF THE HOLOGIC SELENIA FFDM SYSTEM
WITH TUNGSTEN TUBE
Vesna GERSHAN(1), Mimoza RISTOVA(1) and Zoran IVANOVSKI(2)
(1)Institute of Physics, Faculty of Natural Sciences and Mathematics, Skopje, MACEDONIA
(2)Faculty of Electrical Engineering and Information Technologies, Skopje, MACEDONIA
Improvements in FFDM for better image quality - short
CsI detector (indirect signal conversion)
a-Se detector (direct signal conversion)
 Improvements in image processing, display performances, etc.
Anode targets – Mo, Rh
Filters – Mo, Rh
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
1. Introduction
 Several major manufactures of full field digital mammography systems (FFDM) have
introduced new models which incorporate X-Ray tubes with tungsten rather than
molybdenum anodes;
The main motive for using tungsten to reduce the dose to the breast while maintaining
the same image quality [1]
 It was found that for an a-Se detector, the W/Rh target/filter combination is the best
choice for all the breast thicknesses and composition and for the detection of both micro
calcifications and tumors [2]
The first FFDM system with W/Rh and W/Ag combination installed in the Republic of
of Macedonia was the HOLOGIC Selenia.
This paper presents part of results of evaluation of that system.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
2. Materials and methods (1)
 Dosimetry parameters measurements were done by
Barracauda cabinet (with W/Rh and W/Ag spectra calibration) and Ocean
Professional Software;
 Image quality assessment was done using TOR MAX and CDMAM
phantoms; CDMAM was evaluated by CDMAM 3,4 software (ARTINIS)
 ImageJ software for Pixel Value (PV) determination;
MATLAB software for evaluation of Modulation Transfer Function (MTF)
CDMAM 3.4
software
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
2. Materials and methods
(2)
1. Radiation output and beam quality – relationship between delivered tube dose vs mAs
and penetrating beam property
2. Detector response function - relationship between detector output variable displayed on
the monitor (Pixel Value) and Air Kerma at the image receptor (a-Se detector)
(Flat Field Image mode – unprocessed image)
3. Detector uniformity and ghosting – Assessment whether detector flat fielding correction
has been correctly applied by the manufacture or the local service;
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
2. Materials and methods
(3)
4. Automatic Exposure Control (AEC) - adjustment of mAs value according to lowest PV
Consistency, Signal to Noise Ratio variation (SNR) and Relative Contrast Noise Ratio (CNR) to 5.0 cm
PMMA
SNR i 
PV Al ,i  PV backgroud
PV i
CNR
St .dev i
i , 5 .0

,i
St .dev i
PV Al ( 5 .0 )  PV backgroud
St .dev backgroud
, 5 .0
, 5 .0
5. Mean Glandular Dose – dose to the glandular tissue in breast
MGD  K  g  c  s
-K is the entrance surface air Kerma (ESAK),
-g, c and s are conversion factors for x-ray beam and breast characteristics,
- For the W/Rh and W/Ag spectra, a value of 1,042 and 1,063 for the s-factor were used from the
recent publication by Dance and Young [4].
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
2. Materials and methods
(3)
6. Image quality - contrast detectability
Ability to detect objects with different contrast and sizes;
Contrast-detail performance of the a-Se detector depends on the detective quantum
efficiency (DQE) of the detector
7. Image quality - resolution
In DM the major physical factor which affect spatial resolution is the signal blurring in
the detector and the integration of the signal over the area of the del;
This can be assessed by calculating the MTF from the spread of the signal in the image of
a test resolution objects in TOR MAX phantom.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
1. Radiation output and beam quality
•For W/Rh combination and 28 kV, a radiation output was calculated to be
100.9 Gy/mAs at 50 cm focus –measuring detector distance.
•The Half Value Layer (HVL) at 28 kV was determined to be 0.547 mm for W/Rh and
0.600 mm for W/Ag spectra.
(higher HVL values than typical Mo/Mo or Mo/Rh mammography spectra)
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
2. Detector response function
It was established that there is a linear dependence of the a-Se detector output
variable – PV and the Air Kerma
 The detector response gradient value, offset and SNR2
linearity (R2) are calculated to be 4.88, 60.99 and 1.0
respectively.
 For these values, a reference air Kerma of 98.9 Gy was
calculated as an average of 548.3 Pixel Values
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
3. Detector uniformity and ghosting
 For W/Rh the maximum PV deviation is 1.2% and maximum SNR deviation is 9.3%;
 While as for W/Ag, the maximum PV deviation is 2.7% and maximum SNR
deviation is 7.9%.
These findings suggest that the detector flat fielding correction has been correctly
applied.
 The calculated value of the ghost factor was 0.01 (EUREF limit <0.3), which means
that there are no residual artifacts at the image from the previous exposure.
*According to EUREF protocol, the limitation values are 15% for PV and 10% for SNR deviation.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
4. Automatic Exposure Control (AEC)
Signal to Noise Ratio variation
AEC consistency
Set 28 kV,
4 cm PMMA,
Dose settings=0,
AEC region 2
mAs
Avg PV
SNR
62.7
512.6
64.5
kV
ind.
Target
/Filter
mAs
Avg
PV
SNR
57.0
PMMA
(cm)
547.5
59.8
2
25
W/Rh
32.2
514
58.0
65.5
554.1
60.3
3
26
W/Rh
48.7
520
58.3
66.7
561.2
61.1
4
28
W/Rh
64.5
530
58.5
average
64.9
543.8
59.6
5
28
W/Rh
110.9
507
56.9
max deviation
3.3%
5.8%
4.3%
6
30
W/Rh
134.6
503
55.3
< 5.0%
7
28
W/Ag
177.1
547
55.7
average
520.0
57.1
5%
3%
EUREF limits
max deviation
AEC device responds properly
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
4. Automatic Exposure Control (AEC)
Relative CNR to 5.0 cm PMMA
PMMA
(cm)
kV
ind.
Target
/Filter
mAs
RelativeCNR5.0
EU limits
2
25
W/Rh
32.2
122
>115
3
26
W/Rh
48.7
113
>110
4
28
W/Rh
64.5
105
>105
4.5
28
W/Rh
84.3
104
>103
5
28
W/Rh
110.9
100
>100
6
30
W/Rh
134.6
89
>95*
7
28
W/Ag
177.1
79
>90*
*there are doubts about these limits (should be lower)
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
5. Mean Glandular Dose
HOLOGIC Selenia
with W tube
Due to the higher penetration of the W/Rh and W/Ag spectra, compared to the more
common Mo/Mo or Mo/Rh spectra, the calculated MGD was found to be considerably
below the European limits.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
6. Image quality - Contrast detectability
A CDMAM phantom was exposed, using the
AUTOFILTER mode and the AEC at a standard dose.
(at 30 kV and an average of 84.7 mAs)
From the Contrast-detail curve, it was found that the detection rate was 72.8%.
(threshold value 62,5%)
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
3. Results
7. Image quality - resolution (evaluations of the MTF)
The fall of the MTF to 0.5 (50 %) was found to occur at the spatial frequency of 8 lines per mm
The highest transmitted spatial frequency is approximately 14 lp/mm
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
4. Conclusion
By comparing the obtained results with the results from the literature,
it can be concluded that the HOLOGIC Selenia system with W/Rh target/filter
combination is superior to the systems with Mo/Mo or Mo/Rh combination in
terms of ratio image quality/patient dose.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
References
1.
J. M. Oduko et al., Effect of using tungsten anode X-Ray tube on dose and image quality in full field
digital mammography, 9th International Workshop IWDM 2008, Tucson, USA, Proceedings
2. Bernhardt P, Mertelmeier T, Hoheisel M., X-Ray spectrum optimization of full-digital
mammography: simulation and phantom study. Med Phys 2006; 33:4337-49
3. Williams MB, Raghunathan P, More MJ, Seibert JA, Kwan A, Lo JY, et al., Optimization of exposure
papameters in full digital mammography, Med Phys 2008; 36:2414-23
4. Dance DR, Thilander Klang A, Sandborg M, Skinner Cl, Castellano Smith IA, Carlsson GA., Influence
of anode/filter material and tube potential on contrast, signal-to-noise ratio and average absorbe
dose in mammography: a Monte Carlo study, Br j Radiol 2000; 73:1056-67.
5. N W Marshall, Detective quantum efficiency measured as a function of energy for two full-field
digital mammography systems, Phys.Med.Biol. 2009, 54, issue 9, 2845-61.
6.
H. Fujita, D-Y. Tsai, T. Itoh, K. Doi, IEEE Trans. Med. Imag. 11/1(1992) 34-39.
7.
M. Hoheisel, L. Batz, T. Mertelmeier, J. Giersh, A. Korn, Modulation transfer function of a
selenium-based digital mammography system, IEEE Nuclear Science Symposium Conference
Record 2004, Vol.6, 3589–93.
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012
Acknowledgment
The authors would like to kindly acknowledge to Mile Dukovski from
General Private Hospital Remedika, Skopje, R. Macedonia, for the access
and the possibility to perform testing of their HOLOGIC Selenia system.
Thank you for your attention!
The First International Conference on Radiation and Dosimetry in Various Fields of Research (RAD 2012)
APRIL 25 – 27, 2012