Approaches to Dose Reduction in Women's Health

Dose Reduction Advances in Women's Health

 

Breast cancer is the most common cancer in women worldwide. More than 10% can expect some manifestation of the disease during their lifetime. Although earlier detection and better treatment may have reduced mortality in recent years, 30% of women with breast cancer will still die from the disease. But several randomized controlled clinical trials have proven that mammography screening can reduce breast cancer mortality.

X-ray mammography is the gold standard of investigational procedures. Digital mammography has improved diagnostics, especially in younger women and in women with dense breasts. In most countries, screening programs have been established in order to support early breast cancer detection. The right balance between low dose and high image quality for diagnostic confidence is of the utmost importance. 


Full-Field Digital Mammography

Numerous clinical studies1 have shown that full-field digital mammography (FFDM) may provide some diagnostic advantages over screen/film mammography for certain population subgroups, such as young women with dense breasts and pre- and perimenopausal women. During a screening, presumed healthy women are examined for breast cancer. In these cases, low dose becomes particularly significant, as mentioned before.

Up until now, lower dose meant lower image quality. The continuous low dose discussion challenged ourselves to rethink technology and do what seemed impossible: develop a mammography machine with considerable dose reduction without compromising on image quality. This is possible with the MAMMOMAT Inspiration PRIME-Technology.

 

1 Pisano E. et al. Diagnostic Performance of Digital versus Film Mammography for Breast-Cancer Screening. N Engl J Med 2005;353.



Dose Reduction Advances with MAMMOMAT Inspiration in Full Field Digital Mammography

1. PRIME-Technology
Progressive Reconstruction, Intelligently Minimizing Exposure The world’s first software based anti-scatter solution for mammography. It saves a considerable amount of dose with uncompromised image quality.


2. Tungsten/Rhodium anode/filter combination
Siemens is a pioneer in offering digital mammography with a bimetal X-ray tube with tungsten (W) in addition to the conventional molybdenum (Mo) target. To match the individual breast density and thickness, three anode/filter combinations (Mo/Mo, Mo/Rh, and W/Rh) are offered. Compared to film based systems, it can save up to 50% dose by using Tungsten/Rhodium combination. And, it is especially good at capturing dense breast tissue.


3. Direct-to-digital amorphous Selenium detector:
MAMMOMAT Inspiration provides an amorphous Selenium (aSe) detector – directly converting X-ray energy into an electric charge. Compared to indirect technologies, the absorption rate of aSe is higher in the lowenergy range of mammography. And at the same time the Detective Quantum Efficiency (DQE) is higher, which results in high image quality at a low dose.

 

4. OpComp
Siemens’ intelligent OpComp® function applies compression only as long as the patient’s breast is soft and pliable. For best image quality, it stops at the point of optimal compression. It works in combination with OpDose.
 

5. OpDose
OpDose automatically selects the best anode/filter combination and selects in connection to the automatic exposure control the optimal imaging parameters. Settings can be made for every 10 mm different thickness interval which gives a “personalized” optimal dose for each individual breast characteristics.

 

6. Automatic Exposure Control (AEC)
The adaptive AEC modus reads out the complete area of the detector that is covered by the breast. The system searches the densest part of the breast tissue and selects the lowest possible exposure parameters based on the individual breast size and composition.


7. OpView1
This image processing software is especially designed for digital mammography to produce superior image quality. The algorithms provide significantly more details with higher image contrast, particularly of dense breasts. The settings can be customized for viewing preferences, providing versatility. In sum, better image quality and easier image reading can help avoiding the need for repeated images.


8. Automated Quality Control1 (AQC) and Siemens Remote Service1 (SRS)

It helps to ensure the quality and security of MAMMOMAT Inspiration, since quality assurance tests including dose settings need to be performed regularly. AQC can perform these tests easily and intuitively. Thanks to Siemens Remote Service’s constant monitoring, deviating parameters are detected before problems occur. 

 

It is well known that digital radiation detectors that are part of an FFDM system may have different absorption characteristics than a screen-film receptor in an analog mammography system. Therefore, the question arises whether the X-ray spectrum and the beam quality applied in screen-film mammography are also suitable for FFDM systems. In digital mammography, the radiographic technique can be optimized independently of the exposure to the image receptor, thus exploiting the wide dynamic range and the linear characteristic curve of digital detectors. Image quality and patient dose can be optimized at the same time.

 
PRIME is an Option and is for a maximum breast thickness of 7 cm under compression.

1 Option.



Anode/Filter Combinations in Digital Mammography

Sometimes molybdenum/molybdenum (Mo/Mo) for the examination of smaller breasts and rhodium (Rh) as the filter material for thicker breasts is recommended. Other users switch from molybdenum to rhodium or tungsten (W) as the anode material for thicker breasts, or recommend the general use of rhodium or tungsten as the anode material, in combination with rhodium as the filter material for all breast thicknesses and tissue composition.

 

A specific dose-related study was conducted to compare the average glandular dose (AGD) of Mo/Mo, Mo/Rh and W/Rh in full-field digital mammography based on an amorphous selenium detector with clinical data.1 The main purpose of the study was to determine whether W/Rh can be used to reduce the glandular dose without loss of image quality in all breast thicknesses of the examined population.

 

The average glandular dose corresponding to the images acquired with Mo/Mo was 2.29 ± 1.15 mGy with a mean compressed breast thickness of 46 ± 10 mm. For the Mo/Rh cases with a mean compressed thickness of 64 ± 9 mm, an AGD of 2.76 ± 1.31 mGy was obtained. The W/Rh cases with a mean compressed thickness of 52 ± 13 mm resulted in an AGD of 1.26 ± 0.44 mGy (Figure 1).

 

The image quality of all mammograms in the study was evaluated visually on order to be adequate for the diagnostic task. In a few example cases that were imaged with both X-ray spectra no degradation of the evaluated lesion’s signal-to-noise ratio was found. This MLO image of a 67-year-old patient with a compressed breast thickness of 72 mm had been acquired with an average glandular dose of 3.8 mGy for Mo/Mo and 2.4 mGy for W/Rh (Figure 2).

 

Analysis of 4867 images revealed that the anode/filter combination W/Rh has advantages over Mo/Mo or Mo/Rh in terms of glandular dose, especially in patients with large breasts. Whereas the dose reduction with W/Rh is relatively low for small breasts, the effect increases with breast thickness, particularly above a compression thickness of 50 mm. For the largest compression thickness, W/Rh reduces the patient dose by more than a factor of 2 compared to Mo/Rh.1

 

1 Uhlenbrock DF et al. Comparison of anode/filter combinations in digital mammography with respect to the average glandular dose. Rofo. 2009 Mar;181(3):249-54.

 



A White Paper Gives the Proof

The composition of low-dose efforts make MAMMOMAT Inspiration a low-dose system, and it is even the lowest of comparable systems with advanced FFDM detector technology in its class1.

 

White Paper: Hilde Bosmans, Koen Michielsen, Kim Lemmens, Jurgen Jacobs, 2011.

 

“Mean glandular dose survey of 2D mammograms acquired with the Siemens MAMMOMAT Inspiration system.”

 

In a very comprehensive study (January 2009–August 2010) on 10,502 mammograms, Hilde Bosman et al. (Leuven, Belgium) evaluated the mean glandular doses from mammographic examinations performed with ten MAMMOMAT Inspiration digital mammography systems. Dose data from the Siemens systems were compared to data from nine other DR systems of other vendors and to the Diagnostic Reference Level (DRL) derived from Leuven’s regional survey results. The Siemens systems are adjusted to operate at patient dose levels significantly below the achievable levels of the European Guidelines. For breasts 5 cm thick, the doses range between 35–50% of the desirable level. Its mean glandular dose is significantly lower
than film-screen data. MAMMOMAT Inspiration operates with the second-lowest dose data curve of all DR systems, but the lowest in its class of FFDM detector technology. 

1 White Paper: Hilde Bosmans, Koen Michielsen, Kim Lemmens, Jurgen Jacobs, 2011. “Mean glandular dose survey of 2D mammograms acquired with the Siemens MAMMOMAT Inspiration system.”



MAMMOMAT Inspiration now with PRIME-Technology1

What is behind this Progressive Reconstruction, Intelligently Minimizing Exposure? 

The world’s first software based anti-scatter solution for mammography saves a considerable amount of dose with uncompromised image quality. 

Scattered radiation decreases image contrast in mammography, so anti-scatter grids are used in analog film/screen as well as full-field digital mammography (FFDM) to attenuate the scattered radiation and improve image contrast. However, anti-scatter grids also attenuate valuable primary radiation. By removing the mechanical grid, there is no longer a fixed object between the patient and the detector that absorbs radiation. Thereby more primary radiation can be used and dose can be saved.
In order to ensure the same image quality the anti-scatter correction can be performed software-based. 

FFDM with PRIME-Technology, a specially developed software algorithm, the Progressive Reconstruction, replicates the effects of the missing grid. This has the effect that image quality is not compromised while necessary patient dose is clearly reduced.

 

MAMMOMAT Inspiration PRIME Edition