Detection of Early Markers in Mammography

Dear-Mama project, funded by FP5 program under contract QLRT-2001-01308, started in 2001 and it was concluded in 2006.
M. Chmeissani, as IFAE principle investigator, has lead and coordinated the project from incept to its realization. Dear-Mama aimed to construct two X-ray machines, one for mammography and one for general radiography. 

The Dear-Mama detector is based on the modular photon counting sensor using Medipix2 chip coupled, by bump-bonding, to two different types of room temperature solid state sensors, Si and CdTe.

The Dear-Mama consortium consisted of 6 partners as can be seen in the map below

The Dear-Mama modular sensor has 55µm pixel pitch which gives excellent Modular Transfer Function (MTF) when compared to existing technology in the market. It also uses room temperature solid state detectors such as Si and CdTe and this allows us to have a direct conversion from X-ray photons to electric signal. This feature allows a 20keV X-ray photon to generate around 5000 electrons while the same X-ray photon could generate around 10 electrons in indirect detector such as CsI deposited on amorphous Si. Having so many electrons from the X-ray photon, it is possible to operate the sensor in photon counting mode and this makes the sensor immune from the noise generated by the dark current of the detector. With photon counting detector one can detect a cosmic muon passing through as seen below, shomething that is not possible with other radiograpy detectors.

The below image shows the tracks of cosmic Muon particle detected by the Dear-Mama sensor. As the Muon particle passes through the sensor material, Si in this case, it deposits energy (around 0.4keV/µm or 8keV/20µm), enough to trigger the pixel and set its counter to 1. This image can only be acquired when the sensor is operated in photon counting mode, otherwise the front-end electronics gets saturated by the dark current of the sensor. 

On the left hand side one can side the radiography images of phantom type CIRS 084 taken by Hologic Selenium detector (above) and Dear-Mama (below) at the same kV and mAs settings. It is vivid to the naked eye that the Dear-Mama spatial resolution is qualitatively much better than that of Hologic detector. On the right hand side, the data of the same images are presented as Modular Transfer Function (MTF) plot, where one can see quantitatively Dear-Mama detectors are better than existing mammography detectors.

The left hand side image shows the radiography of a phantom with Dear-Mama-II machine (CdTe sensor) using 40kV and 2mAs dose which corresponds to 5.7µGy. One can see easily the separation of 8 lines per mm. The right hand side image shows the radiography of the same phantom with AGFA CR 75.0 system using 40kV and 5mAs dose which corresponds to 35.7µGy. One can hardly see any line at such dose. Dear-Mama-II machine is unique of its type in the world that has a CdTe sensor with 55um pixel pitch and operating in photon counting mode.

On the left hand side is the radiography image of human wrist taken by Dear-Mama-II machine with a dose of11µGy. On the right hand side is the image of the same wrist taken by DR-System with a dose of 12µGy. It is evident that the image provided by Dear-Mama-II is by far much sharper than the other one. This analysis was carried out by the Hospital of University of Vienna, partner of Dear-Mama Consortium  

Dear-Mama-II machine was also evaluated for the use of chest radiology by Prof. Jean-Philippe Montagne from Hôpital d’Enfants Armand-Trousseau, Partner of Dear-Mama Consortium

A quality control chest phantom for digital radiography (Nuclear associates, Carle place NY) was used for Dear-Mama-II evaluation. Due to detector field of view limitation (7cm x 11cm) only the right inferior third of the phantom was used. It simulates the lower part of the right lung. To simulate lesions of micronodules bird seeds were used of various diameters 1mm, 2mm, and 3mm. To simulate nodules we used bee-wax spheres of three different diameters = 5, 10 and 15 mm. Ground glass opacities were represented by cotton soacked with contrast medium (Hexabrix – Guerbet – France). Linear interstitial lesions were simulated by cotton thread soacked with contrast medium (Hexabrix – Guerbet – France). Two detectors systems were used: 1-Agfa – Storage phosphor plates; 2- Dear Mama II for general radiology. The detection parameters were as follows :

- Source to objet distance 1 m

- 110 kVp

- 4 mAs for Agfa and 1 mAs for Dear-Mama-II



All simulated lesions but bird seeds Ø 1 mm were accurately detected with both machines. The test was done with Dear-Mama-II machine using 110kV, 1mAs, and 300um Copper filter yielding a radiation dose of 36.64  µGy. For the AGFA-CR75.0 system we used the settings of 110kV, 4mAs, and its Al filter, yielding a radiation dose of 370.08 µGy

Thus one can conclude that one can achieve a good chest radiology image with 90% reduction in radiation dose when using Dear-Mama-II X-ray machine in comparison to AGFA-CR75.0 system.

The Dear-Mama method of capturing its digital image has been protect by the patent application: (WO/2003/019215) METHOD AND DEVICE FOR THE PRODUCTION OF DIGITAL IMAGES

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