The invention relates to a mammography apparatus com- prising a mainframe and a subframe mounted in the mainframe, which subframe supports an x-ray source, a paddle and a detector with a detector cover, and which paddle is connected with the subframe through a suspension.

The invention further relates to a method to monitor and/or adjust the settings of such a mammography apparatus.

A mammography apparatus according to the preamble is known from WO2011/102713 in the name of the applicant.

In such a known mammography apparatus it is day to day practice to place and compress a patient's breast between the detector and the paddle before executing an x-ray measurement in order to optimize the image quality and minimize the required x-ray doses. During the procedure the patient is standing next to the mammograph. The compression is applied by bringing the patient's breast in between the x-ray detector and the paddle, which paddle can thereafter be lowered in the direction and relative to the detector by hand or by activating a motor built in the mammography apparatus. Generally speaking there is a minimum pressure required to provide sufficient flattening to the breast to suit the requirements of the x-ray imaging. For safety reasons there is a maximum amount of force that can be applied which is set at a value of 20 daN. Consequently a wide variety of pressures can be applied depending on the contact area of the compressed breast on which the force is exercised. For that reason the upper limit of compression that can be applied depends on the size of the women's breasts. It is commonly known that this procedure may inflict serious pain on the patient. Also bruises and hematomas are reported on a regular base. To alleviate these problems it is important that the amount of pressure applied to the breast remains restricted. There are, however, situations during examination that may require that the pressure applied to the breast is increased in order to meet the required x-ray imaging conditions. This may for instance occur during a cranio caudal examination of the breast when a skin crease or stretch of the skin reduces the effectivity of the applied pressure. It may also occur during a medial lateral oblique examination of the breast when the paddle pressure is applied in part to the shoulder area and/or the breast muscle. Also this adversely affects the effective pressure applied to the breast. In the prior art these problems are addressed by increasing the pressure applied to the breast, therewith worsening the pain sensations and inflicting other adverse effects for the patient.

It is one of the objectives of the invention to improve the effectivity of the pressure applied to the breast.

It is a further objective of the invention to reduce the patient's experience of pain.

It is another objective of the invention to improve the reliability and repeatability of the x-ray measurement by providing a more reliable and reproducible compression of the breast .

It is still another objective of the invention to provide an improved mammography apparatus which ensures that the objectives of an optimal trade-off between reduced pain and more reliable and repeatable x-ray measurements can be achieved .

These and other objectives of the invention which will become apparent from the following disclosure, are at- tained with the method and mammography apparatus according to one or more of the appended claims.

According to a first aspect of the invention, the suspension of the paddle comprises force sensors for providing a measurement signal that is indicative of an amount of com- pression applied with the paddle to a breast. Providing the force sensors in the suspension of the paddle ensures that a very accurate and reliable measurement of the compression applied to the breast can be obtained.

Preferably there is at least a first force sensor and a second force sensor, that are placed at mirror image positions with reference to the subframe. This makes the measurement possible of the forces that are applied to the left and right side of the patient's breast.

Preferably further a measurement and control unit is provided to actuate a drive motor for controlling an inclination of the paddle with reference to the detector cover depending on the measurement signals from the force sensors. In this way a desirable distribution of forces along the breast can be obtained.

In one embodiment the measurement and control unit is arranged to actuate the drive motor for controlling an inclination of the paddle with reference to the detector cover so as to equalize the forces as measured with the respective force sensors. This provides the best estimate for a uniform distribution of forces along the breast during compression and imaging, can provide important diagnostic information and can be helpful in mitigating the pain that the patient experiences to the least possible extent.

The force sensors are advantageously placed at a position to prevent interference with the X-ray beam. This makes possible that a force exerted with the paddle during pressurizing of a breast is measured with said force measurement means during pressurizing and imaging so as to enable balanc- ing or equalizing the force exerted on the contact area between the paddle and the breast during the imaging process.

The balancing of the measured forces can be done manually or automatically, in the latter case for instance using springs or a motor drive.

Particularly when manual adjustment of the mammography apparatus is carried out, it is advantageous that the measurement and control unit is arranged to indicate a differential force of the first force sensor and the second force sensor that are placed on mirror image positions with respect to the subframe. This may of course also be applied when the balancing of the measured forces is carried out automatically.

As mentioned the measurement and control unit is arranged to actuate a drive motor for controlling an inclination of the paddle with reference to the detector cover depending on the measurements with the force sensors provided at mirror image positions with respect to the subframe so as to automatically equalize the forces as measured with these respective force sensors. This adjustment of the inclination of the paddle with reference to the detector cover will be limited to only a few degrees to maintain image quality, but enough to largely circumvent the influence of the earlier mentioned skin crease or the shoulder or breast muscle. This may apply both to a cranio caudal examination and with a medial lateral oblique examination of the breast.

Furthermore the distribution of forces as measured with the force sensors during compression may indicate important differences in tissue stiffness, which can indicate a mass which can potentially be invisible in the mammographic image. If the differential force between the forces measured by the first force sensor and by the second force sensor exceeds a predefined value, preferably an indicator signal is provided to warn an operator of the mammography apparatus that repositioning of the breast is indicated. If the disbalance persists the information can be transferred to the radiologist. The disbalance can for instance be expressed as the ratio between the measured forces at or near the respective sides of the paddle. The warning signal is particularly useful to indicate the operator that on one side of the paddle the compression is less or not useful and the desired goal of the compression i.e. flattening and immobilization of the breast during exposure cannot be achieved, and repositioning of the breast should be considered.

The invention will hereinafter be further elucidated with reference to the drawing.

In the drawing:

-figure 1 shows schematically a cranio caudal breast examination;

-figure 2 shows schematically a medial lateral oblique examination of the breast;

-figure 3A and 3B show schematically a frontal view and a side view respectively, of a mammography apparatus according to the invention;

-figure 4 shows a first embodiment of the mammography apparatus of the invention wherein the force sensors are applied at the back rods of the suspension; and

-figure 5 shows a second embodiment of the mammography apparatus of the invention wherein the force sensors are applied at the side rods of the suspension. Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

With reference first to figure 3A a frontal view is shown of a mammography apparatus 1 which has a mainframe 1 ' that is provided with an x-ray source 2, a paddle 3 and a detector 4 with a detector cover 5 that during use contacts the underside of a patient's breast. The person skilled in the art is aware that the x-ray source 2, the paddle 3 and the detector 4 are placed on a subframe 1'' (also called c-arm) that is mounted in the mainframe 1'. The subframe 1'' may be moved up and down and is rotatable.

With reference to figure 1 a cranio caudal examination of a patient's breast 6 is shown, wherein for clarity only the paddle 3, the detector 4 and the detector cover 5 are shown with reference to said breast 6. In figure 2 the so- called medial lateral oblique examination of the breast 6 is shown, which is featured by the oblique positioning of the subframe 1 ' ' with reference to the frame 1 ' to cause that the paddle 3 and the detector 4 with the detector cover 5 are placed at an angle with reference to the horizontal.

Turning again to figure 3A and also making reference to figure 4 and 5 it is shown that the paddle 3 has measurement means embodied as force sensors 7, 8 that are provided at positions 3', 3'' as part of the suspension 12 of the paddle 3 and because thereof outside the X-ray beam originating from x- ray source 2. In figure 4 two force sensors 7, 8 are shown positioned in the back rods 13, 14 of the suspension 12; in figure 5 two force sensors 7, 8 are shown positioned in the side rods 15, 16 of the suspension 12. Both embodiments of figure 4 and figure 5 enable that the force that is exerted with the paddle 3 during pressurizing of a breast 6 is measured with said force sensors 7, 8 so that these respective forces at both sides of the paddle 3 can be balanced or equalized.

Figure 3B further shows that the mammography appa- ratus 1 according to the shown preferred embodiment is further provided with a measurement and control unit 9 that is connected to the first force sensor 7 which is placed at a first position 3' in the suspension 12 of the paddle 3 and to the second force sensor 8 which is placed at a second position 3' in the suspension 12 of the paddle 3. The two said positions 3', 3'' are mirror image positions with reference to the sub- frame 1''. The measurement and control unit 9 is further arranged to indicate, preferably with indicator means 10, a dif- ferential force of the first force sensor 7 and the second force sensor 8. This can then be suitably used to actuate the paddle either manually or automatically depending on the measurements with the force sensors 7, 8 provided at the mirror image positions 3', 3'' in the suspension 12 of the paddle 3.

Figure 3B shows that the measurement and control unit

9 is arranged to actuate a drive motor 11 for controlling an inclination of the paddle 3 with reference to the detector cover 5 depending on the measurements with the force sensors 7, 8 provided at the mirror image positions 3', 3'' in the suspension 12 of the paddle 3 so as to equalize the forces as measured with these respective force measurement means 7, 8.

It is emphasized that the invention should not be deemed restricted to the exemplary embodiment of a mammography apparatus according to the invention with reference to the drawing. This exemplary embodiment merely serves to elucidate the wording as used in the appended claims. The protective scope that merits the invention is, however, exclusively determined by the appended claims, wherein the meaning of the wording used in the claims can be explained with reference to the description and this exemplary embodiment.