Tailored compression and pain experience in mammography

There are many complaints concerning the compression procedure in mammography.
Over 25% of the examined women experience moderate to severe discomfort and
pain. At an estimated number of 500 millions compressions per year worldwide a
disconcerting number of complaints. Nearly all interventions have failed to
relieve the number of these complaints (Cochrane 2008).
Paddle and force
At the routinely used technique in compression of the breast a so called
'paddle' is being used, which is down pressed by means of a motor. During the
procedure an increasing force is measured. This force is a reflection of the
counterforce which is experienced by the paddle-arm during the compression
procedure. This force is expressed in decanewtons (daN), approximately
corresponding to 1 kilogram of force (1 kgf). The compression is a rather
standardized way of working which is, however, dependent on the experience and
the impression of the technician concerning what the woman can tolerate. The
applied force is being monitored and is maximized (maximum 20 daN). Because of
this the desired goal (flatness of the breast) is realized. When reasoned from
the apparatus, this is a reasonable approach.
Flattening and pressure
From the breast of the woman which is compressed, however, this is different.
During the compression, the breast experiences an increasing pressure. It is
eventually this pressure, which results in the desired flattening of the
breast. The final effect depends on the exercised force and the area on which
that force is exercised (N/m2, Pascal, pressure). The size of a breast can
strongly differ between individual women. From a small sample of 50 patients it
has become clear that the volume can differ a factor 10. That means that the
contact area of the breast with the paddle can equally strongly differ during
maximum compression; in this group a factor 4. In the current routine procedure
we measured at the extremes in a number of women a maximum pressure under 100
mmHg, but we found also women where this pressure can run up to 500 mmHg. It
will be clear that this has large consequences for the desired flattening, and
possibly also for the accompanying complaints.

The aim of the research up till now was, during a number of months, to examine
a total of 500 participants referred for mammography to the AMC. The different
parameters which are relevant to compression were measured. Particularly the
influence of pressure was never systematically examined in this respect. After
more than 200 patients we have sufficient insight in these parameters.

We now want to use a pressure-controlled compression protocol for only one of
the breasts of the test person in the CC-direction. We can then compare this
with the standard force-controlled compression within one person. This is done
by randomly selecting one breast and applying the pressure-controlled protocol
and use the standard force-controlled protocol for the other breast.
The radiologist will blindly judge the image quality afterwards. The pain
experienced by the test person (NRS-score) will be recorded directly after each
compression for later evaluation.

The patients will be subjected to a normal routine mammographic investigation
except for a pressure-controlled compression with one of the CC-mammograms.
Both MLO-mammograms are processed with the present standard (force-controlled)
protocol; the reason for this is that the MLO-mammograms are considered
diagnostically as most important. During the research periode one type of
paddle will be used.

The image quality of both CC-mammograms is blindly judged by the radiologist
afterwards. In addition the image quality will be judged directly as usual by
the technician, who after consulting the radiologist may decide to make an
addtional mammogram because of insufficient quality.
The test person will directly after each compression indicate the pain
experienced by giving a number 0 to 10 (Numerical Rating Scale) to the
technician, who will record these in a computer program.
Technical aspects of the method:
The mammographic machine will be equipped with an (optical) contact area meter.
In the advancement to and during the maximum compression in same period of time
the thickness reduction, incurring force, and the incurring contact area of the
paddle with the breast is recorded. These other parameters are already measured
in the machine itself. From the dynamic force and the contact area parameters
an estimation of the dynamic mean pressure can be obtained.
The measured parameters will be stored directly in a database.
The mammograms will routinely be scored according the clinical BI-RADS lexicon.
The breast density will receive an ACR density score.
The number of prior mammograms will be taken in to account.
The size and thickness of the breasts will be compared to samples from
anonymous data from digital screening units of various regions to trace a
selection bias. This because of the specific profile of the academic population
of the AMC.
At the informed consent, women will be asked if they are willing to participate
in a future inquiry.

Compared to a normal routine mammographic investigation, no extra risk can be
identified.

In case the technician judges the pressure-controlled compression to be
inadequate, the mammogram will be repeated using the standard
(force-controlled) compression protocol; it is expected that this will happen
in practice only exceptionally (less than 4% of the cases).