Key words
mammography - iPad - CDMAM phantom - patient consultation - education/teaching
Schlüsselwörter
Mammografie - iPad - CDMAM-Phantom - Patientenkonsultation - Ausbildung/Lehre
Abbreviations and Acronyms
MRI:
Magnetic Resonance Imaging
TC:
Tablet Computers
FFDM:
Full Field digital Mammography
PACS:
Picture Archiving and Communication System
CDMAM:
phantom Contrast Detail Mammography Phantom
Introduction
Breast cancer is the most frequent cancer in women in the world. It accounts for 23 % of all female
cancers [1], [2]. Imaging techniques, such as
mammography, digital tomosynthesis, ultrasound and magnetic resonance imaging (MRI) play a major role in
breast diagnostics. Especially mammography is crucial for the early detection of breast cancer which
allows a decrease in mortality by 15 % [3]. Therefore screening mammography is
recommended every 2–3 years for women older than 50 in many countries [4], [5]. Well-trained radiologists and technicians as well as
high-quality technical equipment are required to properly perform breast diagnostics.
Traditionally a film-based method mammography has nowadays virtually been replaced by digital techniques
which imply the possibility of direct on-screen reading. Whilst for decades computers consisted of a
distinct separation of user interface (e.g. keyboard and/or computer mouse) and reading unit which is
the monitor, modern tablet computers (TC) are becoming increasingly popular [6]. Especially the introduction of the iPad® by Apple (Cupertino, California, USA) in 2010
was a decisive moment in the development of this technology, but other manufacturers and operating
systems, such as Googleʼs Android (Mountain View, California, USA), were also able to gain a foothold in
the market. As the screen serves as both user interface and reading unit, TCs such as the iPad provide a
high level of mobility and universal employability and therefore became of interest for image reading as
well as for educational purposes [7], [8], [9], [10], [11], [12], [13]. However, to the best of our knowledge,
no studies have been conducted so far in the field of breast imaging. Using the iPad could be a feasible
way to customize the highly-demanded tasks of patient consultations, clinical demonstrations or
educational and teaching purposes.
As digital mammography is one of the most demanding imaging modalities in terms of image resolution, the
purpose of this study was to evaluate the display quality with a standardized phantom on the iPad 2 and
the iPad 3 in comparison to a dedicated 10 megapixel mammography screen and thus to determine if modern
TCs such as the iPad can serve as mobile and user-friendly devices for non-diagnostic mammography
reading purposes.
Materials and Methods
This investigation was conducted in coordination with the local institutional review board.
Contrast Detail Mammography (CDMAM) phantom
For phantom studies we X-rayed the well-known Contrast Detail Mammography (CDMAM) phantom (version
3.4, Artinis Medical Systems B. V., AS Zetten, the Netherlands) ([Fig. 1]). The phantom consists of an aluminum base with gold discs of various thickness and
diameter. The gold discs are arranged in a matrix of 16 rows by 16 columns. Within a row the disc
diameter is constant, with (partly) logarithmic increasing thickness. Within a column the thickness
of the discs is constant and the diameter increases logarithmically. The thickness is between 0.03
and 2.00 µm and the diameter between 0.06 and 2.0 mm. Each field contains two identical discs (same
thickness, same diameter), one in the center and one in a randomly chosen corner. The matrix grid is
silkscreen printed with X-ray contrasting paint and the aluminum base is attached to a Plexiglas
cover [14], [15]. The observer visibly
determines the field with the gold discs at each contrast level that is barely detectable in the
image. This phantom analysis allows the evaluation of spatial resolution, contrast, and noise
associated with the mammography device.
Fig. 1 Contrast Detail Mammography (CDMAM) phantom was X-rayed for phantom studies. It
consists of an aluminum base with gold discs of various thickness and diameter. The gold discs
are arranged in a matrix of 16 rows by 16 columns. Within a row the disc diameter is constant,
with increasing thickness, and within a column the thickness off the discs is constant and the
diameter increases. The thickness is between 0.03 and 2.00 µm and the diameter is 0.06 between
2.0 mm.
Image acquisition
Contrast Detail Mammography (CDMAM) phantom was X-rayed with a full field digital mammography (FFDM)
system (Mammomat Inspiration®, Siemens, Erlangen, Germany) on an anode/filter combination of
tungsten/rhodium using automated dose regulation. Image data were stored in the well established
DICOM (Digital Imaging and Communications in Medicine) format.
Devices and data analysis
We used a commercially available iPad 2 and iPad 3 (Apple, Cupertino, California, USA) and a 10
megapixel 30-inch LCD screen (Coronis Fusion 10 MP, Barco, Kortrijk, Belgium). The iPad screen is
about 9.7 inches diagonally in size (about 24.6 cm) in both versions. The iPad 2 comes with a
resolution of 1024 × 768 at 132 pixels per inch (ppi) whereas the iPad 3 has a screen resolution of
2048 × 1536 at 264 pixels per inch (ppi). The readers (three radiologists with work experience in
breast imaging of 11, 5.5 and 3.5 years) interacted directly on the iPadʼs touch screen display
(e.g. zooming in or out) using either their fingertips or a dedicated pen (Kensington, Redwood
Shores, California, USA). The DICOM data of the x-rayed CDMAM phantom were displayed with the Syngo
Plaza® software (Siemens AG, Erlangen, Germany) on the 10 MP screen and with the OsiriX software
(OsiriX, version 5.0.2, OsiriX Foundation, GNU General Public License) on both iPads. No image
information was added or removed. The phantom images were visually analyzed by the 3 readers in
consensus in a routine breast imaging workplace with dedicated standard illumination. The result
(= position of the gold pallets in 3, 6, 9 or 12 oʼclock position) was documented for each field of
the phantom on a purpose-built form ([Fig. 2]). If there was no agreement
between the readers regarding the correct marker position (2 : 1 decisions), the field was
considered as uncertainty and the marker position of the majority (the two agreeing readers) was
chosen. In case of total disagreement (1 : 1 : 1) or if the readers agreed that the markers could
not be detected anymore the field was considered as “non readable”. Afterwards results were checked
in regard to correctness, a correct field was classified as “readable”.
Fig. 2 Blanco evaluation form used for consensus reading of the Contrast Detail
Mammography (CDMAM) phantom on each reading device.
Additionally the phantom was reviewed again at the end of the study in consensus on all three devices
side by side ([Fig. 3]) to judge the subjective image quality in direct
comparison (1 to 6; 1 = excellent quality; 6 = bad quality).
Fig. 3 Contrast Detail Mammography (CDMAM) phantom displayed on the dedicated 10 megapixel
screen and on the iPads (version 2 [white] on the left and version 3 [black] on the right
side).
Statistical analysis
Statistical analysis was performed using SPSS (version 15.0, SPSS Inc., Chicago, IL, USA). Studentʼs
t-test was applied. A p-value < 0.05 was considered as significant.
Results
Technical realization
During the evaluation no technical problem occurred. The CDMAM phantom could be assessed on the three
devices without any limitation.
Objective display quality
When using the 10 megapixel screen the gold disc position was assessed correctly in 105 of 205
phantom fields (= 51.2 % readable). 102 of 205 fields were assessed correctly in the case of iPad 3
(= 49.8 % readable) and 99 of 205 in the case of iPad 2 (= 48.3 % readable) ([Fig. 4 a]).
Fig. 4 a and b a Phantom interpretation results of consensus decisions are
shown for the three devices. Numbers/percentages of readable phantom fields are shown. Dark
green = readable; red = non readable; light green = uncertain but readable (2 : 1 decisions).
b Differences of the phantom interpretation results for the three devices are shown.
Green/red = equal, blue = benefit 10 megapixel screen, turquoise = disadvantage 10 megapixel
screen, pink = disadvantage iPad 3 screen, yellow = disadvantage iPad 2 screen.
In comparison to both iPads assessment with the 10 MP screen lead to additional correctly detected
gold disc position in four phantom fields (10 MP screen superior in four phantom fields). In
contrast to the 10 MP screen, the iPads allowed the correct detection of the gold disc position in
two different phantom fields (iPad screens superior in two phantom fields). Comparing both iPad
screens, the results of version 3 were superior in four phantom fields and version 2 was superior in
just one phantom field ([Fig. 4 b]). However, none of these differences
were significant (p > 0.05).
In case of a non-agreement between the readers (2 : 1 decision), the phantom field was considered as
uncertainty. Evaluation uncertainties occurred for all screens. In the case of the 10 megapixel
screen 15 fields were uncertain. In the case of the iPad screens, 16 uncertainties occurred with
version 2 and 17 with version 3. The differences between the devices were not significant
(p > 0.05). The number of uncertain but readable fields (two correct decisions versus one
incorrect decision) was four with the 10 MP screen, seven with the iPad 2 and eight with the iPad 3
screen ([Fig. 4 a]).
Subjective display quality
Subjective image quality assessment favored the iPad 3 and 10 MP screen over the iPad 2. Image
quality of the iPad 3 and the 10 MP screen was judged as comparable.
Discussion
The purpose of this study was to collect first experiences as to whether or not modern tablet computers
(TCs) such as the iPad can be deployed in mammographic imaging. We compared two versions of the tablet
PC with a high-quality dedicated 10 megapixel LCD screen concerning display quality. Our results showed
that subjective image quality was moderately worse in the case of the iPad 2 and, although not
significant, both evaluated iPad versions were slightly inferior to a dedicated 10 MP reading screen in
detecting finer contrast details of a standardized mammography phantom. Therefore and as the iPadʼs
9.7-inch screen is not suitable for primary mammographic reading, especially not for side by side
assessment, iPads should not be used for primary diagnostic reading. However TC could be used for a wide
range of tasks, such as patient consultation, clinical demonstrations or educational purposes as
especially for these tasks a mobile, easy to handle device can be useful.
Some authors have already evaluated the potential benefits of tablet PCs in the field of medicine and
were able to show the benefit of video- and iPad-assisted patient briefings [16], [17], [18]. In general, however,
there still seems to be a great deal of demand for information on the part of patients [19]. Hence, tablet PCs with customized software could assist doctors to
satisfy patientsʼ demands. Due to the TCʼs mobility, user friendliness and the option to add customized,
foreknowledge- and age-appropriate multimedia content such as informative films, it allows a more
understandable and transparent patient briefing and may help to increase the understanding among
patients of their disease and of the planned procedures [18], [19], [20].
Furthermore, some studies showing TCʼs possible application for clinical purposes such as contrast media
safety [21] or for radiological image evaluation [7], [8], [9], [12], [13], [22] have already been
published. In these studies, TCʼs versatility regarding image quality and diagnostic performance was
assessed for different tasks, such as the review of magnetic resonance (MR) spinal emergency cases,
emergency brain computed tomography (CT) or screening purposes for tuberculosis on chest radiographs.
However, no data about the assessment of mammography image quality on tablet PCs have been published so
far. As many patients are interested in taking a look at their images, one of the most promising scopes
of iPad-based mammography display is the patient consultation. Considering what is going on in her
breast potentially supports patients in dealing with their disease and may have a positive impact on a
patientʼs compliance. The iPad can be a convenient device to present images during a consultation
providing maximum mobility as image demonstration can be virtually conducted anywhere.
Additionally, TCs may be used during clinical interdisciplinary demonstrations. Given adequate data
security, especially cloud-based image evaluation on a mobile device in particular makes image
presentation to colleagues much easier. Moreover, TCs such as the iPad facilitate education and
self-improvement in breast imaging because more and more dedicated applications are available [23], [24].
As mammography is one of the most demanding imaging modalities in terms of display resolution the results
of our study suggest that for these purposes the iPadʼs screen quality is sufficient not only in breast
imaging but also for other radiological fields such as CT, MRI, ultrasound or even plain film
radiography of any body region.
Some limitation needs to be addressed. As this was a phantom based study we are aware that further
clinical investigations need to be conducted to prove our results. However, in this study, we wanted to
report first experiences with tablet PCs regarding mammogram interpretation and the results from our
phantom evaluation suggest that the iPadʼs screen quality should be sufficient to utilize it for
displaying mammograms e.g. during patient consultations or for education purposes. A clinical follow-up
study including lesion-free mammograms and mammograms showing pathologies, such as invasive ductal
carcinoma or DCIS could prove this. Moreover, it should analyze to what extent individual factors such
as breast density or lesion size and type have an influence on the interpretation performance.
The benefits of iPad-based patient consultations, novice reader education or clinical demonstration have
to be confirmed in greater detail on a larger patient number and acceptance among clinical colleagues
and patients should be investigated. It is important to note that country-specific legal frameworks,
such as data protection guidelines, need to be taken into consideration when the tablet PCs are used,
especially concerning data transmission (cloud, etc.).
The assessment of mammograms requires comparison with prior examinations or with the contralateral breast
in a side-by-side fashion. However, as the iPadʼs screen size does not allow the display of multiple
mammograms at once in a diagnostic size, side-by-side reading may not be recommended. Moreover, as the
screen resolution of the evaluated TCs does not meet the national legal requirements, primary
mammography reading must not be performed on TCs. Nevertheless this could change in the future with
further technical development.
Conclusions
Modern tablet computers (TCs) such as the iPad are promising devices for medical purposes due to their
straightforward user interface, broad employability and mobility. Our results show that TCs seem
suitable for displaying mammograms for a variety of tasks such as patient consultation, clinical
demonstrations or educational and teaching purposes. Nevertheless, to perform primary mammogram reading
as well as follow-up and side by side assessment, a large screen with a high resolution meeting the
legal requirements is necessary.
Acknowledgements
The authors thank Evelyn Wenkel for support with the imagework and Martina Wabel for excellent
collaboration of gynaecologic radiology.
