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PACS Storage
Te c h n o l o g y Update :
Hologra p h i c Storage
By John E. Colang a n d James N. Johnston
The credit earned from the Quick Credit test
accompanying this article may be applied to the
AHRA certified radiology administrator (CRA)
communication and information
management domain.
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V
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• This paper focuses on the emerging technology of holographic storage and its effect on picture a rchiving and communication systems
(PACS). A review of the emerg i n g technology is presented, which
includes a high level description of holographic drives and the associated substrate media, the laser and optical technology, and the
spatial light modulator.
• The potential advantages and disadvantages of holographic drive
and storage technology are e valuated. PACS administrators face myriad complex and expensive storage solutions and selecting an appropriate system is time-consuming and costly.
• Storage technology may become obsolete quickly because of the
exponential nature of the advances in digita l storage media. Holographic storage may turn out to b e a l ow cost, high speed, high
volume storage solution of the future; however, data is inconclusive
at this early stage of the technology lifecycle.
• Despite the current lack of quantitative data to support t h e hypothesis that holographic technology will have a significant effect on
PACS and standards of practice, it seems likely f rom the current
information that holographic technology will generate significant efficiencies. This paper assumes the reader has a fundamental understanding of PAC S technology.
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A
s the trend in diagnostic imaging moves away from
traditional film to digital imaging, the traditional hard
copy film storage center is being replaced by electronic
recording and storage media. A properly implemented PACS
can significantly increase efficiency within a radiology
department. Increasing the efficiency in throughput of the
medical image through the stages of image capture, interpretation, result-reporting and subsequent retrieval is a major
benefit to a fully digital medical imaging department. A new
technology is emerging that may prove to enable a more efficient image lifecycle. PACS users are demanding more storage and faster retrieval times. Holographic storage and
retrieval systems hold promise as future technology leaders
in this market segment. More data can be stored because
holographic images record data in three dimensions instead
of just on the surface of the media. This technology could
someday replace magnetic, single layer storage with optical,
three dimensional (3D) holographic storage.
Literature Review Strategy
A review of the literature was performed using the Academic Search Premier database via the EBSCOhost® search
engine. Key words “holographic storage” were entered into
the EBSCO database search field for default fields and the
search yielded several pages of results. Selected articles had
been peer-reviewed and published between 1999-2005,
limiting the search to the most recent literature. A secondary search was also performed at Google Scholar using the
same key words and limiting the search for articles published between 2001-2005. The filter for “peer reviewed”
documents was removed because many of the documents
returned were extremely technical in content. This search
returned over 300 relevant articles. Materials were selected
for high level content readability.
As more radiology departments move from conventional film and paper media toward digital systems,
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Accord i n g to a st u d y by t h e University of California Berkeley
School of Information Management and Syste m s , i n o rd e r to
meet escalating requirements there w i l l b e a n e e d to i m p rove
today ’ s stora g e o fferings by 10 t i m e s . T h e study shows by
2010 , a 100-fold incre a s e w i l l l i kely b e n e c e s s a ry.
and as diagnostic imaging procedures produce larger
image files, the strain on storage and archival systems
becomes acute. Physicians are also becoming more
reliant on sophisticated imaging modalities such as CT
scans, MRI scans, nuclear medicine scans, and ultrasound scans. These modalities produce image files that
range from 10 Megabytes (MB) to 90 MB in size per
procedure. As a result of this shift from plain-film
radiography to more advanced imaging modalities,
PACS administrators are demanding greater storage
capacities and faster retrieval times.
PACS administrators, and healthcare in general, are
not the only consumers of data storage technology
clamoring for more storage capacity. According to
“How Much Information,” a study by the University of
California Berkeley School of Information
Management and Systems, in order to meet escalating
requirements there will be a need to improve today’s
storage offerings by 10 times. The study shows by 2010,
a 100-fold increase will likely be necessary.
This need for increased data storage is even more
acute in PACS technologies where there are requirements to store large volumes of data. Nagy and Farmer1
classify storage as online, near line, or offline. “Online
storage refers to data that is stored on magnetic hard
drives with access times in milliseconds and transfer
times in the range of 10s and 100s of megabytes
(MB)/second. Online storage is immediately available to
your PACS application. Near line storage typically refers
to a tape or jukebox in which robotic arms can retrieve
the tapes automatically and insert them into a drive to
read or write data. Generally, a near line system can
access data within 60 seconds and is able to transfer data
at a few MB/sec. Offline storage is removable tape or
optical media that is stored on a shelf in a catalog and is
retrieved manually.”1
Nagy and Farmer concluded that the relationship
between online and near line storage is a direct trade-off
between cost and performance. PACS administrators
would have to make choices regarding how long to keep
medical images online commensurate with online storage capacity, budget, and amount of data. Estimates vary
depending on the source, but most hospitals require
approximately 10 terabytes (TB) of storage annually for
every 225,000 radiologic procedures performed. Nagy
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and Farmer point out that, relative to other healthcare
applications, PACS requires disproportionate amounts
of data storage—100 to 1000 times as much. PACS
administrators must be able to scale capacity commensurate with this requirement. The peak loading on a
PACS storage system for a large hospital with multiple
simultaneous requests is approximately 30 to 50
MB/second. Early technology was expensive and
plagued with mechanical failures. Storing data on disk
is less expensive than using jukebox technology.
Typically, PACS administrators use dedicated storage
systems for the PACS archive database. According to
International Data Corp., in fiscal year 2003, Fortune
500 companies spent $7 billion on approximately 1200
TB (1 TB = 1000 gigabytes) of data stored on magnetic
tape.2 The primary purpose of the PACS database is to
move large radiologic images through the network as
quickly as possible so users of the system can work with
the data and images. Capacity, speed, reliability, and cost
per TB are all performance factors that are critical to the
success of a PACS archive database. Technological gains
in the areas of storage media, disk types, and networks
are exponential in nature. Therefore, the risk of selecting a storage or retrieval technology that may quickly
become cost prohibitive or obsolete always exists.
Current Storage Require ments
Various types of conventional magnetic storage are available, each with its own set of advantages and disadvantages. From a PACS administrator’s point of view, there
never seems to be enough storage. From high resolution
CT scans that are as large as 30 MB per scan to multiple
diagnostic imaging studies done on long term chronic
patients, the need for more capacity continues to grow.
Eventually, scientists hope to advance the holographic
memory technology so that one single disk the size of a
CD-rom could potentially hold 1 TB of data (equivalent to
images from thousands of exams). Companies that market
this technology are announcing prototypes that can hold
200 times the amount of data that standard disks currently
hold. Ultimately, the amount of data a system can store
and the speed at which the archive performs retrievals are
key to its success. Storage needs vary depending on the frequency and type of studies an imaging department per-
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PAC S Storage Technology Update: Holographic Storage
Table 1. Typical Uncompressed Storage Requirements by Modality per Study
Pe r Study Basis
No. of Images
M B o f Storage
Ave
Range
Ave
Range
X
Image Size
Y
Z
CR
2000
2500
2
3
2–5
30
2 0 to 5 0
DR
3000
3000
2
3
2–5
54
3 6 to 9 0
Modality
CT
512
512
2
60
40–300
32
21 to 157
Multi-slice CT+
512
512
2
500
200–1000
262
10 5 to 524
MR
256
256
2
200
80–1000
26
11 to 131
Mammography***
3000
3000
2
6
4–8
108
7 2 to 144
Ultrasound*
640
480
2*
30
20–60
18
12 to 3 7
Echo Cardio**
640
480
1
1125
750–1500
346
230 to 4 61
Nuclear Medicine
256
256
2
10
4–30
1.3
0.5 to 3.8
Film Digitizer
2000
2500
2
3
2–5
30
2 0 to 5 0
Digital Fluoro
1024
1024
1
20
10–50
20
10 to 5 0
Radiology Angio
1024
1024
1
15
10–30
15
10 to 3 0
Cardiac Catheterization+
1024
1024
1
150
120–240
450
360 to 720
Angioplasty+
1024
1024
1
150
120–240
450
360 to 720
Peripheral Vascular Angio++
1024
1024
1
150
120–180
450
360 to 540
*Monochrome 8 bits, color 24 bits, average 16 b i t s o r 2 bytes
**15 frames per sec, 5 sec loops, 10 to 20 loops per study, average 15 loops, monochrome—1 byte deep
***Image size will vay with digital mammography vendor
+Multi-slice CT study may e xceed 1GB when thin (1mm or less) are acquire d for virtual presentation
++The typical acquisition matrix for some vendors is 512 x 512 rather than 10 2 4 x 10243
(Table courtesy of Smith E, University of Rochester, 2004.)
forms and data exists to help PACS
Ta b l e 2 . Typical Uncompressed Storage Requirements per
administrators extrapolate the
100,000 Studies per Year Excluding Multi-Slice CT, 3 T M R
capacity that will be needed. Table 1
and Mammography
describes uncompressed storage
requirements by modality per
% of
Ave. MB
GB per year per
study.3,4 Modalities such as cardiac
Modality
Studies
per study
100,000 studies
catheterization, angioplasty, and
Angiography
3
20
60
peripheral vascular angiography,
CR & DR
64
35
2240
followed by echo cardiography and
CT
20
32
640
multi-slice CT, produce the most
MR
5
21
105
number of images and consequentNM
3
1.3
3.9
ly exert an increased demand on
US
5
18
90
storage. Some estimates call for 3.1
TB of storage capacity for every
Tota l T B p e r 100,000 studies
3.1 TB
100,000 exams (see Table 2).3 Table
2 summarizes typical uncom(Table courtesy of Smith E, University of Rochester, 2004.)
pressed storage requirements per
100,000 studies per year excluding
multi-slice CT, 3T MR, and mammography. CT, MR, CR, Holographic Drive Technology
DR, and angiography exert the greatest demand for storage
with estimates ranging from 20-35 MB (average) per study. Holographic media is an emerging technology which could
Holographic storage technology could potentially provide replace conventional magnetic and optical drive and storthe ability to assure PACS administrators of future storage age systems connected to PACS in the near future. Many
technologists and materials scientists have pondered the
capacity.
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future of digital storage technologies. Dahr5 suggests that
holography holds great promise as a technology that can
overcome two approaching physical barriers to data storage
through a powerful combination of high storage transfer
densities and fast data transfer rates.
What Is Holographic Storage?
The fundamentals of holographic storage consist of a few
key technologies that work together to exploit light sensi-
tive media in three dimensions. Holographic storage,
according to Dahr, differs from other recording technologies in two fundamental ways. First, holography enables
massively parallel recording and reading of data rather than
the serial approach of traditional methods. Second, and
more importantly, holography exploits the entire thickness
of a recording medium rather than just the surface. Figure
1 outlines the basic lifecycle of a hologram from the recording phase, where two laser beams intersect to create an
interference “checkerboard” of bright and dark regions that
Figure 1. Simplification of how a hologram is created. (Courtesy of InPhase
Technologies, Longmont, Colorado)
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PAC S Storage Technology Update: Holographic Storage
is subsequently recorded by a photosensitive medium. The
hologram is the actual image of that interference pattern
that is now stored within the medium. This hologram is
activated or read by shining one beam of light on the hologram, thereby reconstructing it.
One technology developer sums up the differences by
saying, “Instead of laying down the data on the surface
layer of the medium like in conventional digital recordings, holography uses lasers and light to record data in
three dimensions. Unlike other technologies that record
one datum at a time, holography allows a million bits of
data to be written and read in parallel with a single flash
of light. This enables transfer rates significantly higher
than current optical storage devices.”6
Physics World describes the process: “Since an entire
page of data can be retrieved by a photo detector at the
same time, rather than bit-by-bit, the holographic
scheme promises fast read-out rates as well as high
storage densities. If a thousand holograms, each containing a million pixels, could be retrieved every
second, for example, then the output data rate would
reach 1 gigabit per second.”7
Figure 2 demonstrates how data is recorded using
light from a single beam that is split into two beams.
The spatial light modulator encodes data onto the signal beam.
The beam is split into two beams, the signal
beam (which carries the data) and the reference
beam. The hologram is formed where these
two beams intersect in the recording medium.
The process for encoding data onto the signal
beam is accomplished by a device called a spatial light modulator (SLM). The SLM translates
the electronic data of 0’s and 1’s into an optical
“checkerboard”pattern of light and dark pixels.
The data is arranged in an array or page of
around a million bits. The exact number of bits
is determined by the pixel count of the SLM. At
the point of intersection of the reference beam
and the data carrying signal beam, the hologram is recorded in the light sensitive storage
medium. A chemical reaction occurs in the
medium when the bright elements of the signal
beam intersect the reference beam, causing the
hologram stored. By varying the reference
beam angle, wavelength, or media position
many different holograms can be recorded in
the same volume of material.6
It is the variation of the reference beam angle, wavelength, or media position that significantly increases
the storage capacities of this new technology since
many holograms can exploit the same physical space in
three dimensions.
How Are Data Read?
In order to read the data, the reference beam deflects off the
hologram, thus reconstructing the stored information. This
hologram is then projected onto a detector that reads the
data in parallel. This parallel read-out, according to industry
specialists, is the innovation that allows the fast transfer rate.
Figure 3 illustrates how data are read by using the reference
beam to deflect off of the hologram. It creates several parallel
reads, thus allowing ultra fast recovery and presentation of
data. Note the 3D nature of the rendered holograms.
Figure 2 . Demonstration of how d a t a i s
recorded using light from a single beam
that is split into t wo beams. (Courtesy
of InPhase Technologies, Longmont,
Colorado)
How Are Data Recorded?
Unlike conventional digital recording where the information is stored on the surface of the recording media (the
CD or the DVD), the hologram recording technology uses
3D layers by bouncing light from a single laser beam. Technologists describe the data recording technology:
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The Spatial Light Modulator
According to Physics World, to use volume holography as a
storage technology, digital data must be imprinted onto the
object beam for recording and then retrieved from the
reconstructed object beam during readout. The SLM is the
device used to insert data into the system and it is a planar
array consisting of thousands of pixels.
Physics World sums it up nicely by describing each
pixel as an “independent microscopic shutter that can
either block or pass light using liquid-crystal or micromirror technology.”7 The authors of the Physics World
article point out that this is dependent upon the power
of the laser and the sensitivities of the materials used for
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properties. They will have to record holograms
quickly, preserve them faithfully, and erase old
data to make room for new. For now, materials
that can preserve holograms for long periods
are often slow to record them or can’t be erased;
materials that record data quickly often lose the
optical traces over time.8
Materials Science Is the Key
Figure 3 . Illustration showing how data
are re a d by u s i n g t h e reference beam to
deflect off the hologram. (Courtesy of
InPhase Technologies, Longmont, Colorado)
To understand how this technology works, a good understanding of materials science is important since the media
used to capture the data is perhaps the most problematic
and challenging component of holographic technology.
Scientists have been trying for years to overcome the technical barriers related to the media and materials. Hellemans’ article explains how the actual materials and their
limitations created opportunities for advancement.
Materials problems may be slowing developments now, but, ironically, it was a materials
problem that kicked off the field of holographic storage in the first place. More than 3
decades ago, researchers found that bright
light changes the optical properties of lithium
niobate, a material they were studying as a
possible optical switch because its refractive
index changes in response to an electric field.8
the substrate. The data are read using an array of detector pixels, such as a CCD camera or a semiconductor
sensor. The object beam often passes through a set of
lenses that image the SLM pixel pattern onto the output
pixel array. Figure 4 offers a graphical representation of
this mechanism. To maximize the storage density, the
hologram is usually recorded where the object beam is
tightly focused. When the hologram is
reconstructed by the reference beam, a
weak copy of the original object beam conTwo Basics of a Holographic Data-Storage System
tinues along the imaging path to the
camera, where the optical output can be
detected and converted to digital data.7
Technology Barriers
A review of the literature indicates that government and private enterprise seem to be on track
to solve many of the technical issues that once
prevented widespread use of holographic drive
technology. The most challenging technical
issue has been selection of a suitable storage
media. Materials science problems and related
technologies have proven to be the most significant barriers. The problem in the past was primarily with the materials used in the actual
holographic disk.Many advances have occurred
since Hellemans’analysis in 1999, which said:
… turning holographic storage into the
equivalent of a super-disk drive, able to
speedily write as well as retrieve vast
amounts of data, will take optical materials with an elusive combination of
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Data are i mprinted onto the object beam by shining the light
through a pixelate d d evice called a spatial light modulator. T h e reference beam overlaps with the object beam on the storage material,
where t h e i n terference patte r n i s s tore d a s a change in absorption,
refractive index or thickness of the medium. A pair of lenses image
the data through the storage material onto a p i xelated detector array,
such a s t h e charge coupled device (CCD).
Figure 4 . Basics of a holographic data-storage
system. The spatial light modulato r i s a key p a rt
of the holographic image technology. (Courtesy of
Physics World)
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Materials Science Challenges
There are some technical shortcomings associated with the
use of lithium niobate. Niobate crystals, according to Hellemans, are expensive and have to be grown individually. The
storage media must have a high dynamic range, high photosensitivity, dimensional stability and optical clarity. Many of
the outstanding challenges reported in the literature have to
do with the materials science engineering aspect of this technology. One of the most perplexing problems with implementation of holographic data storage using photorefractive
materials is the ultimate erasure of the data due to volatile
readout.9 Electrons are excited to higher energy levels in
areas where the light is intense, enabling them to migrate
through the material. The displaced electrons generate local
electric fields that distort the crystal lattice, in effect creating
a pattern of minute optical flaws in the material.8
The material used must be easy to manufacture and
must be able to withstand this potentially destructive
readout process. The new generation media must also
have precise optical qualities and must exhibit thermal
and environmental stability.
Many innovative companies have already
announced product advances and releases in this area.
Some companies have plans to release products that
they claim have overcome the limitations mentioned
several years ago by Hellemans.
Other Technical Obstacles
Lasers were a limiting factor in the development of holographic drive and storage technology because they were costly and unreliable. These limitations have been eliminated by
the advances made in laser technology. Another limiting factor in this technology was the detector mechanism. The first
generation detectors were expensive and performed poorly.
Because of the popularity of digital cameras, active pixel sensor arrays are now readily available at lower cost and higher
quality. Other technical problems, such as high operating
temperatures, slow performance of the spatial light modulators, and commercial availability of the micro-mirrors and
ferroelectric modulators, have been resolved or are in the
process of refinement in the prototypes. 6
Some scientists report that they are confident they
have overcome these technical obstacles reported by
other scientists and technologists in the field.
We believe the substantial advances in recording media, recording methods, and the demonstrated densities described here coupled with
the recent commercial availability of system
components remove many of the obstacles that
previously prevented the practical consideration of holographic data storage and greatly
enhance the prospects for holography to
become a next-generation storage technology.6
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Cost of Storage and Other
Variables
PACS administrators are demanding more storage at a
lower cost, more reliable hardware, and a smaller footprint.
Most hospitals have limited physical infrastructure and
have run out of room to place additional media storage
devices. As the demand for more storage increases, holographic drives may solve the problem of storing large
amounts of medical images in small spaces. This technology is still too immature to determine what the actual cost
per gigabyte (GB) of storage will be. Some analysts predict
that the cost could range up to $20 per GB of storage. Next
to cost, speed and footprint are the two biggest concerns.
Straub explains in his 2004 article that changing the input
angle of one of the beams permits a new hologram to be
stored in the same volume of material. This adjustment
could offer terabit storage capacities in small spaces. The
superimposition of many holograms within the same volume of storage media will exponentially increase future
storage capacity thresholds.1
Cost Comparison
The cost of storage is evaluated on a case by case basis
depending upon the type of media selected and the estimated capacity. Comparative data suggests that the cost for
the new holographic media will probably be somewhere in
the neighborhood of $.06-$.20 per GB compared to data
tape which costs between $.25 and $1, and video tape
which costs between $1 and $3 per GB. The most expensive
storage media is hard disk drives which start at around $3
per GB and go up from there. The average archive life of
holographic media is predicted to be approximately 50
years by the companies positioning their prototypes in the
market. If this prediction is substantiated by solid research
in the months ahead, this would compare nicely with other
optical type drives, but is vastly better than data tape, video
tape, or hard disk drives.6
Other Physical Comparisons
Table 3 compares various parameters from magnetic, optical, and tape drives. Holographic drives are not included in
this comparison. Note that there are pros and cons associated with each type of currently deployed media. PACS
administrators must evaluate which technology is best suited for present needs.
Is the Future Bright for
Holographic Technology?
Holography was discovered in the 1940s, but it was not
until the development of the laser in the 1960s that it was
considered a storage potential.
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The rapid development of holography for displaying 3-D images led to the realization that
holograms could potentially store data at a
volumetric density of one bit per cubic wavelength. Given a typical laser wavelength of
around 500 nm, this density corresponds to
1012 bits (1 terabit) per cubic centimeter or
more. (In comparison, a DVD optical-disk
player reads data 100 times slower.)
In the mid-1970s, research into holographic
data storage all but died out due to the lack of
suitable devices that could transfer 2-D pixilated images.6
Recent advances in technology have led to increased
consumer interest in holographic storage as a viable
alternative for storing medical images. Although the
initial focus for product development has not been
specifically pointed at healthcare applications, there is
potential that once the technology is released, it would
have tremendous application in the PACS environment. Holographic technology is about to hit
mainstream. Quain10 reported at the National
Association of Broadcasters conference in mid-April
(2005) that optical storage technology companies had
demonstrated a new prototype optical drive that can
store digital information not just on the surface of an
optical disk, but also within a disk as 3D images. The
prototype stores up to 300 GB on a single disk. This
was accomplished by developing a unique photopolymer. The initial holographic drives, ready for release to
market in Q3 of 2006, will be write-once designs for
professional archiving with models priced at about
$10,000 and $15,000. Manufacturers are expected to
offer an inexpensive ROM product for consumers.10
Development of the prototype holographic drive
has been a collaborative effort between government
and private enterprise, according to Electronic News.11
The industry credits the innovation of key recording
techniques and holographic media, along with commercial availability of critical components, to strong
partnerships with leading storage companies and government funding. Advances have been made to
increase data storage capacities up to 1.6 TB on a single disk. The prototype writes the data with a single
flash of a 407 nm laser beam. Multiple pages of data,
referred to as a book, are recorded in one spot on the
Ta b l e 3 . Parameters from Magnetic, Optical, and Tape Drives
Parameter
Retrieval
Magnetic Disk
Random
Optical Disk
Typically Serial
Magnetic Tape
Serial
Study retrieval time
A few seconds
Typically 10 seconds
or more
Typically a minute o r
more
Use
On-line immediate
access
Departmental or
enterprise archive
Disaste r recovery
Near-line access
Long-term archive
Disaste r recovery
Long-term archive
Disaste r recovery
Uncompressed storage
capacity
Up to 300 plus GB,
access time will
tend to decrease
with capacity of
disk
Currently
approximately 3 0 G B
U p to 500 GB
Life expectancy and
reliability of media
Excellent, but can
be corrupted
Excellent if properly
handled
Finite a n d varies by type
of tape
Human intervention
required
Minimal to none
Some and varies by
type of optical disk
jukebox
Some and varies by type
of tape and jukebox
Relative cost
Must be evaluate d o n a c a s e by case basis
(Table courtesy of Smith E, University of Rochester, 2004.)
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PAC S Storage Technology Update: Holographic Storage
disk, providing approximately 12 MB of data in a single book location. Electronic News explains the actual
technology that makes this type of innovation possible:
The prototype drive includes all drive subsystems such as the auto load/unload mechanics,
servo system, holographic read/write head,
data channel and electronics. The media cartridge is loaded and unloaded automatically
using a mechanism designed by private enterprise. The servo system regulates both radial
and rotational movement of the media and
the angle of the reference beam. The holographic read/write head is the heart of the system, and in the past availability of high quality,
yet affordable optical components was an
issue. However, the 407 nm blue lasers recently available in other optical devices provide the
wavelength required for high capacity holographic storage. CMOS active pixel sensor
arrays used in digital cameras are also available, as are spatial light modulators used in
digital TVs and projectors. This technology
depends on its industry partners to continue
to optimize these components for use in holographic storage.11
Some of these breakthrough technologies were
funded partially by the NTA for the eventual use in
geospatial image archive applications. This technology
represents a true collaboration between private and
public sectors.
Conclusion
PACS for medical imaging require vastly increased storage
technologies that are affordable and reliable. Expanded
interest by physicians to image patients using sophisticated
modalities such as CT and MRI scans have produced terabytes of medical imaging data that need to be stored. A
commensurate increase in the need for storage capacity
and speed of retrievals for online and near-line storage of
medical images by PACS administrators has developed.
Current storage technologies are expensive to implement
and quick to become obsolete. Holographic drive technology holds hope to change the current paradigms held by
PACS administrators by offering a fast and affordable storage solution for the future. This technology is still in its
infancy, but recent technological advances in the media and
the technology within the components offers hope that
holographic drives may prove to be a viable storage solution for the future. Further research is needed to clarify
whether or not holographic storage will become the preferred drive and storage technology for PACS. PACS
administrators should carefully educate themselves regard-
46
M AY / J U N E 2 0 0 6
ing possible storage solutions before committing to an
enterprise-wide solution that may soon become obsolete
due to emerging technologies. Data is not currently available to explicitly define the cost and reliability of this technology since it has not been deployed commercially at the
time this paper was written. Scientists remain concerned
with the long term stability of the materials and with
potential destructive readout issues. However, indications
are that by 2010, holographic storage devices may make
their way into mainstream PACS deployment to provide a
solution for fast, reliable, and inexpensive storage.
References
1Nagy P, Farmer J. Demystifying data storage: Archiving
options for PACS. Appl Radiol. 2004;May:18-22.
2Straub J. The Digital Tsunami: A perspective on data storage.
Information Management Journal. 2004;38:42.
3Smith E. What’s in Storage? ADVANCE for Imaging and
Oncology Administrators. 2004;May:27-30.
4Konkachbaev A, Elmaghraby A. Interface for digital medical
image databases. 4th International IEEE EMBS Special
Topic Conference on Information Technology Applications
in Biomedicine 2003. Piscataway, NJ: IEEE Computer Society Press; 2003:238-241.
5Dhar L. A new venture in holographic storage. Industrial
Physicist. 2001;7(3):26.
6InPhase Technologies: What is holographic storage. 2005.
7Burr GW, Coufal H, Hoffnagle JA et al. Optical data storage
enters a new dimension. Physics World. 2000;6:37-42.
8Hellemans A. Holograms can store terabytes, but where? Science. 1999;286:1502.
9Liu Y, Kitamura K, Ravi G, Takekawa S, Nakamura M. Growth
and two-color holographic storage properties of Mn-doped
lithium nibate crystals with varying Li/Nb ratio. J Appl
Phys. 2004;96(11):5996-6001.
10Quain J. A new dimension in storage. PC Magazine. 2005;24.
11Lucent venture unveils holographic drive prototype. Electronic News. 2005;51(2).
John Colang, RT, i s a g raduate student at Midwestern
State University and is a candidate for the Maste r o f
Science in Radiologic Sciences degree in December of
2 0 0 6 . H e i s a P M I c e rtified Project Manager and is
employe d by I n tel Corp. in Albuquerque as a Project
Manager fo r I T. J o h n i s a l s o a m e m b e r o f t h e A R RT
and ASRT a n d m ay b e c o n tacte d a t
[email protected].
Dr. James Johnston is an assistant professor of Radiologic
Sciences at Midweste r n State Univers i t y i n Wichita Falls,
Texas where h e teaches in the associate’s, bachelor’s,
radiologist assistant, and master’s programs. James may
be contacted at [email protected].
R ADIOLOGY M A NAGEMENT
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Page 47
AHRA Home-Study Resources
PAC S Storage
Technology Update :
Holographic Storage
Home-Study Test
1.0 Category A credit • Expiration date 6-30-2008
Carefully read the following multiple choice questions. Mark your answe r s
on the answer sheet found on page 49 and mail or fax the answer sheet to:
The credit earned from the Quick
Credit test accompanying this article
may be applied to the AHRA certified
radiology administrator (CRA)
communication and information
management domain.
AHRA
Attn: Continuing Education Credit
490-B Bosto n Post Road, Suite 101
Sudbury, M A 01776
Fax: (978) 443-8046
Questions
Instructions: Choose the answer that is most correct.
1. Which of the following are major benefits to a fully
digital medical imaging department?
a.
b.
c.
d.
Increasing efficiency in the stages of image capture
Increasing efficiency in the result-reporting
Increasing efficiency in interpretation
All of the above
2. Holographic storage increases capacity because the
images record data:
a.
b.
c.
d.
On the surface of the media
In three dimensions
on magnetic tape
none of the above
3. What are some reasons that the strain on storage and
archival systems has become acute?
a.
More department have moved from conventional film to
digital systems
b. Diagnostic imaging procedures produce larger image files
c. There is more dependency on sophisticated imaging
modalities
d. All of the above
R ADIOLOGY M A NAGEMENT
4. According to a study at the University of California
Berkeley, by 2010 departments will need to improve
today’s storage offerings by:
a.
b.
c.
d.
10 times
100 times
1000 times
No improvement will be necessary
5. Data storage may be classified as:
a.
b.
c.
d.
Online
Near line
Offline
All of the above
6. When data is stored on magnetic hard drives with
access times in milliseconds and transfer times in the
range of 10s and 100s MB/second is defined as:
a.
b.
c.
d.
Online storage
Offline storage
PACS
None of the above
M AY / J U N E 2 0 0 6
47
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Page 48
7. A tape or jukebox is generally used in what type of
storage?
a.
b.
c.
d.
Online
Near line
Offline
All of the above
8. When removable tape or optical media is stored on a
shelf in a catalog and is retrieved manually, this is
referred to as:
a.
b.
c.
d.
Online storage
Jukebox storage
Offline storage
Near line storage
9. For every 225,000 radiologic procedures performed,
it is estimated that most hospital require
approximately:
a.
b.
c.
d.
10 MB of storage annually
10 TB of storage annually
1000 gigabytes
None of the above
10. The primary purpose of the PACS database is to move
large Radiologic images through the network as
quickly as possible.
a. True
b. False
11. Relative to other healthcare applications, PACS
requires less data storage capacity.
a. True
b. False
12. Eventually, scientists hope to advance the holographic
memory technology so that one single disk the size of
a CD-rom could potentially hold:
a. 1 TB of date
b. Images from thousands of exams
c. 200 times the amount of data that standard disks
currently hold
d. All of the above
14. Holographic media is an emerging technology which
could replace conventional magnetic and optical drive
and storage systems connected to PACS in the near
future.
a. True
b. False
15. Which of the following is true of holography?
a.
b.
c.
d.
Enables massively parallel recording of data
Enables massively parallel reading of data
Exploits the entire thickness of a recording medium
All of the above
16. Instead of laying down the data on the surface layer of
the medium like in conventional digital recordings,
holography uses:
a.
b.
c.
d.
One datum at a time
A photo detector to retrieve data bit-by-bit
Lasers and light to record data in three dimensions
None of the above
17. The device that translates the electronic data of 0’s
and 1’s into an optical “checkerboard”patterns of
light and dark pixels is called a(an):
a.
b.
c.
d.
Digital video recorder
Hologram refractor
Spatial light modulator
All of the above
18. At the present time, lasers are a limiting factor in the
development of holographic drive and storage
technology because they are costly and unreliable.
a. True
b. False
19. When compared to other types of storage, holographic media will probably cost about:
a.
b.
c.
d.
$.06-$.20 per GB
$.25-$1 per GB
$3 plus per GB
The same as other types of storage
20. Holography was first discovered in the:
13. What type(s) of procedures produce the most number of images and exert the most demand on storage?
a.
b.
c.
d.
48
Multi-slice CT
Cardiac Catheterization
Peripheral vascular angiography
All of the above
M AY / J U N E 2 0 0 6
a.
b.
c.
d.
1930s
1940s
1950s
1960s
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ANSWER SHEET
AHRA Home-Study Resources
PAC S Storage
Technology Update:
Holographic Storage
1.0 Category A c redit • Expiration date 6-30-08
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Address
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Telephone
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Home Study Fees: AHRA Members: $12 . 0 0
Non-members: $20.00 Payment accepted in US dollars only.
Indicate your answers to the post-test questions by entering the correct letter(s) on the lines provided.
PAC S Storage Technology Update:
Holographic Storage
Questions?
Call 978/443-7591
or 800/334-2472
Mail or fax this answer sheet to:
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Attn: Continuing Education Credit
490-B Bosto n Po s t Road, Suite 101
Sudbury, M A 01776
Fax: (978) 443-8046
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M AY / J U N E 2 0 0 6
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