Hi cogg,
I think you'll find that although the quality of digitized
conventional x-ray films is very high, 100% accuracy probably is not
routinely achieved. I've copied and pasted relevant sections of some
websites below but please click on the links for full details.
>>> Equipment
2004
The Ubiquitous Digitizer
"The first digitizers to come on the market used lasers to scan x-ray
film line by line and translate light and dark areas on the film into
numbers. Those numbers would be sent as electronic signals that would
then be decoded into images on a PACS or workstation on the receiving
end of the transmission."
"There is an alternative that is nearly as accurate, less expensive,
and easier to maintain. The latest digitizers use CCD technology,
short for charge coupled devices. Cannavo says that for most purposes
CCD images are indistinguishable from those produced by a laser
digitizer."
"Munie says the first CCDs presented only 256 shades of gray. Current
models present up to 4,096 shades, more than the 600 to 700 shades
that the human eye can detect "at a brightness of 1,000 candelas per
meter squared," he adds. "But a CT or an MRI image is presented in 256
shades anyway so presumably there was never a loss. When you go to the
plain film analog world, there are an infinite number of gray shades."
While more shades may marginally benefit interpretation in a very
bright image, the added gray tones take longer to digitize, so there
is a time tradeoff, Munie adds."
"That may be true for a lot of facilities. The niche for the digitizer
may get smaller. But as long as there is film to be transferred to
soft copy, there will always be a need for a digitizer. For the
foreseeable future, every facility will have at least one."
http://www.imagingeconomics.com/library/200406-08.asp
Hancock Medical Center: Solving the Problem of Low-Quality Film Copies:
"The largest benefit of the system is the image quality it delivers,"
Patterson says. "We asked the radiologists to compare copies created
with the CopyExpress system against the original films, and they said
they wouldn't have any qualms about reading from the copies. The
ability to produce high-quality duplicates allows us to keep our
originals in the department, which cuts down on the number of lost
films."
http://www.imagingeconomics.com/case/case_study_vidar-101002.asp
"Post-acquisition digitization has evolved over the years due to the
improvement in digital camera technology (see 4. Digital Cameras).
While flatbed scanning can still produce high quality images,
top-of-the-line transparency scanners are expensive and the process is
time consuming. With the advent radiographs are discussed. Digital
radiography systems and dedicated film scanners for postacquisition
digitization are considered acceptable because they meet the
resolution requirements and stamp the image with the appropriate data
to make it a legal document."
http://www.ivis.org/proceedings/aaep/2001/91010100437.pdf
How are plain films captured?
"Standard radiographs or plain film can be digitized by a film scanner
designed to produce the optical density and spatial resolution
acceptable to radiologists."
"Film scanners come in two basic configurations, CCD (Charged Coupled
Device) and laser. Laser film scanners are more expensive than their
CCD counterparts but they yield a much better image."
http://www.dataviewimaging.com/faq.htm#plainfilms
How are plain film (standard radiograph) images captured?
"Standard radiographs can be digitized by either a video camera or a
film scanner. Video cameras (commonly referred to as a"camera on a
stick") were in fact the method of digitizing ANY image for
transmission as recently as 5 years ago. Typical camera systems
utilize a light box designed to illuminate radiographs, an extension
arm for holding the camera above the film, and a high-sensitivity
video camera with a zoom lens. This is an inexpensive but poor-quality
method of image acquisition."
http://www.lumisys.com/support/techref/telerad_faqNew.html
VIDAR Film Digitizers:
http://www.ampronix.com/content/web/vidar_film_digitizer_index.asp
2001
Radiology goes filmless
Digitization of plain film radiographs
"Although conversion of conventional plain radiographic film to
digital data by means of a digitizer is the least efficient method, it
may prove useful in radiology departments that have a relatively low
volume of studies. In addition, this method is useful in larger
departments during the transition from a film-based system to PACS
(1). Traditional radiographic studies can be digitized so they can be
easily compared with the newer digital images."
http://www.postgradmed.com/issues/2001/06_01/naul.htm
U.S. National Archives & Records Administration (NARA)
Managing X-ray Films as Federal Records
X-ray Film Types
"The first X rays were recorded on glass plates coated with a
photographic emulsion. In 1918 Eastman Kodak introduced X-ray sheet
film coated on both sides. Over the years there have been three basic
film types: nitrocellulose or nitrate, safety cellulose acetate, and
polyester. Currently some X rays (and other medical imaging scans) are
made and stored as digital files or scanned from film originals;
either source can be printed out to hard copies on film or paper. NARA
plans to include a section on digital X-ray files in its guidance on
the management of electronic records."
Reproductions
* Several copying methods are available:
o Film to film
o Camera copies
o Microfilm
o Slides
o Film to glossy paper
o Digital processes which can yield hard-copy printouts
* Film copies should be made in accordance with ANSI
specifications (ANSI/PIMA IT9.1).
* For record or documentation purposes, reducing images to less
than half their original size is not recommended.
http://www.archives.gov/records_management/publications/print_friendly.html?page=managing_xray_films_content.html&title=NARA%20%7C%20Records%20Management%20%7C%20Resources%20-%20Managing%20X-Ray%20Films%20as%20Federal%20Records
>>> Studies
2003
Acad Radiol. 2003 May;10(5):536-42.
Conversion of teaching file cases from film to digital format: a
comparison between use of a diagnostic-quality digitizer and use of a
flatbed scanner with transparency adapter.
RESULTS:
"There was no statistically significant difference in diagnostic
accuracy between analog film and scanned images, but there was such a
difference between these two groups and digitized images. Accuracy was
97% for analog film, 94% for scanned, and 89% for digitized images.
Results of the McNemar test showed no statistically significant
difference in agreement between the analog film images and the scanned
images for any of the reviewers (P > .05)." CONCLUSION:
"A high-end flatbed scanner with transparency adapter provided
accurate, simple, and inexpensive conversion of analog film teaching
files to digital format, with no loss of the ability to detect or
diagnose subtle abnormalities such as interstitial lung disease."
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12755543
2003
Orthopaedic Traumatology from Afar: Are the Commonly Used Forms of
Digitized Radiographs Equal?
Results: A total of 180 questionnaires were completed for each subset
of radiographs. The fracture detection sensitivity was 99% for the
analog radiographs, 96% for the digital photographs, 94% for the
scanned images, and 93% for the eTrauma images. The differences
between groups were not statistically significant (P<0.05), except for
eTrauma images and original radiographs evaluated by resident
physicians. The original radiographs were significantly different in
their ability to show fracture comminution when compared with the
eTrauma images, but not in regard to articular involvement, timing of
treatment, or the type of treatment. Intraobserver and interobserver
reliability for all reviewers showed kappa values of greater than 0.40
for fracture detection, comminution, articular involvement, type and
timing of treatment, but not for assessment of image quality. All
values were statistically significant.
Conclusion: A wide variety of cost-effective readily available methods
can be used to digitize analog radiographs for transmission via email,
the Internet, or local area network with good diagnostic accuracy.
However, our investigation demonstrated that digitized images are not
a perfect representation of the originals in regard to fracture
detection, fracture specifics, or treatment plan. The gold standard
remains original radiographs, and our data supported their continued
use when rendering final treatment decisions. Original radiographs
should always be reviewed prior to obtaining additional diagnostic
studies."
http://www.aaos.org/wordhtml/anmt2004/poster/p212.htm
2004
Digitized analog radiographs are diagnostically accurate, but are not
perfect representations of the original analog radiographs.
Orthopaedic Traumatology from afar: Are the Commonly Used Forms of
Digitized Radiographs Equal?
Results: The fracture detection sensitivity was 99% for analog
radiographs, 96% for digital photographs, 94% forcanned images, and
93% for eTrauma? images. The differences between groups were not
statistically significant (p<0.05) except for eTrauma? images compared
to original radiographs evaluated by resident physicians. The
original radiographs were significantly different in their ability to
show fracture comminution when compared to the eTrauma? images.
Intraobserver and interobserver reliability for all reviewers showed
kappa values of greater than 0.40 for fracture
http://www.lumisys.com/support/techref/telerad_faqNew.html
2000
Evaluation of a digital camera for acquiring radiographic images for
telemedicine applications.
"Many rural sites cannot afford a digitizer to digitize radiographic
films and transmit them via a telemedicine network for review by a
radiology specialist. This project tested the feasibility of using a
consumer digital still camera to photograph radiographic images and
transmit them via a telemedicine network to a consulting hub site. In
this study, the feasibility of using a digital camera to photograph
plain film radiographs of 40 bone trauma cases from a rural health
center in Arizona was tested. The cases were transmitted to the
Arizona Telemedicine Program hub site using a private asynchronous
transfer mode network based on T1 carriers. Two orthopedic surgeons
and two radiologists reviewed the cases on a color monitor and the
original film images. The readers also rated image quality. There were
no significant differences in diagnostic accuracy between conventional
film and telemedicine reading. Diagnostic agreement between film and
monitor viewing was quite high, as was agreement in confidence
ratings. Image quality was generally rated as excellent to good in
both viewing conditions. Cases that did not correlate well were judged
to have poor image quality, or diagnoses were based on photographs
that had part of the diagnostic region of interest cropped off. It was
determined that a digital still camera can be used effectively in many
cases to photograph radiographic images for transmission and viewing
via a telemedicine network, as long as adequate views, zoomed in
regions of interest, and good quality original films are used in the
acquisition process."
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11110633&dopt=Abstract
2004
A Comparison of Scanned Lateral Cephalograms to Corresponding Original
Radiographs.
Conclusions: Although distortion was found, the relatively small
horizontal and vertical discrepancies did not impact cephalometric
analysis. Landmark identification errors on scanned images contributed
to the discrepancies in the cephalometric analysis. Therefore, for
most clinical orthodontic applications scanned cephalograms can be
used. However caution must be taken when determining Po and Or.
http://iadr.confex.com/iadr/2004Hawaii/techprogram/abstract_40966.htm
>>> Additional Links of Interest:
Participate in a study!
ORTHOPAEDIC DIGITAL IMAGE QUALITY
A Comparative Study
http://www.hwbf.org/dims/
Radiologic Science Web Resources: Medical and Radiology:
http://www.western.tec.wi.us/rad/wsrtlinks.htm#med%20resources
Taking X-ray Images to the Web, the process and use in Radiography Education:
http://www.micsymposium.org/mics_2001/raasch.pdf
The use of a QTVR image database for teaching veterinary radiology and
diagnostic ultrasound to distance education students. 2001
http://www.ascilite.org.au/ajet/ajet17/phillips.html
High Quality X-ray Film Duplication and Digital Imaging
http://www.medimaging.ws/pages/752213/index.htm
I hope this is what you were hoping for. If you have any questions,
please post a clarification request *before* closing/rating my answer
and I'll be happy to reply.
Thank you,
hummer
Google Search Terms Used:
Film Digitizers medical
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post acquisition digitization radiographs
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x-ray duplication |
