Advances
in Imaging--The Changing
Environment for the Imaging Specialist |
to pdf >>
By
John
Rego, MD; KM Tan, MD
Over
the last two to three decades, the demand for imaging services has
blossomed at an unprecedented rate. New modalities have either been
introduced as in magnetic resonance imaging (MRI) and positron emission
tomography (PET) or significantly improved as in computed tomography
(CT) and ultrasound (US).
The
increasing sophistication of cross-sectional imaging with very rapid
development and integration of interventional radiology into the
clinical arena has had a dramatic impact on patient care. The imaging
specialist now faces a remarkable transition in his/her work environment.
Bryan
refers to two separate but related phenomena.1 The marked
increase in information available from modality advances, and now
available in three dimensions, accompanied by technology allowing
extensive digital manipulation of such data presages a new era in
medical imaging.
Digital
data and technology have revolutionized the imaging field. The electronic
acquisition, interpretation, transmission and storage of image data
has not only increased access for patients but also benefits their
referring physicians. Imaging interpretations are available earlier
and more readily, and there is almost instantaneous access to these
examinations on their office computers. This, of course, mandates
an integrated information enterprise that all Kaiser Permanente
(KP) Regions have now or will have soon. Picture archiving and communications
systems (PACS), radiology information systems (RIS), and hospital
information systems (HIS) all contribute to seamless acquisition
of image data through PACS, which, together with information from
the RIS and the HIS, result in rapid interpretation available to
clinicians together with the original images pulled from archival
storage. Thus, images and reports are at the right place at the
right time.
This
technology has inevitably resulted in increasing efficiencies, particularly
during off hours, allowing one radiologist to offer interpretation
coverage for 17 hospitals in Northern California. A similar situation
prevails in Southern California (see article here). It allows immediate
access during the working day to subspecialty imaging expertise
of multiple experts located throughout the Region and also allows
the ability to provide interpretation services to some of the personnel-strapped
Regions both within and outside of California.
|
Radiologist
Kurt Dibbern with a digital PACS setup for reading apropos.
|
Perhaps
nowhere else in medicine has there been such rapid advance in technology
than in CT scanning. With the advent of multidetector CT (MDCT)
five years ago and, more recently volume CT (VCT), a relatively
quiet revolution has taken place. CT scanners are now capable of
obtaining 128 slices in less than one second. The entire chest,
abdomen and pelvis can now be examined with submillimeter imaging
in less than 15 seconds. This has led for the first time to true
CT volume imaging where image reconstruction can take place in any
plane with equal resolution.
We
are just beginning to feel the impact of this very valuable tool
in such areas as vascular imaging and virtual colonoscopy. The VCT
has replaced peripheral diagnostic angiography in many centers and
is poised to do the same for diagnostic coronary angiography. In
the study of the colon, VCT has been shown to be superior to barium
enema, approaching the sensitivity of colonoscopy in the detection
of polyps larger than 9 mm.2
Advances
in software have allowed almost instantaneous display of the images
in shaded 3-D representations. This is proving invaluable in preoperative
planning. The addition of CT fluoroscopy has allowed rapid, accurate
real-time placement of biopsy needles, drainage catheters, and therapy
devices.
As
the technology advances, several vendors plan to introduce scanners
that will acquire up to 512 images per half second with coverage
of 12 cm. This will allow for perfusion imaging where viability
of tissue can be evaluated. Coronary arterial and myocardial viability
will be able to be evaluated simultaneously. Beyond 512 imaging,
scanners are being tested that will use large-area detectors that
will allow examination of the entire abdomen in just one pass of
the x-ray tube.
Advances
in MRI are equally as remarkable. As the 1.5T technology matures,
there is new technology in the form of 3T-fieldstrength magnets
that allow for faster, more detailed, and thinner imaging sections
than its 1.5T counterpart. MRI is showing that it can compete with
CT in noninvasive imaging of the heart. Multiplanar real-time images
of the beating heart can now be obtained that allow for full, functional
assessment of the heart. With contrast, perfusion studies can also
be obtained.
MRI
remains the imaging examination of choice for musculoskeletal and
neurologic applications and will continue to compete with CT in
evaluation of the vascular tree. And many new applications of MRI
will spur further growth. For example, in the breast, with the use
of gadnolinium contrast agents, MRI is proving to be very sensitive
for detection of small breast cancers. Its role in this regard is
still being evaluated. When coupled with focused high-energy ultrasound,
MRI can be used to guide noninvasive tumor therapies. It has shown
its usefulness in treating such tumors and uterine fibroids and
in limited applications of other visceral tumors.
Spurred
on by miniaturization and by advances in computing power, the applications
of ultrasound continue to grow. It is now possible to do high-quality
ultrasound on devices the size of a laptop computer. Some devices
in development are no larger than a PDA; these may indeed be the
stethoscopes of the future. Three- and 4-D ultrasound have been
further refined and are now being used in fetal imaging and ultrasound
contrast imaging. Voice recognition and real-time image optimization
(tuning of the image to the patient's own acoustic properties) have
improved patient workflow. With the pending approval of ultrasound
contrast agents, ultrasound will compete with CT and MRI in the
evaluation of the liver.
Interventional
radiology continues to grow as procedures migrate from the OR to
the IR suite. Stents and stent grafts have dramatically changed
the practice of vascular surgery. Vascular surgeons and interventional
radiologists have joined forces in many labs with a merging of their
two specialties. Percutaneous tumor ablation, stabilization of vertebral
body fractures, tumor embolization, venous ablation and recanalization
are all procedures now common to the interventional labs.
64 slice CT scanner now used for cardiac work. |
New
flat panel detectors have improved image quality and decreased radiation
dose. New rotation angiographic techniques have allowed 3-D vascular
image displays. With tube rotation it is now possible through post
processing to obtain multislice CT images from the IR equipment.
Digital
image acquisition has replaced film throughout the Radiology Department.
Digital detectors are now used instead of film to allow immediate
image review. This advance has lead to an increase in image quality
and a 50% decrease in imaging time. Dual-energy subtraction has
allowed improved evaluation of the lungs by subtraction of the bony
structures. Additional application of computer-aided diagnosis (CAD)
has led to a 10% increase in tumor detection in the chest and breast.
This same application is being trialed in CT colonoscopy as well.
Thus
several trends are becoming clearer. The earlier and more frequent
use of imaging will continue with a shortening of the initial clinical
evaluation. As indicated above, the 64-slice CT scanner will allow
immediate evaluation of a patient's chest pain, allowing differentiation
between a benign situation and the possibility of a heart attack,
an aneurysm, or a pulmonary embolism.
Technology
will continue to drive care from the hospital. Decreasing cost and
size of equipment will allow CT and MRI to devolve outside the hospital
Radiology Department into freestanding situations.
The
readily available image distribution process ironically will decrease
reliance on the radiologist and there will be an enhanced shift
to proactive, prophylactic screening in imaging. Computer-assisted
detection and diagnosis in the areas of breast, lung, and colon
disease are but a harbinger of such use in all clinical areas. Last
but not least, functional and metabolic imaging is becoming a reality,
and the promise of genetic and molecular marker imaging is not far
behind.
One
issue merits ongoing discussion and research. Advances in technology
serve as one of the most important drivers of health care spending
growth. Currently in the United States, medical care consumes more
than 14% of the gross domestic product and is likely to reach 17.7%
by 2012.3
Increases
in the supply of specific technologies such as CT and MRI are associated
with higher numbers of procedures per population and with consequent
higher health care spending. Experience has shown that co-existence
of CT and MRI is not complementary but supplementary. Thus, MRI
availability does not offset CT use.4
While
there may be a legitimate argument for bypassing the current progression
of imaging tests from the least expensive to more costly examinations
in favor of expensive high-tech imaging as a first-time test that
provides more information, the effect is a distinct overall increase
in health care spending. With the number of uninsured Americans
approaching 50 million and with more of us unable to afford soaring
health care costs, it is appropriate to question to what extent
we can and should continue to spend dollars in pursuit of increasing
diagnostic capabilities that in turn increase the probability of
detecting multiple benign abnormalities and the consequent need
to resolve them. Can we afford an "arms race" among manufacturers
as they continue to outdo one another in the increasing detail and
sophistication of their imaging devices? Is it appropriate to tolerate
surging health care costs, especially in view of the lack of well-planned
cost effectiveness and outcomes studies to support the increasing
use of such modalities?
References
-
Bryan RN. The digital rEvolution: the millennial change in medical
imaging. Radiology 2003 Nov;229(2):299-304.
-
Pickhardt PJ, Choi JR, Hwang I, et al. Computed tomographic virtual
colonoscopy to screen for colorectal neoplasia in asymptomatic
adults. N Engl J Med 2003 Dec 4;349(23):2191-200. Epub2003 Dec1.
-
Gazelle GS, McMahon PM, Siebert U, Beinfeld MT. Cost-effectiveness
analysis in the assessment of diagnostic imaging technologies.
Radiology 2005 May;235(2):361-70.
-
Baker L, Birnbaum H, Geppert J, Mishol D, Moyneur E. The relationship
between technology availability and health care spending. Health
Aff (Millwood) 2003 Jul-Dec; Suppl Web Exclusives:W3-537-51.
