Coronary Artery Calcification Scanning in Asymptomatic
Patients: A Controversial Examination Further Complicated by
Electron Beam CT versus Multislice CT Battles
Our practice has been involved in the detection and
quantification of coronary artery calcifications by electron beam
CT (EBCT) scanning for well over a decade. We have been involved in
numerous research projects initiated by many services: Radiology,
Cardiology, Preventive Medicine, Hypertension, Endocrinology, and
the Emergency Department. We have participated in multicenter
studies, international workshops and symposia, and have tried to
stay abreast of what is happening in academic and private practice
settings. I presented one of the first studies correlating
conventional angiography with EBCT at the 1990 RSNA meeting. We are
still actively involved in several calcium projects. With that
fairly extensive background, the following points sum up all what I
really know about the topic of CT-detected coronary calcium:
* Having no calcium is probably a good thing.
* Having lots of calcium, especially when compared to your age
group, is probably bad thing.
* Having some calcium, but not lots for your age, is probably
not as good as having no calcium, but it might be years before we
know what it really means.
* The public currently wants this exam.
The last point, public demand, might be the worst reason to
perform this examination, but it is the only point that I am sure
about. Direct marketing of this "painless, inexpensive, 10-minute
exam promising to tell you if you are at risk of dying from the big
one" has literally forced traditional radiology practices into
selling gift certificates for scans that you buy for your loved
ones and business partners. If they don't, their competitors will.
Should the people who have promoted this situation be called
villains or visionaries? You will find support in the literature
for either position.
Radiologists (and pathologists) have reported the use of X-rays
for detecting coronary calcifications as a marker of
atherosclerotic disease for more than a half century with the
initial reports from autopsied hearts. One of the most often quoted
studies supporting the prognostic value of coronary artery calcium
detection was performed in the 1970s and utilized fluoroscopy.
Despite what appeared to be a useful, simple, and painless
noninvasive test to predict future coronary events, fluoroscopy for
coronary disease never flourished and quietly went away. In the
early 1980s, CT scanning of the chest began and it was obvious that
coronary calcium deposits could be seen with greater sensitivity
than fluoroscopy. But it was not until the late 1980s, with the
ability to freeze cardiac motion by EBCT, that the detection of
small calcific deposits could be made reliably. This also resulted
in a standardized method to attempt to quantify the amount of
coronary calcium present. An "Agatston Score" could be determined
by multiplying the area of calcified plaque by a density-weighting
factor based on the peak Hounsfied number of the calcium deposit.
While standardized, the method remains controversial as to the
reliability and reproducibility of Hounsfield numbers in patients
of various sizes and on serial examinations. A calcium score can
easily be doubled by the change in a few Hounsfield units due to
the multiplying weighting factors that were initially arbitrarily
assigned by Agatston et al.
Partial volume averaging is another variable that compounds the
problem of measuring very small deposits with the standardized 3-mm
slice thickness utilized by the EBCT method. Some investigators
have abandoned the weighted score for what appears to be a more
accurate and reproducible measurement of the area of calcium that
meets a minimum CT number threshold. There are other potential
pitfalls to accurate and reproducible measurements. The scan
acquisition is triggered by the ECG and therefore ectopy can
significantly affect accurate detection and scoring. Despite the
very short acquisition 100-msec acquisition time, relatively rapid
heart rates will result in blurring and smearing of calcium
deposits, especially in the right coronary. The figures that
accompany this article are representative of the problems we see on
a daily basis. Our clinical and research practice is to routinely
perform dual scans on all patients in an attempt to minimize
Notwithstanding the known limitations, recommendations for
asymptomatic patient care based on EBCT calcium scores have been
published by Rumberger et al
and are often quoted not only in the literature, but also on the
report forms of many imaging centers offering coronary scans. This
is common practice at both EBCT and spiral CT sites. These
recommendations, intended specifically for EBCT examinations, are a
result of a consensus statement from an experienced group of
investigators and their review of the literature available up to
1999. While there is little debate that a score of 0 indicates an
extremely low likelihood of any significant obstructive disease,
the remaining absolute score guidelines remains controversial.
Using these guidelines, a score of 10 in a 40-year-old woman
implies "very low risk," however a score of 11 triggers a "moderate
risk" for future cardiac events and a much more aggressive
treatment plan. In reality, and the authors of the guidelines will
also espouse, a reliable score of 10 in a 40-year-old woman places
her above the 99% rank for quantity of calcium when compared with
age- and gender-matched controls and probably should result in very
aggressive risk-factor modification. Recent literature supports the
matching of scores with their age and gender controls to provide a
more accurate estimation of risk for future cardiac events.
In my opinion, the bigger problem is the accuracy of such low
scores and their reproducibility (Figures 1 through 4). Some
authors (and especially vendors) have suggested that ECG-gated
spiral multislice CT (MSCT), with better signal-to-noise and
spatial resolution compared with EBCT, might provide a more
accurate detection, and therefore measurement, of coronary calcium.
In addition, MSCT can offer 4 to 16 thinner contiguous slices to be
obtained per scanned heartbeat compared with the single-slice only
mode of EBCT; therefore improving partial volume averaging errors.
EBCT supporters will quickly point out the still significant
temporal resolution advantage of EBCT (100 msec scans) over even
the fastest MSCT (approximately 250 msec) in conventional
ECG-triggered step-and-shoot mode. Continuous spiral mode with
retrospective ECG reconstruction can result in MSCT effective
imaging times of under 100 msec, but at the cost of significantly
increased radiation dose and with potential additional motion
Nonetheless, once you have measured a volume of calcium, you can
apply the same Agatston scoring method with the generation of a
calcium score. With the more photon-rich image, the signal-to-noise
will be improved over EBCT, but the reliance on Hounsfield numbers
and density multipliers will remain a source of significant
potential reproducibility errors. The potentially more accurate and
reliable volume measurement of calcium might be further improved by
MSCT. Whatever type of scoring you wish to report, CT vendors of
spiral scanners all provide scoring software packages along with
marketing aids and strategies that will get your site up and
running before you competing radiology or cardiology group can
promote their coronary calcium screening exam.
When trying to risk stratify an individual scanned on a spiral
scanner, does it matter that the huge database that exists for
trying to make sense of a calcium score is from EBCT?
This is a great question that awaits adequate validation or
refutation. EBCT supporters vocally state that current claims by
MSCT vendors are unsubstantiated. Peer-reviewed literature of
existing comparison would suggest that MSCT and EBCT calcium score
measurements are similar and both with clinical utility.
We are one of numerous sites that have EBCT scanners installed feet
away from MSCT scanners and are performing side-by-side comparison
studies. My best guess, based on our comparison scans performed to
date, is that both EBCT and MSCT will have clinical utility. Both
will likely provide more than sufficient quantification data for
the necessary longitudinal outcome studies that someday might
enlighten us all as to the prognostic value for measuring calcium.
I am not alone in being both a believer and somewhat of a skeptic.
The American Heart Association states support of various clinical
uses for coronary calcium scanning, but stops short of recommending
widespread scanning of the asymptomatic public.
It may be that knowing your calcium score or volume is more
important than knowing your lipid profile, but third-party payers
and the government are not yet convinced. Most likely, cash or
credit cards, and not your policy number, will be needed to buy
that gift certificate for screening for you and your loved ones
next holiday season, and possibly for many more seasons to
Coronary artery disease will remain the number one killer for
the foreseeable future. Diagnosing and treating it will remain a
very big business; calcium screening is now established as part of
that business. CT scanning for coronary calcium, whether by EBCT or
MSCT, is probably the most practical, sensitive, noninvasive way to
document the presence of the atherosclerotic process in the
coronary circulation. Isn't that what a screening test should do
for this often silent killer? The test is not perfect by either
method and further proof of clinical efficacy will be needed to
convince those controlling reimbursements. But if you would like to
know if you have none, some, or lots of atherosclerotic disease in
your coronary arteries compared with your peers, these tests will
do just that. I know my calcium score, and I sleep better knowing
that it remained 0 over a recent 5-year period. Do you know your
score? Are your curious or would you rather not know, especially if
you have the dreaded "some calcium, but not lots" for your age? We
can hope that future investigations will answer all of our
questions, but we are likely years away from any consensus. In the
meantime, you can fill those years reading the volumes of
literature that has already been generated. The references listed
below are but a minute fraction of what is in print. See if you can
sort it all out. If you do, please give me a call.
1. Agatston AS, Janowitz WR, Hildner FJ, et al. Quantification
of coronary artery calcium using ultrafast computed tomography.
J Am Coll Cardiol.
2. Rumberger JA, Brundage BH, Rader DJ, Kondos G. Electron beam
computed tomography calcium scanning: A review and guidelines for
use in asymptomatic persons.
Mayo Clin Proc.
Pediatric Helical CT: Radiation Issues
Caroline L. Hollingsworth, MD and George S. Bisset, MD
Pediatric body CT is a well-established and increasingly
utilized diagnostic tool. During the past decade, helical
technology has accelerated this trend with increased options for
scan technique including kilovoltage, tube current, collimation,
and pitch, as well as dramatic further reduction in time necessary
for acquisition of volume data sets. The fast-paced technological
advances and increasing availability of multidetector CT will
provide further available options for scanning. Although there are
numerous articles in the current literature addressing contemporary
techniques and evolving applications of adult helical CT, there is
little information on the optimization of pediatric helical CT.
This may be due to the fact that many more variables must be
addressed including techniques for intravenous and oral contrast
material administration, variable delays in onset of scanning, and
consideration of the size of the child when choosing parameters
that affect radiation dose. Although successful helical CT data
acquisition in children is complex and often requires attention to
each individual child rather than adherence to protocol, diagnostic
scanning can be achieved. Recently, guidelines for size-based
scanning with single-detector helical CT have been published.
However, CT parameters are not always adjusted for pediatric
scanning. Given the complexities of helical scanning, there is
potential for children to be imaged with scan parameters that
impart increased radiation dose.
Although the radiation imparted by CT has been an important
consideration since its introduction more than 30 years ago, this
issue has recently gained much more attention with the introduction
of multislice CT (MSCT). This technology potentially delivers a
higher radiation dose than conventional (helical) CT. Radiation
dose due to CT can be considered a public health concern for
several reasons. First, CT has become a significant source of
radiation to the general population, second only to background
sources, and children account for approximately 11% of all CT
Moreover, although guidelines for size-based scanning have been
published, children are often scanned without adjustments in
technique, exposing them to unnecessary radiation.
This is important both because children are more radiosensitive to
the same organ dose than adults, and because there is a potentially
longer time in which radiation-induced malignancies could develop.
We now realize that the relationship between low-level CT radiation
and cancer is much closer than previously believed.
Together, these facts mandate that radiation be minimized.
A number of strategies for reducing radiation dose to children
have been put forth including use of other modalities that can
provide sufficient diagnostic information and changing the paradigm
of image quality from optimal (high dose) to acceptable. These
suggestions support limiting use of multiphasic examinations,
basing the scan on clinical question examinations may also be
limited in their scope, for example, patients may not need pelvic
CT to evaluate pancreatitis. Also, adjusting scan parameters for
the region and using size-based techniques (adjusting tube current)
are valuable. A weight-based protocol has been suggested by
Donnelly et al.
Another size-based system is a color-coded format derived from the
Broselow-Luten pediatric color-coded system.
This system assigns a color to each child based on length or weight
and designates appropriate resuscitation and support equipment
based on the specific color. The color zones were created based on
anatomic and physiologic parameters affecting emergency support of
children and, therefore, are not divided by equal weight
increments. This system has been shown to decrease error rates in
pediatric emergency rooms
and can be applied to many other health care issues affecting
children. This last point is particularly important as healthcare
continually becomes more complex. By providing a single protocol
scheme for many facets of children's healthcare, medical errors may
The color-coded approach to pediatric body CT scanning is used
at our institution. Protocols address scan parameters affecting
table speed, gantry rotation, radiation dose, and administration of
contrast media. Children are classified into specific color zones,
which were established in the original study,
with the addition of a ninth color zone for children between 40.5
and 55 kg (children in this weight range were not included in the
original Bruselow-Luten color scheme). Children who weigh more than
55 kg (approximately 120 pounds) are scanned with adult protocols
regardless of age. Importantly, recent work at our institution has
shown that our technologists strongly prefer the color-coded
protocols over standard weight-based protocols. In a survey, there
were fewer errors and the technologists overwhelmingly favored the
color-coded system to a standard weight-based protocol.
Helical CT scanning has become an invaluable tool for imaging
children. Although scanning children often presents unique
challenges, diagnostic scanning can be achieved. Attention to the
individual child and diagnostic question to be addressed, and the
use of appropriate scan techniques can provide excellent results
while minimizing risks, even in the most complex circumstances. The
implementation of a color-coded system for pediatric helical body
CT allows a reproducible format for CT protocols and reduction of
radiation dose while helping to minimize errors in scan technique.
Reduction in radiation dose can be achieved while preserving
acceptable scan quality and standardized imaging. This system has
potential applications across a wide array of care issues in the
Practical Approach to Adult Renal Masses: Emphasis on
Brian J. Jellison, MD and Fred T. Lee Jr., MD
Historically, the role of the radiologist in the work-up of
potentially malignant renal neoplasms has been limited to detection
and preoperative staging. If the patient was a surgical candidate,
the majority of these masses were removed via radical nephrectomy.
Recently however, nephron-sparing surgery, laparoscopic
nephrectomy, and less-invasive percutaneous ablative techniques
(most notably cryotherapy and radiofrequency ablation) have become
more standard therapy for small renal masses. These treatment
options require a thorough investigation of the anatomy of the
kidney, renal vessels, and surrounding tissue. Therefore,
multislice CT, sometimes combined with CT angiography, now plays a
dominant role in the pretreatment evaluation of renal masses.
Malignant solid renal masses include renal cell carcinoma (RCC),
transitional cell carcinoma, lymphoma, and metastases. Any renal
mass with solid components should be viewed as malignant until
proven otherwise. Renal cell carcinoma is characterized at CT by a
solid or mixed solid and cystic (heterogenous) enhancing mass that
is less dense than enhancing renal parenchyma. Hemorrhage and
necrosis are common. In up to 10% of cases, central calcifications
are identified. Staging of RCC depends on accurate evaluation of
local spread, including invasion through the renal capsule, fascia,
lymph nodes, and into vascular structures, such as the renal vein
and inferior vena cava (Figure 1).
Benign solid masses include oncocytoma, adenoma, angiomyolipoma,
and xanthogranulomatous pyelonephritis. No imaging features
reliably distinguish oncocytomas and adenomas from RCC, therefore,
they are treated as malignant neoplasms. Cystic renal masses
include simple and complex cysts, abscesses, cystic RCC, and
multilocular cystic nephromas. Because of the overlap in appearance
of cystic RCC and complex renal cysts, the Bosniak classification
was introduced in 1986 in an attempt to separate cystic renal
masses into two groups: surgical (high risk of malignancy), and
non-surgical (low risk of malignancy).
More recently, this classification has expanded to include the use
of ultrasound and MRI.
The exact CT protocol for evaluating potential renal masses will
depend to a degree on the type of CT scanner, but several
fundamental principles are important. There are two reasons why
noncontrast scans are performed prior to contrast-enhanced scans:
1) enhancement of a renal mass by >10 HU is a worrisome sign of
malignancy, and 2) noncontrast scans allow the radiologist to
evaluate calcifications without mistaking them for excreted
contrast material. Therefore, the kidney should be scanned without
IV contrast (preferably by ¾5 mm increments), followed by scanning
after the administration of contrast. The timing of the scan
through the kidneys after IV contrast is controversial, but
numerous studies have demonstrated improved detection of small
renal masses during the later nephrographic phase (approximately 2
minutes after injection) versus the earlier corticomedullary phase
(approximately 40 to 90 seconds after injection).
At The University of Wisconsin, we perform noncontrast,
corticomedullary phase, and nephrographic phase sequences (Table
1). For CTA, three-dimensional postprocessing of the CT datasets,
including volume rendering and maximum intensity projections, are
obtained with the Advantage Windows Workstation 4.0 Software (GE
Medical Systems, Waukesha, WI) with volume-rendering
Detection of small renal masses can be difficult during the
corticomedullary phase due to lack of contrast opacification of the
renal medulla (Figure 2). Many centers now perform multiphase CT,
including noncontrast, corticomedullary, nephrographic, and delayed
images when evaluating renal masses. Multiphase CT has also been
assessed in the initial evaluation of microscopic hematuria.
Although the nephrographic phase remains important in the detection
of small renal masses, the corticomedullary phase is essential for
detection of renal vein extension and parenchymal organ involvement
by metastases. The pattern of contrast enhancement of renal masses
could also prove helpful, with one recent study describing
characteristic enhancement patterns of papillary subtypes of RCC.
Contrast-enhanced CT remains the study of choice in the
evaluation and staging of renal masses, with staging accuracy
reportedly as high as 91%.
However, two indications for MRI include: the patient with renal
insufficiency and/or with a history of contrast allergy who is
unable to receive IV contrast material; and to evaluate the renal
veins and inferior vena cava (IVC) for tumor thrombus prior to
nephrectomy. MRI has the advantage of multiplanar capability, thus
the renal veins and IVC can be imaged in an oblique coronal format.
MRA sequences for the renal veins and IVC can also be useful to
characterize tumor thrombus. Compared with CT, MRI most likely has
increased sensitivity for the diagnosis of renal vein and IVC tumor
invasion, although this has not been studied recently. MRI
protocols vary depending on the particular sequence, but generally
T1 pre- and post-gadolinium injection (especially with fat
suppression), T2, and gradient-echo sequences with IV contrast are
As with CT, enhancement of a renal mass is highly suspicious for
Three-dimensional postprocessing of CT datasets provides a more
complete evaluation of renal masses than axial images alone,
including the relationship to renal vessels and the collecting
system (Figure 3). The use of advanced processing techniques and
optimal protocols is likely to increase in importance as newer,
less-invasive treatment options become more widespread.
1. Bosniak MA. The current radiological approach to renal cysts.
2. Cohan RH, Sherman LS, Korobkin M, et al. Renal masses:
Assessment of corticomedullary-phase and nephrographic-phase CT
3. Lang EK, Macchia RJ, Thomas R, et al. Computerized tomography
tailored for the assessment of microscopic hematuria.
4. Herts BR, Coll DM, Novick AC, et al. Enhancement
characteristics of papillary renal neoplasms revealed on triphasic
helical CT of the kidneys.
AJR Am J Roentgenol.
5. Kopka L, Fischer U, Zoeller G, et al. Dual-phase helical CT
of the kidney: Value of the corticomedullary and nephrographic
phase for evaluation of renal lesions and preoperative staging of
renal cell carcinoma.
AJR Am J Roentgenol.
6. Bechtold RE, Zagoria RJ. Imaging approach to staging of renal
Urol Clin North Am.
7. Narumi Y, Hricak H, Presti JC Jr., et al. MR imaging
evaluation of renal cell carcinoma.
8. Pretorius ES, Wickstrom ML, Siegelman ES. MR imaging of renal
MRI Clin North Am.
9. Silverman PM.
Multislice Computed Tomography: A Practical Approach to
New York: Lippincott, Williams, & Wilkins; 2002.
eHealth Act of 2002: Grants for Provider Groups
Payers and larger healthcare entities are successfully adopting
new technologies for transaction processing and patient data
management at astounding rates. They do this in the face of smaller
operating margins and regulatory requirements, such as HIPAA and
CMS. This shift promises to follow in the footsteps of the
financial services industry by creating efficiencies through
standardized transaction processing and improvements.
The transition is creating substantial financial and patient
management burdens for provider groups and smaller acute care
clinics. Groups of all sizes face broad-based changes in
requirements for reimbursement processing and patient information
storage and security. Even small provider groups now face a
confusing array of different and seemingly incompatible systems and
requirements. On average, more than a half-dozen software
applications are used to gain a current "snapshot" of a single
patient's overall status, diagnosis, treatment, and reimbursement.
While a comprehensive electronic medical record software package
may solve many of these issues, provider groups often find
implementation costs and decision-making prohibitive. The net
result is providers struggle with disparate and legacy systems that
require significant increases in manual processing by already
overwhelmed administrative staff who manage patient information
across multiple applications routinely. Experts estimate an
additional $17.6 billion must be spent over the next several years
for more efficient and secure record processing.
Help for Providers
Help in moving to a consistent secured standard for software and
Internet transactions and data retrieval may be on the way for some
provider groups. Unlike other recent regulatory bills such as
HIPAA, The Efficiency in Health Care Act, S. 2638, also know as the
"eHealth Act of 2002," if passed, requires payers and providers to
increase their use of information technology (IT)
it authorizes at least $350 million in grants to assist
Introduced by Senator Edward Kennedy (D-MA), the Bill is
intended to "encourage health care facilities, group health plans,
and health insurers to reduce administrative costs, and to improve
access, convenience, quality, and safety, and for other purposes."
Kennedy echoes government and business analysts in his belief that
widespread use of IT in the healthcare industry will save lives and
dollars each year "Reducing administrative costs to the level of
other industries would save enough to finance universal health care
several times over."
The Bill requires "each group health plan and insurer...to have
in effect an automated, integrated system that allows for efficient
and effective adjudication of claims and the detection of fraud and
These systems must be capable of accepting and accurately
processing claims with 99% accuracy.
The proposed legislation requires the "installation and use of a
computerized physician order entry by all healthcare facilities"
to reduce medication errors. The Bill specifies that the Secretary
of Health, acting through the Agency for Healthcare Research and
Quality and with assistance from an advisory group, would establish
standards for computerized order entry.
To assist providers, the Bill authorizes $250 million for fiscal
year 2003 "and such sums as may be necessary for each of fiscal
years 2004 through 2007."
The proposed legislation provides grant preference for providers
operating in rural areas and those treating large numbers of
uninsured patients or those "in determination of the Secretary have
special needs for awards."
Additionally, the Bill authorizes matching grants for fiscal year
2003, "and such sums as may be necessary for each fiscal year
thereafter," to assist not-for-profit healthcare facilities with
implementing physician order-entry systems.
Critics focus on this lack of clarity in light of the healthcare
industry's frustration with continually changing guidelines for
HIPAA compliance. The Health Information and Management Systems
Society of Chicago expect that "Provider and payer organizations
likely will argue the true cost of the Bill would be billions of
dollars higher." The Bill's failure to provide grants to insurers,
healthcare facilities, and providers could substantially undermine
legislative approval and compliance.
The eHealth Act of 2002 compliance deadlines of 5 to 10 years
before withholding Federal plan payments is inconsistent with the
pace of technology. More than 70% of Information Technology
executives responding to an informal survey conducted by Health
Data Management said they expect the Bill will fall short of
positively impacting the healthcare focused software and
information technology industry.
While the Bill's goals are consistent with the healthcare
industry's substantial need for cost containment and quality
improvement, the eHealth Act of 2002 seems an unlikely vehicle for
dramatic change in healthcare information management.
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©2003 Anderson Publishing, Ltd.