*From the Northwestern University Medical School (Drs. D. Rabin and Mintzer), Highland Park Hospital, Highland Park; and Loyola University Chicago (Dr. S. Rabin), Maywood, IL.
Correspondence to: David N. Rabin, MD, Northwestern University Medical School, Highland Park Hospital, 718 Glenview Ave, Highland Park, IL 60035
Coronary artery calcification quantification (scoring) has been
done with electron beam CT (EBCT), but is now being done with spiral or
helical CT. Many radiologists and cardiologists who do not have EBCT
but do have access to spiral CT will now be able to do coronary artery
calcification scoring, and will now need to know the spiral CT
appearance of the coronary artery anatomy. This pictorial review will
demonstrate the anatomy needed for coronary artery calcium
beam CT (EBCT) has been used for years to quantify coronary artery
calcification, although the clinical utility of screening for coronary
artery calcification is still controversial. Coronary artery
calcification quantification is now starting to be done with spiral CT
technology. Spiral CT for coronary artery calcification scoring will
change this formerly esoteric technique into a common and perhaps
almost universally available screening test. Knowledge of coronary
artery anatomy as seen on spiral CT is now becoming important to
radiologists and cardiologists, since spiral CT is commonly available
and EBCT is expensive and has limited availability. This review article
will demonstrate the coronary artery anatomy as seen on spiral CT. The
images have been obtained with a CT/i Spiral CT scanner (General
Electric; Milwaukee, WI). These images demonstrate the image
quality that can be expected from routine spiral CT evaluation
of the coronary arteries using special cardiac imaging software
(Smartscore; General Electric).
Evaluation of the coronary arteries is performed with images from near
the carina of the lung to the bottom of the heart. Each rotation of the
scanner attempts to capture data for one 3-mm image. The acquisition
technique is selected as a function of heart rate and CT-scanner
rotation speed, such that the table advances by 3 mm in each heartbeat.
From the acquisition images, the software creates reconstructed images
every 0.1 s or 0.3 mm, so that 10 reconstructed images span each
cardiac cycle. The study is retrospectively gated with the patient’s
ECG, which was obtained during the image acquisition. Diastolic images
are selected from the reconstructions, so that images used in coronary
artery calcification scoring have the least amount of motion, since
motion blurring would increase the apparent size and score of
calcium. Heart rates > 90 beats/min are currently not scanned.
Misregistration artifact is decreased by acquiring the images in the
same part of the cardiac cycle.1
Coronary artery calcification quantification is then performed on
selected diastolic reconstructions using Smartscore at a workstation.
Early reports indicate that coronary artery calcification
quantification of retrospectively cardiac gated spiral CT are highly
correlated with the results obtained from EBCT.2
Coronary artery calcification scoring requires a thorough understanding
of the anatomy of the coronary arteries that are evaluated in the
study. Coronary artery calcium quantification is performed for
the left main coronary artery (LMA), left anterior descending
artery (LAD), left circumflex artery (LCX), right coronary artery
(RCA), and the posterior descending artery (PDA). These are all easily
recognized using these special spiral CT techniques. We trace each
individual coronary artery from its origin to the inferior aspect of
the heart on contiguous images.
The first coronary artery seen (starting superiorly from its origin) is
the LMA. The LMA arises from the left sinus of Valsalva (Fig 1
) and courses to the left posterior to the main pulmonary artery. The
LMA bifurcates into the LAD and the LCX (Fig 2
). The LAD runs anteriorly in the anterior interventricular groove. The
LAD gives off septal and diagonal branches (Fig 3
), and we quantify the calcium seen in branches of the coronary
arteries. Septal or diagonal calcium would be counted as calcium in the
LAD. The LCX runs to the left and inferiorly in the posterior
atrioventricular groove (Fig 4
).3 The LCX gives off marginal branches, which supply the
The RCA originates more caudally from the aorta than the LMA. The RCA
arises from the right sinus of Valsalva (Fig 5
). The RCA runs anteriorly and to the right, and then courses
inferiorly. The RCA runs in the anterior atrioventricular groove. The
RCA and LCX can be followed inferiorly toward the apex of the heart
, top and bottom).
The PDA usually arises from the RCA. Coronary artery dominance is
defined by which coronary artery gives rise to the PDA. The RCA is
dominant in 70% of people with the RCA giving rise to the PDA (Fig 7
). In 10% of people, the left coronary artery is dominant, and the LCX
reaches the crux of the heart and continues as the PDA. In 20% of
people, there is a balanced system in which the RCA gives rise to the
PDA, but the LCA also supplies branches which supply this area of the
left ventricle. The LCA supplies the majority of blood to the left
ventricle, even in people who have a right dominant
system.4 The PDA extends to the apex of the heart in the
posterior interventricular groove, and frequently meets branches of the
LAD at the apex of the heart.
There are potential pitfalls when using CT to evaluate coronary
artery anatomy. The LAD may extend above or in a cephalic direction, so
that portions of the LAD may be more cephalic than the LMA (Fig 8
). If this is not recognized, then calcification in this part of the LAD
will not be scored, resulting in a score that is incomplete and
potentially misleading. Coronary veins may be confused with coronary
arteries (PDA; Fig 9
) at the caudal aspect of the heart. These vascular structures, however,
can be traced back to the coronary sinus on contiguous images, proving
that they are veins.
Spiral CT can demonstrate coronary artery anatomy and can demonstrate
coronary artery calcification (Fig 5) when the coronary artery anatomy
Abbreviations: EBCT = electron beam
CT; LAD = left anterior descending artery; LCX = left circumflex
artery; LMA = left main coronary artery; PDA = posterior descending
artery; RCA = right coronary artery
General Electric paid another institution for electron beam CT studies
and paid Highland Park Hospital for some spiral CT studies so that we
could compare spiral CT and electron beam CT results in a current
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