Kevin R. Johnson, PhD
kevin.johnson@jax.ufl.edu
Department of Radiology
University of Florida College of Medicine - Jacksonville
Electron Beam CT
1980s
4 Slice Spiral CT
1998
16 Slice
2001
64 Slice
2004
Dual Source
2005
128, 256, 320 Slice
2006 to present
Flat Panel CT
???
Voros, JCCT, doi: 10.1016/j.jcct.2008.12.010
Scanners getting larger and getting faster
Gantry rotation times decrease from
1s
500ms
400ms
370ms
330ms
300ms
Faster rotation speed, better temporal
resolution and image quality
Best temporal resolution:
270ms
68 ms with bisector reconstruction (HR dependent)
75 ms with dual source (HR independent)
Shortening
Thickening
Twisting
15 male patients
Avg: 55yrs, 66bpm
P
M
P
M
D
Angiography at 30
frames/sec
D
Motion tracked for one heart beat.
Motion was averaged and interpolated
to 5% increments of the cardiac cycle.
Result: 3D trajectories during the cardiac
cycle of proximal, mid, and distal
segments of the RCA, LAD, and LCX
coronary arteries.
Johnson, et al. J of CV M R 2004;6:663-673.
Early
Systole
Early
Diastole
Atrial
Systole
Late
Systole
Mid
Diastole
165 msec
83 msec
trot = 330ms
HR = All heart rates
Temporal
resolution
½ trot = 165ms
trot = 330ms
HR = 81bpm
Effective temporal
resolution
¼ trot = 84ms
Overlapping,
redundant data
trot = 330ms
HR = 70bpm
Missing data
Effective Temporal Resolution (msec)
180
Trot = 330 ms
160
140
120
100
80
60
50
60
70
80
Heart Rate (bpm)
90
100
110
PROS
CONS
Improved temporal resolution
Decreased motion artifacts
Increased dose
Beat-to-beat variation
Figure courtesy of Siemens Medical Solutions
Blood and surrounding tissue mostly water
Must use high attenuation contrast agent
Contrast volume and injection rate
dependent on body part and scanner speed
Dual Energy Index, DEI =
µ80 – µ140
µ80 + µ140 + 2000
Visualization of iodine in the myocardium
Visualize perfusion defects
Tight proximal
stenosis D1
74-year old woman with chest pain and abnormal SPECT
Courtesy of Dr. U. Joseph Schöpf, MUSC, Charleston, USA
SPECT
Dual Energy CT: Iodine image
74-year old woman with chest pain and abnormal SPECT
Courtesy of Dr. U. Joseph Schöpf, MUSC, Charleston, USA
Anatomy and “perfusion” in a single image
Stenosis
Perfusion defect
Dual Energy CT
74-year old woman with chest pain and abnormal SPECT
Courtesy of Dr. U. Joseph Schöpf, MUSC, Charleston, USA
Mahnken, et al. Int J Cardiovasc Imaging; 2008; 8:883-90
Nieman et al. Radiology; 2008; 247(1):49-56
Quantification of calcified
plaque
Zero score reported 99.9%
NPV for 10 year cardiac
events (Shareghi, et al., JCCT, 2007; 1(3))
But 8.7% with 0 – low
score have significant
stenosis (Cheng, et al., AmJCardiol,
2007; 99(9))
Agatston Score
Mass
Volume
Calcium Coverage Score
ISSUES
No standard technique
0.5 – 4 mSv
10 – 20% variability
Overuse
FUTURE DIRECTIONS
Pharmaceutical studies
Screening for single vs.
dual energy CTA
One scan calcium score
plus CTA
More than just calcium…
fibrous, fatty, mix of all three
“Stable” plaque vs. “vulnerable” plaque
Gold standard: IVUS or histology
Mixed results in literature
Barreto, et al. JCCT, 2008. 2(4):234
Lumen
High density
Calcium
Low density
• Single energy, HU based
• > 80% sensitivity vs. IVUS
calcified, noncalcified, mixed
• Mean densities different but
significant overlap
Akram, et al. J Nucl Cardiol, 2008. 15(6):818
Thalassaemia, Sickle Cell
Disease
Iron deposition increases
attenuation in
myocardium and liver
Strong correlation to T2*
values from MRI
Mean dose: 0.7 mSv
Hazirolan, et al.; Eur J Radiol. 2008; 68:442
now EVERYONE is talking about me.
JAMA, 2009. 301(5):500-7
50 international sites
1965 CCTA examinations
64-slice from four vendors
and dual source
Radiation dose
Scan technique
Patient characteristics
Dose reduction strategies
Median DLP per site
331 – 2146 mGy*cm
Range of 25 mSv!
Overall median: 12 mSv
IQR: 8 – 18 mSv
Conventional fixed collimation
Dynamic collimation
Conventional Technology
Full radiation of breast
Breast is included in any
diagnostic thoracic scan, but
rarely organ of interest
Organ-sensitive dose reduction
40% dose reduction on breast
Constant noise and image level
Ideal for all dose sensitive organs:
e.g. breast, thyroid, lens
Cardiac CT not just for anatomical imaging
Growth areas: function, perfusion, plaque
characterization
Technological advancement keeping clinical
usefulness in mind
Continued awareness of dose
Permissions, slides, figures provided by:
Sandra Halliburton
The Cleveland Clinic Foundation
Szilard Voros
Piedmont Hospital, Atlanta, GA
Jörg Hausleiter
Deutsches Herzzentrum München
Richard White
University of Florida - Jacksonville
Siemens Medical Systems