Lawrence N' Tanenbaum, MD FACR

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CT Angiographyfundamental principles

• Lawrence N. Tanenbaum, MD FACR
• Seton Hall University NJ Neuroscience Institute
• Edison Imaging JFK Medical Center
• www.drtmasters.com drt_at_drtmasters.com
• Edison, New Jersey

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CT Angiographyadvantages vs. MRA

• accessibility
• 24 / 7 access
• MR incompatibilities
• speed
• uncooperative, unstable patients
• spatial resolution
• contrast resolution
• bony landmarks

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CT angiographyadvantages vs. conventional
angiography
CTA

• quicker, less invasive
• lower radiation dose
• 3D data set
• infinite reprojections
• retrospective analysis
• contrast resolution
• CT imaging information
• perivascular abnormalities

conv angio
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Helical CT

• volumetric data set
• slice position and interval adjustable
• slice shifting
• match or bracket slice location to lesion
• slice overlap
• prospective, retrospective
• superior 3D, multiplanar reformats

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Slice overlap

• helical scan
• 2.5 mm x 2.5 mm
• 30 slices, 75 mm volume
• reconstructed slice overlap
• 2.5 mm x 2 mm
• 38 slices, 75 mm volume
• 2.5 mm x 1.25 mm
• 60 slices, 75 mm volume

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Helical CT scanningslice thickness

• effective slice thickness related to slice
  thickness selection and pitch
• slice thickness selection is equal to the
  dimension of (the combination of detector) cells
  supplying each imaging channel

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4 channel cluster configurations
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8 channel detector configurations
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LightSpeed16 32 cell matrix detector
16 x 1.25
16 x .625
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Multi-channel detectorvolume CT
64 x .625
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Helical CT scanningslice thickness

• effective slice thickness related to selection of
  collimation and pitch
• pitch
• beam (profile) pitch
• slice (speed) pitch

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Helical scanningpitch definitions

• beam (profile) pitch
• table movement w/r/t dimension of exposed
  detector (beam width)
• reflects slice profile and dose
• slice (speed) pitch
• table movement w/r/t detector collimation
• reflects speed

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Helical pitch

• each channel of helical data contributes to each
  individual slice created
• the more unique (channels of) data acquired the
  less slice profile broadens with extended pitch
• progressive increase in acceptable table speed
  (slice pitch) as number of imaging channels
  increases

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Multi-channel pitch4 channel system

• distance table travels per tube revolution /
  activated detector dimension
• collimation x number of imaging channels
• 0.75 pitch (3)
• 4 x 5 mm slice, 15 mm table incrementation / rev
• 4 clusters of 4 x 1.25 mm cells
• 150 mm covered in 10 revolutions (5-10 sec)
• 1.5 pitch (6)
• 4 x 3.75 mm slice, 22.5 mm incrementation / rev
• 4 clusters of 3 x 1.25 mm cells
• 225 mm covered in 10 revolutions (5-10 sec)

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Multi-channel pitch8 channel system

• distance table travels per tube revolution /
  activated detector dimension
• collimation x number of imaging channels
• 0.625 pitch (5)
• 0.875 pitch (7)
• 1.350 pitch (10.8)
• 1.675 pitch (13.4)
• 8 x 1.25 mm slice
• 16.75 mm incrementation /revolution
• 1000 mm in 30 sec 60 revolution scan

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Multi-channel pitch16 channel system

• distance table travels per tube revolution /
  activated detector dimension
• collimation x number of imaging channels
• 0.5625 pitch (9)
• 0.9375 pitch (15)
• 1.375 pitch (22)
• 1.75 pitch (28)
• 16 x 1.25 mm slice
• 33.5 mm incrementation /revolution
• 1050 mm in 15 sec 30 revolution scan

16 x .625
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Multi-channel pitch64 channel system

• distance table travels per tube revolution /
  activated detector dimension
• collimation x number of imaging channels
• 0.531 pitch (34)
• 0.984 pitch (63)
• 1.375 pitch (88)

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Helical pitch

• extending pitch leads to slice profile broadening
• effective slice thickness gt collimation
• overextending pitch leads to artifacts due to
  undersampling

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4 channel 3.75
16 channel .625
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8 channel 1.25
16 channel .625
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16 channel
4 x 1.25 mm
.625 mm
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4 channel CTPET
16 channel
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CTPET 4 channel 2.5 /1.25
16 channel .625/.55
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2.5/1.25
1.25/1.0
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1.25/1.0
2.5/1.25
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1.25
3.75
.625
2.5
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.625
2.5
1.25
3.75
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Z axis resolution step and shoot
4 channel
16 channel
1.25 / 2.5 mm
.625 / 1.25 mm
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microvoxel isotropic volumetric acquisition
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Helical pitch

• each channel of helical data contributes to each
  individual slice created
• the more unique data acquired the less slice
  profile broadens with extended pitch
• progressive increase in acceptable table speed
  (slice pitch) as number of imaging channels
  increases

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Helical scanningdefinitions

• slice (speed) pitch
• table movement w/r/t detector collimation
• reflects speed
• beam (profile) pitch
• table movement w/r/t dimension of exposed
  detector (beam width)
• reflects slice profile and dose

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Multi-channel SPEED

• 1 channel system
• 1.5 pitch / speed routine
• 4 channel system
• 3 (0.75)
• 6 (1.5)
• 8 channel system
• 5 (0.625)
• 7 (0.875)
• 10.8 (1.35)
• 13.4 (1.675)

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Multi-channel SPEED

• 16 channel system
• 9 (.5625)
• 15 (.9375)
• 22 (1.375)
• 28 (1.75)
• 64 channel system
• 34 (0.531)
• 63 (0.984)
• 88 (1.375)

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Sub (0.35-0.9) second scanningbenefits

• up to more than twice the coverage per given
  breathhold
• more effective utilization of injected contrast
• reduced motion effects
• cardiovascular

dorsalis pedis
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segmented data
Original Image
.35
.40
.50
250 ms
50 ms
100 ms
motion
resolution
CNR / SNR
Courtesy of E. Nagel, M.D. German Heart
Institute, Berlin
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rotation speed

• blurring / Ca blooming
• temporal resolution
• shutter speed
• .33 - .35 sec
• .40 - .50 sec

0.5 sec
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64 channels .5 sec
64 channels .35 sec
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.35 sec
.5 sec
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.35 sec
.5 sec
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.625 mm
.5 sec
.4 sec
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64 ch .4 sec
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64 ch .4 sec
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Intravenous contrast

• Chest 18 grams
• Abdomen-pelvis 37 grams
• Pelvis 23 grams
• Head (standard dose) 40 grams
• Neck, orbit 23 grams
• CT angiography 37 grams
• significant overall savings over conventional
  CT

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Intravenous contrast

• Chest 18 grams
• Abdomen-pelvis 37 grams
• Pelvis 23 grams
• Head (standard dose) 37 grams
• Neck, orbit 23 grams
• CT angiography 18-37 gms

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CT Angiography370 concentration

• Brain 50 (40) cc - 18 grams
• Full neuro 75 (50)cc - 28 grams
• Aorto-iliac 75 (50)cc - 28 grams
• Runoff to feet 100 (75) cc -37 grams
• Pulmonary 100 (75) cc -37 grams
• Coronary 80-100 cc -37 grams

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CT angiographybasic technique

• 18 - 22 gauge catheter
• inject 2.5 - 5 cc / sec through peripheral vein
• SmartPrep (or empiric scan delay)
• process at console workstation

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CT Angiography
SmartPrep
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CT angiographyclinical applications

• coronary
• aortic disease
• aneurysm, dissection
• renal artery stenosis
• celiac, SMA ASVD
• runoff
• pulmonary emboli
• carotid ASVD
• arch to circle of Willis
• intracranial
• ASVD, aneurysm

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Coronary CTA16 channel

• .625 mm
• prospective recon at 75
• pitch set by HR
• e.g., HR 50-60 - pitch .23
• 120 kV, max mA, 25 FOV
• segment helical 0.4 sec
• retrospective gating
• render on workstation or scanner

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Coronary CTA64 channel

• .625 mm
• prospective recon _at_ 75 cardiac cycle
• pitch set by HR (.16 -.24)
• e.g., HR 65 (pitch .22)
• recon set according to HR
• 30-74 segment
• 75-113 two sector burst
• gt114 four sector burst
• 120 kV, max mA, 25 (35) FOV
• segment helical .35 sec

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Retrospective ECG-Gated Helical Scanning
X-ray On Off
Segment Mode
Burst Mode
Helical Scanning
Z - Axis Location
Recon
Phase Loc
Time

• Continuous Volume Coverage with lower pitch
  Cardiac Helical
• Retrospectively gated Reconstruction
• Single Sector (Segment recon) and multi-sector
  (Burst) Cardiac
• Images at multiple cardiac phases within a
  cardiac cycle

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Coronary CTA64 channel

• dose modulation
• 70-80 for HR lt65
• 50-90 for HR gt65
• cardiac filter 2
• heavy patients
• 35 - 45 FOV
• C3 filter
• soft algorithm

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259 mA .40 sec 5 251 mA .40 sec 15 251 mA .40
sec 25 251 mA .40 sec 35 281 mA .40 sec 45 475
mA .40 sec 55 612 mA .40 sec 65 613 mA .40 sec
75 613 mA .40 sec 85 446 mA .40 sec 95
EKG dose modulation
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Patient preparation

• no caffeine x 24 hours
• beta blockade for HR gt65
• 60 minutes before procedure
• Lopressor 100 mg
• supplement with IV beta blockade on table prn
• calm and relaxed setting for study
• anxiolytic prn
• sublingual nitroglycerine
• immediately before test bolus

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EBCT 3 mm
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4 ch CT 1.25 mm
EBCT 3 mm
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EBCT 3 mm
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Volume CT 16 coronary CTA .4 sec .625
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16 ch .4 sec rotation .625 mm
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80 cc .625 mm
VCT 64 .35 sec
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64 channel .625mm .35 sec
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.625 mm 0.35 sec
VCT 64 - 80 cc
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64 x .625 mm
.35 sec
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16 ch .4 sec rotation .625 mm
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64 ch .625 mm
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VCT 64
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64 ch .625 mm
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64 ch .625 mm
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64 ch .625 mm
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64 ch .625 mm
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64 ch .625 mm
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LIMA to LAD
64 ch .625 mm
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64 ch .625 mm
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Gated aortic CTA VCT 30 sec
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12 sec
VCT
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CT Angiography arch to Circle of Willis- 4
channel

• 1.25 mm cuts
• neck pitch 1.5 (6) (1.25 mm / 7.5 mm/rev)
• brain pitch .75 (3) (1.25 mm / 3.75 mm/rev)
• overlap q 1 mm
• 120 kV 380 mA 0.5 sec
• SmartPrep left ventricle
• 12 sec prep delay
• right arm1

1Barmeir et al AJR 170, June 1998, 1657-8
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CT Angiography arch to Circle of Willis
8 channel

• 1.25 mm cuts, overlap q .8 mm
• neck
• pitch 1.35 (10.8)
• 1.25 mm / 13.5 mm/rev
• 120 kV 380 mA 0.5 sec
• brain
• pitch .625 (5)
• 1.25 mm / 6.25 mm/rev
• 120 kV 380 mA 0.7 sec
• SmartPrep left ventricle
• 12 sec prep delay
• right arm1

1Barmeir et al AJR 170, June 1998, 1657-8
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CT Angiography arch to Circle of Willis
16 channel

• neck pitch 1.375 (22)
• .625 mm / .5 mm
• 17.5 mm/rev
• 120 kV 380 mA 0.5 sec
• brain pitch .5625 (9)
• .625 mm / .5 mm
• 5.63 mm/rev
• 120 kV 380 mA 1 sec
• SmartPrep left ventricle
• right arm1

1Barmeir et al AJR 170, June 1998, 1657-8
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CT Angiography arch to Circle of Willis
64 channel

• neck pitch .984
• .625 mm / .5 mm
• 39 mm/rev (64 ch)
• 120 kV 200/800 mA 0.4 sec (NI 14)
• brain pitch .531
• .625 mm / .5 mm
• 10.62 mm/rev (32 ch)
• 120 kV 200/800 mA .4 sec (NI 14)
• SmartPrep left ventricle
• right arm1

1Barmeir et al AJR 170, June 1998, 1657-8
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40 cc VCT 64
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CTA .625 / .55
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carotid occlusion
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Volume rendering
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siphon ASVD LS 16 .625 mm
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16 x.625
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40 cc VCT
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VCT
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64 ch
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CT Angiography Aorta-runoff 4 channel

• 2.5 mm cuts
• pitch 1.5 (6)
• HS, 2.5 mm / 15 mm/rev
• overlap q 2 mm
• 120 kV 380 mA 0.5 sec
• SmartPrep left heart
• 20 sec prep delay

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CT Angiography Aorta-runoff
8 channel

• 1.25 mm cuts
• pitch 1.675 (13.4)
• 1.25 mm / 16.75 mm/rev
• overlap q .8 mm
• 120 kV 380 mA 0.5 sec
• SmartPrep left heart
• 20 sec prep delay

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CT Angiography Aorta-runoff
16 channel

• .625 or 1.25 mm cuts
• pitch 1.75(28)
• .625 mm / 17.5 mm/rev
• overlap q 0.55 -0.8 mm
• 120 kV 380 mA 0.5 sec
• SmartPrep left heart
• 20 sec prep delay

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aortic occlusion
failed conventional angiography
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16 x .625 .4 sec 75 cc 370
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CT Angiography Aorta-runoff
64 channel

• .625 mm cuts
• pitch .984
• .625 mm / 39 mm/rev
• overlap q .6
• 120 kV 300-800 mA (NI 15)
• 0.4 sec
• SmartPrep abdominal aorta

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VCT 64
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VCT 64
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endoleak
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CT Angiography renal, celiac, SMA 4ch

• 1.25 mm cuts
• pitch 1.5 (6)
• HS, 1.25 mm / 7.5 mm/rev
• overlap q 1 mm
• 120 kV 380 mA 0.5 sec
• 20 sec prep delay
• SmartPrep left heart

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CT Angiography renal, celiac, SMA
8 channel

• 1.25 mm cuts
• pitch 1.675 (13.4)
• 1.25 mm / 16.75 mm/rev
• overlap q .8 mm
• 120 kV 380 mA 0.5 sec
• 20 sec prep delay
• SmartPrep thoracic aorta

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16 channel .625 / .55 mm
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CT Angiography pulmonary arteries 4 channel

• 1.25 mm cuts
• pitch 1.5 (6)
• HS, 1.25 mm / 7.5 mm/rev
• overlap q 1 mm
• 120 kV 380mA 0.5 sec
• timing run
• scan bottom to top

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Duke U.
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CT Angiography pulmonary arteries
8 channel

• 1.25 mm cuts
• pitch 1.675 (13.4)
• 1.25 mm / 16.75 mm/rev
• overlap q .8 mm
• 120 kV 380mA 0.5 sec
• timing run
• scan bottom to top

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CT Angiography pulmonary arteries
16 channel

• 1.25 mm cuts
• pitch .9375 (19)
• 1.25 mm / 18.75 mm/rev
• overlap q .8 mm
• 120 kV 380mA 0.5 sec
• timing run
• scan bottom to top

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CT Angiography pulmonary arteries
64 channel

• .625 mm cuts
• pitch 1.375
• .625 mm / 18.75 mm/rev
• overlap q .8 mm
• 120 kV 140-800 mA (NI 15) 0.4 sec
• test bolus PA outflow
• scan bottom to top

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VCT 64
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Multichannel channel CTpatient benefits

• increase in channels reduces patient dose
• increased imaging / scatter ratio
• shared helical data more dose efficient
• reduced mAs

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140 kV 91 mAs
140 kV 68 mAs
140 kV 55 mAs
140 kV 230 mAs
SmartMA
140 kV 230 mAs
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CTA CPT codes

• Head 70496
• Neck 70498
• Chest 71275
• Pelvis 72191
• Abdomen 74175
• Extremity upper 73206, lower 73706
• Abd Ao bilat iliofemoral LE runoff 75635

Las Vegas 2000
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Cardiac CTA
0144T Computed tomography, heart, without
contrast material, including image post
processing and quantitative evaluation of
coronary calcium
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JFK Medical Center
Shan Yang 2001