How to optimally perform cardiac CT in clinical

Transcription

How to optimally perform cardiac CT in clinical
How to optimally perform cardiac CT in clinical
practice by using A Siemens CT device in 2011
X. HAMOIR*, J. KIRSCH*
V. HAMOIR**
*Medical Imaging and **Cardiology
CHWAPI site Notre-Dame
Tournai Belgium
Royal Belgian Radiological Society
Antwerp - 2011 october 1st
DSCT FLASH
1st device in Belgium in september 2009
FLASH
2009
95°
*Rot time 285ms
*2×128×0,6mm slices
spat resol 0,33mm
*pitch up to 3,4 in Flash
table feed up to 460mm/s
heart=120mm in 0,27s
*TR (1 seg) = Rot time
4
= 71ms but 5°shift
:75ms
Patient preparation
• Goal 1: « Primum non nocere »
-To reduce the radiation dose
-ALARA: never > 20 mSv
Cardiac frequency
dose
Beta-blockers
Patient preparation
• Goal 2: to obtain best imaging quality
to suppress or reduce potential artefacts due to irregular cardiac
rythm
beta-blockers
to facilitate image interpretation by
vessel diameter (30%)*
nitroglycerine spray
*Decramer et al.AJR 2008 Jan;190(1):219-25
Patient preparation
•
HR > 60bpm
Cardiologist prescribes :
*3 days before CT: Bisoprolol 2,5-10mg/day (depending of HR and
tolerance), stop or reduce some regular treatment, hydratation
*The day of the CT examination :
3-4 hours fast, no coffee or tea,
Bisoprolol 2,5mg-5mg
ECG one hour before CT : if HR > 70 bpm: Bisoprolol 2,5-5mg
If Asthma, spastic COPD, severe arteritis,
Anticalcic:
Diltiazem® retard 120-300mg/day or Verapamil® 3×80-120mg/d
Nitroglycerine spray:
-Nitrolingual® spray 3 minutes before acquisition, sublingual
-contraindications: severe aortic stenosis, obstructive HCM,
hypotension < 10 mmHg, Viagra-Cialis-Levitra (recent)
-100-120 mmHg: 1 puff
≥130 mmHg: 2 puffs
Acquisition protocols
3 acquisition modes with ECG synchronisation:
Prospective triggering – Adaptative Cardio Sequence
(ACS) = Sequential (= Step and shoot)
Classical retrospective gating - helicoidal
Flash = prospective triggering- helicoidal with very
high pitch
Prospective triggering = adaptative cardio
sequence (ACS) = step and shoot
Scan
Move
Scan
MoveReact
Scan
DSCT
Temp reolution= 87,5 ms
2.5 mSv
Scheffel, et al Heart, June 2008
What happens If extra-systole?
Management of extrasystoles
1000 ms 980 ms
990 ms
Scan!
Scan! Repetition!
 
 Scan start is determined prospectively based on last three heart
cycles

Scan is omitted and delayed when extra systole is detected before
scan

Scan is repeated if extra systole occurs during or shortly after scan
Adjustable acquisition window
(New flex padding)
70
Selection of acquisition window
Free phase shifting for postprocessing reconstruction
Pulsing can be applied like in spiral mode
ACS flex padding
BUT:
• If window = 0-100% of RR’
• If window = 30-80% of RR’( on a 600 to 700ms large
window)
We found no dose reduction in comparison with
classical spiral CT (with ECG pulsing)
We select 68-72% (205ms large) acq. window
Classical helicoidal retrospective
n >1 cycles
Recon
Recon
Recon
z Position
small pitch ~0.2
Time
 2x90° Segments DMS A+B.
 Temporal resolution Trot/4
Apnée of 7
to 12
seconds

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