Fast CT Angiography on a Fast Track to Your

Practice: Promises and Limitations

S. AchenbachDepartment of Radiology, Massachusetts General Hospital

Department of Cardiology, University of Erlangen

Coronary artery imaging:

- small diameters (~1-4 mm)

- complex anatomy

- rapid motion

CT Techniques

- High spatial resolution

- Good contrast

- Problem: temporal resolution

Electron Beam Tomography (EBT)

50 - 100 ms image acquisition time1.5 mm - 3.0 mm slice thickness

Electron Beam Tomography (EBT)

CT coronary imaging feasible

Limitations: 1.5 -3.0 mm slice thickness

X-ray power

„e-Speed“: 1.5 mm slice thickness

50 ms temporal resolution

Multislice spiral CT with retrospective ECG gating- Tube rotation: 420-500 ms- Data acquisition in 4-16 slices simultaneously

- Partial scan reconstruction using ~ 210-250 ms

4 slice CT: ~1.3 mm slices 16 slice CT: ~0.75 mm slices

MSCT 4 Slice

EBT

MSCT 16 slice

MSCT 16 slice

MSCT 16 slice

MSCT 16 slice

MSCT 16 slice

n Sens. Spec. n.e.

Schmermund JACC 1998 28 82% 88% 12%Reddy Radiology 1998 23 88% 79% 8%Achenbach N Engl J Med 1998 125 92% 94% 25%Ropers Z Kardiol 2000 118 90% 82% 24%Achenbach Heart 2000 36 92% 91% 20%

Nieman Lancet 2001 31 81% 97% 27%Achenbach Circulation 2001 64 91% 84% 32% Knez Am J Cardiol 2001 42 78% 98% 6%Kopp Eur Heart J 2002 102 86% 96% 16%Becker JCAT 2003 28 78% 71% 11%Nieman Heart 2002 53 82% 93% 30%

Nieman Circulation 2002 59 95% 86% 7%Ropers Circulation 2003 77 93% 92% 12%

MSCT:

Heart Rate < 60/min desirable:

oral ß-blockade to all patients

EBT/MSCT:

Coronary calcium

LIMITATIONS:Contrast, radiationSinus rhythmUnevaluable arteriesAccuracy = 100%

Diagnostic tool with high negative predictive value (~95%) if image quality is sufficient

CT to replace cardiac cath?

„A man with a hammer sees a lot of things that need to be hammered.“

(A radiologist/cardiologist with a spiral CT ...)

Clinical Indications for MSCT?

... Not for screening

... Not in patients with typical symptoms

... Possibly in patients with relatively low likelihood of signficant stenosis (atypical symptoms, equivocal stress test ...)

> 20% „rule out“ coronary angiograms

100 patients prior to valve surgery: All 36 patients with stenoses identified by EBT. 54 patients: stenoses ruled out.

Anomalous coronary arteries

Bypass Grafts:

EBT 4-slice MSCT 16 slice MSCT

Nieman et al, Circulation 2002

STENT?

Detection of Plaque

4- slice MSCT

Schröder et al. JACC 2001

Detection of Plaque

16-slice MSCT

Detection of Plaque

Potential role in risk assessment?

- Accuracy / Quantification?

- Reproducibility?

- Progression over time?

- Prognostic value?

„Fast CT Coronary Angiography“:- Technical issues

Heart rate, technology, protocols

- „Coronary Angiography“

Potential role to rule out stenoses

- „Plaque imaging“?

(Potential role for risk stratification)