Multi-Slice CT for Coronary Calcium Scoring and Coronary ...
Transcript of Multi-Slice CT for Coronary Calcium Scoring and Coronary ...
Multi-Slice CT for Coronary Calcium Scoring and Coronary Angiography
John D. Symanski, M.D., F.A.C.C
The Sanger Clinic, PA and Carolinas Medical Center
No Disclosures
Objectives
• Show lots of pretty pictures
• Overview fundamental principles of MSCT technology
• Review strengths and limitations of MSCT
• Raise awareness of current indications and clinical scenarios for which to consider CT angiography
Case Presentation
• 64-year-old female with stage 1 CLL
• Dyslipidemia (untreated); No HTN, diabetes, or tobacco use
• Negative stress echo previously
• Atypical chest pain
• Stress echo: septal hypokinesis at rest, LVEF: 50%
• Referred for calcium scoring and CTA
CT Angiogram Interpretation
• Calcium Volume Score: ZERO
• CT angiography:
– Left Main, Circumflex, and Right coronary arteries: normal
– LAD: eccentric, soft plaque adjacent to origin of first diagonal (~60% stenosis)
• Correlation recommended
SummaryCardiovascular Imaging - State of the Art
• Multi-slice CT (MSCT) not likely to replace conventional angiography
• Post-processing of images for MSCT angiography time & labor intensive
• Major strength of CTA is its high negative predictive value
• CMR to become the preferred cardiac imaging modality in the future
Which Test for Which Patient?
• All modalities are improving
• No single modality fits all applications and all patients
• Choice of initial test depends on the specific clinical question in individual patient
Cardiac Magnetic Resonance
Viability AssessmentCMR Delayed Hyper-Enhancement
Hazards of MRIMagnet-Seeking Projectiles
First whole-body CT cross-section through a human thorax, generated by Ledley et al in 1974 (Science 1974;186:207)
The Examination
Current Generation Scanners
• Spatial resolution 0.4 mm - conventional coronary angiography 0.15-0.25 mm
• Temporal resolution (shutter speed) improved to 166 msec with faster gantry rotation (330 msec) – conventional angiography 6 msec
• Up to 64 slices in one rotation
4 to 64 Slice ScansFive Heart Beats
10 mm detectorPitch ~0.25
3 cm in 5 sec
20 mm detectorPitch ~0.25
6.2 cm in 5 sec
40 mm detectorPitch ~0.25
12.5 cm in 5 sec
64-Slice CT Scanner
• More coverage (volume) with each heart beat
• Entire heart imaged in 5-15 seconds
• Less contrast required
• No increase in rotation speed, but with overlapping slices, can use segments from different heart beats to improve temporal resolution
3-D Volume Rendered Image
Maximum Intensity ProjectionSoft Plaque in Proximal LAD
Curved Planar Image
Quantification of Obstructive and Nonobstructive Coronary Lesions by 64-Slice
Computed Tomography
• 59 patients with stable angina subjected to CTA before catheter-based angio
• Diagnostic image quality in 55 of 59• Sensitivity for detection of stenosis
<50%, >50%, and >75%: (79%, 73%, and 80%, respectively)
• Excellent accuracy with proximal lesions
Leber AW et al. J Am Coll Cardiol. July 5, 2005;46:147-54
Diagnostic Accuracy of Noninvasive Coronary Angiography Using 64-Slice
Spiral Computed Tomography• 70 patients undergoing invasive cath• Of 1,065 segments, 935 evaluated (88%)• Quantitative assessment in 773 of 935
segments by MSCT and QCA• Sensitivity, specificity, (+) PV, (-) PV:
– By segment- (86%, 95%, 66%, and 98%)– By artery- (91%, 92%, 80%, and 97%)– By patient- (95%, 90%, 93%, and 93%)
Raff GL et al. J Am Coll Cardiol. Aug 2, 2005;46:552-7.
Coronary Calcium Scoring
• Initial ACC/AHA guidelines “may be useful in selected patients”…
• Added prognostic power to conventional risk stratification tools (Framingham)
• Revised guidelines (and reimbursement for service) likely forthcoming
Hn x-factor(Agatston Scoring)
130-199 1
200-299 2
300-399 3
>400 4
Area = 15 mmArea = 15 mm22
Peak CT = 450Peak CT = 450Score = 15 x 4 = 60Score = 15 x 4 = 60
Area = 8 mmArea = 8 mm22
Peak CT = 290Peak CT = 290Score = 8 x 2 = 16Score = 8 x 2 = 16
Total Score = S
Calcium Volume Scoring
The Calcium Scale
The calcium scale is a linear scale with 4 calcium score categories:
0 none
1–99 mild
100–400 moderate
>400 severe
*Calcium score correlates directly with risk of events and likelihood of obstructive CAD*
Ethnic Differences in Coronary CalcificationThe Multi-Ethnic Study of Atherosclerosis (MESA)
Bild DE et al. Circulation. 2005;111:1313-1320.
6814 men and women aged 45-84 years
Five-Year Mortality Rates in Framingham Risk Subsets by Coronary Calcium Score
Shaw et al. Radiology 2003; 228:826-833
*
*
**p<0.001
• MI in 41 pts during 3.2 + 0.7 years
• LDL levels similar in MI and non-MI pts
• Relative risk of MI in presence of CAC progression was 17.2-fold higher (P<0.0001)
Progression of Coronary Artery Calcium and Risk of First MI
495 Asymptomatic Patients Started on Statin Therapy
Raggi P et al. Arterioscler Thromb Vasc Biol. 2004;24:1272-77.
Coronary Disease Progression
? Role for CTA >60% stenosis (+)
stress/imaging
Calcified Plaque Detected by CT
Soft Plaque Visualization
CTA Limitations
• Rapid (>80 bpm) and irregular HR
• High calcium scores (>800-1000)
• Stents
• Contrast requirements (Cr > 2.0 mg/dl)
• Small vessels (<1.5 mm) and collaterals
• Obese and uncooperative patients
• RADIATION EXPOSURE
Effective Dose of Selected Radiologic Examinations
• PA/Lateral CXR 0.04-0.06 mSv
• Head CT 1-2 mSv
• Chest CT 5-7 mSv
• Abd/Pelvis CT 8-11 mSv
• Diagnostic Cor Angiogram 3-5 mSv
• MSCT angiography 9.3-11.3 mSv
Morin et al. Circulation 2003;107:917-22.
*Average annual background radiation in U.S ~ 3.6 mSv
Radiation Risks
• Exact quantification of harmful effects of radiation difficult to ascertain
• For a child under age 15, the risk of cancer death from a single CT scan is approximately 1 in 500
• For a 45 year old adult, the risk of death from cancer from a single CT exam is about 1 in 1,250
Brenner et al. Radiology, 231(2):440-445.
Clinical Indications for MSCT
• Calcium Scoring (CS) - risk stratification in the intermediate risk patient
• Non-invasive coronary angiography (CTA) in the symptomatic low-risk patient or asymptomatic intermediate-risk patient*A negative test (normal CTA) has a 98% chance of revealing normal coronary arteries on invasive angiography*
Test Selection According to Pretest Probability of CAD
Association for the Eradication of Heart Attacks (AEHA.org)
When to Consider MSCT
• Equivocal stress test or persistent symptoms despite negative stress test
• Prior to non-coronary cardiac surgery (valve or congenital repair)
• Patients with difficult access or on therapeutic warfarin
• Suspected coronary anomalies
Lt Main
CFX
RCA
LAD
• Idiopathic dilated cardiomyopathy
• Cardiac transplant evaluation
• Patients to undergo electrophysiologic intervention (AF ablation, BiV pacing)
• Selected patients pre- and post-bypass surgery (aortic pathology, graft patency)
When to Consider MSCT(continued)
Mikaelian BJ et al. Circulation. 2005;112:e35-e36.
Pulmonary Vein Stenosis
Vasamreddy et al. Heart Rhythm (2004) 1, 78-81.
Aortic Coarctation Visualized by 16-Row Detector MSCT
Fröhlich, G et al. Circulation. 2005;112:e81.
Pericardial CalcificationMulti-Slice CT Scanning Superior to MRI
Hoffmann et al. Circulation 108 (7): 48e Figure IG1
Nikolaou et al. Cardiology Clinics. 21;(2003):639-655.
Future Indications
The Great Promise of MSCTThe “Triple Rule-Out”
“an appropriate imaging study is one in which the expected incremental information together with clinical judgment exceed the expected negative consequences* by a sufficiently wide margin that the procedure is generally considered acceptable care and a reasonable approach for the indication.”
Appropriateness Criteria
*include risks of the procedure and the downstream impact of poortest performance such as delay in diagnosis (false -) or inappropriatediagnosis (false +)