Cardiac CT halpern EDocFind com

Cardiac CT and CT Angiography: Techniques & Clinical Applications Ethan J Halpern, MD Director, Cardiac CT Thomas Jefferson University Cardiac Imaging Technique • Patient Preparation • Contrast Injection • Scan Positioning • mAs and kVp • ECG Gating • Multicycle Reconstruction • Editing of ECG Gating • ECG Gated Dose Modulation • Image reconstruction Patient Preparation Prior to CT ■ ■ ■ Ask patient to refrain from stimulants (i.e coffee) on the day of the scan No solid food for hours prior to the study Premedicate for asthma & allergic history – Medrol 32mg po 12hrs and hrs prior to study ■ ■ Patient should have good IV access (18G antecubital) Adequate EKG tracing – good contact Patient Preparation - Heart ■ Rate IV Beta Blockade (preferred) – 2.5 – 30 mg Metoprolol » Titrate to heart rate of 55-60 » Monitor BP while giving metoprolol – If asthmatic, consult physician » No more than 10mg metoprolol » Consider calcium channel blockers ■ ■ Diltiazem (bolus 0.25mg/kg) Oral Beta Blocker – 50 – 100 mg Metoprolol – hour prior to examination – Who will monitor the patient ? Objective of the Contrast Injection Uniform enhancement of the left heart to greater than 300 HU ■ Minimize streaking due to contrast in SVC and RV ■ Impact of Iodine Concentration 140cc injection ■ HU in aorta ■ Cademartiri F et al Intravenous Contrast Material Administration at Helical 16–Detector Row CT Coronary Angiography: Effect of Iodine Concentration on Vascular Attenuation Radiology 236:661-665, 2005 Contrast Injection ■ ■ ■ ■ ■ ■ Use high iodine density contrast ≥ 350 mgI/mL – We use Optiray 350 (Mallinckrodt Inc.) 16 detector system (25-30 second scan) – 100-150 cc contrast @ cc/s – 40 cc @ cc/s 40 detector system (15-20 second scan) – 100 cc contrast @ 5-5.5 cc/s – 40 cc saline @ cc/s 64 detector system (15 second scan) – 75 cc contrast @ 5-5.5 cc/s – 40 cc saline @ cc/s Start scan seconds after the contrast reaches the left heart Contrast volume = scan duration * injection rate – Want sufficient contrast to enhance PDA at end of scan Scan Start Position ■ Native coronary arteries – Begin above carina – Tortuous aorta or prominent upper left heart border – begin scan 1-2cm higher ■ Bypass Grafts – Veins: top of arch – LIMA: above clavicles Scan Ending Position ■ Need to image PDA – Note overlap of heart & diaphragm – Observe contour of heart – Extend scan ~2cm below the caudal extent of the heart – Position of heart will change with inspiratory effort Center the Scan on the Heart ■ Maximize spatial resolution for coronaries – CT resolution is greatest in the center of scan field – Set left-right position on AP scout view – Move table up-down to center on aortic root and Left ventricle EKG Dose Modulation ■ Best images obtained at mid-diastole – RCA sometimes is best at end-systole ■ Dose modulation can achieve dose reduction of 40-50% – Use only with stable heart rate ■ Limitations – Cannot review coronary anatomy at end-systole – Cannot correct for errors in gating Image Reconstruction ■ Reconstruction slice thickness – 3mm for function – 0.5-0.8mm for coronary arteries – 1.0-1.2mm for photon limited scans ■ Reconstruction kernel – Sharper kernel: noisier image, but may be required to visualize coronary lumen with stents and calcified vessels Slice thickness vs noise 0.8mm 1.0mm Reconstruction filter vs noise Reconstructions ■ Choose appropriate filter – Sharper filter for patients with heavy coronary calcium or stents ■ Perform targeted reconstructions – 3mm reconstruction of contiguous slices @ 10 phases for cardiac function analysis – 0.8mm reconstruction of overlapping slices @ 40%, 70%, 75% and 80% for coronary anatomy 1.0mm recons for heavy patients Clinical Application of Coronary CTA ■ ■ ■ ■ Indications Rendering & display modes Characterization of Plaque Grading of stenosis Cardiac Indications ■ The MDCT angiography of the chest for cardiac assessment (0146T-0149T) is indicated for the following signs or symptoms of disease: – Emergency evaluation of acute chest pain – Cardiac evaluation of a patient with chest pain syndrome (e.g anginal equivalent, angina), who is not a candidate for cardiac catheterization – Management of a symptomatic patient with known coronary artery disease (e.g., post-stent, post CABG) when the results of the MDCT may guide the decision for repeat invasive intervention – Assessment of suspected congenital anomalies of coronary circulation Rendering Modes ■ MIP & slab MIP ■ Surface Display ■ Vessel tracking – Curved MIP – Globe view Plaque Characterization ■ Calcified vs Soft ■ Positive remodeling ■ Irregularity ■ Ulceration Grading of Stenosis Leber AW et al Quantification of Obstructive and Nonobstructive Coronary Lesions by 64-Slice Computed Tomography: A Comparative Study With Quantitative Coronary Angiography and Intravascular Ultrasound JACC 46(1):147-54, 2005 Bland-Altman Analysis of Stenosis Grading Dashed lines 95% CI Hoffmann: JAMA, Volume 293(20).May 25, 2005.2471–2478 Impact of Calcified Vessels on detection Low of stenosis CS High>50% CS Age Male/female Heart rate Calcium score 57 +/-10 55/5 57 +/-7 14 +/-16 58 +/-11 55/5 58 +/-7 578 +/-716 Weight (kg) 70 +/-6 72 +/-8 ■ Calcium score – Cutpoint = 55 CTA: 1310 segs ■ Low CS pts ■ – Sens = 90% – Spec = 92% ■ High CS pts – Sens = 97% – Spec = 91% Cademartiri F et al Impact of coronary calcium score on diagnostic accuracy for the detection of significant coronary stenosis with multislice computed tomography angiography American Journal of Cardiology 95(10):1225-7, 2005 Impact of Coronary Calcium All segments Ca Score < 1000 Patients 60 46 Segments 780 598 True positive 54 39 False positive 21 10 Sensitivity 72% 98% Specificity 97% 98% PPV 72% 80% NPV 97% 100% Kuettner A et al Noninvasive detection of coronary lesions using 16-detector multislice spiral computed tomography technology: initial clinical results JACC 44(6):1230-7, 2004 Proximal versus Distal Segments All segments Proximal segs Patients 33 33 Segments 530 438 True positive 34 27 False positive 19 13 Sensitivity 63% 82% Specificity 96% 93% PPV 64% 68% NPV 96% 97% Hoffmann F et al., Predictive value of 16-slice multidetector spiral computed tomography to detect significant obstructive coronary artery disease in patients at high risk for coronary artery disease patient-versus segment-based analysis Circulation 110: 2638–2643 Non-coronary Assessment ■ ■ ■ ■ Valvular assessment Cardiac morphology Cardiac function EP planning ... Reconstruction Single Heart beat Uses 180o per heart beat Temporal Res = (rot time)/2 Multi-Cycle Reconstruction ■ ■ Combine a portion of projections from one heart cycle with a portion of projections... 93% PPV 64% 68% NPV 96% 97% Hoffmann F et al., Predictive value of 16-slice multidetector spiral computed tomography to detect significant obstructive coronary artery disease in patients at high... heart rate EKG Gating ■ Coronary CTA requires EKG gating to overcome cardiac motion ■ Heart is most quiescent in mid-diastole and end-systole ■ Best time for reconstruction – 70-80% of R-R interval