Presentation is loading. Please wait.

Presentation is loading. Please wait.

Cardiac CT and CT Angiography: Techniques & Clinical Applications Ethan J Halpern, MD Director, Cardiac CT Thomas Jefferson University.

Similar presentations


Presentation on theme: "Cardiac CT and CT Angiography: Techniques & Clinical Applications Ethan J Halpern, MD Director, Cardiac CT Thomas Jefferson University."— Presentation transcript:

1 Cardiac CT and CT Angiography: Techniques & Clinical Applications Ethan J Halpern, MD Director, Cardiac CT Thomas Jefferson University

2 Patient PreparationPatient Preparation Contrast InjectionContrast Injection Scan PositioningScan Positioning mAs and kVpmAs and kVp ECG GatingECG Gating Multicycle ReconstructionMulticycle Reconstruction Editing of ECG GatingEditing of ECG Gating ECG Gated Dose ModulationECG Gated Dose Modulation Image reconstructionImage reconstruction Cardiac Imaging Technique

3 Patient Preparation Prior to CT n Ask patient to refrain from stimulants (i.e. coffee) on the day of the scan n No solid food for 4 hours prior to the study n Premedicate for asthma & allergic history –Medrol 32mg po 12hrs and 2 hrs prior to study n Patient should have good IV access (18G antecubital) n Adequate EKG tracing – good contact

4 Patient Preparation - Heart Rate n IV Beta Blockade (preferred) –2.5 – 30 mg Metoprolol »Titrate to heart rate of »Monitor BP while giving metoprolol –If asthmatic, consult physician »No more than 10mg metoprolol »Consider calcium channel blockers n Diltiazem (bolus 0.25mg/kg) n Oral Beta Blocker –50 – 100 mg Metoprolol –1 hour prior to examination –Who will monitor the patient ?

5 Objective of the Contrast Injection n Uniform enhancement of the left heart to greater than 300 HU n Minimize streaking due to contrast in SVC and RV

6 Impact of Iodine Concentration 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: , 2005 n 140cc injection n HU in aorta

7 Contrast Injection n Use high iodine density contrast  350 mgI/mL –We use Optiray 350 (Mallinckrodt Inc.) n 16 detector system (25-30 second scan) – cc 4 cc/s –40 4 cc/s n 40 detector system (15-20 second scan) –100 cc cc/s –40 cc 5 cc/s n 64 detector system (15 second scan) –75 cc cc/s –40 cc 5 cc/s n Start scan 5 seconds after the contrast reaches the left heart n Contrast volume = scan duration * injection rate –Want sufficient contrast to enhance PDA at end of scan

8 Scan Start Position n Native coronary arteries –Begin above carina –Tortuous aorta or prominent upper left heart border – begin scan 1-2cm higher n Bypass Grafts –Veins: top of arch –LIMA: above clavicles

9 Scan Ending Position n 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

10 Center the Scan on the Heart n 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

11 Voltage kV 90 kV, 120 kV, 140 kV Cardiac protocols These values determine the Peak value of X-ray photons. The effective energy is about half of these values A higher voltage means: Lower contrast Less noise Higher Patient dose: dose proportional to ~ kV 2.7 Longer recovery time between scans (shorter life)

12 Tube Current: mA/mAs Axial: mAs = mA x Rotation-time/slice Helix: mAs = mA x (Rotation-time/360°)/ Pitch For most scanners: tube provides mA A higher mAs means: Less noise: noise proportional to 1/(mAs) 0.5 Higher Patient dose: dose proportional to mAs Larger X-ray tube damage/scan Longer recovery time between scans

13 Scan Parameters n kVp –Generally set at 120kVp –For heavy patients (>200lbs) use 140kVp –For patients with calcified arteries and stents also use 140kVp n mAs –Effective mAs = mA x (rotation time / pitch) –Effective mAs in the range of –Increase for heavy patients to minimize noise n Pitch –Generally , but adjust for heart rate

14 EKG Gating n Coronary CTA requires EKG gating to overcome cardiac motion n Heart is most quiescent in mid- diastole and end-systole n Best time for reconstruction –70-80% of R-R interval for LAD, CRX –70-80 or 40% for RCA n Single cycle vs. multicycle

15 EKG Based Techniques n Fixed time offset –Example: 500 ms after R peak –Window centered at 500 ms n Percentage of R-R interval –Example: 60% of R-R interval –For 60 bpm, R-R interval = 1000 ms –Window centered at 600 ms

16 Heart rate variation during CTA Diastole varies in length 70% Timing of Intervals in Different Heart Rates n Systole remains stable n Changes in heart rate primarily effect diastole 58 bpm r-r interval = 1021 msec r-t interval = 258 msec 104 bpm r-r interval = 576 msec r-t interval = 204 msec 79 bpm r-r interval = 757 msec r-t interval = 230 msec

17 Consistent Phase Selection Beat-to-Beat Variable Delay Algorithm 70% n Fixed time and percent of R-R may not pick a consistent phase n Beat-to-Beat variable delay algorithm –Always pick same percentage delay in diastole n Improves image quality 58 bpm r-r interval = 1021 msec r-t interval = 258 msec 104 bpm r-r interval = 576 msec r-t interval = 204 msec 79 bpm r-r interval = 757 msec r-t interval = 230 msec

18 Single Heart beat Uses 180 o per heart beat Temporal Res = (rot time)/2 Single Cycle Reconstruction

19 Multi-Cycle Reconstruction n Combine a portion of projections from one heart cycle with a portion of projections from another to make the full n Improves temporal resolution, because each segment of data covers the same (smaller) region in time.

20 Single Cycle vs. Multicycle Stenosis= 50%Single CycleMulticycle Nonassessable21% (28/136)2% (3/136) Sensitivity74% (31/42)88% (37/42) Specificity71% (67/94)91% (86/94) PPV84% (31/37)88% (37/42) NPV94% (67/71)95% (86/91) Accuracy72% (98/136)90% (123/136) Dewey et al. Investigative Radiol 39: , 2004 Toshiba Aquilion 16-slice: 27/34 patients with HR>65

21 Temporal Window & Heart Rate Hoffmann MHK: Radiology 234:86-97, % phase ____ 80% phase + __ + multicycle reconstruction

22 Image Quality & Heart Rate Hoffmann MHK: Radiology 234:86-97, 2005

23 Correction of Gating Errors

24 EKG Dose Modulation n Best images obtained at mid-diastole –RCA sometimes is best at end-systole n Dose modulation can achieve dose reduction of 40-50% –Use only with stable heart rate n Limitations –Cannot review coronary anatomy at end-systole –Cannot correct for errors in gating

25 Image Reconstruction n Reconstruction slice thickness –3mm for function – mm for coronary arteries – mm for photon limited scans n Reconstruction kernel –Sharper kernel: noisier image, but may be required to visualize coronary lumen with stents and calcified vessels

26 Slice thickness vs. noise 0.8mm1.0mm

27 Reconstruction filter vs. noise

28 Reconstructions n Choose appropriate filter –Sharper filter for patients with heavy coronary calcium or stents n Perform targeted reconstructions –3mm reconstruction of contiguous 10 phases for cardiac function analysis –0.8mm reconstruction of overlapping 40%, 70%, 75% and 80% for coronary anatomy. 1.0mm recons for heavy patients.

29 Clinical Application of Coronary CTA n Indications n Rendering & display modes n Characterization of Plaque n Grading of stenosis

30 Cardiac Indications n 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

31 Rendering Modes n MIP & slab MIP n Surface Display n Vessel tracking –Curved MIP –Globe view

32 Plaque Characterization n Calcified vs. Soft n Positive remodeling n Irregularity n Ulceration

33 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

34 Bland-Altman Analysis of Stenosis Grading Dashed lines % CI Hoffmann: JAMA, Volume 293(20).May 25, –2478

35 Impact of Calcified Vessels on detection of stenosis >50% 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 Low CSHigh CS Age57 +/ /-11 Male/female55/5 Heart rate57 +/-758 +/-7 Calcium score14 +/ /-716 Weight (kg)70 +/-672 +/-8 n Calcium score –Cutpoint = 55 n CTA: 1310 segs n Low CS pts –Sens = 90% –Spec = 92% n High CS pts –Sens = 97% –Spec = 91%

36 Impact of Coronary Calcium 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, All segmentsCa Score < 1000 Patients6046 Segments True positive5439 False positive2110 Sensitivity72%98% Specificity97%98% PPV72%80% NPV97%100%

37 Proximal versus Distal Segments All segmentsProximal segs Patients33 Segments True positive3427 False positive1913 Sensitivity63%82% Specificity96%93% PPV64%68% NPV96%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.

38 Non-coronary Assessment n Valvular assessment n Cardiac morphology n Cardiac function n EP planning


Download ppt "Cardiac CT and CT Angiography: Techniques & Clinical Applications Ethan J Halpern, MD Director, Cardiac CT Thomas Jefferson University."

Similar presentations


Ads by Google