CT ANGIOGRAPHY

Dr Mohamed El Safwany, MD

Intended learning outcome

• The student should learn at the end of this lecture CT IMAGE OF THE BLOOD VESSEL OPACIFIED BY CONTRAST.

CT IMAGE OF THE BLOOD VESSELS OPACIFIED BY

CONTRAST

REQUIREMENTS FOR CTA

• PATIENT PREPARATION

• ACQUSITION PARAMETERS

• CONTRAST MEDIUM ADMINISTRATION

• POSTPROCESSING TECHNIQUES

PATIENT PREP.

INFORMED CONSENT

                                         

PATIENT PREP.

• CREAT.- 0.6 –1.2 mg/dl

• IODINE ALLERGY- STEROID THERAPY

• HYPERVENTILATION BEFORE EXAM FOR BETTER BREATHOLD

UTILIZED

GAUGE SUITABLE FOR CTA

18 OR 20

CONTRAST ADMINISTERED WITH POWER INJECTOR

ACQUSITION PARAMETERS

PARAMETERS

• USUALLY ROUTINE CT PRECEDES A CTA EXAM. THE ROUTINE EXAM IS USED AS A REFERENCE SCAN HELPING TO DETERMING THE SCANNING RANGE IN CTA.

SLICE THICKNESS

• SLICE THICKNESS

• SPATIAL RESOLUTION

• CEREBRAL CTA

• ABDOMINAL CTA

• THORACIC CTA

• 1MM (LOWER mA)

• 3MM

• 3MM

SLICE THICKNESS

SPIRAL PITCH

• PITCH • SPATIAL RESOLUTION

SPIRAL PITCH

• UP TO 2

kVp, mA, TIME

• SIMILAR TO NON- CTA EXAM OF THE SAME BODY PART

RECONSTRUCTION INTERVAL

• 50% OF OVERLAP

CONTRAST ADMINISTRATION

POWER INJECTOR

POWER INJECTOR PARAMETERS

VOLUME OF CONTRAST-ml

RATE ml/sec

TIME OF INJECTION – sec

SCAN DELAY TIME - sec

CONTRAST WARMER

WHY???

RATE OF INJECTION

3-5 ml/sec

ORAL CONTRAST????

WATER

NEGATIVE CONTRAST

AUTOMATED CONTRAST ADMINISTRATION

SYSTEMS • SMARTPREP

• CARE

• SURESTART

CONTRAST ADMINISTRATION AND SCANNING METHODS

• BOLUS TRACKING

• BOLUS TIMING

• MANUAL PRESET TIME

CARE BOLUS

                                                                                            

SMART PREP

                                                         

Bolus tracking- PE

PE?

Tracking slice

Bolus tracking- Carotids and Circle of Willis

Circle of Willis

Circle of Willis?!

40 SEC

Renal arteries 25-30 sec.

ABDOMINAL AND FEMORAL RUNOFF

MANUAL DELAYS

• CERBRAL CTA

• CAROTID CTA

• CHEST CTA (PE)

• 15 SEC

• 12 SEC

• 10-20 SEC

CARDIAC CT

TWO TECHNIQUES TO REDUCE MOTION ARTIFACTS IN CARDIAC

CT

• PROSPECTIVE TRIGGERING

• RETROSPECTIVE GATING

Prospectively ECG-Triggered Sequential Scanning

Cardiac CT applications require the synchronization of data acquisition to the cardiac cycle, i.e. to the movement of the heart. For sequential imaging, a prospective trigger is derived from the ECG-trace to initiate the CT-scan with a certain delay time after the R-wave. Usually, the delay is defined such that the scans are acquired during the diastolic phase of the heart

Retrospectively ECG-Gated Spiral Scanning

For "retrospectively ECG-gated spiral scanning" a continuous spiral scan is acquired with the ECG-signal recorded simultaneously. The acquired scan data is selected for image reconstruction with respect to a pre-defined cardiac phase. Similar to ECG-triggered sequential scanning a certain R-wave delay time defines the start point of data that is used for image reconstruction. ECG-gated spiral scanning has several advantages over ECG-triggered sequential scanning. The continuous acquisition allows for reconstruction of overlapping slices. Due to the retrospective analysis of the ECG, the technique is less sensitive to arrhythmia.

BOTH METHODS REQUIRE ECG MONITORING

DIASTOLIC PHASE

SCANNING DURING RR INTERVAL

Retrospective ECG-Gating

                                                                                                                                                              

CARDIAC CT PROCEDURES

• CARDIAC ANGIOGRAM

• CALCIUM SCORING

CARDIAC ANGIOGRAM

PERFORMED WITH CONTRAST INJECTION

4-5 cc/sec

150 cc total volume

CALCIUM SCORING

NO IV CONTRAST USED

CARDIAC ANGIOGRAM

CALCIUM SCORING

3-D VISUALIZATION TOOLS IN CTA

• MPR

• MIP

• SSD

• VR

• CINE

CARDIAC ANGIOGRAM

CTA - MPR

PLANE?

MPR

PLANE?

MIP - CTA

                                                           

SSD -CTA

VR - CTA

CINE CTA

MPR

• SIMPLE• FAST• ANY PLANE

VISUALIZATION

• LESS USEFUL IN COMPLEX VESSEL VISUALIZATION

SSD

• FAST• LITTLE EDITING• LITTLE AXIAL

DATA USAGE• CONTOUR ,

RELATIONSHIP OF VESSELS

• ARTIFACT GENERATION

• INACCURATE

MIP

• CALCIFICATION DETECTION

• THROMBUS DETECTION

• AILIASING ARTIFACT

• EDITING REQUIRED

VR

• ACCURATE• ALL DATA USED• GOOD STENOSIS

DETECTION

• COMPLEX COMPUTER PROCESSING (PAST)

STEREOSCOPIC VIEWING

Text Book

• David Sutton’s Radiology

• Clark’s Radiographic positioning and techniques

Assignment

• Two students will be selected for assignment.

Question

• Define Care bolus technique?

• Thank You