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This article discusses the requirements for performing CT angiography, including patient preparation, acquisition parameters, contrast medium administration, and postprocessing techniques. It also provides information on contrast reactions and suitable gauge and canula selection.
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CTANGIOGRAPHY Dr. DevadasAcharya Prof. and H.O.D Department of Radio-Diagnosis Yenepoya Medical College YENEPOYAUNIVERSITY www.yenepoya.edu.in
REQUIREMENTS FOR CTA • PATIENT PREPARATION • ACQUSITION PARAMETERS • CONTRAST MEDIUM ADMINISTRATION • POSTPROCESSING TECHNIQUES
PATIENT PREPARATION • Blood Urea 15-40 mg/dl • CREAT.- 0.6 –1.2 mg/dl • IODINE ALLERGY • Pregnancy? • eGFR >45 ml/min/1.73 m2 (Ideally >60) • NPO – 4-5 Hours
High Risk Patients • Hypersensitivity towards iodine • Diabetes Mellitus • Asthma • Dehydration • Chronic/Acute renal disease
GAUGE SUITABLE FOR CTA CANULA SELECTION • 22G • Paediatric • Peripheral Smaller veins • Slow Flow rate <3ml/sec • 18G • CT Angiography • High Flow rate 4-5ml/sec • ` • 20G • Routine CECT/Angio • Flow rate 3-4ml/sec
300 vs. 370 Iodine • 300mg/ml • Routine: • Cerebral Angio • Peripheral Angio • Pulmonary Angio • 370mg/ml • Selective Visceral Angio • Coronary Angio • Paediatric Angiocardiography
How to Calculate Total Volume of Contrast Ideally volume of CM Adapted to concentration and Patient’s weight 1.7–2.0 ml/kg of 300 mgI/ml CM OR 1.4–1.6 ml/kg of 370 mgI/ml C
CreatinineGuidlines • If the creatinine is ≤ 1.5 and the GFR is >60mL/min/1.73m2 – go ahead and administer contrast. • If the creatinine is >1.5 in a diabetic, >2.0 in a non-diabetic, or GFR is <30 mL/min/1.73m2, radiologist must discuss with the clinician.
Visipaque It is the only iso-osmolar contrast agent, with an osmolality of 290 mOsm/kg H2O: The same as blood Used in Creatinine level upto 2.4 mg/dl
PARAMETERS • Usually routine CT precedes a CTA exam • The routine exam is used as a reference scan helping to determine the scanning range in CTA.
SLICE THICKNESS SPATIAL RESOLUTION SLICE THICKNESS
CEREBRAL CTA ABDOMINAL CTA THORACIC CTA 1MM (LOWER mA) 3MM 3MM SLICE THICKNESS
PITCH SPATIAL RESOLUTION SPIRAL PITCH 0.984 : 1
kVp, mA, TIME • SIMILAR TO NON- CTA EXAM OF THE SAME BODY PART RECONSTRUCTION INTERVAL 0.625
POWER INJECTOR POWER INJECTORS
POWER INJECTOR PARAMETERS VOLUME OF CONTRAST-ml RATE ml/sec TIME OF INJECTION – sec SCAN DELAY TIME - sec
Pushes contrast in tubing and peripheral veins into central veins (20 – 30 cc) Reduced streak artifacts from veins and right heart SALINE CHASER Dual Injector
Timing Bolus • Select target location from scout topogram • Inject small test-bolus; 15 – 20 mL contrast • Acquire low-dose scan at specified location • ROI in target structure • Measure time-attenuation curve • Contrast material arrival time in aortic root Scan Timing
Bolus Triggering • Select trigger location • Acquire reference image • •Place ROI in vascular structure of interest • Inject contrast bolus • Monitor attenuation in ROI • Start scan when desired threshold reached Scan Timing