Ct aortogram by vikas kumar of rit .pptx

Ct aortogram by vikas kumar of rit

1. CT AORTOGRAPHY VIKAS KUMAR 220513008 M.Sc. RIT 4 TH Semester

2. Introduction Computed tomography based Aortogram is an imaging procedure where rotating beam of X-rays are used to scan and create an image of the blood vessel by injecting contrast media . This procedure is mainly done to visualize the major blood vessel carrying blood out of the heart called Aorta. These images helps to detect and diagnose various disorders of the aorta and its branches.

3. Aorta It is the largest artery in the body. It receives the cardiac output from the left ventricle and supplies the body with oxygenated blood via systemic circulation. Aorta can be divided into four sections as ascending aorta, aortic arch, descending aorta and abdominal aorta. At L4 it terminates as left and right common illiac arteries. Main clinical indications of Aorta are Aortic aneurysm, Aortic dissection & Aortic stenosis

4. AORTA

5. INDICATION breathlessness Aortic aneurysm Aortic dissection Suspected bleeding Major trauma Suspected aortic rupture/thrombosis.

6. AORTIC ANEURYSM

7. AORTIC DISSECTION

8. AORTIC STENOSIS

9. Contra Indication  Pregnant women Hypersensitive to iodinated contrast media CKD Allergic to some medications

10. Patient preparation Patient shou ld NPO 6-7hrs prior to exam. RFT, BUN, Creatine blood test should be normal. Hence the patient will be in a critical situation we must be prepared with emergency drugs like adrenaline etc. to treat with life threatening or allergic reactions. Procedure should explain to patient . Consent form should be signed.

11. Procedure 22g cannula is injected to the patients body to inject the contrast. P atient is held in supine position with head first. Now the length of the area to be scanned is measured and the scan is started and planned. Take topogram. Land mark –Chin to Mid of Femur. ROI – Ascending Aorta. T he patient is adviced about the contrast injection and about the discomfort during injection. Now the contrast media is injected and visualized.

12. TECHNICAL PARAMETERS Kvp - 120 m As – 250 ROI – Ascending Aorta Scan direction - Craniocaudal Bolus timing - Test bolus Contrast – Iohexol Flow rate – 110ml at 4.5ml/s Pitch - Depends upon the heart rate

13. MRI AORTOGRAM

14. INTRODUCTION MR imaging allows for comprehensive evaluation of thoracic aorta without exposure to iodinated contrast or ionizing radiation. Basic knowledge of pulse sequences and common artifacts and ways to avoid them is essential for successful MR imaging of the aorta.

15. INDICATION Aortic Aneurysm Acute aortic syndrome Large vessel vasculitis

16. PATIENT PREPARATION Have the patient micturate before the study Explain the procedure to the patient. Ask the patient to remove anything containing metal (hearing aids, hairpins, body jewelry, etc.) Have a large-gauge intravenous line inserted and flushed extension set connected Patient Positioning Supine Body Coil (or body array coil) Cushion the knees. If necessary, offer the patient ear protectors.

17. Sequences Scout Axial Sagittal Coronal If a test bolus is being used then Para coronal slice or Sequence 1 axial

18. The aortic lumen can also be imaged without intravenous administration of a contrast material.  A commonly used sequence for this method is the balanced steady-state free-precession (bSSFP) sequence, with contrast determined by the T2/T1 ratios of the different tissues. As blood intrinsically has a high T2/T1 ratio when compared with the ratio of stationary tissues, this technique yields bright-blood images without the use of intravenous contrast.  NOTE: Veins will also appear bright with this technique. BRIGHT BLOOD

19. It can be implemented as 2D or 3D sequence.  2D sequence can be obtained with ECG synchronization to provide cine images depicting aortic blood flow, as well as generating dark signal in the setting of dephasing caused by nonlaminar flow associated with valve stenosis or coarctation. 3D with CE rarely used, due to long scan time.

20. Dark Blood Sequences It can be obtained with spin echo or inversion recovery sequences; with nulling of signal from moving blood, the aortic wall is clearly depicted. The aortic wall anatomy and tissue characteristics may be defined based on T1, T2, and T2* signal characteristics. Many different methods are used to acquire black-blood images, including breath-hold, respiratory-triggered, and rapid single-shot techniques

21. Aortic arch intramural hematoma (arrows). (A) CE-MRA, (B) dark-blood MRA, and (C) noncontrast CT. Although the imaging method of choice for acute aortic syndromes is CT/CTA, MRA

22. Phase Contrast Sequences It can be used to quantify aortic flow.  PC quantification was founded on the observation that protons passing through a magnetic field gradient undergo a phase change in proportion to velocity.   This technique allows for evaluation of aortic forward flow and stenotic and regurgitant valves and is helpful in the assessment of congenital heart disease.  PC imaging is most commonly acquired as a single through-plane or in-plane direction, with more recent developments allowing for flow analysis in multiple directions, albeit with longer acquisition time.

23. Sequence 1 axial T1- weighted across the aorta, GRE (total acquisition time per slice is 1 second; 30 slices in series in the sane slice position). Start sequence simultaneously with the injection of 2 ml contrast (preinjected into the line and followed by 20 ml saline; e.g., Gd-BOPTA or gadobutrol) TR = 5–8.5 TE = 3–4.0 Flip angle 10–40°

24. Injection rate: Bolus injection (approx. 2–3 ml/s) Determine the time required from the start of the injection until maximum signal in the thoracic aorta is reached (= contrast circulation time); Divide the total duration of the angiography sequence (= sequence 2 below) by 2 and subtract the time to maximum signal (contrast circulation time) from this result. This yields the time in seconds needed to start the contrast injection ahead of (for negative values) or after (for positive values) the start of the sequence. Injection of the contrast agent depends on the duration of the sequence (e.g., 34 seconds) and the contrast circulation time (measured) (e.g., 10 seconds). The contrast peak must be in the center of the k-space = usually in the middle of the sequence (in our case = 34/2=17 seconds; since the contrast agent will start flooding after 10 seconds, contrast injection will have to begin 7 seconds before the start of the sequence).

25. SEQUENCE 2 (PARA) CORONAL, 3D GRE BREATHHOLD This sequence will be taken in inspiration with contrast enhancement. Eg : FISP. Slab thickness: 60–80 mm No. of partitions: 28–36 FOV: large (500 mm) Matrix: 512 (256)

26. Example — TR = 5.8 TE = 1.8 Flip angle 30° 3-D FFE: TR = 2.5–5 TE = 1–2 Flip angle 25–40° Possibly after another respiration cycle (delay to start of sequence 3 approx. 5–7 seconds)

27. Sequence 3 coronal as sequence 2, but after contrast enhancement (late image) Post Processing MIP analysis Tips & Tricks Note: use a large-gauge intravenous line Note: some companies use sequences where the center of the k-space does not coincide with the middle of the acquisition period; check with the company and adjust the timing accordingly The rule of thumb for the injection rate is: Volume of injection/half the duration of the sequence = injection rate in ml/s With manual contrast injection an additional 3 seconds may be needed to compensate for the reaction time