Ct abdomen protocols IMAGING guidelines.pptx

Ct abdomen protocol

1. Ct abdomen protocols

2. CONTENTS INTRODUCTION Noncontrast ct TRIPHASIC PROTOCOL PANCREAS PROTOCOL ADRENAL PROTOCOL RENAL PROTOCOL TRAUMA PROTOCOL CTA ABDOMINAL AORTA PROTOCOL

3. introduction The  CT abdomen protocol  serves as an outline for an examination of the whole abdomen . Ct scan is fast, painless, noninvasive and accurate. Common uses: 1) Diagnose the causes of abdominal pain. 2) Infections such as appendicitis ,pyelonephritis ,infected fluid collections 3) Inflammatory bowel disease such as ulcerative colitis or crohns disease ,pancreatitis ,cirrhosis of liver. 4) Cancers of liver, kidneys, pancreas, ovaries and bladder. 5) Abdominal aortic aneurysms ,injuries to abdominal organs such as spleen , liver, kidneys and other internal organs in cases of trauma.

4. 6) Guide biopsies and other procedures abcess drainages. 7) Plan for assess the results of surgery such as organ transplants. 8) Stage , plan and properly administer treatments for tumors as well as monitor response to chemotherapy.

5. GENERAL PRINCIPLES CT abdomen protocols refer to the specific procedures and settings used to conduct a CT scan of the abdomen. 1. Patient Preparation: - Fasting: Patients are often asked to fast for 4-6 hours before the scan. - Hydration: Encourage hydration unless contraindicated. - Bowel preparation : For certain indications, bowel preparation with oral contrast agents may be required. 2. Contrast Use: - Non-contrast : No contrast agent is used. Useful for detecting calcifications, stones, and hemorrhage.

6. - Intravenous (IV) contrast: Enhances vascular structures and helps in characterizing lesions. - Oral contrast: Used to opacify the gastrointestinal tract. 3. Positioning: - Supine position is standard. - Arms are usually placed above the head to avoid artifacts .

7. NON CONTRAST CT USEFUL IN DETECTION OF : 1) Stones in kidney , ureter, sometimes in cbd . 2) Calcifications in liver and pancreas. 3) Fat in liver tumors . 4) Fat-stranding as seen in inflammation like appendicitis, diverticulitis, omental infarction 5) Fat in adrenal adenoma or myelolipoma.

8. Contrast enhanced ct CECT helps in finding pathology by enhancing the contrast between a lesion and the normal surrounding structures. Enhancement in the different phases : Early arterial phase Late arterial phase Hepatic or late portal phase Nephrogenic phase Delayed phase

9. Early arterial phase 15-20 sec p ost injection or immediately after bolustracking this is the phase when the contrast is still in the arteries and has not enhanced the organs and other soft tissues. DETECTION OF : Dissection of aorta Arterial bleeding

10. Late arterial phase  Aka "arterial phase" or "early venous portal phase“ - 35-40 sec p ost injection or 15-20 sec after bolustracking ENHANCEMENT OF : Hypervascular lesions Stomach Bowel Pancreas Spleen Kidney outer cortex

11. DETECTION OF : Liver lesions Bowel ischemia Pancreas- adenocarcinoma-insulinoma

12. Hepatic phase  70-80 sec p.i. or 50-60 sec After bolustracking .  Enhancement of: Hepatic parenchyma Detection of: Hypovascular liver lesions like cyst , abcess , Most metastasis

13. Nephrogenic phase 100 sec p.I. Or 80 sec after bolustracking . ENHANCEMENT OF: All renal parenchyma including medulla.  DETECTION OF: Renal cell carcinoma

14. Delayed phase   - 6-10 minutes p.i. or 6-10 Minutes after bolustracking . Aka "wash out phase" or "equilibrium phase".  ENHANCEMENT OF: Fibrotic lesions Still enhancement of kidney and urinary tract DETECTION OF: Cholangiocarcinoma Fibrotic metastasis Transitional cell carcinoma

15. PATIENT POSITION Supine position, abdomen centered within the gantry Both arms elevated TUBE VOLTAGE ≤120 kvp TUBE CURRENT As suggested by the  automatic exposure control.   SCOUT Above the diaphragm to the lesser trochanter SCAN EXTENT Arterial phase: diaphragm to the iliac crest Venous phase: above the  diaphragm  to the  symphysis SCAN DIRECTION Craniocaudal technique

16. technique SCAN GEOMETRY Field of view (FOV): 350 mm (should be adjusted to increase in-plane resolution) Slice thickness: ≤0.75 mm, interval: ≤0.5 mm Reconstruction algorithm: soft tissue, bone kernel ORAL CONTRAST Positive contrast agent (abscesses, infectious conditions): as per preparation guide Neutral contrast agent (nonacute conditions): 1000 ml water 20-30 min before the scan RESPIRATION PHASE Single breath-hold: inspiration MULTIPLANAR RECONSTRUCTIONS Axial images:   strictly axial to the body axis Coronal images: strictly coronal to the body axis Sagittal images: strictly sagittal to the body axis Slice thickness: soft tissue 4-5 mm, bone 2-3 mm overlap 20-40%

17. technique contrast injection considerations non-contrast (optional) biphasic arterial ± venous acquisition Contrast volume: 70-100ml  (0.1 ml/kg) with 30-40 ml saline chaser at 3-5 ml/s Bolus tracking: abdominal aorta Arterial phase: minimal scan delay Portal venous phase: 30-50 seconds after the arterial phase or 60-80 seconds after contrast injection single acquisition with a monophasic injection (venous phase): Contrast volume: 70-100ml  (0.1 ml/kg) with 30-40 ml saline chaser at 3 ml/s Portal venous acquisition: 60-80 sec after contrast injection single acquisition with a biphasic injection or split bolus 70 ml contrast media at 3 ml/s 50 ml contrast media and 30-50 ml saline chaser at 4 ml/s starting 30 sec after contrast injection Venous acquisition: 60-80 sec after contrast injection

18. Common protocols 1. Routine Abdomen and Pelvis CT: - Indications: General abdominal pain, suspected tumors , infections, trauma. - PHASES: - Non-contrast phase (optional based on indication). - Portal venous phase (70-80 seconds post-contrast injection). - Delayed phase (optional, 5-10 minutes post-contrast for specific indications like ureteric pathology).

19. Routine whole abdomen Indications: Screening, detection and confirmation of the lesions, follow ups, control or baseline scans. Patient positioning: Head first , supine with arms extending above the level of head Topogram position / landmark : Anteroposterior , level of the nipples to 3 cms below the inferior border of pubic symphysis. Mode of scanning : Helical with single breath hold technique. scan orientation : Craniocaudal direction. Starting location: 1cm above the highest point on the dome of diaphragm. End location : 1 cm below the apex of prostate.

20. Routine whole abdomen Contrast administration : Oral, rectal and intravenous. Volume of contrast : A) 750-1000 ml of 1-2 % positive oral contrast B) 500-700 ml of 2% positive rectal contrast C) 60- 100 ml of contrast intravenously Rate of injection of contrast: 2-3 ml/sec Slice thickness : 5 mm Slice interval : 5 mm 3d reconstruction : mrp , mip

21. liver Normal parenchyma is supplied for 80% by the portal vein and only for 20% by the hepatic artery All  liver tumors however get 100% of their blood supply from the hepatic artery. So a  hypervascular  tumor will be best seen in the late arterial phase. A  hypovascular  liver tumor however will enhance poorly in the late arterial phase, because it is hypovascular and the surrounding liver does also enhance poorly in that phase. This tumor is best seen when the surrounding tissue enhances, i.E. In the late portal (or hepatic) phase at 75-80 sec p.I.

22. LIVER PROTOCOLS Oral Prep: None Scanning: Injection rate: 4-5cc/sec 1. I+ Late arterial phase – liver only - 25 sec after start injection 2. I+ PV phase – entire abdomen - 60-70 sec after start injection 3. I+ Delay- liver only ~5 minutes after start injection

23. Pancreas protocol INDICATIONS Typical indications include an evaluation of the following  1-4 : Jaundice Evaluation of  pancreatic tumors  and/or  cystic lesions Acute  or  chronic pancreatitis Complications of pancreatic diseases Unclear findings on ultrasound or  CT abdomen Pancreatic interventions ( e.G.   Ct-guided biopsy ,  drainage )

24. Pancreas protocol Oral preparation : Scanning : injection rate 4-5 cc/sec BIPHASIC PANCREATIC ± VENOUS ACQUISITION Contrast volume: 70-120ml  (1 ml/kg) with 30-40 ml saline chaser at 3-5 ml/s Optional bolus tracking: abdominal aorta Pancreatic phase: scan delay 15-20 sec after trigger or 35-40 sec after contrast injection  1 Portal venous phase: 30 sec after the pancreatic phase or 65-70 sec after contrast injection  Water: 500-700ml within 30 minutes of scan

25. Renal protocol

26. Renal protocol

27. Renal stone protocol

28. Adrenal protocol INDICATIONS Characterize incidentally discovered adrenal nodules and seek adrenal abnormalities when clinically suspected. PURPOSE To characterize adrenal nodules on the basis of the density on non-contrast and post-contrast imaging, and  washout characteristics . Nodules with lipid density measurements on the non-contrast series can be diagnosed as lipid-rich adenomas. Nodules that are not lipid-rich, washout calculations can be used to differentiate between lipid-poor adenomas and indeterminate lesions, Differentials for the latter including  adrenocortical carcinoma  and  pheochromocytoma

29. Adrenal wash out Adrenal washout  can be calculated using the density value of an  adrenal mass  on non-enhanced, portal venous phase and 15-minute delayed  CT scans  (density measured in  hounsfield units (HU) ). It is primarily used to diagnose  adrenal adenoma . absolute washout [( HU portal venous phase ) - ( HU delayed )] / [( HU portal venous phase ) - ( HU non -enhanced )] x 100 >60% washout is highly suggestive of adrenal adenoma relative washout [( HU portal venous phase ) - ( HU delayed )] / ( HU portal venous phase ) x 100 >40% washout is highly suggestive of adrenal adenoma

30. Trauma protocol

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