Here is Multi Phases Contrast Abdomen Scan summary without bracket:

1. Definition
Multi phases contrast scan is CT or MRI of abdomen taken at different time intervals after IV contrast injection. It shows how organs and lesions enhance over time. It helps to characterize tumor, identify blood supply and differentiate benign vs malignant lesions.

2. Why Multi Phase Needed
Single phase may miss lesions. Some tumors enhance early and washout early. Some enhance late. Multi phase shows pattern of enhancement.

3. Contrast Used
Non ionic iodinated contrast for CT - dose about 80 to 120 ml depending on body weight
Injection rate 3 to 5 ml per second using power injector
Saline flush 20 to 30 ml after contrast
Gadolinium based contrast for MRI

4. Main Phases in CT Abdomen

1. Non Contrast Phase
No contrast
Base line scan
Useful to see calcification, fat, hemorrhage, kidney stones
Hyperdense lesion suggests hemorrhage or calcified lesion

2. Arterial Phase
Time: 20 to 35 sec after injection
Contrast in arteries only
Best for: arterial anatomy, aneurysm, hypervascular tumors like hepatocellular carcinoma, renal cell carcinoma, neuroendocrine tumor of pancreas
Aorta and hepatic artery bright, organs not fully enhanced yet

3. Late Arterial / Pancreatic Phase
Time: 35 to 45 sec
Pancreas enhances maximally
Best for: pancreatic tumor detection, as pancreatic cancer remains hypoenhancing compared to normal pancreas

4. Portal Venous Phase
Time: 60 to 80 sec
Most important phase, called workhorse phase
Contrast in portal vein and liver parenchyma
Liver enhances maximally, hypovascular metastases best seen here
Bowel wall, spleen, kidneys well seen

5. Nephrographic Phase
Time: 80 to 100 sec
Kidney parenchyma enhances homogeneously
Best for: renal masses, pyelonephritis

6. Delayed / Equilibrium / Excretory Phase
Time: 3 to 10 min after injection
Contrast in collecting system, ureters, bladder
Best for: washout pattern of lesions, cholangiocarcinoma shows delayed enhancement, urinary tract pathology, urinary leak, renal excretion assessment

5. Organ Wise Protocol

Liver Triphasic: non contrast plus arterial plus portal venous plus delayed. For HCC, hemangioma, FNH
Pancreas: non contrast plus pancreatic phase plus portal venous phase
Kidney: non contrast plus corticomedullary plus nephrographic plus excretory - called CT Urography
Adrenal: non contrast plus portal venous plus 15 min delayed for washout calculation

6. Washout Pattern - Key to Diagnosis
HCC: arterial hyperenhancement plus portal venous washout
Hemangioma: peripheral nodular arterial enhancement plus centripetal filling in delayed phase
FNH: arterial enhancement plus isoenhancing in portal venous, no washout
Cholangiocarcinoma: peripheral rim enhancement plus progressive delayed enhancement

7. Advantages
Accurate lesion detection and characterization
Shows vascularity and staging of tumor
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