Pancreatic Protocol CT

What Is It?

Pancreatic protocol CT (also called dedicated pancreatic CT or multiphasic pancreatic CT) is a specialized multi-phase CT technique optimized to detect and characterize pancreatic pathology - especially pancreatic ductal adenocarcinoma (PDAC), neuroendocrine tumors (NETs), cystic lesions, and pancreatitis. It differs from a routine abdominal CT in its timing, slice thickness, and oral contrast selection.

Indications

Indication	Preferred Phases
Suspected PDAC / pancreatic mass	Pancreatic (late arterial) + portal venous
Neuroendocrine tumor	Arterial + portal venous
Cystic pancreatic lesion	Pancreatic + portal venous
Acute pancreatitis (severity, necrosis)	Portal venous (±arterial if pseudoaneurysm suspected)
Chronic pancreatitis / calcifications	Non-contrast + portal venous

Technique Overview

Patient Preparation

Position: Supine, arms elevated above head
Oral contrast: Neutral contrast (water), not positive (barium/iodine-based). Approximately 800 mL water 20-30 min before scan - distends the stomach and duodenum to define the duodenal loop without obscuring vascular enhancement
Breath-hold: Required for all phases

Scan Parameters

Tube voltage: ≤120 kVp
Slice thickness: ≤1 mm (thin slices, typically 0.625 mm), interval ≤0.5 mm
FOV: ~350 mm, adjusted for patient size
Reconstruction: Soft tissue algorithm; 3D reconstructions as needed
Scan extent: Mid-diaphragm to iliac crest for arterial/pancreatic phase; above diaphragm to iliac crest for venous phase (to capture hepatic metastases)

IV Contrast

Volume: 70-120 mL (1 mL/kg) with 30-40 mL saline chaser
Injection rate: 3-5 mL/s (minimum 22G IV; 18G preferred)
Timing: Bolus tracking or test bolus technique using the abdominal aorta as the reference

Phases of Acquisition

1. Non-Contrast Phase (optional but recommended)

Identifies calcifications (chronic pancreatitis), hyperdense lesions, baseline density
Establishes baseline Hounsfield units for enhancement analysis
Bailey and Love: "An initial unenhanced CT scan is essential to determine the presence of calcification within the pancreas and gallbladder."

2. Pancreatic Phase (Late Arterial Phase)

Timing: ~35-45 seconds after contrast injection (or 15-20 sec after bolus trigger)
Also called the pancreatic parenchymal phase
Maximum parenchymal enhancement of the pancreas occurs here
Provides maximum contrast difference between the normally enhancing parenchyma and hypoenhancing PDAC - best phase to detect PDAC
Best phase for evaluating tumor-artery relationships (SMA, celiac, hepatic artery) and identifying aberrant arterial anatomy
The arterial opacification in this phase also limits the need for a separate dedicated arterial phase in most cases

3. Portal Venous Phase

Timing: ~60-70 seconds after injection
Best for evaluating hepatic metastases (most liver mets are hypovascular and best seen here)
Assesses variant venous anatomy and tumor involvement of the portal vein, SMV, and splenic vein (abutment, encasement, thrombosis)
Standard phase for assessing venous thrombosis

4. Delayed / Hepatic Phase (optional)

Timing: ~180 seconds
May be added for characterization of indeterminate liver lesions
Some institutions include for assessing biliary anatomy or certain cystic lesions

Why These Specific Phases?

PDAC is typically desmoplastic and hypovascular - it enhances less than the surrounding normal pancreatic parenchyma. The pancreatic phase maximizes the attenuation difference (tumor-to-pancreas contrast), making even small tumors (1-2 cm) visible. By contrast, NETs are hypervascular and light up brightly in the arterial phase.

Sabiston Textbook of Surgery: "The late-arterial phase is usually the best phase to identify PDAC because the timing provides the maximum contrast difference between normally enhancing pancreatic parenchyma and the PDAC, which is generally hypoenhancing. In addition, this is the best phase for analyzing the tumor-artery relationships and noting the presence of any aberrant arterial anatomy. The portal-venous phase is valuable for assessing variant venous anatomy and tumor-vessel abutment or encasement."

What the Scan Evaluates (for PDAC)

Tumor location - head (most common), body, or tail
Resectability - key surgical decision:
- Arterial involvement: SMA, celiac axis, hepatic artery (assessed on pancreatic phase)
- Venous involvement: portal vein, SMV (assessed on venous phase)
Distant metastases - liver (venous phase), peritoneum, lung (include chest CT)
Biliary/pancreatic duct dilation - double duct sign in periampullary tumors
Nodal involvement
Vascular anatomy variants - critical for surgical planning (e.g., replaced right hepatic artery from SMA)

Unenhanced CT of chronic pancreatitis showing calcification in the head of the pancreas (arrow)

Unenhanced pancreatic CT showing calcification (arrow) in the head of the pancreas - Bailey and Love's Surgery

Limitations and Additional Imaging

If indeterminate liver lesions or suspicious nodal involvement exist on CT, add MRI (better soft tissue characterization) or PET-CT (metabolic activity)
CT should always be done before any invasive procedure (ERCP, EUS-FNA). ERCP-related pancreatitis causes peripancreatic inflammation that obscures the tumor-vessel relationship and degrades staging accuracy
For vascular planning, CT angiography reconstructions from the same dataset are often produced

Summary Table

Phase	Timing	Key Purpose
Non-contrast	Before injection	Calcifications, baseline
Pancreatic (late arterial)	~35-45 sec	PDAC detection, arterial anatomy
Portal venous	~60-70 sec	Venous anatomy, liver mets
Delayed (optional)	~180 sec	Indeterminate liver lesions

Sources:

Sabiston Textbook of Surgery - Diagnostic Studies (PDAC chapter)
Bailey and Love's Short Practice of Surgery, 28th ed. - Computed Tomography of the Pancreas
Radiopaedia: CT Pancreas Protocol
Applied Radiology: Imaging of the Pancreas

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