Abdominal MRI Recognition Pattern

Systematic approach to interpreting abdominal MRI with sequences, contrast phases, and organ-specific protocols

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1. Essential MRI Sequences

A. Basic Sequences

• T1-weighted (in/opposed phase):
  - Liver fat quantification
  - Adrenal adenomas (signal dropout on OP)
  - Hemorrhage characterization
• T2-weighted (SSFSE/HASTE):
  - Biliary/pancreatic ducts
  - Cystic lesions
  - Bowel wall pathology
• DWI (b=50-800):
  - Restricted diffusion in tumors/abscesses
  - Lymph node detection
  - Prostate/cervical cancer evaluation

B. Contrast-enhanced Protocols

• Dynamic phases (Gadolinium):
  - Arterial (20-30s)
  - Portal venous (60-70s)
  - Delayed (3-5min)
  - Hepatobiliary phase (Eovist, 20min)
• MRCP:
  - Heavily T2-weighted
  - Non-contrast biliary/pancreatic duct evaluation

2. Organ-Specific Protocols

Organ	Key Sequences	Pathology Focus
Liver	T1 in/OP, DWI, Dynamic CE	HCC, metastases, hemangioma
Pancreas	T2 fat-sat, DWI, CE-MRI	Adenocarcinoma, pancreatitis
Kidneys	T2 HASTE, DCE-MRI	RCC, angiomyolipoma
Prostate	T2, DWI, DCE, MRS	PI-RADS scoring

3. Liver Lesion Patterns

A. Benign Lesions

Lesion	T1	T2	Enhancement
Hemangioma	Hypo	Very hyper	Peripheral nodular → fill-in
FNH	Iso/hypo	Iso/hyper	Homogeneous arterial, central scar
Cyst	Hypo	Very hyper	None

B. Malignant Lesions

• HCC:
  - Arterial hyperenhancement
  - Washout + capsule on PV/Delayed
  - Restricted diffusion
  - T1 variable, T2 mildly hyper
• Metastases:
  - Variable signal
  - Peripheral enhancement
  - Target DWI appearance

4. Dynamic Enhancement Patterns

Phase	Timing	Optimal Evaluation
Arterial	20-35 sec	Hypervascular tumors (HCC, NET)
Portal venous	60-80 sec	Hypovascular mets, washout
Delayed	3-5 min	Fibrosis (cholangiocarcinoma)
Hepatobiliary	20 min (Eovist)	FNH (retains contrast)

5. Pancreaticobiliary Evaluation

A. Pancreatic Masses

• Adenocarcinoma:
  - T1 hypointense
  - Delayed enhancement
  - DWI restriction
  - Vascular encasement
• Pancreatitis:
  - Stranding
  - Fluid collections
  - Duct dilation/strictures

B. MRCP Findings

• Choledocholithiasis:
  - Filling defects
  - Upstream dilation
• PSC:
  - Beaded ducts
  - Peripheral pruning

6. Artifacts & Pitfalls

• Motion artifacts:
  - Use breath-hold sequences
  - Radial k-space sampling
• Metallic artifacts:
  - View all sequences
  - Adjust bandwidth
• Pseudolesions:
  - Transient hepatic intensity differences (THIDs)
  - Vascular variants

7. MRI Abdomen Reporting Template

1. Technique: Sequences, contrast agent
2. Liver:
   - Morphology
   - Focal lesions (LI-RADS if applicable)
   - Biliary dilation
3. Pancreas:
   - Ducts
   - Parenchymal lesions
   - Peripancreatic findings
4. Retroperitoneum:
   - Lymph nodes
   - Vascular findings
5. Incidental findings:
   - Adrenal
   - Kidneys
   - Bowel

Always correlate with clinical history and prior imaging. For liver evaluation, use LI-RADS criteria when appropriate. In oncology patients, measure lesions consistently (RECIST 1.1). For cholangiopathies, combine MRCP with T2/DWI. Document incidental findings with appropriate follow-up recommendations. Consider contrast contraindications (GFR, allergies) and use hepatobiliary agents (Eovist) for specific indications.

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