Functional MR Urography
Functional MR Urography
Key Points
- Non-ionizing radiation imaging modality
- Provides both anatomical and functional information
- Superior soft tissue contrast
- Evaluates renal function independently
- Allows 3D reconstruction of urinary tract
Functional MR Urography combines high-resolution anatomic imaging with dynamic contrast-enhanced sequences to evaluate renal function and urinary tract anatomy simultaneously. It offers comprehensive assessment without radiation exposure.
Technical Aspects
Basic Requirements
- Hardware Requirements
- 1.5T or 3T MRI scanner
- Phased-array body coils
- Respiratory gating capability
- IV contrast injection system
- Patient Preparation
- 4-6 hours fasting
- IV hydration protocol
- Bladder catheterization when needed
- Sedation protocols for young children
Contrast Agents
- Gadolinium-based contrast agents
- Standard dose: 0.1 mmol/kg
- Consideration of NSF risk
- Timing of administration
Imaging Protocol
Sequence Components
- Static Sequences
- T2-weighted FSE/TSE
- T1-weighted pre-contrast
- 3D heavily T2-weighted urography
- Post-contrast T1-weighted
- Dynamic Sequences
- T1-weighted 3D gradient echo
- Temporal resolution 4-8 seconds
- Multiple phases post-contrast
- Excretory phase imaging
Acquisition Parameters
- T2-weighted Urography
- TR/TE: 2000/700 ms
- Slice thickness: 1.5-2mm
- Respiratory triggering
- Dynamic Study
- 3D spoiled gradient echo
- Fat suppression
- Parallel imaging
- 20-30 phases acquisition
Functional Parameters
Quantitative Measurements
- Volumetric Analysis
- Renal volume
- Cortical volume
- Pelvic volume
- Transit Times
- Calyceal arrival time
- Pelvic transit time
- Parenchymal transit time
- Functional Indices
- Differential renal function
- Split renal function
- Renal transit time
- Excretion curves
Post-Processing
- Time-Intensity Curves
- ROI placement
- Enhancement patterns
- Washout characteristics
- 3D Reconstructions
- Maximum intensity projections
- Volume rendering
- Curved planar reformations
Clinical Applications
Primary Indications
- Congenital Anomalies
- Ureteropelvic junction obstruction
- Megaureter
- Complex genitourinary anomalies
- Duplicated collecting systems
- Acquired Conditions
- Post-operative assessment
- Urinary tract obstruction
- Complex stone disease
- Tumor evaluation
Special Considerations
- Pediatric Applications
- Prenatal hydronephrosis follow-up
- Complex congenital anomalies
- Surgical planning
- Post-operative surveillance
- Advantages Over Other Modalities
- No ionizing radiation
- Superior soft tissue contrast
- Functional assessment
- 3D anatomical details
- Independent kidney evaluation
