MRI Prostate (mpMRI)

Multiparametric prostate MRI (mpMRI) combines high-resolution T2-weighted, diffusion-weighted, and dynamic contrast-enhanced imaging to detect and localize clinically significant prostate cancer and guide targeted biopsy. Interpretation follows the PI-RADS framework, which standardizes acquisition and reporting. mpMRI improves detection of significant tumors while reducing detection of indolent disease and unnecessary biopsies. It is integral to biopsy planning, staging, and active surveillance.

Indications

Elevated or rising PSA with prior negative biopsy or biopsy-naive risk stratification
Detection and localization of clinically significant prostate cancer before targeted biopsy
Local staging of known cancer including extracapsular extension and seminal vesicle invasion
Active surveillance monitoring of low-risk disease
Assessment of suspected recurrence after treatment (with modified protocol)
Guidance and fusion for MRI-targeted biopsy

Contraindications & Cautions

Non-MRI-conditional implanted devices and hip prostheses causing severe DWI artifact (relative)
Severe renal impairment (eGFR <30) limits gadolinium for the DCE component; a biparametric approach may be used
Gadolinium hypersensitivity
Recent prostate biopsy causing post-biopsy hemorrhage that degrades interpretation (defer 6-8 weeks)
Inability to lie still; bowel motion/gas degrading DWI
Non-conditional endorectal coil considerations if used

Patient Preparation

MRI safety screening for devices and implants
Ideally image 6 or more weeks after biopsy to allow hemorrhage to resolve
Consider antispasmodic (e.g., hyoscine/glucagon) to reduce rectal peristalsis artifact
Empty rectum (enema per local protocol) to minimize gas/stool DWI distortion
Check eGFR and obtain contrast consent if DCE is performed
Establish IV access for gadolinium; position supine with pelvic phased-array (endorectal coil optional)
Advise voiding before scanning for a moderately full but not distended bladder

Technique & Parameters

3T preferred (1.5T acceptable) with pelvic phased-array coil; endorectal coil optional
High-resolution T2-weighted in three planes, slice thickness 3 mm, small field of view
Diffusion-weighted imaging with high b-values (>=1400 s/mm2, calculated) and ADC map
Dynamic contrast-enhanced T1 fat-saturated series with temporal resolution <=10-15 s after gadolinium
PI-RADS v2.1 scoring: DWI dominant in peripheral zone, T2 dominant in transition zone
Coverage from prostate base to apex including seminal vesicles
Axial images aligned perpendicular to the rectal wall/prostate long axis

Systematic Review

Assess prostate volume and zonal anatomy (peripheral, transition, central zones)
Systematically review sectors using the PI-RADS 39-region diagram
Evaluate the peripheral zone on DWI/ADC as the dominant sequence
Evaluate the transition zone on T2 for morphology of nodules
Use DCE to upgrade equivocal PI-RADS 3 peripheral zone lesions
Assess the capsule, neurovascular bundles, and seminal vesicles for extension/invasion
Review pelvic lymph nodes and bony pelvis for metastatic disease
Check for post-biopsy hemorrhage that may mask or mimic tumor

Key Findings & Significance

Focal markedly restricted diffusion (low ADC, high b-value signal) in the peripheral zone indicates significant cancer
Lenticular/homogeneously low-T2 transition-zone nodule with ill-defined margins suggests cancer
Focal early enhancement corresponding to a DWI/T2 abnormality supports malignancy
Broad capsular contact, bulge, or measurable extraprostatic tumor indicates extracapsular extension
Low T2 signal filling/expanding the seminal vesicles indicates seminal vesicle invasion
Diffuse peripheral zone T2 hypointensity often reflects prostatitis rather than tumor
PI-RADS category 4-5 indicates high likelihood of clinically significant cancer warranting biopsy

Differential Considerations

Peripheral zone low T2/restriction: cancer, prostatitis, post-biopsy hemorrhage, atrophy
Transition zone nodule: BPH nodule (encapsulated, round) vs cancer (lenticular, ill-defined, erased charcoal)
Cystic prostatic lesion: BPH cystic degeneration, utricle/Mullerian cyst, ejaculatory duct cyst
Seminal vesicle abnormality: invasion, amyloid, post-treatment change, congenital cyst
Diffuse restriction: prostatitis, granulomatous prostatitis, diffuse tumor
Enhancing focus without DWI correlate: prostatitis, benign vascularity

Pearls & Pitfalls

ADC map, not high-b signal alone, defines significant restriction; correlate both
Post-biopsy hemorrhage is high on T1; the 'exclusion sign' helps distinguish tumor (no hemorrhage) from benign
Transition-zone cancer is a common miss; look for erased-charcoal margins and lenticular shape
Prostatitis is the leading mimic of peripheral-zone cancer; use morphology and clinical context
Hip prostheses cause severe DWI distortion; T2/DCE become more important
Report ECE and SVI carefully as they change surgical management
Do not upgrade a benign BPH nodule based on DCE alone

Structured Report

State indication, PSA, prior biopsy history, technique, and image quality
Report prostate volume and PSA density
Localize each lesion by sector, size, and sequence findings with a PI-RADS category (1-5)
Assess and report extracapsular extension, seminal vesicle invasion, and neurovascular bundle involvement
Report nodal and osseous findings
Impression: overall PI-RADS assessment, dominant lesion, staging, and biopsy recommendation
Provide a labeled sector map for targeted biopsy planning

References

PI-RADS v2.1 (ACR/ESUR/AdMeTech) prostate MRI reporting and data system
ACR Appropriateness Criteria: Prostate Cancer - Pretreatment Detection, Staging
ESUR prostate MRI guidelines
Weinreb et al., PI-RADS steering committee publications
RadioGraphics reviews on prostate mpMRI interpretation and pitfalls

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

MRI Prostate (mpMRI)

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References