← Back to Browse
Ask AleraHome
MRI
PelvisDemonstration data

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.