What MRI protocol is recommended for evaluating prostate cancer?

MRI Protocol for Prostate Cancer Evaluation

For initial prostate cancer detection and staging, order a multiparametric MRI (mpMRI) that includes T2-weighted imaging, diffusion-weighted imaging with ADC maps, and dynamic contrast-enhanced sequences, following PI-RADS version 2.1 technical standards. 1

Core MRI Sequences Required

The standard mpMRI protocol consists of three essential sequences that work synergistically to detect clinically significant prostate cancer:

• T2-weighted imaging provides anatomic detail of prostate zones and is the primary determinant for lesions in the transitional zone 1, 2
• Diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps detects areas of restricted diffusion and serves as the primary determinant for peripheral zone lesions 1, 2
• Dynamic contrast-enhanced (DCE) imaging requires intravenous gadolinium contrast and provides secondary classification information 1, 2

Technical Specifications

• Use either 1.5T or 3T MRI scanner, with 3T preferred for improved signal-to-noise ratio 1
• Apply a pelvic phased-array surface coil placed over the pelvis 1
• Do not routinely use an endorectal coil—it is neither mandatory nor preferred at either field strength 1
• High b-value images (typically b=1400-2000) are critical for cancer detection, with focal high signal on high b-value images being more reliable than ADC maps alone 1

When Contrast Is Mandatory vs. Optional

Contrast Is Mandatory For:

Post-focal therapy surveillance: DCE becomes the dominant sequence and cannot be omitted—a biparametric protocol is inadequate in this setting 3, 1. Focal nodular strong early enhancement is the most suspicious finding for recurrence 3, 1. In this context, DWI and T2-weighted sequences are downgraded to joint minor supporting sequences 3, 1.

Contrast Provides Modest Benefit For:

Initial cancer detection: The incremental diagnostic benefit of DCE over T2-weighted + DWI alone is relatively modest, adding minimal improvement in sensitivity and specificity for ruling out clinically significant disease 3, 1. For biopsy-naïve patients, biparametric MRI (T2 + DWI without contrast) provides equivalent cancer detection when image quality meets standards 1.

Contrast Does Not Improve:

Local staging assessment: T2-weighted imaging is the critical sequence for evaluating extracapsular extension (91% specificity, 57% sensitivity) and seminal vesicle invasion (96% specificity, 58% sensitivity)—contrast does not enhance these assessments 1

Clinical Context-Specific Protocols

For Initial Detection (Biopsy-Naïve Patients)

• Order biparametric MRI (T2 + DWI) as first-line—provides equivalent detection with shorter scan time and no contrast risk 1
• Reserve full multiparametric MRI with DCE for equivocal cases 1
• Perform MRI ideally at least 6 weeks after any prior prostate biopsy to avoid hemorrhage artifact 1

For High-Risk Disease Staging

• Order full multiparametric MRI with contrast when evaluating patients with clinical stage T3-T4, PSA >20 ng/mL, or Gleason score ≥8 1
• Recognize that negative MRI cannot exclude microscopic extracapsular extension due to limited 57% sensitivity, though positive findings are highly specific (91-96%) 1
• Include pelvic lymph node assessment when pre-test probability exceeds 10%—a threshold met by all high-risk patients 1

For Post-Focal Therapy Surveillance

• Always perform full multiparametric MRI including DCE—contrast is non-negotiable 3, 1
• Schedule the first surveillance MRI at 12 months after treatment to minimize treatment-induced artifacts 3, 1
• Avoid using standard PI-RADS category scores for assessing recurrence within the ablation zone 3
• Use an alternative 5-point scoring system that prioritizes DCE as the major sequence 3

Essential Information to Provide When Ordering

Include the following clinical details to optimize interpretation 1:

• Recent PSA values
• Gleason scores from any prior biopsies
• Details of any prior focal therapy (modality, date, treatment zone)
• Specific indication for the study (detection, staging, surveillance)
• Any contraindications to gadolinium contrast

Interpretation Standards

• Reports should use PI-RADS version 2.1 for standardized interpretation 3, 1, 2
• PI-RADS categories 1-5 describe increasing likelihood of clinically significant prostate cancer 2
• The interpreting radiologist should read at least 20 prostate MRI examinations annually 1
• New readers should consider independent double-reporting by an experienced reader 1

Common Pitfalls to Avoid

• Do not accept incomplete studies: If any required sequence is missing or of inadequate quality, repeat the study before making treatment decisions 1
• Do not omit contrast for post-focal therapy surveillance—this is the most common and consequential error 3, 1
• Do not rely on negative MRI to exclude extracapsular extension—nearly half of pathologic extensions may be missed due to 57% sensitivity 1
• Do not use biparametric MRI when T2-weighted or DWI image quality is suboptimal—repeat with adequate sequences 1
• Do not use MRI alone to defer biopsy—tissue diagnosis remains mandatory 1

Contraindications to Contrast

For patients with severe renal impairment, prior nephrogenic systemic fibrosis, or severe contrast allergy, use biparametric MRI (T2 + DWI) for initial detection and staging, but recognize this approach cannot be used for post-focal therapy surveillance 1.