MRI is the best non-invasive diagnostic tool to diagnose prostate cancer; it is known to be superior in resolution and tissue characterization compared to ultrasound and CT imaging.

70-75% of prostate cancers arise in the peripheral zone and the remainder in the transitional zone.

Fig 1
Normal zonal anatomy: PZ= peripheral zone TZ= Transitional Zone

 

Seen above: excellent image quality is obtained with the use of a 1.5 Tesla magnet (such as ours), and without the use of an endorectal coil. In most men, the diagnosis can be made without the use of intravenous gadolinium and does not require any special preparation.

 

The main diagnostic parameters used in prostate MRI:

  • T2-weighted imaging. The appearance is most sensitive in the transitional zone.
  • Diffusion-weighted imaging (DWI) and Apparent diffusion co-efficient (ADC). These are most sensitive in the peripheral zone.
  • Dynamic contrast-enhanced (DCE) imaging
The arrows demonstrate areas of prostate cancer in the transitional and the peripheral zones, respectively, using the various parameters in the same patient.

 

The most common indications for prostate MRI:

  1. Elevated PSA and/or abnormal digital rectal exam
  2. To define the location and size of a nodule for biopsy
  3. Elevated PSA with negative TRUS (transrectal ultrasound) biopsy
  4. Staging and extent of prostate cancer confirmed by biopsy. (Number of lesions, extra-prostatic extension)
  5. Map lymph nodes for dissection
  6. Evaluate rise in PSA after treatment
  7. Define local versus distant recurrence.

 

Relevant patient information required:

The following information should be available to the radiologist at the time of MRI exam performance and interpretation:

  • Recent serum prostate-specific antigen (PSA) level and PSA history
  • Date and results of prostate biopsy, including number of cores, locations and Gleason scores of positive biopsies (with
    percentage of core involvement when available)
  • Other relevant clinical history, including digital rectal exam (DRE) findings, medications (particularly in the setting of
    hormones/hormone ablation), prior prostate infections, pelvic surgery, radiation therapy, and family history

 

PROSTATE MRI Report:

A written report is prepared, along with a schematic diagram of any abnormalities detected.

(Sampled portion below)

 

Up to four (4) nodules are assigned a rating scale as shown below:

 

PIRADS RATING SCALE (Prostate Imaging- Reporting and Data System)

PIRADS 1– very low (the presence of clinically significant cancer is highly unlikely)
PIRADS 2– low (the presence of clinically significant cancer is unlikely)
PIRADS 3– intermediate (the presence of clinically significant cancer is equivocal)
PIRADS 4– high (clinically significant cancer is likely to be present)
PIRADS 5– very high (clinically significant cancer is highly likely to be present)

 

Important Staging information:

  • Tumor confined to prostate: stages TI, T2
  • Extra-prostatic spread: stage T3 (seminal vesicles, neurovascular bundle, lymph nodes)

 

Sensitivity and Clinical significance:

In general, the sensitivity of multi-parametric MRI to detect clinically significant cancer is 85-90%. (The Lancet volume 389
issue 10071 February 25, 2017. Diagnostic accuracy of multi parametric MRI and TRUS biopsy in prostate cancer)

Clinically significant prostate cancer is defined as:
Histology: Gleason score 7 or >7 (including 3+4 with prominent but not predominant Gleason 4 component)
And/ or volume greater than 0.5 cc, and/or extra-prostatic extension.

 

Contributor: By Dr. Konrad Kirlew-Consultant Radiologist