Prostate imaging reporting and data system (PI-RADS)

Dr Henry Knipe and Dr Marcin Czarniecki et al.

PI-RADS (Prostate Imaging Reporting and Data System) refers to a structured reporting scheme for evaluating the prostate for prostate cancer. It is designed to be used in a pre-therapy patient.

The original PI-RADS score was annotated, revised and published as the second version, PI-RADSv2 6 by a steering committee with the joint efforts of ACR, ESUR, and AdMeTech Foundation. The following article reflects this newest revision.

The score is assessed on prostate MRI. Images are obtained using a multiparametric technique including T2 weighted images, a dynamic contrast study (DCE), and DWI. If DCE or DWI are insufficient for interpretation, the newest guidelines recommend omitting them in the scoring 6.

A score is given according to each variable. The scale is based on a score from 1 to 5 (which is given for each lesion), with 1 being most probably benign and 5 being highly suspicious of malignancy:

  • PI-RADS 1: very low (clinically significant cancer is highly unlikely to be present)
  • PI-RADS 2: low (clinically significant cancer is unlikely to be present)
  • PI-RADS 3: intermediate (the presence of clinically significant cancer is equivocal)
  • PI-RADS 4: high (clinically significant cancer is likely to be present)
  • PI-RADS 5: very high (clinically significant cancer is highly likely to be present)

Parameters

T2-weighted imaging
Peripheral zone (PZ)
  • 1: uniform high signal intensity
  • 2: linear or wedge-shaped hypointensity or diffuse mild hypointensity, usually indistinct margin
  • 3: heterogeneous signal intensity or non-circumscribed, rounded, moderate hypointensity; includes others that do not qualify as 2, 4, or 5
  • 4: circumscribed, homogenous moderately hypointense focus or mass confined to prostate and <1.5 cm in the greatest dimension
  • 5: same as 4 but ≥1.5 cm in greatest dimension or definite extraprostatic extension/invasive behaviour
Transition zone (TZ)
  • 1: homogenous intermediate signal intensity
  • 2: circumscribed hypointense or heterogeneous encapsulated nodule(s) (benign prostatic hyperplasia)
  • 3: heterogeneous signal intensity with obscured margins. Includes others that do no qualify as 2, 4, or 5
  • 4: lenticular or non-circumscribed, homogenous moderately hypointense, and <1.5cm in greatest dimension
  • 5: same as 4, but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior
Diffusion-weighted imaging (DWI)
  • 1: no abnormality on ADC or high b-value DWI
  • 2: indistinct hypointense on ADC
  • 3: focal mildly/moderately hypointense on ADC and isointense/mildly hyperintense on high b-value DWI
  • 4: focal markedly hypointense on ADC hyperintense on high b-value DWI; <1.5 cm in greatest dimension
  • 5: same as 4 but ≥1.5 cm in greatest dimension or definite extraprostatic extension/invasive behaviour
Dynamic contrast enhancement (DCE)
  • negative: no early enhancement, or diffuse enhancement not corresponding to a focal finding on T2 and/or DWI or focal enhancement corresponding to a lesion demonstrating features of benign prostatic hyperplasia on T2
  • positive: focal, and earlier than or contemporaneously with enhancement of adjacent normal prostatic tissues, and corresponds to suspicious finding on T2 and/or DWI
Changes from PI-RADS v1 to v2

Determining sequences for PZ and TZ were defined. 

For the PZ, DWI is the primary determining sequence (dominant technique).

  • PIRADS score for a PZ lesion is based on DWI unless the DWI score is PIRADS 3
  • in this scenario, DCE is used to decide between PIRADS 3 (no focal or early enhancement) or upgrade to PIRADS 4 (focal and early enhancement present).

For the TZ, T2W is the primary determining sequence. 

  • PIRADS score for a TZ lesion is based on T2W unless the T2W score is PIRADS 3. 
  • in this scenario, DWI is used to decide between PIRADS 3 (DWI score <5) or upgrade to PIRADS 4 (DWI score 5). 

The number of mapping lesions was limited up to four findings with the highest PIRADS Assessment Category of 3, 4, or 5. The index (dominant) intraprostatic lesion should be identified. Thus, a smaller lesion with extraprostatic extension should be defined as the index lesion despite the presence of a larger tumour with the identical PIRADS Assessment Category.

MR spectroscopy was omitted in PI-RADS scoring.

The sector map of v1 was adapted in v2.

Prostate pathology
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Article information

rID: 27968
System: Urogenital
Synonyms or Alternate Spellings:
  • PI-RADS
  • Prostate Imaging Reporting and Data System
  • PIRADS

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Cases and figures

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    Figure 1: PZ lesion flowchart
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    There is a large ...
    Case 1: PI-RADS 5 lesion - anterior tumour TZ
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    Figure 2: TZ lesion flowchart
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    Avid early enhanc...
    Case 2: PIRADS 3 lesion - apical nodule
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    PZ = peripheral z...
    Figure 3: summary flowchart
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