KP Murphy, A Walsh, C Donagh, R Aljurayyan, AC Harris, SD Chang

Department of Abdominal and GU Radiology, Vancouver General Hospital & University of British Columbia, Vancouver,

Canada

PI-RADS V2 IN PRACTICE – A PICTORIAL REVIEW

The authors have no financial or other disclosure

GOALS & OBJECTIVES

•  To help clarify the key sequences in establishing a prostate MRI protocol •  To demonstrate key findings in both transition zone & peripheral zone lesions

•  To assist in correct PI-RADS classification of findings

•  The target audience is residents, fellows and staff radiologists that are involved in prostate imaging

INTRODUCTION •  Prostate imaging and reporting and data system (PI-RADS) version 1 was

introduced by the European Society of Urogenital Radiology (ESUR) as a standardized scoring system to grade lesions on prostate MRI in 2012.

•  PI-RADS v2 was introduced in 2015 in a collaboration between the American College of Radiology (ACR), AdMeTech Foundation and ESUR as an update to version 1.

•  The update further simplifies key sequences plus simplifies terminology and reporting: •  T2 weighted images are now the most important images in transition zone

evaluation •  High B-value DWI images are of key importance in assessing peripheral

zone lesions •  Spectroscopy is not part of PI-RADS v2 assessment and dynamic contrast

enhancement only plays a minor role

MRI PROTOCOL •  The use of an endorectal coil (ERC) is not a requirement under the new

guidelines but may be essential in older 1.5T systems to maintain SNR •  Newer external phased array coils maintain SNR and image quality, even in

1.5T magnets

•  Protocols need to include:

•  T2W – ideally 3 plane

•  DWI – to a max B-value of 1400 sec/mm2 or greater

•  ADC •  Dynamic contrast enhancement

INTERPRETATION: T2W & DWI

•  High B-value DWI series are of key importance in peripheral zone assessment

•  T2W series are of key importance in transition zone analysis

•  Findings are labeled as PIRADS 1 to 5 for focal abnormalities

1 Uniform hyperintense signal intensity (normal)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 moderate hypointense focus/mass confined to prostate and <1.5 cm in greatest dimension

5 Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

1 2 3 4 5

INTERPRETATION: T2W PERIPHERAL ZONE

1 Homogeneous intermediate signal intensity (normal)

2 Circumscribed hypointense or heterogeneous encapsulated nodule(s) (BPH)

3 Heterogeneous signal intensity with obscured margins Includes others that do not qualify as 2, 4, or 5

4 Lenticular or non‐circumscribed, homogeneous, moderately hypointense, and <1.5 cm in greatest dimension

5 Same as 4, but ≥ 1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

1 2 3 4 5

INTERPRETATION: T2W TRANSITION ZONE

1 No abnormality (i.e. normal) on ADC and 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 hypontense on ADC and markedly hyperintense on high b value DWI; <1.5cm in greatest dimension

5 Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

1, 2 3 4 5

INTERPRETATION: DWI BOTH ZONES

INTERPRETATION: ADC

•  Qualitative assessment, with or without a colour map, is recommended for ADC series

•  1400:1400 (W:L) is a useful window for ADC series to maximize lesion conspicuity

•  Quantitative assessment of ADC values has not been standardized across vendors •  Despite this caveat, ADC values less than 750‐900 µm2/sec, raises

concern for a clinically significant PZ cancers

(-) 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 BPH onT2WI

(+) focal, and; earlier than or contemporaneously with enhancement of adjacent normal prostatic tissues, and; corresponds to suspicious finding on T2W and/or DWI

(-) (+)

INTERPRETATION: DCE

70-75% of neoplasms are in the PZ

20-30% of neoplasms are in the TZ

INTERPRETATION: PZ & TZ PIRADS

•  The 4 highest grade lesions can be given a PI-RADS v2 label on any one study when there are multiple lesions

•  The highest scoring lesion is the index lesion

PI-RADS V2 CATEGORIES

INTERPRETATION: PRACTICAL TIPS I •  Open & link Ax T2W, DWI, ADC and DCE series in adjacent windows •  Use Cor & Sag T2W series to cross reference findings and act as a final

check •  Use Ax T1W to check for intraprostatic haemorrhage

•  It is best to assess the PZ & TZ separately hence it is key to delineate the two zones

•  Having the PI-RADS v2 document as reference at the time of reporting is useful

•  Assess for adenopathy, ascites, osseous lesions and incidental GI lesions at the very beginning or end

INTERPRETATION: PRACTICAL TIPS II - PZ •  PZ DWI findings should be correlated with T2W & ADC and PZ DWI restriction

should be compared to signal intensity of the normal prostatic tissues •  The ADC value of 750‐900 µm2/sec is useful in labeling restriction as mild/

moderate or marked •  PZ T2W findings are only of importance for PI-RADS scoring when DWI imaging

is not available and in assessing for extracapsular extension (ECE) when a lesion is identified

•  PZ DCE is only of importance when positive DCE of a PIRADS 3 lesion will result in upgrading to PIRADS 4

•  Use ADC series to measure PZ lesion size

INTERPRETATION: PRACTICAL TIPS III - TZ •  T2W features of TZ tumours include:

•  non‐circumscribed homogeneous moderately hypointense lesions (“erased charcoal” or “smudgy fingerprint” appearance)

•  spiculated margins

•  lenticular shape

•  absence of a complete hypointense capsule

•  invasion of the urethral sphincter or anterior fibromuscular stroma

•  TZ DWI label of P5 can upgrade a TZ T2W P3 lesion to P4 •  DCE does not have a role in TZ lesion classification

•  Use T2W series to measure TZ lesion size

PIRADS V2

T2 - Transition Zone 1 No abnormality (i.e. normal) on ADC and

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 hypontense on ADC and markedly hyperintense on high b‐value DWI; <1.5cm in greatest dimension

5 Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

T2 - Peripheral Zone 1 Uniform hyperintense signal intensity (normal)

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 moderate hypointense focus/mass confined to prostate and <1.5 cm in greatest dimension

5 Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

DWI – PZ and TZ

1 No abnormality (i.e. normal) on ADC and 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 hypontense on ADC and markedly hyperintense on high b‐value DWI; <1.5cm in greatest dimension

5 Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior

DCE – Peripheral and Transition Zone

(-) 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 BPH onT2WI

(+) focal, and; earlier than or contemporaneously with enhancement of adjacent normal prostatic tissues, and; corresponds to suspicious finding on T2W and/or DWI

Overall Peripheral Zone DWI T2 DCE PIRADS

1 Any Any 1

2 Any Any 2

3 Any - 3

+ 4

4 Any Any 4

5 Any Any 5

Overall Transition Zone

T2 DWI DCE PIRADS

1 Any Any 1

2 Any Any 2

3 <4 Any 3

5 Any 4

4 Any Any 4

5 Any Any 5

Having a PI-RADS v2 summary as reference at the time of reporting is useful

A B PZ PIRADS 1

•  Normal PZ •  Homogeneous T2W high signal with no diffusion

restricted on DWI or ADC

DWI ADC T2

A B TZ PIRADS 1

•  Normal low signal T2W central fibrous stroma anteriorly

•  Intermediate T2W signal TZ •  Normal TZ ADC & DWI

DWI ADC T2

A B PZ PIRADS 2

•  9 mm PIRADS 2 lesion left posterior midgland PZ with minor ill defined restriction on ADC but with not focal finding on high B-value DWI

•  No focal abnormality is demonstrated on T2W or DCE

DWI DCE ADC

T2

A B TZ PIRADS 2

•  16 mm PIRADS 2 lesion right midgland to apex TZ with well circumscribed T2W heterogeneous nodule

•  Restricted diffusion is seen on ADC and DWI but the T2W findings are in keeping with a PIRADS 2 lesion

DWI

DCE

ADC T2

A B PZ PIRADS 3

•  17 mm PIRADS 3 lesion right posterior midgland PZ with minor restriction on high B-value DWI and focally abnormal on ADC (value 880)

•  Lesion is abnormal on T2W but DCE-

DWI DCE ADC

T2

A B TZ PIRADS 3

•  16 mm PIRADS 3 lesion left midgland TZ with T2W crescentic hypointensity that is relatively well circumscribed

•  ADC and DWI are mild to moderately abnormal; DCE- •  Biopsy was negative

DWI

DCE

ADC T2

A B PZ PIRADS 4

•  11 mm right posterior midgland PZ lesion markedly hyperintense on high B-value DWI and abnormal on ADC (value 792)

•  DCE+ confirmed it as PIRADS 4

DWI DCE ADC

T2

A B TZ PIRADS 4

•  14 mm PIRADS 4 lesion right anterior midgland TZ with a smudged T2W appearance

•  Lesion is also abnormal on DWI and ADC (value 856) plus DCE+ but cannot be labeled P5 with these extra findings

DWI

DCE

ADC T2

A B

DWI DCE ADC

T2

PZ PIRADS 5

•  16 mm PIRADS 5 lesion left midgland PZ with marked restriction on high B-value DWI and abnormal ADC (value 499)

•  Lesion is also abnormal on T2W and DCE+ but these findings not required for P5 label

A B TZ PIRADS 5

•  21 mm PIRADS 5 lesion right midgland TZ with ill defined smudged T2 hypointensity

•  Lesion is also abnormal on ADC (value 877) & DWI plus shows DCE+

DWI

DCE

ADC T2

Histology: Gleason grade 3+4 involving 70 and 80% of the two target cores.

MRI-US guided fusion biopsy

PZ PIRADS 5 with ECE

DWI DCE ADC

T2 •  18 mm PIRADS 5 lesion left midgland to base PZ significant restriction on high B-value DWI, ADC restriction and DCE+

•  A focal abnormality with capsular breach is seen on T2W

T2

T2

CONCLUSION

•  PI-RADS v2 attempts to standardize prostate MRI reporting plus simplify terminology and content of prostate MRI reports

•  Radiologists that report prostate MRI need to be aware of the updated system

•  Key changes with respect to version 1 are:

•  dynamic contrast enhancement is no longer a key entity in determining PI-RADS score

•  DWI images are key for peripheral zone assessment

•  T2 images are most important in transition zone analysis

REFERENCES & CONTACT DETAILS

•  Weinreb JC, Barentsz JO, Choyke PL, Cornud F, Haider MA, Macura KJ, et al. PI-RADS Prostate Imaging - Reporting and Data System: 2015, Version 2. Eur Urol. 2015 Sep 28;69(1):16–40.

•  Prostate Imaging - Reporting and Data System. Version 2. American College of Radiology. 2015. Available from: http://www.acr.org/~/media/ACR/Documents/PDF/QualitySafety/Resources/PIRADS/PIRADS V2.pdf

•  Kevin.Murphy@vch.ca; Silvia.Chang@vch.ca