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
• 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