PI-RADS V2 IN PRACTICE A PICTORIAL REVIEW

Transcription

1 PI-RADS V2 IN PRACTICE A PICTORIAL REVIEW 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 The authors have no financial or other disclosure

2 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

3 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 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

4 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/mm 2 or greater ADC Dynamic contrast enhancement

5 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

6 INTERPRETATION: T2W 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

7 INTERPRETATION: T2W TRANSITION 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

8 INTERPRETATION: DWI BOTH ZONES 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,

9 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 µm 2 /sec, raises concern for a clinically significant PZ cancers

10 INTERPRETATION: DCE (-) 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 (-) (+)

11 INTERPRETATION: PZ & TZ PIRADS 70-75% of neoplasms are in the PZ 20-30% of neoplasms are in the TZ

12 PI-RADS V2 CATEGORIES 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

13 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

14 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 µm 2 /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

15 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

16 Having a PI-RADS v2 summary as reference at the time of reporting is useful T2 - Peripheral Zone PIRADS V2 1 Uniform hyperintense signal intensity (normal) 2 Linear or wedge shaped hypointensity or diffuse mild hypointensity, usually indistinct margin 3 Heterogeneous signal intensity or noncircumscribed, 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 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 Overall Peripheral Zone DWI T2 DCE PIRADS 1 Any Any 1 2 Any Any 2 3 Any Any Any 4 5 Any Any 5 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 Transition Zone T2 DWI DCE PIRA DS 1 Any Any 1 2 Any Any 2 3 <4 Any 3 5 Any 4 4 Any Any 4 5 Any Any 5

17 PZ PIRADS 1 DWI ADC T2 Normal PZ Homogeneous T2W high signal with no diffusion restricted on DWI or ADC

18 TZ PIRADS 1 T2 ADC DWI Normal low signal T2W central fibrous stroma anteriorly Intermediate T2W signal TZ Normal TZ ADC & DWI

19 PZ PIRADS 2 DWI ADC DCE T2 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

20 TZ PIRADS 2 T2 ADC DWI DCE 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

21 PZ PIRADS 3 DWI ADC DCE T2 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-

22 TZ PIRADS 3 T2 ADC DWI DCE 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

23 PZ PIRADS 4 DWI ADC DCE T2 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

24 TZ PIRADS 4 T2 ADC DWI DCE 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

25 PZ PIRADS 5 DWI ADC DCE T2 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

26 TZ PIRADS 5 T2 ADC DWI DCE 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+

27 MRI-US guided fusion biopsy Histology: Gleason grade 3+4 involving 70 and 80% of the two target cores.

28 PZ PIRADS 5 with ECE DWI ADC DCE T2 T2 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

29 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

30 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 Sep 28;69(1): Prostate Imaging - Reporting and Data System. Version 2. American College of Radiology Available from: PIRADS/PIRADS V2.pdf Kevin.Murphy@vch.ca; Silvia.Chang@vch.ca