Pi-Rads version 2

Masoom Haider, MD, FRCP(C)Professor of Radiology, University of TorontoClinician Scientist, Ontario Institute of Cancer ResearchSenior Scientist, Sunnybrook Research InstituteChief, Dept of Medical ImagingSunnybrook Health Sciences Centermasoom.haider@sunnybrook.ca

www.mybodymri.com

Addressing the Sampling Problem

• Variability is introduced by sampling error making it much hard to get a handle on tumor behavior in population studies

JAMA 2015 n = 1003• In men (mostly with a prior negative

systematic biopsy) MR/ultrasound fusion biopsy, c/w systematic biopsy had increased detection of Gleason >=4+3, (+30%) and decreased detection of low-risk prostate cancer (-17%)

• Prostatectomy cohort Sens 77% vs 53% Spec 68 vs 66% (Gleason 3+4 in >20% of prostate)October 22, 2016

Siddiqui MM, et al. Comparison of MR/ultrasound fusion-guided biopsy with ultrasound-guided biopsy for the diagnosis of prostate cancer. Jama. Jan 27 2015;313(4):390-7.

3 October 22, 2016

StandardizationPi-Rads v2.0 – 5 point scale

acr.org

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PiRads Assessment Categories

• PIRADS 1 – Very low (clinically significant cancer is highly unlikely to be present)

• PIRADS 2 – Low (clinically significant cancer is unlikely to be present)

• 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)

October 22, 2016

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Pirads 1 or 2 means no CS cancer on BiopsyReduction in need for biopsyPirads 3 means low risk of CS cancerPirads 4/5 means much higher chance of CS cancer

October 22, 2016

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Coil Combinations

1.5T 3T

No endorectal Thinner patients, current MRI, cardiac coil

Cardiac coil in thinner patients

Endorectal w/ Surface Thinner patients, cardiac coil Thinner patients, cardiac coil

Endorectal w/o surface Fatter patients Fatter patients partial phase FOV

October 22, 2016

3T 2NEX, ER only0.4x0.4x3mm, 18x9cm, 259s

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Clinically Significant Cancer

Gleason score >= 7

And/or

Volume > 0.5cc

And/or

Extraprostatic extension (EPE)

October 22, 2016

8 October 22, 2016

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Normal Anatomy(McNeal)

• 4 distinct zones– Peripheral Zone (PZ)– Central Zone (CZ)

• Lateral to Ejaculatory ducts towards base– Transition Zone (TZ)

• BPH nodules– Anterior Fibromuscular Stroma (AFMS)

• Non glandular tissues contiguous with the detrusor

October 22, 2016

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Interpretation SchemeSimplifications in v 2

• Hierarchical scheme• In PZ DWI is dominant (PiRads = DWI score)• In TZ T2 is dominant (PiRads = T2 score)• The DCE interpretation has been reduced to positive or

negative (binary) and only has influence in PZ tumors that are equivocal on DWI (pushing Pi-Rads 3 to a 4 in some cases)– DCE assessment does not require curve analysis or typing

• Pirads 4 is the same as 5 but size is >15mm or ECE• B-values increased to >=1400 s/mm2

October 22, 2016

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Overall Score for a Lesion

October 22, 2016

DWI T2 DCE Overall

1 Any Any 1

2 Any Any 2

3 Any- 3

+ 4

4 Any Any 4

5 Any Any 5

T2 DWI DCE Overall

1 Any Any 1

2 Any Any 2

3≤4 Any 3

5 Any 4

4 Any Any 4

5 Any Any 5

PZ TZ

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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.

4Focal markedly hypointense 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

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Hambrock T et al. Radiology 2011

ADCCorrelates with Gleason Grade

Az =0.9 >G6

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Technique – B-Values?

• Lower 0, 50, 100 s/mm2

• Higher 1400-2000s/mm2 best

• Minimum 2 b-valsbut can do more

• Can extrapolate from b values done less than 1000

October 22, 2016

0

0.5

1

1.5

2

2.5

3

0 500 1000 1500

Ln(S

I)

Flow driven

Slow Diffusion (ECF)

CalculatedDiffusion

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DCE – PZ and TZ

-

• No early enhancementOR• diffuse enhancement not corresponding to a focal

finding on T2 and/or DWIOR• focal enhancement corresponding to a lesion

demonstrating features of BPH on T2WI

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

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Kinetic Analysis Models

C(t)

Time (min)

ve = 50%

Ktrans = 0.5 min-1Ktrans = 1.0 min-1Ktrans = 1.5 min-1Ktrans = 2.0 min-1Ktrans = 2.5 min-1Ktrans = 3.0 min-1Ktrans = 2.0 min-1

ve = 20%ve = 40%ve = 60%ve = 80%

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DCE

• In plane dimension: ≤2mm X ≤2mm• Temporal resolution: ≤15sec (<7sec is preferred)• Total observation: >2min• Dose: 0.1mmol/kg standard GBCA or equivalent high relaxivity

GBCA• Injection rate: 2‐3cc/sec starting with continuous image data

acquisition (should• be the same for all exams)• 3D seq, FS typically off• If doing quantitation, modelling then follow manufacturers

suggestions– Multi flip angle T1 mapping

• Subtraction images if interpreting raw images• Watch for motion

October 22, 2016

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T2 TZ

1 Homogeneous intermediate signal intensity(normal)

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

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

4Lenticular 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

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Other Nuances

• Up to 4 findings of category 3, 4 or 5• Index tumor should be identified (highest Pi-Rads

category)• Measure largest dimension o axial images using ADC in

PZ and T2 in TZ– Can measure additional planes

• If DWI fails then T2 dominates with DCE positivity pushing a 3 to a 4

• No overall score

October 22, 2016

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Making Recommendations – Not in PiRads 1 or 2A work in progress

• PIRADS 1 or 2 – Biopsy* if high risk else followup MRI**• PIRADS 3- Biopsy* if intermediate or high risk otherwise

followup MRI**• PIRADS 4 & 5 – Biopsy*

*Biopsy– targets (if any) + systematic if no systematic in the last 2 years– targets only if systematic biopsy in the last two years

**Followup MRI– No consensus q1 or q2 years

• Risk profile– Being debated

October 22, 2016