PI-RADS

PI-RADS is an acronym for Prostate Imaging Reporting and Data System, defining standards of high quality clinical service for multi-parametric Magnetic Resonance Imaging (mpMRI), including image creation and reporting.

History

Since 2007, the AdMeTech Foundation's International Prostate MRI Working Group [1] convened the key global experts, including members of the American College of Radiology (ACR) and European Society of Urogenital Radiology (ESUR). They reviewed emerging scientific evidence, developed research strategy and by early 2010, recommended development of the PI-RADS standardization, modeled after BI-RADS for Breast Imaging-Reporting and Data System, a quality assurance tool in breast imaging [2],.[3] The goal of this recommendation was to expedite large-scale clinical evaluation and implementation of high quality mpMRI for improved early detection and accurate diagnosis of clinically significant prostate cancer.

In response to this recommendation, ESUR developed PI-RADS version 1 (PI-RADS v1). Upon review of PI-RADS v1 in early 2011, AdMeTech Foundation's International Prostate MRI Working Group initiated development of global consensus for PI-RADS standardization (PI-RADS v2) and stimulated the interest of ACR and ESUR to ensure global acceptance and implementation.[4] In late 2011, AdMeTech Foundation, ACR and ESUR formed a Joint Steering Committee, and by December 2014, developed and released an online version of PI-RADS v2,[5][6] With support of the AdMeTech Foundation and ESUR, ACR trademarked the PI-RADS v2 version in order to provide leadership in education and training.[7] In 2015, a scholarly article on PI-RADS v2 was accepted for publication in the Journal of European Urology; it was accompanied by the editorial detailing extensive differences between PI-RADS v1 and PI-RADS v2.[8]

Since 2011, AdMeTech Foundation has also taken the lead in designing and managing a clinical trial, in partnership with the American College of Radiology Imaging Network, with the goal to provide a definitive scientific evidence on the value of mpMRI and PI-RADS v2 in addressing the central challenges in patient care: 1) Improving early detection of clinically significant prostate cancer, as defined by Gleason Grade 4 and higher and informed by volume of > 0.5 cc of the index lesion (which is considered the most clinically relevant); and 2) Reducing over-diagnosis and over-treatment of benign diseases and dormant cancer, which are not likely to cause harm in a man's lifetime. The first phase of this trial, which was undertaken by AdMeTech jointly with scientists of the Harvard Medical School (Brigham and Women's Hospital, Dana Farber Cancer Institute and the Massachusetts General Hospital), is expected to be completed in June 2016. If successful, this trial will expedite global clinical implementation of mpMRI and PI-RADS v2.

Purpose

The PI-RADS v2 system is designed to standardize image acquisition and reporting, and to be used by medical professionals in the initial evaluation of patients to assess the risk of clinically significant prostate cancer that may require biopsy and treatment. The online document and the related publications in the Journal of European Urology, which represent an international scientific consensus, are written for medical professionals, not "lay" patients or members of the general public.

PI-RADS score

A PI-RADS v2 score is given according to each variable parameter. The scale is based on a score "Yes" or "No" for Dynamic Contrast-Enhanced (DCE) parameter, and from 1 to 5 for T2-weighted (T2W) and Diffusion-weighted imaging (DWI). The score is given for each lesion, with 1 being most probably benign and 5 being highly suspicious of malignancy:

PI-RADS v.1[9] PI-RADS v2[10]
Published by ESUR (PI-RADS v1) ACR/AdMeTech Foundation/ESUR (PI-RADS v2)
Stratification of localized prostate cancer according the likelihood of tumor spread and recurrence Low-risk: PSA <10 ng/mL, and biopsy Gleason score ≤6, and clinical stage T1–T2a

Intermediate-risk: PSA 10–20 ng/mL, or biopsy Gleason score 7, or clinical stage T2b or T2c
High-risk: PSA >20 ng/mL, or Gleason score 8–10, or clinical stage >T2c

Focused on the detection and exclusion of clinically significant prostate cancer
Timing of imaging Not mentioned > 6 weeks after biopsy
Investigating men post-therapy with PSA rise when curative aggressive treatment (e.g. salvage ra- diotherapy) is considered, in addition to T2WI, DCE-MRI and DWI should always be performed using the “detection protocol Not applicable
Definition of clinically significant cancer Not defined Gleason Grade 4 and above, and/or volume > 0.5cc
DWI 5 mm at 1.5 T, 4 mm at 3 T; in-plane resolution: 1.5 mm × 1.5 mm to 2.0 mm × 2.0 mm at 1.5 T and 1.0 mm × 1.0 mm to 1.5 mm × 1.5 mm at 3 T. ADC map should be calculated. At least 3 b-values should be acquired in three orthogonal directions and adapted to quality of SNR: 0, 100 and 800–1000 s/mm2. For calculation of ADC, the highest b-value that should be used is 1000 s/mm2. Free breathing spin echo EPI sequence combined with spectral fat saturation is recommended. oTE:≤90msec;TR:>3000msec o Slice thickness: ≤4mm, no gap. Locations should match or be similar to those used for T2W and DCE o FOV: 16‐22 cm o In plane dimension: ≤ 2.5mm phase and frequency.
DCE 4 mm at 1.5 T and 3 T; in plane resolution: 1.0×1.0 mm at 1.5 T and 0.7×0.7 mm at 3 T. Quantitative or semi-quantitative DCE-MRI analysis does not have to be performed. Maximum temporal resolution should be 15 s following single dose of contrast agent with an injection rate of 3 mL/s. For DCE-MRI, imaging acquisition should be continued for 5 min to detect washout. Unenhanced T1WI images from this sequence can be used to detect post-biopsy haematomas. DCE is generally carried out for several minutes to assess the enhancement characteristics. In order to detect early enhancing lesions in comparison to background prostatic tissue, temporal resolution should be <10 seconds and preferably <7 seconds per acquisition in order to depict focal early enhancement. Fat suppression and/or subtractions is recommended.

Although either a 2D or 3D T1 gradient echo (GRE) sequence may be used, 3D is preferred. o TR/TE: <100msec/ <5msec o Slice thickness: 3 mm, no gap. Locations should be the same as those used for DWI and DCE o FOV: encompass the entire prostate gland and seminal vesicles o In plane dimension: ≤2 mm × ≤2 mm o Temporal resolution: ≤15 sec (<7 sec is preferred) o Total observation rate: >2min o Dose: 0.1 mmol/kg standard GBCA or equivalent high relaxivity GBCA o Injection rate: 2–3 cc/sec starting with continuous image data acquisition (should be the same for all exams)

T2WI for the peripheral zone (PZ)
  1. Uniform high signal intensity (SI)
  2. Linear, wedge shaped, or geographic areas of lower SI, usually not well demarcated
  3. Intermediate appearances not in categories 1/2 or 4/5
  4. Discrete, homogeneous low signal focus/mass confined to the prostate
  5. Discrete, homogeneous low signal intensity focus with extracapsular extension/invasive behaviour or mass effect on the capsule (bulging), or broad (>1.5 cm) contact with the surface.
  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 ≥1.5 cm in greatest dimension or definite extraprostatic extension/invasive behavior
T2WI for the transition zone (TZ)
  1. Heterogeneous TZ adenoma with welldefined margins: “organised chaos”
  2. Areas of more homogeneous low SI, however well marginated, originating from the TZ/BPH
  3. Intermediate appearances not in categories 1/2 or 4/5
  4. Areas of more homogeneous low SI, ill defined: “erased charcoal sign”
  5. Same as 4, but involving the anterior fibromuscular stroma or the anterior horn of the PZ, usually lenticular or waterdrop shaped.
  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. Lenticlular or non-circumscribed, homogeneous, moderately hypointense, and <1.5 cm in greatest dimension
  5. Same as 4 but ≥1.5 cm in greatest dimension or definite extraprostatic extension/invasive behavior
Scoring of extraprostatic disease
Extracapsular extension
Abutment: 1
Irregularity: 3
Neurovascular bundle thickening: 4
Bulge, loss of capsule: 4
Seminal vesicles
Expansion: 1
Low T2 signal: 2
Filling in of angle: 3
Enhancement and impeded diffusion: 4
Distal sphincter
Adjacent tumor: 3
Effacement of low signal sphincter muscle: 3
Abnormal enhancement extending into sphincter: 4
Bladder neck
Adjacent tumor: 2
Loss of low T2 signal in bladder muscle: 3
Abnormal enhancement extending into bladder neck: 4
 Extraprostatic extension/ invasive behavior as PI-RADS 5 assessment independent of lesion localization in peripheral or transition zone on T2w or DWI

PI-RADS Performance

Various studies have compared the predictive performance of PI-RADS v1 for detecting significant prostate cancer against either image-guided biopsy results (definitive pathology) and/or prostatectomy specimens (histopathology). In a 2015 articles in the Journal of Urology, Thompson reported multiparametric MRI detection of significant prostate cancer had sensitivity of 96%, specificity of 36%, negative predictive value and positive predictive values of 92% and 52%; when PI-RADS was incorporated into a multivariate analysis (PSA, digital rectal exam, prostate volume, patient age) the area under the curve (AUC) improved from 0.776 to 0.879, p<0.001.[11] A similar paper in European Radiology found that when correlated with histopathology, PI-RADS v2 correctly identified 94-95% of prostate cancer foci ≥0.5 mL, but was limited for the assessment of GS ≥4+3 (significant) tumors ≤0.5 mL; in their series, DCE-MRI offered limited added value to T2WI+DW-MRI.[12] Other applications for which PI-RADS may be useful include prediction of termination of Active Surveillance due to tumor progression/aggressiveness,[13] detection of extraprostatic extension of prostate cancer,[14] and supplemental information when considering whether to re-biopsy patients with a history of previous negative biopsy.[15]

PI-RADS v2 is designed to improve detection, characterization and risk stratification in patients suspected of prostate cancer with a goal of better treatment decisions, improved outcomes and simplified reporting. However, multi-center validation trials are needed and expected to lead to modifications in the scoring system.[16]

References

  1. ↑ "AdMeTech Foundation's International Prostate MRI Working Group". www.admetech.org. Retrieved 2015-09-19.
  2. ↑ "AdMeTech". www.admetech.org. Retrieved 2015-09-19.
  3. ↑ Shtern, Faina (December 1, 2014). "Global Standardization of Prostate MRI (PI-RADS v2)". AdMeTech Foundation. AdMeTech Foundation. Retrieved December 1, 2014.
  4. ↑ Shtern, Faina (September 19, 2015). "Leading International Scientists Announce New Guidelines for Improved Prostate Cancer Diagnosis". AdMeTech Foundation. AdMeTech Foundation. Retrieved December 1, 2014.
  5. ↑ Shtern, Faina (September 19, 2015). "Global Standardization". AdMeTech Foundation. AdMeTech Foundation. Retrieved December 1, 2014.
  6. ↑ Weinreb, Jeffrey (December 1, 2014). "PI-RADS v2". American College of Radiology. American College of Radiology. Retrieved December 1, 2014.
  7. ↑ Weinreb, et. al., Jeffrey (September 19, 2015). "PI-RADS v2" (PDF). American College of Radiology. American College of Radiology. Retrieved December 1, 2014.
  8. ↑ Barentsz, Jelle O.; Weinreb, Jeffrey C.; Verma, Sadhna; Thoeny, Harriet C.; Tempany, Clare M.; Shtern, Faina; Padhani, Anwar R.; Margolis, Daniel; Macura, Katarzyna J.; Haider, Masoom A.; Cornud, Francois; Choyke, Peter L. (January 2016). "Synopsis of the PI-RADS v2 Guidelines for Multiparametric Prostate Magnetic Resonance Imaging and Recommendations for Use". European Urology 69 (1): 41–49. doi:10.1016/j.eururo.2015.08.038.
  9. ↑ http://link.springer.com/article/10.1007%2Fs00330-011-2377-y
  10. ↑ http://www.acr.org/Quality-Safety/Resources/PIRADS
  11. ↑ Thompson, J.E.; van Leeuwen, P.J.; Moses, D.; Shnier, R.; Brenner, P.; Delprado, W.; Pulbrook, M.; Böhm, M.; Haynes, A.M.; Hayen, A.; Stricker, P.D. (October 2015). "The Diagnostic Performance of Multiparametric Magnetic Resonance Imaging to Detect Significant Prostate Cancer". The Journal of Urology. doi:10.1016/j.juro.2015.10.140.
  12. ↑ Vargas, H. A.; Hötker, A. M.; Goldman, D. A.; Moskowitz, C. S.; Gondo, T.; Matsumoto, K.; Ehdaie, B.; Woo, S.; Fine, S. W.; Reuter, V. E.; Sala, E.; Hricak, H. (22 September 2015). "Updated prostate imaging reporting and data system (PIRADS v2) recommendations for the detection of clinically significant prostate cancer using multiparametric MRI: critical evaluation using whole-mount pathology as standard of reference". European Radiology. doi:10.1007/s00330-015-4015-6.
  13. ↑ Abdi, Hamidreza; Pourmalek, Farshad; Zargar, Homayoun; Walshe, Triona; Harris, Alison C.; Chang, Silvia D.; Eddy, Christopher; So, Alan I.; Gleave, Martin E.; Machan, Lindsay; Goldenberg, S. Larry; Black, Peter C. (February 2015). "Multiparametric Magnetic Resonance Imaging Enhances Detection of Significant Tumor in Patients on Active Surveillance for Prostate Cancer". Urology 85 (2): 423–429. doi:10.1016/j.urology.2014.09.060.
  14. ↑ Schieda, Nicola; Quon, Jeffrey S.; Lim, Christopher; El-Khodary, Mohammed; Shabana, Wael; Singh, Vivek; Morash, Christopher; Breau, Rodney H.; McInnes, Matthew D.F.; Flood, Trevor A. (October 2015). "Evaluation of the European Society of Urogenital Radiology (ESUR) PI-RADS scoring system for assessment of extra-prostatic extension in prostatic carcinoma". European Journal of Radiology 84 (10): 1843–1848. doi:10.1016/j.ejrad.2015.06.016.
  15. ↑ Sperling, MD, Dan. "MRI Biopsy Guidance Better than TRUS". Sperling Prostate Center. Retrieved 5 February 2016.
  16. ↑ Turkbey, Baris; Choyke, Peter L. (27 August 2015). "PIRADS 2.0: what is new?". Diagnostic and Interventional Radiology 21 (5): 382–384. doi:10.5152/dir.2015.15099.
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