PI-RADS® calculator

This calculator is based upon the American College of Radiology (ACR), AdMeTech Foundation and European Society of Urogenital Radiology (ESUR) Prostate Imaging Reporting & Data System (PI-RADS®), however it is neither supported, nor endorsed by the aforementioned organization.

Notes

Please make sure to thoroughly read the complete technical documentation of the PI-RADS system, the following section is only a brief summary of some of the major points.

PI-RADS categories

Based on multiparametric MRI a score between 1-5 is assigned to each prostatic lesion, increasing scores indicating elevated risk of malignancy:

  • PI-RADS 1: very low risk (clinically significant cancer is highly unlikely to be present)
  • PI-RADS 2: low risk (clinically significant cancer is unlikely to be present)
  • PI-RADS 3: intermediate risk (the presence of clinically significant cancer is equivocal)
  • PI-RADS 4: high risk(clinically significant cancer is likely to be present)
  • PI-RADS 5: very high risk (clinically significant cancer is highly likely to be present)
  • PI-RADS X: component of exam technically inadequate or not performed

PI-RADS has no formal recommendations for further management, as this is also dependent on other factors such as prostate specific antigen levels, history, local and patient preferences. Biopsy should be considered for PI-RADS 4-5 lesions in particular.

Assessment

The location of the lesion within the prostate is of key importance:

  • Transition zone lesions are primarily evaluated on T2-weighted imaging (T2WI), a score of 2 or 3 can be upgraded by their diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) appearance
  • Peripheral zone lesions are primarily evalulated based on their DWI/ADC appearance, a score of 3 can be upgraded based on the presence of dynamic contrast enhancement (DCE)
Absent or inadequate DWI or DCE
  • If DWI is non-diagnostic/absent: both peripheral and transition zone lesions are primarily assessed on T2WI, upgrade is based on DCE (the calculator automatically displays the required extra fields if the inadequate/missing DWI option is selected)
  • If DCE is non-diagnostic/absent: Peripheral zone lesions are judged solely on the basis of DWI
Practical points
  • DWI /ADC whould be compared to the average signal of normal prostate tissue in the same histologic zone
  • Up to four lesions with a PI-RADS score of 3, 4, or 5 may each be assigned and the index (dominant) intraprostatic lesion should be chosen
  • The index lesion is the one with the highest PI-RADS score
  • If more than one lesion is assigned the highest category the one showing extraprostatic extension (EPE) should be chosen, if none of the lesions show EPE the largest tumor should be selected
Further reading

Last updated: 2022-05-08