PI-RADS v2.1 Calculator

This calculator combines reader-assigned sequence scores for one lesion. It does not assign scores from images or verify the lesion’s morphology, zone of origin or image quality.

With adequate DWI, DWI determines the peripheral-zone category, except that DWI 3 with positive DCE gives category 4. In the transition zone, T2W is dominant: T2W 2 with DWI 4 or 5 gives category 3, and T2W 3 with DWI 5 gives category 4. T2W 1, 4 and 5 give categories 1, 4 and 5.

A score left blank was not entered into this calculator. It does not represent a normal finding, a negative DCE result or an inadequate sequence.

PI-RADS v2.1 assigns typical round, completely encapsulated TZ nodules a T2W score of 1. Findings similar to the background TZ should not be scored as separate suspicious abnormalities. Assess TZ shape and margins in at least two planes.

Atypical TZ nodules with T2W score 2 are upgraded to category 3 when DWI is 4 or 5. DWI 3 does not upgrade T2W 1 or 2. This was the change to the overall-category derivation from sequence scores in v2.1; the revision also changed some sequence-score definitions.

DCE is positive when enhancement is focal, earlier than or contemporaneous with adjacent normal prostatic tissue, and corresponds to a suspicious finding on T2W and/or DWI. Enhancement of a lesion with BPH features is included in the negative DCE definition.

When DWI is inadequate or absent and DCE is positive or negative, both zones use the inadequate-DWI table. T2W 3 gives category 4 with positive DCE and category 3 with negative DCE; the other T2W scores give a category equal to the T2W score. If DCE is also inadequate or absent, no assessment category is assigned and assessment is limited to staging for EPE.

When DCE is inadequate or not performed but DWI is adequate, PZ assessment follows DWI and TZ assessment is unchanged. PZ DWI 3 is not upgraded.

This tool does not provide an assessment pathway for technically inadequate or absent T2W.

For an AFMS lesion, PI-RADS v2.1 applies PZ or TZ criteria by the zone from which the lesion appears most likely to originate. It has no separate CZ table; it notes that cancer originating in the CZ is uncommon and that most cancer in the CZ arises in the adjacent PZ or TZ.

PI-RADS v2.1 assigns category 2 to an encapsulated, circumscribed, round nodule in the PZ or CZ (likely an extruded BPH nodule), even if it is hypointense on ADC; the PZ table here does not apply to that finding.

Score 5 keeps the applicable score-4 signal and shape features; its size/extension criterion is greatest dimension ≥1.5 cm or definite extraprostatic extension/invasive behavior. Size alone does not establish score 5. The reader incorporates these features when assigning the sequence score; this calculator does not re-score lesion size.

Measure PZ lesions on ADC and TZ lesions on T2W. If measurement is compromised on that sequence, use the sequence that depicts the lesion best. Report the largest axial dimension, and report a larger sagittal or coronal dimension and its plane when present. Identify the sequence used for measurement.

The calculator assesses one lesion at a time. PI-RADS v2.1 generally prioritizes up to four suspicious lesions, while allowing more in appropriate circumstances. The index lesion has the highest assessment category; ties favor EPE, then the largest lesion if none shows EPE. An examination with no finding above category 1 is reported overall as category 1.

PI-RADS v2.1 is intended for patients with suspected cancer in treatment-naïve prostate glands. It does not address suspected recurrence after therapy or progression during surveillance.

Sequence scores require image interpretation and may differ between readers. This calculator verifies neither those scores nor the underlying diagnosis. The category describes MRI suspicion, not a pathological diagnosis.

PI-RADS v2.1 assigns the assessment category from MRI findings without incorporating PSA, digital rectal examination or clinical history. PI-RADS v2.1 does not include management recommendations; these require information beyond the MRI findings. For prostate volume and PSA density, use the separate prostate volume calculator.

As of 9 November 2026, the ACR lists PI-RADS v2.1 (2019) as its current release. AJR commentaries in 2025 argued for and against an update; they do not replace the v2.1 assessment tables.

How is the PI-RADS v2.1 category calculated?

With adequate DWI, the peripheral-zone category follows DWI, except that DWI 3 with positive DCE gives category 4. In the transition zone, T2W is dominant: T2W 2 with DWI 4 or 5 gives category 3, and T2W 3 with DWI 5 gives category 4. Separate rules apply when DWI is inadequate.

What does PI-RADS 3 mean?

PI-RADS v2.1 defines category 3 as “Intermediate (the presence of clinically significant cancer is equivocal)”. It summarizes the MRI findings; PI-RADS v2.1 does not include management recommendations.

What does PI-RADS 4 mean?

Category 4 means “High (clinically significant cancer is likely to be present)”. With adequate DWI, category 4 comes from PZ DWI 4 or DWI 3 with positive DCE, and TZ T2W 4 or T2W 3 with DWI 5. Without adequate DWI, either zone can also reach category 4 through T2W 4, or T2W 3 with positive DCE.

What does PI-RADS 5 mean?

Category 5 means “Very high (clinically significant cancer is highly likely to be present)”. PI-RADS v2.1 defines a sequence score of 5 as “Same as 4 but ≥1.5cm in greatest dimension or definite extraprostatic extension/invasive behavior”. The overall category follows the applicable zone and sequence-quality table.

When does DCE change the PI-RADS category?

With adequate DWI, positive DCE upgrades a PZ lesion with DWI 3 to category 4. Without adequate DWI, positive DCE upgrades T2W 3 to category 4 in either zone. If DWI and DCE are both X, no assessment category is assigned.

What changed in PI-RADS v2.1 for the transition zone?

Atypical TZ nodules with T2W score 2 and DWI score 4 or 5 give category 3. ACR’s revision summary identifies this as the only change to deriving the overall assessment category from the sequence scores; other sequence-score definitions also changed.

What if DWI or DCE is inadequate?

Without adequate DWI, both zones use T2W: T2W 3 gives category 4 with positive DCE and category 3 with negative DCE; the other T2W scores give a category equal to the T2W score. Without adequate DCE but with adequate DWI, PZ assessment follows DWI and TZ assessment is unchanged. If both DWI and DCE are X, assessment is limited to staging for EPE, without a PI-RADS assessment category. This tool provides no assessment pathway for inadequate T2W.

Which PI-RADS version does this calculator use?

PI-RADS v2.1 (2019). The ACR lists it as the current release (checked 9 November 2026).

Does PSA density change the PI-RADS category?

No. PI-RADS v2.1 assigns the assessment category from MRI findings, without incorporating PSA. For prostate volume and PSA density, use the separate prostate volume calculator.