理解您的前列腺磁共振成像（MRI）报告：PI-RADS 评分的含义

最后更新： 8 月 25, 2026

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Not long ago, a man with a raised PSA had one route available: a biopsy. Most of those biopsies came back clear — which meant a great many men went through an uncomfortable procedure, and occasionally a complication from it, to be told nothing was wrong.

MRI of the prostate, performed 之前 any biopsy, is what changed that. It does not replace the biopsy; it decides who needs one. And it comes back with a score most men have never heard of.

What PI-RADS is

PI-RADS stands for Prostate Imaging Reporting and Data System. It is a standardised way for a radiologist to record how suspicious an area on the scan looks, on a scale of 1 to 5. It is not a measure of how much cancer is present, and it is not a diagnosis — only tissue gives a diagnosis.

Two things about the score are worth knowing before reading your report.

• It scores a lesion, not a man. A report may describe more than one area with different scores; the highest one generally drives the decision.
• It depends heavily on who is reading and what scanner was used. The same prostate can be scored differently in different hands, which is why an unexpected result is sometimes worth a second opinion rather than immediate action.

What each score means

Approximate likelihoods of finding clinically significant cancer. The figures vary between studies and centres, so read them as orders of magnitude rather than precise probabilities.

分数	Wording in the report	Roughly how often significant cancer is found
1	Very unlikely to be cancer	Low — but not zero
2	Unlikely to be cancer	Low — but not zero
3	Genuinely uncertain	Around one in ten
4	Likely to be cancer	Roughly one in five
5	Very likely to be cancer	The majority

A correction: a low score is not a zero

An earlier version of this article gave PI-RADS 1 and 2 as a 0% chance of aggressive prostate cancer. That was wrong, and it is the most important correction on this page.

A reassuring MRI is genuinely reassuring — significant cancer is unlikely, and that is exactly why a low score can justify following the PSA instead of proceeding to biopsy. But MRI misses some cancers, particularly certain patterns that do not show up well, and a small proportion of men with a normal-looking scan do have significant disease.

The practical consequence is what matters: a low PI-RADS score means you are followed, not discharged. If the PSA keeps climbing, or the examination is abnormal, or there is a strong family history, the question stays open regardless of what the scan said. A man told he has a 0% risk has been given a reason to ignore a rising PSA, and that is the harm the old wording could do.

PI-RADS 3 is a conversation, not an instruction

The earlier version of this article stated that biopsy must be recommended for anyone scoring at least 3, and then said in the following sentence that the score is only additional information requiring careful counselling. Those two statements contradicted each other, and the first has been corrected.

PI-RADS 3 means the radiologist genuinely cannot tell. It is the largest source of uncertainty in the whole system, and treating it as an automatic biopsy sends a great many men to a procedure most of them do not need. What resolves it is the surrounding information:

• PSA density — the PSA in relation to the size of the prostate. A moderately raised PSA in a large gland means something quite different from the same PSA in a small one, and this is the single most useful figure for deciding what to do with a PI-RADS 3.
• Whether you have had a biopsy before, and what it showed.
• The examination, family history, age and general health — including what you would want done if a low-grade cancer were found.

For scores of 4 and 5 the discussion is much shorter: those areas are sampled.

If a biopsy follows

The MRI images are fused with live ultrasound so the suspicious area is sampled directly, and some additional systematic samples are usually taken as well — because MRI does not see everything, which is the same reason a low score is not a discharge. The needle is passed through the skin of the perineum rather than through the rectal wall, which is what keeps serious infection uncommon.

See 磁共振成像融合经会阴前列腺活检术 和 what to expect afterwards. If the biopsy confirms cancer, note that finding it does not automatically mean operating — some prostate cancers are correctly managed by monitoring, and the grade determines what follows. The treatment options are set out under robotic radical prostatectomy.

If you arrived here holding a raised PSA rather than a scan report, start with what a high PSA actually means.

Symptoms that need attention rather than a scan report

In an emergency in Thailand, call 1669.

• Inability to pass urine with a painful full bladder.
• Visible blood in the urine or semen.
• New bone pain in the back, hips or ribs, or unexplained weight loss.
• New leg weakness or numbness, or loss of bladder or bowel control, in a man known to have prostate cancer — emergency assessment.

Frequently Asked Questions About PI-RADS

My MRI is PI-RADS 2. Does that mean I definitely do not have cancer?

No. It means significant cancer is unlikely, which is genuine reassurance and often a good reason not to biopsy — but not a zero. MRI misses some cancers. An earlier version of this article stated a 0% risk for PI-RADS 1 and 2, which was wrong. A low score means you are followed rather than discharged, and a PSA that keeps rising still needs acting on.

PI-RADS 3 评分意味着什么？我需要做活检吗？

Not automatically. PI-RADS 3 means the radiologist genuinely cannot tell, and most men in this group do not have significant cancer. The decision rests on PSA density, any previous biopsy, examination findings, family history, age and your own view — an earlier version of this article said biopsy must be recommended at 3 or above, which overstated it.

Can PI-RADS tell how aggressive a cancer is?

Not directly. A higher score raises the likelihood that significant cancer will be found, but grade comes from the pathologist examining tissue. PI-RADS estimates suspicion; it does not diagnose or grade.

My report lists two different scores. Which one counts?

PI-RADS scores individual areas rather than the whole man, so a report may contain several. The highest score generally drives the decision, and the location of each area matters for planning where to sample.

Would a different radiologist give the same score?

Not necessarily. Scoring depends on the quality of the scan and on the experience of the person reading it, and agreement between readers is imperfect — particularly around PI-RADS 3. Where a result is unexpected or does not fit the clinical picture, review of the images is reasonable before acting on the number.

Arranging a consultation

Dr. Soarawee Weerasopone sees patients at 曼谷医院总部 and at Samitivej Sriracha Hospital in Chonburi on 088-022-1445. Bring the MRI images themselves rather than only the report, and every previous PSA result with its date.

曼谷医院远程医疗服务适用于无法亲自就诊的患者，包括国际患者——请通过电子邮件提前向泌尿科预约： bhquro@bdms.co.th. Samitivej Sriracha is in-person only. Enquiries about cost are answered by the hospital, not by this website.

免责声明 This content is written and reviewed by Dr. Soarawee Weerasopone, a board-certified urologist at Bangkok Hospital Headquarters, and is intended for education only. It is not medical advice, diagnosis or a prescription for any individual, and no advice, diagnosis or prescription is given through personal messaging channels or social media. Dr. Soarawee operates no public social media account; any account offering private consultation in his name is fraudulent. In an emergency in Thailand, call 1669.