I’ve been ordered to have a prostate MRI. Why is this test being requested, what exactly is it looking for, and what conclusions can be drawn from it? I’ll explain the principles, indications, and possible follow-up investigations in simple terms.
What is an MRI?
MRI (magnetic resonance imaging) is an X-ray-free examination based on a powerful magnetic field. This field aligns the water molecules in cells and allows for a very precise image of the tissues, generally finer than that of a CT scan.
Main advantages:
- No radiation : MRI does not use X-rays.
- No iodine injection : useful in case of iodine allergy or kidney failure.
Why request a prostate MRI?
The two main indications are:
- A high PSA level.
- An abnormal clinical examination, for example a suspicious rectal examination.
To give you an idea, a PSA level between 4 and 10 ng/ml corresponds to an approximately 30% risk of having prostate cancer. Previously, systematic biopsies were performed on all patients with elevated PSA, which was imprecise and led to many unnecessary biopsies. MRI now allows for better targeting of patients for biopsies and avoids unnecessary examinations.
What are we looking for on an MRI?
The goal is to identify a suspicious lesion, which is called a “target”. If an abnormality is detected, it is classified according to a standardized score: the PI-RADS.
The PI-RADS (Prostate Imaging Reporting and Data System) score
The PI-RADS is a probability score. It does not indicate the aggressiveness of a potential cancer, but the probability that an observed lesion is cancerous:
- PI-RADS 1 : normal prostate → simple monitoring.
- PI-RADS 2 : image of inflammatory origin → no biopsy, monitoring.
- PI-RADS 3 : doubtful → decision on a case-by-case basis according to family history or genetic factors (monitoring or biopsy).
- PI-RADS 4 : risk of approximately 75% → biopsy recommended.
- PI-RADS 5 : risk of approximately 95% → biopsy essential (PI-RADS 5 often corresponds to a large and highly suspicious lesion).
What to do after an MRI?
The driving course depends on the PI-RADS score:
- PI-RADS 1–2 : clinical and biological monitoring (PSA).
- PI-RADS 3 : monitoring or biopsy depending on the clinical context, family history and risk factors.
- PI-RADS 4–5 : Prostate biopsy recommended.
During the biopsy, I always perform:
- Targeted biopsies of the lesion identified by MRI.
- A systematic or mapping sample of the prostate to detect any lesions not visible on MRI.
This allows for increased accuracy of diagnosis and proper assessment of the presence of cancer.
Practical procedure and benefits for the patient
A prostate MRI is a non-invasive examination. The radiologist will ask you to remain still during the scan to obtain good quality images. In most cases, the MRI does not involve the injection of iodine; some scans may use a specific contrast agent, depending on the radiologist’s recommendations and your kidney function.
Concrete benefits:
- Reduction of unnecessary biopsies.
- More targeted and precise biopsies when necessary.
- Improved detection of clinically significant lesions.
In summary
- Prostate MRI has become a central tool for the screening and diagnosis of prostate cancer.
- It is mainly requested in cases of high PSA or abnormal digital rectal examination.
- The PI-RADS score guides the decision: monitoring if 1–2, case-by-case decision if 3, biopsy if 4–5.
- When a biopsy is performed, it combines targeted biopsies and systematic mapping to optimize detection.
If you have an elevated PSA level or a concerning clinical examination, MRI now offers a more precise and less invasive approach than older methods. I am available to answer your questions and tailor the treatment plan to your individual situation.
