MRI – prostate cancer imaging

In the last few years, MRI (Magnetic Resonance Imaging) has become by far the most effective and versatile diagnostic procedure for prostate carcinomas.

This is why an endorectal MRI of the prostate has been listed as the best imaging procedure in the current German S3 Guidelines for prostate cancer. It is now the leading procedure for prevention, diagnosis and therapy planning.

With a detection sensitivity of over 85%, the prostate MRI detects cancer at least twice as reliably as ultrasound, elastography or the usual punch biopsy. An MRI that does not show any cancer is reliable: it is at least 90% accurate in precluding cancer.

But not only that—a prostate MRI is non-invasive, painless, and doesn't expose the body to any radiation.

But: not every so-called prostate MRI fulfills the requirements of a high-quality examination. So ask an expert. As a physician and physicist, Prof. Stehling, together with the Nobel Prize winner Sir Peter Mansfield, has himself had a substantial influence on the development of magnetic resonance imaging and is one of the leading international experts in the field of prostate MRIs.

Parameters measured in order to accurately diagnose prostate cancer

As opposed to other imaging procedures [CAT (Computer Tomography) scan, ultrasound, scintigraphy or PET (Positron Emission Tomography)], an MRI provides several independent parameters to evaluate the prostate: T1 and T2 relaxations, tissue susceptibility, water diffusion, tissue perfusion and spectroscopic information about the metabolism. For this reason, it is also called a multiparametric MRI.

In many places, only one or two different physical weightings are performed, but for many years, we have always performed all technically available weightings in order to achieve the maximum validity of the examination. This makes an MRI significantly superior to other imaging techniques, particularly ultrasound and elastography.

The most important applications of prostate MRI

Today, MRI technology, which continues to develop very quickly, is the leading procedure for many urological issues concerning the prostate:

  1. Early detection or exclusion of cancer: when the PSA level is elevated or there is a suspicious palpation finding before the biopsy. This can prevent many unnecessary biopsies from being performed.

    For more information: 
    Allow us to analyze your PSA level to decide if an MRI is a good idea for you.

  2. Biopsy planning or exclusion of cancer: when the PSA level increases again after a negative biopsy or biopsies, because punch biopsies without MRI planning are shots in the dark.

    For more information: 
    Ask our experts on modern diagnostics for prostate cancer, including the 3D biopsy.

  3. Staging and therapy planning: to make a therapy plan for prostate cancer that has been detected or to determine the exact magnitude of the disease in the pelvis (staging).

    For more information:
    Ask our experts about possible prostate cancer therapy.

     

  4. Detection of recurrent cancer and re-staging: when the PSA level increases again after treatment of prostate cancer (radical removal of the prostate, radiation therapy, HIFU, etc.), to detect, exclude or localize a recurring tumor (local recurrence).

    For more information:
    Ask our experts about NanoKnife and its capabilities.

     

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Each procedure in detail:

  1. Multiparametric MRI for biopsy-free examination, early detection or exclusion

    Prostate cancer is becoming more and more common, even in younger men. Unlike BPH (Benign Prostatic Hyperplasia), cancer is usually painless. Because of this, it is now recommended that every man have an annual early detection examination of the prostate starting at age 50 (age 40 if there is a family history of prostate cancer). The early detection examination usually consists of determining the PSA (prostate-specific antigen) level and palpating the prostate. But with this procedure, carcinomas are often overlooked or “false positive” findings are made, i.e. a carcinoma is believed to be found where there actually is none.

    The percentage of men with prostate cancer (PCa) relative to the PSA level is used as indication for diagnostics. In Germany, a biopsy is recommended for levels at or above 4 ng/ml; in the USA, a biopsy is recommended at or above 2.5 ng/ml.

    To further clarify the diagnosis, a tissue sample is usually taken through the rectum (transrectal biopsy). But this only provides a definite result in an average of 30-35% of all cases.

    In general, between six and twelve tissue samples are taken from the prostate. Although this procedure is generally established, it has several disadvantages. Patients often find it painful, and it usually doesn't provide an exact localization of any tumors. Because the operation is done through the rectum, which is not sterile, bacteria are transported into the prostate, which can lead to a prostate infection (prostatitis).

    Alternative: biopsy-free prostate diagnosis.

    As an alternative to a biopsy, non-invasive (biopsy-free) diagnostic techniques using endorectal magnetic resonance imaging (MRI) and spectroscopy (MRS) may be performed. These procedures make it possible to detect prostate cancers (PCa) with certainty rates of 85%.

  2. Biopsy planning or exclusion
    As explained under the point above, punch biopsies have a very low accuracy rate, which often leads to unsatisfactory results. Existing carcinomas may be found only after several years of repeated testing or not at all. Conversely, a negative biopsy result is very unreliable, i.e. does not really help the patient to relax, knowing he does not have prostate cancer.

    MRI technology is highly reliable in finding “suspicious zones”, not only in the entire 3D volume of the prostate, but also in the surrounding organs. These “suspicious zones” are divided into categories of suspicion, called PI-RADS 1-5. An MRI does not replace a biopsy in the sense that it provides certain detection of cancer and classification of the tissue. But it is much better at exclusion and at localization for punch biopsies.

    Thus, MRI technology can be used to reliably plan 3D biopsies or provide your urologist with images that help to more accurately target a rectal biopsy, so that fewer samples are necessary.


    A classic case: two punch biopsies performed on the patient one year apart from each other, and neither had found cancer. His PSA level continued to increase, and he came to us. All of the MRI images showed a clear suspicion. It was as good as certain that there was a carcinoma. Now a targeted biopsy could be performed. The targeted 3D biopsy determined that the carcinoma was medium grade and did not find any other foci. Now focal therapy was possible. The patient chose NanoKnife therapy, and since then, he has been cancer-free and symptom-free.

  3. Staging, therapy planning and recommendation
    To make a good therapy decision, you need two types of information: grading and staging. Grading is done in a biopsy, but staging is never based solely on the results obtained in a biopsy.

    For staging, it must be determined where exactly the carcinoma is, how large it is and whether surrounding organs or lymph nodes are affected.


    An endorectal MRI for staging known prostate cancer: the biopsy revealed four positive samples, ultrasound did not show any abnormalities. The MRI shows a carcinoma in the right prostate lobe that has grown through the prostate capsule and has begun to infiltrate the rectum (yellow arrows) and the seminal vesicle (red arrow). Lymph node metastases (green arrows). Tumor stage T4b N2.

    Although skeleton scintigraphy an
    d CAT (Computer Tomography) scan are being used more and more frequently, they only provide useful information about bone metastasis. These procedures do not make it possible to see the distribution of a carcinoma in the prostate capsule, so it is also impossible to use them to see any growths through the capsule.

    Before clarity has been achieved regarding these facts, we believe that it is hardly possible to make a solid therapy decision. The only option without this information is radical therapy in the form of removal of the prostate. This is an option that, although it is a legitimate method that has been in practice for many decades, would often not have been necessary and with similar frequency does not offer the patient any statistical improvement in his life expectancy.

    Especially low-grade carcinomas can be treated much more quickly and with many fewer side effects with targeted focal therapy, e.g. using NanoKnife technology. In this case, MRI images are essential to the planning.

    A solitary, small carcinoma locus. A classic case for focal therapy, because the benefit of radical removal of the prostate and/or radiation therapy would not outweigh the side effects.

    Other methods that are often legitimate and satisfactory variations involving the least amount of time and effort are “watchful waiting” or “active surveillance”. Especially with these methods, MRI imaging is essential, not only for the decision but also for the process of “watching” or “surveillance”, because it is the only means of adequately assessing the growth process.

  4. Detection or exclusion of recurrences
    After every type of focal therapy, regular MRIs in 6- to 18-month intervals are standard procedure. But after radical therapy, the situation is different. Because no healthy prostate cells whatsoever are supposed to be left, a PSA level approaching 0 is to be expected. If the PSA level begins to increase after radical therapy, this is usually an indication of a recurrence. Which therapy options are available can only be decided if and when the recurrence has been localized. MRIs and PSMA/choline PET-CTs are the only imaging technologies that can locate the recurrence with a high probability and thereby make therapy decisions and planning possible.



    Left: recurrence of a prostate carcinoma on a patient's bladder after radical removal of the prostate using DaVinci and after radiation therapy. Right: because no other treatment options were possible, the tumor was removed using NanoKnife. There was no pain or damage and the recurrence was completely removed.

    Prostate spectroscopy determines the chemical substances in prostate cells. Healthy cells have a high concentration of citrate and little choline. Cancer cells have less citrate because they use it to produce energy, and more choline, which is needed to build the cell membranes of the tumor cells. (Please note: The y axes are scaled differently — see red circles.)

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