MRI targeted prostate biopsy

MRI targeted prostate biopsy refers to an imaging targeted technique rather than the traditional systematic approach of a prostate biopsy after respective imaging with multiparametric MRI (mpMRI) of the prostate.

As a consequence of advances with multiparametric MRI (mpMRI) of the prostate in the detection and characterization of prostate cancer ^1,2, three different targeted MRI-guided biopsy techniques have been established and are in use ³: cognitive fusion biopsy, ultrasound-MRI fusion biopsy and MRI-guided in-bore biopsy ^3,8-10.

MRI-targeted prostate biopsy (all three different targeted techniques included) has been shown to detect more clinically significant prostate cancer and less clinically insignificant cancer when compared with systematic biopsies, requiring fewer cores ^4-7.

Indications

There is a consensus about the strategy of repeat biopsy with image-guided targeting in patients with an initial negative biopsy and PI-RADS assessment category of 3-5 after multiparametric MRI (mpMRI) of the prostate ³.

An advantage of the MR-imaging targeted approach in patients with a clinical suspicion of prostate cancer who have not undergone a prior biopsy of the prostate over an initial systematic biopsy has been suggested ^4-6.

Contraindications

Contraindications are basically the same as with a systematic prostate biopsy and include uncooperative behavior by the patient and uncorrectable bleeding disorders. Depending on the technique used other contraindications may apply, e.g. claustrophobia or MR incompatible implants or devices.

Procedure

Preprocedural evaluation

• antibacterial prophylaxis

• acquisition and review of coagulation parameters and platelet count depending on institutional protocol

• review of previous imaging data such as a previous multiparametric MRI (mpMRI) and other relevant data

MRI-targeted biopsy techniques

Cognitive fusion biopsy

A suspicious lesion is identified on mpMRI prior to biopsy and then targeted using transrectal ultrasound (TRUS) guidance by the physician conducting the respective cognitive fusion biopsy (usually a urologist or less often radiologist).

The exact location of the lesion may be demonstrated on a diagram, snapshot or on a mpMRI image file. Original mpMR images should be reviewed immediately prior to the biopsy.

MRI in-bore biopsy

This is conducted in the MRI scanner under direct MR image guidance with direct visualization of the MR imaging target and the needle.

It can be undertaken with an endorectal approach or with a transperineal approach.

The endorectal approach is usually performed with the patient in the prone position. The biopsy device contains a transrectal needle guide, which is used as a fiducial reference point.

The transperineal approach is usually performed with the patient in the supine position and the biopsy is generally performed with a guidance grid.

Both MRI-targeted in-bore biopsy techniques usually utilize planning software for target localization and to achieve a more accurate needle placement.

Transrectal ultrasound-MR imaging fusion biopsy

Lesion detection capabilities of multiparametric MR imaging (mpMRI) and the real-time capabilities of transrectal ultrasound are synergized. Previously acquired MR images are registered and fused with real-time transrectal ultrasound images, which allows tracking of the ultrasound biopsy probe.

The lesions shown at multiparametric MR images can be targeted under ultrasound guidance outside the MRI gantry, and thus allowing a much faster intervention. Different ultrasound probes and tracking mechanisms exist ⁹.

Postprocedural care

• does not differ from postprocedural care of a systematic biopsy of the prostate

• recovery time depends on the local anesthetic used

• observation until urination in order to timely pick up urinary retention

• the patient should be informed about light urinary and/or rectal bleeding and heamtospermia

Complications

Complications are not different from a systematic prostate biopsy and include hematuria and hematospermia, rectal bleeding, rarely urinary retention or infection (prostatic abscess and/or sepsis). Though it has been suggested that they occur less often because of the lesser number of biopsy cores required ⁴.

Outcomes

Cognitive fusion biopsy

Advantages include:

• short intervention time and can be done in a urology clinic setting

• can be easily combined with systematic biopsy

Drawbacks of a cognitive fusion biopsy are:

• least accurate of the above mentioned targeted biopsy methods

• lack of standardization, no accurate biopsy and target location documentation

• operator dependent

MRI in-bore biopsy

The advantages of an MRI in-bore biopsy include the following:

• high contrast resolution, improved targeting, accurate biopsy and target location documentation ^9,10

• seems to be most accurate in the detection of clinically significant cancer ¹¹

• potentially fewer cores and thus less risk of complications

Disadvantages of an MRI in-bore biopsy are:

• long intervention time, no real-time feedback

• requires MRI scanner time and MR compatible equipment

• very high costs ^9,10

Transrectal ultrasound-MR imaging fusion biopsy

A transrectal ultrasound-MR imaging fusion biopsy has the following benefits: 

• good biopsy and target location documentation are possible

• faster intervention time than MR in-bore biopsy ^9,10

• can be easily done in conjunction with systematic biopsy

Disadvantages and challenges include:

• special registration and fusion software and hardware necessary, high initial costs ^9,10

• registration errors/misalignment

• a steep learning curve 

• requires good cooperation between urologist, radiologist and pathologist

See also

• prostate biopsy