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 the recent advances of multiparametric MRI (mpMRI) of the prostate in the detection and characterization of prostate cancer , three different targeted MRI-guided biopsy techniques have been established and are in use : cognitive fusion biopsy, ultrasound-MRI fusion biopsy and MRI-guided in-bore biopsy .
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 .
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.
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 .
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.
Preprocedural evaluation
Antibacterial prophylaxis.
Coagulation parameters and platelet count depending on instutional protocol should be obtained and reviewed for safe procedure.
Data or images of a previous multiparametric MRI (mpMRI) of the prostate should be reviewed and used for planning the procedure.
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.
Advantages
- short intervention time and can be done in a urology clinic setting
- can be easily combined with systematic biopsy
Disadvantages
- 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
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.
Advantages
- high contrast resolution, improved targeting, accurate biopsy and target location documentation
- seems to be most accurate in the detection of clinically significant cancer
- potentially fewer cores and thus less risk of complications
Disadvantages
- long intervention time, no real-time feedback
- requires MRI scanner time and MR compatible equipment
- very high costs
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 .
Advantages
- good biopsy and target location documentation possible
- faster intervention time than MR in-bore biopsy
- can be easily done in conjunction with systematic biopsy
Disadvantages and challenges
- special registration and fusion software and hardware necessary, high initial costs
- registration errors/misalignment
- steep learning curve, requires good cooperation between urologist, radiologist and pathologist
Postprocedural care
Does not differ from postprocedural care of a systematic biopsy of the prostate.
Recovery time depending on 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 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 .
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