Use of MRI-ultrasound Fusion to Achieve Targeted Prostate Biopsy

This method of prostate biopsy allows for precise targeting of suspicious regions within the organ, allowing a specificity and precision of the biopsy method not previously available. With this new technology, we can specifically target regions of interest within the prostate regions detected by the MRI, allowing a precision of biopsy and an accuracy of prostate pathology characterization not previously available. After powering on the ARTEMIS device workstation computer and cart, help the patient into the left lateral decubitus position, with the back nearly parallel to the edge of the bed and the legs folded towards the chest.

This position provides the maximum range of motion for the tracker arm of the biopsy device. When the patient is in position, attach the needle guide to a transrectal ultrasound probe and gently insert the lubricated end fire transrectal ultrasound probe into the patient's rectum. Advance the probe until a two dimensional transverse view of the prostate is clearly visible on the monitor.

When the approximate center of the prostate is visible, rotate and advance the probe until the junction between the prostate and seminal vesicle is visible, representing the area where the prostatic neurovascular bundle enters the gland. Insert a 22 gauged spinal needle through the needle guide channel on the transrectal ultrasound probe and advance the needle into the junction between the prostate and the seminal vesicle. Infiltrate this space with 10 cubic centimeters of 1%lidocaine, creating an ultrasonic wheel and causing a separation of the seminal vesicles and prostate from the rectal wall.

Then readjust the transrectal ultrasound probe to administer periprostatic nerve block on the contralateral side. After waiting for one minute to ensure adequate anesthesia, place the tracking arm in the park position, approximately 90 degrees from the other tracking arm. Then lift the tracker arm to place the transrectal ultrasound probe into the cradle of the tracking arm and secure the clasp.

For three dimensional image acquisition, slowly rotate the transrectal ultrasound probe clockwise along its long axis for approximately 200 degrees until the entire prostate is scanned. Then outline the prostate with six to eight digital markers along the border in both the transverse and sagittal images. Review the 3D ultrasound model of the prostate to ensure that the entire prostate is visible in all of the slices, clicking on the correct prostate boundary on the gray scale image to refine the proposed boundaries of the 3D reconstructed prostate as necessary.

Next, perform rigid registration of the magnetic resonance image, or MRI, then place digital markers on two landmarks on the MRI and add corresponding landmarks on the ultrasound image. After performing rigid registration, press the Next button on the console to perform elastic registration. This adjusts for prostatic deformation that occurs secondary to compression by the transrectal ultrasound probe.

For patients undergoing a repeat prostate biopsy, the clinician can remove coordinates that were negative for malignancy during a prior biopsy session from the display. For target acquisition, depress the clutch near the tracker arm handle to release the tracker arm braking system and gently move the tracker arm toward the desired target. Push the lever just left of the tracker arm handle forward to disengage the rotation brake and gently rotate the tracker arm to align the yellow digital marker until it is superimposed onto the desired target.

Once the yellow digital marker is in the desired location over the target and the target is highlighted in red, release the clutch to reengage the brakes on the tracker arm, securing the arm in space. Then pull the lever to reengage the rotational brakes. Prior to each biopsy, assess whether the live ultrasound images remain registered within the ultrasound reconstruction.

If the patient moves or the prostate moves during the procedure, the coregistration of MRI and ultrasound images may be distorted, causing the operator to miss the target. Therefore, this process incorporates motion compensation software. If the green digital markers on the live ultrasound no longer correctly demarcate the border of the prostate, select the motion compensation option on the monitor and place digital markers on three landmarks on the 3D prostate reconstruction and on the corresponding landmarks on the live ultrasound view of the prostate.

This returns the 3D model into registration with the live ultrasound. To perform a biopsy, first place an 18 gauge biopsy gun into the needle guide mounted on the transrectal ultrasound probe. Using the image on the monitor, advance the needle toward the red bowtie-shaped visual aid displayed over the live ultrasound image until the needle tip intersects the middle of the marker.

Depress the foot switch pedal to begin recording the sequence of the 2D ultrasound images with the 3D biopsy location recording and depress the trigger on the biopsy gun to fire the biopsy needle. Pay careful attention to the streak of the needle on the ultrasound. Then release the foot switch to stop the needle recording.

For needle segmentation, review the needle trajectory recording and compare the white streak on the recorded ultrasound frames to the red needle auto segmentation line that appears as an overlay within the pop-up window. Mark the points corresponding to the beginning and the end of the needle and click on the tip of the streak to define the needle tip and on the bottom of the streak to define the needle trajectory and remove the biopsy gun from the needle guide for collection of the biopsy core. When all of the biopsies have been collected, unlock the stabilizer arm and gently remove the transrectal ultrasound probe from the patient's rectum.

Among the 825 patients in this representative clinical study with a region of interest greater than or equal to grade three, combination biopsy had the greatest detection rate for clinically significant cancer, with 89 cases of high-risk prostate cancer identified, compared to 74 via targeted biopsy, or 51 with systematic biopsy alone. The identification of clinically significant prostate cancer was directly related to the region of interest grade, as 80%of men with a grade five region of interest were found to have Gleason greater than or equal to seven disease compared to 24%for men with a grade three region of interest. Combination biopsy also outperformed both targeted biopsy and systematic biopsy for grade four regions of interest.

An important function of image fusion biopsy is the ability to track specific cancer foci within the prostate over time. We can return within a few millimeters to a previously identified cancer spot within the prostate, therefore, for example in active surveillance patients, greatly improve our ability to follow changes that may occur within the prostate over various time intervals. Now that fusion technology's been around for a decade, we're beginning to see evidence in the literature regarding the long term benefits of targeting and tracking technology in active surveillance cohorts.

We recently demonstrated that by fusing MRI data with live transrectal ultrasound images, we're able to individually target tumors for ablation using a laser. This focal laser ablation therapy is based on MRI ultrasound fusion technology and may spare patients from some of the traditional side effects associated with radical treatment, such as incontinence or erectile dysfunction. The greatest risk with any prostate biopsy are infection and septicemia.

Using your center's antibiogram to properly select antibiotics is essential in lowering the risk of prostate biopsy sepsis.