Patient preparation is just the same as for transrectal prostate biopsy: the patient will use a microenema in the morning of the procedure. Antibiotic prophylaxis is indicated, as it is for biopsy, to be started the day of the examination and continued for 3–4 days after the implantation. A few days before, the radiotherapist will have provided the patient with the specific informed consent form, illustrating the relative risks and benefits that must be signed prior to commencing the procedure.

Unless contraindicated, there will be suspension of any antiaggregant/anticoagulant therapy 7 days before; if necessary, this can be replaced by low molecular weight heparin. The hemorrhagic risk during the implant is less than during biopsy. The procedure can be performed without suspending low-dose aspirin therapy.

US-guided implantation of markers can be done by either the transrectal or the transperineal approach. In the latter, a US device with an endocavitary end-fire probe (6–8 MHz) is used, with disposable biopsy forceps. In patients with a history of infections or immune depression, instead, transperineal access using a linear/biplanar probe is advisable.

Transrectal access is the technique most commonly employed nowadays, and no particular complications have been reported. However, it is important to implement all possible precautions to prevent infection; from that standpoint, the transperineal approach is more advantageous. Nevertheless, in our experience, based on more than 100 cases performed using the transrectal technique and adopting proper precautions to prevent infection, no clinically relevant infections were recorded [4].

The materials needed include a local anesthesia needle (21 gauge, 25 cm length for the transrectal approach, spinal needle for the transperineal approach) and three needles containing the gold or carbon fiducial markers, mounted on an 18 gauge cannula that will release the markers, measuring 0.35/0.9 mm in diameter x 3/4 mm in length, as well as an enema with povidone-iodine (2.5 cc in a 2.5 ml syringe), to be administered rectally before the procedure. Carbon markers are preferable if a CBCT is available, because they produce less artifacts than gold markers (Fig. 30.2a), whereas gold is preferable for MVCT TomoTherapy (Fig. 30.2b).

Neither gold nor carbon markers preclude later magnetic resonance imaging.

The examination findings (two copies, one for the patient and one for the radiotherapy unit) will include images and a description of the procedure: sites where the markers were positioned and the technique employed, any complications, and the antibiotic prophylaxis adopted. The marker labels must be attached to the patient’s radiotherapy record and archived with the signed informed consent form. The procedure is performed in an outpatient regimen.

With the patient in left lateral decubitus, an antiseptic enema with 2.5 ml povidone-iodine is administered immediately prior to the procedure. This can be combined, before starting the procedure, with a local application of anesthetic cream (lidocaine-prilocaine) or lidocaine spray to the rectum and anus as painkiller before probe insertion to ensure patient comfort. Nowadays, hydrophilic gels containing lidocaine and antiseptic (lidocaine and chlorhexidine gel (Farcosedan ®)) are available on the market in prefilled syringes, fitted with a plastic cannula for endorectal insertion of the gel.

The endocavitary probe is introduced, and a periprostatic nerve block is then induced with 10 ml of lidocaine 1 % bilaterally at the vesicle-prostate angle under longitudinal US scanning.

The next steps are to prepare a sterile field, open the preloaded disposable needles (each contains just one marker), and push the needle down through the cannula to release the marker in the prostatic tissue.

The three radiopaque markers (we employ 0.9 × 3 mm) are positioned under US guidance; by convention, they are placed in the base and apex of the left lobe and mid gland in the right lobe. This arrangement may vary, but it is important in all cases to specify the final positioning in the record and to avoid overlap of the markers (Fig. 30.3).

The markers should lie on different planes, avoiding overlap on the spatial lines uniting them (Figs. 30.4, 30.5, and 30.6).

This spatial distribution is ideal in order to monitor the prostate position and movements. Once the ideal position has been identified with the aid of biopsy tracer on the US screen (Fig. 30.6c), the needle is inserted inside the gland parenchyma, at a depth of about 10 mm from the capsule margin to prevent one end of the marker from remaining in the rectum. The plunger is pushed to release the gold seed through the needle point and the barrel is retracted with the plunger fully inserted. The fiducial marker is left in position. Two scanning plane images are printed to document its position (Figs. 30.4 and 30.5). Once the needle is withdrawn, checked to see that it is empty, it is thrown out, while the product label is attached to the record. If the marker is seen partially inserted in the rectum not the prostate, this suggests a partial spontaneous expulsion. If it is seen to be inserted in the rectum and only partially in the prostate, a US/radiological control is necessary, and endoscopic removal of the marker is advisable with gastroenterologist. The positioning scheme of the markers is decided in concordance with the radiotherapist.

The best scheme is termed the “triangulation scheme” that avoids overlap of the markers on the three orthogonal visualization planes. This scheme is successful when only one marker is visualized on each US scanning plane, not two simultaneously. Especially during the learning curve period, it is useful to make fluoroscopic X-ray controls after the procedure to correlate the US and radiographic geometries (Fig. 30.7a, b). In our experience, we did this in the first 50 cases, thereby progressively improving our awareness of when the markers were correctly positioned.