Figure 1.
Gold bladder fiducial markers, Gelfoam™ plug, and custom-made coaxial deployment needles.
A. Each 24-K gold micro-tined fiducial marker is manufactured with four length-wise rows of tines, whose points all face toward the center of the marker. The purpose of the micro-tines is to prevent the marker from migrating within the submucosal space. Each marker is deployed via a custom-made 30-cm. coaxial 18G needle into bladder submucosa. To prevent the marker from falling-out via the hole created by the placement needle, a small “plug” made of morcellated Gelfoam™ is deployed with (behind) the marker. B. 2.1×0.65 mm. gold fiducial markers are shown beside a custom-made 30-cm. coaxial 18G needle, and a U.S. dime.
Figure 2.
The tumor resection site is marked by a minimum of three fiducial markers placed circumferentially.
Electrocautery will cause necrosis of mucosa immediately adjacent to the resection site (purple). For this reason, we place the fiducial markers into healthy mucosa ∼5–10 mm lateral to the resection margin (“X”).
Figure 3.
A.During placement, the tip of the deployment needle should be tunneled (approximately parallel to the bladder wall) a short distance beneath the mucosa before the stylet is advanced to deploy the marker and Gelfoam™ plug. Submucosal tissue collapses upon the micro-tines, to anchor the fiducial marker in place and prevent marker migration. B. A minimum of three markers are placed around a single tumor site. Markers should be oriented circumferentially in a trident (e.g. Mercedes®-sign) rotated 30–60-degrees, such that when the three+ markers are viewed by radiograph from either an anterior-posterior view and a lateral view, each is distinct and does not overlap with the others.
Figure 4.
Plain-film X-Ray images of the pelvis without (left) and with (right) three 2.1×0.65 mm.
24K gold micro-tined fiducial markers surrounding the resection site of a right posterior-lateral bladder wall tumor.
Figure 5.
Intraoperatively, we completed a bladder map pictogram of the anterior and posterior walls of the bladder.
On this bladder map we drew the location of the bladder tumor, additional biopsy sites, and, abnormal anatomy (e.g. diverticulae, ectopic ureteral orifice, etc.), and, the location of each fiducial marker placed (A.). We numbered each marker on the bladder map, and also referred to the numbered markers in the dictated operative note. The bladder map was entered into each patient's electronic medical record, for future reference by our Radiation Oncology colleagues during dosimetry planning. Intraoperative fluoroscopic images of the catheterized bladder following placement of three fiduciary markers at the site of a left anterior-lateral bladder wall tumor: (B.) Bladder empty. The location of the tumor and resection margin are outlined by three fiducial markers; center is filled in color. The bladder was then filled with 300 cc. of saline (C.), and separately with diluted contrast (D.), to assess marker movement with bladder filling and to compare the location of each marker during independent filling studies of equal volume.
Figure 6.
In order to confirm that the fiducial markers move apart with bladder filling and move together with bladder emptying, motion, immediately after all markers were placed, we performed a volumetric filling/emptying cystogram.
Using diluted contrast, the bladder was serially filled 0-arm remained fixed in position. The same procedure was repeated, separately, with saline. At each incremental 60 ml. change in bladder volume, we obtained a spot-fluoro image. We compared images of a patient's bladder filled with equal volumes of dilute contrast (A) and saline (B). We then used the digital image measurement App (MedMeasure!; U.S. and International Patents Pending) [https://itunes.apple.com/us/app/medmeasure!/id654898049?mt=8] to measure the distance between pairs of markers in paired images of the bladder filled with the same volume of saline or contrast. The digital, scalable caliper provided by the MedMeasure! App is first calibrated to one of the fiducial markers visible in lateral view– whose length of which is known to equal 2.9 mm. (C). Upon calibration, the actual distance between any two markers can be measured with the caliper. We measured the difference in distance between each marker-pair in paired images. (D, E).
Figure 7.
Computed Tomography (CT), Digitally Reconstructed Radiograph (DRR), and on-table Portal images with fiducial markers present.
(A.) Computed Tomography (CT-scan) dosimetry imaging of pelvis with bladder fiducial markers in place. The gross tumor volume (GTV; dark blue) received 56-Gy in 25 fractions. The clinical tumor volume (CTV; light blue) equals the bladder and received 50 Gy in 25 fractions. The planning tumor volume (PTV; purple) equals the CTV+1 cm + the ipsilateral pelvic side-wall. (B.) Digitally reconstructed radiograph (DRR) of pelvis; shows the anticipated location of the three markers we placed at the tumor site (large black rectangles), based on the gold markers visible on planning CT. (C.) Gold markers seen on an AP portal image of pelvis, (circled), (D) Fusion of the DRR and AP portal images showing the predicted position for gold markers (red arrow) compared to the true position of the gold markers (green arrow) prior to any patient adjustment.
Table 1.
Summary of Patient Clinical Data.