Initial experience of using an iron-containing fiducial marker for radiotherapy of prostate cancer: Advantages in the visualization of markers in Computed Tomography and Magnetic Resonance Imaging

Abstract

Visualization of markers is critical for imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). However, the size of the marker varies according to the imaging technique. While a large-sized marker is more useful for visualization in MRI, it results in artifacts on CT and causes substantial pain on administration. In contrast, a small-sized marker reduces the artifacts on CT but hampers MRI detection. Herein, we report a new ironcontaining marker and compare its utility with that of non-iron-containing markers. Five patients underwent CT/MRI fusion-based intensity-modulated radiotherapy, and the markers were placed by urologists. A Gold Anchor™ (GA; diameter, 0.28 mm; length, 10 mm) was placed using a 22G needle on the right side of the prostate. A VISICOIL™ (VIS; diameter, 0.35 mm; length, 10 mm) was placed using a 19G needle on the left side. MRI was performed using T2*-weighted imaging. Three observers evaluated and scored the visual qualities of the acquired images. The mean score of visualization was almost identical between the GA and VIS in radiography and cone-beam CT (Novalis Tx). The artifacts in planning CT were slightly larger using the GA than using the VIS. The visualization of the marker on MRI using the GA was superior to that using the VIS. In conclusion, the visualization quality of radiography, conebeam CT, and planning CT was roughly equal between the GA and VIS. However, the GA was more strongly visualized than was the VIS on MRI due to iron containing.

Comparison of MRI visualization between linearly placed iron-containing and non-iron-containing fiducial markers for prostate radiotherapy

“…Interobserver variations significantly affect estimated prostate volume and shape. [4][5][6][7][8][9][10][11][12][13] Various markers are used worldwide, with diameters of 0.28-2.0 mm. The aim of using GM was to make registration of CT and MRI on radiotherapy planning and minimizing interfraction daily variation.…”

Clinical Implications of a Novel, Iron-containing Fiducial Marker in Radiotherapy for Liver Tumors: An Initial Experience

“…The GA used in the present study contains 0.5% iron, and its visibility on MRI has been reported to be superior to that of markers containing no iron [ 7 - 9 ]. Tanaka, et al have directly compared the visibility of the GA with a marker containing no iron in the same patient with prostate cancer and reported the superiority of the GA in terms of the detectability on MRI compared with a marker containing no iron in five patients [ 8 - 9 ]. We assessed four patients with liver tumors as an initial report here; further clinical study is needed in order to compare the possible benefits from the features of the GA objectively.…”

“…The fiducial marker was percutaneously placed, under local anesthesia, near the tumor by a hepatobiliary surgeon. The GA was 0.28 mm in diameter, 20 mm in length, and had a shape that could be bent to fold the marker [ 8 - 9 ].…”

Radiotherapy for prostate cancer: Effect of gold fiducial markers on diffusion‐weighted magnetic resonance imaging

“…Parameters established in previous studies were used, 11,14,15 except for field of view, which was different from that used in routine MRI. We focused on the clarity of the prostate and surrounding structures.…”