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

PURPOSE: There has been an increase in the use of gold fiducial markers to ensure precise radiotherapy delivery in prostate cancer patients. However, metal artifacts may affect the quality of subsequent imaging used to assess disease status following treatment. In this study, we evaluated the effect of gold fiducial markers on magnetic resonance imaging (MRI), particularly on diffusion-weighted imaging (DWI). MATERIAL AND METHODS: Among 57 patients with prostate cancer, 21 patients in whom two gold markers were placed in the prostate tumor with abnormal signal intensity on DWI were evaluated. The effect of the markers on DWI was evaluated on a scale of 1-5, with a high score indicating clinical usefulness. Change inapparent diffusion coefficient (ADC; 10-3 mm2 /s) from before to after marker placement was also evaluated. RESULTS: The mean effect of the markers on DWI was 4.3 (standard deviation [SD] 1.3, range 2-5) points. The mean change in ADC was 0.045 (SD 0.041, range 0.025-0.089) × 10-3 mm2 /s. CONCLUSIONS: The gold fiducial markers demonstrated negligible effect on DWI quality. Therefore, gold markers do not affect MRI quality, particularly DWI, and may be used during follow-up in prostate cancer patients.

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

OBJECTIVE: Visualizing the gold marker (GM) in CT and MRI is critical, especially for registration in high-precision radiotherapy. GM sizes vary. Large markers are easily visualized in MRI. Small GMs show fewer artefacts in CT but are harder to detect in MRI because the signal is influenced by metal in MRI. Therefore, we compared MRI visualization between linearly placed new iron-containing marker and non-iron containing marker. METHODS: 27 patients underwent CT/MRI fusion-based intensity-modulated radiotherapy. The gold markers were placed by urologists. An iron-containing Gold Anchor™ (GA) marker (diameter, 0.28 mm; length, 10 mm) was placed by using a 22 G needle on one side of the prostate linearly. A non-iron-containing VISICOIL™ (VIS) marker (diameter, 0.35 mm; length, 10 mm) was placed by using a 19 G needle on the opposite side linearly. T2* weighted MRI was mostly performed. Two Radiation Oncologists and one Radiation Technologist evaluated and assigned visual quality scores (GA shape, CT artefacts, MRI signal voids). RESULTS: The mean visualization scores of artefacts were similar between GA and VIS in planning CT. GM visualization in MRI of the prostate was better for GA than for VIS. The visibility of the linear shape of the GA was 3.4-4.1 points when the VIS was 5 points (1 is worst and 5 is best). CONCLUSION: Visualization quality was similar between GA (iron-containing marker) and VIS (non-iron-containing marker) in planning CT, but was better for GA than for VIS in MRI. To achieve high-precision radiotherapy, an iron-containing gold marker was useful for CT and MRI registration. Advances in knowledge: An iron-containing fiducial marker was useful for CT and MRI registration, especially in high-precision radiotherapy, such as stereotactic body radiotherapy and intensity-modulated radiotherapy.

Comparison of MRI sequences in ideal fiducial maker-based radiotherapy for prostate cancer.

AIM: Prostate contouring using CT alone is difficult. To overcome the uncertainty, CT/MRI registration using a fiducial marker is generally performed. However, visualization of the marker itself can be difficult with MRI. This study aimed to determine the optimal MRI pulse sequence for defining the marker as well as the prostate outline among five sequences. MATERIALS AND METHODS: A total of 21 consecutive patients with prostate cancer were enrolled. Two gold fiducial markers were placed before CT/MRI examination. We used the following five sequences: T1-weighted spin-echo (T1WI; TR/TE, 400-650/8 ms); T2-weighted fast spin-echo (T2WI; 4000/80); T2*-2D-weighted gradient echo (T2*2D; 700/18); T2*-3D-weighted gradient echo (T2*3D; TR/TE1/deltaTE, 37/14/7.3); and contrast-enhanced T1-weighted spin-echo (CE-T1WI; 400-650/8). Qualitative image analysis of the sequences was performed by three observers. These observers subjectively scored all images on a scale of 1-3 (1 = unclear, 2 = moderate, 3 = well visualized). A higher score indicated better visualization. RESULTS: T2WI was significantly superior to the other sequences in terms of prostate definition. T2*2D and T2*3D were strongly superior to the other sequences and were significantly superior in terms of fiducial marker definition. CONCLUSIONS: T2*2D and T2*3D are superior to the other sequences for prostate contouring and marker identification. Therefore, we recommend initial T2*3D and T2*2D examinations.

The advantage of iron-containing fiducial markers placed with a thin needle for radiotherapy of liver cancer in terms of visualization on MRI: an initial experience of Gold Anchor.

Radiotherapy for liver malignancy is increasing due to advances in radiotherapy technique. Visualization of the tumor as well as fiducial markers is essential. To see if improved visibility exists on computed tomography (CT) and magnetic resonance imaging (MRI), we evaluated an iron-containing fiducial marker. A patient with hepatocellular carcinoma and a patient with cholangiocarcinoma were enrolled. Pain caused by placement of marker and the best MRI sequence for visualization of both the fiducial marker as well as the liver tumor on MRI was evaluated. CT was obtained in 2.5-mm thickness, and MRIs were obtained in eight sequences (ie, T2-weighted image). 22G preloaded needles were used for marker placement in both patients; this caused little pain during placement under local anesthesia with xylocaine. No complication occurred in either patient. Both markers and tumors were well visualized by the same MRI sequence. The iron-containing fiducial marker is safe and useful for detecting fiducial markers in the liver and for registration using CT and MRI.

Efficacy of butylscopolamine in obtaining clear MR image for intensity-modulated radiotherapy for prostate cancer.

PURPOSE: The use of butylscopolamine in magnetic resonance imaging (MRI) of the prostate is controversial in the context of diagnostic imaging where local invasion and the presence of metastases are evaluated. However, in radiation oncology, MRI is performed as part of the simulation process, and the objectives differ to the diagnostic setting. MRI is primarily used for accurate target delineation; hence, the use of an agent to reduce intestinal peristalsis and increase image quality may be beneficial. The impact of butylscopolamine on MRI for radiation oncology purposes has not previously been described. The aim of this study was to evaluate the efficacy of butylscopolamine in MRI acquired for radiation oncology simulation of the prostate. METHODS AND MATERIALS: In total, 67 patients were enrolled in this study. Thirty-five patients received intramuscular injection of butylscopolamine (group A) and 32 patients did not (group B). Visualization of the prostate outline and detection of fiducial gold markers (GMs) in the prostate were evaluated on MRI. Two blinded radiation oncologists (ROs) and one radiation technologist (RT) scored the image quality of the detection of prostate outline and recognition of GMs in the prostate on a scale of 1-5 (1 = poor; 5 = excellent), and the results were evaluated using Mann-Whitney U test and p < 0.05 was considered as statistically significant. RESULTS: On MRI, group A was statistically superior to group B in terms of fiducial marker detection by two ROs (p < 0.01). However, there was no significant difference in RT scoring. Furthermore, on MRI, group A was statistically superior to group B in terms of the detection of the prostate outline by an RT. CONCLUSIONS: Butylscopolamine is effective with respect to detection of the prostate outline and GM recognition (without endorectal coil). The addition of butylscopolamine is simple and cost efficient. We recommend the use of butylscopolamine routinely to obtain good MR images, particularly in the detection of GMs.