Implantation Of Fiducial Markers Research Articles

Safety and Efficacy of Percutaneous Fiducial Marker Implantation for Image-guided Radiation Therapy

To evaluate the safety and technical success rate of percutaneous fiducial marker implantation in preparation for image-guided radiation therapy. From January 2003 to January 2008, we retrospectively reviewed 139 percutaneous fiducial marker implantations in 132 patients. Of the 139 implantations, 44 were in the lung, 61 were in the pancreas, and 34 were in the liver. Procedure-related major and minor complications were documented. Technical success was defined as implantation enabling adequate treatment planning and computed tomographic simulation. The major and minor complication rates were 5% and 17.3%, respectively. Pneumothorax after lung implantation was the most common complication. Pneumothoraces were seen in 20 of the 44 lung implantations (45%); a chest tube was required in only seven of the 44 lung transplantations (16%). Of the 139 implantations, 133 were successful; in six implantations (4.3%) the fiducial markers migrated and required additional procedures or alternate methods of implantation. Percutaneous implantation of fiducial marker is a safe and effective procedure with risks that are similar to those of conventional percutaneous organ biopsy.

Automatic coregistration of volumetric images based on implanted fiducial markers

The accurate delivery of external beam radiation therapy is often facilitated through the implantation of radio-opaque fiducial markers (gold seeds). Before the delivery of each treatment fraction, seed positions can be determined via low dose volumetric imaging. By registering these seed locations with the corresponding locations in the previously acquired treatment planning computed tomographic (CT) scan, it is possible to adjust the patient position so that seed displacement is accommodated. The authors present an unsupervised automatic algorithm that identifies seeds in both planning and pretreatment images and subsequently determines a rigid geometric transformation between the two sets. The algorithm is applied to the imaging series of ten prostate cancer patients. Each test series is comprised of a single multislice planning CT and multiple megavoltage conebeam (MVCB) images. Each MVCB dataset is obtained immediately prior to a subsequent treatment session. Seed locations were determined to within 1 mm with an accuracy of 97 +/- 6.1% for datasets obtained by application of a mean imaging dose of 3.5 cGy per study. False positives occurred in three separate instances, but only when datasets were obtained at imaging doses too low to enable fiducial resolution by a human operator, or when the prostate gland had undergone large displacement or significant deformation. The registration procedure requires under nine seconds of computation time on a typical contemporary computer workstation.

The Risk of Urosepsis in Patients Undergoing Fiducial Marker Placement for Image Guided Radiation Therapy (IGRT) of Prostate Cancer

The Risk of Urosepsis in Patients Undergoing Fiducial Marker Placement for Image Guided Radiation Therapy (IGRT) of Prostate Cancer

Comparison of Kilovoltage Cone-Beam Computed Tomography With Megavoltage Projection Pairs for Paraspinal Radiosurgery Patient Alignment and Position Verification

Implanted gold markers and megavoltage (MV) portal imaging are commonly used for setup verification of paraspinal tumors treated with high-dose, single-fraction radiotherapy. We investigated whether the use of kilovoltage cone-beam computed tomography (CBCT) imaging eliminates the need for marker implantation. Patients with paraspinal disease who were eligible for single-fraction stereotactic body radiotherapy were accrued to an institutional review board-approved protocol. Each of 16 patients underwent implantation of fiducial markers near the target. The markers were visible on the MV images. Three MV image pairs were acquired for each patient (initial, verification, and final) and were registered to the reference images. Every MV pair was complemented by a CBCT scan. CBCT image registration was performed automatically by maximizing the mutual information using a region of interest that excluded the markers. The corrections, as determined from the MV images, were compared with these from CBCT and were used for actual patient setup. The mean and standard deviation of the absolute values of the differences between the CBCT and MV corrections were 1.0 +/- 0.7, 1.0 +/- 0.6, and 1.0 +/- 0.8 mm for the left-right, anteroposterior, and superoinferior directions, respectively. The absolute differences between the corresponding pre- and post-treatment kilovoltage CBCT image registration were 0.6 +/- 0.5, 0.6 +/- 0.5, and 1.0 +/- 0.8 mm. The setup corrections found using CBCT without the use of implanted markers were consistent with the marker registration on MV projections. CBCT has additional advantages, including better positioning precision and robust automatic three-dimensional registration, as well as eliminating the need for invasive marker implantation. We have adopted CBCT for the setup of all single-fraction paraspinal patients. Our data have also demonstrated that target displacements during treatment are insignificant.

Technique for Implantation of Fiducial Markers in the Prostate

To describe our experience in developing a technique for implanting fiducial markers (gold markers and electromagnetic transponders) in the prostate by the transrectal approach under ultrasound guidance. Our technique requires an endocavitary probe (ultrasound transducer) designed for prostate imaging, an ultrasound system with software to visualize the biopsy trajectory on the imaging screen, and a needle guide specifically designed to fit the probe. Critical aspects of the technique include identifying appropriate implantation locations in the gland, correctly orienting the bevel of the implantation needles, ensuring that the bevel is completely within the gland before deploying markers, and achieving adequate spacing of the markers. Since 1999 we have successfully implanted gold markers in 705 patients. Only 1 patient has developed a urinary tract infection requiring additional antibiotic therapy. There have been no instances of severe rectal bleeding or gross hematuria requiring further intervention. Complication rates have been similarly low for electromagnetic transponders implanted in 44 patients. Implantation of fiducial markers is being used to achieve greater accuracy of external beam radiation therapy for prostate cancer. Our experience can serve as a guide to clinicians for performing this increasingly important procedure in an effective and problem-free manner.

Technique for Implantation of Fiducial Markers in the Prostate

OBJECTIVES To describe our experience in developing a technique for implanting fiducial markers (gold markers and electromagnetic transponders) in the prostate by the transrectal approach under ultrasound guidance. METHODS Our technique requires an endocavitary probe (ultrasound transducer) designed for prostate imaging, an ultrasound system with software to visualize the biopsy trajectory on the imaging screen, and a needle guide specifically designed to fit the probe. Critical aspects of the technique include identifying appropriate implantation locations in the gland, correctly orienting the bevel of the implantation needles, ensuring that the bevel is completely within the gland before deploying markers, and achieving adequate spacing of the markers. RESULTS Since 1999 we have successfully implanted gold markers in 705 patients. Only 1 patient has developed a urinary tract infection requiring additional antibiotic therapy. There have been no instances of severe rectal bleeding or gross hematuria requiring further intervention. Complication rates have been similarly low for electromagnetic transponders implanted in 44 patients. CONCLUSIONS Implantation of fiducial markers is being used to achieve greater accuracy of external beam radiation therapy for prostate cancer. Our experience can serve as a guide to clinicians for performing this increasingly important procedure in an effective and problem-free manner.

Development of Multiorgan Finite Element-Based Prostate Deformation Model Enabling Registration of Endorectal Coil Magnetic Resonance Imaging for Radiotherapy Planning

Endorectal coil (ERC) magnetic resonance imaging (MRI) provides superior visualization of the prostate compared with computed tomography at the expense of deformation. This study aimed to develop a multiorgan finite element deformable method, Morfeus, to accurately co-register these images for radiotherapy planning. Patients with prostate cancer underwent fiducial marker implantation and computed tomography simulation for radiotherapy planning. A series of axial MRI scans were acquired with and without an ERC. The prostate, bladder, rectum, and pubic bones were manually segmented and assigned linear elastic material properties. Morfeus mapped the surface of the bladder and rectum between two imaged states, calculating the deformation of the prostate through biomechanical properties. The accuracy of deformation was measured as fiducial marker error and residual surface deformation between the inferred and actual prostate. The deformation map was inverted to deform from 100 cm(3) to no coil. The data from 19 patients were analyzed. Significant prostate deformation occurred with the ERC (mean intrapatient range, 0.88 +/- 0.25 cm). The mean vector error in fiducial marker position (n = 57) was 0.22 +/- 0.09 cm, and the mean vector residual surface deformation (n = 19) was 0.15 +/- 0.06 cm for deformation from no coil to 100-cm(3) ERC, with an image vector resolution of 0.22 cm. Accurately deformed MRI scans improved soft-tissue resolution of the anatomy for radiotherapy planning. This method of multiorgan deformable registration enabled accurate co-registration of ERC-MRI scans with computed tomography treatment planning images. Superior structural detail was visible on ERC-MRI, which has potential for improving target delineation.

Potential and limitations of the automatic detection of fiducial markers using an amorphous silicon flat-panel imager

Amorphous silicon electronic portal imaging devices (a-Si EPIDs) allow fast acquisition of high resolution portal images (PI). A visualization of organ movement for adaptive image-guided radiotherapy (IGRT) can be reached by implantation and automatic detection of fiducial markers. A method of automatic detection has been developed for fiducial spherical tungsten markers on PIs, acquired with an a-Si flat-panel imager. The detection method consists of a 2D Mexican hat filter (MHF), whose parameters are tuned to the particular marker signal. The high selectivity of this filter allows a reliable and precise detection of tungsten markers down to a diameter of 1.5 mm. The presented method allows fast, automatic and unsupervised detection of markers. Inevitably, the detection is hampered by image background (bone structures, etc) and noise. A detection success rate higher than 95% was reached, analysing PIs of patients with markers fixed on their skin. Furthermore, this approach to automatic marker detection can also be generalized to elliptic MHFs for the detection of cylindrical markers. The accuracy and detection probability of this method may allow accurate and fast online localization of the considered organ.

C-Arm-Based Three-Dimensional Navigation: A Preliminary Feasibility Study

Objective: With the new Siremobil Iso-C3D C-arm, three-dimensional (3D) datasets can be acquired intraoperatively in near-real time. Preliminary studies investigated the advantages of this system for depiction in joint and spinal surgery. Three-dimensional navigation seems feasible using the DICOM dataset of the Siremobil Iso-C3D in navigation devices. An experimental study was designed to investigate the feasibility and accuracy of this new technique.Materials and Methods: After implantation of fiducial markers (titanium mini-screws, Leibinger), a Siremobil Iso-C3D C-arm with standard imaging options was used to acquire preinterventional 3D datasets of the specimens. These isotropic voxel data were transferred via DICOM to a medivision navigation system using the spine module. After registration of the fiducials, a total of 20 pedicle screws were implanted (in 4 artificial-bone vertebral bodies and 6 cadaver vertebrae in situ) with the use of the navigation system in real-time mode. Post-interventionally, Iso-C3D and CT scans were obtained to control for implant position in the cadaver study.Results: Fiducial marker implantation and registration require a special protocol to ensure correct identification and patient orientation in the DICOM dataset. The obtained accuracy was within 2 mm. Post-interventional imaging of the cadaveric vertebrae showed 10 of 12 screws to be correctly placed, with the other two in marginal intraosseous positions.Conclusions: Three-dimensional navigation with the Siremobil Iso-C3D data set is feasible, the accuracy being comparable to that of CT-based navigation and adequate for clinical interventions. Fiducial marker-based registration allows navigation of different bones in the same dataset without additional 3D scanning. This method is very useful as an additional tool in registration-free Iso-C3D-based navigation, since the navigation system allows the use of only one dynamic reference base (DRB).