Implanted Fiducial Markers Research Articles

Development of a Margin Determination Framework for Tumor-Tracking Radiation Therapy With Intraoperatively Implanted Fiducial Markers.

PurposeTo develop an internal target volume (ITV) margin determination framework (or decision-supporting framework) for treating multiple lung metastases using CyberKnife Synchrony with intraoperatively implanted fiducial markers (IIFMs). The feasibility of using non-ideally implanted fiducial markers (a limited number and/or far from a target) for tracking-based lung stereotactic ablative radiotherapy (SABR) was investigated.MethodsIn the developed margin determination framework, an optimal set of IIFMs was determined to minimize a tracking uncertainty-specific ITV (ITVtracking) margin (margin required to cover target-to-marker motion discrepancy), i.e., minimize the motion discrepancies between gross tumor volume (GTV) and the selected set of fiducial markers (FMs). The developed margin determination framework was evaluated in 17 patients with lung metastases. To automatically calculate the respiratory motions of the FMs, a template matching-based FM tracking algorithm was developed, and GTV motion was manually measured. Furthermore, during-treatment motions of the selected FMs were analyzed using log files and compared with those calculated using 4D CTs.ResultsFor 41 of 42 lesions in 17 patients (97.6%), an optimal set of the IIFMs was successfully determined, requiring an ITVtracking margin less than 5 mm. The template matching-based FM tracking algorithm calculated the FM motions with a sub-millimeter accuracy compared with the manual measurements. The patient respiratory motions during treatment were, on average, significantly smaller than those measured at simulation for the patient cohort considered.ConclusionUse of the developed margin determination framework employing CyberKnife Synchrony with a limited number of IIFMs is feasible for lung SABR.

Feasibility of Vascular Matching for Image Guided Pancreatic Stereotactic Body Radiation Therapy

Implanted fiducial markers (IFM) and biliary stents are established as targets for image-guidance during high dose stereotactic body RT (SBRT) in the treatment of pancreatic adenocarcinoma (PDAC). IFM are often well tolerated, but may delay treatment. Furthermore, the potential for IFM/stent migration may cause insufficient target volume coverage and normal tissue toxicity. This study evaluated the use of vascular matching (VM), IFM and stent matching for image-guidance in delivery of SBRT for patients with PDAC. We hypothesize that there is no difference in shifts or efficacy between IFM, stents, and VM. Between April 2011- November 2015, 39 patients received SBRT for treatment of PDAC at our institution. Cone beam CT (CBCT) was performed for setup verification. We retrospectively analyzed 221 CBCT images for setup shifts based on either IFM, stent or celiac and SMA vasculature contoured using electronic patient information management system, version 2.60 (IMPAC Medical Systems, Inc. Sunnyvale, CA). Average shift magnitudes in each axis and average vector magnitudes were calculated. RTOG acute gastrointestinal (GI) radiation morbidity scoring criteria were used to assess toxicity. Statistical analyses were performed using JMP 12.1.0 (SAS Institute Inc., Cary, NC). Kaplan-Meier calculations as well as analysis of variance, likelihood ratio, and Wilcoxon tests were used to evaluate local control and survival and compare groups. Fifteen patients (38.5%) were treated with IFM, 9 (23%) with stents, and 15 (38.5%) with VM. Waiting times from initial consult to radiation treatment in the IFM, stent, and VM groups were 24 days (range 2-91 days), 14 days (range 9-56 days), and 19 days (range 5-39 days), respectively. The average magnitude for superior/inferior shifts was 0.45 ± 0.42 mm (IFM), 0.48 ± 0.46 mm (stent), and 0.37 ± 0.33 mm (VM) (P = 0.24), lateral shifts 0.42 ± 0.99 mm, 0.29 ± 0.35 mm, and 0.26 ± 0.22 (P = 0.26), and anterior/posterior shifts were 0.33 ± 0.40 mm, 0.34 ± 0.28 mm, and 0.37 ± 0.28 mm (P = 0.70). Vector magnitudes were 0.85 ± 1.04 mm, 0.74 ± 0.53 mm, and 0.67 ± 0.36 mm, respectively (P = 0.24). There were no documented complications from IFM or stent placement. There were no significant differences in GI toxicities between groups (P = 0.25), with a single instance of Grade 3 toxicity in the stent group. There were no significant differences in tumor resectability (P = 0.70), margin status (P = 0.43), local control (P = 0.31), or overall survival (P = 0.88). Vascular matching is a feasible, less invasive image-guidance technique that allows for reproducible and convenient SBRT delivery to PDAC and shorter treatment delays. There was no difference in positional shifts, toxicity, or outcomes for patients planned with IFM, stents, or VM. VM may be preferable over more invasive methods of target localization.

SU‐F‐J‐78: Characterization of Deformable Image Registration for the Pelvic Region Based On Prostate Shifting, Image Noise and the Existence of Implanted Fiducial Markers

Purpose:To assess the impact of prostate shifting, image noise and the existence of fiducial markers on deformable image registration (DIR) performance in the pelvic region using original digital phantoms.Methods:A digital phantom of the pelvic region of a prostate cancer patient was created using contoured anatomy as a base image set. Two simulated fiducial markers were implanted at the apex and base of the prostate. With and without markers, the prostate was shifted by 6.00 and 10.0 mm superior, 5.63 and 9.38 mm posterior, and 5.63 and 9.38 mm left, respectively. We also added image noise with a standard deviation (SD) of 9, 21, or 28. A phantom with a noise SD of 9 and zero prostate shift was defined as the target, and the other phantoms were defined as the sources. DIR was performed using MIM Maestro (MIM Software Inc., Cleveland, OH, USA) on the digital phantoms. A dice similarity coefficient (DSC) was used as the index of correspondence level of the prostates on the target images and the results of the DIR. Also, we calculated the motion distance of the fiducial markers.Results:The DSC decreased with increasing prostate distance. The degree of correspondence of the fiducial markers and the DIR performance were worse when the bladder volume changed after the prostate shifted in the superior direction than when it shifted in the other directions. Changes in the image noise and the existence of fiducial markers produced minimal impact on the DIR results.Conclusion:We found that DIR was not affected by image noise, and the reproduction of prostate position by maintaining the bladder volume was important to preserve DIR performance. Further, the existence of two fiducial markers had no impact on DIR performance.This work was supported by Japan Society for the Promotion of Science (JSPS) KAKEN Grant‐in‐Aid for Scientific Research (C) Grant number 26460724.

Audit of Offline Imaging in Men with Prostate Cancer and Implanted Fiducial Markers

Audit of Offline Imaging in Men with Prostate Cancer and Implanted Fiducial Markers

Comparison of implanted fiducial markers and self-expandable metallic stents for pancreatic image guided radiation therapy localization

PurposeThe delivery of high-quality radiation therapy to pancreatic adenocarcinoma requires accurate localization. Radiopaque implanted fiducial markers (IFM) and self-expandable metallic stents (SEMS) have both been proposed as means of achieving accurate localization in image guided radiation therapy (IGRT). The suitability of IFM and SEMS for localization were evaluated in this study based on geometric and dosimetric surrogates. Methods and materialsIn a retrospective study of 54 patients with pancreatic cancer who underwent tumor-directed IGRT, 9 were identified as having both IFM and SEMS. For each patient, cone beam computed tomography (CT) scans from each of 6 weeks of treatment were selected for review and comparison with the simulation CT. The centroids of both the IFM and SEMS on each cone beam CT were aligned with those on the planning CT to quantify geometric differences between IFM- and SEMS-based localization. This difference was used to mark the isocenter displacement from the original IFM-localized treatment plan to evaluate the dosimetric implications of SEMS localization. IFM were used as the localization standard given their intratumoral location, and the stability of IFM was evaluated by variability of intrafiducial distance. The original treatment plan was computed on the planning CT at the isocenter shifted by the determined displacement, and dose-volume histograms were calculated for the target volume and organs at risk. ResultsThe average displacement for SEMS localization over all fractions in all patients was 7.7 mm. Planning target volume coverage by 90% of prescription dose was significantly reduced (mean, 11.1%; range, 0.5% to −46.6%) for SEMS compared with IFM localization (P < .05). Dose tolerances were exceeded for stomach, duodenum, and small bowel for 3, 3, and 5 of 9 patients, respectively, when SEMS localization was used. ConclusionsSEMS-based compared with IFM-based localization results in significant variability of radiation therapy localization for pancreatic cancer. IFM-based localization should be considered the standard of care for tumor-directed pancreatic cancer IGRT.

Radiopaque Polymer Hydrogel Used as a Fiducial Marker in Gynecologic Brachytherapy

Implantable fiducial markers are radiopaque materials used to aid in the clinical and radiographic localization of tumors and normal tissues. We assessed a novel FDA-approved hydrogel synthesized as absorbable iodinated particles not previously used as a marker in patients undergoing gynecologic brachytherapy after external beam radiation.

Radiopaque Polymer Hydrogel Used as a Fiducial Marker in Gynecologic Brachytherapy

Implantable fiducial markers are radiopaque materials used to aid in the clinical and radiographic localization of tumors and normal tissues. We assessed a novel FDA-approved hydrogel synthesized as microbeads impregnated with iodine contrast material (TRACE-IT, Augmenix, Waltham, MA) not previously used as a marker in patients undergoing gynecologic brachytherapy.

Evaluation of different fiducial markers for image-guided radiotherapy and particle therapy

Modern radiotherapy (RT) techniques are widely used in the irradiation of moving organs. A crucial step in ensuring the correct position of a target structure directly before or during treatment is daily image guidance by computed tomography (CT) or X-ray radiography (image-guided radiotherapy, IGRT). Therefore, combinations of modern irradiation devices and imaging, such as on-board imaging (OBI) with X-rays, or in-room CT such as the tomotherapy system, have been developed. Moreover, combinations of linear accelerators and in-room CT-scanners have been designed. IGRT is of special interest in hypofractionated and radiosurgical treatments where high single doses are applied in the proximity of critical organs at risk. Radiographically visible markers in or in close proximity to the target structure may help to reproduce the position during RT and could therefore be used as external surrogates for motion monitoring. Criteria sought for fiducial markers are (i) visibility in the radiologic modalities involved in radiotherapeutic treatment planning and image guidance, such as CT and kilovoltage (kV) OBI), (ii) low production of imaging artifacts, and (iii) low perturbation of the therapeutic dose to the target volume. Photon interaction with interstitial markers has been shown to be not as important as in particle therapy, where interaction of the particle beam, especially with metal markers, can have a significant impact on treatment. This applies especially with a scanned ion beam. Recently we commenced patient recruitment at our institution within the PROMETHEUS trial, which evaluates a hypofractionation regime, starting with 4 x 10 Gy (RBE), for patients with hepatocellular carcinoma. The aim of this work is, therefore, to evaluate potential implantable fiducial markers for enabling precise patient and thus organ positioning in scanned ion beams. To transfer existing knowledge of marker application from photon to particle therapy, we used a range of commercially available markers of different forms and sizes, consisting of carbon and gold materials, and evaluated them for their potential use in the clinical setup with scanned ion beams at our institution. All markers were implanted in a standardized Alderson phantom and were examined using CT scans and orthogonal kV OBI in our clinical routine protocol. Impact on beam perturbation downstream of the markers in the plateau region of a spread-out Bragg peak (SOBP) was estimated by using radiographic films for clinical proton and carbon ion beams of high and low energies. All tested markers achieved good visibility in CT and kV OBI. Disturbances due to artifacts and dose perturbation were highest in the arbitrarily folded gold and the thickest gold marker, but especially low in the carbon marker. Dose perturbation was highest in the arbitrarily folded gold marker. In summary, the analyzed markers offer promising potential for identifying target structures in our treatment setup at HIT and will soon be used in clinical routine. However, a careful choice of marker, depending on the tumor localization and irradiation strategy, will need to be made.

Assessment of Fiducial-based 2D kV Orthogonal Imaging, Fiducial-based CBCT, and Soft-tissue-based CBCT for Prostate Cancer Patients With Implanted Fiducial Markers

Purpose/Objective(s): To assess the geometric accuracy and imaging performance of a newly developed phased array coil system optimized for MR imaging of patients immobilized with the type S frame for head and neck radiation therapy. Materials/Methods: Protocol optimization for the novel coil was undertaken using a GE Optima450-GEM 70cm wide bore unit adapted for radiation therapy MR-SIM localization. Pulse sequence parameters for T1FSE, T2 FRFSE and T1 and T2 CUBE (including matrix, slice thickness, bandwidth) were optimized to maximize SNR while minimizing the effect of chemical shift. Phantom measurements were then performed to quantify system related residual geometric distortions after application of a 3D commercial gradient distortion correction algorithm for the effective FOV and the pulse sequences utilized. The optimized protocols were used to image seven volunteers positioned using an MR compatible type S system with neutral head supports. MRI images (from the base of brain to below the clavicles) were acquired using the novel phased array coil combination placed over the head, neck and thoracic region. The volunteers were re-imaged without immobilization in a standard diagnostic head coil, which served as the benchmark for image quality. Signal to noise, image homogeneity and image artifacts were compared between the two image datasets in a blinded study. Visibility of ten anatomical structures was evaluated. For statistical analysis, Cohen’s kappa, Wilcoxon matched pairs and t-testing were utilized. Results: A geometrically accurate, high resolution MR-SIM imaging protocol (T1/T2CUBE. 2D T1/T2 FSE) was developed with 3mm slice thickness/no gap that provides excellent image quality from the base of brain to below the clavicles in the treatment position. From phantom studies, residual distortions were found to be 1.0mm within a 10 cm radius and < 1.5 mm within a 15 cm radius of the scan centre. Using a RBWof 50-62.5 minimized chemical shift (<1mm within a 10cm radius) at 1.5T while providing acceptable SNR. The coil provided higher SNR values in all anatomical structures, but less uniformity than the standard diagnostic head coil (full comparative SNR/CNR/geometric data will be presented). No significant difference for image quality and artifacts were demonstrated between the coils in the blinded study. Conclusions: The novel open architecture purpose built phased coil array provides unparalleled coverage and good image quality of the subject immobilized for head and neck radiation therapy and is a promising solution for MR-SIM in the head and neck region. Author Disclosure: G. Perkins: None. R. Hammoud: None. S. Pienaar: None. S. Paloor: None. N. Al Hammadi: None.

Treatment-Related Morbidity in Prostate Cancer: A Comparison of 3-Dimensional Conformal Radiation Therapy With and Without Image Guidance Using Implanted Fiducial Markers

To estimate the prevalence of rectal and urinary dysfunctional symptoms using image guided radiation therapy (IGRT) with fiducials and magnetic resonance planning for prostate cancer. During the implementation stages of IGRT between September 2008 and March 2010, 367 consecutive patients were treated with prostatic irradiation using 3-dimensional conformal radiation therapy with and without IGRT (non-IGRT). In November 2010, these men were asked to report their bowel and bladder symptoms using a postal questionnaire. The proportions of patients with moderate to severe symptoms in these groups were compared using logistic regression models adjusted for tumor and treatment characteristic variables. Of the 282 respondents, the 154 selected for IGRT had higher stage tumors, received higher prescribed doses, and had larger volumes of rectum receiving high dosage than did the 128 selected for non-IGRT. The follow-up duration was 8 to 26 months. Compared with the non-IGRT group, improvement was noted in all dysfunctional rectal symptoms using IGRT. In multivariable analyses, IGRT improved rectal pain (odds ratio [OR] 0.07 [0.009-0.7], P=.02), urgency (OR 0.27 [0.11-0.63], P=<.01), diarrhea (OR 0.009 [0.02-0.35], P<.01), and change in bowel habits (OR 0.18 [0.06-0.52], P<.010). No correlation was observed between rectal symptom levels and dose-volume histogram data. Urinary dysfunctional symptoms were similar in both treatment groups. In comparison with men selected for non-IGRT, a significant reduction of bowel dysfunctional symptoms was confirmed in men selected for IGRT, even though they had larger volumes of rectum treated to higher doses.

Comparison of Respiratory Gate Triggered kilovoltage (kV) Portal Images (GTPI) versus kV Cone-Beam Computed Tomography Images (CBCT) for Patient Alignment and Verification in Thoracic Stereotactic Body Radiotherapy (SBRT) Patients With Implanted Fiducial Markers

SBRT is currently being used for the treatment of medically inoperable non-small cell lung cancer. Accurate delivery of radiation to the target with this modality is vital to success. Current on-board imaging methods for target localization such as CBCT frequently are not respiratory gated and do not account for tumor motion with respiration. We investigated target localization differences between gate triggered kV portal images (GTPI) and nongated kV cone-beam computed tomography (CBCT) images.

Clinical Usefulness of Implanted Fiducial Markers for Hypofractionated Radiotherapy of Prostate Cancer

Clinical Usefulness of Implanted Fiducial Markers for Hypofractionated Radiotherapy of Prostate Cancer

IGRT Stereotactic Radiotherapy for Liver Metastases: Local Control with or without Implanted Fiducial Markers

IGRT Stereotactic Radiotherapy for Liver Metastases: Local Control with or without Implanted Fiducial Markers

Matching on Bony Anatomy vs. Implanted Fiducial Markers for Daily Patient Setup in SBRT of Lung Tumors

Matching on Bony Anatomy vs. Implanted Fiducial Markers for Daily Patient Setup in SBRT of Lung Tumors

Design of a Novel Device to Provide Assured Seating of Bone Implanted Fiducial Markers

Microstereotactic frames are a subset of stereotactic frames. They are smaller than traditional frames, and they employ small discrete anchors that are screwed into a patient’s bony anatomy, typically the skull. These anchors provide points of attachment for the frame and also serve as markers that provide a bridge between image space and physical space. Both these markers and the anatomy of interest are imaged in a CT or MRI scanner, and their positions are established relative to one another. The microstereotactic frame is then custom made so that, when it is attached to the anchors, it will guide a surgical instrument to an anatomical target. These frames offer advantages over stereotactic frames, including increased targeting accuracy and patient comfort. Firm placement of these anchors is critical as any movement will cause errors in the imaging localization, frame design, or frame attachment. Anchor placement is complicated by the variation in bone density and by the obscuring tissue and bleeding that make visual confirmation of seating very difficult. A novel device called the PosiSeat™ is presented that provides assured seating for bone-implanted anchors.

Implications of Artefacts Reduction in the Planning CT Originating from Implanted Fiducial Markers

The efficacy of metal artefact reduction (MAR) software to suppress artefacts in reconstructed computed tomography (CT) images originating from small metal objects, like tumor markers and surgical clips, was evaluated. In addition, possible implications of using digital reconstructed radiographs (DRRs), based on the MAR CT images, for setup verification were analyzed. A phantom and 15 patients with different tumor sites and implanted markers were imaged with a multislice CT scanner. The raw image data was reconstructed both with the clinically used filtered-backprojection (FBP) and with the MAR software. Using the MAR software, improvements in image quality were often observed in CT slices with markers or clips. Especially when several markers were located near to each other, fewer streak artefacts were observed than with the FBP algorithm. In addition, the shape and size of markers could be identified more accurately, reducing the contoured marker volumes by a factor of 2. For the phantom study, the CT numbers measured near to the markers corresponded more closely to the expected values. However, the MAR images were slightly more smoothed compared with the images reconstructed with FBP. For 8 prostate cancer patients in this study, the interobserver variation in 3D marker definition was similar (<0.4 mm) when using DRRs based on either FBP or MAR CT scans. Automatic marker matches also showed a similar success rate. However, differences in automatic match results up to 1 mm, caused by differences in the marker definition, were observed, which turned out to be (borderline) statistically significant (p = 0.06) for 2 patients. In conclusion, the MAR software might improve image quality by suppressing metal artefacts, probably allowing for a more reliable delineation of structures. When implanted markers or clips are used for setup verification, the accuracy may slightly be improved as well, which is relevant when using very tight clinical target volume (CTV) to planning target volume (PTV) margins for planning.

Analysis of Setup Accuracy of Prostate Patients Comparing Implanted Fiducial Markers to Pelvic Bony Anatomy

Analysis of Setup Accuracy of Prostate Patients Comparing Implanted Fiducial Markers to Pelvic Bony Anatomy

Comparison of CT on Rails With Electronic Portal Imaging for Positioning of Prostate Cancer Patients With Implanted Fiducial Markers

The objective of this investigation was to measure the agreement between in-room computed tomography (CT) on rails and electronic portal image (EPI) radiography. Agreement between the location of the center of gravity (COG) of fiducial markers (FMs) on CT and EPI images was determined in phantom studies and a patient cohort. A secondary analysis between the center of volume (COV) of the prostate on CT and the COG of FMs on CT and EPI was performed. Agreement was defined as the 95% probability of a difference of <or=3.0 mm between images. Systematic and random errors from CT and EPI are reported. From 8 patients, 254 CT and EPI pairs were analyzed. FMs were localized to within 3 mm on CT and EPI images 96.9% of the time in the left-right (LR) plane, 85.8% superior-inferior (SI), and 89% anterior-posterior (AP). The differences between the COV on CT and the COG on EPI were not within 3 mm in any plane: 87.8% (LR), 64.2% (SI), and 70.9% (AP). The systematic error varied from 1.2 to 2.9 mm (SI) and 1.8-2.9 mm (AP) between the COG on EPI and COV on CT. Considerable differences between in-room CT and EPI exist. The phantom measurements showed slice thickness affected the accuracy of localization in the SI plane, and couch sag that occurs at the CT on rails gantry could not be totally corrected for in the AP plane. Other confounding factors are the action of rotating the couch and associated time lag between image acquisitions (prostate motion), EPI image quality, and outlining uncertainties.

Effectiveness of Using Fewer Implanted Fiducial Markers for Prostate Target Alignment

To evaluate the impact of the number and location of intraprostatic fiducial markers on the accuracy and reproducibility of daily prostate target alignment and to evaluate the migration of such markers. Three gold fiducial markers were implanted transrectally under ultrasound guidance near the apex, middle, and base of the prostate in 10 prostate cancer patients. The patients had pretreatment in-room computed tomography (CT) scans three times a week, for approximately 25 CT scans per patient during the 8-week treatment course. A total of 1280 alignments were performed using different alignment scenarios: whole-prostate soft tissue alignment (the gold standard), bone alignment, and seven permutations of alignments using one, two, or three fiducial markers. The results of bone alignment and fiducial alignment were compared with the results of whole-prostate alignment. Fiducial migration was also evaluated. Single-fiducial-marker alignment was more accurate and reproducible than bone alignment. However, due to organ deformation, single fiducial markers did not always reliably represent the position of the entire prostate. The use of two-fiducial combinations was more accurate and reproducible than single-fiducial alignment, and use of all three fiducials was the best. Use of an apex fiducial together with a base fiducial rivaled the use of all three fiducials markers together. Fiducial migration was minimal. The number and the location of implanted fiducial markers affect the accuracy and reliability of daily prostate target alignment. The use of two or more fiducial markers is recommended.

Characterization of Target Volume Changes During Breast Radiotherapy Using Implanted Fiducial Markers and Portal Imaging

To determine target volume changes by using volume and shape analysis for patients receiving radiotherapy after breast conservation surgery and to compare different methods of automatically identifying changes in target volume, position, size, and shape during radiotherapy for use in adaptive radiotherapy. Eleven patients undergoing whole breast radiotherapy had fiducial markers sutured into the excision cavity at the time of surgery. Patients underwent imaging using computed tomography (for planning and at the end of treatment) and during treatment by using portal imaging. A marker volume (MV) was defined by using the measured marker positions. Changes in both individual marker positions and MVs were identified manually and using six automated similarity indices. Comparison of the two types of analysis (manual and automated) was undertaken to establish whether similarity indices can be used to automatically detect changes in target volumes. Manual analysis showed that 3 patients had significant MV reduction. This analysis also showed significant changes between planning computed tomography and the start of treatment for 9 patients, including single and multiple marker movement, deformation (shape change), and rotation. Four of the six similarity indices were shown to be sensitive to the observed changes. Significant changes in size, shape, and position occur to the fiducial marker-defined volume. Four similarity indices can be used to identify these changes, and a protocol for their use in adaptive radiotherapy is suggested.