Fiducial Migration Research Articles

Intra-prostatic gold fiducial marker insertion for image-guided radiotherapy (IGRT): five-year experience on 795 patients

IntroductionProstate cancer is the second most commonly diagnosed cancer in males. The use of intra-prostatic fiducial markers (FM) for image-guided radiotherapy (IGRT) has become widespread due to their accuracy, relatively safe use, low cost, and reproducibility. FM provides a tool to monitor prostate position and volume changes. Many studies reported low to moderate rates of complications following FM implantation. In the current study, we present our five years’ experience regarding the insertion technique, technical success, and rates of complication and migration of intraprostatic insertion of FM gold marker.MethodsFrom January 2018 to January 2023, 795 patients with prostate cancer candidate for IGRT (with or without a history of radical prostatectomy) enrolled in this study. We used three fiducial markers (3*0.6 mm) inserted through an 18-gauge Chiba needle under transrectal ultrasonography (TRUS) guidance. The patients were observed for complications up to seven days after the procedure. Besides, the rate of marker migration was recorded.ResultsAll procedures were completed successfully, and all patients tolerated the procedure well with minimal discomfort. The rate of sepsis after the procedure was 1%, and transient urinary obstruction was 1.6%. Only two patients experienced marker migration shortly after insertion, and no fiducial migration was reported throughout radiotherapy. No other major complication was recorded.DiscussionTRUS-guided intraprostatic FM implantation is technically feasible, safe, and well-tolerated in most patients. The FM migration can seldom occur, with negligible effects. This study can provide convincing evidence that TRUS-guided intra-prostatic FM insertion is an appropriate choice for IGRT.

Real-Time Motion Tracking and Correction During Tomotherapy for Prostate Cancer: Impact of Fiducial Migration

A real-time motion tracking technique has been recently implemented in our clinic to manage intrafraction prostate motion (IPM) during helical tomotherapy for prostate cancer. It involves detecting motion of multiple fiducials implanted in prostate based on real-time x-ray radiographs acquired at various beam angles and correcting the motion using dynamic jaw and MLC. The purpose of this study was to study interfractional fiducial migration (IFM) and its impact on intrafraction motion tracking.Daily MVCT and radiographs acquired during tomotherapy with real-time motion tracking for 5 prostate cancer patients were analyzed to quantify IFM and IPM. All patients were treated with either 70 Gy in 28 or 75.6 Gy in 42 fractions based on plans generated on planning CTs acquired 14-70 days after the implantation of 4 fiducials for each patient. Time intervals between the first treatment and the planning CT acquisition ranged 4-16 days. The IPM was measured based on the maximum target position difference between the radiographs. Daily migration of each fiducial was obtained by (1) rigidly registering the daily MVCT with the planning CT based on prostate matching, and (2) calculating coordinate differences between the fiducial positions on the daily and plan images. To investigate the impact of fiducial migration on motion tracking that uses fiducial positions on the planning CT as baseline, we compared the maximum fiducial pair distance change (RigidBody, a tracking parameter) calculated from the planning CT to radiographs (default) to the value calculated from daily MVCT to radiographs. The daily target offsets (another tracking parameter) determined between the planning CT and radiographs were assessed if the fiducial migrations were removed.The average daily IPM was 3.2 ± 2.9 (up to 5.8 ± 4.0 for a patient) mm. The average IFM was 2.0 ± 1.1 mm (ranging 1.5-2.5 mm among the patients) with median and interquartile range (IQR) values of 1.8 and 1.2 mm, respectively. The fiducials migrated differently in the longitudinal (std/IQR = 1.8/2.2 mm), vertical (1.2/1.6 mm), and lateral (0.7/0.8 mm) directions. The daily fiducial COM deviated from its plan position by 1.6 ± 0.8 mm (ranging 1.3-2.0 mm among the patients) with median/IQR = 1.5/1.0 mm. The overall average of RigidBody reduced from 2.6 ± 0.7 mm (default) to 1.3 ± 0.4 mm if from daily MVCT. The average daily target offsets decreased from 3.2 ± 1.5 to 2.2 ± 1.0 mm if the fiducial migrations were removed.The fiducial-based real-time prostate motion tracking during tomotherapy is advantageous, even in the presence of the measurable IFMs. Our results indicate that, to reduce/eliminate the effect of the fiducial migration on motion tracking stability and accuracy, the fiducial positions on the daily MVCT, instead of the planning CT in the current setting, should be used as the baseline.G. Chen: North Central Chapter of AAPM, Medical College of Wisconsin. A. Tai: None. E.A. Omari: None. M. Bedi: None. C.A. Lawton: None. A. Li: Research Grant; Elekta AB, Accuray Inc, Siemens Healthineers, Manteia Med. Honoraria; Elekta AB, Accuray Inc. Patent/License Fees/Copyright; Manteia Med.

Endoscopic ultrasound-guided fiducial marker placement in pancreatic cancer: A systematic review and meta-analysis

BACKGROUNDPancreatic cancer (PC) mortality remains high despite advances in therapy. Combination chemoradiotherapy offers modest survival benefit over monotherapy with either. Fiducial markers serve as needed landmarks for image-guided radiotherapy (IGRT). Traditionally, these markers were placed surgically or percutaneously with limitations of each. Endoscopic ultrasound-guided placement overcomes these limitations.AIMTo evaluate the safety, efficacy, and feasibility of endoscopic ultrasound (EUS)-guided fiducial placement for PC undergoing IGRT.METHODSArticles were searched in MEDLINE, PubMed, and Ovid journals. Pooling was conducted by fixed and random effects models. Heterogeneity was assessed using Cochran’s Q test based upon inverse variance weights.RESULTSInitial search identified 1024 reference articles for EUS-guided fiducial placement in PC. Of these, 261 relevant articles were reviewed. Data was extracted from 11 studies (n = 820) meeting inclusion criteria. Pooled proportion of successful placement was 96.27% (95%CI: 95.35-97.81) with fiducial migration rates low at 4.33% (95%CI: 2.45-6.71). Adverse event rates remained low, with overall pooled proportion of 4.85% (95%CI: 3.04-7.03).CONCLUSIONEUS-guided placement of fiducial markers for IGRT of PC is safe, feasible, and efficacious. The ability to target deep structures under direct visualization while remaining minimally invasive are added benefits. Moreover, the ability to perform fine needle aspiration or celiac plexus neurolysis add value and increase patient-care efficiency. Whether EUS-guided fiducial placement improves outcomes in IGRT or offers any mortality benefits over traditional placement remains unknown and future studies are needed.

Prospective evaluation of fiducial migration and complications after placement for hepatocellular carcinoma treated with stereotactic body radiotherapy using cyberkinife and influence on treatment delivery: A tertiary cancer centre experience

Background: Hepatocellular carcinoma (HCC) is the most common primary tumor of the hepatobiliary system. The Cyberknife represents a new, frameless stereotactic radiosurgery system with image-guided radiation delivery using fiducials as markers to overcome the movement of intra-abdominal organs due to respiration. However fiducial placement and treatment have its issues such as migration and other complications. Objectives: We evaluated the accuracy and feasibility of fiducial placement under image guidance and complications during and after placement such as migration including pain score. Materials and methods: A prospective observational study was carried out on 36 subjects with clinically and radiologically diagnosed hepatocellular carcinoma receiving Cyberknife based stereotactic based radiotherapy (SBRT). Fiducial markers for SBRT were introduced under percutaneous Ultrasound (US) or CT guidance. After placement, fiducial migration rate, pain score, fiducial placement related complications were noted during and after therapy. IBM SPSS statistical software version 21 was used for statistical analysis. Results: 8.4% had gross fiducial displacement on the day of the procedure. 90.9% had minimal migration during treatment.There was no gross migration seen during treatment or post-treatment. Post fiducial placement, 2.8 % had a major complication in the form of liver decompensation resulting in death while minor complications were observed in 13.9%. The average pain score was minimal (0.86) post fiducial placement. There was no pain in any of the patients during or after the treatment. Conclusion: Image-guided implantation of fiducial markers in the liver for stereotactic body radiation therapy had a high technical success rate and is a safe procedure with rare complications.There is minimal fiducial migration seen during the treatment. But being a descriptive study with a small sample size limits the generalizability of our study findings..

Prospective Evaluation Fiducial Migration after Placement for Liver SBRT and Influence on Treatment Delivery

Fiducial placement in liver tumors (HCC) for Robotic Radiosurgery (CK) treatment is critical. There is a possibility of migration and related issues. Present study evaluating the impact of fiducial migration after simulation and during treatment. Between Mar 2017-Mar 2018, 53 HCCs accrued in the ethical & scientific committee approved prospective study for CK treatment. Three fiducials were place in liver (CT/USG guided) for tracking. Fiducials placed by radiologist with ‘ideal’ fiducials will be equidistance from each other (max distance 5 cm, min distance 2 cm). CT scan imaging was done at immediate post-placement (D0), at Day-3 and Day-8 to evaluate migration. During treatment (Day-4-8) intra-fraction imaging done to track the fiducials position. Fifty three patients (Male 92%, mean age 60.2 yrs, ECOG 0-1 92%, Child-Pugh A 89%, B&C 11%, majority in seg II & VI, PVT disease 64%) with HCCs underwent fiducial placement under guidance (CT scan 69%). Among 159 fiducial placement, six (3.4%)[lung 2, spleen 1, Heart 1, abdomen 2] had displacement outside liver at immediate post-fiducial period (Day-0). Day-0 CT scan, min and max inter-fudicial distance, min & max distance from tumor, max & min inter-fiducial angle are 2.66 (0.819) & 4.8 (1.08) mm; 2.1 (0.7) & 5.12 (1.25) mm; 28.5 (11.8) & 83 (25.25) degree respectively. Maximum and minimum fiducial migration on Day 3 was 0.85 (0.22) and 028 (1.04) mm. Tracking range, co-linearity, tracking uncertainty on Day1-5 of treatment was 5.07, 4.5, 4.9, 5.1, 5.1; 27.02, 25.9, 27.2, 27.6, 27.8; 40.9, 44.3, 47.3, 49.7, 47.06 respectively. Maximum migration during treatment (Day 1-5) was 0.29, 0.27, 0.27, 0.28, and 0.31 respectively. Total migration after treatment (Day 8) from day 0 was 2.35 (0.271) mm. Migration score evaluated on Day 3 and Day 8 did not show any significant difference in fiducial position compared with day 0. Displacement of fiducials occurs at immediate post-fiducial period. There is no significant change in fiducial positions at Day-3 and Day 8 from baseline (D-0). Liver SBRT treatment after fiducial placement may be started immediate post-fiducial placement (Day 1). No additional advantage of waiting for 3 days or more for fiducial stabilization.

Addition of Iodinated Contrast to Rectal Hydrogel Spacer to Facilitate MRI-Independent Target Delineation and Treatment Planning for Prostate Cancer

Rectal hydrogel spacers are increasingly used to reduce dose and thereby limit toxicity to the rectum during prostate radiotherapy. Commercially available products require magnetic resonance imaging (MRI) for hydrogel visualization and treatment planning, with only anecdotal reports of treatment planning with computed tomography (CT) alone. MRI-incompatible hardware, patient intolerance, and added cost provide incentives for MRI-independent alternatives for treatment planning. This case series evaluates the addition of iodinated contrast to spacer gel and assesses its impact on CT visualization. Three prostate cancer patients underwent contrasted rectal spacer placement in preparation for external beam radiotherapy. Standard low-osmolar iodinated contrast was added to a commercially available rectal hydrogel. 0.5cc of contrast was added to 4.5cc of accelerator and subsequently combined with 5cc of diluent. The resultant 10cc of hydrogel was injected into each patient as per standard procedure, utilizing transrectal ultrasound guidance. Two patients were simulated with MRI; a third with a non-MRI compatible pacemaker was planned with CT alone. CT was performed on the day of hydrogel placement within 2 hours of procedure and again 7-12 days later to account for fiducial migration and dissipation of injected air. The second CT was used for treatment planning. Hydrogel visibility was compared between CT and MRI through standardized symmetry scoring, volume calculation, and measurements taken at prostate base, mid-gland, and apex. Spacer contrast was visible only on the day of hydrogel placement by CT, allowing target delineation for treatment planning. On comparison to MRI delineation of spacer one week later, minimal changes in relevant spacer measurements were observed. In one patient, a significant amount of injected air dissipated between the time of hydrogel placement and repeat CT. CT visualization of rectal hydrogel with iodinated contrast on day of placement is feasible and allows MRI-independent treatment planning with spacer gel, but requires repeat CT on a subsequent day to allow for resolution of prostatic edema, fiducial migration, and air within the hydrogel spacer.Abstract 3673; Table 1PatientSimulation Type (Day)Spacer Volume (cc)CC Dimension (mm)AP Dimension (mm)TV Dimension (mm)Base Thickness (mm)Mid-gland Thickness (mm)Apex Thickness (mm)Symmetry Score1CT* (0)16.661.416.430.815.714.715.91CT (8)15.951.417.629.519.017.716.91MR (8)15.555.817.32616.516.816.212CT* (0)12.636.613.839.215.813.811.82CT (12)14.138.812.641.512.811.502MR (12)14.748.615.343.213.212.511.213CT* (0)18.1†58.7†11†40.5†11.8†12.3†15.7†3†CT (7)11.352.41030.411.910.59.52*Spacer contrast visible, †Includes injected air Open table in a new tab

Evaluation of a strategy using pretherapeutic fiducial marker placement to avoid missing liver metastases.

BackgroundHepatic surgery is appropriate for selected patients with colorectal liver metastases (CRLM). Advances in chemotherapy have led to modification of management, particularly when metastases disappear. Treatment should address all initial CRLM sites based on pretherapeutic cross‐sectional imaging. This study aimed to evaluate pretherapeutic fiducial marker placement to optimize CRLM treatment.MethodsThis pilot investigation included patients with CRLM who were considered for potentially curative treatment between 2009 and 2016. According to a multidisciplinary team decision, lesions smaller than 25 mm in diameter that were more than 10 mm deep in the hepatic parenchyma and located outside the field of a planned resection were marked. Complication rates and clinicopathological data were analysed.ResultsSome 76 metastases were marked in 43 patients among 217 patients with CRLM treated with curative intent. Of these, 23 marked CRLM (30 per cent), with a mean(s.d.) size of 11·0(3·4) mm, disappeared with preoperative chemotherapy. There were four complications associated with marking: two intrahepatic haematomas, one fiducial migration and one misplacement. After a median follow‐up of 47·7 (range 18·1–144·9) months, no needle‐track seeding was noted. Of four disappearing CRLM that were marked and resected, two presented with persistent active disease. Other missing lesions were treated with thermoablation.ConclusionPretherapeutic fiducial marker placement appears useful for the curative management of CRLM.

Endoscopic ultrasound-guided fiducial placement in pancreatic tumors: safety and technical feasibility.

stereotactic body radiation therapy (SBRT) for pancreatic malignancies requires the placement of fiducials to guide treatment delivery. The aim of this study was to assess the safety and feasibility of endoscopic ultrasound (EUS) guided fiducial placement using a 22-gauge needle, in patients with pancreatic cancer undergoing SBRT. this single-center retrospective study included 47 patients with biopsy-proven advanced pancreatic cancer who underwent EUS-guided fiducial placement between February 2014 and February 2018. Primary outcome measurements included technical success, fiducial migration rate and procedural complications. all 47 patients received a sufficient number of fiducials and could therefore undergo a successful SBRT. The mean number of fiducials inserted per case was 2 ± 1 (range 1-3) and no fiducial migration was noted. The adverse event rate was 4.2%, as one patient developed mild pancreatitis and another patient required one week of hospitalization one month after fiducial placement due to a duodenal abscess. EUS-guided fiducial placement is a safe and technically feasible procedure in centers with endosonographers that are well trained in EUS with FNA.

Evaluation of CyberKnife® Fiducial Tracking Limitations to Assist Targeting Accuracy: A Phantom Study with Fiducial Displacement.

Introduction The underlying assumptions of the CyberKnife® (Accuray, Sunnyvale, CA, US) fiducial tracking system are: i) fiducial positions are accurately detected; ii) inter-fiducial geometry remains consistent (rigid); iii) inter-fiducial geometric array changes are detected and either accommodated with corrections or treatment is interrupted. However: i) soft-tissue targets are deformable & fiducial migration is possible; ii) the accuracy of the tracking system has not previously been examined with fiducial displacement; iii) treatment interruptions may occur due to inter-fiducial geometric changes, but there is little information available to assist subsequent troubleshooting. The purpose of this study was to emulate a clinical target defined with a two, three, or four-fiducial array where one fiducial is displaced to mimic a target deformation or fiducial migration scenario. The objectives: evaluate the fiducial positioning accuracy, array interpretation, & corresponding corrections of the CyberKnife system, with the aim of assisting troubleshooting following fiducial displacement.MethodsA novel solid-water phantom was constructed with three fixed fiducials (F1,F2,F3) & one moveable fiducial (F4), arranged as if placed to track an imaginary clinical target. Using either two fiducials (F1,F4), different combinations of three fiducials (F1,F2,F4; F1,F3,F4; F2,F3,F4) or four fiducials (F1,F2,F3,F4), repeat experiments were conducted where F4 was displaced inferiorly at 2-mm intervals from 0-16 mm. Data were acquired at each position of F4, including rigid body errors (RBE), fiducial x, y, & z coordinate displacements, six degrees of freedom (DOF) corrections, & robot center-of-mass (COM) translation corrections.ResultsMaximum positioning difference (mean±SD) between the reference and live x, y, & z coordinates for the three fixed fiducials was 0.08±0.30 mm, confirming good accuracy for fixed fiducial registration. For two fiducials (F1,F4), F4 registration was accurate to 14-mm displacement and the F4 x-axis coordinate change was 2.0±0.12 mm with each 2 mm inferior displacement validating the phantom for tracking evaluation. RBE was >5 mm (system threshold) at 6-14 mm F4 displacement: however, F1 was misidentified as the RBE main contributor. Further, F1/F4 false-lock occurred at 16 mm F4 displacement with corresponding RBE <3 mm & COM corrections >13 mm. For combinations of three fiducials, F4 registration was accurate to 10-mm displacement. RBE was >5 mm at 6-16 mm F4 displacement: however, F4 false-lock occurred at 12-16 mm with RBE 5-6 mm. For four fiducials, F4 registration was accurate to 4 mm displacement: however, F4 false-lock occurred at 6-16 mm displacement with concerning RBE <2 & <5 at 6 & 8-mm F4 displacement, respectively. False-locks were easily identified in the phantom but frequently uncorrectable.ConclusionsResults indicate fiducial positioning accuracy and system output following fiducial displacement depends on the number of fiducials correlated, displacement distance, and clinical thresholds applied. Displacements ≤4 mm were accurately located, but some displacements 6-16 mm were misrepresented, either by erroneous main contributor (two-fiducial array only) or by false-locks and misleading RBE, which underestimated displacement. Operator vigilance and implementation of our practical guidelines based on the study findings may help reduce targeting error and assist troubleshooting in clinical situations.

EP-1653: PolymarkTM fiducial markers migration in Prostate Image Guided Radiation Therapy using CBCT images

EP-1653: PolymarkTM fiducial markers migration in Prostate Image Guided Radiation Therapy using CBCT images

TH-B-204-03: TG-199: Implanted Markers for Radiation Treatment Verification

Implanted markers as target surrogates have been widely used for treatment verification, as they provide safe and reliable monitoring of the inter- and intra-fractional target motion. The rapid advancement of technology requires a critical review and recommendation for the usage of implanted surrogates in current field. The symposium, also reporting an update of AAPM TG 199 - Implanted Target Surrogates for Radiation Treatment Verification, will be focusing on all clinical aspects of using the implanted target surrogates for treatment verification and related issues. A wide variety of markers available in the market will be first reviewed, including radiopaque markers, MRI compatible makers, non-migrating coils, surgical clips and electromagnetic transponders etc. The pros and cons of each kind will be discussed. The clinical applications of implanted surrogates will be presented based on different anatomical sites. For the lung, we will discuss gated treatments and 2D or 3D real-time fiducial tracking techniques. For the prostate, we will be focusing on 2D-3D, 3D-3D matching and electromagnetic transponder based localization techniques. For the liver, we will review techniques when patients are under gating, shallow or free breathing condition. We will review techniques when treating challenging breast cancer as deformation may occur. Finally, we will summarize potential issues related to the usage of implanted target surrogates with TG 199 recommendations. A review of fiducial migration and fiducial derived target rotation in different disease sites will be provided. The issue of target deformation, especially near the diaphragm, and related suggestions will be also presented and discussed. Learning Objectives: 1. Knowledge of a wide variety of markers 2. Knowledge of their application for different disease sites 3. Understand of issues related to these applications Z. Wang: Research funding support from Brainlab AG Q. Xu: Consultant for Accuray; Q. Xu, I am a consultant for Accuray planning service

TH-B-204-00: Implanted Markers for Radiation Therapy and TG 199 Update

Implanted markers as target surrogates have been widely used for treatment verification, as they provide safe and reliable monitoring of the inter- and intra-fractional target motion. The rapid advancement of technology requires a critical review and recommendation for the usage of implanted surrogates in current field. The symposium, also reporting an update of AAPM TG 199 - Implanted Target Surrogates for Radiation Treatment Verification, will be focusing on all clinical aspects of using the implanted target surrogates for treatment verification and related issues. A wide variety of markers available in the market will be first reviewed, including radiopaque markers, MRI compatible makers, non-migrating coils, surgical clips and electromagnetic transponders etc. The pros and cons of each kind will be discussed. The clinical applications of implanted surrogates will be presented based on different anatomical sites. For the lung, we will discuss gated treatments and 2D or 3D real-time fiducial tracking techniques. For the prostate, we will be focusing on 2D-3D, 3D-3D matching and electromagnetic transponder based localization techniques. For the liver, we will review techniques when patients are under gating, shallow or free breathing condition. We will review techniques when treating challenging breast cancer as deformation may occur. Finally, we will summarize potential issues related to the usage of implanted target surrogates with TG 199 recommendations. A review of fiducial migration and fiducial derived target rotation in different disease sites will be provided. The issue of target deformation, especially near the diaphragm, and related suggestions will be also presented and discussed. Learning Objectives: 1. Knowledge of a wide variety of markers 2. Knowledge of their application for different disease sites 3. Understand of issues related to these applications Z. Wang: Research funding support from Brainlab AG Q. Xu: Consultant for Accuray; Q. Xu, I am a consultant for Accuray planning service

TH-B-204-02: Application of Implanted Markers in Proton Therapy

Implanted markers as target surrogates have been widely used for treatment verification, as they provide safe and reliable monitoring of the inter- and intra-fractional target motion. The rapid advancement of technology requires a critical review and recommendation for the usage of implanted surrogates in current field. The symposium, also reporting an update of AAPM TG 199 - Implanted Target Surrogates for Radiation Treatment Verification, will be focusing on all clinical aspects of using the implanted target surrogates for treatment verification and related issues. A wide variety of markers available in the market will be first reviewed, including radiopaque markers, MRI compatible makers, non-migrating coils, surgical clips and electromagnetic transponders etc. The pros and cons of each kind will be discussed. The clinical applications of implanted surrogates will be presented based on different anatomical sites. For the lung, we will discuss gated treatments and 2D or 3D real-time fiducial tracking techniques. For the prostate, we will be focusing on 2D-3D, 3D-3D matching and electromagnetic transponder based localization techniques. For the liver, we will review techniques when patients are under gating, shallow or free breathing condition. We will review techniques when treating challenging breast cancer as deformation may occur. Finally, we will summarize potential issues related to the usage of implanted target surrogates with TG 199 recommendations. A review of fiducial migration and fiducial derived target rotation in different disease sites will be provided. The issue of target deformation, especially near the diaphragm, and related suggestions will be also presented and discussed. Learning Objectives: 1.Knowledge of a wide variety of markers 2.Knowledge of their application for different disease sites 3.Understand of issues related to these applications Z. Wang: Research funding support from Brainlab AG Q. Xu: Consultant for Accuray; Q. Xu, I am a consultant for Accuray planning service

TH-B-204-01: Real-Time Tracking with Implanted Markers

Implanted markers as target surrogates have been widely used for treatment verification, as they provide safe and reliable monitoring of the inter- and intra-fractional target motion. The rapid advancement of technology requires a critical review and recommendation for the usage of implanted surrogates in current field. The symposium, also reporting an update of AAPM TG 199 - Implanted Target Surrogates for Radiation Treatment Verification, will be focusing on all clinical aspects of using the implanted target surrogates for treatment verification and related issues. A wide variety of markers available in the market will be first reviewed, including radiopaque markers, MRI compatible makers, non-migrating coils, surgical clips and electromagnetic transponders etc. The pros and cons of each kind will be discussed. The clinical applications of implanted surrogates will be presented based on different anatomical sites. For the lung, we will discuss gated treatments and 2D or 3D real-time fiducial tracking techniques. For the prostate, we will be focusing on 2D-3D, 3D-3D matching and electromagnetic transponder based localization techniques. For the liver, we will review techniques when patients are under gating, shallow or free breathing condition. We will review techniques when treating challenging breast cancer as deformation may occur. Finally, we will summarize potential issues related to the usage of implanted target surrogates with TG 199 recommendations. A review of fiducial migration and fiducial derived target rotation in different disease sites will be provided. The issue of target deformation, especially near the diaphragm, and related suggestions will be also presented and discussed. Learning Objectives: 1.Knowledge of a wide variety of markers 2.Knowledge of their application for different disease sites 3.Understand of issues related to these applications Z. Wang: Research funding support from Brainlab AG Q. Xu: Consultant for Accuray; Q. Xu, I am a consultant for Accuray planning service

Practical Assessment of Bronchoscopically Inserted Fiducial Markers for Image Guidance in Stereotactic Lung Radiotherapy

IntroductionStereotactic radiotherapy is a high-dose precision technique necessitating accurate target visualization through either cone beam computed tomography (CBCT) or planar imaging with implanted fiducial markers. We have investigated the properties for image guidance using fiducial markers implanted through minimally invasive bronchoscopy. MethodsTwo fiducial marker types were implanted endobronchially in 10 patients undergoing radical radiation treatment for non–small cell lung cancer (eight using Visicoil linear fiducial markers [IBA Dosimetry GmbH, Schwarzenbruck Germany] and two using superDimension and superLock two-band markers [Covidien Inc., Minneapolis, MN]). Patients underwent four-dimensional computed tomography imaging for treatment planning and after completion of treatment to investigate marker movement. As part of the image guidance assessment, megavolt electronic portal images (EPIs) were acquired in addition to kilovolt planar and CBCT (Varian Medical Systems, Palo Alto, CA) images. ResultsIn two of 10 patients (both receiving Visicoil markers), marker migration was observed before treatment. In patients with stable markers, both types were clearly visible in planar kilovolt imaging; however, in EPIs the markers could be detected only in selected beam directions in which bony interference was minimal. Diagnostic computed tomography scanning was able to demonstrate the markers with clarity, but significant starring artifacts were observed in CBCT. This was particularly problematic in patients with some lateral component of tumor motion during breathing. ConclusionsThe potential for fiducial migration must be considered and investigated if bronchoscopic implantation of fiducial markers is performed. The choice of marker is a compromise between trying to minimize CBCT artifacts while enabling visualization in EPI imaging, which is an ideal tool to verify gated radiotherapy delivery.

Endoscopic ultrasound-guided fiducial marker placement for image-guided radiation therapy without fluoroscopy: safety and technical feasibility.

Background and study aims: Endoscopic ultrasound (EUS)-guided fiducial marker placement for image-guided radiation treatment (IGRT) is becoming more widespread. Most case series report the procedure performed using fluoroscopy for spatial geometry although the benefits of this are unclear. The aim of our study is to report the technical feasibility, safety, and migration rate of fiducial marker placement in a large cohort of patients with gastrointestinal malignancies who underwent EUS-guided fiducial marker placement for IGRT without fluoroscopy. Patients and methods: A retrospective chart review was performed on all patients referred for EUS-guided fiducial marker placement from 08/1/07 to 7/31/14 at Moffitt Cancer Center. Results: During the study period, 514 patients underwent placement of 1093 gold fiducial markers under EUS-guidance. Two hundred and forty patients with esophageal/gastro-esophageal junction cancer had 405 fiducials placed. In 188 patients with pancreatic ancer, 510 fiducials were placed. In 54 patients with rectal cancer, 103 fiducials were placed and 32 patients had 75 fiducials placed into other gastrointestinal tract lesions. Minor bleeding, which resolved spontaneously, occurred in two patients. Technical difficulty in placing fiducials was noted in 18 patients. Intraprocedural fiducial migration was noted in two patients and only 2/1093 fiducials (.002%) in two esophageal patients migrated as noted on simulation computed tomography scan. Conclusions: EUS-guided fiducial marker placement without fluoroscopy is technically feasible and safe. There were minimal intraprocedure/post-procedure complications. Imaging at the time of simulation also revealed the migration rate to be extremely low. These results may allow for more widespread adoption of EUS-guided fiducial marker placement.

Minimal Inter-Fractional Fiducial Migration during Image-Guided Lung Stereotactic Body Radiotherapy Using SuperLock Nitinol Coil Fiducial Markers.

ObjectivesStereotactic body radiotherapy (SBRT) is being increasingly used for the treatment of patients with lung cancer or lung metastasis who are medically unfit to undergo resection. In order to improve accuracy and confidence in targeting tumors, many centers rely on fiducial implantation. We evaluated the migration of a novel fiducial marker specifically designed for lung tissue implanted via electromagnetic navigation bronchoscopy (ENB).MethodsWe retrospectively quantified the individual and group migrations of SuperLock nitinol coil fiducials for 15 patients receiving lung stereotactic body radiotherapy (SBRT), in order to evaluate the reliability of using these fiducials as a target surrogate for cases where tumors cannot be clearly delineated on cone beam CTs (CBCTs). For each fraction, we compared the individual and group migrations of the fiducials between the planning CT and the acquired CBCT. The group migration was defined as the distance between the centroids of the fiducial group and GTV.ResultsA total of 16 lung targets were included in our study for these 15 patients (one patient with two targets). Of 55 fiducials placed, we observed a 100% retention rate. The mean individual migration was 1.87 mm (range, 0.63–5.25 mm) with a standard deviation of 1.26 mm. The mean group migration was 1.94 mm (range, 0.03–6.19 mm) with a standard deviation of 1.45 mm. Overall, there was minimal change in the relative locations of the markers with respect to each other, as well as to the target.ConclusionsWe found that the SuperLock nitinol coil fiducial marker positions are stable throughout the radiation treatment, and can be used as a reliable surrogate to target, and to avoid geometric misses during gated treatments.

Mo1496 Endoscopic Ultrasound Guided (EUS) Fiducial Marker Placement Without Fluoroscopy - Safety and Technical Feasibility

Mo1496 Endoscopic Ultrasound Guided (EUS) Fiducial Marker Placement Without Fluoroscopy - Safety and Technical Feasibility

No Need to Wait: Fiducial Migration in Immediate Versus Delayed Simulation for Prostate IGRT

Image-guided radiation therapy (IGRT) for prostate cancer utilizes interstitial fiducial markers, on-board imaging, and three-dimensional table shifts to align the prostate at the time of treatment with its position in the computed tomography (CT) scan used for treatment planning. To allow for an initial migration or “settling” of the fiducial markers, some clinicians wait several days after marker placement to perform CT simulation. Others feel that no significant settling occurs and perform CT simulation on the same day as marker placement.

Evaluation of Fiducial Migration in Stereotactic Body Radiation Therapy for Lung Patients

Evaluation of Fiducial Migration in Stereotactic Body Radiation Therapy for Lung Patients