Liquid Fiducial Marker Research Articles

Single high-dose radiation therapy and liquid fiducial markers can be used in dogs with incompletely resected soft tissue sarcomas.

To evaluate the outcome and effects of single high-dose radiation therapy with the aid of liquid fiducial markers in dogs following resection of soft tissue sarcomas (STSs). 36 client-owned dogs. Dogs with a histologic diagnosis of a grade II or III STS that underwent liquid fiducial guided single fraction, 20-Gy stereotactic radiation therapy following surgical excision of an STS between May 2017 and March 2019 were prospectively enrolled in this study. Data collected from the medical records included patient signalment, tumor-related information, treatment details, and outcome. Kaplan-Meier survival analysis was performed for overall survival time (OST) and disease-free interval (DFI). The median OST and DFI were not reached, so restricted mean OST and DFI were also calculated. 36 dogs were included in the study. All dogs underwent radiation therapy a mean of 36.1 days (range, 20 to 59 days) after surgery. Acute and delayed radiation toxicity effects occurred in 80.5% and 36.1% of dogs, respectively, all of which affected the skin. Tumor recurrence was noted in 24.3% of dogs with a median time to recurrence of 272 days (range, 14 to 843 days). The restricted mean OST was 1,556 days (range, 1,383 to 1,728 days) and restricted mean DFI was 1,330 days (range, 1,101 to 1,559 days). The results of this study showed that administering a single 20-Gy fraction of radiation in combination with a liquid fiducial marker to treat marginally or incompletely resected STS in the absence of gross disease resulted in similar OST and DFI compared to other previously reported radiation protocols.

BioXmark® liquid fiducials to enable radiotherapy tumor boosting in rectal cancer, a feasibility trial

Background and purposeDose-escalation in rectal cancer (RCa) may result in an increased complete response rate and thereby enable omission of surgery and organ preservation. In order to implement dose-escalation, it is crucial to develop a technique that allows for accurate image-guided radiotherapy. The aim of the current study was to determine the performance of a novel liquid fiducial marker (BioXmark®) in RCa patients during the radiotherapy course by assessing its positional stability on daily cone-beam CT (CBCT), technical feasibility, visibility on different imaging modalities and safety. Materials and methodsProspective, non-randomized, single-arm feasibility trial with inclusion of twenty patients referred for neoadjuvant chemoradiotherapy for locally advanced RCa. Primary study endpoint was positional stability on CBCT. Furthermore, technical aspects, safety and clinical performance of the marker, such as visibility on different imaging modalities, were evaluated. ResultsSeventy-four markers from twenty patients were available for analysis. The marker was stable in 96% of the cases. One marker showed clinically relevant migration, one marker was lost before start of treatment and one marker was lost during treatment. Marker visibility was good on computed tomography (CT) and CBCT, and moderate on electronic portal imaging (EPI). Marker visibility on magnetic resonance imaging (MRI) was poor during response evaluation. ConclusionThe novel liquid fiducial marker demonstrated positional stability. We provide evidence of the feasibility of the novel fiducial marker for image-guided radiotherapy on daily cone beam CT for RCa patients.

Evaluation of computed tomography settings in the context of visualization and discrimination of low dose injections of a novel liquid soft tissue fiducial marker in head and neck imaging

BackgroundIntraoperative incorporation of radiopaque fiducial markers at the tumor resection surface can provide useful assistance in identifying the tumor bed in postoperative imaging for RT planning and radiological follow-up. Besides titanium clips, iodine containing injectable liquid fiducial markers represent an option that has emerged more recently for this purpose. In this study, marking oral soft tissue resection surfaces, applying low dose injections of a novel Conformité Européenne (CE)-marked liquid fiducial marker based on sucrose acetoisobutyrate (SAIB) and iodinated SAIB (x-SAIB) was investigated.MethodsVisibility and discriminability of low dose injections of SAIB/x-SAIB (10 µl, 20 µl, 30 µl) were systematically studied at different kV settings used in clinical routine in an ex-vivo porcine mandible model. Transferability of the preclinical results into the clinical setting and applicability of DE-CT were investigated in initial patients.ResultsMarkers created by injection volumes as low as 10 µl were visible in CT imaging at all kV settings applied in clinical routine (70–120 kV). An injection volume of 30 µl allowed differentiation from an injection volume of 10 µl. In a total of 118 injections performed in two head and neck cancer patients, markers were clearly visible in 83% and 86% of injections. DE-CT allowed for differentiation between SAIB/x-SAIB markers and other hyperdense structures.ConclusionsInjection of low doses of SAIB/x-SAIB was found to be a feasible approach to mark oral soft tissue resection surfaces, with injection volumes as low as 10 µl found to be visible at all kV settings applied in clinical routine. With the application of SAIB/x-SAIB reported for tumors of different organs already, mostly applying relatively large volumes for IGRT, this study adds information on the applicability of low dose injections to facilitate identification of the tumor bed in postoperative CT and on performance of the marker at different kV settings used in clinical routine.

PO-1209: A novel liquid fiducial marker for imageguided adaptive radiotherapy in bladder cancer.

PO-1209: A novel liquid fiducial marker for imageguided adaptive radiotherapy in bladder cancer.

Intraoperative marking of the tumour resection surface for improved radiation therapy planning in head and neck cancer: preclinical evaluation of a novel liquid fiducial marker.

To evaluate a novel liquid fiducial marker for intraoperative marking of the tumour resection surface in oral cancer patients to facilitate precise postoperative delineation of the interface between the tumour resection border and reconstructed tissue for intensity-modulated radiation therapy. A total of 200 markers were created by injecting the volumes of 10 µl, 20 µl, 30 µl, 40 µl and 50 µl of a liquid marker composed of sucrose acetoisobutyrate (SAIB) and iodinated sucrose acetoisobutyrate (x-SAIB) into the soft tissue of porcine mandible segments. Visibility of the resulting markers was quantified by threshold-based segmentation of the marker volume in CT- and CBCT imaging and by a comparison of signal intensities in MRI. Even the lowest volume of SAIB-/x-SAIB investigated (10 µl) resulted in a higher visibility (CTSoft tissue: 88.18 ± 13.23 µl; CTBone: 49.55 ± 7.62 µl; CBCT: 54.65 ± 12.58 µl) than observed with the incorporation of titanium ligature clips (CTSoft tissue: 50.15 ± 7.50 mm3; CTBone: 23.90 ± 3.39 mm3; CBCT: 33.80 ± 9.20 mm3). Markers created by the injection of 10 µl and 20 µl could reliably be delineated from markers created by the injection of higher volumes. SAIB/x-SAIB, which has recently become available as a Conformité Européenne (CE)-marked fiducial marker, provides an option for fast and reliable production of markers with excellent visibility in imaging modalities used in oral cancer radiation therapy (RT) planning routine.

In vitro and in vivo evaluation of the safety and efficacy of a novel liquid fiducial marker for image-guided radiotherapy.

The true extent of a tumor is difficult to visualize, during radiotherapy, using current modalities. In the present study, the safety and feasibility of a mixture of N-butyl cyanoacrylate and lipiodol (NBCA/Lip) was evaluated in order to investigate the optimal combination for application as a fiducial marker for radiotherapy. Four combinations of NBCA/Lip injection (1:1–0.1, 1:1–0.15, 1:3–0.1 and 1:3–0.15 ml) were injected into the subcutaneous tissue of BALB/c mice. The changes in gross histopathology, body weight, skin score, marker volume, neutrophil and macrophage counts were observed to analyze the effects of the different mixing ratios and injection volumes, in order to identify the best combination. Evaluation according to the International Organization for Standardization criteria was further conducted in order to test the biocompatibility of the mixture, including an acute systematic assay with mice, cytotoxicity with L929 fibroblasts and delayed-type hypersensitivity tests with guinea pigs and an intradermal test with rabbits. The results revealed that at the seventh week, 42 markers (42/48; 87.5%) were still visible using computed tomography (CT) imaging. No serious adverse effects were observed throughout the study period; however, the combination of 1:1–0.1 ml had the lowest body weight and worst skin score. A review of the histopathological reaction to NBCA/Lip revealed a combination of acute inflammation, chronic inflammation, granulation tissue, foreign-body reaction and fibrous capsule formation. The 1:1 NBCA combination ratio resulted in the most intense tissue repair reaction and a slower degradation rate of markers. In general, the combination of 1:3–0.15 ml had a better fusion with local tissue, maintained a stable imaging nodule on CT images for 7 weeks and the final biocompatibility test demonstrated its safety. Overall, the findings of the present study demonstrated NBCA/Lip as a safe and feasible fiducial marker, when using the 1:3–0.15 ml combination.

A Novel EUS-guided Liquid Fiducial Marker for Image-Guided Radiotherapy in Esophageal Cancer: the Safety and Efficacy in Vitro and Vivo Evaluations

e15573Background: The true tumor extent of esophageal cancer is hard to visualize on current modalities during radiotherapy. In this study, we evaluated the safety and feasibility of the mixture of...

A Novel Liquid Fiducial Marker in Esophageal Cancer Image Guided Radiation Therapy: Technical Feasibility and Visibility on Imaging

PurposeTo assess the technical feasibility of injection, visibility on imaging modalities, and positional stability of a novel liquid fiducial marker (ie, BioXmark) for radiation therapy in patients with esophageal cancer. MethodsFirst, the visibility on imaging of different volumes of the liquid marker was analyzed ex vivo in porcine tissue (ie, on computed tomography [CT], cone beam CT (CBCT), and magnetic resonance imaging [MRI]). Next, for the in vivo part, the liquid fiducial markers were injected under endoscopic (ultrasound) guidance in 10 patients with curable esophageal cancer. The technical feasibility of the injection procedure and the clinical performance (ie, visibility and positional stability on imaging) were evaluated. Planning CT, daily CBCT, and serial MRI images (before, during, and after chemoradiation therapy in a subset of 3 patients) were acquired. ResultsEx vivo, the optimal volume for good visibility without artifacts was 0.1 mL per injected marker. In vivo, a total of 28 markers were injected in 10 patients (range, 0.025-0.1 mL). No adverse effects were identified. The first 2 cases (4 markers) were considered as learning cases. A total of 19 of 24 of the liquid markers (79%) were visible on CT, 3 of 4 (75%) on MRI, and 19 of 24 (79%) on the first CBCT. All markers with an injected volume of >0.05 mL were visible on the different imaging modalities. Positional stability analysis on CBCT identified no time trend during the radiation therapy course. No artifacts could be detected for liquid marker volumes of 0.05 and 0.025 mL in CT or CBCT. ConclusionsInjection of a liquid fiducial marker for esophageal cancer radiation therapy is technically feasible with no adverse events identified. Volumes of >0.05 mL have an appropriate visibility on CT, CBCT, and MRI, with an excellent positional stability. Liquid fiducial markers are therefore promising for use in image guided radiation therapy.

Detectability and structural stability of aliquid fiducial marker in fresh ex vivo pancreas tumour resection specimens on CT and 3T MRI.

To test the detectability of aliquid fiducial marker injected into ex vivo pancreas tumour tissue on magnetic resonance imaging (MRI) and computed tomography (CT). Furthermore, its injection performance using different needle sizes and its structural stability after fixation in formaldehyde were investigated. Liquid fiducial markers with avolume of 20-100 µl were injected into freshly resected pancreas specimens of three patients with suspected adenocarcinoma. X‑ray guided injection was performed using different needle sizes (18 G, 22 G, 25 G). The specimens were scanned on MRI and CT with clinical protocols. The markers were segmented on CT by signal thresholding. Marker detectability in MRI was assessed in the registered segmentations. Marker volume on CT was compared to the injected volume as ameasure of backflow. Markers with avolume ≥20 µl were detected as hyperintensity on X‑ray and CT. On T1- and T2-weighted 3T MRI, marker sizes ranging from 20-100 µl were visible as hypointensity. Since most markers were non-spherical, MRI detectability was poor and their differentiation from hypointensities caused by air cavities or surgical clips was only feasible with areference CT. Marker backflow was only observed when using an 18-G needle. Avolume decrease of 6.6 ± 13.0% was observed after 24 h in formaldehyde and, with the exception of one instance, no wash-out occurred. The liquid fiducial marker injected in ex vivo pancreatic resection specimen was visible as hyperintensity on kV X‑ray and CT and as hypointensity on MRI. The marker's size was stable in formaldehyde. Amarker volume of ≥50 µL is recommended in clinically used MRI sequences. In vivo injection is expected to improve the markers sphericity due to persisting metabolism and thereby enhance detectability on MRI.

A novel EUS-guided liquid fiducial marker for image-guided radiotherapy in esophageal cancer: The safety and efficacy in vitro and vivo evaluations.

e15573 Background: The true tumor extent of esophageal cancer is hard to visualize on current modalities during radiotherapy. In this study, we evaluated the safety and feasibility of the mixture of N-Butyl Cyanoacrylate and lipiodol to find the most optimal application as the fiducial marker to marking the true tumor extent in esophageal radiotherapy. Methods: Four types of injection matches (1:1-0.1ml, 1:1-0.15ml, 1:3-0.1ml, 1:30.15ml) were injected via syringes in subcutaneous tissue in rats model. Gross histopathological changes, weight, skin score, nodule volume, neutrophil counts and macrophage counts were observed to analyses the effect of different mixing ratios and injection volumes to find the best match. Evaluations following ISO standard criteria are further delivered to test the biocompatibility of the best applicable setting of this fiducial maker. Results: At 7th week, 42 markers (42/48, 87.5%) were still visualized on CT images. No serious adverse events or obvious artifacts were noted through the study. The overall review about the histopathological reaction of the NBCA/Lipiodol was considered to be a combination of acute inflammation, chronic inflammation, granulation tissue, foreign-body reaction and fibrous capsule formation in development. The quantitative analysis showed that when the density of NBCA was low (1:3), lower injection volume (0.1ml) brought the lower weights (p < 0.001). When the injection volume is high (0.15ml), the high NBCA (1:1) caused the lower weight (p < 0.001). At the most time points, the lower injection volume had the lower weights. High injection volume created a 0.079 cm3 increase in nodule size than low volume and high NBCA density also increased the nodule size. As for the inflammatory cells counts, the 3rd week was a key time point, before which the neutrophils decreased sharply and the macrophages keep almost steady, but after that the neutrophils stayed a low level and the macrophages started a rapid growth. On the comparisons of different index (Table), it is showed that the 1:3-0.15ml had an excellent performance as the fiducial marker and final biocompatibility test proved its safety. Conclusions: Overall, our results show that the mixture of NBCA/Lip as the fiducial marker is safe and feasible and the setting of 1:3-0.15ml was most optimal.[Table: see text]

Long term safety and visibility of a novel liquid fiducial marker for use in image guided radiotherapy of non-small cell lung cancer

Safety and clinical feasibility of injecting a novel liquid fiducial marker for use in image guided radiotherapy in 15 patients with non-small cell lung cancer are reported. No major safety or toxicity issues were encountered. Markers present at start of radiotherapy remained visible in cone beam computed tomography and fluoroscopy images throughout the treatment course and on computed tomography images during follow-up (0–38 months). Marker volume reduction was seen until 9 months after treatment, after which no further marker breakdown was found. No post-treatment migration or marker related complications were found.

Feasibility of a novel liquid fiducial marker for use in image guided radiotherapy of oesophageal cancer.

To evaluate the feasibility of a new liquid fiducial marker for use in image-guided radiotherapy for oesophageal cancer. Liquid fiducial markers were implanted in patients with metastatic or inoperable locally advanced oesophageal or gastro-oesophageal junction cancer receiving radiotherapy. Markers were implanted using a conventional gastroscope equipped with a 22 G Wang needle. Marker visibility was evaluated on fluoroscopy, CT, MRI and conebeam CT scans. Liquid markers (n = 16) were injected in four patients. No Grade 2 or worse adverse events were observed in relation to the implantation procedure, during treatment or in the follow-up period. 12/16 (75%) markers were available at the planning CT-scan and throughout the treatment- and follow-up period. The implanted markers were adequately visible in CT and cone beam CT but were difficult to distinguish in fluoroscopy and MRI without information from the corresponding CT image. Liquid fiducial marker placement in the oesophagus proved safe and clinically feasible. This paper presents the first clinical use of a new liquid fiducial marker in patients with oesophageal cancer and demonstrates that marker implantation using standard gastroscopic equipment and subsequent use in three-dimensional image-guided radiation therapy is safe and clinically feasible.

Characterization of a novel liquid fiducial marker for multimodal image guidance in stereotactic body radiotherapy of prostate cancer.

Liquid fiducial markers have shown to be a promising alternative to solid gold markers in terms of imaging artifact reduction, patient comfort, and compatibility with different imaging modalities. This study aims to investigate the performance of the novel BioXmark® liquid marker for state-of-the-art multimodal imaging used in prostate cancer (PCa) radiotherapy, encompassing kV CT/CBCT, multiparametric MRI, and kV x-ray imaging. In addition, automatic detection of the liquid markers in x-ray imaging for prostate motion monitoring during treatment was investigated. A total of eight BioXmark® liquid markers with varying volumes (range 5-300 μL) were casted on a square grid into a gelatin phantom insert. A cylindrical gold marker (QLRAD, length = 7 mm, Ø = 1 mm) was inserted for reference. Liquid marker visibility and streaking artifacts in CT/CBCT imaging were evaluated by placing the gelatin phantom into a CIRS anthropomorphic phantom. Relevant MRI characteristics such as the T2 and T1 relaxation times, the ADC value, and the relative proton density (ρH) were quantified by placing the gelatin phantom insert next to a T1MES mapping phantom and a water-filled syringe for reference. Ex vivo multiparametric MRI images were acquired by placing the gelatin phantom next to a resected prostate specimen. Anterior-posterior x-ray projection images were obtained by placing the gelatin phantom insert on top of an anthropomorphic pelvic phantom with internal pelvic bony structures and were acquired for five positions relative to the bony anatomy and 24 clinically relevant x-ray exposure settings. To quantify individual automatic marker detection, single markers were artificially isolated in the x-ray images using postprocessing. Markers of all sizes were clearly visible on CT and CBCT images with only the largest marker volumes (100-300 μL) displaying artifacts similar in size to the gold fiducial marker. Artifact size increased with increasing liquid marker volume. Liquid markers displayed good contrast in ex vivo T1-weighted and ρH-weighted images. The markers were not visible in the ex vivo T2-weighted image. The liquid markers induced a chemical shift artifact in the obtained ADC-map. Automated detection in x-ray imaging was feasible with high detection success (four of five positions) for marker volumes in the range of 25-200 μL. None of the liquid markers were detected successfully when superimposed on a bony edge, independent of their size. This study is the first to show the compatibility of BioXmark® liquid markers with multimodal image-guided radiotherapy for PCa. Compared to a solid gold marker, they had favorable results in both visibility and induced imaging artifacts. Liquid marker visibility in MRI imaging of the prostate does not solely depend on the low ρH value (not visible on T2-weighted image) but is also influenced by its relaxation times. Automated marker detection in x-ray images was feasible but better adapted marker detection algorithms are necessary for marker localization in the presence of bony edges. Hence, the liquid marker provides a minimally invasive (fine needles) and highly applicable alternative to current solid gold markers for multimodal image-guided prostate radiotherapy treatments.

Quantification of MRI visibility and artifacts at 3T of liquid fiducial marker in a pancreas tissue-mimicking phantom.

X-ray-based position verification of the target volume in image-guided radiation therapy (IGRT) of patients with pancreatic ductal adenocarcinoma (PDAC) is currently performed on solid fiducial markers that are implanted under endoscopic ultrasonography. A new biodegradable liquid fiducial marker has recently been introduced. To assess its potential use for magnetic resonance imaging (MRI)-guided photon or proton radiotherapy of PDAC, the MRI visibility and artifacts of this marker were quantified and compared against solid gold markers. Different spherical volumes (10 μL, 25 μL, 50 μL, and 100 μL) of a biodegradable liquid fiducial marker as well as seven differently sized and oriented solid gold (0.35 mm diameter; 5 mm and 10 mm length) and iron-gold alloy fiducial markers (0.28 mm diameter; 1 cm and 2 cm length) were implanted in a spherical gel phantom, mimicking the proton spin relaxation properties of healthy pancreatic tissue at 3 Tesla. MR relaxometry was performed to quantify the size and magnitude of the decrease in the effective transversal relaxation time T2∗ and relative proton density ρ(H) as a measure of potential visibility and to quantify the size and magnitude of the increase in magnetic field inhomogeneity ΔB0 as a measure of potential signal artifacts. The phantom was scanned in a 3.0 T PET/MR scanner with an eight-channel head coil. The solid fiducial markers showed a direct linear relationship between the potentially visible size and artifact size. The liquid fiducial marker showed a tendency toward a potentially visible size at smaller artifacts. Liquid markers from 25 to 100 μL generated visible volumes comparable to the size of the solid markers. The magnitude of visibility was the highest for the liquid fiducial marker with volumes of 25-100 μL showing no correlation with the magnitude of artifact. The solid markers showed a strong nonlinear correlation between magnitude of visibility and artifact, whereas the solid marker consisting of a gold-iron alloy induced the strongest artifacts. The liquid fiducial marker causes signal voids on MRI due to its absence of water hydrogen atoms without strongly affecting the magnetic field in the surrounding tissue. The alteration of the static magnetic field was found to be the main effect leading to the visibility of the solid fiducial markers. Hence, especially when a low level of image distortion is required, MRI characteristics of the liquid marker surpass those of solid gold markers currently being used for IGRT of PDAC.

PO-0860: Characterization of a novel liquid fiducial marker for organ motion monitoring in prostate SBRT

PO-0860: Characterization of a novel liquid fiducial marker for organ motion monitoring in prostate SBRT

Liquid fiducial marker applicability in proton therapy of locally advanced lung cancer

Background and purposeWe investigated the clinical applicability of a novel liquid fiducial marker (LFM) for image-guided pencil beam scanned (PBS) proton therapy (PBSPT) of locally advanced lung cancer (LALC). Materials and methodsThe relative proton stopping power (RSP) of the LFM was calculated and measured. Dose perturbations of the LFM and three solid markers, in a phantom, were measured. PBSPT treatment planning on computer tomography scans of five patients with LALC with the LFM implanted was performed with 1–3 fields. ResultsThe RSP was experimentally determined to be 1.164 for the LFM. Phantom measurements revealed a maximum relative deviation in dose of 4.8% for the LFM in the spread-out Bragg Peak, compared to 12–67% for the solid markers. Using the experimentally determined RSP, the maximum proton range error introduced by the LFM is about 1mm. If the marker was displaced at PBSPT, the maximum dosimetric error was limited to 2 percentage points for 3-field plans. ConclusionThe dose perturbations introduced by the LFM were considerably smaller than the solid markers investigated. The RSP of the fiducial marker should be corrected in the treatment planning system to avoid errors. The investigated LFM introduced clinically acceptable dose perturbations for image-guided PBSPT of LALC.

Liquid fiducial marker performance during radiotherapy of locally advanced non small cell lung cancer

Background and purposeWe analysed the positional and structural stability of a long-term biodegradable liquid fiducial marker (BioXmark) for radiotherapy in patients with locally advanced lung cancer. Material and methodsMarkers were injected via endoscopic- or endobronchial ultrasound in lymph nodes and reachable primary tumours. Marker volume and Hounsfield Units (HU) changing rates were estimated using breath-hold CBCT. Inter-fraction variation in marker position relative to gross tumour volume (GTV) position was established, as well as the inter-fraction variation in mediastinal marker registration relative to a carina registration through the treatment. ResultsFifteen patients were included and 29 markers analysed. All markers that were in situ at planning were visible through the treatment. Mean HU was 902±165HU for lymph node and 991±219HU for tumour markers. Volume degradation rates were −5% in lymph nodes and −23% in primary tumours. Three-dimensional inter-fraction variation for marker position relative to the GTV position was −0.1±0.7mm in lymph nodes and −1.5±2.3mm in primary tumours. Inter-fraction variations in marker registration relative to carina registration were −0.4±1.2mm in left–right, 0.2±2.0mm in anterior–posterior and −0.5±2.0mm in cranio-caudal directions. ConclusionsThe liquid fiducial markers were visible and stable in size and position throughout the treatment course.

PO-0964: Artefact quantification of liquid and solid fiducial marker in single and dual energy CT with MAR

PO-0964: Artefact quantification of liquid and solid fiducial marker in single and dual energy CT with MAR

Injectable Colloidal Gold for Use in Intrafractional 2D Image-Guided Radiation Therapy.

In the western world, approximately 50% of all cancer patients receive radiotherapy alone or in combination with surgery or chemotherapy. Image-guided radiotherapy (IGRT) has in recent years been introduced to enhance precision of the delivery of radiation dose to tumor tissue. Fiducial markers are often inserted inside the tumor to improve IGRT precision and to enable monitoring of the tumor position during radiation therapy. In the present article, a liquid fiducial tissue marker is presented, which can be injected into tumor tissue using thin and flexible needles. The liquid fiducial has high radio-opacity, which allows for marker-based image guidance in 2D and 3D X-ray imaging during radiation therapy. This is achieved by surface-engineering gold nanoparticles to be highly compatible with a carbohydrate-based gelation matrix. The new fiducial marker is investigated in mice where they are highly biocompatible and stable after implantation. To investigate the clinical potential, a study is conducted in a canine cancer patient with spontaneous developed solid tumor in which the marker is successfully injected and used to align and image-guide radiation treatment of the canine patient. It is concluded that the new fiducial marker has highly interesting properties that warrant investigations in cancer patients.

Bronchoscopic Delivery of Lipiodol as a Fiducial Marker in Lung Tumors Before Radiotherapy

Definitive radiotherapy treatment of thoracic tumors may be hampered by poor tumor visualization on radiological imaging and the effects of tumor motion. Fiducial markers act to enhance tumor visualization and tracking. Traditional solid fiducial markers, however, may result in complications, particularly in proximal lung lesions. These complications may be mitigated through the use of a liquid fiducial marker. This article presents four cases which demonstrate the feasibility of bronchoscopic delivery of lipiodol as a fiducial marker, to aid in guided radiotherapy for certain lung tumors.