Gold Seeds Research Articles

P11. Hounsfield CT-values correction with iMAR, impact on dosimetrics calculation for radiation therapy

Introduction Some artifacts caused by prosthesis implants or gold seeds for prostate treatment create uncertainties in CT-Scan images (SOMATOM Scope). This will cause several approximations in radiation therapy (contouring, dose calculation). To improve the treatment, Siemens Healthineers, developed an iterative metal artifact reduction algorithm: iMAR. The aim of this study is to compare HU values reconstructed by the CT-Scan with and without iMAR for prostate treatment. And finally, evaluating dosimetrics effects by calculation of dose on iMAR corrected images. Methods The study is based on three steps. Firstly, on 30 patients with and without prosthesis/gold seeds to evaluate the average of HU into and outside prostate, before and after iMAR correction. Secondly, created customized phantom (QuasarTM) with known material inserts (CIRS Model 062) to simulate human pelvic linked with previous results. We have done CT-Scan acquisitions of the phantom to evaluate accuracy in retrieving correct HU values and Standard Deviation (SD). The reference acquisition is made with QuasarTM acrylic insert, and an acquisition with double metals prosthesis inserts (with/without iMAR reconstruction) is performed. Same ROI (4 cm2) are calculated in this three reconstructions CT images to compare HU values and SD. Thirdly, 23MV VMAT treatment plan in the TPS Eclipse® is performed for both reconstruction (iMAR and no iMAR) to evaluate the dose distribution and to be able to do a dose measurement on the Clinac to determine if iMAR reconstruction is more accurate in dose calculation. Results On patients CT images, iMAR allows to regain information lost by metals artefacts. Moreover, the phantom study demonstrating that lost information (up to −100 HU and ± 100 SD) are improved with iMAR correction (up to + 10 HU and ± 15 SD) and outside the streaking artifact, HU and SD are constant. From a dosimetry point of view, the TPS variation in dose calculation may increase up to + 3.32 Gy in one pixel and the dose covering is improved by iMAR for muscle insert (dose constraint is applied). Therefore, iMAR has an impact in the dose calculation. Finally, the dose verification between treatment in Linac and calculation in TPS (in two measured points) shows that calculation in TPS is more accurate with iMAR ( ≠ 3% out of dose constraint and ≠ 0.2% in dose constraint) compared without iMAR ( ≠ 8.1% out of dose constraint and ≠ 1% in dose constraint). Conclusions iMAR algorithm increases confidence in contouring due to a visualisation of organ’s outlines with a very close reproduction of the HU values and SD. This, enables a stability of the information in TPS for dose calculation. Therefore, dose calculation is improved for the dose covering and dose calculation in TPS is closer to reality.

In situ synthesis of graphene oxide/gold nanorods theranostic hybrids for efficient tumor computed tomography imaging and photothermal therapy

Graphene oxide/gold nanorod (GO/GNR) nanohybrids were synthesized with a GO- and gold-seed-mediated in situ growth method at room temperature by mixing polystyrene sulfonate (PSS) functionalized GO, secondary growth solution, and gold seeds. Compared with ex situ preparation methods of GO/GNRs or graphene (G)/GNRs, the in situ synthesis of GO/GNRs addressed the issue of the aggregation of the GNRs before their attachment onto the GO. The method is straightforward and environment-friendly. The GO/GNRs showed a remarkable photothermal effect in vitro. The temperature of the GO/GNR nanohybrids increased from 25 to 49.9 °C at a concentration of 50 μg/mL after irradiation with an 808-nm laser (0.4 W/cm2) for 6 min. Additionally, the GO/GNRs exhibited good optical and morphological stability and photothermal properties after six cycles of laser irradiation. Upon injection of the GO/GNRs into xenograft tumors, excellent computed tomography (CT) imaging properties and photothermal effect were obtained. The preclinical CT agent iohexol was combined with the GO/GNRs and further enhanced CT imaging. Therefore, the GO/GNR nanohybrids have great potential for precise CT-image-guided tumor photothermal treatment.

Facile Synthesis of Au-Coated Magnetic Nanoparticles and Their Application in Bacteria Detection via a SERS Method

This study proposes a facile method for synthesis of Au-coated magnetic nanoparticles (AuMNPs) core/shell nanocomposites with nanoscale rough surfaces. MnFe2O4 nanoparticles (NPs) were first modified with a uniform polyethylenimine layer (2 nm) through self-assembly under sonication. The negatively charged Au seeds were then adsorbed on the surface of the MnFe2O4 NPs through electrostatic interaction for Au shell formation. Our newly developed sonochemically assisted hydroxylamine seeding growth method was used to grow the adsorbed gold seeds into large Au nanoparticles (AuNPs) to form a nanoscale rough Au shell. Au-coated magnetic nanoparticles (AuMNPs) were obtained from the intermediate product (Au seeds decorated magnetic core) under sonication within 5 min. The AuMNPs were highly uniform in size and shape and exhibited satisfactory surface-enhanced Raman scattering (SERS) activity and strong magnetic responsivity. PATP was used as a probe molecule to evaluate the SERS performance of the synthesized AuMNPs with a detection limit of 10(-9) M. The synthesized AuMNPs were conjugated with Staphylococcus aureus (S. aureus) antibody for bacteria capture and separation. The synthesized plasmonic AuNR-DTNB NPs, whose LSPR wavelength was adjusted to the given laser excitation wavelength (785 nm), were conjugated with S. aureus antibody to form a SERS tag for specific recognition and report of the target bacteria. S. aureus was indirectly detected through SERS based on sandwich-structured immunoassay, with a detection limit of 10 cells/mL. Moreover, the SERS intensity at Raman peak of 1331 cm(-1) exhibited a linear relationship to the logarithm of bacteria concentrations ranging from 10(1) cells/mL to 10(5) cells/mL.

Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds.

Herein, we present the formation of gold nanorods (GNRs) on novel gold–poly(methyl methacrylate) (Au–PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer Mw and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower Mw PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.

SU‐F‐E‐04: A Paris System‐Based Implant Approach to Hyperthermia Cancer Tumor with Gold Seeds and Ultrasound

Purpose:To apply the Paris system‐based implant for an uniform bio‐heat distribution from implanted gold rods in tissue insonated with ultrasound.Methods:Experiments with single‐plane implants using parallel equidistant 1.018 ± 0.015 cm height and 0.136 ± 0.001 cm diameter 24‐K gold rods) arranged in triangular and square shapes were performed in Mus Musculus white mice (medial dorsal region). The mice were anesthetized and gold rods were implanted by means of a trocar needle and the implanted region was insonated with a 4‐cm diameter transducer oscillating with a nominal frequency of 1 MHz and power of about 75 W. Intramuscular tissue temperature measurements were taken using implantable needle type thermocouples affixed to a portable Fluke thermometer. Superficial tissue temperature profile was also measured with a FLIR infrared camera and thermographic analysis were performed using the ImageJ computer software. In both cases, the central implant planes have been assigned to that approximately bisects all the implanted rods.Results:Measured with the needle type thermistor, for the triangular implant, the percentage deviation between the maximum and minimum temperature within the triangular plane was 5%. For a square shape, this percentage deviation was 6%. The thermographic analysis have shown a deviation of 3% and 5% for the triangular and square shapes, respectively.Conclusion:Based on the temperature measurements with needle type thermistor and thermographic analysis, the Paris system‐based implant approach for gold rods implanted in tissue and exposed to ultrasound may greatly improve the bio‐heat propagation and sustain a constant temperature profile inside triangular and square patterns formed by gold rods implants. Additionally, the Paris system may minimize ablations areas and treatment length in hyperthermia if used in cancer tumor treatment.

SU-G-JeP1-10: Feasibility of CyberKnife Tracking Using the Previously-Implanted Permanent Brachytherapy Seed Cloud

Purpose: Robotic radiosurgery is a salvage treatment option for patients with recurrent prostate cancer. We explored the feasibility of tracking the bolus of permanent prostate implants (PPI) using image recognition software optimized to track spinal anatomy. Methods: Forty-five inert iodine seeds were implanted into a gelatin-based prostate phantom. Four superficial gold seeds were inserted to provide ground-truth alignment. A CT scan of the phantom (120 kVp, 1 mm slice thickness) was acquired and a single-energy iterative metal artifact reduction (MAR) algorithm was used to enhance the quality of the DRR used for tracking. CyberKnife treatment plans were generated from the MAR CT and regular CT (no-MAR) using spine tracking. The spine-tracking grid was centered on the bolus of seeds and resized to encompass the full seed cloud. A third plan was created from the regular CT scan, using fiducial tracking based on the 4 superficial gold seeds with identical align-center coordinates. The phantom was initially aligned using the fiducial-tracking plan. Then the MAR and no-MAR spine-tracking plans were loaded without moving the phantom. Differences in couch correction parameters were recorded in the case of perfect alignment and after the application of known rotations and translations (roll/pitch of 2 degrees; translations XYZ of 2 cm). Results: The spine tracking software was able to lock on to the bolus of seeds and provide couch corrections both in the MAR and no-MAR plans. In all cases, differences in the couch correction parameters from fiducial alignment were <0.5 mm in translations and <1 degree in rotations. Conclusion: We were able to successfully track the bolus of seeds with the spine-tracking grid in phantom experiments. For clinical applications, further investigation and developments to adapt the spine-tracking algorithm to optimize for PPI seed cloud tracking is needed to provide reliable tracking in patients. One of the authors (MD) has received research support and speaker honoraria from Accuray.

Size- and Shape-Controlled Synthesis and Properties of Magnetic-Plasmonic Core-Shell Nanoparticles.

Magnetic-plasmonic core-shell nanomaterials offer a wide range of applications across science, engineering and biomedical disciplines. However, the ability to synthesize and understand magnetic-plasmonic core-shell nanoparticles with tunable sizes and shapes remains very limited. This work reports experimental and computational studies on the synthesis and properties of iron oxide-gold core-shell nanoparticles of three different shapes (sphere, popcorn and star) with controllable sizes (70 to 250 nm). The nanoparticles were synthesized via a seed-mediated growth method in which newly formed gold atoms were added onto gold-seeded iron oxide octahedrons to form gold shell. The evolution of the shell into different shapes was found to occur after the coalescence of gold seeds, which was achieved by controlling the amount of additive (silver nitrate) and reducing agent (ascorbic acid) in the growth solution. First principles calculation, together with experimental results, elucidated the intimate roles of thermodynamic and kinetic parameters in the shape-controlled synthesis. Both discrete dipole approximation calculation and experimental results showed that the nanopopcorns and nanostars exhibited red-shifted plasmon resonance compared with the nanospheres, with the nanostars giving multispectral feature. This research has made a great step further in manipulating and understanding magnetic-plasmonic hybrid nanostructures and will make important impact in many different fields.

Using Golden Seed Treatment of Prostate Cancer

Submit Manuscript | http://medcraveonline.com The marker used is a gold seed implant that is inserted inside the body, transrectal ultrasound guided is to be located in the affected prostate tissue. These implanted gold seeds are used to focus the radiation treatments for prostate cancer. Performing previous insertion of these seeds, function as a specific marker which allows limit thus very accurately irradiating the affected area, and thus reducing maximum healthy tissue that radiate treatment. Results The results obtained with the implementation of these gold seeds in the affected prostate tissue, show that the use of bright seeds act as locators, which allows reducing the number of complications and thus increases the effectiveness of treatment radiotherapy. This positive effect is produced to limit and minimize the irradiation field of X-ray beams generated by tissue damage to the area affected by the cancer cells dying to do. Gold seeds have no internal migration between them. That is why the simulations show the added convenience of correction protocols based on gold seeds. Since gold seeds are representative of the position of the prostate. To identify the area to be irradiated, the damage to healthy tissue surrounding the affected is imperceptible, which increases the radiation dose. Without affecting healthy organs surrounding the prostate. Conclusion

Metallic Nanoshells with Sub-10 nm Thickness and Their Performance as Surface-Enhanced Spectroscopy Substrate.

As a crucial structural parameter, shell thickness greatly influences the optical properties of metallic nanoshells. However, there still lacks a reliable approach to prepare ultrathin core-shell nanoparticles. To solve this problem, a two-step gold seeding process was pointed out to increase the packing density of gold seeds on the silica core. With use of this method, the packing density of gold seeds reaches ∼60%, enabling us to successfully reduce the shell thickness to the sub-10 nm range. Afterward, we investigated optical properties of the as-prepared ultrathin nanoshells. It is found that thinner nanoshells exhibit a wider optical tunability and a greater electromagnetic field enhancement than their thicker counterparts, which makes ultrathin nanoshells an ideal substrate for surface-enhanced spectroscopes.

MRI-alone radiation therapy planning for prostate cancer: Automatic fiducial marker detection.

The feasibility of radiation therapy treatment planning using substitute computed tomography (sCT) generated from magnetic resonance images (MRIs) has been demonstrated by a number of research groups. One challenge with an MRI-alone workflow is the accurate identification of intraprostatic gold fiducial markers, which are frequently used for prostate localization prior to each dose delivery fraction. This paper investigates a template-matching approach for the detection of these seeds in MRI. Two different gradient echo T1 and T2* weighted MRI sequences were acquired from fifteen prostate cancer patients and evaluated for seed detection. For training, seed templates from manual contours were selected in a spectral clustering manifold learning framework. This aids in clustering "similar" gold fiducial markers together. The marker with the minimum distance to a cluster centroid was selected as the representative template of that cluster during training. During testing, Gaussian mixture modeling followed by a Markovian model was used in automatic detection of the probable candidates. The probable candidates were rigidly registered to the templates identified from spectral clustering, and a similarity metric is computed for ranking and detection. A fiducial detection accuracy of 95% was obtained compared to manual observations. Expert radiation therapist observers were able to correctly identify all three implanted seeds on 11 of the 15 scans (the proposed method correctly identified all seeds on 10 of the 15). An novel automatic framework for gold fiducial marker detection in MRI is proposed and evaluated with detection accuracies comparable to manual detection. When radiation therapists are unable to determine the seed location in MRI, they refer back to the planning CT (only available in the existing clinical framework); similarly, an automatic quality control is built into the automatic software to ensure that all gold seeds are either correctly detected or a warning is raised for further manual intervention.

Simultaneous MV-kV imaging for intrafractional motion management during volumetric-modulated arc therapy delivery.

The purpose of this study was to evaluate the accuracy and clinical feasibility of a motion monitoring method employing simultaneously acquired MV and kV images during volumetric‐modulated arc therapy (VMAT). Short‐arc digital tomosynthesis (SA‐DTS) is used to improve the quality of the MV images that are then combined with orthogonally acquired kV images to assess 3D motion. An anthropomorphic phantom with implanted gold seeds was used to assess accuracy of the method under static, typical prostatic, and respiratory motion scenarios. Automatic registration of kV images and single MV frames or MV SA‐DTS reconstructed with arc lengths from 2° to 7° with the appropriate reference fiducial template images was performed using special purpose‐built software. Clinical feasibility was evaluated by retrospectively analyzing images acquired over four or five sessions for each of three patients undergoing hypofractionated prostate radiotherapy. The standard deviation of the registration error in phantom using MV SA‐DTS was similar to single MV images for the static and prostate motion scenarios (σ=0.25 mm). Under respiratory motion conditions, the standard deviation of the registration error increased to 0.7 mm and 1.7 mm for single MV and MV SA‐DTS, respectively. Registration failures were observed with the respiratory scenario only and were due to motion‐induced fiducial blurring. For the three patients studied, the mean and standard deviation of the difference between automatic registration using 4° MV SA‐DTS and manual registration using single MV images results was 0.07±0.52 mm. The MV SA‐DTS results in patients were, on average, superior to single‐frame MV by nearly 1 mm — significantly more than what was observed in phantom. The best MV SA‐DTS results were observed with arc lengths of 3° to 4°. Registration failures in patients using MV SA‐DTS were primarily due to blockage of the gold seeds by the MLC. The failure rate varied from 2% to 16%. Combined MV SA‐DTS and kV imaging is feasible for intratreatment motion monitoring during VMAT of anatomic sites where limited motion is expected, and improves registration accuracy compared to single MV/kV frames. To create a clinically robust technique, further improvements to ensure visualization of fiducials at the desired control points without degradation of the treatment plan are needed.PACS number(s): 87.55.km, 87.55.N‐

Synthesis of gold Nanoshells through Improved Seed-Mediated Growth Approach: Brust-like, in Situ Seed Formation.

Gold nanoshells have shown great potentials in various fields. However, the widely used seed-mediated growth method based on a silica template for gold nanoshells is a complex and time-consuming procedure. In this work, mercaptosilica was first used as a template to synthesize gold nanoshells through improved seed-mediated growth method. It is verified that gold seeds were formed and attached onto the mercaptosilica nanospheres through Brust-like, in situ process, which makes this method extremely time-saving and easy to manipulate. Importantly, the key factors affecting the in situ process were demonstrated, allowing fine control on the synthesis in a highly reproducible manner. The as-synthesized nanoshells are monodisperse with well-defined morphology and tunable near-IR plasmon resonance. Furthermore, other metal nanoparticles such as Pt and Pd could be grafted onto the surface of mercaptosilica nanospheres through the same Brust-like, in situ process. These provide new insights into seed attachment, and the improved seed-mediated growth approach based on Brust-like, in situ seed formation will take an important step forward toward the widespread application of gold nanoshells.

In situ monitoring, separation, and characterization of gold nanorod transformation during seed-mediated synthesis.

The control of gold nanorod (GNR) solution-based syntheses has been hindered in part by the inability to examine and control the conversion of precursor seed populations to anisotropic materials, which have resulted in low yields of desired products and limited their commercial viability. The advantages offered by tandem separation and characterization methods utilizing asymmetric-flow field flow fractionation (A4F) are principally achieved as a result of their non-disruptive nature (minimizing artefacts), fast throughput, and in-situ analysis. With hyphenated A4F methods, resolved populations of seeds and secondary products, up to long aspect ratio rods, have been achieved and exemplify progress towards elucidating mechanistic aspects of formation and thus rational design. While there have been previously reported studies on A4F separation of GNRs, to our knowledge, this is the first published investigation of in situ GNR growth, separation, and characterization based on A4F, where its utilization in this capacity goes beyond traditional separation analysis. By using hydroquinone as the reducing agent, the conversion of the initial seed population to a distribution of products, including the GNRs, could be monitored in real time using A4F hyphenated with a diode array detector. Transmission electron microscopy confirms that the number of peaks observed during fractionation corresponds with size and shape dispersity. This proof-of-principle study introduces A4F as a technique that establishes a foundation for future mechanistic studies on the growth of GNRs from gold seeds, including conversion of the seed population to initial products, a topic highly relevant to advancing progress in nanomanufacturing.

An online x-ray based position validation system for prostate hypofractionated radiotherapy.

Accurate positioning of the target volume during treatment is paramount for stereotactic body radiation therapy (SBRT). In this work, the authors present the development of an in-house software tool to verify target position with an Elekta-Synergy linear accelerator using kV planar images acquired during treatment delivery. In-house software, SeedTracker, was developed in matlab to perform the following three functions: 1. predict intended seed positions in a planar view perpendicular to any gantry angle, simulating a portal imaging device, from the 3D seed co-ordinates derived from the treatment planning system; 2. autosegment seed positions in kV planar images; and 3. report the position shift based on the seed positions in the projection images. The performance of SeedTracker was verified using a CIRS humanoid phantom (CIRS, VA, USA) implanted with three Civco gold seed markers (Civco, IA, USA) in the prostate. The true positive rate of autosegmentation (TPRseg) and the accuracy of the software in alerting the user when the isocenter position was outside the tolerance (TPRtrig) were studied. Two-dimensional and 3D static position offsets introduced to the humanoid phantom and 3D dynamic offsets introduced to a gel phantom containing gold seeds were used for evaluation of the system. SeedTracker showed a TPRseg of 100% in the humanoid phantom for projection images acquired at all angles except in the ranges of 80°-100° and 260°-280° where seeds are obscured by anatomy. This resulted in a TPRtrig of 88% over the entire treatment range for considered 3D static offsets introduced to the phantom. For 2D static offsets where the position offsets were only introduced in the anterior-posterior and lateral directions, the TPRtrig of SeedTracker was limited by both seed detectability and positional offset. SeedTracker showed a false positive trigger in the projection angle range between 130°-170° and 310°-350° (a maximum of 24% of treatment time) due to limited information that can be derived from monoscopic images. The system accurately determined the dynamic trajectory of the isocenter position in the superior and inferior direction for the studied dynamic offset scenarios based on the seed position in monoscopic images. The developed software has been shown to accurately autosegment the seed positions in kV planar images except for two 20° arcs where seeds are obscured by anatomical structures. The isocenter trajectories determined by the system, based on the monoscopic images, provide useful information for monitoring the prostate position. The developed system has potential application for monitoring prostate position during treatment delivery in linear accelerator based SBRT.

Synthesis and Characterization of Monodisperse Metallodielectric SiO2@Pt@SiO2 Core-Shell-Shell Particles.

Metallodielectric nanostructured core-shell-shell particles are particularly desirable for enabling novel types of optical components, including narrow-band absorbers, narrow-band photodetectors, and thermal emitters, as well as new types of sensors and catalysts. Here, we present a facile approach for the preparation of submicron SiO2@Pt@SiO2 core-shell-shell particles. As shown by transmission and scanning electron microscopy, the first steps of this approach allow for the deposition of closed and almost perfectly smooth platinum shells onto silica cores via a seeded growth mechanism. By choosing appropriate conditions, the shell thickness could be adjusted precisely, ranging from ∼3 to ∼32 nm. As determined by X-ray diffraction, the crystalline domain sizes of the polycrystalline metal shells were ∼4 nm, regardless of the shell thickness. The platinum content of the particles was determined by atomic absorption spectroscopy and for thin shells consistent with a dense metal layer of the TEM-measured thickness. In addition, we show that the roughness of the platinum shell strongly depends on the storage time of the gold seeds used to initiate reductive platinum deposition. Further, using polyvinylpyrrolidone as adhesion layer, it was possible to coat the metallic shells with very homogeneous and smooth insulating silica shells of well-controlled thicknesses between ∼2 and ∼43 nm. After depositing the particles onto silicon substrates equipped with interdigitated electrode structures, the metallic character of the SiO2@Pt particles and the insulating character of the SiO2 shells of the SiO2@Pt@SiO2 particles were successfully demonstrated by charge transport measurements at variable temperatures.

Fabrication of photoactive heterostructures based on quantum dots decorated with Au nanoparticles

Silica based multifunctional heterostructures, exhibiting near infrared (NIR) absorption (650–1200 nm) and luminescence in the visible region, represent innovative nanosystems useful for diagnostic or theranostic applications. Herein, colloidal synthetic procedures are applied to design a photoactive multifunctional nanosystem. Luminescent silica (SiO2) coated quantum dots (QDs) have been used as versatile nanoplatforms to assemble on their surface gold (Au) seeds, further grown into Au spackled structures. The synthesized nanostructures combine the QD emission in the visible region, and, concomitantly, the distinctive NIR absorption of Au nanodomains. The possibility of having multiple QDs in a single heterostructure, the SiO2 shell thickness, and the extent of Au deposition onto SiO2 surface have been carefully controlled. The work shows that a single QD entrapped in 16 nm thick SiO2 shell, coated with Au speckles, represents the most suitable geometry to preserve the QD emission in the visible region and to generate NIR absorption from metal NPs. The resulting architectures present a biomedical potential as an effective optical multimodal probes and as promising therapeutic agents due to the Au NP mediated photothermal effect.

Synthesis of large uniform gold and core–shell gold–silver nanoparticles: Effect of temperature control

The temperatures of nucleation and growth for gold and silver nanoparticles are quite close to each other in citrate-based seeded-growth synthesis. Hence, thorough temperature control during the synthesis of gold and gold–silver core–shell nanoparticles is expected to improve the yield of uniform non-aggregated nanoparticles suitable for selective contrasting of surface defects. Gold and gold–silver core–shell nanoparticles of size ranging from 20 to 160 nm were synthesized using various means of temperature control. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and UV–Vis spectroscopy. Model nanocracks were milled on pipeline steel specimen by focused ion beam (FIB). It was found that to produce large uniform core–shell nanoparticles, thorough temperature control is required during formation of the gold seeds and the silver shell. Moreover, the synthesized nanoparticles were used for selective contrasting of defects on metal surface.

Transperineal implantation of gold fiducial markers (goldseeds) for prostate image-guided radiation therapy: afeasible technique associated with a low risk of complications.

IntroductionThe purpose is to describe the method, safety and efficacy of transperineal gold seed placement for image‐guided radiation therapy.MethodsAn ethics committee approved database was used to review records of consecutive patients from October 2008 through December 2013, who underwent transperineal implantation of three gold markers into the prostate using staged local anaesthesia and transrectal ultrasound. Seeds were counted on radiographs from CT simulation, first treatment and last treatment. Retention and use of at least three markers for kV/kV matching was considered a successful implant. A visual analogue scale (VAS) pain assessment was performed. SAS was used for data analysis.ResultsFiducial marker placement was successful for kV/kV matching in 556/581 patients (95.7%). The procedure was aborted due to pain in two patients. Additional sedation during the procedure was required in two patients. Complications include urinary infections (2 patients, <0.5%) and transient haematuria (2 patients, <0.5%). There were no recorded calls requesting additional pain medication or delays in radiation due to complications. The number of seeds identified at simulation: 4 (2 patients), 3 (554 patients), 2 (21 patients), 1 (1 patient), 0 (1 patient). One patient with three seeds and two patients with <2 seeds had cone beam CT instead of kV/kV imaging for image guidance. No seeds were lost after simulation. The mean visual analogue pain score associated with transperineal gold seed insertion met patients' expectations (respectively 4.1 vs. 4.4 P = 0.19).ConclusionOutpatient transperineal insertion of fiducials avoids the rectum, is effective, convenient, well tolerated and has few side effects.

Retention Rate of Electromagnetic Navigation Bronchoscopic Placed Fiducial Markers for Lung Radiosurgery

Radiosurgery is becoming an increasingly used modality for the medically inoperable early stage lung cancer patient. The optimal fiducial marker with respect to retention rate has yet to be identified. We retrospectively reviewed our experience with electromagnetic navigational bronchoscopic fiducial marker placement in preparation for stereotactic radiosurgery. Forty-eight patients, treated between 2010 and January 2013, were retrospectively reviewed. All patients had a diagnosis of early stage lung cancer. Comparison of initial fiducial placement procedure data with imaging at the time of treatment was accomplished for all patients in this data set. Fiducial retention rates were as follow: VortX coil fiducials were retained in 59 of 61 (96.7%) cases; two-band fiducials were retained in 24 of 33 (72.7%) of instances; and gold seed fiducials were retained in 23 of 33 (69.7%) of cases. Retention was statistically superior when comparing the VortX coil with the two-band fiducial or the gold seed (p = 0.004 and p = 0.0001). Anatomic location by lobe was analyzed, but no statistically significant differences were observed. The VortX coil fiducial marker showed a statistically significant increase in retention rate compared with gold seeds or two-band fiducials. This may translate to cost savings through placing fewer markers per patient as retention is high.

Stranded Seeds and Seed Displacement as Estimated By Day 0 Fluoroscopy and Four Month Post-Implant Pelvic X-Ray

Loose seed placement in permanent prostate brachytherapy (PPB) is associated with seed migration to the lung and other locations in the body whereas seed placement with stranded seeds is associated with reduced seed migration. However, some reports indicate that seed displacement of stranded seed trains in and around the prostate may occur such that prostate dosimetry is adversely affected. The purpose of this study is to examine a large series of sequential plain 2D images to determine if obvious and substantial seed displacement occurs. Between 10/2010 and 5/2014 a series of 102 patients underwent PPB at our institution who had routine post-implant fluoroscopy (PIF), Day 0 post-implant dosimetry (PID) and gold marker placement near the prostate base and apex. Since 2004, 686 patients have undergone implant with stranded seeds only and in 2011, a general policy of including pelvic in addition to chest x-rays at four month follow up visits was implemented by one of the brachytherapists. Implants routinely included seed placement in the base and apex with separate seed trains of only two or three seeds in length as opposed to seed trains traversing the entire length of the prostate. Apical seed placement was at or typically within 8 mm of the apex. In order to determine if any seed displacement occurred a comparison of the PIF taken at day zero and standing pelvic image four months later using the gold seed length of 3 mm as the reference length. Measurements and observations include: 1) an X-axis measurement (horizontal) measuring the distances between the two furthest seeds in that direction. 2) Y-axis measurement (vertical) with seeds measurement including distance between gold seeds, superior seed and inferior seed from the gold seed placement. A total of 102 cases were available for analysis. The Y-axis distance of day 0 Fluoroscopy images (range:38mm-81mm), and four month standing pelvic x-ray (range: 34mm-106mm). The mean for Day 0 Y-axis distance was 54mm and the mean for the 4 month Y-axis distance was 52mm. The X-axis distance of day 0 Fluoroscopy image was (range 33mm-66mm), and the four month standing x-ray image (range: 45mm-76mm). The mean for Day 0 X-axis distance was 51mm and for the 4 month mean X-axis distance was 59mm. One patient lost 10 seeds through apparent seed migration through the bladder and urethra with no apparent adverse clinical consequences. Four patients had significant local migration of 1 or 2 seeds from the prostate, 3 moved superior to the prostate and 1 inferior to the prostate. 3 patients also had migration of seeds to the chest. Despite the limitations evident in method employed in this study comparing two disparate plain imaging techniques (PIF vs pelvic x-ray) with different source to subject distance, and patients in different positions (extended dorsal lithotomy and standing), some general observations are possible: 1) no repetitive or systematic loss of seeds through the bladder or urethra occurred, 2) no seed displacement in the caudal direction appeared routinely, 3) technique-related factors may explain the finding in this study as compared to prior reports, and 4) sequential CT or MR-based dosimetry is necessary in order to further substantiate these findings.