Clinical utility and value contribution of an MRI-positive line marker for image-guided brachytherapy in gynecologic malignancies

PurposeThe purpose of this study was to investigate the utility of a novel MRI-positive line marker, composed of C4:S (cobalt chloride–based contrast agent) encapsulated in high-density polyethylene tubing, in permitting dosimetry and treatment planning directly on MRI.Methods and MaterialsWe evaluated the clinical feasibility of the C4:S line markers in nine sequential brachytherapy procedures for gynecologic malignancies, including six tandem-and-ovoid and three interstitial cases. We then quantified the internal resource utilization of an intraoperative MRI-guided procedural episode via time-driven activity-based costing, identifying opportunities for cost-containment with use of the C4:S line markers.ResultsThe C4:S line markers demonstrated the strongest positive signal visibility on 3D constructive interference in steady state (CISS)/FIESTA-C followed by T1-weighted sequences, permitting accurate delineation of the applicator lumen and thus the source path. These images may be fused along with traditional T2-weighted sequences for optimal tumor and anatomy contouring, followed by treatment planning directly on MRI. By eliminating postoperative CT for fusion and applicator registration from the procedural episode, use of the C4:S line markers could decrease workflow time and lower total delivery costs per procedure.ConclusionsThis analysis supports the clinical utility and value contribution of the C4:S line markers, which permit accurate MRI-based dosimetry and treatment planning, thereby eliminating the need for postoperative CT for fusion and applicator registration.     

Reprogramming of the heavy-chain CDR3 regions of a human antibody repertoire

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Genome editing in human hematopoietic stem and progenitor cells via CRISPR-Cas9-mediated homology-independent targeted integration

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Design and characterization of an economical 192Ir hemi-brain small animal irradiator

Abstract

Purpose: To describe the design and dosimetric characterization of a simple and economical small animal irradiator.

Materials and methods: A high dose rate (HDR) ¹⁹²Ir brachytherapy source from a commercially available afterloader was used with a 1.3 cm thick tungsten collimator to provide sharp beam penumbra suitable for hemi-brain irradiation of mice. The unit was equipped with continuous gas anesthesia to allow robust animal immobilization. Dosimetric characterization of the device was performed with Gafchromic film measurements.

Results: The tungsten collimator provided a sharp penumbra suitable for hemi-brain irradiation, and dose rates on the order of 200 cGy/minute were achieved. The sharpness of the penumbra attainable with this device compares favorably to those measured experimentally for 6 MV photons, and 6 and 20 MeV electron beams from a linear accelerator, and was comparable to those measured for a 300 kVp orthovoltage beam and a Monte Carlo simulated 90 MeV proton beam.

Conclusions: Due to its simplicity and low cost, the apparatus described is an attractive alternative for small animal irradiation experiments requiring steep dose gradients.     

Infectious bursal disease virus rescued efficiently with 3′ authentic RNA sequence induces humoral immunity without bursal atrophy

A reverse genetics infectious bursal disease virus (RG-IBDV) that contained authentic 3′ RNA sequence was characterized both in vitro and in vivo. LP1-IBDV, a cell line-adapted IBDV strain variant E (VE) was used as the parent virus for constructing viral cDNA clones. Authentic 3′ RNA sequence was generated by using cis-acting hepatitis delta virus ribozyme (HDR). The absence of HDR in the clones did not affect viral protein expression, but the obtained viral titers were reduced by 200-folds when compared to the clones with HDR sequence. RG-IBDV generated from clones with HDR sequence was similar to LP1-IBDV by plaque size, growth kinetics and electron microscopic morphology. RG-IBDV did not cause bursal atrophy in 3-week-old chickens at 3, 7 and 17 days post infection (DPI) and induced high ELISA and neutralizing antibody titers to IBDV at 7 and 17 DPI. The results indicated that RG-IBDV can be generated efficiently with an authentic 3′ RNA terminus and the obtained RG-IBDV is non-pathogenic and immunogenic with the potential as a vaccine strain that can be further genetically modified to broaden its application.     

A novel method for accurate needle-tip identification in trans-rectal ultrasound-based high-dose-rate prostate brachytherapy

Purpose

In real-time trans-rectal ultrasound (TRUS)-based high-dose-rate prostate brachytherapy, the accurate identification of needle-tip position is critical for treatment planning and delivery. Currently, needle-tip identification on ultrasound images can be subject to large uncertainty and errors because of ultrasound image quality and imaging artifacts. To address this problem, we developed a method based on physical measurements with simple and practical implementation to improve the accuracy and robustness of needle-tip identification.

Methods and Materials

Our method uses measurements of the residual needle length and an off-line pre-established coordinate transformation factor, to calculate the needle-tip position on the TRUS images. The transformation factor was established through a one-time systematic set of measurements of the probe and template holder positions, applicable to all patients. To compare the accuracy and robustness of the proposed method and the conventional method (ultrasound detection), based on the gold-standard X-ray fluoroscopy, extensive measurements were conducted in water and gel phantoms.

Results

In water phantom, our method showed an average tip-detection accuracy of 0.7 mm compared with 1.6 mm of the conventional method. In gel phantom (more realistic and tissue-like), our method maintained its level of accuracy while the uncertainty of the conventional method was 3.4 mm on average with maximum values of over 10 mm because of imaging artifacts.

Conclusions

A novel method based on simple physical measurements was developed to accurately detect the needle-tip position for TRUS-based high-dose-rate prostate brachytherapy. The method demonstrated much improved accuracy and robustness over the conventional method.