MALDI-TOF Mass Spectrometry Based on Parylene-Matrix Chip for the Analysis of Lysophosphatidylcholine in Sepsis Patient Sera.

In this work, medical diagnosis of sepsis was conducted via quantitative analysis of lysophosphatidylcholine 16:0 (LPC 16:0) by using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry based on a parylene-matrix chip. In the first step, specific mass peaks for the diagnosis of sepsis were searched by comparing MALDI-TOF mass spectra of sepsis patient sera with healthy controls and pneumonia patient sera. Two mass peaks at m/z = 496.3 and 518.3 were chosen as those that are specifically different for sepsis sera to compare with healthy controls and pneumonia patient sera. These mass peaks were identified to be protonated and sodium adducts of LPC 16:0 by using tandem mass spectra (MS2 and MS3) of purely synthesized LPC 16:0 and extracted LPC 16:0 from a healthy control and a sepsis patient. In the next step, a standard curve for LPC 16:0 for the quantitative analysis of LPC 16:0 with MALDI-TOF MS based on the parylene-matrix chip was prepared, and the statistical correlation to the LC-MS analysis results was demonstrated by using the Bland-Altman test and Passing-Bablok regression. Finally, MALDI-TOF MS based on the parylene-matrix chip was used for the quantification of LPC 16:0 with sera from patients with severe sepsis and septic shock (n = 143), pneumonia patients (n = 12), and healthy sera (n = 31). The sensitivity and the selectivity of medical diagnosis of sepsis was estimated to be 97.9% and 95.5% by using MALDI-TOF MS based on the parylene-matrix chip, respectively.

Air-electron stream interactions during magnetic resonance IGRT : Skin irradiation outside the treatment field during accelerated partial breast irradiation.

PURPOSE: To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). MATERIALS AND METHODS: In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. A 1 cm thick bolus was placed in front of the patient's jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3 films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated. RESULTS: For a single fraction delivery, the average areas of the measured isodoses of 14% (0.54 Gy), 12% (0.46 Gy), and 10% (0.39 Gy) at the front of the boluses were as large as 3, 10.4, and 21.4 cm2, respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times. CONCLUSION: During radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field.

Newborn screening by matrix-assisted laser desorption/ionization mass spectrometry based on parylene-matrix chip.

Newborn screening for diagnosis of phenylketonuria, homocystinuria, and maple syrup urine disease have been conducted by analyzing the concentration of target amino acids using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) based on parylene-matrix chip. Parylene-matrix chip was applied to MALDI-ToF MS analysis reducing the matrix peaks significantly at low mass-to-charge ratio range (m/z < 500). Reproducibility of inter-spot and intra-spot analyses of amino acids was less than 10%. Methanol extraction was adopted for simple and rapid sample preparation of serum before mass spectrometric analysis showing 13.3 to 45% of extraction efficiency. Calibration curves for diagnosis of neonatal metabolic disorders were obtained by analyzing methanol-extracted serum spiked with target amino acids using MALDI-ToF MS. They showed good linearity (R2 > 0.98) and the LODs were ranging from 9.0 to 22.9 µg/mL. Effect of proteins in serum was estimated by comparing MALDI-ToF mass spectra of amino acids-spiked serum before and after the methanol extraction. Interference of other amino acids on analysis of target analyte was determined to be insignificant. From these results, MALDI-ToF MS based on parylene-matrix chip could be applicable to medical diagnosis of neonatal metabolic disorders.

Parylene-matrix chip for small molecule analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RATIONALE: In matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), analyte molecules are known to be ionized by mixing with organic matrix molecules. As the organic matrix molecules are ionized, they generate unreproducible mass peaks such that MALDI-TOF MS is nearly impossible in the low mass-to-charge (m/z) range (<1000). In this work, we aimed to develop a parylene-matrix chip for the detection of small molecules in the low m/z range by using MALDI-TOF MS. METHODS: The parylene-matrix chip was fabricated by the deposition of a partially porous parylene-N thin film on a dried organic matrix array. The properties of the parylene thin film were analyzed by atomic force microscopy (AFM) and cyclic voltammetry (CV). Mass spectrometry was performed by using a parylene-matrix chip with eight amino acids as model analytes. RESULTS: The surface roughness and the electric conductivity of the parylene-N film were analyzed by AFM and CV analysis to determine its suitability for a parylene-matrix chip. The ionization of samples on the parylene-matrix chip was optimized by adjusting the laser intensity. The feasibility of applying a parylene-matrix chip for small molecule analysis was tested by using eight kinds of amino acids as model analytes and the simultaneous detection of multiple analytes from the amino acid mixture was also demonstrated. CONCLUSIONS: The parylene-matrix chip can be applied for the detection of multiple analytes in the m/z ratio range of small molecules (<1000) using MALDI-TOF MS.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of small volatile molecules using a parylene-matrix chip.

RATIONALE: In matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), volatile small molecules have been nearly impossible to analyze because (1) such molecules evaporate under drying and vacuum conditions and (2) the organic matrix creates matrix peaks in the low mass-to-charge (m/z) range (m/z <500). In this work, the analysis of volatile small molecules using MALDI-TOFMS was realized using (1) a parylene-matrix chip to eliminate the matrix peaks of the organic matrix and (2) graphene for the effective adsorption of the small volatile molecules. METHODS: The parylene-matrix chip was produced by deposition of a partially porous parylene-N thin film on a dried organic matrix array. The sample solution of volatile small molecules was mixed with the graphene and then placed on the parylene-matrix chip for MALDI-TOFMS. Analogs of chemical agents called dimethyl methyl phosphonate (DMMP) and 2-chloroethylethylsulfide (CEES) were used as model compounds for the small volatile molecules, and the sensing parameters were estimated, such as the limit of detection (LOD) and the detection range. RESULTS: MALDI-TOFMS based on the parylene-matrix chip and graphene as the adsorbent could achieve a LOD of approximately 1 ppb in the detection range of 1 ppm-1 ppb for the highly volatile DMMP and CEES. CONCLUSIONS: The parylene-matrix chip with graphene can be applied for the detection of volatile small molecule analytes in the m/z ratio range of small molecules (m/z <500) using graphene as an effective adsorbent.

Assessment of potential jaw-tracking advantage using control point sequences of VMAT planning.

This study aims to evaluate the potential jaw-tracking advantage using control point sequences of volume volumetric modulated arc therapy (VMAT) planning. VMAT plans for patients with prostate and head and neck (H&N) cancers were converted into new static arc (SA) plans. The SA plan consisted of a series of static fields at each control point of the VMAT plan. All other machine parameters of the SA plan were perfectly identical to those of the original VMAT plan. The jaw-tracking static arc (JTSA) plans were generated with fields that closed the jaws of each SA field into the multileaf collimators (MLCs) aperture. The dosimetric advantages of JTSA over SA were evaluated in terms of a dose-volume histogram (DVH) of organ at risk (OAR) after renormalizing both plans to make the same target coverage. Both plans were delivered to the MatriXX-based COMPASS system for 3D volume dose verification. The average jaw size reduction of the JTSA along the X direction was 3.1 ± 0.9 cm for prostate patients and 6.9 ± 1.9 cm for H&N patients. For prostate patients, the organs far from the target showed larger sparing (3.7%-8.1% on average) in JTSA than the organs adjacent to the target (1.1%-1.5%). For the H&N plans, the mean dose reductions for all organs ranged from 4.3% to 11.9%. The dose reductions were more significant in the dose regions of D80, D90, and D95 than the dose regions of D5, D10, and D20 for all patients. Likewise, the deliverability and reproducibility of jaw-tracking plan were validated. The measured dosimetric advantage of JTSA over SA coincided with the calculated one above.

Scanning methodology for contact lens-type ocular in vivo dosimeter (CLOD) dosimetry applying a silicone material.

PURPOSE: Contact lens-type ocular in vivo dosimeters (CLODs) were recently developed as the first in vivo dosimeter that can be worn directly on the eye to measure the dose delivered to the lens during radiotherapy. However, it has an inherent uncertainty because of its curved shape. Newton's ring effect inevitably occurs because the spacing between the glass window and the active layer is not constant. Furthermore, it involves a large uncertainty because the objective of the CLOD with such morphological characteristics is to measure the dose delivered to an out-of-field lens. In this study, we aimed to investigate the effects of various compensating materials on the sensitivity, accuracy, and uniformity of analysis using a curved CLOD. We developed a new scanning methodology that involves applying a compensating material to reduce the uncertainty caused by the air gap. METHODS: Four compensating materials-Dragon Skin™ 10 (DS), a transparent silicon material, SORTA-Clear™ 40 (SC), optical grease (OG), and air (no compensating material)-were used in this study. The CLOD was scanned in the reflective mode and transmission mode using each compensating material. We then examined the sensitivity, accuracy, and scan uniformity to evaluate the scanning methodology using compensating materials. RESULTS: The increase in sensitivity was the highest for OG compared to that for air in the reflective mode. On average, the sensitivity in the reflective mode was higher than that in the transmission mode by a factor of 2.5 for each dose. Among the four compensating materials, OG had the smallest uncertainty. Therefore, the best scan uniformity was achieved when OG was used. CONCLUSIONS: Scanning methodology was proposed in which a compensating material is applied for a curved lens-type dosimeter. Our results show that OG is the most suitable compensating material to obtain the best accuracy of dose analysis. Following this methodology, the scan uncertainty of curved dosimeters significantly decreased.

Comparison of treatment plans between static jaw and jaw tracking techniques in postmastectomy intensity-modulated radiation therapy.

This study reports a dosimetric comparison between treatment plans using static jaw and jaw tracking techniques in intensity-modulated radiation therapy (IMRT) for postmastectomy radiation therapy (PMRT). Seventeen patients treated for left-sided breast cancer with implant-based reconstruction were subjected to IMRT plans. Another group of 22 patients treated for left-sided breast cancer without reconstruction was also subjected to IMRT plans. The plans were generated using the Eclipse treatment planning system with static jaw and jaw tracking techniques. The dose-volume histograms and dosimetric indices, such as mean dose (Dmean), V20 Gy, V10 Gy, and V5 Gy (volumes receiving 20, 10, and 5 Gy at the least, respectively), and generalized equivalent uniform dose for organs at risk (OARs) were analyzed. A significant difference in the value of the dosimetric indices between the static jaw and jaw tracking plans was observed. For jaw tracking plans, the Dmean of the heart for the patients with implant-based reconstruction reduced from 11.6 ± 1.1 Gy to 10.0 ± 1.8 Gy, whereas the V5 Gy reduced from 92.0 ± 4.5% to 85.1 ± 8.4%. The Dmean of the heart for patients without reconstruction reduced from 11.0 ± 2.3 Gy to 9.8 ± 2.6 Gy, whereas the V5 Gy reduced from 81.4 ± 13.6% to 66.7 ± 17.4%. The dosimetric indices of OARs in the jaw tracking plans were significantly lower than those of the OARs in the static jaw plans. The jaw tracking technique was more effective for patients without reconstruction than for those with implant-based reconstruction.

Silicon Tetrapyrazinoporphyrazine Derivatives-Incorporated Carbohydrate-Based Block Copolymer Micelles for Photodynamic Therapy.

Developing nonaggregated photosensitizers (PSs) for efficient photodynamic therapy (PDT) using polymeric micelles (PMs) has been challenging. In this study, axially substituted nonaggregated silicon tetrapyrazinoporphyrazine (SiTPyzPz) derivatives in carbohydrate-based block glycopolymer-based PMs were designed and used as PSs for PDT. To achieve the nonaggregated PSs, SiTPyzPz was axially substituted with trihexylsiloxy (THS) groups to form SiTPyzPz-THS, which exhibited highly monomeric behaviors in organic solvents. Moreover, three block copolymers were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Each copolymer comprised hydrophobic polystyrene blocks and loadable SiTPyzPz-THS, and one or two consisted of two possible hydrophilic blocks, polyethylene glycol or poly(glucosylethyl methacrylate). The self-assembly of SiTPyzPz-THS and the block copolymers in aqueous solvents induced the formation of spherical PMs with core-shell or core-shell-corona structures. The SiTPyzPz-THS in the PMs exhibited monomeric state, intense fluorescence emission, and outstanding singlet oxygen generation; moreover, it did not form aggregates. During the in vitro test, which was performed to investigate the PDT efficiency, the PMs, which consisted of poly(glucosylethyl methacrylate) shells, exhibited high photocytotoxicity and cellular internalization ability. Consequently, the PM systems of nonaggregated PSs and carbohydrate-based block copolymers could become very promising materials for PDT owing to their photophysicochemical properties and considerable selectivity against cancer cells.

Dose calculation of 3D printing lead shield covered by biocompatible silicone for electron beam therapy.

This study aims to calculate the dose delivered to the upstream surface of a biocompatible flexible absorber covering lead for electron beam treatment of skin and subcutaneous tumour lesions for head and neck. Silicone (Ecoflex™ 00-30, Smooth-On, Easton, PA, USA) was used to cover the lead to absorb backscattered electrons from lead. A 3D printer (Zortrax M300, Zortrax, Olsztyn, Poland) was used to fabricate the lead shield. Analytic calculation, simplified Monte Carlo (MC) simulation, and detailed MC simulation which includes a modeling of metal-oxide-semiconductor field-effect transistor (MOSFET) detector were performed to determine the electron backscatter factor (EBF) for 6 MeV and 9 MeV electron beams of a Varian iX Silhouette. MCNP6.2 was used to calculate the EBF and corresponding measurements were carried out by using MOSFET detectors. The EBF was experimentally measured by the ratio of dose at the upstream surface of the silicone to the same point without the presence of the lead shield. The results derived by all four methods agreed within 2.8% for 6 MeV and 3.4% for 9 MeV beams. In detailed MC simulations, for 6 MeV, dose to the surface of 7-mm-thick absorber was 103.7 [Formula: see text] 1.9% compared to dose maximum (Dmax) without lead. For 9 MeV, the dose to the surface of the 10-mm-thick absorber was 104.1 [Formula: see text] 2.1% compared to Dmax without lead. The simplified MC simulation was recommended for practical treatment planning due to its acceptable calculation accuracy and efficiency. The simplified MC simulation was completed within 20 min using parallel processing with 80 CPUs, while the detailed MC simulation required 40 h to be done. In this study, we outline the procedures to use the lead shield covered by silicone in clinical practice from fabrication to dose calculation.

TRITC-Loaded PLGA Nanoparticles as Drug Delivery Carriers in Mouse Oocytes and Embryos.

The structural layers around oocytes make it difficult to deliver drugs aimed at treating infertility. In this study, we sought to identify nanoparticles (NPs) that could easily pass through zona pellucida (ZP), a special layer around oocytes, for use as a drug delivery carrier. Three types of NPs were tested: quantum dot NPs, PE-polyethylene glycol (PEG)-loaded poly(lactic-co-glycolic acid) (PLGA) NPs (PEG/PL), and tetramethylrhodamine-loaded PLGA NPs (TRNPs). When mouse oocytes were treated with NPs, only TRNPs could fully pass through the ZP and cell membrane. To assess the effects of TRNPs on fertility and potential nanotoxicity, we performed mRNA sequencing analysis to confirm their genetic safety. We established a system to successfully internalize TRNPs into oocytes. The genetic stability and normal development of TRNP-treated oocytes and embryos were confirmed. These results imply that TRNPs can be used as a drug delivery carrier applicable to germ cells.

Improvement in sensitivity of radiochromic 3D dosimeter based on rigid polyurethane resin by incorporating tartrazine.

We investigated the influence of incorporating tartrazine on the dose response characteristics of radiochromic 3D dosimeters based on polyurethane resin. We use three types of polyurethane resins with different Shore hardness values: 30 A, 50 A, and 80 D. PRESAGE dosimeters are fabricated with different chemical components and concentrations. Tartrazine (Yellow No. 5) helps incorporate a yellow dye to fabricate the dosimeter. Elemental composition is analyzed with the Zeff. Three sets of six different PRESAGE dosimeters were fabricated to investigate the effects of incorporating yellow dye on the dose response characteristics of the dosimeter. The dose response curve was obtained by measuring the optical absorbance using a spectrometer and optical density using optical CT, respectively. The energy and dose rate dependences are evaluated for the dosimeter with the highest sensitivity. For the optical density measurement, significant sensitivity enhancements of 36.6% and 32.7% were achieved in polyurethane having a high Shore hardness of 80 D and 50 A by incorporating tartrazine, respectively. The same results were obtained in the optical absorbance measurements. The ratio of the Zeff of the dosimeter with 80 D Shore hardness to water was 1.49. The polyurethane radiochromic dosimeter with a Shore hardness of 80 D showed the highest sensitivity and energy and dose rate independence upon the incorporation of tartrazine.

A transport system based on a quantum dot-modified nanotracer is genetically and developmentally stable in pregnant mice.

The use of nanoscale materials (NMs) could cause problems such as cytotoxicity, genomic aberration, and effects on human health, but the impacts of NM exposure during pregnancy remain uncharacterized in the context of clinical applications. It was sought to determine whether nanomaterials pass through the maternal-fetal junction at any stage of pregnancy. Quantum dots (QDs) coated with heparinized Pluronic 127 nanogels and polyethyleneimine (PEI) were administered to pregnant mice. The biodistribution of QDs, as well as their biological impacts on maternal and fetal health, was evaluated. Encapsulation of QDs with a nanogel coating produces a petal-like nanotracer (PNt), which could serve as a nano-carrier of genes or drugs. PNts were injected through the tail vein and accumulated in the liver, kidneys, and lungs. QD accumulation in reproductive organs (uterus, placenta, and fetus) differed among phases of pregnancy. In phase I (7 days of pregnancy), the QDs did not accumulate in the placenta or fetus, but by phase III (19 days) they had accumulated at high levels in both tissues. Karyotype analysis revealed that the PNt-treated pups did not have genetic abnormalities when dams were treated at any phase of pregnancy. PNts have the potential to serve as carriers of therapeutic agents for the treatment of the mother or fetus and these results have a significant impact on the development and application of QD-based NPs in pregnancy.

Simultaneous Analysis of Multiple Cancer Biomarkers Using MALDI-TOF Mass Spectrometry Based on a Parylene-Matrix Chip.

Recently, the parylene-matrix chip was developed for quantitative analysis of small molecules less than 1 kDa. In this study, MALDI-TOF MS based on the parylene-matrix chip was performed to clinically diagnose intrahepatic cholangiocarcinoma (IHCC) and colorectal cancer (CRC). The parylene-matrix chip was applied for the detection of small cancer biomarkers, including N-methyl-2-pyridone-5-carboxamide (2PY), glutamine, lysophosphatidylcholine (LPC) 16:0, and LPC 18:0. The feasibility of MALDI-TOF MS based on the parylene-matrix chip was confirmed via analysis of spot-to-spot and shot-to-shot reproducibility. Serum metabolite markers of IHCC, N-methyl-2-pyridone-5-carboxamide (2PY), and glutamine were quantified using MALDI-TOF MS based on the parylene-matrix chip. For clinical diagnosis of CRC, two water-insoluble (barely soluble) biomarkers, lysophosphatidylcholine (LPC) 16:0 and LPC 18:0, were quantified. Finally, glutamine and LPC 16:0 were simultaneously detected at a range of concentrations in sera from colon cancer patients using the parylene-matrix chip. Thus, this method yielded high-throughput detection of cancer biomarkers for the mixture samples of water-soluble analytes (2PY and glutamine) and water-insoluble analytes (LPC 16:0 and LPC 18:0).

A 3D-printed patient-specific applicator guide for use in high-dose-rate interstitial brachytherapy for tongue cancer: a phantom study.

A patient-specific applicator guide system (PSAG) for tongue-cancer high-dose-rate (HDR) interstitial brachytherapy (ISBT) was developed by utilizing a 3D printing technique. An effectiveness of the 3D-printed PSAG (3D-PSAG) was evaluated for HDR ISBT. Six patients with tongue cancer were retrospectively selected for this study. For each patient, a total of three virtual clinical target volumes (CTV) requiring the insertion of four catheters (CTV4), six catheters (CTV6), and eight catheters (CTV8) were defined. For each CTV, treatment plans were generated to deliver 45 Gy in nine fractions. The 3D-PSAG was fabricated using a 3D-printer and the patient's CT-images. The resulting 3D-PSAG took the form of a shell conforming to the patient's contours with tubes for catheter insertion. For each CTV, catheters were inserted into the phantom with and without the 3D-PSAG. After that, CT-images of the phantom with the inserted catheters were acquired. Differences between the planned positions and those of the actually inserted catheters were evaluated from the CT-images. Given the actual catheter insertion positions, the dose distributions were reconstructed and analyzed. The maximum positional errors with and without the 3D-PSAG were 0.2 mm and 4.5 mm, respectively. For CTV6, the D 90% values of the original plan, the reconstructed plan with the 3D-PSAG, and the reconstructed plan without the 3D-PSAG, were 48.8 ± 1.7 Gy, 49.0 ± 2.9 Gy, and 45.6 ± 3.3 Gy, respectively. The D 1cc values for the mandible were 51.3 ± 9.2 Gy, 61.6 ± 8.3 Gy, and 81.1 ± 16.7 Gy, respectively. The dose homogeneities in the CTVs into which the catheters had been inserted with the 3D-PSAG were always superior to those into which the catheters had been inserted without the 3D-PSAG. The present phantom study demonstrated the feasibility of more accurate interstitial tongue brachytherapy while simplifying the treatment process by utilizing the 3D-PSAG.

Bio-compatible patient-specific elastic bolus for clinical implementation.

We investigated two types of materials with very low Shore hardness, silicon rubber (Dragon Skin) and urethane liquid rubber (Clear Flex 30), for use in 3D printing patient-specific boluses. Boluses were manufactured with these materials using a mold casting method. NinjaFlex was also used to manufacture the bolus using a direct printing method. These patient-specific boluses were designed for 3D-printed elaborate human phantoms and their biological, physical, and dosimetric properties were comprehensively assessed. The results of cytotoxicity, skin irritation, and skin sensitization tests showed that Dragon Skin was the most biologically stable material. Furthermore, Dragon Skin exhibited excellent physical properties in terms of flexibility (Shore hardness 10A), durability (tensile strength of 475 psi and elongation at break of 1000 (%)), and preparation (5 h curing time). Accordingly, Dragon Skin was finally selected for the bio-compatible patient-specific elastic (BPE) bolus. The dosimetric characteristics were thoroughly investigated with depth dose curves and surface dose. Dragon Skin showed the lowest differences between the calculated dose under virtual bolus and the measured dose at the surface of the phantom head and the lowest amount of unwanted air gap between the bolus and phantom. Overall, Dragon Skin is a suitable material for patient-specific elastic bolus, and it could be implemented effectively in the clinic.

Impact of plan parameters and modulation indices on patient-specific QA results for standard and stereotactic VMAT.

PURPOSE: To demonstrate the impact of modulation indices and plan parameters on the gamma passing rates (GPR) of patient-specific quality assurance of standard and stereotactic volumetric modulated arc therapy (VMAT) plans. METHODS: A total of 758 patients' QA plans were utilized, including standard VMAT plans with Trilogy (n = 87, group A) and TreuBeam STx (n = 332, group B), and 339 stereotactic VMAT plans with TrueBeam STx (group C). Modulation indices were obtained considering the speed and acceleration of the multileaf collimator (MLC) (MIs, MIa), and MLC, gantry speed, and dose rate changes (MIt). The mean aperture size (MA), monitor unit (MU), and amount of jaw tracking (%JT) were acquired. Gamma analysis was performed with 2 mm/2% and 1 mm/2% for the standard and stereotactic VMAT plans, respectively. Statistical analyses were performed to investigate the correlation between modulation index/plan parameters and GPR. RESULTS: Spearman's rank correlation to GPRs with MIs, MIa, and MIt, were -0.44, -0.45, and -0.46 for group A; -0.39, -0.37, and -0.38 for group B; and -0.04, -0.11, and -0.10 for group C, respectively. While MU and MA showed significant correlations in all groups, %JT showed a significant correlation only with stereotactic VMAT plans. The most influential parameter combinations were MU-MA (rs = 0.50), MIs-%JT (rs = 0.43), and MU-%JT (rs = 0.38) for groups A, B, and C, respectively. CONCLUSIONS: MLC modulation mostly affected the GPR in the delivery of standard VMAT plans, while MU and %JT showed more importance in stereotactic VMAT plans.

Comparison of the IPSA and HIPO algorithms for interstitial tongue high-dose-rate brachytherapy.

PURPOSE: This study aimed to compare the inverse planning simulated annealing (IPSA) stochastic algorithm with the hybrid inverse planning and optimization (HIPO) algorithm for interstitial tongue high-dose-rate (HDR) brachytherapy. METHODS: Twenty patients who received radiotherapy for tongue cancer using interstitial HDR brachytherapy were retrospectively selected for this study. Oncentra Brachy v. 4.3 was used for IPSA and HIPO planning. Four to eight fixed catheter configurations were determined according to the target shape. During the optimization process, predetermined constrain values were used for each IPSA and HIPO plan. The dosimetric parameters and dwell time were analyzed to evaluate the performances of the plans. RESULTS: The total dwell time using IPSA was 4 seconds longer than that of HIPO. The number of active positions per catheter for the IPSA plans were approximately 2.5 fewer than those of the HIPO plans. The dose-volumetric parameters related to the clinical target volume with IPSA were lower than those with HIPO. In terms of the dose-volumetric parameters related to normal tissue, HIPO tended to associate with slightly higher values than IPSA, without statistical significance. After GrO, the target coverages were satisfied to clinical goal for all patients. The total dwell times was approximately increased by 10%. CONCLUSIONS: The IPSA and HIPO dose optimization algorithms generate similar dosimetric results. In terms of the dwell time, HIPO appears to be more beneficial.

Hypersensitive antibiotic susceptibility test based on a ß-lactamase assay with a parylene-matrix chip.

Many kinds of susceptibility test for ß-lactam antibiotics have been used to determine the antibiotic resistance of bacterial strains. Here, a sensitive antibiotic susceptibility test was presented by using a specialized reaction tool for laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) based on parylene-matrix chip. The ß-lactamase assay was carried out in a specialized reaction tool by (1) concentrating the bacterial strain and (2) incubating the bacteria with penicillin-G. The parylene-matrix chip was produced by deposition of a partially porous parylene-N thin film on a dried organic matrix array, and the products of ß-lactamase reaction in the low range of mass-to-charge ratio (m/z<500) could be effectively analyzed by using a parylene-matrix chip. The sensing parameters were compared with conventional chromogenic antibiotic susceptibility test for ß-lactam antibiotics. Finally, LDI-TOF MS with a specialized reaction tool and parylene-matrix chip could achieve a limit of detection as low as 600 cells/spot for penicillin-G.

A highly sensitive carbapenemase assay using laser desorption/ionization mass spectrometry based on a parylene-matrix chip.

A quantitative carbapenemase assay was developed using laser desorption/ionization mass spectrometry (LDI-MS) based on a parylene-matrix chip. As a first step, the reproducibility (spot-to-spot, shot-to-shot, and day-to-day) of LDI-MS based on a parylene-matrix chip and the quantification ranges for four carbapenem antibiotics (doripenem, ertapenem, imipenem, and meropenem) were determined. A carbapenem-susceptibility test was performed using the four carbapenems and 51 bacterial strains that displayed (1) carbapenem resistance with carbapenemase, (2) carbapenem resistance without carbapenemase, or (3) carbapenem susceptibility. The susceptibility test results showed that LDI-MS based on a parylene-matrix chip was more sensitive and selective for detecting the carbapenemase reaction than conventional MALDI-TOF MS based on a 2,5-dihydroxybenzoic acid matrix.