Cylindrical Vials Research Articles

Tuning the optimal diffusion-weighted MRI parameters on a 0.35-T MR-Linac for clinical implementation: A phantom study.

This study aims to assess the quality of a new diffusion-weighted imaging (DWI) sequence implemented on an MR-Linac MRIdian system, evaluating and optimizing the acquisition parameters to explore the possibility of clinically implementing a DWI acquisition protocol in a 0.35-T MR-Linac. All the performed analyses have been carried out on two types of phantoms: a homogeneous 24-cm diameter polymethylmethacrylate (PMMA) sphere (SP) and a homemade phantom (HMP) constating in a PMMA cylinder filled with distilled water with empty sockets into which five cylindrical vials filled with five different concentrations of methylcellulose water solutions have been inserted. SP was used to evaluate the dependence of diffusion gradient inhomogeneity artifacts on gantry position. Four diffusion sequences with b-values of 500 s/mm2 and 3 averages have been acquired: three with diffusion gradients in the three main directions (phase direction, read direction, slice direction) and one with the diffusion gradients switched off. The dependence of diffusion image uniformity and SNR on the number of averages in the MR sequences was also investigated to determine the optimal number of averages. Finally, the ADC values of HMP have been computed and then compared between images acquired in the scanners at 0.35 and 1.5 T. In order to acquire high-quality artifact-free DWI images, the "slice" gradient direction has been identified to be the optimal one and 0° to be the best gradient angle. Both the SNR ratio and the uniformity increase with the number of averages. A threshold value of 80 for SNR and 85% for uniformity was adopted to choose the best number of averages. By making a compromise between time and quality and limiting the number of b-values, it is possible to reduce the acquisition time to 78 s. The Passing-Bablok test showed that the two methods, with 0.35 and 1.5 T scanners, led to similar results. The quality of the DWI has been accurately evaluated in relation to different sequence parameters, and optimal parameters have been identified to select a clinical protocol for the acquisition of ADC maps sustainable in the workflow of a hybrid radiotherapy system with a 0.35-T MRI scanner.

Usefulness of 99mTc-Pertechnetate SPECT-CT in Thyroid Tissue Volumetry: Phantom Studies and a Clinical Case Series.

An accurate measurement of the target volume is of primary importance in theragnostics of hyperthyroidism. Our purpose was to evaluate the accuracy of a threshold-based isocontour extraction procedure for thyroid tissue volumetry from SPECT-CT. Cylindrical vials with a fixed volume of 99mTcO4 at different activities were inserted into a neck phantom in two different thickness settings. Images were acquired by orienting the phantom in different positions, i.e., 40 planar images and 40 SPECT-CT. The fixed values of the isocontouring threshold for SPECT and SPECT-CT were calculated by means of linear and spline regression models. Mean, Median, Standard Deviation, Standard Error, Mean Absolute Percentage Error and Root Mean-Square Error were computed. Any difference between the planar method, SPECT and SPECT-CT and the effective volume was evaluated by means of ANOVA and posthoc tests. Moreover, planar and SPECT-CT acquisitions were performed in 8 patients with hyperthyroidism, considering relevant percentage differences greater than > 20% from the CT gold standard. Concerning phantom studies, the planar method shows higher values of each parameter than the other two methods. SPECT-CT shows lower variability. However, no significant differences were observed between SPECT and SPECT-CT measurements. In patients, relevant differences were found in 7 out of 9 lesions with the planar method, in 6 lesions with SPECT, but in only one with SPECT-CT. Our study confirms the superiority of SPECT in volume measurement if compared with the planar method. A more accurate measurement can be obtained from SPECT-CT.

Impact of diatomaceous earth on adults and larvae of the yellow mealworm, Tenebrio molitor L

Although the efficacy of diatomaceous earths (DEs) against most major stored product insects has been extensively evaluated, studies on the effect of DEs on the yellow mealworm, Tenebrio molitor, are rather limited. Apart from being a secondary colonizer of stored commodities, T. molitor is currently one of the most promising species reared to obtain protein sources. In order to update the available information on the tolerance of T. molitor to DEs, we carried out a series of laboratory bioassays with both adults and larvae of T. molitor at a range of DE doses (20, 50, 100, 250 and 1000 ppm). Briefly, 10 g of treated bran were placed in plastic cylindrical vials together with 10 T. molitor adults, 10 large or 10 small larvae. Untreated bran served as control. Mortality was recorded after 7, 14 and 21 d of exposure. After this interval, vials with larvae were examined for adult emergence once a week. Based on our results, adult survival was not significantly affected by DE application. Similarly, mortality of small and large larvae was low, regardless of the exposure interval and the DE dose. Finally, adult emergence was in most cases not significantly affected by the DE treatment in both bioassays with small and large larvae. In general, the results of the present study clearly illustrate that the DE doses used here do not drastically affect adults and larvae of T. molitor. Considering the increased interest for the production of T. molitor at a global scale, and given that this species is typically reared on commodities that are suitable for the development of other major stored product insects, the addition of small doses of DEs in rearing material may be used as a means to mitigate the “cross-infestation” in T. molitor-producing lines by other storage insect species.

Effect of dispenser type, trap design and placement on catches of pine-tree lappet moth, Dendrolimus pini

Dendrolimus pini is one of the most harmful defoliators of Scots pine in Poland and other countries in Europe and Central Asia. The monitoring of this insect needs to be improved and to include the use of pheromone traps. Laboratory studies were conducted to compare changes in the residual amounts of (Z,E)-5,7-dodecadienal and (Z,E)-5,7-dodecadien-1-ol, the major components of the D. pini pheromone, in four types of dispensers. The two most promising dispensers, red rubber cylindrical dispensers (rubber cylinders) and polyethylene vials, were tested in the field for their ability to attract D. pini males. In addition, the effects of trap type (sticky wing, non-sticky cross-vane, bucket, funnel and modified gypsy moth milk carton) and height of trap placement (1.5 m, 5–6 m and tree crown) on trap catches were tested in the field. The vials provided the longest half-lives for both the aldehyde and alcohol under laboratory conditions. These dispensers were also significantly more effective in attracting D. pini males to the traps than the rubber cylinders in the field experiment. The cross-vane and bucket traps were the most effective among the tested traps. The height of trap placement had a significant effect on catches, with more males caught in traps that were hung at 5–6 m above the ground than those hung in the tree crowns. Our results may be useful for developing a monitoring system for D. pini in Europe and other regions where it occurs.

Population Growth of Alphitobius diaperinus (Coleoptera: Tenebrionidae) on Various Commodities.

The lesser mealworm, Alphitobius diaperinus (Panzer), is a serious pest, but at the same time has been authorized in European Union (EU) for feed in aquaculture. In this study, we investigated, in laboratory bioassays, the population growth of this species, on a wide variety of commodities. In four series of bioassays, we studied the development of A. diaperinus population on various intact cereal grains, on soft wheat grains with different percentages of cracked kernels, on non-grain amylaceous commodities and on a variety of non-amylaceous commodities. Briefly, 20 g of each commodity were put separately inside plastic cylindrical vials. Then, 20 A. diaperinus adults were placed inside each vial and all vials were incubated at 30°C and 55% r.h. After 30 d, the vials were opened and the progeny production was evaluated. Alphitobius diaperinus showed a clear preference in amylaceous commodities, but in contrast, poor development was recorded on the non-amylaceous commodities tested. Hence, it developed well in most of the cereal intact grains tested, with the hard and soft wheat being the most suitable. Additionally, most non-grain amylaceous commodities were suitable, to a various degree, for the population growth of A. diaperinus. The increase of the percentage of cracked wheat positively affected the population growth of A. diaperinus. To our knowledge, this is the first study that examined the suitability of a wide range of commodities for the population growth of A. diaperinus.

Evaluation of image quality and recovery coefficient of corn starch-bonded Rhizophora spp. particleboards as phantom for SPECT/CT imaging

The aim of this study was to evaluate the performance of corn starch-bonded Rhizophora spp. particleboards as phantom for SPECT/CT including the image contrast, source dimension ratio and recovery coefficient values. Phantom set made of the Rhizophora spp. particleboards was constructed according to the Jaszczak phantom commonly used in SPECT/CT with external dimension of 22 and 18 cm diameter and length respectively. Cylindrical vials with different diameter sizes filled with 99mTc unsealed source were inserted in drilled holes of the constructed particleboards phantom. The particleboards phantom was scanned by using SPECT/CT scanning mode and the SPECT images were reconstructed using clinical protocol. The results showed that the contrast value, source dimension ratio and recovery coefficient of Rhizophora spp. particleboards in good agreement with Jaszczak phantom. The overall results showed an excellent agreement of performance between corn starch-bonded Rhizophora spp. particleboards to the Jaszczak (water) as standard phantom material. The overall results indicated that the corn starch-bonded Rhizophora spp. can be highly recommended to be used as tissue-equivalent phantom material for Quality Assurance and dosimetry works in SPECT/CT imaging.

3D gel dosimeters offer the potential for real-time quality assurance in MR-IGRT

To investigate the use of 3D gel dosimeters for real-time quality assurance (QA) in MR-image guided radiotherapy (MR-IGRT). Polymer gel dosimeters were prepared in cylindrical glass vials (5 cm diameter, 4 cm height) by MGS Research Inc. (Madison, CT) and kept at room temperature. Fricke-type gel dosimeters were made in-house (8.5 cm diameter, 6 cm height) and stored at 4⁰C for 24 hours prior to irradiation. Two separate irradiation setups were used for this study. Polymer gels were irradiated at isocenter distance at 6 cm depth inside a full phantom. A dose of 15 Gy was delivered with an integrated 1.5 T MRI – 7 MV linear accelerator system (MR-Linac). Fricke gels were irradiated in air to 10 Gy with a gantry angle of 0⁰ and to an additional 20 Gy with a gantry angle of 270⁰ in the center of the dosimeter. MR images were acquired in real-time for both setups using a balanced-Fast Field Echo (b-FFE) sequence. The sequence was started 30 seconds before irradiation and was stopped 30 seconds and 1 minute after irradiation for polymer gels and Fricke gels, respectively. Polymer gels were imaged with TR/TE = 3.4/1.7 ms and a temporal resolution of 277 ms. TR/TE = 4.4/2.2 ms and a temporal resolution of 1800 ms was selected for Fricke gels. Signal intensities (SI) inside and outside the radiation field were measured on all MR images. The difference in SI was calculated and normalized to the maximum value that was measured at the end of image acquisition. For both polymer and Fricke gels, the difference in SI was measured as early as the beam was turned on. The SI difference measured with polymer gels increased logarithmically up to 97% of the maximum value at the completion of the exposure. The ongoing polymerization of the gel until 30 seconds after beam-off was indicated by the slow, continuous logarithmic increase in SI differences and appeared to have reached a plateau at the end of image acquisition. The oxidation reaction of the Fricke gels continued after the exposure was completed, reaching a maximum at 1 minute following beam off. The SI difference increased linearly up to 32% of the maximum value with the gantry at 0⁰ and continued to increase linearly from 33% to 90% of maximum after the gantry was rotated to 270⁰. The appearance of a difference in SI at beam initiation showed that both gels reacted immediately to the delivered radiation. These results encourage further investigation and use of the gels for QA of MR-IGRT treatment units such as the MR-Linac, and especially for real-time QA. An optimization of the real-time imaging parameters is recommended to lower the noise of the MR images and obtain more qualitative and quantitative data.

An FIM-Based Long-Term In-Vial Monitoring System for Drosophila Larvae.

Drosophila larvae are an insightful model and the automated analysis of their behavior is an integral readout in behavioral biology. Current tracking systems, however, entail a disturbance of the animals, are labor-intensive, and cannot be easily used for long-term monitoring purposes. Here, we present a novel monitoring system for Drosophila larvae, which allows us to analyze the animals in cylindrical culture vials. By utilizing the frustrated total internal reflection in combination with a multi-camera/microcomputer setup, we image the complete housing vial surface and, thus, the larvae for days. We introduce a calibration scheme to stitch the images from the multi-camera system and unfold arbitrary cylindrical surfaces to support different vials. As a result, imaging and analysis of a whole population can be done implicitly. For the first time, this allows us to extract long-term activity quantities of larvae without disturbing the animals. We demonstrate the capabilities of this new setup by automatically quantifying the activity of multiple larvae moving in a vial. The accuracy of the system and the spatio-temporal resolution are sufficient to obtain motion trajectories and higher level features, such as body bending. This new setup can be used for in-vial activity monitoring and behavioral analysis and is capable of gathering millions of data points without both disturbing the animals and increasing labor time. In total, we have analyzed 107 671 frames resulting in 8650 trajectories, which are longer than 30 s, and obtained more than 4.2 × 106 measurements.

Effect of two TiO2 nanoparticles on the growth of unicellular green algae using the OECD 201 test guideline: influence of the exposure system

ABSTRACTThis work aimed at assessing the influence of different exposure systems to perform the commonly used OECD 201 freshwater algal growth inhibition test in the context of nanoparticles hazard assessment. Two distinct TiO2 nanoparticles were considered and three different exposure systems were investigated: Erlenmeyers flasks and 24-well microplates (both using an orbital shake system), and an alternative system using cylindrical vials and magnetic stirring. All three systems are in accordance with the OECD 201 test guideline recommendations. We concluded that the exposure systems applied to achieve the test can substantially affect the ecotoxicological results and the subsequent calculated ECx. The selected systems influenced both the interaction between algal cells and TiO2 nanoparticles as well as the growth inhibition recorded. Disparities in ecotoxicity relative to the TiO2 nanoparticles tested were also observed and are finally discussed.

Modular vaccine packaging increases packing efficiency

BackgroundWithin a typical vaccine supply chain, vaccines are packaged into individual cylindrical vials (each containing one or more doses) that are bundled together in rectangular “inner packs” for transport via even larger groupings such as cold boxes and vaccine carriers. The variability of vaccine inner pack and vial size may hinder efficient vaccine distribution because it constrains packing of cold boxes and vaccine carriers to quantities that are often inappropriate or suboptimal in the context of country-specific vaccination guidelines. MethodsWe developed in Microsoft Excel (Microsoft Corp., Redmond, WA) a spreadsheet model that evaluated the impact of different packing schemes for the Benin routine regimen plus the introduction of the Rotarix vaccine. Specifically, we used the model to compare the current packing scheme to that of a proposed modular packing scheme. ResultsConventional packing of a Dometic RCW25 that aims to maximize fully-immunized children (FICs) results in 123 FICs and a packing efficiency of 81.93% compared to a maximum of 155 FICs and 94.1% efficiency for an alternative modular packaging system. ConclusionsOur analysis suggests that modular packaging systems could offer significant advantages over conventional vaccine packaging systems with respect to space efficiency and potential FICs, when they are stored in standard vaccine carrying devices. This allows for more vaccines to be stored within the same volume while also simplifying the procedures used by field workers to pack storage devices. Ultimately, modular packaging systems could be a simple way to help increase vaccine coverage worldwide.

SU-E-T-105: Development of 3D Dose Verification System for Volumetric Modulated Arc Therapy Using Improved Polyacrylamide-Based Gel Dosimeter

Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl2). Methods: PAGAT gel containing MgCl2 as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 T MRI system (GE), and dose calibration curves were obtained using T2 relaxation rate (R2 = 1/T2). Dose rate (100-600 MU min−1) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm3) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.

SU-E-T-231: Measurements of Gold Nanoparticle-Mediated Proton Dose Enhancement Due to Particle-Induced X-Ray Emission and Activation Products Using Radiochromic Films and CdTe Detector

Purpose: There have been several reports of enhanced cell-killing and tumor regression when tumor cells and mouse tumors were loaded with gold nanoparticles (GNPs) prior to proton irradiation. While particle-induced xray emission (PIXE), Auger electrons, secondary electrons, free radicals, and biological effects have been suggested as potential mechanisms responsible for the observed GNP-mediated dose enhancement/radiosensitization, there is a lack of quantitative analysis regarding the contribution from each mechanism. Here, we report our experimental effort to quantify some of these effects. Methods: 5-cm-long cylindrical plastic vials were filled with 1.8 mL of either water or water mixed with cylindrical GNPs at the same gold concentration (0.3 mg Au/g) as used in previous animal studies. A piece of EBT2 radiochromic film (30-µm active-layer sandwiched between 80/175-µm outer-layers) was inserted along the long axis of each vial and used to measure dose enhancement due to PIXE from GNPs. Vials were placed at center-of-modulation (COM) and 3-cm up-/down-stream from COM and irradiated with 5 different doses (2–10 Gy) using 10-cm-SOBP 160-MeV protons. After irradiation, films were cleaned and read to determine the delivered dose. A vial containing spherical GNPs (20 mg Au/g) was also irradiated, and gamma-rays from activation products were measured using a cadmium-telluride (CdTe) detector. Results: Film measurements showed no significant dose enhancement beyond the experimental uncertainty (∼2%). There was a detectable activation product from GNPs, but it appeared to contribute to dose enhancement minimally (<0.01%). Conclusion: Considering the composition of EBT2 film, it can be inferred that gold characteristic x-rays from PIXE and their secondary electrons make insignificant contribution to dose enhancement. The current investigation also suggests negligible dose enhancement due to activation products. Thus, previously-reported GNP-mediated proton dose enhancement/radiosensitization needs to be attributed to one or more of the other mechanisms listed earlier. Supported in part by NIH/NCI grant R01CA155446;This investigation was supported in part by NIH/NCI grant R01CA155446.

Measuring SPIO and Gd contrast agent magnetization using 3 T MRI

Traditional methods of measuring magnetization in magnetic fluid samples, such as vibrating sample magnetometry (VSM), are typically limited to maximum field strengths of about 1 T. This work demonstrates the ability of MRI to measure the magnetization associated with two commercial MRI contrast agents at 3 T by comparing analytical solutions to experimental imaging results for the field pattern associated with agents in cylindrical vials. The results of the VSM and fitted MRI data match closely. The method represents an improvement over VSM measurements since results are attainable at imaging field strengths. The agents investigated are Feridex, a superparamagnetic iron oxide suspension used primarily for liver imaging, and Magnevist, a paramagnetic, gadolinium-based compound used for tumors, inflammation and vascular lesions. MR imaging of the agents took place in sealed cylindrical vials in the presence of a surrounding volume of deionized water where the effects of the contrast agents had a measurable effect on the water's magnetization in the vicinity of the compartment of contrast agent. A pair of phase images were used to reconstruct a B(0) fieldmap. The resultant B(0) maps in the water region, corrected for shimming and container edge effects, were used to predict the agent's magnetization at 3 T. The results were compared with the results from VSM measurements up to 1.2 T and close correlation was observed. The technique should be of interest to those seeking quantification of the magnetization associated with magnetic suspensions beyond the traditional scope of VSM. The magnetization needs to be sufficiently strong (M(s) >or= 50 Am(2)/kg Fe for Feridex and X(m) >or=5 x 10(-5) m(3)/kg Gd for Magnevist) for a measurable dipole field in the surrounding water. For this reason, the technique is mostly suitable for undiluted agents.

Evaluation of dose delivery accuracy of gamma knife using MRI polymer gel dosimeter in an inhomogeneous phantom

Polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. MRI Polymer gel dosimeters are tissue equivalent and can act as a phantom material. Because of high dose response sensitivity, the MRI was chosen as readout device.In this study dose profiles calculated with treatment-planning software (LGP) and measurements with the MR polymer gel dosimeter for single-shot irradiations were compared.A custom-built 16 cm diameter spherical plexiglas head phantom was used in this study.Inside the phantom, there is a cubic cutout for insertion of gel phantoms and another cutout for inserting the inhomogeneities. The phantoms were scanned with a 1.5T MRI (Siemens syngo MR 2004A 4VA25A) scanner. The multiple spin-echo sequence with 32 echoes was used for the MRI scans. Calibration relations between the spin-spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the PAGAT polymer gel from the same batch as for the spherical phantom.1D and 2D data obtained using gel dosimeter for homogeneous and inhomogeneous phantoms were compared with dose obtained using LGP calculation.The distance between relative isodose curves obtained for homogeneous phantom and heterogeneous phantoms exceed the accepted total positioning error (>±2mm).The findings of this study indicate that dose measurement using PAGAT gel dosimeter can be used for verifying dose delivering accuracy in GK unit in presence of inhomogeneities.

Detection efficiency calculation for photons, electrons and positrons in a well detector. Part II: Analytical model versus simulations

A comparison is made between the results of Monte Carlo simulations and a new analytical model (cf. Part I) for the detection efficiency of a well-type NaI detector for photons, electrons and positrons in the energy range of 0.01MeV–10MeV. Using MCNP 5.1.40, GEANT3 and PENELOPE simulation results as benchmark, it was found that the analytical model was quite successful at reproducing the total detection efficiency for photons and positrons, and at giving rough indications on the photon peak-to-total ratio and the electron detection efficiency. It was also able to deal with cylindrical volume sources and vials, eccentric positioning of the source inside the detector well and the possible contribution of scattering or pair production in the surrounding lead shield.

SU‐FF‐T‐413: The Response Of The Fricke Dosimeter To Sunlight

Purpose: To test the Fricke dosimeter response to sunlight near the Equator. Materials and Methods: Fifty cylindrical glass vials filled with Fricke solution (FS) were placed horizontally floating in a polyethylene water tank in such a way that half of their volumes were underneath the water. These vials were exposed to sunlight 5 hours per day for a period of 10 days in the city of Recife, Brazil (8°3′S, 34°56′W). During the course of the exposure the water temperature was monitored by means of a thermocouple. Every day 5 vials were removed from the water thank, and their optical densities (OD) were measured using a spectrophotometer. The OD was corrected for the mean temperature of the water tank during exposure and the solution's temperature during readout. Vials with Fricke solution were also kept in an oven for 5 hours per day at the same mean temperature as those exposed to sunlight. The change in the OD caused by the sunlight was obtained by subtracting the OD of the exposed vials from the corresponding ones stored in the oven. Both sets of vials were the stored in a refrigerator at 15°C until the next exposure. Results: The mean temperature during the irradiation was 33 ± 1.4 °C. The net OD of the Fricke solution was proportional to the sunlight exposure time with a slope of 0.0010 ODh−1 (r2=0.99). For a 50 hours exposure the net OD was 0.05 (± 5%), which would correspond to an exposure of 14 Gy from a source which produces 0.000023 M of . Conclusions: The FS is relatively sensitive to direct sunlight exposure. Because this dosimeter relies on the oxidation of to by free radicals, it could be evaluated as means to estimate the free radical exposure in humans for various sunlight conditions.

Evaluation of dose delivery accuracy of Gamma Knife by polymer gel dosimetry

The BANG™ polymer gel dosimeter was used to evaluate 3D absorbed dose distributions in tissue delivered with Gamma Knife stereotactic radiosurgery systems. We compared dose distributions calculated with Leksell GammaPlan (LGP) treatment‐planning software with dose distributions measured with the polymer gel dosimeter for single‐shot irradiations. Head‐sized spherical glass vessels filled with the polymer gel were irradiated with Gamma Knife. The phantoms were scanned with a 1.0T MRI scanner. The Hahn spin‐echo sequence with two echoes was used for the MRI scans. Calibration relations between the spin‐spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the polymer gel from the same batch as for the spherical phantom. We made voxel‐by‐voxel comparisons of measured and calculated dose distributions for 31×31×31 dose matrix elements. With the 3D dose data we calculated the tumor control probability (TCP) and normal tissue complication probability (NTCP) for a simple model. For the maximum dose of 100 Gy, the mean and one standard deviation of differences between the measured and the calculated doses were the following: –0.38±4.63 Gy,1.49±2.77 Gy, and –1.03±4.18 Gy for 8‐mm, 14‐mm, and 18‐mm collimators, respectively. Tumor control probability values for measurements were smaller than the calculations by 0% to 7%, whereas NTCP values were larger by 7% to 24% for four of six experiments.PACS numbers: 87.53.‐j, 87.53.Dq, 87.53.Ly

Noise in polymer gel measurements using MRI.

With the development of conformal radiotherapy, particularly intensity modulated radiation therapy (IMRT), there is a clear need for multidimensional dosimeters. A commercial polymerizing gel, BANG-2 gel (MGS Research, Inc., Guilford, CT), has recently been developed that shows potential as a multi-dimensional dosimeter. This study investigates and characterizes the noise and magnetic resonance (MR) artifacts from imaging BANG-2 gels. Seven cylindrical vials (4 cm diam, 20 cm length) were irradiated end on in a water bath and read using MRI (B0=1.5 T, TE=20 ms/100 ms, TR=3000 ms). The gel calibration compared the measured depth-dose distributions in water against the change in solvent-proton R2 relaxivity of the gel. A larger vial (13 cm diam, 14 cm length) was also irradiated to test the calibration accuracy in a vial of sufficient volume for dose distribution measurements. The calibration curve proved accurate to within 1.3% in determining the depth dose measured by the larger vial. An investigation of the voxel-to-voxel (IXIX 3 mm3) noise and sensitivity response curve showed that the voxel-to-voxel variation dominated the dose measurement uncertainty. The voxel-to-voxel standard deviation ranged from 0.2 Gy for the unirradiated gel to 0.7 Gy at 20 Gy. Slice-to-slice R2 magnitude deviations were also observed corresponding to 0.2 Gy. These variations limited the overall accuracy of the gel dose measurements and warrant an investigation of more accurate MR readout sequences.

Lens correction for the implementation of cylindrical vessels in a spectrophotometer

A simple optical correction system for allowing cylindrical vials to be used as sample vessels in a spectrophotometer is described. Light within the spectrophotometer enters and exits the liquid samples through the curved glass wall of the vials. Absorption spectra can be obtained conveniently without the need for solution transfer into standard rectangular spectrophotometer cuvettes.

Dielectric Properties of Raw and Cooked Chicken Egg at 3 GHz, 23 — 140°C

We report the dielectric properties of fresh and cooked chicken egg at 3 GHz over the temperature range 23<T< 140°C. The dielectric properties of egg white are discussed in terms of its potential as a browning agent in microwave cooking. A dynamic cavity perturbation technique has been used; constituents were measured in cylindrical vials as they were heated, and then reheated from the cooked state. We discuss the precision and accuracy of the method in general as well as the predictable variability of this particular material. The measurement technique is simple and convenient; it has precision and acceptable accuracy (better than, we estimate, ± 7% over a wide range of values of €′, €”) for viscous fluids and pastes, which include most browning agents and susceptor materials used in microwave cooking.