Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans.

This study evaluated the effect of pitch on 256-slice helical computed tomography (CT) scans. Cylindrical water phantoms (CWP) were measured using axial and helical scans with various pitch values. The surface dose distributions of CWP were measured, and reconstructed images were obtained using filtered back-projection (FBP) and iterative model reconstruction (IMR). The image noise in each reconstructed image was decomposed into a baseline component and another component that varied along the z-axis. The baseline component of the image noise was highest at the center of the reconstructed image and decreased toward the edges. The normalized 2D power spectra for each pitch were almost identically distributed. Furthermore, the ratios of the 2D power spectra for IMR and FBP at different pitch values were obtained. The magnitudes of the components varying along the z-axis were smallest at the center of the reconstructed image and increased toward the edge. The ratios of the 3D power spectra on the fx axis for IMR and FBP at different pitch values were obtained. The results showed that the effect of the pitch was related to the component that varied along the z-axis. Furthermore, the pitch had a smaller effect on IMR than on FBP.

Development of a novel acetyl glucose-modified gefitinib derivative to enhance the radiosensitizing effect.

Various radiosensitizers are being developed to increase the radiation sensitivity of hypoxic cancer cells, which show resistance to radiation. Previously, we demonstrated that an acetyl glucose-modified nitroimidazole derivative showed a high radiosensitizing effect by inhibiting glucose uptake and glycolysis. Based on this finding, we designed and synthesized novel sugar hybrid radiosensitizers, wherein acetyl glucose was introduced into gefitinib. Among them, UTX-114 had higher autophosphorylation and radiosensitizing activity than gefitinib and inhibited glucose uptake. This result supports our hypothesis that an acetyl glucose moiety improves the radiosensitizing effect of the drug, and UTX-114 can be expected to be a leading compound with a radiosensitizing effect.

Usability of detecting delivery errors during treatment of prostate VMAT with a gantry-mounted transmission detector.

Volumetric-modulated arc therapy (VMAT) requires highly accurate control of multileaf collimator (MLC) movement, rotation speed of linear accelerator gantry, and monitor units during irradiation. Pretreatment validation and monitoring of these factors during irradiation are necessary for appropriate VMAT treatment. Recently, a gantry mounted transmission detector "Delta4 Discover® (D4D)" was developed to detect errors in delivering doses and dose distribution immediately after treatment. In this study, the performance of D4D was evaluated. Simulation plans, in which the MLC position was displaced by 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm from the clinically used original plans, were created for ten patients who received VMAT treatment for prostate cancer. Dose deviation (DD), distance-to-agreement (DTA), and gamma index analysis (GA) for each plan were evaluated by D4D. These results were compared to the results (DD, DTA and GA) measured by Delta4 Phantom + (D4P). We compared the deviations between the planned and measured values of the MLC stop positions A-side and B-side in five clinical cases of prostate VMAT during treatment and measured the GA values. For D4D, when the acceptable errors for DD, DTA, and GA were determined to be ≤3%, ≤2 mm, and ≤3%/2 mm, respectively, the minimum detectable errors in the MLC position were 2.0, 1.5, and 1.5 mm based on DD, DTA, and GA respectively. The corresponding minimum detectable MLC position errors were 2.0, 1.0, and 1.5 mm, respectively, for D4P. The deviation between the planned and measured position of MLC stopping point of prostate VMAT during treatment was stable at an average of -0.09 ± 0.05 mm, and all GA values were above 99.86%. In terms of delivering doses and dose distribution of VMAT, error detectability of D4D was comparable to that of D4P. The transmission-type detector "D4D" is thus suitable for detecting delivery errors during irradiation.

One-Step Synthesis of Cyclophanes as Crystalline Sponge and Their [2]Catenanes through SN Ar Reactions.

This work reports that cyclophanes and their [2]catenanes were synthesized by the SN Ar reactions of disubstituted adamantanes bearing halophenol units and 3,6-dichlorotetrazine in moderate yields. In the crystalline state, the cyclophanes had hexagonal structures with a cavity. The [2]catenanes were composed of two macrocycles that were singly interlocked and orthogonally arranged, indicating the construction from eight component molecules through eight C-O bonds in a one-step reaction in up to 33 % yield. The cyclophanes were assembled to afford a supramolecular organic framework in the solid state, which exhibited permanent intrinsic porosity and adsorption of leaf alcohol or aldehyde in a single-crystal to single-crystal fashion. The molecular structures of the liquid guests were determined by single-crystal X-ray analysis. The formation of catenanes and the use of cyclophane-based porous crystals in the crystalline sponge method may be largely ascribed to the solvophobic effects and the van der Waals interactions that originate in the aliphatic and bulky nature of the adamantane units.

Synthesis and chiroptical properties of cylindrical macrocycles comprising two calix[3]aramide moieties.

Calix[3]aramide-based cylindrical macrocycles were synthesized by the one-step amide coupling reaction of a monomer containing two meta-alkylaminobenzoic acid units linked by para-phenylene bridges. The major products included a meso-form and an enantiomeric pair, with stereochemistry derived from the direction of the amide bonds and their fixed conformation. Mirror-image ECD, VCD, and CPL spectra were observed in the enantiomeric pair and the absolute structure was determined by comparing measured and calculated ECD and VCD spectra.

Hollow and Solid Spheres Assembled from Functionalized Macrocycles Containing Adamantane.

An adamantane-based macrocycle possessing eight hydroxyl groups (1) was synthesized, in which the macrocyclic framework comprises two disubstituted adamantane molecules bearing phenyl derivatives connected to two biphenylene spacers by oxygen atoms. Furthermore, functionalized macrocycles containing methyl (2) and methoxycarbonylmethyl (3) groups were prepared. From the X-ray crystallographic analysis, the backbone of the macrocycles in all crystals had a nearly hexagonal shape with a cavity and these macrocycles could be arranged into different tubular structures dependent on the substituents. In acetone, macrocycle (1) formed stable hollow spherical aggregates with multilayer membranes. In contrast, macrocycle (3) exhibited no production of self-assembled materials in chloroform. The addition of hexane into the solution caused the generation of solid spheres and their fused network aggregates, which were finally transformed into crystals owing to the solvent effects.

Hollow sphere formation from a three-dimensional structure composed of an adamantane-based cage.

An adamantane-based cage with a three-dimensional (3D) framework was synthesized by the copper-mediated acetylene coupling reaction, in which two 1,3,5-triethynyladamantane units were linked by phenyldiacetylenic bridges possessing ester groups. X-ray crystallography revealed that the cage has an internal space and accommodates a solvent molecule, which afforded molecular networks through CH/O interactions between cage molecules. Furthermore, the cage containing six ester groups spontaneously self-assembled into hollow spherical aggregates with an average diameter of 230 nm in a mixed solvent.

Experience of low volume split-dose bowel preparation for computed tomography colonography.

We propose a new preparation method for the computed tomography colonography (CTC). This method consists of giving a small volume (400 ml) of cleansing solution on the day before the examination and the same volume of solution on the day of the examination [low volume split-dose (LVSD) method]. Using this method, we compared the volume of residual fluid in the colon, the CT value of the residual fluid, and the quality of stool tagging with those for patients undergoing the conventional bowel preparation method. Polyp detectability of the CTC using this method and the acceptability of the preparation were also investigated. The volume of residual fluid in the colon with this method was smaller than that with the conventional method. The CT value of the residual fluid with this method was higher than that with the conventional method. Visual assessment of the quality of stool tagging with this method gave similar results to those obtained using the conventional method. The sensitivities were 95% for 5-10 mm polyps and 100% for polyps larger than 10 mm. The PPVs were 91% for 5-10 mm polyps and 100% for polyps larger than 10 mm. These results appear to be as good as in previous reports. In the questionnaires, about 80% of the answers were favorable regarding the volume and the taste of laxative. We conclude that LVSD bowel preparation method for CTC maintains polyp detectability and is better tolerated.

Comparative analysis of two dose-volume histogram prediction tools for treatment planning in volumetric-modulated arc therapy: A multi-planner study.

The increase in high-precision radiation therapy, particularly volumetric-modulated arc therapy (VMAT), has increased patient numbers and expanded treatment sites. However, a significant challenge in VMAT treatment planning is the inconsistent plan quality among different planners and facilities. This study explored the use of dose-volume histogram (DVH) prediction tools to address these disparities, specifically focusing on RapidPlan (Varian Medical Systems) and PlanIQ (Sun Nuclear). RapidPlan predicts achievable DVHs and automatically generates optimization objectives. While it has demonstrated organ-at-risk (OAR) dose reduction benefits, the quality of the plan used to build its model significantly affects its predictions. On the other hand, PlanIQ offers ease of use and does not require prior model-building. Five planners participated in this study, each creating two treatment plans: one referencing RapidPlan and the other using PlanIQ. The planners had the freedom to adjust parameters while referencing the DVH predictions. The plans were evaluated using "Plan Quality Metric" (PQM) scores to assess the planning target volume excluding the rectum and OARs. The results revealed that RapidPlan-referenced plans often outperformed PlanIQ-based plans, with less interplanner variability. PlanIQ played a pivotal role in the construction of the RapidPlan model. This study is the first to compare plans generated by multiple planners using both tools. This study provides insights into optimizing treatment planning by considering the characteristics of both RapidPlan and PlanIQ.

[Clinical evaluation of automatic contours for head and neck region using deformable image registration software].

The purpose of this study was to clinically evaluate the automatic outline extraction properties using general-purpose deformable image registration (DIR) software for the head and neck region. To this end, we evaluated the following: (1) the difference between manual outline extraction carried out by a radiation therapy specialist and automatic outline extraction using the DIR software, and (2) the precision of the automatic outline extraction for the diachronic figure change and change in the organ shape. The manually-extracted outline and that extracted using the DIR software closely resembled each other at 0.70. Further, in the same case, the automatic outline extraction precision of the DIR software was greater at about 0.80. Our findings suggest DIR software to be useful for lessening the work involved in outline extraction.

Measurements of multidetector CT surface dose distributions using a film dosimeter and chest phantom.

PURPOSE: This paper uses film dosimetry to investigate the relationship between multiple scan parameters of multidetector CT with automatic exposure control (AEC) and the surface dose distribution produced on a chest phantom. METHODS: The characteristics of the film used in the film dosimeter were evaluated with regard to linearity, relative film response, and directional dependence. Measurements with an ionization chamber dosimeter and a water phantom were used to evaluate the accuracy of the film dosimeter measurements and to validate the dose profile measurements while changing the tube current, detector dimensions and pitch. When using AEC, the surface dose distribution on the chest phantom was analyzed while changing the detector dimensions and pitch. RESULTS: The linearity, relative film response, and directional dependence of the film were established. The measurement difference between the film dosimeter and ionization chamber dosimeter was within +/- 5% and the dose profile measurement results were validated. It was found that the surface dose distribution changed helically in the direction of the body axis depending on the scan parameters and the phantom. CONCLUSIONS: Using a film dosimeter, the relationship between various multidetector CT scan parameters and the surface dose distribution on a chest phantom was investigated and clarified.

Fibrous architectures and organogels of tris(phenylethynylphenyl)adamantane molecules with amino acid moieties: their solvato-controlled helicity induction.

Non-disk-shaped molecules self-assembled to form columnar-type helical aggregates with gel ability through π-stacking interactions among the central tris(phenylethynylphenyl)adamantane moieties, hydrogen-bonding interactions among the alanine parts with amide groups, and van der Waals interactions among the alkyl groups in nonpolar n-alkanes. The structural analyses of fibrous architectures with helicity were examined by FTIR, UV-Vis, and circular dichroism (CD) spectroscopy and FE-SEM measurements. In contrast, the formation of fibrous structures was observed from adamantane-based tripodal molecules due to solvophobic interactions in polar EtOH, which showed no detectable Cotton effect in the CD measurement, indicating the induction of solvato-controlled helicity in the self-assembly process.

Estimation of imaging intervals and intrafraction displacement in CyberKnife image-guided radiotherapy for intracranial lesions.

PURPOSE: A recent report by the American Association of Physicists in Medicine Task Group 75 and 180 provided imaging dose estimates for image-guided CyberKnife radiotherapy. However, to our knowledge, there have been no concrete demonstrations of imaging intervals that are directly linked to exposure dose. We hypothesized that setting a rational standard may be clearer through a balance of treatment accuracy and reducing imaging doses if the margin of the planned treatment volume is controlled through the imaging interval. This study was conducted to simulate the association between the imaging interval and intrafraction displacement and to estimate a reasonable internal margin (IM). METHODS: We retrospectively analyzed data from 21 shell-fixed heads of patients treated with CyberKnife G3 using our dedicated monitoring system. This system comprises pressure sensors that can monitor head displacement every 0.2 s in the absence of any imaging dose. First, the root sum square of head displacements was calculated in 76 treatment fractions with an imaging interval of 10-1440 s. The cumulative frequency of a root sum square displacement (which was less than the IM) was evaluated in image verifications that were undertaken 546 274 times for every imaging interval. RESULTS: We found that the mean values and SDs of the displacement were larger in proportion to the imaging interval (p < 0.002) and that the maximum displacements did not correlate in any combination within 720 s (p > 0.056). The cumulative frequencies of displacement of 0.6 and 1.4 mm (i.e., less than an IM) were 99.2% and 99.1% for imaging intervals of 10 and 360 s, respectively. CONCLUSIONS: In the current study, we found that imaging intervals were directly proportional to intrafraction displacement and that there was no correlation in any combination within 720 s. Imaging intervals for an IM of 0.6 and 1.4 mm were 10 and 360 s, respectively, with a 99% confidence interval of intrafraction displacement. With CyberKnife M6 or a previous version of this system, the imaging dose could be reduced by 0.4760 mSv per 24-min treatment as the imaging dose ranged from 0.4896 to 0.0136 mSv for imaging intervals of 10 and 360 s with an IM of 0.6 and 1.4 mm, respectively. A rational method that includes X-ray imaging guidance may be achieved with modulation of the imaging interval via the CyberKnife system.

Influence of distant scatterer on air kerma measurement in the evaluation of diagnostic X-rays using Monte Carlo simulation.

The evaluation of the entrance surface dose (ESD) ensures safe radiation doses for X-ray imaging patients. The air kerma free-in-air value used to estimate ESD may be affected by those X-rays that scatter from the scatterer placed behind the chamber at the time of measurement, thereby leading to assessment errors. Therefore, the influence of scattered radiation on air kerma measurements was investigated. Monte Carlo simulations were performed for various detector-to-scatterer distances and scatterer materials. The simulation results were compared with actual measurements to confirm the simulation accuracy. The source-chamber distance was set to 50 and 100 cm for the experimental measurements and simulation, respectively, and the chamber-scatterer distance was varied. The Monte Carlo simulation results reproduced the actual measurements with an accuracy of 3.5%. The effect of backscattering varied with the tube voltage and irradiation field size. The effect was observed in the order of prominence for the following scatterer materials: water-equivalent phantom, acrylic, concrete, lead, and iron. Furthermore, this effect decreased exponentially with increasing chamber-scatterer distance. For a field size of 10 × 10 cm2, the finite-distance backscatter factor decreased with an increasing chamber-scatterer distance for all materials. The cause of backscattering in diagnostic X-ray energy regions differs depending on the scatterer material, as well as the photon energy and field size. Backscattering decreases exponentially as the distance between the detector and scatterer increases.

Evaluation of sodium orthovanadate as a radioprotective agent under total-body irradiation and partial-body irradiation conditions in mice.

PURPOSE: Our previous study indicated that sodium orthovanadate (vanadate), a strong inhibitor of p53, effectively suppressed the lethality from the hematopoietic (HP) and gastrointestinal (GI) syndromes after 12 Gy total-body irradiation (TBI) in mice. This conclusion, however, was inconsistent with the fact that p53 plays a radioprotective role in the intestinal epithelium. The death after TBI of around 12 Gy was attributed to a combined effect of HP and GI syndromes. To verify the effect from prophylactic administration of p53 inhibitor on protection of HP and GI syndromes, in this study, the radioprotective effects from vanadate were investigated in TBI and lower half-body irradiation (partial-body irradiation: PBI) mouse models. METHODS: Female ICR mice were given a single injection of vanadate or vehicle, followed by a lethal dose of TBI or PBI. Radioprotective effects of vanadate against the irradiations were evaluated by analyzing survival rate, body weight, hematopoietic parameters, and histological changes in the bone marrow and intestinal epithelium. RESULTS: TBI-induced HP syndrome was effectively suppressed by vanadate treatment. After TBI, the vanadate-treated mice retained better bone marrow cellularity and showed markedly higher survival rate compared to the vehicle-treated animals. In contrast, vanadate did not relieve loss of intestinal crypts and failed to rescue mice from GI death after PBI. CONCLUSION: Vanadate is a p53 inhibitor that has been shown to be beneficial as a radiation protective agent against HP but was not effective in protecting against acute GI radiation injury.

[Comparison of dose distribution on radiographic film and radiochromic film for intensity modulated radiation therapy].

PURPOSE: Radiographic film is generally used for inspection of dose distribution in intensity modulated radiation therapy (IMRT) at many institutions. However, the distribution of filmless systems can be expected to be used increasingly in the future. Therefore, we confirmed the utility of radiochromic film by comparing it with radiographic film that does not need an automatic processor. RESULT: Difference in does measured by radiographic film and radiochromic film tended to increase in the low does area, but it was limited in a range of 1.5%. CONCLUSION: When the dose distribution was verified in a highly accurate radiation therapy such as IMRT, the results suggested that radiochromic film can be useful in addition to radiographic film.

Self-assembly of an M6L12 coordination cube.

A 3x3x3 nm cubic coordination compound quantitatively self-assembled from 6 palladium ions and 12 bent ligands with a 90 degrees bend angle.

Construction and charge-transfer complexation of adamantane-based macrocycles and a cage with aromatic ring moieties.

Adamantane-based macrocycles and a cage with aromatic ring moieties have been developed and structurally revealed by X-ray crystallographic analysis. The dimerized (1) and trimerized (2) macrocycles of binary molecules based on adamantane with acetylenic aromatic ring moieties were designed and effectively synthesized. Similarly, a cryptand-like macrobicyclic cage (3) was constructed from a trisubstituted adamantane derivative. Single-crystal X-ray analysis revealed that both cyclic compounds have nearly a rectangular shape with or without a solvent molecule in the cavity. The macrobicyclic cage has an inner space and accommodates a chloroform molecule via C-H...pi interactions. Macrocycles and cage encapsulate 1,3,5-trinitrobenzene (4) as an electron-poor guest in a one-to-one complex via charge-transfer interactions in a parallel fashion, and showed the formation of molecular networks such as columns, tubes, 2D layers, and 3D networks composed of two different types through noncovalent interactions in the solid state.

Effect of aromatic-aromatic interactions on the conformational stabilities of macrocycle and preorganized structure during macrocyclization.

The crystal structures and dynamic behavior in solution of aromatic amides containing terphenyl groups were revealed by X-ray crystallographic analysis and VT-NMR measurements. Controlling the synthetic yield and molecular shape of the macrocycles with intramolecular aromatic-aromatic interactions was successfully achieved. N,N'-Diethyl-N,N'-diterphenyl-1,3-benzenedicarboxamide (2) exists in the syn conformation and two terphenyl groups are on the same side of the plane of the central benzene ring due to attractive aromatic-aromatic interactions between the two terphenyl moieties. The yield of the macrocyclization reaction of 1,3-benzenedicarboxylic acid with bis(ethylamino)terphenyl (4) was relatively high (55% yield) because an intermediate in the macrocyclization reaction was preorganized in the syn conformation, which is similar to the diamide 2. On the other hand, N,N'-diethyl-N,N'-diterphenyl-1,4-benzenedicarboxamide (3) exists in the anti conformation and two terphenyl groups are positioned on opposite sides of the plane of the central benzene ring. In contrast to the 1,3-derivative, the yield of the macrocyclization reaction of the 1,4-benzenedicarboxylic acid with the diamine 4 was low (19% yield). Although macrocycle 5 exists in a planar conformation in the crystal and in solution, macrocycle 6 exists in a twisted conformation. A deformation of the twist was induced by a tilted T-shaped aromatic-aromatic interaction between the central phenylene rings of the macrocycle.

In vivo drug screening method of radiosensitizers using tumor-bearing chick embryo.

In radiotherapy, tumor hypoxia is the main factor responsible for treatment resistance, and the development of radiosensitizers that can overcome this is imperative. However, many drugs that are effective in vitro and in vivo fail in clinical trials, and thus it is necessary to develop an animal model that can be used for the correct evaluation of pharmacokinetics and activity. Developing chicken eggs are commonly used in various research fields such as anticancer drug sensitivity tests and cardiotoxicity tests. We examined whether the radiosensitizing activity of etanidazole, as a hypoxic cell radiosensitizer, could be evaluated using tumor-bearing chick embryo. Following the transplantation of mouse mammary carcinoma EMT6 cells on day 11, a solid tumor was formed on day 15 and an evaluation of the time-course of the tumor revealed that the tumor weight was the highest on day 18. The maximum dose of etanidazole that did not affect tumor growth and fetal survival was 1.0mg and the maximum X-ray dose was 8Gy. Etanidazole was intravenously administered 10min prior to single dose X-ray irradiation. A significant tumor growth inhibitory effect was confirmed with 1.0mg of etanidazole in combination with 8Gy X-ray. In the case of mouse colon cancer colon26 cells, the combination of 3.0mg of etanidazole and 2Gy X-ray showed 2.79 times higher radiosensitizing activity than that observed for the control group. These results demonstrate that it is possible to evaluate the activity of radiosensitizers using tumor-bearing chick embryo.