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PubMed1994

Mechanical properties of dry and wet cellulosic and acrylic films prepared from aqueous colloidal polymer dispersions used in the coating of solid dosage forms.

The mechanical properties of dry and wet polymeric films prepared from various aqueous polymeric dispersions were evaluated by a puncture test. They were studied with respect to type of polymer dispersion [cellulosic: Aquacoat and Surelease; acrylic: Eudragit NE, L, RS, and RL 30 D], plasticizer type (water-soluble or water-insoluble), drying or curing conditions, method of film preparation (pseudolatex-vs solvent casting) and ratio of Eudragit RS/RL 30 D in mixed Eudragit RS/RL films. Dry and wet mechanical strengths of the polymeric films depended primarily on the types of the colloidal polymer dispersion and the plasticizer. Films prepared from ethylcellulose dispersions resulted in very weak and brittle films when compared to the acrylic films. Pseudolatex-cast ethylcellulose films showed lower puncture strength and elongation values when compared to those of the solvent-cast films. Curing of the pseudolatex-cast ethylcellulose films had minimal effects on their mechanical properties. Eudragit L 30D, an enteric polymer dispersion, resulted in brittle films in the dry state, but in very flexible films in the wet state because of the plasticization effect of water. Wet Eudragit RS 30 D polymer films plasticized with water-insoluble plasticizers were significantly more flexible than the corresponding wet films plasticized with water-soluble plasticizers. The water-soluble plasticizers leached from the films during exposure to the aqueous medium, while the water-insoluble plasticizers were almost completely retained within the wet films. The low permeability of a water-soluble drug, chlorpheniramine maleate, and the weak mechanical properties of Aquacoat films could suggest osmotic driven/rupturing effects as the release mechanisms from Aquacoat-coated dosage forms.

Acrylates↗
PubMed2000

Skin edge perception in mammograms: a comparison of two film-screen combinations.

The entire skin edge is not always seen on mammograms. The importance of demonstrating the full extent of the breast on a mammogram is uncertain, but there are implications for optimizing film design and use. The new Agfa HDR film has been designed to improve visualization of the skin edge without compromising overall contrast. A quantitative and qualitative comparison between Agfa HDR and the Fuji UMMA film has been performed. A total of 216 mammograms from 54 symptomatic women were analysed. For each view on each woman, one breast was imaged using Fuji UMMA film and the other using Agfa HDR film. The target density achieved on quality control films of PMMA blocks was 1.70 +/- 0.10 for both film types. A radiologist graded the skin edges of all the films as visible, just visible or dark. Measurements were made of the optical densities in the skin edge region and on the fully exposed black part of the film, adjacent to the skin line. 70% of the HDR films had visible skin edges compared with 43% of the UMMA films. 2% of the HDR films had dark skin edges compared with 26% of the UMMA films. Optical densities at the skin edge were broadly similar for the two films and in the range 3.6 +/- 0.3. However, the density of the black part of the Agfa film was about 0.5 higher than with the Fuji film and it appears that this was the main reason the skin edge region was better visualized with the Agfa film.

Female↗
PubMed1996

Dosimetry of high energy photon and electron beams with CEA films.

With all the advantages of film dosimetry in the megavoltage energy range, the use of film as a dosimeter is still limited due to the various difficulties associated with films such as energy dependence, film orientation, and sensitometric nonlinearity. Recently, therapy verification and localization films (CEA TVS and TLF films) from a Swedish manufacturer have become available in vacuum-sealed water-proof packaging in the US. The packaging renders the CEA films useful in a water phantom and ideal for photon and electron dosimetry. A systematic study has been carried out to investigate the potential of dosimetric application of the new films for high energy photon and electron beams. For the TVS films, the characteristic curve is generally energy independent but appears to be dependent on the source of the radiation, i.e., whether it is gamma rays or bremsstrahlung x rays. Compared to Kodak Readypack XV films, the CEA TVS film is linear in optical density over a much larger range of radiation dose. The inter- and intra-variation of the TVS films is less than 2%. For electrons, the characteristic curve is linear over a similar density range as photons but exhibit a slight energy dependence. TVS film is slightly directional dependent on the incident radiation for both photons and electrons. The perpendicular orientation results in higher optical density than the parallel orientation. The differences are within +/- 2% except in the buildup region for photons and in the exponential fall-off region of the electron beams where differences up to 4% are noted. For the CEA TLF film which is about three times faster than the TVS film, the characteristic curve is reasonably linear over the dose range of 0-15 cGy and energy independent within the experimental uncertainty (+/- 5%). Percent depth dose and isodose measurements with the TVS films are in good agreement with ion chamber results.

Biophysical Phenomena↗
PubMed2007

Thin wetting films from aqueous solutions of surfactants and phospholipid dispersions.

The microscopic thin wetting film method was used to study the stability of wetting films from aqueous solution of surfactants and phospholipid dispersions on a solid surface. In the case of tetradecyltrimethylammonium bromide (C(14)TAB) films the experimental data for the receding contact angle, film lifetime, surface potential at the vapor/solution and solution/silica interface were used to analyze the stability of the studied films. It is shown that with increasing C(14)TAB concentration charge reversal occurs at both (vapor/solution and solution/silica) interfaces, which affects the thin-film stability. The spontaneous rupture of the thin aqueous film was interpreted in terms of the earlier proposed heterocoagulation mechanism. The presence of the mixed cationic/anionic surfactants was found to lower contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants hetero-coagulation could arise through the formation of ionic surfactant complexes. The influence of the melting phase-transition temperature T(c) of the dimyristoylphosphatiddylcholine (DMPC) on the stability of thin films from dispersions of DMPC small unilamellar vesicles on a silica surface was studied by measuring the film lifetime and the TPC expansion rate. The stability of thin wetting films formed from dispersions of DMPC small unilamellar vesicles was investigated by the microinterferometric method. The formation of wetting films from diluted dispersions of DMPC multilamellar vesicles was studied in the temperature range 25-32 degrees C. The stability of thin film of lipid vesicles was explained on the basis of hydrophobic interactions. The results obtained show that the stability of wetting films from aqueous solutions of single cationic and mixed cationic-anionic surfactants has electrostatic origin, whereas the stability of the phospholipid film is due to hydrophobic interaction.

Amines↗
PubMed2000

Solubility, tensile, and color properties of modified soy protein isolate films.

Protein solubility (PS) values of different soy protein isolate (SPI) films were determined in water, 0.01 N HCl, 0.01 N NaOH, 4 M urea, and 0.2 M 2-mercaptoethanol. Tensile and color (L, a, and b values) properties of films also were determined. Control films were cast from heated (70 degrees C for 20 min), alkaline (pH 10) aqueous solutions of SPI (5 g/100 mL of water) and glycerin (50% w/w of SPI). Additional films were cast after incorporation of dialdehyde starch (DAS) at 10% w/w of SPI or small amounts of formaldehyde in the film-forming solutions. Also, control film samples were subjected to heat curing (90 degrees C for 24 h), UV radiation (51.8 J/m(2)), or adsorption of formaldehyde vapors. PS of control films was highest (P < 0.05) in 2-mercaptoethanol, confirming the importance of disulfide bonds in SPI film formation. All treatments were effective in reducing (P < 0.05) film PS in all solvents. Both DAS and adsorbed formaldehyde rendered the protein in films practically insoluble in all solvents. Adsorption of formaldehyde vapors and heat curing also substantially increased (P < 0.05) film tensile strength from 8.2 to 15.8 or 14.7 MPa, respectively. However, heat curing decreased (P < 0.05) film elongation at break from 30 to 6%. Most treatments had small but significant (P < 0.05) effects on b color values, with DAS-containing films having the greatest (P < 0. 05) mean b value (most yellowish). Also, DAS-containing, heat-cured, and UV-irradiated films were darker, as evidenced by their lower (P < 0.05) L values, than control films. It was demonstrated that PS of SPI films can be notably modified through chemical or physical treatments prior to or after casting.

Color↗
PubMed2004

Anisotropic thermal expansion behavior of thin films of polymethylsilsesquioxane, a spin-on-glass dielectric for high-performance integrated circuits.

Thin films of poly(methylsilsesquioxane) (PMSSQ) are candidates for use as interdielectric layers in advanced semiconductor devices with multilayer structures. We prepared thin films of PMSSQ with thicknesses in the range 25.0-1151.0 nm by spin-casting its soluble precursor onto Si and GaAs substrates with native oxide layers and then drying and curing the films under a nitrogen atmosphere at temperatures in the range 250-400 degrees C. The out-of-plane thermal expansion coefficient alpha(perpendicular) of each film was measured over the temperature range 25-200 degrees C using spectroscopic ellipsometry and synchrotron X-ray reflectivity, while the in-plane thermal expansion coefficient alpha(parallel) of each film was determined over the temperature range 25-400 degrees C by residual stress analysis. PMSSQ films cured at higher temperatures exhibited reduced thermal expansion, which is attributed to the denser molecular packing and higher degree of cross-linking that arises at higher temperatures. Surprisingly however, all the PMSSQ films were found to exhibit very strong anisotropic thermal expansion; alpha(perpendicular) and alpha(parallel) of the films were in the ranges 140-329 ppm/ degrees C and 12-29 ppm/ degrees C respectively, depending on the curing temperature. This is the first time that cured PMSSQ thin films have been shown to exhibit anisotropic thermal expansion behavior. This anisotropic thermal expansion of the PMSSQ thin films might be due to the anisotropy of cross-link density in the films, which arises because of a combination of factors: the preferential orientation of methyl groups toward the upper film surface and the preferential network formation in the film plane that occurs during curing of the confined film. In addition, the film electron densities were determined using synchrotron X-ray reflectivity measurements and the film biaxial moduli were obtained using residual stress analysis.

Journal Article↗
PubMed2006

Redox properties of the ferricyanide ion on electrodes coated with layer-by-layer thin films composed of polysaccharide and poly(allylamine).

Polyelectrolyte multilayer thin films were prepared by an alternate deposition of poly(allylamine hydrochloride) (PAH) and anionic polysaccharides {carboxymethylcellulose (CMC) and alginic acid (AGA)} on the surface of a gold (Au) disk electrode, and the binding of ferricyanide [Fe(CN)(6)](3)(-) and hexaammine ruthenium ions [Ru(NH(3))(6)](3+) to the films was evaluated. Poly(acrylic acid) (PAA) was also employed as a reference polyanion bearing carboxylate side chains. A quartz-crystal microbalance study showed that PAH-CMC and PAH-AGA multilayer films grow exponentially as the number of depositions increases. The thicknesses of five bilayers of (PAH-CMC)(5) and (PAH-AGA)(5) films were estimated to be 150 +/- 20 and 90 +/- 15 nm, respectively, in the dry state. The PAH/polysaccharide multilayer film-coated Au electrodes exhibited a redox response to the [Fe(CN)(6)](3)(-) ion dissolved in solution, irrespective of the sign of the surface charge of the film, suggesting the high permeability of the films to the [Fe(CN)(6)](3)(-) ion. In contrast, the PAH-PAA film-coated Au electrodes exhibited a redox response only when the outermost surface of the film was covered with a positively charged PAH layer. However, the permeation of the [Ru(NH(3))(6)](3+) cation was severely suppressed for all of the multilayer films. It was possible to confine the [Fe(CN)(6)](3)(-) ion in the films by immersing the film-coated electrodes in a 1 mM [Fe(CN)(6)](3)(-) solution for 15 min. Thus, the [Fe(CN)(6)](3)(-)-confined electrodes exhibited a cyclic voltammetric response in the [Fe(CN)(6)](3)(-) ion-free buffer solution. The loading of the [Fe(CN)(6)](3)(-) ion in the films was higher when the surface charge of the film was positive and increased with increasing film thickness. It was also found that the [Fe(CN)(6)](3)(-) ion confined in the films serves as an electrocatalyst that oxidizes ascorbic acid in solution.

Catalysis↗
PubMed2006

Partial poly(glutamic acid) <--> poly(aspartic acid) exchange in layer-by-layer polyelectrolyte films. Structural alterations in the three-component architectures.

Layer-by-layer (LBL) polyelectrolyte films were constructed from poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA) as polyanions, and from poly(L-lysine) (PLL) as the polycation. The terminating layer of the films was always PLL. According to attenuated total reflection Fourier transform infrared measurements, the PGA/PLL and PAA/PLL films, despite their chemical similarity, had largely different secondary structures. Extended beta-sheets dominated the PGA/PLL films, while alpha-helices and intramolecular beta-sheets dominated the PAA/PLL films. The secondary structure of the polyelectrolyte film affected the adsorption of human serum albumin (HSA) as well. HSA preserved its native secondary structure on the PGA/PLL film, but it became largely deformed on PAA/PLL films. Both PGA and PAA were able to extrude to a certain extent the other polyanion from the films, but the structural consequences were different. Adding PAA to a (PGA/PLL)5-PGA film resulted in a simple exchange and incorporation: PGA/PLL and PAA/PLL complexes coexisted with their unaltered secondary structures in the mixed film. The incorporation of PGA into a (PAA/PLL)5-PAA film was up to 50% and caused additional beta-structure increase in the secondary structure of the film. The proportions of the two polyanions were roughly the same on the surfaces and in the interiors of the films, indicating practically free diffusion for both polyanions. The abundance of PAA/PLL and PGA/PLL domains on the film surfaces was monitored by the analysis of the amide I region of the infrared spectrum of a reporter molecule, HSA, adsorbed onto the three-component polyelectrolyte films.

Adsorption↗
PubMedDate not supplied

[Conformation and molecular and ionic transformations of polycytidylic acid immobilized in multilayer Langmuir and polyelectrolyte films].

Multilayer films of complexes of polycytidylic acid with dioctadecyldimetylammonium were obtained by the Langmuir-Blodgett method (LB films), and complexes of poly(C) with polycations (poly-L-lysisne, polyethyleneimine, polyallylamine) were obtained by the method of alternate adsorption (polyionic assembly) from solutions of oppositely charged polyelectrolytes on the solid carrier (SA films). It was shown that poly(C) exists in SA films in a single-stranded state irrespective of whether in the starting solution it occurred in the single-stranded nonprotonated or double-stranded protonated conformation. Conversely, in the LB film poly(C) preferred to be in a double protonated conformation. UV-spectra of water-insoluble LB and SA films at different pH values of surrounding water medium were investigated. Proton titration curves of poly(C) immobilized in LB films were obtained. The analysis of the shape of titration curves showed that the molecular-ionic transformation of poly(C) in LB films is accompanied by both the conformational transition of the polynucleotide and the molecular rearrangement in the whole film. Poly(C) was found to transform from the double- to single-stranded state and vice versa in the "deprotonation-protonation" cycle of LB film due to cooperative release/binding of hydrogen ions by cytosine bases. In contrast, poly(C) "protonation-deprotonation" in SA films occurred without conformational transitions of the polynucleotide. As opposed to poly(C) in solution a rather big hysteresis of forward and back titration curves was found for both types of multilayer films, indicating molecular rearrangements in films. The reason for the structural transformations of poly(C) upon fabrication of LB or SA films and the mechanism of molecular ionic transformations of poly(C) in films are discussed in terms of a simple model of ion exchange. An assumption about the nature of structural transformations of LB and SA films during their protonation-deprotonation is put forward.

Electrolytes↗
PubMed2005

Method of duplicating film using the CR system: evaluation of detectability in a simulated nodule.

PURPOSE: Since film processors used for screen-film systems have been decreasing recently, it is becoming difficult to develop duplicating film (Dup film) used conventionally. The purpose of this study was to evaluate the usefulness of the method of duplicating film using a computed radiography (CR) system. MATERIALS AND METHODS: The process of duplicating film using CR is 1) to eliminate energy accumulated on the imaging plate (IP) using white light, 2) to accumulate energy on the whole surface, and 3) to place the original film in piles. 4) After an exposure of white light, duplicated films can be obtained by CR system. In order to evaluate the reproducibiliy of our system, duplicated films were read by experienced observers and receiver operating characteristic (ROC) analysis was carried out. Observers read 50 images with a simulated nodule and 50 images without a simulated nodule. RESULTS: The average Az values were 0.94 for the original films, 0.91 for films duplicated using Dup film, and 0.90 for films duplicated using the CR system. When the two-tailed paired-T test was performed for each result, there were no statistically significant differences at p<0.05. CONCLUSION: The detectability of a simulated nodule for films duplicated using the CR system did not differ from the detectability of films duplicated using Dup film. This method may be a reasonable substitute for the conventional duplication system.

Copying Processes↗
PubMed1995

Dynamic surface activity of films of lung surfactant phospholipids, hydrophobic proteins, and neutral lipids.

Surface pressure-area (pi-A) isotherms during dynamic cycling were measured for films of dipalmitoyl phosphatidylcholine (DPPC) and column-separated fractions of calf lung surfactant extract (CLSE). Emphasis was on defining the relative importance of lung surfactant phospholipids (PPL), neutral lipids (N), and hydrophobic proteins (SP) in facilitating dynamic respreading and surface tension lowering within the interfacial film itself. Solvent-spread films in a Wilhelmy balance were studied at 23 degrees and 37 degrees C over a range of cycling rates for initial concentrations giving both monomolecular and surface-excess films. A striking finding was that PPL films containing the complete mix of surfactant phospholipids had greatly improved dynamic respreading compared to DPPC, particularly in surface excess films (30 and 15 Angstrum 2/molecule). Hydrophobic SP gave an additional increase in dynamic respreading in SP&PL compared to PPL films for initial concentrations of 60, 30, and 15 Anstrum 2/molecule. Neutral lipids also improved respreading slightly in N&PL versus PPL films, but maximum surface pressures in N&PL films at 37 degrees C were consistently the lowest of any surfactant subfraction. Spread films of SP&PL at 60 and 30 Angstrum 2/molecule had lower maximum pressures than PPL, but maximum pressures were slightly larger for SP&PL films at high initial concentration (15 Anstrum 2/molecule). Supplementary oscillating bubble studies involving both adsorption and film dynamics at rapid cycling rate (20 cycles/min) showed that dispersions of CLSE and SP&PL lowered surface tension to < 1 mN/m, while PPL and N&PL had elevated minimums of 21 mN/m. These results show that secondary surfactant phospholipids in addition to DPPC are important in the film behavior of pulmonary surfactant, giving improved respreading and overall pi-A isotherms very different from disaturated phospholipids. Hydrophobic SP also increase respreading in the interfacial film, in addition to their known action in increasing surfactant adsorption. SP may also improve film stability at high interfacial concentrations of phospholipid, although they were destabilizing in more dilute films. Neutral lipids contributed minor increases in surfactant respreading, but were consistently detrimental to surface tension lowering.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Precautions and strategies in using a commercial flatbed scanner for radiochromic film dosimetry.

The purpose of this study was to investigate the value of a commercially available flatbed scanner for film dosimetry with radiochromic film for external radiotherapy. The EPSON Pro 1680 Expression scanner was examined as a densitometer for two-dimensional film dosimetry with Gafchromic EBT film. An accurate and efficient scanning procedure was established. Possible drift and warm-up effects of the scanner were studied and the direct physical influence of the scanner light on the radiochromic film was assessed. Next, we investigated the scan field uniformity. Also, we examined if the accuracy of radiochromic film was improved by subtracting the optical density of the unirradiated blank film from the optical density of the irradiated film. To assess the accuracy of Gafchromic EBT film when the EPSON scanner was used as a densitometer, the depth dose of a 2 x 15 cm(2) field and the in-plane and cross-plane profiles of a 15 x 15 cm(2) field were measured and compared with diamond detector measurements. When taking consecutive scans, we found that the optical density taken from the first scan was about 1% higher than the optical density taken from subsequent scans. We attribute this to the warming up of the lamp of the scanner. Longer-term drift of the scanner was found to be absent. We found that the use of a correction matrix was necessary to correct for the non-uniform scanner response over the scan field. Subtracting the optical density of the unirradiated blank film from the irradiated film improves the precision of the Gafchromic EBT film. Depth dose and profile measurements with Gafchromic EBT film and the diamond detector are in agreement within 2.5%. The EPSON Pro 1680 Expression scanner is an excellent tool for accurate two-dimensional film dosimetry with Gafchromic EBT film provided that some precautions and corrections are taken into account.

Calibration↗
PubMed2002

Rapid radiographic film calibration for IMRT verification using automated MLC fields.

A method for measuring a film sensitometric curve using a single sheet of film exposed with a two field step-and-shoot MLC treatment was developed and tested with Kodak XV2 and EDR2 films. With this technique a film sensitometric curve can be completed in only 10 minutes, making it practical to generate new film calibrations daily. This method is applicable to film calibrations for all purposes, but is particularly useful in IMRT treatment verification due to the method's use of small fields. This method agrees with the traditional large-field multifilm calibration within 0.5% and will produce sensitometric curves with errors less than 1% throughout the dose range, including uncertainties in dose delivery, film response, and optical density measurements. OD values for XV2 and EDR2 films were consistent in the middle of exposure areas at high depths, but the XV2 film penumbra regions showed large amounts of over-response as the calibration depth increased. If XV2 film is used for IMRT treatment verification, it is necessary to reduce the fluence of low energy photons in areas around the film by using thin lead shields. EDR2 film was shown to have minimal energy dependence, as it accurately represented penumbra areas and yielded identical sensitometric curves generated with 6 and 18 MV photons. However, its darker tint may make it more sensitive to scanning laser film digitizers' horizontal nonuniformities. This single film method proved to be superior to the traditional calibration method and allows fast daily calibrations of films for highly accurate IMRT delivery verifications.

Calibration↗
PubMed1994

Cost-effective filming sequence for intravenous urography.

To define an intravenous urography (IVU) film sequence that maximizes sensitivity and minimizes filming costs, we evaluated the effect of omitting films from a standard IVU sequence. We reviewed 82 IVU series that demonstrated abnormalities. Each series comprised 11 films: preliminary abdominal radiograph and nephrotomogram, three 1-minute nephrotomograms, 5-minute abdominal film, 10-minute radiograph with abdominal compression, one frontal and two oblique 15-minute films, and postvoid film. Sensitivity was determined for each film. Eighty-two standard IVUs showed 120 abnormalities. Omitting any one film from the sequence decreased sensitivity by 0% to 12%. Omitting the preliminary film resulted in failure to detect 15 abnormalities (12%). Omitting any nephrotomogram, the 10-minute compression view, or either 15-minute oblique film did not decrease sensitivity. Omitting combinations of these films lowered overall sensitivity. The postvoid film was essential in only one case. We conclude that a sequence of nine radiographs decreases film and processing expenses by 18% without sacrificing sensitivity. Sequences with fewer films substantially reduce detection of common urinary tract abnormalities.

Cost-Benefit Analysis↗
PubMed2002

Evaluation of Kodak EDR2 film for dose verification of intensity modulated radiation therapy delivered by a static multileaf collimator.

A new type of radiographic film, Kodak EDR2 film, was evaluated for dose verification of intensity modulated radiation therapy (IMRT) delivered by a static multileaf collimator (SMLC). A sensitometric curve of EDR2 film irradiated by a 6 MV x-ray beam was compared with that of Kodak X-OMAT V (XV) film. The effects of field size, depth and dose rate on the sensitometric curve were also studied. It is found that EDR2 film is much less sensitive than XV film. In high-energy x-ray beams, the double hit process is the dominant mechanism that renders the grains on EDR2 films developable. As a result, in the dose range that is commonly used for film dosimetry for IMRT and conventional external beam therapy, the sensitometric curves of EDR2 films cannot be approximated as a linear function, OD = c * D. Within experimental uncertainty, the film sensitivity does not depend on the dose rate (50 vs 300 MU/min) or dose per pulse (from 1.0 x 10(-4) to 4.21 x 10(-4) Gy/pulse). Field sizes and depths (up to field size of 10 x 10 cm2 and depth = 10 cm) have little effect on the sensitometric curves. Percent depth doses (PDDs) for both 6 and 23 MV x rays were measured with both EDR2 and XV films and compared with ion chamber data. Film data are within 2.5% of the ion chamber results. Dose profiles measured with EDR2 film are consistent with those measured with an ion chamber. Examples of measured IMRT isodose distributions versus calculated isodoses are presented. We have used EDR2 films for verification of all IMRT patients treated by SMLC in our clinic. In most cases, with EDR2 film, actual clinical daily fraction doses can be used for verification of composite isodose distributions of SMLC-based IMRT.

Adult↗
PubMed2006

Pencil beam approach for correcting the energy dependence artifact in film dosimetry for IMRT verification.

The higher sensitivity to low-energy scattered photons of radiographic film compared to water can lead to significant dosimetric error when the beam quality varies significantly within a field. Correcting for this artifact will provide greater accuracy for intensity modulated radiation therapy (IMRT) verification dosimetry. A procedure is developed for correction of the film energy-dependent response by creating a pencil beam kernel within our treatment planning system to model the film response specifically. Film kernels are obtained from EGSnrc Monte Carlo simulations of the dose distribution from a 1 mm diameter narrow beam in a model of the film placed at six depths from 1.5 to 40 cm in polystyrene and solid water phantoms. Kernels for different area phantoms (50 x 50 cm2 and 25 x 25 cm2 polystyrene and 30 x 30 cm2 solid water) are produced. The Monte Carlo calculated kernel is experimentally verified with film, ion chamber and thermoluminescent dosimetry (TLD) measurements in polystyrene irradiated by a narrow beam. The kernel is then used in convolution calculations to, predict the film response in open and IMRT fields. A 6 MV photon beam and Kodak XV2 film in a polystyrene phantom are selected to test the method as they are often used in practice and can result in large energy-dependent artifacts. The difference in dose distributions calculated with the film kernel and the water kernel is subtracted from film measurements to obtain a practically film artifact free IMRT dose distribution for the Kodak XV2 film. For the points with dose exceeding 5 cGy (11% of the peak dose) in a large modulated field and a film measurement inside a large polystyrene phantom at depth of 10 cm, the correction reduces the fraction of pixels for which the film dose deviates from dose to water by more than 5% of the mean film dose from 44% to 6%.

Algorithms↗
PubMed1995

A comparison of six intra-oral X-ray films.

OBJECTIVES: To compare objectively and subjectively national-brand dental X-ray films with widely available and less costly brands. METHODS: A range of dental films, including the recently released Kodak Ektaspeed Plus, was purchased from mail-order suppliers at the lowest published price. Objective measurements (film speed, contrast, fog levels, costs, physical characteristics) and subjective evaluations (ease of use, film graininess, overall appearance) were made. RESULTS: Private-label films were obtained at less cost than those of major vendors. Not all film speeds, sizes and wrapping materials were available from individual manufacturers. Objective measures and subjective appraisals showed that Ektaspeed Plus was the fastest film and had good contrast with the clinically useful density ranges. Agfa Dentus was the next fastest film, but it had rather low contrast and was grainier than the other films. The non-proprietary brands were difficult to open with primary glove barriers, making effective infection control practices arduous. All films were relatively stable over a 16-week period regardless of storage location. CONCLUSIONS: The major manufacturers offered more choices of film sizes and speeds than did private label suppliers. The films from the major manufacturers, although more expensive, were more conducive to effective infection control practices. Ektaspeed Plus had a performance comparable with or better than the other available films. Based on this preliminary study, it is recommended that this new film is considered as an alternative to D-speed films.

Absorptiometry, Photon↗
PubMed2004

Psychophysical properties of a new F-speed intraoral film.

OBJECTIVES: To compare the psychophysical properties of the new Kodak InSight F-speed intraoral dental film with those for the E-speed Ektaspeed Plus film by means of the perceptibility curve (PC) test. METHODS: A specially designed test object was used. The test object was made of aluminium and was 10 mm thick. It contained ten holes, contrast details, with the same diameter of 1.5 mm but with different depths. The depths ranged from 0.03 mm to 0.30 mm in steps of 0.03 mm. The holes were placed randomly within a square area with a total of 16 possible positions. Radiographs of the test object were obtained over the full exposure ranges of the two films. A Combex DX-907 dental X-ray unit was used operating at 10 mA and two tube potentials, 70 kVp and 90 kVp. The focus-to-object distance was 50 cm. Ten observers evaluated the radiographs under uniform artificial lighting using a view box and stated the number of perceptible representations of contrast details. In order to construct perceptibility curves, absolute values of the reciprocal of the minimum perceptible logarithmic exposure differences, 1/(DeltalogE)min, were plotted as functions of the logarithm of exposures, logE, registered by the tested films. Comparisons between the two films were made separately for the two tube potentials, 70 kVp and 90 kVp. RESULTS: The results are presented graphically. PCs for the InSight film had higher peaks than those for the Ektaspeed Plus film. This indicates that the viewers were able to perceive smaller exposure differences in the former compared with the latter. PCs for the InSight film were shifted towards the left along the exposure axis relative to the PCs for the Ektaspeed Plus film indicating that the former film is more sensitive than the latter. The integrals of the PCs for InSight film were larger than those for Ektaspeed film indicating superior psychophysical properties of the InSight film. CONCLUSIONS: From the point of view of perception, the new InSight film has such psychophysical properties in comparison with Ektaspeed Plus film that it will be the more favourable of the two in clinical radiographic practice.

Absorptiometry, Photon↗