Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Films”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed1995

A sensitometric comparison of Fuji Super HR-G and Kodak T-mat G panoramic films.

Film contrast, relative speed, and resolution of Fuji Super HR-G panoramic film were determined according to specifications of the American National Standards Institute and compared with those of Kodak T-mat G panoramic film. The films were simultaneously exposed by Kodak Lanex regular intensifying screens with time-scale sensitometry. Optical density was read with a digital densitometer, and characteristic curves were plotted and analyzed by polynomial and linear regression. The average gradients of the linear regression curves between 0.25 and 2.00 optical density units above base plus fog were taken as contrast (HR-G: 1.831, T-mat G: 1.712). Relative speed, when exposed with Lanex regular intensifying screens and calculated at 1.00 optical density unit above base plus fog, was 412 for HR-G. A speed of 400 was chosen for T-mat G to match Kodak consumer information. Resolution for both films was similar. These findings suggest that Fuji Super HR-G panoramic film develops similar contrast, speed, and resolution to Kodak T-mat G panoramic film.

Linear Models↗
PubMed1996

In vitro comparison of Kodak Ultra-speed, Ektaspeed, and Ektaspeed Plus, and Agfa M2 Comfort dental x-ray films for the detection of caries.

The aim of this study was to compare the diagnostic accuracy of two new dental x-ray films, Kodak Ektaspeed Plus (Plus) and Agfa M2 Comfort (M2), respectively, with the current Kodak Ultra-speed (Ultra) and Ektaspeed (Ekta) films for the detection of caries. A total of 103 occlusal and 224 proximal surfaces were examined independently by three observers. A histologic examination performed after the teeth were sectioned served as the validation method for lesion depth. Receiver operating characteristic curve areas were calculated to express the diagnostic accuracy. In the occlusal surfaces the receiver operating characteristic curve areas ranged from 0.764 (in Ultra films) to 0.800 (in Ekta films). In the proximal surfaces the receiver operating characteristic curve areas ranged from 0.550 (in Ultra films) to 0.696 (in Plus films). No statistically significant differences were found between the different film types.

Dental Caries↗
PubMed1997

An evaluation of the diagnostic yield from bitewing radiographs of small approximal and occlusal carious lesions in a low prevalence sample in vitro using different film types and speeds.

AIM: To compare diagnostic yield in caries diagnosis from D- and E-speed films. DESIGN: A laboratory study. SETTING: A UK dental school between 1992 and 1994. MATERIALS AND METHODS: 96 extracted teeth containing approximal and occlusal lesions, but representing a low caries prevalence sample, were set in occluding dental arches. Bitewing radiographs were taken and interpreted by 5 examiners for the presence or absence of caries. Each examiner was also asked which film image he or she subjectively liked best. MAIN OUTCOME MEASURES: The teeth were subsequently sectioned and histologically examined to validate diagnostic decisions. RESULTS: For all film types the percentage of lesions with caries histologically in dentine correctly identified radiologically (sensitivity) was low (approximal caries 8-22%; occlusal caries 0-30%). The number of sound dentine sites correctly identified (specificity) was high (approximal caries 98-100%; occlusal caries 79-100%). There were no significant differences between D- and E-speed films. Sensitivity was unaffected by each examiner's subjective preference for a particular film. The variation in sensitivity of diagnosis was due to differences between examiners. CONCLUSIONS: The reluctance of many GDPs to use E-speed film because they 'do not like the image' cannot be endorsed or supported. Both E-speed film types examined can be recommended for use in general practice.

Analysis of Variance↗
PubMed1999

The effect of developer age on the detection of approximal caries using three dental films.

OBJECTIVES: To compare the diagnostic accuracy for the detection of approximal caries of three dental X-ray films using fresh and aged processing chemicals. METHODS: Fifty-six extracted unrestored premolars were radiographed under standardized conditions using the new Dentus M2 (Agfa-Gevaert, Mortsel, Belgium), Ektaspeed Plus and Ultra-speed (Kodak Eastman Co, Rochester, USA) dental films. The films were processed manually using Agfa chemicals (Heraeus Kulzer, Dormagen, Germany). The procedure was repeated once a week until the complete exhaustion of the chemicals (6 weeks). Three independent observers assessed 210 radiographs using the following rating scale: 0 = sound, 1 = enamel lesion; 2 = lesion reaching the ADJ; 3 = dentinal lesion. True caries depth was determined by histological examination (14 sound surfaces, 11 enamel lesions, eight lesions reaching the ADJ and 23 dentinal lesions). True caries depth was subtracted from the values given by the observers and an analysis of variance was performed. The null hypothesis was rejected when P < 0.05. RESULTS: No significant differences were found in the diagnostic accuracy between the three films when using chemicals of up to 3 weeks old (P = 0.056). After the third week, Ultra-speed was significantly better than the other two films (P = 0.012). On average caries depth was underestimated. CONCLUSION: A similar level of diagnostic accuracy for approximal caries is achieved when using the three films. Dentus M2 and Ektaspeed Plus are at present the fastest available films and they should therefore be recommended for clinical practice. Agfa chemicals should be renewed every 3 weeks. Fifty per cent reduction in average gradient is indicative of renewing processing chemicals.

Analysis of Variance↗
PubMed2001

Sensitometric comparison of speed group E and F dental radiographic films.

OBJECTIVE: To evaluate the sensitometric characteristics of Insight, (Eastman Kodak, Rochester, NY, USA) a new F-speed film, in fresh and depleted processing solutions and compare them with Ektaspeed Plus. METHODS: Two sets each of Insight (IP) and Ektaspeed Plus (EP) films were exposed to radiation levels ranging from 10.7 to 685.2 microGy. One set of films was processed in fresh chemicals while the other set was processed in solutions that had been used for 5 days to process over 500 radiographs. Unexposed films of both types were processed in both solutions to determine base-plus-fog density. Speed and contrast were measured according to ISO definitions and at other levels of density. RESULTS: IP was in speed group F as measured at optical density 1 above base-plus-fog when processed under both conditions. It was 25% faster than EP when both were processed in new solutions and 35% faster in the old solutions, permitting a 20-24% reduction in exposure time. The speeds of both film types decreased when processed in used solutions, but the decrease was smaller for IP than for EP. Speeds at other density levels were greater for IP than EP. Contrast as defined by ISO, and over other density ranges, was similar for both films. CONCLUSIONS: Insight is an F-speed film with a speed at least 25% greater than Ektaspeed Plus. IP is more resistant than Ektaspeed Plus to decreases in speed when processed in used chemicals. Contrast of IP and EP is comparable over several density ranges.

Absorptiometry, Photon↗
PubMed2005

Development of a novel UV indicator and dosimeter film.

A novel UV indicator is described, comprising nanocrystalline particles of titania dispersed in a film of a polymer, hydroxyl ethyl cellulose (HEC), containing: a mild reducing agent, triethanolamine (TEOA) and a redox indicator, methylene blue (MB). The UV indicator film is blue-coloured in the absence of UV light and loses colour upon exposure to UV light, attaining within a few min a steady-state degree of bleaching that can provide a measure of the irradiance of the incident light. The original blue colour of the film returns once the source of UV light is removed. The spectral characteristics of a typical UV indicator film, and its components, are discussed and the UV-absorbing action of the titania particles highlighted. From the measured %bleaching undergone by a typical UV indicator as a function of light irradiance the indicator appears fully bleached, within 7 min, by a UV irradiance of 3 mW cm(-2) or greater. The mechanism by which the UV indicator works is described. The reversible nature of the UV indicator is removed by covering a typical UV indicator with a thin, largely oxygen impermeable, polymer film, such as the regenerated cellulose found in Sellotape. The product is a UV dosimeter, the response of which is related to the intensity and duration of the incident UV light, as well as the amount of titania in the film. A typical UV dosimeter film is fully bleached by 250 mJ cm(-2) of UV light. The possible use of these novel indicators to measure UV exposure levels, irradiance and dose, is discussed.

Film Dosimetry↗
PubMed2001

Characteristics of Kodak Insight, an F-speed intraoral film.

OBJECTIVES: This study reports film speed, contrast, exposure latitude, resolution, and response to processing solution depletion of Kodak Insight intraoral film. METHODS: Densitometric curves were generated by using International Standards Organization protocol. Additional curves were generated for Ultra-speed, Ektaspeed Plus, and Insight films developed in progressively depleted processing solutions. Eight observers viewed images of a resolution test tool for maximum resolution assessment. Images of an aluminum step-wedge were reviewed to determine useful exposure latitude. RESULTS: Insight's sensitivity in fresh automatic processor solutions places it in the F-speed group. An average gradient of 1.8 was found with all film types. Insight provided 93% of the useful exposure latitude of Ektaspeed Plus film. Insight maintained contrast in progressively depleted processing solutions. Like Ektaspeed Plus, Insight was able to resolve at least 20 line-pairs per millimeter. CONCLUSIONS: Under International Standards Organization conditions, Insight required only 77% of the exposure of Ektaspeed Plus film. Insight film provided stable contrast in depleted processing solutions.

Analysis of Variance↗
PubMed2002

Contrast perception in digitized panoramic radiographs compared with their film-based origin.

OBJECTIVES: We sought to compare the visual image quality of film-based and digitized panoramic radiographs through use of a hole-containing test wedge. STUDY DESIGN: An aluminum wedge containing 100 cells, of which 90 were given shallow holes, was exposed in the film-based Orthophos CD panoramic unit. Two radiographs subjectively exhibiting optimum contrast were selected. Films were digitized with a charge-coupled device flatbed scanner at 300 dpi. Films and digitized images were rated cellwise by 2 similar groups of 50 observers each with respect to spot perception. RESULTS: The mean sensitivity was 0.26 +/- 0.09 for film and 0.20 +/- 0.07 for digitized images (P =.000), with a pronounced decline in the latter in regions of high background density. The average specificity was 0.93 +/- 0.07 for film versus 0.92 +/- 0.08 for digitized images (P = 0.213). CONCLUSION: Film yielded a significantly higher sensitivity, but this absolute difference was actually small compared with that of the digitized images.

Absorptiometry, Photon↗
PubMed1997

A time-scale sensitometric method for evaluating screen-film systems.

An x-ray sensitometer is used to measure the characteristic curve of radiographic films exposed with fluorescent intensifying screens. The series of relative exposures, necessary to cover the full density range of the film, can be obtained by either time-scale or intensity-scale sensitometric methods. We have developed a convenient method of exposing film-screen systems for time-scale sensitometry. In this method, during exposure the x-ray kilovoltage, tube current and x-ray intensity remain constant and a geometric series of exposures of the film is modulated by varying the exposure time. This time variation can be obtained when a lead disc with different sector openings is rotated in front of the film system by a stepping motor. The conditions normally used are 70 kVp x-rays, 3.5 mm Al total filtration at the tube, and 2.4 m focal spot-film distance. This exposure latitude gives a complete characteristic curve of film-screen systems.

Calibration↗
PubMed1999

A new approach to film dosimetry for high-energy photon beams using organic plastic scintillators.

This study is concerned with dose measurement of photon beams, both dynamic and static, by using x-ray film. As discussed in our last study (Burch et al 1997, Yeo et al 1997), x-ray film, as an integrating dosimeter, can be an ideal candidate if the over-response problem to low-energy photons (energies below 400 keV) is solved. In summary, the problem of the over-response can be explained as follows. Because the mass energy absorption coefficient of x-ray film increases as photon energy decreases, softening of the photon spectra with depth in a phantom makes the extent of film over-response a function of phantom depth (Burch et al 1997, Yeo et al 1997). Film dosimetry is based upon (a) calibration of the film response (i.e. optical density) at some specific depth in a phantom and (b) conversion of the film density which can cover whole depths in a phantom to dose by using the calibration curve. In megavoltage dosimetry, this normally causes over-response in doses at depths greater than the calibration depth.

Dose-Response Relationship, Radiation↗
PubMed1999

The use of GAFchromic film to determine the absolute activity of beta emitters.

A method of using GAFchromic film to determine the absolute activity of beta emitters by immersing the film in a bath of activity is described. This includes calculations of the effect of part of the radioactive solution being displaced by the film that is performing the measurement. Calculations have been performed for 90Y, 32P and 188Re. It is shown that for the film used in this study, this effect will cause a correction of the order of 15-20% for the three radionuclides studied. The results of the GAFchromic film measurement are compared with results obtained from liquid scintillation counting and from a commercial dose calibrator. It is shown that for 32P all methods were in reasonable agreement, but for 188Re, although the GAFchromic film and the liquid scintillation counting methods give similar results, the dose calibrator measurement differed by more than 20%. The GAFchromic film was also used to perform a direct measurement of the radiation dose at a distance of 0.5 mm from the surface of a cylindrical source of 188Re activity. This gave good agreement with the value of the dose predicted from theoretical calculations.

Beta Particles↗
PubMed2001

Use of multiple layers of Gafchromic film to increase sensitivity.

This note investigates the increase of the sensitivity of radiochromic film by layering the film together. Investigations with up to five layers of radiochromic film placed together as a single dosimeter have allowed accurate two-dimensional dosimetry at low radiotherapy doses. The sensitivity of the response of the layered film increases with the number of layers, with the five-layer dosimeter increasing the change in optical density by 4.3 +/- 0.2 times that for a single layer film at 670 nm readout wavelength. Measurements in the penumbral region of a 6 MV x-ray beam show that the spatial resolution is slightly reduced with the layered film. The distance across the region from 20 to 80% of the maximum dose at the beam edge (20/80% penumbra) measured at 1.5 cm depth was measured as 3.1 +/- 0.3 and 3.5 +/- 0.3 mm for one and five layers, respectively. Thus no major reduction in spatial resolution was found by layering the film to five layers but the sensitivity was increased by 430% at 670 nm readout wavelength.

Particle Accelerators↗
PubMed2001

Visible dye light absorption properties of processed radiographic film.

The visible absorption spectra of Kodak X-Omat V film, which had been exposed to various doses of radiation, have been investigated to analyse the dosimetry characteristics of the film with various densitometers. Common densitometers can use fluorescent light (broad band visible), helium-neon (632 nm) or other spectra of specific bandwidth. The visible absorption spectra show a slight peak in absorption at approximately 580 nm and another at 630 nm caused by the base material of the film. The optical density of the film is shown to increase almost equally at all wavelengths within the visible region with increases in applied dose. By evaluating the results for the broad band spectra and specific wavelength optical density it is shown that a relatively uniform response is expected for all densitometers that work within the visible region as well as in selected infrared wavelengths. Thus similar optical density to dose response curves for X-Omat V radiographic film should be produced for all types of densitometers, no matter what type of light source is used for illumination. Thus it is most efficient to have a densitometer with a light source suitable for radiochromic film, which can also be used with radiographic film.

Absorption↗
PubMed2003

Polarization effects on a high-sensitivity radiochromic film.

A new high-sensitivity radiochromic film has been tested for its polarization properties. Gafchromic HS film has been shown to produce a relatively small (less than 3%) variation in the optical density measured at 660 nm wavelength when the light source is fully linear polarized and the film is rotated through a 360 angle. Similar variations are seen when the detector is linearly polarized. If both the light source and the detector are linearly polarized, variations in the measured optical density can reach 15% when the film is rotated through a 360 angle. This seems to be due to a phase shift in polarized light caused by the radiochromic film resulting in the polarized light source becoming out of phase with the polarized detector. Gafchromic HS radiochromic film produces a minimal polarization response with varying angle of rotation; however, we recommend that a polarization test be performed on a densitometry system to establish the extent of its polarization properties before accuracy dosimetry is performed with radiochromic HS film.

Absorptiometry, Photon↗
PubMed2003

Source and detector polarization effects on radiographic film dosimetry.

Kodak X-Omat V radiographic film has been tested for its polarization properties when using polarized and non-polarized light sources and detectors. The radiographic film has been shown to produce a relatively small but not negligible (less than 5%) variation in 90 degrees cycles in measured optical density within the visible spectrum when the light source is fully linear polarized and the film is rotated through 360 degrees angle. Negligible variations are seen when the detector is linearly polarized. If both light source and detector are linearly polarized, variations in measured optical density can reach 35% when the film is rotated through 360 degrees angle. This seems to be due to variations in the degree and axis of rotation in polarized light caused by the radiographic film and is independent of exposure level as the intensity of variation in absolute optical density is relatively the same for all film exposures. We recommend that a polarization test be performed on a densitometry system to establish the extent of its polarization properties before accurate dosimetry is performed with radiographic film.

Artifacts↗
PubMed2005

Dose measurements near a non-radioactive gold seed using radiographic film.

The dose distribution near a non-radioactive gold seed under a 6 MV photon beam was measured using radiographic film, water equivalent bolus and solid water slabs. This type of small seed is typically used as a marker in target positional verification using a portal imager for conformal prostate treatment such as intensity modulated radiation therapy. A stack of three films was placed on top of the seed located on a soft bolus. Solid water slabs were then placed on top of the film. The films were exposed using a small 1x1 cm2 field. Then, using a similar experimental set-up and exposure, another stack of three films was placed under the seed, which was then covered by the soft bolus and solid water slabs. The cross-plane axial beam profiles at different depths, depending on the thickness of the film package, were measured. From the group of beam profiles above and below the seed, the dose distribution along a selected vertical line within the profiles was easily plotted. Compared to the dose with no seed at the isocentre and 5 cm of solid water, there was about a 21% increase in dose at 0.35 mm above the seed. On the other hand, there was about a 22% decrease in dose at the same distance below the seed. The dosimetry of the calibrated film was verified with a MOSFET detector. The change in dose due to the seed by varying the incident beam angles was also measured for this note.

Calibration↗
PubMed1993

The use of E-speed film for root canal length determination.

This study compared the use of D-speed and E-speed dental X-ray film for assessing the working length of root canals. Root canal files of varying size (ISO 06, 08, 10 and 15) were placed in the root canals of a maxillary molar and a mandibular molar in a dried skull and mandible. Files were set at various lengths relative to the radiographic apex. The X-ray projections were kept constant. Exposure settings for the two film types that gave comparable radiographic density were selected. Films were developed manually under standardized conditions. A total of 48 films of each type were examined at various magnifications by four trained examiners for the estimation of distance between the file tip and radiographic apex. There were no differences between examiners in estimating working length. The effect of file size, root and magnification were also not significant. The differences between the film types were not significant (P > 0.05). It is concluded that clinicians should use E-speed film instead of D-speed film for root canal length measurement, because the exposure time was reduced by over 40% but the quality of the radiographic image was not significantly different.

Dental Pulp Cavity↗
PubMed1988

Blackening of unprotected dental X-ray films due to scattered radiation.

Unexposed films awaiting exposure as well as exposed films awaiting processing are subjected to scattered radiation if kept unprotected in the dental X-ray clinic. The purpose of the present study was to analyze the influence of various storing principles, film speed, and distance from X-ray source upon the degree of film blackening. Test films were subjected to scattered radiation from 150 exposures. Maximum additional blackening (0.27 D) was recorded for type E films not protected by lead foil at the shortest distance studied (55 cm). At a distance of 200 cm blackening was reduced to 0.02 D and could be further reduced by utilizing the inherent protective effect of the lead foil. It is concluded that if dental X-ray films not in use are kept at a distance of 200 cm from the X-ray source and protected by lead foil additional blackening due to scattered radiation is negligible and further protective precautions are unnecessary.

Lead↗