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At least 1,261 records · Page 70Linked to original sources
PubMed2006

Independence of calibration curves for EBT Gafchromic films of the size of high-energy X-ray fields.

The EBT Gafchromic radiochromic film is a relatively new product designed specifically for dosimetry in radiation therapy. Due to the weak dependence of its response on the photon energy (variations are below 10% in the 50 kVp-10 MVp range), the film is ideal for dosimetry when the photon energy spectrum may be changing or unknown. In order to convert a map of optical densities into a map of absorbed radiation doses, a calibration curve constructed on the basis of standard calibration films is necessary. Our results have shown that, with the EBT Gafchromic film, one can use the same calibration curve for 6-MV X-ray fields of any size in the range from 5 x 5 cm(2) up to 40 x 40 cm(2). This is not the case for radiographic films, such as Kodak X-Omat V, whose response to the same dose varies approximately by 10% depending on the field size in this range. This insensitivity of the EBT Gafchromic film to size of the radiation field makes it possible to assess doses delivered by small radiation fields. With the help of this film, it was shown that the output factor for a 0.5 x 0.5 cm(2) field is 0.60+/-0.03 (2SD) relative to the 10 x 10 cm(2) field.

Calibration↗
PubMed2004

Visible absorption properties of radiation exposed XR type-T radiochromic film.

The visible absorption spectra of Gafchromic XR type-T radiochromic film have been investigated to analyse the dosimetry characteristics of the film with visible light densitometers. Common densitometers can use photospectrometry, fluorescent light (broad-band visible), helium neon (632 nm), light emitting diode (LED) or other specific bandwidth spectra. The visible absorption spectra of this film when exposed to photon radiation show peaks at 676 nm and 618 nm at 2 Gy absorbed doses which shift to slightly lower wavelengths (662 nm and 612 nm at 8 Gy absorbed dose) at higher doses. This is similar to previous models of Gafchromic film such as MD-55-2 and HS but XR type-T also includes a large absorption at lower visible wavelengths due to 'yellow' dyes placed within the film to aid with visible recognition of the film exposure level. The yellow dye band pass is produced at approximately 520 nm to 550 nm and absorbs wavelengths lower than this value within the visible spectrum. This accounts for the colour change from yellow to brown through the added absorption in the red wavelengths with radiation exposure. The film produces a relatively high dose sensitivity with up to 0.25 OD units per Gy change at 672 nm at 100 kVp x-ray energy. Variations in dose sensitivity can be achieved by varying wavelength analysis.

Absorption↗
PubMed2005

An unexpected artefact with low-contrast high-energy film.

Kodak recently introduced new packaging for its X-Omat V verification film, including a label on the exterior of the packet. Patient images taken using the film in an image intensification cassette showed artefacts which appeared to be related to the label. Investigation showed the effect was only observed in conditions of high-Z build-up or backscatter or when the film was used without additional backscatter. The label provides extra build up when in front of the film and an increase in optical density of up to 0.04 units. When the label is on the rear of the film it absorbs backscattered particles, causing a decrease in optical density. It is concluded that X-Omat V film packets with labels are unsuitable for use in imaging cassettes unless they are used in conditions of low-Z build-up. Alternatively the film must be removed from the labelled envelope if it is to be used in high-Z build-up conditions.

Artifacts↗
PubMed1999

Portal dosimetry using x-ray film: an experimental and computational study.

To evaluate the accuracy and precision of relative portal dosimetry using x-ray film, we compared the radiation doses measured by x-ray film and by an ion chamber at various portal planes that were 0 to 50 cm behind an 18 cm thick phantom. In addition, we calculated photon spectra at the measurement planes by using the Monte Carlo particle transport technique. The experiments showed that the film usually measured relative doses to within 5% of the measurements by the ion chamber and that the errors were associated with the changes in the spectra of photon energy fluence at portal planes. The relative magnitude of low-energy fluence in the photon fluence spectrum and its variance across the portal plane caused the film response to differ from the ion-chamber response especially with lead screen on top of film in the film cassette. Relative film dosimetry may be improved to accuracy of better than 2% by using solid water or other tissue equivalent cassettes.

Algorithms↗
PubMed1993

Zymogram of proteases made with developed film from nondenaturing polyacrylamide gels after electrophoresis.

A simple, extremely versatile method for preparing zymograms from proteases after nondenaturing Phast-System gel electrophoresis is described. After completion of the run and before staining, an electropherogram and a piece of developed, single-side coated X-ray film are brought into contact for 5 min at room temperature. The film overlay is then separated and the gel is stained for protein. The zymogram on the X-ray film is generated by simply pouring about 10 ml of a suitable buffer solution at 30 to 50 degrees C over the film strip. Clearing zones appeared within a few seconds to a few minutes depending on protease amount. For the alkaline protease subtilisin BL the lower limit of detectability was 10 ng applied to the gel prior to electrophoresis. For preservation and archiving the zymogram film is simply rinsed with distilled water and air-dried. The film can be cut to size and mounted for a slide projector, or the film can serve as a negative for photographic enlargements. The clearing zone area is proportional to the amount of protease from 10 to 100 ng of protein.

Bacillus subtilis↗
PubMed2002

An investigation into the source of low energy scattered radiation of significance in film dosimetry.

The nature of the background optical density on films exposed to orthovoltage x-rays and electron beams has been studied for correction purposes. A higher than expected background value can be demonstrated by comparing the film scanned beam profile with water phantom ionisation scans of the same beam. A range of 3-5% increased background in the penumbral tail, with energy dependence, has been shown experimentally. Testing the assumption that this increased background is due to Cerenkov radiation produced in the film, Filmstrips were interleaved in a solid water equivalent phantom and exposed to 300kV orthovoltage x-ray beams and 5MeV to 12MeV electron beams. The film stacks were made up of single or multiple bare filmstrips, multiple filmstrips interleaved with black paper, and multiple filmstrips interleaved with overhead transparency sheet. The experimental result demonstrated that visible light was not significantly responsible for an enhanced film optical density, but rather that this was due to scattered radiation, with a complex low energy spectrum, arising from the film silver halide emulsion or base. An improved background correction technique is developed which incorporates this unexpected background value as an added component in the correction applied to the measured optical density. The resulting profiles exhibit improved agreement between film and ionization chamber measurements in the penumbra and tail regions.

Artifacts↗
PubMed2003

Intensity modulated radiation therapy: film verification of planar dose maps.

A new slow response radiographic film (Kodak EDR) is compared with a more traditional faster responding dosimetry film (Kodak XV) in an intensity modulated radiation therapy x-ray field. Dose profiles derived from the two films are compared with doses obtained using a radiotherapy dose planning system (Philips-Pinnacle) which calculates planar dose using a collapsed cone convolution algorithm. Comparisons of the dose maps delivered from film with the Pinnacle dose maps are useful to ensure accurate dose delivery. The Pinnacle dose maps agreed with measurement using both film types to within +/- 3% (in the umbral region) at depths ranging from d(max) to 15 cm. Both XV and EDR films can be used to verify IMRT. EDR film is better suited for dosimetry for combined field dose maps due to its useful dose range of 1-5 Gy. We found XV to be more suitable for individual field dose maps (dose range 0-1 Gy) as no scaling of monitor units were required to achieve acceptable optical density response.

Algorithms↗
PubMed1984

Effects of solution depletion on films developed in the Peri-Pro automatic processor.

The changes in image quality and archival quality of dental films processed successively at room temperature in a Peri-Pro automatic processor without replenishment were measured. The changes in base-plus-fog density, film density and image contrast were measured for each of four processing solutions. All films to be developed in a solution were processed within 4 1/2 hours. The results cannot be generalized to solutions left overnight in the Peri-Pro processor or to solutions used in other automatic processors at different time-temperature cycles. If about 500 films are to be processed in a single day, the Peri-Pro solution, regular X-Omat, and RP X-Omat without part C are the solutions of choice. If about 1,000 films are to be processed in a single day, the Peri-Pro solution and RP X-Omat solution without part C are the solutions of choice. Only the Peri-Pro solution produced films (the first 600 films) of acceptable archival storage quality.

Radiographic Image Enhancement↗
PubMed1987

Diagnostic imaging assessment of experimental intraoral "folded film".

"Folded film" is an experimental technique of film preparation that provides diagnostic imaging of intraoral structures with one-half the radiation required to produce conventional images. In this study, folded film periapical images were compared with similar conventional D- and E-speed film images with the use of 12 criteria for diagnostic visualization. Nineteen examiners judged folded films to be slightly less diagnostic than D-speed film images and somewhat more diagnostic than E-speed films. All systems were judged adequate for diagnostic visualization of bone and teeth.

Radiographic Image Enhancement↗
PubMed1987

A comparison of Ektaspeed and Ultraspeed films using manual and automatic processing solutions.

Kodak's Ektaspeed (E) dental film is twice as fast as Ultraspeed (D) film and thereby significantly reduces radiation exposure to the patient. The film quality of the E film and D film was compared following processing with two manual and two automatic processing techniques. E-speed film processed manually or automatically produces diagnostically acceptable radiographs, with film densities within the recommended density limits commonly used in dentistry. High-contrast and low-contrast radiographs can be achieved by varying processing techniques.

Absorptiometry, Photon↗
PubMed1989

Comparative evaluation of the sensitometric properties of screen-film systems and conventional dental receptors for intraoral radiography.

This investigation determined the sensitometric properties of 27 rare-earth screen-film combinations and compared them to E- and D-speed films and xeroradiography, the current standards for intraoral radiography. A series of exposures from base plus fog to film saturation were made to determine the Hurter and Driffield curve of each image receptor. The base plus fog, film saturation, speed, gamma, average gradient, and resolution were determined. When dental receptors and screen-film systems are compared on the basis of radiographic quality (contrast and resolution), many screen-film systems have similar resolution (greater than 10 line pairs/mm), significantly greater contrast (greater than 2.0), and a substantial speed advantage (greater than 10). Thus selected screen-film systems may be an alternative to conventional dental receptors for intraoral radiography.

Evaluation Studies as Topic↗
PubMed1989

A subjective study of dental diagnostic utility comparing xeroradiography and film radiography.

This study determined the perceived strengths and weaknesses of xeroradiography, D-speed film, and E-speed film for intraoral radiography. Results indicated that xeroradiography was preferred for the imaging of structures useful in periodontics and endodontics whereas film demonstrated a low level of image artifacts and was judged to be better for the imaging requirements of routine restorative dentistry. D-speed film was rated higher than E-speed film. These subjective assessments are similar to previously reported pilot studies but differ from previously published objective studies, which showed no significant difference between the three imaging techniques. Although there are substantial subjective differences between xeroradiography, D-speed film radiography, and E-speed film radiography, all the techniques provide more than the threshold level of necessary diagnostic information and all techniques portray adequate information for evaluation of common abnormalities encountered in the oral cavity.

Dental Restoration, Permanent↗
PubMed1991

Automatic processing: effects of temperature and time changes on sensitometric properties of ULTRA-SPEED and EKTASPEED films.

The effects of changes in the processing temperature and time of automatic processors were studied with Kodak ULTRA-SPEED and EKTASPEED dental x-ray films. Speeds and inherent contrasts were derived for the two films from sensitometric curves at seven different temperatures and at five different processing times. As opposed to manual processing, only a slight change in film fog was observed with increases in automatic processing temperature or time. Film speed and contrast could be increased by increasing the processing temperature or time. The EKTASPEED film was more sensitive to these changes than was the ULTRA-SPEED film. Temperature had a stronger influence than processing time. All films were of archival storage quality except those processed at the low processing times of 2.5 or 3.5 minutes, and at the low processing temperature of 21 degrees C.

Evaluation Studies as Topic↗
PubMed1993

Noise in D- and E-speed radiographic film.

The purpose of this investigation was to compare image noise in D- and E-speed radiographic film and to establish a basis for choosing a particular speed of film for study of trabecular changes in alveolar bone. Eleven D-speed and 11 E-speed radiographs were made at varying exposures and developed along with unexposed film of each type to produce uniform optical densities that range from approximately 0.05 to 2.5. Profiles (scan lines) were made of each film at a spatial resolution of 0.02 mm. Noise was quantified for each profile using three measures: the standard deviation of the profile pixel intensity, I(x), about the mean, I(x); the coefficient of variation of I(x) about I(x); and Wiener spectral analysis. Results indicate that the average magnitude of noise for D- and E-speed film over this range of optical densities exceeds 4% and 6%, respectively; the average noise content of E-speed film was 25% to 35% greater than D-speed; and noise energy of both films is concentrated at low spatial frequencies and low optical densities.

Alveolar Process↗
PubMed1993

Exit dose measurements by portal film dosimetry.

Portal in vivo dosimetry is a very attractive tool for patient dose measurements because of the large amount of information that portal film systems can easily collect, once positioned at the exit surface of the patient. The first step in the verification of the reliability of portal films as in vivo dosimeters is the evaluation of the agreement between exit patient dose profiles and optical density profiles measured on the portal film. We checked the possibilities for exit dose measurements of a commercial portal film system (Film Kodak X-Omat V and Localization Kodak Cassette) verifying the agreement between relative exit doses (measured by ionization chamber and film dosimetry, calculated by our treatment planning system (Cadplan Dosetek)) and relative optical densities on portal films in cubic homogeneous and inhomogeneous, cylindrical and humanoid phantoms. In particular, a good agreement (mean difference in absolute value: 2%) between optical densities and calculated exit doses for the Rando phantom were found, once the optical densities values are corrected for an inverse square correction factor, taking into account the variation of the profile of the phantom.

Absorptiometry, Photon↗
PubMed1995

A laboratory evaluation of Ektaspeed Plus dental X-ray film.

OBJECTIVES: The aim of this study was to make a laboratory evaluation of the image quality of a new dental X-ray film, Ektaspeed Plus, compared with Ektaspeed and Ultraspeed films. METHODS: Films of each emulsion type underwent a range of exposures at both 50 kVp and 70 kVp, and characteristic curves were constructed to give a comparison of fog, speed and contrast. Line pair and contrast detail test objects were used to assess the resolution of radiographs and the ability of the two film types to reproduce minor differences in subject contrast. The sensitivity of the emulsions to safelighting for a range of times was also tested. RESULTS: Ektaspeed Plus had the same speed, a slightly higher base plus fog density but a higher contrast (50 and 70 kVp) than Ektaspeed. The speed of Ektaspeed Plus was higher and the contrast similar to that of Ultraspeed film. Limiting resolutions of the three films were the same. There was a slightly better imaging of one contrast detail phantom with Ektaspeed Plus compared to Ektaspeed at 70 kVp only. All three emulsions were insensitive to recommended safelighting conditions. CONCLUSION: The improved image contrast of Ektaspeed Plus may be more acceptable to dentists than Ektaspeed and lead to a greater acceptance of E-speed film, contributing to dose reduction.

Emulsions↗
PubMed2005

Two-dimensional mapping of underdosed areas using radiochromic film for patients undergoing total skin electron beam radiotherapy.

PURPOSE: To demonstrate the viability of radiochromic film as an in vivo, two-dimensional dosimeter for the measurement of underdosed areas in patients undergoing total skin electron beam (TSEB) radiotherapy. The results were compared with thermoluminescent dosimeter measurements. METHODS AND MATERIALS: Dosimetry results are reported for an inframammary fold of 2 patients treated using a modified version of the Stanford six-position (i.e., six-field and dual-beam) TSEB technique. The results are presented as contour plots of film optical density and percentage of dose. A linear dose profile measured from film was compared with the thermoluminescent dosimeter measurements. RESULTS: The results showed that the percentage doses as measured by film are in good agreement with those measured by the thermoluminescent dosimeters. The isodose contour plots provided by film can be used as a two-dimensional dose map for a patient when determining the size of the supplemental patch fields. CONCLUSION: Radiochromic film is a viable dosimetry tool that the radiation oncologist can use to understand the surface dose heterogeneity better across complex concave regions of skin to help establish more appropriate margins to patch underdosed areas. Film could be used for patients undergoing TSEB for disorders such as mycosis fungoides or undergoing TSEB or regional skin electron beam for widespread skin metastases from breast cancer and other malignancies.

Breast Neoplasms↗
PubMed2003

Perceived quality of radiographic images after rapid processing of D- and F-speed direct-exposure intraoral x-ray films.

OBJECTIVE: We sought to compare the densitometric properties and perceived image quality of InSight (F-speed) and Ultra-Speed (D-speed) film radiographs processed with rapid chemistry. The effects of density, contrast, and film speed on perceived image quality were also studied. STUDY DESIGN: Images were made of a human cadaver phantom with exposures to achieve background densities approximating 1.5, 2.0, and 3.0. Films were processed in a radiographic darkroom by using Insta-Neg and Insta-Fix rapid chemistry as the manufacturer had recommended. Five endodontic residents independently analyzed images of varying density, speed, and contrast that were presented in a randomized manner. They were required to evaluate the perceived image quality of 5 specifically designated areas on the film, using a labeled photograph as a guide. These areas included root canal obturation, periodontal ligament space, dentinoenamel junction, and crestal bone height. In addition, they were also asked to assess the overall perceived image quality. Statistical analysis consisted of ordinal regression and 2-factor analysis of variance. RESULTS: No statistically significant differences were proved between F- and D-speed radiographs within the same density group. Higher density and higher contrast resulted in a statistically significant positive impact (P <.01) on the ranking for all 5 subjective determinations. Observers preferred the films exposed to a background density of 3.0 over those of a lower density (P <.01). CONCLUSIONS: InSight (F-speed film) can be used with rapid chemistry to ensure less radiation exposure to patients than is necessary with D-speed film. The observers participating in this study preferred radiographs from the 3.0 background density group to those from the 2.0 and 1.5 density groups.

Absorptiometry, Photon↗