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At least 973 records · Page 54Linked to original sources
PubMed2005

Low dose fraction behavior of high sensitivity radiochromic film.

A high sensitivity (HS) model of radiochromic film is receiving increasing use. The film's linear sensitometric response in the range of 0.5-40 Gy would make this film an ideal candidate for complex dosimetry applications that require tissue equivalence. This study investigates the potential use for clinical dosimetry of typical radiotherapy fractions at relatively low doses (0.5-5 Gy). The experiment involved exposing 25 pre-exposed pieces of HS film to five equal fractions of doses from 0.5 to 5 Gy 24 hours apart. The cumulative dose for each film was carefully monitored and optical density measurements were used as the sole determination of film response to dose. The average behavior of the various fractionation schemes was roughly consistent with previous observations of the MD-55 radiochromic film with about twice the overall sensitivity as expected. However, at low doses and low dose increments, unexpected variations beyond a well-documented low dose nonlinearity were observed. These unexpected variations may indicate complex polymer kinetics at low doses. This type of film would require extra care beyond that described in TG-55 for accurate use at low doses or low dose fraction schemes.

Dose Fractionation, Radiation↗
PubMed2005

Fast radiographic film calibration procedure for helical tomotherapy intensity modulated radiation therapy dose verification.

Film dosimetry offers an advantageous in-phantom planar dose verification tool in terms of spatial resolution and ease of handling for quality assurance (QA) of intensity modulated radiation therapy (IMRT) plans. A critical step in the success of such a technique is that the film calibration be appropriately conducted. This paper presents a fast and efficient film calibration method for a helical tomotherapy unit using a single sheet of film. Considering the unique un-flattened cone shaped profile from a helical tomotherapy beam, a custom leaf control file (sinogram) was created, to produce a valley shaped intensity pattern. There are eleven intensity steps in the valley pattern, representing varying dose values from 38 to 265 cGy. This dose range covers the most commonly prescribed doses in fractionated IMRT treatments. An ion chamber in a solid water phantom was used to measure the dose in each of the eleven steps. For daily film calibration the whole procedure, including film exposure, processing, digitization and analysis, can be completed within 15 min, making it practical to use this technique routinely. This method is applicable to film calibration on a helical tomotherapy unit and is particularly useful in IMRT planar dose verification due to its efficiency and reproducibility. In this work, we characterized the dose response of the KODAK EDR2 ready-pack film which was used to develop the step valley dose maps and the IMRT QA planar doses. A comparison between the step valley technique and multifilm based calibration showed that both calibration methods agreed with less than 0.4% deviation in the clinically useful dose ranges.

Calibration↗
PubMed2002

The electronic portal imaging system Siemens Beamview Plus versus the conventional verification films CEA-TVS and DuPont COL-7. A critical appraisal of visual image quality.

AIM: The aim of this study was the validation of the visual image quality of electronic portal imaging devices (EPID) and conventional verification films from the point of view of the end-viewers of portal films, the radiotherapists. MATERIAL AND METHODS: The verification image was represented in two different forms, viz. an electronic portal image employing Siemens Beamview Plus (on a computer monitor) and two different portal films using the conventional verification films CEA-TVS and DuPont CQL-7 (on a negatoscope). A total of 270 image sets (simulation film and portal image) were evaluated by each radiotherapist, evaluation extending to 90 sets of each type of verification film. Each set was evaluated by three specialists in radiotherapy examining subjective visual image quality whereby the following aspects served as evaluation criteria: contrast, artifacts, determination of actual radiation field edge position, anatomical structures and main structural feature for the determination of treatment field position. In addition, the anatomical structures employed for visual feature correlation between reference and portal films were classified according to their importance. RESULTS: In general the electronic portal image was rated significantly "visible" or better. Only the evaluation of artifacts showed an appreciable disadvantage for electronic portal imaging caused by physical artifacts due to radiographic technique and data processing aspects peculiar to the Siemens Beamview Plus 1.1. and also caused by different image processing tools reducing physical artifacts and enhancing the visibility of anatomical structures and likewise of anatomical artifacts (e.g. intestinal gas). By calculating the Spearman correlation coefficient to detect a possible relationship between the different criteria of subjective visual image quality, the research demonstrated that artifacts when limited to a tolerable proportion had no significant impact on the other criteria. CONCLUSIONS: As data of EPIDS are digital, images can be postprocessed and enhanced in a wide variety of ways. Using this tool the electronic portal imaging device provides images that, in terms of visual image quality, are at least comparable to the two evaluated types of radiographic films and also have the added advantage that such images are stored and can be transferred electronically being presupposition for digital patient documentation.

Artifacts↗
PubMed1987

A comparative clinical study of group D and E dental film.

Dental clinicians were asked to distinguish differences in radiographic detail between complete mouth surveys taken with the use of D- and E-speed films. In complete mouth surveys consisting of one half D-speed and one half E-speed films, clinicians could not correctly identify the half of the survey taken with D-speed film 55% of the time. When asked to distinguish surveys consisting entirely of either D- or E-speed films, evaluators could not distinguish D-speed film surveys from E-speed film surveys 42.7% of the time. E-speed film produces diagnostically acceptable radiographs similar in quality to those of D-speed film with the added advantage of an approximate 50% reduction in patient exposure.

Dentists↗
PubMed1988

External beam profiles measured with film or ionization chamber.

Radiation therapy beam profiles measured with an ionization chamber in a scanning water phantom are compared with profiles measured with a standard film dosimetry technique. An 18 cm field was filmed with 4 MV photons in a polystyrene phantom at depths of 1, 7, and 13 cm. The film was scanned with a scanning densitometer and the resulting profiles were converted to dose profiles with a sensitometric curve. To determine the effect of backscatter on the film a special phantom was constructed to eliminate the backscatter from the film measurement. This provided a comparison with the solid film phantom where full backscattering was present. The beam profiles measured with the film differed by less than 3% from the ionization chamber profiles and there was less than 1% difference between the film techniques.

Film Dosimetry↗
PubMed1996

Evaluation of several Dupont portal film systems.

The sensitometric curves (also known as the characteristic curves, or more commonly as the H-D curves after Hurler and Driffield who first used such curves in 1890 to describe the response of photographic film to light) of three DuPont portal films (CRONEX 10T, 10TL and Ultra-Vision C) in combination with two DuPont cassettes (CRONEX Radiation Therapy and Radiation Therapy Verification) were produced utilizing a 60Co beam and a 18 MV beam. The results are compared with that of a Kodak portal film system (T-Mat G/RA film and X-Onratic V cassette). The sensitometric curves of the DuPont films in the Kodak cassette were also measured. The results show that the Kodak system is superior to the DuPont systems with respect to the imaging quality and the feasibility of film techniques, and that if the DuPont films are used, significant improvements can be made by combining the DuPont films with the Kodak cassette.

Cobalt Radioisotopes↗
PubMed1991

Clinical utility of high-resolution portal films.

We have evaluated the film quality and overall clinical utility of a unique high-resolution portal film system which utilizes high contrast graphics art film. A total of 127 unselected patients had their conventional portal films and high-resolution films of the same site, compared and graded subjectively for a variety of parameters by an independent panel of radiotherapists and radiographers. Although consistent improvements in most aspects of image quality were noted, improved overall clinical usefulness of the high-resolution portal film system in comparison to the conventional films, when subjected to multiple regression analysis, was confined to lateral neck views only. High-resolution portal film utility was also found to depend significantly on field size with areas less than 110 cm2 having a markedly worse clinical utility score.

Humans↗
PubMed1996

Effects of tomographic motion, slice thickness, and object thickness on film density.

The experiment used the computer-aided CommCat model IS 2000 tomographic machine (Imaging Sciences International, Roebling, N.J.). The objective of the experiment was to study the influence of tomographic tube motion, tomographic slice thickness, and object thickness on film density. The experiment was conducted by x-radiating an aluminum step-wedge placed along the x-axis. Exposures were made for different tube motions and for different slice thicknesses. In linear horizontal and linear vertical motions, an increased slice thickness decreased film density. Slice thickness had a stronger effect on film density when the object to be x-radiated was thinner. In circular, elliptical, spiral, and hypocycloidal motions, changes in slice thickness had no noticeable effect on film density because the manufacturer had programmed the machine to produce approximately similar exposure times by increasing the x-ray tube velocity thickness had a greater effect on film density for circular, elliptical, spiral, and hypocycloidal tube motions than for linear horizontal and linear vertical tube motions. Clinical observation showed that except for the linear vertical motion (motion that was oriented in the same direction as that of the tube travel) all other motions produced a zone of diffusion along the edges of the steps of the step-wedge. An increase in slice thickness had an effect on film density. Slice thickness had a noticeable effect on film density in linear but not in multidirectional tomography. Object thickness had a greater effect on film density in multidirectional than in linear tomography.

Absorptiometry, Photon↗
PubMed1998

Endodontic working length assessment. Comparison of storage phosphor digital imaging and radiographic film.

OBJECTIVE: This study compared the difference in interpretation of the position of endodontic file tips between two imaging systems: photostimulable storage phosphor luminescence imaging versus radiographic film. STUDY DESIGN: Thirteen patients were selected at random. Preoperative and trial file length radiographs were made with a dual image receptor composed of a Digora Digital Imaging Plate and a piece of Ektaspeed Plus film. Exposure techniques for E-speed film were used. Root length and file length measurements were made from digital images with the Digora system's measuring tools. Measurements were also made on radiographic film with a 7 x measuring magnifier. Root length, file length, and their difference were compared for both film and digital images. RESULTS: Differences were found to be less in digital than in film images. Photostimulable storage phosphor luminescence imaging performed similarly to Ektaspeed Plus film for measuring root lengths, but file tip positions (especially of small file sizes) were difficult to visualize with E-speed film. CONCLUSIONS: The smaller difference between file tip and root apex found with digital imaging suggests that this technique is more accurate to assess trial file length. This imaging modality for assessing file positions during root canal treatment may be beneficial to the practitioner.

Bicuspid↗
PubMed2001

Sensitometric and clinical evaluation of a new F-speed dental X-ray film.

OBJECTIVE: To compare the sensitometric properties, diagnostic efficacy and image quality of the InSight (F-speed) and Ektaspeed Plus (E-speed) dental X-ray films (Kodak Eastman Co, Rochester, USA). METHODS: Characteristic curves were constructed, using manual and automatic processing, in order to compare film speed and average gradient. The diagnostic yield was compared by assessment of endodontic file length. Endodontic files, sizes 10 and 15, were placed at the root apex or 1.5 mm short. The exposure time for the InSight films was 20% lower than that of Ektaspeed Plus. Seven dentists rated the position of file tip using a 5-point confidence scale. ROC data were analysed by means of analysis of variance. The null hypothesis was rejected when P<0.05. In order to compare the image quality, 100 pairs of bitewing radiographs of the left (using Ektaspeed Plus) and the right sides (using InSight) of the same patient were made. Four dentists viewed the radiographs and the data were analysed using Kendall's coefficient of concordance. RESULTS: InSight was faster than Ektaspeed Plus. It was an E-speed film when processed in manual conditions and an F-speed film when processed automatically. The films had comparable average gradient. No significant difference was found in the diagnostic yield using the two films (P=0.648). Two observers showed a significant preference for Ektaspeed Plus. CONCLUSIONS: The first results of the new InSight film are promising: the exposure time can be reduced by 20% in comparison with Ektaspeed Plus at no detriment to diagnostic efficacy.

Absorptiometry, Photon↗
PubMed2001

Radiochromic film dosimetry in water phantoms.

Radiochromic film is investigated for use in dosimetry in water phantoms as opposed to solid phantoms. Investigations are performed to measure the penetration rates of water into radiochromic film and to assess the effects on optical density that this penetration causes. The effects of film orientation during irradiation in water are also tested. Results show that only a small penetration rate is seen from water into the film which only affects the outer areas of the film, with penetration being less than 0.5 mm per hour. The optical density measurements of the film at 660 nm remain unchanged in the unaffected regions of the radiochromic film. Minimal effects are seen due to beam orientation in a water phantom as opposed to solid water phantoms in which an overestimation in dose is normally seen for parallel irradiation. Radiochromic film seems to be an adequate detector for dosimetry in a water phantom where high spatial resolution is needed and angle of beam incidence at the point of interest is important.

Dose-Response Relationship, Radiation↗
PubMed2003

Composite depth dose measurement for total skin electron (TSE) treatments using radiochromic film.

Total skin electron (TSE) radiotherapy is routinely used to treat cutaneous T-cell lymphomas and can be implemented using a modified Stanford technique. In our centre, the composite depth dose for this technique is achieved by a combination of two patient positions per day over a three-day cycle, and two gantry angles per patient position. Due to patient morphology, underdosed regions typically occur and have historically been measured using multiple thermoluminescent dosimeters (TLDs). We show that radiochromic film can be used as a two-dimensional relative dosimeter to measure the percent depth dose in TSE radiotherapy. Composite depth dose curves were measured in a cylindrical, polystyrene phantom and compared with TLD data. Both multiple films (1 film per day) and a single film were used in order to reproduce a realistic clinical scenario. First, three individual films were used to measure the depth dose, one per treatment day, and then compared with TLD data; this comparison showed a reasonable agreement. Secondly, a single film was used to measure the dose delivered over three daily treatments and then compared with TLD data; this comparison showed good agreement throughout the depth dose, which includes doses well below 1 Gy. It will be shown that one piece of radiochromic film is sufficient to measure the composite percent depth dose for a TSE beam, hence making radiochromic film a suitable candidate for monitoring underdosed patient regions.

Electrons↗
PubMed2004

Experimental energy response verification of XR type T radiochromic film.

This short note investigates the energy response characteristics of a relatively new high sensitivity radiochromic film (XR type T) and compares it to other radiochromic and radiographic films and thermoluminescent dosimeters. Results show that the energy response of the new XR type T film is relatively large over the range of therapeutic energies from 50 kVp superficial x-ray treatment to 18 MV high energy radiotherapy treatment. When normalized to 1 at a standard 6 MV radiotherapy x-ray energy the XR type T film produced a normalized dose response of approximately 6 in the energy range of 30 keV to 70 keV thus representing an increase in sensitivity at lower energies similar to that observed for radiographic x-ray films. This is quite different from previous versions of Gafchromic film where the energy response of the film decreases at lower energies down to levels approximately 0.6-0.7 for the same effective energies. This type of film has been optimized for use in diagnostic energy ranges producing a relatively uniform dose response in the 30 keV to 70 keV range.

Dose-Response Relationship, Radiation↗
PubMed2006

Absorption spectra of irradiated XRCT radiochromic film.

Gafchromic XRCT radiochromic film is a self-developing high sensitivity radiochromic film product which can be used for assessment of delivered radiation doses which could match applications such as computed tomography (CT) dosimetry. The film automatically changes colour upon irradiation changing from a yellow to green/brown colour. The absorption spectra of Gafchromic XRCT radiochromic film as measured with reflectance spectrophotometry have been investigated to analyse the dosimetry characteristics of the film. Results show two main absorption peaks produced from irradiation located at 636 nm and 585 nm. This is similar to EBT Gafchromic film. A high level of sensitivity is found for this film with a 1 cGy applied dose producing an approximate net optical density change of 0.3 at 636 nm. This high sensitivity combined with its relatively energy independent nature around the 100 kVp to 150 kVp x-ray energy range provides a unique enhancement in dosimetric measurement capabilities over currently available dosimetry films for CT applications.

Absorption↗
PubMed2006

New developments in radiochromic film dosimetry.

NIST has been a pioneer in the use of radiochromic film for medical dosimetry applications. Beginning in 1988 with experiments with (90)Sr/Y ophthalmic applicators, this work has continued into the present. A review of the latest applications is presented, which include high activity low-energy photon source dosimetry and ultra-high resolution film densitometry for dose enhancement near stents and microbeam radiation therapy dosimetry. An exciting recent development is the availability of a new radiochromic emulsion which has been developed for IMRT dosimetry. This emulsion is an order of magnitude more sensitive than was previously available. Measurements of the sensitivity and uniformity of samples of this new film are reported, using a spectrophotometer and two scanning laser densitometers. A unique feature of the new emulsion is that the peak of the absorbance spectrum falls at the wavelength of the HeNe lasers used in the densitometer, maximising sensitivity. When read at a wavelength of 633 nm, sensitivities on the order of 900 mAU Gy(-1) were determined for this new film type, compared with about 40 mAU Gy(-1) for type HS film, 20 mAU Gy(-1) for type MD-55-2 film, and 3 mAU Gy(-1) for type HD-810. Film uniformities were found to be good, on the order of 6% peak to peak. However, there is a strong polarisation effect in the samples examined, requiring care in film orientation during readout.

Dose-Response Relationship, Radiation↗
PubMed1993

Comparison of a videodisc system with a conventional film file for medical student teaching.

PURPOSE: The authors assessed the effectiveness of a videodisc film file compared with a conventional film file for teaching radiology to medical students. METHODS: Fourth-year medical students (N = 134) studied 116 cases selected from the American College of Radiology Learning File. Half the students studied 58 skeletal cases using conventional films and half studied the same cases on a videodisc system. Student groups were then switched and those who studied skeletal cases on films studied 58 chest cases on videodisc and vice versa. Students received the same skeletal and chest tests and completed a questionnaire. RESULTS: For both skeletal and chest radiology, students studying films scored minimally higher than students using the videodisc. Students rated films superior to the videodisc for amount learned, convenience of use, and ability to detect lesions. CONCLUSIONS: Conventional film and videodisc methods resulted in similar levels of learning; however, students perceived conventional films to be a superior learning experience.

Education, Medical, Undergraduate↗
PubMed2004

Comparison of small photon beams measured using radiochromic and silver-halide films in solid water phantoms.

In this study, we compared the dosimetric properties of four of the most commonly used films for megavoltage photon-beam dosimetry when irradiated under identical conditions by small multileaf-collimator (MLC) defined beamlets. Two silver-halide films (SHFs), Kodak XV2 and EDR2, and two radiochromic films (RCFs), Gafchromic HS and MD55-2, were irradiated by MLC-defined 1 x 1 cm2 beamlets from a Varian 2100 C/D linac equipped with a 120-leaf MLC. The beamlets were delivered with the accelerator gantry set laterally (90 degrees rotation) upon a solid-water compression film phantom at 100 cm source-to-surface distance which was positioned with the films parallel to the beam axis. Beamlets were delivered at central axis, 5.0 cm, and 10.5 cm off-axis for both leaf-end and leaf-side defined beamlets. The film dosimetry was performed using a quantitative optical density (OD) imaging system that was validated in a previous study. No significant differences between SHF and RCF measurements were observed in percentage depth doses, horizontal depth profiles, or two-dimension spatial isodose distributions in both the central axis and off-axis measurements. We found that regardless of the type of film used, RCF or SHF, a consistent data set for small beam dose modeling was generated. Previous validation studies based on the use of RCF and OD imaging system would indicate that all film produce an accurate result for small beam characterization.

Equipment Failure Analysis↗
PubMed2006

Characterization and use of EBT radiochromic film for IMRT dose verification.

We present an evaluation of a new and improved radiochromic film, type EBT, for its implementation to IMRT dose verification. Using a characterized flat bed color CCD scanner, the film's dose sensitivity, uniformity, and speed of development post exposure were shown to be superior to previous types of radiochromic films. The film's dose response was found to be very similar to ion chamber scans in water through comparisons of depth dose and lateral dose profiles. The effect of EBT film polarization with delivered dose and film scan orientation was shown to have a significant effect on the scanner's OD readout. In addition, the film's large size, flexibility, and the ability to submerge it in water for relatively short periods of time allowed for its use in both water and solid water phantoms to verify TomoTherapy IMRT dose distributions in flat and curved dose planes. Dose verification in 2D was performed on ten IMRT plans (five head and neck and five prostate) by comparing measured EBT dose distributions to TomoTherapy treatment planning system calculated dose. The quality of agreement was quantified by the gamma index for four sets of dose difference and distance to agreement criteria. Based on this study, we show that EBT film has several favorable features that allow for its use in routine IMRT patient-specific QA.

Dose-Response Relationship, Radiation↗