Focus-film Distance Research Articles

Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie

Calculation of conversion coefficients for the reconstruction of organ doses from entrance doses for chest radiographs of 0, 1, 5, 10, 15, and 30-year-old patients in conventional pediatric radiology for the radiographic settings recommended by the German and European guidelines for quality management in diagnostic radiology. The conversion coefficients for pediatric chest radiographs were calculated using the commercially available personal computer program PCXMC developed by the Finnish Centre for Radiation and Nuclear Safety (Säteilyturvakeskus STUK). PCXMC is a Monte Carlo program for computing organ and effective doses in about 40 organs of mathematical hermaphrodite phantom models describing patients of different ages. The possible clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation fields on the phantoms' surfaces. Conversion coefficients for the reconstruction of organ doses from measured entrance doses during chest radiographs for 0, 1, 5, 10, 15, and 30-year-old pediatric patients were presented. Conversion coefficients were calculated for the standard sagittal and lateral beam projections and the standard focus film distances of 100 cm, 115 cm, and 150 cm using the standard radiation qualities according to the recommendations of the German and European guidelines for quality management in diagnostic radiology. These conversion coefficients allow the reconstruction of the absorbed dose in about 40 organs and tissues of the human body for optimal and suboptimal radiation field collimations. The conversion coefficients presented in this paper may be used for organ dose assessments from entrance doses measured during chest radiographs of patients of all age groups with all beam collimations within optimal and suboptimal standard beam collimations. While the influence of the beam collimation on organ doses of organs localized near the center of the beam is expectedly low, the radiation exposure of organs and tissues near the boundaries of the radiation field can be considerably reduced by an optimal beam collimation. The conversion coefficients calculated for the STUK phantoms are in good conformity with values published for the GSF phantoms "Adam", "Golem" and "Visible Human".

Clubbed fingers: Radiological evaluation of the nail bed thickness

It is established that there is an increase in soft tissue of the clubbed digits as demonstrated on previous histopathological examinations. In the present study, the nail bed thickness was assessed and measured on plain radiographs of index fingers in two groups of patients: one group with lung disease and fingers clubbing and one group of normal controls. A vertical x-ray beam was used with a focus-film distance of 1.0 m, with the index finger placed in lateral view directly over the film, without anti-diffusion grid. Three investigators, blinded to prevent bias measured the thickness of soft tissues between the nail root and the terminal phalanx on the radiographs. This method was used to evaluate a group of 85 clinically clubbed (hyponychial angle > 192.0 degrees) adult patients with lung disease and a control group of a 100 normal adult individuals with no clubbing (hyponychial angle < 188.0 degrees). The mean nail bed thickness in the patients with clubbing (n = 85) was 3.88 +/- 0.55 mm (3.00-5.50 mm). In comparison, in the normal subjects (n = 100), the mean was 2.38 +/- 0.27 mm (1.75-3.10 mm), revealing a significant difference (P < 0.001). Only two normal individuals presented nail bed thickness >or=3.0 mm. A good interobserver agreement on the measurements was found (P > 0.900). The radiographic evaluation of the nail bed thickness was easily performed, with good interobserver concordance. It is possible to distinguish between clubbed from nonclubbed fingers, in vivo, using plain radiograph.

Reduction of radiation exposure in full spine images in youth

With a phantom of the vertebral column in 16 measuring series using diagnostic dosimeters the influence of grid, recording voltage, focus-film distance (FFD) and film-foil-systems on the radiation exposure was examined. With identical film-foil systems this resulted in a dose reduction by a factor of 4 to 7 for X-rays without grid compared to X-rays using grid. Therefore in case of follow-ups with questions about the statics of the vertebral column it is recommended to X-rays without grid. The studies can substantiate also the recommendations aiming at the avoidance of long exposure times to apply small mAs-products and voltages as high possible, to use highly sensitive film-screen systems (e.g. EU 600) and not to exceed a FFD of 2 m). These actions even when used separately and certainly when used simultaneously cause a considerable cut in radiation exposure. A radiation exposure decreasing effect is given by taking total X-rays compared to partial X-rays which is appropriate especially with slim patients.

Chest radiographic findings in Human Immunodeficiency Virus disease in Benin City, Nigeria.

This study was carried out to determine findings on chest radiographs in HIV positive/AIDS patients at the University of Benin Teaching Hospital (UBTH) Benin City. All consecutive HIV positive/AIDS patients, managed at the UBTH between 1991 and 2001 were included in the study. Patients had postero-anterior (PA) chest radiographs done in full inspiration, with a Roentgen 301 radiographic machine (GEC Medical) using the following factors; KVp = 65, focus-film distance = 150cm and 12 – 15mAs. A total of 308 confirmed HIV- positive patients had chest radiographic examinations. Ninety-nine (32.14%) patients had normal findings, while 209 (67.86%) were abnormal. Abnormal findings included, cardiomegaly, 84 (27.27%) patients; radiological features of cardiac failure, 44 (14.28%) patients; lung cavitations, 47 (15.4%) patients; pleural effusions, 40 (13.09%) patients, fibrocystic changes, 40 (13.09%) patients, lobar consolidation, 29 (09.52%) patients, non-specific (atypical) infiltrates 70 (22.62%) patients, and hilar-adenopathy 7 (02.38%) patients. Soft tissue wasting was seen in 47 (15.25%) patients. Chest radiography remains a good instrument for detecting pulmonary and cardiovascular abnormalities even in HIV positive/AIDS patients Keywords: HIV/AIDS patients, Chest radiographic findings Annals of Biomedical Science Vol. 1 (2) 2002: pp. 131-135

Quantitative determination of radio-opacity: Equivalence of digital and film X-ray systems

Objectives To evaluate the equivalence of a digital X-ray system (DenOptix) to conventional X-ray film in terms of the measured radio-opacity of known filled-resin materials and the suitability of attenuation coefficient for radio-opacity determination. Methods Discs of five thicknesses (0.5–2.5 mm) and step-wedges of each of three composite materials of nominal aluminum-equivalence of 50%, 200% and 450% were used. X-ray images of a set of discs (or step-wedge), an aluminum step-wedge, and a lead block were taken at 65 kV and 10 mA at a focus-film distance of 400 mm for 0.15 s and 1.6 s using an X-ray film or imaging plate. Radio-opacity was determined as equivalent aluminum thickness and attenuation coefficient. The logarithm of the individual optical density or gray scale value, corrected for background, was plotted against thickness, and the attenuation coefficient determined from the slope. The method of ISO 4049 was used for equivalent aluminum thickness. Results The equivalent aluminum thickness method is not suitable for materials of low radio-opacity, while the attenuation coefficient method could be used for all without difficulty. The digital system gave attenuation coefficients of greater precision than did film, but the use of automatic gain control (AGC) distorted the outcome unusably. Conclusion Attenuation coefficient is a more precise and generally applicable approach to the determination of radio-opacity. The digital system was equivalent to film but with less noise. The use of AGC is inappropriate for such determinations.

Radiographic techniques for medical–dental research with minipigs

Techniques were developed to obtain standardised intra- and extra-oral radiographs in minipigs for use in medical–dental research. Twelve male minipigs (BR-1 Minipigs) were chosen at random. Two animals each at 3, 5, 7, 9, 12 and 15 months of age were anaesthetised and subjected to radiographic examinations to assess six techniques. Three intra-oral and three extra-oral techniques, standardised for humans, were used with variations of the angle of incidence of the X-ray beams, focus-film distance and exposure time. Two film positioners were developed for the intra-oral techniques. Two examiners then chose the radiographs with the least image distortion, greatest clarity and least superimposition of images. For each technique, the suitable angle of incidence of the X-ray beams, the focus-film distance and exposure time that produced the highest quality radiographs were standardised.

Source to image receptor distance

CorrespondenceSource to image receptor distanceP C Brennan and D O'learyP C BrennanSchool of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin 4, IrelandSearch for more papers by this author and D O'learySchool of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin 4, IrelandSearch for more papers by this authorPublished Online:5 Mar 2014https://doi.org/10.1259/bjr/60546865SectionsPDF/EPUBFull Text ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About"Source to image receptor distance." The British Journal of Radiology, 79(939), p. 266 References 1 Poletti JL, McLean D. The effect of source to image-receptor distance on effective dose for some common X-ray projections. Br J Radiol 2005;78:810–5. Link ISI, Google Scholar2 O'Leary D, McDonnell S, Brennan PC. Increasing film focus distance (FFD) reduces radiation dose for X-ray examinations. Radiat Prot Dosim 2004;108:263–8. Crossref Medline ISI, Google Scholar Previous article Next article FiguresReferencesRelatedDetailsCited byA comparison of effective dose and risk for different collimation options used in AP shoulder radiographyRadiography, Vol. 265Does collimation affect patient dose in antero-posterior thoraco-lumbar spine?Radiography, Vol. 23, No. 3 Volume 79, Issue 939March 2006Pages: 183-270 © The British Institute of Radiology History Published onlineMarch 05,2014 Metrics Download PDF

In vitro radiographic analysis of Nd:YAG-laser-irradiated dentin

The aim of this study was to evaluate the effects of Nd:YAG laser irradiation on the dentin radiographic image. Previous studies have shown that Nd:YAG laser irradiation is capable of promoting morphological and chemical changes of the dentin surface, indicating the possibility of an alteration of its radiographic image. Dentin of 2-mm-thick mid-coronal sections from 68 extracted posterior teeth was irradiated for 30 s by a Nd:YAG laser (lambda=1,064 nm) on one half of its surface area. The other half was left as a control. The irradiation parameters were: 80 mJ/pulse, 0.8 W, 10 Hz, with a 320-mum flexible quartz optic fiber in contact mode. The 68 samples were radiographed with a 70-kV X-ray setup. The focus-film distance was established as 30 cm and there was no distance between the object and the film. The X-ray exposure time was set as 0.16 s and the radiographic film used was an F-speed dental film. The obtained radiographic images were submitted to a densitometric analysis. The images analyzed showed that there were statistically significant differences between the density of the irradiated dentin images and the non-irradiated dentin images. The image density data showed that the irradiated dentin radiographic images were 6.36% more radiopaque than the non-irradiated dentin images. The Nd:YAG laser irradiation of dentin is able to alter its radiographic image, producing more radiopaque images of the irradiated dentin.

Estimation of patient doses for common diagnostic X-ray examinations in Latvian hospitals, analysis of radiographic techniques and comparison with European guidelines

This article deals with the estimation of doses received by patients undergoing radiological examinations in order to establish dose reference levels (DRLs) in Latvia. Several large hospitals, small hospitals and private practices were selected for patient dose measurements. The measurements were carried out using calibrated thermoluminiscence dosemeters attached to the patient's skin. Exposure parameters and patient's data were recorded. The entrance surface doses (ESDs) to patients undergoing several common X-ray examinations (chest AP/PA, chest LAT, lumbar spine AP/PA, lumbar spine LAT and pelvis) were measured. Data concerning the kV(p) settings, used type of films, focus-film distance and the ESD values were analysed and compared with those recommended by the European Community (EC). Among the different hospitals and private practices, discrepancies in the patient doses and techniques used for the examination were found, where the doses exceeded the EC recommended values owing to a very low kV(p) and a very low sensitivity of the screen film combinations used.

Letter to the Editor

Sir, Comments on ‘Increasing film-focus distance (FFD) reduces radiation dose for X-ray examinations’ by P.C. Brennan, S. McDonnell and D. O'Leary. In a recent publication, Brennan et al.(1) claim that increasing the film-focus distance (FFD) from 100 to 130 cm will reduce effective doses (E) by 33% for a pelvic X-ray examination. This conclusion is based on a reported 33% reduction in the entrance surface dose (ESD), by the use of the same effective dose per unit ESD conversion coefficient (E/ESD) at both FFD values. However, E/ESD values are only valid for the specific geometry used in the Monte Carlo simulations, and will generally vary with FFD. To obtain values of E at different FFDs, one should calculate the kerma area product (KAP) values at each FFD distance, and obtain effective doses using E/KAP conversion factors provided by the National Radiological Protection Board (NRPB)(2). For a given X-ray beam quality and anatomic projection, the KAP is directly proportional to energy imparted to the patient, which in turn will be (approximately) proportional to effective dose.

Influence of Image-Capturing Parameters on Digital X-Ray Radiogrammetry

The purpose of this study was to evaluate the importance of different image-capturing conditions, which might influence the characteristics of radiographs and, consequently, impact calculations of bone mineral density (BMD) and Metacarpal Index (MCI) using digital X-ray radiogrammetry (DXR). Radiographs of the left hand of deceased males were acquired three times using systematically varied parameters: 4-8 miliamp seconds (mA); 40-52 kV; film-focus distance (FFD); 90-130 cm; film sensitivity, 200/400; and different image modalities (conventional vs original digital radiographs as well as digital printouts). Furthermore, the interradiograph reproducibility using both conventional equipment and printouts vs originals of digital images and the intraradiograph reproducibility (either conventional or digital printouts) were evaluated. All BMD and MCI measurements were obtained with the DXR technology. The interradiograph reproducibility of DXR-BMD using conventional images under standardized conditions (6 mAs; 42 kV; 1 m FFD; film sensitivity of 200) was calculated to be coefficient of variation (CV) = 0.49% for Agfa Curix film and CV = 0.33% for Kodak T-MAT-Plus film, whereas reproducibility error using digital images ranged from CV = 0.57% (digital printouts; Philips) to CV = 1.50% (original digital images; Siemens). The intraradiograph reproducibility error was observed to be CV = 0.13% (conventional; Kodak film) vs CV = 0.27% (digital printouts; Philips). The BMD calculation was not noticeably affected by changes of FFD, exposure level, or film sensitivity/film brand, but was influenced by tube voltage (CV = 0.99% for Kodak film to CV = 2.05% for Siemens digital printouts). No significant differences were observed between the BMD and MCI data. DXR provides measurements of MCI and BMD with high precision and reproducibility. The measurements are unaffected by all tested image-capturing conditions, with the exception of tube voltage. In addition, different digital image devices clearly have an effect on DXR reproducibility.

Descriptive patterns of severe chronic pulmonary hypertension by chest radiography

To find chest roentgenographic (CXR) features to help differentiate two representative diseases with severe chronic pulmonary hypertension (PH). Thirty-six consecutive patients with chronic thromboembolic PH (CTEPH), 38 with primary PH (PPH), and 37 with left heart disease and PH. CXRs were reviewed about 6 features (left 2nd arc protrusion, right descending pulmonary artery diameter (rPAD), cardiothoracic ratio (CTR), right 2nd arc width, avascular area and pleural abnormality). Hemodynamic data and the degree of tricuspid regurgitation (TR) on echocardiography were compared with CXR findings. The diagnostic pattern of CTEPH was the presence of one of two findings, an avascular area or marked rPAD (>20mm) together with pleuritic change. The diagnostic pattern of PPH was one of the two features; without pleuritic abnormality, marked left 2nd arc protrusion (>10mm) or moderate left 2nd arc protrusion (5-10mm) with marked rPAD (<20mm). The sensitivity for the diagnosis of CTEPH among the three diseases was 78% and specificity was 92%. The sensitivity for the diagnosis of PPH was 45% and specificity was 88%. CTR and right 2nd arc width were related to the degree of TR in CTEPH and PPH. Characteristic roentgenographic findings can help differentiate two frequent diseases associated with chronic pulmonary hypertension and reflect the severity of disease.

The impact of technical conditions of X-ray imaging on reproducibility and precision of digital computer-assisted X-ray radiogrammetry (DXR).

To evaluate the reproducibility of imaging and analysis for bone mineral density (BMD) determination using digital computer-assisted X-ray radiogrammetry (DXR; Pronosco X-posure, version V.2, Sectra Pronosco, Denmark); to verify potential factors that influence BMD extrapolation such as tube voltage, film-focus distance (FFD), film quality and brand (Kodak T-MAT-Plus, Konika SRH, Agfa Scopix), imaging technology (conventional, digital), imaging system (Kodak, Agfa) and exposure level (mAs); and to clarify whether DXR analysis based on printouts of digital images is comparable to analysis of conventional images. The hand of a cadaver was X-rayed using varied parameters: 4-8 mAs, 40-52 kV, 90-130 cm FFD. Radiographs under standardised conditions were performed 10 times using a conventional machine (Philips Super 80 CP) and the printouts of a digital system (Digital Diagnost Philips Optimus) for the analysis of reproducibility. One image was scanned and analysed 10 times additionally for imaging reproducibility. Reliability error of the system for the imaging process using conventional radiographs-rays was 0.49% (standard conditions: 6 mAs, 40 kV, 1 m FFD), using printouts of digital images was 2.89% (4 mAs, 42 kV, 1 m FFD) and regarding the analysis process was 0.22%. BMD calculation is not affected by alterations in FFD (precision error 1.21%), mAs (0.83%) or film quality/brand (0.38%), but differs significantly depending on tube voltage (2.70%). The system was not able to analyse conventional images with tube voltages of 49/52 kV. DXR technology is stable with most of the tested parameters. Normative data should exclusively be used for calculations using similar tube voltage or correction factors. All other parameters had no significant influence on the BMD calculation. Reproducibility is high. For technical reasons it is not recommended to use the printouts of digital images for BMD determination.

The status of Spain's dental practices following the European Union directive concerning radiological installations

Objectives To assess the influence of new European Union (EU) legislation on dental radiology practices and the reduction in patient radiation exposure. Study design A total of 7176 official reports from Spanish dental offices or clinics covering the period 1996 to 2001 were analyzed. Results Of the dental radiological installations inspected in 2001, 72.79% used the kilovoltage recommended by the EU (70 kVp) and 98.85% used at least 1.5 mm Al filtration. At least 90.11% of the installations had a focal film distance of 20 cm although there were no cases with a rectangular collimator as adapted to the size of film. Thirty percent of the installations showed a mechanical fault every year. In 17.62% of cases the radiological film was stored in the exposure room. Few clinics (10.24%) used high-speed films and only 11.95% of clinics employed digital systems. The mean dose received by patients fell during the 5 years studied by 18.75%. Radiological equipment fulfilling the EU specifications emitted significantly lower doses than other nonapproved equipment. Conclusions The introduction of legislation has resulted in a gradual improvement in dental radiology practices.

The status of Spain's dental practices following the European Union directive concerning radiological installations

Objectives To assess the influence of new European Union (EU) legislation on dental radiology practices and the reduction in patient radiation exposure. Study design A total of 7176 official reports from Spanish dental offices or clinics covering the period 1996 to 2001 were analyzed. Results Of the dental radiological installations inspected in 2001, 72.79% used the kilovoltage recommended by the EU (70 kVp) and 98.85% used at least 1.5 mm Al filtration. At least 90.11% of the installations had a focal film distance of 20 cm although there were no cases with a rectangular collimator as adapted to the size of film. Thirty percent of the installations showed a mechanical fault every year. In 17.62% of cases the radiological film was stored in the exposure room. Few clinics (10.24%) used high-speed films and only 11.95% of clinics employed digital systems. The mean dose received by patients fell during the 5 years studied by 18.75%. Radiological equipment fulfilling the EU specifications emitted significantly lower doses than other nonapproved equipment. Conclusions The introduction of legislation has resulted in a gradual improvement in dental radiology practices.

Dose-reducing strategies in combination offers substantial potential benefits to females requiring X-ray examination

This work, using an adult anthropomorphic phantom, aimed to establish an optimised technique for ladies of child-bearing age undergoing antero-posterior (AP) pelvis and AP and lateral lumbar spine examinations. Phase one of the work involved introducing the following dose-reducing measures individually: increased kVp, increased focus-film distances, a carbon fibre cassette, a faster film/screen combination. The second phase established an optimised technique based on a combination of the parameters listed above. Radiation dose was measured using thermoluminescent dosimeters and image quality was evaluated using anatomical criteria. All dose-reducing methods were compared with a standard technique, currently being used in a Dublin hospital. The results demonstrated that the optimised procedure reduced effective dose by 77, 62 and 66% for AP pelvis and AP and lateral lumbar spine respectively (p < 0.05) compared with the standard technique, with no significant changes in image quality. Dose-reducing measures used in combination offer substantial potential for optimisation of radiological procedures.

Effect of age, breast size, menopausal and hormonal status on mammographic skin thickness.

The localized or generalized skin thickness detected on mammography may reflect an underlying pathology of breast or a systemic disease involving the skin. The aim of this report is to describe the range of normal breast skin thickness in women using a film-screen mammographic technique. Measurement of the mammographic skin thickness over different parts of the breast was performed in 144 women who had normal findings in a combined mammographic and ultrasonographic examination. Patients were grouped as premenopause, postmenopause and surgical menopause who were under continuous oestrogen treatment. The skin thickness in four regions (superior, inferior, medial, lateral) of both breasts was compared, and their relations with age, breast size, menopausal and hormonal status were investigated. The interobserver reliability was tested in a small subgroup of patients. Interobserver agreement was good for all measurements. The range of normal breast skin thickness was between 0.50 and 3.10 mm. There were no differences in skin thickness between the corresponding regions of the breasts, with significant differences between the regions in the same breast. While breast size increased with age, skin thickness decreased in all regions. The breast size, age, regional variations and hormonal status of the patients should be considered when defining the normal range of skin thickness in mammographic examinations. We assume that upper limit of mammographic skin thickness should be set as 3.0 mm, regardless of the focal spot size and film-focus distance.

Investigation of dose reduction in neonatal radiography using specially designed phantoms and LiF:Mg,Cu,P TLDs.

Many departments still do not use recommended radiographic parameters to X-ray neonates. Direct, accurate dose measurements of individual examinations may assist a department in justifying technique modifications that provide a substantial dose reduction without a significant loss of image quality. The aim of this study was to investigate dose reduction techniques for neonates in the intensive care unit. Alterations in beam energy (kVp and filtration) and collimation were investigated using specially designed phantoms mimicking a 700 g and 2000 g neonate, and ultrasensitive LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs). Differences in entrance surface dose (ESD) and dose at depth (3 cm or 5 cm) were compared for two, overlapping fields centred individually on the chest and abdomen (Technique 1) and one large chest-abdomen field (Technique 2 or babygram). The large phantom was irradiated at 54 kVp, 60 kVp and 70 kVp without additional filtration and at 66 kVp and 70 kVp with a rare-earth hafnium filter. Focus-film distance (FFD) and mAs were adjusted to maintain optical density (OD) on each radiograph. The baseline dose at 54 kVp and 100 cm FFD was (46+/-2) micro Gy. Increasing the tube potential from 54 kVp to 70 kVp without additional filtration reduced the ESD by 27%. However, the addition of a 0.05 mm hafnium filter at 66 kVp further reduced the radiation dose by 13%, to produce an ESD of (28+/-2) micro Gy. All contrast details were observable at 66 kVp with hafnium filtration. Technique 1 may lead to an increase in effective dose due to field overlap, which diverges at depth, and increased scatter at the periphery of the fields.

An overview of doses to patients and irradiation conditions of diagnostic chest x ray examinations carried out in hospitals of the City of São Paulo, Brazil.

Recently the Brazilian health organisation published information conceming the number of hospitals, details of radiological equipment and frequency of medical examinations in the country. The information concerning the city of São Paulo is compiled here, complemented by a survey of absorbed doses to patients undergoing the most frequent examination: chest radiographs (postero-anterior (PA) and lateral (LAT) projections), as well as the physical parameters employed (tube voltage, current-time product, focus-film distance, field size). To collect the data, a sample of 12 hospitals (a representative sample of the 199 located in the city) was chosen, totalling 27 X ray machines. An anthropomorphic phantom was irradiated to simulate the patient. Absorbed doses were determined with thermoluminescence dosemeters placed in the phantom, externally and internally. Mean values of entrance surface dose (ESD) for PA and LAT projections were 0.22 mGy (from 0.07 to 0.61 mGy) and 0.98 mGy (from (1.30 to 4.01 mGy), respectively. The average organ doses per complete examination (PA and LAT) were 0.15 and 0.24 mGy to thyroid and lung, respectively. The thyroid was thus in the primary beam in many cases. The large variation in the ESD and organ doses indicates that much can be done in order to reduce the patient doses by adequate changes of physical parameters, without loss of image quality.

Cervical Spine Growth in Children

Nag, H. L. MS; Gupta, P. MS; Lakhey, S. MS; Roposch, Andreas MD; Linhart, Wolfgang E. MD Author Information