Chest radiography doses with film screen : is further reduction possible?

Peer reviewedPublisher PD

Mimicking the Chest Radiograph: Patient Equivalence of the CDRH Chest Phantom with Added Insert

Objective: To evaluate medical X-ray doses and image quality, so called phantoms that mimic particular aspects of the patient are used. The Centre for Devices and Radiological Health (CDRH) chest phantom has been used for studies of radiation exposure to the lung fields under automatic exposure (AEC) conditions. Recently, a quasi-anatomical insert was introduced to create contrast between chest organs. Direct comparison of the phantom performance with clinical chest images has not been reported previously. This study applies the phantom to conventional radiography imaging of the chest to establish its patient equivalence. Methods: Entrance doses with backscatter and chest radiographs of 77 patients were mirrored in the phantom at the same exposure factors. Optical density (OD) as well as beam transmission through the different regions of both media were also compared. A 2-sample t-test was used to test for differences while the Pearson's correlation coefficient (r) was used to test the strength of (any) linear relationship between the measured parameters in both media. Results: Results show a 13.5% difference in entrance surface doses (ESD). Beam transmission through both media showed statistically significant differences (P = 0.05). ODlung was higher in CXR than the phantom images. OD(lung + ribs) on the CXR was not statistically different (P = 0.09) from the phantom ODlung. Mean OD for the mediastinum varied by 28%. Differences are statistically significant (P < 0.05) in all areas except the diaphragm (P = 0.8). There is good +ve correlation in ESD and beam transmission for all regions. A weaker +ve correlation was found for OD in all areas. In both cases correlation is significant (P < 0.05). The phantom and CXR parameters vary linearly together, but are not of equal value. Conclusion: A linear relationship was found between measurements made with the phantom and CXR for beam transmission and for optical density. Thus the phantom can provide a useful test tool for both perceptual studies and quality assurance (QA) in chest radiograph

Adapting the CDRH Abdominal Phantom for Dose-image Quality Optimisation in Abdominal Radiography

To evaluate medical X-ray doses and image quality, so calledphantoms that mimic particular aspects of the patient are used.The Centre for Devices and Radiological Health (CDRH) haddesigned a phantom for studying radiation exposure to thehuman abdomen. An abdominal phantom for image qualitystudies has not been found in the literature. Direct comparisonof the CDRH phantom performance with clinical abdominalimages has not been reported previously. This study appliedthe phantom to conventional radiography imaging of theabdomen to establish its patient equivalence and therefore itsapplicability in quality control studies in radiologydepartments. Results show a difference in beam transmission(BT) of 21.2% (r = 0.3; p>0.05) and an optical density (OD)of 1.62 against 1.65 for patient abdominal films (p=0.54).Despite the variations and a poor linearity with patient data,the phantom satisfied Optical density requirements, isportable, adjustable, and simple to assemble. It can thereforefind application in image quality studies in diagnosticradiology

An Evaluation of Some Common Laboratory Materials by Xray Attenuation, for use as Human Tissue Substitutes

To develop readily available laboratory materials for probableuse as imaging phantoms or test objects, Laboratory MagnesiumSulphate (MgSO4) and Table salt (NaCl) were used in the ratio80:20% by weight with paraffin wax to form test materials(MgSO4:PW1) and (NaCl:PW2). Rice powder, gelatineseparately, and a combination of gelatine (20g in 100ml of warmwater) and 100g rice powder were also made into test objects.The ratios used were confirmed by matching differentconstituents by weight of the test samples with the web basedphoton interaction software XCOM designed by the NationalInstitute of Science and Technology, USA, to obtain closematching with tissue data. Each test object was made into 1 cmblocks for exposure to narrow beam x-rays over the diagnosticenergy range (50 – 150kV) under automatic exposure conditions.Good agreement within 10%, was found between the measuredand calculated values for four of the five tested samples.Matching of the tested materials with mass attenuationcoefficients of simulated tissue showed acceptable match at highphoton energies of 0.04 – 0,05 MeV and above for gelatine, PW1(paraffin wax + MgSO4.6H2O) and Rigel (Rice + gelatine). Thesematerials can therefore be used as tissue substitutes in imagequality studies

Contributions of Practicing Radiographers to Research in Nigeria

Background: Research has been identified as a key component that ensures high level of professionalism among health practitioners, especially in the field of imaging science. A measure of research engagements among professionals, particularly practicing radiographers, for the attainment of international standard is very important, which has not been so far ascertained in the country.   Objectives: To assess the contributions of practicing radiographers to research, and to determine the extent to which research findings are being integrated into the current day practice.   Methods: A 16-item, self-administered, structured, paper-pencil and web-based questionnaire was used to assess 113 practicing radiographers with work experience graded from < 1 year to > 25 years. Respondents were recruited via volunteerism. A 68.0% (n = 77) return rate was recorded for questionnaires. Data obtained were recorded, grouped and tabulated.   Results: A good proportion (98.23%) of the respondents identified the need for research in the improvement of current day clinical practice. About 33.63% conducted research while 10.62% published their findings in peer-reviewed journals. Also, 91.15% of the respondents read Radiography journals while 73.79% applied the results in their day-to-day clinical practice.   Conclusion: The results obtained in the present study showed that research activities among practicing Radiographers in Nigeria is low, despite the claims of improved application of research results into practice. More efforts by academic mentors and relevant authorities is desirable to encourage younger radiographers to venture into research.   &nbsp

Estimates of Paediatric Doses for Common Radiographic Procedures in some Nigerian Hospitals

Purpose: To determine and establish doses in paediatric radiography for hospitals which have no previous data. Materials and Methods: X-ray examination data were collected and used as input in a dose calculation software (DOSECAL, from St. Georges’ Hospital, London) to obtain absorbed doses to the skin (entrance surface dose, ESD) as well as organ and effective doses. The study covered five common radiological examinations. Results: Entrance surface and effective doses were found to be generally higher in agreement with an earlier study using thermoluminescent dosimetry, while organ doses were lower than the values for similar age groups in the literature. Causes of these high doses are attributed to the type, age and conditions of radiographic equipment, radiographic exposure factors (low kVp - which also accounts for low organ doses, and high mAs in some cases), film processing conditions and lack of quality assurance programmes. Suggestions and recommendations are outlined for dose reduction to within recommended international limits. Conclusion: Doses obtained in this study will serve as a basis for comparison of future studies in the area

Cyclic peptide production using a macrocyclase with enhanced substrate promiscuity and relaxed recognition determinants

This project was supported by grants from the ERC (no. 339367, MJ), BBSRC IBCatalyst (no. BB/M028526/1, MJ, WEH), BBSRC FoF (no. BB/M013669/1, MJ, WEH), IBioIC Exemplar (no. 2014-2-4, MJ, WEH), an AstraZeneca studentship (MJ, WEH, LT, KR), the Academy of Finland (no. 259505, DPF) and the SULSA leaders award (WEH). The authors like to thank the Aberdeen Proteomics Facility and the Aberdeen School of Natural and Computing Sciences MS Facility for LCMS analysis. Electronic supplementary information (ESI) available: Experimental section, Fig. S1–S60 and Tables S1–S3. See DOI: 10.1039/c7cc05913bPeer reviewedPublisher PD

Measurement of dose in diagnostic radiology and the effect of dose reduction on image quality

In computed radiography (CR) images, dose reduction up to 0.10 mGy is possible in chest radiography without image manipulation.  A lower dose of 0.06 mGy can be achieved when image manipulation is used for detection of lesions in the mediastinum.  Both clarity and detectability in the mediastinum improved by between 48 to 66% with image manipulation.  Abdominal images showed a significant difference at 2.69 mGy for the soft tissue area, suggesting caution in further dose reduction.  Image quality in the spinal area was improved significantly by 21 – 78.6% (for clarity) and 3 to 77% (for detectability) when image manipulation was employed. Comparatively, the image quality at the low doses studied was better for the film screen radiography than both processed and unprocessed CR images suggesting that low doses achieved in FSR may not be applicable to CR.  This difference may be attributed to the differences in the image receptors’ response to high photon energies, and the reduced number of x-ray quanta which produce lower subject contrast in FSR and reduced signal to noise ratio (SNR) as a result of increased noise in CR. Nigerian clay in its natural and salted forms cannot be used in radiation dosimetry in diagnostic radiology.  Paraffin wax/MgSO4.6H20, and rice-gelatine (rigel) combinations as well as rice and gelatine used separately, have shown tissue equivalent x-ray attenuation at tube potentials above 80 kVp.  Paraffin wax/MgSO4.6H20 and rigel can therefore be used as tissue substitutes.  Low patient entrance surface doses achieved in FSR may not produce equivalent image quality when applied to imaging with CR systems.  With respect to dose reduction, both modalities show the possibility of further dose reduction below current dose values by about 40% (chest) and 20% (abdomen), respectively, when used alone.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Compliance of Radiation Dose and Image Quality in a Nigerian Teaching Hospital with the European Guidelines for Pediatric Screen-Film Chest Radiography

Introduction Blue light is a part of the spectrum with the highest energy content, which can reach the retina. The damage that it can cause to the retina is called photochemical or blue-light retinal injury. For the retinal injury assessment of the photochemical and aphakic retinal hazards in the wavelength range of 300-700 nm, use of effective spectral radiance limits (W.m-2.sr-1) seems to be slightly perplexing for ophthalmologists. However, in this study, the temperature (OC) that can emit the same effective spectral radiance limit was detected using a computer code; this method could help prevent blue-light retinal injury. Materials and Methods The limits proposed by International Commission on Non-Ionizing Radiation Protection for blue-light induced photochemical and aphakic eye hazards were expressed in terms of temperature by a computer code for 13 Planckian sources that produce the same radiance. The calculated temperature by the computer code, here known as threshold temperature, is the maximum source temperature that for a specified viewing distance and source diameter does not cause the exposure at the receptor position to exceed the exposure limit. Results In terms of threshold temperature, the exposure limits for aphakia or infant retinal injury are much lower than retinal photochemical damage. For light sources with more effective radiances, these differences reach 800 K. Conclusion This method allows evaluation of photochemical and aphakic retinal hazard only by comparing the calculated threshold temperature by a computer code with the temperature of the radiant source, which may be beneficial for hygienist and ophthalmic clinicians

X-ray absorption by sodium chloride

In vitro Sodium Chloride absorption of X-rays was studied with concentrations of 46 mg/mol to 460 mg/mol, which include the range of sodium and chloride ion concentrations in the human body. Irradiation was done with an incident x-radiation dose equivalent of 0.0309 m Sv, with Lithium Fluoride as detector. Absorbed doses read off the thermoluminiscent detectors (TLD) with a TLD reader showed a non uniform variation, but linear relationship between concentration and absorbed dose, with a strong positive correlation of 0.8140. The radiobiological implications of these results are discussed. Keywords: Sodium Chloride, X-ray, Absorption, concentration, phosphors, selection, patients (Global Journal of Pure and Applied Sciences: 2002 9(1): 133-138