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P C Brennan

Publications and source records attributed to P C Brennan.

At least 19 recordsLinked to original sources
PubMed2006

Radio-protective aprons during radiological examinations of the thorax: an optimum strategy.

The current work investigates the most effective type/position of aprons for postero-anterior (PA) and lateral projections of the chest. Two apron-types were investigated: 'Mavig' half apron and Amray light plus' wrap-around apron. The half apron was positioned at the X-ray tube or image receptor side of an anthropomorphic phantom for PA and lateral projections. Radiation dose at positions corresponding to ovaries, uterus and testes was measured with thermoluminescent dosemeters. The wrap-around apron offers a higher level of protection for PA and lateral projections compared with the half apron, regardless of where the latter was positioned, with dose reductions of up to 88% compared with no apron. For the PA position, the half apron should be positioned in a gender-specific way, facing the X-ray tube for females and the image receptor for males. With all apron types/positions, gonadal dose is still clearly evident, from internal scatter, emphasising the importance of other protective practices such as collimation.

Body Burden↗
PubMed2005

Protective aprons in imaging departments: manufacturer stated lead equivalence values require validation.

The composition of protective aprons worn by X-ray personnel to shield against secondary radiation is changing. Lead is being replaced by either lead-free or composite (lead with other high atomic numbered elements) materials. These newer aprons are categorised by manufacturers in terms of lead equivalent values, but it is unclear how these stated values compare with actual lead equivalent values. In this work, the actual lead equivalence of 41 protective aprons from four manufacturers, all specified as having 0.25 mm lead equivalence, were investigated with transmission experiments at 70 and 100 kVp. All aprons were in current use. The aprons were screened for defects, and age, weight and design was recorded along with details of associated quality assurance (QA). Out of the 41 protective aprons examined for actual lead equivalence, 73% were outside tolerance levels, with actual levels in some aprons demonstrating less than half of the nominal values. The lack of compatibility between actual and nominal lead equivalent values was demonstrated by aprons from three of the four manufacturers investigated. The area of the defects found on screening of the protective aprons were within recommendations. The results highlight the need for acceptancy and ongoing checks of protective aprons to ensure that radiation exposure of imaging personnel is kept to a minimum.

Equipment Design↗
PubMed2004

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.

Carbon↗
PubMed2004

Increasing film-focus distance (FFD) reduces radiation dose for x-ray examinations.

Increasing film-focus distance (FFD) from the traditional 100 cm has been shown to be an effective method of reducing dose whilst maintaining image quality. In particular, previous work increasing the FFD from 100 to 130 cm for lumbar spine examinations demonstrated an effective dose reduction of 44%. Objective. The current study continues on from this work by investigating the dose-reducing efficacy of this FFD change for pelvis X-ray examinations. Materials and methods. Dose measurements at 100 and 130 cm using thermoluminescent dosemeters were undertaken using an anthropomorphic phantom and patients. Image quality was assessed using CEC anatomical criteria and psychophysical tests. Results. The results showed that increasing the FFD results in a reduction in effective dose of 33%, with no change in image quality. The data provided in this and previous studies demonstrate the need for rapid implementation of this simple cost-effective procedure across imaging departments, leading to an important reduction in collective dose. Conclusion. The CEC recommendation of using 115 cm FFD for a number of procedures, although useful compared with 100 cm, undervalues by a factor between 2 and 3 the potential of this dose-reducing tool.

Adult↗
PubMed2004

Assessment of monitor conditions for the display of radiological diagnostic images and ambient lighting.

Diagnostic efficacy is related to viewing conditions. An increasing number of radiology departments are using workstations for reporting and it was the aim of this study to assess monitor performance and ambient lighting in areas allocated to soft-copy reporting and review. The study was performed in 4 Dublin hospitals and 20 monitors were examined. Using a Society of Motion Pictures and Television Engineers' (SMPTE) test pattern, maximum luminance, spatial uniformity of luminance, temporal luminance stability, brightness and contrast resolution (gamma), geometry and ambient lighting was assessed. The results demonstrated that although temporal luminance stability and spatial uniformity appeared to be at acceptable levels, maximum luminance and gamma value variations were noted, with maximum luminance and geometry values often not complying with published guidelines. Cleaning the monitor face had no impact. 90% of viewing areas had acceptable ambient lighting levels. The data presented demonstrate that monitors examined were not operating at optimal levels for all performance parameters and inclusion of regular assessments of monitors should be part of an imaging department's ongoing quality assurance programme.

Computer Terminals↗
PubMed2003

Do CEC guidelines under-utilise the full potential of increasing kVp as a dose-reducing tool?

Increasing beam energies are well established as a radiation dose-reducing tool in diagnostic radiology. This has led to useful recommendations by the Commission of European Communities (CEC) for appropriate kVp values to be employed for a variety of examinations. The current work tests the hypothesis that kVp levels above those recommended by the CEC will result in reduced patient dose while still producing images of acceptable quality. This study explored the effect of a range of kVp levels within and above CEC recommendations for lumbar spine radiology. A phantom investigation facilitated selection of appropriate kVp levels for a patient study ( n=59): 81 kVp (CEC) and 96 kVp (non-CEC) for the AP projection and 90 kVp (CEC) and 102 kVp (non-CEC) for the lateral projection. Entrance surface and effective dose were calculated and image quality quantified using CEC image criteria and images of a detail contrast test tool. Data analysis demonstrated significant reduction in effective radiation dose for AP (29.9%) and lateral (24.6%) when a kVp value above the CEC range was employed compared with a kVp recommended by the CEC. Although significant reductions in total image quality of 18.3% and 10.1% for the antero-posterior and lateral projections, respectively, were noted, all patient images produced with all kVp values were considered acceptable by each member of the evaluative panel with all image criteria receiving a score of 2 (out of 3) or better. The psychophysical tests revealed minor non-significant reductions in visualisation scores. The current study demonstrated that kVp values outside the CEC recommended range offer reductions in dose while producing acceptable images. Practitioners should be guided, rather than constrained, by the CEC recommendations on good radiographic technique. The need for further work exploring the effect of higher energies on visualisation of subtle pathological lesions has been identified.

Female↗
PubMed2003

Investigation into patient doses for intravenous urography and proposed Irish diagnostic reference levels.

With the introduction of Council Directive 97/43/Euratom, all member states should establish relevant diagnostic reference levels for X-ray examinations. Diagnostic reference levels help to facilitate standardisation and optimisation within departments and attempt to reduce dose variations between hospitals. High variation of individual patient doses for plain-film examinations by up to a factor of 75 was demonstrated by a previous Irish study, which highlighted the necessity for further investigation into other examinations in Ireland. The current work aimed to establish reference values for intravenous urography (IVU) examinations, an important contributor to collective dose. Eleven Irish hospitals were randomly selected, representing 30% of the total number of hospitals. Dose-area product (DAP) readings for IVUs were recorded along with technical and procedural details. Resultant data demonstrated mean hospital and individual patient DAP variations of a factor of 4 and 58, respectively. Stepwise regression analysis demonstrated that number of images taken, method of image acquisition and patient weight were the main causal agents for dose variations recorded. A proposed diagnostic reference level of 12 Gy cm(2) was established at the level of the third-quartile value of the mean hospital DAP values. This article provides evidence of large variations in DAP values for IVU examinations. It is hoped that application of the proposed DRL of 12 Gy cm(2 )will reduce the size of these variations.

Female↗
PubMed2003

Radiation doses for barium enema and barium meal examinations in Ireland: potential diagnostic reference levels.

Wide variations in patient dose for the same examinations have been demonstrated by several studies throughout Europe. By investigating patient dose, variations can be acknowledged, causal agents sought and the necessary adjustments made. Diagnostic reference levels (DRLs) provide a framework with which dose levels from individual hospitals are compared, and when exceeded, corrective actions can be taken where appropriate. This study aimed to establish DRLs for barium enema and barium meal examinations in Ireland. Measurements were recorded using a dose-area product meter in 12 hospitals representing 33% of relevant hospitals. Results demonstrated wide mean hospital dose variation, by up to a factor of 7.8 and 4.2 for barium enema and barium meal examinations, respectively. Minimum and maximum individual patient dose values varied by a factor of 45 for barium enemas and 90 for barium meal examinations. Reasons for dose variations were complex, but major factors for both examinations were fluoroscopy time, secondary radiation grid type and level of filtration. Some examination-specific factors were also noted. DRLs, established using the quantity dose-area product, were calculated to be 47 Gy cm(2) for barium enemas and 17 Gy cm(2) for barium meal examinations. Although the DRL value for barium meals was the same as the reference value established in the UK for that examination in 1996, the barium enema DRL in this study was 45% higher than the relevant UK value.

Barium Sulfate↗
PubMed2003

Viewing conditions for diagnostic images in three major Dublin hospitals: a comparison with WHO and CEC recommendations.

Accurate interpretation of X-ray images is dependent on image viewing conditions. A recent study in Ireland demonstrated that even with the advent of digital departments the majority of images are still viewed using viewing boxes. This investigation aimed to measure average viewing box brightness, percentage uniformity and ambient light levels in radiology and radiographer viewing areas and wards within three major Dublin hospitals. The results were compared with published recommendations by the World Health Organization and Commission of the European Communities. Following analysis of more than 4650 measurements, it was shown that mean values for average viewing box brightness for all departments failed to achieve recommended levels. Only one third of areas met the most lenient guideline for percentage uniformity. Ambient lighting was shown to be unacceptable for ward areas. For all three parameters, radiology areas generally fared best, with wards gaining the poorest scores. Following a 3 min cleaning regimen of viewing boxes, the average brightness and percentage uniformity were improved in 100% and 80%, respectively, of viewing boxes, but average brightness values remained below recommended levels. The importance of comprehensive quality assurance programmes for viewing boxes has been highlighted so that visualization of images is not reduced to sub-optimal levels. The need for consistent and more informative recommendations has been emphasized.

Hospitals, District↗
PubMed2002

Irish X-ray departments demonstrate varying levels of adherence to European guidelines on good radiographic technique.

The Commission of European Communities (CEC) publication "European Guidelines on Quality Criteria for Diagnostic Radiographic Images" includes examples of good radiographic technique for a number of common X-ray examinations. If these guidelines are followed, compliance with dose and image quality criteria as specified in the CEC document should be demonstrated. Studies in England, Germany and Greece have shown that a number of X-ray departments are not using optimum techniques. The aim of this study is to demonstrate the level of adherence to CEC guidelines in Irish hospitals 3-4 years following publication of the above document. 16 hospitals were randomly chosen and the following details on technique and equipment were recorded for chest, abdomen, pelvis and lumbar spine examinations of standard sized patients: tube potential, focus-to-film distance, automatic exposure control (AEC), film-screen combination, X-ray tube filtration and secondary radiation grid. Varying levels of adherence to the guidelines were evident depending on the parameter being investigated, with no hospital demonstrating 100% compliance and no hospital demonstrating 100% non-compliance. For all parameters, with the exception of AEC use, the majority of hospitals exhibited non-adherence for at least one projection. The results suggest that if hospitals in Ireland observe the straightforward examples of good radiographic technique described in the CEC publication, significant reductions in collective dose can be achieved.

European Union↗
PubMed2001

An assessment of the usefulness of screen-film speed classifications.

Speed classifications of screen-film combinations are frequently quoted in the day-to-day functioning of X-ray departments. These values are utilised for a variety of functions by X-ray personnel. This study aimed to compare a range of commonly used screen-film combinations in order to establish the level of agreement between stated speed classifications and actual speed of systems. Relationships between system speed class and image quality were also investigated. Six commonly used screen-film systems were studied; three had a speed classification of 200 while the remaining systems had a classification of 400. Characteristic curves for each system were produced, from which relative speeds were calculated at four beam energies. Psychophysical tools and visual grading analyses were used to assess image quality. The sensitometric results demonstrated that at all energies the speed class quoted did not predict the actual relative speeds of the film-screen systems. The image quality study demonstrated disagreement with conventional assumptions regarding speed classifications with mean values for 400 speed systems being higher or at least equal to the 200-system scores. There is no evidence from this study to support the ongoing use of current screen-film classifications. Personnel within all X-ray departments should carry out rigorous speed measurements and image quality assessments of all systems within their department before nominal classifications are used.

Radiography↗
PubMed2001

Diagnostic ultrasound induces change within numbers of cryptal mitotic and apoptotic cells in small intestine.

Recent work on gas filled organs, including the lung and small intestine, has concentrated on the hemorrhaging effects of ultrasound, with little attention paid to cell cycle perturbations and apoptosis--two very sensitive indicators of environmental insult. This study addresses this by exploring the effects of ultrasound on these two features. The anterior abdominal surface of anaesthetised male, adult CD1 mice was shaved and exposed to ultrasound. An 8 MHz linear array transducer was manually swept from the midline to the left mouse flank on a continuous basis. Each mouse was scanned for 15 minutes with B mode and color flow modes selected. The Thermal Index registered 1.0. Groups of mice were killed at various times after treatment, the small intestine was excised and histologically examined. Analysis of the data demonstrates a statistically significant 22% reduction in numbers of mitotic figures at 4.5 hours after the ultrasonic insult (p = 0.011). Numbers of apoptotic bodies increased by 153% (p=0.003), 166% (p=0.014) and 160% (0.001) at 1, 3 and 4.5 hours post-treatment respectively. These preliminary results suggest that bioeffects of ultrasound maybe more diverse than previously described. Further work will establish thresholds and explore mechanisms for these deterministic effects.

Animals↗
PubMed2001

BB-10010, an analog of macrophage inflammatory protein-1alpha, protects murine small intestine against radiation.

Irradiation of the small intestine can result in depletion of the epithelial stem cell compartment and is often the dose-limiting factor for radiotherapeutic treatment of tumors in the abdominal and pelvic region. Since mitotic cells are most sensitive to radiation, significant radioprotection can be achieved by reducing the number of cells in mitosis at the time of irradiation. We have previously shown that administration of macrophage inflammatory protein (MIP) -1alpha induces a transient 50% reduction in the number of mitotic cells in small intestinal crypts, including the stem cell region, and therefore, MIP-1alpha pretreatment before radiation exposure could result in a substantial reduction of the side effects associated with radiotherapy. Groups of adult mice were exposed to different doses of radiation (6, 8, 10, or 12 Gy), with or without prior administration of 200 microg BB-10010/kg 3 hr before irradiation and radiation damage was assessed by means of the microcolony survival assay. MIP-1alpha pretreatment resulted in significantly increased numbers of surviving crypts (10%) when compared to untreated irradiated animals. The observed radioprotective effects of MIP-1alpha in the small intestine should translate into reduced side effects in a clinically relevant radiotherapy context and could allow larger doses of radiation to be delivered to patients with tumors in the abdominal or pelvic region.

Animals↗
PubMed2001

Patient dose variation investigated in four Irish hospitals for barium meal and barium enema examinations.

Four hospitals have been studied, intra- and inter-hospital variations examined and the mean DAP values recorded for barium enemas and barium meals. Mean DAP values for barium meals and barium enemas at 11.4 Gy x cm2 and 20.1 Gy x cm2 respectively have been shown. Differences between individual examinations for barium meals varied by up to a factor of 185 and for barium enemas, up to a factor of 19, with hospital means for barium meal and enema examinations each differing by up to a factor of 3. The data provided by this study have suggested that large variations in patient dose do exist in Ireland for barium meal and barium enema examinations. Fluoroscopy time was shown to be a major contributor to the variations reported, with number of images playing a minor role. Results have demonstrated the need for standardisation of technique throughout the country for these examinations.

Barium Sulfate↗
PubMed2000

Lumbar spine radiology: analysis of the posteroanterior projection.

The use of the posteroanterior (PA) technique as a means of dose reduction has been used effectively in radiology departments for chest and abdominal examinations. The aim of this investigation was to establish if the PA lumbar spine projection offers any advantages over the traditional anteroposterior (AP) view in terms of radiation dose and image quality. The contribution of tissue displacement to any dose reduction was also evaluated. The first part of the study involved the use of an anthropological phantom where entrance surface and an internal dose were measured for both the PA and AP projections. Entrance surface doses for both projections were then measured on randomly allocated female patients. Resultant image quality was assessed using CEC quality criteria. Anterior to posterior patient diameter was also recorded. The results demonstrated that with the PA compared with the AP projection, reductions of 38.6% (p = 0.016) and 38.9% (p = 0.02) in patient entrance surface dose and internal phantom dose, respectively. No significant differences in image quality were noted between the two projections. Patient diameter decreased by 1.8 cm with the PA view. The authors conclude that tissue displacement is the main factor for the patient dose reduction and recommend employment of the PA procedure for routine lumbar spine examinations.

Humans↗
PubMed2000

Dose-effect relationship of BB-10010/MIP-1 alpha on proliferation in murine small intestinal epithelium: single and double administration protocols.

BB10010/MIP-1 alpha reduces the number of proliferating cells in the small intestine, strongly suggesting a radioprotective potential in this organ. This study was designed to optimize BB10010 administration for maximal radioprotection. In single administration protocols 1 or 4 mg/kg of BB10010 was injected into mice 2, 4 or 10 hr before death. In double administration protocols an initial dose of either 0.4 or 200 microg/kg, and a second dose (2.5 hr apart) of 200 microg/kg 4 hr before death were administered. The number of vincristine-arrested metaphases were counted on individually microdissected crypts from the midpoint of the small intestine. When compared to the smaller doses of BB 10010 used in our previous studies, the higher doses used in these experiments did not result in any further reduction in the number of proliferating cells under any of the protocols assessed. Furthermore, some values were found to be above not only those observed with the smaller doses, but also above untreated controls. It is concluded that a single dose of 200 microg/kg of BB10010 offers the most consistent reduction of mitotic cells, and is, therefore, considered optimal for assessment of radioprotection.

Animals↗