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PubMedDate not supplied

Dose reduction in multislice computed tomography.

OBJECTIVE: Evaluation of the attenuation-based on-line modulation of tube current on multislice computed tomography (CT) to explore the potential of this dose-saving technique. METHODS: Fifty-five patients with follow-up CT examinations were scanned without and with a CARE Dose (Siemens Medical Solutions, Erlangen, Germany). The applied dose, image noise, and subjective image quality were evaluated. The reduction in patient exposure was determined by obtaining the effective milliamperes per second for each reconstructed scan and the absolute dosage requirement for the whole scan. RESULTS: The dose reduction achieved by applying the attenuation-based on-line modulation of tube current was 29.4% +/- 3.1% (P=0.002) for all scans, 30.5% +/- 3.2% (P=0.002) for the thorax scans, 29.7% +/- 2.9% (P=0.002) for the abdomen scans, and 28.7% +/- 2.7% (P=0.003) for the thorax and abdomen scans together. No significant restrictions in image quality were observed. CONCLUSIONS: Remarkable dose reduction can be obtained using the attenuation-based on-line modulation of tube current on multislice CT without compromising image quality.

Aged↗
PubMed1978

[Dose reduction in xeromammography (author's transl)].

The use of a total filter of 3 mm of aluminium permits a considerable reduction of the radiation dose in xeromammography using the senographe. In comparison with conventional xeroradiography radiation is reduced by a factor of 2 to 3, in comparison with foilless film by a factor of 10 to 12. The applied tissue dose is between 0.14 and 0.30 rad per exposure. The presently still hypothetic radiogenic risk of carcinoma due to mammography is thus lower for this system than with other systems. The quality of the radiograph and the diagnostic validity are not reduced by this technique.

Female↗
PubMed2003

Radiation dose reduction to medical staff during vertebroplasty: a review of techniques and methods to mitigate occupational dose.

STUDY DESIGN: Case crossover design was conducted. OBJECTIVES: The purpose of the current study was to determine the radiation exposure level of operators performing fluoroscopically assisted vertebroplasty and to determine optimal techniques to reduce this exposure. SUMMARY OF BACKGROUND DATA: The use of ionizing radiation to provide quality imaging during minimally invasive orthopedic procedures has dramatically increased. One such procedure, vertebroplasty, which is the percutaneous fixation of fractured vertebrae with polymethylmethacrylate, requires the use of ionizing radiation of biplanar fluoroscopy. The adverse effects of excessive radiation exposure to occupational personnel may not be realized for several years. METHODS: Twelve months of occupational dose data for a single operator were evaluated and correlated to the modifications of practice habits implemented and shielding techniques used to reduce the operator's exposure while maintaining adequate image quality. RESULTS: Before the implementation of radiation-reduction procedures, the average whole-body dose per vertebroplasty procedure was 1.44 mSv/vertebrae, and the measured hand dose was 2.04 mSv/vertebrae. After implementation of radiation-reducing procedures and shielding techniques, the average whole-body dose per vertebroplasty procedure was 0.004 mSv/vertebrae, and the average hand dose was 0.074 mSv/vertebrae. Testing of the shielding device indicated a significant reduction in whole-body and hand doses. For the fluoroscopic modes investigated, the shielding used resulted in reductions ranging from 42.9% to 86.1%. CONCLUSION: It is critical that operators performing vertebroplasty procedures have a fundamental understanding of radiation physics and radiation protection to minimize radiation exposure.

Fluoroscopy↗
PubMed2003

Dose reduction in patients undergoing chest imaging: digital amorphous silicon flat-panel detector radiography versus conventional film-screen radiography and phosphor-based computed radiography.

OBJECTIVE: We sought to compare the radiation dose delivered to patients undergoing clinical chest imaging on a full-field digital amorphous silicon flat-panel detector radiography system with the doses delivered by a state-of-the-art conventional film-screen radiography system and a storage phosphor-based computed radiography system. Image quality was evaluated to ensure that the potential reduction in radiation dose did not result in decreased image acuity. SUBJECTS AND METHODS. Three groups of 100 patients each were examined using the amorphous silicon flat-panel detector, film-screen, or computed radiography systems. All patient groups were matched for body mass index, sex, and age. To measure the entrance skin dose, we attached 24 calibrated thermoluminescent dosimeters to every patient. The calculation of the effective dose, which represents the risk of late radiation-induced effects, was based on measurements on an anthropomorphic phantom. Image quality of all three systems was evaluated by five experienced radiologists, using the European Quality Criteria for Chest Radiology. In addition, a contrast-detail phantom study was set up to assess the low-contrast detection of all three systems. RESULTS: The amorphous silicon flat-panel detector radiography system allowed an important and significant reduction in both entrance skin dose and effective dose compared with the film-screen radiography (x 2.7 decrease) or computed radiography (x 1.7 decrease) system. In addition, image quality produced by the amorphous silicon flat-panel detector radiography system was significantly better than the image quality produced by the film-screen or computed radiography systems, confirming that the dose reduction was not detrimental to image quality. CONCLUSION: The introduction of digital flat-panel radiography systems based on amorphous silicon and cesium iodide is an important step forward in chest imaging that offers improved image quality combined with a significant reduction in the patient radiation dose.

Adult↗
PubMed1991

Evaluation of the use of a niobium filter for patient dose reduction in chest radiography.

The performance characteristics of a 50 microns niobium filter and a copper filter of equivalent thickness (0.15 mm) were compared for postero-anterior chest X-ray examination. Radiographs of 20 patients obtained using an automatic exposure control device showed no significant differences in image quality and exposure setting between the filters. Radiation dose distributions measured in a Rando phantom revealed a higher reduction in the patient dose with the niobium filter. The reduction in the effective dose equivalent, produced by the addition of the niobium and copper filters to the standard filter of 2.5 mm aluminium, of 17% and 10%, was relatively small compared with the reductions in the entrance surface dose of 31% and 26%. Our study confirms that drastic alterations in the patient dose by the addition of a dose reduction filter to the usual filtration cannot be expected.

Copper↗
PubMed2001

Predictive markers of asthma exacerbation during stepwise dose reduction of inhaled corticosteroids.

To determine predictors for failed reduction of inhaled corticosteroids (ICS), in 50 subjects with well-controlled asthma (age 43.7 [18-69]; 22 males) taking a median dose of 1,000 microg ICS/d (100-3,600 microg/d), ICS were halved every 8 wk. Airway hyperresponsiveness (AHR) to a bronchial provocation test (BPT) with histamine was measured at baseline. AHR to BPT with mannitol, spirometry, exhaled nitric oxide (eNO), and, in 31 subjects, sputum inflammatory cells were measured at baseline and at monthly intervals. Thirty-nine subjects suffered an asthma exacerbation. Seven subjects were successfully weaned off ICS. Using a Kaplan- Meier survival analysis, the significant predictors of a failure of ICS reduction were being hyperresponsive to both histamine and mannitol at baseline (p = 0.039), and being hyperresponsive to mannitol during the dose-reduction phase of the study (p = 0.02). Subjects older than 40 yr of age tended to be at greater risk of ICS reduction failure (p = 0.059). Response to mannitol and percentage sputum eosinophils were significantly greater before a failed ICS reduction than before the last successful ICS reduction, whereas there were no significant differences in symptoms, spirometry, or eNO. These findings suggest that documentation of patient's AHR or sputum eosinophils may be useful in guiding the reduction of ICS doses.

Adolescent↗
PubMed2005

Digital cine angiography permits radiation dose reduction without reduction in image quality.

PURPOSE: To investigate how much the radiation dose in digital cine angiography (DCA) systems can be reduced while maintaining an image quality equivalent to that of conventional cine angiography (CCA). MATERIALS AND METHODS: Simulated vessel phantoms were subjected to DCA and CCA. In DCA, the input dose value to the image intensifier built in the system was 0.10, 0.12, 0.14, 0.17, 0.2, and 0.24 microGy. The detectability for simulated vessel phantoms was visually evaluated by five observers. The radiation dose was measured using radiofluorescent glass-rod dosimeters. Doses of digital cine imaging were measured as relative values with the dose of CCA considered as 1.0. RESULTS: The relative DCA/CCA values in DCA, measured by radiofluorescent glass-rod dosimeters, ranged from 0.414 to 0.901 for simulated vessel phantoms CONCLUSION: DCA allows a reduction by 59% of the radiation dose compared with CCA without reduction of image quality.

Analysis of Variance↗
PubMed1982

A preliminary investigation of radiation dose reduction on an EMI CT5005 whole body scanner using a copper wedge.

The effects of the existing filtration system upon a narrow, parallel beam of X rays were considered. The profile of a Cu filter to be placed on the tube-side A1 wedge was calculated on the basis that the total energy incident on the detector box would remain unchanged when the other A1 wedge was removed. A Cu wedge was machined according to this profile. The effects of this modification on surface radiation dose delivered to a 25 cm EMI water phantom were both predicted and measured for horizontal traverses, and were in broad agreement. The reduction in integral radiation dose to the 25 cm water phantom was predicted as 39%. Dose reductions measured at several points on the surface and within an Alderson Rando anthropomorphic phantom head averaged 53% and 20% respectively. The modified system was evaluated in terms of imaging ability, and although some degradation was seen, images of the EMI composite phantom remained "diagnostic" in quality, despite non-ideal responses of some photomultiplier tubes at intermediate and extreme positions of the traverse periphery.

Copper↗
PubMed1983

Gonadal dose reduction in lumbar spine radiography.

Different ways to minimize the gonadal dose in lumbar spine radiography have been studied. Two hundred and fifty lumbar spine radiographs were reviewed to assess the clinical need for lateral L5/S1 projection. Modern film/screen combinations and gonadal shielding of externally scattered radiation play a major role in the reduction of the genetic dose. The number of exposures should be minimized. Our results show that two projections, anteroposterior (AP) and lateral, appear to be sufficient in routine radiography of the lumbar spine.

Adult↗
PubMed2005

Dose reduction for CT in children with cystic fibrosis: is it feasible to reduce the number of images per scan?

BACKGROUND: Reducing the dose for each CT scan is important for children with cystic fibrosis (CF). OBJECTIVE: To determine whether the number of CT images and therefore the dose per CT scan could be reduced without any significant loss of information in children with CF. MATERIALS AND METHODS: A cohort of children with CF was followed with biennial surveillance CT scans, obtained in inspiration after a voluntary breath-hold as 1-mm thick images at 10-mm intervals from lung apex to base. A random set of 20 baseline CT scans and 10 follow-up CT scans were blinded. Sets of every image (10-mm intervals), every second image (20-mm intervals), every third image (30-mm intervals) and a selection of three and five images were scored randomly using a published CT scoring system by one experienced observer. RESULTS: The 20 subjects were 10 years of age with a range of 3.7-17.6 years at baseline. Fewer CT images resulted in a significantly lower (less abnormal) CT score and the number of patients positive for abnormalities decreased subsequently. At intervals greater than 20 mm no significant change in CT score over 2 years could be detected, while the CT scores at 10-mm (P=0.02) and 20-mm (P=0.02) intervals worsened significantly. CONCLUSIONS: A reduction in the number of inspiratory CT images by increasing the interval between images to greater than 10 mm is not a valid option for radiation dose reduction in children with CF.

Adolescent↗
PubMed1996

Radiology in the neonatal intensive care unit: dose reduction and image quality.

This paper describes a prospective study of the diagnostic radiation doses received in a neonatal intensive care unit (NICU) for a representative radiological technique used at our institution for a number of years and a "low dose" technique similar to that recommended by the Commission of the European Communities (CEC). A 400 speed film-screen combination was used in both techniques. A total of 363 anteroposterior (AP) chest and abdominal films of 77 neonates were accrued. For each radiograph, the entrance skin dose (FSD), energy imparted (EI) and mean whole body dose were determined. For a neonatal AP chest, there was an 18% reduction in the mean ESD per radiograph from 20.0 muGy for the representative technique to 16.4 muGy for the low dose technique (p < 0.0005). The reduction in the mean EI per radiograph values for the two techniques from 7.9 muJ to 7.1 muJ (10%) was statistically significant at the p < 0.017 level, after compensating for the difference in mean field dimensions between the two patient cohorts. The mean whole body dose per radiograph reduction from 4.4 to 3.5 muGy (20%) was statistically significant at the p < 0.0028 level. It was determined that the ESD and EI could be fitted by an exponential function in the equivalent patient diameter, a single parameter indicative of neonate size. Absolute excess childhood cancer mortality risk per film was estimated using risk factors derived for fetal exposures. A "worst case" absolute excess mortality risk per chest radiograph was estimated to be 1.40 x 10(-7) for the conventional technique and was further reduced to 1.11 x 10(-7) for the low dose technique. A blind comparison of patient-matched film pairs for each technique was performed by three radiologists using criteria similar to those specified by the CEC. No statistically significant difference in clinical image quality was found between the two techniques.

Analysis of Variance↗
PubMed1986

Filter materials for dose reduction in screen-film radiography.

A computer program was developed to calculate both integral absorbed dose in a water phantom and entrance exposure, for the imaging of iodine contrast with x-ray intensifying screens. The effect of filtration of the x-ray beam on integral absorbed dose and entrance exposure was studied for 27 different filter materials and four types of intensifying screens. The dose and exposure were calculated, keeping the image contrast and energy absorption in the screens constant. To check the validity of the calculations, a number of measurements were performed, the results of which agreed well with our calculations. A remarkable result is that dose and exposure reduction can be achieved almost equally well with conventional filters (aluminum and copper) as with a number of K-edge filters. This was found for situations commonly encountered in diagnostic radiology (60-80 kV, 20 cm water). This finding is in contrast to a number of earlier studies, in which K-edge filters were found to be superior to conventional filters.

Aluminum↗
PubMed2004

Side-effects of fluticasone in asthmatic children: no effects after dose reduction.

To assess long-term effects and side-effects of fluticasone propionate (FP), a 2-yr study was performed, comparing a step-down dose approach (1,000 microg.day(-1), with reductions every 2 months to 500, 200 and 100 microg.day(-1) for the remainder of the study) versus a constant dose (200 microg.day(-1)). In 55 children with chronic persistent asthma, aged 6-10 yrs, airways hyperresponsiveness (AHR) and systemic side-effects (height, bone parameters and adrenal cortical function) were assessed at predetermined intervals in a double-blind prospective 2-yr study. AHR improved after 4 months treatment with 1,000 microg.day(-1) FP followed by 500 microg.day(-1), without significant differences during long-term treatment between the two approaches. Dose-dependent reduction of growth velocity, adrenal cortical function and biochemical bone turnover was found during therapy with 1,000 and 500 microg.day(-1) FP when compared with 200 microg.day(-1). In conclusion, doses of 1,000 and 500 microg.day(-1) fluticasone propionate are associated with marked reductions of growth velocity, bone turnover and adrenal cortical function. However, conventional doses (< or =200 microg.day(-1) fluticasone propionate) appear to be safe in the long-term management of childhood asthma. From a safety point of view, high doses of fluticasone propionate should only be prescribed in exceptions, e.g. in persistent severe asthma.

Adrenal Cortex↗
PubMed1993

Dose reduction in panoramic radiography.

A modern programmable panoramic radiography unit was used to irradiate an anthropomorphic phantom in order to assess the variation in organ absorbed dose and calculated effective dose with program selection. The results of the measurements for five of the 12 programs available are presented, together with those obtained from an older, non-programmable unit. The results of dosimetry measurements are compared between units, between programs, and with previous data. Variations in radiation dose and their implications are discussed, and the opportunities for reductions in organ dose and effective dose of up to 85% and 50%, respectively, demonstrated.

Humans↗
PubMed2001

Paediatric dose reduction with the introduction of digital fluorography.

Fluoroscopy guided examinations in a paediatric X ray department were initially carried out on a unit that used a conventional screen-film combination for spot-films. A new fluoroscopy unit was installed with the facilities of digital fluorography and last image hold. Comparison of equipment performance showed that the dose per image for screen-film and digital fluorography was 3 microGy and 0.4 microGy, respectively. Although the screen-film had superior image quality, the department's radiologist confirmed that digital fluorography provided a diagnostic image. Patient dose measurements showed that introduction of the new unit caused doses to fall by an average of 70%, although fluoroscopy time had not changed significantly. The new unit produced 40% less air kerma during fluoroscopy. The remaining 30% reduction in dose was due to the introduction of digital fluorography and last image hold facilities. It is concluded that the use of digital fluorography can be an effective way of reducing paediatric dose.

Adolescent↗
PubMed1999

Serum eosinophil cationic protein (ECP) as a mediator of inflammation in acute asthma, during resolution and during the monitoring of stable asthmatic patients treated with inhaled steroids according to a dose reduction schedule.

OBJECTIVE AND DESIGN: The main objective was to establish the level of serum ECP in a group of adult asthmatic patients with acute exacerbation and the following resolution and in another group of adult, stable asthmatic patients during reduction of inhaled steroids. SUBJECTS AND TREATMENT: Acute group: Twenty-one asthmatic patients admitted to the asthma clinic with acute deterioration of their asthma were set on oral steroids which were reduced to 0 within one week. Reduction group: Forty-four stable asthmatic patients on maintenance inhaled steroids were included and, on the basis of their peak expiratory flow (PEF) values, adjustments in the doses of steroids were made. CONTROL GROUP: Twenty stable asthmatics on a constant dose of inhaled steroids were enrolled as controls. METHODS: All patients registered daily PEF measurements and spirometry was performed at each visit. Blood samples were drawn and analysed for eosinophil cationic protein (ECP), myeloperoxidase (MPO), eosinophils and neutrophils. RESULTS: ECP was low and within the normal range for all three groups at study entry. (Acute group = 8.4 microg/l, reduction group = 3.7 microg/l and control group = 4.6 microg/l). Nevertheless, the value in the acute group was significantly higher than in the control group (p=0.005). The levels in the acute group decreased significantly (p=0.004) after one week on oral steroids. No significant changes in ECP were observed in the reduction group or in the control group during the follow-up period. The lung function was low in the acute group at inclusion, forced expiratory volume in one second (FEV1)=47.1% of predicted, and increased significantly during the treatment period (p = 0.006). The patients in the reduction- and control group showed small variations in lung function during the whole study, FEV1 >70% and PEF > 80% of predicted, respectively. No correlation between atopy and ECP was found in the patients irrespective of the stage of disease. CONCLUSIONS: This study suggests that the resolution of acute asthma exacerbations during treatment could be followed using ECP determinations. In stable asthmatics on inhaled steroids and with normal ECP levels, a dose reduction could be indicated. A longer period after tapering off steroids is proposed to confirm the benefit of ECP measurements for controlling asthma.

Acute Disease↗
PubMed1996

Short communication: staff dose reduction during coronary angiography using low framing speed.

Radiation exposure of cardiac catheterization laboratory staff is a known occupational hazard, and efforts are made to obtain dose levels which are "as low as reasonably achievable". This study assessed the reduction in staff radiation exposure using cine framing at 12.5 f s-1 during coronary cineangiography, instead of 25 f s-1. Thermoluminescent dosemeters were used to measure equivalent dose at several sites for the operator, nurse assistant, and X-ray technician during 15 procedures at both frame rates. Patient-related and procedure-related variables were similar in the two groups of examinations. Mean equivalent dose absorbed (microSv) at the left side of the forehead was reduced by 61%, 60% and 36%, for the operator, nurse assistant and X-ray technician, respectively. With use of the lower frame rate similar reductions by 42%, 62% and 62% were measured at the thyroid level, and by 51%, 40% and 61% at the mid-thorax level. Cinefilming at low frame rates during coronary arteriography allows a substantial X-ray dose reduction at all body sites for all staff. Use of lower frame rates wherever possible is of special interest since it may also reduce patient radiation exposure.

Cineradiography↗