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At least 145 records · Page 8Linked to original sources
PubMed1997

Simulated dose reduction in conventional chest CT: validation study.

PURPOSE: To validate a technique of computer-simulated dose reduction for conventional chest computed tomography (CT). MATERIALS AND METHODS: In 27 patients, CT scans were obtained at 200, 100, and 40 mAs at two levels. The raw data from the 200-mAs scan were modified on a computer workstation to simulate the increased noise present on 100- and 40-mAs scans. Real and simulated 100- and 40-mAs images were independently assessed in random order for overall image quality and radiologic findings by four subspecialty-trained chest radiologists who were blinded to the technique. The four observers were given paired real and simulated images. They were asked to identify the real image and note any difference in diagnostic quality. RESULTS: No difference was seen in overall image quality or radiologic findings between real and simulated images (P > .05). In the paired comparison, 433 of 864 (50.1%) real images were correctly identified. CONCLUSION: Computer modification of 200-mAs raw scan data to simulate 100- and 40-mAs noise levels produces reconstructed images indistinguishable from real 100- and 40-mAs scans. This technique provides realistic reduced-dose images without patient radiation exposure and with identical image registration and motion artifact.

Adult↗
PubMed1984

Dose reduction in paediatric radiology using rare earth filtration.

Rare earth filters are known to reduce radiation dose in radiological investigations. The present investigation used Er and Sm filters that were selected because of their chemical stability and ability to withstand prolonged exposure to the atmosphere. They were used in a comparison with a conventional aluminium filter in a range of paediatric radiological procedures. Introduction of the filters instead of the conventional filter, resulted in a dose reduction of up to twofold with no discernible deterioration in image quality.

Aluminum↗
PubMed1996

Radiation dose reduction in computed skeletal radiography. Effect on image quality.

PURPOSE: To evaluate the effect of radiation dose reduction on image ++quality in computed musculoskeletal radiography and determine optimal exposure range. MATERIAL AND METHODS: In 11 corpses, 1 hand and 1 hip were examined with film-screen radiography, and a series of computed radiographs was obtained using exactly the same technique except for the exposure, which was 100, 50, 25, 12.5, 6.25, and 1.56% of the mAs numbers used for the film-screen images. The computed hip radiographs were processed in 2 different ways, one simulating the film-screen images and one using contrast enhancement. Four radiologists reviewed the images regarding the following parameters: cortical bone, trabecular bone, joint space, and soft tissue, giving each a diagnostic quality rating on a scale from 1 to 5. The median and mean values were found for the pooled results. RESULTS: For the hands, the computed radiographs were ranked inferior to the film-screen images for all parameters except soft tissue, where the computed radiographs scored higher. The computed images with 50 and 25% exposure were ranked equal to the 100% ones. The quality rating slowly declined with lower exposures. For the hips, the 100 and 50% computed radiographs were generally similar to or slightly better than the film-screen images. The decline was somewhat faster than for the hands. The contrast-enhanced hip images scored less than the nonenhanced images at any given exposure for all parameters except soft tissue, where the contrast-enhanced images scored better at all exposures. The difference between nonenhanced and enhanced images became less at the lower exposures. CONCLUSION: Lowering the exposure in computed musculoskeletal radioagrphy below the level of film-screen radiography is feasible, especially in the peripheral skeleton. Contrast enhancement seems to be valuable only in the evaluation of soft-tissue structures.

Bone and Bones↗
PubMedDate not supplied

[Modeling the processes of cell recovery from radiation injury and the effective dose reduction principle. Model of postradiation recovery with a finite number of recovery channels].

Using the effective dose reduction principle for the description of the postirradiation recovery a mathematical model has been developed with the definite number of recovery channels in a cell. It was established that the number of recovery channels in Megri 139-B yeast cells was of the order of 10. The model may be applied for co-ordination of studies in the repair of radiation-induced lesions in a DNA molecule and in the postirradiation survival of exposed cells.

Cells↗
PubMed2003

Vincristine in childhood leukaemia: no pharmacokinetic rationale for dose reduction in adolescents.

AIM: To investigate whether there is any pharmacokinetic rationale for the common practice of administering vincristine to adolescents at relatively lower doses than those to younger children. METHODS: A total of 98 children, aged 1.3-17.3 y, with acute lymphoblastic leukaemia (ALL) were studied on day 1 of induction therapy. Plasma samples were drawn before and 10, 30, 360 and 1380 min after injection of vincristine 2.0 mg/m2 (maximum dose 2.0 mg) and analysed by high-performance liquid chromatography. RESULTS: The median value (and range) for distribution half-life was 6.4 min (0.8-11.8), elimination half-life 1014 min (258-2570), volume of distribution 445 L/m2 (137-1241) and total body clearance 362 ml/min/m2 (134-2553). No correlation was found between age and any of these pharmacokinetic parameters. The area under the concentration time curve (AUC) was significantly correlated to age (p = 0.002; p - 0.31), as expected from the dosage of vincristine. The lower AUC in children with a body surface area > 1 m2, which is reached at 8-9 y of age, indicates that they received a less intense treatment because of the capping of the vincristine dose at 2.0 mg. CONCLUSIONS: Vincristine pharmacokinetics were not age dependent in this paediatric population. Thus, we found no pharmacokinetic rationale for dose reduction in adolescents. The common practice of limiting the vincristine dose to 2.0 mg should be carefully reconsidered.

Adolescent↗
PubMed1978

[Dose reduction during radiological examination using high intensity rare earth screens or increased kV (author's transl)].

Using a procedure which resembles actual practice, it has been shown that an increase in kV. results in a reduction of radiation dose similar to that obtained by using the new high intensity rare earth screens while maintaining similar detail. In practical terms this means that there is only limited usefulness for the new rare earth screens. An exception to this is the screen which reduces dose while producing similar, or better, detail than a standard screen. We could demonstrate this for the film-screen combination Trimax alpha4XD.

Humans↗
PubMed2002

Radiation dose reduction in chest radiography using a flat-panel amorphous silicon detector.

AIM: The aim of this study was to evaluate the image quality and the potential for radiation dose reduction with a digital flat-panel amorphous silicon detector radiography system. MATERIAL AND METHODS: Using flat-panel technology, radiographs of an anthropomorphic thorax phantom were taken with a range of technical parameters (125kV, 200mA and 5, 4, 3.2, 2, 1, 0.5, and 0.25mAs) which were equivalent to a radiation dose of 332, 263, 209, 127, 58.7, 29, and 14 microGy, respectively. These images were compared to radiographs obtained by a conventional film-screen radiography system at 125kV, 200mA and 5mAs (equivalent to 252 microGy) which served as reference. Three observers evaluated independently the visibility of simulated rounded lesions and anatomical structures, comparing printed films from the flat-panel amorphous silicon detector and conventional x-ray system films. RESULTS: With flat-panel technology, the visibility of rounded lesions and normal anatomical structures at 5, 4, and 3.2mAs was superior compared to the conventional film-screen radiography system. (P< or =0.0001). At 2mAs, improvement was only marginal (P=0.19). At 1.0, 0.5 and 0.25mAs, the visibility of simulated rounded lesions was worse (P< or =0.004). Comparing fine lung parenchymal structures, the flat-panel amorphous silicon detector showed improvement for all exposure levels down to 2mAs and equality at 1mAs. CONCLUSION: Compared to a conventional x-ray film system, the flat-panel amorphous silicon detector demonstrated improved image quality and the possibility for a reduction of the radiation dose by 50% without loss in image quality.

Humans↗
PubMed2006

The effect of dose reduction on the detection of anatomical structures on panoramic radiographs.

OBJECTIVES: The aim was to evaluate the effect of dose reduction on diagnostic accuracy using different screen-film combinations and digital techniques for panoramic radiography. METHODS: Five observers assessed 201 pairs of panoramic radiographs (a total of 402 panoramic radiographs) taken with the Orthophos Plus (Sirona, Bensheim, Germany), for visualization of 11 anatomical structures on each side, using a 3-point scale -1, 0 and 1. Two radiographs of each patient were taken at two different times (conventional setting and setting with decreased dose, done by increasing tube potential settings or halving tube current). To compare the dose at different tube potential settings dose-length product was measured at the secondary collimator. Films with medium and regular intensifying screens (high and low tube potential settings) and storage phosphor plates (low tube potential setting, tube current setting equivalent to regular intensifying screen and halved) were compared. The five observers made 27 610 assessments. Intrarater agreement was expressed by Cohen's kappa coefficient. RESULTS: The results demonstrated an equivalence of regular screens (low tube potential setting) and medium screens (high and low tube potential settings). A significant difference existed between medium screens (low tube potential setting, mean score 0.92) and the group of regular film-screen combinations at high tube potential settings (mean score 0.89) and between all film-screen combinations and the digital system irrespective of exposure (mean score below 0.82). There were no significant differences between medium and regular screens (mean score 0.88 to 0.92) for assessment of the periodontal ligament space, but there was a significant difference compared with the digital system (mean score below 0.76). The kappa coefficient for intrarater agreement was moderate (0.55). CONCLUSIONS: New regular intensifying screens can replace medium screens at low tube potential settings. Digital panoramic radiographs should be taken at low tube potential levels with an exposure equivalent at least to a regular intensifying screen.

Alveolar Process↗
PubMed1998

Dose reduction in a paediatric X-ray department following optimization of radiographic technique.

A survey of radiation doses to children from diagnostic radiography has been carried out in a dedicated paediatric X-ray room. Entrance surface dose (ESD) and dose-area product (DAP) per radiograph were simultaneously measured with thermoluminescent dosemeters (TLDs) and a DAP meter to provide mean dose values for separate age ranges. Results of ESD and DAP were lower than the mean values from other UK studies for all ages and radiographs, except for the infant pelvis AP radiograph. Comparison of ESD and radiographic technique with CEC quality criteria highlighted a need for reduction of dose to infants and implied an increase in tube filtration might overcome the limitations of the room's three-phase, 12-pulse generator, allowing higher tube potentials to be used on infants. Additional tube filtration of 3 mmA1 was installed following assessment of dose reduction and image quality with test objects and phantoms, and confirmation from the paediatric radiologist that clinical image quality was not-significantly altered. The tube potential was increased from 50 to 56 kVp for the infant pelvis AP radiograph. The resulting ESD and effective dose fell by 51% and 38%, respectively. The CEC quality criteria have proved useful as a benchmark against which technique in X-ray departments can be compared, and as such are a useful tool for optimizing radiographic technique and reducing patient dose.

Adolescent↗
PubMed1999

Protection of human gastric mucosa against aspirin-enteric coating or dose reduction?

BACKGROUND: Aspirin is widely used for cardiovascular prophylaxis. AIM: To compare the effectiveness of two widely-used strategies-dose reduction and enteric coating-for the minimization of gastric mucosal injury or toxicity. METHODS: Twelve healthy volunteers were studied. On four separate occasions each received, under blinded conditions, five daily doses of plain aspirin 300 mg, plain aspirin 75 mg, enteric-coated aspirin 300 mg or placebo. Ex vivo prostaglandin E2 synthesis was stimulated by the vortex mixing of gastric mucosal biopsies in Tris saline and measured by radioimmunoassay. Mucosal injury was quantified both by counting erosions and with a visual analogue scale. RESULTS: All three preparations reduced prostaglandin E2 synthesis by day five, by (median) 84% for plain aspirin 300 mg, by 80% for enteric coated aspirin 300 mg and by 63% for plain aspirin 75 mg. There was little mucosal injury prior to the start of each dose and period and no significant change with placebo. Plain aspirin caused a dose-dependent mucosal injury, with two (median, IQR 0-7) gastric erosions after five days of plain aspirin 75 mg, and 18 (2-26) after five days of plain aspirin 300 mg. With enteric-coated aspirin 300 mg there were 0 (0-1) gastric erosions (P = 0.003 compared to plain aspirin 300 mg P = 0.11, compared to plain aspirin 75 mg). CONCLUSION: Enteric coated aspirin reduces acute gastric mucosal injury to placebo levels, despite its inhibition of prostaglandin synthesis. Enteric coating is an appropriate strategy for the prevention of gastric mucosal damage induced by low-dose aspirin, which warrants systematic clinical evaluation.

Adult↗
PubMed1994

A double-blind dose-reduction trial of fluphenazine decanoate for chronic, unstable schizophrenic patients.

OBJECTIVE: This study evaluated the feasibility and impact of gradually reducing relatively high doses of fluphenazine decanoate by one-half for chronically impaired, poor inner-city patients with schizophrenia. METHOD: Forty-three patients currently receiving an average of 23 mg (0.3 mg/kg) of fluphenazine decanoate every 2 weeks were divided alternately into a group to remain at current doses (control group) and a group to undergo stepwise 50% dose reduction over 5 months under double-blind conditions. Clinical status and side effects were assessed quarterly for a year. Relapse was determined clinically and by changes in psychopathology ratings. RESULTS: Eighty-six percent (N = 37) of the patients (control group, N = 17; reduced-dose group, N = 20) completed the study. The groups did not differ at baseline in demographic or clinical variables or neuroleptic dose. In the reduced-dose group, doses were lowered to an average of 11.5 mg every 2 weeks. The two groups did not differ throughout the year in number of relapses, and hospitalization rates fell similarly in both (overall, by about 67%). Clinical measures changed little. Extrapyramidal symptoms worsened in the control group but improved slightly in the reduced-dose group. Tardive dyskinesia worsened in both groups, but less in the reduced-dose group. CONCLUSIONS: Maintenance neuroleptic doses much lower than the conventional ones can be achieved safely in schizophrenic patients by gradual reduction, without clinical worsening and perhaps with fewer extrapyramidal symptoms and less tardive dyskinesia. The two-thirds lower hospitalization rate, with substantial financial savings, apparently was due to nonspecific effects of research intervention.

Adult↗
PubMed2007

The effect of dose reduction and feasibility of edge-preserving noise reduction on the detection of liver lesions using MSCT.

The purpose of this study was to assess the effect of dose reduction and the potential of noise reduction filters on image quality and the detection of liver lesions using MSCT. Twenty-nine patients with a total of 40 liver lesions underwent 16-slice CT (120 kV; 180 mAs). Virtual noise was added to CT raw datasets simulating effective mAs levels of 155, 130, 105, 80, 55, 30 and 10 mAs. All datasets were post-processed with an edge-preserving noise-reduction filter (ANR-3D), yielding a total of 15 datasets per patient. Ten radiologists performed independent evaluations of image quality, the presence of liver lesions and diagnostic confidence. Quantitative noise and contrast-to-noise ratios (CNR) were obtained. Superior image quality (P < 0.02), reduction of image noise (P < 0.001) and the increase of lesion-to-liver CNR (P < 0.001) were observed in images processed with the ANR-3D filter. Sensitivity for lesion detection remained unchanged down to 105 mAs (CTDI(w) 6.6 mGy) without filter and 80 mAs (CTDI(w) 5.1 mGy) with ANR-3D. Confidence was rated significantly higher for datasets reconstructed with ANR-3D. The use of a noise-reducing, but edge-preserving filter (ANR-3D) is a promising option to reduce further the radiation dose in liver CT.

Adult↗
PubMed2000

A dose reduction x-ray beam positioning system for high-speed multislice CT scanners.

The introduction of multislice CT scanners and the associated dose increase compared to single and dual slice scanners has concerned many radiologists, health and medical physicists, as well as members of the regulatory community. Since multislice CT scanners are inherently post-patient collimated, they are less dose efficient than single slice CT scanners, which use prepatient collimation. The x-ray beam must be wide enough in the Z axis so that the beam remains on the detector in spite of typical movements due to thermal and mechanical flexing. We describe the x-ray beam tracking system that is employed on a GE LightSpeed QX/i scanner to substantially reduce the multislice dose. The tracking system stabilizes the beam on the detector allowing a narrower x-ray exposure profile compared to the x-ray exposure profile without tracking. The tracking system measures the position of the beam every few milliseconds and continually repositions a source aperture to hold a narrow beam fixed on the detector. Using a standard LightSpeed QX/i source collimator and segmented detector, dose reductions of up to 40% were measured when tracking was employed. We also show that tracking has the potential to provide a dose efficiency approaching single slice scanners.

Humans↗
PubMed2006

Dose reduction and image quality in MDCT colonography using tube current modulation.

OBJECTIVE: The purpose of our study was to evaluate the dose reduction potential of combined online (x- and y-axes) and topogram-based (l) X-ray tube current modulation in CT colonography in a screening population. MATERIALS AND METHODS: Eighty asymptomatic individuals underwent CT colonography screening for colon polyps. A 16-MDCT scanner (Somatom Sensation 16) was used. Forty patients were examined at 120 kVp and 120 effective mAs (supine) and 40 effective mAs (prone) using online x- and y-axis tube current modulation. Another 40 patients were scanned using combined x-, y-, and z-axis tube current modulation. Individual patient radiation exposure was determined using the dose-length product. Image noise was determined by Hounsfield unit measurements in the colonic lumen at four anatomic levels. Image quality was rated on a 5-point confidence scale by two independent reviewers. The unpaired Student's t test (for radiation dose, image noise) and Wilcoxon's test (for image quality) were used to test for statistically significant differences between these values. RESULTS: Radiation dose was significantly lower in the patient group scanned with x-, y-, and z-axis tube current modulation than in the group scanned with x- and y-axis tube current modulation (supine: 4.24 vs 6.50 mSv, p < 0.0001; prone: 1.61 vs 2.38 mSv, p < 0.0001). Radiation dose was reduced by 35% (supine) and 33% (prone). No statistically significant difference was seen in overall image noise (supine: 15.9 vs 16.3 H, p = 0.13; prone: 23.5 vs 24.8 H, p = 0.44) or image quality (supine: 4.6 vs 4.5, p = 0.62; prone: 3.5 vs 3.6, p = 0.54). CONCLUSION: Combined x-, y-, and z-axis tube current modulation leads to a significant reduction of radiation exposure in CT colonography without loss of image quality.

Aged↗
PubMed2004

[5 years of "concerted action dose reduction in CT" -- what has been achieved and what remains to be done?].

In May 1998, the German "Concerted Action Dose Reduction in CT" was founded by all parties involved in CT. Its intention was to achieve a significant reduction of the radiation exposure caused by CT, a matter that has increasingly been considered a major challenge since the early nineties. As a result of a number of joint efforts, the essential preconditions have been established by now. The fifth anniversary of the Concerted Action gave rise for both retrospection and outlook on the tasks that have already been accomplished and those that still need to be done. For this purpose, a one-day symposium took place in Berlin on November 4, 2003. The contents of a total of 18 contributions will be outlined here in brief.

Adult↗
PubMed2004

Realtime digital magnification of the fluoroscopic and digital subtraction angiography images: randomized prospective study to show dose reduction during segmental chemoembolization for hepatocellular carcinoma.

PURPOSE: To show efficacy of realtime digital magnification of fluoroscopic and digital subtraction angiography images for dose reduction both of the medical personnel and the patient during segmental chemoembolization for hepatocellular carcinoma. MATERIALS AND METHODS: Thirty patients were randomized into two groups; chemoembolization was performed with digital magnification (group A; n = 15) or with shorter field of view (group B; n = 15). Dose area product was used as a convenient and reasonable analog of the patient dose. Medical personnel dose and dose area product were compared. RESULTS: Medical personnel dose and dose area product were 7.0 +/- 3.4 micro Sv and 71060 +/- 24653 cGy. cm(2)in group A, and 21.4 +/- 16.2 micro Sv and 110379 +/- 48065 cGy. cm(2) in group B, respectively. There were statistically significant differences in both the medical personnel dose (P =.002, Student t test) and the dose area product (P =.009, Student t test). CONCLUSION: Digital magnification decreased the medical personnel dose by 67% and the patient dose by 36% during segmental chemoembolization for hepatocellular carcinoma.

Adult↗
PubMed1986

Neuroleptic bioavailability, psychosocial factors, and clinical status: a 1-year study of schizophrenic outpatients after dose reduction.

Serum neuroleptic levels, prolactin levels, and clinical state were assessed for 1 year in 29 schizophrenic outpatients whose clinically determined neuroleptic dose had been reduced by 50%. Fifty-five percent of the subjects remained stable. Neuroleptic dose did not differ between relapsed and stable patients. Serum prolactin (PRL) assessed 2 weeks after dose reduction and mean PRL after reduction were significantly lower among relapsers. Serum neuroleptic levels were significantly lower for relapsers in patients on haloperidol. Among relapsers, there were no serum PRL or neuroleptic level differences between stable periods and the relapse episode. Among patients with relatively low neuroleptic bioavailability, relapsers reported lower levels of social activity and had social networks that were less enjoyable, more aversive, and less helpful than those of stable patients.

Adult↗
PubMed2003

[Dose reduction of radiographs of the pediatric pelvis for diagnosing hip dysplasia using a digital flat-panel detector system].

PURPOSE: To evaluate a possible dose reduction in pediatric pelvic radiographs in congenital hip dysplasia using a digital flat-panel system instead of a phosphor-storage system. MATERIALS AND METHODS: During a six-month period, all pediatric patients referred for pelvic radiography for the evaluation of congenital hip dysplasia were randomly assigned to be examined by either a phosphor-storage system or a digital flat-panel system, whereby the latter system was operated with half the radiation dose. Thirty pairs of radiographs were assessed for the visibility of 16 anatomic details and for 5 orthopedic-radiographic measurements (5-point scale with 1 = excellent; three independent observers). The projection indices of Ball and Kommenda and of Tönnis and Brunken were calculated for all radiographs. The Student's t-test was used to compare the flat-panel and the phosphor-storage radiographs for observers' assessments, patients' age and projection indices. RESULTS: In a total of 7560 observations, the scores for the visibility of anatomic details and orthopedic-radiographic measurements were respectively 2.72 and 2.64 for the flat-panel system and 2.93 and 2.79 for the phosphor-storage system. No significant differences were found between both systems (p > 0.05) and between patient age and projection indices (p > 0.05). CONCLUSION: Pediatric pelvic radiographs can be obtained with a digital flat-panel system using half the radiation dose instead of a phosphor-storage system without sacrificing relevant information in the diagnosis of congenital hip dysplasia.

Age Factors↗