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PubMed2000

Digital radiography of the skeleton using a large-area detector based on amorphous silicon technology: image quality and potential for dose reduction in comparison with screen-film radiography.

AIM: The purpose of this study was to evaluate a large-area, flat-panel X-ray detector (FD), based on caesium-iodide (CsI) and amorphous silicon (a-Si) with respect to skeletal radiography. Conventional images were compared with digital radiographs using identical and reduced radiation doses. MATERIALS AND METHODS: Thirty consecutive patients were studied prospectively using conventional screen-film radiography (SFR; detector dose 2.5 microGy). Digital images were taken from the same patients with detector doses of 2.5, 1.25 and 0.625 microGy, respectively. The active-matrix detector had a panel size of 43 x 43 cm, a matrix of 3 x 3K, and a pixel size of 143 microm. All hard copies were presented in a random order to eight independent observers, who rated image quality according to subjective quality criteria. Results were assessed for significance using the Student's t -test (confidence level 95%). RESULTS: A statistically significant preference for digital over conventional images was revealed for all quality criteria, except for over-exposure (detector dose 2.5 microGy). Digital images with a 50% dose showed a small, statistically not significant, inferiority compared with SFR. The FD-technique was significantly inferior to SFR at 75% dose reduction regarding bone cortex and trabecula, contrast and overall impression. No statistically significant differences were found with regard to over- and under-exposure and soft tissue presentation. CONCLUSION: Amorphous silicon-based digital radiography yields good image quality. The potential for dose reduction depends on the clinical query.

Aged↗
PubMed1983

The application of matched filtering to contrast material dose reduction in digital subtraction angiography.

Temporal filtering methods were applied to a 50% reduction of contrast material dose in intravenous digital subtraction angiography (DSA). The performance of matched filtering was reviewed, indicating a 50% reduction of noise through the integration of an entire (greater than 10 sec) DSA image sequence spanning the contrast material bolus arrival and washout. Used in conjunction with 50% contrast material dose reduction, matched filtering could provide final iodine signal-to-noise ratios (SNR) comparable to those of conventional DSA. Half-contrast-material-dose (20 ml) filtered DSA runs were compared with full-contrast-material-dose (40 ml) unfiltered runs for 5 carotid, 2 cerebral, and 4 peripheral studies. In all but 2 studies, the half-contrast-material-dose runs were judged to be diagnostic. In all 4 peripheral studies and in some of the 7 carotid and cerebral studies the 20-ml results were judged to be equivalent to the 40-ml results. It is concluded that the half-contrast-material-dose temporally filtered approach is appropriate for peripheral runoff studies. Matched filtering was experimentally compared with simple integrated remasking. If the identical image sequence was used for each, the two had virtually identical performance for integration times less than 10 sec, consistent with theoretical predictions. Two other applications of matched filtering, SNR enhancement and x-ray exposure reduction, are discussed schematically.

Angiography↗
PubMed2004

Olanzapine treatment for tardive dyskinesia in schizophrenia patients: a prospective clinical trial with patients randomized to blinded dose reduction periods.

BACKGROUND: Tardive dyskinesia (TD) is a potentially persistent and disabling abnormal involuntary movement disorder. The aim of this 8-month study was to determine if olanzapine treatment could lead to a significant and persistent reduction in preexisting TD. METHODS: Eligible schizophrenia patients met restricted Research Diagnosis criteria of TD requiring, in part, a rating of at least moderate severity (score > or = 3) in one or more of seven body regions on the Abnormal Involuntary Movement Scale (AIMS). Patients received olanzapine, 5-20 mg/day, for 8 months. During this period, they underwent one to two dose reduction periods under blinded conditions. Concurrent changes in TD, psychopathology, parkinsonism and akathisia were assessed with the AIMS, the Positive and Negative Syndrome Scale (PANSS), and the Simpson-Angus and Barnes Akathisia Scales, respectively. RESULTS: A significant reduction in mean AIMS total score was demonstrated at endpoint (n = 92; p < 0.001) as well as at each visit (p < 0.001) and as early as Week 1 on olanzapine. Approximately 70% of patients no longer met the restricted Research Diagnostic criteria for persistent TD (RD-TD) after 8 months of treatment. No statistically significant rebound worsening of TD was found during either blinded drug reduction period. Significant improvement in psychopathology (p = 0.001) and parkinsonism (p < 0.001) was observed. CONCLUSIONS: Improvement in the severity of preexisting TD was achieved with olanzapine and persisted throughout the 8-month study and during each dose reduction period. Overall improvement in clinical status suggests that olanzapine may be effective for the long-term management of schizophrenia patients with preexisting TD.

Adult↗
PubMed2005

Method of simulating dose reduction for digital radiographic systems.

The optimisation of image quality vs. radiation dose is an important task in medical imaging. To obtain maximum validity of the optimisation, it must be based on clinical images. Images at different dose levels can then either be obtained by collecting patient images at the different dose levels sought to investigate-including additional exposures and permission from an ethical committee-or by manipulating images to simulate different dose levels. The aim of the present work was to develop a method of simulating dose reduction for digital radiographic systems. The method uses information about the detective quantum efficiency and noise power spectrum at the original and simulated dose levels to create an image containing filtered noise. When added to the original image this results in an image with noise which, in terms of frequency content, agrees with the noise present in an image collected at the simulated dose level. To increase the validity, the method takes local dose variations in the original image into account. The method was tested on a computed radiography system and was shown to produce images with noise behaviour similar to that of images actually collected at the simulated dose levels. The method can, therefore, be used to modify an image collected at one dose level so that it simulates an image of the same object collected at any lower dose level.

Algorithms↗
PubMed1982

Dose reduction in radiography of the spine in scoliosis.

Measurements of skin doses during radiography in scoliosis have been performed with a.p. and p.a. direction of the beam. In order to keep the doses to the patients low, high kV, a film-focus distance of at least 3 m, a fast screen-film combination, lead shielding, a collimator with rotating compensating filter, and a grid of the moving anti-scatter type are recommended. By using the p.a. direction the dose to the breast is reduced by a factor in the range of 88 to 97 per cent. Further dose reduction might be achieved by removal of the anti-scatter grid and use of the air gap technique. Relinquishment of the radiographic principle of bringing the object to be examined as near the film as possible did not reduce the diagnostic information.

Adolescent↗
PubMed2006

Dose reduction of intraoral dental radiography in Spain.

OBJECTIVES: To assess the influence of new European Union (EU) legislation on radiation doses in intraoral dental radiography in Spain. METHODS: A total of 10 109 official reports from Spanish dental offices covering the period 1996-2003 were analysed. RESULTS: The results point to a dose reduction of 19% in 7 years, with a mean dose of 3.11 mGy being administered in 2003. The third quartile value in 2002 was 4.8 mGy. Taking the EU recommended dose of 4 mGy as standard, 73.3% (2002) and 77.3% (2003) of installations are in compliance with the EU recommendations in Spain. However, there has been no further reduction in the last 3 years. The results showed that Ultraspeed dental X-ray film was used by 77.6% of the dentists in 1996-1997 and 82.3 in 2003. There was infrequent use of E-speed films (0.6%) and F-speed films (9.6%) in 2003. Statistical analysis pointed to significant differences between the doses administered and the type of processing used, the lowest exposures being measured in digital systems, which used significantly lower doses than both manual and automatic development, and when conventional radiographic films were used. CONCLUSION: The introduction of new legislation has resulted in a gradual reduction in the dose administered in intraoral dental radiology in Spain.

Analysis of Variance↗
PubMed2000

Chemotherapy dose reduction and delay in clinical practice. evaluating the risk to patient outcome in adjuvant chemotherapy for breast cancer.

Randomised clinical trials demonstrate the importance of maintaining chemotherapy dose and dose intensity in the systemic adjuvant treatment of breast cancer, and show that the strategies of dose delay and dose reduction carry the risk of suboptimal outcome. Such dose modifications are usually necessitated by the myelosuppressive effects, specifically neutropenia, thrombocytopenia and anaemia, resulting from the previous cycle of chemotherapy. The Canadian Database Initiative was designed to determine the incidence of neutropenic complications (an episode of febrile neutropenia or dose delay or reduction) and the frequency of complications by cycle of therapy using data from patients with breast cancer treated at centres across Canada. The centres used a variety of adjuvant chemotherapy regimens and the database covered the treatment of 444 patients, average age 47.7 years, who were treated between 1991 and 1996. Across all chemotherapy regimens, 42% of patients experienced at least one complication. Of those, 72% went on to have additional complications in subsequent cycles. The neutropenic complications usually occurred early in the treatment schedule.

Adult↗
PubMedDate not supplied

Lead shielding thickness for dose reduction of 6-MeV electrons for different square fields.

The relative percent dose reduction by lead (Pb) of 6-MeV electrons produced by Clinac 1800 for 6 X 6, 10 X 10, 15 X 15, 20 X 20, and 25 X 25 cm2 cones both with and without buildup is measured. The thickness of Pb required to attenuate the intensity of the primary electron beam to 95% and 98% depends upon the cone size and upon the depth in phantom at which transmission measurements are made.

Electrons↗
PubMed2002

Dose reduction of inhaled corticosteroids under concomitant medication with montelukast in patients with asthma.

The present study aimed at comparing the effects of a dose reduction of inhaled corticosteroids on lung function, indirect measures of airway inflammation and clinical scores during treatment with a leucotriene receptor antagonist. In 50 patients (mean forced expiratory volume in one second (FEV1) 94% predicted), steroid doses (800 microg beclomethasone dipropionate) were first reduced to 50% and then to 25%, for 6 weeks each. One group received a placebo and the other group received montelukast (10 mg). The first reduction did not cause significant effects. During the second, FEV1 and peak expiratory flow decreased in both groups (p<0.001). Daytime symptoms were not altered with placebo but were reduced by montelukast (p<0.05). Night-time symptoms were slightly elevated with placebo (p<0.05) but not montelukast, as well as the use of supplemental salbutamol. Changes in provocative concentration of methacholine causing a 20% fall in FEV1 (PC20), sputum eosinophils and exhaled nitric oxide were mostly nonsignificant for both placebo and montelukast. These data demonstrate that a 75% reduction in the dose of steroid given to patients with asthma led to a deterioration in lung function not prevented by montelukast, whereas changes in clinical state seemed to favour montelukast treatment. It therefore appears that potential effects of montelukast, in the presence of low-dose steroids, could not be attributed to single indices of lung function or airway inflammation.

Acetates↗
PubMed2004

CT colonography: feasibility of substantial dose reduction--comparison of medium to very low doses in identical patients.

In a feasibility study, the authors compared polyp detection and interobserver variability at computed tomographic (CT) colonography in 15 patients with doses ranging from medium to very low (12.00-0.05 mSv). At levels down to 2% of the medium dose, the mean detection of polyps 5 mm or larger remained at least 74%, while the number of false-positive results decreased and the interobserver agreement remained constant. Initial observations indicate that it is feasible to reduce the radiation dose required for CT colonography. Further studies are needed, however, to investigate the clinical value of very low-dose CT colonography.

Adult↗
PubMed2001

Guidelines for premeal insulin dose reduction for postprandial exercise of different intensities and durations in type 1 diabetic subjects treated intensively with a basal-bolus insulin regimen (ultralente-lispro).

OBJECTIVE: To evaluate and validate appropriate premeal insulin dose reductions for postprandial exercises of different intensities and durations to minimize the risk of exercise-induced hypoglycemia in type 1 diabetic subjects. RESEARCH DESIGN AND METHODS: Eight male type 1 diabetic patients on a basal-bolus insulin regimen of ultralente (UL) as basal insulin and lispro (LP) as premeal insulin were tested in a randomized, crossover fashion during postprandial exercise at 25% VO2max for 60 min, 50% VO2max for 30 and 60 min, and 75% VOmax for 30 min starting 90 min after a standardized mixed breakfast (600 kcal, 75 g carbohydrates). Each subject served as his own control and was rested after a full dose of insulin LP (LP 100%) and/or 50% (LP 50%) and/or 25% (LP 25%) of the current dose. RESULTS: At all intensities, the full premeal insulin dose was associated with an increased risk of hypoglycemia. At 25% VO2max for 60 min, a 50% reduction in the premeal insulin dose resulted in plasma glucose of -0.62 mmol/l compared with baseline at the end of exercise. At 50% VO2max for 30 and 60 min, 50 and 75% reductions of the premeal insulin dose were associated with plasma glucose of -0.39 and +0.49 mmol/l, respectively, at the end of the exercise. At 75% VO2max, a 75% reduction of the premeal insulin dose was required to achieve appropriate postexercise plasma glucose (+0.71 mmol/l). Such reductions in the premeal insulin dose resulted in a 75% decrease in the incidence of exercise-induced hypoglycemia. CONCLUSIONS In well-controlled type 1 diabetic subjects on intensive insulin therapy with the basal-bolus (UL-LP) insulin regimen, risk of hypoglycemia can be minimized during postprandial exercises of different intensities and different durations by appropriate reduction of premeal insulin LP.

Adult↗
PubMed1998

[Low-dose computerized tomography of the jaw bone in pre-implantation diagnosis. Limits of dose reduction and accuracy of distance measurements].

Absorbed radiation doses delivered by computed tomography and panoramic radiography were measured in 16 anatomic sites using a head and neck phantom and thermoluminescent dosimetry. The recommended kilovoltage and scan time for dental scanning was reduced step by step, rating the quality of the low-dose scans. A reduction of up to 76% could be achieved without loss of diagnostic accuracy. Measured absorbed radiation dose ranges from 0.30 mGy (thyroid) to 29 mGy (skin) at 187.5 mAs and 1.0 mm-slices (25 mm scanning distance for maxilla, 30 mm for mandible). After reduction to 45 mAs, 0.07 mGy (thyroid) to 6.9 mGy (skin) was measured. Distance measurements on human jaw specimens were compared with corresponding CT image measurements. Average deviation was 0.1-0.3 mm. A dose reduction of 75% had no effect on the results. However, the doses of CT-scans reduced by 76% exceed by an average factor of 10 the doses of conventional panoramic radiography. Therefore, CT should be reserved for the planning of complex implant treatment in the direct vicinity of the maxillar sinus and nerves and for multiple implant insertion.

Body Burden↗
PubMed2003

Pretreatment with a single, low dose of recombinant human thyrotropin allows dose reduction of radioiodine therapy in patients with nodular goiter.

In patients with nodular goiter, radioiodine ((131)I) therapy results in a mean reduction in thyroid volume (TV) of approximately 40% after 1 yr. We have demonstrated that pretreatment with a single, low dose of recombinant human TSH (rhTSH) doubles 24-h radioactive iodine uptake (RAIU) in these patients. We have now studied the safety and efficacy of therapy with a reduced dose of (131)I after pretreatment with rhTSH. Twenty-two patients with nodular goiter received (131)I therapy, 24 h after im administration of 0.01 (n = 12) or 0.03 (n = 10) mg rhTSH. In preceding diagnostic studies using tracer doses of (131)I, 24-h RAIU without and with rhTSH pretreatment (either 0.01 or 0.03 mg) were compared. Therapeutic doses of (131)I were adjusted to the rhTSH-induced increases in 24-h RAIU and were aimed at 100 micro Ci/g thyroid tissue retained at 24 h. Pretreatment with rhTSH allowed dose reduction of (131)I therapy by a factor of 1.9 +/- 0.5 in the 0.01-mg and by a factor of 2.4 +/- 0.4 in the 0.03-mg rhTSH group (P < 0.05, 0.01 vs. 0.03 mg rhTSH). Before and 1 yr after therapy, TV and the smallest cross-sectional area of the tracheal lumen were measured with magnetic resonance imaging. During the year of follow-up, serum TSH, free T(4) (FT(4)), T(3), and TSH receptor antibodies were measured at regular intervals. TV before therapy was 143 +/- 54 ml in the 0.01-mg group and 103 +/- 44 ml in the 0.03-mg rhTSH group. One year after treatment, TV reduction was 35 +/- 14% (0.01 mg rhTSH) and 41 +/- 12% (0.03 mg rhTSH). In both groups, smallest cross-sectional area of the tracheal lumen increased significantly. In the 0.01-mg rhTSH group, serum FT(4) rose, after (131)I treatment, from 15.8 +/- 2.8 to 23.2 +/- 4.4 pM. In the 0.03-mg rhTSH group, serum FT(4) rose from 15.5 +/- 2.5 to 23.5 +/- 5.1 pM. Individual peak FT(4) levels, reached between 1 and 28 d after (131)I treatment, were above the normal range in 12 patients. TSH receptor antibodies were negative in all patients before therapy and became positive in 4 patients. Hyperthyroidism developed in 3 of these 4 patients between 23 and 25 wk after therapy. In conclusion, in patients with nodular goiter pretreatment with a single, low dose of rhTSH allowed approximately 50-60% reduction of the therapeutic dose of radioiodine without compromising the efficacy of TV reduction.

Aged↗
PubMed1994

Radiation dose reduction in CT of the pediatric pelvis.

PURPOSE: To determine whether a lower radiation dose technique can be used for computed tomography (CT) of the pediatric pelvis without significant loss of diagnostic image quality. MATERIALS AND METHODS: Thirty-six pediatric patients underwent CT at 80 mAs (experimental group), and 42 underwent CT at 240 mAs (control group). Anatomic details, image quality, and the degree of confidence in reaching a diagnosis were graded on a scale of 1 (poor) to 4 (excellent). RESULTS: The difference in perceived image quality between the experimental and control groups was not statistically significant. The mean scores for scans evaluated by the first reader were 3.88 for the experimental group and 3.92 for the control group (P = .2804). The mean scores for the second reader were 3.78 and 3.77 for the experimental and control groups, respectively (P = .8131). CONCLUSION: A substantial dose reduction can be achieved if pelvic CT is performed at 80 mAs, without a recognizable deterioration of diagnostic image quality.

Child↗
PubMed1992

Long-term diuretic therapy: effects of dose reduction on antihypertensive efficacy and counterregulatory systems.

In the present study, the effects of a dose reduction on antihypertensive efficacy and metabolic side effects of diuretic therapy were investigated in 36 hypertensive patients. During the first treatment period of 1 year, the patients were treated with 25 mg of the thiazide diuretic bemetizide (n = 18) or 25 mg bemetizide plus 50 mg of the potassium-sparing agent triamterene (n = 18). Mean blood pressure (BP) values decreased significantly (p less than 0.01) during the first year of the trial. Thereafter, doses were reduced to 10 mg bemetizide or 10 mg bemetizide plus 20 mg triamterene in patients whose BP became normal during the first year (n = 16 in both groups). At the end of the second year, equal BP control was achieved with doses more than twice smaller than those used during the first year. During the second year of the trial, activation of the renin-angiotensin system (RAS) was significantly less pronounced as compared with the first year and the percentage of patients with hypokalemia (less than 3.5 mM) decreased from 62.5 to 25% in the bemetizide group. Thus, this long-term study provides additional evidence that diuretics have a flat dose-response curve with respect to their antihypertensive efficacy, whereas lower doses might cause less pronounced activation of counter-regulatory systems. Furthermore, our results indicate that long-term studies might be necessary to assess the full antihypertensive potential of low doses of antihypertensive agents.

Aldosterone↗
PubMed2006

Direct detector radiography versus dual reading computed radiography: feasibility of dose reduction in chest radiography.

The image quality of dual-reading computed radiography and dose-reduced direct radiography of the chest was compared in a clinical setting. The study group consisted of 50 patients that underwent three posteroanterior chest radiographs within minutes, one image obtained with a dual read-out computed radiography system (CR; Fuji 5501) at regular dose and two images with a flat panel direct detector unit (DR; Diagnost, Philips). The DR images were obtained with the same and with 50% of the dose used for the CR images. Images were evaluated in a blinded side-by-side comparison. Eight radiologists ranked the visually perceivable difference in image quality using a three-point scale. Then, three radiologists scored the visibility of anatomic landmarks in low and high attenuation areas and image noise. Statistical analysis was based on Friedman tests and Wilcoxon rank sum tests at a significance level of P<0.05. DR was judged superior to CR for the delineation of structures in high attenuation areas of the mediastinum even when obtained with 50% less dose (P<0.001). The visibility of most pulmonary structures was judged equivalent with both techniques, regardless of acquisition dose and speed level. Scores for image noise were lower for DR compared with CR, with the exception of DR obtained at a reduced dose. Thus, in this clinical preference study, DR was equivalent or even superior to the most modern dual read-out CR, even when obtained with 50% dose. A further dose reduction does not appear to be feasible for DR without significant loss of image quality.

Adult↗
PubMed2002

Effect of dose reduction in digital dental panoramic radiography on image quality.

OBJECTIVES: To investigate the effect of dose reduction in digital panoramic radiography on subjective image quality and diagnostic performance. METHODS: Two digital panoramic radiographs were obtained with the Orthophos DS(Sirona, Bensheim, Germany) of patients (n=100) receiving dental care. The first image was taken at the standard exposure setting. For the second image the tube current was reduced by between 48 and 53%, 63 and 69%, 75 and 80% and 80 and 81% respectively. Ten observers rated both images for 21 specific anatomical details and 30 pathological findings. RESULTS: All radiographs taken at reduced mA levels had a significantly inferior score (P<0.01) for anatomical details. There was no difference in the scores for pathological findings. CONCLUSION: Radiographs obtained at reduced mA had inferior subjective image quality, but there was no difference in diagnostic performance. Thus, a reduction in tube current of approximately 50% is recommended. In certain circumstances such as follow-up radiographic examinations, a reduction of up to 65% should be considered.

Analysis of Variance↗
PubMed2005

Phantom studies for possible dose reduction in CT head procedures.

This paper presents the results of phantom studies to investigate possible dose reduction in relation to image quality in head examinations. The studies were performed using five single-slice computed tomography (CT) scanners. Beginning from the manufacturer's protocols (i.e. default protocols in the scanner software) for routine head (adult) examinations, the values of kV(p), anode current and time were modified. Low-contrast resolution and spatial resolution were controlled using a Catphan 424 phantom. Radiation dose was checked using a polymethylmethacrylate phantom and a pencil ionisation chamber. It was found that CT dose index may be reduced up to three times with practically no loss of image quality.

Head↗