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PubMed2000

Dose reduction associated with various countermeasures in freshwater fish contamination in Hong Kong.

Based on a model developed specifically for the local freshwater fish culture system, a dose transfer coefficient for 137Cs of 1.15 mSv per MBq m(-2) is obtained for the consumption of freshwater fish in the first year after deposition. Several countermeasures are suggested to reduce the ingestion dose resulting from a nuclear accident. These countermeasures include suspension of fish culture for a period of time after deposition of radionuclides, the removal of the contaminated pond water and, in the more severe cases, the removal of the sediment. The dose reductions that could be achieved by these countermeasures and the effects of their implementation times relative to the input are investigated. The time of resumption of fish culture in affected ponds and the resulting ingestion dose have also been studied in detail. It is found that reusing a pond for fresh fish culture after 6 months would reduce the ingestion dose in the following year by half as compared with that if the pond was reused a short period of time after deposition. An empirical formula linking the peak concentration in fish and the ingestion dose has been derived. The results are useful to decision-makers in limiting the ingestion dose arising from consumption of contaminated freshwater fish after nuclear accidents.

Animals↗
PubMed1998

Patient and staff radiation dose in fluoroscopy-guided TIPS procedures and dose reduction, using dedicated fluoroscopy exposure settings.

Fluoroscopy guided interventions, such as transjugular intrahepatic portosystemic shunt (TIPS) procedures, can results in relatively high radiation doses to patients and staff. The purpose of this study was to evaluate the possible benefit of dedicated fluoroscopy exposure factors in the reduction of doses. Doses to patients and staff were measured during fluoroscopy-guided TIPS procedures in two Dutch university hospitals. Patient doses were calculated from dose-area product (DAP) measurements, entrance beam dimensions and DAP conversion factors. Staff doses were measured outside lead aprons using electronic personal dosemeters. Average patient entrance skin dose (ESD) rate during fluoroscopy was 49 mGy min-1 (13 cases, average fluoroscopy duration 32 min) in one hospital, and 6 mGy min-1 (10 cases, average fluoroscopy duration 50 min) in the other. Estimated staff effective dose per procedure was 28 microSv average in the first hospital compared with 4 microSv average in the other. The use of dedicated fluoroscopy exposure factors, with a relatively high tube voltage and lower tube current resulted in a significant dose reduction for patient and staff in this type of radiological intervention.

Fluoroscopy↗
PubMed1993

Diagnostic image quality and dose reduction using niobium filtration for cephalometric radiography.

The usefulness of added filtration is contingent upon the maintenance of high image quality while effectively reducing the radiation dose. High-quality cephalometric radiographs, defined objectively by a panel of orthodontists, were obtained of a tissue-equivalent phantom both without and with 30 microns and 50 microns supplemental niobium filtration. Skin entrance doses in the temporomandibular joint region were compared at diagnostically acceptable exposures where there was no significant difference in radiographic image quality. Dose reductions ranged from 17% to 31% with 30 microns niobium filtration, and 17% to 39% with 50 microns. However, as kVp and HVL were increased to maintain the same level of perceived image quality, image contrast decreased. Contrast loss with 30 microns and 50 microns niobium filtration averaged 8% and 22% respectively compared with standard aluminium filtration. It would appear that additional niobium filtration can be used to reduce radiation dose without significant loss of image quality.

Analysis of Variance↗
PubMed2005

TNF dose reduction in isolated limb perfusion.

AIMS: Isolated limb perfusion with TNF and melphalan (TM-ILP) is highly effective in the local treatment of advanced sarcoma and melanoma of the limb. The optimal dose of TNF for this procedure is not well established. The aim of this study was to assess the efficacy and toxicity of TM-ILPs with reduced TNF dose. METHOD: Largest single institution prospective database on TNF-based ILP. Out of 339 TM-ILPs performed between 1991 and 2003, 64 procedures were performed with reduced TNF dose (<3 mg in arm perfusions, <4 mg in leg perfusions). Response rates and toxicity of the procedure and outcome of the patients are evaluated. RESULTS: Complete response in melanoma patients after reduced-dose ILP was 75 vs 69% after standard-dose ILPs (overall response 94 vs 95%, respectively); overall response in non-melanoma patients was 69 (reduced) vs 74% (standard). Response rates and outcome were comparable with the procedures performed with standard-dose TNF (p=NS for response, local/systemic progression and survival after multivariate analysis, both in melanoma and in non-melanoma patients). Systemic and local toxicity did not differ statistically between reduced- and standard dose TM-ILPs. CONCLUSION: Provided doses at 1mg or higher are used, TM-ILP with TNF dose reduction for both melanoma and non-melanoma patients seems to be as effective as the standard dose procedure in terms of response rate and patient outcome. Numbers to formally confirm or reject this hypothesis are too large for such a non-inferiority trial to be conducted in patients with these rare conditions.

Adolescent↗
PubMed2006

Dose reduction in multidetector CT of the urinary tract. Studies in a phantom model.

A novel ureter phantom was developed for investigations of image quality and dose in CT urography. The ureter phantom consisted of a water box (14 cm x 32 cm x 42 cm) with five parallel plastic tubes (diameter 2.7 mm) filled with different concentrations of contrast media (1.88-30 mg iodine/ml). CT density of the tubes and noise of the surrounding water were determined using two multidetector scanners (Philips MX8000 with four rows, Siemens Sensation 16 with 16 rows) with varying tube current-time product (15-100 mAs per slice), voltage (90 kV, 100 kV, 120 kV), pitch (0.875-1.75), and slice thickness (1 mm, 2 mm, 3.2 mm). Contrast-to-noise ratio as a parameter of image quality was correlated with dose (CTDI) and was compared with image evaluation by two radiologists. The CT densities of different concentrations of contrast media and contrast-to-noise ratio were significantly higher when low voltages (90 kV versus 120 kV, 100 kV versus 120 kV) were applied. Smaller slice thickness (1 mm versus 2 mm) did not change CT density but decreased contrast-to-noise ratio due to increased noise. Contrast phantom studies showed favourable effects of low tube voltage on image quality in the low dose range. This may facilitate substantial dose reduction in CT urography.

Phantoms, Imaging↗
PubMed2002

Dose reduction fluoroscopy in pediatrics.

BACKGROUND: It is essential that we find ways to reduce radiation exposure to children and maintain image quality. OBJECTIVES: We compared radiation dose, image quality, and spatial resolution when continuous and pulse fluoroscopy with a full and half dose are applied to a phantom. The film-screen technique was compared to fluoroscopy with the digitized spot technique (fluoro grab image) in procedures such as voiding cystourethrogram (VCUG). MATERIALS AND METHODS: Using a 15.1-cm Plexiglas phantom, we obtained dosimetry in milligrays (mGy), spatial resolution in number of line pairs per millimeter (lp/mm), and threshold contrast resolution in number of visible holes. To measure total radiation dose, we calculated the average elapsed fluoroscopy time for VCUG to be approximately 3 min and estimated the average number of exposures as 10. Dosimetry was obtained for full dose and half dose continuous, for 15 pulses per second (pps), 7.5 pps, and 3.75 pps. These were also calculated with normal, magnification 1, and magnification 2 factors. RESULTS: Results of the two most relevant parameters are shown: continuous full-dose fluoroscopy, 3 min, 10 photo spots, total dose of 28.7 mGy with 2 lp/mm of resolution and a threshold contrast of 2.2%, versus 3.75 pps half-dose fluoroscopy, 3 min, grab images, total dose of 3.7 mGy with 1.9 lp/mm of resolution and a threshold contrast of 2.3%. CONCLUSION: With minimal loss of resolution there is significant dose reduction (87%) when using 3.75 pps with digitized imaging.

Fluoroscopy↗
PubMed1999

Effect of blood tamoxifen concentrations on surrogate biomarkers in a trial of dose reduction in healthy women.

PURPOSE: Tamoxifen administered at 20 mg/d has been shown to decrease breast cancer incidence in at-risk women by 50%, but toxicity may limit its broad use, particularly in postmenopausal women. Because toxicity may be dose-dependent, we studied the biologic activity of low concentrations of tamoxifen to determine the plausibility of a dose reduction. PATIENTS AND METHODS: We measured the blood concentrations of tamoxifen and its main metabolites in a dose titration study in 105 healthy women (placebo, tamoxifen 10 mg on alternate days, tamoxifen 10 mg/d, and tamoxifen 20 mg/d). Drug levels measured after 2 months of treatment were correlated with the changes in surrogate biomarkers of different diseases, including lipid profile, blood cell count, fibrinogen, antithrombin III, osteocalcin, and insulin-like growth factor I, a promising surrogate biomarker of breast cancer. RESULTS: The means (+/- SD) for tamoxifen and N-desmethyltamoxifen (metabolite X) concentrations (ng/mL) were dose-related, being, respectively, 0 and 0 with placebo, 26.8 +/- 15.1 and 43.7 +/- 22.5 with 10 mg every other day, 51.2 +/- 24.1 and 90.7 +/- 48.0 with 10 mg/d, and 136.0 +/- 52.7 and 230.6 +/- 75.0 with 20 mg/d of tamoxifen. At variance, the biomarker changes were of comparable magnitude at any drug concentration except for platelet count and triglycerides levels, the latter showing a trend to an increase with increasing tamoxifen concentrations. CONCLUSION: An 80% reduction in blood concentrations does not seem to affect the activity of tamoxifen on biomarkers of cardiovascular or breast cancer risk and may in fact have a more favorable safety profile. Additional studies are warranted to determine the most appropriate dose of this agent.

Antineoplastic Agents, Hormonal↗
PubMed1999

[Dose reduction is not recommended for elderly patients undergoing chemotherapy for non-Hodgkin lymphoma].

The treatment of choice for patients over 60 years of age with aggressive non-Hodgkin's lymphoma (NHL) consists of chemotherapy with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP). Because of poor tolerance, dose reductions and delays occur frequently. However, because of the relatively low dose intensity significantly more patients die of refractory or relapse lymphoma. If it is intended to cure these patients, unmitigated CHOP chemotherapy should be applied. When needed additional supportive care can be provided.

Aged↗
PubMed1994

Therapy for small cell lung cancer using carboplatin, ifosfamide, etoposide (without dose reduction), mid-cycle vincristine with thoracic and cranial irradiation.

The aim of this study was to assess the efficacy and toxicity of intensive chemotherapy, administered without dose reduction, with cranial and thoracic radiotherapy given when possible as a single fraction in small cell lung cancer. 87 patients were eligible on the basis of good performance status, normal or near normal biochemistry and clinical staging, 73 limited and 14 extensive stage, computed tomography scanning was not mandatory. Six cycles of carboplatin, ifosfamide and etoposide with vincristine on day 15 at 4 weekly intervals were planned. Dosages were not reduced in response to myelosuppression. Prophylactic cranial irradiation (PCI) as a single fraction after the first cycle and thoracic irradiation (when possible as a single fraction) following the third cycle were delivered. Seventy-two per cent of patients completed the protocol. Complete response rate was 55% and 26% of patients had a partial response. The median nadirs of neutropenia were 0.5 x 10(9)/l and thrombocytopenia 14 x 10(9)/l, with 6% probable treatment-related deaths. Performance status and dyspnoea improved markedly to normal or near normal levels following the second course. Brain metastases occurred in 13% of patients. The median survival was 16.2 months with a 2-year survival of 31% (95% confidence interval, 24-41%) for a minimum follow-up of 26 months. These results compare favourably with other combined modality studies, using multiple radiotherapy fractions with cisplatin-based combinations and dosage reduction for patients staged in more anatomical detail. The toxicity spectrum and efficacy data could lead to the use of this chemotherapy regimen with haematopoietic growth factors and, in the future, peripheral blood progenitor cell rescue.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1980

Smokers' response to shortened cigarettes: dose reduction without dilution of tobacco smoke.

This study was designed to examine the response of smokers to shortening their usual brand of cigarettes. The shortening reduces the dose of smoke available from each cigarette without affecting concentration and therefore differs from dose reduction by dilution, which occurs when smokers switch to cigarettes with lower tar and nicotine deliveries. Measures of smoking behavior (e.g., cigarette consumption, puff rate), mouth-level nicotine intake (calculated from butt content), and intake to the lungs (plasma nicotine and COHb) were made in 10 smokers after 48 hr ad libitum smoking of full, three-quarter, and half-length cigarettes in a Latin square design. Mouth-level smoke intake was maintained on shortened cigarettes due to a combination of 2 types of compensatory maneuver: (1) by increasing the intensity of puffing and thereby extracting proportionately more of the smoke available from each cigarette and (2) by smoking more cigarettes. The amount of smoke inhaled, on the other hand, was only partially maintained (58% compensation). This was achieved by increase in cigarette consumption alone. There was achieved by increase in cigarette consumption alone. There was no evidence of any compensatory increase in the amount of smoke inhaled from each cigarette. Increase in consumption was thus the only maneuver that contributed to maintaining smoke intake at lung level; mouth-level intake was regulated by increasing intake per cigarette as well as consumption.

Adult↗
PubMed1996

Effects of dose reduction on digital chest imaging using a selenium detector: a study of detecting simulated diffuse interstitial pulmonary disease.

OBJECTIVE: The purpose of this study was to evaluate the effect of dose reduction on the diagnostic performance of a new digital chest imaging system in which amorphous selenium is used as the X-ray detector. Diagnostic performance was assessed for the detection of simulated diffuse interstitial pulmonary disease (DIPD). MATERIALS AND METHODS: DIPD was simulated by superimposing plastic sheets that contained small radiopaque objects (birdseed) on an anthropomorphic chest phantom. We varied the number of sheets from zero to four to simulate the degree of abnormality. We made 80 images with a standard X-ray dose, 80 images with 55% of the standard dose, and 80 images with 35% of the standard dose. Six observers were asked to indicate the presence of DIPD using a five-level scale of confidence. Two hundred forty chest images were then analyzed using receiver operating characteristic (ROC) curves. RESULTS: The area under the ROC curve was 87.2 for all readers with standard-dose imaging (95% confidence interval [CI], 83.7-90.7), 91.7 with 55% of the standard dose (95% CI, 88.8-94.6), and 90.0 with the 35% dose (95% CI, 87.1-92.9). The area under the ROC curve for subtle DIPD (one superimposed sheet) was 75.3 for all readers with standard-dose imaging (95% CI, 67.1-83.5), 79.7 with 55% of the standard dose (95% CI, 71.9-87.5), and 70.3 with the 35% dose (95% CI, 61.7-78.9). For each dose, we observed a gradual improvement of the ROC curves with each additional sheet superimposed on the chest phantom (p < .001). CONCLUSION: We found no significant difference in diagnostic performance among images made with standard X-ray dose, those made with a 55% dose, and those made with a 35% dose (95% CI).

Humans↗
PubMed2004

The dynamic range of digital radiographic systems: dose reduction or risk of overexposure?

OBJECTIVES: To investigate the range of diagnostically acceptable digital radiographs and film as a function of exposure time, as well as the relationship to dose reduction and consequences for dental practice. METHODS: Five systems for intraoral radiography were used to take a series of radiographs, with increasing exposure times, of five different dry bone specimens. Seven observers evaluated the 25 series of radiographs. The observers had to determine which radiographs of each series were acceptable for dental diagnostics and which radiograph of each series they preferred. RESULTS: For Ektaspeed Plus film, the exposure time for the preferred radiograph was 0.52 s, with a range of diagnostically acceptable radiographs from 0.23-1.02 s. The preferred radiograph of the solid-state systems required less radiation than film (Sirona, 0.13 s; MPDx 0.35 s). The exposure range of these systems is narrow. In contrast, the exposure range of the phosphor plate systems is very wide. The preferred radiograph of the phosphor plate systems required high exposure (Digora, 1.21 s; Gendex DenOptix, 1.16 s). CONCLUSIONS: All digital systems require less exposure than film for diagnostically acceptable radiographs, but this is less obvious for preferred radiographs. Solid-state systems alert the dentist when a too long exposure time is used by a lack of image quality; phosphor plate systems, however, produce good quality radiographs even at high exposure times, which may result in an unnecessarily high dose.

Analysis of Variance↗
PubMed2004

Fetal dose reduction in head and neck radiotherapy of a pregnant woman.

BACKGROUND AND PURPOSE: A pregnant woman was referred for post-operative radiotherapy of a malignant schwannoma in the head and neck region. A best-treatment plan was devised in order to minimize the fetal dose. MATERIAL AND METHODS: The fetal dose resulting from radiological examinations was determined according to international protocols, that resulting from radiotherapy was calculated according to Recommendation 36 of the American Association of Physicists in Medicine (AAPM) Task Group. Pre-treatment dosimetry was performed with an anthropomorphic phantom. Several alternative treatment plans were evaluated. The use of a multileaf collimator (MLC) and a virtual wedge (VW) was compared to cerrobend blocks (CB) and physical wedge (PW). In-vivo dosimetry was performed using a vaginal probe containing thermoluminescent dosimeters (TLD). RESULTS: The total fetal dose resulting from diagnostic and radiotherapy procedures was estimated to be 36 mGy. The technique based on MLC and VW was elected for patient treatment. Measurements for this configuration resulted in afetal dose reduction of 82%. The shielding of the patient's abdomen further reduced the fetal dose by 42%. CONCLUSION: The use of VW and MLC for the treatment of a pregnant woman is highly recommended. Each case should be individually studied with pre-treatment and in-vivo dosimetry.

Adult↗
PubMed2004

Dose reduction in subsecond multislice spiral CT examination of children by online tube current modulation.

The potential of online tube current modulation in subsecond multislice spiral CT (MSCT) examinations of children to reduce the dose without a loss in image quality is investigated in a controlled patient study. The dose can be reduced for oval patient sectional view without an increase in noise if the tube current is reduced where the patient diameter and, consequently, attenuation are small. We investigated a product version of an online control for tube current in a SOMATOM Sensation 4 (Siemens, Forchheim). We evaluated image quality, noise and dose reduction for examinations with online tube current modulation in 30 MSCT of thorax/abdomen and abdomen and compared mA s for tube current modulation to the mA s in standard weight-adapted children protocols. Image quality was rated as "very good," "good," "diagnostic" and "poor" in a consensus by three radiologists. Noise was assessed in comparison to 24 MSCT examinations without tube current modulation measured as SD in ROIs. The dose was reduced from 26 to 43% (mean 36%), depending on the patient's geometry and weight. In general, no loss of image quality was observed. Measured noise showed a decrease up to 26% and an increase up to 36%, although there was no decrease of image quality. Online tube current modulation is now used as a standard in MSCT at our institution. Dose in MSCT examinations of children can be reduced substantially in routine examinations by online tube current modulation without a loss of image quality.

Child↗
PubMed1992

Predicting septic complications of chemotherapy: an analysis of 382 patients treated for small cell lung cancer without dose reduction after major sepsis.

The incidence and risk of septic complications in 382 patients treated for small cell lung cancer with combination chemotherapy at a single centre have been analysed. Full protocol doses were employed throughout with no dose reduction after episodes of severe or life-threatening sepsis (SLTS). 50 (13%) patients experienced 66 episodes of SLTS associated with 1978 cycles of chemotherapy (3.2% cycles affected). 20 (5.2%) patients died due to sepsis (SD) of whom only 4 had experienced SLTS with a previous cycle of treatment. The others died as a result of their first septic episode. A model comprising four variables, age (< or = 50 or > 50 years), Karnofsky performance status (KP < or = 50 or > 50), treatment (two- or three-drug regimen) and previous sepsis (SLTS or no SLTS with previous cycles) was found to satisfactorily describe the incidence of SLTS and SD in the study population and once validated in another patient groups this model should allow identification of high-risk individuals before treatment starts. If so, we propose that high-risk patients (age > 50 years, KP < or = 50, treatment with three-drug regimen) receive 50% of protocol doses in the first cycle of treatment with escalation to 75% and eventually 100% doses in subsequent cycles if sepsis does not supervene. Those with one or two risk factors present run a relatively low risk of SLTS or SD and we consider that full-dose chemotherapy should be used throughout in these individuals.

Age Factors↗
PubMed1991

A new approach to dose reduction in chronic schizophrenia.

The bromocriptine growth hormone test (BGHT) was used to monitor D2 receptor activity in a group of 16 chronic schizophrenics who during the baseline phase were receiving greater than or equal to 20 mg/day haloperidol. In all subjects at baseline, the rise in plasma GH in response to the oral administration of bromocriptine (50 micrograms/kg) was blocked. The dose of haloperidol was then gradually reduced; the BGHT was repeated as each new dose was established. No escape from blockade of the GH response was observed until the dose of haloperidol was lowered to 10 mg/day (3 of 16 subjects escaped from blockade). At this dose the average plasma haloperidol level was 4 ng/ml. Two additional subjects escaped as the dose was reduced to 5 mg/day and six more escaped as the dose was reduced to 2.5 mg/day. The average haloperidol plasma level at 5 and 2.5 mg/day was 1.6 and 1.2 ng/ml respectively. The remaining five subjects escaped from blockade as the dose was reduced to 0 mg/day. In five subjects, escape from blockade was associated with a significant decrease in positive psychotic symptoms; in these subjects reestablishing the "just" blockade dose of haloperidol did not increase psychotic symptoms. In nine subjects escape from blockade was associated with an increase of positive psychotic symptoms; in six of these patients, reestablishing the "just" blockade dose of haloperidol attenuated psychotic symptoms to near baseline levels. We conclude that the GH challenge test is a useful adjunct to dose-reduction in the chronic patient. Furthermore, for some patients the "just" blockade dose appears to be near the minimum dose with the maximum therapeutic effect.

Adult↗
PubMed2002

Routine chest radiography using a flat-panel detector: image quality at standard detector dose and 33% dose reduction.

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of a large-area, flat-panel X-ray detector for performing routine chest radiography at two different detector doses. MATERIALS AND METHODS: The chest radiographs of 50 patients (age range, 16-79 years; mean age, 57 years) were obtained at two different detector dose levels. Digital images were taken from the same patients in posteroanterior and lateral views with detector doses of 2.5 microGy and 1.8 microGy, respectively, at 125 kVp tube voltage. The cesium iodide-amorphous silicon active-matrix imager had a panel size of 43 x 43 cm, a matrix of 3000 x 3000, and a pixel pitch of 143 microm. Images were presented in a random order to three independent radiologists who were unaware of the dose level at which the images had been obtained. They subjectively rated image quality on a 4-point scale, according to six criteria (presentation of obscured lung, unobscured lung, airways, mediastinum and hilum, bony thorax, and overall impression). Statistical significance of differences was evaluated with Student's t test for paired samples (confidence level, 95%). RESULTS: Digital radiographs obtained at 2.5 and 1.8 microGy were equivalent on all quality criteria. No statistically significant differences and no tendency toward a preference for images obtained at one or the other dose level were observed. According to the registered mAs values, the average difference in patient dose was 33%. CONCLUSION: Use of flat-panel digital imagers based on the cesium iodide-amorphous silicon technique allows a considerable dose reduction during routine chest radiography without loss of image quality.

Adolescent↗
PubMed1989

Evaluation of contrast dose reduction for excretory urography using computed radiography.

We prospectively investigated whether performing excretory urography by computed radiography (CR) - with CR's broader dynamic range and potential for post-processing - would permit lower contrast dose while maintaining usual image quality. The rationale for this experiment was to evaluate whether CR had potential in reducing the risks and costs associated with urography. Sixty sequential patients were randomly assigned to undergo computed urography with either our full (282 mg I/kg body weight) or half our usual dose (141 mg I/kg body weight) of intravenous 60% diatrizoate meglumine. Three blinded observers judged automatically post-processed full dose tomograms and KUBs as qualitatively superior to both automatically post-processed and individually, interactively post-processed half dose images. Thus, post-acquisition image manipulation could not fully compensate for diminished image quality due to contrast dose reduction.

Diatrizoate Meglumine↗