Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dose reduction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2006

[Variation in X-ray dose quantity using an amorphous selenium based flat-panel detector -- a study on the dose reduction rate up to the limit of diagnostical utilization].

PURPOSE: To evaluate the diagnostic quality and minimum required dose to obtain acceptable images for diagnostic purposes in the field of musculoskeletal radiology. MATERIALS AND METHODS: A critical comparison of the image quality produced by a novel flat panel detector and the conventional screen/film system using a contrast-detail phantom was performed in phase I. Images from both systems were obtained with the same dose and displayed with similar contrast and density. In phase II images of significant anatomical structures in cadaver extremities obtained using the digital detector system and the standard film/screen system were critically evaluated. After a successive reduction in the X-ray dose for 84 patients in phase III, eight independent radiologists compared the image quality of the screen/film system to that of the novel flat panel detector. RESULTS: Phases I and II revealed a difference in the image quality achieved by the standard screen/film system and the digital detector system to the advantage of the digital detector system. In 77 of 84 patients (91.7 %), phase III showed equal image quality after a 50 % reduction in the X-ray dose. In 3 cases (3.6 %) the image quality and the level of contrast were better. No unified statement could be made for 4 patients (4.7 %). CONCLUSION: Digital imaging of skeletal disorders using the novel flat panel detector makes it possible to reduce the X-ray dose by 50 % with equal or even better image quality.

Adult↗
PubMed1997

Skin dose reduction by a clinically viable magnetic deflector.

A variable magnetic deflector which attaches onto the treatment head of a linear accelerator has reduced skin dose by as much as 65% for 6MV x-rays. The magnetic deflector is constructed from Neodymium Iron Boron (NdFeB) rare earth magnets. It weighs approximately 15 kg and is designed to easily fit onto the accessory mount of a clinical linear accelerator. All field sizes are attainable up to 35 cm x 35 cm at 100 cm SSD. The gap between the magnetic poles can be adjusted, providing the highest field strength for each field size. Magnetic field strengths up to 0.55 Tesla are attainable. For a 6MV x-ray beam with a 10 mm perspex block tray, surface dose is reduced from 29% to 14% and from 59% to 37% for a 20 cm x 20 cm and 35 cm x 35 cm field size, respectively. Results at varying SSD's have shown at least 10 cm of space must be allowed between the magnets and patient for adequate reduction of skin dose through removal of electron contaminants.

Humans↗
PubMedDate not supplied

Dose reduction for body composition measurements with CT.

The purpose was to obtain reliable measures of fat and muscle tissue areas with CT at a reduced radiation dose level. Repeated CT-scans with four different levels of reduced radiation dose were perfomed on a water phantom and a volunteer at the L4-L5 level. Dose measurements were performed in a phantom and free in air. A histogram model function for fat, muscle and partial volume affected voxels was proposed and used in the analysis of image noise. The result was at most a 25-fold reduction in radiation dose with an image noise of 40 HU but only a minor influence on the tissue area determination [corrected].

Adult↗
PubMed2002

Dose reduction in CT examination of children by an attenuation-based on-line modulation of tube current (CARE Dose).

In a controlled patient study we investigated the potential of attenuation-based on-line modulation of the tube current to reduce milliampere values (mAs) in CT examinations of children without loss of image quality. mAs can be reduced for non-circular patient cross sections without an increase in noise if tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. We investigated a technical approach with an attenuation-based on-line control for the tube current realised as a work-in-progress implementation. The CT projection data are analysed in real time to determine optimal mAs values for each projection angle. We evaluated mAs reduction for 100 spiral CT examinations with attenuation-based on-line modulation of the tube current in a group of children. Two radiologists evaluated image quality by visual interpretation in consensus. We compared the mAs values read from the CT scanner with preset mAs of a standard protocol. Four different scan regions were examined in spiral technique (neck, thorax, abdomen, thorax and abdomen). We found the mAs product to be reduced typically by 10-60% depending on patient geometry and anatomical regions. The mean reduction was 22.3% (neck 20%, thorax 23%, abdomen 23%, thorax and abdomen 22%). In general, no deterioration of image quality was observed. There was no correlation between the age and the mean mAs reduction in the different anatomical regions. By classifying the children respectively to their weight, there is a positive trend between increasing weight and mAs reduction. We conclude that mAs in spiral CT examinations of children can be reduced substantially by attenuation-based on-line modulation of the tube current without deterioration of image quality. Attenuation-based on-line modulation of tube current is efficient and practical for reducing dose exposure to children.

Adolescent↗
PubMed1998

Long-term use and tapered dose reduction of intranasal desmopressin in the treatment of enuretic children.

OBJECTIVE: To determine the time taken to achieve complete dryness, the management of desmopressin dosage to reduce the relapse rate, the mean dosage in those responding and any side effects of long-term treatment. PATIENTS AND METHODS: Enuretic children (155, 68% boys and 32% girls, mean age 8 years, range 5-19) were treated with desmopressin and assessed. Treatment (intranasal spray) was started with 20 microg desmopressin and titrated to 40 microg (maximum 50 microg) after 2 days if the child did not become dry within 48 h. The maximum dosage was maintained for at least 4-6 weeks. After 4 weeks of complete dryness, the dosage was reduced by 10 microg initially, and after each additional 4 dry weeks, by a further 10 microg; medication was stopped only after 4 dry weeks at 10 microg. RESULTS: Of the children, 85% responded to intranasal desmopressin therapy; 71% achieved complete dryness with no relapses, remaining dry with no further treatment, 7% achieved dryness after relapses during or after therapy, 7% improved (no more than two wet nights per week) and 15% did not respond to therapy or improved only slightly (> 2 wet nights per week). The mean duration of therapy was 28 weeks, the mean dose of desmopressin was 30 microg and the median follow-up 18 months. There were no significant side-effects. CONCLUSION: This study indicates that rapid titration until dryness within 1-3 days, a long maintenance therapy of at least 4-6 weeks and a slow stepwise reduction of dose decreases the frequency of relapse and improves the outcome.

Administration, Inhalation↗
PubMed2005

Radiation dose reduction without degradation of low-contrast detectability at abdominal multisection CT with a low-tube voltage technique: phantom study.

PURPOSE: To reduce radiation dose from abdominal computed tomography (CT) without degradation of low-contrast detectability by using a technique with low tube voltage (90 kV). MATERIALS AND METHODS: The institutional review board approved the participation of the radiologists in the observer performance test, and informed consent was obtained from all participating radiologists. A phantom for measurement of the radiation dose and a phantom containing low-contrast objects were scanned with a 16-detector row CT scanner at 120 kV and 90 kV. For determination of the radiation dose at both 90 kV and 120 kV, the tube current-time product settings were 100-560 mAs, and the doses at the center and periphery of the phantom were measured. To assess low-contrast detectability, we used a 300-mAs setting at 120 kV and 250-560-mAs settings at 90 kV. Five observers participated in the receiver operating characteristic analysis. Area under the receiver operating characteristic curve (A(z)) values were calculated in each observer. A(z) values obtained with each of the scanning techniques were recorded, and differences were examined for significance by using the Dunnet method. RESULTS: The mean A(z) value was 0.951 at 120 kV and 300 mAs. A(z) values were 0.927-0.973 at 90 kV and 450-560 mAs, and the differences between those values and values obtained at 120 kV and 300 mAs were not significant (P = .937-.952). A value of 100% was assigned to the radiation dose delivered to the center of the phantom at 120 kV and 300 mAs. The relative dose delivered at 90 kV ranged from 65% at 450 mAs to 79% at 560 mAs. CONCLUSION: A reduction from 120 kV to 90 kV led to as much as a 35% reduction in the radiation dose, without sacrifice of low-contrast detectability, at CT.

Analysis of Variance↗
PubMed2003

Radiotherapy with 16 Gy may fail to eradicate testicular intraepithelial neoplasia: preliminary communication of a dose-reduction trial of the German Testicular Cancer Study Group.

Low-dose radiotherapy to the testis is effective in eradicating testicular intraepithelial neoplasia (TIN, carcinoma in situ of the testis) at the risk of androgenic deficiency. The present trial was designed to define the lowest dose effective to control TIN assuming a dose-response relation of radiation-induced endocrinological damage. Patients with TIN in a solitary testicle or with bilateral TIN were treated with 18 Gy (14 patients) and 16 Gy (26 patients) (5 x 2 Gy per week). Biopsies to ascertain clearance of TIN were performed after 6 and 24 months. The median time of follow-up is 20.5 months. There were three adverse events. In one patient, relapse of TIN along with microinvasive seminoma was observed 2 years after 16 Gy irradiation. In two other patients, persistent spermatogonia were observed with the 16 and 18 Gy regimen after 6 and 24 months, respectively. All other post-treatment biopsies showed the Sertoli cell-only pattern. These results confirm that TIN is a radiosensitive lesion efficiently controlled in most cases with doses below 20 Gy. However, sporadic failures may occur. A dose of 16 Gy is probably unsafe and should no longer be used. Future investigations should not only focus on total dosage of irradiation but also on fractionation schedules.

Adult↗
PubMed1987

Order of magnitude dose reduction in intraoral radiography.

This comparative clinical investigation concerns the radiation dose from intraoral radiography using E-speed film and rectangular and circular beam collimation. Dose to organs not of diagnostic importance (brain, lens of the eye, thyroid, and breast) is reduced by approximately an order of magnitude when rectangular collimation and E-speed film are used in periapical radiography. And dose to the thyroid and breast is further reduced by a third with the use of a full leaded apron and thyroid shield.

Breast↗
PubMed2002

The ChatterVox portable voice amplifier: a means to vibration dose reduction?

By speaking loudly for extended periods, teachers are vulnerable to laryngeal and voice changes associated with vocal fold "vibration overdose." Voice clinicians frequently recommend voice amplification ostensibly designed to reduce vibration dose and improve voice. However, there are few data regarding the degree of vocal loudness attenuation achieved by specific amplification devices. The purpose of this investigation was to examine the effectiveness of the ChatterVox Portable Voice Amplification System (Siemens Hearing Instruments) for reducing the sound pressure level (SPL) of a speaker's voice during a simulated classroom lecture. Ten participants were instructed to continuously read one of two phonetically balanced passages while amplified and unamplified. Voice intensity measurements were obtained at three inches from the mouth (i.e., mouth level) and at the back of a classroom in both amplified and unamplified conditions. When amplified with the ChatterVox, speakers experienced an average decrease in vocal intensity at mouth-level of 6.03 dB SPL (p < 0.002). Furthermore, an average increase of 2.55 dB SPL (p < 0.038) at the back of the classroom was observed. Collectively, these results indicate that the ChatterVox amplification device reduced the speaker's vocal intensity level at the microphone, while it augmented the voice heard at the back of the classroom. By inference, this degree of vocal attenuation at mouth level should contribute to a desirable reduction in vibration dose, thus lowering the risk of vibration overdose.

Acoustics↗
PubMed1991

Maintenance medication for schizophrenia: strategies for dose reduction.

Balancing the demonstrated effectiveness of antipsychotic medication for long-term maintenance treatment of schizophrenia with the risk of developing tardive dyskinesia (TD) has led to attempts to reduce dosage. Research using two methods is reviewed in this article; continuous low dose and intermittent or targeted medication. Both methods require monitoring of patients and treating decompensations with medication. Studies reviewed in this article indicate that these strategies are feasible for many patients, but are associated with higher risk of relapse than maintaining an established moderate dose. For low dose, relapse rates are higher if treatment continues for a second year, if dosage is very low, or if patients are not stable. However, low dose administration also leads to reduce adverse effects (including TD in at least one study) and improved subjective well being. Targeted medication leads to reduction of administered dose and side effects but to no clear benefit in terms of TD or social functioning. No studies reported to date have compared these strategies directly. Ongoing and future research will do this and identify those patients for whom these strategies can be implemented without increased relapse risk.

Antipsychotic Agents↗
PubMed2003

[Enhanced MR-angiography (CE-MRA) of the supraaortic arteries: dose reduction with a contrast agent of high relaxivity (Gd-BOPTA)].

PURPOSE: Reducing the amount of contrast medium in contrast-enhanced MR-angiography (CE-MRA) of the cervical vessels could lead to considerable cost reduction. This study investigates whether the amount of contrast medium possessing high relaxivity can be reduced without loss of diagnostic information. MATERIALS AND METHODS: In a prospective study the supraaortic vessels of 40 patients were examined on a 1.5 T MR-system using 10 or 20 ml Gd-BOPTA (MultiHance). The examinations were evaluated by measurement of the signal increase in the common carotid arteries in 38 patients. Furthermore, CE-MRA was rated by two independent observers, who were blinded to the amount of contrast medium and degree of stenosis. Rating criteria were quality of arterial contrast and image impression. RESULTS: Signal increase in the carotid artery was identical for 10 and 20 ml Gd-BOPTA in 12 patients with optimal bolus timing (10 ml: 454 +/- 58; 20 ml: 458 +/- 63). Signal intensities were significantly lower for 10 ml when bolus timing was suboptimal (281 +/- 80 vs 353 +/- 65; p < 0.02). The quality of the CE-MRA using 10 and 20 ml Gd- BOPTA was rated as identical by the observers, and the amount of contrast medium used could not be deduced from the images. CONCLUSION: Image quality and signal values of the carotid arteries did not differ in CE-MRA performed with either 10 ml or 20 ml Gd-BOPTA (MultiHance) as long as the examination is adequate. Thus, cost reduction can be achieved with a reduced standard dose of 10 ml Gd-BOPTA without loss of diagnostic information.

Aged↗
PubMed2006

ABVD for Hodgkin's lymphoma: full-dose chemotherapy without dose reductions or growth factors.

BACKGROUND: We investigated whether administration of full-dose ABVD (Adriamycin, bleomycin, vinblastine, dacarbazine) chemotherapy without growth factors, and irrespective of the granulocyte count, caused treatment delays or increased the number of infective episodes, in patients with Hodgkin's lymphoma (HL). PATIENTS AND METHODS: Thirty-eight patients with confirmed predominantly early-stage HL were treated with ABVD outside clinical trial protocols over a 5-year period on an outpatient basis. RESULTS: Ninety-five per cent of patients completed their scheduled ABVD regimen without adverse effects despite the development of neutropenia. Anaemia and thrombocytopenia did not present problems. Febrile neutropenia complicated 0.57% of combination chemotherapy injections. No growth factors were used and no dose modifications were carried out apart from the omission of bleomycin in one patient for the last two cycles of treatment due to the development of lung toxicity. All patients are currently disease-free, although three (7.8%) required salvage high-dose therapy (one relapsed and two with refractory disease). CONCLUSIONS: ABVD administration irrespective of granulocyte counts allowed the treatment to be given at full dose without delays or significant number of infective episodes. There was no need for growth factor support, minimising treatment costs. The use of full-dose ABVD irrespective of granulocyte count should be evaluated in future protocols for HL.

Adolescent↗
PubMed2004

Dose reduction to radiosensitive tissues in CT. Do commercially available shields meet the users' needs?

AIM: To assess the effectiveness and economy of routinely using commercially available in-plane bismuth shielding during CT scanning of the chest and brain. METHODS AND MATERIALS: Forty patients were scanned with thermoluminescent dosemeters (TLDs) in situ to measure the radiation dose to the thyroid and eye during CT scanning of the brain and chest. Half of the patients had the "AttenuRad" shield in place during scanning. RESULTS: Use of the shielding reduced the mean dose to the eye from 6.0 +/- 0.3 mGy to 4.9 mGy +/- 0.2 mGy and the thyroid dose from 16.4 mGy +/- 1.2 mGy to 7.1 mGy +/- 0.5 mGy. CONCLUSION: Use of the thyroid shield is recommended for all CT scanning of the chest. The eye shield does not produce as marked a reduction in radiation dose to the lens of the eye, when an angled gantry is used, since the eyes are not in the primary beam. Use of the eyeshield is justifiable where irradiation of the orbit is unavoidable, although whether artifacts would be a problem if the shield was used in this way was not assessed.

Dose-Response Relationship, Radiation↗
PubMed2000

Light weight concrete: 226Ra, 232Th, 40K contents and dose reduction assessment

Four types of light weight concrete (LWC) commonly used in Hong Kong, namely, autoclave aerated concrete (plus lime), autoclave aerated concrete (plus Pulverized Fuel Ash or PFA), concrete with synthetic aggregate 'Leca' and concrete with polystyrene bean as aggregate were measured for their 226Ra, 232Th and 40K contents using high-resolution gamma spectrometry. All the radionuclide contents except those for the PFA autoclave aerated concrete were below the world averages of building materials. The Ra-equivalents for these four LWC were 49.6, 249, 122 and 44.2 Bq kg(-1), respectively, and were much smaller than a recommended limit of 370 Bq kg(-1) for construction materials for dwellings. The gamma-dose rate for an indoor environment with partition walls built with LWC was estimated to be about 20 x 10(-8) Gy h(-1), which corresponded to a reduction in the effective dose of about 0.25 mSv y(-1) when compared to that obtained for an indoor environment built with normal concrete (NC) only. The Rn exhalation rates from the three lowest Ra-equivalent LWC were calculated as 0.509, 1.28, and 0.335 mBq m(-2) s(-1), respectively, which corresponded to a reduction in the indoor Rn concentration of around 14 Bq m(-3) and reduction in the tracheobronchial dose reaching 1 mSv y(-1) by using the James lung-dosimetry model, when compared to the case of NC.

Journal Article↗
PubMed2005

Dose reduction for the management of indinavir-related toxicity in human immunodeficiency virus type 1-infected patients in Taiwan: clinical and pharmacokinetic assessment.

This study evaluated the feasibility of reducing the indinavir (IDV) dosage in Taiwanese patients receiving the standard IDV/ritonavir (RTV) dosage of 800/100 mg twice a day who had undetectable plasma human immunodeficiency virus type 1 (HIV-1) RNA but had developed IDV-related toxicities. After dosage reduction to IDV/RTV 600/100 mg twice a day, the dose-related toxicity decreased and plasma HIV RNA remained undetectable at 24 weeks post-switch in all patients. The maximal plasma concentration (Cmax) and area under the plasma concentration-time curve of IDV decreased significantly (median, 6.3 vs 4.3 microg/mL and 1892 vs 1292 microg.min/mL, p=0.01 and 0.001, respectively) but the minimal plasma concentration remained at a similar level (median, 1.0 vs 0.8 microg/mL, p=0.12). This study found that the reduction in the dosage of IDV in HIV-1 infected patients receiving the standard IDV/RTV regimen guided by therapeutic drug monitoring decreased the Cmax, dose-related toxicity and medical cost without compromising viral control.

Acquired Immunodeficiency Syndrome↗
PubMed2002

[Radiation dose and dose reduction in multidetector row CT (MDCT)].

Since its introduction a few years ago, multidetector row CT (MDCT) has become a widely used diagnostic procedure and has been proven to be a valuable tool for various indications. A major issue using this new modality is the inherent risk of applying increased radiation exposure, when compared to single-slice CT or other imaging modalities.However, MDCT offers some valuable options to save radiation exposure, such as choosing optimized exposure parameters or its superior dose efficiency in comparison to single-slice CT. Multi-phasic examinations should be restricted to indications where definitely necessary. Modern scanners offer intelligent tools for further reduction of radiation dose, such as ECG- or bodyshape-based realtime dose modulation. A new field of applications is the low-dose CT for early detection of diseases. While acquiring thin slices with high spatial resolution, the dose can be reduced to similar values as in conventional radiography, especially when examining under high-contrast conditions. Using all these various options available, radiation exposure can sometimes even be lower than using a conventional single-slice helical CT.

Artificial Intelligence↗
PubMed1992

Lynestrenol induced therapeutic amenorrhea: effects of dose reduction on serum sex-hormones and lipids.

The effect of reducing the dose of peroral lynestrenol by half on serum sex-hormone, lipid and lipoprotein status was studied in 21 mentally retarded women with therapeutic amenorrhea (TA). They had previously received 5 or 10 mg peroral lynestrenol daily for periods ranging from 32 to 196 months. Dose halving of lynestrenol resulted in an increase in serum total testosterone (T) by 16% (p less than 0.05), sex-hormone binding globulin (SHBG) by 39% (p less than 0.01) and high-density lipoprotein cholesterol (HDL-C) by 28% (p less than 0.001). Both the mean serum total and free concentrations of norethisterone (NET and fNET) decreased by 60% (p less than 0.001). The serum concentrations of 17-beta-estradiol (E2), its free fractions (fE2) and free T (fT) were not significantly altered. Significant correlations were observed between the change in HDL-C and the change in T (r = 0.45, p less than 0.05), between the change in SHBG and the change in T (r = 0.62, p less than 0.01), fT (r = 0.43, p less than 0.05) and E2 (r = 0.51, p less than 0.05). The elevation of HDL-C was probably caused by the reduced serum NET concentrations. This also resulted in an increase in serum SHBG concentration, which is regarded as an indicator of the overall estrogen/androgen ratio.

Adult↗