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 271 records · Page 15Linked to original sources
PubMed1996

The potential for dose reduction in diagnostic radiology using low attenuation materials in table tops.

It is important to be able to assign priorities to the purchase of radiological equipment. The ability to incorporate potential dose savings into a ranking procedure involving costs is therefore of interest. In this paper we have considered the question of the dose saving made available by the selection of low attenuation table tops and have described how to generate a factor which can be used in a ranking procedure such as cost effectiveness analysis. We describe how data on the expected dose saving can be obtained from measurements of the aluminium equivalent thickness in air used in conjunction with theoretical spectral data. The magnitude of the overestimate when in air measurements alone are used is presented, as is a ready reckoner for determining the true dose saving when changes in table top are considered. Unless the table to be replaced is of some age, the expected dose saving will vary between 6% and 1%.

Cost-Benefit Analysis↗
PubMed1991

Dose reduction during fluoroscopic placement of feeding tubes.

By both increasing the optical iris of the video camera and removing the grid in fluoroscopic procedures involved in placement of a Dubbhoff feeding tube, the radiation dose to patients and staff was reduced by five to seven times. An average expected dose to a patient of about 300 mGy per procedure was reduced by two to three times when the grid was removed and by an additional three times when an iris of increased diameter was used. Because Dobbhoff procedures do not involve obtaining a diagnosis, the image degradation was acceptable and did not affect the total exposure times or ability to conduct the procedure. With the grid out, the difference between the mean exposure times of 5.1 minutes in 96 patient studies done with a normal iris opening and 4.0 minutes in 52 studies done with an enlarged iris was not statistically significant. The importance of reducing patient dose is reinforced by the finding that one-third of the patients underwent repeated procedures, accounting for almost 60% of the total.

Environmental Exposure↗
PubMed2000

Augmented experimental pulse-spray thrombolysis with tissue plasminogen activator, enabling dose reduction by one or more orders of magnitude.

PURPOSE: To critically evaluate and optimize methodologic details of pulse-spray thrombolysis with tissue plasminogen activator (tPA) in a subacute rabbit inferior vena cava thrombosis model. MATERIALS AND METHODS: Occlusive inferior vena cava thrombi were produced in 104 rabbits and 2 days later were treated for 1 hour with pulse-spray thrombolysis using tPA. Methodologic variables included pulse frequency, concentration and amount of tPA, infusion versus pulse therapy, and admixture of heparin. After the rabbits were killed, residual thrombus was weighed. RESULTS: The authors' earlier standard regimen (3 mg of tPA in 6 mL of heparinized saline, 0.2-mL hand pulses, frequency 1 pulse per 2 minutes) produced 60% mean lysis. Optimization involved increasing the pulse frequency to two per minute and decreasing tPA concentration by 98% to 0.01 mg/mL, modifications that produced 22% more thrombolysis, despite 92% reduction in amount of tPA to 0.25 mg. CONCLUSION: Consistent with the in vitro work of other investigators, a roughly bell-shaped dose-response curve was elicited in vivo for pulse-spray with tPA. By diluting tPA to an optimal level, and increasing pulse frequency to two per minute, thrombolysis was markedly augmented. These results suggest that the conventional dose of tPA used for clinical pulse-spray thrombolysis can be reduced by one to two orders of magnitude, possibly markedly reducing procedural risk.

Animals↗
PubMed1995

Improving the safety of BCG immunotherapy by dose reduction. Cooperative Group CUETO.

The preliminary results of a randomized, multicentre, prospective trial conducted by the Spanish Oncology Group (CUETO) are presented. The primary aim of the trial was to determine whether or not lowering the dose of bacillus Calmette-Guérin (BCG) could reduce toxicity without compromising efficacy. From February 1991 to June 1992, 500 patients with superficial bladder cancer (TaG2-3, T1G1-3) entered the trial. Of these patients, 252 were included in group A (BCG, 81 mg) and 248 in group B (BCG, 27 mg). There were no significant differences in clinical and pathological characteristics between the two groups. Following treatment, significant differences arose between groups A and B in local severe toxicity (22.6 vs. 4.2%, respectively; p < 0.01). Systemic toxicity was more common in group A than in group B (p < 0.01): pulmonary effects (2.3 vs. 0.4%), fever (26.9 vs. 12.9%) and malaise (16.2 vs. 8.4%), all p < 0.01. Regarding efficacy, 204 patients in group A and 210 in group B were evaluated after a mean follow-up of 18.6 months. No significant differences in recurrence rate (18.1 vs. 19.5%) or progression rate (2.4 vs. 4.8%) were found. However, in patients with superficial bladder cancer with high risk of recurrence and progression (carcinoma in situ and G3), caution must be exercised in selecting the dose.

Administration, Intravesical↗
PubMed2004

Portal donor-specific blood transfusion and mycophenolate mofetil allow steroid avoidance and tacrolimus dose reduction with sustained levels of chimerism in a pig model of intestinal transplantation.

BACKGROUND: In a pig model of intestinal transplantation, we previously showed that hepatic conditioning through portal donor-specific blood transfusion (pDSBT), high-dose tacrolimus (TAC), and steroids prevented rejection and increased survival Our current study tests a protocol of pDSBT, short-term mycophenolate mofetil (MMF), and low-dose TAC to eliminate the use of steroids, reduce TAC dosage, and increase the level of chimerism in the peripheral blood. MATERIALS AND METHODS: Four groups of outbred, mixed lymphocyte culture (MLC)-reactive pigs underwent bowel transplants and pDSBT. Immunosuppression (group 1, high-dose TAC and steroids; group 2, low-dose TAC and MMF; group 3, low-dose TAC, MMF, and aminoguanidine; group 4, low-dose TAC, MMF, and arginine) was discontinued after 28 days. RNA was extracted from intestinal graft and native liver biopsies for cytokine measurements. Chimerism levels were determined using a Q-PCR analysis. RESULTS: Pig survival and death rates due to rejection did not significantly differ between the four groups. Chimerism levels determined by Q-PCR analysis were not different until day 28. After discontinuation of immunosuppression, we noted a trend (P = 0.15) toward higher mean chimerism levels on day 60 for groups 2, 3, and 4 (9%) vs. group 1 (0.5%). Tissue cytokine and serum nitrate levels did not significantly differ between the four groups. Attempts to modify nitric oxide synthase activity offered no added benefit. CONCLUSIONS: The combination of pDSBT, MMF, and low-dose TAC (vs. high-dose TAC and steroids) allowed sustained levels of mixed chimerism to develop after discontinuation of immunosuppression.

Animals↗
PubMed2004

Strategies for dose reduction in ordinary radiographic examinations using CR and DR.

Uncoupling of display from acquisition in computed radiography (CR) and digital radiography (DR) introduces the potential for systematic overexposure without necessarily compromising image quality. Although the magnitude of radiation doses in general radiography is low compared to computed tomography and fluoroscopy, the dose to the patient is more critical in pediatric examinations than in adults, because of the greater radiosensitivity of children. This manuscript examines a variety of countermeasures for managing radiation doses in pediatric CR and DR examinations, including use of derived exposure indicators, modifications of imaging practice, and development of more efficient radiographic detectors.

Child↗
PubMed1987

Spinal cord dose reduction using an anterior 13 MeV electron field situated between a split anterior 60Co supraclavicular field.

As part of the treatment for lymphoma, disease involving the supraclavicular region has been treated with megavoltage 60Co photons to a midline dose of 30 to 45 Gy through an anterior involved field and a supplementary posterior field when necessary. The spinal cord was shielded with a 5 cm lead block during treatment to the posterior field. A typical 40 Gy treatment results in a dose to the lower cervical and upper thoracic spinal cord in the range of 22 to 26 Gy, a level that could compromise subsequent mediastinal treatment in the event of a relapse. To reduce this cord dose, the midportion of the anterior supraclavicular 60Co To reduce this cord dose, the midportion of the anterior supraclavicular 60Co field was replaced with a high-energy (13 MeV) electron port, which reduces the dose to the cord to below 6 Gy in the average adult patient. This modification of the routine supraclavicular treatment allows greater flexibility in future treatment in the event of a mediastinal relapse.

Clavicle↗
PubMed2000

Dose reduction in computed tomography by attenuation-based on-line modulation of tube current: evaluation of six anatomical regions.

This study investigated the potential of attenuation-based on-line modulation of tube current to reduce the dose of computed tomography (in milliamperes) without loss in image quality. The dose can be reduced for non-circular patient cross-sections by reducing the tube current at the angular positions at which the diameter through the patient diameter is smallest. We investigated a new technical approach with attenuation-based on-line modulation of tube current. Computed tomographic projection data were analyzed to determine the optimal milliampere values for each projection angle in real time, instead of performing prior measurements with localizer radiographs. We compared image quality, noise pattern, and dose for standard scans and for scans with attenuation-based on-line modulation of tube current in a group of 30 radiation therapy patients. Six different anatomical regions were examined: head, shoulder, thorax, abdomen, pelvis, and extremities (knee). Image quality was evaluated by four radiologists in a blinded fashion. We found the dose to be reduced typically by 15-50 %. In general, no deterioration in image quality was observed. Thus the dose in computed tomography be reduced substantially by technical measures without sacrificing image quality. Attenuation-based on-line modulation of tube current is an efficient and practical means for this.

Humans↗
PubMed2005

Radiation dose reduction in four-dimensional computed tomography.

Four-dimensional (4D) CT is useful in many clinical situations, where detailed abdominal and thoracic imaging is needed over the course of the respiratory cycle. However, it usually delivers a larger radiation dose than the standard three-dimensional (3D) CT, since multiple scans at each couch position are required in order to provide the temporal information. Our purpose in this work is to develop a method to perform 4D CT scans at relatively low current, hence reducing the radiation exposure of the patients. To deal with the increased statistical noise caused by the low current, we proposed a novel 4D penalized weighted least square (4D-PWLS) smoothing method, which can incorporate both spatial and phase information. The 4D images at different phases were registered to the same phase via a deformable model, thereby, a regularization term combining temporal and spatial neighbors can be designed for the 4D-PWLS objective function. The proposed method was tested with phantom experiments and a patient study, and superior noise suppression and resolution preservation were observed. A quantitative evaluation of the benefit of the proposed method to 4D radiotherapy and 4D PET/CT imaging are under investigation.

Biophysical Phenomena↗
PubMed1986

The use of carbon fibre material in table tops, cassette fronts and grid covers: magnitude of possible dose reduction.

The X-ray transmission of a number of radiographic components, some of conventional construction and some incorporating carbon fibre material, has been measured under clinically realistic conditions. At 80 kVp the use of carbon fibre materials enables the patient dose to be reduced by 30-50% depending on the existing equipment, type of examination and technique used. Typically the dose can be reduced by 3-15% by changing the table top, 6-12% by changing the front of the film cassette and 20-30% by using a grid with carbon fibre covers and fibre interspace. The higher cost of carbon fibre components can normally be justified by such dose savings. An indication of the absorption of all such components should be provided by manufacturers.

Carbon↗
PubMed2001

A case of relapsed tardive dyskinesia due to clozapine dose reduction.

There is no proven effective treatment for tardive dyskinesia (TD). However, clozapine has been reported to be effective in suppressing TD symptoms. In this article, we report a TD case who received clozapine. The patient recovered from TD symptoms with a dose of 450 mg/day clozapine. At the end of the first year, clozapine was decreased to a dose of 250 mg/day and TD symptoms re-emerged.

Antipsychotic Agents↗
PubMedDate not supplied

Achieving dose reduction in lumbar spine radiography.

Conventional lumbar spine examinations are performed by placing the patient in the supine position. The alternative prone position is less commonly used. In this study, researchers measured entrance skin exposure for both supine and prone positioning techniques and the radiation dose to the eyes, thyroid, ovaries, testes and bone marrow. Compared with the AP projection, the PA projection produced a moderately higher bone marrow dose (28%), but resulted in a slightly reduced dose (17%) to the thyroid and greatly reduced doses (200+%) to the eyes, ovaries, uterus and testes. The PA projection also produced an ESE 52% lower than the AP projection. Results suggest an advantage to using prone positioning for lumbar spine examinations.

Adult↗
PubMed2002

A 20% dose reduction of the original CISCA/VB regimen allows better tolerance and similar survival rate in disseminated testicular non-seminomatous germ-cell tumors: final results of a phase III randomized trial.

BACKGROUND: This prospective randomized clinical trial was designed to compare the efficacy of a low-dose regimen of cisplatin, doxorubicin and cyclophosphamide alternated with vinblastine and bleomycin (CISCA/VB) with the original CISCA/VB regimen in patients with disseminated nonseminomatous germ-cell tumors (NSGCT) and a predicted favorable outcome. PATIENTS AND METHODS: One hundred and twenty-five patients with disseminated NSGCT and a predicted favorable outcome according to the M.D. Anderson Cancer Center classification [testicular primary and human chorionic gonadotropin (hCG) serum level <50000 mIU/ml] were randomized to receive the original CISCA/VB regimen (100% dose) or a low-dose CISCA/VB regimen (80% dose). RESULTS: Among the 124 eligible patients, there was no significant difference in the number of patients in the two treatment arms who achieved a complete response to therapy: 53 of 65 patients (82%) on the original CISCA/VB regimen and 53 of 59 patients (90%) on the low-dose CISCA/VB regimen (P = 0.29). Overall, the original CISCA/VB regimen resulted in a significantly higher relative dose intensity (P <0.0001). After a median follow-up of 6.8 years (range 0.37 to 12.94 years), there was no significant difference in disease-free survival (P = 0.87) or in overall survival (P = 0.88) between the two treatment arms. The 5-year overall survival rate was 93.7% [95% confidence interval (CI) 88% to 100%] and 94.1% (95% CI 84% to 100%) in the original CISCA/VB arm and the low-dose CISCA/VB arm, respectively. The 5-year overall survival rate for the entire study population was 98% (95% CI 94% to 100%) and 88% (95% CI 76% to 100%) in the good- and intermediate-prognosis groups, respectively, as defined by the International Germ Cell Consensus Classification Group (IGCCCG). The low-dose CISCA/VB regimen resulted in significantly less neutropenic fever (P <0.001), grade 4 thrombocytopenia (P <0.03) and severe mucositis (P <0.01) than the original CISCA/VB regimen. CONCLUSIONS: CISCA/VB is highly efficient in patients with good or intermediate prognosis NSGCT according to the IGCCCG criteria. Although equivalent antitumor efficacy cannot be claimed, the low-dose CISCA/VB regimen appears to be a better mode of delivery than the original CISCA/VB regimen with respect to toxicity, since survival is comparable.

Adolescent↗