Biomedical subjects

R S Andrade

Publications and source records attributed to R S Andrade.

3 recordsLinked to original sources

PubMed2003

Conventional 3D conformal versus intensity-modulated radiotherapy for the adjuvant treatment of gynecologic malignancies: a comparative dosimetric study of dose-volume histograms.

OBJECTIVE: The goals of this study were to evaluate the feasibility of pelvic intensity-modulated radiotherapy (IMRT) in the adjuvant treatment of gynecologic malignancies and to compare the dose-volume histograms (DVHs) and determine the potential impact on acute and long-term toxicity based on the dose to target and nontarget tissues for both planning techniques. METHODS: Ten consecutive patients referred for adjuvant radiotherapy for gynecologic malignancies at the University of Pittsburgh School of Medicine and Magee-Womens Hospital were selected for CT-based treatment planning using the ADAC 3D version 4.2g and the NOMOS Corvus IMRT version 4.0. Normal tissues and critical structures were contoured on axial CT slices by both systems in conjunction with a gynecologic radiologist. These regions included internal, external, and common iliac nodal groups, rectum, upper 4 cm of vagina, bladder, and small bowel. Conventional treatment planning included 3D four-field box using 18-MV photons designed to treat a volume from the L(5)/S(1) border superiorly to the bottom of the ischial tuberosity on the AP/PA field and shaped blocks on the lateral fields to minimize the dose to the rectum and small bowel. A seven-field technique using 6-MV photons was used for IMRT. Restraints on small bowel for IMRT were set at 23.0 Gy +/- 5% and 35.0 Gy+/- 5% for the rectum and 37.5 Gy +/- 5% for the bladder while simultaneously delivering full dose (45.0 Gy) to the intrapelvic nodal groups in 1.8-Gy daily fractions. The dose-volume histograms where then compared for both treatment delivery systems. RESULTS: The volume of each organ of interest (small bowel, bladder, and rectum) receiving doses in excess of 30 Gy was compared in the 3D and IMRT treatment plans. The mean volume of small bowel receiving doses in excess of 30 Gy was reduced by 52% with IMRT compared with 3D. A similar advantage was noted for the rectum (66% reduction) and the bladder (36% reduction). The nodal regions at risk and the upper vagina all received the prescribed dose of 45.0 Gy. CONCLUSIONS: Intensity-modulated radiotherapy appears to offer several advantages over conventional 3D radiotherapy (3D CRT) planning for adjuvant radiotherapy for gynecologic malignancies. These include a significant reduction in treatment volume for bladder, rectum, and small bowel. It is anticipated that this reduction in volume of normal tissue irradiated would translate into overall reduction in acute and potentially late treatment-related toxicity. Prospective trials are necessary to better evaluate the advantages in a larger group of patients.

Dose-Response Relationship, Radiation↗

PubMed2000

Effect of hypothermic pulmonary artery flushing on capillary filtration coefficient.

BACKGROUND: We previously demonstrated that surfactant dilution and inhibition occur immediately after pulmonary artery flushing with hypothermic modified Euro-Collins solution. Consequently, we speculated that increased capillary permeability contributed to these surfactant changes. To test this hypothesis, we evaluated the effects of hypothermic pulmonary artery flushing on the pulmonary capillary filtration coefficient (Kfc), and additionally performed a biochemical analysis of surfactant. METHODS: We used a murine isolated, perfused lung model to measure the pulmonary capillary filtration coefficient and hemodynamic parameters, to determine the wet to dry weight ratio, and to evaluate surfactant by biochemical analysis of lung lavage fluid. We defined three study groups. In group I (controls), we harvested lungs without hypothermic pulmonary artery flushing, and measured Kfc immediately. In group II (in situ flush), we harvested lungs after hypothermic pulmonary artery flushing with modified Euro-Collins solution, and then measured Kfc. Experiments in groups I and II were designed to evaluate persistent changes in Kfc after pulmonary artery flushing. In group III (ex vivo flush), we flushed lungs ex vivo to evaluate transient changes in Kfc during hypothermic pulmonary artery flushing. RESULTS: Groups I and II did not differ significantly in capillary filtration coefficient and hemodynamics. Group II showed significant alterations on biochemical surfactant analysis and a significant increase in wet-to-dry weight ratio, when compared with group I. In group III, we observed a significant transient increase in capillary filtration coefficient during pulmonary artery flushing. CONCLUSIONS: Hypothermic pulmonary artery flushing transiently increases the capillary filtration coefficient, leads to an increase in the wet to dry weight ratio, and induces biochemical surfactant changes. These findings could be explained by the effects of hypothermic modified Euro-Collins solution on pulmonary capillary permeability.

Airway Resistance↗

PubMed1995

Surfactant dysfunction in lung preservation.

We studied the effect of lung preservation on the surfactant system in rats. Lung surfactant is necessary to maintain normal lung mechanics, and hence normal lung function. We evaluated lung mechanics with pressure-volume (P-V) curves, and analyzed biochemical changes of surfactant in bronchoalveolar lavage (BAL) fluid. Additionally, we determined wet to dry weight ratios (W/D). We defined five study groups. In group I (controls) we harvested lungs without pulmonary artery flushing, then evaluated them immediately. In group II we flushed lungs through the pulmonary artery (PA) with hypothermic modified Euro-Collins solution (mECS), then removed and studied them immediately to determine the consequences of PA flushing alone. In groups III, IV, and V we flushed lungs with mECS, then stored them in normal saline (NS) for 6 hr (group III); in NS for 12 hr (group IV); or in mECS for 12 hr (group V). In groups III, IV, and V we evaluated lungs after storage. All four experimental groups showed significant changes in lung mechanics and surfactant biochemistry, compared with controls. Lungs in groups III, IV, and V showed additional changes in lung mechanics and surfactant biochemistry compared with group II. The W/D in stored lungs (groups III, IV, and V) was significantly higher than in controls and group II. We conclude that lung preservation induces deleterious changes in the surfactant system. Surfactant alterations are evident immediately after pulmonary artery flushing, and increase in severity with storage.

Animals↗