Biomedical subjects

R B Barnett

Publications and source records attributed to R B Barnett.

10 recordsLinked to original sources

PubMed1995

Surface and internal absorbed doses in mandibular and maxillary occlusal radiography.

The objective of this study was to determine the absorbed radiation doses to various structures within the head and neck as a result of routine mandibular and maxillary occlusal radiography. Five projections were investigated: the anterior mandibular; true mandibular; anterior maxillary; lateral maxillary; and maxillary vertex occlusal radiographic views. Standard thermoluminescent dosimetry methodology was employed using a humanoid phantom of the skull. Multiple exposures were done for each view to ensure adequate precision. The absorbed doses to various locations following a single occlusal exposure are presented in centiGray (cGy). It was found that the absorbed dose values for occlusal radiography observed in this study were similar in magnitude to previously reported absorbed dose values for other forms of dental radiography. Values ranged from 0.0014 cGy to 1.301 cGy. The highest absorbed doses were generally the skin entrance doses. The results of this study provide an accurate, concise summary of surface and internal absorbed radiation doses for five commonly used occlusal radiographs. They can be used in the calculation of risk estimates for dental radiography, and may assist dentists in their discussions with patients concerned about radiation exposure.

Absorption↗

PubMed1994

Extracorporeal shock wave lithotripsy: multicenter study of kidney and upper ureter versus middle and lower ureter treatments.

Six institutions throughout the United States participated in this study. Each center used a multifunctional flat table lithotriptor (Dornier MFL-5000) to treat 658 patients with kidney and upper ureteral stones (766 treatments) and 323 with middle and lower ureteral stones (391 treatments), for a total of 925 patients (1,157 treatments). Some patients received more than 1 treatment (that is the kidney and ureter), for a total of 981 patient events. Complete followup was available for 81% of the patients. The overall stone-free rate at followup of approximately 90 days was greater in the middle and lower ureter group (83%) than in the kidney and upper ureter group (67%). The proportion of single stones treated was greater for the former group (89.5%) than for the latter group (72%). A larger proportion (18%) of the middle and lower ureter group required 2 or more treatments to the targeted stone than did the kidney and upper ureter group (13%). Anesthesia was required or selected in only 26.7% of the kidney and upper ureteral stone patients and in 18.5% of those with middle and lower ureteral calculi, usually at the request of the patient or physician, or for performance of an adjunctive procedure. The relative safety of this treatment is demonstrated by a low overall rate of complications reported during and after treatment, including a ureteral obstruction rate of 2.1% for kidney and upper ureteral stones and 2.5% for middle and lower ureteral stones. There were no demonstrated trends in a review of laboratory data to suggest significant treatment side effects. The diastolic blood pressure increased to more than 95 mm. Hg after extracorporeal shock wave lithotripsy (ESWL*) in 6% of the kidney and upper ureteral and 4% of the middle and lower ureteral stone patients, while pretreatment hypertension resolved after ESWL in 11% of both groups. The results of this clinical evaluation indicate somewhat greater effectiveness for the specified indications of ESWL of stones in the ureter below the upper rim of the bony pelvis, as opposed to those in the kidney and upper ureter, with a low incidence of complications and side effects.

Adolescent↗

PubMed1993

Commissioning and quality assurance of treatment planning computers.

The process of radiation therapy is complex and involves many steps. At each step, comprehensive quality assurance procedures are required to ensure the safe and accurate delivery of a prescribed radiation dose. This report deals with a comprehensive commissioning and ongoing quality assurance program specifically for treatment planning computers. Detailed guidelines are provided under the following topics: (a) computer program and system documentation and user training, (b) sources of uncertainties and suggested tolerances, (c) initial system checks, (d) repeated system checks, (e) quality assurance through manual procedures, and in vivo dosimetry, and (f) some additional considerations including administration and manpower requirements. In the context of commercial computerized treatment planning systems, uncertainty estimates and achievable criteria of acceptability are presented for: (a) external photon beams, (b) electron beams, (c) brachytherapy, and (d) treatment machine setting calculations. Although these criteria of acceptability appear large, they approach the limit achievable with most of today's treatment planning systems. However, developers of new or improved dose calculation algorithms should strive for the goal recommended by the International Commission of Radiation Units and Measurements of 2% in relative dose accuracy in low dose gradients or 2 mm spatial accuracy in regions with high dose gradients. For brachytherapy, the aim should be 3% accuracy in dose at distances of 0.5 cm or more at any point for any radiation source. Details are provided for initial commissioning tests and follow-up reproducibility tests. The final quality assurance for each patient is to perform an independent manual check of at least one point in the dose distributions, as well as the machine setting calculation. As a check of the overall treatment planning process, in vivo dosimetry should be performed on a select number of patients.

Brachytherapy↗

PubMed1993

The relative biological effectiveness of ytterbium-169 for low dose rate irradiation of cultured mammalian cells.

PURPOSE: An important step in the development of 169Yb as a new brachytherapy source is to determine its biological effectiveness relative to other commonly used radioisotopes. The purpose of this paper is to determine the relative biological effectiveness of 169Yb, with respect to 60Co, for a range of low dose rates. METHOD AND MATERIALS: The relative biological effectiveness of photon radiation from encapsulated 169Yb was determined by exposing Chinese hamster ovary cells, in exponential growth, to graded doses of radiation from either 169Yb or 60Co. Clonogenic cell survival was determined for continuous low dose rates ranging from 6.5 cGy/hr to 52 cGy/hr. RESULTS: The relative biological effectiveness of 169Yb, with respect to 60Co, was determined to be 1.2 +/- 0.3 and did not vary significantly over the dose-rate range from 13 cGy/hr to 50 cGy/hr. An inverse dose-rate effect was observed, but only for 60Co irradiation at 8.9 cGy/hr. Therefore, relative biological effectiveness values could not be determined reliably for dose rates less than 13 cGy/hr. CONCLUSIONS: We have established that 169Yb is approximately 20% more effective than 60Co in vitro. It is hoped that this study will guide the introduction of 169Yb into clinical brachytherapy practice.

Animals↗

PubMed1992

Pulmonary changes after laparoscopic cholecystectomy.

Laparoscopic cholecystectomy has become a widely used procedure. Upper abdominal surgery and particularly open cholecystectomy are known to be associated with marked declines in lung volume and a high risk of postoperative pulmonary complications. The pulmonary effects of laparoscopic cholecystectomy have not yet been studied. We prospectively evaluated 22 patients admitted for laparoscopic cholecystectomy for lung volume changes and development of postoperative pulmonary complications. The procedure was associated with a marked decline in forced vital capacity (FVC, 41.2 +/- 20.7%) and forced expiratory volume in one second (FEV1, 41.4 +/- 20.8%) in the immediate postoperative period. There was no significant difference in loss of lung function according to age (p = 0.18), sex (p = 0.33), or smoking history (p = 0.58). Despite the marked loss in lung function in the immediate postoperative period, no major pulmonary complications occurred. We conclude that laparoscopic cholecystectomy, although associated with early loss of lung function, is a safe and effective procedure with an incidence of postoperative pulmonary complications much less than with open cholecystectomy.

Adult↗

PubMed1989

Prolonged exposure of neutrophils to saline or bronchoalveolar lavage fluid does not alter superoxide anion generation.

The role played by neutrophils (PMNs) in the genesis of lung injury in diverse clinical situations, such as bronchial asthma, idiopathic pulmonary fibrosis, and the adult respiratory distress syndrome, is an area of intensive investigation. Functional studies of PMNs, particularly those obtained from the alveoli by bronchoalveolar lavage, should shed light on their contribution to lung injury. However, it has not been demonstrated whether procedures used to harvest cells from the lung (bronchoalveolar lavage), particularly the potentially prolonged exposure to saline, commonly used to perform lavage, and other components of lavage fluid, can alter the functional characteristics of PMNs. In this report we demonstrate that a 2- to 3-hour exposure of neutrophils to saline from both humans and sheep in vitro does not alter the functional characteristics of PMNs as determined by superoxide anion generation after activation with phorbol myristate acetate (PMA; 6.96 +/- 0.44 vs. 7.60 +/- 0.32 nmol O2-/250,000 PMNs for control and saline-treated human cells, respectively, after a 45-min incubation with 10(-7) M PMA, and 4.73 +/- 0.30 vs. 4.50 +/- 0.42 nmol O2-/250,000 PMNs for control and saline-treated sheep cells). In a second series of experiments, we studied the effect of exposure of human PMNs to bronchoalveolar lavage fluid supernatants obtained from normal volunteers on superoxide anion generation by neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Nutritive value of new cultivars of triticale and wheat for broiler chick diets.

Three experiments were conducted with broiler chicks from 1 to 21 days of age to evaluate Florida 301 variety of wheat and Beagle 82 variety of triticale. In Experiment 1, a completely randomized design (CRD) was used for five dietary treatments: yellow corn-soy (control), triticale-soy, yellow corn-triticale-soy, wheat-soy and yellow corn-wheat-soy. Diets were balanced to maintain equal levels of sulfur amino acids and lysine and were kept isocaloric (3,124 kcal/kg) using corn oil. In Experiment 2, a CRD was used for 10 dietary treatments. Each grain was substituted partially and totally for corn on both iso and nonisocaloric basis. Animal fat was the supplemental fat source. In Experiment 3, a CRD was used for 8 dietary treatments. Each grain was substituted for corn isocalorically using corn oil, animal fat, or both as supplemental fat sources. Results from these experiments showed that Florida 301 wheat is an excellent cereal grain for broiler chicks as measured by feed efficiency and growth response, which was numerically but not significantly greater than with a corn-soy control diet. Growth response was inconsistent with Beagle 82 triticale throughout the three experiments. However, feed efficiency was better with triticale diets than corn-based diets.

Animal Feed↗

PubMed1975

Therapy questionably infarcted testis.

Observations made upon dogs and humans with apparent infarction of the testis secondary to torsion of the spermatic cord suggest that the treatment of choice for questionably viable testis is detorsion of the cord, replacement of the testis in its hemiscrotum, and fixation of the opposite testis. This form of therapy may be applicable to all "torsed testes" regardless of viability.

Animals↗

PubMedDate not supplied

Measurements in high-intensity beams from medical linear accelerators.

There is a potential to produce very high doses and dose rates on dual mode (electron and x-ray capability) medical electron accelerators [C. J. Karzmark, Br. J. Radiol. 40, 697 (1967)]. Measurements were taken on two accelerators to determine the size of the doses which were possible. The experiments demonstrate the limitations of many of the commonly used dosimeters when they are used outside of the dose and dose rate ranges normally encountered in a radiotherapy department. Dose rates from 110 to 165 cGy/pulse were measured using ionization chamber, ferrous sulphate and thermoluminescent dosimetry, and water calorimetry.

Calorimetry↗

PubMedDate not supplied

Ytterbium-169: calculated physical properties of a new radiation source for brachytherapy.

Seeds containing radioactive Ytterbium-169 (169Yb) have recently been manufactured for possible application to brachytherapy. Ytterbium-169 emits photons with an average energy of 93 keV (excluding energies less than 10 keV), and decays with a half-life of 32 days. Analytic and Monte Carlo computations have been used to predict physical quantities useful in treatment planning and radiation protection. Analytic calculations based on the primary photon spectrum of 169Yb (excluding energies less than 10 keV) yield an air-kerma rate constant of 0.0427 cGy cm2 h-1 MBq-1, and an exposure rate constant of 1.80 R cm2 mCi-1 h-1 for this radionuclide. Calculated fmed factors are 0.922 cGy/R for soft tissue and 2.12 cGy/R for bone. The first half-value layer in lead is 0.2 mm; the first tenth-value layer is 1.6 mm. Using Monte Carlo simulations, the relative dose distributions around 169Yb seeds (Amersham, prototypes 4 and 5) are provided, and are then compared with those around an 125I seed (3M model 6702). The 169Yb seeds produce more isotropic dose distributions, and for permanent implants, can deliver it at a greater initial dose rate. A value of 1.19 cm-2 was also calculated for the specific dose constant D0, a value which is applicable to both seed types. Radiation protection is not as easily achieved for permanent implants with 169Yb because of the higher energy emissions (vs 125I). However, for temporary implants, Ytterbium-169 may prove to be a useful substitute for 192Ir or 137Cs because of its relatively lower energy emissions. It is concluded that 169Yb merits further investigation, including dosimetry, radiobiological, and clinical studies.

Brachytherapy↗