PubMed Health⌕ Search

Biomedical subjects

J E Aldrich

Publications and source records attributed to J E Aldrich.

At least 19 recordsLinked to original sources
PubMed1994

Chronic infiltrative lung disease: comparison of diagnostic accuracies of radiography and low- and conventional-dose thin-section CT.

PURPOSE: To compare the accuracy of low-dose thin-section computed tomography (CT), chest radiography, and conventional-dose thin-section CT in diagnosis of chronic infiltrative lung disease (CILD). MATERIALS AND METHODS: Chest radiographs and low-dose (80-mAs) and conventional-dose (340-mAs) thin-section (1.5-mm) CT scans from 50 patients with CILD and 10 healthy control subjects were randomized and analyzed retrospectively. For CT, three images were obtained: at the aortic arch, at the tracheal carina, and 1 cm above the right hemidiaphragm. Two independent observers listed three likely diagnoses and recorded the degree of confidence in their first choice. RESULTS: A correct first-choice diagnosis was made more often with either CT technique than with radiography (P < .02). A high confidence level in the diagnosis was reached in 42% of radiographic, 61% of low-dose CT, and 63% of conventional-dose CT interpretations, which were correct in 92%, 90%, and 96% of the studies, respectively. CONCLUSION: The superior diagnostic accuracy of low-dose thin-section CT was achieved without an increase in effective radiation dose.

Adult↗
PubMed1992

The surface doses from orthovoltage x-ray treatments.

Measurements have been made of the surface dose with treatment cones and lead shielding used with orthovoltage x-ray systems. Both devices significantly increase the surface dose, probably by the generation of photoelectrons. The surface dose depends upon the shape and material of the cone and the x-ray energy. The surface dose can be 500% higher than the dose measured with a Baldwin-Farmer chamber. The significance of these doses is discussed in the light of recent information on the thickness of the epithelium. It is suggested that every effort be made to reduce the surface dose by using low atomic number material between the lead and the patient surface.

Humans↗
PubMed1992

A comparison of manual and remote afterloading in the treatment of carcinoma of the cervix: increasing dose rate with a flexible applicator.

A historical cohort design was used to assess the effect of introducing a remote afterloading system with a flexible applicator for the intracavitary treatment of cervical cancer. One hundred and sixty-eight patients treated for the 5 years prior to its introduction were compared to 84 patients treated for the first 3 years of its use. Patients were comparable with respect to age and stage. Treatment policies and techniques remained the same during the study period. Average dose rate to point A increased from 0.46 Gy/hr to 0.67 Gy/hr. The 3-year actuarial survival was equivalent between the two treatment modalities: 67.7% (manual), and 60.6% (remote). Patterns of local recurrence and distant failure were also equivalent between the two groups. Severe complication rates were comparable (8.3% manual, 6.3% remote) despite the increase in dose rate, confirming that the remote afterloading system can be safely adapted to a flexible applicator. The introduction of the remote afterloading system resulted in a 72% reduction in radiation exposure to staff.

Adult↗
PubMed1992

Changes in the paramagnetic centres in irradiated and heated dental enamel studied using electron paramagnetic resonance.

The EPR signals in dental enamel produced by radiation and by heat were studied. The inherent background signal at g = 2.005, and a radiation-produced signal at g = 2.002 have different saturation behaviour with microwave power, and this affords a method of signal optimization. Heating enamel at temperatures from 100 degrees C to 450 degrees C produces a range of radical species from g = 2.002 to g = 2.005, which have been characterized by their g-values, line widths and saturation behaviour. Standard dental drilling produces a range of radicals which appear to be similar to those produced by heat.

Dental Enamel↗
PubMed1991

Surface topography for patient repositioning.

For many years, this group has been interested in the measurement of patient surface contours in order to prepare radiotherapy compensators. Recently, these surface measurements have been made using optical ranging techniques (Medical Physics 16:425; 1989). A laser line is projected onto the patient surface and the video image of the line is digitized and used to calculate the coordinates of each point on the line. This surface information can be used not only for the calculation of compensators but can also be used to verify patient position from simulation to treatment and from one treatment to another. Because the calculation of surface coordinates takes approximately 30 seconds, the technique has been modified to allow the comparison of setup position in real time. In the new system, a series of narrow fan beams is projected to intersect the patient surface. At simulation, the reference video image of the lines is digitized and stored. At treatment setup, repeat video images are digitized and compared with the reference in real time. Operator adjustments to patient position are immediately shown on the composite image, and a congruency value is calculated to help in this process of alignment. Uses and accuracy of the technique will be discussed.

Humans↗
PubMed1990

An analysis of paramagnetic centers in irradiated dentin using electron spin resonance.

The ESR spectra produced in irradiated dentin have been studied over a range of incident radiation energies from 50 kVp to 25 MVp. The behavior of the dentin ESR signal strength is similar to that of enamel as a function of the energy of the incident radiation. The magnitude of the dentin ESR signals are, however, up to 10 times smaller than the signals of dental enamel for a given radiation energy. The possible contributions of radiation interaction coefficients, chemical structure, and crystallite size to the differences in ESR spectra are discussed.

Dentin↗
PubMed1990

Radioactive gold ring dermatitis.

A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy.

Carcinoma, Squamous Cell↗
PubMed1990

The use of digitized port films in assessing new treatment modalities.

An inexpensive computer-based imaging system has been used to compare simulator and portal radiographs. The films were digitized, normalized, and then overlaid for measurement. In a test group of patients, a new treatment protocol for pelvis irradiation was evaluated using this technique. For 90% of the patients, the average error was found to be smaller than 5 mm, and there were no field placement errors greater than 1 cm.

Female↗
PubMed1981

Measurement of x-ray exposures using mailed thermoluminescent dosimeters.

Thermoluminescent dosimeters (TLD) have been sent by mail to all hospitals in Nova Scotia to survey the radiographic and fluoroscopic x-ray exposures to patients, For each radiographic system a TLD was placed in the x-ray field during a routine abdominal radiographic procedure on an average size patient (20 cm AP). The TLD was not visible on the film and in no way effected the examination. Fluoroscopic exposure rates were measured using TLD and a 20 cm water phantom. The dosimeter was exposed for one minute using technique factors for an abdomen of average size. The average abdominal exposure to a 20 cm thick patient on 137 different radiographic units was .74 R. The average fluoroscopic exposure rat to a 20 cm water phantom using 54 different fluoroscopic systems was 5.4 R/min.

Fluoroscopy↗