Occupational radiation exposure to interventional radiologists: a prospective study.

This study investigates the occupational radiation dose to interventional radiologists and the operator-controlled factors that may affect dose. Thirty interventional radiologists wore radiation badges over and under lead aprons for 2 months and answered a questionnaire. The relationships between dose and caseload, case mix, experience, optional fluoroscopy features, lead apron type, and additional lead shielding were evaluated.

Precision of hyaline cartilage thickness measurements.

Measurement of cartilage thickness in vivo is an important indicator of the status of a joint as the various degenerative and inflammatory arthritides directly affect the condition of the cartilage. In order to assess the precision of thickness measurements of hyaline articular cartilage, we undertook a pilot study using MR imaging, plain radiography, and ultrasonography (US). We measured the cartilage of the hip and knee joints in 10 persons (4 healthy volunteers and 6 patients).

A simple method for use in QC of CT for radiation therapy treatment planning.

A simple procedure for monitoring constancy of spatial measurement and CT number determination from CT images used in radiation therapy treatment planning is described. The procedure uses low-Z material rods glued to the underside of the CT table insert and does not require a special phantom. Measurements are made on the same patient images used for treatment planning.

Radiation exposure during radiofrequency catheter ablation of accessory atrioventricular connections.

Background: Catheter ablation of accessory atrioventricular (AV) connections has been demonstrated to be effective in more than 85% of patients. One of the risks of this procedure is radiation exposure during the fluoroscopic imaging necessary to guide catheter manipulation. The objective of the present study was to measure the radiation received by patients and physicians during radiofrequency catheter ablation and to estimate the resultant somatic and genetic risks.

Overview: new methods in imaging osteoarthritis.

The new imaging modalities, namely computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography (US) provide potentially powerful tools for in vivo assessment of osteoarthritis (OA), monitoring the progress of the disease and understanding its natural course. However, to use these tools effectively, we need more prospective research focused on correlating imaging data with biochemical and gross and microscopic pathologic findings. MRI is clearly the most powerful tool for demonstrating the various articular components which may be affected in OA.

Measurement of ventilation and respiratory mechanics during continuous positive airway pressure (CPAP) treatment in infants.

A new method has been evaluated for measuring ventilation and lung mechanics in spontaneously breathing infants by means of a face chamber. Airway flow is measured with a pneumotachograph inserted between the face chamber and a stable pressure source. Oesophageal pressure is measured via a water-filled oesophageal catheter.

CT densitometry of pulmonary nodules in a frozen human thorax.

The influence of (1) calcium concentration, (2) exposure technique, (3) reconstruction algorithm, (4) nodule size, and (5) nodule location on the CT attenuation values (CT density) of pulmonary nodules was examined in a frozen human thorax. Nodules with calcium concentrations of 0-310 mg/ml and diameters of either 0.95 or 1.

Dual-energy digital radiographic quantification of calcium in simulated pulmonary nodules.

The presence or absence of calcium in solitary pulmonary nodules may indicate whether a nodule is benign or malignant. Because current techniques for measuring the amount of calcium in these nodules are unsatisfactory, a study was carried out to assess the capability of dual-energy digital chest radiography to identify and quantify the calcium content of simulated pulmonary nodules of known calcium content. Measurements were carried out on 280 nodules of various sizes and calcium content that were placed within the lungs of a frozen human-chest phantom.

Calcification in pulmonary nodules: detection with dual-energy digital radiography.

The authors undertook a clinical study to determine the accuracy of dual-energy digital radiography in revealing nodule calcification because calcification in a pulmonary nodule almost excludes the possibility of malignancy. Over a 6-month period, 61 patients with pulmonary nodules (less than or equal to 3 cm) or masses (greater than 3 cm) were examined on a prototype scanned projection unit using a dual-energy detector. In 49 of 61 patients, nodules were noncalcified, and in 12, they were calcified.

Simulated pulmonary nodules: detection with dual-energy digital versus conventional radiography.

Performance of a prototype dual-energy digital chest radiography unit in detecting calcified and noncalcified simulated pulmonary nodules was compared with that of a highly optimized, conventional system. Nodules ranging in size (0.5, 1.

Gas exchange during controlled ventilation in children with normal and abnormal pulmonary circulation: a study using the single breath test for carbon dioxide.

Carbon dioxide single breath tests (SBT-CO2) were obtained during anesthesia and controlled ventilation in 42 children about to undergo thoracic surgery. The tests were obtained with a computerized system based on the Servo ventilator. The system made on-line corrections for compressed volume, apparatus deadspace, and rebreathing.

On-line measurement of gas-exchange during cardiac surgery.

This paper describes an on-line system for continuously monitoring expired CO2 during controlled ventilation. Signals from a Servo ventilator 900B or C and a CO2 Analyzer 930 are processed and corrected by the computer to produce a CO2 single breath test (SBT-CO2). This is the tracing of expired CO2 concentration or fraction against expired volume, from which the computer calculates the airway deadspace (VDaw).

Mammography phototimer technique chart.

A phototimer technique chart for mammography is presented along with the methodology used to design it. The chart is based on accurate measurement of breast thickness and helps overcome the inability of the phototimer to track as breast thickness varies. In clinical practice, the chart results in the consistent attainment of optimally exposed films and decreased number of retakes.

Effectiveness of antiscatter grids in digital subtraction angiography.

An analysis of the potential value of antiscatter grids for digital subtraction angiography (DSA) is presented. Using the Rose criterion for signal detection, and assuming quantum limited statistical noise, it is shown that grid selectivity and primary transmission are the two most important parameters of grid performance for DSA. In comparison with conventional grids commonly in current use in radiology departments, a grid having a higher level of primary transmission, (approximately 90%) and a moderate level of selectivity (approximately 6) could provide comparable imaging signal-to-noise ratios, but with 20% to 45% smaller patient dose.

Clinical evaluation of unsharp masking and slit scanning techniques in chest radiography.

Conventional, unsharp masking, and slit-mask (combining slit radiography and unsharp masking) techniques were compared in a clinical nodule detection study in cancer patients who were at risk for metastatic lung disease. Unsharp masking improved detection rates for nodules located in poorly penetrated areas of the chest (25% vs. 52%), with no difference in detection rates for other areas of the image and no change in false-positive detection rates.

Scattered radiation in chest radiography.

Luminance scatter fractions were measured for patients and phantoms in various regions of the chest film. Scatter fractions were found to be highly variable, being quite high in the regions of the chest with a large equivalent tissue thickness (e.g.

Photographic unsharp masking in chest radiography.

A photographic unsharp masking technique for improving the latitude of chest radiographs without sacrificing image contrast or detail is described. An unsharp mask film, prepared from a scout film of the patient's chest, is placed between the film and the front (entrance) screen in the cassette. A second radiograph then is recorded using technique factors that provide a well-penetrated view of the central mediastinum, etc.

Dual energy film subtraction technique for detecting calcification in solitary pulmonary nodules.

A simple film subtraction technique has been devised that isolates calcium image contrast and mutes tissue image contrast. Two exposures are required. The first is made on XL film using a 65 kVp beam filtered with 2 mm aluminum.

Simulation of lung nodules for nodule detection studies.

Two techniques for simulating lung nodules in nodule detection studies were evaluated. In one technique, radiographs were obtained with plastic beads placed on the surface of a chest phantom to simulate lung nodules. In the second technique, the same plastic beads were radiographed against a uniform background, and their radiographic images were then superimposed photographically onto a radiograph of the same chest phantom.

Performance characteristics of improved antiscatter grids.

The performance characteristics of prototype grids constructed with 0.1-mm-thick Ta strips were investigated. Significant improvement in scatter cleanup was noted in comparison to commercially manufactured grids, which are constructed with 0.

Rotating disk device for slit radiography of the chest.

A pair of rapidly rotating disks was assembled with multiple radial slits for obtaining chest radiographs in 1/60-1/20 sec., using automatic exposure timing, without visible images of individual slits. Substantial reduction of scattered radiation levels is achieved (one half to one fourth), especially in the retrocardiac and central mediastinal areas of the chest film.