Effect of US contrast agents on spectral velocities: in vitro evaluation.

Purpose: To evaluate the effect of ultrasonographic (US) contrast agents on measurements of peak velocity with spectral Doppler US in stenotic and nonstenotic flow states.

Materials And Methods: Nonpulsatile flow was established in a flow phantom with 0%, 50%, 75%, and 90% stenoses. SH U 508A, perflenapent emulsion, and perfluorohexane emulsion were the contrast agents evaluated.

Computed radiography dual energy subtraction: performance evaluation when detecting low-contrast lung nodules in an anthropomorphic phantom.

A dedicated chest computed radiography (CR) system has an option of energy subtraction (ES) acquisition. Two imaging plates, rather than one, are separated by a copper filter to give a high-energy and low-energy image. This study compares the diagnostic accuracy of conventional computed radiography to that of ES obtained with two radiographic techniques.

Establishing minimum performance standards, calibration intervals, and optimal exposure values for a whole breast digital mammography unit.

Methods are developed to establish minimum performance standards, calibration intervals, and criteria for exposure control for a whole breast digital mammography system. A prototype phantom was designed, and an automatic method programmed, to analyze CNR, resolution, and dynamic range between CCD components in the image receptor and over time. The phantom was imaged over a 5 month period and the results are analyzed to predict future performance.

Breast calcification and mass detection with mammographic anode-filter combinations of molybdenum, tungsten, and rhodium.

Purpose: To determine whether contrast loss on mammograms obtained with tungsten (W)-molybdenum (Mo), rhodium (Rh)-Rh, and W-Rh anode-filter units affects calcification and mass detection relative to that on mammograms obtained with Mo-Mo anode-filter units.

Materials And Methods: Three unfixed cadaveric breasts of 4.0-, 5.

Mammography film processor replenishment rate: bromide level monitoring.

The effects of the mammography film processing replenishment rate on contrast and speed are studied sensitometrically. Two experiments studied decreasing replenishment rates in the Kodak RP developer and quantified changes in the developer by measuring bromide ion concentrations. First, values of NaBr concentration from 1.

Effects of ambient light and view box luminance on the detection of calcifications in mammography.

Objective: Viewing conditions can affect diagnostic performance differently depending on background optical densities. We quantified detection accuracy when viewing calcifications in glandular tissue under recommended viewing conditions versus accuracy with lower view box luminance and higher ambient lighting.

Materials And Methods: A phantom with adipose, 50% adipose and 50% glandular, and glandular-simulating material was imaged, and images were interpreted by five medical imaging physicists using two lighting conditions: the recommended one, high view box luminance (4365 nits) with low ambient light (25 lx), and a suboptimal one, low view box luminance (1763 nits) with moderate ambient lighting (290 lx).

Detection of simulated lung nodules with computed radiography: effects of nodule size, local optical density, global object thickness, and exposure.

Rationale And Objectives: We quantified differences in the detection of simulated lung nodules on computed radiographs on the basis of variations in nodule size, local contrast, body habitus (global contrast), and exposure.

Methods: A step-wedge phantom was developed to simulate the attenuation ranges of the lung, retrocardiac, and subdiaphragmatic regions of the adult human chest. Additional Lucite wedges were used to simulate two different body thicknesses and to provide variable structural noise.

Mammographically guided fine-needle aspiration cytology of the breast: reducing the rate of insufficient specimens.

Objective: The purpose of our study was to reduce the rate of insufficient specimens from fine-needle aspiration cytology (FNAC) of impalpable mammographically detected breast lesions.

Subjects And Methods: Our previous rate of insufficient specimens for FNAC was 27%. We implemented the following strategies to reduce this rate and improve accuracy: retraining of radiologists in FNAC procedures, more vigorous sampling, on-site evaluation of specimens by cytopathologist or cytotechnologist, exclusive use of stereotaxic guidance, stereotaxic equipment calibration program, and verification of initial needle placement.

Validation of volume flow measurements in blood vessels with quantitative color velocity imaging using a physiologic model of the circulation.

Rationale And Objectives: Color velocity imaging-quantitative (CVI-Q) is a new sonographic technique designed to measure volume flow (VF) in blood vessels. We attempted to validate VF measurements with CVI-Q in an in vitro model of the circulation.

Methods: We validated CVI-Q in a flow phantom mimicking physiologic conditions by connecting isolated porcine arteries 4-14 mm in diameter to a calibrated perfusion roller pump generating pulsatile flow with porcine blood.

Using tissue texture surrounding calcification clusters to predict benign vs malignant outcomes.

The positive predictive value of mammography is between 20% and 25% for clustered microcalcifications. For very early cancers there is often a lack of concordance between mammographic signs and pathology. This study examines the usefulness of computer texture analysis to improve the accuracy of malignant diagnosis.

Mammography fixed grid versus reciprocating grid: evaluation using cadaveric breasts as test objects.

In this study we use unfixed cadaveric breasts to obtain mammography images with fixed and reciprocating grids. Sheets of acrylic, containing one or more clusters of simulated calcifications and masses, were superimposed on two fresh cadaveric breasts (3.4 and 6.

Effects of reduced exposure on computed radiography: comparison of nodule detection accuracy with conventional and asymmetric screen-film radiographs of a chest phantom.

Objective: Radiographic exposure has been thought to have little impact on the diagnostic quality of chest computed radiography because of automatic digital control of global optical density. The objectives of this study were to compare images obtained with two different exposures in computed radiography with conventional and asymmetric screen-film images of the chest for the detection of simulated lung nodules by use of receiver operating characteristic analysis and to relate differences in observer performance to parameters of image noise measured for each receptor condition.

Materials And Methods: At 110 kVp (fixed), exposures for the two screen-film systems were those necessary to achieve adequate optical densities over the lung and mediastinal regions of an anthropomorphic phantom.

Strategies for developing effective computer-assisted instruction: a computer-based teaching module on color Doppler US.

Computer-assisted instruction is an effective method for teaching visually oriented subjects such as ultrasonography. Although many different forms of instructional strategy can be effective, the process of designing a teaching program should follow the same general procedures, regardless of the format. The first step is to consider the subject material and the target audience; this helps to determine the style of the computer-user interaction (eg, whether the program should be more interactive or dissertative in nature).

Acceptance testing prone stereotactic breast biopsy units.

When the Mammography Quality Standards Act becomes law in October, 1994, stereotactic breast biopsy units may require yearly physicist calibration. Upright stereotactic units can be easily tested using conventional mammography procedures and a gelatin phantom containing simulated calcifications, but prone units are difficult to assess because of the under-table tube configuration. The two current manufacturers of these units have made different design decisions which affect each unit's calibration.

Mammograms obtained with rhodium vs molybdenum anodes: contrast and dose differences.

Objective: A mammography unit with both a molybdenum anode and a rhodium anode, filtered with molybdenum and rhodium, respectively, was evaluated to determine which types of women would benefit from the dose savings of the rhodium combination despite some loss of contrast.

Subjects And Materials: In 100 women, the molybdenum anode and molybdenum filtration (Mo/Mo) were used to obtain mammograms of the right breast, and the rhodium anode and rhodium filtration (Rh/Rh) were used for mammograms of the left breast. All mammograms were obtained at 26 kVp.

Use of a Doppler guide wire for intravascular blood flow measurements: a validation study for potential neurologic endovascular applications.

Purpose: To conduct a validation study of a Doppler guide wire for potential neuroendovascular applications.

Methods: A 12-MHz, 0.018-inch Doppler guide wire was evaluated in eight swine under various blood flow conditions using two types of in vivo cerebrovascular models (physiologic and arteriovenous shunting).

Mammography quality assurance from A to Z.

Quality assurance (QA) refers to all planned, systematic activities that instill confidence that quality mammography is being performed. Quality control (QC) refers only to the technical aspects of the examination. Standardized labeling of mammograms and the format for mammographic reports are important parts of a QA program; recommendations for both have been published by the American College of Radiology.

Mammography focal spot measurement with a star pattern: techniques to avoid inaccuracies.

The increased emphasis on mammography acceptance testing and quality control make the star pattern test an essential component of the procedure for diagnosing poor resolution due to large focal spots. In this paper procedures for calculating magnification and the correct angle of the star pattern to use are described. The preferred placement of the star pattern in the field and proper exposure technique is also discussed.

Testing mammography equipment: evolution over a 4-year period.

The results of quality control (QC) tests on 70 mammography units in Southern California from 1986 to 1990 are reported. Thirteen facilities, selected because they housed all of the mammography units in three communities involved in a National Institutes of Health research project, had their units tested twice at an interval of 1 year. Fourteen self-selected units were also tested twice at intervals ranging from 1-3 years.

Effect of poor control of film processors on mammographic image quality.

With the increasingly stringent standards of image quality in mammography, film processor quality control is especially important. Current methods are not sufficient for ensuring good processing. The authors used a sensitometer and densitometer system to evaluate the performance of 22 processors at 16 mammographic facilities.

Mammography screen-film selection: individual facility testing technique.

Variations in tube output, film processing, and radiologist's preferences affect the screen-film combination that is appropriate for any particular mammographic facility. A technique to test a variety of screen-film combinations for screening mammography is described. Films are selected for testing because of their densitometric characteristics.