Biomedical subjects
E L Nickoloff
Publications and source records attributed to E L Nickoloff.
Value of the coronal plane in MRI of internal derangement of the knee.
Sagittal images usually receive the most scrutiny in the magnetic resonance evaluation of meniscal and anterior cruciate ligament tears. We assessed the relative contribution of the coronal view. All knee magnetic resonance examinations performed over a 2-year period that had surgical confirmation were reviewed with respect to the presence of meniscal and anterior cruciate ligament tears. The appearance of an attenuated but uninterrupted anterior cruciate ligament was also evaluated. The coronal and sagittal plane images were evaluated separately. The study included 68 medial menisci, 67 lateral menisci, and 71 anterior cruciate ligaments. The coronal view is especially useful in the evaluation of the lateral meniscus. An anterior cruciate ligament that appears attennated but uninterrupted should be considered intact. The anterior cruciate ligament may be evaluated on the coronal view. The coronal view should be regarded as similar to the lateral chest radiograph, which supplements, but does not replace, the frontal chest radiograph.
Optimal resources for the examination and endovascular treatment of the peripheral and visceral vascular systems. AHA Intercouncil report on peripheral and visceral angiographic and interventional laboratories.
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Factors affecting x-ray spectra.
The x-ray spectrum is defined as the energy distribution of the radiation produced in an x-ray exposure. The x-ray spectrum has a major impact on image quality and radiation dose delivered to patients. The authors explored the effects of three key factors on x-ray spectra: generator type, peak tube potential, and filtration. Different generator types are characterized by the amount of ripple in the kilovoltage waveform. Those with high (100%) ripple such as single-phase units produce less penetrating radiation than units with low (4%) ripple such as three-phase, 12-pulse generators. As peak tube potential increases, the half-value layer increases nearly linearly; radiation output increases by approximately the square of the tube potential. Filtration materials with atomic numbers less than 42, such as aluminum, titanium, copper, and niobium, produce similar spectra, with only slight variations in efficiency. Although aluminum has the lowest efficiency, this may be compensated for by increasing milliampere seconds. Filtration in addition to the inherent filtration provided by the tube reduces both skin surface dose and average depth-dose, with the optimal amount being approximately 2-3 mm or less of aluminum-equivalent material.
Radiographic detail and variation of the nominal focal spot size: the "focal effect".
It is not generally appreciated that there is a gradation of the focal spot size from the anode to cathode end of an x-ray field that can dramatically affect radiographic detail from one end of a radiograph to the other. The authors name this gradation the "focal effect." Gradations in radiation intensity and focal spot size were measured from anode end to cathode end of a 14 x 17-inch field and were visually demonstrated with lymphangiograms and line-pair patterns. The degradation in spatial resolution along the anode-cathode axis was found to be as much as 75%, depending on the orientation of the patient with respect to the x-ray tube. Radiographic detail is, therefore, significantly improved (even when the large focal spot is used) by exploiting the focal effect and placing the body part requiring the best radiographic detail at the anode end of the table.
Technologic advances in diagnostic radiology.
Technologic advances in radiographic equipment and procedures for four different areas of diagnostic radiology are reviewed: bone mineral assessments, musculoskeletal imaging, mammography, and chest imaging. For bone mineral assessments the accuracy and precision obtained using single- and dual-energy photon absorptiometry, dual-energy x-ray absorptiometry, and quantitative CT are summarized. Various digital systems employed in musculoskeletal imaging are reviewed. In mammography, papers related to accreditation and research interests are highlighted. The use of photo-simulated phosphor plates and scanned equalization radiographic systems for chest imaging are discussed. Finally advances in radiographic film processing are noted.
A quality-control phantom for digitization of radiographs.
Quality control is fundamental to the clinical application of digital radiography. A 14 x 17-in phantom radiograph was designed to test digital image quality by measurement of five parameters: high-contrast spatial resolution, low-contrast discrimination, linearity of gray-scale response, high-frequency noise, and geometric distortion. The phantom was used to evaluate the AT&T-Philips CommView picture archival and communications system (AT&T Bell Laboratories, West Long Branch, NJ; Philips Medical Systems, Shelton, CT). High-contrast resolution was found to be greater along the diagonal axis of the system than along either the horizontal or vertical axis. Problems with low-contrast discrimination and linearity of gray-scale response were identified. This phantom provides a simple tool for daily quality assurance testing and an objective standard for comparison of image quality between different digital radiography systems.
Excretion of radioiodine in breast milk.
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Measurement of the PSF for a CT scanner: appropriate wire diameter and pixel size.
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A predictive test for adverse reactions to contrast media. Preliminary results.
In a prospective study, whole blood samples drawn from patients prior to their being injected with contrast media were incubated with zymosan to activate the complement cascade. The samples were tested for various analytes, including C3a, thromboxane B2 (TxB2), beta thromboglobulin and platelet factor 4 (PF4). Of 207 patients receiving contrast media, only eight experienced reactions, which were mild. Levels of the platelet constituents were generally elevated in these patients. Specificity and sensitivity were 89% and 83%, respectively, for the combined TxB2 and PF4 radioimmunoassay data. Using the Wilcoxon-Mann-Whitney rank sum test, both PF4 and TxB2 were collected with RCM reactions at the R less than .05 level. Although preliminary, the results suggest that RCM reactions are predictable by the in vitro test procedures described.
Bone mineral assessment: new dual-energy CT approach.
Most clinical quantitative computed tomographic (CT) determinations of bone mineral content are hampered by inability to properly account for the various substances contained within the spongiosa (spongy bone). In general, the presence of adipose tissue lowers the CT numbers (Hounsfield units) and leads to underestimation of bone mineral content. Collagen matrix has the opposite effect. A new approach to obtaining data from postreconstruction dual-energy CT scans accounts for five principal constituents of the spongiosa. In addition to bone mineral values, the method also provides the adipose tissue concentration, calcium content, and density of the total trabecular space. Since calcium values are provided, the measurements can be compared with prereconstruction dual-energy data that are acquired simultaneously. A new solid-plastic calibration phantom was utilized in this study, and data were obtained from 26 subjects. Dual-energy data were correlated with single-energy measurements (r greater than .96), and calcium measurements were correlated with the bone mineral determinations (r = .97) in these 26 cases. All measurements of the various vertebral constituents agreed with published values.
Use of gypsum drywall as shielding material for mammography.
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Prekallikrein activation, C1 esterase inhibitor, and factor XII as predictors of adverse reaction to contrast media. A prospective study.
The susceptibility of 152 patients to idiosyncratic reactions resulting from the administration of radiographic contrast media was studied. The rate of activation of plasma prekallikrein was measured in samples taken from these patients before they received contrast agents. Kallikrein inhibitor and factor XII levels were also determined. The tests were of no value in selecting the ten patients who subsequently experienced mild reactions. However, the possibility remains that one or more of the tests may have predictive value for patients who experience moderate or severe reactions.
Evaluation of a cinevideodensitometric method for measuring vessel dimensions from digitized angiograms.
A cinevideodensitometric method for measuring the dimensions of small vessels by computer analysis of digitized cineangiograms was developed and validated in radiographic phantom models. With this method, which is based on full-width-at-half-maximum analysis of videodensitometric profile curves, the diameters of contrast-filled plexiglass cylinders ranging from 1.78 mm to 4.14 mm in diameter were measured to within 2% mean error. The theoretical basis for this method of cinevideodensitometric analysis is provided.
Radionuclide administration to nursing mothers: mathematically derived guidelines.
We determined a formula to establish objective guidelines for the administration of radionuclides to nursing mothers. The formula is based on the maximum permissible dose to the infant's critical organ, serial measurements of breast milk activity, milk volume, and dose to the critical organ per microcurie in milk. Using worst-case assumptions, we believe that cessation of nursing for 24 hours after administration of technetium labeled radiopharmaceuticals is sufficient for safety. Longer-lived agents require greater delays. Iodine-123 radiopharmaceuticals are preferable to iodine-131 agents and should always be used when studying the unblocked thyroid.
Effect of coronary stenotic lesions on regional myocardial blood flow at rest.
To determine the effect of atherosclerotic coronary lesions on myocardial blood flow in patients at rest, regional myocardial blood flow was measured distal to stenotic lesions in 29 patients with isolated proximal lesions of the left anterior descending artery. Severity of coronary stenosis was measured by computer-assisted cinevideodensitometric analysis of digitized coronary arteriograms. Regional myocardial blood flow was measured from the clearance rate of intracoronary 133Xe injected into the left main coronary artery and recorded with a multicrystal scintillation camera. In 21 patients with stenotic lesions ranging from 19% to 84% area reduction, distal regional myocardial blood flow was normal. In all eight patients with reduced regional myocardial blood flow distal to left anterior descending lesions, the minimum area of each stenotic lesion was less 0.80 mm2 (mean 0.34 +/- 0.2 mm2), minimum calculated diameter was less than 1 mm (mean 0.59 +/- 0.3 mm), and percent stenosis, based on the reduction in cross-sectional area, was greater than 85% (mean 94 +/- 4%). For all patients, distal flow, expressed as a fraction of normal flow, correlated with the lesion cross-sectional area (r = .84), minimum luminal diameter (r = .84), and percent area stenosis (r = -.70). Thus, resting myocardial blood flow distal to stenotic lesions of the proximal coronary arteries remains normal until the degree of narrowing is severe. The dimensions observed for critical coronary stenotic lesions correlate well with theoretical predictions based on fluid mechanics and with experimental preparations in laboratory animals.
Normal thermographic standards for the cervical spine and upper extremities.
Although thermography has been used for a variety of abnormal conditions, extensive data on large, relatively asymptomatic populations has heretofore not been available. More specifically, no data deal with the upper extremities and, more particularly, no analyses are based on simultaneous thermograms of the posterior neck and shoulders. The current study undertook this task. The results confirm the existence of thermal symmetry in the overwhelming majority of 100 normal relatively asymptomatic, actively employed factory workers. Conversely, if persistent, statistically significant thermal asymmetry exists, as outlined and correlates with patient symptomatology, an organic basis for it should be sought.
A radioimmunoassay for total captopril in human serum or plasma samples.
A radioimmunoassay for the measurement of total captopril in serum and heparinized plasma has been developed. Prior to the assay, serum or heparinized plasma samples are subjected to tri-n-butyl-phosphine reduction followed by N-ethylmaleimide (NEM) derivatization. The assay utilizes in-house NEM-captopril antibody, [125I]NEM-captopril radiolabel and human serum standards. Satisfactory zero binding and sensitivity are obtained after 3 h of incubation at room temperature. Separation of the antibody-bound and free radiolabeled antigen is achieved by employing a polyethylene glycol solution. The assay was shown to have excellent parallelism, recovery, and precision. Cross-reactivities with potentially interfering substances were low.