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E L Nickoloff

Publications and source records attributed to E L Nickoloff.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of computed radiography and film/screen combination using a contrast-detail phantom.

The purpose of this work is to compare computed radiography (Kodak CR 400) and film/screen combination (Speed 400) systems in regards of patient dose, technique settings, and contrast-detail detectability. A special contrast-detail phantom with drilled holes of varying diameter (detail) and varying depth (contrast) was utilized. Various thicknesses of the Lucite sheets were utilized to simulate scattering tissues. Images of the phantom were acquired using a range of 60-120 kVp for film/screen and CR with a conventional x-ray tube and then for CR with additional 2 mm aluminum added filtration to the x-ray beam. The patient entrance skin dose was measured while maintaining 1.6 o.d. for film/screen images and 1900 Exposure Index for CR images. CR phantom images were displayed on the diagnostic workstation for soft copy reading as well as printed on films for hard copy reading on viewbox. Four physicists evaluated the images by scoring the threshold target depth along the row of the same target diameter. Detection ratio was calculated by counting the number of detectable targets divided by the total number of targets in the phantom. The overall score was related to the patient entrance skin dose, kVp, and the thickness of the scattering material. The patient entrance skin dose was reduced as the additional aluminum filter was added to the x-ray beam. Our findings suggested using a higher kVp setting and additional added filtration would reduce the patient entrance skin dose without compromising the contrast-detail detectability, which was compensated by the contrast manipulation on soft-copy display workstations.

Phantoms, Imaging↗
PubMed2000

Radiation doses during CT fluoroscopy.

CT fluoroscopy (CTF) is a relatively new imaging modality that is particularly useful for performing complex biopsy procedures. Despite the obvious benefits, the potential exists to deliver considerable radiation doses to both the patients and medical staff. The purpose of our study was to quantify the radiation levels based upon typical clinical procedures. To assess the potential radiation risks, the patient radiation doses via the CT dose index (CTDI) method were measured during CTF for a GE Pro-Speed CT scanner using standardized head and body phantoms and a CT ionization chamber. The measurements were performed for a variety of kVp, mA, and slice thickness settings. To determine patient radiation doses, the CT kVp, mA, and total CTF scan times were recorded for various biopsy procedures. To determine the radiation doses to the hands of the radiologists, a radiation survey meter was used to measure the scattered radiation from standard phantoms. The effectiveness of various types of leaded gloves and shields were also determined. The measured CTDI values ranged from 20.4 cGy min(-1) to 63.1 cGy min(-1) of CTF. For a group of 78 patients, the clinically utilized imaging times varied from 13.0 to 407 s with an mean time of 96.6 s +/- 78.9 s (1 standard deviation). The scattered x-ray radiation at the position of the radiologists hands performing the biopsy procedures was measured to be 0.6 to 1.5 mGy min(-1). The thin leaded gloves provided a relatively minimal reduction in the scattered radiation to the hands between 11% and 44% dependent upon the kVp and the type of glove. However, floor mounted radiation shields reduced the scattered radiation levels to the body by 94% to 99%. In comparison to standard x-ray fluoroscopy, CTF employs much higher radiation dose rates due to the higher kVp, mA, and rotating geometry. It is important to minimize the radiation dose to patients and staff by limiting the imaging times, employing lower mA settings, and using appropriate radiation protection measures.

Fluoroscopy↗
PubMed1999

Monthly monitoring program on DryView laser imager: one year experience on five Imation units.

Dry-processing film systems have become popular particularly in a network environment. This is mainly due to its ability to produce high quality images without wet chemistry processing. In this paper we describe a monthly monitoring program on five Model 8700 DryView Laser Imagers in our institution. A SMPTE pattern is generated via DryView Laser Imager software. The 100% patch is used for checking the base-plus-fog of the Imager. The 40% patch is used as the speed index. The optical density difference between patches 10% and 70% is used as the contrast index. These numbers are plotted for testing system consistency. In addition, the SMPTE pattern is examined to verify the sharpness of the bar patterns and the visibility of subtle contrasts-95% inset in the 100% patch and a 5% inset in the 0% patch. The clinical films are checked for processor artifacts, such as residuals from the drum. Stability of the dry processors has also been studied using three strips per day obtained at three different times of the day over a period of ten consecutive working days. The coefficient of variation is 0.05 for the speed index and 0.04 for the contrast index. The monthly monitoring program has been carried out in our institution since January 1997. The problems found by this monthly monitoring program assess the necessity of routine QC for DryView Laser Imagers. The instability of the post-processing dry silver films, and, consequently, the film handling requirements, are also discussed.

Biophysical Phenomena↗
PubMed1999

Proposition: a pregnant resident physician should be excused from training rotations such as angiography and nuclear medicine because of the potential exposure of the fetus.

It has been reasonably well documented that a pregnant resident physician can assume radiology rotations, including higher-exposure rotations such as angiography and nuclear medicine, without exposing the fetus to radiation levels that exceed national and international guidelines. Hence, many medical physicists support the contention that rotations should not be altered because a resident is pregnant. On the other hand, many if not most physicists subscribe to the ALARA (as low as reasonably achievable) principle, especially in cases of fetal exposure where increased radiation susceptibility is combined with an inability to decide for one-self. In addition, altered rotations usually can be accommodated by swapping rotations with other residents, with the pregnant resident taking high exposure rotations after delivery of the child. Policies on this issue vary among institutions, possibly because medical physicists have not come to closure on the issue. This issue of Point/Counterpoint is directed toward that objective.

Education, Medical, Graduate↗
PubMed1996

Medical physics.

Explore the source record for details and available documents.

Biophysics↗
PubMed1994

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.

Anterior Cruciate Ligament↗
PubMed1993

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.

Filtration↗
PubMed1992

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.

Contrast Media↗
PubMed1992

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.

Bone Density↗
PubMed1990

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.

Quality Control↗
PubMed1988

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.

Complement Activation↗
PubMed1988

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.

Bone and Bones↗
PubMed1987

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.

Complement Activating Enzymes↗