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M Basic

Publications and source records attributed to M Basic.

8 recordsLinked to original sources
PubMed1998

Evaluation of the detectability of breast cancer lesions using a modified anthropomorphic phantom.

UNLABELLED: During the development and characterization of imaging technology or new imaging protocols, it is usually instructive to perform phantom experiments. Often, very simplified forms of the realistic patient anatomy are used that may be acceptable under certain conditions; however, the implications for patient studies can be misleading. This is particularly true in breast and axillary node imaging. The complexities presented by the anatomy, variable object scatter, attenuation and inhomogeneous distribution of activity in this upper thoracic region provide a significant challenge to the imaging task. METHODS: A tissue-equivalent anthropomorphic phantom of the thorax (Radiology Support Devices, Inc., Long Beach, CA) containing fillable cavities and organs was modified for the studies. The phantom was filled with realistic levels of FDG activity and scanned on a Siemens ECAT HR+ whole-body PET scanner. Breast attachments containing 2.0- and 2.55-cc lesions with lesion-to-background ratios of 5:1 and 7:1, respectively, were imaged. Scatter and attenuation effects were analyzed with various experimental setups. A lymph node experiment and a multibed position whole-phantom scan also were performed to illustrate the extent to which the phantom represents the human thorax. RESULTS: Regions of interest were drawn on the lesions as well as the background breast tissue in all studies. It was found that the signal-to-noise ratio decreased 65% when a more realistic phantom (lesions plus breasts plus thorax, all containing activity) was used, as compared to a simple phantom (lesions plus breasts containing activity; no thorax), due to the effects of increased scatter and attenuation. A 23% decrease in the contrast also was seen from the scan of the more realistic phantom due to surrounding activity from nearby organs such as the heart, as well as an increase in the volume of attenuating media. CONCLUSION: This new phantom allows us to more realistically model the conditions for breast and lymph node imaging, leading to preclinical testing that will produce results that better approximate those that will be found in vivo. The phantom will be a valuable tool in comparing different imaging technologies, data collection strategies and image reconstruction algorithms for applications in breast cancer using PET, SPECT or scintimammography systems.

Axilla↗
PubMed1997

Mapping sequence specific DNA-protein interactions: a versatile, quantitative method and its application to transcription factor XF1.

We have developed a method for the quantitative, exhaustive sequence specificity determination of DNA-binding proteins. The QuESSD method overcomes the limitations inherent in other published in vitro selection methods, not only defining the consensus sequence, but also quantifying the effect on DNA-protein affinity of replacing each base in the recognition domain with every other base. The features distinguishing this method from other in vitro selection approaches are: (1) instead of synthesizing one target oligonucleotide population containing a long randomized domain, we synthesize several oligonucleotide populations, each randomized at two positions. (2) Instead of carrying out several cycles of selection and amplification, we carry out a single cycle. (3) We have developed data collection and analysis procedures that eliminate artifacts and allow generation of quantitative results. The QuESSD method yields accurate measures of: (a) the selectivity of the protein for each base at each position within the recognition domain (normalized relative selectivity), (b) the contributions of individual sites within the recognition domain to the binding affinity (selectivity variance), (c) the relative binding affinity of any given sequence (global selectivity). We confirmed results by (1) tabulating directly the frequency of appearance of individual species in the pool of protein-bound oligonucleotides by cloning and sequencing individual oligonucleotides, and (2) competition EMSA analysis of oligonucleotides designed on the basis of QuESSD data. We have used this method to map the sequence specificity of the nuclear protein XF1 and to distinguish the sequence specificities of XF1 and the AH receptor complex, both of which bind to XRE1, a xenobiotic responsive element (XRE) located upstream of the CYP1A1 gene. Using data obtained by the QuESSD method, we designed oligonucleotides specific for XF1 or for the AH receptor, and prepared CAT reporter gene constructs carrying these oligonucleotides, or wild-type XRE1, upstream of a minimal promoter. Transfection studies using these constructs indicated that XF1 can function as a weak activator of basal transcription, and can, under some circumstances, compete with the AH receptor for binding to XRE1.

Animals↗
PubMed1997

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 1.7 to 8.4 g/L, achieved by reducing the replenishment rate, were tested with sensitometry strips. Second, the developer replenishment rate of a high volume dedicated mammography processor was reduced by one-third, to 20 cm3/1560 cm2, so that the NaBr concentration rose from 2.0 to 12.36. Sensitometric results for four film types and patient films were tested for changes from standard values as NaBr concentration was restored to 3.31 g/L. Fifty-five clinical images obtained at 7.3-9.3 NaBr g/L were compared to their matching previous films, with NaBr levels of 2-3 g/L, for contrast and visibility of the skin line. For the range of the NaBr ion from 1.7 to 7 g/L, no significant sensitometric differences were found. Above 7 g/L, different film types had different sensitometric results. From 7.3 to 9.3 NaBr g/L, 47.5% of the clinical films reviewed by four radiologists had less contrast compared to previous films. Dedicated mammography processors with high film volume (i.e., those that do not have excessive oxidation or foreign dye problems) can operate at lower replenishment rates than are currently employed. All common mammography film types are stable at these lower replenishment rates up to 7.0 NaBr g/L.

Biophysical Phenomena↗
PubMed1994

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. All milliampere-second values used to radiograph the breasts of these women were recorded. Mammograms of 54 women (30 with previous mammograms available), representing the four types of breasts as defined by the American College of Radiology, were interpreted by three radiologists. Each mammogram was assigned a grade for breast type, preference (Rh/Rh, Mo/Mo, or previous mammograms), contrast, and sharpness. RESULTS: Overall, mammograms obtained by using the Mo/Mo combination were preferred. However, for images of types 3 and 4 breasts, Rh/Rh was preferred twice as often as it had been for mammograms of types 1 and 2 breasts. The mean glandular dose for all breast types when the Rh/Rh combination was used was 42% of the dose used for the Mo/Mo combination. For a 6-cm-thick dense breast, the Rh/Rh combination required 40% of the dose required for the Mo/Mo combination. CONCLUSION: Mammograms obtained with the Rh/Rh combination carried an overall decrease in contrast and mean glandular dose. However, for young women and some women with large dense breasts, the Rh/Rh mammograms were equivalent to or better than the mammograms obtained with the Mo/Mo combination. Effective use of Rh/Rh units requires careful selection of women based on age or the amount of glandular tissue seen on previous mammograms.

Breast↗
PubMed1989

Acute effect of electroconvulsive therapy on brain perfusion assessed by Tc99m-hexamethylpropyleneamineoxim and single photon emission computed tomography.

Regional cerebral blood flow (rCBF) was measured in relative terms with Tc99m-hexamethylpropyleneamineoxim and single photon emission computed tomography in 11 patients undergoing electroconvulsive therapy (ECT). The patients suffered from major depressive disorder (n = 8) or schizoaffective disorders (n = 3). rCBF was measured under general anesthesia 3 days prior to the ECT treatment and coinciding with the ECT stimulation. ECT caused a redistribution of the tracers uptake. The uptake became more pronounced in frontal parts of the brain and in the basal ganglia than in posterior parts of the cortex, and the thalamus. This selective effect of ECT on rCBF may be related to catecholaminergic projections to anterior parts of the brain.

Brain↗
PubMed1989

Cerebral perfusion inhomogeneities in schizophrenia demonstrated with single photon emission computed tomography and Tc99m-hexamethylpropyleneamineoxim.

Cerebral blood flow was measured in relative terms with Tc99m-hexamethylpropyleneamineoxim (HMPAO) and single photon emission computed tomography (SPECT) in 28 female schizophrenic patients (20 acute and 8 chronic) classified according to DSM-III. Eleven normals served as controls. The acute patients were classified according to positive and negative symptoms. Patients with predominantly positive symptoms showed by and large normal and homogeneous cerebral isotope uptake. Those with negative symptoms, and the chronic patients, showed inhomogeneous tracer uptake with multiple regions of hypoperfusion in slices 4-6 cm above the orbitomeatal line. The findings support in principle the notion that schizophrenia with negative or chronic symptoms does not affect the whole brain homogeneously. Brain imaging with Tc99m-HMPAO and SPECT might be used to distinguish various types of schizophrenia.

Adult↗